JP3548493B2 - Wastewater treatment method - Google Patents

Description

【００７６】
実施例６〜９、比較例１
再生時の処理温度を下記表２に示した値にした以外は、実施例２と同じ触媒、同じ処理方法、同じ処理条件、同じ装置を用いて実施例２に準じて再生処理を行なった。この結果を下記表２に併記する。尚、実施例８は、処理温度を１６０℃としたため、処理圧力を０．９ＭＰａ（Ｇａｕｇｅ）とした。また、比較例１は、処理温度を２２０℃としたため、処理圧力を２．５ＭＰａ（Ｇａｕｇｅ）とした。
【００７７】
【表２】

【００７８】
実施例１０〜１５
再生時の処理時間を下記表３に示した値にした以外は、実施例２と同じ触媒、同じ処理方法、同じ処理条件、同じ装置を用いて実施例２に準じて再生処理を行なった。この結果を下記表３に併記する。尚、実施例１４および１５では、再生処理温度を１２５℃として実施例８に準じて再生処理を行なった。
【００７９】
【表３】

【００８０】
実施例１６〜２２
メタノールを含有する触媒再生液のＣＯＤ（Ｃｒ）濃度を下記表４に示した値にした以外は、実施例２に準じた方法で再生処理を行なった。この結果を下記表４に併記する。尚、実施例２０および２１では、再生処理時間を２４時間として実施例１１に準じて再生処理を行なった。また、酸素含有ガス（空気）の供給量は、いずれもＯ_２／ＣＯＤ（Ｃｒ）＝０．５であった。更に、実施例２２では、再生時間５時間で、酸素含有ガス（空気）の供給量をＯ_２／ＣＯＤ（Ｃｒ）＝０．２に変更して処理を行なった。
【００８１】
【表４】

【００８２】
実施例２３〜２７
触媒再生液として、エタノール、プロパノール、アセトン、テトラヒドロフランの夫々を、ＣＯＤ（Ｃｒ）で１５ｇ／リットル相当を含有する液を使用する以外は、実施例２と同じ触媒、同じ処理方法、同じ処理条件、同じ装置を用いて実施例２に準じて再生処理を行なった。この結果を、下記表５に示す。また、実施例２４では、脂肪酸カルボン酸および脂肪酸カルボン酸エステル製造設備から排出された炭素数１〜４のアルコール類を多く含有する排水を用いて再生処理を行なった。排水の濃度は、ＣＯＤ（Ｃｒ）２３ｇ／リットルであった。尚、酸素含有ガス（空気）の供給量は、Ｏ_２／ＣＯＤ（Ｃｒ）＝０．５であった。
【００８３】
【表５】

【００８４】
比較例２，３
酸素含有ガスの供給量を下記表６に示した値にした以外は、実施例２と同じ触媒、同じ処理方法、同じ処理条件、同じ装置を用いて実施例２に準じて再生処理を行なった。その結果を、下記表６に示す。
【００８５】
【表６】

【００８６】
実施例２８
図２に示す装置を使用した。図２に示した装置における基本構成は、前記図１に示した装置と類似し、対応する部分には同一の参照符号を付してある。この図２に示した装置では、加熱器３によって加熱された排水が、反応塔２１（２２は電気ヒーター）の底部から供給されると共に、酸化・分解処理された後の廃水は、反応塔２１の上部から排出される様に構成されたものである。即ち、図２に示した反応塔２１は、触媒層における気液の流通方式が気液上向並流のものである。
【００８７】
そして、実施例１と同じ要領（同じ排水、同じ処理方法、同じ処理条件）で排水の処理を実施した。５０時間経過後のＣＯＤ（Ｃｒ）処理効率は８７％であった。引き続き、実施例２と同じ処理方法、同じ処理条件で、実施例２に準じて触媒の再生処理を行なった。その結果を、下記表７に示す。尚、酸素含有ガス（空気）の供給量は、Ｏ_２／ＣＯＤ（Ｃｒ）＝０．５であった。
【００８８】
【表７】

【００８９】
実施例２９
再生処理時間が０〜１時間までは１６０℃、１〜３時間までは１２５℃で実施した以外は、実施例２と同じ触媒、同じ処理方法、同じ処理条件、同じ装置で実施例２に準じて再生処理を行なった。その結果を、下記表８に示す。
【００９０】
【表８】

【００９１】
実施例３０，３１
実施例１に示した図１と同じ装置を使用し、排水処理を実施した。反応塔１の内部には、活性炭とパラジウムを主成分とし、パラジウムを０．６質量％含有する３ｍｍφのペレット状の固体触媒を１リットル（４２０ｇ）、１８８０ｍｍＨ充填した。また、処理に供した排水は、発電設備から排出された排水で、硫安とナトリウムイオンと炭酸イオンを含有する排水であった。また、排水中のアンモニア濃度は、４，２００ｍｇ／リットル、ｐＨ７．８であった。
【００９２】
該排水は、排水供給ポンプ５によって１リットル／ｈの流量で昇圧フィードした後、加熱器３で１３０℃に加熱し、反応塔１の上部より供給して気液下向並流で処理した。また、空気を酸素含有ガス供給ライン８から導入し、コンプレッサー７で昇圧した後、この空気を酸素含有ガス流量調節弁９によって供給量を調整しつつ加熱器３の手前で排水に供給した。
【００９３】
反応塔１では、電気ヒーター２を用いて１３０℃に保温し、酸化・分解処理を実施した。処理液は、冷却器４で冷却した後、圧力制御弁１２から解圧して排出し、気液分離器１１で気液分離した。尚、前記圧力制御弁１２では、圧力コントローラーＰＣで反応塔１内の圧力を検出し、反応塔１内の圧力が０．９ＭＰａ（Ｇａｕｇｅ）となる様に制御した。また、気液分離器１１内の排気ガス中の酸素濃度を、酸素濃度計１６を用いて測定し、また気液分離器中の処理液のアンモニアの処理効率を求めた。
【００９４】
まず、運転開始から５０時間、排気ガス中の酸素濃度が０．５％となるように空気供給量を制御した。その結果、反応開始から５０時間経過後のアンモニアの処理効率は９５％であった。
【００９５】
次に、５０〜１００時間経過後まで、気液分離中の排気ガスの酸素濃度が１０％となるように空気を供給し、触媒活性が低下するようにした。更に、１００〜１５０時間経過後まで、再度、排気ガス酸素濃度が０．５％となるように空気供給量を制御した。１５０時間経過後のアンモニアの処理効率は５４％に低下していた。
【００９６】
（再生処理過程）
上記において、アンモニアの処理効率が９５％から５４％に低下した触媒に対して、以下に記載する再生処理を実施した。
【００９７】
再生処理の方法は、排水供給ポンプ５によって触媒再生液１リットル／ｈの流量で昇圧フィードした後、加熱器３で１５０℃に加熱して反応塔１の上部より再生液を供給し、気液下向並流で流した。尚、この再生処理に用いた触媒再生液は、メタノールを約８ｇ／リットル含有した液であり、ＣＯＤ（Ｃｒ）１２ｇ／リットルであった。また、空気を酸素含有ガス供給ライン８より導入し、コンプレッサー７で昇圧した後、下記表９に示す各々の量で酸素含有ガス（空気）を加熱器３の手前で再生液に供給した。触媒層を通過した再生液は、冷却器４で冷却した後、圧力制御弁１２から解圧して排出し、気液分離器１１で気液分離した。尚、圧力制御弁１２は圧力コントローラーＰＣで圧力を検出し、０．９ＭＰａ（Ｇａｕｇｅ）の圧力を保持する様に制御した。
【００９８】
この再生処理を７時間実施し、その後、先の排水処理条件と同じ条件で、排水の処理を再度５０時間実施した。その結果を、下記表９に示す。
【００９９】
【表９】

【０１００】
【発明の効果】
本発明は以上の様に構成されており、性能が低下した触媒を効果的に再生することができ、固体触媒の耐久性を飛躍的に向上させることができる様になった。また、本発明によって長時間安定的に排水を浄化することができるようになり、排水の処理費を低く抑えることができることになる。
【０１０１】
また、本発明が基本的に採用している湿式酸化法による排水の処理方法は、排水の処理設備および排水の処理費を安価にでき、しかも高度に排水を処理することができる優れた処理方法である。従って、こうした湿式酸化法において本発明の再生による効果を付加することによって、その方法による効果を著しいものとすることができる。
【０１０２】
更に、本発明によって処理した排水の処理液は、他の用途にも用水として再利用することができ、資源のリサイクルとの面からも優れており、これによってコストダウンを図れると共に、資源を有効に活用できる、等の効果も期待できる。
【図面の簡単な説明】
【図１】本発明を実施する為に構成される装置の一構成例を示す概略説明図である。
【図２】本発明を実施する為に構成される装置の他の構成例を示す概略説明図である。
【符号の説明】
１，２１ 反応塔
２，２２ 電気ヒーター
３ 加熱器
４ 冷却器
５ 排水供給ポンプ
６ 排水供給ライン
７ コンプレッサー
８ 酸素含有ガス供給ライン
９ 酸素含有ガス流量調節弁
１０ 処理液ライン
１１ 気液分離器
１２ 圧力制御弁
１３ ガス排出ライン
１４ 処理液排出ポンプ
１５ 処理液排出ライン
１６ 酸素濃度計[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for purifying wastewater. More specifically, the present invention relates to a method for wet-oxidizing waste water containing organic and / or inorganic oxidizable substances using a solid catalyst while supplying an oxygen-containing gas, and in particular, treating the waste water by appropriately performing a regeneration treatment. The present invention relates to a method capable of effectively regenerating a solid catalyst having reduced performance and treating wastewater stably for a long period of time.
[0002]
[Prior art]
As a method of treating wastewater containing an organic or inorganic oxidizable substance, for example, a biological treatment method or a wet oxidation method is known. Of these, biological treatment requires a long time to decompose oxidizable substances in wastewater, and can only treat low-concentration substances, so when wastewater contains high-concentration oxidizable substances, It is necessary to dilute to an appropriate concentration, which has the disadvantage that the equipment area of the processing facility becomes large. Moreover, since the microorganisms used are greatly affected by the temperature and the like, it has been difficult to maintain stable operation.
[0003]
On the other hand, in the wet oxidation method, wastewater is treated under high temperature and high pressure in the presence of oxygen, and oxidizable substances in the wastewater are oxidized and / or decomposed (hereinafter, also referred to as “oxidation / decomposition treatment”). There is a method. In this method, as a means for increasing the reaction rate and relaxing the reaction conditions, for example, a catalyst wet oxidation method using a catalyst using an oxide or a catalyst combining these oxides with a noble metal element has been proposed.
[0004]
However, in order to purify the wastewater by oxidizing and decomposing various oxidizable substances contained in the wastewater by this method, it is necessary to treat the wastewater at a treatment temperature of 170 ° C. or more, and therefore, the treatment pressure is also 1 MPa ( Gauge) was often required. For example, Japanese Patent Application Laid-Open No. H11-347574 describes a method in which acetic acid is wet-oxidized at a processing temperature of 170 ° C. using a catalyst in which platinum is supported on titania. There is a need for treatment conditions, and further development of a wastewater treatment method capable of advanced treatment under low-temperature and low-pressure conditions of less than 170 ° C is desired.
[0005]
For these reasons, the present inventors have conventionally studied a new catalyst and a new treatment method. As a result, as one of the means to further reduce the reaction conditions, when a solid catalyst containing activated carbon is used, organic and inorganic oxidizable substances can be reduced under low-temperature and low-pressure processing conditions of less than 170 ° C. The specific activity was confirmed to be high.
[0006]
By the way, when a solid catalyst containing activated carbon is used, there is a problem that the activated carbon itself burns under the conventional wet oxidation conditions, and it is impossible to use the activated carbon as a wet oxidation catalyst stably for a long time. Met. Therefore, the present inventors have proposed that by maintaining the oxygen concentration in the exhaust gas after treatment using a solid catalyst containing activated carbon at 0 to 5%, combustion of the activated carbon itself can be suppressed, and wastewater can be treated efficiently. Since the headline and its technical significance were recognized, the application was filed earlier (Japanese Patent Application No. 12-5198).
[0007]
The development of such technology has made it possible to treat wastewater containing organic and / or inorganic oxidizable substances to a high degree even at low temperatures and low pressures. However, in recent years, it is a fact that it has been desired to maintain the activity of the catalyst for a longer period of time and to treat the wastewater more efficiently. For example, when the wastewater contains a hardly decomposable oxidizable substance, the treatment temperature condition needs to be relatively high in order to realize advanced treatment of the wastewater. In such a case, the durability of the catalyst containing activated carbon tends to decrease. Activated carbon also has the property of adsorbing oxidizable substances in wastewater. However, if the rate of decomposition of the adsorbed oxidizable substances is extremely slow, there is also a problem that the oxidation / decomposition treatment activity of the catalyst gradually decreases. Further, when the wastewater treatment is performed for a long period of time, it is expected that the activity of the catalyst containing the activated carbon is deactivated due to troubles in the wastewater treatment such as equipment troubles and operation errors. For these reasons, there is a demand for the development of an excellent method for reactivating the activity of an activated carbon-containing catalyst whose activity has decreased.
[0008]
In order to solve such a problem, several catalyst regeneration methods have been proposed so far. For example, Japanese Patent Publication No. 3-66018 discloses an acid washing treatment using an acid aqueous solution containing at least one selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, acetic acid and propionic acid, and hydrazine hydrate. Liquid phase reduction using an aqueous solution containing at least one selected from the group consisting of formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate, glucose, potassium formate and sodium formate, or hydrogen and / or monoxide A method has been proposed which combines with a gas phase reduction treatment using a carbon-containing gas reducing agent.
[0009]
However, the reduction treatment of this method is not sufficient to restore the activity of the catalyst containing activated carbon, and on the contrary, there is a possibility that the activity of the catalyst may be deteriorated. In addition, it is difficult to carry out the reduction treatment using a gas such as hydrogen or carbon monoxide while the catalyst is filled in an actual wastewater treatment device. Therefore, it is necessary to use a reduction firing furnace or the like dedicated to the reduction treatment, which is practically impossible. Further, Japanese Patent Publication No. 4-45214 discloses that after contacting a catalyst with an aqueous solution containing formic acid and / or oxalic acid at 40 to 85 ° C., heat treatment is performed to decompose formic acid and / or oxalic acid, and to form a catalyst. A method for performing a reduction process has been proposed. However, such a catalyst regeneration method is not enough to recover the activity of the catalyst containing activated carbon, and on the contrary, it may cause deterioration of the activity of the catalyst or corrosion of the material of the apparatus.
[0010]
On the other hand, Japanese Patent Application Laid-Open No. 9-10602 discloses that at least one ammonium salt selected from the group consisting of ammonium sulfate, ammonium chloride and ammonium carbonate, or an ammonium salt thereof, is used as a solid catalyst whose activity has been reduced by oxidation with excess oxygen. There has been proposed a method of regenerating a catalyst by using a regenerant containing ammonia and ammonia and having a pH of 3 to 10 and contacting the catalyst substantially without supplying oxygen. Although this method has some effects on the regeneration of a catalyst containing activated carbon, it is desired to realize a more effective method.
[0011]
[Problems to be solved by the invention]
The present invention has been made in view of such a situation, and an object of the present invention is to treat wastewater containing organic and / or inorganic oxidizable substances at a relatively low temperature and low pressure of less than 170 ° C. When oxidizing and decomposing using a solid catalyst containing activated carbon at a temperature and a pressure at which the wastewater retains a liquid phase, the solid catalyst having a reduced oxidizing and decomposing activity is effectively regenerated. It is an object of the present invention to provide a wastewater treatment method capable of purifying wastewater stably for a period.
[0012]
[Means for Solving the Problems]
The wastewater treatment method of the present invention that can achieve the above object is a wastewater treatment method in which organic and / or inorganic oxidizable substances contained in the wastewater are oxidized and / or decomposed using a catalyst. At a treatment temperature of 50 ° C. or more and less than 170 ° C. and a pressure at which the waste water maintains a liquid phase, the waste water is treated using a catalyst containing activated carbon by supplying an oxygen-containing gas, and is easily decomposable and oxidizable. The gist lies in supplying a catalyst regenerating solution containing a substance to a solid catalyst and operating the solid catalyst while regenerating the solid catalyst at a temperature of 55 ° C. or more and less than 200 ° C.
[0013]
In carrying out the method of the present invention, the operation is preferably performed such that the catalyst regenerating liquid remains at the outlet of the catalyst layer. Further, it is desirable that the regeneration treatment temperature of the solid catalyst is a temperature higher by 5 to 100 ° C. than the wastewater treatment temperature. Examples of the catalyst regeneration solution used in the present invention include a solution containing alcohols. Furthermore, it is desirable to operate while maintaining the oxygen concentration in the exhaust gas after treating the wastewater using a solid catalyst containing activated carbon in the range of 0 to 5 vol%.
[0014]
In the method of the present invention, when the catalyst regenerating solution is supplied to the catalyst layer, an oxygen-containing gas or a non-oxygen-containing gas is supplied, and the amount of oxygen in these supply gases is [oxygen in supply gas] / [regeneration of catalyst]. Oxygen in the catalyst regenerating liquid when the liquid processing efficiency is maximizedconsumptionAmount] is desirably set to be in the range of 0 to 1.3. In the present invention, it is preferable that the gas-liquid distribution method in the catalyst layer filled with the solid catalyst is a gas-liquid downward cocurrent flow.
[0015]
The solid catalyst used in the present invention basically contains activated carbon, and further contains one or more elements selected from the group consisting of Pt, Pd, Rh, Ru, Ir, Ag and Au. It is desirable that
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The inventors of the present invention oxidize and decompose an oxidizable substance using a solid catalyst containing activated carbon under a wet oxidation treatment condition of 50 ° C. or more and less than 170 ° C. Various studies have been made on a method capable of effective reproduction. As a result, if the catalyst regenerating solution containing the easily decomposable oxidizable substance is supplied to the solid catalyst, and the solid catalyst is operated while regenerating the solid catalyst at a temperature of 55 ° C. or more and less than 200 ° C., the above-mentioned object is excellently achieved. The present invention was completed. It has also been found that it is more effective to operate the catalyst regenerating solution so that the catalyst regenerating solution remains at the outlet of the catalyst layer.
[0017]
In regenerating a catalyst by the method of the present invention, it is necessary to “supply a catalyst regenerating solution containing a readily decomposable oxidizable substance to a solid catalyst” as described above. It is more preferable to make it remain at the exit, but this point will be described first. The causes of the decrease in the activity of the catalyst include the following. The first is that the catalyst is oxidized by the influence of oxygen in the gas phase and oxygen adsorbed on the catalyst surface in the wet oxidation treatment, and it is expected that activated carbon is particularly susceptible to oxidation. Secondly, when the treatment is performed for a long period of time, it is conceivable that the hardly decomposable oxidizable substance contained in the wastewater covers the catalytically active sites and the catalytic activity is reduced.
[0018]
In the present invention, the catalyst is reformed by bringing the catalyst regenerating solution into contact with the catalyst to perform the treatment, and furthermore, the effect of facilitating the desorption of the substance adsorbed on the catalyst is exhibited. That is, it is considered that under the condition where the oxygen-containing gas is not supplied or under the shortage condition, for example, the substance adsorbed on the catalyst is decomposed and easily desorbed by a substance generated by thermal decomposition of the catalyst regenerating solution. Further, under the supply of an oxygen-containing gas, the easily decomposable catalyst regenerating solution easily undergoes an oxidation reaction, and is considered to have an effect of promoting the catalytic reaction. Thus, it is considered that the hardly decomposable oxidizable substance adsorbed on the catalyst is easily oxidized and decomposed at the same time. Further, in order to sufficiently exhibit such effects, it is preferable to supply a catalyst regenerating solution of such a degree that “the catalyst regenerating solution remains at the outlet of the catalyst layer”. It is difficult to be displayed. In addition, by adopting such a structure, the easily decomposable catalyst regenerating solution protects the catalyst, preventing the catalyst activity from decreasing even under somewhat high-temperature regenerating treatment conditions. It is thought to promote improvement.
[0019]
Even if the catalyst regenerating solution does not remain at the exit of the catalyst layer, if the easily decomposable substance of the catalyst regenerating solution can contact the solid catalyst in most of the solid catalyst layer, the activity should be improved to some extent. Can be done. This is because the regeneration efficiency of wastewater can be improved by regenerating an amount of the catalyst corresponding to the degree of supply of the easily decomposable substance without regenerating the entire catalyst in the solid catalyst layer.
[0020]
The solid catalyst used in the present invention only needs to contain at least activated carbon as a catalyst component. The type of the activated carbon is not particularly limited, and examples thereof include those made from charcoal, coconut shell charcoal, coal, coke, peat, lignite, pitch, and the like, and acrylonitrile-based activated carbon fibers and phenol. Activated carbon fibers such as activated carbon fibers, activated carbon fibers, activated carbon fibers, and activated carbon fibers based on pitch may be used. Regarding the shape of the solid catalyst, various shapes such as a spherical shape, a granular shape, a pellet shape, a ring shape, a crushed shape, and a honeycomb shape can be used.
[0021]
In the present invention, even if a solid catalyst consisting only of activated carbon is used, depending on the type and concentration of the oxidizable substance, the substance exhibits the oxidizing activity necessary for oxidizing and decomposing it, but is used in the present invention. As the solid catalyst, it is also effective to further contain at least one element selected from the group consisting of Pt, Pd, Rh, Ru, Ir, Ag, and Au. can do. This is desirable because the efficiency of oxidizing and decomposing the oxidizable substance contained in the wastewater can be improved and the processing temperature can be further reduced. The content of these elements is not particularly limited, but is desirably contained in the solid catalyst at a ratio of preferably 0.01 to 5% by mass, more preferably 0.05 to 2% by mass. The solid catalyst contains at least one element selected from the group consisting of titanium, zirconium, aluminum, silicon, iron, manganese, chromium, cobalt, nickel, copper, zinc, cerium, praseodymium, tellurium and bismuth. You can also.
[0022]
The “oxidizable substance” targeted in the present invention means an organic and / or inorganic compound that can be purified by oxidation / decomposition treatment, and can also be expressed as an organic compound, a sulfur compound, a nitrogen compound, and the like. Furthermore, although not particularly limited, organic halogen compounds and organic phosphorus compounds may be used. Specifically, for example, organic compounds such as methanol, ethanol, acetaldehyde, formic acid, acetone, acetic acid, propionic acid, tetrahydrofuran (THF) and phenol; nitrogen such as ammonia, hydrazine, nitrite, dimethylformamide (DMF) and pyridine Compounds: Sulfur compounds such as thiosulfate ion, sodium sulfide, dimethyl sulfoxide, and alkylbenzene sulfonate, and the like. These may be dissolved in water or may be present as suspended substances.
[0023]
In the method of the present invention, wastewater is basically treated at a temperature of 50 ° C. or higher and lower than 170 ° C. If the temperature is lower than 50 ° C., the oxidation and oxidation of organic and / or inorganic oxidizable substances is prevented. It becomes difficult to perform the decomposition process efficiently. The treatment temperature is preferably higher than 80 ° C, more preferably higher than 100 ° C, and further preferably higher than 110 ° C. Even when the treatment temperature is 110 ° C. or less, advanced treatment of organic compounds such as methanol, formic acid, and formaldehyde is possible, but for advanced treatment of organic compounds having 2 or more carbon atoms, the treatment temperature exceeds 100 ° C. Often a reaction temperature is required. If the treatment temperature is 170 ° C. or higher, the combustion of the activated carbon itself is likely to occur, which is not practical. For this reason, the processing temperature is preferably set to 160 ° C. or lower, more preferably 150 ° C. or lower, and further preferably 140 ° C. or lower.
[0024]
On the other hand, the pressure at which the wastewater is treated may be any pressure at which the wastewater retains a liquid phase at the treatment temperature described above, but is usually from atmospheric pressure to about 1 MPa (Gauge). For example, when the treatment temperature is 50 to 90 ° C., the wastewater is often in a liquid phase even at atmospheric pressure, and therefore may be at atmospheric pressure from the viewpoint of economy, but in order to improve the treatment efficiency, It is preferable to apply pressure. Further, when the treatment temperature exceeds 95 ° C., the wastewater often evaporates under the atmospheric pressure. Therefore, it is preferable to pressurize to about 0.2 to 1 MPa (Gauge). However, a pressure exceeding 1 MPa (Gauge) is not preferable from the viewpoint of economy. In addition, when the processing pressure is increased, as in the case where the processing temperature is increased, the problem of combustion of the activated carbon itself is likely to occur. Further, the activity of the catalyst may be reduced.
[0025]
The catalyst regeneration liquid used in the present invention is not particularly limited as long as it contains a readily decomposable oxidizable substance. Specifically, an easily decomposable oxidizable substance is a substance that can be easily oxidized and decomposed using a solid catalyst containing activated carbon under wet oxidation treatment conditions of 50 ° C. or more and less than 170 ° C. good. This substance is preferably a substance that is easily oxidized and decomposed at a temperature of 50 ° C. or more and less than 140 ° C., and is a substance that is easily oxidized or decomposed at a temperature of 50 ° C. or more and less than 120 ° C. More preferably, it is a substance that is easily oxidized and decomposed under the condition of 50 ° C. or more and less than 100 ° C., and is a substance that is easily oxidized or decomposed under the condition of 50 ° C. or more and less than 90 ° C. Most preferred.
[0026]
Further, the pH of the aqueous solution containing the easily decomposable substance is desirably neutral, and the acidity or alkalinity is not desirable because it causes corrosion and deterioration of the apparatus and the catalyst. Such a catalyst regenerating liquid is desirably a liquid containing, for example, alcohols. Specifically, a liquid containing methanol, ethanol, propanol and the like can be mentioned, and a liquid containing glycol and glycerin may be used. Effectively, alcohols having 1 to 4 carbon atoms are desirable in view of their easy decomposability and the like, more preferably methanol, ethanol, and propanol, and most preferably methanol. Therefore, the normal wastewater to be treated may contain methanol or the like, or may further contain methanol or the like in the wastewater. However, the catalyst regeneration liquid is not limited to this, and an aqueous solution containing various easily decomposable substances can be used. For example, organic substances such as acetaldehyde, acetone, tetrahydrofuran, and phenol, and inorganic substances such as sodium sulfite and sodium bisulfite can be used.
[0027]
In the present invention, the concentration of the catalyst regenerating solution is not particularly limited, but the COD (Cr) concentration is preferably 0.1 to 50 g / l, more preferably 0.5 to 30 g / l. is there. If this concentration is less than 0.1 g / liter, the regeneration effect of the catalyst regeneration liquid will be low. On the other hand, if it exceeds 50 g / l, a large amount of oxidizable substances for the catalyst regenerating solution will be required and the cost will increase, which is not preferable.
[0028]
In the present invention, the concentration of the catalyst regenerating solution at the outlet of the catalyst layer is not particularly limited, and a high catalyst regenerating effect can be obtained as long as the catalyst regenerating solution remains. Preferably, the COD (Cr) concentration at the outlet of the catalyst layer is 0.05 to 50 g / l, more preferably 0.1 to 30 g / l. If this concentration is less than 0.05 g / liter, the regeneration effect near the catalyst layer outlet will be low. On the other hand, if it exceeds 50 g / liter, not only the cost is increased but also the post-treatment of the regenerating solution becomes complicated, which is not preferable.
[0029]
In the present invention, the method of supplying the catalyst regenerating solution is not particularly limited, but is sent to the heater by, for example, a drainage supply pump 5 shown in FIG. After that, the heated catalyst regenerating liquid is supplied to the reaction tower 1, and the solid catalyst is regenerated. The space velocity in the catalyst layer is not particularly limited, and may be the same as the ordinary wastewater treatment conditions, but the space velocity per catalyst layer is usually 0.1 hr.^-1~ 10hr^-1, More preferably 0.1 hr^-1~ 5hr^-1, More preferably 0.1 hr^-1~ 3hr^-1What is necessary is just to make it. Space velocity is 0.1hr^-1If it is less than this, it takes a long time for the reproduction process, which is not practical. Conversely, 10 hr^-1If it exceeds, the amount of the regenerating solution is required to be large, which is not preferable.
[0030]
In the apparatus for carrying out the present invention, the number, type, shape, and the like of the reaction towers are not particularly limited, and may be a single-tube reaction tower or a multi-tube reaction used in ordinary wet oxidation treatment. A tower or the like can be used. In addition, by installing a plurality of reaction towers and arranging the reaction towers in series or in parallel, it is also possible to carry out a regeneration treatment as needed from a catalyst having reduced oxidation / decomposition performance.
[0031]
In the present invention, the method of flowing gas and liquid in the catalyst layer filled with the catalyst is not particularly limited, but a more preferable method is a method of flowing gas and liquid downward in parallel. It is thought that by flowing gas and liquid in a parallel flow downward, the gas-liquid contact efficiency is improved and the amount of dissolved oxygen is increased, and the contact efficiency between the liquid and the catalyst is improved, so that the processing efficiency is considered to be improved. Can be Further, when gas-liquid is caused to flow in parallel, the liquid containing a large amount of the oxidizable substance comes into contact with the gas having a high oxygen concentration at the inlet of the catalyst layer, so that the combustion of the activated carbon itself is considered to be suppressed.
[0032]
Further, when the solid catalyst is regenerated in the present invention, the method of gas-liquid circulation in the catalyst layer filled with the catalyst is not particularly limited. However, a preferred method is to make it the same as the gas-liquid flow direction in the wastewater treatment. By making the flow direction the same as the gas-liquid flow direction in the wastewater treatment, it can be more easily implemented in terms of operability and the like. For this reason, as a preferable method, a method of flowing in a gas-liquid downward co-current flow as shown in FIG. Further, gas-liquid upward flow as shown in FIG. 2 to be described later can be performed, or a fluidized bed type can be used. In addition, it is possible to flow in the gas-liquid countercurrent, but the gas-liquid cocurrent is more preferable. It is considered that when the gas-liquid flows in parallel, the liquid containing a large amount of the oxidizable substance comes into contact with the gas having a high oxygen concentration at the inlet of the catalyst layer, so that the combustion of the activated carbon itself is suppressed.
[0033]
Further, in the present invention, it is possible to start and stop the apparatus by supplying only the catalyst regenerating liquid without supplying gas to the catalyst layer, but it is difficult to control the pressure if no gas is supplied. The pressure change at that time often has a bad influence on the catalyst. In such a case, by supplying gas from the rear of the catalyst layer and maintaining the pressure in the apparatus, not only stable pressure control is possible, but also the activity of the catalyst is reduced because oxygen is not supplied to the catalyst layer. It can be suppressed effectively. Since the present invention relates to a method for treating wastewater by the wet oxidation method, it is desirable to use an oxygen-containing gas used for wastewater treatment in this case in terms of operability and economy.
[0034]
In the wastewater treatment method according to the present invention, the type of the solid catalyst layer of the wastewater treatment device may be a fluidized bed type (fluidized bed type). In the wet oxidation treatment using the solid catalyst, when the catalyst containing the activated carbon according to the present invention is used, a fluidized bed type wastewater treatment apparatus is more easily adopted than in the case where a conventional solid catalyst is used. be able to. The fluidized-bed type wastewater treatment apparatus is less likely to generate a hot spot due to the reaction, and thus can perform a higher-concentration wastewater treatment than a fixed-bed type (fixed-bed type) apparatus. In addition, the treatment of waste water, which tends to cause deterioration of the catalyst containing activated carbon, is facilitated by the characteristics of the apparatus. This is because it is possible to add a new catalyst or a recycled catalyst while extracting the deteriorated waste catalyst in the fluidized bed type wastewater treatment apparatus. Conventionally, in a wet oxidation treatment using a solid catalyst, as a cause of catalyst deterioration, there has been a problem that an active component in the solid catalyst moves behind a fixed bed. This problem can also be solved in a fluidized bed apparatus because the solid catalyst itself moves. In the case of a fluidized bed system, a catalyst having a smaller particle size than a solid catalyst generally employed in a fixed bed system can be employed, and the contact efficiency with gas and liquid can be further improved, so that the processing performance can be improved. In the case of a fluidized bed type, even wastewater containing a small amount of solids, which was difficult to treat in a fixed bed type, can be treated because the problem of clogging of the reaction tower hardly occurs. The range can be further expanded.
[0035]
In the case of this fluidized bed type apparatus, although not particularly limited, the number of reaction towers may be one or plural, and from the viewpoint of operability and equipment cost, one reaction tower may be used. Is more desirable. Further, although not particularly limited, the inside of the reaction tower may be one chamber, but the division into a plurality of chambers (multistage) improves the processing performance more, and also from the viewpoint of operation control. desirable.
[0036]
The physical property value of the catalyst containing activated carbon in the present invention is not particularly limited, but preferably, the total volume of the pores having a pore diameter of 0.1 to 10 μm is 0.1 to 0.8 ml /. g and the specific surface area is 100 to 2,500 m²/ G is good. Further, the total volume of the pores having a pore diameter of 0.1 to 10 μm is more preferably 0.15 to 0.7 ml / g, and further preferably 0.2 to 0.6 ml / g. is there. The specific surface area is 500-2,000m²/ G, more preferably 800 to 1,700 m²/ G, most preferably from 900 to 1,500 m²/ G. The reasons for these provisions are as follows.
[0037]
In the wet oxidation treatment of wastewater of the present invention, the macropore diameter of the catalyst pores of 0.1 to 10 μm greatly affects the diffusion of oxidizable substances and oxygen contained in the wastewater. For this reason, in a catalyst having a large pore diameter of 0.1 to 10 μm, the oxidation of the oxidizable substance and oxygen becomes easy, so that the reaction easily proceeds. That is, the processing efficiency at low temperature and low pressure is improved. In contrast, a catalyst having a small pore diameter of 0.1 to 10 μm has poor diffusion of oxidizable substances and oxygen. This makes it difficult for the oxidizable substance to be adsorbed to the catalytically active sites, and the reaction does not proceed efficiently. In addition, oxygen is not efficiently used for the decomposition of the oxidizable substance, and the activated carbon itself is generated by excess oxygen. It becomes easy to burn. On the other hand, in the case of a catalyst having a very large pore diameter of 0.1 to 10 μm, there is a problem that the mechanical strength of the catalyst is reduced. For this reason, a catalyst having a total pore volume in the above range having a pore diameter of 0.1 to 10 μm is desirable.
[0038]
In addition, the larger the specific surface area of the catalyst, the more the adsorption of the substance to be contained in the wastewater increases, and accordingly, the treatment efficiency of the wastewater tends to improve. For this reason, a catalyst having a small specific surface area is undesirable. However, in the case of a catalyst having a very large specific surface area, the mechanical strength of the catalyst is reduced. Therefore, a catalyst having a specific surface area of the catalyst within the above-mentioned range is desirable.
[0039]
In general, it is known that, when activated carbon is subjected to a treatment such as an oxidation treatment or a reduction treatment, a polar group is introduced into the surface or, conversely, is removed, and the physical properties thereof are significantly changed. Similarly, also in the catalyst according to the present invention, the catalytic performance significantly changes according to the amount of the polar group in the catalyst. In particular, the relationship between the amount of the polar group and the catalytic activity varies greatly depending on the component to be treated (oxidizable substance) in the wastewater. For example, when the component to be treated (oxidizable substance) is an organic substance or an anionic inorganic substance, the catalyst containing activated carbon needs to have a small amount of polar groups and a highly hydrophobic catalyst (activated carbon). For this reason, the catalyst which has been subjected to the reduction treatment tends to show higher activity. Conversely, in the case of a cationic inorganic substance such as ammonia or hydrazine, the amount of polar groups in the catalyst containing activated carbon needs to be large. Therefore, the more the catalyst is oxidized, the higher the activity may be.
[0040]
It is considered that the reason for this is that the ease with which the component to be treated is adsorbed on the catalyst has a large effect. Many of the polar groups in catalysts containing activated carbon are oxygen-containing functional groups such as hydroxyl groups and carboxyl groups. Therefore, in the catalyst containing activated carbon in the present invention, although not particularly limited, the amount of oxygen / the amount of carbon (hereinafter also referred to as O / C ratio) in the catalyst is correlated with the amount of the polar group in the catalyst. In a relationship. Therefore, a catalyst having a small amount of polar group has a small O / C ratio, and a catalyst having a large amount of polar group has a large O / C ratio. Further, in the catalyst according to the present invention, a preferable catalyst and an unfavorable catalyst for the component to be treated can be classified by O / C ratio. More specifically, when the component to be treated (oxidizable substance) is an organic substance or an anionic inorganic substance, a desirable catalyst has an O / C ratio of 0 to 0.12, and more preferably 0 to 0. .10, and more preferably 0 to 0.08. Conversely, when the component to be treated (oxidizable substance) is a cationic inorganic substance such as ammonia or hydrazine, a catalyst having an O / C ratio of 0.08 to 0.30, more preferably 0.10 To 0.25, and more preferably 0.12 to 0.20. However, a catalyst having an excessively large O / C ratio causes a problem that the mechanical strength of the catalyst is reduced.
[0041]
As described above, the catalyst containing activated carbon in the present invention is not particularly limited, but in producing the catalyst, the catalyst may be subjected to various treatments so as to have an O / C ratio suitable for various treatment purposes. desirable. Specifically, in order to reduce the O / C ratio in the catalyst and reduce the amount of the polar group, the catalyst is preferably subjected to various reduction treatments. For example, a method using a gas phase reduction using hydrogen or a liquid phase reduction using a reducing substance such as sodium sulfite or hydrazine may be used. By this treatment, it is considered that the active component of the catalyst is reduced and / or the activated carbon (the activated carbon surface) is hydrogenated, so that a catalyst highly active against organic substances and anionic inorganic substances can be produced. It can also be carried out by various activation treatments usually performed in the step of producing activated carbon. For example, it can be carried out by contacting with steam, carbon dioxide, or nitrogen gas at a high temperature. Conversely, in order to increase the O / C ratio in the catalyst and increase the amount of the polar group, it is desirable to perform various oxidation treatments on the catalyst. For example, gas-phase oxidation or oxidation using various gases such as oxygen-containing gas, ozone, and NOx, hydrogen peroxide, ozone aqueous solution, bromine water, permanganate, dichromate, hypochlorite, nitric acid And a method by liquid phase oxidation using a chemical such as phosphoric acid. By this treatment, the active component of the catalyst is oxidized and / or a polar group such as an oxygen-containing functional group is introduced into the activated carbon (activated carbon surface), and a catalyst having a high activity against cationic inorganic substances such as ammonia and hydrazine is obtained. It is thought that it can be manufactured. In addition, the catalyst containing activated carbon in the present invention may be subjected to treatment such as nitration, sulfonation, or amination, or treatment with an alkali metal compound.
[0042]
As described above, in the catalyst containing activated carbon in the present invention, a catalyst excellent in adsorption performance for a component to be treated (oxidizable substance) tends to be a catalyst having high catalytic activity. For this reason, the physical property value of the catalyst containing activated carbon in the present invention may include the adsorption performance for the component to be treated (oxidizable substance). For example, when the component to be treated (oxidizable substance) in the wastewater is an organic substance, not only the adsorption performance of the organic substance itself but also the adsorption performance of the oxidizable substance generated by oxidizing and decomposing the organic substance are mentioned. You can also. Furthermore, when an organic substance having 2 or more carbon atoms is the component to be treated, the acetic acid is generally, but not limited to, easily remaining in the treatment liquid after the wet oxidation treatment. Therefore, a catalyst prepared using activated carbon having excellent acetic acid adsorption performance tends to be a catalyst having high catalytic activity for organic substances. Conversely, when the component to be treated (oxidizable substance) is a cationic inorganic substance such as ammonia or hydrazine, a catalyst prepared using activated carbon having excellent ammonia adsorption performance has a catalytic activity against them. It tends to be a high catalyst. Further, although not particularly limited, activated carbon used for a catalyst having excellent adsorption performance for a component to be treated tends to be an activated carbon having excellent adsorption performance for a component to be treated. For this reason, in producing the catalyst according to the present invention, it is desirable to use, as the activated carbon to be used, activated carbon having excellent adsorption performance for the component to be treated.
[0043]
In the present invention, “excellent in adsorption performance” means, for example, the saturation adsorption amount of a target component per unit amount of activated carbon under a specific condition, and the larger the amount, the better the adsorption performance. In addition, it is represented by an adsorption rate of a target component per unit amount of activated carbon under a specific condition, and the higher the rate, the better the adsorption performance. This adsorption speed can be expressed by an initial adsorption speed or an arbitrary post-adsorption speed, and is not particularly limited. However, preferably, it is expressed by the initial adsorption rate. Particularly, when activated carbon having a high initial adsorption rate is used, the activity of the catalyst is high, and when it is converted to a catalyst, the catalyst tends to have excellent adsorption performance. .
[0044]
The catalyst containing activated carbon in the present invention can be defined by various physical properties as described above. However, the range of other physical properties not described above does not limit the range of the activated carbon-containing catalyst according to the present invention. Other various physical property values include, for example, the amount of various functional groups, the amount of ash and impurities, the structural form of carbon, the acidity, the volume of pores other than macropores (mesopores, micropores, submicropores), and the like. There are ratios, values of the external specific surface area and the internal specific surface area, and those relating to the ratio.
[0045]
Since the spent catalyst regenerating solution discharged by performing the method of the present invention often contains easily decomposable oxidizable substances, it is not preferable to directly release the regenerated solution into rivers, the sea, and the like. There are many. Therefore, it is preferable that the used catalyst regenerating solution is returned to the drain tank, the catalyst regenerating solution or the catalyst regenerating solution and the waste water are both subjected to wet oxidation treatment and purified, and it is also preferable to repeatedly use the catalyst regenerating solution. After the biological treatment or the chemical treatment is performed as the post-treatment, the water may be directly discharged to a river, the sea, or the like.
[0046]
The regeneration treatment in the present invention needs to be performed in a temperature range of 55 ° C. or more and less than 200 ° C. When the temperature of the regeneration treatment is lower than 55 ° C., it is difficult to sufficiently obtain the regeneration effect of the catalyst regeneration liquid. From such a viewpoint, the catalyst regeneration temperature is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 120 ° C. or higher. On the other hand, when the catalyst regeneration temperature is 170 ° C. or more, the combustion of the activated carbon itself is likely to occur, so long-term treatment is not preferable. The effect is recognized. At the time of regeneration, it is desirable that the catalyst regeneration liquid keeps a liquid phase. Further, when the catalyst regeneration temperature is 200 ° C. or higher, combustion of activated carbon occurs, so that even a temporary treatment is not preferable. From such a viewpoint, the upper limit of the catalyst regeneration temperature is preferably lower than 170 ° C, more preferably lower than 160 ° C, and further preferably lower than 150 ° C.
[0047]
The present invention is carried out at a wastewater treatment temperature of 50 ° C. or more and less than 170 ° C., but by treating the catalyst at a temperature 5 to 100 ° C. higher than the wastewater treatment temperature (normal wastewater treatment temperature). It is preferable because a high reproduction effect can be obtained. Further, if the regeneration treatment is performed at a temperature higher by 10 to 60 ° C. than the waste water treatment temperature, a higher regeneration effect can be obtained, and a more favorable result can be obtained at a regeneration treatment temperature higher by 15 to 40 ° C. than the above waste water treatment temperature. .
[0048]
However, a higher regeneration temperature may be required in order to decompose the oxidizable substance adsorbed on the activated carbon in the long-term treatment. From such a viewpoint, it is also effective to change the regeneration temperature when performing the catalyst regeneration treatment. That is, it is also effective to perform the regeneration treatment by setting the temperature of the regeneration treatment within the above range at a temperature 20 to 100 ° C. higher than the normal wastewater treatment temperature at the beginning of regeneration and lowering the temperature at the end of regeneration. It is. In this case, the temperature which is higher than the normal wastewater treatment temperature at the beginning of the regeneration is more preferably a temperature higher by 25 to 80 ° C, and further preferably a temperature higher by about 30 to 60 ° C.
[0049]
The processing pressure at the time of regeneration in the present invention may be a pressure at which the catalyst regenerating liquid maintains a liquid phase. When the processing pressure at the time of regeneration is excessively increased, the combustion of the activated carbon itself is likely to occur as in the case where the processing temperature is increased. Also, the activity of the catalyst may be reduced. For this reason, when pressurizing, as shown in FIG. 1 described below, a pressure control valve 12 is provided at the outlet side of the wet oxidation treatment apparatus (reaction tower 1) so that the wastewater can maintain a liquid phase in the reaction tower 1. It is desirable to appropriately adjust the pressure to a predetermined value according to the processing conditions.
[0050]
In order to improve the processing performance and the durability of the catalyst, it is desirable to control the fluctuation of the processing pressure within ± 20%, more preferably within ± 10%, and further preferably within ± 5%. The reproduction time is not particularly limited, but is appropriately selected from about 1 to 100 hours, preferably 3 to 50 hours, more preferably about 5 to 24 hours.
[0051]
The regeneration treatment in the present invention may be carried out with or without supply of oxygen, but it is desirable to maintain the oxygen concentration in the exhaust gas after the regeneration treatment in the range of 0 to 5 vol%. By setting the oxygen concentration to 0 to 5 vol%, the regenerating effect of the catalyst becomes more remarkable. On the other hand, if the oxygen concentration in the exhaust gas exceeds 5 vol%, combustion of the activated carbon due to excess oxygen is not preferred. Therefore, it is preferable to perform the treatment in a state where oxygen is insufficient. From such a viewpoint, it is desirable that the oxygen concentration in the exhaust gas be closer to 0 vol%, and most preferably 0 vol% in which no oxygen remains. Therefore, the oxygen concentration in the exhaust gas is preferably maintained in the range of 0 to 4 vol%, more preferably 0 to 2 vol%, and still more preferably 0 to 1 vol%. In other words, as long as the pressure inside the device can be maintained during the operation of the device, the regeneration of the catalytic activity is more desirable as the amount of supplied oxygen is smaller. However, if the supplied gas amount is too small, a problem may occur in the contact between the catalyst regenerating solution and the catalyst, and the effect may be reduced.
[0052]
In the present invention, in order to maintain the oxygen concentration in the exhaust gas in the range of 0 to 5 vol%, the oxygen concentration in the exhaust gas is measured using an oxygen concentration meter 16 as shown in FIGS. The supply amount of the oxygen-containing gas may be adjusted or controlled by the oxygen-containing gas flow control valve 9 based on the measured value. The oxygen concentration meter used for measuring the oxygen concentration in the exhaust gas may be any one that can be used for ordinary oxygen measurement, and a commercially available oxygen concentration meter can be used. Examples of such an oxygen concentration meter include an oxygen concentration meter using an oxygen sensor of zirconia, an oxygen dumbbell-type oxygen concentration meter, a gas chromatograph, and the like, and these are not particularly limited by the method of use. The method of adjusting or controlling the supply amount of the oxygen-containing gas is not particularly limited. For example, the method can be adjusted or controlled by the flow rate control valve 9, but it is needless to say that other means may be used.
[0053]
In the present invention, “oxygen concentration in exhaust gas” means the oxygen concentration in the gas phase immediately after the regenerating treatment of the solid catalyst containing activated carbon, and is usually performed as shown in FIG. Oxygen concentration in exhaust gas generated when gas-liquid separation processing is performed on gas-liquid after processing.
[0054]
The regeneration treatment in the present invention can be carried out with or without supply of an oxygen-containing gas, but is preferably carried out with a small amount of oxygen-containing gas supplied. By supplying a small amount of the oxygen-containing gas, the contact between the catalyst regenerating liquid and the catalyst is improved, and the regenerating property of the catalyst is further improved. In order to maintain the processing pressure to some extent, it is desirable to supply a small amount of gas. Further, an inert gas such as a nitrogen gas or a gas containing no oxygen can be used instead of the oxygen-containing gas. However, since the present invention relates to a method for treating wastewater by the wet oxidation method, it is desirable to use an oxygen-containing gas used for wastewater treatment in terms of operability, economy, and the like.
[0055]
In the present invention, it is preferable to operate while maintaining the oxygen concentration in the exhaust gas in the range of 0 to 5 vol% during the regeneration treatment. ] / [Oxygen demand of the catalyst regenerating solution when the treatment efficiency of the catalyst regenerating solution is maximized] (hereinafter, the value of this ratio may be referred to as “D value”) = 0 to 1.3. The setting is made as follows. That is, the catalyst can be effectively regenerated by, for example, adjusting or controlling the gas supply amount so that the D value represented by the above ratio is in the range of 0 to 1.3. Note that the [amount of oxygen in the supply gas] may be hereinafter referred to as an oxygen supply amount.
[0056]
In the present invention, since the catalyst regenerating solution contains a readily decomposable oxidizable substance, the oxidizable substance does not remain at the catalyst layer outlet side when the D value is about 1.0 to 1.3. Sometimes. Further, when the oxygen supply amount is 1.0 or more in the above D value, especially larger than 1.3, the amount of oxygen required for the oxidation / decomposition treatment of the catalyst regenerating liquid is larger than that of the activated carbon. It is easy to occur. From such a viewpoint, the D value is preferably about 0 to 0.8, more preferably about 0 to 0.6, and further preferably about 0 to 0.4.
[0057]
However, an excessive amount of air may be required to decompose the oxidizable substance adsorbed on the activated carbon in a long-term treatment. For this reason, it is also effective to change the oxygen supply amount in performing the catalyst regeneration treatment. In this case, at the beginning of the regeneration, the oxygen supply amount is set to the above-mentioned D value of about 1.0 to 1.3, and at the end of the regeneration, the above-mentioned D value is about 0 to 1.0, preferably 0 to 0.1. The oxygen supply amount is preferably about 8, more preferably about 0 to 0.6, and still more preferably about 0 to 0.4.
[0058]
In the present invention, the [oxygen of the catalyst regenerating solution when the treatment efficiency of the catalyst regenerating solution is maximized]consumptionAmount] means the processing efficiency of the catalyst regenerating liquid when only the oxygen supply amount is changed while the regeneration processing conditions such as the regeneration processing temperature, the processing pressure, the LHSV, the air flow system, and the catalyst used are kept constant. Of the catalyst regenerant when the pressure is maximumconsumptionIt is about quantity. That is, the D value is calculated by changing the oxygen supply amount at the temperature at which the regeneration process is performed and based on the treatment efficiency of the catalyst regeneration solution at this time. However, when most of the oxidizable substances in the catalyst regenerating solution are easily decomposable substances, the processing efficiency often does not change even if the processing temperature slightly changes. In such a case, the treatment efficiency of the catalyst regeneration solution often depends only on the oxygen supply amount. For this reason, when the oxygen supply amount is constant, the D value often does not change even when the regeneration processing temperature changes.
[0059]
Therefore, this D value is an index of the excess rate of the oxygen supply amount in performing the catalyst regeneration treatment. More specifically, the chemical oxygen demand (COD (Cr)) treatment efficiency when the solid catalyst is regenerated by the catalyst regenerating solution while changing the oxygen supply amount under an arbitrary regeneration treatment condition is the maximum. Is 90%, the oxygen-containing gas O 2_TwoIf supplied at a rate of /COD(Cr)=0.9, the D value is 1.0. Also, if the oxygen-containing gas is O_TwoIf supplied at a rate of /COD=1.0, the D value is 1.11. However, the denominator of this D value is “Oxygen of the catalyst regenerating solution when the treatment efficiency of the catalyst regenerating solution is maximized.consumptionThe "amount" is not necessarily the same as the "amount of oxygen in the supply gas when the treatment efficiency of the catalyst regenerating liquid is maximized". That is, the “denominator of the D value” and the “oxygen supply amount when the processing efficiency of the catalyst regenerating liquid is maximized” are not necessarily the same. When the oxygen supply amount exemplified above is O_TwoIf the processing efficiency of COD (Cr) is 90% and the maximum when /COD(Cr)=0.9, the oxygen supply amount and the "denominator of D value" are the same. However, if the oxygen supply is O_TwoWhen /COD(Cr)=2.0, the COD (Cr) processing efficiency may be 90% and the maximum. The D value at this time is 2.22.
[0060]
The “treatment efficiency of the catalyst regenerating solution” described in “the required amount of oxygen of the catalyst regenerating solution when the treating efficiency of the catalyst regenerating solution is maximized” according to the present invention is, for example, the COD treatment efficiency of the catalyst regenerating solution, TOC Various treatment efficiencies such as treatment efficiency, nitrogen treatment efficiency, BOD treatment efficiency, TOD treatment efficiency, or treatment efficiency of a specific substance can be employed depending on the catalyst regenerating solution, and are not particularly limited. However, the catalyst regenerating solution contains a readily decomposable oxidizable substance, and in this case, since the consumption of oxygen is particularly important, it is desirable to express the COD treatment efficiency of the catalyst regenerating solution.
[0061]
In the present invention, "oxidation / decomposition treatment" refers to oxidative decomposition treatment for converting acetic acid to carbon dioxide and water, decarboxylation treatment for converting acetic acid to carbon dioxide and methane, hydrolysis treatment for converting urea to ammonia and carbon dioxide, and ammonia. Decomposition treatment to convert dimethylsulfoxide and hydrazine into nitrogen gas and water, oxidation and oxidative decomposition treatment to convert dimethylsulfoxide to ash such as carbon dioxide, water, sulfate ions, and oxidation treatment to convert dimethylsulfoxide to dimethylsulfone and methanesulfonic acid In other words, the process of decomposing easily decomposable oxidizable substances into nitrogen gas, carbon dioxide, water, ash, etc., the process of decomposing hardly decomposable organic substances and nitrogen compounds into low molecular weight, or the oxidation process of oxidizing The meaning includes various oxidations and / or decompositions.
[0062]
The type of wastewater to be treated to which the present invention is applied is not particularly limited, for example, from various industrial plants such as chemical plants, electronic component manufacturing equipment, food processing equipment, metal processing equipment, metal plating equipment, printing and plate making equipment, and photographic equipment. Or waste water from power generation facilities such as thermal power generation and nuclear power generation. Specifically, wastewater from EOG production equipment, alcohol production equipment such as methanol, ethanol, and higher alcohols, particularly aliphatic carboxylic acids and esters thereof such as acrylic acid, acrylic acid ester, methacrylic acid and methacrylic acid ester, or terephthalic acid And organic matter-containing wastewater discharged from a process for producing an aromatic carboxylic acid or an aromatic carboxylic acid ester such as terephthalic acid ester. Further, waste water containing nitrogen compounds such as amine, imine, ammonia, and hydrazine may be used. In addition, wastewater containing sulfur compounds such as thiosulfate ions, sulfide ions, and dimethyl sulfoxide may be used. It may also be domestic wastewater such as sewage or human waste. Alternatively, wastewater containing harmful substances such as organic halogen compounds such as dioxins and fluorocarbons, diethylhexyl phthalate, and nonylphenol, and environmental hormone compounds may be used.
[0063]
Hereinafter, the operation and effect of the present invention will be more specifically described with reference to Examples. However, the following Examples do not limit the present invention. It is included in the technical scope of the invention.
[0064]
【Example】
Examples 1 to 5
First, ordinary wastewater treatment was performed using the apparatus shown in FIG. The reaction tower 1 has a cylindrical shape with a diameter of 26 mmφ and a length of 3,000 mm, in which 1 liter of a 4 mmφ pellet-shaped solid catalyst containing activated carbon and platinum as main components and containing 0.3% by mass of platinum is contained. 390 g) and a catalyst layer length of 1880 mmH. The usual wastewater to be treated is wastewater discharged from a fatty acid carboxylic acid and aliphatic carboxylic acid ester production facility and contains organic compounds having 2 or more carbon atoms such as alcohols, aldehydes, and carboxylic acids, and COD (Cr) is reduced. 15,000 mg / liter, pH 2.8. Also, 53% of the total TOC component was acetic acid.
[0065]
Wastewater sent from a wastewater supply source (not shown) is fed through a wastewater supply line 6 at a flow rate of 1 liter / h by a wastewater supply pump 5 and then heated to 120 ° C. by a heater 3 to form a reaction tower. 1 and processed in a gas-liquid downward cocurrent flow. At this time, the pressure of the waste water heated by the heater 3 was measured by the pressure gauge PI on the gas-liquid inlet side of the reactor 1. After air (oxygen-containing gas) is introduced from the oxygen-containing gas supply line 8 and the pressure is increased by the compressor 7, the air is drained before the heater 3 while the supply amount is adjusted by the oxygen-containing gas flow control valve 9. Supplied.
[0066]
In the reaction tower 1, the temperature is kept at 120 ° C. by using the electric heater 2, and the solid catalyst filled in the reaction tower 1 is included in the wastewater when the wastewater (and air) passes from above to below. The oxidizable substance is oxidized and decomposed. The treatment liquid after the wastewater has been oxidized and decomposed is discharged from the bottom of the reaction tower 1, cooled through the processing line 10 by the cooler 4, decompressed from the pressure control valve 12 and discharged, and Gas-liquid separation was performed by the separator 11. In the pressure control valve 12, the pressure in the reaction tower 1 was detected by the pressure controller PC, and the pressure in the reaction tower 1 was controlled to be 0.6 MPa (Gauge).
[0067]
In the gas-liquid separator 11, the oxygen concentration in the exhaust gas in the gas-liquid separator 11 was measured using an oxygen concentration meter 16, and the exhaust gas was discharged from a gas discharge line 13. The level of the processing liquid in the gas-liquid separator was detected using a liquid level controller LC, and the processing liquid discharge pump 14 was controlled so as to have a constant liquid level. The processing liquid discharged from the processing liquid discharge pump 14 was discharged through a processing liquid discharge line 15, and the processing liquid was sampled as needed to measure the COD (Cr) concentration.
[0068]
First, the air supply amount was controlled such that the oxygen concentration in the exhaust gas became 0.5% for 50 hours from the start of operation. As a result, the COD (Cr) treatment efficiency after 50 hours had passed was 94%.
[0069]
Next, until after 50 to 100 hours, air was supplied so that the oxygen concentration of the exhaust gas during the gas-liquid separation became 10%, so that the catalytic activity was reduced. Further, the air supply amount was controlled again until the exhaust gas oxygen concentration became 0.5% until 100 to 150 hours had elapsed. After 150 hours, the COD (Cr) treatment efficiency was reduced to 66%.
[0070]
(Reproduction process)
In the above, each of the following regeneration treatments was performed on the catalyst whose COD (Cr) treatment efficiency was reduced from 94% to 66%.
[0071]
The method of the regeneration treatment is as follows. After the pressure is fed at a flow rate of 1 liter / h of the catalyst regeneration liquid by the drainage supply pump 5, the regeneration liquid is supplied from the upper part of the reaction tower 1 by heating to 140 ° C. It flowed in a downward parallel flow. The catalyst regenerating solution used for this regenerating treatment was a solution containing about 10 g / l of methanol and 15 g / l of COD (Cr). After air was introduced from the oxygen-containing gas supply line 8 and the pressure was increased by the compressor 7, oxygen-containing gas (air) was supplied to the regenerating solution before the heater 3 in the respective amounts shown in Table 1 below.
[0072]
The regenerated liquid that passed through the catalyst layer was cooled by the cooler 4, released from the pressure control valve 12 and discharged, and separated into gas and liquid by the gas-liquid separator 11. In addition, the pressure control valve 12 detected the pressure with the pressure controller PC, and controlled so that the pressure of 0.6 MPa (Gauge) was maintained.
[0073]
This regeneration treatment was carried out for 5 hours in each test, and then the wastewater treatment was carried out again for 50 hours under the same conditions as the above wastewater treatment. The residual amount of the regenerating solution during the regeneration treatment and the treatment efficiency of the wastewater during the wastewater treatment are shown in Table 1 below.
[0074]
In Example 5, nitrogen gas was supplied in place of the oxygen-containing gas during the regeneration treatment. The supply amount of the nitrogen gas at this time was the same as the supply amount of the oxygen-containing gas supplied in Example 2.
[0075]
[Table 1]

[0076]
Examples 6 to 9, Comparative Example 1
A regeneration process was performed according to Example 2, using the same catalyst, the same processing method, the same processing conditions, and the same apparatus as in Example 2, except that the processing temperature during regeneration was set to the values shown in Table 2 below. The results are shown in Table 2 below. In Example 8, since the processing temperature was 160 ° C., the processing pressure was 0.9 MPa (Gauge). In Comparative Example 1, since the processing temperature was 220 ° C., the processing pressure was 2.5 MPa (Gauge).
[0077]
[Table 2]

[0078]
Examples 10 to 15
A regeneration process was performed according to Example 2 using the same catalyst, the same processing method, the same processing conditions, and the same apparatus as in Example 2, except that the processing time during regeneration was set to the values shown in Table 3 below. The results are shown in Table 3 below. In Examples 14 and 15, the regeneration process was performed according to Example 8 with the regeneration process temperature set to 125 ° C.
[0079]
[Table 3]

[0080]
Examples 16 to 22
The regeneration treatment was performed in the same manner as in Example 2 except that the COD (Cr) concentration of the catalyst regeneration solution containing methanol was changed to the value shown in Table 4 below. The results are shown in Table 4 below. In Examples 20 and 21, the reproduction processing was performed according to Example 11 with the reproduction processing time set to 24 hours. The supply amount of the oxygen-containing gas (air) is O₂/COD(Cr)=0.5. Furthermore, in Example 22, the supply amount of the oxygen-containing gas (air) was changed to O with a regeneration time of 5 hours.₂/ COD (Cr) = 0.2
[0081]
[Table 4]

[0082]
Examples 23 to 27
The same catalyst, the same processing method, and the same processing conditions as in Example 2 were used, except that ethanol, propanol, acetone, and tetrahydrofuran were used as the catalyst regenerating liquid, each containing 15 g / liter of COD (Cr). Using the same apparatus, a regenerating process was performed according to Example 2. The results are shown in Table 5 below. In Example 24, the regeneration treatment was performed using wastewater containing a large amount of alcohols having 1 to 4 carbon atoms discharged from the fatty acid carboxylic acid and fatty acid carboxylic acid ester production equipment. The concentration of the wastewater was 23 g / liter of COD (Cr). The supply amount of the oxygen-containing gas (air) is O₂/COD(Cr)=0.5.
[0083]
[Table 5]

[0084]
Comparative Examples 2 and 3
The regeneration treatment was performed according to Example 2 using the same catalyst, the same processing method, the same processing conditions, and the same apparatus as in Example 2, except that the supply amount of the oxygen-containing gas was set to the value shown in Table 6 below. . The results are shown in Table 6 below.
[0085]
[Table 6]

[0086]
Example 28
The apparatus shown in FIG. 2 was used. The basic configuration of the apparatus shown in FIG. 2 is similar to that of the apparatus shown in FIG. 1, and corresponding parts are denoted by the same reference numerals. In the apparatus shown in FIG. 2, the wastewater heated by the heater 3 is supplied from the bottom of the reaction tower 21 (22 is an electric heater), and the wastewater after the oxidation and decomposition treatment is supplied to the reaction tower 21. It is configured to be discharged from the upper part of. That is, in the reaction tower 21 shown in FIG. 2, the gas-liquid circulation system in the catalyst layer is of the gas-liquid upward co-current flow type.
[0087]
Then, the wastewater was treated in the same manner as in Example 1 (the same wastewater, the same treatment method, and the same treatment conditions). The COD (Cr) treatment efficiency after 50 hours had passed was 87%. Subsequently, a catalyst regeneration treatment was carried out in the same manner as in Example 2 under the same treatment conditions as in Example 2. The results are shown in Table 7 below. The supply amount of the oxygen-containing gas (air) is O₂/COD(Cr)=0.5.
[0088]
[Table 7]

[0089]
Example 29
According to Example 2, using the same catalyst, the same processing method, the same processing conditions, and the same apparatus as Example 2, except that the regeneration processing time was 160 ° C for 0 to 1 hour and 125 ° C for 1 to 3 hours. To perform the reproduction process. The results are shown in Table 8 below.
[0090]
[Table 8]

[0091]
Examples 30 and 31
Drainage treatment was performed using the same apparatus as in FIG. 1 shown in Example 1. The inside of the reaction tower 1 was filled with 1 liter (420 g) of 1880 mmH of a 3 mmφ pellet-shaped solid catalyst containing activated carbon and palladium as main components and containing 0.6% by mass of palladium. The wastewater subjected to the treatment was wastewater discharged from the power generation equipment, and was wastewater containing ammonium sulfate, sodium ions and carbonate ions. Further, the concentration of ammonia in the waste water was 4,200 mg / liter, and the pH was 7.8.
[0092]
The wastewater was fed under pressure at a flow rate of 1 liter / h by a wastewater supply pump 5, heated to 130 ° C. by a heater 3, supplied from the upper part of the reaction tower 1, and treated in a gas-liquid downward cocurrent manner. After air was introduced from the oxygen-containing gas supply line 8 and the pressure was increased by the compressor 7, this air was supplied to the drainage before the heater 3 while adjusting the supply amount by the oxygen-containing gas flow rate control valve 9.
[0093]
In the reaction tower 1, the temperature was kept at 130 ° C. using the electric heater 2, and the oxidation and decomposition treatment was performed. After the treatment liquid was cooled by the cooler 4, the pressure was released from the pressure control valve 12, discharged, and separated by the gas-liquid separator 11. In the pressure control valve 12, the pressure in the reaction tower 1 was detected by the pressure controller PC, and the pressure in the reaction tower 1 was controlled to be 0.9 MPa (Gauge). Further, the oxygen concentration in the exhaust gas in the gas-liquid separator 11 was measured using the oxygen concentration meter 16, and the processing efficiency of ammonia in the processing liquid in the gas-liquid separator was determined.
[0094]
First, the air supply amount was controlled such that the oxygen concentration in the exhaust gas became 0.5% for 50 hours from the start of operation. As a result, the treatment efficiency of ammonia 50 hours after the start of the reaction was 95%.
[0095]
Next, until after 50 to 100 hours, air was supplied so that the oxygen concentration of the exhaust gas during the gas-liquid separation became 10%, so that the catalytic activity was reduced. Further, the air supply amount was controlled again until the exhaust gas oxygen concentration became 0.5% until 100 to 150 hours had elapsed. After 150 hours, the treatment efficiency of ammonia was reduced to 54%.
[0096]
(Reproduction process)
In the above, the regeneration treatment described below was performed on the catalyst whose ammonia treatment efficiency was reduced from 95% to 54%.
[0097]
The method of the regeneration treatment is as follows. After the pressure is fed at a flow rate of 1 liter / h of the catalyst regenerating solution by the drainage supply pump 5, the regenerating solution is supplied from the upper part of the reaction tower 1 by heating to 150 ° C. by the heater 3. It flowed in a downward parallel flow. The catalyst regenerating solution used for this regenerating treatment was a solution containing about 8 g / l of methanol, and 12 g / l of COD (Cr). After air was introduced from the oxygen-containing gas supply line 8 and the pressure was increased by the compressor 7, the oxygen-containing gas (air) was supplied to the regenerating liquid before the heater 3 in the respective amounts shown in Table 9 below. The regenerated liquid that passed through the catalyst layer was cooled by the cooler 4, released from the pressure control valve 12 and discharged, and separated into gas and liquid by the gas-liquid separator 11. The pressure control valve 12 detects the pressure with a pressure controller PC and controls the pressure to maintain a pressure of 0.9 MPa (Gauge).
[0098]
This regeneration treatment was performed for 7 hours, and then the wastewater treatment was performed again for 50 hours under the same conditions as the above wastewater treatment. The results are shown in Table 9 below.
[0099]
[Table 9]

[0100]
【The invention's effect】
The present invention is configured as described above, and can effectively regenerate a catalyst whose performance has been reduced, and can dramatically improve the durability of a solid catalyst. Further, according to the present invention, it becomes possible to stably purify wastewater for a long time, and it is possible to reduce wastewater treatment costs.
[0101]
Further, the method for treating wastewater by the wet oxidation method which is basically adopted by the present invention is an excellent treatment method capable of reducing the cost of treating wastewater and the cost of treating wastewater, and also capable of treating wastewater to a high degree. It is. Therefore, by adding the effect of the regeneration of the present invention to such a wet oxidation method, the effect of the method can be remarkable.
[0102]
Furthermore, the treated liquid of wastewater treated according to the present invention can be reused as water for other uses, and is excellent in terms of resource recycling, thereby reducing costs and using resources efficiently. It can also be used for other purposes.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing one configuration example of an apparatus configured to carry out the present invention.
FIG. 2 is a schematic explanatory view showing another configuration example of an apparatus configured to carry out the present invention.
[Explanation of symbols]
1,21 reaction tower
2,22 electric heater
3 heater
4 Cooler
5 Drainage supply pump
6 Drainage supply line
7 Compressor
8 Oxygen-containing gas supply line
9 Oxygen-containing gas flow control valve
10 Treatment liquid line
11 Gas-liquid separator
12 Pressure control valve
13 Gas discharge line
14 Treatment liquid discharge pump
15 Treatment liquid discharge line
16 Oxygen concentration meter

Claims (4)

In a method for treating wastewater in which organic and / or inorganic oxidizable substances contained in the wastewater are oxidized and / or decomposed by using a catalyst, a treatment temperature of 50 ° C or more and less than 170 ° C, and the wastewater retains a liquid phase Under the pressure of, an oxygen-containing gas is supplied to treat wastewater using a catalyst containing activated carbon , and a catalyst regenerating solution containing alcohols is supplied to a solid catalyst, and the temperature is 5 to 100 ° C. higher than the wastewater treatment temperature. A method for treating wastewater, comprising operating while regenerating the solid catalyst at a temperature. The method according to claim 1, wherein the operation is performed such that the catalyst regenerating liquid remains at the entrance of the catalyst layer. 3. The method according to claim 1, wherein the oxygen concentration in the exhaust gas at the time of catalyst regeneration is maintained in the range of 0 to 5% vol. When the catalyst regenerating solution is supplied to the catalyst layer, an oxygen-containing gas or a non-oxygen-containing gas is supplied, and the amount of oxygen in the supplied gas is [oxygen amount in the supplied gas] / [the processing efficiency of the catalyst regenerating solution is reduced. The method according to any one of claims 1 to 3, wherein the oxygen consumption of the catalyst regenerating solution at the maximum is set to be in the range of 0 to 1.3.

Images