JP4629880B2 - How to recover hydrogen chloride gas - Google Patents

Description

【０１２２】
実施例１２〜２２
実施例１〜１１において、放散塔１７の塔頂からガスを取り出すライン２０に、凝縮器を設け、該凝縮器出口ガス温度を５℃に調整してガスの一部を凝縮せしめ、該凝縮器より凝縮液を放散塔に還流しながらガスを取り出した以外は、同様にして塩化水素ガスを回収した。
【０１２３】
その結果を表２に示す。
【０１２４】
尚、得られた塩化水素ガスを使用したＥＤＣ合成反応の塩化水素転化率について、１２０時間連続運転した結果を併せて示す。また、前記参考例１において、１２０時間連続運転した場合の塩化水素転化率は、７０．８％であった。
【０１２５】
【表２】

【図面の簡単な説明】
【図１】本発明方法の代表的な態様を示すフローチャート
【図２】本発明方法の他の代表的な態様を示すフローチャート
【図３】本発明方法の他の代表的な態様を示すフローチャート
【図４】本発明方法の他の代表的な態様を示すフローチャート
【符号の説明】
１ 熱分解装置
５ 燃焼装置
９ 冷却装置
１１ 吸収塔
１７ 放散塔
２２ フッ化水素ガス除去塔
２４ フッ化水素除去塔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for recovering purified hydrogen chloride gas from exhaust gas generated by pyrolyzing a chlorine-containing resin or a synthetic resin containing the chlorine-containing resin. Specifically, this is a method for efficiently removing fluorine-based compounds and other impurities in the exhaust gas and recovering hydrogen chloride gas having a reduced hydrogen fluoride concentration.
[0002]
[Prior art]
In recent years, the number of synthetic resins as general waste and industrial waste has increased rapidly, and the synthetic resins discarded in this way contain about 15% of chlorine-containing resins on average.
[0003]
The chlorine-containing resin may generate dioxins depending on the conditions during combustion, and disposal by combustion is being restricted. On the other hand, in order to protect limited resources, social movements regarding the reuse of waste are becoming active.
[0004]
Against this background, waste synthetic resins containing chlorine-containing resins, especially waste vinyl chloride resins, are dehydrochlorinated by thermal decomposition and recovered as carbides that do not substantially contain chlorine. Various attempts have been made to reuse the fuel as a problem-free fuel.
[0005]
For example, a waste synthetic resin containing a chlorine-containing resin is indirectly heated to about 350 ° C. in a non-combustion atmosphere and thermally decomposed to obtain dehydrochlorinated carbide, and the obtained carbide is used as a cement manufacturing fuel, The method of reusing as fuel, such as blast furnace fuel, is mentioned.
[0006]
On the other hand, in the pyrolysis of the chlorine-containing resin, hydrogen chloride is generated together with the carbide. Taking the vinyl chloride resin as an example, the amount of the hydrogen chloride is a gas amount containing as much as 0.6 t of hydrogen chloride per 1 t of the vinyl chloride resin.
[0007]
Therefore, it is desired to develop a technique for recovering the hydrogen chloride and reusing it as a raw material in the manufacturing process of other chlorinated products. In particular, when the recovered hydrogen chloride is used as a raw material for chlorination of hydrocarbons by oxychlorination, a raw material for vapor phase chlorination of alcohols, a raw material for chlorination of silicon, etc., it does not substantially contain water. It must be gaseous hydrogen chloride.
[0008]
Further, the above reaction is a reaction using a catalyst, and the reaction rate may be rapidly lowered depending on a trace component contained in the hydrogen chloride gas.
[0009]
However, technology for recovering and recycling hydrogen chloride in the form of gas in a purified state from exhaust gas generated by pyrolysis of chlorine-containing resin to a level that can be reused as a raw material in the production process of other chlorinated products Has not been studied, and even more, there is no disclosure of issues.
[0010]
[Problems to be solved by the invention]
The present inventors have examined that the exhaust gas obtained by thermal decomposition of the chlorine-containing resin is reused as a raw material in the production process of other chlorinated products, and the following problems exist. I found it.
[0011]
That is, when the hydrogen chloride gas obtained by the above method is used as a reaction raw material in the production of ethylene dichloride (EDC) by direct oxychlorination, the reaction rate of ethylene and hydrogen chloride is rapidly increased. It turned out to be worse.
[0012]
The above phenomenon is presumed to be caused by the fluorine compound contained as an additive in the chlorine-containing resin acting as a catalyst poison for the reaction.
[0013]
The route through which such a fluorine compound is mixed into the chlorine-containing resin is due to the use of a fluorine-based organic substance as an antifogging agent that is generally added to impart antifogging properties to the film in film applications such as agricultural films. Most of the cases. In addition, since the transparent chlorine-containing resin to which an antifogging agent is added is not colored, it can be recycled as a raw material for chlorine-containing resins for various uses that use chlorine-containing resins, for example, wire coating materials and building materials. Most of the chlorine-containing resins recovered as waste contain fluorine-based organic substances.
[0014]
And, by pyrolysis of the chlorine-containing resin, a part of the fluorine-based compound is decomposed to produce low boiling organic fluoride such as hydrogen fluoride and tetrafluoroethylene, and in the pyrolysis gas mainly composed of hydrogen chloride gas. Mixed in.
[0015]
Accordingly, an object of the present invention is to obtain highly purified hydrogen chloride gas having a very low content of fluorine-based compounds from exhaust gas generated by thermal decomposition of waste synthetic resin containing chlorine-containing resin.
[0016]
[Means for Solving the Problems]
As a result of repeated researches to achieve the above object, the inventors of the present invention burned exhaust gas generated by thermal decomposition of a chlorine-containing resin and converted a fluorine-based compound into hydrogen fluoride, thereby obtaining a combustion gas. By combining a hydrogen chloride absorption process for absorbing water with aqueous hydrochloric acid solution and a hydrogen chloride gas emission process for releasing hydrogen chloride from the hydrochloric acid aqueous solution obtained from the process, the fluorine compound content is reduced. It has been found that the hydrogen chloride can be recovered in gaseous form.
[0017]
Moreover, it has been found that the hydrogen chloride gas thus obtained has a high purity and can be sufficiently used as a raw material for products such as the EDC, and the present invention has been completed.
[0018]
That is, the present invention provides (a) a chlorine-containing resin containing a fluorine compound. In a non-oxidizing atmosphere A pyrolysis step of pyrolyzing to obtain a gas phase mainly composed of hydrogen chloride and a solid phase mainly composed of carbide;
(B) a combustion step in which the gas phase obtained from the thermal decomposition step is burned, and the fluorine-based compound contained in the gas phase is converted into hydrogen fluoride;
(C) a hydrogen chloride absorption step in which a combustion gas obtained from the combustion step is brought into contact with an absorption liquid comprising water or a hydrochloric acid aqueous solution to obtain a hydrochloric acid aqueous solution containing hydrogen fluoride;
as well as
(D) A hydrogen chloride gas diffusion step in which an aqueous hydrochloric acid solution obtained from the hydrogen chloride absorption step is led to a diffusion tower, and hydrogen chloride is recovered in a gaseous form from the top of the diffusion tower
A method for recovering hydrogen chloride gas.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the thermal decomposition step thermally decomposes a chlorine-containing resin containing a fluorine compound such as a fluorine-based surfactant to obtain a gas phase mainly composed of hydrogen chloride and a solid phase mainly composed of carbide. It is a process.
[0020]
The chlorine-containing resin treated in this thermal decomposition step includes not only the use of the chlorine-containing resin alone, but also a mixture or composition obtained by mixing the chlorine-containing resin with another synthetic resin.
[0021]
Examples of the chlorine-containing resin include vinyl chloride resin, vinylidene chloride resin, and chlorinated polyolefin. Of these, vinyl chloride resin is typical and is preferably used in the method of the present invention. Examples of other synthetic resins include polyolefins such as polypropylene, polyethylene, and polystyrene, and polyamides and polyesters.
[0022]
Moreover, what was collect | recovered as a waste is normally used for the said chlorine containing resin.
Examples of such waste include soft vinyl-containing resin wastes such as agricultural vinyl, various packaging films, leather products, cushion floors, wallpaper, etc., hard chlorine-containing resin wastes such as pipes and covered electric wires, and such Examples include waste synthetic resins containing chlorine-containing resins.
[0023]
In this case, processing such as crushing and cutting according to the type of waste and processing to a size of about 10 to 1 mm in the shape of a glass or fluff is preferable from the viewpoint of ease of handling.
[0024]
In the present invention, the thermal decomposition step is a step of performing the dehydrochlorination reaction by heating the chlorine-containing resin under non-oxidizing conditions. In the thermal decomposition step, a conventional thermal decomposition method for chlorine-containing resin using a known thermal decomposition apparatus is employed without any particular limitation.
[0025]
As an example of a typical aspect of the thermal decomposition method, a sealed rotary kiln having a chlorine-containing resin piece inlet at the upstream end, a content outlet at the downstream end, and an exhaust gas outlet at the gas phase portion Chlorine-containing pyrolysis furnaces such as indirect heating furnaces of the type, indirect heating furnaces that stir and move the chlorine-containing resin with stirring blades and rotary blades, and indirect heating furnaces of the extruder type that have an exhaust gas outlet An embodiment in which resin is supplied and heated to a predetermined temperature and thermally decomposed can be mentioned.
[0026]
The pyrolysis conditions in the pyrolysis step are generally implemented by adjusting the temperature inside the furnace to be 250 to 450 ° C. The chlorine-containing resin is dechlorinated in the furnace, separated into a solid phase mainly composed of carbide and a gas phase containing hydrogen chloride, and each is taken out from the outlet.
[0027]
Moreover, it is preferable to replace the inside of the furnace with a known inert gas such as nitrogen and argon, or hydrogen chloride gas as an inert gas in advance in order to create a non-oxidizing atmosphere. Moreover, you may supply the said inert gas as carrier gas as needed also during thermal decomposition of a chlorine containing resin.
The exhaust gas obtained from the pyrolysis step contains water and organic compound components supplied along with the chlorine-containing resin together with hydrogen chloride generated by pyrolysis of the chlorine-containing resin, and further supplied a carrier gas. In some cases, the carrier gas is contained.
[0028]
Among them, the fluorine-based compound varies depending on the kind of the chlorine-containing resin to be used, but in general, the weight ratio of fluorine to hydrogen chloride may be 100 ppm or more, and in some cases, 1000 ppm or more. This is presumed to be generated by thermally decomposing a chlorine-containing resin containing a fluorine-containing organic compound such as a fluorine-based surfactant.
[0029]
In addition, according to the confirmation of the present inventors, there are extremely many kinds of low-boiling fluorine compounds mixed in the exhaust gas, and in addition to hydrogen fluoride, there are over 30 kinds including tetrafluoroethylene. Such low-boiling fluorine compounds such as tetrafluoroethylene are extremely difficult to separate by a known method such as distillation because they range from a very low boiling point to a high boiling point than hydrogen chloride.
[0030]
The greatest feature of the method of the present invention is that the exhaust gas obtained in the thermal decomposition step is passed through a combustion step, a hydrogen chloride absorption step, and a hydrogen chloride gas diffusion step. By combining this process, the impurities in the exhaust gas are converted into a compound with good separability in the subsequent process by the combustion process, and the hydrogen fluoride concentration is reduced by combining the hydrogen chloride absorption process and the hydrogen chloride gas emission process. The purified hydrogen chloride gas thus obtained can be obtained.
[0031]
Hereinafter, these steps will be described in more detail.
[0032]
The exhaust gas obtained from the pyrolysis process is sent to the combustion process that continues through the pipe. In this case, the exhaust gas in the pipe is sent while maintaining the state of the hot gas. Therefore, it is preferable to carry out the method of the present invention stably for a long period of time.
[0033]
That is, in the exhaust gas, high-boiling organic components contained as additives for chlorine-containing resins, for example, phthalic acid esters such as dioctyl phthalate (DOP) and the decomposition products phthalic anhydride and phthalic acid are chlorinated. It is contained at a concentration of several thousand ppm to several tens of percent by weight with respect to hydrogen.
[0034]
Therefore, the exhaust pipe obtained from the thermal decomposition process is effectively prevented from being blocked by supplying the combustion process with the high-boiling organic compound not solidified and maintaining the high-temperature hot gas state. Can do.
[0035]
The exhaust gas is usually obtained as a hot gas at 250 to 450 ° C. from the thermal decomposition step, but the operation for maintaining the state of the hot gas may be performed as long as the boiling point of the high-boiling organic compound is maintained. Specifically, it is preferably maintained at 250 ° C. or higher, preferably 300 ° C. or higher, particularly at the same temperature as the thermal decomposition temperature.
Here, the method for maintaining the exhaust gas at the above temperature is not particularly limited. For example, a method of keeping the exhaust gas pipe warm, a method of heating the exhaust gas pipe, and the like are common.
[0036]
In the present invention, the combustion step is a step for burning and removing the organic compound component contained in the exhaust gas by burning the exhaust gas obtained as a gas phase from the thermal decomposition step.
[0037]
Specifically, by combustion, high-boiling organic substances such as phthalates such as dioctyl phthalate (DOP) and low-boiling organic substances such as ethylene and vinyl chloride monomers are converted into carbon dioxide gas and water, and fluorine compounds are fluorinated. Convert to hydrogen.
[0038]
The above combustion not only improves the separability of impurities in the post-process, but also causes a phenomenon in which high-boiling organic substances in the exhaust gas obtained from the thermal decomposition process condense in the pipe in the post-process and block the pipe. Can also be effectively prevented.
[0039]
In addition, since many types of fluorine-based compounds generated in the thermal decomposition step become one type of hydrogen fluoride, the separability from hydrogen chloride gas by a combination of specific post-processes can be remarkably improved.
[0040]
As a combustion method in the combustion process, a combustion method using a known combustion furnace is employed without any particular limitation. For example, a tube heating system in which the exhaust gas and air are circulated in a tube and the outer tube is heated by a burner can be adopted. However, a method of directly contacting the exhaust gas with a burner flame, fuel and air supplied to the burner, and the exhaust gas Combustion methods such as a method of forming a flame after mixing are suitable. Liquid or gaseous fuel can be used as the fuel for combustion.
[0041]
In the above combustion method, when complete combustion is performed with a small excess air ratio, the absorption device in the next hydrogen chloride absorption process can be made small, and the recovered hydrogen chloride is reused as a raw material in the production process of other chlorinated products In order to obtain effects such as substantially not including a sulfur component that may cause a decrease in the reaction rate, it is preferable to use a gaseous fuel. As such a gaseous fuel, LPG, propane and the like are particularly preferable.
[0042]
As described above, the combustion gas obtained from the combustion process is hydrogen chloride, water vapor, carbon dioxide gas, hydrogen fluoride, and when a carrier gas is used in the thermal decomposition process, the carrier gas is used in the combustion process. In some cases, it is exhausted as a hot gas consisting of a small amount of chlorine generated from a part of excess air or hydrogen chloride.
[0043]
In addition, since the combustion gas discharged from the combustion process is generally a hot gas exceeding 800 ° C., considering the efficiency of the hydrogen chloride absorption process, heat is generated from the combustion gas between the combustion process and the hydrogen chloride absorption process. It is preferable to install a removing device, for example, a waste heat boiler or a cooling device that sprays water or hydrochloric acid to lower the gas temperature.
[0044]
In the present invention, in the hydrogen chloride absorption step, the combustion gas obtained from the combustion step is brought into contact with an absorption liquid comprising water or hydrochloric acid, and hydrogen chloride contained in the supply gas phase is absorbed into the absorption liquid to obtain a hydrochloric acid aqueous solution. It is a process.
[0045]
Hydrogen chloride contained in the combustion gas is absorbed in the absorbing solution in the hydrogen chloride absorbing step to become an aqueous hydrochloric acid solution, and the water vapor is also aggregated into water. Similarly, hydrogen fluoride contained in the combustion gas is also absorbed by the absorbent.
[0046]
On the other hand, components other than hydrogen chloride, hydrogen fluoride, and water vapor contained in the combustion gas, that is, carbon dioxide gas, carrier gas in the thermal decomposition process, excess air in the combustion process, and trace chlorine are substantially contained in the absorption liquid. It is separated as a gas phase without being absorbed.
[0047]
Therefore, in the hydrogen chloride absorption step, an aqueous hydrochloric acid solution in which the content of other impurities other than hydrogen fluoride is significantly reduced can be obtained.
[0048]
In the hydrogen chloride absorption step of the present invention, water or hydrochloric acid aqueous solution capable of dissolving hydrogen chloride is used as the absorbing solution. When an aqueous hydrochloric acid solution is used as the absorbing solution, it is preferable to use an aqueous solution having an initial concentration of hydrogen chloride of 25% by weight or less, preferably 20% by weight or less, considering the absorption efficiency.
[0049]
Moreover, the absorption conditions in an absorption process are not specifically limited, A well-known condition is employ | adopted without a restriction | limiting. For example, the absorption temperature is generally 20 to 80 ° C., and the pressure is generally near atmospheric pressure.
[0050]
Furthermore, as a device used for absorption, a known absorption tower is used without particular limitation. In general, there are a multi-stage absorption tower having a tower-shaped absorption section such as a packed tower or a cap tray and circulating a liquid phase through a cooler, a wet wall-type absorption tower, and the like.
The concentration of hydrogen chloride in hydrochloric acid taken out from the hydrogen chloride absorption step is preferably as high as possible, but considering the absorption efficiency and the like, it is higher than the hydrogen chloride concentration of the absorption liquid and is 10 to 40% by weight. It is preferable to take out at a hydrogen chloride concentration of. In particular, taking into account the equipment cost of the subsequent hydrogen chloride diffusion step, it is preferable to take out the hydrogen chloride and water at a concentration higher than the azeotropic composition. Such an azeotropic composition varies depending on the operating pressure, but is 20.2% by weight under normal pressure and 16% by weight at 500K Pascal gauge.
[0051]
In the present invention, in the hydrogen chloride stripping step, an aqueous hydrochloric acid solution that simultaneously dissolves hydrogen fluoride obtained from the hydrogen chloride absorption step is introduced into the stripping tower, the hydrogen chloride is stripped in the stripping tower, and the bottom of the tower is fluorinated. This is a step of concentrating hydrogen and recovering gaseous hydrogen chloride having a reduced hydrogen fluoride concentration from the top of the column.
[0052]
Even if the hydrochloric acid aqueous solution after absorption of hydrogen chloride contains phosphorus and sulfur components, it is removed to the liquid phase side at the bottom of the tower in this hydrogen chloride diffusion step.
[0053]
The inventors of the present invention introduced an aqueous hydrochloric acid solution in which hydrogen fluoride is dissolved into a diffusion tower, and the concentration of hydrogen fluoride in the recovered hydrogen chloride gas is about 40 ppm even when all gas components at the top of the tower are extracted. In the above stripping, a reflux operation is performed in which a condenser is provided at the top of the stripping tower, and a part of the gas discharged from the stripping tower is condensed and returned to the stripping tower. Thus, it has been found that the concentration of hydrogen fluoride in the recovered hydrogen chloride gas can be further reduced.
[0054]
In the present invention, when hydrogen fluoride is contained in the aqueous hydrochloric acid solution supplied to the stripping tower in the hydrogen chloride gas stripping step, the stripping tower is provided with a distillation stage at the top of the feed liquid feed stage. This is preferable in order to further reduce the amount of hydrogen fluoride in the hydrogen gas.
[0055]
More specifically, when the concentration of hydrogen fluoride in the aqueous hydrochloric acid solution is less than 300 ppm by weight with respect to hydrogen chloride, a theoretical distillation column having more than 0 stages is provided above the feed liquid supply stage to the stripping tower, When the concentration of the hydrogen fluoride is 300 ppm or more, a purified hydrogen chloride gas in which the concentration of hydrogen fluoride is controlled in the range of 100 to 40 ppm by weight with respect to hydrogen chloride by providing one or more theoretical distillation stages. Can be recovered. However, the upper limit of the theoretical plate is preferably 10 or less in consideration of economy.
[0056]
Further, as described above, by performing a reflux operation at the top of the stripping tower, the concentration of hydrogen fluoride is less than 40 ppm by weight with respect to hydrogen chloride, and in some cases, the chloride is reduced to about 0.2 to 15 ppm. Hydrogen gas can be obtained.
[0057]
In the above reflux operation, the condenser cooling temperature is preferably adjusted so that the condenser outlet gas temperature is −90 to 40 ° C., preferably −20 to 10 ° C. The condensate obtained by the condenser is preferably partly or wholly refluxed to the stripping tower.
[0058]
In this case, in order to perform the operation smoothly, it is preferable to set the cooling temperature to a temperature not lower than the freezing point of the condensed water.
[0059]
As the type of the stripping tower, a known method is employed without any particular limitation. For example, it can be carried out using a stripping tower type or a shelf type type having a reboiler at the bottom.
[0060]
In the hydrogen chloride gas diffusion step, known conditions can be applied as the hydrogen chloride gas diffusion conditions, but a temperature of 90 to 150 ° C. and a pressure of 50 to 500 K Pascal gauge are common.
[0061]
Moreover, in the use of hydrogen chloride gas, when the concentration may be low, it is also possible to perform the diffusion by supplying a carrier gas that does not adversely affect the use.
[0062]
Also, in the hydrogen chloride gas stripping step, the hydrochloric acid aqueous solution at the bottom of the stripping tower should be used as part or all of the absorbing solution by providing a hydrochloric acid aqueous solution circulating step for circulating part or all of the hydrochloric acid aqueous solution to the hydrogen chloride absorbing step. Is preferred.
[0063]
In this case, since the concentration of hydrogen fluoride in the circulating fluid increases with circulation, the circulating fluid is partially purged or brought into contact with an agent that becomes a solid by reacting with hydrogen fluoride or an adsorbent. Thus, it is preferable to circulate to the hydrogen chloride absorption step through the hydrogen fluoride removal step of removing hydrogen fluoride.
[0064]
In the hydrogen fluoride removal step, a method in which a circulating hydrochloric acid aqueous solution is brought into contact with an agent having a solid reaction product with hydrogen fluoride or an adsorbent is particularly preferable because there is little loss of hydrogen chloride.
[0065]
About the chemical | medical agent or adsorbent used in the said process, the thing in which conditions correspond can be arbitrarily selected from the chemical | medical agent or adsorbent illustrated in the hydrogen fluoride gas removal process mentioned later.
[0066]
The concentration of the hydrochloric acid aqueous solution taken out from the bottom of the hydrogen chloride gas stripping step is preferably 15% by weight or more in view of the stripping efficiency during circulation, in particular, hydrogen chloride and water at atmospheric pressure. It is preferable to adjust the emission conditions so that the hydrogen chloride concentration is as close as possible to the azeotropic composition.
[0067]
In the present invention, after the hydrogen chloride gas diffusion step, it is possible to further provide a hydrogen fluoride gas removal step for removing hydrogen fluoride gas from the hydrogen chloride recovered in a gaseous state, so that the concentration of hydrogen fluoride is further increased. Preferred for obtaining reduced purified hydrogen chloride gas.
[0068]
Here, the concentration of hydrogen fluoride to be controlled is such that when the recovered hydrogen chloride is reused as a manufacturing raw material in the manufacturing process of various chlorinated products, the decrease in the reaction rate is caused by the hydrogen fluoride in the recovered hydrogen chloride used as the raw material. It has become clear from the study by the present inventors that the amount depends on the amount of be brought in. For this reason, it is preferable that the concentration of hydrogen fluoride in the recovered hydrogen chloride gas is as low as possible. Usually, it is not more than the azeotropic composition of hydrochloric acid and hydrogen fluoride, that is, not more than 40 ppm, preferably not more than 30 ppm, more preferably not more than 10 ppm. Particularly, 5 ppm or less is preferable because a large amount of recovered hydrogen chloride gas can be used.
[0069]
In addition, it is also possible to provide the said hydrogen fluoride removal process before a hydrogen chloride diffusion process. In the hydrogen fluoride gas removal step, as a method of removing hydrogen fluoride, a gas phase obtained from the top of the stripping tower of the hydrogen chloride gas stripping step, and a chemical that reacts with hydrogen fluoride to become a solid or liquid Can be selected from the method of contacting the adsorbent, the method of contacting the adsorbent, and the method of contacting with hydrochloric acid or sulfuric acid.
[0070]
As a drug that reacts with hydrogen fluoride to become a solid or liquid, a known drug that does not substantially react with hydrogen chloride can be used without any limitation. Specifically, alkaline earth metal salts such as calcium chloride, calcium oxide, calcium hydroxide, and calcium carbonate, a carrier in which alkaline earth metal salts are supported, silica, silica alumina, zeolite, activated clay, alumina, etc. Solid oxides, metal chlorides such as aluminum chloride and trimethylchlorosilane, boric anhydride, boric acid, chlorinated pyridine and the like.
[0071]
Such a drug can be used in a solid state or in a state dissolved or dispersed in water. Furthermore, the solid drug can be used in any form of granular, crushed or molded.
[0072]
Examples of the hydrogen fluoride adsorbent include activated carbon and calcium fluoride.
[0073]
The concentration in the case of contact with hydrochloric acid or sulfuric acid is not particularly limited, but if it is too thin, loss of hydrogen chloride increases, so in the case of hydrochloric acid, it is usually 10 to 40% by weight, especially saturated hydrogen chloride under operating conditions. In the case of sulfuric acid, the concentration is 100 to 60% by weight, particularly 98 to 70% by weight because it is easily available.
[0074]
Among these drugs, it is particularly preferable to use granular calcium chloride or sulfuric acid because it can remove trace moisture in the diffused hydrogen chloride.
[0075]
In the hydrogen fluoride gas removal step, a known method can be adopted without any limitation as a method for contacting the hydrogen chloride gas with the above-mentioned chemicals. For example, when used in a solid state, a packed tower format, a fluidized bed format, when dispersing solids in a liquid or when using a liquid chemical, mention a plate tower, a stationary mixer format, a bubble column, etc. Can do.
[0076]
Contact conditions such as contact temperature and flow rate can be determined by measuring the reaction rate and adsorption rate of each chemical and hydrogen fluoride and taking into account the concentration of hydrogen fluoride in the outlet hydrogen chloride to be controlled.
[0077]
In this way, purified hydrogen chloride gas having a reduced hydrogen fluoride concentration can be obtained.
[0078]
Hereinafter, the method of the present invention will be described more specifically with reference to the accompanying drawings. However, the present invention is not limited to these accompanying drawings.
[0079]
1-4 are flowcharts illustrating exemplary embodiments of the method of the present invention. That is, FIG. 1 shows a method including a pyrolysis step, a combustion step, a hydrogen chloride absorption step, and a hydrogen chloride gas diffusion step, and FIG. 2 shows a hydrochloric acid aqueous solution extracted from the tower bottom of the hydrogen chloride gas diffusion step in the above step. 3 includes a hydrogen fluoride removing step for removing the concentrated hydrogen fluoride, and FIG. 3 shows a fluoride fluoride for removing a trace amount of hydrogen fluoride in the hydrogen chloride gas obtained from the top of the hydrogen chloride gas releasing step of the above step. Including the hydrogen gas removal step, FIG. 4 shows an embodiment in which both of these steps are provided. Moreover, in all the aspects, the circulation process which circulates the tower bottom liquid of a hydrogen chloride gas diffusion tower to a hydrogen chloride absorption tower is provided.
[0080]
Hereinafter, each figure will be described in more detail.
[0081]
In FIG. 1, the chlorine-containing resin is supplied from a line 2 to a thermal decomposition apparatus 1, and contains a solid phase 3 made of carbide and a fluorine compound, a high-boiling organic substance, and an organic compound component made of these decomposition products. And a gas phase containing hydrogen chloride as a main component.
[0082]
The solid phase is taken out from the line 3 and the gas phase is supplied from the line 4 to the combustion device 5 in the combustion process. In the combustion apparatus, a flame is formed by the fuel supplied from the line 6 and the air supplied from the line 7, and the gas phase supplied from the line 4 has a fluorine compound and a decomposition product of the fluorine compound contained therein. High-boiling organic substances, decomposition products thereof, or other organic compounds are decomposed into carbon dioxide gas and water vapor to form high temperature hot gas.
[0083]
This hot gas is taken out from the line 8 and supplied to the cooling device 9. In the cooling device 9, the hydrogen chloride-absorbed hydrochloric acid extracted from the bottom of the absorption tower in the hydrogen chloride absorption process by heat exchange is sprayed from the line 15 as a coolant to remove the heat of the hot gas. To do.
[0084]
Next, the gas phase is supplied to an absorption tower 11 as a hydrogen chloride absorption process via a line 10. In the absorption tower 11, hydrogen chloride, hydrogen fluoride, and water vapor are absorbed by spraying the absorbing liquid from the line 12, and are taken out from the line 16 as an aqueous hydrochloric acid solution.
[0085]
Here, a part of the extracted hydrochloric acid aqueous solution is circulated and used for the absorption tower 11 via the line 13, and a part is circulated and used for the cooling device 9 via the line 15.
[0086]
In the hydrogen chloride absorption tower, carbon dioxide gas, excess air in the combustion process, and when a carrier gas is used in the thermal decomposition process, impurities such as the carrier gas are separated from the top of the absorption tower 11 and taken out from the line 14. It is. This gas may be sent to a processing facility such as a detoxification tower for processing.
[0087]
Next, the aqueous hydrochloric acid solution taken out from the line 16 is dispersed in a diffusion tower 17 including a diffusion stage 19 and a distillation stage 18 provided as a hydrogen chloride gas diffusion step. In the stripping tower 17, hydrogen chloride gas having a reduced hydrogen fluoride concentration is recovered from the line 20 at the top of the tower.
[0088]
At this time, when the concentration of hydrogen fluoride in the liquid supplied to the stripping tower is less than 300 ppm by weight with respect to hydrogen chloride, the distillation stage 18 is more than 0 theoretical stages or more, and when it is 300 ppm or more, 1 stage or more. By providing a distillation stage so as to be a theoretical stage, hydrogen chloride gas in which the concentration of hydrogen fluoride is controlled to a low concentration range of 100 to 40 ppm by weight ratio to hydrogen chloride is recovered.
[0089]
Although not shown in FIG. 1, a condenser is attached to the top of the stripping tower, and a part of the gas discharged from the top of the stripping tower is condensed to return the condensed liquid to the stripping tower. By carrying out the reflux operation with a part, it is possible to obtain hydrogen chloride gas of extremely high purity in which the hydrogen fluoride concentration is reduced to less than 40 ppm by weight with respect to hydrogen chloride, and in some cases, reduced to about 0.2 to 15 ppm. Is possible.
[0090]
On the other hand, the liquid after hydrogen chloride diffusion with increased hydrogen fluoride concentration obtained from the bottom of the diffusion tower is an aqueous hydrochloric acid solution.
[0091]
This hydrochloric acid aqueous solution is taken out from the line 21, and in order to maintain the temperature of the hydrogen chloride gas stripping tower, a part of the hydrochloric acid aqueous solution is heated by a heat exchanger and returned to the stripping tower from the line 25. It is cooled and circulated from the line 26 to the absorption tower 11. Furthermore, another part may be purged from the line 27.
[0092]
The hydrochloric acid purged from the line 27 may be sent to a detoxification facility such as a neutralization tank for treatment.
[0093]
FIG. 2 shows an embodiment in which a hydrogen fluoride removing step for removing hydrogen fluoride is added to the hydrochloric acid aqueous solution after the hydrogen chloride gas releasing step in the embodiment shown in FIG. That is, the hydrogen chloride-dissipated liquid having an increased hydrogen fluoride concentration obtained from the bottom of the stripping tower 17 is taken out from the line 21 and supplied to the hydrogen fluoride removing tower 24 for processing. A part of the treated hydrochloric acid aqueous solution is heated by a heat exchanger and returned to the stripping tower from the line 30, and a part is cooled by the heat exchanger and circulated and used from the line 29 to the absorption tower 11.
[0094]
In this case, the purge line 27 is not necessarily required for the aqueous hydrochloric acid solution because the hydrogen fluoride is removed by the hydrogen fluoride removal tower.
[0095]
FIG. 3 shows a mode for further reducing the concentration of hydrogen fluoride in the recovered hydrogen chloride by adding a hydrogen fluoride removing step in the step of FIG. That is, the hydrogen chloride gas obtained from the top of the stripping tower 17 in the hydrogen chloride gas stripping step is taken out from the line 20 and supplied to the hydrogen fluoride gas removing tower 22 so that the hydrogen fluoride concentration from the line 23 corresponds to the hydrogen chloride. Purified hydrogen chloride gas controlled to 40 ppm or less by weight is recovered.
[0096]
FIG. 4 is a mode in which both the steps of FIGS. 2 and 3 are combined, and purified hydrogen chloride gas having a hydrogen fluoride concentration controlled to 40 ppm or less by weight ratio with respect to hydrogen chloride is recovered from the line 23.
[0097]
In any of the embodiments shown in FIGS. 2 to 4, it is possible to further reduce the concentration of hydrogen fluoride in the obtained hydrogen chloride gas by providing a reflux section in the stripping tower and performing the reflux operation. .
[0098]
【The invention's effect】
As can be understood from the above description, according to the present invention, the exhaust gas generated by the thermal decomposition of the chlorine-containing resin avoids blockage of piping and the like, and the content of the fluorine-based compound is extremely low, which is highly purified. The recovered hydrogen chloride gas can be recovered stably for a long period of time.
[0099]
Therefore, the industrial value of the present invention is extremely high.
[0100]
【Example】
EXAMPLES Hereinafter, examples will be shown to describe the present invention more specifically, but the present invention is not limited to the following examples.
[0101]
In Examples, as a method for analyzing a fluorine-based compound in exhaust gas, as for hydrogen fluoride, a method of absorbing by water and eliminating the influence of impurities and analyzing by ion chromatography, and for an organic fluorine compound, In the presence of oxygen and water, it was brought into contact with a known chlorofluorocarbon decomposition catalyst at a high temperature to decompose into hydrogen fluoride, and analyzed by the above method.
[0102]
Example 1
According to the process shown in FIG. 1, hydrogen chloride was recovered from waste synthetic resin containing chlorine-containing resin.
[0103]
That is, as the chlorine-containing resin 2, waste electric wire covering resin pieces crushed to an average particle diameter of 5 mm are supplied to the thermal decomposition apparatus 1 using a rotary kiln type thermal decomposition apparatus, and the temperature is increased to 350 ° C. in an atmosphere of nitrogen gas. Heated and pyrolyzed.
[0104]
In addition, when elemental analysis of the waste electric wire coating resin was performed, C; 43.1%, H; 5.71%, N; 0.49%, O; 1.30%, Cl; 24.6%, F: 0.025%.
[0105]
The carbide obtained by the above pyrolysis is recovered from the line 3, and exhaust gas containing hydrogen chloride as a gas is supplied to the combustion apparatus 5 with a waste heat boiler from the line 4 that is maintained at 300 ° C. or higher. Air is supplied from the line 7 and burned at a temperature of 1200 ° C., the gas after combustion is cooled by a waste heat boiler, and the gas that has passed through the combustion device is supplied to the cooling device 9 via the line 8 to A 23 wt% hydrochloric acid aqueous solution obtained from the bottom of the absorption tower 11 adjusted to 65 ° C. through an exchanger was sprayed from the line 15 and cooled.
[0106]
Next, the gas that has passed through the cooling device is supplied to the absorption tower 11 from the line 10, and a 20 wt% hydrochloric acid aqueous solution is sprayed from the line 12 to absorb hydrogen fluoride and hydrogen chloride in the gas. The aqueous hydrochloric acid solution was recovered from line 16. (Hydrogen chloride concentration: 23% by weight, hydrogen fluoride concentration: 810 ppm (relative to hydrogen chloride weight)).
[0107]
Next, the aqueous hydrochloric acid solution containing hydrogen fluoride obtained from the line 16 was supplied to the diffusion tower 17 to diffuse hydrogen chloride. As the stripping tower 17, one having a packed bed filled with a filler was used, and one having a theoretical stage above the supply stage was used.
[0108]
The emission conditions were a column bottom temperature of 110 ° C. and atmospheric pressure. A 20% aqueous hydrochloric acid solution obtained from the bottom of the tower was supplied to the absorption tower 11 via a line 26.
[0109]
As described above, the gas from the stripping tower 17 was extracted through the line 20 and led to a gas cooler cooled to −20 ° C. to recover hydrogen chloride gas.
[0110]
Impurities in the recovered hydrogen chloride were analyzed by gas chromatography, ion chromatography, etc., and as a result, water was 20 ppm and hydrogen fluoride was 63 ppm.
[0111]
The recovered hydrogen chloride gas was supplied to a catalyst fixed layer filled with 25 g of 13% Cu / alumina catalyst at a rate of 0.0328 mol / min hydrogen chloride, 0.0328 mol / min ethylene, and 0.0164 mol / min oxygen. The EDC synthesis reaction was performed at a temperature of 215 ° C. The conversion rates of hydrogen chloride at 1 hour and 20 hours after the start of the reaction were 84% and 74.3%, respectively.
[0112]
Examples 2-5
Table 1 shows the results obtained in the same manner as in Example 1 except that the wastes shown in Table 1 were used as the chlorine-containing resin 2.
[0113]
Examples 6-9
The same procedure as in Example 1 was performed except that the wastes shown in Table 1 were used as the chlorinated resin 2 and that the theoretical stage shown in Table 1 above the supply stage was used as the stripping tower. The results are shown in Table 1.
[0114]
Examples 10-11
In Example 1, the hydrogen chloride gas obtained from the line 20 is supplied to the hydrogen fluoride removing tower 22 filled with calcium chloride (Example 10) and 98% sulfuric acid (Example 11) as the chemical shown in FIG. Then, the same procedure as in Example 1 was performed except that hydrogen chloride gas was taken out from the line 23. The results are shown in Table 1.
[0115]
Moreover, when the EDC synthesis reaction using the hydrogen chloride gas taken out from the line 23 was further continuously performed for 80 hours (100 hours in total), both of the Examples 10 and 11 had 70% or more. The hydrogen chloride conversion was maintained.
[0116]
Comparative Example 1
The pyrolysis gas obtained from the line 4 in Example 1 was cooled to 215 ° C. and used as it was, and an EDC synthesis reaction was performed under the same conditions as in Example 1.
[0117]
The results are shown in Table 1.
[0118]
Reference example 1
An EDC synthesis reaction was carried out under the same conditions as in Example 1 using hydrogen chloride gas from a hydrogen chloride gas cylinder (hydrogen fluoride 0 ppm) manufactured by Tatsumi Soda.
[0119]
The results are shown in Table 1.
[0120]
As is clear from the comparison between this result and the results of the examples of the present invention, the hydrogen chloride gas obtained by the method of the present invention can be used in the EDC synthesis reaction in the same manner as commercially available high-purity hydrogen chloride. It is understood that it can be done.
[0121]
[Table 1]

[0122]
Examples 12-22
In Examples 1 to 11, a condenser is provided in the line 20 for extracting gas from the top of the stripping tower 17, and the condenser outlet gas temperature is adjusted to 5 ° C. to condense part of the gas. Hydrogen chloride gas was recovered in the same manner except that the gas was taken out while the condensate was refluxed to the diffusion tower.
[0123]
The results are shown in Table 2.
[0124]
The results of continuous operation for 120 hours are also shown for the hydrogen chloride conversion rate in the EDC synthesis reaction using the obtained hydrogen chloride gas. In Reference Example 1, the hydrogen chloride conversion rate during continuous operation for 120 hours was 70.8%.
[0125]
[Table 2]

[Brief description of the drawings]
FIG. 1 is a flowchart showing a typical embodiment of the method of the present invention.
FIG. 2 is a flowchart showing another exemplary embodiment of the method of the present invention.
FIG. 3 is a flowchart showing another representative embodiment of the method of the present invention.
FIG. 4 is a flowchart showing another exemplary embodiment of the method of the present invention.
[Explanation of symbols]
1 Pyrolysis device
5 Combustion device
9 Cooling device
11 Absorption tower
17 Stripping Tower
22 Hydrogen fluoride gas removal tower
24 Hydrogen fluoride removal tower

Claims (6)

(A) a pyrolysis step in which a chlorine - containing resin containing a fluorine compound is thermally decomposed in a non-oxidizing atmosphere to obtain a gas phase mainly composed of hydrogen chloride and a solid phase mainly composed of carbide;
(B) a combustion step in which the gas phase obtained from the thermal decomposition step is burned, and the fluorine-based compound contained in the gas phase is converted into hydrogen fluoride;
(C) a hydrogen chloride absorption step in which a combustion gas obtained from the combustion step is brought into contact with an absorption liquid comprising water or a hydrochloric acid aqueous solution to obtain a hydrochloric acid aqueous solution containing hydrogen fluoride;
And (d) a hydrogen chloride gas recovery step comprising a hydrogen chloride gas diffusion step in which the hydrochloric acid aqueous solution obtained from the hydrogen chloride absorption step is led to a diffusion tower and hydrogen chloride is recovered in a gaseous form from the top of the diffusion tower. Method.   The method for recovering purified hydrogen chloride gas according to claim 1, wherein a distillation stage is provided above the feed liquid supply stage in the stripping tower of the hydrogen chloride gas stripping step.   2. The method for recovering purified hydrogen chloride gas according to claim 1, further comprising (e) a hydrogen fluoride gas removal step of separating and removing hydrogen fluoride gas in the hydrogen chloride gas obtained from the top of the hydrogen chloride gas diffusion step. . Hydrogen fluoride gas removal process
(1) A method in which a drug whose reaction product with hydrogen fluoride is solid or liquid is brought into contact with hydrogen chloride gas,
(2) A method of bringing the adsorbent into contact with hydrogen chloride gas,
(3) A method of bringing hydrochloric acid or sulfuric acid into contact with hydrogen chloride gas,
4. The method for recovering purified hydrogen chloride gas according to claim 3, wherein the method is at least one method selected from the group consisting of: Furthermore, (f) a hydrochloric acid aqueous solution present at the bottom of the stripping tower in the hydrogen chloride gas stripping step is brought into contact with a drug or adsorbent in which the reaction product of hydrogen fluoride is a solid, 5. A hydrogen fluoride removing step for removing hydrogen fluoride, and (g) a hydrochloric acid aqueous solution circulation step in which a hydrogen chloride aqueous solution obtained from the hydrogen fluoride removal step is circulated and used as an absorption liquid in the absorption step. The method for recovering purified hydrogen chloride gas according to claim 1.   The manufacturing method of ethylene dichloride which uses the refinement | purification hydrogen chloride gas collect | recovered by the method in any one of Claims 1-5 for manufacture of ethylene dichloride by oxychlorination.

Images