JPH048368B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for efficiently removing O ₂ from an O ₂ -containing gas containing CO as a main component, and further separating and recovering CO by the COSORB method. [Prior Art] Recently, _C1 chemistry that uses compounds with one carbon number as starting materials, such as CO, CO ₂ and CH ₃ OH, has been attracting attention, but among the above _C1 compounds, especially CO ( 1)
It has extremely strong reaction activity, (2) can be easily produced by gasifying heavy oil, tar sand, coal, etc., which have been considered to have low utility value, and (3) steelworks byproduct gas, methanol. It is considered to be a particularly promising raw material because it can be obtained in large quantities as a by-product gas from various industries such as plant virgin gas. Known CO separation and purification technologies include the ammoniacal copper solution cleaning method and the cryogenic separation method.
The so-called "COSORB process" (see Japanese Patent Publication No. 1983-3504), jointly developed by Tenneco Chemical Company and Etsuo Research and Engineering Company in the United States, produces high-purity CO from various mixed gases in high yield and at low cost. As a recovery process, it is expected to play an important role in the future development of _C1 chemistry. Absorbent liquid used in the COSORB process (hereinafter referred to as
(referred to as COSORB solution) is expressed as M〓M〓Xn・aromatic (a solution of an aromatic hydrocarbon of a salt complex consisting of two metals), and a particularly preferred solution is a halogenated primary An aromatic hydrocarbon (e.g. toluene) solution of a bimetallic salt complex having the general formula CuAlX ₄ (X: halogen atom, e.g. Cl) produced by reacting copper and ammonium halide in a suitable solvent. It is.
However, the composition of the COSORB solution is not specified in the present invention, and will be developed in the future.
All COSORB solutions are included in the scope of the present invention. According to various literature, COSORB solution contains H ₂ , CO ₂ ,
CH ₄ , N ₂ , O _{2 ,} etc. are treated as chemically inert, and in fact, when O ₂ -containing gas containing CO as its main component is processed in the COSORB process, O ₂ is removed. CO is separated and recovered by contacting it directly with the COSORB solution without removing it. [Problems to be solved by the invention] For example, when recovering CO from converter gas in a steel mill (converter gas generally contains about 70% CO and CO ₂ :
Approx. 17%, N ₂ : approx. 10%, H ₂ : approx. 2%, O ₂ : 0.2~
This mixed gas is pressurized and supplied to an activated carbon adsorption tower etc. to remove trace impurities such as
After removing H ₂ S, SO ₂ , NH ₃ , HCN, etc., and further removing water to below 1 ppm by supplying it to an adsorption tower filled with synthetic zeolite, COSORB
It is supplied to the process and CO is separated and recovered. The converter gas supplied to the COSORB process is in countercurrent contact with the COSORB solution in the absorption tower, and at room temperature
CO is selectively absorbed. absorbed CO
The COSORB solution is sent to a stripping tower where it is heated and CO is stripped off, while the COSORB solution is recovered and recycled. The obtained CO is used as a raw material for C ₁ compounds or for various other purposes. CuAlCl ₄・C ₇ H ₈ +CO Room temperature → ← High temperature CuAlCl ₄・CO＋C ₇ H _8However , it is difficult to use converter gas as a raw material for a long period of time.
When running the COSORB process, COSORB
Problems have arisen with solution deterioration and heat exchanger blockage in the COSORB process. As a result of studies by the present inventors, it has been found that these problems are caused by O ₂ contained in the mixed gas, as will be described later. Therefore, the main focus of the present invention is to develop a technology that can effectively remove O ₂ from the mixed gas before introducing the COSORB process, and as a result,
The purpose of this study is to establish a CO purification method that prevents COSORB solution deterioration and COSORB process heat exchanger blockage, and enables long-term operation of the COSORB process. [Means for solving the problems] What is the present invention that can solve the above problems?
A mixed gas containing CO as the main component and 3% by volume or less of O ₂ is introduced at 80°C or below into a deoxidizer packed with a catalyst containing at least copper, and
100% _O2 content by converting _O2 to _CO2
The gist of this method is to purify CO by reducing the volume to below ppm and then supplying it to an aromatic hydrocarbon solution of a metal complex salt. [Action] The COSORB solution reacts with a Lewis base stronger than cuprous chloride (CuCl) or an oxygen-containing organic compound, and the COSORB solution decomposes to form cuprous chloride, cuprous chloride,
Generates hydrogen chloride or room temperature tar. (a) Deterioration of COSORB solution, (b) COSORB
While tracking problems such as heat exchanger blockage in the process, it was discovered that the formation of room temperature tar in the COSORB solution was increasing exponentially, and the generation of hydrogen chloride was also increasing exponentially. In order to study the cause of this, the present inventors conducted the following experiment. (Experiment 1) Put 300c.c. of COSORB solution (liquid temperature 130℃) into a 500c.c. volumetric flask, and blow in 250c.c./min of mixed standard gas of 2% O ₂ - 98% N ₂ . Figure 3 and Table 1 show the results when pure N ₂ gas and pure CO gas were blown into the liquid at the same temperature at 250 c.c./min. As is clear from the above, when O ₂ was included, the COSORB solution reacted with O ₂ and the amount of copper dissolved in the solution decreased. The amount of room temperature tar has increased. Hydrogen chloride continued to evolve. On the other hand, when gas from which O ₂ was removed, ie, pure N ₂ and pure CO, was blown into the COSORB solution, the above-mentioned deterioration phenomenon of the COSORB solution was not observed. Furthermore, when a COSORB solution treated with O2 _- containing gas, which is mainly composed of CO, for a long period of time is analyzed by gas chromatography, methylenebismethylbenzene is detected.

The existence of [Formula] has been confirmed. From the above, it can be concluded that hydrogen chloride (HCl) dissolved in the COSORB solution, toluene and the processing gas
O ₂ reacts, and the following (1), (2), (3), (4) [(4) formula is (1),
(2) and (3) are summarized]
This occurred in the COSORB solution, resulting in deterioration of the COSORB solution, including the formation of room temperature tar, generation of hydrogen chloride, and a decrease in the amount of copper dissolved in the solution, which was thought to have caused serious problems for the COSORB process. . H ₂ O＋CuAlCl ₄ →CuCl↓＋AlOCl＋2HCl↑ ……(3) *However, Polymer COSORB is a gas containing O ₂ whose main component is CO
Processing causes liquid deterioration, resulting in expensive
As the COSORB solution is lost, the generated room temperature tar and the generated CuCl or AlOCl scale as sludge in the heat exchanger, clogging the heat exchanger and making long-term operation difficult.

[Table] (Experiment 2) Under the same conditions as Experiment 1, after blowing 250 c.c./min of standard mixed gas of 2% O ₂ -98% N ₂ into the liquid for about 60 hours, pure N ₂ gas was added. When the switch was made, the hydrogen chloride generation rate suddenly decreased after several hours as shown in FIG. From this result, it was confirmed that with O ₂ -containing gas, hydrogen chloride, which is an indicator of the deterioration phenomenon of the COSORB solution, continues to be generated, and with gas that does not contain O ₂ , hydrogen chloride is not generated. Therefore, after removing O ₂ in the mixed gas
I came to believe that these troubles could be eliminated by supplying the COSORB process, but as a result of various considerations, I found that 3.
If the raw material gas contains O ₂ less than % by volume,
It has been found that by using the catalyst specified in the present invention, it is possible to easily reduce the amount by volume to 100 ppm or less, and depending on the conditions, to 10 to 1 ppm or less, and the intended purpose can be achieved. Also, the raw material gas
Before feeding to the COSORB process
Purified CO to remove _O2 below 100ppm
The secondary effect is that the O ₂ concentration inside is also reduced and the purity of purified CO is improved. Furthermore, the catalyst used in the present invention is copper-based or has a binary composition of copper and other metals such as zinc, manganese, chromium, nickel, etc., and has particularly excellent reaction activity and reaction selectivity, and is compatible with COSORB solutions. extremely harmful
40-60% in terms of ability to adsorb and remove impurity gases such as _H2S
Copper oxide/60-40% zinc oxide is optimal. below
Further explanation will be given focusing on the O ₂ removal process. A mixed gas containing CO as the main component and less than 3% by volume of O ₂ is fed into the deoxidizer filled with the above catalyst.
When introduced at 10-80℃, preferably 20-50℃,
O ₂ becomes mainly CO ₂ and O ₂ is removed. CO + 1/2O ₂ → CO ₂ In the present invention, it has been stated that the upper limit of O ₂ content is 3% by volume, but as a practical matter, the amount of O ₂ in converter gas or blast furnace gas will not exceed 3% by volume. In practical terms, it can be considered unlimited. Even when a catalyst is used, there is a problem of reaction selectivity like other general catalytic reactions, and reactions such as H ₂ + 1/2O ₂ → H ₂ O 3H ₂ + CO → H ₂ O + CH ₄ may proceed. If the gender is even 1%
Since H ₂ O degrades the COSORB solution, it is necessary to dehumidify it in a later step. The catalyst specified by the present invention has very high low-temperature activity and reaction selectivity for CO + 1/2O ₂ → CO ₂ , but it also has a high reaction selectivity for the side reaction H ₂ + 1/2O ₂ →
In order to suppress reactions such as H ₂ O as much as possible, it is better to lower the inlet gas temperature in the deoxidizer, which is 80℃.
Hereinafter, it is better to introduce the O ₂ -containing gas preferably at a temperature below 50°C. Cu-based catalysts are also used as methanol synthesis catalysts, so the following reaction may occur: CO+2H ₂ →CH ₃ OH 2CO+4H ₂ →CH ₃ OCH ₃ +H ₂ O 2CO+2H ₂ →CH ₃ COOH. It is assumed that deterioration of COSORB solution due to oxygen-containing organic compounds occurs. Therefore, it is preferable to keep the outlet temperature of the deoxidizer at 230°C or lower, and the O2 _- containing gas introduced into the deoxidizer is
Serve at 80°C, preferably 20-50°C. When the O ₂ concentration is high, install a cooler etc. inside the deoxidizer to keep the outlet temperature below 230℃.
It is desirable that the content of oxygen-containing organic compounds be 50 ppm or less, preferably 10 ppm or less. Methanol etc. can be removed in the same way as water using an adsorption tower filled with synthetic zeolite etc., but methanol etc. decomposes because the temperature is raised during regeneration of the adsorption tower.
There is a possibility that carbon precipitation may occur or a chemical reaction may occur with the synthetic zeolite, resulting in no longer being desorbed. Therefore, it is desirable that the concentration of oxygen-containing organic compounds at the outlet of the oxygen absorber is 50 volume ppm or less. Thus reducing the _O2 content to 100 ppm by volume, preferably 10 ppm
The mixed gas reduced to below is supplied to the COSORB process after dehumidification and demethanolization as required.
The reason why the O ₂ content is set to 100 ppm or less by volume is as follows. That is, based on the above test results, the relationship between the O ₂ concentration of the O ₂ -containing gas in the COSORB solution and the rate of liquid deterioration is shown in Table 2, where the life of the solution at the same O ₂ concentration is expressed in correspondence.

[Table] For example, when the O ₂ concentration in O _2- containing gas is 0.5%,
The COSORB solution has a service life of only about one year, but if the O ₂ concentration is at least 100 ppm or less, the solution can be used for about three years, which makes it economically reasonable. Naturally, the lower the O ₂ concentration, the longer the liquid life will be, especially if it is 10 ppm or less, it will be about 7 years, and there will be no problems in use. Also, if the concentration is less than 1 ppm, the liquid life will be more than 15 years. [Embodiment] FIGS. 1 and 2 are flow diagrams showing an embodiment of the present invention. CO: 68%, _CO2 : 16%, _N2 :
13.5%, _H2 : 2%, _O2 : 0.5%, and _O2- containing gas whose main component is CO, containing other trace impurities.
LDG (converter gas: 40℃) is compressed by compressor 1 (oil-filled screw compressor or oil-free compressor) to 1 to 100Kg/cm ² G, for example 3Kg/
After being compressed to cm ² G, it is cooled to 40° C. through a heat exchanger 2, and after draining the condensed water through a drain 3, it is passed through a preliminary dehumidification device A. LDG introduced into the preliminary dehumidifier A is cooled by heat exchangers 4 and 5,
The generated condensed water is drained through a drain 6. In particular, in the heat exchanger 5, the brine cools down to a dew point temperature of 2 to 8°C, so the dehumidification effect is large.
The purpose of preliminary dehumidification here is to distribute the dehumidification load, i.e. to reduce the final dehumidification load, to prevent water condensation in the packed bed in the downstream process, and to prevent the presence of a large amount of water vapor in the downstream activated carbon tower. This is because the performance will decrease, and it may be omitted in some cases. Next, the LDG cooled to 2 to 8 degrees Celsius is heated to 25 degrees Celsius in a heat exchanger 4, and packed towers 7 and 8 filled with activated carbon and acid-impregnated/alkali-impregnated activated carbon.
Pass through. The purpose of the packed tower 7 is to remove oil when an oil-filled screw compressor is used as the compressor 2, and if the compressor 2 is an oil-free compressor, the packed tower 7 can be omitted. Next, in the packed column 8, trace impurities such as H ₂ S, HCN, SO ₄ , NH ₃ , CS ₂ , HF, etc. contained in the LDG are removed. This dehumidifies and removes impurities.
LDG is heated with a copper-based catalyst (e.g. 50% Cu - 50%
O ₂ in LDG is converted to CO ₂ by passing through a reaction tower (deoxygenation device) 9 filled with ZnO). At this time, the temperature rises to about 125° C. due to the oxidation reaction, so it is cooled down to room temperature by a heat exchanger 10 and passed through a dehumidifier B.
The dehumidifier B consists of packed towers 11 and 11' filled with, for example, synthetic zeolite, etc., and removes water by one volume.
Dehumidify to below ppm. LDG is then fed to the COSORB process to purify CO. In addition, in dehumidification equipment B, CO + H ₂ → CH ₃ OH, or
Produced by the reaction H ₂ + 1/2O ₂ →H ₂ O
CH ₃ OH and H ₂ O are also removed. If the reaction in reaction tower 9 is substantially limited to CO + 1/2O ₂ → CO ₂ , install dehumidifier B in front of reaction tower 9 as shown in the flow diagram of Figure 2. This may also be used as a final dehumidification device. Note that 13 and 14 are filters,
The heat exchangers 2 and 10 are based on cooling water. The LDG obtained as above has an O ₂ concentration of 1
It was confirmed that the volume was less than ppm, the concentration of oxygen-containing organic compounds such as methanol was less than the lower limit of gas chromatography quantification, and the production of H ₂ O by H ₂ and O ₂ was less than 1% as a selectivity to the O ₂ contained. Ta. When this LDG was introduced into the COSORB process to purify CO, the results shown in Table 3 as examples were obtained. A comparison example that does not remove O ₂ is also shown.

[Table] From the above, after removing O _{2 from O 2 -} containing gas,
It was confirmed that when supplied to the COSORB process, the deterioration rate of the COSORB solution was extremely suppressed. [Effects of the Invention] As described above, according to the present invention, deterioration of the COSORB solution in the COSORB process can be prevented by removing O ₂ in the mixed gas containing O ₂ as a main component to a certain concentration in advance. This also prevents clogging of the heat exchanger and enables long-term stable operation of the COSORB process.

[Brief explanation of drawings]

FIGS. 1 and 2 are flowcharts showing an embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing the relationship between the amount of gas blown and the rate of hydrogen chloride generation. 1... Compressor, 2, 4, 5, 10... Heat exchanger, 3, 6... Drain, 7, 8, 11, 11'
... Packed tower, 9 ... Reaction tower, 13, 14 ... Filter, A ... Preliminary dehumidification device, B ... Dehumidification device.

Claims (1)

[Claims] 1 A mixed gas containing CO as the main component and 3% by volume or less of O ₂ is introduced at 80°C or below into a deoxidizer packed with a catalyst containing at least copper, converting mainly O ₂ to CO ₂ A method for purifying CO, which comprises reducing the O ₂ content to 100 ppm or less by volume, and then supplying the metal complex salt to an aromatic hydrocarbon solution to purify CO.