JPH048369B2 - - 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 purge 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
COSORB solution) is expressed as M〓M〓Mo_・aromatic (a solution of aromatic hydrocarbons in a salt complex consisting of two metals), and a particularly preferable solution is a halogenated solution. An aromatic hydrocarbon (e.g. toluene) salt complex of two metals having the general formula CuAlX ₄ (X: halogen atom, e.g. Cl) produced by reacting copper 1 and ammonium halide in a suitable solvent. ) solution.
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
_{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 a main component and not more than 3% by volume of O ₂ is introduced into a deoxidizer packed with a catalyst containing at least a group metal at 80-200°C, preferably 100-150°C. , primarily by converting O ₂ to H ₂ O and separating this H ₂ O to reduce the O ₂ content to 100 ppm by volume, preferably below 10 ppm, and then converting the metal complex salt into an aromatic hydrocarbon solution. The purpose of this project is to purify CO by supplying it to CO. [Operation] The COSORB solution reacts with a Lewis base or an oxygen-containing organic compound, which is stronger than cuprous chloride (CuCl), and the COSORB solution separates to produce cuprous chloride, hydrogen chloride, room temperature tar, etc. (a) Deterioration of COSORB solution, (b) COSORB
While tracking a problem related to a blockage in a process heat exchanger, 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 investigate the cause of this, the present inventors conducted the following experiment. (Experiment 1) Put 300 c.c. of COSORB solution (liquid temperature 130°C) into a 500 c.c. volumetric flask, and blow in 250 c.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 the same rate of 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 O ₂ gas containing CO as its main component for a long period of time is analyzed using a gas chromatograph, 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),
A combination of equations (2) and (3)] The reaction as shown in equation
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 In other words, when O ₂ gas containing CO as its main component is treated with the COSORB process, the liquid deteriorates and becomes 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, a standard gas mixture of 2% O ₂ -98% N ₂ was used at 250 c.c. /min into the liquid for about 60 hours, and then switched to pure N ₂ gas. As shown in Figure 4, the hydrogen chloride generation rate suddenly decreased after several hours. 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,
100 by using the catalyst specified in the present invention.
It has been found that it is possible to easily reduce the capacitance to below ppm, and depending on the conditions, to below 10 to 1 ppm, and that the intended purpose can be achieved. Further explanation will be given below, focusing on the O ₂ removal process. A mixed gas containing CO as a main component and 3% by volume or less of O ₂ (in the present invention, the O ₂ content is limited to 3% by volume, and mixed gases to which the present invention is applied, such as converter exhaust gas and blast furnace exhaust gas) (O ₂ content of which rarely exceeds 3% by volume) is introduced into the deoxidizer. O ₂ in the mixed gas selectively reacts with H ₂ in the mixed gas using a carrier such as alumina impregnated with about 0.1 to 1.0 wt% of a group metal such as platinum or palladium as a catalyst. H ₂ + 1/2O ₂ →H ₂ O Also, if H ₂ is insufficient, it will be compensated for by the reaction CO + 1/2O ₂ → CO ₂ , and the O ₂ content will quickly increase.
100 ppm, preferably lower than 10 ppm. That is, the catalyst specified in the present invention is
When applied to _O2- containing gas whose main component is CO,
A major feature of this method is that it can react with CO even if there is no more than a stoichiometric amount of hydrogen in the O ₂ gas, and can quickly reduce the O ₂ content. _O2 content 100
The reason why the capacity is set to be less than ppm is as follows. That is, based on the above test results, Table 2 shows the relationship between the O _{2 concentration of the O 2 -containing} gas in the COSORB solution and the solution deterioration rate, and the relationship between the O ₂ concentration and the solution life.

[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, and if it is preferably 10 ppm or less, it will be about 7 years, and there will be no problems in use. or,
If the concentration is less than 1ppm, the liquid life will be more than 15 years. In addition, at this time, a reaction of CO ₂ + 2H ₂ → CH ₃ OH may also occur. The outlet gas temperature of the deoxidizer is
In order to prevent activity from decreasing due to carbon precipitation on the catalyst, it is necessary to keep the temperature below 350°C, preferably below 300°C. Therefore, when the O ₂ content in the O ₂ gas is high, the catalyst packed bed is divided into multiple stages.
It was necessary to install coolers between each stage and within the packed bed to keep the temperature within the bed below 350°C. H ₂ O (and CH ₂ OH) generated in the deoxidizer
is dehumidified (and dealcoholized) to less than 1 volume ppm in a dehumidifier. _H2O greater than 1 ppm by volume,
CH ₃ OH causes deterioration of the COSORB solution and must be removed. In addition, it is a trace impurity.
H ₂ S, HCN, SO ₂ , NH ₃ , CS ₂ , HF, etc. are removed in a step before or after the deoxidizer. The mixed gas deoxidized as described above is supplied to the COSORB process. [Embodiment] FIGS. 1 and 2 are flowcharts showing an embodiment of the present invention. Example 1 This will be explained with reference to FIG. CO: 68%, _O2 : 16%, _N2 : 14.7%, _H2 : 0.8
%, _O2 : 40℃ converter exhaust gas consisting of 0.5% (hereinafter
LDG) is compressed to 3 kg/cm ² G by compressor 1 (oil-filled screw compressor or oil-free compressor), then cooled to 40°C by heat exchanger 2, and drained to drain 3. After removing condensed water, it is introduced into heat exchanger 4 and heated to 100℃.
The mixture is heated to a temperature of 100.degree. C. and passed through a reaction tower (deoxygenation device) 5 in which an Al carrier is filled with 0.5% by weight of a Pd catalyst. Note that since this is an exothermic reaction, the temperature of the inlet gas may be raised by the sensible heat of the gas exiting the reaction tower. In the reaction tower 5, H ₂ +
The reaction of 1/2O ₂ →H ₂ O occurs, then CO ₂ + 1/2O ₂
→A reaction called CO ₂ occurs and O ₂ disappears. At this time
The reaction CO ₂ + 2H ₂ → CH ₃ OH may occur.
This oxidation reaction raises the temperature of LDG to about 180°C, so it is cooled down to about 40°C by a heat exchanger 6, cooled by a preliminary dehumidifier A, and the condensed water is removed by a drain 9. The LDG that has entered the preliminary dehumidification device A is transferred to the heat exchanger 7,
Particularly in the heat exchanger 8, the brine cools down to a dew point temperature of about 5° C., so the dehumidification effect is large. The cooled LDG is heated to 25°C in a heat exchanger 7 and introduced into packed towers 10 and 11 filled with activated carbon and acid-impregnated/alkali-impregnated activated carbon, where H ₂ S, SO ₂ and NH contained in LDG are removed. ₃ ,
HF etc. are removed. The purpose of the packed tower 10 is to remove oil when an oil-filled screw compressor is used as the compressor 1. If the compressor 1 is an oil-free compressor, the packed tower 10
can be omitted. The LDG is then passed through the dehumidification tower B, and the dehumidification packed tower 12 is filled with synthetic zeolite.
After passing through 12' and removing water to less than 1 ppm by volume (CH ₃ OH, if present, is also removed in packed columns 12 and 12'), it is fed to the COSORB process. The LDG adjusted as above is COSORB
It is introduced into the process to purify CO. Note that 14 and 15 are filters, heat exchangers 2 and 6 are based on cooling water, and 4 and 14 are based on steam. Example 2 This will be explained with reference to FIG. LDG with the above composition was compressed to 3 kg/cm ² G by a compressor, cooled to 40°C by a heat exchanger 21, and then drained to a drain 3.
Drain the condensed water. Next, heat exchanger 4 is 50
℃, oil or trace impurities are removed in packed towers 10 and 11, and then heated to 100℃ using a heat exchanger 14.
is heated to. O ₂ disappears in the reaction tower 5 and the temperature is oxidized to 180°C, so it is cooled to 40°C in the heat exchanger 6, cooled and dehydrated in the preliminary dehumidifier A, and further dehumidified in the dehumidifier B. and fed to the COSORB process. The details are the same as in Example 1. Note that it is possible to change the flow without changing the spirit of the present invention. of LDG obtained in Example 1 and Example 2
The O ₂ concentration was below 1 ppm by volume, and the concentration of oxygen-containing compounds such as methanol was below the lower limit of quantification by gas chromatography. The LDG with an O ₂ capacity ppm or less obtained in Example 1 was
When CO was purified by introducing it into the COSORB process, the results shown in Table 3 as examples were obtained. A comparison example that does not remove O ₂ is also shown.

【table】

[Table] From the table 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, the COSORB solution in the COSORB process can be improved by removing O ₂ in the mixed gas containing CO as a main component and O ₂ to a certain concentration or less in advance. This prevents deterioration and blockage of the heat exchanger, enabling 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, 6, 7, 8... Heat exchanger, 3, 9... Drain, 5... Reaction tower, 10,
11, 12, 12'... Packed column, 14, 15...
Filter, A... preliminary dehumidification device, B... dehumidification device.

Claims (1)

[Claims] 1 A mixed gas containing CO as a main component and 3% by volume or less of O ₂ is introduced at 80°C or above into a deoxidizer packed with a catalyst containing at least a group metal, and the O ₂ is mainly converted into H ₂ O. The method is characterized in that the O ₂ content is reduced to below 100 ppm by volume by separating this H ₂ O, and then supplied to an aromatic hydrocarbon solution of a metal complex salt to purify CO. A method for purifying CO.