KR830002405B1 - Unreacted Gas Purification Process - Google Patents

Abstract

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Description

Unreacted Gas Purification Process

1 is a simplified diagram of the flow of a device suitable for use in the process of the present invention for gas purification,

FIG. 2 shows a reprocessing apparatus similar to that of FIG. 1 but used non-aqueous adsorption solution and a re-operation apparatus for circulating the regeneration solution to the liquid-gas contactor for further use.

3 shows a curve showing the removal efficiency of CO ₂ for a large number of thermal regeneration cycles in a purification system using four different alkali or alkaline earth metals.

4 is a simplified flow diagram of a plant using a continuous gas purification system in which no carbonic acid precipitates are produced during operation.

5 is a flow chart of a test plant of a continuous purification system in which a purification cycle in which an insoluble carbonate precipitate is generated during operation and is removed during operation is used.

The present invention relates to the purification of certain effluent gases, ie the removal of trace impurities from the gases.

It is already known that basic alkalis, alkaline earth metals, hydroxides or weak acid salts react with acids. Such chemistry is basic but has been an important basis for commercial applications. For example, in the purification of industrial gases such as hydrogen, carbon monoxide, air, oxygen, nitrogen, argon, helium, low monoolefins and low diolefins, layers or suspensions of solid particles of sodium or potassium hydroxide remove large amounts of acid gas. It has been used to make. Such processes have been found to be relatively ineffective for removing small amounts of impurities such as hydrogen sulfide, carbon dioxide, sulfur dioxide and mecaptan with such a gas stream. In fact, it is shown in the US patent (U.S. 2,742,517) that alkali metal hydroxides are used as absorbents to separate acetylene from ethylene.

U.S. Patent No. 2,185,332, filed on January 2, 1940, shows a process for dehydrating and deoxidizing the system by supplying an alkali alcoholate, particularly sodium methyloleate, to the refrigeration system. The alcoholate is fed to the system to remove water by methanation, yielding alkali hydroxides and sodium hydroxide. It remains inside the sodium hydroxide or caustic soda system, which is corrosive and, if it is present in the refrigeration gas, will eventually suffer economic damage. In addition, the patent appears to remove the acid. The patent further states that hydrogen chloride is converted to sodium chloride. Of course, hydrogen chloride is more corrosive than sodium chloride, but it is clearly not beneficial if sodium chloride remains in the freezer. To solve this problem, the patent uses known chemistry, but it is not an excellent improvement because the process creates another problem. An unfavorable problem that cannot be seen as a marked improvement is that water forms corrosion.

U.S. Patent No. 2,177,068 (filed Oct. 24, 1939) relates to the treatment of natural gas to remove water and acid gases. In this patent, polyhydric alcohols are used in combination with amines, for example alkanol amines, for the treatment of natural gas. The use of such amines and polyols known as moisturizers to remove acid gases is an old method.

The gas treated in the above two overhead wells is the well known saturated hydrocarbon. The impurities removed do not affect the behavior of these gases, but only affect the surrounding devices or the environment in which they are used. In either case, the process has a drawback that it relies on amines to extract acid gases. These amines are known to be corrosive.

As the impurity capacity improved, the industrial gas purification process was further developed. As the analytical methods that can be applied to industrial gases have been improved, there is a need for better processes for the removal of newly discovered impurities. The terms "non-reactive" and "inert gas" refer to industrial gases that can be treated according to the process of the present invention without reacting with the selected alkali / polyhydric alcohol solution.

In general, olefins may contain traces of all or part of the impurities in the ppm range, such as water vapor, hydrogen sulfide, carbon dioxide, sulfur dioxide, and charcoal, due to their production or storage and handling issues. Many commercial manufacturing processes require an olefin raw material containing less than 1 ppm of impurities, and even less than 0.5 ppm. For example in order to create the appropriate amount of ethylene for the preparation of certain quality level of polyethylene olefin containing CO ₂ (degree of approximately 10-25ppm) it is lowered the CO ₂ concentration of 1ppm or less. The two major problems associated with this process are

(i) Only about 3% of NaOH in the reaction layer is converted to NaCO ₃ .

(ii) After the outer surface of the particles is converted to carbohydrates, the water produced here causes the particles to agglomerate and eventually harden the entire layer.

The latter is particularly difficult because the contents of the layers must be removed by hand from time to time. Aqueous solutions of sodium hydroxide have been proposed as an improvement, but using this requires a zeolite layer that adsorbs moisture because water vapor from the solution penetrates into ethylene. However, installing it would (i) be large and expensive to install, and (ii) expensive to reprocess.

The process of the present invention essentially uses a liquid of a non-aqueous treatment medium, i.e., a liquid that does not have an influence of moisture on the gas to be treated. This liquid

(i) has high efficiency against alkalis (ie solubility)

(ii) very low vapor pressure, and (iii) the system is chemically stable when combined with alkali,

(iv) The viscosity is very low so that the gas being treated is adequately hydrated.

In the process of the present invention, an alkali (or alkaline earth) metal liquid polyhydric alcohol solution is used to remove the above-mentioned impurities, and in particular, all harmful trace impurities can be substantially removed at the same time when they are present.

The process of the present invention is hydrogen or CO, air, nitrogen, oxygen, helium, argon, diolefin, paraffin, or acetylene containing 4 to 5 carbon atoms per molecule of monoolefin containing 2 to 5 carbon atoms per molecule. It is a purification process of the above gases by removing reaction impurities, such as hydrogen fluoride, CO ₂ , SO ₂ , hydrogen chloride, nitric acid, and charcoal, which have been introduced into the copper for preparing or treating industrial gases. In this process, the above-mentioned industrial gas is a liquid aliphatic polyhydric alcohol solution in which the ratio of carbon to oxygen at a temperature of 15 ° -100 ° C. is 1 to 5 and at least two of its oxygen are separated from terminal carbon atoms of not more than 2. Purification is achieved by contact with a non-aqueous solution containing about 0.5 to 15 wt% of alkali or alkaline earth metal as measured by its hydroxides or inorganic weak acid salts within. In addition, in this process, industrial gas, which is a raw material of the treatment process, is continuously introduced into an alkali / polyhydric alcohol solution maintained at a temperature of 15 ° to 100 ° C., and then contacted with the solution, and then exits to the atmosphere. The partial pressure of water vapor in the water is not high enough to increase the water concentration in the gas stream. In a preferred embodiment, the concentration of water in the solution and the gas stream exiting the atmosphere is lower than that contained in the source gas injected into the solution. Alkali and alkaline earth metals mentioned in the text belong to the IA and II A groups of the periodic table. Lithium, sodium, potassium, libidium, cesium, magnesium, calcium, strontium and barium. Among them useful are sodium and potassium, in particular potassium being most suitable for the process of the present invention. Hereinafter, the term "alkali" shall mean alkali metal and alkaline earth metal as before.

For simplicity and convenience, the process of the present invention will first deal with the case of removing trace impurities from ethylene gas. Alkali groups present in polyhydric alcohol solutions can be obtained from inorganic weak acids and hydroxides of alkali or alkaline earth metals.

Polyhydric alcohols include glycerol and alkylene glycols, for example ethylene glycol with 12 carbon atoms (ethylene glycol, diethylene glycol, triethylene glycol, tetaethyleneglytol, propylene glycol, dipropylene glycol, 1, 2 Butylene glycol, di-1, 2-butylene glycol, etc.), and alkylene oxidant. Alkylene oxide precursors here are used for alkylene oxides such as glycols, glycerol, and other triols (e.g., 1, 2, 6-hexanetriol of erythritol, monomethyl ether and pentaerythritol). Monomethyl ether). Ethylene oxide and propylene oxide precursors of polyols are more effective. The best protons are either ethylene oxide protons or in the form in which they react with propylene oxide.

The gas treated in this gas purification process contains an inert gas that does not react with the alkali / polyhydric alcohol used in the process and a small amount of impurities that react with the alcohol solution described above. The main unreacted gases include hydrogen, CO, air, oxygen, helium, argon low monoolefins, low diolefins and their derivatives paraffins like methane and ethane and acetylene.

“Olefin” herein means only those selected from the group consisting of monoolefins having 2 to 5 carbon atoms per molecule, diolefins having 4 to 5 carbon atoms per molecule, and derivatives thereof. Representative of such olefins include ethylene, propylene, butylene, pentylene, 1, 3-butadiene; 1, 4-pentadiene and its derivatives are mentioned.

Reactive components are those which first form an acid in aqueous solution. These substances react with the alkali in the solvent to produce inorganic or organic salts, which allow them to be separated more efficiently from the source gas. Examples of acidic or reactive components are hydrogen sulfide, carbonyl sulfide, CO ₂ , SO ₂ , mercaptans, hydrogen chloride, hydrogen cyanide, nitrogen oxides and the like.

그리고 알칼리/폴리하이드릭 알콜용액에 의한 수분의 제거는 원료인 공업용 가스중의 수분함량에 영향을 받을 수 있고, 그것은 가스류중의 포화의 한계점까지 나타낼 수 있다(보통 노점.) 수분 흡수(보통 수소결합 메카니즘)를 유도하는 폴리하이드릭 알콜의 흡습성은 알칼리/폴리올용액이 불순물이 포함된 다른 용액과 반응할 수 있는 능력을 감소시키지 않는 것으로 밝혀졌다. 따라서 수분이 평형성분이 되는 반응성분의 반응을 포함한 그런 반응은 용액중에 물이 많이 들어있어도 영향을 받지 않는 것으로 보인다.In testing this process, it was found that even if the source gas contained more moisture than impurities, it was simultaneously raised with the impurities. The mechanism by which water is removed using an alkali / polyhydric solution is considered to be completely different from the mechanism by which small amounts of impurities are removed. The mechanism by which water is removed appears to be due to the wetting nature of the polyhydric alcohols. In addition, the volume of solution can be influenced by

And the removal of water by alkali / polyhydric alcohol solution can be influenced by the water content in the industrial gas as a raw material, which can indicate the limit of saturation in the gas stream (usually dew point). The hygroscopicity of polyhydric alcohols leading to hydrogen bonding mechanisms has not been shown to reduce the ability of the alkali / polyol solution to react with other solutions containing impurities. Thus, such reactions, including the reaction of reactive components with equilibrium of moisture, do not appear to be affected by the presence of large amounts of water in the solution.

It is therefore understood that relatively small amounts of water vapor contained in unreacted gas (during or before the treatment or preparation of the unreacted gas) are removed by the polyhydric alcohol and alkali in the adsorption solution. Similarly, the water generated during the process itself is also removed by the alkaline solution component as indicated above. Thus, the adsorption solution used here is characterized as a "complete non-aqueous" solution during the purge to remove small amounts of impurities from unreacted gases.

Keep in mind that the partial pressure of water vapor maintained in the gas phase is lower than that in the unreacted gas, so that no water will ever penetrate back into the unreacted gas. Representative non-aqueous solutions are obtained by adding alkali or alkaline earth metals to selected liquid polyhydric alcohols (glycerols and glycols of the aforementioned groups). When added to polyhydric alcohols, alkali metals can be added directly (by the addition of sodium running), alkalis or alkaline earth metals can be added in their hydroxide form, or in the form of non-hydride carbonate or bicarbonate or weak inorganic salts. It may also be added in the form. The carbonate form is first hydrolyzed by water with hydroxide prior to alcoholate formation.

Alkali / polyhydric alcohol solutions can be obtained by placing the alkali component in the polyhydric alcohol component and simply mixing until it is a solution of the two components. This can be done at room temperature or at an elevated temperature, i.e. at the temperature at which the alcohol is boiling. In practice the mixing of the two components is affected by temperatures between about 30 ° C. and 250 ° C., preferably between about 40 ° and about 220 ° C. The alkali values supplied to the polyhydric alcohols are present in the form of hydroxides or inorganic weak acids, ie salts of carboxylic acids. Alkali is supplied as hydroxide, carbonate and / or bicarbonate. The most efficient removal of impurities when alkali is used in hydroxide form, but the safest system is when used in carbonate form. Examples of suitable alkalis for use include lithium hydroxide, sodium hydroxide, lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, rubidium hydroxide, lithium carbonate, lithium bicarbonate, cesium hydroxide , Cesium carbonate, cesium bicarbonate, magnesium hydroxide, magnesium carbonate, magnesium bicarbonate, calcium hydroxide, calcium carbonate, calcium bicarbonate, strontium hydroxide, strontium carbonate, barium hydroxide, barium carbonate, barium bicarbonate and the like.

0.5-15 wt.% Of alkali or alkaline earth metal value. By addition of about%, after the reaction, a small amount of liquid polyhydric alcohol (glycerol or glycol of choice) can be made with a satisfactory salt concentration. Increasing the temperature by about 200 ° C causes carbide activity to affect the hydroxides. Alkali in hydroxide form leads to an equilibrium reaction that produces an alcoholate and a small amount of water. It is difficult to determine what such alcoholate contributes to the process of the present invention but it seems certain that it plays an important role in the formation of alcoholate.

In order to develop the design data of the process and to study the characteristics of the column operation, a high pressure test unit plant was set up, in which an oldershaw-type column with a glass diameter of 28 mm and 20 plates was used. The column was attached on a pressure gauge (manufactured by Gergus Sen) for high pressure operation. Raw material gas (ethylene) was heated to a column temperature in a heat exchanger. Another heat exchanger between the circulation pump and the column was used to control the temperature of the liquid entering the column. The caustic alkali / glycol solution was obtained by mixing the required sodium hydroxide with glycol in a mixing tank. The solution is agitated well at 50-70 ° C. It takes about three hours to become a complete solution. This solution is then transferred to the column's reservoir to remove water. The solution was circulated in nitrogen gas and countercurrent at 50 ° C. and 50 psig. Removal of water was continued until the water concentration in nitrogen was lowered below 10 ppm.

Oldershaw columns have three sampling ports for the analysis of incoming and outgoing gases. Gas samples were continuously analyzed for CO ₂ and H ₂ O. In addition, a liquid sample was periodically taken for the measurement of the viscosity. The columns were tested under various operating conditions. In summary:

* Reactant weight percentage is based on the weight of the total solution.

For good gas-liquid contact and stable operation, the gas velocity should not exceed the column overflow rate. The results of calculating the overflow rate for the 5% NaOH / TEG solution are shown in Table 1.

TABLE 1

Overflow rate for older shaw columns

Solution: 5% NaOH / TEG

Gas: C ₂ H ₄

Column diameter: 28mm

* Based on the total area of the tower.

When the column is operated at a pressure of 250 psig or more, the calculation of the overflow speed is about 1.0 ft / sec. The data used in this calculation was obtained from most industrial operations with aqueous solutions and therefore did not include the viscosity of the liquid. Therefore, it is uncertain whether it can be applied to viscous media such as caustic sodium / glycol solution.

The test unit plant was operated with a gas velocity of 0.15-0.30 ft / sec and the operation became unstable when the speed exceeded 0.7 ft / sec. This value is about 60% of the calculated value, indicating that viscosity should be considered in the calculation. In the case of ethylene glycol and triethylene glycol / caustic solution, the single action was good in the indicated operating range.

The results of the CO ₂ removal experiments are shown in Table II.

TABLE II

Removal of CO ₂ by Glycol / Sodium Solution

* Same batch run continuously for 3 weeks.

** Unit of mass.

L / G: flow ratio of liquid to gas

UG: gas velocity through the column

EG: ethylene glycol

TEG: triethylene glycol.

Based on these results, the following conclusions can be drawn.

1. Ethylene glycol and triethylene glycol / caustic mixtures are very effective for CO ₂ removal. Triethylene glycol is preferred because of its low vapor pressure.

2. When the number of columns in the column is 10, the concentration of CO _{2 in} ethylene can be lowered to 0.5 ppm or less. Good gas-liquid contact is maintained.

3. CO ₂ removal is effective when the flow ratio of liquid to gas is as low as 0.05.

4. The 5% NaOH / THG solution flows easily at 40-50 ° C. with good single action. The viscosity of this solution is 110 cps at 40 ° C.

5. After adding a batch of 5% NaOH / TEG solution for 3 weeks and analyzing it, no increase in viscosity was observed and it was contained in Na ₂ CO ₃ solution as a by-product of the reaction.

6. A precipitation device for Na ₂ CO ₃ solids is not present in the column storage but some solids are hung in the liquid filter. The rate of charge seems to be very low.

7. The removal of CO ₂ was effective both before and after the water content of the solution was removed.

A 5% NaOH / T ㄸ G solution was added once and operated continuously for 3 weeks until the CO ₂ concentration at the column outlet began to increase due to a decrease in NaOH content for the total solution. In order to investigate whether the decrease in CO ₂ removal efficiency was due to lack of water in the system or a decrease in NaOH content, it was put in a small TEGfmf liquid reservoir containing 0.1 wt% H ₂ O and operated again. It is shown here that the efficiency of the column is lowered due to a decrease in NaOH content since the CO ₂ removal efficiency is not further improved.

Liquid samples were taken three times for determination of the viscosity during continuous operation. There was no change in viscosity, indicating that dichotolysis and oligomerization do not play an important role. The solution is filtered to remove Na ₂ CO ₃ solids because no noticeable precipitation occurs in the liquid reservoir. This observation is consistent with the calculation of the settling velocity using the Stokes equation. The calculations show that the precipitation rate in a 5% NaOH / TEG solution for one micron diameter of Na ₂ CO ₃ particles is 0.005 ft / day at 40 °. Na ₂ CO ₃ particle sizes from scanning electron microscopy observations ranged from 1-10 microns to mostly smaller sizes. Therefore, the step of filtration for the removal of solids is essential.

In the case of using sodium and lithium as alkali metals to react in-house with selected glycols to make a non-aqueous adsorption solution, the effects of different glycolate loadings on various alkaline earth metal products were tested. The following Tables III and IV show the equivalent weight percentages of strontium hydroxide, barium hydroxide, calcium hydroxide, and CO ₂ loss results for diethylene glycol, respectively, and the theoretical CO ₂ substituted in nine retreatments using these alkaline earth metals. % Is shown.

3 shows non-aqueous reversible CO ₂ removal efficiencies in a system using barium, calcium, sodium, and potassium through nine reprocesses. Potassium-based systems show the best efficiency through all nine operations.

TABLE III

Initial CO ₂ content in various glycolates

Experimental condition: room temperature

CO ₂ pressure units are atm.

Table VI

Reprocessing result of alkaline earth metal glycolate

Experimental condition: room temperature, 1 atmosphere

Reprocess at 200 ℃

Solvent weight = 125 gm.

An apparatus for commercial use of the process of the present invention is shown in FIG. As shown, the contactor may alternatively fill the meselle with a solution of caustic (NaOH) extract through which the gas to be treated passes.

In this process, source gases containing impurities such as CO ₂ , H ₂ O, SO ₂ , H ₂ S, COS and mercaptan are mixed with the non-aqueous solution in a gas-solid contactor. If impurities are needed to be dissolved or reacted and removed in the solution, the purified gas leaving the contactor can be treated to remove trace non-aqueous solution components.

The solution is adjusted according to the amount of raw gas and the amount of impurities in it.

(1) removing the solid that is the product of the reaction, or

(2) purify the used solution or

(3) It can carry out continuously by isolate | separating the used solution and adsorbed impurity. Regulate the introduction of non-aqueous solution preparation into the process to compensate for the removal of any solution by washing or by vaporization or capture into the purge gas. Demisters can also be placed on top of the column to remove large particles. The ethylene gas passing through the demister passes through a filter where it removes glycol particles of submicron size. Depending on the scale, the liquid can be returned to the evaporation process or, in small cases, collected in a drum and withdrawn periodically. An activated carbon stage may be installed after the filter to remove the last trace of TEG from ethylene. At 450 psig and 50 ° C, the TEG concentration in ethylene is less than 0.1 ppm. If the removal of TEG is required below this level, adsorption using activated carbon is necessary.

Double filters may also be used to remove solids from the solution. The solution exiting the filter is divided into two parts. About 20% of the pressure is forced down to 20 psig, followed by an evaporation step, and the remaining 80% is circulated to the top of the adsorber through a circulation pump. When operating the column with 40,000 lbs / hr ethylene per hour, the liquid volume should be around 10 gallon / min. The evaporation process is operated at 100 ° C and 10-20 psig.

1. Reduce the water content of caustic sodium / glycol solution to below 10ppm. This is possible by purifying with nitrogen at 100 ° C.

2. The water in the solution absorbed in the circulation step is removed by continuous purification with nitrogen at 100 ° C. The water content in the incoming ethylene is so small (about 5 ppm) that only a small amount of circulating solution is needed for adsorption. The evaporator should be sized to hold 120 gallons of a 10% NaOH / TEG solution.

The evaporator is equipped with a turbine type stirrer to dissolve the solid caustic sodium in the glycol solution. As NaOH is removed from the system by reaction with CO ₂ , fresh potassium hydroxide must be added. To add solid caustic sodium, the evaporator is forced down, washed with nitrogen, the tank is opened and caustic sodium is added to make the solution 15% NaOH. After the water content of nitrogen is less than 10ppm, the liquid of high concentration gradually becomes mixed with the circulating solution. During the caustic sodium addition step and the water removal step, all liquid leaving the filter is circulated to the column.

Low pressure steam can be used as the heat source for the evaporator, which must be capable of heating the solution to 150 ° C. Table V below shows the various changes of source gas in the test of the process using the sodium and potassium adsorption system.

In the process of the present invention, it can be seen that most of the glycol / glycolate solution is affecting gas purification by lowering the impurity concentration of CO ₂ , COS, and H ₂ S in ppm units.

TABLE V

* Added as 2.9% Na metal

** Liquid flow in the column, 100 g / hr

+ Raw material gas pressure-atmospheric pressure.

The test plant shown in the flow diagram of FIG. 5 shows the process of the present invention. Primary ethylene gas purified from a commercial ethylene plant was passed through a non-aqueous adsorption solution containing 6% sodium hydroxide (94% triethylene glycol) in a non-aqueous scrubber for 56 days. The pressure of the ethylene flowing into the scrubber 30 ℃ was 450 psig. During that period, the incoming CO ₂ concentration ranged from 1-6 ppm and the outflowed CO ₂ concentration ranged from 0.05-0.15 ppm. The incoming amount of ethylene was 30 lb / hr and the flow rate in the scrubber was 0.6 ft / min. On the last day of operation, the scrubber dropped the CO ₂ concentration in the inlet gas from 5.35 ppm to 0.10 ppm.

In the initial experiment of this process, the process of sodium system was tested. At this time, the adsorption solution was added sodium hydroxide, sodium carbonate, or metal sodium to an excess of glycol or glyceride solution and sodium glycol in unreacted glycol or glycerol solvent. You will make a glyceride salt. Adsorption solutions using NaOH and liquid polyhydric alcohols require a filtration process to remove the fine (1-40 micron) Na ₂ CO ₃ solid particles produced by the presence of any moisture from the solution after it is used. do.

Potassium-based systems have many advantages over sodium. In this case, the non-aqueous adsorption solution is potassium glycolate or glycerite obtained by reacting potassium hydroxide or potassium carbonate with a polyol such as glycol and glycerol, for example, glycol and / or glycerol. When potassium carbonate is used as the source of potassium, a thermal activation step is required at about 200 ° C. for the optimization of alcoholate production. Typical examples of continuous operation systems are thermal regeneration systems of glycolate or glycerite using potassium containing solutions used to remove CO ₂ from various source gases. It has already been found that K ₂ CO ₃ dissolved in glycol solution is soluble up to a concentration range of 10 wt% at an appropriate temperature (about 20-25 ° C.). In addition, when this K ₂ CO ₃ continuous solution is heated to 180-200 ° C., K ₂ CO ₃ decomposes to generate CO ₂ and at the same time to generate potassium glycolylate salt. Its reaction scheme is believed to be as follows.

(A)

(A)

Where ROH stands for glycol. Potassium glycolate salts, ROK, are therefore the same kind as originally derived from KOH. In other words,

(B)

(B)

When ROK occurs in the presence of water, H ₂ O is replaced by N ₂ gas and removed from the system through a regenerator because KOH is used as the alkali metal source.

The reaction to remove CO ₂ without water is as follows.

는 과량의 글리콜 용매에 용해되며 또한 180-200℃에서 분해되어 CO₂를 내보내고 ROK로 되돌아오게되어 재 사용이 가능하다. 원료와 함께 미량의 물이 세정기로 들어가면 탄산무기물인 K₂CO₃가 생성될 것으로 보이지만 그냥 고체로 남아있는 Na₂CO₃와는 달라서 K₂CO₃는 용액중에 용해되어 있어서 열을 가해 재생시켜 쓸 수 있다. 따라서 칼륨을 사용하는 잇점으로는 통상의 조작조건하에서는 침전물이 생성되지 않아서 모든 탄산물질은 열분해 되고 세정부분으로 되돌리기전 적당히 식혀주면 재활성된 CO₂를 제거시키는 용액으로 된다.product

Is dissolved in excess glycol solvent and decomposes at 180-200 ° C to release CO ₂ and return to ROK for reuse. When trace amount of water enters the scrubber together with the raw material, it seems that carbon dioxide inorganic K ₂ CO ₃ will be produced, but unlike Na ₂ CO ₃ which remains as a solid, K ₂ CO ₃ is dissolved in solution and can be regenerated by applying heat. have. Therefore, the advantage of using potassium is that no precipitate is formed under normal operating conditions, so that all carbonic acid is thermally decomposed and cooled to a suitable temperature before returning to the cleaning part, thereby removing a reactivated CO ₂ solution.

From this point of view, it is a system that removes CO ₂ that can be regenerated without the need for a filtration device. The KOH-K ₂ CO ₃ / glycol process for CO ₂ removal is based on the use of stable non-aqueous solvents such as triethylene glycol with low vapor pressure and high solubility.

The chemical nature of the KOH-K ₂ CO ₃ / glycol solution is not completely known at present. It does not appear that potassium carbonate is simply physically dissolved in glycol.

Commercially available triethylene glycol (TEG) contains about 0.1 wt% water. Water also occurs in the KOH / TEG reaction. Therefore, if you make glycol or glycerite, the mixture must contain some water. This water is removed before the solution is used. The equilibrium continues to move as water leaves the system during the removal operation. If most of the water is removed from the system, the solution will contain potassium glycolate, unreacted glycols and small amounts of unreacted KOH and / or K ₂ CO ₃ (if used as starting material). In the KOH / glycol solution there is a chemically condensed hydrate with excess glycol, which remains in solution even after the drying step. In order to remove this moisture, a method such as heating or purifying with an inert gas is used. However, the presence of this water is not a weak point of the present invention and the KOH / glycol solution plays a role in water removal. Table V above shows test results of the process of the present invention with varying source gas at NaOH and KOH / solvent system flow rates and operating temperatures used.

From the examples listed above, most of the glycol / glycolate adsorption solutions remove the impurities such as CO ₂ , COS, and H ₂ S from relatively high concentrations to low ppm levels. (Nitrogen or ethylene) shows a great effect.

The use of a potassium system has the advantage of simultaneously purifying CO _{2 and} removing water without generating solids. For ethylene feed gas containing trace amounts of water, this system eliminates the need for a water sorbent and reduces the size of the unit. The ideal application is to remove atmospheric CO ₂ and H ₂ O from air in the production of N ₂ or O ₂ by cold air separation.

The non-aqueous adsorption solution used as mentioned above is regenerated in the recovery process as shown in the flow chart of FIG. Nitrogen gas is used for solution regeneration and heated to 180 ° -200 ° C. to break up the carbonic acid produced in the solution (with carbon dioxide) and to remove CO ₂ and other gaseous impurities along the water vapor.

4 shows a process employing a system that does not produce precipitation of solid carbonate in the adsorption solution. The valves V ₁ and V ₂ in FIG. 4 are opened for the classification of the daily continuous process. For continuous operation, a cooling device is required between the regeneration and storage containers. It is important to keep in mind that the solution must be cooled before being transferred to the reservoir.

The device diagram in this figure is designed for the purification process of ethylene using 6wt% K ₂ CO ₃ in TEG solution. It is optional for this system of nitrogen purge gas to remove developed CO ₂ and other impurities.

Prolonged use of a non-aqueous adsorption solution with sodium produces a fine precipitate of sodium carbonate, which can only be removed using a filtration device. Such fine precipitates aggregate into large chunks and can only be removed from the solution by direct filtration. 5 shows its apparatus.

Non-aqueous scrubbers using NaOH have the disadvantage that, under certain operating conditions, precipitation such as Na ₂ CO ₃ is produced. However, as compared to solid NaOH adsorption systems, a non-aqueous scrubber of NaOH is still advantageous. The K ₂ CO ₃ system has the advantage of being free of solid precipitation and thermally stable compared to the NaOH system. But . K ₂ CO ₃ is only half as efficient as a NaOH system for CO ₂ removal. In other words . The results show that the NaOH system can replace about 42% CO ₂ , while the K ₂ CO ₃ system replaces about 20% CO ₂ .

Table VI shows the results of the CO ₂ removal test using a solution of 3 wt% LiOH dissolved in diethylene, triethylene, and dipropylene glycol. In theory, 5.5 gm of CO ₂ could be adsorbed into 100 gm of 3 wt% LiOH solvent. Based on 5.5 gm of total CO ₂ adsorption, the fraction of CO ₂ substituted in each CO ₂ adsorption / desorption cycle can be theoretically calculated. 3wt% LiOH / diethylene glycol solution through the CO ₂ absorption / desorption process of the step circuit 5 is thus theoretically substituting each party sunhoegwa average theoretical primary CO ₂ and 14.7%. On the other hand, dipropylene and TEG solutions using LiOH showed average substitution rates of 15.7% and 14.3%, respectively. Therefore, from the point of view of CO ₂ substitution, the choice of solution is not considered to be very important. Furthermore, in the VI table, the CO ₂ substitution efficiency is lowered as the CO ₂ adsorption / desorption cycle is repeated regardless of the glycol selection. For comparison, Table VII shows the result of using a non-aqueous diethylene glycol solution using NaOH, K ₂ CO ₃ , and LiOH. In Table VII, non-aqueous scrubbers with NaOH have better chemical efficiencies than scrubbers with K ₂ CO ₃ and LiOH. This result of examining the back was five times circulating CO ₂ each sunhwagwa party NaOH theoretically whereas that replacing the CO ₂ of 42.0% when using K ₂ CO ₃ and LiOH is that replacing the CO ₂ of 19.9% and 17.4%, respectively fact You can see that.

Table VI

Non-aqueous reversible CO ₂ cleaning using 3wt% LiOH in glycol solvent (regeneration temperature 200 ℃)

TABLE VII

Cleaning Efficiency of CO ₂ in Systems Using Na, K, and Li

Claims (1)

Removes trace impurities such as one or more moisture, H ₂ S, CO ₂ , COS, SO ₂ , HCL, HCN, nitric acid, mercaptan, hydrogen, CO, air, nitrogen, oxygen, helium, argon, A method for purifying the impurities from industrial gases of monoolefins having 2 to 5 carbon atoms per molecule, diolefins having 4 to 5 carbon atoms per molecule, paraffin or acetylene, wherein the industrial gases are about 15 and 100. Its hydroxide or inorganic weak acid salt in a liquid aliphatic polyhydric alcohol solution separated from the terminal minimum atom with a carbon-to-oxygen ratio of about 1 to about 5 at a temperature between < RTI ID = 0.0 > A process for purifying unreacted gas, characterized in that it is contacted with a non-aqueous solution containing about 0.5 to 15 wt% of alkali or alkaline earth metal as measured by.

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