Process for cleaning a gas stream

[Detailed Description of the Invention]

The gas air current by which the present invention was made impure with at least 2 carbon monoxide and hydrogen sulfide, It sanctifies by alternative acidic gas washing for hydrogen sulfide, and takes out the first waste gas by which hydrogen sulfide was condensed from now on, It is related with the cleaning method of the gas air current which hydrogenates the second waste gas containing at least 2 carbon monoxide and the sulfuric compound which supply sulfur recovery and arise in the case of sulfur recovery, and it returns to acid washing after that. A process often required when processing a raw gas style is separation of acidic gas. In most, carbon dioxide, hydrogen sulfide, sulfuration carbon monoxide, hydrogen cyanide, and mercaptan are expressed as acidic gas. Carbon dioxide and hydrogen sulfide are contained in the gas air current at most frequent and, general very high concentration among the compounds which should be avoided from the device which was touched also from the substance or other reasons of these for the corrosive action or a catalyst damage operation in the back. as the example of such a gas air current -- natural gas and cracked gas -- and hydrogen content mixed gas is pointed out especially. For example, in order to build hydrogen richness mixed gas which is used as hydrogenation, ammonia synthesis, methanol synthesis, and other material gas mixtures for composition, crude oil, oil refinery residual substance oil, coal, or a similar carbon content substance is usually left nowadays. Oxidization thermal decomposition using oxygen is performed in the temperature raised to these materials that contain sulfur in many cases, and the heightened pressure. The mixed gas which mainly consists of hydrogen, a carbon acid ghost, hydrogen sulfide, the nitrogen of a trace, argon, and methane exists after separation of a detrimental constituent like carbon, tar, naphthalene, higher hydrocarbon, and water. When it is the object to build the materials mixture for oxo processes, i.e., the synthesis gas which mainly consists of carbon monoxide, from this gas, acidic gas is immediately removed from this gas. When obtaining the gas which mainly consists only of hydrogen, for example, hydrogen for hydrogenation, and the materials mixed gas for ammonia synthesis unlike this is meant, Conversion which uses vapor for the carbon monoxide contained in gas for the time being is performed, and, as a result, carbon monoxide oxidizes to carbon dioxide, and also hydrogen forms. Since mercaptan and sulfuration carbon monoxide which are contained by the case in raw gas are fully returned in such conversion and it becomes hydrogen sulfide, the acidic gas which should be succeedingly removed from this gas actually consists only of carbon dioxide and hydrogen sulfide. in separating acidic gas from raw gas, hydrogen sulfide differs from carbon dioxide -- the toxicity sake -- environment -- completely -- or since it must be cautious of the ability to emit only at very slight concentration, in the device which was usually touched in the back, post-processing of these ingredients is carried out to element-like sulfur. However, since it is only considered in a sulfur recovery unit to environment that harmless carbon dioxide is the ballast which is not only preferred, in order to remove these acidic gas from a gas air current, alternative washing to hydrogen sulfide acts extensively. it is this method -- the Remaining gas air current of the carbon dioxide content which does not contain hydrogen sulfide with the gaseous convection containing some carbon dioxide separated by hydrogen sulfide richness at the time of reproduction of Is a cleaning agent can arise, and it can emit this into the atmosphere directly. By a case, pure carbon dioxide can also be isolated from this gas air current for other purposes of use. For selective separation, the chemical cleaning method and the physical cleaning method are developed. When sanctifying the gas air current especially made impure comparatively strongly with carbon dioxide, a physical cleaning method is used advantageously extensively several years before. In this case, the cleaning fluid used can dissolve an acidic gas ingredient without chemical combination, and can remove it again by expansion, heating, and/or distillation after this. In order to separate carbon dioxide and hydrogen sulfide especially, it was proved that especially the methanol that may dissolve remarkable acidic gas at the polar organic solvent, among these a temperature especially lower than 0 degreeC is suitable. By the hydrogen sulfide content of the gas air current which should be sanctified, the amount of [ which arises in alternative washing to hydrogen sulfide / which hydrogen sulfide concentration increased ] Remaining gas drawing usually contains 10~70 mol of hydrogen sulfide %, for example, it processes it to element-like sulfur in the sulfur recovery unit by the Clowes reaction. For the purpose, Clowes reaction: 2H₂S+SO₂->3S+2H₂O In order are alike and to build the suitable gas used, it is required to oxidize to sulfur dioxide in some hydrogen sulfide. This kind of method is indicated to for example, the "hydrocarbon process Thing" (Hydrocarbon Processing) April, 1973 item and the 107th page. The fault of the sulfur recovery by the Clowes reaction is observed in the point which a sulfuric compound and the waste gas which contains hydrogen sulfide and sulfur dioxide especially always produce rather than has perfect conversion to element-like sulfur. Although post-processing of most sulfuric compounds separated from the gas air current is carried out to element-like sulfur in the sulfur recovery by the Clowes reaction, the sulfuric compound contained in waste gas is found out at the concentration forbidden in addition when discharge to the atmosphere is many. For this reason, in order to further sanctify this waste gas, many methods are already developed, but the fault that investment expense is high is all inherent in these methods. Such a method is indicated to for example, the "hydrocarbon process Thing" April, 1973 item and 11th page ~ the 116th page. Therefore, the subject which makes the bottom of the present invention is forming the method of the form described first so that discharge of the sulfuric compound from the waste gas of the sulfur recovery unit in the atmosphere may decrease at the slightest possible expense. Therefore, the possible method of simplifying device expenses and actually obtaining sulfur completely by the shape of an element is proposed. In the method proposed as compared with additional different-species washing like the process of the daily use for sanctifying waste gas, for example, amine washing, a contact target, or the adsorption method, a hydrogenation process is only required. The waste gas which arises with liquefied sulfur in a sulfur recovery unit mainly contains hydrogen sulfide, sulfur dioxide, and carbon dioxide. Before returning this waste gas to acidic gas washing, hydrogenation is required, but failure occurs in alternative washing which was met with in the front, and it can attribute this to a sulfur dioxide content above all. After changing into hydrogen sulfide of the sulfur dioxide between hydrogenation, in alternative washing, hydrogen sulfide is separated from the gas returned to acidic gas washing. Although hydrogen sulfide and the carbon dioxide of a small part are anew supplied to sulfur recovery together with the waste gas of washing, the ballast gas which mainly consists of carbon dioxide is emitted together with the carbon dioxide separated as a part for the drawing which does not have sulfur at the time of acidic gas washing. In a described method, since the waste gas containing a sulfuric compound which arises in the case of sulfur recovery is returned to a method and it does not flow out of a device, it is considered that it is another advantage of a described method that it is not necessary to design sulfur recovery so that the sulfur yield greatest by only one passage may be obtained. Although it strives for the method of daily use by the Clowes reaction to obtain more yield than 99%, in a described method, a good result is already obtained by sulfur yield of about 85~95% which can be attained in the Clowes device of for example, two processes or three processes. If sulfur recovery is designed to such yield in one passage that decreased, as compared with the device by the publicly known method, a sulfur recovery unit will be remarkably made cheap. Compensation [ by saving in sulfur recovery / enough ] in this excess expense, although the waste gas which arises in large quantities in slight sulfur yield actually produces a fixed expansion of a device portion by which waste gas is returned -- it is divided. In each case, an advantageous conversion rate and the quantity of return gas which arises in this case are clear from the conditions of a method and a selected form of acidic gas washing which exist each time. The waste gas which arises in the case of sulfur recovery exists, for example in the pressure of 1.2~5 bars under usually comparatively low pressure. Therefore, since the raw gas style which should be sanctified arises by usually high pressure, it needs compression to return the hydrogenated waste gas. The amount of return of the hydrogenated waste gas does not need to mix with the gas air current which should be sanctified unconditionally. Rather, it can also take into consideration returning to the regenerating section of acidic gas washing in many cases. This is possible when carrying out using the detergent which has solubility which is different to hydrogen sulfide and carbon dioxide in for example, acidic gas washing and which acts physically, for example, methanol. In such a cleaning method, acidic gas washing has a regenerating section which has a hydrogen sulfide concentration stage, and a Noodle gas phase is separated from the detergent loaded all over the hydrogen sulfide concentration stage as carbon dioxide is [ not having hydrogen sulfide and ] thick. The first ingredient for the detergent containing all the hydrogen sulfide which was partially reproduced about carbon dioxide and was separated in addition to dissolve in the reproduction which follows is removed completely. When applying such a cleaning method, in one example of the present invention method, it is advantageous to introduce the hydrogenated waste gas all over the hydrogen sulfide concentration stage, and to separate the great portion of carbon dioxide here. Since such a hydrogen sulfide concentration device is operated by slight pressure more remarkable than the cleaning equipment of raw gas as compared with returning this method into the gas air current which should be sanctified, it has the advantage that energy expenditure required for compression of the hydrogenated waste gas decreases. When returning the waste gas hydrogenated in this case into the gas air current which should be sanctified, since the waste gas hydrogenated anyway is washed away and goes into a regenerating section, it means the additional load of a washing tower. The present invention method is enforced using the detergent of the physical action which has solubility which is different to hydrogen sulfide and carbon dioxide in acidic gas washing, Including the regenerating section in which acidic gas cleaning equipment has a washing section and a hydrogen sulfide concentration stage, it returns to the hydrogen sulfide concentration stage, and the second hydrogenated waste gas is all over the hydrogen sulfide concentration stage, Stripping is performed at the same time it condenses hydrogen sulfide under reverse washing which uses the detergent partially loaded from the washing stage. In described physical washing, before supply all over the hydrogen sulfide concentration stage, large Listen expansion of the loaded detergent which is picked out from cleaning equipment under high pressure is carried out. in this case, the easy-volatility ingredient which dissolved into the detergent -- gas -- an intermediary outflow is carried out. In this case, when sanctifying a hydrogen content gas air current, a hydrogen richness gas phase forms, and after re-compression, this gas phase is returned into a gas air current, and is usually anew introduced into cleaning equipment. In other examples of the present invention, in such a method, the partial style of the hydrogen content gas phase which arises in the case of expansion branches, and it is used as hydrogenation gas for hydrogenating the waste gas of sulfur recovery. In other examples of this method, a part of gas air current by which hydrogen content was sanctified for hydrogenation can be used. As already stated first, in the case of a hydrogen richness gas air current device, carbon monoxide conversion is often connected especially. In such a case, it is advantageous to mix with the gas air current which should be hydrogenated by the present invention and which should supply the waste gas from sulfur recovery to carbon monoxide conversion directly, and to let it pass to this reaction zone. Since this conversion advances under the condition by which waste gas is hydrogenated, in this case, it can exclude an additional hydrogenation device. While returning to carbon monoxide conversion, returning to other reaction processes that hydrogenation of waste gas is performed is also considered. Then, for example, as long as the process for the gas air current manufacture which should be sanctified of starting is established, returning to coal or petroleum gas-ization is also possible. Other details of the present invention method are explained below per [ which was sketched on the drawing ] example. In the example shown in Drawing 3, the raw gas obtained by hydrogen richness raw gas, for example, partial oxidization, and following carbon monoxide conversion is Arrival(ed) by lead pipe 17, after mixing with return gas by 18, is introduced into heat exchanger 19 and cooled by low temperature, for example, the temperature of -20~-40-degreeC, here. In order to prevent the ice formation by the vapor contained in the gas air current in the case of cooling before cooling of a gas air current, a small amount of methanol is injected by lead pipe 20. The condensation liquid which formed the cooled gas in separation machine 21 at the time of cooling, the water contained mainly in raw gas, and heavy hydrocarbon are separated. Subsequently, the cooled gas air current goes into the lower part of washing tower 23 by lead pipe 22. Washing of a gas air current is carried out in this special example all over washing tower 23 which has two different portions. From the tower top part of a washing tower, the pure methanol reproduced by lead pipe 24 is supplied as a detergent. Thereby, in the upper part of a washing tower, refining of gas is performed and the trace of the last of acidic gas dissolves into methanol in that case. The methanol which flows down by Countercurrent to the gas air current going up absorbs the great portion of carbon dioxide contained in the gas air current. In this case, in order to derive the large heat of solution which occurred, methanol is cooled with a refrigerant in condensator 25. The hydrogen sulfide which partial style 26 of this methanol beforehand loaded with carbon dioxide was supplied to the lower part of washing tower 23, and was contained in raw gas is separated. Since slight generation of heat of methanol only occurs by washing away of the carbon dioxide contained by hydrogen sulfide and the case in the gas air current, at this process, cooling is not required. The raw gas with which hydrogen sulfide and carbon dioxide were removed for the time being by washing tower 23 on the flow way is taken out from the tower top part of washing tower 23 by lead pipe 27, After heat-exchanging with the gas air current which should be cooled in heat exchanger 19 and which is not sanctified and being heated, it is taken out from the portion the device was considered to be as sanctified hydrogen. The methanol ball and methanol in which hydrogen sulfide and carbon dioxide were loaded into the bottom part of washing tower 23 are taken out by lead pipe 28, and after they expand in valve 29, they are introduced into separation machine 30. The hydrogen richness gas phase which arises in the case of expansion is led to compressor 33 by lead pipes 31 and 32, is re-compressed into the pressure of the gas air current which should be sanctified here, and is mixed by 18 by the happiness-in-the-next-life gas stream which took out heat of compression in the back condensator. The ingredient which the methanol on which it was taken out by lead pipe 34 and carbon dioxide was loaded by the method of Suitableing expands in valve 35 from the upper part of washing tower 23, and it emits in this case in separation machine 36 is separated. A gas phase goes into lead pipe 32, and is returned into raw gas together with a part for the gas drawing from separation machine 30. The methanol loaded with hydrogen sulfide and carbon dioxide which arise in separation machine 30 is supplied to the central part of hydrogen sulfide concentration tower 38 by lead pipe 37. Some carbon dioxide which dissolved in methanol all over this tower is separated by stripping by nitrogen. For this reason, nitrogen is supplied to the lower part of a hydrogen sulfide concentration tower by lead pipe 39. In order to prevent that hydrogen sulfide flows out of the tower top part of hydrogen sulfide concentration tower 38, methanol from separation machine 36 loaded on the tower top part of tower 38 by lead pipe 40 with carbon dioxide is supplied. This methanol loaded partially works as a detergent to the hydrogen sulfide separated by stripping, As a result, the gas air current which does not have sulfur by lead pipe 41 is taken out from the tower top part of tower 38, and it mainly consists only of carbon dioxide and nitrogen, and after the gas air current heat-exchanges with the gas air current which should be sanctified in heat exchanger 19 and heated, it can be emitted to environment. The methanol which arises in the bottom part of hydrogen sulfide concentration tower 38 contains some of all the hydrogen sulfide separated from the gas air current, sulfuration carbon monoxide contained by the case in the gas air current, and washed-away carbon dioxide. This methanol is taken out by lead pipe 42, is fed into following regeneration tower 44 with pump 43, is heat-exchanged with the reproduced methanol which is cooled in heat exchanger 45 before supply all over a regeneration tower, and is heated. The ingredient which is dissolving in addition into methanol all over a regeneration tower starts running with methanol vapour. In order to build methanol vapour, heating device 46 which operates with steam in the lower part of regeneration tower 44 is formed. Methanol vapour is again condensed with cooling device 47 by the tower top part of a tower, and the ingredient only separated from methanol by lead pipe 48 as a result is taken out. The refined methanol which arises in the bottom part of a regeneration tower is taken out by lead pipe 49, with pump 50, it passes along heat exchanger 45 for the time being, is succeedingly fed into lead pipe 24, and is anew supplied to washing tower 23. The partial style of the reproduced methanol is introduced all over another separation tower 53 through lead pipe 52 with pump 51, and the water contained in addition in the methanol reproduced in this is separated. The condensation liquid separated from the gas air current which should be sanctified in separation machine 21 all over this separation tower 53 is also introduced. For this reason, condensation liquid is Arrival(ed) by lead pipe 54, in heat exchanger 55, is heat-exchanged with methanol, is heated, and expands to the pressure of separation tower 53 in iris diaphragm valve 56. The condensation liquid which expanded is introduced into upper part 57 of tower 53 constituted as a separation machine. The ingredient emitted at the time of expansion is taken out by lead pipe 58, and is introduced all over regeneration tower 44. The condensation liquid which remains pours in all over tower 53 by lead pipe 59. The methanol from which water was removed is taken out by lead pipe 60, and after being cooled in heat exchanger 55, it is supplied into the upper part of regeneration tower 44. The separated water is taken out from the bottom part of separation tower 53 by lead pipe 61. The amount of [ which is taken out from the tower top part of regeneration tower 44 by lead pipe 48 ] drawing contains some of hydrogen sulfide separated from the gas air current, and separated carbon dioxide. A part for this drawing is introduced into sulfur recovery unit 62 by the Clowes reaction. In order to build sulfur dioxide required for the Clowes reaction, an oxygen containing gas air current is supplied to the partial combustion equipment of hydrogen sulfide by lead pipe 63. Since combustion is introduced into a device [ amount / by nitrogen / of inactive gas / remarkable ] in the case of combustion with air, combustion is advantageously carried out using oxygen. The element-like sulfur built in the sulfur recovery unit is liquefied, and is taken out by lead pipe 64, and the waste gas air current which contains carbon dioxide, hydrogen sulfide, and sulfur dioxide in most by lead pipe 65 produces it. This waste gas is hydrogenated in hydrogenation process 66 which was touched in the back. Hydrogen required for hydrogenation is a partial style of the hydrogen content gas which Arrival by lead pipe 67 and is taken out from separation machine 30 by lead pipe 31. Hydrogenation device 66 of the waste gas from sulfur recovery unit 62 is provided with the heat exchanger in order to obtain required reaction temperature by Then and a case with a contact reaction machine, and in order to cool the gas after hydrogenation which reacted. Especially this hydrogenating method for working at the temperature of the waste gas which arises by lead pipe 65 mostly is advantageous. The temperature of the waste gas of the Clowes device is usually about 150degreeC. The hydrogenated waste gas is supplied to compressor 69 by lead pipe 68, and, thereby, is compressed into the pressure of hydrogen sulfide concentration tower 38. The waste gas hydrogenated after removal 71 of the water formed at the time of compression, derivation 70 of heat of compression, and hydrogenation is supplied to the lower part of hydrogen sulfide concentration tower 38. The gas which consists of other inactive gas, for example, nitrogen, by carbon dioxide and a case passes through tower 38, and is taken out from a tower top part by lead pipe 41. After [ most ] hydrogenation consist only of hydrogen sulfide, and the sulfuric compound contained in waste gas is washed away with the methanol which flows down all over tower 38 and which was loaded partially, is anew taken out from the bottom part of tower 38, and is returned into back sulfur recovery unit 62 by which post-processing was further carried out all over tower 44. In one example of the present invention method according to Drawing 1, The gas air current containing 7.7 ppm of 6.43 mol of hydrogen % and 2.8 mol of inactive gas (nitrogen, carbon monoxide, argon, methane) % and 32.3 mol of carbon dioxide % and 0.65 mol of hydrogen sulfide % and second-class-ized carbon obtained by partial oxidization and following carbon monoxide conversion is sanctified. This gas air current is Arrival(ed) under temperature 36degreeC and the pressure of 75.6 bars by lead pipe 17. The remainder consists of nitrogen and very a small amount of hydrogen. Gas is taken out by C with a temperature of 25 degrees about 1.5 bars pressing-down power, is introduced into the Clowes device, and post-processing is carried out to element-like sulfur. By lead pipe 65, the waste gas by which carbon dioxide and 3.4-mol % consist of nitrogen in 93.9-mol % flows out of the Clowes device 62. As for the sulfuric compound and the deer, this gas is made impure at 1.8 mol of hydrogen sulfide % and 0.9 mol of sulfur dioxide %. Therefore, in hydrogenation device 66, it is changed by the hydrogenation gas which consists of 61.8 mol of hydrogen % and 5.5 mol of inactive gas % and 32.4 mol of carbon dioxide % and 0.3 mol of hydrogen sulfide % and 3 ppm of carbon oxide sulfides. Finally, the quantity of hydrogenation gas is about 5% of the gas air currents which should be hydrogenated. The Clowes waste gas which passes by temperature of about 150 degreeC along a hydrogenation device arises in 0.3 mol of hydrogen % and 3.7 mol of inactive gas % and 93.4 mol of carbon dioxide % and 2.6 mol of hydrogen sulfide% of composition, and is returned all over hydrogen sulfide concentration tower 38. In this example, the Clowes device of three processes of having sulfur yield of 95% was formed. In other examples, recovery of sulfur is carried out in two steps of Clowes devices which have yield of 85%. From now on, the waste gas volume containing 3.3 mol of nitrogen % and 89.2 mol of carbon dioxide % and 5.0 mol of hydrogen sulfide % and 2.5 mol of sulfur dioxide % high about 18% will be obtained. This waste gas reacts to the hydrogenation gas volume which reaches about 13% of waste gas volume, and the return gas containing 0.7 mol of hydrogen % and 3.8 mol of inactive gas % and 88.4 mol of carbon dioxide % and 7.1 mol of hydrogen sulfide % produces it by this. In the case of the first example, in the case of the second example, the quantity of the hydrogenated waste gas which is returned to a syringe reaches to about 1.5% about 1.3% of the gas air currents which should be sanctified.

[Brief Description of the Drawings]

Drawing 1 is a flowchart of one example of the present invention method. 19 ...... A heat exchanger, 21 ...... A separation machine, 23 ...... A washing tower, 25 ...... A condensator, 29 ...... An expansion valve, 30 ...... A separation machine, 33 ...... A compressor, 36 ...... A separation machine, 38 [ ...... A heat exchanger, 46 / ...... A heating device, 47 / ...... A cooling device, 53 / ...... A separation tower 62 / ...... A sulfur recovery unit, 66 / ...... Hydrogenation device. ] ...... A hydrogen sulfide concentration tower, 43 ...... A pump, 44 ...... A regeneration tower, 45