RU2040464C1 - Method for production of sulfur from hydrogen sulfide-containing gas - Google Patents

Abstract

FIELD: processing of hydrogen sulfide-containing gases. SUBSTANCE: method for production of sulfur from hydrogen sulfide-containing gases consists in that hydrogen sulfide-containing gas in processed by Klaus method including high-temperature oxidation of initial gas, three-stage catalytic oxidation of obtained gas mixture to separate formed gas sulfur after thermal, first and second catalytic stages of gas mixture cooling and absorption of formed sulfur in the third catalytic stage to which gas mixture is fed with volumetric ratio of SO₂/H₂S = 0,1-0,4 and waste gas containing not more than 0.5 vol. of hydrogen sulfide is directed to the fourth catalytic stage. In so doing, the process in the fourth catalytic stage is effected, either, by direct oxidation of hydrogen sulfide with air oxygen and absorption of formed sulfur, or by chemisorption of hydrogen sulfide by metal oxides taken from group of oxides of zinc, iron and copper. EFFECT: increased yield of elementary sulfur up to 99.9% 9 cl, 1 dwg, 2 tbl

Description

 The invention relates to processes for the processing of hydrogen sulfide-containing gases to produce elemental sulfur and can be used in the purification of hydrogen sulfide from natural gas, gas from oil refining, coal or shale.

A method of processing sulfur-containing gases by the Claus method with a thermal and catalytic three steps [1] In the thermal stage hydrogen sulfide oxidation to sulfur is carried out with atmospheric oxygen at 800-1400 ^{° C,} and in the first and second catalytic stages of the sulfur dioxide contained in the reaction gas mixture , at temperatures of the incoming gas mixture of 250 and 220 ^about C, respectively.

S_n+2H₂O
(1) которая сопровождается побочными реакциями

S_n+2H₂O __→ 2H₂S+SO₂
(2)
S_n+nO₂ __→ nSO₂ __→ где n=2,8
(3)
Основной реакцией в каталитических ступенях является
2H₂S+SO₂

S_n+2H₂O
(4)
Сера, образующаяся в термической и двух каталитических ступенях по реакции (1) и (4), выводится из реакционного газового потока после каждой из этих ступеней за счет конденсации паров серы при 127-160^оС. Перед первой и второй каталитическими ступенями газовая смесь подогревается до необходимой температуры.In the thermal stage, the main reaction proceeds, namely, the direct oxidation of hydrogen sulfide by oxygen
2H ₂ S + O ₂ __ →

S _n + 2H ₂ O
(1) which is accompanied by adverse reactions

S _n + 2H ₂ O __ → 2H ₂ S + SO ₂
(2)
S _n + nO ₂ __ → nSO ₂ __ → where n = 2.8
(3)
The main reaction in the catalytic steps is
2H ₂ S + SO ₂

S _n + 2H ₂ O
(4)
Sulfur formed in the thermal and two catalytic stages according to reaction (1) and (4) is removed from the reaction gas stream after each of these stages due to condensation of sulfur vapor at 127-160 ^о С. Before the first and second catalytic stages, the gas mixture is heated to the required temperature.

The third catalytic stage a gas mixture is supplied after a sulfur condenser temperature ^of 127-130 C without heating and oxidation of hydrogen sulfide to sulfur as well as in the two preceding steps, is carried out with sulfur dioxide contained in the reaction gas mixture, but at a temperature below the dew point sulfur. The resulting sulfur and sulfur vapors contained in the incoming gas are adsorbed in the pores of the catalyst due to capillary condensation. As the catalyst layer is saturated with sulfur, its catalytic activity decreases, and when the sulfur capacity specified for a given catalyst is reached, the spent layer switches to the stage of thermal regeneration [2]
The main disadvantage of this method is that a thermodynamically possible (maximum) sulfur yield of 99.6% is achieved only if the concentration ratio of H ₂ S: SO ₂ 2 is maintained with high accuracy, which is practically impossible and complicates the process. For any other ratio of the concentrations of these components, the stoichiometric excess component passes through the third catalytic stage into the afterburner, thereby reducing the sulfur output and increasing the emission of sulfur dioxide into the atmosphere.

 A technical solution is known that ensures the conversion of all sulfur compounds contained in the reaction gas mixture after the second catalytic step by hydrogenating them into hydrogen sulfide followed by direct oxidation of the resulting gas stream. In this case, the hydrogen sulfide content is significantly higher than 1.0 vol. due to the fact that sulfur vapor and sulfur dioxide are converted to hydrogen sulfide and therefore the process of direct oxidation of hydrogen sulfide is carried out at a temperature above the sulfur dew point and, therefore, hydrogen sulfide and sulfur dioxide generated by reaction (2) will be present in the exhaust gases sulfur after the capacitor, i.e. the sulfur yield will be lower than in the proposed process.

Closest to the proposed method is a method for processing hydrogen sulfide-containing gas, including high-temperature thermal oxidation of the source gas and a three-stage catalytic oxidation of the resulting gas mixture to produce sulfur, in which the oxidation of hydrogen sulfide in the thermal stage is carried out with a lack of air of 2.1-2.5% of stoichiometry, and the reaction gases after the second catalytic stage are sent to the stage of direct oxidation of hydrogen sulfide to sulfur by oxygen according to reaction (1), for which I mix with these gases air and gas mixture is heated to 145-155 ° ^C. Vapors formed sulfur trapped in the condenser at the temperature ≈130 ^{° C} and the gases leaving the condenser are directed into the furnace afterburner to oxidize any remaining sulfur compounds therein to sulfur dioxide [3]
The main disadvantage of this modification of the Klaus process is that, due to a decrease in the air supply to the thermal stage, it is impossible to completely eliminate sulfur dioxide in the reaction gas mixture after the second catalytic reactor, since at the indicated temperature the sulfur formed is in the gas phase, and taking into account the reversibility of the reaction ( 4) in the reaction gas mixture contains SO ₂ . Therefore, the gas mixture entering the direct hydrogen sulfide oxidation reactor contains two oxidizing agents: in addition to dosed oxygen, it also contains sulfur dioxide about 20% of the residual hydrogen sulfide. Thus, competing reactions take place in the direct oxidation reactor: the reversible Klaus reaction (4) and the practically irreversible direct oxidation of hydrogen sulfide (1) with the common reaction product sulfur. As a result, both hydrogen sulfide and sulfur dioxide are present at the outlet of the direct oxidation reactor. The sulfur yield in this embodiment of the Klaus process does not exceed 99.2%
The basis of the invention is the task of increasing the yield of elemental sulfur to 99.9% and a corresponding reduction in toxic emissions of sulfur dioxide in the atmosphere.

The problem is solved by the method of producing sulfur from a hydrogen sulfide-containing gas according to the Klaus method, including high-temperature oxidation of the source gas, three-stage catalytic oxidation of the obtained gas mixture with the release of the formed gas sulfur after the thermal, first and second catalytic stages by cooling the gas mixture and with the adsorption of sulfur formed in the third catalytic stage , to which the gas mixture is supplied with a volume ratio of SO ₂ / H ₂ S of 0.1-0.4, and exhaust gases containing not more than 0.5 vol. hydrogen sulfide, sent to the fourth catalytic stage.

When implementing the proposed method, these conditions at the third and fourth stages are supported either by supplying a gas mixture with a volume ratio of H ₂ S / O _{2 of} 2.1-2.5 to the stage of thermal oxidation, or by supplying a gas mixture to the first catalytic stage with a volume ratio H ₂ S / SO ₂ 2,1-2,7 or to the second catalytic stage with a volume ratio of H ₂ S / SO ₂ 2,1-3,0, or by filing 0.5-2 vol. source gas before the third stage of catalytic oxidation.

The third stage catalytic oxidation is carried out in the presence of catalytic Claus reaction based on aluminum oxide or titanium and / or active carbon with its periodic regeneration purge gas heated at 300-350 ° ^C.

The implementation of the proposed method at the fourth catalytic stage is carried out by one of the following two options:
1. Direct oxidation of hydrogen sulfide with atmospheric oxygen with adsorption of the sulfur formed, for which purpose air is additionally introduced into the gas mixture in front of this stage in an amount providing a volume ratio of O ₂ / H ₂ S 0.5-5.0, and the process is carried out on active carbon with adsorption of the formed sulfur and with periodic regeneration by blowing it with a heated gas not containing oxygen, at 300-350 ^о С.

 Periodic regeneration of the sorbent catalysts of the third and fourth stages can also be carried out with the initial hydrogen sulfide-containing gas, which is then supplied to the thermal stage.

2. Chemisorption of hydrogen sulfide by metal oxides selected from the group of metal oxides of zinc, iron and copper, with periodic regeneration of saturated chemisorbent by blowing gases heated to 400-450 ^о С containing 3-6 vol. oxygen. In this case, the generated regeneration gases are returned to the thermal stage.

 The combination of claimed techniques allows the Klaus process to a total sulfur output of 99.9%, which, accordingly, reduces the amount of harmful emissions into the atmosphere.

The advantage of the proposed method is that the sulfur yield of 99.9% is achieved at the installation when changing these parameters within the specified limits. Moreover, the regulation of H ₂ S / O ₂ ratios in the thermal stage or H ₂ S / SO ₂ in the catalytic steps is not carried out at fixed values of these quantities, but in the indicated intervals, which is easily technically feasible.

 PRI me R. Two cases of the implementation of this invention for the processing of acid gases characteristic of the gas processing and oil refining industries are given.

1. The composition of the source gas, vol. H ₂ S 50.0; CH ₄ 0.5; H ₂ O 4.0; CO ₂ 45.5. The volumetric flow rate of the source gas is 50,000 nm ³ / h. Inlet gas pressure 1.6 ata.

2. The composition of the source gas, vol. H ₂ S 95.0; C ₂ H ₆ 1.0; H ₂ O 4.0. The volumetric flow rate of the source gas of 3000 nm ³ / h Inlet gas pressure 1.6 ata.

 The results of the balance calculations of the installation for the production of elemental sulfur for each composition of the source gas, confirming the achievement of the goals and the feasibility of the proposed method, are presented in table. 1 and 2. Consider the description of the processes and parameters of the modes of the installation for the production of elemental sulfur from hydrogen sulfide-containing gas using the first composition of the initial gas as an example.

 The installation diagram is presented in the drawing.

In accordance with the technology of the invention the initial hydrogen sulfide-containing gas, mixed with oxygen, is supplied to the furnace reactor generator 1, combined with a heat recovery boiler 2. In the furnace at ^about 905 C causes partial combustion of hydrogen sulphide to form sulfur dioxide and elemental sulfur, which is condensed with sequential cooling of the gas stream in a recovery boiler 2 to 300 ^{° C} and in the condenser 3 to 170 ^o C.

In the first catalytic stage acid gas is mixed with cooled air and is directed to the furnace-heater 4, where the combustion gas and heating the reaction to 250 ^C. The heated reaction gas enters the catalytic reactor 5 in which at 347 ^{° C} the process proceeds elemental sulfur formation according to reaction (4). Then the reaction gas is cooled to 160 ^° C and the sulfur formed is condensed in the condenser 6.

The second stage catalyst similar to the first catalytic reaction stage gas is heated to 230 ^{° C} in the furnace-heated preheater 7. Then, the gas enters the catalytic reactor 8, where at 257 ^{° C} proceeds the process of formation of elemental sulfur according to reaction (4). In the boiler-economizer 9, the reaction gas is cooled to a temperature of ≈130 ^о С and the sulfur formed condenses.

 At the third catalytic stage, the cooled reaction gas sequentially passes the catalytic reactor 10, in which elemental sulfur is formed during the interaction of hydrogen sulfide and sulfur dioxide by reaction (4), and then the reaction gases are mixed with a metered amount of oxygen and sent to the fourth catalytic stage (reactor 11) , in which the process of "direct" oxidation of hydrogen sulfide proceeds with the production of elemental sulfur according to reaction (1). Both catalytic reactors 10 and 11 operate at temperatures below the sulfur dew point. As a result, all sulfur formed by reactions (1) and (4) is adsorbed in the catalyst bed, gradually deactivating it.

 Upon reaching the maximum sulfur intensity of the catalysts, the reactors 10 and 11 are switched to thermal regeneration mode. The ultimate sulfur intensity is determined by the porous structure of the catalyst used.

 The remaining reaction gases after the reactor 11 are sent to the afterburner, and then released into the atmosphere.

 In the catalytic reactors 5, 8, 10, Klaus process catalysts based on active alumina are used and in the reactor 11 is activated carbon of the AG-2 grade.

 Similarly, the calculation of the installation for the production of elemental sulfur for the second composition of the source gas, the results of which are presented in table. 2.

1

100%
(5) где S_вых количество сернистых соединений в пересчете на серу в выходном газовом потоке, поступающем в печь дожига; S_вх количество сероводорода в пересчете на серу, поступающего на установку.The total sulfur yield by the proposed method is determined by the formula
EXIT S

1

100%
(5) where S _{o is the} amount of sulfur compounds in terms of sulfur in the outlet gas stream entering the afterburner; S _{in the} amount of hydrogen sulfide in terms of sulfur entering the installation.

1

100% 99,98 (первый состав)
^{ВЫХОД S =}

^-

^{= 99,97 (второй состав)}
т.е. составляют более 99,9 против 99,2% в прототипе. При этом значения избыточного содержания сероводорода перед четвертой ступенью, равные 0,455 и 0,11 об. получаемые при переработке первого и второго составов исходного кислого газов соответственно, практически полностью охватывают предлагаемый диапазон избытка сероводорода 0,1-0,5 об. и обеспечивают высокий выход серы и снижение вредных выбросов в атмосферу по предлагаемому способу.The sulfur yield values of the proposed method for the first and second compositions of the source gas are equal
EXIT S

1

100% 99.98 (first composition)
^{OUTPUT S =}

^-

^{= 99.97 (second composition)}
those. make up more than 99.9 against 99.2% in the prototype. Moreover, the values of the excess hydrogen sulfide content before the fourth stage, equal to 0.455 and 0.11 vol. obtained by processing the first and second compositions of the initial acid gas, respectively, almost completely cover the proposed range of excess hydrogen sulfide of 0.1-0.5 vol. and provide a high sulfur yield and reduction of harmful emissions into the atmosphere by the proposed method.

Claims (9)

1. METHOD FOR PRODUCING SULFUR FROM HYDROGEN-SULFUR-CONTAINING GAS according to the Klaus method, including high-temperature oxidation of the source gas, three-stage catalytic oxidation of the obtained gas mixture with evolution of the generated sulfur sulfur after the thermal, first and second catalytic steps by cooling the gas mixture and with the adsorption of the formed sulfur on the third characterized in that in the third catalytic stage a gas mixture is fed in a volume ratio sO ₂ / H ₂ S 0,1 0,4, and waste gases containing not used Lee 0.5. hydrogen sulfide, sent to the fourth catalytic stage. 2. The method according to claim 1, characterized in that the said conditions in the third and fourth steps are maintained by supplying a gas mixture with a volume ratio of H ₂ S / O _{2 of} 2.1 2.5 to the thermal oxidation step. 3. The method according to claim 1, characterized in that the conditions in the third and fourth stages are supported by supplying the gas mixture to the first catalytic stage with a volume ratio of H ₂ S / SO _{2 of} 2.1 - 2.7 or to the second catalytic stage at volume ratio of H ₂ S / SO ₂ 2.1 3.0.  4. The method according to p. 1, characterized in that the said conditions at the third and fourth steps are supported by supplying 0.5 to 2 vol. source gas before the third stage of catalytic oxidation. 5. The method according to claims 1 to 4, characterized in that the third stage of catalytic oxidation is carried out in the presence of a Claus reaction catalyst based on aluminum or titanium oxides and / or activated carbon with its periodic regeneration by blowing with a heated gas at 300 350 ^o C. 6. The method according to claims 1-5, characterized in that an oxygen-containing gas (air) is additionally introduced into the gas mixture before the fourth stage in an amount providing a volume ratio of O ₂ / H ₂ S 0.5 to 5.0, and the process is carried out on activated carbon with adsorption of the formed sulfur and with periodic regeneration by blowing it with a heated gas that does not contain oxygen, at 300 350 ^o C.  7. The method according to PP.5 and 6, characterized in that the periodic regeneration of the sorbent catalysts of the third and fourth stages is carried out with the initial hydrogen sulfide-containing gas, which is then supplied to the thermal stage.  8. The method according to PP. 1-5, characterized in that the process at the fourth stage is carried out in the presence of a chemisorbent selected from the group of metal oxides: zinc, iron and copper. 9. The method according to claim 8, characterized in that the regeneration of the chemisorbent is carried out by blowing heated to 400 450 ^o With a gas containing 3 to 6 vol. oxygen, and the resulting regeneration gases are fed into the thermal stage.

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