JP2004345904A - Method and apparatus for recovering sulfur - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for recovering sulfur in which the quantity of a sulfur compound to be discharged in the start and the stop of the operation is reduced. <P>SOLUTION: In the sulfur recovering method for recovering and removing sulfur from a hydrogen sulfide-containing gas using the apparatus provided with a sulfur recovering part 110 and a tail gas treating part 111, a hydrogenation reaction gas in the tail gas treating part is circulated and supplied to a reaction combustion furnace 2. In the sulfur recovering part 110, the hydrogen sulfide-containing gas and an oxygen-containing gas are introduced into the reaction combustion furnace 2 to be subjected to a thermal Claus reaction, the reaction gas is cooled to separate elementary sulfur, the cooled gas after sulfur is removed is heated again to be subjected to a catalytic Claus reaction and the reaction gas is cooled to further separate elementary sulfur. In the tail gas treating part 111, gaseous hydrogen is added into the tail gas discharged from the sulfur recovering part to convert the sulfur compound in the tail gas into hydrogen sulfide by the hydrogenation reaction and the hydrogen sulfide is absorbed and removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method and an apparatus for recovering elemental sulfur by treating a hydrogen sulfide-containing gas (hereinafter, referred to as an acid gas) by the Claus method, and more specifically, an amount of sulfur compounds emitted at the start and stop of operation. The present invention relates to a sulfur recovery method and a sulfur recovery apparatus effective for reducing air pollution and preventing air pollution.
[0002]
[Prior art]
The Claus-type sulfur recovery device is a device that recovers a sulfur atom contained in hydrogen sulfide as elemental sulfur by a partial oxidation reaction from an acid gas as a raw material, and is mainly used in a refinery and a natural gas processing plant. Since the sulfur recovery rate is usually 95 to 98%, in order to prevent air pollution, a tail gas treatment section is installed in the downstream stream to increase the sulfur recovery rate to 99.9% in many cases. As the tail gas treatment unit, a hydrogen sulfide recycling type process of converting a sulfur compound in the tail gas into hydrogen sulfide by a catalytic reaction represented by the Scott method and then absorbing and removing the hydrogen sulfide with an amine solution has been widely adopted ( For example, see Patent Documents 1 to 3.
[0003]
FIG. 1 is a diagram showing an example of a conventional sulfur recovery apparatus, in which reference numeral 102 is a sulfur recovery apparatus. The sulfur recovery device 102 includes a sulfur recovery unit 100 that recovers hydrogen sulfide in an acid gas in a state of elemental sulfur (hereinafter, referred to as sulfur), and a tail gas processing unit 101 that processes the tail gas. .
The sulfur recovery section 100 burns the air and acid gas sent from the air blower 1 to perform a thermal Claus reaction at a high temperature, and a high-pressure or medium-pressure steam using thermal energy generated in the reactive combustion furnace. The waste heat boiler 3 that is generated, the first sulfur condenser 4 that separates sulfur from the reaction gas discharged from the reaction combustion furnace 2, and the cooling gas after sulfur separation is reheated by the first reheater 5, A first Claus reactor 6 for performing a contact Claus reaction, a second sulfur condenser 7 for cooling the reaction gas to further separate sulfur, and similarly reheat the cooling gas to cause a contact Claus reaction to separate sulfur. A second reheater 8, a second Claus reactor 9 and a third sulfur condenser 10 are provided.
Further, the tail gas processing unit 101 is provided with a gas heater 11 which is sent from the third sulfur condenser 10 through the valve A and heats the tail gas mixed with the hydrogen gas, and a water for causing a hydrogenation reaction of the sulfur in the gas with hydrogen. The addition reactor 12, the gas cooler 13 for cooling the gas after the hydrogenation reaction, the gas quenching tower 16 for quenching the cooling gas, and the gas after quenching sent via the valve C and the amine solution are brought into contact with each other. An amine absorption tower 17 for absorbing and removing hydrogen sulfide, and a gas circulation line 15 for circulating the quenched gas from the gas quenching tower 16 to the upstream side of the gas heater 11 via the valve D and the recycle gas blower 14. And a tail gas bypass line 18 for directly discharging the tail gas from the sulfur recovery unit 100 as a processing gas via a valve B. During the steady operation of the sulfur recovery apparatus 102, the raw acid gas is burned in the reaction combustion furnace 2 together with the air, and is subjected to a plurality of stages of sulfur recovery processing including a catalytic Claus reaction to recover sulfur. The subsequent exhaust gas (tail gas) is subjected to a hydrogenation reaction in the hydrogenation reactor 12, and then the generated hydrogen sulfide is absorbed and removed with an amine solution, and then discharged as a processing gas.
[0004]
[Patent Document 1]
Japanese Patent Publication No. 2-57978
[Patent Document 2]
JP-A-8-290904
[Patent Document 3]
JP 2001-270706 A
[0005]
[Problems to be solved by the invention]
When starting and stopping the operation of the conventional sulfur recovery apparatus, it is necessary to incinerate the acid gas with a flare stack (not shown) and to operate the apparatus with the tail gas processing section separated. That is, at the start of the operation of the sulfur recovery device, the acid gas cannot be introduced into the device until the acid gas amount reaches the lower limit of the operation of the burner, and the flare stack must be incinerated. Furthermore, since the sulfur dioxide concentration in the tail gas may increase even after the introduction of the acid gas, the tail gas processing unit is bypassed, and after the acid gas combustion stabilizes in the reaction combustion furnace and the sulfur dioxide concentration falls below the predetermined value. To the tail gas treatment section. Therefore, even though for a short period of time, the emission of acid gas to the flare stack before the introduction and the bypass operation after the introduction significantly increase the amount of sulfur compounds released into the atmosphere from the time of normal operation. There is a problem in prevention.
When the operation of the sulfur recovery device is stopped, when the amount of the acid gas reaches the lower limit of the operation of the burner, the introduction of the acid gas into the device is stopped, and the flare stack must be incinerated. Further, after stopping the combustion of the acid gas in the reaction combustion furnace, it is necessary to burn the fuel gas to remove the sulfur in the system. Since this gas contains oxygen and cannot be received by the tail gas processing unit, the tail gas processing unit is bypassed. Therefore, although short-term, the release of acid gas to the flare stack after the stoppage of acid gas introduction and the amount of sulfur compounds released to the atmosphere by bypass operation increase significantly compared to during normal operation. There is a problem in prevention.
As described above, in the conventional method, the acid gas is incinerated by the flare stack at the time of starting and stopping the operation, and there is a problem that the sulfur compound emission increases due to the bypass operation of the tail gas processing unit.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sulfur recovery method and a sulfur recovery apparatus that can reduce the amount of sulfur compounds discharged at the time of starting operation and at the time of stopping operation.
[0007]
[Means for Solving the Problems]
In order to achieve the object, the present invention introduces an acid gas and an oxygen-containing gas into a reaction and combustion furnace to cause a thermal Claus reaction, cools the reaction gas to separate sulfur, and recycles the cooling gas after sulfur separation. After the heating, a contact Claus reaction is performed, and a sulfur recovery section for cooling the reaction gas to further separate sulfur, and hydrogen gas are added to a tail gas discharged from the sulfur recovery section, and a sulfur compound in the tail gas is hydrogenated. A tail gas processing unit that absorbs and removes hydrogen sulfide after converting to hydrogen sulfide; and a sulfur recovery method that recovers and removes sulfur from a hydrogen sulfide-containing gas. A sulfur recovery method is provided, wherein a reaction gas is circulated and supplied to the reaction combustion furnace.
In the sulfur recovery method of the present invention, it is preferable that a catalyst for oxidizing hydrogen sulfide is filled in an upper portion of the Claus catalyst in the Claus reactor used for the catalytic Claus reaction. Examples of the catalyst for oxidizing hydrogen sulfide include Fe ₂ O ₃ -Al ₂ O ₃ , NiO-Al ₂ O ₃ , TiO ₂ , V ₂ O ₃ -TiO ₂ , MoO ₃ -TiO ₂ It is preferable that one or two or more selected from the group consisting of
[0008]
Further, the present invention provides a reaction combustion furnace for generating a sulfur-containing reaction gas by subjecting an acid gas and an oxygen-containing gas to a thermal Claus reaction, and a sulfur condenser for cooling the sulfur-containing reaction gas to recover sulfur. A sulfur recovery unit having a Claus reactor for producing a reaction gas containing sulfur by subjecting the cooling gas from the sulfur condenser to a contact Claus reaction and adding hydrogen to a tail gas from the sulfur recovery unit; A hydrogenation reactor for converting sulfur compounds in the tail gas into hydrogen sulfide by hydrogenation reaction, and contacting the hydrogenation reaction gas from the hydrogenation reactor with an amine solution to absorb and remove hydrogen sulfide from the hydrogenation reaction gas And a tail gas treating section having an amine absorption tower that performs the reaction, when the operation starts and stops, the hydrogenation reaction gas of the tail gas treating section reacts in the sulfur collecting section. Providing a sulfur recovery unit, characterized in that to circulate and supply gas circulation line is provided Furnace.
In the sulfur recovery apparatus of the present invention, it is preferable that a catalyst for oxidizing hydrogen sulfide is filled in an upper portion of the Claus catalyst in the Claus reactor. Examples of the catalyst for oxidizing hydrogen sulfide include Fe ₂ O ₃ -Al ₂ O ₃ , NiO-Al ₂ O ₃ , TiO ₂ , V ₂ O ₃ -TiO ₂ , MoO ₃ -TiO ₂ It is preferable that one or two or more selected from the group consisting of
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 is a configuration diagram showing an embodiment of the sulfur recovery apparatus according to the present invention, and reference numeral 112 in the figure denotes a sulfur recovery apparatus. The sulfur recovery device 112 includes a sulfur recovery unit 110 that recovers hydrogen sulfide in an acid gas in a sulfur state, and a tail gas processing unit 111 that processes the tail gas.
[0010]
The sulfur recovery section 110 generates a reaction combustion furnace 2 for performing a thermal Claus reaction between the air sent from the air blower 1 and the acid gas at a high temperature, and generates high-pressure or medium-pressure steam using the heat energy generated in the reaction combustion furnace 2. A waste heat boiler 3, a first sulfur condenser 4 for cooling a sulfur-containing reaction gas discharged from the reaction combustion furnace 2 and separating sulfur from the reaction gas, and a first recycle of the cooling gas after the sulfur separation. After reheating by the heater 5, a first Claus reactor 6A for performing a contact Claus reaction, a second sulfur condenser 7 for cooling the reaction gas and further separating sulfur, and similarly reheating the cooling gas, The apparatus includes a second reheater 8, a second Claus reactor 9A, and a third sulfur condenser 10 for performing a contact Claus reaction and separating sulfur. An oxidizing air line 19 for supplying air from the air blower 1 is connected to the gas inlet side of the first and second reheaters 5 and 8.
[0011]
The first and second Claus reactors 6A and 9A are provided with a catalyst layer for oxidizing hydrogen sulfide remaining in the cooling gas, and a reaction between sulfur dioxide and hydrogen sulfide in the reaction gas at a stage subsequent to the catalyst to reduce sulfur. And a Claus catalyst layer for generating a contained reaction gas. Examples of the catalyst for oxidizing hydrogen sulfide include Fe ₂ O ₃ -Al ₂ O ₃ , NiO-Al ₂ O ₃ , TiO ₂ , V ₂ O ₃ -TiO ₂ , MoO ₃ -TiO ₂ It is preferable that one or two or more selected from the group consisting of As the Claus catalyst, alumina or titania used in a conventional method can be used.
[0012]
The tail gas processing unit 111 includes a gas heater 11 that is sent from the third sulfur condenser 10 and heats a tail gas mixed with hydrogen gas, and a hydrogenation reactor 12 that hydrogenates hydrogen in sulfur in the gas. A gas cooler 13 for cooling the gas after the hydrogenation reaction, a gas quenching tower 16 for quenching the cooling gas, and contacting the quenched gas sent via the valve E with the amine solution to remove hydrogen sulfide. And an amine absorption tower 17 for absorbing and removing. The processing gas from which the hydrogen sulfide has been absorbed and removed in the amine absorption tower 17 is discharged through a discharge line having a valve H.
[0013]
Further, the sulfur recovery device 112 is provided with a gas circulation line 20 for supplying the quenching gas from the gas quenching tower 16 via the valve G and / or the processing gas from the amine absorption tower 17 via the valve F to the reaction combustion furnace 2. Is provided. The gas circulation line 20 is provided with a recycled gas blower 21 and a recycled gas heater 22, and can heat each gas supplied through the valve G and / or the valve F to an appropriate temperature and supply the gas to the reaction combustion furnace 2. It has become.
[0014]
The sulfur recovery apparatus 112 shown in FIG. 2 is different from the conventional sulfur recovery apparatus 102 shown in FIG.
(1) After installing a recycle gas heater 22 in the discharge line (gas circulation line 20) of the recycle gas blower 21 and heating the outlet gas from the gas quenching tower 16 and / or the outlet gas from the amine absorption tower 17, The point that it can be circulated to the reaction combustion furnace 2,
(2) The point that the tail gas bypass line 18 is deleted,
(3) A point where a catalyst for oxidizing hydrogen sulfide with oxygen is filled on the first Claus reactor 6A or the Claus catalyst of the first Claus reactor 6A and the second Claus reactor 9A, and (4) air for oxidation is used. Injection can be performed upstream of the first reheater 5 and the second reheater 8.
[0015]
Next, methods of starting and stopping the operation of the conventional sulfur recovery device 102 shown in FIG. 1 and the sulfur recovery device 112 according to the present invention shown in FIG. 2 will be described.
[0016]
[Conventional method]
With reference to FIG. 1, a method of starting and stopping the operation in the conventional sulfur recovery apparatus 102 will be described.
First, a method of starting operation will be described. At the start of operation, the sulfur recovery unit 100 and the tail gas processing unit 101 are disconnected, and operation is started independently. That is, the operation is started with the inlet valve A of the tail gas processing unit closed and the bypass valve B opened.
[0017]
<Start of operation of conventional method-sulfur recovery section>
At the start of operation, the sulfur recovery unit 100 activates the air blower 1 to circulate air through the system. Next, a heating medium is supplied to the first reheater 5 and the second reheater 8 to raise the temperature of the first Claus reactor 6 and the second Claus reactor 9 to a predetermined temperature.
When the temperature of each of the reactors 6 and 9 reaches about 100 ° C., the fuel gas burner of the reaction combustion furnace 2 is ignited and the combustion of the fuel gas is started. The combustion amount of fuel gas is increased, and when the temperature in the furnace reaches about 750 ° C., the thermal Claus reaction can proceed in the furnace. Therefore, the acid gas burner of the reaction combustion furnace 2 is ignited, and the acid gas combustion is performed. To start. By that time, the temperature of each of the reactors 6 and 9 is increased to a temperature required for the reaction.
[0018]
When the acid gas is ignited, the amount of the acid gas generated must reach the lower limit of operation of the burner. Therefore, the acid gas is sent to the flare stack for incineration from the generation of the acid gas to the ignition. When the amount of acid gas combustion is increased and the flame is stabilized, the amount of fuel gas combustion to the reaction combustion furnace 2 is reduced, and the fuel gas burner is extinguished. Adjust the air-fuel ratio and adjust the H in the tail gas. ₂ S / SO ₂ When the ratio is stable at 2 or more, the tail gas is introduced into the tail gas processing unit 101.
Thereafter, the combustion amount of the acid gas is increased to a predetermined value, and the operation shifts to a steady operation.
[0019]
As described above, in the conventional method, it is necessary to incinerate the acid gas with the flare stack until the introduction of the acid gas amount at the start of operation, and to introduce the tail gas into the tail gas processing unit 101 even after the introduction. Until the tail gas processing unit 101 is bypassed, a larger amount of sulfur compounds is released to the atmosphere than during steady operation.
[0020]
<Start of operation of conventional method-Tail gas treatment unit>
The tail gas processing unit 101 closes the inlet valve A of the tail gas processing unit 101 and the inlet valve C of the amine absorption tower 17, opens the valve D, activates the recycle gas blower 14, and circulates nitrogen gas. The circulating gas is heated by the gas heater 11, and the temperature of the hydrogenation reactor 12 is raised to a predetermined temperature. If presulfurization of the hydrogenation catalyst is necessary, it is carried out at this time.
[0021]
H in the tail gas of the sulfur recovery unit 100 ₂ S / SO ₂ When the ratio becomes stable at 2 or more, the operation of opening the inlet valve C of the amine absorption tower 17, then gradually closing the bypass valve B and gradually opening the inlet valve A of the tail gas processing unit 101 is repeated to process the tail gas into the tail gas. Introduced to the unit 101. After the introduction of the tail gas, when the operation load of the sulfur recovery unit 100 increases, the valve D is closed, the recycle gas blower 14 is stopped, and the operation shifts to a steady operation.
[0022]
Next, a method of stopping the operation will be described.
When the combustion amount of the acid gas is reduced to about 30% of that in the normal operation, the sulfur recovery unit 100 and the tail gas processing unit 101 are separated, and the operation is independently stopped. That is, the operation is stopped with the inlet valve A of the tail gas processing unit 101 closed and the bypass valve B opened.
[0023]
<Operation shutdown of conventional method-sulfur recovery section>
When the operation is stopped, the combustion amount of the acid gas is reduced to about 30% of that in the normal operation, and then the fuel gas burner is ignited to start the fuel gas combustion. When the amount of fuel gas burned is increased and the flame stabilizes, the acid gas burner is extinguished and the acid gas is sent to a flare stack for incineration. The fuel gas combustion amount is increased to a predetermined value. By flowing the combustion gas through the system, elemental sulfur adhering to the system (particularly, the catalyst layer) is evaporated, and condensed and removed by the sulfur condensers 4, 7, and 10. When the combustion of the fuel gas is continued and the liquid sulfur stops flowing out of each of the sulfur condensers 4, 7, and 10, a small amount of air is injected into the reaction combustion furnace 2 so that a small amount of oxygen is present in the combustion gas. Is removed by oxidizing it with oxygen. The injection amount of air is gradually increased, and when the temperature rise in the catalyst layer is no longer observed, the fuel gas combustion amount is reduced, and finally the fire is extinguished. The supply of the heating medium to the first reheater 5 and the second reheater 8 is stopped. After the air is replaced in the system, the air blower 1 is stopped, and the operation stop procedure ends.
As described above, in the conventional method, a larger amount of sulfur compounds is released to the atmosphere by the discharge of the acid gas to the flare stack after the stop of the introduction of the acid gas and by the bypass operation than in the normal operation.
[0024]
<Conventional shutdown operation-tail gas treatment unit>
When the operation is stopped, the sulfur recovery unit 100 and the tail gas processing unit 101 activate the recycle gas blower 14 before separation, and start gas circulation. The operation of gradually opening the bypass valve B and gradually closing the inlet valve A of the tail gas processing unit 111 is stopped, and the introduction of the tail gas to the tail gas processing unit 111 is stopped and the bypass is performed.
After the tail gas is bypassed, the gas circulation is continued and the temperature of the hydrogenation reactor 12 is lowered. Next, a small amount of air is injected into the circulating gas so that a small amount of oxygen is present in the circulating gas to perform a partial oxidation treatment of the hydrogenation catalyst. SO generated in this process ₂ Is absorbed and removed by the circulating water of the gas quenching tower 16. The injection amount of air is gradually increased, and when the temperature rise in the catalyst layer is no longer observed, the temperature of the reactor is lowered. After the air is replaced in the system, the recycle gas blower 14 is stopped, and the operation stop procedure is terminated.
[0025]
[Method of the present invention]
Referring to FIG. 2, a method of starting and stopping the operation of the sulfur recovery device 112 according to the present invention will be described.
[0026]
<At the start of operation of the method of the present invention>
The air volume of the recycle gas blower 21 may be 50% to 80% of the design tail gas volume, and its head is set between 50 kPa and 80 kPa. When the air blower 1 has a spare unit, the spare unit can be used as a recycled gas blower by changing the specifications of the spare unit.
[0027]
The recycle gas heater 22 is an ordinary heat exchanger that can heat the recycle gas to at least 150 ° C. to 200 ° C., and desirably has a small pressure loss on the heated side. Usually, high-pressure steam is used as the heating medium. Further, instead of the heat exchanger, it is also possible to use an inline burner which raises the temperature by mixing the combustion gas of the fuel gas with the recycle gas.
[0028]
The catalyst for oxidizing hydrogen sulfide filled on the Claus catalyst of the first Claus reactor 6A or the Claus catalyst of the first Claus reactor 6A and the second Claus reactor 9A with oxygen is a so-called H ₂ An S direct oxidation catalyst that promotes the next reaction.
H ₂ S + 1 / 2O ₂ → S + H ₂ O
H ₂ S + 3 / 2O ₂ → SO ₂ + H ₂ O
[0029]
The inlet temperatures of the first Claus reactor 6A and the second Claus reactor 9A are usually operated at about 150 to 200 ° C., and the GHSV (space velocity) of the direct oxidation catalyst is operated in the range of 2000 to 100001 / hour.
The other components in FIG. 2 are the same as those in the conventional sulfur recovery device 102 shown in FIG.
[0030]
At the start of operation, the valves E, F and H are closed and the valve G is opened. After the inside of the system is replaced with nitrogen gas, the recycle gas blower 21 is activated to circulate nitrogen gas. Next, a heating medium is supplied to the recycle gas heater 22, the first reheater 5, the second reheater 8, and the gas heater 11, and the reaction combustion furnace 2, the first Claus reactor 6, the second Claus reaction The temperature of the reactor 9 and the hydrogenation reactor 12 is raised to a predetermined temperature. When the acid gas starts to be generated, the gas is immediately introduced into the reaction combustion furnace 2, the valves E and H are opened, and the lean amine solution is supplied to the amine absorption tower 17. ₂ When the S concentration reaches 1 mol%, oxidizing air corresponding to the introduced acid gas is introduced, and H is passed through the Claus reactors 6A and 9A. ₂ The direct oxidation reaction of S proceeds to recover sulfur.
[0031]
When the generation amount of the acid gas reaches 10%, while circulating the gas, the oxidizing air is stopped, the acid gas burner is ignited, and the combustion of the acid gas is started. At this time, the thermal Claus reaction does not occur in the reaction combustion furnace 2 because the temperature in the furnace is low. SO contained in combustion gas ₂ Is sent directly to the downstream reactor.
However, the SO ₂ Since the concentration has been diluted by the circulating gas, the concentration has been reduced to a value suitable for the catalytic Claus reaction to proceed in the Claus reactors 6A and 9A. Therefore, the catalytic Claus reaction proceeds in the same manner as during normal operation, and sulfur is recovered.
[0032]
In the hydrogenation reactor 12, immediately after introducing the oxidizing air, SO 2 ₂ And elemental sulfur begin to progress. H at the start of acid gas combustion ₂ Since the acid gas is ignited under S atmosphere, even if the air-fuel ratio deviates ₂ Is generated more than expected, the Claus reaction proceeds in the Claus reactors 6A and 9A, and SO ₂ The concentration decreases. Therefore, temperature runaway in the hydrogenation reactor 12 does not occur.
[0033]
When the combustion amount of the acid gas is increased and the furnace temperature reaches about 750 ° C., the thermal Claus reaction starts to proceed in the reaction combustion furnace 2, so that the gas circulation amount is gradually reduced. As the gas circulation decreases, the furnace temperature rises. When the gas circulation amount is reduced by half, the recycle gas blower 14 is stopped, and at the same time, the valve G is closed. If it is necessary to shorten the temperature rise time due to acid gas combustion, it is possible to raise the temperature inside the furnace to a required temperature in advance by fuel gas combustion before starting the acid gas combustion. Thereafter, the combustion amount of the acid gas is increased to a predetermined value, and the operation shifts to a steady operation.
[0034]
As described above, according to the method of the present invention, it is possible to avoid incineration of the acid gas by the flare stack at the start of the operation, and it is not necessary to bypass the tail gas. ₂ Since the exhaust gas containing S is always treated in the amine absorption tower 17 and then discharged out of the system, the sulfur compound discharge amount can be reduced to about the same level as during normal operation.
[0035]
<When the method of the present invention is stopped>
When the operation is stopped, the amount of acid gas burned is reduced to about 30% of the steady operation, the recycle gas blower 21 is started, the valve F is opened at the same time, and the heating medium is supplied to the recycle gas heater 22. The heated outlet gas of the amine absorption tower 17 is circulated to the reaction combustion furnace 2. Then, the gas circulation amount is gradually increased, and the temperature of the reaction combustion furnace 2 is lowered. When the temperature of the reaction combustion furnace 2 becomes lower than about 750 ° C., the thermal Claus reaction does not occur, but the H contained in the combustion gas is the same as in the case of starting the operation. ₂ S and SO ₂ Is diluted with the circulating gas and drops to a value suitable for the catalytic Claus reaction to proceed, and the catalytic Claus reaction proceeds as in normal operation, and sulfur is recovered. When the acid gas supply rate drops to 10%, the acid gas burner is extinguished and the introduction of oxidizing air is started at the same time. ₂ The direct oxidation reaction of S proceeds to recover sulfur.
[0036]
When the generation of the acid gas is stopped, the supply of the oxidizing air is stopped, the valve H is closed, and the supply of the lean amine solution to the amine absorption tower 17 is stopped. The circulation of the heated gas is continued to evaporate elemental sulfur adhering to the inside of the system (particularly, the catalyst layer), and is condensed and removed by the sulfur condenser. The elemental sulfur remaining in the tail gas is converted into H by the hydrogenation reaction in the hydrogenation reactor 12. ₂ It is converted to S and accumulated in the circulating gas.
[0037]
When the liquid sulfur stops flowing from each sulfur condenser, the supply of the lean amine solution to the amine absorption tower 17 is restarted, and the H accumulated in the circulating gas is resumed. ₂ S is absorbed and removed. Since the amine solution used at this time is a small amount, it can be stored in an amine drain recovery pit or the like, and can be regenerated and reused after restarting operation.
[0038]
H in circulating gas ₂ After absorbing and removing S, the valves E and F are closed, the valve G is opened, the suction line of the recycle blower 14 is switched to the outlet of the gas quenching tower 16, and the gas circulation is continued. A small amount of air is injected into the reaction furnace 2 to cause a small amount of oxygen to exist in the circulating gas, and the remaining sulfur that could not be removed by gas circulation alone is removed by oxidizing with oxygen. In the vessel 12, a partial oxidation treatment of the hydrogenation catalyst is performed. SO generated in this process ₂ Is absorbed and removed by the circulating water of the gas quenching tower 16. When the injection amount of air is gradually increased, and the temperature rise in each catalyst layer is no longer observed, the temperature of each reactor is lowered. After the air is replaced in the system, the recycle gas blower 14 is stopped, and the operation stop procedure is terminated.
[0039]
As described above, according to the method of the present invention, it is possible to avoid incineration of the acid gas by the flare stack when the operation is stopped, and it is not necessary to bypass the tail gas. ₂ Since the exhaust gas containing S is always treated in the amine absorption tower 17 and then discharged out of the system, the sulfur compound discharge amount can be reduced to about the same level as during normal operation.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to avoid incineration of the acid gas by the flare stack at the time of starting and stopping the operation, and it is not necessary to bypass the tail gas. ₂ Since the exhaust gas containing S is always treated in the amine absorption tower and then discharged out of the system, the sulfur compound discharge amount can be reduced to the same level or less as in the normal operation.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of a conventional sulfur recovery device.
FIG. 2 is a configuration diagram showing one embodiment of a sulfur recovery device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Air blower, 2 ... Reaction combustion furnace, 3 ... Waste heat boiler, 4 ... 1st sulfur condenser, 5 ... 1st reheater, 6, 6A ... 1st Claus reactor, 7 ... 2nd sulfur condenser , 8 ... second reheater, 9, 9A ... second Claus reactor, 10 ... third sulfur condenser, 11 ... gas heater, 12 ... hydrogenation reactor, 13 ... gas cooler, 14 ... recycled gas Blower, 15: gas circulation line, 16: gas quenching tower, 17: amine absorption tower, 18: tail gas bypass line, 19: oxidation air line, 20: gas circulation line, 21: recycled gas blower, 22: recycled gas Heaters, 100, 110: sulfur recovery section, 101, 111: tail gas processing section, 102, 112: sulfur recovery apparatus.

Claims (6)

A hydrogen sulfide-containing gas and an oxygen-containing gas are introduced into a reaction combustion furnace to cause a thermal Claus reaction, the reaction gas is cooled to separate elemental sulfur, and the cooled gas after the sulfur separation is reheated to cause a contact Claus reaction. A sulfur recovery unit that cools the reaction gas to further separate elemental sulfur,
A hydrogen gas is added to the tail gas discharged from the sulfur recovery unit, and after converting a sulfur compound in the tail gas to hydrogen sulfide by hydrogenation reaction, a tail gas processing unit for absorbing and removing the hydrogen sulfide is provided. In the sulfur recovery method of recovering and removing sulfur from
A method for recovering sulfur, characterized in that the hydrogenation reaction gas of the tail gas processing section is circulated and supplied to the reaction combustion furnace at the time of starting and stopping the operation. 2. The sulfur recovery method according to claim 1, wherein a catalyst for oxidizing hydrogen sulfide is filled in an upper portion of the Claus catalyst in the Claus reactor used for the contact Claus reaction. 3. Catalyst to oxidize the hydrogen sulfide _is selected from _{Fe 2 O 3 -Al 2 O 3} , NiO-Al 2 O 3, TiO 2, V 2 O 3 -TiO 2, the group consisting of MoO 3 -TiO ₂ 1 3. The method for recovering sulfur according to claim 2, wherein the sulfur is at least one species. A reaction combustion furnace that generates a reaction gas containing elemental sulfur by subjecting a hydrogen sulfide-containing gas and an oxygen-containing gas to a thermal Claus reaction, and cools the reaction gas containing elemental sulfur to recover elemental sulfur A sulfur condenser, and a sulfur recovery unit including a Claus reactor for producing a reaction gas containing elemental sulfur by subjecting a cooling gas from the sulfur condenser to a contact Claus reaction,
A hydrogenation reactor for adding hydrogen to the tail gas from the sulfur recovery unit to convert a sulfur compound in the tail gas into hydrogen sulfide by hydrogenation, and a hydrogenation reaction gas and an amine solution from the hydrogenation reactor A tail gas treatment unit having an amine absorption tower that contacts and absorbs and removes hydrogen sulfide from the hydrogenation reaction gas; and
A sulfur recovery device, comprising: a gas circulation line for circulating the hydrogenation reaction gas of the tail gas processing unit to the reaction combustion furnace of the sulfur recovery unit at the time of starting and stopping the operation. The sulfur recovery device according to claim 1, wherein a catalyst for oxidizing hydrogen sulfide is filled above the Claus catalyst in the Claus reactor. Catalyst to oxidize the hydrogen sulfide _is selected from _{Fe 2 O 3 -Al 2 O 3} , NiO-Al 2 O 3, TiO 2, V 2 O 3 -TiO 2, the group consisting of MoO 3 -TiO ₂ 1 The sulfur recovery device according to claim 5, wherein the sulfur recovery device is at least one species.

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