Sulfur recovery method and system suitable for crushed coal pressure gasification technology

Abstract

The invention provides a sulfur recovery method and system suitable for a crushed coal pressure gasification technology, the system comprises an acid gas pretreatment unit, a sulfur recovery unit and a desulfurization unit, the acid gas pretreatment unit comprises a washing tower, an absorption tower and a regeneration tower which are arranged in sequence, the method comprises the following steps of: washing low-temperature methanol washing acid gas in a washing tower to remove quantitative ammonia gas and methanol, performing countercurrent contact absorption on the low-temperature methanol washing acid gas and amine liquid to separate heavy hydrocarbon and take away a part of # imgabs 0 #, absorbing # imgabs 1 # and the other part of # imgabs 2 # in the acid gas by the amine liquid, feeding into a regeneration tower to separate out pretreated acid gas containing # imgabs 3 # and concentrated # imgabs 4 #, and feeding into a sulfur recovery unit to recover liquid sulfur, and the generated tail gas is sent into a desulfurization unit to be treated and then discharged. Therefore, the low-temperature methanol washing acid gas with complex components is treated, and the long-period stable operation of the sulfur recovery process is ensured.

Description

Technical Field

[0002] The invention relates to sulfur recovery technology, and in particular to a sulfur recovery method and system suitable for crushed coal pressurized gasification technology. Background Art

[0004] When selecting gasification technology, existing coal-to-syngas projects usually widely choose crushed coal pressurized gasification technology. In particular, most coal-to-natural gas projects will choose Lurgi crushed coal pressurized gasification technology. The reason is that the methane content in the raw gas at the outlet of the gasifier in this type of process is usually much higher than that of the water-coal slurry gasifier and the pulverized coal gasifier. It has the advantages of wide applicability to a wide range of coal types and low construction cost of the main device. However, the disadvantages are also obvious. For example, the gasifier temperature is low, and the raw gas contains more prominent hydrocarbon substances. The raw gas needs to be cooled by conversion to adjust the hydrogen-carbon ratio, and then it is sent to the methane synthesis system for methane synthesis after desulfurization and decarbonization by low-temperature methanol washing.

[0005] Therefore, in the low-temperature methanol washing process, methanol has a great influence on C 2 , C 3 Hydrocarbon substances such as hydrogen sulfide and carbon dioxide have a certain solubility. As hydrogen sulfide and carbon dioxide are absorbed by methanol, some hydrocarbons dissolve in methanol. After the circulation and concentration of hydrogen sulfide tail gas in the sulfur concentration section, the hydrocarbon composition continues to increase and is analyzed into the low-temperature methanol washing tail gas together with hydrogen sulfide and carbon dioxide, which eventually results in a low hydrogen sulfide concentration and a high hydrocarbon concentration. In the enriched tail gas (acid gas) after low-temperature methanol washing, the heavy hydrocarbon C 3 and C 4 The content of H is between 5 and 20 mol%. 2 The S content is generally between 15 and 35 mol%, and the tail gas mostly carries 200 to 600 ppm of ammonia.

[0006] The low-temperature methanol-washed acid gas with such complex composition has far exceeded the impurity range allowed by the conventional Claus sulfur recovery process. If it is forced to operate under this feeding condition, it will lead to overheating of the sulfur-making furnace, low conversion rate of the sulfur-making furnace, carbon deposition in the sulfur-making furnace, carbon particles clogging the heat exchange tubes of the waste heat boiler or the sulfur condenser, and catalyst bed clogging, which will cause the catalyst to fail in a short period of time, unqualified sulfur quality (such as bluish sulfur, black in severe cases), overheating damage to the exhaust gas incinerator and unqualified NOx emissions, ammonium sulfate crystallization in the low-temperature outlet section of the exhaust gas waste boiler, and clogging of the heat exchange tubes. As a result, the sulfur recovery device cannot be operated for a long period of time and often needs to be stopped for maintenance, which brings a heavy burden to the enterprise. Summary of the invention

[0008] To this end, the main purpose of the present invention is to provide a sulfur recovery method and system suitable for crushed coal pressurized gasification technology to cope with low-temperature methanol-washed acid gas with complex components and ensure long-term stable operation of the sulfur recovery process.

[0009] In order to achieve the above-mentioned object, according to one aspect of the present invention, a sulfur recovery system suitable for crushed coal pressurized gasification technology is provided, which comprises: an acid gas pretreatment unit, a sulfur recovery unit, and a desulfurization unit, wherein the acid gas pretreatment unit comprises: a washing tower, an absorption tower, and a regeneration tower arranged in sequence, so that the acid gas is washed with low-temperature methanol. After the acid gas is washed in the washing tower to remove a certain amount of ammonia and methanol, it is countercurrently contacted and absorbed with amine liquid to separate heavy hydrocarbons and take away part of the acid gas. , while in acidic gas , and other parts After being absorbed by the amine solution, it is sent to the regeneration tower to precipitate the and concentrated After the pre-treatment of the acid gas, it is sent to the sulfur recovery unit to recover liquid sulfur, and the generated tail gas is sent to the desulfurization unit for treatment and then discharged.

[0010] In a possible preferred embodiment, the residual ammonia and methanol content of the low-temperature methanol-washed acid gas after washing and removal in the washing tower are both ≤20 mg / m 3 .

[0011] In a possible preferred embodiment, the sulfur recovery unit includes: a preheater, a sulfur-making furnace, a steam generator, a sulfur condenser, a heater, a Claus reactor, a selective oxidation reactor, a tail gas collector, and a tail gas treatment module connected in sequence, wherein the pretreated acid gas is heated by the preheater, enters from the burner of the sulfur-making furnace, is mixed with the double cyclone of oxygen to generate a high-temperature process gas in the furnace, and is cooled and condensed by the steam generator and the sulfur condenser to separate the sulfur, the process gas is heated by the heater, and is sequentially sent to the Claus reactor and the selective oxidation reactor for reaction, and is sequentially condensed and separated by the sulfur condenser equipped with each reactor, and the process gas enters the tail gas treatment module through the tail gas collector.

[0012] In a possible preferred embodiment, the number of stages of the heater is determined according to the number of stages of the Claus reactor and the selective oxidation reactor, and is one, two or three stages.

[0013] In a possible preferred embodiment, the Claus reactor is provided with two stages, wherein the upper 2 / 3 of the two-stage Claus reactor is filled with a titanium-grade sulfur recovery catalyst, and the lower 1 / 3 is filled with a selective hydrogenation catalyst.

[0014] In a possible preferred embodiment, a ratiometer is provided at the outlet of the secondary Claus reactor to The concentration and the fine-tuning wind control loop of the sulfur-making furnace form a cascade regulation to control The concentration is 0.5-0.8%, The value is close to zero.

[0015] In a possible preferred embodiment, the exhaust gas treatment module includes: an exhaust gas burner, an exhaust gas incinerator, and a waste heat boiler connected in sequence, wherein the exhaust gas burner is an ultra-low nitrogen burner, and the exhaust gas discharged from the exhaust collector is divided into two stages. The first-level exhaust gas is sprayed at an angle of 30~90° to the axis of the exhaust gas incinerator furnace at the outlet of the ultra-low nitrogen burner fire channel, and the combustion-supporting air is sprayed into the exhaust gas burner twice in a direction perpendicular to the axis of the furnace to mix and react with the first-level exhaust gas, and then the second-level exhaust gas is added to the exhaust gas incinerator furnace.

[0016] In a possible preferred embodiment, the desulfurization unit includes: a heat exchanger, a desulfurization tower, and a water scrubber arranged in sequence, wherein the exhaust gas output by the sulfur recovery unit is mixed with the blue-eliminating solvent and enters the desulfurization tower through the heat exchanger for cyclic desulfurization, and the output flue gas is sent to the water scrubber to remove entrained particulate matter, and then discharged after being heated by the heat exchanger.

[0017] In order to achieve the above object, according to another aspect of the present invention, a sulfur recovery method suitable for crushed coal pressurized gasification technology is also provided, and the steps include:

[0018] After the low-temperature methanol-washed acid gas is washed with water to remove ammonia and methanol, it is subjected to countercurrent contact absorption with amine liquid to separate heavy hydrocarbons and take away part of the , thereby concentrating the acid gas , to generate pre-treated acid gas; the pre-treated acid gas is subjected to sulfur recovery treatment, and the generated tail gas is desulfurized and then discharged.

[0019] In a possible preferred embodiment, the sulfur recovery step includes: heating the pretreated acid gas, sending it into a sulfur-making furnace burner to mix it with oxygen double cyclone to output high-temperature process gas, cooling and condensing it through a steam generator and a sulfur condenser to separate the sulfur, and after the process gas is heated, sending it to a Claus reactor and a selective oxidation reactor for reaction in sequence, and condensing and separating the sulfur through the sulfur condensers equipped with each reactor in sequence, separating the sulfur through a tail gas collector, and then sending it into a tail gas treatment module to first perform oxygen-deficient and low-nitrogen combustion and then perform over-oxygen complete incineration of the combustibles.

[0020] In a possible preferred embodiment, the desulfurization step includes: mixing the tail gas after sulfur recovery treatment with a blue-eliminating solvent, performing ammonia desulfurization after heat exchange and cooling, washing the flue gas after desulfurization with water to remove entrained particulate matter, and then discharging it after heat exchange and heating.

[0021] Through the sulfur recovery method and system suitable for pulverized coal pressurized gasification technology provided by the present invention, a pretreatment process for acidic gas in cold methanol wash is ingeniously designed. After removing a certain amount of ammonia and methanol and removing impurities, the acidic gas is purified and the concentration of in it is increased, heavy hydrocarbon gas is separated and part of is carried away, thereby solving the problem that in the existing pulverized coal pressurized gasification technology, the concentration of in the acidic gas fed into the cold methanol wash is too low (such as ≯30%), containing ammonia and heavy hydrocarbons, which does not meet the basic requirements of Claus sulfur production, and further leads to defects such as various production problems in the background technology. Thus, the problem of abnormal impurities carried by the fed acidic gas is overcome, thereby ensuring that the sulfur recovery device suitable for the pulverized coal pressurized gasification process can operate normally, stably and in a long cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 is a schematic structural diagram of the acidic gas pretreatment unit in the sulfur recovery system suitable for pulverized coal pressurized gasification technology of the present invention;

[0025] Figure 2 is a schematic structural diagram of the sulfur recovery unit in the sulfur recovery system suitable for pulverized coal pressurized gasification technology of the present invention;

[0026] Figure 3 is a schematic structural diagram of the tail gas treatment module in the sulfur recovery system suitable for pulverized coal pressurized gasification technology of the present invention;

[0027] Figure 4 is a schematic structural diagram of the desulfurization unit in the sulfur recovery system suitable for pulverized coal pressurized gasification technology of the present invention.

[0028] Figure 5 is a schematic diagram of the steps of the sulfur recovery method suitable for pulverized coal pressurized gasification technology of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to enable those skilled in the art to better understand the technical solution of the present invention, the specific technical solution of the present invention will be clearly and completely described in conjunction with the embodiments below to help those skilled in the art further understand the present invention. Obviously, the embodiments described in this case are only embodiments of a part of the present invention, not all of the embodiments. It should be pointed out that for those of ordinary skill in the art, the embodiments in this application and the features in the embodiments can be combined with each other without departing from the concept of the present invention and without conflicting with each other. Based on the embodiments in the present invention, all other embodiments obtained without creative work by those of ordinary skill in the art should belong to the disclosure and protection scope of the present invention.

[0031] In addition, the terms "first", "second", "S100", "S200", etc. in the specification, claims and drawings of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the features used in this way can be interchanged where appropriate, so that the embodiments of the present invention described here can be implemented in an order other than those described here. At the same time, the stages recorded in each step are not mandatory to be implemented in the same step. It should be understood that the implementation order of the contents in each step stage can be adjusted and interchanged without violating the inventive concept, so that the step embodiments of the present invention described here can be implemented in an order other than those described here. In addition, the terms "including" and "having" and any of their variations in the present invention are intended to cover non-exclusive inclusions. Unless otherwise clearly specified and limited, the terms "set", "layout", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this case can be understood according to specific circumstances and in combination with the prior art.

[0032] Considering that according to the Claus sulfur recovery and treatment process technology ideas of the existing technology, such as the diversion method, the acid gas is generally transported to the burner and the sulfur-making furnace separately, and then connected to the two-stage Claus, tail gas incineration, steam superheater, waste heat boiler and ammonia desulfurization process. This process flow design will allow the ammonia-containing acid gas and 2 / 3 of the low-temperature methanol-washed acid gas to enter the burner, and about 1 / 3 of the low-temperature methanol-washed acid gas will enter from the front section of the sulfur-making furnace to increase the ammonia burning temperature in the front area of ​​the furnace. This acid gas diversion is based on the acid gas. Designed for concentration ≮35mol%.

[0033] However, the actual operation conditions are often quite different. When the raw material of the coal-to-gas device is low-sulfur coal, the low-temperature methanol enriched in the washing The concentration is generally between 20 and 35 mol%, but The actual concentration is often only 20~25mol% or even lower, while 25~35% The temperature of the front zone of the sulfur-making furnace corresponding to the concentration is about 1110℃, and the temperature of the rear zone is 850~900℃. Under this condition, it is no longer possible to process ammonia-containing gas. When the temperature of the sulfur-making furnace is lower than 950℃, the sulfur-making effect is very poor. In severe cases, the flame of the sulfur-making furnace is unstable or even shuts down, which can easily lead to the failure of the sulfur recovery device to operate normally. Acid gas is not allowed to be flared. If there is no spare sulfur recovery device, it will cause the whole plant to stop production, causing serious losses to the enterprise. Therefore, in the existing conventional Claus process, when the acid gas When the concentration is lower than 30%, even with oxygen enrichment, the lower limit of sulfur production temperature of 950°C cannot be reached.

[0034] Moreover, this type of conventional Claus process cannot solve the problem of ammonia in acid gas. It can only be decomposed under the condition of lack of oxygen and high temperature above 1250℃ In the coal chemical industry, the temperature of the front zone in the Claus sulfur furnace is usually 950~1100℃. Even if the pure oxygen process is used, the acid gas When the concentration is lower than 50%, the temperature cannot reach the ammonia burning temperature, and the low-temperature methanol washing tail gas The concentration usually fluctuates between 20 and 35 mol%. If the furnace temperature is raised by supplementary combustion, the energy consumption of the device will increase significantly, and supplementary combustion will easily cause carbon deposition, which greatly increases the difficulty of operation. On the whole, in the coal-to-gas industry, there has not been a well-functioning case of burning ammonia in a sulfur-making furnace, and other technical means are urgently needed to eliminate the negative impact of ammonia.

[0035] Therefore, in order to cope with the low-temperature methanol-washed acid gas with complex components and ensure the long-term stable operation of the sulfur recovery process, the present invention proposes a sulfur recovery system suitable for crushed coal pressurized gasification technology, which includes: an acid gas pretreatment unit, a sulfur recovery unit, and a desulfurization unit, wherein Figure 1 As shown, the acid gas pretreatment unit in this example includes: a washing tower, an absorption tower, and a regeneration tower arranged in sequence, so that the acid gas is washed with low-temperature methanol. After the acid gas is washed and removed with a certain amount of ammonia and methanol in the washing tower, it is countercurrently contacted and absorbed with amine liquid to separate heavy hydrocarbons and take away some , while in acidic gas , and other parts After being absorbed by the amine solution, it is sent to the regeneration tower to precipitate the and concentrated After the pre-treatment of the acid gas, it is sent to the sulfur recovery unit to recover liquid sulfur, and the generated tail gas is sent to the desulfurization unit for treatment and then discharged.

[0036] Specifically, in the process of pre-treating low-temperature methanol washing acid gas, firstly, in order to remove trace ammonia and methanol entrained in the acid gas, the washing tower can be set to 1 or 2 stages, such as Figure 1 As shown in the figure, the washing tower can be equipped with a packing tower and a washing circulating pump for circulating water washing. The external drainage produced by the water washing contains dissolved ammonia and methanol, which can be sent to the plant area bacteria culture pool for secondary use. The content is reduced to ≤20mg / m 3 , The content is reduced to ≤20mg / m 3 This indicator after washing can effectively solve the problems of subsequent ammonium salt blockage and incomplete carbon deposition due to methanol combustion.

[0037] Afterwards, the acid gas after water washing to remove ammonia and methanol will enter the decarbonization absorption tower and undergo countercurrent contact absorption with the amine liquid input from the top of the tower (for example: a composite solvent with a main component of 30wt% concentration of methyldiethanolamine, which has the advantages of good selectivity, energy saving and non-degradability).

[0038] Its function is that the absorption tower uses a composite amine solvent to absorb the acid gas At the same time, some will also be absorbed at the same time, but at a lower level For composite amine solvents, It has stronger selectivity, which can make the acid gas , is absorbed by the amine liquid and flows out from the bottom of the tower along with the amine liquid, while the heavy hydrocarbon gas such as / , and some The purified gas of substances such as chlorinated hydrocarbons is sent from the top of the tower to the fuel gas pipeline network or gas-using equipment. The rich liquid of the composite solvent enters the regeneration tower to parse out the high-concentration and a small amount The acid gas enters the sulfur recovery unit for the Claus sulfur production process.

[0039] This design not only can separate heavy hydrocarbon gas, but also It is carried away with the heavy hydrocarbon gas, thereby reversely concentrating the low-temperature methanol-washed acid gas. concentration (concentration> 60%), so even if the low-sulfur coal is used, the Claus sulfur production temperature will not be lower than the lower limit of 950℃, which can make the sulfur recovery unit operate normally. The increase in concentration also allows the temperature of the sulfur-making furnace to be increased, which is beneficial to the positive reaction of the Claus reversible reaction, thereby increasing the total sulfur recovery rate by about 0.5% or more.

[0040] Finally, including / The rich amine liquid enters the regeneration tower and is stripped by steam, so that the acid gas flows out from the top of the tower and is sent to the sulfur recovery unit, while the lean amine liquid at the bottom of the tower is sent back to the upstream device for recycling.

[0041] The acid gas pretreatment unit can effectively remove the , so that when the operating temperature in the sulfur furnace is lower than 1250℃, it will not cause the ammonium salt in the boiler tube of the tail gas treatment module to be blocked and the exhaust gas to be discharged. At the same time, the main components of the acid gas after water washing after absorption by composite organic amine solvent are and part , the acid gas The separation of heavy hydrocarbons and above can avoid problems such as incomplete combustion and sulfur carbon deposition caused by heavy hydrocarbons entering the sulfur-making furnace.

[0042] And for acidic gas After concentration, the temperature of the sulfur-making furnace can be significantly increased, thereby increasing the total sulfur recovery rate to more than 0.5%, reducing the gas volume of the sulfur recovery unit process, and thus optimizing and reducing the equipment size, reducing the floor space and investment of the entire device.

[0043] Further, such as Figure 2 As shown, the sulfur recovery unit of this example preferably includes: a preheater, a sulfur making furnace, a steam generator, a sulfur condenser, a heater, a Claus reactor, a selective oxidation reactor, a tail gas collector, and a tail gas treatment module connected in sequence, wherein the pretreated acid gas is heated by the preheater, enters from the burner of the sulfur making furnace, is mixed with the double cyclone of oxygen to generate a high-temperature process gas in the furnace, and is cooled and condensed by the steam generator and the sulfur condenser to separate the sulfur, and the process gas is heated by the heater, and then sent to the Claus reactor and the selective oxidation reactor for reaction, and is condensed and separated by the sulfur condenser equipped with each reactor in sequence, and the process gas enters the tail gas treatment module through the tail gas collector.

[0044] Specifically, the pre-treated acid gas after the removal of ammonia and hydrocarbons enters the separator to separate the free water, enters the preheater and is preheated to about 180-220°C by the 4.4MPa saturated medium-pressure steam produced by the sulfur-making waste boiler, and then enters the sulfur-making furnace burner. The key equipment of the sulfur recovery unit is the burner of the sulfur-making furnace, which directly determines the performance indicators of the sulfur recovery unit.

[0045] Therefore, in order to adapt to the acid gas components and characteristics of the coal gasification industry, the burner of the sulfur-making furnace can be set to adopt a high-intensity mixed swirl structure and use oxygen-enriched (30~50mol%O 2) or pure oxygen; the start-up fuel spray gun and the supplementary combustion spray gun are designed independently to reduce the flame temperature of the supplementary combustion spray gun fuel under oxygen-rich conditions, increase the service life of the gas spray gun and the burnout rate of the supplementary combustion fuel; at the same time, an oxygen spray gun and an air premixing device are set to improve the oxygen-rich supply method of the burner, improve the uniformity of oxygen concentration, and increase the mixed turbulence intensity of the burner, which can increase the sulfur conversion rate and reduce Emissions, extend burner life.

[0046] Among them, due to the pretreatment of acid gas concentration>60%, and removes ammonia, hydrocarbons and part of Therefore, the Claus sulfur-making system no longer uses the traditional acid gas diversion (for example, about 2 / 3 of the acid gas enters the sulfur-making furnace burner, and about 1 / 3 of the acid gas enters the middle and rear section of the sulfur-making furnace). Instead, all the acid gas enters from the sulfur-making furnace burner. In this way, impurities in the acid gas, such as residual trace hydrocarbons and methanol, are concentrated in the high-temperature area for combustion, and the acid gas and air have a high-intensity premixing effect when passing through the burner inlet, which can ensure that the residual hydrocarbons and other difficult-to-decompose substances in the acid gas are completely burned.

[0047] Furthermore, since the components in coal are more complex than those in oil and natural gas, and because coal is formed in different years and has various types, the sulfur-containing raw gas, i.e., acid gas, produced after desulfurization in the coal chemical project has different components and large fluctuations in concentration. In addition, there is no device in the entire coal chemical process to adjust the large fluctuations in acid gas concentration. Therefore, sulfur recovery in principle requires a simple and easy-to-operate process, and therefore traditionally, a two-stage Claus process is often used.

[0048] Secondly, coal chemical projects do not have hydrogen production equipment and therefore have no hydrogen supply. Although the SCOT process has a sulfur recovery rate of more than 99.8%, the process flow and operation process are relatively complicated and require additional hydrogen production. Therefore, the SCOT process based on hydrogenation reduction is basically not used in the coal chemical industry. At the same time, in order to reduce one-time investment and save land, the sulfur recovery equipment built in the early industry usually adopts conventional two-stage or three-stage Claus + tail gas incineration + ammonia desulfurization or tail gas sent to power boilers for treatment in order to reduce one-time investment and save land, and the environmental protection standards are not high. The total sulfur recovery rate of this conventional process is about 96%, and the corresponding SO in the tail gas incineration flue gas is 2.5%. 2 Content 15000~20000mg / m 3 .

[0049] In the past two years, with the increasingly stringent environmental protection standards, such as GB31570-2015 "Petroleum Refining Industry Pollutant Emission Standard", the "acid gas recovery device" has been added. The emission limit is 150 / 100 mg / m 3 (General Area / Specially Excluded Area), at the same time The emission limit is also 100 mg / m 3For enterprises that cannot send sulfur recovery tail gas to power boilers for treatment and have to set up separate exhaust pipes, environmental protection pressure increases, that is, the sulfur recovery device is required to be connected to the Environmental Protection Bureau and the CEMS analyzer is required to monitor in real time. , , and the instantaneous emission data of particulate matter indicators do not exceed the emission limits required by the latest environmental protection standards.

[0050] It can be seen that the SCOT process is difficult to apply in the coal chemical industry because it requires a hydrogen source and has a long process and high investment. Therefore, in order to comprehensively consider the investment cost-effectiveness while taking into account the total sulfur recovery rate, in this example, it is preferred to add a first-stage selective oxidation reactor on the basis of the original two-stage Claus reactor, and at the same time upgrade the catalyst grading of the original two-stage Claus reactor, that is, fill the upper 2 / 3 with titanium-grade sulfur recovery catalyst and the lower 1 / 3 with selective hydrogenation catalyst (the selective hydrogenation catalyst will be Selective reduction to S, not , in order to reduce the load of the selective oxidation reactor, reduce the total amount of sulfide entering the tail gas incineration, and maximize the recovery rate). In this way, the total sulfur recovery rate can be increased from the original 96% to 98.5~99%.

[0051] Taking the traditional two-stage Claus sulfur recovery process as an example, compared with the "two-stage Claus + partial selective hydrogenation + selective oxidation" process in this example, under the premise of the same supporting ammonia desulfurization, the 30,000 tons / year sulfur recovery scale index is taken as an example (see Table 1 for comparison): First, the total sulfur recovery rate is significantly improved by 2.5~3%, and the flue gas in the tail gas incinerator is The concentration (before desulfurization) is reduced by 50%, and the pressure of the desulfurization unit is greatly reduced, which provides a premise for the long-term sustainable development of the enterprise. Secondly, the desulfurization agent consumption is reduced by about half, and the environmental protection emission is more reliable, without the risk of exceeding the emission standard, meeting the ≤100mg / Nm³; Overall, the process scheme in this example has obvious advantages.

[0052]

[0053] Table 1

[0054] Furthermore, in order to suppress The air distribution in the sulfur-making furnace in this example is different from the traditional sulfur-making furnace operation. In the traditional process, the acid gas flow rate and the main air flow rate are used to form a ratio control, and an adjustable ratio coefficient is provided. The main air flow rate into the sulfur-making furnace changes in proportion to the acid gas flow rate, which plays a rough regulation role. For example, the ratio meter at the outlet of the secondary reactor is set according to / = 2:1, forming cascade control with the fine-tuning air of the sulfur-making furnace. When the composition of the sour gas changes, it makes up for the deficiency of the main air regulation and plays a fine-tuning role, enabling the total air volume of the sulfur-making furnace to achieve / = 2:1 control.

[0055] However, since the ratio meter detects the data after the reaction, when the ratio meter detects / ≠ 2:1, although it can be adjusted back in time through the fine-tuning air, there has been a factual deviation in the air distribution ratio, and there is a lag in the overall control loop. Therefore, in this example, while retaining the function of the main adjustment control loop in the traditional process, the ratio meter is preferably set at the outlet of the secondary Claus reactor (i.e., the outlet of the selective hydrogenation reactor) to form cascade control with the fine-tuning air control loop of the sulfur-making furnace according to concentration, and control concentration to be within 0.5 - 0.8%, value is close to zero, so as to make the under-oxygen degree in the sulfur-making furnace higher.

[0056] With this setting, the control target of the traditional process is that the sulfur-making furnace maintains an under-oxygen environment, / = 2:1 at one point, while the process control target of this example is that the sulfur-making furnace maintains an under-oxygen environment, = 0.5 - 0.8% within a range. Obviously, the latter is easier to achieve. The optimized control loop can more effectively prevent the excessive air distribution volume in the sulfur-making furnace, thereby resulting in low conversion rate in the sulfur-making furnace, local over-oxygen or oxygen leakage, and possible formation of combined generation, which may lead to high emissions of the downstream tail furnace problem.

[0057] Furthermore, as Figures 2 to 3 shown, the example of the tail gas treatment module includes: a tail gas burner, a tail gas incinerator, and a waste heat boiler connected in sequence. The tail gas burner is an ultra-low nitrogen burner. The tail gas discharged from the tail gas trap is divided into two levels. The primary tail gas is sprayed at an angle of 30 - 90° to the axis of the tail gas incinerator furnace at the outlet of the ultra-low nitrogen burner flue. The combustion-supporting air is sprayed twice into the tail gas burner in a direction perpendicular to the axis of the furnace to mix and react with the primary tail gas, and then the secondary tail gas is introduced into the tail gas incinerator furnace.

[0058] Specifically, since the waste heat boiler after the incineration of tail gas produces steam with a by-product of more than 4.0MPaG, the flue gas temperature at the outlet of the waste boiler is appropriately increased to above 270℃ to avoid the problem of waste heat boiler heat exchange tube blockage caused by upstream ammonia escape due to abnormal operation. Once ammonia cannot be decomposed in the sulfur making furnace, it will flow downstream with the sulfur making process gas. Although the tail gas incinerator burns with oxygen, the conventional operating temperature of 650~750℃ is far from the ammonia burning temperature. Ammonia is easy to crystallize and generate NH in the low temperature section of the tail furnace waste boiler. 4 HSO 3 or (NH 4 ) 2 SO 4 After the crystals block the furnace tubes, the system pressure drop increases, which will cause the sulfur recovery system to shut down. If the sulfur unit does not have a backup series, it will bring serious consequences such as the entire plant shutting down.

[0059] Therefore, in this example, it is preferred to design the tail gas burner as an ultra-low nitrogen burner solution, using steam nitrogen reduction technology and oxygen-deficient combustion technology and tail gas diversion technology to effectively control generate, The combustion of fuel and air in the burner mainly generates thermal energy. The burner adopts oxygen-deficient combustion, and the first-stage combustion air uses 80-90% of the equivalent to form sub-equivalent combustion with the fuel in the fire channel. At the same time, a stream of steam is injected into the root of the flame to reduce the temperature of the flame zone. At the same time, the water vapor reacts with hydrocarbons under high temperature conditions to generate reducing gas, which inhibits thermal type Although the ammonia-containing gas is washed with water and converted into sulfur, the ammonia content carried by the sulfur-making tail gas may still be around 20~50mg / m³. This trace amount of ammonia enters the tail gas incinerator. Once it comes into contact with the high-temperature burner flue gas above 1100℃ under peroxygen conditions, About 50% will be converted into .

[0060] To this end, this example uses diversion technology to divide the exhaust gas into two stages and distribute them to the incinerator in sequence. The first-stage exhaust gas is sprayed into the exhaust gas incinerator through an annular cavity nozzle or a multi-nozzle form at the outlet of the ultra-low nitrogen burner fire channel. The spray direction is 30~90° with the axis of the exhaust gas incinerator. The combustion adopts oxygen-deficient combustion. The high-temperature flue gas at the outlet of the fire channel contains almost no excess oxygen. The first-stage exhaust gas is mixed with the high-temperature flue gas of the fire channel, which can quickly reduce the flame temperature. The exhaust burner flame is cooled under oxygen-deficient conditions, and the exhaust gas Under hypoxic conditions, it is difficult to be oxidized to The temperature in the furnace after cooling is controlled between 900℃ and 950℃. If it is lower than 1000℃, and Oxidation reaction is difficult to occur.

[0061] The secondary combustion air is introduced into the furnace after the primary exhaust gas. The secondary combustion air is injected into the furnace in a direction perpendicular to the furnace axis using multiple nozzles. In the temperature range of 900℃~950℃, the secondary combustion air participates in the mixing reaction of the primary exhaust gas, which can effectively control the fuel type. The remaining tail gas is used as secondary tail gas and is fed into the furnace after the secondary combustion air. And other hydrocarbons can be completely reacted.

[0062] Furthermore, considering that the flue gas from the coal chemical sulfur recovery in the above example is different from that in the oil refining industry, due to the short process, the flue gas before desulfurization contains The content can still be as high as 7500mg / m³. If the emission is ≤100mg / m³, the desulfurization efficiency must reach more than 99%.

[0063] Considering that the coal chemical industry has its own ammonia source, there is no need to purchase ammonia water, and the cost of absorbent consumption is greatly reduced. Ammonia desulfurization is the most economical choice, and no wastewater is produced. The by-product solid ammonium sulfate can be used as fertilizer, achieving a combination of environmental protection and economic benefits. Therefore, the unrecovered sulfide can be incinerated and the waste heat is recovered by the ammonia desulfurization process, and the sulfide containing The low-temperature flue gas is subjected to ammonia desulfurization, which is the best combination with the "two-stage Claus + partial selective hydrogenation + selective oxidation" process of the above-mentioned example of the present invention. While producing more sulfur, it achieves environmentally friendly ultra-low emissions.

[0064] However, ammonia-based desulfurization easily produces aerosols, which leads to tailing of flue gas and has a certain negative impact on the environment. The composition of aerosols is complex, and in addition to the salt particles, there are also To eliminate the smoke tailing phenomenon, in this example, Figure 4 As shown, the preferred configuration of the desulfurization unit includes: a heat exchanger, a desulfurization tower, and a water scrubber, in which the tail gas output by the sulfur recovery unit is mixed with a blue-eliminating solvent and enters the desulfurization tower through a heat exchanger for cyclic ammonia desulfurization, and the output flue gas is sent to a water scrubber to remove entrained particulate matter, and then heated by a heat exchanger before being discharged, while eliminating white smoke. This eliminates the aerosol and blue plume problems existing in the existing ammonia desulfurization technology.

[0065] On the other hand, Figure 5 As shown, corresponding to the above system example, the present invention also provides a sulfur recovery method suitable for crushed coal pressurized gasification technology, the steps of which include:

[0066] After the low-temperature methanol-washed acid gas is washed with water to remove ammonia and methanol, it is subjected to countercurrent contact absorption with amine liquid to separate heavy hydrocarbons and take away part of the , thereby concentrating the acid gas , to generate pre-treated acid gas; the pre-treated acid gas is subjected to sulfur recovery treatment, and the generated tail gas is desulfurized and then discharged.

[0067] In an optional example, the sulfur recovery treatment step includes: heating the pretreated acid gas, sending it into a sulfur-making furnace burner to mix it with oxygen double cyclone to output high-temperature process gas, cooling and condensing it through a steam generator and a sulfur condenser to separate the sulfur, and after the process gas is heated, sending it to a Claus reactor and a selective oxidation reactor for reaction in sequence, and condensing and separating the sulfur through the sulfur condensers equipped with each reactor in sequence, separating the sulfur through the tail gas collector, and then sending it into the tail gas treatment module for oxygen-deficient and low-nitrogen combustion and then oxygen-superoxide complete incineration of the combustibles.

[0068] In an optional example, the desulfurization step includes: mixing the exhaust gas after sulfur recovery treatment with a blue-eliminating solvent, performing ammonia desulfurization after heat exchange and cooling, washing the flue gas after desulfurization with water to remove entrained particulate matter, and then discharging it after heat exchange and heating.

[0069] In summary, the sulfur recovery method and system suitable for crushed coal pressurized gasification technology provided by the present invention cleverly designs a low-temperature methanol washing acid gas pretreatment process to remove a certain amount of ammonia and methanol and improve the acid gas content. concentration, and separate the heavy hydrocarbon gas and take away part , thus solving the problem of low-temperature methanol washing feed acid gas in the existing crushed coal pressurized gasification technology The concentration is low (e.g. ≯30%), contains ammonia and heavy hydrocarbons, which cannot meet the basic requirements of Claus sulfur production, thus leading to various production problems as described in the background technology. In this way, the problem of abnormal impurities carried by the feed acid gas is overcome, thereby ensuring that the sulfur recovery device suitable for the crushed coal pressurized gasification process can operate normally, stably and for a long period of time.

[0070] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is only limited by the claims and their full scope and equivalents. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0071] Those skilled in the art can understand that, in addition to implementing the system, device, unit and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be regarded as structures within the hardware component; the modules for implementing various functions can also be regarded as both software programs for implementing the method and structures within the hardware component.

[0072] In addition, all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including a number of instructions to enable a single-chip microcomputer, a chip or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), disk or optical disk and other media that can store program codes.

[0073] In addition, various implementation modes of the embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed by the embodiments of the present invention.

Claims

1. A sulfur recovery system suitable for crushed coal pressurized gasification technology, comprising: Acid gas pretreatment unit, sulfur recovery unit, desulfurization unit, wherein the acid gas pretreatment unit includes: a washing tower, an absorption tower, and a regeneration tower arranged in sequence, so that the acid gas is washed with low-temperature methanol. After the acid gas is washed and removed with a certain amount of ammonia and methanol in the washing tower, it is countercurrently contacted and absorbed with amine liquid to separate heavy hydrocarbons and take away some , while in acidic gas , and other parts After being absorbed by the amine solution, it is sent to the regeneration tower to precipitate the and concentrated After the pre-treatment of the acid gas, it is sent to the sulfur recovery unit to recover liquid sulfur, and the generated tail gas is sent to the desulfurization unit for treatment and then discharged.

2. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 1, wherein: The residual ammonia and methanol content of the low-temperature methanol-washed acid gas after washing and removal in the washing tower are both ≤20mg / m 3 .

3. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 1, wherein the sulfur recovery unit comprises: The preheater, sulfur-making furnace, steam generator, sulfur condenser, heater, Claus reactor, selective oxidation reactor, tail gas collector and tail gas treatment module are connected in sequence, wherein the pretreated acid gas is heated by the preheater, enters from the burner of the sulfur-making furnace, is mixed with the double cyclone of oxygen to generate high-temperature process gas in the furnace, is cooled and condensed by the steam generator and the sulfur condenser to separate the sulfur, the process gas is heated by the heater, and is sequentially sent to the Claus reactor and the selective oxidation reactor for reaction, and is sequentially condensed and separated by the sulfur condensers equipped with each reactor, and the process gas enters the tail gas treatment module through the tail gas collector.

4. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 3, wherein: The number of stages of the heater is determined according to the number of stages of the Claus reactor and the selective oxidation reactor, and can be one stage, two stages or three stages.

5. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 3, wherein: The Claus reactor is provided with two stages, wherein the upper 2 / 3 of the second-stage Claus reactor is filled with a titanium-grade sulfur recovery catalyst, and the lower 1 / 3 is filled with a selective hydrogenation catalyst.

6. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 5, wherein: The outlet of the secondary Claus reactor is provided with a ratiometer to The concentration and the fine-tuning wind control loop of the sulfur furnace form a cascade regulation to control The concentration is 0.5-0.8%, The value is close to zero.

7. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 3, wherein: The exhaust gas treatment module includes: an exhaust gas burner, an exhaust gas incinerator, and a waste heat boiler connected in sequence, wherein the exhaust gas burner is an ultra-low nitrogen burner, and the exhaust gas discharged from the exhaust collector is divided into two stages. The first-level exhaust gas is sprayed at an angle of 30~90° to the axis of the exhaust gas incinerator furnace at the outlet of the ultra-low nitrogen burner fire channel, and the combustion-supporting air is sprayed into the exhaust gas burner twice in a direction perpendicular to the axis of the furnace to mix and react with the first-level exhaust gas, and then the second-level exhaust gas is added to the exhaust gas incinerator furnace.

8. The sulfur recovery system suitable for crushed coal pressurized gasification technology according to claim 3, wherein the desulfurization unit comprises: The heat exchanger, desulfurization tower and water scrubber are arranged in sequence, wherein the tail gas output by the sulfur recovery unit is mixed with the blue-scavenging solvent and enters the desulfurization tower for cyclic desulfurization through the heat exchanger, and the output flue gas is sent to the water scrubber to remove the entrained particulate matter, and then discharged after being heated by the heat exchanger.

9. A sulfur recovery method suitable for crushed coal pressurized gasification technology, comprising the following steps: After the low-temperature methanol-washed acid gas is washed with water to remove ammonia and methanol, it is subjected to countercurrent contact absorption with amine liquid to separate heavy hydrocarbons and take away part of the , thereby concentrating the acid gas , to generate pretreated acid gas; The pre-treated acid gas is subjected to sulfur recovery treatment, and the generated tail gas is desulfurized before being discharged.

10. The sulfur recovery method suitable for crushed coal pressurized gasification technology according to claim 9, wherein the sulfur recovery treatment step comprises: The pretreated acid gas is heated and sent to the sulfur-making furnace burner to mix with oxygen double cyclone to output high-temperature process gas. The sulfur is separated by cooling and condensation through the steam generator and sulfur condenser. After being heated, the process gas is sent to the Claus reactor and the selective oxidation reactor for reaction, and condensed and separated by the sulfur condenser connected to each reactor. The sulfur is separated by the tail gas collector and then sent to the tail gas treatment module for low-oxygen and low-nitrogen combustion and then over-oxygen complete incineration of the combustibles.

11. The sulfur recovery method suitable for crushed coal pressurized gasification technology according to any one of claims 9 or 10, wherein the desulfurization step comprises: The tail gas after sulfur recovery treatment is mixed with blue-scavenging solvent, and after heat exchange and cooling, ammonia desulfurization is carried out. The flue gas after desulfurization is washed with water to remove entrained particulate matter, and then discharged after heat exchange and heating.

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