Dry gas deep desulfurization process and desulfurization system

Abstract

The application discloses a dry gas deep desulfurization process. The process comprises the following steps: (1) removing hydrogen sulfide from refinery dry gas through a first-stage amine liquid absorption tower; (2) removing organic sulfur from tail gas of the first-stage amine liquid absorption tower in a low-temperature absorption tower; (3) sequentially exchanging heat between the absorption tail gas and raw dry gas, and between the absorption tail gas and hydrolysis tail gas, and then heating the absorption tail gas, and then inputting the absorption tail gas into a hydrolysis reactor to convert carbonyl sulfur into hydrogen sulfide; and (4) inputting the hydrolysis tail gas into a second-stage amine liquid absorption tower, and countercurrently absorbing the hydrolysis tail gas with lean amine liquid in the tower to remove hydrogen sulfide in the dry gas. The application can purify and remove sulfides in the dry gas, reduce the content of organic sulfur and hydrogen sulfide in the gas, reduce the content of SO2 in flue gas discharged from a heating furnace of each subsequent device, and ensure safe, environmentally-friendly and efficient and stable operation of the heating furnace of the whole plant.

Description

Technical Field

[0001] This invention belongs to the field of energy-saving technology, specifically relating to a dry gas deep desulfurization process and desulfurization system. Background Technology

[0002] In the petroleum refining process, refining units produce a large amount of light hydrocarbon dry gas, mainly composed of hydrocarbons such as methane, ethane, ethylene, propane, and propylene, as well as non-hydrocarbon components such as H2, N2, and sulfides. Sulfides in the dry gas can be divided into two main categories: inorganic sulfur and organic sulfur, with the inorganic sulfur content typically being higher. According to the existing refinery process, the dry gas is usually first pressurized by a compressor before being sent to a desulfurization tower, after which it is fed into the gas pipeline network. Existing desulfurization towers mostly use amine liquid desulfurization, primarily targeting the removal of hydrogen sulfide gas (inorganic sulfur). However, amine liquid desulfurization has very little effect on the removal of organic sulfur, resulting in a high total sulfur content in the gas collected and fed into the gas pipeline network after desulfurization. Gas with a high total sulfur content is sent to the combustion furnace for combustion, leading to a series of problems such as excessive sulfur content in the flue gas, high acid dew point temperature in the flue gas, increased heat loss in the exhaust gas, and reduced furnace thermal efficiency.

[0003] Patent CN116286089A discloses a dry gas desulfurization device and method. This method involves setting up a mercaptan conversion tower and a diesel absorption desulfurization tower. A mercaptan conversion agent is placed in the mercaptan conversion tower, and packing, a coalescing separator, and a liquid distributor are installed in the diesel absorption tower. This two-step desulfurization process efficiently removes organic sulfur from dry gas. First, the dry gas passes through the mercaptan conversion tower where, under the action of oxygen and the mercaptan conversion agent, the methanethiol in the dry gas is converted to dimethyl disulfide. Simultaneously, hydrogen sulfide is converted to elemental sulfur and adsorbed into the micropores of the mercaptan conversion agent. Then, an alkali is used to wash away the elemental sulfur from the mercaptan conversion agent. Further, the dimethyl disulfide in the dry gas is removed by diesel absorption and washing. However, this process not only generates waste alkali and solid waste pollutants but also contains other organic sulfur compounds besides mercaptans, such as carbonyl sulfur, which are difficult to convert and treat.

[0004] CN 116392947 A discloses a method for cascade desulfurization of rich gas in refineries. The method adopts a process of first mixing and desulfurizing the rich gas in refineries, and then separating and utilizing it. This method improves upon the shortcomings of existing processes that first separate the rich gas and then desulfurize it, making full use of the composition characteristics of the raw materials, increasing the desulfurization rate, and producing ultra-low sulfur rich gas products. The total sulfur content of the refined dry gas is <0.5ppm, and there is no mercaptan sulfur; the total sulfur content of the refined liquefied petroleum gas is <1ppm, and the mercaptan sulfur content is <0.2ppm; at the same time, it reduces equipment investment. Summary of the Invention

[0005] To address the problem of high total sulfur content in the gas pipeline network due to high organic sulfur content in dry gas in existing technologies, this invention provides a deep desulfurization process and system for dry gas. This system can purify and remove organic sulfides and hydrogen sulfide from the dry gas, reducing the sulfur content in the gas and consequently lowering the SO2 content in the flue gas emitted from the heating furnaces of subsequent units, ensuring the safe, environmentally friendly, efficient, and stable operation of all heating furnaces in the plant.

[0006] According to the first objective of the invention, the present invention provides a dry gas deep desulfurization process.

[0007] Specifically, the dry gas deep desulfurization process includes the following:

[0008] (1) The refinery dry gas first passes through a primary amine absorption tower to remove hydrogen sulfide, reducing the hydrogen sulfide content in the dry gas to below 400 mg / m³. 3 The amine liquid used in the primary amine liquid absorption tower comes from the amine liquid discharged from the bottom of the secondary amine liquid absorption tower. The amine liquid is fed from the top of the primary amine liquid absorption tower and is countercurrently absorbed and desulfurized with the dry gas entering from the bottom of the primary amine liquid absorption tower. The desulfurized dry gas is discharged from the top of the primary amine liquid absorption tower through a pipeline. The rich amine liquid is discharged from the bottom of the tower.

[0009] (2) After removing hydrogen sulfide in step (1), the dry gas enters the low-temperature absorption tower for organic sulfur removal: the lean absorption oil is cooled by the absorption oil heat exchanger and cooler in sequence and then fed into the upper part of the low-temperature absorption tower. It is then absorbed countercurrently with the dry gas entering from the lower part of the low-temperature absorption tower to remove organic sulfur compounds such as mercaptans, sulfides, and thiophene sulfur from the dry gas. The absorption tail gas is discharged from the top of the low-temperature absorption tower through the absorption tail gas pipeline, and the rich absorption oil is discharged from the bottom of the low-temperature absorption tower.

[0010] (3) After the absorption tail gas exchanges heat with the raw material dry gas, it continues to exchange heat with the hydrolysis tail gas of the hydrolysis reactor. After being heated by the heater, it enters the hydrolysis reactor together with water vapor. Under the action of the hydrolysis catalyst, carbonyl sulfur is converted into hydrogen sulfide and carbon dioxide, and the hydrolysis tail gas is discharged from the hydrolysis reactor.

[0011] (4) After exchanging heat with the hydrolysis tail gas obtained in step (3) and the absorption tail gas obtained in step (2), the tail gas enters the secondary amine liquid absorption tower from the bottom and is absorbed countercurrently with the lean amine liquid entering from the top of the secondary amine liquid absorption tower to remove hydrogen sulfide from the absorption tail gas. The amine liquid after absorbing hydrogen sulfide is discharged from the bottom of the secondary amine liquid absorption tower and pumped to the primary amine liquid absorption tower to remove hydrogen sulfide by the amine liquid pump. The purified dry gas is discharged from the top of the amine liquid absorption tower.

[0012] Furthermore, the total sulfur content of the dry gas is generally around 100 mg / m³. 3 The above, of which the carbonyl sulfur content is greater than 30 mg / m³ 3 Preferably, the carbonyl sulfide content is greater than 50 mg / m3 .

[0013] Furthermore, the operation of the low-temperature absorption tower adopts conventional conditions in the art. For example, the operating temperature is 10–20°C, the absorption pressure is 0.6–1.5 MPaG, and the absorption liquid-to-gas ratio is 40–200 L / m³. 3 The preferred liquid-to-gas ratio is 60–100 L / m³. 3 .

[0014] Furthermore, the absorbent oil used in the low-temperature absorption tower has an initial boiling point of 160–220℃, a final boiling point of 320–360℃, and a density of 850–950 kg / m³ at 20℃. 3 The absorbent oil can be selected from one or more of the following: ordinary second-line diesel, ordinary third-line diesel, catalytic crude diesel, and refined diesel.

[0015] Furthermore, heat exchange occurs between lean and rich absorbent oil within the absorbent oil heat exchanger. After the temperature of the lean absorbent oil drops to 30°C, it is further cooled to 10–20°C in the cooler.

[0016] Furthermore, the feed dry gas and the absorption tail gas exchange heat in the dry gas heat exchanger, and the temperature of the absorption tail gas is increased to 20-30°C.

[0017] Furthermore, the water content in the dry gas entering the hydrolysis reactor is generally controlled at 0.1–0.5 v, preferably 0.2–0.4 v. The water content in the dry gas is achieved by adjusting the amount of steam added to the hydrolysis reactor.

[0018] Furthermore, the reaction temperature of the hydrolysis reactor is 120–130°C, the operating pressure is generally 0.6–1.5 MPaG, and the gas hourly space velocity is 500–1200 h⁻¹. -1 The preferred volume hourly space velocity is 700–900 h⁻¹. -1 .

[0019] Furthermore, the hydrolysis catalyst can be selected from conventional catalysts in the art. For example, the active component of a typical hydrolysis catalyst is an alkali metal oxide. The hydrolysis catalyst is arranged in a fixed bed form inside the hydrolysis reactor. The hydrolysis catalyst typically includes a support and a supported alkali metal oxide. The support is selected from one or more of SiO2, Al2O3, X-type molecular sieves, Y-type molecular sieves, A-type molecular sieves, and granular activated carbon. The active component is selected from one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, ammonia, sodium nitrate, and potassium carbonate. The content of the active component is generally 5-20 wt%.

[0020] Furthermore, the hydrolysis catalyst can be in the shape of a clover, four-leaf clover, strip, or sphere. The preparation of the hydrolysis catalyst is a conventional technique in the art; for example, the preparation process of a hydrogenation catalyst can be referenced.

[0021] Furthermore, after treatment in a hydrolysis reactor, the molar conversion rate of carbonyl sulfur in the dry gas can reach over 98%.

[0022] Furthermore, in step (2), the absorption tail gas and the hydrolysis tail gas exchange heat through the absorption tail gas heat exchanger. After the heat exchange, the temperature of the absorption tail gas rises to 110-120°C, and is further heated to 130-140°C by steam in the heater.

[0023] Furthermore, the total sulfur concentration of the purified dry gas obtained in step (3) is ≤20 mg / m³. 3 .

[0024] Furthermore, the operation of the primary amine absorption tower in step (1) and the secondary amine absorption tower in step (3) are conventional operations in the art. For example, the absorption temperature is room temperature, the absorption pressure is 0.6–1.5 MPaG, and the absorption liquid-to-gas ratio is 3–8 L / m³. 3 .

[0025] Furthermore, the amine liquid used in the secondary amine liquid absorption tower comes from the nearest amine liquid regeneration pipeline; the amine-rich liquid after the primary amine liquid absorption tower absorbs hydrogen sulfide is sent to the nearest amine liquid regeneration tower for regeneration and reuse.

[0026] Furthermore, the heat exchange technology, heating technology, and cooling technology in this invention are all well-known to those skilled in the art.

[0027] According to a second objective of the present invention, the present invention also provides a dry gas desulfurization system.

[0028] The dry gas desulfurization system of the present invention can be used to implement the dry gas deep desulfurization process described above.

[0029] Specifically, the dry gas desulfurization system includes: a low-temperature absorption tower, a hydrolysis reactor, a primary amine liquid absorption tower, a secondary amine liquid absorption tower, an amine liquid pump, a heat exchanger, a cooler, a heater, and connecting pipelines.

[0030] The first-stage amine liquid absorption tower uses amine liquid to absorb and remove hydrogen sulfide from the refinery dry gas. After the refinery dry gas completes the absorption in the first-stage amine liquid absorption tower, it becomes rich amine liquid and dry gas after first-stage amine liquid absorption.

[0031] In the low-temperature absorption tower, after the dry gas is absorbed by the primary amine liquid, it comes into countercurrent contact with the low-temperature absorption oil (lean absorption oil) to efficiently absorb organic sulfides such as thiols, sulfides, dimethyl disulfide, and thiophene in the dry gas. After absorption, rich absorption oil and absorption tail gas are obtained.

[0032] The hydrolysis reactor is used to hydrolyze carbonyl sulfide in the absorption tail gas to produce hydrogen sulfide. The absorption tail gas is hydrolyzed in the hydrolysis reactor to obtain hydrolyzed tail gas. A hydrolysis catalyst bed is set inside the hydrolysis reactor.

[0033] The secondary amine liquid absorption tower uses lean amine liquid to absorb and remove hydrogen sulfide from the hydrolysis tail gas. After the hydrolysis tail gas is absorbed in the secondary amine liquid absorption tower, purified dry gas is obtained.

[0034] Furthermore, the low-temperature absorption tower is a packed tower. The low-temperature absorption tower includes a dry gas inlet at the bottom, a rich absorbent oil outlet at the bottom, a lean absorbent oil inlet at the top, and an absorbent tail gas outlet at the top.

[0035] Furthermore, the desulfurization system also includes a dry gas heat exchanger, in which the absorption tail gas of the low-temperature absorption tower and the dry gas after absorption by the primary amine liquid exchange heat.

[0036] Furthermore, the desulfurization system also includes an absorbent oil heat exchanger and a cooler. The absorbent oil heat exchanger is used for heat exchange between the rich absorbent oil and the lean absorbent oil. The cooler is used to further cool the lean absorbent oil after it has been cooled down.

[0037] Furthermore, the desulfurization system also includes an absorption tail gas heat exchanger, in which the absorption tail gas from the dry gas heat exchanger and the hydrolysis tail gas exchange heat.

[0038] Furthermore, the desulfurization system also includes a heater for heating the preheated absorption tail gas after it has been preheated by the absorption tail gas heat exchanger. The heater can be heated by steam.

[0039] Furthermore, the hydrolysis reactor includes an absorption tail gas inlet at the bottom and a hydrolysis tail gas outlet at the top. The hydrolysis tail gas outlet at the top of the hydrolysis reactor is connected to the hot material inlet of the absorption tail gas heat exchanger via a pipeline, and the absorption tail gas inlet at the bottom of the hydrolysis reactor is connected to the heater outlet via a pipeline; the absorption tail gas inlet is also connected to a steam pipeline to supplement the water vapor required for the hydrolysis reaction.

[0040] Furthermore, the hydrolysate bed in the hydrolysis reactor is a fixed bed. A gas distributor can also be installed at the bottom of the hydrolysis reactor to uniformly distribute the dry gas and steam mixture entering the reactor.

[0041] Furthermore, the primary amine absorption tower and the secondary amine absorption tower can be packed towers or plate towers. The primary amine absorption tower includes a dry gas inlet from the raw material refinery at the bottom, a rich amine liquid outlet at the bottom, a lean amine liquid inlet at the top, and a dry gas outlet after primary amine liquid absorption at the top. The dry gas inlet from the raw material refinery at the bottom of the tower is connected to a dry gas pipeline, the rich amine liquid outlet at the bottom of the tower is connected to a rich amine liquid pipeline, the lean amine liquid inlet at the top of the tower is connected to the amine pump outlet, and the dry gas outlet after primary amine liquid absorption at the top of the tower is connected to the hot material inlet of the dry gas heat exchanger.

[0042] Furthermore, the secondary amine absorption tower includes a lower hydrolysis tail gas inlet, a bottom amine liquid outlet, an upper lean amine liquid inlet, and a top purified dry gas outlet. Specifically, the hydrolysis tail gas inlet of the secondary amine absorption tower is connected to the hot material outlet of the absorption tail gas heat exchanger via a pipeline; the amine liquid outlet is connected to the upper amine liquid inlet of the primary amine absorption tower via a pipeline and an amine liquid pump; the lean amine liquid inlet is connected to a lean amine liquid pipeline; and the purified dry gas outlet is connected to a purified dry gas pipeline.

[0043] Furthermore, according to the present invention, the dry gas outlet pipe after primary amine liquid absorption is connected to the hot material inlet of the dry gas heat exchanger, and the hot material outlet of the dry gas heat exchanger is connected to the dry gas inlet at the bottom of the low-temperature absorption tower. The dry gas undergoes organic sulfur removal treatment in the low-temperature absorption tower, and the gas after absorption is the absorption tail gas. The absorption tail gas outlet at the top of the low-temperature absorption tower is connected to the cold material inlet of the dry gas heat exchanger, the cold material outlet of the dry gas heat exchanger is connected to the cold material inlet of the absorption tail gas heat exchanger, the cold material outlet of the absorption tail gas heat exchanger is connected to the cold material inlet of the heater, and the cold material outlet of the heater is connected to the absorption tail gas inlet at the bottom of the hydrolysis reactor. The lean absorbent oil pipe is connected to the hot material inlet of the absorbent oil heat exchanger, the hot material outlet of the absorbent oil heat exchanger is connected to the cooler inlet, and the cooler outlet is connected to the lean absorbent oil inlet at the top of the low-temperature absorption tower. The lean absorbent oil and the dry gas entering from the bottom of the low-temperature absorption tower are absorbed countercurrently within the tower. After absorption, the lean absorbent oil becomes rich absorbent oil. The rich absorbent oil outlet at the bottom of the low-temperature absorption tower is connected to the cold material inlet of the absorbent oil heat exchanger, and the cold material outlet of the absorbent oil heat exchanger is connected to the rich absorbent oil pipe.

[0044] Furthermore, according to the present invention, in the hydrolysis reactor, carbonyl sulfide is converted into hydrogen sulfide and carbon dioxide under the action of a hydrolysis catalyst to obtain hydrolysis tail gas.

[0045] Furthermore, in the amine absorption tower, the hydrolysis tail gas rich in hydrogen sulfide is absorbed countercurrently with the lean amine liquid to remove the hydrogen sulfide from the hydrolysis tail gas, resulting in purified dry gas and rich amine liquid.

[0046] In this invention, the cooler, heat exchanger and heater can be in the form of shell and tube heat exchangers, plate heat exchangers, etc., and are all well known to those skilled in the art.

[0047] The inventors of this application, through research on existing dry gas desulfurization processes, discovered that dry gas contains not only a high content of hydrogen sulfide, but also various sulfur-containing compounds such as carbonyl sulfide, carbon disulfide, mercaptan sulfides (e.g., methanethiol, ethanethiol, isopropanethiol), sulfides (e.g., dimethyl sulfide, ethyl sulfide, dimethyl disulfide, C5+ sulfide), and thiophene. Existing processes may not be able to effectively desulfurize dry gas, such as reducing the total sulfur content to 20 mg / m³. 3 At or below this level, it may be impossible to reduce desulfurization energy consumption while simultaneously reducing total sulfur. The inventors also discovered through research that the carbonyl sulfur hydrolysis process is greatly affected by the concentration of hydrogen sulfide in the dry gas; high levels of hydrogen sulfide strongly inhibit carbonyl sulfur hydrolysis. In this invention, hydrogen sulfide in the dry gas is first effectively removed using an amine absorption method, reducing it to below 400 mg / m³. 3 Then, a low-temperature absorption method is used to efficiently absorb the organic sulfides contained therein, except for carbonyl sulfide; then, the absorption tail gas is hydrolyzed to remove carbonyl sulfide; finally, hydrogen sulfide generated by hydrolysis is removed again by amine liquid absorption, thereby achieving efficient desulfurization while reducing the total energy consumption of the desulfurization process.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The dry gas deep desulfurization process of this invention adopts a combined technology of amine washing-low temperature oil absorption-hydrolysis-hydrogen sulfide deep absorption. The dry gas, after being pre-treated with amine solution to remove hydrogen sulfide, first passes through a low temperature absorption tower to remove organic sulfur (except for carbonyl sulfide). Then, it passes through a hydrolysis reactor to convert the carbonyl sulfide in the dry gas into hydrogen sulfide. Finally, the hydrogen sulfide is further removed in the amine solution absorption tower, which can reduce the sulfide content in the dry gas to 20 mg / m³. 3 The desulfurization process of this invention significantly reduces the total sulfur content of the gas. It achieves high sulfide removal efficiency, improves the properties of the gas, and consequently reduces the SO2 content in the flue gas emitted from the heating furnaces of subsequent units, ensuring the safe, environmentally friendly, efficient, and stable operation of all heating furnaces in the plant.

[0050] 2. In the dry gas deep desulfurization process of this invention, the combined technology of amine washing-low-temperature oil absorption-hydrolysis-hydrogen sulfide deep absorption is a highly efficient recovery technology. Low-temperature absorption can efficiently recover organic sulfides, with an organic sulfur recovery rate of over 98%; organic sulfur hydrolysis can achieve over 98% conversion of carbonyl sulfur; and organic amine absorption can achieve efficient absorption of hydrogen sulfide. Therefore, this technology can efficiently recover sulfur resources.

[0051] 3. In the dry gas deep desulfurization process of this invention, the combined technology of amine washing-low temperature oil absorption-hydrolysis-hydrogen sulfide deep absorption is an energy-saving technology. The two-stage amine liquid absorption adopts cascade or stepped use of amine liquid. The lean amine liquid first absorbs hydrolyzed hydrogen sulfide in the secondary amine liquid absorption tower, and then enters the primary amine liquid absorption tower to absorb hydrogen sulfide in the refinery dry gas feedstock. This saves the amount of amine liquid used, improves the effect of amine liquid absorption and removal of hydrogen sulfide, and significantly reduces the energy consumption of amine liquid system regeneration.

[0052] 4. In the dry gas deep desulfurization process of the present invention, the combined process of amine washing-low temperature oil absorption-hydrolysis-hydrogen sulfide deep absorption first removes high concentrations of hydrogen sulfide and heavy molecular organic sulfur from refinery dry gas, ensuring efficient conversion of carbon-based sulfur hydrolysis and deep removal of organic sulfur from dry gas.

[0053] 5. In the dry gas desulfurization system of this invention, the combined technology of amine washing-low temperature oil absorption-hydrolysis-hydrogen sulfide deep absorption is a low-energy-consumption, high-efficiency, safe and environmentally friendly recycling technology that does not generate waste. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the dry gas desulfurization process of the present invention.

[0055] Among them, 101-dry gas pipeline, 102-dry gas heat exchanger, 103-low temperature absorption tower, 104-lean absorption oil pipeline, 105-absorption oil heat exchanger, 106-cooler, 107-rich absorption oil pipeline, 108-absorption tail gas heat exchanger, 109-heater, 110-hydrolysis reactor, 111-steam pipeline, 112-secondary amine liquid absorption tower, 113-purified dry gas pipeline, 114-rich amine liquid pipeline, 115-lean amine liquid pipeline, 116-primary amine liquid absorption tower, 117-amine liquid pump. Detailed Implementation

[0056] The present invention will be further illustrated by specific embodiments below, but is not limited to the embodiments described below.

[0057] Example 1

[0058] Combination Figure 1 The dry gas desulfurization system of the present invention includes: a primary amine liquid absorption tower, a low-temperature absorption tower, a hydrolysis reactor, a secondary amine liquid absorption tower, an amine liquid pump, a heat exchanger, a cooler, a heater, and connecting pipes.

[0059] The primary amine absorption tower 116 uses amine liquid to absorb and remove hydrogen sulfide from refinery dry gas. After absorption in the primary amine absorption tower 116, the refinery dry gas is obtained as rich amine liquid and dry gas after primary amine liquid absorption. The primary amine absorption tower 116 includes a raw material refinery dry gas inlet at the bottom, a rich amine liquid outlet at the bottom, a lean amine liquid inlet at the top, and a primary amine liquid dry gas outlet at the top.

[0060] The low-temperature absorption tower 103 has a primary amine solution absorption process in which dry gas is countercurrently contacted with low-temperature absorption oil (lean absorption oil) to efficiently absorb organic sulfides such as thiols, sulfides, dimethyl disulfide, and thiophene in the dry gas. After absorption, rich absorption oil and absorption tail gas are obtained. The low-temperature absorption tower 103 includes a dry gas inlet at the bottom, a rich absorption oil outlet at the bottom, a lean absorption oil inlet at the top, and an absorption tail gas outlet at the top.

[0061] Hydrolysis reactor 110 is used to hydrolyze carbonyl sulfur in the absorption tail gas to generate hydrogen sulfide. After the absorption tail gas is hydrolyzed in the hydrolysis reactor 110, hydrolyzed tail gas is obtained. A hydrolyzing agent bed is provided inside the hydrolysis reactor 110. Hydrolysis reactor 103 includes an absorption tail gas inlet at the bottom and a hydrolyzed tail gas outlet at the top.

[0062] The secondary amine absorption tower 112 uses lean amine liquid to absorb and remove hydrogen sulfide from the hydrolysis tail gas. After absorption in the amine absorption tower, the hydrolysis tail gas is purified into dry gas. The secondary amine absorption tower 112 includes a hydrolysis tail gas inlet at the bottom, an amine liquid outlet at the bottom, a lean amine liquid inlet at the top, and a purified dry gas outlet at the top.

[0063] The low-temperature absorption tower 103 is a packed tower. The dry gas inlet at the bottom of the tower is connected to the hot material outlet of the dry gas heat exchanger 102 through a pipeline. The rich absorption oil outlet at the bottom of the tower is connected to the cold material inlet of the absorption oil heat exchanger 105 through a pipeline. The absorption tail gas outlet at the top of the tower is connected to the cold material inlet of the dry gas heat exchanger 102 through a pipeline. The lean absorption oil inlet at the top of the tower is connected to the outlet of the cooler 106 through a pipeline.

[0064] The hydrolysis reactor 110 is equipped with a hydrolyzing agent bed. The hydrolysis tail gas outlet at the top of the hydrolysis reactor 110 is connected to the hot material inlet of the absorption tail gas heat exchanger 108 through a pipeline, and the absorption tail gas inlet at the bottom of the hydrolysis reactor 110 is connected to the outlet of the heater 109 through a pipeline. The absorption tail gas inlet is also connected to the steam pipeline 111 to supplement the water vapor required for the hydrolysis reaction.

[0065] The primary amine absorption tower 116 and the secondary amine absorption tower 112 can be packed towers or plate towers. The raw material refinery dry gas inlet at the bottom of the primary amine absorption tower 116 is connected to the dry gas pipeline 101. The rich amine liquid outlet at the bottom of the tower is connected to the rich amine liquid pipeline 114 via a pipeline. The lean amine liquid inlet at the top of the tower is connected to the amine pump outlet. The dry gas outlet after primary amine absorption at the top of the tower is connected to the hot material inlet of the dry gas heat exchanger 102. The hydrolysis tail gas inlet at the bottom of the secondary amine absorption tower 112 is connected to the hot material outlet of the absorption tail gas heat exchanger via a pipeline. The amine liquid outlet at the bottom of the tower is connected to the amine liquid inlet at the top of the primary amine absorption tower 116 via a pipeline and the amine pump 117. The lean amine liquid inlet at the top of the tower is connected to the lean amine liquid pipeline. The purified dry gas outlet at the top of the tower is connected to the purified dry gas pipeline.

[0066] Example 2

[0067] Combination Figure 1 The dry gas deep desulfurization process of the present invention includes the following:

[0068] (1) The refinery dry gas first passes through the primary amine liquid absorption tower 116 to remove hydrogen sulfide, so that the hydrogen sulfide content in the dry gas after primary amine liquid absorption is less than 400 mg / m³. 3 The amine liquid used in the primary amine liquid absorption tower 116 comes from the amine liquid discharged from the bottom of the secondary amine liquid absorption tower 112. The amine liquid is fed from the top of the primary amine liquid absorption tower 116 and is countercurrently absorbed and desulfurized with the raw material dry gas entering from the bottom of the primary amine liquid absorption tower 116. The dry gas after absorption and desulfurization is discharged from the top of the primary amine liquid absorption tower through a pipeline. The rich amine liquid is discharged from the bottom of the tower and can be regenerated in the amine liquid regeneration system.

[0069] (2) After absorption by the primary amine liquid, the dry gas undergoes organic sulfur removal treatment in the low-temperature absorption tower 103: the lean absorption oil is cooled by the absorption oil heat exchanger 105 and the cooler 106 in sequence and then fed into the upper part of the low-temperature absorption tower. It is then absorbed countercurrently with the dry gas entering from the lower part of the low-temperature absorption tower to remove organic sulfur compounds such as mercaptans, sulfides, and thiophene sulfur from the dry gas. The absorption tail gas is discharged from the top of the low-temperature absorption tower 103 through the absorption tail gas pipeline, and the rich absorption oil is discharged from the bottom of the low-temperature absorption tower 103.

[0070] (3) After the absorption tail gas exchanges heat with the raw material dry gas, it continues to exchange heat with the hydrolysis tail gas of the hydrolysis reactor 110. After being heated by the heater 109, it enters the hydrolysis reactor 110 together with water vapor. Under the action of the hydrolysis catalyst, carbonyl sulfur is converted into hydrogen sulfide and carbon dioxide, and the hydrolysis tail gas is discharged from the top of the hydrolysis reactor 110.

[0071] (4) After exchanging heat with the absorption tail gas obtained in step (2), the hydrolysis tail gas enters the secondary amine liquid absorption tower 112 from the bottom and is absorbed countercurrently with the lean amine liquid entering from the top of the amine liquid absorption tower to remove hydrogen sulfide from the dry gas; the rich amine liquid is discharged from the bottom of the secondary amine liquid absorption tower 112 and the purified dry gas is discharged from the top of the secondary amine liquid absorption tower 112.

[0072] Example 3

[0073] Examples of applications of the process of this invention are given. Application Figure 1 The desulfurization system treats a type of dry gas. The dry gas from a petrochemical plant's refinery gas holder first enters the primary amine absorption tower 116 to remove hydrogen sulfide, ensuring the conversion efficiency of the carbon-based sulfur hydrolysis reaction. The primary amine absorption tower 116 uses organic amine liquid to absorb and remove H2S, with an amine liquid-to-gas ratio of 4 L / Nm³. 3 Absorption is performed at room temperature and 0.7 MPa. After absorption by the primary amine solution, the dry gas is then fed into the low-temperature absorption tower 103 for organic sulfur removal. Ordinary diesel oil (boiling range: 200-360℃) is used as the absorbent to remove organic sulfur compounds such as thiols, sulfides, and thiophenes from the dry gas in the gas holder. The operating temperature is 20℃, and the liquid-to-gas ratio is 80 L / m³. 3 The rich absorbent oil (diesel) is pumped to downstream units for use.

[0074] After primary amine liquid absorption, the dry gas is then absorbed by low-temperature diesel fuel. The concentration of organic sulfur compounds (excluding carbonyl sulfur) in the exhaust gas is less than 15 mg / m³. 3 The absorption tail gas is heated to 30-40°C in dry gas heat exchanger 102. Further, the absorption tail gas and hydrolysis tail gas exchange heat in absorption tail gas heat exchanger 108, raising the temperature of the absorption tail gas to 110-120°C. It is then further heated to 130-140°C by steam in heater 109. The dry gas then converts carbonyl sulfide to hydrogen sulfide in hydrolysis reactor 110. The hydrolysis reactor tail gas is cooled to 45-50°C in absorption tail gas heat exchanger 108. Finally, the dry gas enters organic amine absorption tower 112 to remove hydrogen sulfide, and the purified dry gas is then fed into the pipeline network. The dry gas purification effect is shown in Table 1.

[0075] The hydrolysis temperature of carbonyl sulfide is 120–130 °C, the operating pressure is 0.7 MPa, and the processing space velocity is 800 h⁻¹. -1 The carbonyl sulfide conversion efficiency is above 98 mol%. The carbonyl sulfide hydrolysate consists of a support and an active component. The support is mainly Al2O3, and the active components are sodium nitrate and sodium hydroxide, with the active component content being approximately 10 wt%.

[0076] After hydrolysis, carbonyl sulfide in the dry gas is converted to H2S, which is then removed by organic amine liquid absorption in the secondary amine liquid absorption tower 112. The hydrolyzed dry gas enters the secondary amine liquid absorption tower 112 to remove hydrogen sulfide, with a liquid-to-gas ratio of 4 L / Nm³. 3Absorption at room temperature and 0.7 MPa, with a lean amine solution of 30 wt% MDEA solvent, and a total sulfur concentration ≤20 mg / m³ after dry gas purification. 3 .

[0077] Table 1. Sulfide analysis data of dry gas from refinery gas holders before and after desulfurization (unit: mg / m³) 3 )

[0078]

[0079] Comparative Example 1

[0080] The above-mentioned dry gas is treated using the process flow described in CN116392947A. The raw material dry gas is first hydrolyzed to convert carbon-based sulfur into hydrogen sulfide, and then hydrogen sulfide is removed from the dry gas by absorption with an alcohol amine solution. Further, in a thiol conversion reactor, low-molecular-weight thiols such as methanethiol and ethanethiol are converted into higher-boiling-point sulfides and disulfides. Then, the heavy sulfides are separated from the dry gas by absorption distillation.

[0081] As shown in Table 1, the concentration of hydrogen sulfide in the dry gas is 2.10 × 10⁻⁶. 4 mg / m 3 The high-concentration hydrogen sulfide dry gas was directly introduced into the carbonyl sulfur hydrolysis tower. Due to the influence of chemical equilibrium, the conversion rate of carbonyl sulfur was extremely low, making it difficult to remove carbonyl sulfur. Simultaneously, the presence of other organic sulfides besides carbonyl sulfur in the dry gas also severely affected the hydrolysis reaction. Therefore, Comparative Example 1 clearly could not achieve the same desulfurization effect as Example 1.

[0082] In summary, based on the composition of the dry gas in the refinery gas holder, see Table 1. To achieve deep desulfurization of the dry gas in the gas holder, it is necessary to first remove hydrogen sulfide and heavy sulfides from the dry gas, and then further remove carbon-based sulfur to achieve efficient conversion of carbon-based sulfur hydrolysis. Finally, hydrogen sulfide is removed by absorption with amine solution to achieve deep purification of the dry gas.

Claims

1. A process for deep desulfurization of dry gas, characterized in that, Includes the following: (1) The refinery dry gas first passes through a primary amine absorption tower to remove hydrogen sulfide, reducing the hydrogen sulfide content in the dry gas to below 400 mg / m³. 3 ; The amine liquid used in the primary amine liquid absorption tower comes from the amine liquid discharged from the bottom of the secondary amine liquid absorption tower; the dry gas after absorption and desulfurization is discharged from the top of the primary amine liquid absorption tower through a pipeline, and the rich amine liquid is discharged from the bottom of the tower; (2) In step (1), the dry gas after removing hydrogen sulfide enters the low-temperature absorption tower for organic sulfur removal: the lean absorption oil is cooled by the absorption oil heat exchanger and cooler in sequence and then fed into the upper part of the low-temperature absorption tower. It is then absorbed countercurrently with the dry gas entering from the lower part of the low-temperature absorption tower to remove organic sulfur compounds such as mercaptans, sulfides, and thiophene sulfur from the dry gas. The absorption tail gas is discharged from the top of the low-temperature absorption tower through the absorption tail gas pipeline, and the rich absorption oil is discharged from the bottom of the low-temperature absorption tower. (3) After the absorption tail gas exchanges heat with the raw material dry gas, it continues to exchange heat with the hydrolysis tail gas of the hydrolysis reactor. After being heated by the heater, it enters the hydrolysis reactor together with water vapor. Under the action of the hydrolysis catalyst, carbonyl sulfur is converted into hydrogen sulfide and carbon dioxide, and the hydrolysis tail gas is discharged from the hydrolysis reactor. (4) After exchanging heat with the hydrolysis tail gas obtained in step (3) and the absorption tail gas obtained in step (2), the tail gas enters the secondary amine liquid absorption tower from the bottom and is absorbed countercurrently with the lean amine liquid entering the upper part of the secondary amine liquid absorption tower to remove hydrogen sulfide from the absorption tail gas. The amine liquid after absorbing hydrogen sulfide is discharged from the bottom of the secondary amine liquid absorption tower and pumped to the primary amine liquid absorption tower to remove hydrogen sulfide by the amine liquid pump. The purified dry gas is discharged from the top of the amine liquid absorption tower.

2. The dry gas deep desulfurization process of claim 1, wherein, The operating temperature of the low-temperature absorption tower is 10-20 ℃, the absorption pressure is 0.6-1.5 MpaG, and the absorption liquid-gas ratio is 40-200 L / m 3 .

3. The dry gas deep desulfurization process of claim 1, wherein, The oil-absorbing oil has an initial boiling point of 160-220°C, a final boiling point of 320-360°C, and a density of 850-950 kg / m 3 .

4. The dry gas deep desulfurization process of claim 3, wherein, The absorbent oil is selected from one or more of the following: ordinary second-line diesel, ordinary third-line diesel, catalytic crude diesel, and finished diesel.

5. The dry gas deep desulfurization process according to claim 1, characterized in that, The water content of the dry gas entering the hydrolysis reactor is controlled at 0.1~0.5 v%, preferably 0.2~0.4 v%; the water content in the dry gas is achieved by adjusting the amount of steam added to the hydrolysis reactor.

6. The dry gas deep desulfurization process of claim 1 wherein, The reaction temperature of the hydrolysis reactor is 120-130℃, the operating pressure is 0.6-1.5 MPaG, the gas volume space velocity is 500-1200 h -1 .

7. The dry gas deep desulfurization process of claim 1 wherein, The active component of the hydrolysis catalyst is an alkali metal oxide.

8. The dry gas deep desulfurization process of claim 7, wherein, The hydrolysis catalyst comprises a support and a supported alkali metal oxide. The support is selected from one or more of SiO2, Al2O3, X-type molecular sieve, Y-type molecular sieve, A-type molecular sieve, and granular activated carbon. The active component is selected from one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, ammonia, sodium nitrate, and potassium carbonate. The alkali metal oxide content is 5-20 wt%.

9. The dry gas deep desulfurization process of claim 1 wherein, In step (2), the absorption tail gas and the hydrolysis tail gas exchange heat through the absorption tail gas heat exchanger. After the heat exchange, the temperature of the absorption tail gas rises to 110~120℃, and is further heated to 130~140℃ by steam in the heater.

10. The dry gas deep desulfurization process of claim 1 wherein, The operating conditions of the primary amine liquid absorption tower in step (1) and the amine liquid absorption tower in step (3) are: absorption temperature is normal temperature, absorption pressure is 0.6-1.5 MPaG, absorption liquid-gas ratio is 3-8 L / m 3 .

11. A dry gas desulfurization system characterized by, include: The primary amine absorption tower absorbs and removes hydrogen sulfide from dry gas using amine liquid. After the refinery dry gas completes the absorption in the primary amine absorption tower, it yields a rich amine liquid and dry gas after primary amine liquid absorption. In the low-temperature absorption tower, after the dry gas is absorbed by the primary amine liquid, it comes into countercurrent contact with the low-temperature absorption oil to efficiently absorb organic sulfides such as mercaptans, sulfides, dimethyl disulfide, and thiophene in the dry gas. After absorption, the absorbent oil and the absorption tail gas are obtained. A hydrolysis reactor is used to hydrolyze carbonyl sulfur in the absorption tail gas to generate hydrogen sulfide. The absorption tail gas is hydrolyzed in the hydrolysis reactor to obtain hydrolyzed tail gas. A hydrolysis catalyst bed is set inside the hydrolysis reactor. The secondary amine liquid absorption tower uses lean amine liquid to absorb and remove hydrogen sulfide from the hydrolysis tail gas. After the hydrolysis tail gas is absorbed in the secondary amine liquid absorption tower, purified dry gas is obtained.

12. The dry gas sweetening system of claim 11, wherein, The low-temperature absorption tower is a packed tower; the dry gas inlet at the bottom of the tower is connected to the hot material outlet of the dry gas heat exchanger through a pipeline, the rich absorption oil outlet at the bottom of the tower is connected to the cold material inlet of the absorption oil heat exchanger through a pipeline, the absorption tail gas outlet at the top of the tower is connected to the cold material inlet of the dry gas heat exchanger through a pipeline, and the lean absorption oil inlet at the top of the tower is connected to the cooler outlet through a pipeline.

13. The dry gas sweetening system of claim 11, wherein, The desulfurization system also includes: Dry gas heat exchanger is used to exchange heat between the absorption tail gas and raw material dry gas obtained from the low temperature absorption tower. And / or, an absorption oil heat exchanger and a cooler: the absorption oil heat exchanger is used for heat exchange between rich and lean absorption oil, and the cooler is used for further cooling of the lean absorption oil after cooling. And / or, an absorption tail gas heat exchanger, which is used for heat exchange between the absorption tail gas from the dry gas heat exchanger and the hydrolysis tail gas therein. And / or, a heater, which is used to heat the absorption exhaust gas after it has been preheated by the absorption exhaust gas heat exchanger.

14. The dry gas sweetening system of claim 11, wherein, The amine outlet of the secondary amine absorption tower is connected to the amine inlet at the top of the primary amine absorption tower via a pipeline and an amine pump.

15. The dry gas sweetening system of claim 11, wherein, The primary amine absorption tower and the secondary amine absorption tower are packed towers or plate towers.

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