Coke oven gas fine desulfurization device and double gas holder combined system and control method thereof

Abstract

According to the combined system of the coke oven gas fine desulfurization device and the double gas cabinets and the control method of the combined system, purified gas obtained after coke oven gas fine desulfurization is communicated with the two coke oven gas cabinets of an original gas pipe network for combined operation, and various modes and scenes can be flexibly coped with; the switching of the two coke oven gas cabinets is realized through the opening and closing of the branch valves and the control interlocking, so as to absorb the disordered change and sudden residue of gas used by a fine desulfurization device user, and cooperatively realize the efficient fine desulfurization and supply balance of the coke oven gas.

Description

Technical Field

[0001] The invention relates to coke oven gas technology, and more specifically to a combined system of a coke oven gas fine desulfurization device and a double gas cabinet and a control method thereof. Background Art

[0002] Coke oven gas is a major by-product gas of steel enterprises, and it is also an important secondary energy source for recycling and utilization in the whole plant. After recovery, purification, transportation, storage, pressurization, mixing and other links, coke oven gas is finally burned and applied in various thermal furnaces in various production processes of steel enterprises. Since coke oven gas contains impurities such as tar, naphthalene, inorganic sulfur (H2S), organic sulfur (CS2, COS, etc.), the concentration of sulfur dioxide emitted after combustion is relatively high. With the promotion and implementation of ultra-low emissions in the steel industry, blast furnace hot blast furnaces, steel rolling heat treatment furnaces, etc. need to meet more stringent combustion tail gas SO2 emission limits, so it is necessary to set up coke oven gas purification devices to desulfurize coke oven gas. The current technical routes mainly include source control and end-of-pipe treatment after combustion. This end-of-pipe treatment method requires the installation of desulfurization facilities at multiple points, with a large amount of waste gas to be treated and a large scale of equipment. In contrast, the source control method reduces the sulfur content in coal gas through fine desulfurization, with a small amount of gas to be treated, which can greatly reduce the pressure of end-of-pipe treatment. The basic process flow of fine desulfurization of coke oven gas at the source is: the raw coke oven gas first enters the purification section to remove impurities such as naphthalene, tar, and some H2S; then the gas passes through the pressurization section and enters the hydrolysis section to convert organic sulfur into H2S, and then enters the fine desulfurization section to remove H2S and purify the gas to the user. The principle of the hydrolysis method is that under the catalyst and appropriate temperature, the organic sulfur and the water contained in the gas undergo the following hydrolysis reaction: COS+H2O→H2S+CO2, CS2+H2O→H2S+CO2.

[0003] The by-product gas system of steel enterprises needs to achieve a balance between supply and use of the pipeline network through optimized scheduling, and reduce pipeline pressure fluctuations and gas release. As a hub equipment in the process of gas storage and distribution, the piston of the gas tank needs to be kept running in an appropriate range to store and coordinate the balance of gas production and consumption. Adding a coke oven gas fine desulfurization device to the original steel gas system will inevitably affect the balance management of the original coke oven gas. A new set of large fine desulfurization process units is connected to the original gas pipeline system. The main process control problems it faces include: ensuring the system outlet pressure is stable while coordinating efficient coke oven gas fine desulfurization to reduce gas fluctuations, adapting to large fluctuations in gas load, and avoiding gas backflow.

[0004] Existing patent technologies mainly focus on the optimization of the process and equipment of coke oven gas fine desulfurization, and the system and method for the joint operation of multiple gasholders. However, there is still no detailed disclosure on how to deal with the pipeline pressure fluctuation caused by the addition of coke oven gas fine desulfurization equipment to the steel raw gas management system, especially the gas balance scheduling control between multiple gasholders and the fine desulfurization raw gas and purified gas. Summary of the invention

[0005] In order to solve the above-mentioned problems in the prior art, the present invention provides a combined system of a coke oven gas fine desulfurization device and a dual gas holder and a control method thereof. After the coke oven gas fine desulfurization device is introduced for fine desulfurization treatment, the original gas system is smoothly connected, which can not only ensure efficient desulfurization of the coke oven gas source end, but also ensure stable response to various variable operating conditions, thereby achieving balanced operation of the overall gas pipeline network.

[0006] On the one hand, a combined system of a coke oven gas fine desulfurization device and a dual gasholder and a control method thereof, comprising a coke oven gas fine desulfurization device, a raw gas pipeline and a regeneration gas pipeline respectively connected to the coke oven gas fine desulfurization device, and a purified gas pipeline connected from the coke oven gas fine desulfurization device and connected to the coke oven gas main, characterized in that: it also includes a first gasholder and a second gasholder, a raw gas connecting branch is provided between the first gasholder, the second gasholder and the raw gas pipeline; a pressure maintaining connecting branch is provided between the first gasholder and the purified gas pipeline; a regeneration gas control branch is provided between the coke oven gas fine desulfurization device and the regeneration gas pipeline; a reflux control branch is provided between the coke oven gas fine desulfurization device and the purified gas pipeline; a gasholder communication branch is provided between the first gasholder and the second gasholder.

[0007] The coke oven gas fine desulfurization device comprises a pre-adsorption unit, a pressurizing unit, a hydrolysis unit and a desulfurization unit which are connected in sequence.

[0008] The raw gas connecting branch is provided with a water seal cut-off valve and a stop valve; the gas tank connecting branch is provided with a water seal cut-off valve.

[0009] The pressure-maintaining connecting branch is provided with a pressure-maintaining valve, a coke oven gas flow meter, a second coke oven gas pressure meter, and a stop valve; the coke oven gas main is provided with a first coke oven gas pressure meter.

[0010] A reflux valve is provided on the reflux control branch, and the reflux valve forms an interlocking control with the pressure maintaining valve and the pressure signal of the first coke oven gas pressure gauge.

[0011] The regeneration gas control branch includes a first communication pipe for connecting the backflush gas inlet of the pre-adsorption unit to the regeneration gas pipeline, and a second communication pipe for connecting the raw material gas inlet of the pre-adsorption unit to the regeneration gas pipeline; a regeneration gas flowmeter is provided on both the first communication pipe and the second communication pipe; a flow control valve is provided on the first communication pipe, and the flow control valve forms an interlock control with the monitoring signal of the regeneration gas flowmeter on the second communication pipe; a regeneration gas pressure gauge is provided on the regeneration gas pipeline.

[0012] A bypass water seal cut-off valve is provided between the purified gas pipeline, the coke oven gas main pipe and the raw material gas pipeline.

[0013] On the other hand, a control method for a combined system of a coke oven gas fine desulfurization device and a double gas holder includes:

[0014] If the pressure maintaining valve and the stop valve on the pressure maintaining communication branch are fully closed, the water seal cut-off valve on the gas holder connection branch is closed, and the water seal valves and stop valves on the raw material gas connection branches of the two gas holders are fully opened to form a raw material gas connection single gas holder mode;

[0015] If the pressure maintaining valve and the stop valve on the pressure maintaining communication branch are opened, and the water seal valves and stop valves on the raw material gas connection branches of the two gas holders are fully opened, a purified gas and raw material gas connection double gas holder mode is formed;

[0016] If the pressure maintaining valve and the stop valve on the pressure maintaining communication branch are opened, the water seal valve and the stop valve on the raw material gas connection branch of the first gas holder are opened, and the water seal valve and the stop valve on the raw material gas connection branch of the second gas holder are closed, a purified gas and raw material gas connection single gas holder mode is formed.

[0017] In the raw material gas connection single gas holder mode, the bypass water seal cut-off valve between the purified gas pipeline, the coke oven gas main pipe and the raw material gas pipeline is opened to satisfy Q1 = Q2 + Q3. When Q2 > Q1, Q3 < 0, and part of the purified gas will flow to the gas source side of the coke oven gas main pipe; when Q2 < Q1, Q3 > 0, and part of the raw material gas will flow through the bypass water seal to the user end of the coke oven gas main pipe. Here, Q1 is the COG flow rate sent from the coke oven gas main pipe to the user end, Q2 is the purified gas outlet flow rate of the fine desulfurization device, and Q3 is the COG flow rate passing through the bypass water seal between the coke oven gas main pipe and the fine desulfurization device.

[0018] In the above-mentioned dual-gas-holder mode of connecting clean gas and raw gas, the water seal cut-off valve on the connecting branch of the gas holders is closed. The gas holder with the larger capacity among the first and second gas holders is used as the balance gas holder of the purified gas pipe network system, and the gas holder with the smaller capacity is used as the balance gas holder of the untreated coke oven gas pipe network system to operate, so as to buffer the load distribution fluctuation between the raw gas to the fine desulfurization device and other users. The by-pass water seal cut-off valve between the purified gas pipeline, the main coke oven gas pipeline and the raw gas pipeline is closed, and Q3 = 0. The water seal valves and stop valves on the raw gas connecting branches of the two gas holders are all opened, so that both the first gas holder and the second gas holder are in communication with the gas source side of the main coke oven gas pipeline. For the first gas holder, Q1 = Q2 - Q4 is satisfied. When Q2 > Q1, Q4 > 0, and part of the clean gas will flow into the gas holder; when Q2 < Q1, Q4 < 0, and the gas in the gas holder will flow to the user end of the main coke oven gas pipeline. In the formula, Q1 is the COG flow rate sent from the main coke oven gas pipeline to the user end, Q2 is the clean gas outlet flow rate of the fine desulfurization device, and Q4 is the flow rate between the fine desulfurization clean gas and the gas holder.

[0019] In the above-mentioned dual-gas-holder mode of connecting clean gas and raw gas, the pressurization unit of the fine desulfurization device adopts load frequency conversion control to make Q2 = Q1, so as to reduce the consumption and attenuation of the packing in each tower of the fine desulfurization; the reflux valve on the reflux control branch is fully closed to reduce the reflux loss of the fine desulfurization clean gas; the pressure maintaining valve on the pressure maintaining connecting branch is kept fully open to give full play to the variable volume adjustment ability of the first gas holder.

[0020] In the above-mentioned single-gas-holder mode of connecting clean gas and raw gas, the by-pass water seal cut-off valve between the purified gas pipeline, the main coke oven gas pipeline and the raw gas pipeline is closed to make Q3 = 0, and Q1 = Q2 - Q4 is satisfied. When Q2 > Q1, Q4 > 0, and part of the clean gas will flow into the gas holder; when Q2 < Q1, Q4 < 0, and the gas in the gas holder will flow to the user end of the main coke oven gas pipeline. In the formula, Q1 is the COG flow rate sent from the main coke oven gas pipeline to the user end, Q2 is the clean gas outlet flow rate of the fine desulfurization device, Q3 is the COG flow rate passing through the by-pass water seal between the main coke oven gas pipeline and the fine desulfurization device, and Q4 is the flow rate between the fine desulfurization clean gas and the gas holder.

[0021] In the above-mentioned dual-gas-holder mode or single-gas-holder mode of connecting clean gas and raw gas, by opening the water seal cut-off valve on the connecting branch of the gas holders and closing the stop valve on the pressure maintaining connecting branch, the function of using the first gas holder as the balance gas holder of the purified gas pipe network system is switched to the second gas holder to ensure that the normal operation of the fine desulfurization device is not affected during the maintenance of the first gas holder.

[0022] By adopting a combined system of a coke oven gas fine desulfurization device and a dual gasholder and a control method thereof of the present invention, the purified gas after the fine desulfurization of the coke oven gas is connected with the two coke oven gasholders of the original gas pipeline network and operated jointly, a variety of mode scenarios can be flexibly responded to, and the switching of the two coke oven gasholders is achieved through the opening and closing of branch valves and control interlocking, so as to absorb the disordered changes and sudden surplus of gas consumption of users of the fine desulfurization device, and synergistically achieve efficient fine desulfurization and supply and use balance of coke oven gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a combined system of a coke oven gas fine desulfurization device and a double gas holder of the present invention;

[0024] Figure 2-Figure 4 1 and 2 are simplified schematic diagrams of three modes of the control method of the present invention. DETAILED DESCRIPTION

[0025] The following is a further description of a combined system of a coke oven gas fine desulfurization device and a dual gas cabinet and a control method thereof according to the present invention in conjunction with the accompanying drawings. Figure 1 As shown, specifically including:

[0026] A coke oven gas fine desulfurization device 5 and a gas tank 6 , wherein the gas tank 6 comprises a first gas tank 61 and a second gas tank 62 .

[0027] The coke oven gas fine desulfurization device 5 mainly includes a pre-adsorption unit 51, a pressurizing unit 52, a hydrolysis unit 53 and a desulfurization unit 54 which are connected in sequence.

[0028] The pressurizing unit 52 uses a plurality of pressurizing machines and is provided with a pressurizing machine frequency conversion controller and a bypass pipeline, and a bypass valve is provided on the bypass pipeline.

[0029] A raw gas connecting branch Y1 is provided between the first gas holder 61 and the raw gas pipeline 18, and a raw gas connecting branch Y2 is provided between the second gas holder 62 and the raw gas pipeline 18; a pressure maintaining connecting branch 1 is provided between the first gas holder 61 and the purified gas pipeline 7; a gas holder connecting branch L1 is provided between the first gas holder 61 and the second gas holder 62; a reflux control branch 2 is provided between the connecting pipeline between the pre-adsorption unit 51 and the pressurizing unit 52 of the coke oven gas desulfurization device 5 and the purified gas pipeline 7; a regeneration gas control branch 3 is provided between the pre-adsorption unit 51 of the coke oven gas desulfurization device 5 and the regeneration gas pipeline 8.

[0030] The raw gas connecting branch Y1 is provided with a water seal cut-off valve S1 and a stop valve J1, and the raw gas connecting branch Y2 is provided with a water seal cut-off valve S2 and a stop valve J2.

[0031] The purified gas pipeline 7 delivers the purified gas to the coke oven gas main 9 , and a first coke oven gas pressure gauge 10 is provided at the far end of the coke oven gas main 9 .

[0032] The pressure-maintaining connecting branch 1 is provided with a pressure-maintaining valve 11, a coke oven gas flow meter 12, a second coke oven gas pressure meter 13, and a stop valve J3.

[0033] A water seal cut-off valve S3 is provided on the gas tank connecting branch L1.

[0034] A reflux valve 14 is provided on the reflux control branch 2 , and a control signal of the reflux valve 14 forms an interlocking control with a pressure signal of the pressure-maintaining valve 11 and a first coke oven gas pressure gauge 10 .

[0035] The regeneration gas control branch 3 includes a first connecting pipe 31 for connecting the backwash gas inlet of the pre-adsorption unit 51 with the regeneration gas pipeline 8 , and a second connecting pipe 32 for connecting the raw gas inlet of the pre-adsorption unit 51 with the regeneration gas pipeline 8 .

[0036] The first communicating pipe 31 and the second communicating pipe 32 are both provided with a regeneration gas flow meter 15 .

[0037] A flow control valve 16 is provided on the first communicating pipe 31 , and the flow control valve 16 forms an interlocking control with a monitoring signal of a regeneration gas flow meter 15 on the second communicating pipe 32 .

[0038] A regeneration gas pressure gauge 17 is provided on the regeneration gas pipeline 8 .

[0039] The raw gas entering the coke oven gas fine desulfurization device 5 is transferred from the coke oven gas main pipe 9 to the raw gas pipeline 18. After the raw gas is purified into purified gas by the coke oven gas fine desulfurization device 5, it is sent back to the coke oven gas main pipe 9 through the purified gas pipeline 7. A water seal cut-off valve 4 is arranged between the interfaces of the raw gas pipeline 18, the purified gas pipeline 7 and the coke oven gas main pipe 9.

[0040] The pressure-maintaining connecting branch 1 overlaps the opening of the coke oven gas fine desulfurization device 5 with the gas tank 6. The overlapping point increases the pipeline space from the coke oven gas fine desulfurization device 5 to the connection point of the pressure-maintaining connecting branch 1 as much as possible to avoid mutual interference of the adjustment control methods.

[0041] The control method of the combined system of the coke oven gas fine desulfurization device and the double gas holder of the present invention can flexibly carry out the coke oven gas supply and demand balance scheduling in three modes: raw gas connected to a single cabinet, clean gas and raw gas connected to double cabinets, and clean gas and raw gas connected to a single cabinet, and realize the smooth connection between the coke oven gas fine desulfurization device 5 and the double gas holder 6, as follows:

[0042] First, define Q1 as the COG flow rate sent from the main coke oven gas pipeline 9 to the user end, Q2 as the net gas outlet flow rate of the fine desulfurization device 5, Q3 as the COG flow rate (with directionality) passing through the bypass water seal 4 between the main coke oven gas pipeline 9 and the fine desulfurization device 5, and Q4 as the flow rate (with directionality) between the net gas of the fine desulfurization device 5 and the first gas holder 61.

[0043] Mode 1: The pressure maintaining valve 11 and the stop valve J3 on the pressure maintaining connection branch 1 are fully closed, the water seal cut-off valve S3 on the gas holder connection branch L1 is closed, and the water seal valves S1 and S2 and the stop valves J1 and J2 on the raw gas connection branches Y1 and Y2 are fully open to enable the raw gas connection single gas holder mode. The first gas holder 61 only communicates with the raw gas pipeline 18 (the water seal valve S1 and the stop valve J1 on the raw gas connection branch Y1 are open), the second gas holder 62 only communicates with the raw gas pipeline 18 (the water seal valve S2 and the stop valve J2 on the raw gas connection branch Y2 are open), and there is no flow between the double gas holders 6 and the purified gas pipeline 7, that is, the flow rate Q4 between the fine desulfurized purified gas and the gas holder is 0. The bypass water seal cut-off valve 4 between the purified gas pipeline 7, the main coke oven gas pipeline 9 and the raw gas pipeline 18 is open, satisfying Q1 = Q2 + Q3. When Q2 > Q1, Q3 < 0, and part of the net gas will flow to the gas source side of the main coke oven gas pipeline 9; when Q2 < Q1, Q3 > 0, and part of the raw gas will flow to the user end of the main coke oven gas pipeline 9 through the bypass water seal 4.

[0044] In the raw gas connection single gas holder mode, the pressurization unit 52 of the fine desulfurization device 5 operates at a constant flow rate, that is, the pressurized roots blower maintains a fixed rotational speed or frequency. The fine desulfurization device 5 processes the coke oven gas in excess operation to ensure that the user end of the main coke oven gas pipeline 9 always uses the net gas, and part of the net gas will be supplied to the gas source side of the main coke oven gas pipeline 9.

[0045] Mode 2: Open the pressure-holding valve 11 and the stop valve J3 on the pressure-holding connection branch 1, and fully open the water-seal valves S1 and S2 and the stop valves J1 and J2 on the raw gas connection branches Y1 and Y2 to enable the double-cabinet mode of connecting purified gas and raw gas. Preferably, close the water-seal cut-off valve S3 on the gas-holder connection branch L1, use the first gas-holder 61 with a larger capacity as the balance cabinet of the purified gas pipeline system, and use the second gas-holder 62 with a smaller capacity as the balance cabinet of the untreated coke-oven gas pipeline system to operate, buffering the load distribution fluctuations between the raw gas to the fine desulfurization unit 5 and other users. Close the bypass water-seal cut-off valve 4 between the purified gas pipeline 7, the main coke-oven gas pipeline 9 and the raw gas pipeline 18, and Q3 = 0. The purified gas pipeline system is isolated from the untreated coke-oven gas pipeline system. The first gas-holder 61 is in communication with the raw gas pipeline 18 (the water-seal valve S1 and the stop valve J1 on the raw gas connection branch Y1 are opened), and the second gas-holder 62 is also in communication with the raw gas pipeline 18 (the water-seal valve S2 and the stop valve J2 on the raw gas connection branch Y2 are opened). For the first gas-holder 61, Q1 = Q2 - Q4 is satisfied. When Q2 > Q1, Q4 > 0, and part of the purified gas will flow to the first gas-holder 61; when Q2 < Q1, Q4 < 0, and the gas in the first gas-holder 61 will flow to the user end of the main coke-oven gas pipeline 9.

[0046] In the double-cabinet mode of connecting purified gas and raw gas, a combined control method of load frequency conversion, no reflux, and no pressure-holding is adopted for the pressurization unit 52. The pressurization unit 52 of the fine desulfurization unit 5 adopts load frequency conversion control to make Q2 = Q1, so as to reduce the consumption and attenuation of the packing in each tower of the fine desulfurization. The reflux valve 14 on the reflux control branch 2 is fully closed to reduce the reflux loss of the purified gas in the fine desulfurization. The pressure-holding valve 11 on the pressure-holding connection branch 1 remains fully open to give full play to the variable-capacity regulation ability of the first gas-holder 61.

[0047] The load frequency conversion control of the pressurization unit 52 specifically includes:

[0048] The set frequency Fsp of the frequency converter receives external set signals: Σ + α + β + γ;

[0049] Among them, Σ is the total amount of COG required by the coke-oven gas users in the steel enterprise area; α is the supply-demand deviation correction amount, which is determined by the piston lifting change of the first gas-holder 61; β is the variable amount of the piston directional lifting of the first gas-holder 61, and the parameter value is manually input by the operator to make the first gas-holder 61 change at the expected speed to reach the expected cabinet position; γ is the automatic flow regulation correction coefficient when the manual parameter fails, so that the piston of the first gas-holder 61 fluctuates within a certain range.

[0050] Mode 3: Open the pressure-holding valve 11 and the stop valve J3 on the pressure-holding connection branch 1, and open the water-seal valve S1 and the stop valve J1 on the raw gas connection branch Y1 corresponding to the first gas holder 61; close the water-seal valve S2 and the stop valve J2 on the raw gas connection branch Y2 corresponding to the second gas holder 62 to enable the single-tank mode of connecting purified gas and raw gas. Preferably, close the bypass water-seal cut-off valve 4 between the purified gas pipeline 7, the main coke oven gas pipeline 9 and the raw gas pipeline 18, and Q3 = 0. Only the first gas holder 61 with a larger capacity connects purified gas and raw gas simultaneously, and the mixed gas of purified gas and raw gas is stored in the tank. It still satisfies Q1 = Q2 - Q4. When Q2 > Q1, Q4 > 0, and part of the purified gas will flow to the first gas holder 61; when Q2 < Q1, Q4 < 0, and the gas in the first gas holder 61 will flow to the user end of the main coke oven gas pipeline 9.

[0051] In the single-tank mode of connecting purified gas and raw gas, combined control is carried out by using the load frequency conversion control of the pressurization unit 52, the PIC pressure control of the reflux valve 14, and the PIC pressure control of the pressure-holding valve 11 to achieve real-time automatic variable load regulation that combines the supply and demand balance of the refined gas system and can control the valve position of the reflux valve within a reasonable range, so as to ensure the balanced operation of the fine desulfurization device and the gas pipeline network.

[0052] The PIC pressure control of the reflux valve 14 specifically includes:

[0053] Take the monitored value P0 of the first coke oven gas pressure gauge 10 as the present value of the pressure signal to improve the response timeliness of changes in the operating conditions.

[0054] PID is put into operation and the PIC controls the reflux valve 14 to be in the middle position, adjusts within the normal gas pressure operating range of the user, and returns to the middle position of the reflux valve 14 after the adjustment, so that the reflux valve 14 has a two-way adjustment margin to achieve the voltage stabilization adjustment of the coke oven gas fine desulfurization device 5. The pressure control target value is set on the high side to achieve the positive flow direction of the pressure-holding connection branch 1 under normal conditions, that is, from the coke oven gas fine desulfurization device 5 to the first gas holder 61.

[0055] The PIC pressure control of the pressure-holding valve 11 specifically includes:

[0056] The low-pressure value of the pressure-holding adjustment range of the coke oven gas fine desulfurization device 5 is P1, and the high-pressure value is P2. The coke oven gas fine desulfurization device 5 is subjected to high- and low-pressure interval pressure-holding adjustment, and the pressure-holding adjustment range is P1 ≥ P0 ≥ P2.

[0057] Under normal operating conditions, that is, when entering the interval of P1 < P0 < P2, after passing the anti-oscillation detection or pressure area judgment, the PID controller of the pressure-holding valve 11 starts to a 10% output reduction ramp, reaches 10% locking and PID exits, and the pressure-holding valve 11 maintains the current opening of about 10%.

[0058] When entering the P1≥P0≥P2 interval, after passing the anti-shock detection or pressure area judgment, the controller PID of the pressure maintaining valve 11 is put into operation and the 10% output lock is released. The PIC control further adjusts by increasing the opening of the pressure maintaining valve 11 to stabilize the pipeline pressure of the entire coke oven gas desulfurization device 5.

[0059] The above double-cabinet mode for connecting clean gas and raw gas, and single-cabinet mode for connecting clean gas and raw gas can be achieved by opening the water seal shut-off valve S3 on the gas tank connecting branch L1, closing the stop valve J3 on the pressure-maintaining connecting branch 1, and switching the function of the original first gas tank 61 as the balance cabinet of the purified gas pipeline system to the second gas tank 62, to ensure that the normal operation of the fine desulfurization device is not affected when the first gas tank 61 is overhauled and maintained.

[0060] The operation method of the coke oven gas fine desulfurization device and the double gas holder also includes the regeneration back-blowing gas adjustment control of the pre-adsorption unit 51:

[0061] The flow control valve 16 is controlled by a constant flow FIC, so that the surplus back-blowing regeneration gas is introduced into the coke oven gas fine desulfurization device 5 through the second connecting pipe 32 for treatment.

[0062] Example 1

[0063] Continue to refer Figure 1 As shown in the figure, a steel plant has built a processing capacity of 200,000 Nm 3 / h coke oven gas fine desulfurization device, using the coke oven gas fine desulfurization device and double gas cabinet combined system and control method of the present invention, to implement coke oven gas fine desulfurization treatment. This area originally had a capacity of 30×10 4 m 3 The first gas tank 61, a capacity of 15×10 4 m 3 The second gas tank 62 is used for gas balance scheduling. The coke oven gas is mainly used for 5 hot rolling production line users, and the gas consumption fluctuates significantly.

[0064] The coke oven gas fine desulfurization device 5 includes a pre-adsorption unit 51, a pressurizing unit 52, a hydrolysis unit 53, and a desulfurization unit 54 connected in sequence. The pre-adsorption unit 51 uses 8 composite towers to switch alternately for adsorption and regeneration. When the adsorbent in the composite tower adsorbs the impurities in the coke oven gas raw gas to saturation, it enters the regeneration process. During regeneration, the hydrogen production analysis gas in the steel plant is used as the "regeneration gas" to heat and desorb the impurities entering the inner pores of the adsorbent; after the regeneration is complete, the regeneration gas is used to cool the adsorbent bed to reduce it to room temperature, and the regeneration gas is led to the power plant and blast furnace area for consumption. The pressurizing unit 52 uses 5 Roots blowers, 4 for use and 1 for standby, to pressurize the coke oven gas coming out of the pre-adsorption unit 51 from 2 to 4 kPa to 30 kPa. The hydrolysis unit 53 uses a two-stage preheating and two-stage hydrolysis tower for hydrolysis, and recovers waste heat. The desulfurization unit 54 uses 8 desulfurization towers in parallel, and the desulfurizer is not regenerated.

[0065] The raw gas entering the coke oven gas fine desulfurization device 5 is transferred from the coke oven gas main pipe 9 to the raw gas pipeline 18 for delivery.

[0066] The purified gas pipeline 7 delivers the purified gas to the coke oven gas main 9, and then to the steel rolling user, and the remote outlet pressure P0 is obtained through the first coke oven gas pressure gauge 10 arranged at the remote end of the coke oven gas main 9. A water seal cut-off valve 4 is arranged between the raw gas pipeline 18, the purified gas pipeline 7 and the interface of the coke oven gas main 9.

[0067] A raw gas connecting branch Y1 is provided between the first gas tank 61 and the raw gas pipeline 18, and a raw gas connecting branch Y2 is provided between the second gas tank 62 and the raw gas pipeline 18. A water seal cut-off valve S1 and a stop valve J1 are provided on the raw gas connecting branch Y1, and a water seal cut-off valve S2 and a stop valve J2 are provided on the raw gas connecting branch Y2.

[0068] A gas tank communication branch L1 is provided between the first gas tank 61 and the second gas tank 62 . The diameter of the pipeline of the gas tank communication branch L1 is 2000 mm, and a water seal cut-off valve S3 is provided thereon.

[0069] A pressure-maintaining connecting branch 1 is provided between the purified gas pipeline 7 and the first gas holder 61. The diameter of the pressure-maintaining connecting branch 1 is 2000 mm, and a pressure-maintaining valve 11, a coke oven gas flow meter 12, a second coke oven gas pressure meter 13 and a stop valve J3 are provided thereon. The pressure-maintaining connecting branch 1 overlaps the opening of the coke oven gas fine desulfurization device 5 with the gas holder 6, and the overlapping point is to maximize the pipeline space between the coke oven gas fine desulfurization device 5 and the connection point of the pressure-maintaining connecting branch 1 to avoid mutual interference of the adjustment control method.

[0070] A reflux control branch 2 is provided between the connecting pipeline of the pre-adsorption unit 51 and the pressurization unit 52 of the coke oven gas fine desulfurization device 5 and the purified gas pipeline 7. The pipeline diameter of the reflux control branch 2 is 1400 mm, and a reflux valve 14 is provided thereon. The control signal of the reflux valve 14 forms an interlocking control with the pressure signals of the pressure maintaining valve 11 and the first coke oven gas pressure gauge 10. The pressurization unit 52 uses a Roots blower as the pressurizer, and is provided with a frequency converter controller and a bypass pipeline, and a bypass valve is provided on the bypass pipeline.

[0071] The inlet of the regenerated gas pipeline 8 is connected to the outlet of the steel plant hydrogen production and desorption gas. A regenerated gas control branch 3 is provided between the regenerated gas pipeline 8 and the pre-adsorption unit 51 of the coke oven gas fine desulfurization device 5. It includes a first communication pipeline 31 connected to the back-blowing gas inlets of 8 composite towers in the pre-adsorption unit 51 and a second communication pipeline 32 connected to the raw material gas inlets of 8 composite towers in the pre-adsorption unit 51. Regenerated gas flow meters 15 are provided on both the first communication pipeline 31 and the second communication pipeline 32. A flow control valve 16 is provided on the first communication pipeline 31, and the flow control valve 16 forms an interlocking control with the monitoring signal of the regenerated gas flow meter 15 on the second communication pipeline 32.

[0072] When the coke oven gas fine desulfurization device 5 is started and operated, the coke oven gas supply and demand balance scheduling is flexibly carried out in three modes of connecting the raw material gas to a single gas holder, connecting the purified gas and the raw material gas to a double gas holder, and connecting the purified gas and the raw material gas to a single gas holder in combination with the existing two gas holders 61 and 62. The coke oven gas flows Q1, Q2, Q3, Q4 in each mode are as Figure 2-Figure 4 shown.

[0073] Enable the mode of connecting the raw material gas to a single gas holder, completely close the pressure maintaining valve 11 and the stop valve J3 on the pressure maintaining connection branch 1, and close the water seal cut-off valve S3 on the gas holder connection branch L1. Open the water seal valve S1 and the stop valve J1 on the raw material gas connection branch Y1 and the water seal valve S2 and the stop valve J2 on the raw material gas connection branch Y2. Both the first gas holder 61 and the second gas holder 62 only flow through the raw material gas pipeline 18 and do not flow between the purified gas pipeline 7, that is, the flow Q4 between the fine desulfurized purified gas and the gas holder is 0. Open the bypass water seal cut-off valve 4 to satisfy Q1 = Q2 + Q3. When Q2 > Q1, Q3 < 0, and part of the purified gas will flow to the gas source side of the coke oven gas main pipe 9 to other users such as the self-provided power plant and the blast furnace; when Q2 < Q1, Q3 > 0, and part of the raw material gas will flow to the user end of the coke oven gas main pipe 9 to the rolling mill user through the bypass water seal 4.

[0074] In the mode of connecting the raw material gas to a single gas holder, the pressurization unit 52 operates at a fixed flow rate, that is, the pressurizing Roots blower maintains a fixed speed or frequency, and maintains the amount of coke oven gas processed by the fine desulfurization device 5 to be greater than the amount required by the rolling mill user. Part of the purified gas will be supplied to the gas source side of the coke oven gas main pipe 9 to other users such as the self-provided power plant and the blast furnace.

[0075] Enable the dual-tank mode of clean gas and raw gas connection. Open the pressure-holding valve 11 and the stop valve J3 on the pressure-holding connection branch 1. Open the water-seal valve S1 and the stop valve J1 on the raw gas connection branch Y1, and the water-seal valve S2 and the stop valve J2 on the raw gas connection branch Y2. Since the capacity of the first gas holder 61 is larger than that of the second gas holder 62, after connecting the clean gas to the first gas holder 61, short-term fluctuations can be converted into cumulative fluctuations, absorbing the disorderly changes (sudden surpluses) in the gas consumption of the users of the clean gas system (5 hot rolling mills), and also creating conditions for reducing the frequency of variable load regulation of the Roots blower in the fine desulfurization device. Preferably, the first gas holder 61 is used as the balance tank of the clean gas pipeline system, and the second gas holder operates as the balance tank of the untreated coke oven gas pipeline system. The clean gas pipeline system is isolated from the untreated coke oven gas pipeline system. Close the water-seal cut-off valve S3 on the gas holder connection branch L1 and the bypass water-seal cut-off valve 4, Q3 = 0. The first gas holder 61 is also in communication with the clean gas pipeline 7. For the first gas holder 61, Q1 = Q2 - Q4 is satisfied. When Q2 > Q1, Q4 > 0, and part of the clean gas will flow into the first gas holder 61; when Q2 < Q1, Q4 < 0, and the gas in the first gas holder 61 will flow to the user end of the coke oven gas main pipe 9 to the rolling mill users.

[0076] In the dual-tank mode of clean gas and raw gas connection, the pressurization unit 52 adopts load frequency conversion control to make Q2 = Q1. Completely close the reflux valve 14 on the reflux control branch 2 and fully open the pressure-holding valve 11 on the pressure-holding connection branch 1. That is, adopt the combined method of load frequency conversion control, no reflux, and no pressure-holding of the pressurization unit 52 to reduce the reflux loss of the fine desulfurized clean gas and give full play to the variable capacity regulation ability of the first gas holder 61.

[0077] The load frequency conversion control of the pressurization unit 52 specifically includes:

[0078] The variable load control of the Roots blower adopts frequency conversion control, and the set frequency Fsp of the frequency converter receives an external set signal; Fsp = Σ + α + β + γ; Σ is the total amount of coke oven gas used for 5 hot rolling mills; α is the supply-demand deviation correction amount, which is converted into a supply-demand deviation value according to the piston lifting amplitude of the first gas holder 61 per unit time and is manually corrected regularly to maintain the control accuracy; β is the variable amount of the piston of the first gas holder 61 moving in a fixed direction. For example, if the capacity of the first gas holder 61 needs to be increased at a speed of 20 km³ / h, the operator manually inputs "20"; when the γ function is enabled, when the piston of the first gas holder 61 reaches different levels of upper and lower limits, it automatically enables different flow regulation correction coefficients such as ±10 km 3 / h, ±20 km 3 / , ±30 km 3 / h, etc., to pull the piston of the first gas holder 61 exceeding the limit back to the normal fluctuation range for operation.

[0079] Enable the single-tank mode for connecting purified gas and raw gas. Open the pressure-maintaining valve 11 and the stop valve J3 on the pressure-maintaining connection branch 1. Preferably, the first gas holder 61 with a larger tank capacity is connected to the raw gas pipeline. Only the first gas holder 61 is connected to both the purified gas and the raw gas simultaneously. Open the water seal valve S1 and the stop valve J1 on the raw gas connection branch Y1, and close the water seal valve S2 and the stop valve J2 on the raw gas connection branch Y2. Close the bypass water seal cut-off valve 4. When Q3 = 0, Q1 = Q2 - Q4 is still satisfied. When Q2 > Q1, Q4 > 0, and part of the purified gas will flow to the first gas holder 61; when Q2 < Q1, Q4 < 0, and the gas in the first gas holder 61 will flow to the user end of the coke oven gas main pipe 9 to the rolling mill user.

[0080] In the single-tank mode for connecting purified gas and raw gas, combined control is carried out using the load frequency conversion control of the pressurization unit 52, the PIC pressure control of the reflux valve 14, and the PIC pressure control of the pressure-maintaining valve 11 (the load frequency conversion control logic of the pressurization unit 52 is the same as described above) to achieve real-time automatic variable load regulation that combines the supply and demand balance of the refined gas system and can control the valve position of the reflux valve within a reasonable range.

[0081] For the PIC pressure control of the reflux valve 14 in the reflux control branch 2, the distal outlet pressure P0 obtained by the first coke oven gas pressure gauge 10 is used as the present value of the pressure signal. The low pressure value P1 of the refined gas is 6.3 kPa, and the high pressure value P2 is 7.3 kPa. When P0 is within this range, the reflux valve does not participate in the regulation and keeps the valve position at 50% unchanged. When P0 < P1, the PID reverse action closes the reflux valve 14; similarly, when P0 > P2, the PID direct action opens the reflux valve 14, both controlling the target pressure of the refined gas to 6.8 kPa. After the adjustment action of the reflux valve 14 is triggered, when P0 returns to 6.8 kPa, the PID exits the PIC control, and the valve position of the reflux valve 14 slowly returns to 50%. During the return, if P0 exceeds the limit again (P0 < P1 or P0 > P2), the return program is interrupted and the PID control is re-entered. In this way, the reflux valve 14 has a two-way adjustment margin to facilitate the pressure stabilization adjustment of the coke oven gas fine desulfurization device 5, so as to achieve the positive flow direction of the pressure-maintaining connection branch 2 under normal conditions. That is, from the coke oven gas fine desulfurization device 5 to the first gas holder 61.

[0082] PIC pressure control of the pressure-holding valve 14 in the pressure-holding connection branch 1. Define the low-pressure value P1 of the pressure-holding adjustment range of the fine desulfurization device 5 for coke oven gas as 5.5 kPa and the high-pressure value P2 as 8 kPa. Under normal conditions, that is, when in the range of 5.5 kPa < P0 < 8 kPa, after passing the anti-oscillation detection, the PID controller of the pressure-holding valve 14 starts a 10% output reduction ramp, reaches 10% lockout and the PID exits. The opening of the pressure-holding valve 14 is maintained near 10%, making the pressure of the purified gas in the fine desulfurization unit slightly higher than the pressure of the gas holder 6, which is 6.3 kPa. When entering the range of 5.5 kPa (low-pressure area) ≥ P0 ≥ 8 kPa (high-pressure area), after passing the anti-oscillation detection, the controller PID of the pressure-holding valve 14 is put into operation and the 10% output lockout is released. PIC control stabilizes the pressure of the entire pipe network system by further adjusting the opening of the pressure-holding valve 14.

[0083] Operation example of PIC pressure control of the pressure-holding valve 14: If the current pressure value P0 is greater than 8 kPa and the flow rate of the pressure-holding valve 14 > 2 km3 / h, the pressure-holding control action is started in the high-pressure area. Set the target value to 7.5 kPa. The PIC regulator acts in the reverse direction, and the default 0 position is 10%. When the pressure is lower than 7.5 kPa, the pressure-holding valve 14 is automatically closed to the minimum of 10%, and the pressure-holding valve 14 returns to normal. The pressure reduction after 7.5 kPa is completed by the control of the booster fan frequency converter and the large bypass control. If the current pressure value P0 is less than 5.5 kPa and the flow rate of the pressure-holding valve 14 > 2 km 3 / h, the pressure-holding control action is started in the low-pressure area. Set the target value to 5.7 kPa (only this value when the pressure of the gas holder is low). The PIC regulator acts in the forward direction, and the default 0 position is 10%. When the pressure is higher than 5.7 kPa, the pressure-holding valve 14 is automatically closed to the minimum of 10%, and the pressure-holding valve 14 returns to normal. The pressure increase process after 5.7 kPa is completed by the control of the booster fan frequency converter and the large bypass control. When all the booster fans trip, the pressure-holding valve 14 is fully opened. When it is expected that the refined gas cannot be supplied, the water seal operation on the pressure-holding connection branch 1 is manually started.

[0084] When the first gas holder 61 is under maintenance, open the water seal cut-off valve S3 on the gas holder connection branch L1, close the stop valve J3 on the pressure-holding connection branch 1, and switch the function of the original first gas holder 61 as the balance tank of the purified gas pipe network system to the second gas holder 62. It can also operate in the double-tank mode of connecting purified gas and raw material gas, the single-tank mode of connecting purified gas and raw material gas, etc., to ensure the normal use of the fine desulfurization device.

[0085] The regeneration back-blowing gas of the pre-adsorption unit 51 is regulated and controlled. The regeneration back-blowing gas is hydrogen production and decomposition gas. The FIC constant flow control of the flow control valve 16 is adopted to make the flow of the flow control valve 16 5000Nm3 / h. The surplus hydrogen production and decomposition gas is merged into the raw gas inlet of the pre-adsorption unit 51. After the regeneration gas is used, it is discharged through pipelines and sent to the self-provided power plant of the steel enterprise and the blast furnace user for consumption.

[0086] Based on the implementation of the above coke oven gas fine desulfurization device 5 and the combined system of the dual gas cabinets 61 and 62 and the control method thereof, the steel enterprise reduces the total sulfur concentration of the coke oven gas before treatment to 900 mg / Nm 3 Reduce the total sulfur concentration to 200mg / Nm after treatment 3 , achieving a total sulfur removal rate of ≥ 78%, an organic sulfur removal rate of ≥ 77%, while ensuring orderly connection and stable operation with the original gas management system.

[0087] However, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A combined system of a coke oven gas fine desulfurization device and a double gas holder, comprising a coke oven gas fine desulfurization device, a raw gas pipeline and a regeneration gas pipeline respectively connected to the coke oven gas fine desulfurization device, and a purified gas pipeline connected from the coke oven gas fine desulfurization device to the coke oven gas main, characterized in that: It also includes a first gas holder and a second gas holder, and a raw gas connection branch is provided between the first gas holder, the second gas holder and the raw gas pipeline; a pressure maintaining connection branch is provided between the first gas holder and the purified gas pipeline; a regenerated gas control branch is provided between the fine desulfurization device for coke oven gas and the regenerated gas pipeline; a reflux control branch is provided between the fine desulfurization device for coke oven gas and the purified gas pipeline; a gas holder connection branch is provided between the first gas holder and the second gas holder.

2. The combined system of a coke oven gas fine desulfurization device and a double gas holder as claimed in claim 1, characterized in that: The fine desulfurization device for coke oven gas includes a pre-adsorption unit, a pressurization unit, a hydrolysis unit and a desulfurization unit which are connected in sequence.

3. The combined system of a coke oven gas fine desulfurization device and a double gas holder as claimed in claim 1, characterized in that: A water seal cut-off valve and a stop valve are provided on the raw gas connection branch; a water seal cut-off valve is provided on the gas holder connection branch.

4. The combined system of a coke oven gas fine desulfurization device and a double gas holder as claimed in claim 1, characterized in that: A pressure maintaining valve, a coke oven gas flow meter, a second coke oven gas pressure gauge and a stop valve are provided on the pressure maintaining connection branch; a first coke oven gas pressure gauge is provided on the main coke oven gas pipeline.

5. The combined system of a coke oven gas fine desulfurization device and a double gas holder as claimed in claim 4, characterized in that: A reflux valve is provided on the reflux control branch, and the reflux valve forms an interlocking control with the pressure signals of the pressure maintaining valve and the first coke oven gas pressure gauge.

6. The combined system of a coke oven gas fine desulfurization device and a double gas holder as claimed in claim 1, characterized in that: The regenerated gas control branch includes a first connecting pipeline for connecting the back-blowing gas inlet of the pre-adsorption unit to the regenerated gas pipeline, and a second connecting pipeline for connecting the raw gas inlet of the pre-adsorption unit to the regenerated gas pipeline; regenerated gas flow meters are provided on both the first connecting pipeline and the second connecting pipeline; a flow control valve is provided on the first connecting pipeline, and the flow control valve forms an interlocking control with the monitoring signal of the regenerated gas flow meter on the second connecting pipeline; a regenerated gas pressure gauge is provided on the regenerated gas pipeline.

7. The combined system of a coke oven gas fine desulfurization device and a double gas holder as claimed in claim 1, characterized in that: A bypass water seal cut-off valve is provided between the purified gas pipeline, the main coke oven gas pipeline and the raw gas pipeline.

8. The control method of the combined system of a coke oven gas fine desulfurization device and a dual gas holder as claimed in claim 1, characterized in that: It includes: If the pressure maintaining valve and the stop valve on the pressure maintaining connection branch are fully closed, the water seal cut-off valve on the gas holder connection branch is closed, and the water seal valves and stop valves on the raw gas connection branches of the two gas holders are fully opened to form a raw gas connection single gas holder mode; If the pressure maintaining valve and the stop valve on the pressure maintaining connection branch are opened, and the water seal valves and stop valves on the raw gas connection branches of the two gas holders are fully opened, a purified gas and raw gas connection double gas holder mode is formed; If the pressure maintaining valve and the stop valve on the pressure maintaining connection branch are opened, the water seal valve and the stop valve on the raw gas connection branch of the first gas holder are opened, and the water seal valve and the stop valve on the raw gas connection branch of the second gas holder are closed, a purified gas and raw gas connection single gas holder mode is formed.

9. The control method of the combined system of a coke oven gas fine desulfurization device and a dual gas holder as claimed in claim 8, characterized in that: In the raw gas connection single gas holder mode, the bypass water seal cut-off valve between the purified gas pipeline, the main coke oven gas pipeline and the raw gas pipeline is opened to satisfy Q1 = Q2 + Q3. When Q2 > Q1, Q3 < 0, and part of the purified gas will flow to the gas source side of the main coke oven gas pipeline; when Q2 < Q1, Q3 > 0, and part of the raw gas will flow through the bypass water seal to the user end of the main coke oven gas pipeline. Here, Q1 is the COG flow rate sent from the main coke oven gas pipeline to the user end, Q2 is the purified gas outlet flow rate of the fine desulfurization device, and Q3 is the COG flow rate passing through the bypass water seal between the main coke oven gas pipeline and the fine desulfurization device.

10. The control method of the combined system of a coke oven gas fine desulfurization device and a dual gas holder according to claim 8, characterized in that: In the above-mentioned clean gas and raw material gas connected double-tank mode, close the water seal cut-off valve on the gas holder connection branch line, use the larger-capacity one of the first and second gas holders as the balance tank of the purified gas pipeline system, and use the smaller-capacity one as the balance tank of the untreated coke oven gas pipeline system to operate, so as to buffer the load distribution fluctuations between the raw material gas to the fine desulfurization device and other users; close the bypass water seal cut-off valve between the purified gas pipeline, the main coke oven gas pipeline and the raw material gas pipeline, and Q3 = 0; open the water seal valves and stop valves on the raw material gas connection branch roads of the two gas holders, so that both the first gas holder and the second gas holder are in through-flow with the gas source side of the main coke oven gas pipeline. For the first gas holder, Q1 = Q2 - Q4 is satisfied. When Q2 > Q1, Q4 > 0, and part of the clean gas will flow into the gas holder; when Q2 < Q1, Q4 < 0, and the gas in the gas holder will flow to the user end of the main coke oven gas pipeline. In the formula, Q1 is the COG flow rate sent from the main coke oven gas pipeline to the user end, Q2 is the clean gas outlet flow rate of the fine desulfurization device, and Q4 is the flow rate between the fine desulfurization clean gas and the gas holder.

11. The control method of the combined system of the coke oven gas fine desulfurization device and the double gas holder according to claim 10, characterized in that: In the above-mentioned clean gas and raw material gas connected double-tank mode, the pressurization unit of the fine desulfurization device adopts load frequency conversion control to make Q2 = Q1, so as to reduce the consumption and attenuation of the packing in each tower of the fine desulfurization; fully close the reflux valve on the reflux control branch road to reduce the reflux loss of the fine desulfurization clean gas; keep the pressure maintaining valve on the pressure maintaining connection branch road fully open to give full play to the variable volume adjustment ability of the first gas holder.

12. The control method of the combined system of a coke oven gas fine desulfurization device and a double gas holder according to claim 8, characterized in that: In the above-mentioned clean gas and raw material gas connected single-tank mode, close the bypass water seal cut-off valve between the purified gas pipeline, the main coke oven gas pipeline and the raw material gas pipeline to make Q3 = 0, and satisfy Q1 = Q2 - Q4. When Q2 > Q1, Q4 > 0, and part of the clean gas will flow into the gas holder; when Q2 < Q1, Q4 < 0, and the gas in the gas holder will flow to the user end of the main coke oven gas pipeline. In the formula, Q1 is the COG flow rate sent from the main coke oven gas pipeline to the user end, Q2 is the clean gas outlet flow rate of the fine desulfurization device, Q3 is the COG flow rate passing through the bypass water seal between the main coke oven gas pipeline and the fine desulfurization device, and Q4 is the flow rate between the fine desulfurization clean gas and the gas holder.

13. The control method of the combined system of a coke oven gas fine desulfurization device and a dual gas holder according to claim 8, characterized in that: In the above-mentioned clean gas and raw material gas connected double-tank mode or clean gas and raw material gas connected single-tank mode, by opening the water seal cut-off valve on the gas holder connection branch road and closing the stop valve on the pressure maintaining connection branch road, switch the function of using the first gas holder as the balance tank of the purified gas pipeline system to the second gas holder, so as to ensure that the normal operation of the fine desulfurization device is not affected during the maintenance of the first gas holder.

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