Non-equilibrium stage desulfurization process for high-sulfur flue gas

Abstract

A front desulfurization tower, a rear desulfurization tower, a plurality of front desulfurization tower circulating pumps and a plurality of rear desulfurization tower circulating pumps are included, a plurality of spraying layers are correspondingly arranged in the front desulfurization tower and the rear desulfurization tower respectively, and each spraying layer independently corresponds to one circulating pump. Desulfurization slurry in tower kettles at the bottoms of the front desulfurization tower and the rear desulfurization tower is pumped out by circulating pumps and is fed into corresponding spraying layers at the upper part of the front desulfurization tower through outlet pipelines of the circulating pumps of the front desulfurization tower for spraying desulfurization, and a flue gas outlet of the front desulfurization tower is connected with a flue gas inlet of the rear desulfurization tower through a flue gas pipeline; an inlet flue gas SO2 concentration analyzer is arranged on the inlet flue gas pipeline of the front desulfurization tower, and an outlet flue gas SO2 concentration analyzer is arranged on the outlet flue gas pipeline of the rear desulfurization tower. The method is high in desulfurization efficiency, low in operation power consumption and low in operation cost, and can be easily applied to various high-sulfur and high-fluctuation flue gas systems.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, and more particularly to the field of high-sulfur, high-fluctuation flue gas desulfurization technology, specifically to a non-equilibrium staged desulfurization process for high-sulfur flue gas. Background Technology

[0002] In the field of high-sulfur flue gas desulfurization, although traditional limestone-gypsum method, sodium alkali method, and ion liquid desulfurization method can achieve the standard emission of the desulfurized tail gas, each has its own defects and shortcomings: 1. The traditional limestone-gypsum method has relatively low desulfurization performance, requires a large circulating spray volume, and has high operating energy consumption. In the desulfurization of high-sulfur flue gas, multiple desulfurization towers need to be used in series, resulting in extremely high operating energy consumption.

[0003] 2. The traditional sodium alkali method has high desulfurization agent prices and high operating costs. It also produces a large amount of sodium salt in the desulfurization of high-sulfur flue gas, resulting in high treatment costs.

[0004] 3. Traditional ion liquid desulfurization methods require the use of steam to desorb the absorbed SO2 from sulfur-rich amines. In the desulfurization of high-sulfur flue gas, the steam consumption is large and the operating cost is high. In particular, for enterprises that do not have surplus steam, they need to consume additional fuel to generate steam, resulting in extremely high operating costs.

[0005] The above-mentioned defects of traditional desulfurization methods have brought great inconvenience to the desulfurization of high-sulfur flue gas, increasing the operating costs and burden of enterprises. Summary of the Invention

[0006] To solve the above-mentioned technical problems, this invention designs a non-equilibrium staged desulfurization process for high-sulfur flue gas.

[0007] The present invention adopts the following technical solution: A non-equilibrium staged desulfurization process for high-sulfur flue gas includes a pre-desulfurization tower, a post-desulfurization tower, multiple pre-desulfurization tower circulation pumps, and multiple post-desulfurization tower circulation pumps. The pre-desulfurization tower contains multiple spray layers, each corresponding to a separate pre-desulfurization tower circulation pump. The desulfurization slurry in the bottom of the pre-desulfurization tower is extracted by the pre-desulfurization tower circulation pumps and sent through the outlet pipes of each pre-desulfurization tower circulation pump to the corresponding spray layer at the top of the pre-desulfurization tower for spray desulfurization. The post-desulfurization tower also contains multiple spray layers, each corresponding to a separate post-desulfurization tower circulation pump. The desulfurization slurry in the bottom of the post-desulfurization tower is extracted by the post-desulfurization tower circulation pumps and sent through the outlet pipes of each post-desulfurization tower circulation pump to the corresponding spray layer at the top of the post-desulfurization tower for spray desulfurization. The flue gas outlet of the pre-desulfurization tower and the flue gas inlet of the post-desulfurization tower are connected by a flue gas pipeline. An inlet flue gas SO2 concentration analyzer is installed on the inlet flue gas duct of the front desulfurization tower, and an outlet flue gas SO2 concentration analyzer is installed on the outlet flue gas duct of the rear desulfurization tower. High-sulfur flue gas first enters the pre-desulfurization tower for primary desulfurization. After primary desulfurization, the flue gas then enters the post-desulfurization tower. Based on the SO2 concentration data measured by the SO2 concentration analyzer installed on the inlet flue gas pipeline of the pre-desulfurization tower, the post-desulfurization tower performs secondary desulfurization treatment at different depths on the flue gas after primary desulfurization at the outlet of the pre-desulfurization tower as needed. The desulfurized flue gas is discharged from the top outlet of the post-desulfurization tower. The outlet flue gas SO2 concentration analyzer is used to measure the SO2 concentration of the flue gas at the outlet of the post-desulfurization tower.

[0008] An inlet flue gas SO2 concentration analyzer installed on the inlet flue gas duct of the pre-desulverizing tower can perform real-time analysis, measurement, and display of the SO2 concentration in the flue gas entering the desulfurization system. Because this analyzer is located relatively far from the post-desulverizing tower, when the SO2 concentration at the inlet of the pre-desulverizing tower changes suddenly, the post-desulverizing tower has sufficient reaction time to adjust the number of circulating pumps operating at full frequency. This allows for different depths of desulfurization for flue gas with varying inlet SO2 concentrations, avoiding energy waste caused by over-desulfurization.

[0009] Preferably, a front desulfurization tower demister is installed at the top of the front desulfurization tower; and a rear desulfurization tower demister is installed at the top of the rear desulfurization tower.

[0010] Preferably, the upper part of the front desulfurization tower is provided with a front desulfurization tower demister flushing device, which can flush and remove scale from the front desulfurization tower demister; the upper part of the rear desulfurization tower is provided with a rear desulfurization tower demister flushing device, which can flush and remove scale from the rear desulfurization tower demister.

[0011] Preferably, the desulfurizing agent used in the pre-desulfurization tower is calcium alkali, which can be any one of calcium carbonate, calcium hydroxide, or calcium oxide, and the desulfurizing agent used in the post-desulfurization tower is sodium alkali, which can be any one of sodium carbonate or sodium hydroxide.

[0012] Preferably, the pre-desulfurization tower is an empty tower structure (non-packed tower), and the post-desulfurization tower is an empty tower structure (non-packed tower).

[0013] Preferably, the number of spray layers and the number of circulating pumps in the pre-desulfurization tower are selected according to the SO2 concentration fluctuation of the process flue gas. They can be 3, 4, 5 or 6 layers. The specific number of layers is based on the requirement that when the process flue gas is in most low SO2 concentration conditions, the pre-desulfurization tower alone can achieve the standard emission of the desulfurized flue gas.

[0014] Preferably, all circulating pumps in the pre-desulfurization tower are industrial frequency pumps, and all operate at full frequency during operation.

[0015] Preferably, the number of spray layers and the number of circulating pumps in the post-desulfurization tower are selected based on the highest peak SO2 concentration of the process flue gas. They can be 3, 4, 5 or 6 layers. The specific number of layers is determined to ensure that the desulfurized flue gas can meet the emission standards when the process flue gas is at a high SO2 peak concentration and all desulfurization pumps in both desulfurization towers are running at full frequency.

[0016] Preferably, all the circulating pumps in the post-desulfurization tower are variable frequency pumps. When the SO2 concentration analyzer at the inlet of the current desulfurization tower shows a low SO2 concentration, each circulating pump in the post-desulfurization tower operates in low-frequency standby mode. When the SO2 concentration analyzer at the inlet of the current desulfurization tower shows a high SO2 concentration, a certain number of circulating pumps in the post-desulfurization tower will automatically be interlocked and run at full frequency according to the high SO2 value displayed by the SO2 concentration analyzer at the inlet of the current desulfurization tower. The number of circulating pumps running at full frequency is selected and interlocked according to the data measured by the SO2 concentration analyzer at the inlet of the current desulfurization tower.

[0017] As a preferred option, the installation location of the flue gas SO2 concentration analyzer at the inlet flue of the pre-desulfurization tower should meet the following condition: the flow time of flue gas from the inlet flue gas SO2 concentration analyzer to the inlet of the post-desulfurization tower is greater than the time required for the circulating pump of the post-sodium desulfurization tower to switch from low-frequency standby to full-frequency operation.

[0018] Preferably, each post-desulfurization tower circulating pump outlet pipe is equipped with a reflux branch pipe, and each reflux branch pipe is equipped with a reflux valve. The connection point of each reflux branch pipe to the post-desulfurization tower is higher than the overflow port of the post-desulfurization tower. Furthermore, the reflux valve is an instrument-controlled on / off valve. It is used to open the low-flow liquid reflux channel when the circulating pump corresponding to the post-desulfurization tower is in low-frequency standby mode; and to close the low-flow liquid reflux channel when the circulating pump corresponding to the post-desulfurization tower is running at full frequency.

[0019] As a preferred option, each post-desulfurization tower circulating pump outlet pipe is equipped with a pressure gauge, which can measure and display the liquid pressure on each post-desulfurization tower circulating pump outlet pipe in real time.

[0020] The operation method of the non-equilibrium staged desulfurization process for high-sulfur flue gas is as follows: All circulating pumps in the front desulfurization tower are running at full frequency.

[0021] The SO2 concentration in the flue gas entering the pre-desulfurization tower is measured using an inlet flue gas concentration analyzer installed on the inlet flue gas duct of the pre-desulfurization tower. Different full-frequency start-up SO2 concentration values ​​are set for each circulating pump in the post-desulfurization tower (i.e., a pump only operates at full frequency when the SO2 concentration reaches or exceeds its preset full-frequency start-up concentration). When the inlet flue gas SO2 concentration is greater than the preset full-frequency start-up concentration for a particular pump, that pump starts at full frequency; otherwise, it operates at low frequency in standby mode. When the inlet flue gas SO2 concentration is greater than the preset full-frequency start-up concentration for all circulating pumps in the post-desulfurization tower, all circulating pumps in the post-desulfurization tower operate at full frequency. When the inlet flue gas SO2 concentration is less than the preset full-frequency start-up concentration for all circulating pumps in the post-desulfurization tower, all circulating pumps in the post-desulfurization tower operate at low frequency in standby mode.

[0022] When a circulating pump in the post-desulfurization tower is running at full frequency, the reflux valve on the pump outlet reflux branch is closed, the pump runs at full frequency, and draws a large amount of desulfurization slurry, which is then sent to the corresponding spray layer above for spray desulfurization through the pump outlet pipe. When the pump is running at low frequency in standby mode, the reflux valve on the pump outlet reflux branch is opened, the pump runs at low frequency in standby mode, and only draws a very small amount of desulfurization slurry, which is then returned to the post-desulfurization tower through the pump outlet reflux branch pipe.

[0023] The switching action of each circulating pump in the post-desulfurization tower between full-frequency operation and low-frequency standby operation based on the SO2 concentration of the flue gas at the inlet of the pre-desulfurization tower is automatically interlocked by the control system.

[0024] The beneficial effects of the present invention are: (1) By setting up an inlet flue gas SO2 concentration analyzer on the inlet flue gas pipeline of the front desulfurization tower, the real-time measurement of the SO2 concentration of the flue gas entering the desulfurization system is realized, providing SO2 concentration data for this desulfurization process; (2) The pre-desulfurization tower uses calcium alkali (calcium carbonate, calcium hydroxide or calcium oxide) as desulfurizing agent to remove most of the SO2 in the flue gas using low-cost calcium alkali. Due to the low price of calcium alkali, compared with sodium alkali method and ionic liquid desulfurization, the cost of SO2 removal is greatly reduced. (3) The desulfurization tower uses sodium alkali (sodium carbonate or sodium hydroxide) as the desulfurizing agent. Since the reaction activity of sodium alkali with SO2 is much stronger than that of calcium alkali, the amount of liquid circulation required by the desulfurization circulation pump can be greatly reduced, and the motor power of the desulfurization tower circulation pump can be reduced. (4) The post-desulfurization tower uses sodium alkali as the desulfurizing agent. The strong reactivity of sodium alkali with SO2 improves the post-desulfurization tower's ability to treat high-sulfur flue gas and increases the desulfurization rate of the post-desulfurization tower. Therefore, the desulfurization system can handle higher concentrations of SO2. (5) Each circulating pump in the post-desulfurization tower has its own preset "minimum inlet SO2 concentration for full-frequency operation" (each pump is set separately, and the value of "minimum inlet SO2 concentration for full-frequency operation" is different for each pump). The operating status (full-frequency operation or low-frequency standby operation) of each pump in the post-desulfurization tower is linked to the SO2 concentration of the flue gas at the inlet of the pre-desulfurization tower. This realizes on-demand spraying of the post-desulfurization tower, reduces the full-frequency operation time of each circulating pump in the post-desulfurization tower, and saves the operating power consumption of the post-desulfurization tower while realizing on-demand desulfurization. (6) The pre-desulfurization tower uses calcium alkali to remove most of the SO2 in the flue gas, which greatly reduces the sodium alkali consumption of the post-desulfurization tower. While saving the cost of desulfurization agents, it also greatly reduces the introduction of sodium ions into the desulfurization system. (7) The post-desulfurization tower adopts sodium alkali desulfurization. Since sodium alkali and its desulfurization products will not produce slurry deposition, compared with calcium desulfurization, some or all of the post-desulfurization tower circulation pumps can be adjusted to low-frequency standby operation according to the SO2 concentration of the flue gas at the inlet of the pre-desulfurization tower. Unlike calcium desulfurization, when the calcium desulfurization circulation pump is running at low frequency standby, the slurry stirring in the tower bottom becomes weak, causing the deposition and blockage of desulfurization slurry and desulfurization gypsum. (8) A return branch pipe and a return valve are installed at the outlet of the post-desulfurization tower circulating pump. When the post-desulfurization tower is in low-frequency standby mode, the pump can maintain a very low flow rate by running at a low flow rate, thus avoiding overheating and damage to the post-desulfurization tower circulating pump. (9) The design of the return branch pipe at the outlet of the post-desulfurization tower circulating pump ensures that when the post-desulfurization tower circulating pump is running at low frequency standby and low flow rate, the lifting height of the low flow rate slurry is much lower than the height of the spray layer, which further reduces the standby power consumption of the post-desulfurization tower circulating pump. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a graph showing the SO2 concentration in the flue gas from the pre-desulfurization tower in this embodiment. In the diagram: 1. Pre-desulfurization tower; 2-1, 2-2, 2-3. Pre-desulfurization tower circulation pump; 3. Pre-desulfurization tower demister; 4. Pre-desulfurization tower demister flushing device; 5. Post-desulfurization tower; 6-1, 6-2, 6-3. Post-desulfurization tower circulation pump; 7. Post-desulfurization tower demister; 8. Post-desulfurization tower demister flushing device; 9-1, 9-2, 9-3. Pressure gauge; 10-1, 10-2, 10-3. Return valve; 11. Inlet flue gas SO2 concentration analyzer; 12. Outlet flue gas SO2 concentration analyzer. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: Figure 1 As shown, a non-equilibrium staged desulfurization process for high-sulfur flue gas includes a pre-desulfurization tower 1, pre-desulfurization tower circulation pumps 2-1, 2-2, and 2-3, a post-desulfurization tower 5, and post-desulfurization tower circulation pumps 6-1, 6-2, and 6-3. The desulfurization slurry in the bottom of the pre-desulfurization tower is extracted by circulation pumps 2-1, 2-2, and 2-3 and sent through the outlet pipes of each circulation pump to the corresponding spray layer at the top of the pre-desulfurization tower 1 for spray desulfurization. The slurry in the bottom of the post-desulfurization tower is circulated by the post-desulfurization tower... Pumps 6-1, 6-2, and 6-3 extract the gas and send it through the outlet pipes of each circulating pump into the corresponding spray layer on the upper part of the desulfurization tower 5 for spray desulfurization. The front desulfurization tower 1 and the rear desulfurization tower 5 are connected by a flue gas pipe. The flue gas enters the desulfurization system from the inlet flue gas pipe in front of the front desulfurization tower 1, first undergoes primary desulfurization in the front desulfurization tower 1, and then enters the rear desulfurization tower 5 through the connecting flue gas pipe between the front desulfurization tower 1 and the rear desulfurization tower 5. After desulfurization in the rear desulfurization tower 5, the gas is discharged from the flue gas outlet at the top of the rear desulfurization tower.

[0027] An inlet flue gas SO2 concentration analyzer 11 is installed on the inlet flue gas duct before the pre-desulfurization tower 1, and an outlet flue gas SO2 concentration analyzer 12 is installed on the outlet flue gas duct after the post-desulfurization tower 5.

[0028] The circulating pumps 6-1, 6-2, and 6-3 of the post-desulfurization tower are variable frequency pumps, and each of the circulating pumps of the post-desulfurization tower is equipped with its own return pipe and return valve 10-1, 10-2, and 10-3 on its outlet pipe.

[0029] The non-equilibrium staged desulfurization process for high-sulfur flue gas involves the following method: Each circulating pump (6-1, 6-2, 6-3) in the downstream desulfurization tower has a preset minimum inlet SO2 concentration for full-frequency operation (each pump has a different minimum inlet SO2 concentration for full-frequency operation). This setting links the operating status (full-frequency operation or low-frequency standby operation) of each pump (6-1, 6-2, 6-3) to the SO2 concentration of the inlet flue gas at the upstream desulfurization tower 1. Depending on the SO2 concentration of the flue gas entering the desulfurization system, different numbers of downstream circulating pumps (6-1, 6-2, 6-3) are operated at full frequency, enabling on-demand desulfurization of the downstream desulfurization tower 5. This non-equilibrium staged desulfurization process reduces the full-frequency operation time of the downstream circulating pumps (6-1, 6-2, 6-3), saving power consumption in the downstream desulfurization tower 5.

[0030] Meanwhile, this high-sulfur flue gas non-equilibrium staged desulfurization process: By using calcium alkali to remove most of the SO2 from the flue gas in the pre-desulfurization tower 1, the cost of desulfurization agents is reduced and the amount of sodium ions introduced during the sodium alkali desulfurization process in the post-desulfurization tower 5 is reduced. By using sodium alkali to remove high-value SO2 from flue gas in the post-desulfurization tower 5, the installed power of the motors of the circulating pumps 6-1, 6-2, and 6-3 in the post-desulfurization tower is reduced, the removal capacity of this desulfurization system for flue gas with higher concentrations of SO2 is improved, and the non-deposition property of sodium alkali and the sodium salt produced by desulfurization is utilized, making it possible for the intermittent low-frequency standby operation of the circulating pumps 6-1, 6-2, and 6-3 in the post-desulfurization tower. By installing pressure gauges 9-1, 9-2, and 9-3, reflux branch pipes, and reflux valves 10-1, 10-2, and 10-3 on the outlet pipes of each circulating pump 6-1, 6-2, and 6-3 in the post-desulfurization tower, protection is achieved for each circulating pump 6-1, 6-2, and 6-3 during low-frequency standby operation, and the power consumption of each circulating pump 6-1, 6-2, and 6-3 during low-frequency standby operation in the post-desulfurization tower is further reduced.

[0031] Example: For a fluctuating period of 5 hours and a flue gas volume of 500,000 Nm³ 3 / h, the maximum peak SO2 concentration was 30000 mg / Nm³. 3 The average SO2 concentration was 3000 mg / Nm³. 3 Fluctuating sulfur-containing process flue gas. Its flue gas SO2 concentration curve is as follows: Figure 2 As shown, the SO2 concentration statistics of the flue gas at the inlet of the desulfurization system are as follows: Table 1. Statistics of SO2 Concentration in Flue Gas Inlet of Desulfurization System

[0032] According to embodiments of the present invention, such as Figure 1 As shown: The pre-desulfurization tower 1 uses calcium alkali as the desulfurizing agent, and the post-desulfurization tower 5 uses sodium alkali as the desulfurizing agent; Based on the selection, the parameters of the front desulfurization tower circulation pumps 2-1, 2-2, and 2-3 and the rear desulfurization tower circulation pumps 6-1, 6-2, and 6-3 are as follows: Table 2 Selection Table for Circulating Pumps in Desulfurization Systems

[0033] The minimum inlet flue gas SO2 concentration for full-frequency operation of each circulating pump (6-1, 6-2, 6-3) in the post-desulfurization tower is set as follows: Table 3. Setting Table for "Minimum Inlet Flue Gas SO2 Concentration During Full-Frequency Operation" of the Post-Desulfurization Tower Circulating Pump 6-1 pump 6-2 pump 6-3 pump <![CDATA[Minimum inlet SO2 concentration at full frequency operation mg / Nm3]]> 3000 15000 25000 Before the sulfur-containing flue gas enters the pre-desulfurization tower 1, the SO2 concentration in the flue gas entering the desulfurization system is measured in real time by an inlet flue gas SO2 concentration analyzer 11 installed in front of the pre-desulfurization tower. The control system adjusts the operating status of each circulation pump 6-1, 6-2, and 6-3 of the post-desulfurization tower according to the received SO2 concentration in the flue gas entering the desulfurization system and the set value of "minimum inlet flue gas SO2 concentration for full-frequency operation" of the post-desulfurization tower circulation pump in Table 3.

[0034] Between 0:00 and 0:30: the SO2 concentration in the flue gas at the desulfurization system inlet is 2000 mg / Nm³. 3 <Table 3 shows the "minimum inlet flue gas SO2 concentration for full-frequency operation" set for each pump 6-1, 6-2, and 6-3 of the desulfurization tower. Therefore, before this time period, each circulation pump 2-1, 2-2, and 2-3 of the desulfurization tower operates at full frequency. After starting, the reflux valves 10-1, 10-2, and 10-3 on the outlet reflux branch pipes of the desulfurization tower circulation pumps 6-1, 6-2, and 6-3 operate at low frequency in standby mode.

[0035] Between 0:31 and 0:40: the SO2 concentration in the flue gas at the desulfurization system inlet increased to 7000 mg / Nm³. 3 The concentration of SO2 in the flue gas is greater than the minimum inlet concentration for full-frequency operation set for the circulating pump 6-1 in Table 3; and less than the minimum inlet concentration for full-frequency operation set for the circulating pumps 6-2 and 6-3 in Table 3. Therefore, all circulating pumps in the desulfurization tower will maintain full-frequency operation before this time period. The reflux valve 10-1 on the outlet reflux branch pipe of the circulating pump 6-1 will be closed, and the circulating pump 6-1 will operate at full frequency. The reflux valves 10-2 and 10-3 on the outlet reflux branch pipes of the circulating pumps 6-2 and 6-3 will remain open, and the circulating pumps 6-2 and 6-3 will maintain low-frequency standby operation.

[0036] Between 0:41 and 3:00: the SO2 concentration in the flue gas at the desulfurization system inlet decreased to 2000 mg / Nm³. 3 <Table 3 shows the "minimum inlet flue gas SO2 concentration for full-frequency operation" set for each pump 6-1, 6-2, and 6-3 of the desulfurization tower. Therefore, before this time period, each circulating pump in the desulfurization tower maintains full-frequency operation. Open the reflux valve 10-1 on the reflux branch pipe of circulating pump 6-1 in the desulfurization tower, and circulating pump 6-1 will operate at low frequency in standby mode; keep the reflux valves 10-2 and 10-3 on the reflux branch pipes of circulating pumps 6-2 and 6-3 in the desulfurization tower open, and circulating pumps 6-2 and 6-3 will maintain low-frequency standby operation.

[0037] Between 3:01 and 3:10: the SO2 concentration in the flue gas at the desulfurization system inlet increased to 20,000 mg / Nm³. 3The concentration of SO2 in the flue gas is greater than the minimum inlet concentration for full-frequency operation set for circulating pumps 6-1 and 6-2 in Table 3; and less than the minimum inlet concentration for full-frequency operation set for circulating pump 6-3 in Table 3. Therefore, all circulating pumps in the desulfurization tower will maintain full-frequency operation before this time period. The reflux valves 10-1 and 10-2 on the reflux branch pipes at the outlets of circulating pumps 6-1 and 6-2 will be closed, and circulating pumps 6-1 and 6-2 will switch to full-frequency operation; the reflux valve 10-3 on the reflux branch pipe at the outlet of circulating pump 6-3 will remain open, and circulating pump 6-3 will maintain low-frequency standby operation.

[0038] Between 3:11 and 3:20: the SO2 concentration in the flue gas at the desulfurization system inlet further increased to 30,000 mg / Nm³. 3 The concentration of SO2 in the flue gas is greater than the minimum inlet concentration for full-frequency operation set for the circulating pumps 6-1, 6-2, and 6-3 of the desulfurization tower in Table 3. Therefore, all circulating pumps in the desulfurization tower will maintain full-frequency operation before this time period. The reflux valve 10-3 on the reflux branch pipe at the outlet of the circulating pump 6-3 will be closed, and the circulating pump 6-3 will switch to full-frequency operation. The reflux valves 10-1 and 10-2 on the reflux branch pipes at the outlets of the circulating pumps 6-1 and 6-2 will remain closed, and the circulating pumps 6-1 and 6-2 will maintain full-frequency operation.

[0039] Between 3:21 and 5:00: the SO2 concentration in the flue gas at the desulfurization system inlet decreased to 2000 mg / Nm³. 3 The concentration of SO2 in the flue gas is less than the minimum inlet concentration for full-frequency operation set for the circulating pumps 6-1, 6-2, and 6-3 of the desulfurization tower in Table 3. Therefore, before this time period, all circulating pumps of the desulfurization tower maintain full-frequency operation. After the reflux valves 10-1, 10-2, and 10-3 on the reflux branch pipes at the outlets of the circulating pumps 6-1, 6-2, and 6-3 of the desulfurization tower are turned on, all circulating pumps 6-1, 6-2, and 6-3 of the desulfurization tower switch to low-frequency standby operation.

[0040] The residual SO2 concentration in the flue gas after desulfurization is detected in real time by an outlet flue gas SO2 concentration analyzer 12 installed on the outlet flue gas duct of the post-desulfurization tower, so as to realize the monitoring and tracking of the desulfurization effect of the desulfurization system.

[0041] Through the above process, the installed power of the motors of the post-desulfurization tower circulating pumps 6-1, 6-2, and 6-3 (185+200+110=495 kW) is much smaller than that of the motors of the pre-desulfurization tower circulating pumps 2-1, 2-2, and 2-3 (250+280+280=810 kW). Simultaneously, by interlocking the operating status of the post-desulfurization tower circulating pumps 6-1, 6-2, and 6-3 with the SO2 concentration of the flue gas at the inlet of the pre-desulfurization tower, different numbers of post-desulfurization tower circulating pumps 6-1, 6-2, and 6-3 can be automatically and continuously operated at full frequency according to the SO2 concentration of the flue gas at the inlet of the desulfurization system, thus achieving on-demand desulfurization of the post-desulfurization tower.

[0042] In the above embodiment of the present invention: a fluctuation period of 5 hours and a flue gas volume of 500,000 Nm³. 3 / h, the maximum peak SO2 concentration was 30000 mg / Nm³. 3 The average SO2 concentration was 3000 mg / Nm³. 3 In flue gas desulfurization systems with fluctuating high sulfur flue gas, the implementation of this invention reduces the power consumption of the post-desulfurization tower circulation pump to only about 6% of that of a conventional calcium-based desulfurization tower circulation pump. The power consumption of the entire "high sulfur flue gas non-equilibrium staged desulfurization process (including the pre-desulfurization tower and the post-desulfurization tower)" is about 53% of that of a conventional two-stage limestone desulfurization tower, greatly reducing the power consumption of the desulfurization system.

[0043] Meanwhile, since the desulfurizing agent used in the post-desulfurization tower of the present invention is sodium alkali, the sodium alkali and the sodium salt produced by desulfurization have high solubility, and will not cause precipitation and accumulation in the bottom of the post-desulfurization tower during the low-frequency standby operation of each circulating pump of the post-desulfurization tower.

[0044] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A non-equilibrium staged desulfurization process for high-sulfur flue gas, characterized in that, It includes a pre-desulfurization tower, a post-desulfurization tower, multiple pre-desulfurization tower circulation pumps, and multiple post-desulfurization tower circulation pumps. The pre-desulfurization tower is equipped with multiple spray layers, each corresponding to a separate pre-desulfurization tower circulation pump. The desulfurization slurry in the bottom of the pre-desulfurization tower is extracted by the pre-desulfurization tower circulation pump and sent to the corresponding spray layer in the upper part of the pre-desulfurization tower for spray desulfurization through the outlet pipe of each pre-desulfurization tower circulation pump. The post-desulfurization tower is equipped with multiple spray layers, each corresponding to a separate post-desulfurization tower circulation pump. The desulfurization slurry in the bottom of the post-desulfurization tower is extracted by the post-desulfurization tower circulation pump and sent to the corresponding spray layer in the upper part of the post-desulfurization tower for spray desulfurization through the outlet pipe of each post-desulfurization tower circulation pump. The flue gas outlet of the pre-desulfurization tower and the flue gas inlet of the post-desulfurization tower are connected by a flue gas pipe. An inlet flue gas SO2 concentration analyzer is installed on the inlet flue gas duct of the front desulfurization tower, and an outlet flue gas SO2 concentration analyzer is installed on the outlet flue gas duct of the rear desulfurization tower. High-sulfur flue gas first enters the pre-desulfurization tower for primary desulfurization. After primary desulfurization, the flue gas then enters the post-desulfurization tower. Based on the SO2 concentration data measured by the SO2 concentration analyzer installed on the inlet flue gas pipeline of the pre-desulfurization tower, the post-desulfurization tower performs secondary desulfurization treatment at different depths on the flue gas after primary desulfurization at the outlet of the pre-desulfurization tower as needed. The desulfurized flue gas is discharged from the top outlet of the post-desulfurization tower. The outlet flue gas SO2 concentration analyzer is used to measure the SO2 concentration of the flue gas at the outlet of the post-desulfurization tower.

2. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 1, characterized in that, A desulfurization tower eliminator is installed at the top of the front desulfurization tower; a desulfurization tower eliminator is installed at the top of the rear desulfurization tower.

3. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 2, characterized in that, The upper part of the front desulfurization tower is equipped with a front desulfurization tower effluent rinsing device, which can rinse and remove scale from the front desulfurization tower effluent rinsing device; the upper part of the rear desulfurization tower is equipped with a rear desulfurization tower effluent rinsing device, which can rinse and remove scale from the rear desulfurization tower effluent rinsing device.

4. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 1, characterized in that, The desulfurizing agent used in the pre-desulfurization tower is calcium alkali, which can be any one of calcium carbonate, calcium hydroxide, or calcium oxide. The desulfurizing agent used in the post-desulfurization tower is sodium alkali, which can be any one of sodium carbonate or sodium hydroxide.

5. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 1, characterized in that, The number of spray layers and the number of circulating pumps in the pre-desulfurization tower are selected according to the SO2 concentration fluctuation of the process flue gas. They can be 3, 4, 5 or 6 layers. The specific number of layers is based on the requirement that when the process flue gas is in most low SO2 concentration conditions, the pre-desulfurization tower alone can achieve the standard emission of the desulfurized flue gas.

6. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 5, characterized in that, All circulating pumps in the pre-desulfurization tower are industrial frequency pumps, and all operate at full frequency during operation.

7. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 1, characterized in that, The number of spray layers and the number of circulating pumps in the post-desulfurization tower are selected based on the highest peak SO2 concentration of the process flue gas. They can be 3, 4, 5 or 6 layers. The specific number of layers is determined to ensure that the desulfurized flue gas can meet the emission standards when the process flue gas is at a high SO2 peak concentration and all desulfurization pumps in both desulfurization towers are running at full frequency.

8. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 7, characterized in that, All the circulating pumps in the post-desulfurization tower are variable frequency pumps. When the SO2 concentration analyzer at the inlet of the current desulfurization tower shows a low SO2 concentration, each circulating pump in the post-desulfurization tower operates in low-frequency standby mode. When the SO2 concentration analyzer at the inlet of the current desulfurization tower shows a high SO2 concentration, a certain number of circulating pumps in the post-desulfurization tower will automatically be interlocked and run at full frequency according to the high SO2 value displayed by the SO2 concentration analyzer at the inlet of the current desulfurization tower. The number of circulating pumps running at full frequency is automatically selected and interlocked to run at full frequency based on the data measured by the SO2 concentration analyzer at the inlet of the current desulfurization tower.

9. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 1, characterized in that, Each post-desulfurization tower circulating pump outlet pipe is equipped with a reflux branch pipe, and each reflux branch pipe is equipped with a reflux valve; the connection port of each reflux branch pipe to the post-desulfurization tower is higher than the overflow port of the post-desulfurization tower.

10. The non-equilibrium staged desulfurization process for high-sulfur flue gas according to claim 1, characterized in that, Each post-desulfurization tower circulating pump outlet pipe is equipped with a pressure gauge, which can measure and display the liquid pressure on each post-desulfurization tower circulating pump outlet pipe in real time.

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