Alkali liquor circulating desulfurization device

Abstract

The utility model relates to the technical field of rectifying towers, in particular to an alkali liquor circulating desulfurization device which is characterized in that high-sulfur oil in the alkali liquor circulating desulfurization device is fed into a desulfurization tower from a high-sulfur oil alkali washing mixer and is subjected to desulfurization by reacting with alkali liquor in the desulfurization tower, and obtained low-sulfur oil enters a water washing tower to be washed; alkali liquor mixed with alkali residues and generated in the desulfurization tower enters the alkali residue tower; the unsaturated alkali liquor extraction opening is additionally formed in the bottom of the desulfurization tower, efficient cyclic utilization of unsaturated alkali liquor is achieved, the unsaturated alkali liquor at the bottom of the tower is extracted and fed into the high-sulfur oil alkali washing mixer to be mixed with high-sulfur oil and then enters the desulfurization tower again, the desulfurization efficiency is improved, addition of new alkali liquor is reduced, and the production cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of distillation towers, in particular to an alkaline solution circulating desulfurization device. Background Art

[0002] Naphtha is highly volatile and flammable. It is often used as an industrial solvent and is a raw material for the production of olefins, aromatics, and gasoline. It can also be used as a fuel in automobile and aircraft engines. It can also be used in paint, ink, medicine, cosmetics and other industries.

[0003] Desulfurization is an important step in the naphtha preparation process. Its purpose is to remove sulfur compounds in it to meet environmental protection requirements and improve oil quality. Sulfur compounds have destructive effects on human health and the environment. Therefore, the sulfur content in naphtha is crucial to product quality.

[0004] Naphtha desulfurization technology is developing in a more efficient, environmentally friendly and economical direction to meet increasingly stringent environmental standards and oil quality requirements. Alkaline solution desulfurization is a commonly used desulfurization technology in the chemical industry. By using alkaline solution to react chemically with sulfides in the raw materials, the sulfides are converted into easily separated water-soluble compounds, which can effectively remove sulfur compounds in naphtha. The desulfurization efficiency is high, and the alkali solution is extremely active. Therefore, only a low liquid-to-gas ratio is required to achieve a high-efficiency desulfurization effect, and the operating cost is low. The equipment used for alkali solution desulfurization is relatively mature at present, and the equipment operation is stable and reliable with a low failure rate.

[0005] Usually, in the process of desulfurization by alkaline water washing, a special alkali solution reflux device is set up, and the efficiency of sulfur removal is ensured by continuously filling the alkali solution reflux device with high-concentration alkali solution. However, under such a setting, the alkali solution with unneutralized sulfur and the saturated alkali solution with neutralized sulfur cannot be effectively separated, and therefore cannot be recycled, resulting in low recycling efficiency of the alkali solution and high consumption of new alkali solution, which often makes the traditional desulfurization process accompanied by high operating costs; the alkali solution concentration cannot be accurately monitored in the desulfurization tower, and a large amount of by-products may be produced. The treatment of the by-products will also increase the operating cost of the desulfurization process; the alkali solution reflux device needs to be manually monitored and adjusted during the operation of the equipment, which increases the complexity of the operation; in addition, the long-term circulation of alkali solution may cause equipment corrosion and loss, increasing maintenance costs.

[0006] As mentioned above, there is a lack of effective mechanism for cutting out and circulating saturated alkali solution during the desulfurization process, which not only fails to reduce the process operation cost, but also affects the desulfurization efficiency. Therefore, there is a need for an alkali solution circulation desulfurization device that can control the alkali solution during the alkali solution desulfurization process, so as to realize the recycling of alkali solution, recycle and reuse the used alkali solution, accurately control the alkali solution concentration, reduce the consumption of new alkali solution, reduce operating costs, reduce equipment loss, improve desulfurization efficiency, and at the same time ensure product quality and reduce environmental pollution. Utility Model Content

[0007] In order to solve the problems mentioned in the background technology and overcome the above shortcomings, the utility model provides the following technical solutions:

[0008] An alkali liquid circulation desulfurization device comprises an alkali liquid tower, a desulfurization tower, an alkali residue tower, and a water washing tower, wherein the desulfurization tower, the alkali residue tower, and the water washing tower are sequentially connected from front to back through pipelines, and each pipeline is sequentially connected through a separate pipeline connection port; in addition to the above towers, a high-sulfur oil alkali washing mixer and a low-sulfur oil water washing mixer are also provided;

[0009] The alkali liquid tower is used to hold 32% of the fresh alkali liquid transported, and a high-sulfur oil alkali washing mixer is provided between the alkali liquid tower and the desulfurization tower, and the alkali liquid tower, the high-sulfur oil alkali washing mixer and the desulfurization tower are connected in series in sequence through pipelines;

[0010] Furthermore, a fresh alkali liquid control valve is provided on the alkali liquid tower delivery pipeline, which can control the output of 32% of the fresh alkali liquid in the alkali liquid tower;

[0011] Furthermore, the high-sulfur oil alkali washing mixer is provided with a high-sulfur oil delivery inlet, an alkali solution delivery inlet, and a mixed solution delivery outlet:

[0012] The high-sulfur oil is fed into the high-sulfur oil alkali washing mixer cavity from the high-sulfur oil delivery inlet;

[0013] The alkali liquid delivery inlet is connected to the alkali liquid delivery pipeline of the alkali liquid tower. When the pipeline valve is opened, since the high-sulfur oil passes into the high-sulfur oil alkali washing mixer at a very fast speed, a negative pressure will be formed in the cavity of the high-sulfur oil mixer. Under the action of the negative pressure, fresh alkali liquid is sucked from the alkali liquid tower into the high-sulfur oil alkali washing mixer and mixed with the high-sulfur oil in the high-sulfur oil alkali washing mixer.

[0014] The mixed liquid outlet is connected to the desulfurization tower, and the high-sulfur oil mixed with the alkali liquid is pumped into the desulfurization tower.

[0015] The desulfurization tower is also provided with an adsorption layer to assist the high-sulfur oil in desulfurization in the desulfurization tower, completing the adsorption, desorption, sedimentation and separation processes; due to the different densities of naphtha and alkali solution, the low-sulfur oil floats on the alkali solution after desulfurization and washing. After the adsorption layer is added, during the washing process in the desulfurization tower, the low-sulfur oil remains above the adsorption layer, and the alkali solution flows below the adsorption layer and gathers in the inverted cone bottom of the desulfurization tower;

[0016] Furthermore, the connection point between the desulfurization tower and the mixed liquid delivery port pipeline on the high-sulfur oil alkali washing mixer is arranged above the adsorption layer;

[0017] Furthermore, an unsaturated alkali solution extraction outlet is provided below the adsorption layer of the desulfurization tower, and an unsaturated alkali solution extraction outlet valve is provided; the pipeline connected to the unsaturated alkali solution extraction outlet is connected to the alkali solution delivery pipeline of the alkali solution tower, and the connection point is provided below the fresh alkali solution control valve;

[0018] Furthermore, the unsaturated alkali solution extraction port is arranged at a position 1 meter above the connection between the cylindrical tower body and the inverted conical tower bottom of the desulfurization tower;

[0019] The alkali liquid separated in the desulfurization tower is settled at the bottom of the inverted cone tower after passing through the adsorption layer. The unsaturated alkali liquid extraction outlet valve is opened, and the alkali liquid flowing out of the adsorption layer is extracted from the unsaturated alkali liquid extraction outlet and enters the alkali liquid delivery pipeline. The alkali liquid delivery pipeline enters the alkali liquid delivery inlet on the high-sulfur oil alkali washing mixer to be mixed with the high-sulfur oil.

[0020] Furthermore, an alkali solution concentration monitoring device is provided at the bottom of the inverted cone-shaped desulfurization tower.

[0021] The top of the desulfurization tower is connected to the water washing tower through a pipeline, and the bottom of the inverted cone-shaped bottom of the desulfurization tower is connected to the alkali slag tower; the separated low-sulfur oil flows into the water washing tower from the pipeline at the top of the desulfurization tower, and the saturated alkali solution and alkali slag are discharged from the pipeline at the bottom of the desulfurization tower and sent to the alkali slag tower. The bottom of the alkali slag tower is provided with an alkali slag discharge port;

[0022] Furthermore, a low-sulfur oil water-washing mixer is provided between the desulfurization tower and the water-washing tower, the input end of the low-sulfur oil water-washing mixer is connected to the pipeline at the top of the desulfurization tower, and the output end of the low-sulfur oil water-washing mixer is connected to the water-washing tower: after the low-sulfur oil comes out of the desulfurization tower, it is first mixed with clean water in the low-sulfur oil water-washing mixer and then enters the water-washing tower together;

[0023] Furthermore, a fresh water inlet is provided in the middle of the water washing tower to facilitate water washing of the low-sulfur oil; at the same time, an adsorption layer is arranged in the water washing tower to adsorb and separate water and other impurities in the low-sulfur oil, and the low-sulfur oil is collected above the adsorption layer and discharged from the low-sulfur oil outlet provided at the top of the water washing tower; most of the impurities are adsorbed by the adsorption layer, and water is transported back to the low-sulfur oil water washing mixer through a pipeline from the alkaline water outlet provided at the inverted conical bottom of the water washing tower for reuse; when the water cannot be reused, the alkaline water outlet at the bottom is opened to discharge the alkaline water.

[0024] In actual application, high-sulfur oil is pumped into the high-sulfur oil alkali washing mixer from the outside through the high-sulfur oil delivery inlet on the high-sulfur oil alkali washing mixer, and the fresh alkali liquid control valve on the alkali liquid delivery pipeline is opened. Since the high-sulfur oil is pumped into the cavity of the high-sulfur oil alkali washing mixer at a high speed, a negative pressure is generated. 32% of the fresh alkali liquid in the alkali liquid tower is sucked into the high-sulfur oil alkali washing mixer to be mixed with the high-sulfur oil. After mixing, the mixed liquid is delivered to the desulfurization tower from the mixed liquid delivery port on the high-sulfur oil alkali washing mixer.

[0025] Furthermore, when the height of the solution transported to the desulfurization tower reaches 1 / 2 of the height of the desulfurization tower body, the fresh alkali solution control valve is closed to stop the transport of 32% of the fresh alkali solution.

[0026] In the distillation tower, the high-sulfur oil reacts fully with the alkali solution, and the sulfur and other impurities in the high-sulfur oil are further separated by the adsorption layer. The obtained low-sulfur oil remains above the adsorption layer and is transported from the top of the desulfurization tower to the water washing tower through a pipeline for water washing. Before entering the water washing tower, it first enters the low-sulfur oil water washing mixer and is mixed with clean water before entering the water washing tower for water washing reaction. The adsorption layer in the water washing tower is used to separate the low-sulfur oil from the impurities after washing. The low-sulfur oil is discharged from the output port at the top of the water washing tower, and other aqueous solutions and impurities are adsorbed by the adsorption layer and finally gathered at the bottom of the water washing tower for unified treatment.

[0027] Liquid is cut regularly at the bottom of the desulfurization tower. The cut alkali liquid is saturated alkali liquid containing alkali residue. This part of the cut alkali liquid has been fully neutralized with the sulfur in the high-sulfur oil and is transported to the alkali residue tower through the pipeline at the bottom of the desulfurization tower.

[0028] During the desulfurization process of high-sulfur oil, the alkali solution cut out is monitored by the alkali solution concentration monitoring device. When the alkali solution concentration monitoring device detects that the alkali solution concentration is greater than 3%, the cutting of the liquid is stopped, and when it is less than 3%, the cutting of the liquid is continued;

[0029] When the concentration of the alkali solution is greater than 3%, the alkali solution in the desulfurization tower is regarded as unsaturated alkali solution, and the unsaturated alkali solution extraction valve is opened, and the unsaturated alkali solution is recycled separately.

[0030] The separate circulation process of unsaturated alkali solution is as follows: open the unsaturated alkali solution extraction outlet valve, extract the unsaturated alkali solution from the unsaturated alkali solution extraction outlet, the unsaturated alkali solution flows into the alkali solution delivery pipeline along the pipeline, and then enters the high-sulfur oil alkali washing mixer, mixes with the high-sulfur oil, and then is discharged from the mixed liquid delivery port of the high-sulfur oil alkali washing mixer and enters the desulfurization tower; during this process, the fresh alkali solution control valve on the alkali solution delivery pipeline is kept in a closed state, when the solution height in the desulfurization tower is lower than the unsaturated alkali solution extraction outlet, open the fresh alkali solution control valve, replenish fresh alkali solution, and when the solution height in the desulfurization tower reaches 1 / 2 of the height of the desulfurization tower again, close the fresh alkali solution control valve and stop the delivery of 32% of the fresh alkali solution.

[0031] At the same time, as alkali liquid is continuously cut out from the bottom of the desulfurization tower and flows into the alkali slag tower, the fresh alkali liquid control valve needs to be opened every time the alkali slag liquid level in the alkali slag tower rises by 1 meter, and 32% new alkali liquid is re-added into the desulfurization tower to circulate together with the unsaturated alkali liquid. After the liquid level in the desulfurization tower rises by 1 meter, the circulation of 32% new alkali liquid is closed, and the unsaturated liquid is circulated alone, and this process is repeated.

[0032] Compared with the prior art, the beneficial effects of the utility model are:

[0033] The present application provides an alkaline solution circulating desulfurization device, which adds an unsaturated alkaline solution extraction outlet at the lower part of the desulfurization tower, extracts the unsaturated alkaline solution that falls to the bottom of the desulfurization tower, reuses it, mixes it with undesulfurized high-sulfur oil, and then sends it to the desulfurization tower together, so as to achieve efficient desulfurization of the high-sulfur oil in the desulfurization tower.

[0034] In this process, the alkali solution concentration monitoring equipment is used to accurately monitor the concentration of the alkali solution cut out from the alkali solution cut-out at the bottom of the desulfurization tower, so as to achieve multiple cycles of efficient utilization of the alkali solution, optimize the alkali solution circulation and saturated liquid cut-out, reduce the use of new alkali solution, reduce costs, save resources, and realize an efficient and low-cost naphtha desulfurization process, which has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of the alkali liquid circulation desulfurization device of the utility model;

[0036] 1-high sulfur oil alkali washing mixer, 11-mixed liquid output port, 12-alkali liquid delivery inlet, 13-high sulfur oil delivery inlet, 2-desulfurization tower, 21-unsaturated alkali liquid extraction port, 211-unsaturated alkali liquid extraction port valve, 22-adsorption layer, 3-alkali residue tower, 4-water washing tower, 41-low sulfur oil water washing mixer, 5-alkali liquid tower, 51-alkali liquid delivery pipeline, 52-fresh alkali liquid control valve. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0039] Example 1

[0040] like Figure 1 As shown, this application discloses an alkali liquid circulation desulfurization device, through which not only the high-sulfur oil can be desulfurized, but also the circulation mode of the alkali liquid can be flexibly adjusted according to the alkali liquid concentration to save the alkali liquid to the maximum extent. At the same time, the generated alkali slag and the generated alkaline water can be collected separately to avoid environmental pollution.

[0041] like Figure 1 As shown, the main body of the alkali solution circulation desulfurization device is a desulfurization tower 2, and a high-sulfur oil alkali washing mixer 1 is arranged in front of the desulfurization tower 2. After being mixed with the alkali solution from the high-sulfur oil alkali washing mixer 1, the high-sulfur oil enters the desulfurization tower 2 for desulfurization. The alkali solution and alkali residue generated during the desulfurization process are transported to the alkali residue tower 3 through the pipeline at the bottom of the desulfurization tower 2, and the obtained low-sulfur oil passes through the low-sulfur oil water washing mixer 41 and enters the water washing tower 4.

[0042] Specifically, a high-sulfur oil delivery inlet 13, an alkali liquid delivery inlet 12, and a mixed liquid output port 11 are respectively provided on the high-sulfur oil alkali washing mixer 1. High-sulfur oil is pumped into the high-sulfur oil alkali washing mixer 1 from the high-sulfur oil delivery inlet 13, and alkali liquid enters the high-sulfur oil alkali washing mixer 1 from the alkali liquid delivery inlet 12. After mixing, the mixed liquid is discharged from the mixed liquid output port 11 into the desulfurization tower 2.

[0043] An adsorption layer 22 is provided in the desulfurization tower 2, and the position of the pipeline connecting the mixed liquid outlet 11 and the desulfurization tower 2 is above the adsorption layer 22, so that the mixed liquid reacts in the desulfurization tower 2, and the adsorption layer 22 is used to desorb impurities generated during the desulfurization process of high-sulfur oil;

[0044] The alkali liquid delivery inlet 12 provided on the high-sulfur oil alkali washing mixer 1 is connected to the alkali liquid delivery pipeline 51, and the alkali liquid delivery pipeline 51 is not only connected to the alkali liquid tower 5, but also connected to the unsaturated alkali liquid extraction outlet 21 on the desulfurization tower 2, and a fresh alkali liquid control valve 52 is provided below the alkali liquid tower 5, and an unsaturated alkali liquid extraction outlet valve 211 is provided on the pipeline connected to the unsaturated alkali liquid extraction outlet 21; the connection point between the pipeline connected to the unsaturated alkali liquid extraction outlet 21 and the alkali liquid delivery pipeline 51 is below the fresh alkali liquid control valve 52.

[0045] The unsaturated alkali solution extraction port 21 is arranged 1 meter upward from the connection position between the cylindrical tower body and the inverted conical tower bottom of the desulfurization tower 2. The alkali solution flowing down from the adsorption layer 22 gathers at the inverted conical tower bottom. Such a design facilitates the extraction of the unsaturated alkali solution at the bottom of the tower. The extracted alkali solution is transported from the unsaturated alkali solution extraction port 21 to the alkali solution transport pipeline 51 through a pipeline, and then enters the high-sulfur oil alkali washing mixer 1. After being mixed with the high-sulfur oil, it is output from the mixed liquid output port 11 to the desulfurization tower 2 together, so that the unsaturated alkali solution can be recycled, thereby improving the desulfurization efficiency and reducing the amount of new alkali solution added.

[0046] The low-sulfur oil from which sulfur has been removed is transported from the top of the desulfurization tower 2 through a pipeline to the low-sulfur oil water washing mixer 41, and then transported to the water washing tower 4. After being washed with fresh water in the water washing tower 4, the low-sulfur oil is discharged from the low-sulfur oil outlet at the top of the water washing tower 4. The clean water obtained through the adsorption layer can be transported back to the low-sulfur oil water washing mixer 41 through a pipeline by a water circulation pump and mixed with the low-sulfur oil, thereby saving the use of fresh water. The alkaline water generated after multiple washings is discharged from the alkaline water outlet at the bottom of the water washing tower 4.

[0047] The bottom of the desulfurization tower 2 is connected to the alkali slag tower 3 through a pipeline, and the generated alkali slag and alkali liquid are discharged into the alkali slag tower 3 together. The alkali slag and alkali liquid in the alkali slag tower 3 are processed uniformly to reduce environmental pollution.

[0048] In the actual desulfurization process of high-sulfur oil, in the initial state, the fresh alkali solution control valve 52 is opened to allow the fresh alkali solution in the alkali solution tower 5 to flow into the high-sulfur oil alkali washing mixer 1, and output to the desulfurization tower 2 together with the high-sulfur oil through the mixed liquid output port 11. When the solution height in the desulfurization tower 2 reaches 1 / 2 of the height of the entire desulfurization tower 2, the fresh alkali solution control valve 52 is closed, and the unsaturated alkali solution extraction valve 211 is opened.

[0049] During the high-sulfur oil desulfurization process, the alkali solution passes through the adsorption layer 22 and is collected at the inverted cone bottom of the desulfurization tower 2. It is extracted from the unsaturated alkali solution extraction port 21, re-enters the alkali solution delivery pipeline 51, and enters the high-sulfur oil alkali washing mixer 1 again through the pipeline. After being mixed with the high-sulfur oil, it enters the desulfurization tower 2, and repeats this process to achieve full recycling of the alkali solution.

[0050] Alkali liquid containing alkali residue is periodically cut out from below the desulfurization tower 2 and transported to the alkali residue tower 3 through the pipeline at the bottom of the desulfurization tower 2. The cut alkali liquid is monitored by an alkali liquid concentration monitoring device. When the alkali liquid concentration monitoring device detects that the alkali liquid concentration is greater than 3%, the cutting of liquid is stopped. At this time, the alkali liquid in the desulfurization tower 2 is regarded as unsaturated alkali liquid, and the unsaturated alkali liquid can be recycled separately; when it is less than 3%, the cutting of liquid continues. When the liquid level in the desulfurization tower 2 drops below the unsaturated alkali liquid extraction outlet valve 211, the fresh alkali liquid control valve 52 needs to be opened, and 32% of new alkali liquid is continuously added. The new alkali liquid is used together with the unsaturated alkali liquid. When the liquid level in the desulfurization tower 2 reaches 1 / 2 of the liquid level of the desulfurization tower 2, the fresh alkali liquid control valve 52 is closed. During this process, the unsaturated alkali liquid extraction outlet valve 211 is always in an open state.

[0051] As alkali liquid is continuously cut out of the desulfurization tower 2 and flows into the alkali slag tower 3, the alkali slag liquid level in the alkali slag tower 3 rises. Every time the liquid level in the alkali slag tower 3 rises by 1 meter, the fresh alkali liquid control valve 52 is opened to replenish alkali liquid from the alkali liquid tower 5. After the solution level in the desulfurization tower 2 rises by 1 meter, the fresh alkali liquid control valve 52 is closed, and the unsaturated alkali liquid can be circulated alone, and this process is repeated.

[0052] Through such settings, in the desulfurization process of high-sulfur oil, under the same conditions, the amount of 32% alkali solution can be reduced by 1 / 2, the liquid alkali consumption is low, the processing cost is reduced, the sulfur content of the oil is also lower, the one-time removal rate of high-sulfur oil is increased by 30%, and the desulfurization efficiency is higher; for the generated alkali solution, the output of hazardous waste such as alkali residue is reduced by 2 / 3, which is more environmentally friendly.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An alkali liquid circulation desulfurization device, comprising an alkali liquid tower (5), a desulfurization tower (2), an alkali residue tower (3), and a water washing tower (4) connected in sequence, characterized in that: A high-sulfur oil alkali washing mixer (1) is provided between the alkali liquid tower (5) and the desulfurization tower (2); the alkali liquid tower (5) is connected to the high-sulfur oil alkali washing mixer (1) via an alkali liquid delivery pipeline (51), and a fresh alkali liquid control valve (52) is provided on the alkali liquid delivery pipeline (51); the high-sulfur oil alkali washing mixer (1) is connected to the desulfurization tower (2); the desulfurization tower (2) is connected to the alkali liquid delivery pipeline (51) via a pipeline, and the connection point is located below the fresh alkali liquid control valve (52).

2. The alkaline solution circulating desulfurization device according to claim 1, characterized in that: The high-sulfur oil alkali washing mixer (1) comprises a high-sulfur oil delivery inlet (13), an alkali solution delivery inlet (12) and a mixed solution output port (11), wherein the alkali solution delivery inlet (12) is connected to the alkali solution delivery pipeline (51), and the mixed solution output port (11) is connected to the desulfurization tower (2) via a pipeline.

3. The alkaline solution circulating desulfurization device according to claim 2, characterized in that: The desulfurization tower (2) is also provided with an adsorption layer (22), and the connection point between the mixed liquid outlet (11) and the desulfurization tower (2) is arranged above the adsorption layer (22) of the desulfurization tower (2).

4. The alkaline solution circulating desulfurization device according to claim 3, characterized in that: An unsaturated alkali solution extraction outlet (21) is provided below the adsorption layer (22), and the desulfurization tower (2) is connected to the alkali solution delivery pipeline (51) via the unsaturated alkali solution extraction outlet (21).

5. The alkaline solution circulating desulfurization device according to claim 4, characterized in that: The unsaturated alkali solution extraction outlet (21) is arranged 1 meter upward from the connection between the cylindrical tower body and the inverted conical tower bottom of the desulfurization tower (2), and is provided with an unsaturated alkali solution extraction outlet valve (211).

6. The alkaline solution circulating desulfurization device according to claim 1, characterized in that: An alkali solution concentration monitoring device is also provided at the bottom of the desulfurization tower (2).

7. The alkaline solution circulating desulfurization device according to claim 1, characterized in that: The top of the desulfurization tower (2) is connected to the water washing tower (4) through a pipeline, and the bottom of the desulfurization tower (2) is connected to the alkali slag tower (3) through a pipeline.

8. An alkali liquid circulation desulfurization device as claimed in claim 7, characterized in that: A low-sulfur oil water-washing mixer (41) is also provided between the desulfurization tower (2) and the water-washing tower (4); the input end of the low-sulfur oil water-washing mixer (41) is connected to the top pipeline of the desulfurization tower (2), and the output end of the low-sulfur oil water-washing mixer (41) is connected to the water-washing tower (4).

9. The alkaline solution circulating desulfurization device according to claim 7, characterized in that: The top of the water washing tower (4) is provided with a low-sulfur oil outlet; the middle of the water washing tower (4) is provided with a fresh water inlet; and the bottom of the water washing tower (4) is provided with an alkaline water outlet.

10. The alkaline solution circulating desulfurization device according to claim 1, characterized in that: The bottom of the alkali slag tower (3) is provided with an alkali slag discharge outlet.

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