CN102120134A - Electrochemical treatment device and method for removing hydrogen sulfide in methane - Google Patents

Abstract

The invention discloses an electrochemical treatment device and a treatment method for removing hydrogen sulfide in biogas, and relates to a treatment device and a treatment method for removing hydrogen sulfide in biogas. The present invention solves the problem that the existing wet desulfurization device needs desorbent and has poor regeneration effect, and that sulfate and thiosulfate are generated during desulfurization by the existing wet desulfurization method, which leads to a decrease in the absorption capacity of the solution, thereby causing secondary environmental pollution The problem. The settling tank communicates with the regeneration electrolyzer through the second conduit, the upper end of the hydrogen outlet pipe communicates with the bottom end of the regeneration electrolyzer, and the upper end of the regeneration electrolyzer communicates with the upper part of the desulfurization tower through a return pipe, and the return pipe is inserted into the desulfurization tower , the return pipe in the desulfurization tower is equipped with multiple nozzles. Methods Ferric chloride solution was used as the absorbing liquid for desulfurization. The electrochemical treatment device of the present invention is suitable for large and medium-sized biogas desulfurization projects; the electrochemical treatment method of the present invention uses ferric chloride solution as the absorption liquid, and the absorption capacity of the absorption liquid remains unchanged.

Description

Electrochemical treatment device and treatment method for removing hydrogen sulfide in biogas

technical field

The invention relates to an electrochemical treatment device for removing hydrogen sulfide in biogas and an electrochemical method for removing hydrogen sulfide in biogas by using the device.

Background technique

With the wide application of anaerobic biological treatment technology for industrial and agricultural waste, biogas, as a renewable biomass energy, has attracted more and more attention and attention in today's increasingly scarce petrochemical energy. Under normal conditions, the main components of biogas are methane and carbon dioxide, and contain a small amount of carbon monoxide, hydrogen, hydrogen sulfide, oxygen and nitrogen. Hydrogen sulfide in biogas is produced from the degradation process of protein and other sulfur-containing compounds. Therefore, the concentration of hydrogen sulfide depends on the feed of the biogas generator and varies between 0.1% and 2%. Excessive concentration of hydrogen sulfide is one of the biggest limiting factors for the use of biogas as fuel gas, because hydrogen sulfide has a strong corrosive effect on combustion power equipment and metal pipes, and it will also cause deterioration of lubricating oil and accelerate engine wear; in addition, After the biogas is burned, hydrogen sulfide will be converted into sulfur oxides (SO _X ) and released into the air, causing air pollution. Therefore, the hydrogen sulfide in the biogas must be removed before it can be burned and utilized.

The desulfurization devices designed by most sewage treatment plants are divided into two types: dry desulfurization and wet desulfurization. In dry desulfurization, a dry desulfurization tower is used. The tower is filled with multiple layers of desulfurizers. The desulfurizers are often replaced during use, and the desulfurization effect is poor. Dry desulfurization is not suitable for the high concentration of H ₂ S in the digester biogas of sewage treatment plants. remove. The desulfurization device used in wet desulfurization is a wet desulfurization tower. The digested biogas enters the tower from the bottom, contacts and reacts with the absorbent in countercurrent, and then is discharged from the top of the tower. At present, NaOH is used more as absorbent, and the reaction is as follows:

2NaOH+ _H2S → _Na2S + _2H2O

NaOH+ _H2S →NaHS+ _H2O

The desulfurization and regeneration of existing wet desulfurization devices are not separately set up, desorbent is needed and the regeneration effect is poor; the absorption of desulfurization alkali liquor in the existing wet desulfurization method is affected by factors such as flow rate, flow rate, temperature, etc., and the solubility of H ₂ S If it does not reach 100%, it is easy to form NaHS during desulfurization. When NaHS is regenerated, it will react with _O2 to generate sulfate and thiosulfate. environmental pollution.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing wet desulfurization device needs a desorbent and the regeneration effect is poor, and that sulfate and thiosulfate are generated during desulfurization in the existing wet desulfurization method, which leads to a decrease in the absorption capacity of the solution, thereby causing two In order to solve the problem of secondary environmental pollution, an electrochemical treatment device and treatment method for removing hydrogen sulfide in biogas are provided.

The electrochemical treatment device for removing hydrogen sulfide in biogas of the present invention includes a desulfurization tower, a plurality of nozzles, a first conduit, a first water pump, a second water pump, a settling tank, a regenerative electrolyzer, a second conduit, a sludge discharge pipe, and a hydrogen outlet There is a liquid outlet on the bottom end surface of the desulfurization tower, a biogas inlet is opened on the outer wall of the desulfurization tower, a biogas outlet is opened on the top of the desulfurization tower, and the liquid outlet of the desulfurization tower is The port is connected with the settling tank through the first conduit, and the lower part of the settling tank is provided with a mud discharge pipe, which is connected with the settling tank, and the first water pump is installed on the first conduit, and the settling tank is connected with the regenerative electrolyzer through the second conduit , the upper end of the hydrogen outlet pipe communicates with the bottom end of the regenerative electrolyzer, the upper end of the regenerative electrolyzer communicates with the upper part of the desulfurization tower through a return pipe, the second water pump is installed on the return pipe, and the return pipe is inserted into the desulfurization tower, and the desulfurization tower The inner return pipe is equipped with multiple nozzles.

The electrochemical treatment method for removing hydrogen sulfide in biogas of the present invention is realized according to the following steps:

Step 1. Fill the biogas into the desulfurization tower from the biogas inlet. The residence time of the biogas is 5-10 minutes. Use ferric chloride solution as the absorption liquid. The concentration of ferric chloride solution is 0.5-0.7mol/L. The second water pump, the ferric chloride solution in the regenerative electrolytic cell enters the desulfurization tower through the return pipe, and is sprayed out from the nozzle, the biogas filled in the desulfurization tower rises, and the hydrogen sulfide in the biogas and the nozzle spray trichloride The iron absorbing liquid reacts in reverse contact to remove hydrogen sulfide in the biogas;

Step 2: The desulfurized biogas after reacting with the absorption liquid continues to flow to the top of the desulfurization tower, and then flows out from the biogas outlet;

Step 3: After the ferric chloride absorbing liquid reacts with the hydrogen sulfide in the biogas, most of it turns into a ferric chloride solution, and the ferric chloride solution and the sulfur element generated by the reaction flow out from the first conduit at the bottom of the desulfurization tower 8, and open The first water pump makes the ferric chloride solution and the sulfur element generated by the reaction enter the settling tank, and the sulfur element is discharged from the sludge discharge pipe after being settled and separated in the settling tank;

Step 4, the ferric chloride solution in the settling tank enters the regenerative electrolytic tank through the second conduit to carry out regeneration reaction,

The hydrogen gas generated by the reaction is discharged from the hydrogen outlet pipe, and the regenerated ferric chloride solution reacts to generate ferric chloride absorption liquid, and the generated ferric chloride absorption liquid enters the desulfurization tower through the return pipe for circular reaction.

The beneficial effects of the present invention are: the desulfurization and regeneration of the electrochemical treatment device of the present invention are set separately, no desorbent is needed and the regeneration effect is good, the electrochemical treatment device of the present invention is provided with a settling tank, so that the sulfur element is in the settling tank Separation, good desulfurization effect, the removal rate of hydrogen sulfide reaches 99%; the electrochemical treatment device of the present invention is suitable for large and medium-sized biogas desulfurization projects; the electrochemical treatment method of the present invention uses ferric chloride solution as the absorption liquid, desulfurization When no sulfate and thiosulfate are formed, the absorption capacity of the absorption liquid remains unchanged.

Description of drawings

Fig. 1 is a front view of the overall structure of the electrochemical treatment device of the present invention, and Fig. 2 is a sectional view of the regenerative electrolyzer of the present invention.

Detailed ways

Specific Embodiment 1: As shown in Figures 1-2, the electrochemical treatment device for removing hydrogen sulfide in biogas in this embodiment includes a desulfurization tower 8, a plurality of nozzles 4, a first conduit 5, a first water pump 6, and a second water pump 7. Settling tank 9, regenerative electrolyzer 10, second conduit 14, sludge discharge pipe 12, hydrogen outlet pipe 13 and return pipe 11, the bottom end surface of the desulfurization tower 8 is provided with a liquid outlet 8-1, and the There is a biogas inlet 1 on the outer wall of the desulfurization tower 8, and a biogas outlet 8-2 is opened on the top of the desulfurization tower 8, and the liquid outlet 8-1 of the desulfurization tower 8 communicates with the settling tank 9 through the first conduit 5 The bottom of the settling tank 9 is provided with a mud discharge pipe 12, the mud discharge pipe 12 communicates with the settling tank 9, the first water pump 6 is housed on the first conduit 5, and the settling tank 9 communicates with the regenerative electrolyzer 10 through the second conduit 14 The upper end of the hydrogen outlet pipe 13 communicates with the bottom end surface of the regenerative electrolyzer 10, and the upper end of the regenerative electrolyzer 10 communicates with the upper part of the desulfurization tower 8 through the return pipe 11. The second water pump 7 is installed on the return pipe 11, and the return pipe 11 is inserted into the Installed in the desulfurization tower 8, the return pipe 11 in the desulfurization tower 8 is equipped with a plurality of nozzles 4.

Embodiment 2: As shown in FIG. 2, the cathode 10-1 and the anode 10-2 of the regenerative electrolytic cell 10 in this embodiment are both made of graphite. Other components and connections are the same as those in the first embodiment.

Embodiment 3: As shown in FIG. 1 , the processing device in this embodiment further includes a demister 3 , and the demister 3 is located in the desulfurization tower 8 and above the nozzle 4 . With such a design, the mist generated by the reaction in the desulfurization tower 8 can be removed. Other compositions and connections are the same as those in Embodiment 1 or 2.

Specific embodiment four: as shown in Figures 1-2, the steps of the electrochemical treatment method for removing hydrogen sulfide in biogas in this embodiment are as follows:

Step 1. Fill the biogas into the desulfurization tower 8 from the biogas inlet 8-1. The residence time of the biogas is 5-10 minutes. Ferric chloride solution is used as the absorption liquid, and the concentration of the ferric chloride solution is 0.5-0.7 mol /L, open the second water pump 7, the ferric chloride solution in the regenerative electrolyzer 10 enters the desulfurization tower 8 through the return pipe 11, and sprays from the nozzle 4, and the biogas charged in the desulfurization tower 8 rises, and the biogas The hydrogen sulfide in the nozzle 4 sprays out the ferric chloride absorption liquid and reacts in reverse to remove the hydrogen sulfide in the biogas;

The reaction equation is as follows:

H ₂ S+2FeCl ₃ →2FeCl ₂ +2HCl+S(S)↓

or expressed as:

H ₂ S+2Fe ³⁺ →2Fe ²⁺ +2H ⁺ +S(S)↓

Step 2, the desulfurized biogas after reacting with the absorption liquid continues to flow to the top of the desulfurization tower 8, and then flows out from the biogas outlet 8-2;

Step 3, after the ferric chloride absorbing liquid reacts with the hydrogen sulfide in the biogas, most of it becomes a ferric chloride solution, and the ferric chloride solution and the sulfur element generated by the reaction flow out from the first conduit 5 at the bottom of the desulfurization tower 8, Open the first water pump 6 to make ferric chloride solution and the sulfur element generated by the reaction enter the settling tank 9, and the sulfur element is discharged from the sludge discharge pipe 12 after settling and separating in the settling tank 9;

Step 4, the ferric chloride solution in the settling tank 9 enters the regenerative electrolyzer 10 through the second conduit 14 to carry out regeneration reaction,

The reaction equation is as follows:

2H ⁺ +2e ^- →H ₂ (electrolysis)

Fe ²⁺ -e ^- →Fe ³⁺ (electrolysis)

The hydrogen gas generated by the reaction is discharged from the hydrogen outlet pipe 13, and the regenerated ferric chloride solution reacts to generate ferric chloride absorption liquid, and the generated ferric chloride absorption liquid enters the desulfurization tower 8 through the return pipe 11 for circulation reaction.

Claims (4)

1. An electrochemical treatment device for removing hydrogen sulfide in biogas, said treatment device comprising a desulfurization tower (8), a plurality of nozzles (4), a first conduit (5), a first water pump (6), a second water pump (7), settling tank (9), regenerative electrolyzer (10), second conduit (14), sludge discharge pipe (12), hydrogen outlet pipe (13) and return pipe (11), described desulfurization tower (8 ) has a liquid outlet (8-1) on the bottom end surface of the desulfurization tower (8), has a biogas inlet (1) on the outer wall of the desulfurization tower (8), and has a biogas outlet (8) on the top of the desulfurization tower (8) -2), characterized in that: the liquid outlet (8-1) of the desulfurization tower (8) communicates with the settling tank (9) through the first conduit (5), and the lower part of the settling tank (9) is provided with The mud discharge pipe (12), the mud discharge pipe (12) is connected with the settling tank (9), the first water pump (6) is installed on the first conduit (5), and the settling tank (9) is connected to the regeneration tank through the second conduit (14). The electrolyzer (10) is communicated, the upper end of the hydrogen outlet pipe (13) is communicated with the bottom end face of the regenerative electrolyzer (10), and the upper end of the regenerative electrolyzer (10) is communicated with the top of the desulfurization tower (8) through the return pipe (11), A second water pump (7) is installed on the return pipe (11), and the return pipe (11) is inserted in the desulfurization tower (8), and multiple nozzles (4) are installed on the return pipe (11) in the desulfurization tower (8). ). 2. The electrochemical treatment device for removing hydrogen sulfide in biogas according to claim 1, characterized in that: the cathode (10-1) and anode (10-2) of the regenerative electrolyzer (10) are all made of graphite become. 3. The electrochemical treatment device for removing hydrogen sulfide in biogas according to claim 1 or 2, characterized in that: the treatment device also includes a demister (3), and the demister (3) is located in the desulfurization tower (8) and above the nozzle (4). 4. an electrochemical treatment method utilizing the removal of hydrogen sulfide in biogas according to claim 3, characterized in that the steps of the electrochemical treatment method of removal of hydrogen sulfide in biogas are as follows: Step 1. Fill the biogas into the desulfurization tower (8) from the biogas inlet (8-1). The residence time of the biogas is 5 to 10 minutes. Ferric chloride solution is used as the absorption liquid, and the concentration of the ferric chloride solution is 0.5～0.7mol/L, turn on the second water pump (7), the ferric chloride solution in the regenerative electrolyzer (10) enters the desulfurization tower (8) through the return pipe (11), and sprays it from the nozzle (4) out, the biogas charged into the desulfurization tower (8) rises, and the hydrogen sulfide in the biogas reacts with the ferric chloride absorption liquid ejected from the nozzle (4) in reverse contact to remove the hydrogen sulfide in the biogas; Step 2, the desulfurized biogas after reacting with the absorption liquid continues to flow to the top of the desulfurization tower (8), and then flows out from the biogas outlet (8-2); Step 3: after the ferric chloride absorbing liquid reacts with the hydrogen sulfide in the biogas, most of it turns into a ferric chloride solution, and the ferric chloride solution and the sulfur element generated by the reaction pass from the first conduit (5) at the bottom of the desulfurization tower 8 Flow out, open the first water pump (6), make ferric chloride solution and the sulfur element that reaction generates enter in the settling tank (9), the sulfur element is separated from the sludge discharge pipe (12) after sedimentation and separation in the settling tank (9). discharge; Step 4, the ferric chloride solution in the settling tank (9) enters the regenerative electrolyzer (10) through the second conduit (14) to carry out regeneration reaction, The hydrogen generated by the reaction is discharged from the hydrogen outlet pipe (13), and the regenerated ferric chloride solution reacts to generate ferric chloride absorption liquid, and the generated ferric chloride absorption liquid enters the desulfurization tower (8) through the return pipe (11) Perform a cyclic reaction.

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