CN109603455B - Absorbent and method for removing hydrogen sulfide in biogas - Google Patents
Absorbent and method for removing hydrogen sulfide in biogas Download PDFInfo
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- CN109603455B CN109603455B CN201910079906.XA CN201910079906A CN109603455B CN 109603455 B CN109603455 B CN 109603455B CN 201910079906 A CN201910079906 A CN 201910079906A CN 109603455 B CN109603455 B CN 109603455B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
- B01D53/52—Hydrogen sulfide
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/77—Liquid phase processes
- B01D53/78—Liquid phase processes with gas-liquid contact
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/96—Regeneration, reactivation or recycling of reactants
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- B01D2258/05—Biogas
Abstract
The invention provides an absorbent for removing hydrogen sulfide in biogas, which is an aqueous solution, wherein solutes comprise complex iron and complex ferrous iron, N-dihydroxyalkyl piperazine, sodium carbonate and sodium bicarbonate buffer system, nonionic surfactant, ionic surfactant and antioxidant; the concentration of the iron element is 100-2000 mg/L, the molar ratio of the complex iron to the complex ferrous iron is 0.2-5, the pH value of the solution is controlled to be 6.0-9.0 through a sodium carbonate and sodium bicarbonate buffer system, the concentration of the nonionic surfactant is 50-500 mg/L, the concentration of the ionic surfactant is 10-100 mg/L, the concentration of the N, N-dihydroxyethyl piperazine is 10-100 mg/L, and the concentration of the antioxidant is 50-500 mg/L. The invention also provides a method for removing hydrogen sulfide by using the absorbent.
Description
Technical Field
The invention relates to the technical field of gas purification, in particular to an absorbent and a method for removing hydrogen sulfide in biogas.
Background
The biogas is a mixed gas generated by fermenting organic substances such as crop straws, livestock and poultry manure, kitchen waste and the like under an anaerobic condition through microorganisms, and the main components of the biogas are methane and carbon dioxide, and also contain a small amount of nitrogen, oxygen, hydrogen sulfide and other components. The utilization of biogas mainly comprises power generation and natural gas purification, and the biogas serving as renewable energy becomes an important component of the energy strategy in China. The hydrogen sulfide is corrosive and can be converted into sulfur dioxide in the combustion utilization process, and the sulfur dioxide is discharged into the atmosphere to form acid gas pollution, thereby seriously affecting the environment. Therefore, before the biogas is used for power generation or purification, the biogas needs to be purified to remove hydrogen sulfide gas in the biogas.
The method is classified according to the principle of hydrogen sulfide removal, and can be divided into physical hydrogen sulfide removal, chemical hydrogen sulfide removal and biological hydrogen sulfide removal. The removal of hydrogen sulfide by physical methods can be classified into adsorption methods represented by activated carbon and molecular sieves and physical solvent methods represented by organic alcohols; the chemical method can be classified into a dry method represented by iron oxide and a wet method represented by a mixed solution of sodium hydroxide and chlor-alkali and complex iron; biological processes can be divided into acid biological desulfurization and alkaline biological desulfurization. Wherein, dry-method and adsorption-method desulfurization are suitable for the gas with lower hydrogen sulfide concentration, and are mostly used for fine desulfurization of hydrogen sulfide after wet-method desulfurization; acid method and alkaline process biological desulfurization involve the culture of microorganism, and the debugging cycle of device is longer in the engineering application process, and in contrast, the most promising development prospect is the chemical wet process hydrogen sulfide removal technology.
Chinese patent CN104492251A discloses a method for regenerating complexed iron by microorganism catalysis, which utilizes the catalytic action of microorganism to accelerate the oxidation regeneration of the complexed iron. The complexing agent used includes ethylenediaminetetraacetic acid (EDTA), sulfosalicylic acid (FD), Triethanolamine (TEA), nitrilotriacetic acid (NTA), Citric Acid (CA), etc., and a pH of 1.5 to 2.5 is preferred because complexes of FD, NTA, CA and iron are unstable in the medium-high pH region and easily form precipitates. However, in this pH range, compared with the medium-alkaline, the washing effect of the absorbent on hydrogen sulfide in the gas phase is significantly reduced, and a better washing effect can be achieved only by greatly increasing the liquid-gas ratio during gas-liquid washing, which leads to a significant increase in the energy consumption of the system. Meanwhile, as the ligand is mostly a micromolecular organic matter, the ligand has better biocompatibility, and the existence of microorganisms can cause the biodegradation of the ligand, so that the supplement amount of the absorbent is greatly improved.
Chinese patent CN102151476A discloses a method for removing hydrogen sulfide in gas phase by oxidation under a supergravity field, wherein the used mixed solution consists of complex iron, alkali, a sulfur modifier and a defoaming agent, wherein the complex iron consists of EDTA, alkyl alcohol amine, ferric salt and sodium citrate. Because the pH is adjusted by adopting the micromolecular alcamines organic alkali, the existing organic alkali can not be completely acidified to form salt within the range of the operating pH of 8.0-9.2, and has considerable volatility, hydrogen sulfide is removed, meanwhile, partial alkylol amine is carried in the methane, and secondary pollution of nitrogen oxide is always formed in the subsequent combustion process. On the other hand, the molar ratio of the used ligand to iron is too high, namely 1.4-5, and excessive ligand is brought out of the system by solid sulfur particles during the solid-liquid separation of elemental sulfur and cannot be recycled, so that the operation cost of the system is greatly increased.
Chinese patent CN107511045A discloses a method for removing hydrogen sulfide from gas, which adopts a dynamic wave and packed tower, and the device process is mostly suitable for removing hydrogen sulfide from industrial raw gas, and needs a dynamic wave device to perform quenching and pre-removing, and then uses the packed tower to perform fine removal of hydrogen sulfide, and the raw gas has higher temperature and pressure. The temperature and pressure of the biogas are not high, and if the process is adopted, the biogas needs to be pressurized, and excessive energy consumption is generated, so that the process is not suitable for the field of removing hydrogen sulfide from the biogas.
In summary, a technology for removing hydrogen sulfide from biogas, which is applicable to a wide range of hydrogen sulfide concentration, easy to debug, stable and efficient, needs to be developed.
Disclosure of Invention
The invention aims to provide a technology for removing hydrogen sulfide in methane, which is suitable for normal temperature and pressure conditions, has high efficiency, stability, flexibility in starting and stopping, short debugging period and low energy and material consumption, and comprises an absorbent and a method for removing hydrogen sulfide by using the absorbent.
In order to achieve the above object, in a first aspect, the present invention provides an absorbent for removing hydrogen sulfide from biogas, wherein the absorbent is an aqueous solution, and solutes comprise complex iron and complex ferrous iron, N-dihydroxyalkyl piperazine, sodium carbonate and sodium bicarbonate buffer system, a non-ionic surfactant, an ionic surfactant and an antioxidant; the concentration of the iron element is 100-2000 mg/L, the molar ratio of the complex iron to the complex ferrous iron is 0.2-5, the pH value of the solution is controlled to be 6.0-9.0 through a sodium carbonate and sodium bicarbonate buffer system, the concentration of the nonionic surfactant is 50-500 mg/L, the concentration of the ionic surfactant is 10-100 mg/L, the concentration of the N, N-dihydroxyethyl piperazine is 10-100 mg/L, and the concentration of the antioxidant is 50-500 mg/L.
Further, the complexing ligand of the complexing iron and the complexing ferrous iron is one or more of alkyl diamine tetraacetic acid, hydroxyethyl alkyl diamine triacetic acid and dihydroxyethyl alkyl diamine diacetic acid.
Further, the alkyl group in the N, N-dihydroxyalkylpiperazine is an ethylene group or a propylene group.
Further, the N, N-dihydroxyalkyl piperazine is one or two of N, N-dihydroxyethyl piperazine and N, N-dihydroxypropyl piperazine.
Further, the sodium carbonate-sodium bicarbonate buffer system comprises one or both of sodium carbonate and sodium bicarbonate.
Further, the nonionic surfactant comprises one or more of polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether and polyoxyethylene dodecanol ether;
further, the ionic surfactant comprises one or more of sodium dodecyl benzene sulfonate, triethyldodecyl ammonium chloride, tributyl octyl ammonium chloride, tetrabutyl ammonium bromide and dodecyl dimethyl benzyl ammonium chloride.
Further, the antioxidant comprises one or more of polypropylene oxide, hydroquinone, tert-butyl hydroquinone, sodium sulfite, sodium thiosulfate, polyethylene glycol and dibutyl hydroxy toluene.
In a second aspect, the embodiment of the invention provides a method for removing hydrogen sulfide in biogas by using the absorbent, and the method uses equipment comprising a spray absorption tower, a settling and regeneration tank, a barren liquor pump, a discharge pump, an oxidation fan and a solid-liquid separation unit; the method comprises the following steps:
biogas is sucked from the bottom of the absorption tower and is in countercurrent contact with absorbent barren solution sprayed from the upper spraying layer, the contacted absorbent forms rich solution which is collected at the bottom of the absorption tower and automatically flows to a sedimentation regeneration tank under the action of gravity, and hydrogen sulfide in the sprayed and washed biogas is removed and leaves the purification system through a tower top pipeline.
Compared with the prior art, the invention has the following beneficial effects: (1) the method is suitable for removing hydrogen sulfide from the methane rich in carbon dioxide; (2) the unique absorbent formula design ensures that the absorbent can easily absorb the hydrogen sulfide in the gas phase into the liquid phase and efficiently oxidize the negative divalent sulfur into elemental sulfur in the using process, and the long-term stability of the absorbent is ensured by using the organic-inorganic composite antioxidant and the bacteriostatic agent; (3) the device and the method for removing the hydrogen sulfide matched with the absorbent are particularly suitable for purifying the methane with wider hydrogen sulfide concentration range, low gas phase temperature and pressure.
Drawings
FIG. 1 is a flow chart of a method for removing hydrogen sulfide from biogas by using an absorbent provided by the embodiment of the invention.
Detailed Description
The principles and spirit of the present invention will be described with reference to a number of exemplary embodiments shown in the drawings. It should be understood that these embodiments are described only to enable those skilled in the art to better understand and to implement the present invention, and are not intended to limit the scope of the present invention in any way.
The absorbent for removing the hydrogen sulfide in the biogas provided by the embodiment of the invention is an aqueous solution, solute ions comprise complex iron and complex ferrous iron, N-dihydroxyalkyl piperazine, sodium carbonate and sodium bicarbonate buffer system, nonionic surfactant, ionic surfactant and antioxidant. The concentration of iron element is 100-2000 mg/L, the molar ratio of complex iron to complex ferrous iron is controlled within the range of 0.2-5, the pH of the solution is controlled within the range of 6.0-9.0 through a sodium carbonate and sodium bicarbonate buffer system, the concentration of a non-ionic surfactant is 50-500 mg/L, the concentration of an ionic surfactant is 10-100 mg/L, the concentration of N, N-dihydroxyethyl piperazine is 10-100 mg/L, and the concentration of an antioxidant is 50-500 mg/L.
Wherein the complexing ligand is selected from one or more of alkyl diamine tetraacetic acid, hydroxyethyl alkyl diamine triacetic acid and dihydroxyethyl alkyl diamine diacetic acid, and the alkyl is ethylene or propylene; the N, N-dihydroxyalkyl piperazine is selected from one or two of N, N-dihydroxyethyl piperazine or N, N-dihydroxypropyl piperazine; the sodium carbonate-sodium bicarbonate buffer system comprises one or both of sodium carbonate or sodium bicarbonate; the nonionic surfactant comprises one or more of octyl phenol polyoxyethylene ether, nonyl phenol polyoxyethylene ether and dodecyl polyoxyethylene ether; the ionic surfactant comprises one or more of sodium dodecyl benzene sulfonate, triethyldodecyl ammonium chloride, tributyl octyl ammonium chloride, tetrabutyl ammonium bromide and dodecyl dimethyl benzyl ammonium chloride; the antioxidant comprises one or more of polypropylene oxide, hydroquinone, tert-butyl hydroquinone, sodium sulfite, sodium thiosulfate, polyethylene glycol and dibutyl hydroxy toluene.
The hydrogen sulfide belongs to acid gas, and is dissolved into water from a gas phase to be divided into two steps, wherein the first step is physical dissolution, and the second step is reaction of the dissolved hydrogen sulfide and dissolved neutral alkali. The first step is related to the mass percent of water in the absorbent, the higher the water content, the greater the solubility, and the second step is related to the dissolved pH, the higher the reaction efficiency, and the greater the absorbent capacity for absorbing hydrogen sulfide. The pH of the absorbent solution is affected by two factors, one is the absorption of hydrogen sulfide, which leads to acidification of the absorbent, and the other is the solution of carbon dioxide contained in the biogas in the absorbent, which also leads to acidification of the absorbent, and the latter has a more significant effect on the pH of the absorbent, since the content of carbon dioxide in biogas is much greater than that of hydrogen sulfide. The absorption of carbon dioxide by the absorbent also reduces the absorption capacity of the absorbent for hydrogen sulfide. In order to solve the above problems, the pH of the solution is controlled in the present invention using a sodium carbonate-sodium bicarbonate buffer system in the absorbent. The gas composition of biogas is different from other industrial gases, and carbon dioxide gas with higher concentration exists. Because the gas-phase carbon dioxide-dissolved carbon dioxide-bicarbonate radical-carbonate radical gas-liquid equilibrium exists in the system, the sodium carbonate-sodium bicarbonate buffer system is used for replacing the strong base to control the pH of the system, so that the gas-phase pressure reduction caused by excessive absorption of the absorbent on the carbon dioxide in the methane can be prevented, the consumption of the alkali liquor is greatly reduced, the stability of the pH value of the absorbent can be maintained, and the reduction of the absorption effect caused by the severe change of the pH value in the absorption process can be avoided. Generally, the pH value of the solution is controlled to be 6.0-9.0, so that the operation cost is increased and iron ions are precipitated due to too high pH value, and the absorption effect is reduced due to too low pH value. Preferably, the pH value of the absorbent is in the upper limit range of 7.4-8.5, and the lower limit range of 6.8-7.2.
Ferric iron in the absorbent is used as an effective component, has strong oxidation effect on the negative divalent sulfur, and selectively oxidizes the absorbed sulfur ions into elemental sulfur to form precipitates. In this process, ferric iron is reduced to ferrous iron. Both ferric and ferrous iron are susceptible to hydrolysis, forming hydroxides which precipitate from aqueous solutions, leading to absorbent failure. In addition, carbonate precipitates are formed due to carbon dioxide contained in the biogas. In order to avoid the formation of carbonate precipitate and hydroxide precipitate of iron element, a complexing ligand is added into the absorbent, so that a coordination compound of iron is formed, and ferric iron and ferrous iron are both kept in a dissolved state in an aqueous solution. Because of the electron cloud density distribution and the difference of the ionic radius of the ferric iron and the ferrous iron, different ligands are needed to form the iron tri-complex and the iron di-complex with close stability or the iron complex with excessive function in order to facilitate the conversion between the ferric iron and the ferrous iron. The alkyl diamine tetra-ferric acetate II has better stability, and the hydroxyethyl alkyl diamine tri-ferric acetate III has better stability. Experiments show that the stability of the dihydroxyethyl alkyl diamine ferric diacetate III is between that of the alkyl diamine ferric tetraacetate II and the hydroxyethyl alkyl diamine ferric triacetate III, and the transition effect of complex conversion can be achieved. The amount of complex ligand in the absorbent will decrease due to oxidation or biochemical degradation, and if there is not enough ligand, the elemental iron will leave the solution as hydroxide or carbonate precipitate. In order to avoid the above phenomenon, the total mole number of the complexing ligand is slightly higher than that of the total mole number of the divalent and trivalent iron, and the excessive mole number of the complexing ligand and the iron can cause the material consumption to be increased and the operation cost to be increased, and the preferred total mole number of the complexing ligand is 1.1 to 1.15 times of that of the total mole number of the divalent and trivalent iron. Preferably, the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the total amount of the ligand is 0.05 to 0.1, and the mole ratio of the alkyl diamine tetraacetic acid to the hydroxyethyl alkyl diamine triacetic acid is in the range of 2: 1-3: 1.
the equipment used in the method for removing hydrogen sulfide in methane by using the renewable absorbent comprises a spray absorption tower, a settling and regenerating tank, a barren liquor pump, a discharge pump, an oxidation fan and a solid-liquid separation unit. The method comprises the following steps: the biogas enters from the bottom of the absorption tower and is in countercurrent contact with absorbent barren solution sprayed from the upper spraying layer, the contacted absorbent forms rich solution which is collected at the bottom of the absorption tower and automatically flows to a sedimentation regeneration tank under the action of gravity, and the hydrogen sulfide in the biogas after spraying and washing is removed and leaves the purification system through a tower top pipeline.
For the absorption tower, the flow rate and spray density of the biogas need to be controlled. The pressure of the biogas is low, and usually does not exceed 3kpa, and one advantage of the process system of the invention is that the biogas does not need to be pressurized, and the process system is realized by the following aspects: (1) the lower flow rate of the biogas is adopted, so that the pressure drop in the absorption tower can be reduced, the absorbent can be prevented from being carried by the biogas, a defoaming device is not required, and the pressure drop in the absorption tower is further reduced. (2) The lower spraying density is adopted, the resistance drop in the spraying absorption tower is related to the spraying amount, the spraying amount is also a key factor influencing the energy consumption of the system, and the removal efficiency of the hydrogen sulfide can be reduced under the condition that other special means are not used although the energy consumption and the pressure drop can be reduced by the spraying amount reduction. In order to balance the problems, N-dihydroxyalkyl piperazine which is a hydrogen sulfide removal synergist is used in the absorbent, and the hydrogen sulfide can be dissolved in the absorbent and can be accelerated in the acid-base reaction rate, so that the high removal efficiency is realized under the condition of low spray density. Meanwhile, the N, N-dihydroxyalkyl piperazine has extremely high melting point and extremely low vapor pressure, is extremely soluble in water and cannot volatilize in the environment of methane hydrogen sulfide removal, and compared with a common alcohol amine compound, the advantages of the N, N-dihydroxyalkyl piperazine and the alcohol amine compound enable the N, N-dihydroxyalkyl piperazine to be more suitable for the hydrogen sulfide removal process of the methane.
The rich solution contains thinner sulfur particles, the sulfur particles enter the settling regeneration tank from the bottom of the absorption tower through the gravity action at a distance of 1-3 m below the liquid level in the settling regeneration tank, and the sulfur particles settle below the tank body through gravity settling. And introducing air through an oxidation fan above the rich liquid inlet tank to regenerate the rich liquid, wherein the regenerated rich liquid forms barren liquid and overflows to a barren liquid tank from a discharge port above the sedimentation regeneration tank, the barren liquid tank is used for temporarily storing the barren liquid, and the barren liquid in the barren liquid tank is pumped into an absorption tower by a barren liquid pump to spray and wash the methane.
And pumping the sulfur particle absorbent thick slurry below the settling regeneration tank to a solid-liquid separation unit by a discharge pump at the bottom, collecting sulfur particle solids through solid-liquid separation, and pumping the liquid after the solid-liquid separation to a lean liquor tank for storage by a return pump. The sulfur solid is a byproduct of methane removal of hydrogen sulfide.
For the settling regeneration tank, it is necessary to control the flow rate of the oxidizing air and the flow rate of the discharge pump. Biological desulfurization needs to maintain biological activity, so heating and cooling pipelines are arranged to control the temperature of the tank body, the system does not need the auxiliary facilities, and the energy consumption of the system is lower compared with that of biological desulfurization. The rich solution is regenerated into the lean solution by the oxidizing air, and meanwhile, the excessive oxidizing air can oxidize the complexing ligand to cause the failure of the absorbent, and part of sulfur can be oxidized at the same time, so that the total salt content in the system is increased to easily cause local crystallization, and the yield of the byproduct sulfur can be reduced. Meanwhile, the increase of the total salt content can cause the percentage content of water in the absorbent to be reduced, so that the dissolving capacity of the hydrogen sulfide from gas phase to liquid phase is reduced, and the absorption efficiency is reduced, therefore, the total salt content needs to be strictly controlled and generally does not exceed 2.5 wt%. In order to avoid the above problems, organic and inorganic complex antioxidants are used: (1) the inorganic type is thiosulfate and sulfite, the thiosulfate and the sulfite are added at one time when the system is started, and under the condition that the thiosulfate and the sulfite exist in a small amount in the system, elemental sulfur is spontaneously formed in the system in the operation process due to the introduction of oxygen, and the thiosulfate and the sulfite do not need to be supplemented in the operation process and only need to be added in the initial loading process. (2) The polyether alcohol organic antioxidant is added, so that on one hand, the polyether alcohol organic antioxidant can wrap sulfur to reduce the contact area of the sulfur and dissolved oxygen so as to reduce oxidation, and on the other hand, the polyether alcohol organic antioxidant can capture oxygen radicals to prevent chain oxidation reaction. In addition, the polyether alcohol is also a nonionic surfactant, and can reduce the surface tension of the absorbent, so that sulfur particles formed in the absorbent are not too fine, and solid-liquid separation is facilitated.
Because the complex ligand and part of the auxiliary agent are organic matters with good biocompatibility, the complex ligand and part of the auxiliary agent are easily subjected to biochemical degradation by microorganisms, and particularly, the biochemical degradation caused by the microorganisms is easily caused under the condition that methane and oxidizing air enter the system. The method is different from the purification of other industrial gases such as natural gas, the biogas is from anaerobic fermentation, fog drops carried by a fermentation system contain a large amount of microorganisms, and the microorganisms entering a biogas purification system can possibly act on the biochemical degradation of a complexing ligand and other auxiliaries. In addition to quaternary ammonium salt ionic surfactants, other types of bacteriostats may be added, such as isothiazolinones, quaternary phosphonium salts, glutaraldehyde, and the like.
The absorption tower of the invention mainly comprises the following processes:
H2S(g)→H2S(s) (1)
H2S+CO3 2-→HS-+HCO3 - (2)
H2S+HCO3 -→HS-+CO2+H2O (3)
HS-+FeL3+→S+FeL2++H+ (4)
H++CO3 2-→HCO3 - (5)
the following processes mainly occur in the settling and regeneration tanks:
2H2O+O2+4FeL2+→4FeL3++4OH- (6)
OH-+HCO3 -→H2O+CO3 2- (7)
the absorption tower is internally used for removing hydrogen sulfide in a gas phase, oxidizing sulfur ions in a liquid phase, settling and regenerating an absorbent in a regeneration tank.
Example 1 configuration of absorbent and Hydrogen sulfide absorption Properties
Sequentially adding desalted water, ferrous sulfate heptahydrate, polymeric ferric sulfate, a complex ligand, N-dihydroxyalkyl piperazine, sodium carbonate and sodium bicarbonate buffer system, a non-ionic surfactant, an ionic surfactant and an antioxidant into a 5L reactor. Stirring for 15-20 min to obtain a clear and transparent absorbent for absorption performance measurement, wherein the absorption performance measurement is carried out by simulating gas-liquid contact of methane and the absorbent. The configuration conditions and the measurement results are shown in the following table, and the hydrogen sulfide removal efficiency is the measurement result after 24 hours of operation. Wherein, the sample 10 is not added with the dihydroxyethyl alkyl diamine diacetic acid, the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the samples 1, 2, 11 and 12 in the complexing ligand is 0.05, the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the samples 6, 7, 9 and 13 in the complexing ligand is 0.02, the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the sample 3 in the complexing ligand is 0.08, the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the samples 4, 8, 14 and 16 in the complexing ligand is 0.1, and the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the sample 15 in the complexing ligand is 0.12.
TABLE 1 absorbent configuration and Hydrogen sulfide absorption Performance data Table
Example 2 demonstration project for removing hydrogen sulfide from biogas
Biogas flow rate of 2000m3And h, introducing the biogas into a spray tower which is 1.4m in diameter of the tower, 11.5 m in height and comprises three spray layers from the bottom through a gas distributor, wherein the spray tower is in countercurrent contact with absorbent barren solution sprayed from the spray layer above, the absorbent after contact forms rich solution, the rich solution is converged at the bottom of the absorption tower and automatically flows to a sedimentation regeneration tank under the action of gravity, and hydrogen sulfide in the sprayed and washed biogas is removed and leaves a purification system through a pipeline at the top of the tower. The hydrogen sulfide absorbed in the rich solution is oxidized by ferric iron to form elemental sulfur, and the ferric iron is reduced into ferrous iron. After the rich solution enters a settling regeneration tank, the elemental sulfur naturally settles to the tank bodyAt the bottom, the supernatant is contacted with air blown by an oxidation fan to oxidize ferrous iron into ferric iron, the oxidation air is distributed by a gas distributor, and the flow rate of the oxidation air is 260m3H is used as the reference value. The regenerated barren solution is pumped into the absorption tower through a barren solution pump. The elemental sulfur slurry settled to the bottom is pumped into a solid-liquid separation unit through a discharge pump, the elemental sulfur solid phase separated by the solid-liquid separation unit is collected and reused, and the clear liquid of the solid-liquid separation unit is pumped back to the settling regeneration tank through a reflux pump. The volume of the sedimentation regeneration tank is 38m3. The absorbents No. 2 and No. 16 in example 1 were used to demonstrate the operation of the engineering, and a nonionic surfactant, an ionic surfactant and an antioxidant were added thereto, and the operation results are shown in table 2. Wherein No. 2 absorbent is adopted for 1-8 and 13, and No. 16 absorbent is adopted for 9-12. 4-5, the filtering effect is obviously reduced because no nonionic surfactant is added, and 9, the desulfurization efficiency is continuously reduced along with the increase of time because no ionic surfactant is added. When the polyoxyethylene nonyl phenyl ether, the dodecyl dimethyl benzyl ammonium chloride, the sodium sulfite and the polyethylene glycol are adopted, the comprehensive operation performance of the system is optimal. In 13, sodium hydroxide strong base is used for adjusting the pH value, the pH value of the barren solution is not 9.0 when the barren solution enters the tower, the pH value is only 6.7 when the barren solution leaves the absorption tower, and the absorption efficiency of the hydrogen sulfide is unstable due to large pH fluctuation.
Table 2 operating data table of demonstration device for removing hydrogen sulfide from methane
The inventive concept is explained in detail herein using specific examples, which are given only to aid in understanding the core concepts of the invention. It should be understood that any obvious modifications, equivalents and other improvements made by those skilled in the art without departing from the spirit of the present invention are included in the scope of the present invention.
Claims (5)
1. An absorbent for removing hydrogen sulfide in biogas is characterized in that the absorbent is an aqueous solution, and solutes comprise complex iron and complex ferrous iron, N-dihydroxyethyl piperazine, sodium carbonate and sodium bicarbonate buffer system, nonionic surfactant, ionic surfactant and antioxidant; the concentration of iron element is 100-2000 mg/L, the molar ratio of complex iron to complex ferrous iron is 0.2-5, the pH value of the solution is controlled to be 6.0-9.0 through a sodium carbonate and sodium bicarbonate buffer system, the concentration of a non-ionic surfactant is 50-500 mg/L, the concentration of an ionic surfactant is 10-100 mg/L, the concentration of N, N-dihydroxyethyl piperazine is 10-100 mg/L, and the concentration of an antioxidant is 50-500 mg/L; the absorbent can purify biogas with the pressure of not more than 3 KPa; the ionic surfactant is a quaternary ammonium salt ionic surfactant; the complexing ligand of the complexing iron and the complexing ferrous iron consists of alkyl diamine tetraacetic acid, hydroxyethyl alkyl diamine triacetic acid and dihydroxyethyl alkyl diamine diacetic acid; wherein, the mole fraction of the dihydroxyethyl alkyl diamine diacetic acid in the total amount of the complexing ligand is 0.05-0.1, and the mole ratio range of the alkyl diamine tetraacetic acid to the hydroxyethyl alkyl diamine triacetic acid is 2: 1-3: 1.
2. the absorbent for removing hydrogen sulfide in biogas according to claim 1, wherein the nonionic surfactant comprises one or more of polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether and polyoxyethylene dodecylether.
3. The absorbent for removing hydrogen sulfide in biogas according to claim 1, wherein the quaternary ammonium salt ionic surfactant comprises one or more of triethyldodecylammonium chloride, tributyloctylammonium chloride, tetrabutylammonium bromide and dodecyldimethylbenzylammonium chloride.
4. The absorbent for removing hydrogen sulfide in biogas according to claim 1, wherein the antioxidant comprises one or more of polypropylene oxide, hydroquinone, tert-butylhydroquinone, sodium sulfite, sodium thiosulfate, polyethylene glycol and dibutyl hydroxy toluene.
5. A method for removing hydrogen sulfide in biogas by using the absorbent of any one of claims 1 to 4, wherein the method uses equipment comprising a spray absorption tower, a settling and regeneration tank, a barren liquor pump, a discharge pump, an oxidation fan and a solid-liquid separation unit; the method comprises the following steps: the bottom of the absorption tower sucks in biogas, the biogas is in countercurrent contact with absorbent barren solution sprayed from the upper spraying layer, the contacted absorbent forms rich solution, the rich solution is converged at the bottom of the absorption tower and automatically flows to a settling and regenerating tank under the action of gravity, and hydrogen sulfide in the sprayed and washed biogas is removed and leaves the purification system through a tower top pipeline.
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| CN201910079906.XA CN109603455B (en) | 2019-01-28 | 2019-01-28 | Absorbent and method for removing hydrogen sulfide in biogas |
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| CN110302643A (en) * | 2019-07-30 | 2019-10-08 | 北京盈和瑞环境科技股份有限公司 | A kind of device and method removing hydrogen sulfide in methane |
| CN111592920A (en) * | 2020-05-21 | 2020-08-28 | 新沂百川畅银新能源有限公司 | Biogas desulfurization and purification process |
| JP2022048960A (en) * | 2020-09-15 | 2022-03-28 | 株式会社東芝 | Acidic gas absorbent, acidic gas removal method and acidic gas removal apparatus |
| CN112717694B (en) * | 2020-12-11 | 2022-08-05 | 攀钢集团攀枝花钢铁研究院有限公司 | Regeneration method of ineffective complexing denitration agent |
| CN112717668B (en) * | 2020-12-11 | 2023-01-24 | 攀钢集团攀枝花钢铁研究院有限公司 | Efficient and stable complexing denitration agent and preparation method thereof |
| CN112742190B (en) * | 2020-12-11 | 2022-08-05 | 攀钢集团攀枝花钢铁研究院有限公司 | Complexing denitration process capable of recycling |
| CN114797469B (en) * | 2022-03-17 | 2024-04-16 | 双盾环境科技有限公司 | Organic amine desulfurization and desorption accelerator and preparation method and application thereof |
| CN115845924A (en) * | 2022-12-22 | 2023-03-28 | 河北络合科技有限公司 | Catalyst for biogas desulfurization and preparation method and application thereof |
| CN116422130B (en) * | 2023-04-13 | 2024-01-23 | 西安赫立盖斯新能源科技有限公司 | Solvent, solvent production method and production device |
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