System and method for preparing single-cell protein from purified tail gas of synthesis gas

Abstract

The invention discloses a system and a method for preparing single-cell protein from purified tail gas of synthesis gas, and relates to the technical field of microbial fermentation, the system comprises a gas buffer tank, a culture medium tank, an anaerobic fermentation device, an aerator, an aerobic fermentation device and a fermentation material collection and treatment device; the gas buffer tank is communicated with the anaerobic fermentation device and the aerobic fermentation device; the microbial strains take purified synthesis gas tail gas as a carbon source and a nitrogen source. The invention aims to solve the problems of environmental pollution caused by direct emission of the existing synthesis gas purification tail gas, low single-cell protein yield and low crude protein content in the single-cell protein when the existing synthesis gas purification tail gas is used for microbial fermentation. According to the method, the candida tropicalis and the paenibacillus polymyxa are used for fermentation, meanwhile, the aerator is arranged, and the polydimethylsiloxane and the vitamin H are added in the aerobic fermentation process, so that the single-cell protein yield and the corresponding crude protein content are increased, the whole process is convenient to operate, and the method is applied to the field of fish feed preparation.

Description

Technical Field

[0001] The invention relates to the technical field of microbial fermentation, and in particular to a system and method for preparing single-cell protein by purifying tail gas with synthesis gas. Background Art

[0002] In the prior art, crude synthesis gas is mostly prepared from coal using a multi-element slurry gasification process. The crude synthesis gas is then purified by sulfur-resistant wide temperature shift, low-temperature methanol washing and liquid nitrogen washing. The removed acidic gas is converted into sulfur using the super-optimal Claus process. The purified synthesis gas obtained through the above steps is used to synthesize ammonia in a three-bed synthesis tower with an internal heat exchanger.

[0003] However, in the above projects, a large amount of waste gas is discharged, such as: 1) dust removal tail gas from the coal storage and transportation section; 2) dust removal tail gas from the coal slurry preparation section; 3) tail gas from the start-up and accidental discharge of the gasifier in the gasification section, extraction waste gas, burner cooler gas-liquid separator exhaust gas, synthesis gas analysis venting, and gasifier pressure gauge port venting; 4) waste gas from the top of the high-pressure separation tank in the slag water treatment section, air venting from the safety valve of the high-pressure flash tank, and air venting from the separation tank after the vacuum pump; 5) air venting in the conversion section; 6) air venting from the ammonia cooler in the low-temperature methanol washing section, exhaust gas discharged from the tail gas washing tower, and acidic gas containing H2S; 7) waste gas discharged from the sulfur recovery unit; 8) air venting from the synthesis loop of the ammonia synthesis section; 9) dirty nitrogen gas discharged from the air separation unit.

[0004] The above industrial waste gas contains a large amount of carbon dioxide, carbon monoxide, hydrogen, nitrogen and a small amount of carbon disulfide, hydrogen sulfide, carbon oxysulfide, methane, methanol, nitrogen oxides, coal dust, limestone dust, etc. If the above pollutants are discharged directly, they may cause serious consequences to the human body; if the dust is removed and the flare is used for combustion before being discharged into the atmosphere, it will not only waste the effective gas resources such as carbon monoxide and hydrogen, but also increase the carbon dioxide content in the atmosphere, which will cause the risk of environmental pollution.

[0005] Faced with the problem of industrial waste gas being difficult to treat, the conversion of industrial waste gas into economic products has become a popular research direction. On the one hand, the content of one-carbon compounds (CO2, CO, methane, methanol, formic acid, etc.) in industrial waste gas is high, which is an ideal new generation of biomanufacturing raw materials; on the other hand, there are many microorganisms in nature that can utilize one-carbon compounds. By modifying model microorganisms such as Escherichia coli and brewer's yeast, it is also possible to construct synthetic one-carbon utilization microorganisms and realize the conversion of one-carbon resources into a variety of products, such as the preparation of single-cell protein that can be used in fish feed.

[0006] Therefore, in view of the serious environmental pollution caused by the large-scale emission or incineration of tail gas directly discharged from the synthesis gas purification section in the existing technology, it is of great significance to develop a process technology that uses the tail gas discharged from the synthesis gas system purification section as raw material and converts industrial tail gas containing H2, CO, and CO2 into single-cell protein for feed through cell metabolism technology. Summary of the invention

[0007] The purpose of the present invention is to provide a system and method for preparing single-cell protein by purifying tail gas from syngas, so as to solve the problem that the direct discharge or incineration of tail gas from the existing syngas purification section seriously pollutes the environment, and the problem of low crude protein content in the existing single-cell preparation method.

[0008] The purpose of the present invention is achieved through the following technical solutions: A system for preparing single-cell protein by purifying tail gas from syngas, comprising a gas buffer tank, a culture medium tank, an anaerobic fermentation device, an aerator, an aerobic fermentation device and a fermentation material collection and processing device; The gas buffer tank is used to store the syngas-purified tail gas, and the gas buffer tank is also connected to the anaerobic fermentation device and the aerobic fermentation device; The anaerobic fermentation device comprises a primary anaerobic seed tank, a secondary anaerobic seed tank and an anaerobic fermentation tank connected in sequence, and the anaerobic fermentation tank and the culture medium tank are connected through a pipeline; The aerobic fermentation device comprises a primary aerobic seed tank, a secondary aerobic seed tank and an aerobic fermentation tank which are connected in sequence, and the bottom of the aerobic fermentation tank is connected to a fermentation material collection and processing device; an anaerobic discharge pump and an aerator are arranged on the pipeline connecting the anaerobic fermentation tank and the aerobic fermentation tank; The fermentation material collection and processing device comprises a centrifuge and a drum scraper dryer connected in sequence; The system for preparing single-cell protein by purifying tail gas with syngas also includes microbial strains that use the tail gas purified with syngas as a carbon source and a nitrogen source.

[0009] Furthermore, the upper part of the anaerobic fermentation tank is connected to the alkali tank through a pipeline, and an alkali pump is provided on the pipeline connecting the anaerobic fermentation tank and the alkali tank; The top of the aerobic fermentation tank is connected with the acid tank through a pipeline, and a valve is arranged on the pipeline connecting the aerobic fermentation tank and the acid tank. Oxygen and purified tail gas and materials discharged from the anaerobic fermentation tank enter the aerobic fermentation tank after passing through an aerator.

[0010] Furthermore, the microbial strains include Candida tropicalis and Paenibacillus polymyxa.

[0011] A method for preparing single-cell protein by purifying tail gas with synthetic gas, the method comprises utilizing the above-mentioned system for synthesizing single-cell protein to synthesize single-cell protein.

[0012] As a preferred technical solution of the present invention, the method for synthesizing single cell protein comprises the following steps: (a) After the tropical Candida albicans undergoes secondary seed activation and anaerobic fermentation in an anaerobic fermentation device, anaerobic fermentation is completed. After the anaerobic fermentation material is mixed with oxygen and purified tail gas, it enters the aerobic fermentation tank through an aerator. The carbon source and nitrogen source in the secondary seed activation and anaerobic fermentation process are provided by the syngas purified tail gas; The purpose of the secondary seed activation here is to make Candida tropicalis grow stronger.

[0013] (b) Paenibacillus polymyxa is activated by secondary seed in an aerobic fermentation device, and the activated seed liquid and the material in the anaerobic fermentation tank are simultaneously fed into the aerobic fermentation tank for aerobic fermentation, and the carbon source and nitrogen source in the secondary seed activation and aerobic fermentation process are provided by the tail gas of syngas purification; The material discharged from the anaerobic fermentation tank is reused as the culture medium of the aerobic fermentation tank. The material discharged from the anaerobic fermentation tank is mixed with oxygen and purified tail gas and then enters the aerobic fermentation tank through the aerator; The purpose of the secondary seed activation here is to make Bacillus polymyxa and Candida tropicalis grow in a balanced state in the aerobic system to avoid excessive growth of one of the two bacteria.

[0014] In addition, the material in the anaerobic fermentation tank includes tropical Candida in addition to the anaerobic fermentation liquid. The tropical Candida can continue aerobic fermentation in the aerobic fermentation tank. In this way, combined with the polymyxa bacillus after secondary seed activation, the yield of the single-cell protein finally obtained can be increased.

[0015] (c) After the aerobic fermentation is completed, the material flows out from the bottom of the aerobic fermentation tank, and after centrifugation, evaporation, concentration and drying, a granular finished product is obtained.

[0016] Furthermore, the secondary seed activation in step (a) is performed in a primary anaerobic seed tank and a secondary anaerobic seed tank respectively, the fermentation time of the primary anaerobic seed tank and the secondary anaerobic seed tank is 1 hour, and the fermentation temperature is 20-30°C; The formal anaerobic fermentation is carried out in an anaerobic fermentation tank. The fermentation time in the anaerobic fermentation tank is 3 hours, the fermentation temperature is 20-30°C, and the pH of the culture solution in the anaerobic fermentation tank is controlled at 4.0-6.0 by an alkali tank.

[0017] During the secondary activation process, the ventilation rate of the purified tail gas from the syngas in the gas buffer tank entering the primary anaerobic seed tank and the secondary anaerobic seed tank is 30 L / min; during the anaerobic fermentation process, the ventilation rate of the purified tail gas from the syngas in the gas buffer tank entering the anaerobic fermentation tank is 60 L / min.

[0018] The culture medium introduced into the anaerobic fermentation tank comes from the culture medium tank. The culture medium components in the culture medium tank are: 1.59 g / L (NH4)2SO4, 1.05 g / L NaCl, 0.54 g / L MgSO4·7H2O, 0.96 g / L FeSO4·7H20, 0.73 g / L CaCl2·2H2O, 0.09 g / L CuSO4·5H20, 0.07 g / L ZnSO4·7H20, 4.81 g / L KH2PO4, 0.12 g / L 75%H3PO4, 5.47 g / L K2HPO4, 0.1 g / L trace elements, the solvent is deionized water, the pH is 5.0, and the culture medium components are sterilized at high temperature before use.

[0019] Furthermore, the secondary seed activation in step (b) is performed in a primary aerobic seed tank and a secondary aerobic seed tank respectively, and the fermentation time of the primary aerobic seed tank and the secondary aerobic seed tank is 2 hours and the fermentation temperature is 30°C; Formal aerobic fermentation was carried out in an aerobic fermentation tank. Before aerobic fermentation, polydimethylsiloxane with a volume fraction of 2% was added to the aerobic fermentation tank, and vitamin H with a final concentration of 1.5 g / L was added. The final concentration here refers to the concentration of vitamin H added to the fermentation liquid in the aerobic fermentation tank. The fermentation time in the aerobic fermentation tank was 5 hours, the fermentation temperature was 20~40°C, and the pH of the culture liquid in the aerobic fermentation tank was controlled to 6.0±0.5 by an acid tank.

[0020] The Paenibacillus polymyxa seeds were inoculated into the primary aerobic seed tank at a total mass of 2% of the mass of the culture medium, and the mass ratio of the Candida tropicalis seeds in the anaerobic fermentation to the Paenibacillus polymyxa seeds in the aerobic fermentation was 2-4:8-6; During the secondary activation process, the ventilation volume of the syngas purification tail gas and oxygen entering the primary aerobic seed tank and the secondary aerobic seed tank is 40 L / min; the ventilation volume of the syngas purification tail gas and oxygen entering the aerobic fermentation tank is 100 L / min, and the anaerobic fermentation material after the aerator is mixed with the syngas purification tail gas and oxygen to form bubbles smaller than 50 microns.

[0021] Furthermore, the operation of centrifugation, evaporation, concentration and drying is specifically as follows: the fermentation material discharged from the aerobic fermentation tank is dehydrated in a high-speed centrifuge, and when the dry matter concentration is concentrated to 60%, it is sent to a drum scraper dryer; In the drum scraper dryer, the centrifuged material is heated by steam, and most of the water evaporates here. The product after evaporation is a wet floc with little viscosity. The flocs are further dried to reduce the moisture content of the remaining material to less than 5% and granulated at the same time.

[0022] The single-cell protein obtained by the method of preparing single-cell protein by purifying tail gas from synthesis gas, and the application of the single-cell protein in fish feed.

[0023] The beneficial effects of the present invention are: 1. The present invention provides a system and method for preparing single-cell protein by purifying tail gas from syngas. The microbial strains and process waste gas are subjected to an anaerobic-aerobic two-step serial fermentation process to obtain single-cell protein, and the material of anaerobic fermentation is used as the fermentation liquid of aerobic fermentation. Since tropical Candida is a facultative anaerobic yeast, it can continue to be fermented again in the aerobic fermentation system, thereby increasing the final single-cell yield. In addition, before the anaerobic fermentation material enters the aerobic fermentation tank, the aerator is set to allow the syngas-purified tail gas and oxygen to be subsequently fermented in the aerobic fermentation tank in the form of bubbles, thereby improving the fermentation efficiency and shortening the fermentation time.

[0024] 2. The present invention provides a system and method for preparing single-cell protein by purifying tail gas with syngas. The system and method are based on anaerobic fermentation of tropical Candida and subsequent aerobic fermentation of tropical Candida and Bacillus polymyxa. The system and method can withstand high temperatures during the entire fermentation process, and the fermentation process is easy to operate and the fermentation time is short. In addition, by adding vitamin H during the aerobic fermentation process, the crude protein content of the final single-cell protein is increased, and the single-cell protein can be used as part of fish feed.

[0025] 3. The present invention provides a system and method for preparing single-cell protein by purifying tail gas with syngas. After anaerobic fermentation and aerobic fermentation are completed, the nutritional components in the single-cell protein can be well retained by a drum scraper dryer, avoiding the problem of nutrient loss caused by drying operations such as high-temperature treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are merely embodiments of the present disclosure, and a person of ordinary skill in the art can obtain other drawings based on the provided drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the system for preparing single-cell protein by purifying tail gas from syngas according to the present invention.

[0028] Reference numerals: 1-alkali tank; 2-first-level anaerobic seed tank; 3-alkali pump; 4-gas buffer tank; 5-anaerobic fermentation tank; 6-anaerobic discharge pump; 7-culture medium tank; 8-second-level anaerobic seed tank; 9-culture medium pump; 10-aerobic fermentation tank; 11-aerator; 12-drum scraper dryer; 13-second-level aerobic seed tank; 14-first-level aerobic seed tank; 15-acid tank; 16-centrifuge. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0033] The reagents and equipment used in the present invention are all known products or obtained by purchasing commercially available products. It is particularly noted that the microorganisms used in the present invention are all purchased from the China Industrial Microbiological Culture Collection Management Center. The specific information is: Candida tropicalis (Latin name: Candida tropicalis , strain number: CICC 31488); Paenibacillus polymyxa (Latin name: Paenibacillus polymyxa , strain number: CICC 21779). Example 1

[0034] This embodiment provides a system for purifying tail gas from syngas to produce single cell protein, such as Figure 1 As shown, it includes a gas buffer tank 4, a culture medium tank 7, an anaerobic fermentation device, an aerator 11, an aerobic fermentation device and a fermentation material collection and processing device; the gas buffer tank 4 is connected to the synthesis gas purification tail gas input pipeline and the anaerobic fermentation device.

[0035] The anaerobic fermentation device comprises a first-level anaerobic seed tank 2, a second-level anaerobic seed tank 8 and an anaerobic fermentation tank 5 connected in sequence, wherein the anaerobic fermentation tank 5 is connected to the culture medium tank 7 through a pipeline, and a culture medium feed pump 9 is provided on the connected pipeline, and the culture medium in the culture medium tank 7 is input into the anaerobic fermentation tank 5 through the culture medium feed pump 9. The bottom of the anaerobic fermentation tank 5 is connected to the aerobic fermentation tank 10 through a pipeline provided with an anaerobic discharge pump 6 and an aerator 11, the upper part of the anaerobic fermentation tank 5 is connected to the alkali tank 1 through a pipeline, and an alkali pump 3 is provided on the pipeline connected to the anaerobic fermentation tank 5 and the alkali tank 1, and the gas buffer tank 4 is also connected to the first-level anaerobic seed tank 2 and the second-level anaerobic seed tank 8 through a pipeline, and a valve is provided on the connected pipeline, and the syngas purified tail gas passes through an air filter before entering the gas buffer tank 4, thereby filtering out potential bacteria in the purified tail gas, and avoiding entering the subsequent fermentation system to cause bacteria contamination.

[0036] The aerobic fermentation device comprises a primary aerobic seed tank 14, a secondary aerobic seed tank 13 and an aerobic fermentation tank 10 connected in sequence, the top of the aerobic fermentation tank 10 is connected to the anaerobic fermentation tank 5 through a pipeline, and the bottom of the aerobic fermentation tank 10 is connected to the fermentation material collection and processing device; the top of the aerobic fermentation tank 10 is connected to the acid tank 15 through a pipeline, and a valve is provided on the pipeline connecting the aerobic fermentation tank 10 and the acid tank 15. Oxygen and the purified tail gas from the gas buffer tank 4 are mixed and transported to the primary aerobic seed tank 14 and the secondary aerobic seed tank 13. In addition, when the secondary activation is completed, oxygen and the purified tail gas from the gas buffer tank 4 are mixed with the material pumped out from the anaerobic fermentation tank 5, and then pass through the aerator 11 to form bubbles less than 50 microns and enter the aerobic fermentation tank 10 to continue the subsequent aerobic fermentation. The oxygen comes from the oxygen of the air separation drainage evaporator as the gas source.

[0037] The fermentation material collection and processing device comprises a centrifuge 16 and a drum scraper dryer 12 which are connected in sequence, and the bottom of the aerobic fermentation tank 10 is connected to the centrifuge 16 .

[0038] The system for preparing single-cell protein by purifying tail gas with syngas also includes microbial strains that use the tail gas purified by syngas as a carbon source and a nitrogen source. In addition, the tops of the first-level anaerobic seed tank 2, the second-level anaerobic seed tank 8 and the anaerobic fermentation tank 5, as well as the first-level aerobic seed tank 14, the second-level aerobic seed tank 13 and the aerobic fermentation tank 10 are provided with vents, and the waste gas generated in the tank body is discharged through the vent pipe to avoid excessive pressure in the tank body and affect normal fermentation.

[0039] According to the above system for preparing single cell protein by purifying tail gas with syngas, the method for preparing single cell protein by purifying tail gas with syngas comprises the following steps: (a) After secondary seed activation and anaerobic fermentation, the tropical yeast completes anaerobic fermentation in the anaerobic fermentation device. The material after anaerobic fermentation is mixed with oxygen and purified tail gas through the anaerobic discharge pump 6 and enters the aerobic fermentation tank 10 through the aerator 11.

[0040] Specifically, tropical Candida seeds were taken out from a 4°C refrigerator, inoculated into the first-level anaerobic seed tank 2 at a mass ratio of 2% (mass ratio of strain to culture medium in the first-level anaerobic seed tank), cultured at 28°C and 180 r / min for 1 hour, and then inoculated into the second-level anaerobic seed tank 8 at a volume ratio of 5%, and cultured at 28°C and 180 r / min for 1 hour, and then inoculated into the anaerobic fermentation tank 5 at a volume ratio of 10%, the ventilation rate of the syngas purification tail gas in the gas buffer tank 4 entering the first-level anaerobic seed tank 2 and the second-level anaerobic seed tank 8 was 30 L / min, and the ventilation rate of the syngas purification tail gas in the gas buffer tank 4 entering the anaerobic fermentation tank 5 was 60 L / min, and fermented in the anaerobic fermentation tank 5 at 200 r / min and 28°C for 3 hours. Acid was produced during the fermentation process, and the pH of the fermentation liquid was controlled at 4.0-6.0 by the alkali tank 1. The solution in the alkali tank 1 was 20% (mass fraction) ammonia water.

[0041] The culture medium components in the primary anaerobic seed tank 2 and the secondary anaerobic seed tank 8 are: 1.59 g / L (NH4)2SO4, 1.05 g / L NaCl, 0.54 g / L MgSO4·7H2O, 4.81 g / L KH2PO4, 0.12 g / L 75% H3PO4, 5.47 g / LK2HPO4, 0.1 g / L trace elements, the solvent is deionized water, and the pH is 5.5.

[0042] The above culture medium components are sterilized at 0.105 MPa and 121° C. for 20 min, and then added to the primary anaerobic seed tank 2 and the secondary anaerobic seed tank 8 after being cooled to room temperature.

[0043] The culture medium components in anaerobic fermentation tank 5 are: 1.59 g / L (NH4)2SO4, 1.05 g / L NaCl, 0.54 g / LMgSO4·7H2O, 0.96 g / L FeSO4·7H20, 0.73 g / L CaCl2·2H2O, 0.09 g / L CuSO4·5H20, 0.07 g / L ZnSO4·7H20, 4.81 g / L KH2PO4, 0.12 g / L 75% H3PO4, 5.47 g / L K2HPO4, 0.1 g / L trace elements, the solvent is sterilized deionized water, and the pH is 5.5.

[0044] The above culture medium components are sterilized at a pressure of 0.105 MPa and a temperature of 121° C. for 20 min, and then added to the anaerobic fermentation tank 5 after being cooled to room temperature for use.

[0045] After the tropical yeast in the anaerobic fermentation tank 5 completes 2 hours of fermentation, the fermented material is transported to the aerobic fermentation tank 10 through the anaerobic discharge pump 6. During this period, the fermented material in the anaerobic fermentation tank 5 includes tropical yeast and culture medium components, which are mixed with oxygen and purified exhaust gas, and then pass through the aerator 11 to form small bubbles and then enter the aerobic fermentation tank 10.

[0046] In the above-mentioned anaerobic fermentation process, the culture medium in the culture medium tank 7 is introduced from the upper part of the anaerobic fermentation tank 5, and the synthesis gas purification tail gas is introduced from the bottom of the anaerobic fermentation tank 5. Under high hydrostatic pressure, it rises as the gas phase dissolves into the liquid phase. Because the porosity increases, the thrust generated by the gas phase lifting effect causes the liquid in the anaerobic fermentation tank 5 to circulate, and the CO2 and residual gas produced by the fermentation are removed through the venting pipe at the venting port on the top of the anaerobic fermentation tank 5. The density of the degassed liquid increases, and it circulates in the tower anaerobic fermentation tank 5 under the action of the fermentation liquid and gas.

[0047] (b) The polymyxa bacillus in the microbial strain undergoes secondary seed activation in the aerobic fermentation device, and the activated seed liquid and the material in the anaerobic fermentation tank 5 simultaneously enter the aerobic fermentation tank 10 for aerobic fermentation, and the material discharged from the anaerobic fermentation tank 5 enters the aerobic fermentation tank 10 for reuse.

[0048] Specifically, the polymyxa bacillus seeds were taken out from a 4°C refrigerator and inoculated into the primary aerobic seed tank 14 at a mass ratio of 2% (mass ratio of the strain to the culture medium in the primary anaerobic seed tank), wherein the mass ratio of the tropical candida seeds in the anaerobic fermentation to the polymyxa bacillus seeds in the aerobic fermentation was 4:6, and after shaking culture at 30°C and 180 r / min for 2 hours, they were inoculated into the secondary aerobic seed tank 13 at a volume ratio of 5%, and after shaking culture at 30°C and 180 r / min for 2 hours, they were inoculated into the aerobic fermentation tank 10 at a volume ratio of 10%, and the oxygen and syngas purified tail gas entered the primary aerobic seed tank 14 and the secondary aerobic seed tank 13 through a delivery pipeline with a ventilation volume of 40 L / min, the ventilation volume of oxygen and syngas purified tail gas entering aerobic fermentation tank 5 is 100L / min, and fermentation is carried out in aerobic fermentation tank 10 for 5 hours, wherein the volume percentage of oxygen and purified tail gas in the mixed gas is 70:30, and the oxygen is oxygen purified by air separation device, and the oxygen content is 99%. The gas entering aerobic fermentation tank 10 passes through an air filter, which greatly reduces the pollution caused by the use of air.

[0049] The fermentation time in the aerobic fermentation tank 10 is 5 hours, the stirring speed is 180 r / min, the fermentation temperature is 35°C, the pH of the fermentation liquid in the aerobic fermentation tank 10 is controlled to be 6.0 by the acid tank 15, and the solution in the acid tank 15 is 75% (mass fraction) H3PO4.

[0050] The culture medium components in the primary aerobic seed tank 14 and the secondary aerobic seed tank 13 are: 2.15 g / L (NH4)2SO4, 1.74 g / L NaCl, 1.89 g / L MgSO4·7H2O, 0.05 g / L MnSO4·H2O, 4.81 g / L KH2PO4, 0.12 g / L75% H3PO4, 5.47 g / L K2HPO4, 0.1 g / L trace elements, the solvent is deionized water, and the pH is 7.0.

[0051] The above culture medium components are sterilized at 0.105 MPa and 121° C. for 20 min, and then added to the primary aerobic seed tank 14 and the secondary aerobic seed tank 13 after being cooled to room temperature for use.

[0052] In addition to the material from the anaerobic fermentation tank 5, the aerobic fermentation tank 10 also needs to add polydimethylsiloxane with a volume fraction of 2% and vitamin H with a final concentration of 1.5 g / L. The anaerobic fermentation material after passing through the aerator 11 is mixed with the syngas purification exhaust gas and oxygen to form bubbles less than 50 microns and aerobic fermentation is carried out in the aerobic fermentation tank 10.

[0053] The culture medium components used in the primary aerobic seed tank 14 and the secondary aerobic seed tank 13 and the water required for preparing the solution are sterilized at a pressure of 0.105 MPa and a temperature of 121° C. for 20 minutes, and are cooled to room temperature before use.

[0054] During the anaerobic and aerobic fermentation process, the tops of the first-level anaerobic seed tank 2, the second-level anaerobic seed tank 8, the anaerobic fermentation tank 5, the first-level aerobic seed tank 14, the second-level aerobic seed tank 13 and the aerobic fermentation tank 10 are all provided with vents, through which the excess gas in the tank body can be discharged from the tank body to maintain the balance of the internal pressure of the tank body, and at the same time, the gas that is not dissolved in the liquid can be discharged.

[0055] (c) After the aerobic fermentation is completed, the material flows out from the bottom of the aerobic fermentation tank 10 and is centrifuged, evaporated, concentrated and dried to obtain a granular finished product.

[0056] After the aerobic fermentation is completed, the material in the aerobic fermentation tank 10 is discharged from the bottom and enters the centrifuge 16 for centrifugation at 1200rpm. When the material is dehydrated and concentrated to a dry matter concentration of 60%, the centrifuged material is then sent to the drum scraper dryer 12. In the drum scraper dryer, it consists of two sections. In the first section, the material is sprayed onto a vertical disc rotating around a horizontal axis. The disc is heated by steam (low-pressure steam) inside, and most of the water in the material evaporates here. After the disc rotates one circle, the product is scraped off and becomes a wet and very sticky floc. It enters the second section, i.e., the conical dryer, where it is further dried to make the residual humidity less than 5%, and granulated at the same time. The particle size can be selected from fine powder to 1~5 mm. The entire drying process takes only 2 minutes. During the whole process, the temperature is always below 70°C, so that the loss of vitamins and amino acids in the final prepared single-cell protein is extremely small, maintaining a very high physiological index.

[0057] The finished product is in the form of granules and is packaged in airtight plastics for medical vacuum packaging. It can be stored in a warehouse and can be preserved almost indefinitely under suitable conditions. The components of the above-mentioned tail gas purified by synthesis gas are shown in Table 1 below: Table 1: Syngas purification tail gas

[0058] The single-cell protein obtained through the above-mentioned anaerobic-aerobic fermentation has a simple structure and a crude protein content of more than 85%. The specific crude protein detection method is: Kjeldahl nitrogen determination method (GB / T 6432-2018 Determination of crude protein in feed). Its essential amino acid content and structural ratio are close to fish meal and far superior to soybean meal, which also allows it to be widely used in feed. In the foreseeable future, this technology provides a solution to improve the current situation of my country's need to import a large amount of soybeans, and can also reduce the feed costs of farmers.

[0059] In order to verify the use in fish feed, carp was used as the test object, 0.4% titanium dioxide (TiO2) was added to the feed as an indicator, and the apparent digestibility of single-cell protein and total energy was analyzed by testing the crude protein content and total energy in the feeding raw materials and collecting feces. The specific testing standard is: NY / T 2713-2015 (Apparent Digestibility Determination Method for Aquatic Animals), and a comparative test was conducted with commonly used protein feed raw materials: fish meal, brewer's yeast and soybean meal. The test results are shown in Table 2 below, which shows that the nutritional value of single-cell protein is higher than that of fish meal, brewer's yeast and soybean meal.

[0060] Table 2: Comparison of nutritional value of single cell protein and major traditional protein feed ingredients Example 2

[0061] Compared with the method for preparing single-cell protein by purifying tail gas from synthesis gas in Example 1, the difference is that in the aerobic fermentation process in step (b), vitamin H is not added to the aerobic fermentation tank 10, and the final crude protein content is detected to be 70%. It can be seen that adding a certain concentration of vitamin H can promote the synthesis of crude protein and increase the nutrition of single-cell protein. Example 3

[0062] Compared with the method for preparing single-cell protein by purifying tail gas from syngas in Example 1, the difference is that in the aerobic fermentation process in step (b), the mass ratio of tropical yeast seeds in anaerobic fermentation and Paenibacillus polymyxa seeds in aerobic fermentation is 7:3, and the amount of single-cell protein finally obtained is 60% of that in Example 1, and the crude protein content in the single-cell protein is 80.9%. It can be seen that the mass ratio of tropical yeast seeds to Paenibacillus polymyxa seeds has little effect on the crude protein content in the single-cell protein finally obtained, but will affect the growth of the strain in the aerobic fermentation tank and affect the final single-cell protein yield. Example 4

[0063] Compared with the method for preparing single-cell protein by purifying tail gas with syngas in Example 1, the material of anaerobic fermentation before aerobic fermentation, oxygen and purified tail gas do not pass through the aerator 11, but directly enter the aerobic fermentation tank 10 for fermentation, and the final single-cell protein amount obtained is 72% of that in Example 1. During the experiment, the aerator 11 was tried to be set before entering the anaerobic fermentation tank 5, and the final single-cell protein amount obtained was 81% of that in Example 1. It can be seen that the setting and corresponding position of the aerator 11 affect the yield of single-cell protein.

[0064] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A system for purifying tail gas from synthesis gas to produce single cell protein, characterized in that: It comprises a gas buffer tank (4), a culture medium tank (7), an anaerobic fermentation device, an aerator (11), an aerobic fermentation device and a fermentation material collection and processing device; The gas buffer tank (4) is used to store the synthesis gas purification tail gas, and the gas buffer tank (4) is also connected to the anaerobic fermentation device and the aerobic fermentation device; The anaerobic fermentation device comprises a primary anaerobic seed tank (2), a secondary anaerobic seed tank (8) and an anaerobic fermentation tank (5) which are connected in sequence, and the anaerobic fermentation tank (5) and the culture medium tank (7) are connected via a pipeline; The aerobic fermentation device comprises a primary aerobic seed tank (14), a secondary aerobic seed tank (13) and an aerobic fermentation tank (10) which are connected in sequence, and the bottom of the aerobic fermentation tank (10) is connected to a fermentation material collection and processing device; An anaerobic discharge pump (6) and an aerator (11) are sequentially arranged on the pipeline connecting the anaerobic fermentation tank (5) and the aerobic fermentation tank (10); The fermentation material collection and processing device comprises a centrifuge (16) and a drum scraper dryer (12) which are connected in sequence; The system for preparing single-cell protein by purifying tail gas with syngas also includes microbial strains that use the tail gas purified with syngas as a carbon source and a nitrogen source.

2. The system for preparing single cell protein by purifying tail gas from synthesis gas according to claim 1, characterized in that: The upper part of the anaerobic fermentation tank (5) is connected to the alkali tank (1) through a pipeline, and an alkali pump (3) is provided on the pipeline connecting the anaerobic fermentation tank (5) and the alkali tank (1); The top of the aerobic fermentation tank (10) is connected to the acid tank (15) via a pipeline. A valve is provided on the pipeline connecting the aerobic fermentation tank (10) and the acid tank (15). Oxygen and purified tail gas and materials discharged from the anaerobic fermentation tank (5) enter the aerobic fermentation tank (10) after passing through an aerator (11).

3. The system for preparing single cell protein by purifying tail gas from synthesis gas according to claim 1, characterized in that: The microbial strains include Candida tropicalis and Paenibacillus polymyxa.

4. A method for preparing single cell protein by purifying tail gas from synthesis gas, characterized in that: The method is to synthesize single-cell protein using the system for preparing single-cell protein as described in any one of claims 1 to 3.

5. A method for preparing single cell protein by purifying tail gas from synthesis gas, characterized in that: The steps for synthesizing single cell protein are as follows: (a) After the tropical yeast undergoes secondary seed activation and anaerobic fermentation in the anaerobic fermentation device, the anaerobic fermentation is completed, and the material after the anaerobic fermentation is mixed with oxygen and purified tail gas through the anaerobic discharge pump (6), and then enters the aerobic fermentation tank (10) through the aerator (11); The carbon and nitrogen sources in the secondary seed activation and anaerobic fermentation process are provided by the tail gas of syngas purification; (b) Paenibacillus polymyxa is activated through secondary seed activation in an aerobic fermentation device, and the activated seed solution enters an aerobic fermentation tank (10) for aerobic fermentation, and the material discharged from the anaerobic fermentation tank (5) enters an aerobic fermentation tank (10) for reuse; The carbon and nitrogen sources in the secondary seed activation and aerobic fermentation process are provided by the tail gas of syngas purification; (c) After the aerobic fermentation is completed, the material flows out from the bottom of the aerobic fermentation tank (10), and after centrifugation, evaporation, concentration and drying, a granular finished product is obtained.

6. The method for preparing single cell protein by purifying tail gas from synthesis gas according to claim 5, characterized in that: The secondary seed activation in step (a) is performed in the primary anaerobic seed tank (2) and the secondary anaerobic seed tank (8), respectively. The fermentation time of the microbial strain in the primary anaerobic seed tank (2) and the secondary anaerobic seed tank (8) is 1 hour respectively, and the fermentation temperature is 20-30° C.; The formal anaerobic fermentation is carried out in the anaerobic fermentation tank (5). The fermentation time in the anaerobic fermentation tank (5) is 3 hours, the fermentation temperature is 20-30°C, and the pH of the culture solution in the anaerobic fermentation tank (5) is controlled at 4.0-6.0 by the alkali tank (1); The tropical Candida seeds are inoculated into the primary anaerobic seed tank (2) at a rate of 2% of the mass of the culture medium; During the secondary activation process, the ventilation rate of the purified tail gas of the syngas in the gas buffer tank (4) entering the primary anaerobic seed tank (2) and the secondary anaerobic seed tank (8) is 30 L / min; during the anaerobic fermentation process, the ventilation rate of the purified tail gas of the syngas in the gas buffer tank (4) entering the anaerobic fermentation tank (5) is 60 L / min; The culture medium introduced into the anaerobic fermentation tank (5) comes from the culture medium tank (7). The culture medium components in the culture medium tank (7) are: 1.59 g / L (NH4)2SO4, 1.05 g / L NaCl, 0.54 g / L MgSO4·7H2O, 0.96 g / L FeSO4·7H20, 0.73 g / LCaCl2·2H2O, 0.09 g / L CuSO4·5H20, 0.07 g / L ZnSO4·7H20, 4.81 g / L KH2PO4, 0.12 g / L 75% H3PO4, 5.47 g / L K2HPO4, 0.1 g / L trace elements, the solvent is deionized water, the pH is 5.0, and the culture medium components are sterilized before use.

7. The method for preparing single cell protein by purifying tail gas from synthesis gas according to claim 5, characterized in that: The secondary seed activation in step (b) is performed in the primary aerobic seed tank (14) and the secondary aerobic seed tank (13) respectively, and the fermentation time of the primary aerobic seed tank (14) and the secondary aerobic seed tank (13) is 2 hours, and the fermentation temperature is 30° C.; The formal aerobic fermentation is carried out in an aerobic fermentation tank (10). Before the aerobic fermentation, polydimethylsiloxane with a volume fraction of 2% is added to the aerobic fermentation tank (10), and vitamin H with a final concentration of 1.5 g / L is added. The fermentation time of the aerobic fermentation tank (10) is 5 hours, the fermentation temperature is 20-40° C., and the pH of the culture solution in the aerobic fermentation tank (10) is controlled to be 6.0±0.5 by the acid tank (15); The Paenibacillus polymyxa seeds are inoculated into a primary aerobic seed tank (14) at a total mass of 2% of the mass of the culture medium, and the mass ratio of the Candida tropicalis seeds in the anaerobic fermentation to the Paenibacillus polymyxa seeds in the aerobic fermentation is 2-4:8-6; During the secondary activation process, the ventilation rate of the syngas purification tail gas and oxygen entering the primary aerobic seed tank (14) and the secondary aerobic seed tank (13) is 40 L / min; the ventilation rate of the syngas purification tail gas and oxygen entering the aerobic fermentation tank (10) is 100 L / min, and the anaerobic fermentation material after passing through the aerator (11) is mixed with the syngas purification tail gas and oxygen to form bubbles less than 50 microns.

8. The method for preparing single cell protein by purifying tail gas from synthesis gas according to claim 5, characterized in that: The centrifugal, evaporative, concentrated and dried operations are as follows: the fermented material discharged from the aerobic fermentation tank (10) is dehydrated in a centrifuge (16), and when the dry matter concentration is concentrated to 60%, it is sent to a drum scraper dryer (12); The centrifuged material is heated by steam in a drum scraper dryer (12), where most of the water evaporates, and the product after evaporation is a wet floc with little viscosity; The flocs are further dried to reduce the moisture content of the remaining material to less than 5% and granulated at the same time.

9. A single cell protein, characterized in that The single-cell protein is synthesized by the method for preparing single-cell protein according to any one of claims 4 to 8.

10. Use of the single cell protein according to claim 9 in fish feed.

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