CN111254166A

CN111254166A - Method for co-producing alcohol and biogas by utilizing cassava and method for generating power by utilizing biogas

Info

Publication number: CN111254166A
Application number: CN201811453151.7A
Authority: CN
Inventors: 林海龙; 熊强; 刘劲松; 于建东
Original assignee: Sdic Biotechnology Investment Co ltd
Current assignee: Sdic Biotechnology Investment Co ltd
Priority date: 2018-11-30
Filing date: 2018-11-30
Publication date: 2020-06-09

Abstract

The invention relates to the field of biogas fermentation, and discloses a method for co-producing alcohol and biogas by utilizing cassava and a method for generating power by utilizing biogas. The method comprises the following steps: sequentially crushing cassava, mixing, liquefying, saccharifying and fermenting to obtain fermented mash; distilling the fermented mash to obtain alcohol and waste mash; cooling the waste mash, inoculating fermentation strain, and performing anaerobic fermentation at 50-70 deg.C for 18-25 days to generate biogas; anaerobic fermentation is carried out in at least 1 group of anaerobic fermentation systems, each group of anaerobic fermentation systems comprises a plurality of anaerobic fermentation units which are connected in series, and each group of anaerobic fermentation systems are connected in parallel with each other. The method for generating power by utilizing the methane comprises the following steps: preparing desulfurized biogas, burning the desulfurized biogas in a high-temperature high-pressure gas boiler to generate steam, and generating power by the generated steam in a high-temperature high-pressure turbine; the elevated temperature is a temperature of at least 540 ℃ and the elevated pressure is a pressure of at least 9.8 MPa. The invention can obviously improve the yield of the biogas, improve the generated energy and reduce the energy consumption of the whole system.

Description

Method for co-producing alcohol and biogas by utilizing cassava and method for generating power by utilizing biogas

Technical Field

The invention relates to the field of alcohol preparation by cassava and biogas fermentation, in particular to a method for co-producing alcohol and biogas by utilizing cassava and a method for generating power by utilizing the prepared biogas.

Background

Cassava is one of three potato crops in the world and is the first choice raw material for producing bioethanol. As 2005, the cassava planting area in China has reached 657 ten thousand mu, more than 200 cassava starch and alcohol processing plants exist in China, 50 ten thousand tons of starch and 25 ten thousand tons of cassava ethanol are produced every year. Because the wastewater from the preparation of ethanol by cassava fermentation contains high-concentration organic matters, most of the wastewater discharged by ethanol plants is not effectively treated and is directly discharged outwards at present, thereby causing serious influence on local and downstream water environments.

At present, COD of waste mash of ethanol preparation by cassava fermentation is about 50,000-80,000mg/L, and the current treatment methods comprise: 1. the incineration method, namely concentrating the waste mash and then incinerating, has the defects that secondary pollution is easily caused after incineration, and the waste of resources is caused by direct abandonment due to higher COD value in the cassava waste mash; 2. the waste mash is used for preparing the biogas by fermentation, but the biogas yield of the biogas prepared by the waste mash is lower at present, the viscosity of the waste water after the biogas is produced is higher, and the difficulty of solid-liquid separation is higher, so that the energy consumption is higher when the alcohol and the biogas are co-produced by cassava, and the production cost is improved.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provide the method for co-producing the alcohol and the methane by utilizing the cassava, and by utilizing the method, the yield of the methane can be greatly improved, the viscosity of the waste water after the methane is produced is effectively reduced, the difficulty of solid-liquid separation is reduced, and the energy consumption and the cost are reduced.

In order to achieve the above objects, an aspect of the present invention provides a method for co-producing alcohol and biogas using cassava, the method comprising:

(1) sequentially crushing, size mixing, liquefying, saccharifying and fermenting the cassava raw material to obtain fermented mash;

(2) distilling the fermented mash to obtain alcohol and waste mash;

(3) cooling the waste mash, inoculating a fermentation strain, and performing anaerobic fermentation to generate biogas;

wherein the anaerobic fermentation temperature is 50-70 deg.C, and the time is 18-25 days;

wherein the anaerobic fermentation is carried out in at least 1 group of anaerobic fermentation systems, each group of anaerobic fermentation systems comprises a plurality of anaerobic fermentation units which are connected in series, and each group of anaerobic fermentation systems are connected in parallel with each other.

Preferably, the method further comprises: the prepared biogas is desulfurized sequentially through a first desulfurizer and a second desulfurizer to obtain desulfurized biogas, wherein the first desulfurizer is selected from carbonate solution of alkali metal and/or hydroxide solution of alkali metal; the second desulfurizer contains calcium oxide and/or silica gel, iron oxide and/or activated carbon.

Preferably, the method further comprises: adding water-soluble alginate ester, water-soluble alginate and plant polyphenol into the wastewater generated after the anaerobic fermentation to generate the biogas, and carrying out solid-liquid separation to obtain filtrate and filter residue.

Preferably, the crushing mode comprises crushing the materials obtained by impurity removal treatment and sieving the crushed materials by a 1.8mm sieve, wherein the crushing is primary crushing, and the impurity removal is primary impurity removal.

Preferably, the method further comprises the step of conveying the cassava raw materials to a screen by using a self-discharging silo before crushing, so as to screen the cassava raw materials, wherein after impurities are removed from undersize materials, the undersize materials and oversize materials are mixed, and the obtained mixed materials are crushed as materials obtained after impurity removal treatment.

Preferably, the material obtained by crushing is prepared into starch slurry by using water, and a bactericide is added into the starch slurry; the concentration of the starch slurry is 35-40 wt% calculated by solid; the amount of the added bactericide is 50-300ppm based on the weight of the starch slurry; the bactericide is one or more of penicillin, clotrimazole and bleaching powder.

Preferably, the method further comprises subjecting the jet liquefied mash to at least 2-4 stage flash evaporation to reduce the temperature of the liquefied mash to 70-80 ℃; the vacuum degree of flash evaporation is 0.05-0.09 Mpa, and the flash evaporation time is 5-20 seconds.

In a second aspect, the present invention provides a method for generating electricity using biogas, the method comprising: preparing desulfurized biogas according to the method, combusting the desulfurized biogas in a high-temperature high-pressure gas boiler to generate steam, and generating power by the generated steam in a high-temperature high-pressure turbine;

wherein the elevated temperature is a temperature of at least 540 ℃ and the elevated pressure is a pressure of at least 9.8 MPa.

The invention replaces the traditional medium-high temperature anaerobic fermentation by high temperature (50-70 ℃) anaerobic fermentation, prolongs the fermentation time to 18-25 days, and sets at least 1 group of anaerobic fermentation systems, wherein each group of anaerobic fermentation system comprises a plurality of anaerobic fermentation units connected in series, and each group of anaerobic fermentation systems are connected in parallel. The yield of the biogas can be improved by 5-10%, and in addition, the anaerobic fermentation method can promote the degradation of colloid and hemicellulose with larger viscosity in waste mash, reduce the viscosity of feed liquid, reduce the dosage of a flocculating agent during subsequent solid-liquid separation, improve the flux of solid-liquid separation, and avoid secondary pumping of the feed liquid caused by too large viscosity of the feed liquid, thereby greatly reducing energy consumption and cost.

In addition, under the preferable conditions, for example, the energy consumption of the whole system can be further reduced by once crushing and once removing impurities, conveying the cassava raw material to a screen by using a self-discharging silo to screen the cassava raw material, increasing the concentration of starch slurry, adding a bactericide in the pulping process, and performing multi-stage flash evaporation on the liquefied mash after spray liquefaction, thereby further reducing the cost.

Drawings

FIG. 1 is a schematic diagram of the integration of biogas preparation and power generation by using waste mash produced by fermenting alcohol with cassava according to the present invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect of the present invention, there is provided a method for co-producing alcohol and biogas by using cassava, the method comprising:

(2) distilling the fermented mash to obtain alcohol and waste mash;

As is well known to those skilled in the art, the general anaerobic fermentation of biogas is divided into normal temperature fermentation (10-26 ℃), medium temperature fermentation (28-38 ℃) and high temperature fermentation (40-60 ℃), and the growth of fermenting microorganisms will be inhibited below 10 ℃ or above 60 ℃, thereby affecting the biogas yield. At present, the biogas fermentation by using the waste mash of alcohol fermentation usually adopts medium-high temperature fermentation, namely, the fermentation is firstly carried out at medium temperature for a period of time, then the high temperature fermentation is carried out, the fermentation period is usually 15 days, and the fermentation units are generally connected in parallel. However, in the research process, the inventor of the invention finds that the anaerobic fermentation temperature is increased to 50-70 ℃, the anaerobic fermentation period is prolonged to 18-25 days, and meanwhile, the fermentation units are connected in a semi-serial mode (namely, the fermentation units are divided into at least 1 group, each group is connected in parallel, and each group comprises a plurality of fermentation units which are sequentially connected in series), so that the yield of the biogas is not influenced by the growth of fermentation microorganisms, the yield of the biogas is effectively increased, the degradation of colloid and hemicellulose with high viscosity in waste mash is promoted, the viscosity of feed liquid is reduced, the solid-liquid separation flux is increased, and the energy consumption is reduced.

Preferably, the temperature of the anaerobic fermentation is 60-65 ℃, for example, 60 ℃, 60.5 ℃, 61 ℃, 61.5 ℃, 62 ℃, 62.5 ℃, 63 ℃, 63.5 ℃, 64 ℃, 64.5 ℃ and 65 ℃.

According to the invention, the anaerobic fermentation units are anaerobic fermentation tanks, and each group of anaerobic fermentation systems can comprise 2-5 anaerobic fermentation tanks connected in series in sequence. The anaerobic fermentation system can be in 1-3 groups.

In the present invention, in order to further increase the yield of biogas and reduce the viscosity of wastewater after biogas production, it is preferable that the carbon-nitrogen ratio of the waste mash is adjusted to 25-30:1, for example, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, and the pH is adjusted to 6-6.5, for example, 6, 6.1, 6.2, 6.3, 6.4, 6.5, before the waste mash is inoculated with a fermentation broth. The substance for adjusting the carbon-nitrogen ratio can be a common substance used in biogas fermentation, and can be, for example, but not limited to, corncobs, rice hulls, wood chips, straws, cassava dregs, beet pulp, corn husks, peanut shells, plant ash, ammonium sulfate, ammonium phosphate and potassium nitrate.

Further preferably, the anaerobic fermentation is carried out under stirring.

In the present invention, the anaerobic fermentation zymocyte can be various sludge used for biogas fermentation, which is conventional in the art, for example, river bottom sludge, sewage sludge, factory wastewater bottom sludge, pond bottom sludge, lake bottom sludge, and the like. Preferably, the sludge contains at least one of clostridium, bacteroides, butyric acid bacteria, lactic acid bacteria, bifidobacteria and spirochetes, hydrogen-producing acetogenic bacteria, hydrogen-consuming acetogenic bacteria and methanogenic bacteria. Wherein the methanogen comprises methanogen hydrogenotrophus and/or methanogen acetogenic.

Wherein the inoculum size of the fermentation strain can be in accordance with the inoculum size of the fermentation strain in the conventional biogas fermentation in the art, for example, 10-30 wt% of the waste mash.

In the invention, in order to facilitate the high-temperature anaerobic fermentation, before the fermentation strain is inoculated into the waste mash, the sand removal is carried out on the waste mash, and the sand removal method can adopt a conventional sand removal method, for example, the sand removal method can be carried out by standing and utilizing the gravity of the sand to naturally settle.

As is well known to those skilled in the art, the biogas directly collected from the fermentation system usually carries a certain amount of gases such as hydrogen sulfide and a large amount of water vapor, and therefore, before the biogas is used, the water vapor is generally removed (condensed water can be removed by cooling), and then the sulfur is removed. The inventors of the present invention found in the course of their research that the desulfurization efficiency can be effectively improved by passing the obtained biogas sequentially through an alkali metal carbonate solution and/or an alkali metal hydroxide solution as a first desulfurizing agent, and then through a second desulfurizing agent containing calcium oxide and/or silica gel (component a), iron oxide and/or activated carbon (component B). Wherein the weight ratio of the component A to the component B can be 1: 2-5.

Wherein, the carbonate of the alkali metal can be sodium carbonate or potassium carbonate, the hydroxide of the alkali metal can be sodium hydroxide or potassium hydroxide, and the solution can be saturated solution.

In the present invention, the amount of the first desulfurizing agent and the amount of the second desulfurizing agent can be selected in a wide range, for example, the amount of the first desulfurizing agent can be 500-.

The inventor of the invention finds that the viscosity of the waste water can be further reduced by adding the water-soluble alginate ester, the water-soluble alginate and the plant polyphenol into the waste water after the biogas is produced, so that the solid-liquid separation time is remarkably shortened, the treatment capacity of the waste water in unit time is remarkably improved without adding new equipment, and the energy consumption is further reduced.

According to the present invention, the amounts of the water-soluble alginic acid ester, the water-soluble alginate and the plant polyphenol may be changed within a wide range as long as the viscosity of the wastewater can be further reduced to shorten the time for solid-liquid separation, and preferably, the water-soluble alginic acid ester is added in an amount of 0.01 to 0.5 parts by weight, the water-soluble alginate is added in an amount of 0.01 to 0.5 parts by weight, and the plant polyphenol is added in an amount of 0.001 to 0.05 parts by weight, relative to 1000 parts by weight of the wastewater; more preferably, the water-soluble alginate is added in an amount of 0.1 to 0.2 parts by weight, and the plant polyphenol is added in an amount of 0.005 to 0.01 parts by weight, based on 1000 parts by weight of the wastewater.

Wherein, the kind of the water-soluble alginate can be changed in a large range as long as the collision among molecules in the wastewater is intensified, and the small molecules which are not easy to precipitate are combined into large molecules to form large flocculates, preferably, the relative molecular weight of the water-soluble alginate is 30000-200000, and the average mass and nuclide of the molecules or specific units of the substance with the relative molecular weight are preferably 30000-200000¹²1/12 ratio of C atomic mass. The water-soluble alginate can be one or more selected from sodium alginate, potassium alginate and ammonium alginate. Water-soluble alginates satisfying the above requirements are commercially available, for example, sodium alginate manufactured by Nanyang seaweed industries, Inc. of Qingdao, Potassium alginate manufactured by Yoshidao seaweed group, Inc. and ammonium alginate manufactured by Marine medicinal seaweed products, Inc. of Handan.

Wherein, the kind of the water-soluble alginate can be changed in a wide range as long as the collision between molecules in the wastewater is increased, and the small molecules which are not easy to precipitate are combined into large molecules to form large flocculate, preferably, the relative molecular weight of the water-soluble alginate is 30000-200000, and the average mass and nuclide of the molecule or specific unit of the substance with the relative molecular weight are¹²1/12 ratio of C atomic mass. The water-soluble alginate ester can be one or more of propylene glycol alginate, ethylene glycol alginate and butylene glycol alginate, and is preferably propylene glycol alginate. Water-soluble alginic acid esters meeting the above requirements may be synthesized by methods known to those skilled in the art or may be obtained commercially, for exampleFor example, propylene glycol alginate manufactured by Qingdao Mingyue algae group, Inc.

Wherein the plant polyphenol generally has no flocculation property or very weak flocculation property, but the inventor of the present invention finds that it can be used as an enhancer of water-soluble alginate and water-soluble alginate to promote their ability to combine small molecules into large molecules, thereby enhancing flocculation effect. The plant polyphenol may be of any kind, for example, one or more of tannin, anthocyanin, catechin, quercetin, gallic acid, ellagic acid and arbutin, which are commercially available.

According to the present invention, the solid-liquid separation may be any conventional solid-liquid separation method, such as filtration, for example, filtration may be performed by a filter press, for example, a box filter press manufactured by seiko filter press group ltd. The filtration conditions can vary widely and preferably include a filtration pressure of 0.4 to 1MPa and a filtration time of 1 to 3 hours.

In the present invention, the filtration conditions may vary widely, and the filtration conditions are such that the water content of the obtained solid product is less than 60% by weight, and preferably, the filtration conditions include a filtration pressure of 0.4 to 1MPa and a filtration time of 1 to 2 hours.

According to the invention, the method also comprises the step of drying a solid product obtained after solid-liquid separation to obtain solid biogas residues, wherein the solid biogas residues can be used as organic fertilizer raw materials for preparing organic fertilizers. The drying apparatus may be various conventional drying apparatuses, for example, an HZG series dryer manufactured by shenyang teleaf corporation and WJI-900B boiling dryer and XLS-100 flash dryer combination type dryer manufactured by beijing welfare industry and trade limited. In the present invention, the drying condition may be a conventional drying condition, for example, the drying condition includes a drying temperature of 100-; more preferably, the drying temperature is 120-.

According to the present invention, it is preferable that the method of the present invention further comprises aerating the waste water before subjecting the waste water to solid-liquid separation. The conditions of the aeration generally include: relative to 1000m³The flow rate of the gas to be introduced into the wastewater to be treated is preferably 200-400m³The temperature is 0-40 ℃ and the time is 0.5-1.0 h.

According to the present invention, there is no particular limitation on the method for treating the filtrate obtained by the solid-liquid separation, and the treatment of the filtrate may be performed by, for example, the method disclosed in CN 1202032C. For example, the filtrate obtained by the solid-liquid separation is passed to an anaerobic reactor and an aerobic reactor.

In the present invention, the anaerobic reactor is well known to those skilled in the art, and the anaerobic granular sludge is filled with anaerobic microorganisms of a type well known to those skilled in the art, for example, bacteroides succinogenes (Bacteriodes succinogenes), vibrio fibrillis (vibrio fibrillive), Ruminococcus flavigena (Ruminococcus flavacins), Ruminococcus albus (Ruminococcus albus), etc.; when the filtrate passes through the anaerobic reactor, organic matters in the filtrate are degraded; the kind of the anaerobic granular sludge is well known to those skilled in the art and can be commercially obtained, for example, from Pake environmental protection technology (Shanghai) Co., Ltd.

The residence time of the filtrate in the anaerobic reactor can be selected according to the type of the wastewater, and preferably, the residence time is 25 to 35 hours.

The reaction conditions in the anaerobic reactor may vary widely, for example, the reaction conditions in the anaerobic reactor include a volume loading of 20-25kgCOD/m³D, the temperature is 10-40 ℃, the pH value is 6.5-7.5, and the dissolved oxygen is 0.

The aerobic reactor is well known to those skilled in the art, and preferably, the filtrate may be introduced into an a/O reactor (anoxic/aerobic tank) for aerobic treatment, the a/O reactor is filled with aerobic granular sludge, and when the wastewater flows through, the aerobic flora decomposes organic matters in the water and converts the organic matters into self-nutrients, the type of the aerobic granular sludge is well known to those skilled in the art and can be obtained commercially, for example, the aerobic granular sludge produced by beijing fengze green source environmental technology limited. The residence time of the filtrate in the aerobic reactor can be selected according to the type of the wastewater, and preferably, the residence time is 40-60 hours.

The reaction conditions in the aerobic reactor may vary widely, and preferably the reaction conditions in the aerobic reactor comprise a volume loading of from 0.1 to 0.2kgBOD/m³D, the temperature is 20-40 ℃, the pH value is 7-8, and the dissolved oxygen is 1-3mg/L (the dissolved oxygen in the anoxic pond is not more than 1mg/L, such as 0.5-1 mg/L; the dissolved oxygen in the aerobic pond (the oxygen-enriched pond) is 2-4 mg/L).

Wherein the dissolved oxygen is the content of oxygen in water when wastewater is aerated.

Wherein, in the aerobic reactor, the ratio of the flow rate of the reflux liquid returned to the anoxic tank to the flow rate of the wastewater subjected to anoxic treatment in the anoxic tank is 2-4. The ratio of the flow rate of the mixed material after the partial aerobic treatment returned to the anoxic tank to the flow rate of the filtrate after the anoxic treatment in the anoxic tank is called as an "internal reflux ratio" or a "mixed liquid reflux ratio".

According to the invention, after the aerobic treatment is finished, the step of sludge sedimentation is also included, and the method for sludge sedimentation can be carried out according to the conventional method in the field, for example, the method can be carried out in a sludge sedimentation tank, and a flocculating agent can be added to promote the sedimentation. The flocculant may be any of various flocculants which are conventional in the art, and the present invention is not particularly limited herein, and may be, for example, one or more of an aluminum-based flocculant, an iron-based flocculant and a composite flocculant, which are commercially available, for example, polyferric sulfate (PFS), polyferric chloride (PFC), polyferric aluminum diacetate (PFSIC) and polyferric aluminum chloride (PFAS) manufactured by sre chemical industry ltd. The invention preferably carries out primary sedimentation on the wastewater after the aerobic treatment, and then carries out secondary sedimentation on the liquid phase obtained by the primary sedimentation. Wherein, the solid phase obtained by the first-stage sedimentation and the second-stage sedimentation can be used as sludge to be recycled to the anaerobic fermentation stage to be used as at least part of zymocyte.

Wherein, the liquid phase after the first-stage sedimentation and the second-stage sedimentation can be used as reclaimed water to be recycled to the preparation stage of alcohol, for example, the reclaimed water is used for pulp mixing, reverse osmosis and desalination of cassava flour and then enters a boiler to generate steam used for preparing jet liquefaction, and the like, thereby greatly saving the use of fresh water and reducing the cost. The supernatant may also be oxidized by using an oxidizing agent, which is well known to those skilled in the art, such as one or more of sodium hypochlorite, calcium hypochlorite, ferric chloride, sodium ferrate, and fenton reagent, preferably fenton reagent, and the time of the oxidation treatment is 0.5-1.5 hours.

The invention can also discharge the settled and oxidized clear liquid as waste water, more preferably adjust pH and recycle to the preparation stage of alcohol, for example, the clear liquid is used for pulp mixing, reverse osmosis and desalination of cassava flour and then enters a boiler to generate steam used for preparing jet liquefaction, and the like, thereby greatly saving the use of fresh water and reducing the cost.

In the present invention, in the step (1), the pulverization method is not particularly limited, and various pulverization methods commonly used in the art may be used, and in order to improve the effect of the subsequent treatment, the pulverization method preferably includes pulverizing the material obtained by the impurity removal treatment and sieving the pulverized material through a 1.8mm sieve.

The method of removing impurities is not particularly limited, and various methods of removing impurities commonly used in the art may be used, and for example, the method may include removing impurities such as stones, iron pieces, and woven fabrics from the cassava raw material. According to a particular embodiment of the invention, the cassava raw material is sieved, the aperture of the screen being such that the cassava raw material with small particle size with impurities is sieved down, while the cassava raw material with large particle size remains on the sieve. And then, removing impurities from the undersize product, mixing the undersize product with the oversize product, and crushing the obtained mixed material serving as the material obtained by impurity removal treatment.

According to a preferred embodiment of the invention, only one-time crushing and one-time impurity removal are carried out, and in the preferred range, the crushing effect and the impurity removal effect can be ensured, meanwhile, the investment of intermediate links is greatly reduced, the power consumption is reduced, the operation is simple, the labor is less, and the equipment maintenance cost is also greatly reduced.

In the invention, the size mixing mode comprises the following steps: and preparing the material obtained by crushing into starch slurry by using water, and adding a bactericide into the starch slurry. In order to improve the sterilization effect in the size mixing treatment process, improve the later stage liquefaction effect and reduce the energy consumption, preferably, in the size mixing treatment, high-concentration ingredients are adopted, and the concentration of the starch size is controlled to be 35-40 wt% in terms of solid matters; the amount of bactericide added is 50-300ppm based on the weight of the starch slurry. Wherein the temperature of the water for pulping can be 35-40 ℃.

The bactericide is not particularly limited, and may be various bactericides commonly used in the art, and in order to improve the bactericidal effect in the pulp mixing process, the bactericide is preferably one or more of penicillin, iprodione and bleaching powder, and more preferably bleaching powder.

According to a preferred embodiment of the invention, the conditioning water is the liquid phase after primary and secondary sedimentation or the clear liquid after oxidation and sedimentation, thus greatly saving the amount of fresh water.

In the invention, the liquefaction is preferably spray liquefaction, specifically, the cassava pulverized product is mixed with amylase and then spray liquefaction is carried out to obtain a liquefied product, the type and the using amount of the amylase are not particularly limited, and the amylase and the using amount commonly used in the field can be used.

The α -amylase is also called starch 1, 4-dextrinase, and can randomly and irregularly cut α -1, 4-glycosidic bond inside a starch chain to hydrolyze starch into maltose, oligosaccharide containing 6 glucose units and oligosaccharide with branched chain.

The enzyme activity unit of the enzyme of the invention is defined as: the amount of enzyme required to convert 1mg of starch to reducing sugars in 1 minute at a pH of 6.0 and a temperature of 70 ℃ was one enzyme activity unit.

According to the present invention, the conditions for the jet liquefaction may be those commonly used in the art. Preferably, the conditions for jet liquefaction include: the temperature of spray liquefaction is 90-100 ℃, the pH value is 5-6.5, and the time is 90-130 minutes.

According to a preferred embodiment of the invention, the steam used for liquefaction is steam converted from the liquid phase after primary and secondary sedimentation or from the supernatant after oxidation and sedimentation, thus greatly saving the amount of fresh water.

According to the invention, in order to fully recover the heat generated in the whole process, after liquefaction, the invention also preferably adopts a multi-stage flash evaporation mode to cool the liquefied mash to 60-80 ℃, and recovers the heat of flash evaporation steam. The heat can be used for preheating a liquid phase after primary sedimentation and secondary sedimentation or a clear liquid after oxidation reaction and sedimentation, and in addition, flash steam can also be used for jet liquefaction after being heated properly, wherein the heat source used for heating can be the heat of the waste mash obtained after distillation. Therefore, the introduction of an external heat source can be reduced, the energy consumption is reduced, and the production cost is greatly reduced. In addition, the condensed water obtained after the flash evaporation can also be returned for preparing the starch slurry, i.e. for mixing with the crushed product obtained after crushing the cassava raw material to prepare the starch slurry. Wherein flashing means that saturated water at high pressure enters a vessel at a relatively low pressure and then becomes a portion of the saturated vapor and water at the vessel pressure due to a sudden drop in pressure. According to the invention, the flash evaporation conditions can be selected from a wide range as long as the purpose of reducing the temperature after the flash evaporation is achieved, and preferably, the flash evaporation conditions comprise that the vacuum degree of the flash evaporation can be 0.05-0.09 MPa, and the flash evaporation time can be 5-20 seconds. The value read from the vacuum gauge is called the vacuum degree. The vacuum value is a value indicating that the actual value of the system pressure is lower than the atmospheric pressure, that is: the vacuum degree is equal to atmospheric pressure to absolute pressure (absolute value of atmospheric pressure and absolute pressure). "vacuum" is the degree of vacuum. By "vacuum" is meant a gaseous state at a pressure below 101325 pascals (i.e., about 101KPa above one standard atmospheric pressure) within a given space.

According to the present invention, in the step (1), the saccharification step may be performed by a method known to those skilled in the art, for example, by directly adding a saccharifying enzyme to the liquefied product. The kind and amount of the saccharifying enzyme are not particularly limited, and may be those commonly used in the art. Preferably, the saccharifying enzyme is used in an amount of 50 to 100 enzyme activity units, preferably 50 to 60 enzyme activity units, per 1 g of the pulverized product. The saccharifying enzyme can be commercially available, and for example, 4060 complex saccharifying enzyme, sumacro 474 saccharifying enzyme of novacin, saccharifying enzyme of vinca coronaria, and the like available from jenensis are available.

The saccharifying enzyme is also called starch α -1, 4-glucosidase, acts on the non-reducing end of starch molecule, takes glucose as unit, and acts on α -1, 4-glycosidic bond in starch molecule in sequence to generate glucose, the product of saccharifying enzyme acting on amylopectin contains glucose and oligosaccharide with α -1, 6-glycosidic bond, and the product of saccharifying enzyme acting on amylose is almost all glucose.

According to the present invention, the saccharification conditions of the saccharifying enzyme can be various saccharification conditions commonly used in the art. Preferably, the saccharification conditions of the saccharifying enzyme comprise: the pH value of saccharification is 4.2-4.4, the temperature of saccharification is 60-63 ℃, and the time of saccharification is 35-60 hours.

According to the present invention, in step (1), the step of fermentation may be accomplished by methods well known to those skilled in the art. Among them, microorganisms capable of fermenting monosaccharides such as glucose and/or fructose, oligosaccharides such as sucrose and/or galactose can be used for the fermentation process of the present invention, and since Saccharomyces cerevisiae is an alcohol-resistant, by-product-less, ethanol-producing, and hexose-fermenting microorganism commonly used in the Saccharomyces cerevisiae industry, it is preferable that the yeast used for the fermentation is Saccharomyces cerevisiae.

Preferably, the amount of yeast used for the fermentation may be 10 inoculum per gram of saccharification product³-10⁸Colony forming units, more preferably 10⁴-10⁶A colony forming unit.

The colony forming unit is defined as that a certain amount of diluted bacterial liquid is poured or coated to disperse microbial single cells in the bacterial liquid on a culture medium flat plate one by one, and each living cell forms a colony after culture. I.e.the number of single cells contained per ml of bacterial suspension.

The yeast used in the fermentation of the invention can be a commercial yeast solid preparation (such as dried yeast powder) or yeast strains, such as Las No. 2 (Rasse II) yeast, also known as Deguo No. two yeast, Las No. 12 (Rasse XII) yeast, also known as German No. 12 yeast, K-shaped yeast, south-yang No. five yeast (1300) and south-yang mixed yeast (1308), Angel super high-activity dry yeast (purchased from Angel yeast of Hubei). The colony forming units of the yeast can be determined by methods well known in the art, such as methylene blue staining viable count. The specific method of the methylene blue staining viable bacteria counting method is as follows:

1 g of dried yeast powder was dissolved in 10 ml of sterile water, or 1 ml of the strain-activating solution was diluted to 10 ml with sterile water, 0.5 ml of 0.1% by weight methylene blue was added, and the mixture was incubated at 35 ℃ for 30 minutes. Under a 10-time optical microscope, the number of live bacteria in the incubated solution (dead bacteria staining, live bacteria non-staining) is counted by a blood counting plate, and the number of live bacteria in 1 g of dry yeast or 1 ml of strain activation solution, namely the number of colony forming units can be obtained.

The yeast may be inoculated by conventional methods, for example by adding 5-15% by volume of seed liquor to the saccharified product. The seed liquid can be an aqueous solution or a culture medium solution of dry yeast, and can also be activated seed liquid of dry yeast or commercial strains.

The temperature of the fermentation may be any temperature suitable for yeast growth, preferably 30-36 ℃, more preferably 30-33 ℃. The pH value is 4-6, preferably 4-4.5. The fermentation time may be the time from the start of inoculation until the decline phase of yeast growth occurs (i.e. the fermentation time is lag phase, log phase plus stationary phase), preferably the fermentation time is from 50 to 75 hours, more preferably from 60 to 70 hours. The fermentation product ethanol can be separated and refined by conventional methods according to the requirements of different industrial products (such as fuel alcohol requiring ethanol with purity of more than 99%), such as distillation, concentration and water removal.

According to a preferred embodiment of the present invention, the method of distillation comprises: distilling the fermented mash at 75-85 deg.C, 115-125 deg.C and 150-165 deg.C. The energy consumption in the distillation process can be reduced by adopting multiple times of distillation. In addition, because the temperature of the waste mash produced by distillation is higher, in order to utilize the part of heat energy and reduce the external energy consumption, the invention preferably carries out heat exchange on the produced waste mash and the liquid phase after primary sedimentation and secondary sedimentation, the clear liquid after oxidation reaction and sedimentation or provides a part of heat source for the anaerobic fermentation, thereby utilizing the thermal coupling technology to further reduce the energy consumption of the whole system.

Wherein, the COD value of the waste mash can be 50,000-80,000 mg/L. Wherein, the COD is the chemical oxygen demand which is an index for showing the amount of reducing substances in water, the larger the COD value is, the more serious the water body is polluted by organic matters is, and all the COD values related to the invention are numerical values measured by a potassium dichromate oxidation method (GB 11914-89).

In the present invention, the kind or source of the cassava raw material is not particularly limited, and various cassava raw materials commonly used in the art, for example, cassava chips may be used.

According to the second aspect of the invention, the method for generating power by using the biogas is also provided, the desulfurized biogas is prepared according to the method, the biogas is combusted in a high-temperature high-pressure gas boiler to generate steam, and the generated steam is used for generating power in a high-temperature high-pressure steam turbine;

According to the invention, on one hand, the yield of the biogas is improved through the preparation method of the biogas, so that the power generation amount is improved, and on the other hand, the inventor of the invention finds that the power generation amount can be further improved by using a high-temperature high-pressure gas boiler which can bear the pressure of at least 9.8MPa and the temperature of 540 ℃ to combust the biogas to generate steam and further using the obtained steam to generate power in a high-temperature high-pressure steam turbine, and the improvement amount can reach 15-25%. The high-temperature high-pressure gas boiler can be purchased from a Jinan boiler factory (which can produce the high-temperature high-pressure gas boiler with the minimum steam production of 35 t/h) or a Criden thermal energy equipment (Zhejiang) limited company (which can produce boilers with any specification of 6-50 t/h), and the high-temperature high-pressure turbine can be purchased from a Hangzhou steam turbine company Limited.

According to a preferred embodiment of the invention, a high-temperature and high-pressure gas boiler produced by Krementen thermal energy equipment (Zhejiang) limited is selected, and two high-temperature and high-pressure gas boilers of 18t/h are further preferably selected, so that the safety, the power generation capacity and the energy consumption are lower.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples, the reagents used are all commercially available unless otherwise specified.

Saccharomyces cerevisiae (Angel super Saccharomyces cerevisiae high activity dry yeast) was purchased from Angel Yeast, Inc. of Hubei.

α -Amylase was purchased from Jenenaceae.

Saccharifying enzymes were purchased from sumacro 474 of novacin.

The COD value is determined by dichromate method (GB 11914-89);

the method for measuring the ammonia nitrogen content is a nano-reagent spectrophotometry (HJ 535-2009);

the total nitrogen level is determined by alkaline potassium persulfate digestion uv spectrophotometry (HJ 636-2012);

the method for measuring the content of the nitro nitrogen is an ultraviolet spectrophotometry (GB/T5750.5-2006 (5.3))

The content of hydrogen sulfide in the biogas is measured by using a hydrogen sulfide detector online SP-1104Plus (Asahi electronics technologies, Ltd., Shandong).

Example 1

This example is intended to illustrate the method for co-producing alcohol and biogas using cassava and the method for generating electricity according to the invention

(1) Starch pulping

The dry cassava slices are unloaded and then conveyed to a screen mesh by a self-unloading silo to be sieved, wherein stones, iron blocks and braided fabrics are removed from undersize materials, then the undersize materials are mixed with oversize materials and crushed, the mixture is sieved by a 1.8mm sieve, and starch slurry with the solid content of 35 weight percent is prepared by water with the temperature of 40 ℃ and the bleaching powder content of 150ppm in a slurry tank.

(2) Jet liquefaction and saccharification

Uniformly mixing the starch emulsion obtained in the step (1) with α -amylase (high temperature resistant α -amylase, purchased from Jenenaceae) and then carrying out spray liquefaction to obtain a liquefied product, wherein the dosage of the α -amylase is 20 enzyme activity units relative to 1 g of the crushed cassava product, and the spray liquefaction conditions comprise that the spray liquefaction temperature is 90 ℃, the spray liquefaction time is 90 minutes, and the spray liquefaction pH value is 5.68;

performing primary flash evaporation on the liquefied product for 10s under the condition that the vacuum degree is 0.05MPa, reducing the temperature of the liquefied product to 82 ℃ to obtain primary flash steam, then performing secondary flash evaporation for 20s under the condition that the vacuum degree is 0.08MPa, and reducing the temperature of the liquefied product to 65 ℃ to obtain secondary flash steam. Wherein, the obtained flash steam is heated to 90 ℃ and then is circulated to be used as part of steam for spraying liquefaction, and the heat source part is from waste mash obtained by distillation.

Adjusting the pH value of the cooled liquefied product to 4.35, uniformly mixing the cooled liquefied product with saccharifying enzyme (Suhong 474, purchased from Novitin Co.), and saccharifying to obtain a saccharified product; wherein, relative to 1 g of crushed cassava, the dosage of the saccharifying enzyme is 50 enzyme activity units, and the saccharifying conditions are as follows: the temperature of saccharification was 60 ℃ and the time of saccharification was 40 minutes.

(3) Fermentation and distillation

Inoculating alcoholic yeast (Angel super high activity dry yeast for brewing wine, Hubei Angel Yeast Co., Ltd., and activating in the saccharified product obtained in step (4) for 10h in advance) into the saccharified product obtained in step (4) for fermentation, wherein the content of the alcoholic yeast is 1 g of the saccharified productThe inoculation amount of the alcohol yeast is 10⁵Forming a colony forming unit, and performing stirring culture under the conditions of fermentation: fermenting at 31.5 deg.C and pH of 4.25 for 65 hr to obtain fermented product;

distilling the fermentation product at 82 deg.C, distilling the obtained distillation fraction at 120 deg.C for the second time, distilling the obtained distillation fraction at 157 deg.C for the third time, and dehydrating with molecular sieve to obtain fuel ethanol.

(4) Exchanging heat between the distilled waste mash and water for preparing starch slurry, providing partial heat for anaerobic fermentation during biogas preparation, reducing the temperature of the waste mash (COD is 80,000mg/ml) to 70 ℃, preparing biogas according to the flow shown in figure 1, and generating power, specifically as follows:

after standing, settling and desanding the waste mash, adding a proper amount of regulator to regulate the pH value of the waste mash to about 6.0 and regulate the carbon-nitrogen ratio to 30:1, and then introducing the waste mash into a fermentation tank system, wherein the fermentation tank system comprises 3 fermentation tanks which are sequentially connected in series, and the waste mash is introduced into the 1 st fermentation tank.

(5) And (3) inoculating the lotus pond bottom sludge into the waste mash prepared in the step (4), performing strict anaerobic fermentation, transferring into a fermentation tank 2 after fermenting for 7 days, transferring into a fermentation tank 3 after fermenting for 7 days in the fermentation tank 2, finishing fermentation after fermenting for 7 days in the fermentation tank 3, collecting the generated biogas in the fermentation process, and calculating the biogas amount relative to the biogas amount prepared for producing 1 ton of ethanol, wherein the results are shown in Table 1.

Wherein the sludge content in each fermenter was maintained at 20 wt% throughout the fermentation process, the temperature in each fermenter was 63 deg.C, and a portion of the heat was derived from the heat generated during the alcohol distillation process. After the fermentation material in the 1 st fermentation tank is transferred into the second fermentation tank, new waste mash and sludge are introduced into the first fermentation tank to ensure continuous fermentation.

(6) Introducing the wastewater after fermentation into an aeration tank at room temperature according to the length of 300m³Air is introduced at the flow rate/h for aeration for 0.8 h. After aeration is finished, sodium alginate (limited in Qingdao Nanyang seaweed industry) is added into the wastewaterCompany), propylene glycol alginate (Qingdao Mingyue algae group Co., Ltd.), and tannin, wherein the amount of the added sodium alginate is 0.15 part by weight, the amount of the added propylene glycol alginate is 0.15 part by weight, and the amount of the added tannin is 0.008 part by weight, relative to 1000 parts by weight of the wastewater. And then introducing the wastewater into a box filter press (Jingjin filter press group Co., Ltd.), and filtering for 1.5 hours under the pressure of 0.6MPa to obtain filter residues (the water content is less than 60 wt%) and filtrate, wherein the filter residues are dried and then used as organic fertilizer raw materials for subsequent treatment. The electric power consumption and the solid-liquid separation time for the solid-liquid separation are shown in Table 1.

(7) And (3) introducing the filtrate obtained in the step (6) into an anaerobic reactor and an aerobic reactor in sequence for treatment, wherein the dissolved oxygen in the anaerobic reactor is 0, the anaerobic granular sludge is the anaerobic granular sludge produced by Pake environmental protection technology (Shanghai) Limited company, the room temperature is 6.5-7.5, and the hydraulic retention time is 30 hours. The aerobic granular sludge in the aerobic reactor is produced by Beijing Fengze green source environmental technology limited company, has the pH value of 7-8, and the aerobic reactor comprises an anoxic/aerobic treatment tank; wherein the anoxic treatment conditions are as follows: the dissolved oxygen amount is not more than 1mg/L, the room temperature and the hydraulic retention time are 20 hours; the aerobic treatment conditions are as follows: dissolved oxygen of about 3mg/L, room temperature, hydraulic retention time of 40 hours, internal reflux ratio of 3.

And after the treatment is finished, introducing the treatment liquid into a primary sedimentation tank, performing primary sedimentation under the action of polymeric ferric sulfate, introducing the liquid phase into a secondary sedimentation tank after sedimentation is performed for 30min, and performing secondary sedimentation under the action of polymeric ferric sulfate in the secondary sedimentation tank for 30 min. Introducing the solid phase obtained by the primary sedimentation and the secondary sedimentation into the anaerobic fermentation tank in the step (5) as at least part of fermentation strain as fermentation sludge.

The liquid phase part is used as reclaimed water for recycling, heat exchange is carried out on the reclaimed water and waste mash produced by distilling alcohol, and the temperature is raised to 40 ℃ to be used as water for size mixing, and the COD value, ammonia nitrogen content, total nitrogen level and sulfide content in the liquid phase are shown in a table 1.

And in addition, after the other part of the liquid phase is subjected to Fenton oxidation and sedimentation, one part of the liquid phase is used as wastewater to be discharged, and the other part of the liquid phase is used as supplementing water for cassava jet liquefaction after the pH value is adjusted and then the other part of the liquid phase exchanges heat with waste mash produced by distilled alcohol.

(8) And introducing the obtained biogas into a primary desulfurization tower, wherein a saturated aqueous solution of sodium hydroxide is filled in the primary desulfurization tower, the biogas is pre-desulfurized in the primary desulfurization tower and then introduced into a secondary desulfurization tower for re-desulfurization, silica gel and ferric oxide are filled in the secondary desulfurization tower, and the sulfur content of the biogas is shown in table 1. The amount of the saturated aqueous solution of sodium hydroxide can be 1000ml and the amount of the silica gel and the iron oxide (weight ratio is 1:2) is 15g for each cubic meter of methane. And measuring the content of hydrogen sulfide before and after the methane is introduced into the desulfurizing tower, and calculating the desulfurizing efficiency.

(9) Desulfurized biogas was introduced into 2 high-temperature high-pressure gas boilers (9.81MPa, 540 ℃) of 18t/h to be combusted to generate steam, and the generated steam was introduced into high-temperature high-pressure steam turbines (9.81MPa, 540 ℃) to generate electricity, and the amount of electricity generated with respect to 1 ton of steam was calculated, and the results are shown in Table 1.

Wherein, the power consumption, water consumption and steam consumption of the whole system are shown in the table 2.

Example 2

(1) Starch pulping

The dry cassava slices are unloaded and then conveyed to a screen mesh by a self-discharging silo to be sieved, wherein stones, iron blocks and braided fabrics are removed from undersize materials, then the undersize materials are mixed with oversize materials and crushed, the mixture is sieved by a 1.8mm sieve, and starch slurry with the solid content of 38 weight percent is prepared by water with the temperature of 35 ℃ and the bleaching powder content of 300ppm in a slurry tank.

(2) Jet liquefaction and saccharification

Uniformly mixing the starch emulsion obtained in the step (1) with α -amylase (high temperature resistant α -amylase, purchased from Jenenaceae) and then carrying out spray liquefaction to obtain a liquefied product, wherein the dosage of the α -amylase is 15 enzyme activity units relative to 1 g of crushed cassava product, and the spray liquefaction conditions comprise that the spray liquefaction temperature is 92 ℃, the spray liquefaction time is 100 minutes, and the spray liquefaction pH value is 6.34;

and performing primary flash evaporation on the liquefied product for 5s under the condition that the vacuum degree is 0.08MPa, reducing the temperature of the liquefied product to 85 ℃ to obtain primary flash steam, then performing secondary flash evaporation for 10s under the condition that the vacuum degree is 0.08MPa, and reducing the temperature of the liquefied product to 70 ℃ to obtain secondary flash steam. Wherein, the obtained flash steam is heated to 92 ℃ and then is circulated to be used as part of steam for spraying liquefaction, and the heat source part is from waste mash obtained by distillation.

Adjusting the pH value of the cooled liquefied product to 4.35, uniformly mixing the cooled liquefied product with saccharifying enzyme (Suhong 474, purchased from Novitin Co.), and saccharifying to obtain a saccharified product; wherein, relative to 1 g of crushed cassava, the dosage of the saccharifying enzyme is 80 enzyme activity units, and the saccharifying conditions are as follows: the temperature of the saccharification was 63 ℃ and the time of the saccharification was 35 minutes.

(3) Fermentation and distillation

Inoculating alcoholic yeast (Angel super high activity dry yeast for brewing wine, Hubei Angel Yeast Co., Ltd., and activating in the saccharified product obtained in step (4) for 10h in advance) into the saccharified product obtained in step (4) for fermentation, wherein the inoculation amount of alcoholic yeast is 10 per 1 g of the saccharified product⁵Forming a colony forming unit, and performing stirring culture under the conditions of fermentation: the fermentation temperature is 31.5 ℃, the pH value is 4.25, and the fermentation time is 65 hours, so as to obtain a fermentation product;

distilling the fermentation product at 75 ℃, distilling the obtained distillation fraction at 125 ℃ for the second time, distilling the obtained distillation fraction at 150 ℃ for the third time, and dehydrating by using a molecular sieve to obtain the fuel ethanol.

(4) Exchanging heat between the distilled waste mash and water for preparing starch slurry, providing partial heat for anaerobic fermentation during biogas preparation, reducing the temperature of the waste mash (COD is 75,000mg/ml) to 72 ℃, preparing biogas according to the flow shown in figure 1, and generating power, wherein the specific steps are as follows:

after standing, settling and desanding the waste mash, adding a proper amount of regulator to regulate the pH value of the waste mash to about 6.5 and regulate the carbon-nitrogen ratio to 28:1, and then introducing the waste mash into a fermentation tank system, wherein the fermentation tank system comprises 5 fermentation tanks which are sequentially connected in series, and the waste mash is introduced into the 1 st fermentation tank.

(5) And (3) inoculating the lotus pond bottom sludge into the waste mash prepared in the step (4), performing strict anaerobic fermentation, transferring into a fermentation tank 2 after fermenting for 5 days, transferring into a fermentation tank 3 after fermenting for 5 days in the fermentation tank 2, repeating the steps, collecting the generated biogas during the fermentation process after finishing the fermentation in the fermentation tank 5 days, and calculating the biogas amount relative to the biogas amount prepared for producing 1 ton of ethanol, wherein the result is shown in Table 1.

Wherein, in the whole fermentation process, the content of sludge in each fermentation tank is ensured to be 10 wt%, the temperature of each fermentation tank is 60 ℃, and part of heat is from heat generated in the alcohol distillation process. After the fermentation material in the 1 st fermentation tank is transferred into the second fermentation tank, new waste mash and sludge are introduced into the first fermentation tank to ensure continuous fermentation.

(6) Introducing the wastewater after fermentation into an aeration tank at room temperature according to 200m³Air is introduced at a flow rate/h for aeration for 1 h. After aeration, potassium alginate (south island seaweed industries, ltd.), propylene glycol alginate (south island seaweed group, ltd.), and tannin were added to the wastewater, wherein the amount of sodium alginate added was 0.1 part by weight, the amount of propylene glycol alginate added was 0.2 part by weight, and the amount of catechin added was 0.005 part by weight, relative to 1000 parts by weight of the wastewater. And then introducing the wastewater into a box filter press (Jingjin filter press group Co., Ltd.), and filtering for 2 hours under the pressure of 0.5MPa to obtain filter residues (the water content is less than 60 wt%) and filtrate, wherein the filter residues are dried and then used as organic fertilizer raw materials for subsequent treatment. The electric power consumption and the solid-liquid separation time for the solid-liquid separation are shown in Table 1.

(7) And (3) introducing the filtrate obtained in the step (6) into an anaerobic reactor and an aerobic reactor in sequence for treatment, wherein the dissolved oxygen in the anaerobic reactor is 0, the anaerobic granular sludge is the anaerobic granular sludge produced by Pake environmental protection technology (Shanghai) Limited company, the room temperature is 6.5-7.5, and the hydraulic retention time is 25 hours. The aerobic granular sludge in the aerobic reactor is produced by Beijing Fengze green source environmental technology limited company, has the pH value of 7-8, and the aerobic reactor comprises an anoxic/aerobic treatment tank; wherein the anoxic treatment conditions are as follows: the dissolved oxygen amount is not more than 1mg/L, the room temperature and the hydraulic retention time are 10 hours; the aerobic treatment conditions are as follows: dissolved oxygen was about 4mg/L, room temperature, hydraulic retention time 30 hours, internal reflux ratio 4.

The liquid phase part is used as reclaimed water for recycling, heat exchange is carried out on the reclaimed water and waste mash produced by distilling alcohol, and the temperature is raised to 35 ℃ to be used as water for size mixing, and the COD value, ammonia nitrogen content, total nitrogen level and sulfide content in the liquid phase are shown in a table 1.

(8) And introducing the obtained biogas into a primary desulfurization tower, wherein a saturated aqueous solution of sodium hydroxide is filled in the primary desulfurization tower, the biogas is pre-desulfurized in the primary desulfurization tower and then introduced into a secondary desulfurization tower for re-desulfurization, silica gel and ferric oxide are filled in the secondary desulfurization tower, and the sulfur content of the biogas is shown in table 1. Wherein the amount of the saturated aqueous solution of sodium bicarbonate can be 1500ml and the amount of the calcium oxide and the iron oxide (weight ratio is 1:4) is 10g for each cubic meter of the methane. And measuring the content of hydrogen sulfide before and after the methane is introduced into the desulfurizing tower, and calculating the desulfurizing efficiency.

(9) Desulfurized biogas was introduced into 2 high-temperature high-pressure gas boilers (9.81MPa, 540 ℃) of 18t/h to be combusted to generate steam, and the generated steam was introduced into high-temperature high-pressure steam turbines (9.81MPa, 540 ℃) to generate electricity, and the amount of electricity generated with respect to 1 ton of ethanol was calculated, and the results are shown in Table 1.

Example 3

(1) Starch pulping

The dry cassava slices are unloaded and then conveyed to a screen mesh by a self-unloading silo to be sieved, wherein stones, iron blocks and braided fabrics are removed from undersize materials, then the undersize materials are mixed with oversize materials and crushed, the mixture is sieved by a 1.8mm sieve, and starch slurry with the solid content of 38 weight percent is prepared in a slurry tank by water with the temperature of 38 ℃ and containing 150ppm bleaching powder.

(2) Jet liquefaction and saccharification

Uniformly mixing the starch emulsion obtained in the step (1) with α -amylase (high temperature resistant α -amylase, purchased from Jenenaceae) and then carrying out spray liquefaction to obtain a liquefied product, wherein the dosage of the α -amylase is 24 enzyme activity units relative to 1 g of the crushed cassava product, and the spray liquefaction conditions comprise that the spray liquefaction temperature is 95 ℃, the spray liquefaction time is 130 minutes, and the spray liquefaction pH value is 5.15;

performing primary flash evaporation on the liquefied product for 10s under the condition that the vacuum degree is 0.08MPa, reducing the temperature of the liquefied product to 80 ℃ to obtain primary flash steam, then performing secondary flash evaporation for 20s under the condition that the vacuum degree is 0.05MPa, and reducing the temperature of the liquefied product to 60 ℃ to obtain secondary flash steam. Wherein, the obtained flash steam is heated to 95 ℃ and then is circulated to be used as part of steam for spraying liquefaction, and the heat source part is from waste mash obtained by distillation.

Adjusting the pH value of the cooled liquefied product to 4.35, uniformly mixing the cooled liquefied product with saccharifying enzyme (Suhong 474, purchased from Novitin Co.), and saccharifying to obtain a saccharified product; wherein, relative to 1 g of crushed cassava, the dosage of the saccharifying enzyme is 100 enzyme activity units, and the saccharifying conditions are as follows: the temperature of saccharification was 60 ℃ and the time of saccharification was 40 minutes.

(3) Fermentation and distillation

Adding sugar obtained in the step (4)Inoculating alcoholic yeast (Angel super high activity dry yeast, Angel Yeast of Hubei, and activating in saccharified product obtained in step (4) for 10 hr in advance) to the saccharified product, and fermenting, wherein the amount of alcoholic yeast is 10% relative to 1 g of saccharified product⁵Forming a colony forming unit, and performing stirring culture under the conditions of fermentation: fermenting at 31.5 deg.C and pH of 4.25 for 65 hr to obtain fermented product;

distilling the fermentation product at 85 ℃, secondarily distilling the obtained distillation fraction at 115 ℃, thirdly distilling the obtained distillation fraction at 165 ℃, and dehydrating by using a molecular sieve to obtain the fuel ethanol.

(4) Exchanging heat between the distilled waste mash and water for preparing starch slurry, providing partial heat for anaerobic fermentation during biogas preparation, reducing the temperature of the waste mash (COD is 78,000mg/ml) to 75 ℃, preparing biogas according to the flow shown in figure 1, and generating power, wherein the specific steps are as follows:

after standing, settling and desanding the waste mash, adding a proper amount of regulator to regulate the pH value of the waste mash to about 6.3 and regulate the carbon-nitrogen ratio to 25:1, and then introducing the waste mash into a fermentation tank system, wherein the fermentation tank system comprises 2 groups of 3 fermentation tanks which are sequentially connected in series, and the waste mash is introduced into the 1 st fermentation tank of each fermentation tank system.

(5) And (3) inoculating the lotus pond sediment into the waste mash prepared in the step (4), performing strict anaerobic fermentation, transferring to a 2 nd fermentation tank after fermenting for 6 days in a 1 st fermentation tank for a fermentation tank system without group, transferring to a 3 rd fermentation tank after fermenting for 6 days in the 2 nd fermentation tank, finishing fermentation after fermenting for 6 days in the 3 rd fermentation tank, collecting the generated biogas in the fermentation process, and calculating the biogas amount prepared for producing 1 ton of ethanol, wherein the result is shown in Table 1.

Wherein, in the whole fermentation process, the content of the sludge in each fermentation tank is ensured to be 30 weight percent, the temperature of each fermentation tank is 65 ℃, and part of heat is from heat generated in the alcohol distillation process. After the fermentation material in the 1 st fermentation tank is transferred into the second fermentation tank, new waste mash and sludge are introduced into the first fermentation tank to ensure continuous fermentation.

(6) Introducing the wastewater after fermentation into an aeration tank at room temperature according to the volume of 400m³Air is introduced at the flow rate of/h for aeration for 0.5 h. After aeration, ammonium alginate (Handan marine medicinal seaweed product Co., Ltd.), propylene glycol alginate (Qingdao Mingyue seaweed group Co., Ltd.) and tannin were added to the wastewater, wherein the amount of sodium alginate added was 0.2 part by weight, the amount of propylene glycol alginate added was 0.1 part by weight, and the amount of anthocyanins added was 0.01 part by weight, based on 1000 parts by weight of the wastewater. And then introducing the wastewater into a box filter press (Jingjin filter press group Co., Ltd.), and filtering for 1 hour under the pressure of 1MPa to obtain filter residue (the water content is less than 60 wt%) and filtrate, wherein the filter residue is dried and then used as an organic fertilizer raw material for subsequent treatment. The electric power consumption and the solid-liquid separation time for the solid-liquid separation are shown in Table 1.

(7) And (3) introducing the filtrate obtained in the step (6) into an anaerobic reactor and an aerobic reactor in sequence for treatment, wherein the dissolved oxygen in the anaerobic reactor is 0, the anaerobic granular sludge is anaerobic granular sludge produced by Pake environmental protection technology (Shanghai) Limited company, the room temperature is 6.5-7.5, and the hydraulic retention time is 35 hours. The aerobic granular sludge in the aerobic reactor is produced by Beijing Fengze green source environmental technology limited company, has the pH value of 7-8, and the aerobic reactor comprises an anoxic/aerobic treatment tank; wherein the anoxic treatment conditions are as follows: the dissolved oxygen amount is not more than 1mg/L, the room temperature and the hydraulic retention time are 15 hours; the aerobic treatment conditions are as follows: dissolved oxygen of about 2mg/L, room temperature, hydraulic retention time of 35 hours, internal reflux ratio of 2.

And after the treatment is finished, introducing the treatment liquid into a primary sedimentation tank, performing primary sedimentation under the action of polymeric ferric sulfate, introducing the liquid phase into a secondary sedimentation tank after sedimentation is performed for 30min, and performing secondary sedimentation under the action of polymeric ferric sulfate in the secondary sedimentation tank for 30 min. Introducing the solid phase obtained by the primary sedimentation and the secondary sedimentation into the anaerobic fermentation tank in the step (2) as at least part of fermentation strain as fermentation sludge.

The liquid phase part is used as reclaimed water for recycling, heat exchange is carried out on the reclaimed water and waste mash produced by distilling alcohol, and the temperature is raised to 38 ℃ to be used as water for size mixing, and the COD value, ammonia nitrogen content, total nitrogen level and sulfide content in the liquid phase are shown in table 1.

(8) And introducing the obtained biogas into a primary desulfurization tower, wherein a saturated aqueous solution of sodium hydroxide is filled in the primary desulfurization tower, the biogas is pre-desulfurized in the primary desulfurization tower and then introduced into a secondary desulfurization tower for re-desulfurization, silica gel and ferric oxide are filled in the secondary desulfurization tower, and the sulfur content of the biogas is shown in table 1. Wherein the amount of the saturated aqueous solution of sodium hydroxide can be 500ml and the amount of the silica gel and the activated carbon (weight ratio is 1:5) is 20g for each cubic meter of the biogas. And measuring the content of hydrogen sulfide before and after the methane is introduced into the desulfurizing tower, and calculating the desulfurizing efficiency.

Example 4

Alcohol, biogas and power generation were prepared according to the method of example 1 except that tannin was not added in step (3), and the results are shown in tables 1 and 2.

Example 5

Alcohol, biogas and electricity were produced according to the method of example 1 except that the secondary desulfurization tower did not contain silica gel, and the results are shown in tables 1 and 2.

Example 6

Alcohol, biogas and power generation were prepared according to the method of example 1 except that the temperature of fermentation was 50 deg.c, and the results are shown in tables 1 and 2.

Example 7

Alcohol, biogas and electricity were produced according to the method of example 1 except that 1 35t/h high temperature and high pressure gas boiler (9.81MPa, 540 ℃) was used for electricity generation, and the results are shown in tables 1 and 2.

Example 8

Alcohol, biogas and power generation were prepared according to the method of example 1 except that the concentration of the starch slurry was 30% by weight while no bactericide was added, and the results are shown in tables 1 and 2.

Example 9

Alcohol, biogas and electricity were produced according to the method of example 1 except that the temperature of the liquefied solution was lowered to 65 c by using one flash pulping, and the results are shown in tables 1 and 2.

Comparative example 1

This comparative example serves to illustrate the process for the co-production of alcohol and biogas from cassava and the method for generating electricity

Alcohol, biogas and power generation were prepared according to the method of example 1 except that three fermenters were arranged in parallel, and the fermentation time of each fermenter was 21 days, and the results are shown in tables 1 and 2.

Comparative example 2

Alcohol, biogas and power generation were prepared according to the method of example 1 except that the fermentation temperature of the first fermenter was 35 c, the fermentation temperature of the second and third fermentors was 63 c, and the fermentation time of each fermenter was 5 days, and the results are shown in tables 1 and 2.

Comparative example 3

Alcohol, biogas and power generation were prepared according to the method of comparative example 2 except that the sodium alginate was added in an amount of 0.5 parts by weight, the propylene glycol alginate was added in an amount of 1.0 part by weight and the tannin was added in an amount of 0.1 part by weight, with respect to 1000 parts by weight of wastewater, and the results are shown in tables 1 and 2.

Comparative example 4

Alcohol, biogas and power generation were prepared according to the method of example 1, the pressure of the sub-high temperature and high pressure gas boiler was 5.88MPa, the temperature was 510 deg.C, the pressure of the high temperature and high pressure turbine was 8.83MPa, the temperature was 535 deg.C, and the results are shown in tables 1 and 2.

TABLE 2

Example/comparative example numbering	Electricity (ten million hours)/ton of ethanol	Ton of water/ton of ethanol	Steam (ton)/ton ethanol
				Example 1	280	8	1.8
Example 2	250	9	1.9
				Example 3	300	7.5	1.7
Example 4	285	8	1.8
				Example 5	290	8	1.8
Example 6	300	8	1.8
				Example 7	305	8	1.8
Example 8	290	8.2	2.1
				Example 9	284	8.2	2.4
Comparative example 1	293	8	1.8
				Comparative example 2	298	8	1.8
Comparative example 3	295	8	1.8
				Comparative example 4	293	8	1.8

Wherein ethanol is the theoretical ethanol yield

As can be seen from Table 2, the technical scheme of the invention can effectively reduce the energy consumption, especially the power consumption, of the whole system, thereby reducing the production cost.

The results in table 1 show that the technical scheme of the invention can significantly improve the yield and the power generation capacity of the biogas, significantly reduce the solid-liquid separation time and the power consumption, and reduce the consumption of water-soluble alginate, water-soluble alginate ester and plant polyphenol. In addition, compared with the example 1 and the example 4, the mixture of the water-soluble alginate, the water-soluble alginate ester and the plant polyphenol is added before solid-liquid separation, so that the time and the power consumption of the solid-liquid separation can be obviously reduced, and the effluent quality is improved; compared with the embodiment 5, the embodiment 1 has the advantages that the desulfurization efficiency can be obviously improved by adopting the desulfurization method, so that the power generation amount is improved; comparing example 1 with example 6, it can be seen that the fermentation temperature is not in the preferred range of the present invention, although high temperature fermentation is also possible, the overall effect is poor; comparing example 1 with example 7, it can be seen that the power generation amount can be further improved by using 2 high-temperature and high-pressure gas boilers of 18t t/h than by using 1 high-temperature and high-pressure gas boiler of 35 t/h.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for co-producing alcohol and biogas by utilizing cassava is characterized by comprising the following steps:

(2) distilling the fermented mash to obtain alcohol and waste mash;

2. The method of claim 1, wherein the method further comprises: before inoculating fermentation strains to the waste mash, adjusting the carbon-nitrogen ratio of the waste mash to be 25-30:1, adjusting the pH value to be 6-6.5, and carrying out anaerobic fermentation under the condition of stirring.

3. The method according to claim 1 or 2, wherein the fermentation species is a fermentation sludge comprising at least one of clostridium, bacteroides, butyric acid bacteria, lactic acid bacteria, bifidobacteria, spirillum, hydrogen-producing acetogenic bacteria, hydrogen-consuming acetogenic bacteria and methanogenic bacteria.

4. The method of any of claims 1-3, wherein the method further comprises: the method comprises the steps of sequentially carrying out desulfurization on the prepared biogas by a first desulfurizer and a second desulfurizer to obtain desulfurized biogas, wherein the first desulfurizer is an alkali metal carbonate solution and/or an alkali metal hydroxide solution; the second desulfurizer contains calcium oxide and/or silica gel, iron oxide and/or activated carbon.

5. The method of any of claims 1-3, wherein the method further comprises: adding water-soluble alginate ester, water-soluble alginate and plant polyphenol into the wastewater generated after the anaerobic fermentation to generate the biogas, and carrying out solid-liquid separation to obtain filtrate and filter residue;

wherein, relative to 1000 parts by weight of wastewater, the adding amount of the water-soluble alginate is 0.01-0.5 part by weight, and the adding amount of the plant polyphenol is 0.001-0.05 part by weight.

6. The method as claimed in claim 5, wherein the relative molecular weight of the water-soluble alginate is 30000-200000, and the water-soluble alginate is selected from one or more of sodium alginate, potassium alginate and ammonium alginate;

the relative molecular weight of the water-soluble alginate is 30000-200000, and the water-soluble alginate is propylene glycol alginate;

the plant polyphenol is selected from one or more of tannin, anthocyanin, catechin, quercetin, gallic acid, ellagic acid and arbutin.

7. The method of claim 5 or 6, wherein the method further comprises: under the anaerobic treatment condition, enabling the filtrate to be in contact with a material containing activated sludge, and carrying out anaerobic treatment on the filtrate; and under the aerobic condition, the mixture obtained by the anaerobic treatment is subjected to aerobic treatment;

wherein the aerobic treatment comprises anoxic treatment and oxygen enrichment treatment, and part of the mixed material after the oxygen enrichment treatment is returned to the anoxic treatment to be used as part of the material containing the activated sludge.

8. The method of claim 7, wherein the method further comprises: and sequentially carrying out primary precipitation and secondary precipitation on the wastewater after the aerobic treatment to obtain a solid phase and a liquid phase, and taking the solid phase as at least part of the fermentation strain.

9. The method of claim 8, wherein the method further comprises: oxidizing the liquid phase, and settling the oxidized product.

10. The method according to claim 1, wherein the crushing mode comprises crushing the material obtained by impurity removal treatment and sieving the crushed material by a 1.8mm sieve, wherein the crushing is primary crushing, and the impurity removal is primary impurity removal.

11. The method of claim 10, further comprising, prior to the comminuting, conveying the cassava raw materials to a screen using a self-discharging silo to screen the cassava raw materials, wherein the undersize is decontaminated and mixed with the oversize, and comminuting the resulting mixture as an decontaminated material.

12. The method of claim 1, wherein the means for sizing comprises: preparing the material obtained by crushing into starch slurry by using water, and adding a bactericide into the starch slurry;

wherein, the concentration of the starch slurry is 35-40 wt% in terms of solid; the amount of the added bactericide is 50-300ppm based on the weight of the starch slurry;

wherein the bactericide is one or more of penicillin, clofibrate and bleaching powder;

preferably, the water is the liquid phase obtained in claim 8 or the clear solution obtained in claim 9 after settling.

13. The method of claim 1 or 10, wherein the liquefaction is jet liquefaction, the jet liquefaction being at a temperature of 90-100 ℃, a pH of 5-6.5, and a time of 90-130 minutes;

preferably, the steam used for liquefaction comes from the liquid phase obtained in claim 8 or the clear liquid obtained in claim 9 after sedimentation;

preferably, the source of heat for the liquefaction of the steam used is derived at least in part from the heat of the waste mash obtained in step (2).

14. The method of claim 13, further comprising subjecting the jet liquefied mash to at least 2-4 flash evaporation to reduce the temperature of the liquefied mash to 60-80 ℃;

wherein the vacuum degree of flash evaporation is 0.05-0.09 Mpa, and the flash evaporation time is 5-20 seconds.

15. The method of claim 1, 12 or 13, wherein the method of distilling comprises: distilling the fermented mash at 75-85 ℃, 115-125 ℃ and 150-165 ℃ in sequence to obtain alcohol and waste mash, wherein the method further comprises the following steps: heat exchanging the waste mash with the liquid phase obtained in claim 8 and the clear liquid obtained after settling in claim 9 to preheat the liquid phase obtained in claim 8 and the clear liquid obtained after settling in claim 9 or to provide a part of the heat source for said anaerobic fermentation while lowering the temperature of the waste mash to 70-75 ℃.

16. A method of generating electricity from biogas, the method comprising: preparing desulfurized biogas according to the process of claim 3 and combusting said desulfurized biogas in a high temperature high pressure gas boiler to produce steam, the produced steam generating electricity in a high temperature high pressure steam turbine;