CN101914576B - Method for producing ethanol and methane by mixed fermentation of paper-making sludge and monosodium glutamate waste liquid - Google Patents

Abstract

The invention belongs to the field of renewable energy and environmental protection, and relates to a method for producing ethanol and methane through mixed fermentation of papermaking sludge and monosodium glutamate waste liquid. Mix monosodium glutamate waste liquid and papermaking sludge according to the dry weight ratio of 3 to 10:100 to form a raw material mixture, add cellulase, nutrient solution, etc., adjust the pH value to acidity, inoculate Saccharomyces cerevisiae for fermentation to produce ethanol; after fermentation Ethanol is obtained by distillation; the distillation residue is added to anaerobic digestion inoculation sludge for anaerobic digestion to produce methane. The invention uses synchronous saccharification and fermentation to produce ethanol, the process does not require any sterilization operation, the process is simple, and the operability is strong; at the same time, the production of ethanol and methane is carried out under medium temperature conditions, which realizes mild production conditions and low energy consumption; the use of papermaking sludge Mixed fermentation with monosodium glutamate waste liquid can not only improve the living environment of microorganisms in terms of nutritional structure, increase the production of ethanol and methane, but also realize the "harmlessness, reduction and resource utilization" of the two major solid wastes at the same time.

Description

A method for producing ethanol and methane by mixed fermentation of papermaking sludge and monosodium glutamate waste liquid

technical field

The invention belongs to the field of renewable energy and environmental protection, and relates to a method for producing ethanol and methane through mixed fermentation of papermaking sludge and monosodium glutamate waste liquid.

Background technique

Pulping and papermaking is one of the important industries of my country's national economy. At present, the output of paper and cardboard produced in my country has leapt to the first place in the world, but a large amount of papermaking sludge is produced in the papermaking process. With the existing papermaking scale in my country, papermaking The annual output of sludge has reached 23.89 million tons of dewatered papermaking sludge (with a moisture content of 80%). It is estimated that by 2020, my country will produce about 30.88 million tons of dewatered papermaking sludge (with a moisture content of 80%). In the face of such a large amount of papermaking sludge, the traditional treatment and disposal methods are: incineration, landfill and land utilization, etc.; during the treatment of papermaking wastewater, most of the pollutants in the wastewater will be enriched due to coagulation, adsorption, etc. In the sludge, it affects its direct application; landfilling papermaking sludge not only costs money and occupies land, but also easily causes secondary pollution to soil, groundwater and air; incineration of papermaking sludge needs to increase the sludge dehydration rate, but the boiler incineration system The investment and operation costs are high, and it is easy to generate smoke pollution, so it is not suitable for general small and medium-sized papermaking enterprises.

Papermaking sludge refers to the mixed sludge obtained in the primary sedimentation tank and secondary sedimentation tank during the biochemical treatment of wastewater from paper mills. The organic matter with fine fibers as the main component accounts for 70% to 90%. Papermaking fillers and coatings are the main components. The main component of inorganic matter accounts for 10% to 30%. Due to the high content of organic matter in papermaking sludge, it is of great significance to find a biological treatment method for its resource utilization.

The use of anaerobic digestion technology to treat organic solid waste, because anaerobic digestion has low energy consumption, less secondary pollution, and can produce methane to replace part of petroleum fuels, has a very important strategy in today's society where the global warming effect is intensified and energy is in short supply. significance. However, due to the high content of secondary fiber and low protein content in papermaking sludge, the high C/N is not conducive to the normal process of anaerobic digestion, which restricts its application in anaerobic digestion.

The monosodium glutamate industry is one of the oldest fermentation industries in my country. It entered a stage of rapid development in the 1980s. In 2008, the annual output of monosodium glutamate in my country was 630,000 tons, accounting for 47% of the world's annual production of monosodium glutamate. The rapid increase of monosodium glutamate production also brought monosodium glutamate Large discharge of waste liquid. The monosodium glutamate waste liquid mainly includes the fermentation waste liquid after extracting monosodium glutamate and the crystallization mother liquor discarded by concentrated crystallization. Generally, about 25 tons of waste liquid is discharged for every 1 ton of monosodium glutamate produced. This monosodium glutamate waste liquid contains a large amount of organic matter, rich protein, wet bacteria and A variety of K ⁺ , Na ⁺ , NH ₄ ⁺ , Mg ²⁺ , Ca ²⁺ and other nutrient salts are a kind of high-concentration organic waste liquid that is difficult to handle. Direct discharge will seriously pollute the environment. Anaerobic digestion of methane is currently the One of the most active research areas in the field of MSG waste liquid treatment, but because the nitrogen content of waste liquid is too high, it is easy to cause NH ₃ -N poisoning in the system. How to properly treat MSG waste liquid has always been one of the problems that restrict the development of MSG production enterprises in China. .

Contents of the invention

The object of the present invention is to address the deficiencies of the prior art and provide a method that can effectively treat papermaking sludge and kitchen waste, reduce environmental burden and realize resource reuse.

The present invention realizes above-mentioned object through following technical scheme:

The invention provides a method for producing ethanol and methane by mixed fermentation of papermaking sludge and monosodium glutamate waste liquid, which is characterized in that it comprises the following steps: (1) mixing monosodium glutamate waste liquid and papermaking sludge according to the dry weight ratio of 3-10:100 (2) prepare nutrient solution; (3) take nutrient solution, inoculate Saccharomyces cerevisiae in it, become Saccharomyces cerevisiae bacterium liquid after cultivating; (4) add cellulase, Nutrient solution and water, adjust the pH value to be acidic to become the fermentation material, and inoculate the Saccharomyces cerevisiae liquid to ferment and produce ethanol; (5) After the fermentation is completed, distill the fermentation substrate to obtain ethanol; Oxygen digestion inoculation sludge (referring to septic tank sludge, spoiled river mud or one or more kinds of seed sludge obtained after domestication from anaerobic digestion sludge of urban sewage treatment plant), adjust the pH value to be alkaline, Perform anaerobic digestion to produce methane. (The flow chart of the method is shown in Figure 1.)

In step (1), before the papermaking sludge is mixed with the monosodium glutamate waste liquid, the papermaking sludge can also be pretreated in advance, and the pretreatment adopts one of the hydroxides formed by alkali metals, and the concentration of the alkali solution is 0.3%～ 1.0%, the pretreatment time is 15~24h. Monosodium glutamate waste liquid: papermaking sludge = 3-10: 100 (w/w, based on dry matter mass) and mixed evenly, and the C/N of the fermentation substrate was adjusted to be 15-25: 1.

The culture medium in the step (2) is potato-glucose culture medium, which is to peel and cut the potatoes into pieces, add water to boil for 25-35 minutes and filter, then add glucose equivalent to 5-15% of the mass of potatoes to the filtrate to obtain the nutrition liquid, wherein the addition of potatoes in the nutrient solution of step (3) accounts for 10 to 20% of the mass fraction of the nutrient solution; the addition of the nutrient solution in step (4) is 10 to 20% of the mass fraction of potatoes in the fermented material prevail.

The following operation method can be preferred: the potatoes used to prepare the nutrient solution need to be peeled and cut into small cubes with a side length of 1cm, then boiled in 1000mL water for 30 minutes, filtered through 8 layers of gauze, and the filtrate is made up to 1000mL, and then add equivalent Potato mass 5-15% glucose.

In step (3), Saccharomyces cerevisiae is cultured at 30±1° C. and 150 rev/min for 12 to 18 hours to obtain a bacterial liquid with a concentration of 10 ⁸ to 10 ⁹ cfu/mL.

In step (4), the addition of cellulase is 15～30U/gVS, wherein VS refers to the quality of the volatile matter contained in the raw material mixture (referring to the remainder after deducting moisture and ash from the raw material); Saccharomyces cerevisiae The added amount of the bacteria liquid is calculated as 5-10% of the total volume of the fermented material by volume; the mass fraction of dry matter in the fermented material is calculated as 5-10%.

In order to make the reaction proceed smoothly and obtain good co-production ethanol and methane effect, the pH and the reaction time of step (4) and step (6) have specific requirements, wherein the acidity and alkalinity of step (4) and step (6) The pH values are 4.0-5.0 and 6.8-7.2 respectively, and the citric acid solution (10% citric acid solution) and the alkali metal hydroxide solution (adjusted with 10% alkali metal hydroxide solution added with Anaerobic digestion of the distillation residue of inoculated sludge); the fermentation temperature of step (4) and the anaerobic digestion reaction temperature of step (6) are respectively 30±1°C and 37±1°C.

In step (5), the time for fermentation to produce ethanol is 48-60 hours; after the saccharification and fermentation of raw materials, the fermentation substrate is distilled to obtain fuel ethanol with a concentration of 8-10%, and then the anaerobic digestion reaction of step (6) is carried out , first add anaerobic digestion inoculation sludge to the distillation residual species, the amount of anaerobic digestion inoculation sludge accounts for 5-20% of the dry matter of the distillation residue in terms of dry weight; the reaction time of anaerobic digestion is 40-50d, and the reaction Part of the remainder is used as inoculation sludge for a new round of anaerobic digestion, and the other part is used as agricultural biogas manure.

In order to ensure that the reaction is carried out under strict anaerobic conditions, after the materials are placed in the reactor, a rubber stopper with a vent tube can be used to tightly cover the reactor bottle mouth, and the interface between the vent tube and the rubber stopper can be sealed with paraffin, and the reaction Nitrogen was blown into the reactor for 2 min before starting.

The invention utilizes the papermaking sludge which is difficult to be rationally utilized in the prior art, and through mixed fermentation with monosodium glutamate waste liquid, and through proper adjustment, ethanol and methane can be produced while waste treatment reduces harm. With the growth of the world economy and the increase of population, the problem of energy shortage is becoming more and more serious, and the development of renewable energy has become a hot spot of global concern. As a clean and renewable energy source, ethanol has been widely valued by governments and many researchers. At present, the production of fuel ethanol in my country uses sugar or grain as raw materials, and further expansion of production will be limited by resources. Therefore, it will be an inevitable trend for future development to use cheap and easily available fiber raw materials to produce ethanol.

Compared with prior art, the present invention has following advantage:

1. The present invention utilizes synchronous saccharification and fermentation to produce ethanol. The process does not require any sterilization operation, the process is simple, and the operability is strong. At the same time, the production of ethanol and methane is carried out under medium temperature conditions, which realizes mild production conditions and low energy consumption.

2. The present invention uses alkaline solution to pretreat papermaking sludge. The pretreatment process can realize the degradation of macromolecular organic matter in sludge into small molecular substances, thereby shortening the liquefaction and hydrolysis time of subsequent anaerobic fermentation, improving the liquefaction and hydrolysis rate of raw materials and subsequent biotransformation rate.

3. The present invention utilizes the mixed fermentation of papermaking sludge and monosodium glutamate waste liquid to produce fuel ethanol, which can not only improve the living environment of microorganisms in terms of nutritional structure, increase the output of ethanol and methane, but also realize the "no waste" of two major solid wastes at the same time. harm, reduction and resource utilization".

4. The present invention first uses yeast to decompose organic matter in papermaking sludge and monosodium glutamate waste liquid to produce ethanol, and then further uses methane bacteria to decompose organic matter in distillation residues to realize full utilization of raw materials and avoid waste of resources.

5. The ethanol distillation in the present invention is also a heat treatment process for subsequent methanogenic digestion raw materials. Compared with the heat treatment of materials in a single methanogenic process, the present invention reduces energy consumption and saves energy.

6. The present invention has potential environmental benefits, social benefits and economic benefits, and has huge market and application potential in renewable energy production, waste resource recycling, and industrial solid waste treatment and disposal.

Description of drawings

Fig. 1 is a schematic flow chart of the co-production of ethanol and methane by the mixed fermentation of papermaking sludge and monosodium glutamate waste liquid according to the present invention.

Detailed ways

The technical solution of the present invention is further illustrated below through specific examples.

Example 1

(1) The papermaking sludge used in the test was taken from the sludge dehydration workshop of a paper mill in Guangdong Province. The retrieved fresh sludge was evenly dispersed, and then pretreated with 0.6% NaOH solution for 24 hours;

(2) The monosodium glutamate waste liquid used in the test was taken from a monosodium glutamate factory in Guangdong Province. According to the ratio of monosodium glutamate waste liquid: papermaking sludge = 8: 100 (w/w, in dry weight), fresh monosodium glutamate waste liquid was weighed and added to the papermaking sludge. In the mud, adjust the C/N=18:1 of the fermentation substrate;

(3) Weigh 300g of potatoes (peeled), cut into small pieces, put them into 1000mL water and boil for 30min, filter through 8 layers of gauze, make up the filtrate to 1000mL, then add 30g of glucose to make the fermentation system microbial growth required nutrient solution;

(4) Select the saccharomyces cerevisiae colony on the solid medium, inoculate to the nutrient solution with a concentration of 20% obtained in step (3), and cultivate it for 15 hours as the inoculum solution for the ethanol production test;

(5) Add the mixture obtained in step (2) (containing 35.8 g of papermaking sludge dry matter, 2.9 g of monosodium glutamate waste liquid dry matter) into a 1000mL reactor, and then add cellulase according to 30U/gVS, step (3 ) obtained nutrient solution and distilled water, so that the total amount of material in the reactor reaches 600mL, and the dry matter content of the total material in the reactor is 5%, utilize 10% citric acid solution to adjust the pH value of the above-mentioned material to 4.0～5.0, and inoculate step (4) 60mL cultured bacteria solution;

(6) Cover the mouth of the above reactor with a tight cotton plug, and place it in a constant temperature oscillator at 30±1°C to ferment and produce ethanol;

(7) After 50 hours of saccharification and fermentation, the concentration of ethanol in the reactor is substantially constant, and then the fermentation substrate is distilled to obtain fuel ethanol with a concentration of 8.7%. Simultaneously, according to the inoculum size: distillation residue total amount=1: 10 (w /w, in dry mass), add anaerobic digestion inoculum sludge (referring to one or more of septic tank sludge, spoiled river mud or anaerobic digestion sludge of urban sewage treatment plant) to the distillation residue Seed slime obtained after domestication), and adjust the pH of the material with 10% KOH solution to be 6.8;

(8) Seal the reactor in step (7), stir the fermented product regularly with a stirring device, place it in a constant temperature water bath at 37±1°C for anaerobic digestion to produce methane, and obtain a methane yield of 0.27m ³ CH ₄ / kg VS (VS is the quality of the volatile matter of the raw material, which refers to the remainder of the raw material after deducting moisture and ash);

(9) Except that part of the fermentation residue in step (8) is used as inoculation sludge for a new round of anaerobic digestion, the rest can be used as biogas manure for direct agricultural use.

Example 2

(1) The papermaking sludge used in the test was taken from the sludge dehydration workshop of a paper mill in Guangdong Province. The retrieved fresh sludge was evenly dispersed, and then pretreated with 0.6% NaOH solution for 24 hours;

(2) The monosodium glutamate waste liquid used in the test was taken from a monosodium glutamate factory in Guangdong Province. According to the ratio of monosodium glutamate waste liquid: papermaking sludge = 5: 100 (w/w, in terms of dry mass), fresh monosodium glutamate waste liquid was weighed and added to the papermaking sewage. In the mud, adjust the C/N=22:1 of the fermentation substrate;

(3) Weigh 300g of potatoes (peeled), cut into small pieces, put them into 1000mL water and boil for 30min, filter through 8 layers of gauze, make up the filtrate to 1000mL, then add 30g of glucose to make the fermentation system microbial growth required nutrient solution;

(4) Select the saccharomyces cerevisiae colony on the solid medium, inoculate to the nutrient solution with a concentration of 20% obtained in step (3), and cultivate it for 15 hours as the inoculum solution for the ethanol production test;

(5) Add the mixture obtained in step (2) (containing 35.8 g of papermaking sludge dry matter and 1.8 g of monosodium glutamate waste liquid dry matter) into a 1000mL reactor, then add cellulase according to 30U/gVS, step (3 ) obtained nutrient solution and distilled water, so that the total amount of material in the reactor reaches 600mL, and the dry matter content of the total material in the reactor is 5%, utilize 10% citric acid solution to adjust the pH value of the above-mentioned material to 4.0～5.0, and inoculate step (4) 60mL cultured bacteria solution;

(6) Cover the mouth of the above reactor with a tight cotton plug, and place it in a constant temperature oscillator at 30±1°C to ferment and produce ethanol;

(7) After 50 hours of saccharification and fermentation, the concentration of ethanol in the reactor is substantially constant, and then the fermentation substrate is distilled to obtain fuel ethanol with a concentration of 8.1%. Simultaneously, according to the inoculum size: distillation residue total amount=1: 10 (w /w, in dry mass), add anaerobic digestion inoculum sludge (referring to one or more of septic tank sludge, spoiled river mud or anaerobic digestion sludge of urban sewage treatment plant) to the distillation residue Seed slime obtained after domestication), and the pH of the material is adjusted to 7.2 with 10% KOH solution;

(8) Seal the reactor in step (7), stir the fermented product regularly with a stirring device, place it in a constant temperature water bath at 37±1°C for anaerobic digestion to produce methane, and obtain a methane yield of 0.25m ³ CH ₄ / kg VS (VS is the quality of the volatile matter of the raw material, which refers to the remainder of the raw material after deducting moisture and ash);

(9) Except that part of the fermentation residue in step (8) is used as inoculation sludge for a new round of anaerobic digestion, the rest can be used as biogas manure for direct agricultural use.

Claims (5)

1. a kind of method that utilizes papermaking sludge and monosodium glutamate waste liquid mixed fermentation to produce ethanol and methane is characterized in that comprising the following steps: (1) monosodium glutamate waste liquid and papermaking sludge are according to the ratio of dry weight ratio 3～10: 100 (2) prepare nutrient solution; (3) take nutrient solution, inoculate Saccharomyces cerevisiae in it, and become Saccharomyces cerevisiae bacterial liquid after culturing; (4) add cellulase and nutrient solution to the raw material mixture and water, adjust the pH value to be acidic to become a fermentation material, and inoculate Saccharomyces cerevisiae liquid for fermentation to produce ethanol; (5) After the fermentation is completed, distill the fermentation substrate to obtain ethanol; (6) Distill the remaining material into anaerobic digestion Inoculate the sludge, adjust the pH value to be alkaline, and perform anaerobic digestion to produce methane; The papermaking sludge described in the step (1) is also pretreated before being mixed with the monosodium glutamate waste liquid, and the pretreatment adopts a kind of hydroxide formed by an alkali metal, and the concentration of the alkali solution is 0.3% to 1.0%. The time is 15~24h; The nutrient solution described in step (2) is a potato-glucose nutrient solution, which is obtained by peeling and cutting potatoes, adding water to boil for 25-35 minutes and filtering, adding glucose equivalent to 5-15% of the mass of potatoes to the filtrate Nutrient solution; the amount of potato added in the nutrient solution described in step (3) accounts for 10-20% of the mass fraction of the nutrient solution; the amount of nutrient solution added in step (4) is 10-20% based on the mass fraction of potatoes in the fermented material % prevails; The Saccharomyces cerevisiae described in step (3) is cultivated to a concentration of 10 ⁸ ~ 10 ⁹ cfu/mL to become the bacterial liquid; the Saccharomyces cerevisiae described in step (3) is cultivated at 30±1°C and 150 rev/min 12 to 18 hours to become the bacterial liquid; The acidic and alkaline pH values in step (4) and step (6) are 4.0-5.0 and 6.8-7.2 respectively, and the citric acid solution and alkali metal hydroxide solution are respectively used to adjust the pH value. 2. the method for claim 1 is characterized in that the add-on of the described cellulase of step (4) is 15～30U/gVS, wherein VS refers to the quality of the volatile substance contained in the raw material mixture The addition of Saccharomyces cerevisiae bacterium liquid is 5～10% of the total volume of fermented material by volume; The dry matter mass fraction in fermented material is counted as 5～10%, 3. The method according to claim 1, characterized in that the reaction temperatures of the fermentation in step (4) and the anaerobic digestion in step (6) are 30±1° C. and 37±1° C. respectively. 4. The method according to claim 1, characterized in that the fermentation ethanol production time of the step (5) is 48～60h; the addition of the step (6) anaerobic digestion inoculation sludge accounts for the distillation residue in terms of dry weight 5-20% of dry matter. 5. The method according to claim 1, characterized in that the digestion reaction time described in step (6) is 40 to 50 days, and a part of the reaction residue is used as the inoculation sludge of a new round of anaerobic digestion, and another part is used as Agricultural manure.