CN101913747B - Method for producing methane by combination fermentation of paper mill sludge and food waste - Google Patents

Abstract

The invention belongs to the field of renewable energy and environmental protection, and relates to a method for producing methane by joint fermentation of papermaking sludge and kitchen waste. The ratio of 25:5 is mixed evenly, and the inoculum is added to form a fermentation material and after dilution, the fermentation is carried out at 37±2° C. under anaerobic conditions for 30 to 50 days. The present invention mixes papermaking sludge and kitchen garbage to produce methane through anaerobic fermentation, not only processing two solid wastes at the same time, but also improving the bioconversion rate of raw materials and obtaining higher methane yield; It is usually alkaline, and kitchen waste is usually acidic. The mixed fermentation of the two can avoid the pH adjustment of the material during the fermentation process; The "harmless, reduced and resourceful" of the two major solid wastes of garbage.

Description

A method for producing methane by joint fermentation of papermaking sludge and kitchen waste

technical field

The invention belongs to the field of renewable energy and environmental protection, and relates to a method for producing methane by joint fermentation of papermaking sludge and kitchen waste.

Background technique

Papermaking sludge refers to the mixed sludge obtained in the primary settling tank and secondary settling tank during the biochemical treatment of paper mill wastewater, excluding deinking sludge obtained from deinking waste paper in paper mills. Since the paper industry is a large water consumer, a large amount of papermaking wastewater has produced a large amount of papermaking sludge in the process of biochemical treatment. According to statistics, in 2007, China produced about 23.89 million tons of dewatered papermaking sludge (water content 80%), 478 10,000 tons of dry sludge. It is estimated that by 2020, China will produce approximately 30.88 million tons of dewatered papermaking sludge (with a moisture content of 80%, and 6.18 million tons of dry sludge. Faced with such a large amount of papermaking sludge, traditional treatment and disposal methods Yes: incineration, landfill and land use, etc.; during the treatment of papermaking wastewater, most of the pollutants in the wastewater will be enriched into sludge due to coagulation, adsorption, etc., affecting its direct application; landfilling papermaking sludge It not only consumes 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 investment and operation costs of the boiler incineration system are relatively high, and it is easy to generate smoke pollution. Suitable for general small and medium-sized papermaking enterprises. Since papermaking sludge is rich in fine fibers, lignin and its derivatives, sugars and salts, biological treatment has become an important way for resource utilization of papermaking sludge. Patent CN 01429066A utilizes papermaking sludge The sludge is aerobically composted, and the obtained compost is used as a valuable fertilizer, soil improver and regulator. However, there are problems such as large volatile gas production, high energy consumption, and unsolvable odor during the composting process of papermaking sludge.

Kitchen waste is a kind of perishable organic solid waste produced in people's daily life, which is generally produced in catering units such as families, hotels, restaurants, government agencies, enterprises and institutions. The composition of food waste is very complex, containing oil, water, rice noodles, vegetables, fruit peels, fish, meat, bones, etc., with starch, dietary fiber, animal fat and other organic substances as the main components. The generation of kitchen waste is huge. Taking Beijing, Shanghai, Guangzhou and other big cities as examples, the daily output of kitchen waste exceeds 1,000 tons. With the increase of population and the improvement of people's living standards, the generation of kitchen waste The volume is increasing year by year. Because food waste is perishable, deteriorates, produces a large amount of toxins, and emits foul-smelling gases, it seriously pollutes the surrounding environment. Food waste has become an important pollution source of urban domestic waste, and it is urgent to deal with it properly. At present, in addition to being used to raise pigs, most of the food waste in my country is disposed of in the form of landfill, which not only takes up a lot of valuable land resources, but also pollutes the surrounding environment; a small part of the food waste is processed through composting , but it has the same problems as papermaking sludge; therefore, it is particularly important to develop a technical method with a high degree of resource utilization of food waste, less secondary pollution, and reliable operation.

Since papermaking sludge and kitchen waste are biodegradable organic solid wastes, another way of biological treatment is anaerobic digestion to produce methane. Due to the low energy consumption of anaerobic digestion, less secondary pollution, and better aerobic composting It can reduce _CO2 emissions and produce methane to replace some petroleum fuels. In today's society where the global warming effect is intensified and energy is scarce, it has very important strategic 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.

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 methane by mixed fermentation of papermaking sludge and kitchen waste, which is to mix papermaking sludge and broken kitchen waste according to the volatile matter mass ratio of 1 to 25:5 (the preferred ratio is 1～3:1) and mix evenly and dilute, then ferment under anaerobic conditions. The specific steps are as follows:

(1) Sorting the collected food waste, removing solids with larger particle sizes (such as corncobs, plastic bags, etc.), and then mixing it with water in a certain proportion, and crushing it with a food crusher. The particle size should be able to pass through a 40-mesh sieve.

(2) Evenly disperse the fresh papermaking sludge taken from the paper mill;

(3) The food waste broken in step (1) and the dispersed papermaking sludge in step (2) are mixed according to the volatile matter (VS) mass ratio of 1 to 25:5 (the preferred ratio is 1 to 3:1) ) is mixed evenly; the mass ratio of volatile substances refers to the residue after deducting moisture and ash from raw materials;

(4) Add the mixture of step (3) gained in the anaerobic reactor, then add the inoculum (the inoculum is septic tank sludge, spoiled river mud or the anaerobic digestion sludge of urban sewage treatment plant One or more kinds of seed sludge obtained after domestication) are inoculated and mixed, and the addition amount of the inoculum is 5-5% of the dry weight of papermaking sludge and kitchen waste (referring to the quality of raw materials after deducting water) according to dry weight. 20%, and finally add an appropriate amount of water to adjust the solid content of the fermented material (papermaking sludge, kitchen waste and inoculated sludge) in the anaerobic reactor to 5-15%; the preferred solution is to dilute to the solid content of the fermented material 10%.

(5) Utilize the rubber stopper to tightly cover the reaction bottle mouth, and seal the interface between the vent pipe and the rubber stopper with paraffin, feed nitrogen into the reactor for 2min before the reaction begins, to ensure that the reaction system is in a strict anaerobic state, and the reaction system is in a strict anaerobic state. The gas outlet is connected to the gas storage device through the exhaust pipe, the reaction temperature is controlled at 37±2°C, no pH adjustment is required during the fermentation process, and the fermented product is stirred regularly by the stirring device; there is methane within the first day after the start of the test produce.

(6) After 30-50 days of fermentation, the fermentation process can be completed: after 30-50 days, the methane production of the system has dropped significantly, and the method of gas measurement can be used to determine the time to stop fermentation. When the measured daily gas production is lower than At 25% of the average daily gas production (referring to the numerical value obtained from cumulative gas production/fermentation days), the reaction can be terminated and a new round of anaerobic fermentation can be carried out.

In the present invention, papermaking sludge refers to one or more of the pulping wastewater, papermaking wastewater and domestic sewage of the paper mill, which are mixed in the primary sedimentation tank and the secondary sedimentation tank during the biochemical treatment process. For dewatered sludge, the water content of the sludge is 70-80%.

In the present invention, kitchen waste refers to one or several types of kitchen waste produced by catering units such as families, hotels, restaurants, government agencies, enterprises and institutions.

At present, the output of papermaking sludge and kitchen waste is large, the environmental pollution is serious, and it is urgent to deal with it properly.

For the first time in the present invention, papermaking sludge and kitchen waste are mixed and fermented, and raw materials with high C/N ratio and raw materials with low C/N ratio are mixed and fermented to provide the best nutritional structure for the growth of microorganisms in the fermentation system. The inoculum further increases the bioconversion rate of the fermentation material. Due to the high protein content in food waste and the high C/N ratio of raw materials, using the principle of complementary advantages in the properties of raw materials, the mixed fermentation of food waste and papermaking sludge will help to increase the methane yield of the system.

The combination and proportioning of the fermented materials provided by the present invention is an important influencing factor for the methanogenic effect and belongs to the scope of protection of the present invention. The fermented methane-produced materials contain papermaking sludge, kitchen waste and inoculum , wherein the ratio of papermaking sludge and kitchen waste is 1 to 25:5 based on the mass of volatile substances, preferably 1 to 3:1, and the inoculum is septic tank sludge, spoiled river mud or urban sewage treatment One or more of the anaerobic digestion sludge in the plant is domesticated by papermaking sludge and kitchen waste mixture (according to the mass ratio of volatile substances: 1 to 3:1), the content of which accounts for the papermaking sludge and 5-20% of the dry weight of kitchen waste.

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

1. The process is simple and the operability is strong;

2. The anaerobic fermentation of papermaking sludge and kitchen waste to produce methane not only treats two solid wastes at the same time, but also improves the bioconversion rate of raw materials and obtains a higher methane yield;

3. Since papermaking sludge is usually alkaline and food waste is usually acidic, the mixed fermentation of the two can avoid the pH adjustment of the material during the fermentation process;

4. The joint fermentation of papermaking sludge and kitchen waste can effectively improve the buffer capacity of the system, and can also improve the living environment of microorganisms in terms of nutritional structure, promote the arrival of the peak gas production, shorten the fermentation cycle, and thus improve the reactor's efficiency. processing power and processing efficiency.

5. The present invention utilizes the principle of using waste to treat waste, and simultaneously effectively realizes "harmless, reduced and resourceful" of the two major solid wastes of papermaking sludge and kitchen waste.

Description of drawings

Fig. 1 is the variation with time of the daily gas production of the mixed fermentation process of embodiment 1.

Fig. 2 is the variation of the cumulative gas production over time in the mixed fermentation process of Example 1.

Fig. 3 is the variation of volatile organic acids (VFA) over time in the mixed fermentation process of Example 1.

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, and the retrieved fresh sludge was evenly dispersed;

(2) The experimental kitchen waste was taken from a student canteen of a university in Guangdong Province. The retrieved fresh kitchen waste was first sorted to remove solids with larger particle sizes (such as corncobs, plastic bags, etc.), and then mixed with water Mix according to a certain ratio, and crush it with a food crusher until the particle size can pass through a 40-mesh sieve;

(3) Evenly mix the papermaking sludge dispersed in step (1) and the pretreated food waste in step (2) according to the volatile matter (VS) mass ratio of 1:1, wherein the amount of papermaking sludge added is 114.6g, and the amount added to the kitchen waste is 94.7g; the total volatile matter content of the mixture is 29.3g;

(4) the mixture obtained in step (3), the papermaking sludge (the quality of the volatile matter is 29.3g) of the step (1) gained and the kitchen waste (the quality of the volatile matter is 29.3g) of the step (2) gained are respectively Add it into three 1000mL anaerobic reactors, and add 70g of anaerobic sludge with a water content of 89.42% (referring to septic tank sewage) Mud, spoiled river mud or one or more domesticated seed muds obtained from anaerobic digested sludge of urban sewage treatment plants) are inoculated and mixed evenly with the materials in the reactor;

(5) Add water to the mixture obtained in step (4), so that the total dry weight (TS) of the materials in the reactor (papermaking sludge+food waste+inoculation sludge) is 10%;

(6) Utilize the rubber stopper to tightly cover the reaction bottle mouth, and seal the interface between the vent pipe and the rubber stopper with paraffin, feed nitrogen into the reactor before the reaction begins, to ensure that the reaction system is in a strict anaerobic state, and the outlet of the reactor The gas port is connected to the gas storage device through the exhaust pipe, and the reaction temperature is controlled at 37±2°C. There is no need to adjust the pH value during the fermentation process, and the fermented product is stirred regularly by the stirring device;

(7) During the test, the methane production rate and the volatile fatty acid (VFA) production of the system were measured every day to judge whether acid accumulation occurred in the system. After a period of fermentation, the methane production of the system decreased significantly. When the measured daily production When the gas volume is lower than 25% of the average daily gas production (referring to the numerical value obtained from the cumulative gas production/fermentation days), the reaction is terminated.

Figure 1, Figure 2 and Figure 3 show the methane production and volatile fatty acid (VFA) concentration during the mixed fermentation of papermaking sludge and kitchen waste in different proportions. In the anaerobic fermentation process, the mixed fermentation of papermaking sludge and kitchen waste at a ratio of 1:1 (in terms of VS) has the best gas production effect, and its cumulative methane production is higher than that of papermaking sludge and kitchen waste alone by anaerobic digestion. The production increased by 60% and 74% respectively; the VFA concentration of each treatment reached the maximum on the 9th day, and at this time the gas production of each system decreased significantly, indicating that the system had acid accumulation phenomenon, and then due to the decrease of VFA concentration, The gas production of the system gradually increased, and each system reached the peak gas production on the 12th day or so; in the reaction system with a single substrate of food waste, during the entire fermentation process, due to the high content of easily biodegradable organic matter in the food waste, Therefore, the VFA concentration in the system is high (more than 5000mg/L), the acid accumulation phenomenon is serious, and the methane production of the system is the lowest; the reaction system with papermaking sludge as a single substrate has the same methane production potential as papermaking sludge in the late stage of anaerobic fermentation : Food waste = 1:1 treatment is equivalent to or even surpasses the latter. The main reason is that the content of refractory organic matter in papermaking sludge is higher than that of food waste. These relatively refractory organic matter are mainly partially degraded in the late stage of fermentation.

Example 2

(1) The papermaking sludge used in the test was taken from the sludge dehydration workshop of a paper mill in Guangdong Province, and the retrieved fresh sludge was evenly dispersed;

(2) The experimental kitchen waste was taken from the student canteen of a university in Guangdong Province. The retrieved fresh kitchen waste was first sorted to remove solids with larger particle sizes, and then crushed with a food crusher until the particle size could reach Pass 40 mesh sieve;

(3) The papermaking sludge dispersed in step (1) and the pretreated kitchen waste in step (2) are mixed according to the volatile matter (VS) mass ratio of 5:1, 3:1, 1:1, 1: 3, 1:5 for uniform mixing.

(4) Add the mixture obtained in step (3) into the anaerobic reactor of 1000mL respectively. According to the dry matter quality of the inoculated sludge being 10% of the dry weight of the fermentation raw material, add 70g of anaerobic reactor with a water content of 90.71%. Oxygen sludge is inoculated and mixed evenly with the materials in the reactor;

(5) adding water to the mixture obtained in step (4), so that the dry weight (TS) of the total material in the reactor is 10%;

(6) seal the anaerobic reactor, feed nitrogen into the reactor before the reaction begins, to ensure that the reaction system is in a strict anaerobic state, the gas outlet of the reactor is connected with the gas storage device through the exhaust pipe, and the reaction temperature is controlled at 37 ±2°C, the fermentation process does not need to adjust the pH value, and the fermented product is stirred regularly by the stirring device;

(7) During the test, the methane production rate and the volatile fatty acid (VFA) production of the system were measured every day. After a period of fermentation, the methane production of the system decreased significantly. When the measured daily gas production was lower than the average daily gas production (refer to When accumulative gas production/numerical value obtained in days of fermentation) 25%, then end reaction. The cumulative methane production of each treatment is shown in Table 1.

Table 1: Methane production with different material ratios

Papermaking sludge: food waste 5:1 3:1 1:1 1:3 1:5 Cumulative methane production (mL) 3106 7259 11577 3962 1579

Claims (9)

1. one kind is utilized paper mill sludge and the methanogenic method of changing food waste combined ferment; It is characterized in that under anaerobic fermenting with after the even also dilution of mixed of the changing food waste after paper mill sludge and the fragmentation according to volatile material mass ratio 1～3: 1.

2. the method for claim 1; It is characterized in that after described paper mill sludge and changing food waste mixing; Also add inoculum; Form fermentation materials, described inoculum is one or more the kind mud that after paper mill sludge and the domestication of changing food waste mixture, obtain in the anaerobically digested sludge of manure pit mud, corrupt river silt or municipal sewage plant.

3. method as claimed in claim 2, the add-on that it is characterized in that described inoculum are 5～20% of paper mill sludge and changing food waste mixture dry weight.

4. method as claimed in claim 2 is characterized in that in described dilution it being that the solid content that in described fermentation materials, adds water in the fermentation raw material is 5～15%.

5. the method for claim 1 is characterized in that carrying out under 37 ± 2 ℃ of temperature of reaction in described fermentation.

6. the method for claim 1 is characterized in that continuing 30～50 days at described fermenting process.

7. the method for claim 1; It is characterized in that being meant in the sewage in pulp-making waste-water, paper waste and paper mill in paper mill one or more at described paper mill sludge; In the biochemical treatment process; The mixed dehydration mud that in preliminary sedimentation tank and second pond, obtains, the water ratio of mud is 70～80%.

8. the method for claim 1 is characterized in that before described changing food waste fragmentation, choosing earlier except that plastics, and the grain diameter after the fragmentation can pass through 40 mesh sieves.

One kind the fermentation methanogenic material; It is characterized in that containing paper mill sludge, changing food waste and inoculum; Wherein paper mill sludge and changing food waste are 1～3: 1 according to the ratio of volatile material quality meter; Inoculum is one or more the kind mud that after paper mill sludge and the domestication of changing food waste mixture, obtain in the anaerobically digested sludge of manure pit mud, corrupt river silt or municipal sewage plant, and content accounts for 5～20% of paper mill sludge and changing food waste dry weight.

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