阅读说明：本技术 一种造纸白泥预处理提高剩余污泥厌氧消化甲烷产率的工艺 (Process for improving yield of excess sludge anaerobic digestion methane by papermaking white mud pretreatment ) 是由 黄建强 姬杰 郑文颖 钱玉霞 郭鹏 续继峰 赵雅俊 高佩 于 2021-08-18 设计创作，主要内容包括：一种造纸白泥预处理提高剩余污泥厌氧消化甲烷产率的工艺,由以下步骤组成：S1、将剩余污泥经浓缩后得到含水率降低的浓缩污泥；S2、将浓缩污泥与造纸白泥在碱解池内混合,调节第一加药泵和第二加药泵,控制碱解池内的pH为11±0.5,搅拌停留60min,得到碱化污泥；S3、将步骤S2所得的碱化污泥在60±1℃的低温水解池中水解发酵,得到预处理污泥；S4、预处理污泥经泥水换热器降低温度至35℃后,与厌氧消化后的熟污泥混合,由螺杆泵投入厌氧消化池进行厌氧发酵,产生沼气；本发明实现了造纸白泥这一危险固体废弃物的资源化利用,为造纸白泥的处理处置提供了新的处理方法。(A process for improving the yield of residual sludge anaerobic digestion methane by papermaking white sludge pretreatment comprises the following steps: s1, concentrating the excess sludge to obtain concentrated sludge with reduced water content; s2, mixing the concentrated sludge and the papermaking white mud in an alkaline hydrolysis tank, adjusting a first dosing pump and a second dosing pump, controlling the pH value in the alkaline hydrolysis tank to be 11 +/-0.5, and stirring and staying for 60min to obtain the alkalized sludge; s3, hydrolyzing and fermenting the alkalized sludge obtained in the step S2 in a low-temperature hydrolysis tank at 60 +/-1 ℃ to obtain pretreated sludge; s4, after the temperature of the pretreated sludge is reduced to 35 ℃ by a mud-water heat exchanger, the pretreated sludge is mixed with cooked sludge after anaerobic digestion, and the mixture is put into an anaerobic digestion tank by a screw pump for anaerobic fermentation to generate methane; the invention realizes the resource utilization of the papermaking white mud which is a dangerous solid waste, and provides a new treatment method for the treatment and disposal of the papermaking white mud.)

1. A process for improving the yield of residual sludge anaerobic digestion methane by papermaking white mud pretreatment is characterized by comprising the following steps:

s1, concentrating the excess sludge to obtain concentrated sludge with the water content of 93-94%;

s2, mixing the concentrated sludge and the papermaking white mud in an alkaline hydrolysis tank (1), adjusting a first dosing pump (9) and a second dosing pump (12), controlling the pH value in the alkaline hydrolysis tank (1) to be 11 +/-0.5, stirring and staying for 60min to obtain the alkalized sludge;

s3, hydrolyzing and fermenting the alkalized sludge obtained in the step S2 in a low-temperature hydrolysis tank (3) at the temperature of 60 +/-1 ℃ to obtain pretreated sludge;

s4, after the temperature of the pretreated sludge is reduced to 35 ℃ by the mud-water heat exchanger (4), the pretreated sludge is mixed with the mature sludge after anaerobic digestion, and the mixture is put into an anaerobic digestion tank (6) by a screw pump (7) for anaerobic fermentation to generate methane.

2. The process for improving the yield of residual sludge anaerobic digestion methane by papermaking white mud pretreatment according to claim 1, characterized in that: the papermaking white mud is a mud-like byproduct generated in an alkali recovery link in pulping and papermaking, is strong in alkalinity, has a pH value of 10-13.5, and has a concentration of 1-2 g/L in pretreated sludge.

3. The process for improving the yield of residual sludge anaerobic digestion methane by papermaking white mud pretreatment according to claim 2, characterized in that: in the step S2, acid agent HCl solution and alkali agent papermaking white mud leachate are used to adjust the pH, wherein the papermaking white mud leachate is obtained by mixing alkaline white mud from a paper mill according to a ratio of 1kg mud: mixing 5L of water, soaking at room temperature for 24h, and vacuum filtering.

4. The process for improving the yield of residual sludge anaerobic digestion methane by papermaking white mud pretreatment according to claim 1, characterized in that: the pretreated sludge in the step S4 is mixed with the cooked sludge according to the volume ratio of 3:1 after the temperature of the pretreated sludge is reduced by a mud-water heat exchanger (4).

5. The process for improving the yield of residual sludge anaerobic digestion methane by papermaking white mud pretreatment according to any one of claims 1 to 4, wherein the process comprises the following steps: the concentrated sludge and the papermaking white mud are mixed in an alkaline hydrolysis tank (1), the mixed sludge is pumped into a low-temperature hydrolysis tank (3) through a sludge pump (2) through an outlet at the bottom of the alkaline hydrolysis tank (1), the pretreated sludge after hydrolytic fermentation in the low-temperature hydrolysis tank (3) enters a muddy water heat exchanger (4), the muddy water heat exchanger (4) is communicated with a heat exchange system (8), the heat exchange system (8) supplies heat to the low-temperature hydrolysis tank (3), the pretreated sludge after cooling of the muddy water heat exchanger (4) and the mature sludge after anaerobic fermentation in an anaerobic digestion tank (6) are fed into the anaerobic digestion tank (6) through a screw pump (7) for anaerobic fermentation, the mature sludge and the biogas are discharged, an acid tank (10) is communicated with the alkaline hydrolysis tank (1) through a first dosing pump (9) arranged on a pipeline, the alkaline tank (11) is communicated with the alkaline hydrolysis tank (1) through a second dosing pump (12) arranged on the pipeline, the PH regulator (13) is electrically connected with the first dosing pump (9) and the second dosing pump (12).

6. The process for improving the yield of the residual sludge anaerobic digestion methane by the papermaking white mud pretreatment according to the claim 5, characterized in that the alkaline hydrolysis tank (1) is: the lower part of the alkaline hydrolysis tank shell (1-1) is of a conical hollow structure, the upper part of the alkaline hydrolysis tank shell is of a cylindrical hollow structure, an alkaline hydrolysis vertical stirrer (1-3) is arranged inside the alkaline hydrolysis tank shell (1-1), a PH probe (1-2) is arranged on the side wall of the alkaline hydrolysis tank shell (1-1), and the PH probe (1-2) is electrically connected with a PH regulator (13).

7. The process for improving the yield of the residual sludge anaerobic digestion methane by the papermaking white mud pretreatment according to the claim 5, characterized in that the low-temperature hydrolysis tank (3) is: the bottom of the cylindrical hollow hydrolysis tank shell (3-1) is provided with a support (3-5), the hydrolysis vertical stirrer (3-2) is arranged in the hydrolysis tank shell (3-1), the blades of the hydrolysis vertical stirrer (3-2) are spiral blades, the inner side wall of the hydrolysis tank shell (3-1) is provided with a heating coil (3-4), the top of the hydrolysis tank shell is provided with a temperature probe (3-3), and the heat source of the heating coil (3-4) comes from a heat exchange system (8).

Technical Field

The invention belongs to the technical field of sludge pretreatment equipment or devices, and particularly relates to a process for improving the yield of excess sludge anaerobic digestion methane by papermaking white mud pretreatment.

Background

The excess sludge is the product after the biochemical treatment of the municipal sewage treatment plant, and the output of the excess sludge is about 0.3 to 0.5 percent of the treated water. The yield of sludge (water content of 80%) in China in 2013 is more than 4000 ten thousand tons, the sludge yield reaches 6000-9000 ten thousand tons in 2020 according to the sewage treatment capacity planned in 2020, the problem of secondary pollution is an obvious result caused by rapid increase of the sludge yield, in addition, due to the problem of sludge treatment cost, the sludge treatment cost can be about 30-50% of the operation cost, in developed countries, the sludge treatment cost can even reach more than half of the total investment of sewage plants, and the sludge treatment problem is a heavy burden of normal operation of the sewage plants. Therefore, how to reasonably dispose the excess sludge and realize the 'three-transformation' (harmlessness, reduction and resource utilization) of the excess sludge is one of the important problems in various countries in the world.

The anaerobic digestion of the sludge can not only solve the problem that the sludge is difficult to dispose, but also fully utilize the sludge, which is an ideal sludge disposal method. However, the traditional anaerobic digestion of sludge has the defects of slow degradation rate, long reaction period and the like. In anaerobic digestion of sludge, the relatively slow hydrolytic acidification step is an important rate-limiting step, since the cell walls of microorganisms in sludge are hardly degraded by the microorganisms. Pretreatment of the sludge is necessary to increase the hydrolysis rate and shorten the reaction time.

The sludge pretreatment technology mainly destroys the cell structure of sludge microorganisms to release intracellular organic matters, thereby achieving the purposes of accelerating sludge hydrolysis and improving the anaerobic digestion gas production rate of sludge. The sludge pretreatment method mainly comprises heat treatment, alkali heat treatment, electrochemical treatment and the like.

The papermaking white mud (LMP) is also called causticized white mud, which is a sludge-like by-product generated in the alkali recovery process in pulping and papermaking, and accounts for about 70% of the total solid waste of a paper mill. China is a large world-wide paper-making country, and about 500 million tons of paper are made every year, and about 0.5 ton of paper-making white mud is generated every 1 ton of wood pulp is produced. The strong alkalinity of the papermaking white mud causes the papermaking white mud to have strong harm to the ecological environment, and the harm degree of the papermaking white mud is much larger than that of other industrial solid wastes such as coal gangue slag, fly ash and the like, so that how to reasonably dispose the papermaking white mud becomes one of the great problems in the field of environmental protection in China.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a process for improving the yield of residual sludge anaerobic digestion methane by pretreating papermaking white mud, wherein the papermaking white mud is added, and can provide a higher pH condition due to strong basicity, so that microorganisms expand and break, the cell structure of the microorganisms is damaged, and intracellular substances are released and participate in enzymatic reaction; the alkali pretreatment of the papermaking white mud can effectively dissolve the nitrocellulose to degrade the nitrocellulose into soluble organic carbohydrate, and the alkali pretreatment of the papermaking white mud can also promote the hydrolysis of the sludge and the influence of volatile short-chain fatty acid production, thereby improving the anaerobic gas production of the sludge and shortening the anaerobic retention time of the sludge.

The technical scheme for solving the technical problems is as follows: a process for improving the yield of residual sludge anaerobic digestion methane by papermaking white sludge pretreatment comprises the following steps:

s1, concentrating the excess sludge to obtain concentrated sludge with the water content of 93-94%;

s2, mixing the concentrated sludge and the papermaking white mud in an alkaline hydrolysis tank, adjusting a first dosing pump and a second dosing pump, controlling the pH value in the alkaline hydrolysis tank to be 11 +/-0.5, and stirring and staying for 60min to obtain the alkalized sludge;

s3, hydrolyzing and fermenting the alkalized sludge obtained in the step S2 in a low-temperature hydrolysis tank at 60 +/-1 ℃ to obtain pretreated sludge;

s4, after the temperature of the pretreated sludge is reduced to 35 ℃ by a mud-water heat exchanger, the pretreated sludge is mixed with the cooked sludge after anaerobic digestion, and the mixture is put into an anaerobic digestion tank by a screw pump for anaerobic fermentation to generate methane.

The papermaking white mud is a mud-like byproduct generated in an alkali recovery link in pulping and papermaking, is strong in alkalinity, has a pH value of 10-13.5, and has a concentration of 1-2 g/L in pretreated sludge.

In step S2, the pH of the paper mill is adjusted by using an acid agent HCl solution and an alkali agent papermaking white mud leach solution, wherein the papermaking white mud leach solution is prepared by mixing alkaline white mud from a paper mill according to a ratio of 1kg mud: mixing 5L of water, soaking at room temperature for 24h, and vacuum filtering.

In the step S4, the pretreated sludge is mixed with the cooked sludge according to the volume ratio of 3:1 after the temperature of the pretreated sludge is reduced by a mud-water heat exchanger.

The concentrated sludge and the papermaking white mud are mixed in an alkaline hydrolysis tank, the mixture is pumped into a low-temperature hydrolysis tank through a sludge pump through an outlet at the bottom of the alkaline hydrolysis tank, pretreated sludge after hydrolytic fermentation in the low-temperature hydrolysis tank enters a sludge-water heat exchanger, the sludge-water heat exchanger is communicated with a heat exchange system, the heat exchange system supplies heat to the low-temperature hydrolysis tank, the pretreated sludge after the temperature of the sludge-water heat exchanger and cooked sludge after anaerobic fermentation in an anaerobic digestion tank are fed into the anaerobic digestion tank by a screw pump for anaerobic fermentation, the cooked sludge and methane are discharged, an acid tank is communicated with the alkaline hydrolysis tank through a first dosing pump arranged on a pipeline, the alkaline tank is communicated with the alkaline hydrolysis tank through a second dosing pump arranged on the pipeline, and a pH regulator is electrically connected with the first dosing pump and the second dosing pump.

The alkaline hydrolysis tank of the invention comprises: the lower part of the alkaline hydrolysis tank shell is of a conical hollow structure, the upper part of the alkaline hydrolysis tank shell is of a cylindrical hollow structure, an alkaline hydrolysis vertical stirrer is arranged inside the alkaline hydrolysis tank shell, a PH probe is arranged on the side wall of the alkaline hydrolysis tank shell, and the PH probe is electrically connected with a PH regulator.

The low-temperature hydrolysis tank comprises: the bottom of the cylindrical hollow hydrolysis tank shell is provided with a support, the hydrolysis tank shell is internally provided with a hydrolysis vertical stirrer, the blades of the hydrolysis vertical stirrer are spiral blades, the inner side wall of the hydrolysis tank shell is provided with a heating coil, the top of the hydrolysis tank shell is provided with a temperature probe, and the heat source of the heating coil comes from a heat exchange system.

Compared with the prior art, the invention has the following advantages:

(1) compared with the common sludge alkali pretreatment method, the method reduces the dosing cost and is economic and economical.

(2) The invention realizes the resource utilization of the papermaking white mud which is a dangerous solid waste, and provides a new treatment method for the treatment and disposal of the papermaking white mud.

(3) The invention adopts low temperature to process, which can reach preset temperature by using the waste heat of the marsh gas generator set, to realize multi-stage utilization of energy and save resource.

(4) Compared with high-temperature pyrohydrolysis, the invention has the advantages of simple equipment, convenient operation and management, greatly reduced investment and operation cost, and equivalent effect.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Fig. 2 is a schematic structural diagram of the alkaline hydrolysis cell 1 in fig. 1.

Fig. 3 is a schematic structural view of the low-temperature hydrolysis tank 3 in fig. 1.

In the figure: 1. an alkaline hydrolysis pool; 2. a sludge pump; 3. a low-temperature hydrolysis tank; 4. a mud-water heat exchanger; 5. a cooked mud pump; 6. an anaerobic digester; 7. a screw pump; 8. a heat exchange system; 9. a first dosing pump; 10. an acid pool; 11. an alkali pool; 12. a second dosing pump; 13. a pH adjuster; 1-1, alkaline hydrolysis pool shell; 1-2, PH probe; 1-3, alkaline hydrolysis vertical stirrer; 3-1, a hydrolysis tank shell; 3-2, hydrolysis vertical stirrer; 3-3, a temperature probe; 3-4, heating coils; 3-5, a bracket.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples, but the present invention is not limited to these examples.

Example 1

In fig. 1, the process for improving the yield of residual sludge anaerobic digestion methane by papermaking white mud pretreatment comprises the following steps:

s1, concentrating the excess sludge to obtain concentrated sludge with the water content of 93-94%;

s2, mixing the concentrated sludge and the papermaking white sludge in the alkaline hydrolysis tank 1, wherein the papermaking white sludge and the concentrated sludge discharged from the sludge concentration tank are added in an amount of 1-2 kg/m3, namely the dosage of the papermaking white sludge in each m3 of sludge is 1-2 kg. Because the water content of the concentrated sludge is still higher, the water content of the concentrated sludge is different after concentration by different equipment, and according to an experimental result, in order to obtain a reliable alkaline hydrolysis effect of the sludge, the addition of 1-2 kg of papermaking white sludge per cubic meter of the sludge is more reasonable. Mixing in an alkaline hydrolysis tank 1, adjusting a first dosing pump 9 and a second dosing pump 12, controlling the pH value in the alkaline hydrolysis tank 1 to be 11 +/-0.5, stirring and staying for 60min to obtain alkalized sludge; the papermaking white mud is a mud-like byproduct generated in an alkali recovery link in pulping and papermaking, is strong in alkalinity and has a pH value of 10-13.5, the concentration of the papermaking white mud in pretreated sludge is 1-2 g/L, an HCl solution is filled in an acid tank 10, a papermaking white mud leachate is filled in an alkali tank 11, an acid agent HCl solution and an alkali agent papermaking white mud leachate are added through a pH regulator 13 by controlling a first dosing pump 9 and a second dosing pump 12 to regulate the pH value in an alkaline hydrolysis tank 1, and the papermaking white mud leachate is obtained by mixing alkaline white mud of a papermaking factory according to the weight ratio of 1 kg: mixing 5L of water, soaking at room temperature for 24h, and vacuum filtering.

S3, hydrolyzing and fermenting the alkalized sludge obtained in the step S2 in a low-temperature hydrolysis tank 3 at 60 +/-1 ℃, keeping the hydrolysis temperature at 60 ℃, breaking the wall of the sludge, and reducing the PH of the sludge after the wall breaking to obtain pretreated sludge; by adopting a low-temperature thermokalite pretreatment process of the papermaking white mud and combining the alkali treatment and the low-temperature heat treatment of the papermaking white mud, cell walls in the sludge are damaged, the concentration of organic matters in the sludge is improved, the time required by anaerobic digestion of the sludge is shortened, and the biogas yield is improved.

S4, the temperature of the sludge treated in the step S3 is still higher (>50 ℃), the temperature is reduced to 35 ℃ by muddy water heat exchange, the pH value is adjusted to about 7.0 at the same time to ensure the growth of methanogens, the methanogens and the mature sludge after anaerobic digestion in the anaerobic digestion tank 6 are mixed and fermented according to the volume ratio of 3:1, and the mixture is put into the anaerobic digestion tank 6 by a screw pump 7 for anaerobic fermentation to generate methane and regenerate the mature sludge.

The process for improving the yield of excess sludge anaerobic digestion methane by pretreating papermaking white mud specifically comprises the following steps: the concentrated sludge and the papermaking white mud are mixed in an alkaline hydrolysis tank 1, the mixture is pumped into a low-temperature hydrolysis tank 3 through a sludge pump 2 from an outlet at the bottom of the alkaline hydrolysis tank 1, the pretreated sludge after the hydrolytic fermentation in the low-temperature hydrolysis tank 3 enters a mud-water heat exchanger 4, the mud-water heat exchanger 4 is communicated with a heat exchange system 8, the heat exchange system 8 supplies heat to the low-temperature hydrolysis tank 3, the pretreated sludge after the temperature of the mud-water heat exchanger 4 and the mature sludge after the anaerobic fermentation in an anaerobic digestion tank 6 are fed into the anaerobic digestion tank 6 through a screw pump 7 for anaerobic fermentation, the mature sludge and methane are discharged, an acid tank 10 is communicated with the alkaline hydrolysis tank 1 through a first dosing pump 9 arranged on a pipeline, the alkaline tank is communicated with the alkaline hydrolysis tank through a second dosing pump 12 arranged on the pipeline, and a PH regulator 13 is electrically connected with the first dosing pump 9 and the second dosing pump 12, the opening and closing of the first dosing pump 9 or the second dosing pump 12 are controlled according to the pH value in the alkaline hydrolysis tank 1.

Further, in fig. 2, the alkaline hydrolysis tank 1 is formed by connecting an alkaline hydrolysis tank shell 1-1, a PH probe 1-2 and an alkaline hydrolysis vertical stirrer 1-3, the lower part of the alkaline hydrolysis tank shell 1-1 is a conical hollow structure, the upper part of the alkaline hydrolysis tank shell is a cylindrical hollow structure, and the alkaline hydrolysis vertical stirrer 1-3 is installed inside the alkaline hydrolysis tank shell 1-1 and is used for stirring and mixing alkaline papermaking white mud and concentrated sludge to fully contact the alkaline papermaking white mud and the concentrated sludge, so that the alkaline papermaking white mud is uniformly mixed, and the alkaline papermaking white mud accelerates the sludge wall breaking. The side wall of the shell 1-1 of the alkaline hydrolysis tank is provided with a PH probe 1-2, and the PH probes 1-2 can be provided with a plurality of groups which are uniformly distributed at the upper part, the middle part and the lower part of the alkaline hydrolysis tank 1 to monitor the pH value in the whole tank. Meanwhile, the PH probe is electrically connected with a PH regulator 13, transmits the PH value in the pool to the PH regulator 13, is judged by the PH regulator 13, gives an instruction whether to switch on the first dosing pump 9 or the second dosing pump 12, regulates the PH value in the pool, ensures that the pH value in the pool is maintained within the range of 11 +/-0.5, and enables the intracellular substances in the concentrated sludge to be continuously dissolved out.

In fig. 3, the low-temperature hydrolysis tank 3 of the embodiment is formed by connecting a hydrolysis tank shell 3-1, a hydrolysis vertical stirrer 3-2, a temperature probe 3-3, a heating coil 3-4 and a support 3-5, wherein the support 3-5 is installed at the bottom of the cylindrical hollow hydrolysis tank shell 3-1, the hydrolysis vertical stirrer 3-2 is installed inside the hydrolysis tank shell 3-1, and blades of the hydrolysis vertical stirrer 3-2 are helical blades, so that a vertical component force along the axial direction of a stirring rod and a horizontal component force perpendicular to a stirring shaft are generated in the rotation process, and sludge in the tank can be uniformly heated. The inner side wall of the hydrolysis tank shell 3-1 is provided with heating coils 3-4, the heat source of the heating coils 3-4 comes from a heat exchange system 8, and the heating coils are uniformly arranged on the inner side wall of the hydrolysis tank shell 3-1, so that the temperature of sludge in the tank is kept consistent. The top of the hydrolysis tank shell 3-1 is provided with a temperature probe 3-3, so that the temperature in the tank is stably maintained at 60 +/-1 ℃, and the sludge pyrolysis efficiency is improved.

The alkaline hydrolysis tank 1 and the low temperature pyrolysis tank 3 provided by this embodiment can accelerate the sludge cell wall dissolution in a short time and at a low temperature, and increase the SCOD of the sludge to 36.8kg/m after the treatment³The pH was lowered to 9. The final accumulated methane yield of the treated sludge reaches 1.45m³The fermentation period required for the accumulated methane production to reach the stability is shortened to 15 days per kg of sludge.