Organic solid waste recycling treatment method based on pyrohydrolysis-pyrolysis coupling process

Abstract

The invention relates to an organic solid waste recycling treatment method based on a pyrohydrolysis-pyrolysis coupling process, and provides pyrohydrolysis sludge solid-phase product pyrolysis treatment for solving the bottleneck problems of low conversion efficiency of sludge organic matters and poor quality of resource products under the stress of melanin-like byproducts. Therefore, the pyrolysis reaction activity is improved, the pore structure of the biochar is improved, and melanin is inhibited. The pyrohydrolysis sludge derived carbon subjected to low-temperature and high-temperature treatment has a relatively large hysteresis ring and is of a mesoporous structure, and the total surface area and the total pore volume are remarkably increased, so that the pyrolytic reaction activity of volatile components in the development process of a biochar pore structure is promoted. In addition, the biochar derived soluble organic matter degradable component is cracked to form an aromatic component, so that the aromaticity of the biochar is increased. Meanwhile, the humic acid component in the melanoid is effectively fixed by the charcoal, and the melanoid inhibition effect is finally eliminated. The method provides an effective strategy for high-quality product recovery of organic solid waste thermal hydrolysis-pyrolysis practical engineering.

Description

Technical Field

[0001] The invention relates to the technical field of organic solid waste resource recycling, and in particular to an organic solid waste resource disposal method based on a thermal hydrolysis-thermal decomposition coupling process. Background Art

[0002] As a representative degradable organic solid waste, sludge is continuously released and accumulated from sewage treatment plants for a long time, threatening the global environmental ecosystem. Sludge is a typical complex heterogeneous system composed of multiple media such as water, ash, volatile matter, intracellular / extracellular polymers, etc. Because it gathers nutrient matrices such as C, N, and P, the organic content of sludge reaches 30–60%, and it is rich in about 250–300 mg C / g total solid components, making it a promising raw material for energy recovery. However, the sludge used for energy recovery each year only accounts for 6.25% of the total sludge output. As the final "sink and source" of many exogenous pollutants (emerging persistent / refractory pollutants, PPCPs, etc.), sludge has the potential exposure risk of easy release of pollution and environmental toxicity. Sludge has large output, multiple media, complex structure and composition, and has both pollution and resource attributes. Therefore, how to choose sludge treatment strategies and resource recycling paths has become a top priority.

[0003] At present, the mainstream sludge treatment process represented by "thermal hydrolysis + anaerobic digestion" has been widely studied. Studies have shown that thermal hydrolysis can provide soluble organic waste for anaerobic digestion by inducing sludge cell lysis and releasing intracellular and extracellular organic matter, thereby significantly improving the anaerobic conversion efficiency of sludge organic matter and the production of high-value products (CH 4 , H 2 , multi-chain fatty acids, etc.) recovery potential. Thermal hydrolysis has broken through the bottleneck problems of long reaction cycle (>30d) and low conversion rate of organic components (40-50%) of anaerobic digestion of sludge. Compared with low-temperature thermal hydrolysis, high-temperature conditions have significant advantages due to more soluble organic substrates and biodegradability. However, the Maillard reaction occurs between the carbonyl group of reducing sugars and amino acids, peptides, proteins, amines and other components carrying amino groups, and dark brown macromolecular refractory melanin is generated through a series of reactions such as cyclization, dehydration, reverse aldehyde formation, isomerization, and condensation. The biological toxicity of refractory melanin has an adverse effect on the activity of functional enzymes and anaerobic bacteria, thereby reducing the efficiency of anaerobic digestion, which has become a key bottleneck restricting the further application of thermal hydrolysis technology.

[0004] Recently, pyrolysis has attracted widespread attention as an emerging technology for efficient and low-carbon sludge disposal. Under high temperature (~1000°C) conditions without oxygen, pyrolysis effectively destroys the structure of stubborn and refractory compounds through a rapid gradient heating mechanism, and can achieve more than 90% removal of large molecular refractory substances within a few hours, while producing multi-form high-value products such as biochar, bio-oil, and gas. Related studies have found that melanin can be effectively decomposed into biochar, bio-oil, gas and other products when the hydrothermal liquefaction temperature reaches above 200°C, but the negative impact of the release of toxic gas ammonia cannot be avoided. Summary of the invention

[0005] The present invention addresses the bottleneck problems of low sludge organic matter conversion efficiency and poor resource product quality under the stress of melanin-like byproducts, and further provides an organic solid waste resource disposal method based on a thermal hydrolysis-thermal decomposition coupling process, so as to achieve the regulation of limiting factors for efficient conversion of sludge organic matter and the recovery of multi-form high-value products.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] The method for resource disposal of organic solid waste based on thermal hydrolysis-thermal decomposition coupling process of the present invention comprises the following steps:

[0008] Step 1: The original sludge is collected from the secondary sedimentation tank of the sewage treatment plant, and the sludge is sieved with a 20-mesh sieve to remove large inorganic particles and impurities. The sieved sludge is left to stand at 4°C for 24 hours. After obvious stratification occurs at the mud-water interface, the supernatant is slowly poured off to obtain concentrated sludge;

[0009] Step 2, subjecting the concentrated sludge to hydrothermal treatment under high temperature and high pressure conditions in a thermal hydrolysis reactor, after the reactor is cooled, taking out the thermal hydrolysis sludge sample and subjecting it to centrifugal treatment to obtain a solid phase product, and freeze-drying and grinding the solid phase product to obtain a sludge powder sample;

[0010] The thermal hydrolysis process is as follows: the thermal hydrolysis temperature is 70-90℃ at low temperature, 160-180℃ at high temperature, and the pressure is 50×10 3 -600×10 3 Pa, reaction time is 1h;

[0011] The centrifugal treatment process is: the rotation speed is 10000rpm, and the centrifugal time is 10min;

[0012] The freeze-drying temperature of the solid phase product is -55°C, and the freezing time is 24 hours.

[0013] Step 3: The sludge powder sample obtained in step 2 is subjected to pyrolysis treatment by passing it through a pyrolysis reactor.

[0014] During the pyrolysis treatment, nitrogen was purged in the pyrolysis chamber at a flow rate of 150 mL per minute for 10 minutes; then, a certain amount of sludge powder sample was pyrolyzed at 500°C and 700°C for 20 minutes at a nitrogen flow rate of 100 mL / min and a heating rate of 20°C / min;

[0015] Finally, the generated biochar, tar and gas were collected separately. The solid residue was biochar which could be collected directly, and the tar was precipitated with CH in an ice water bath. 2 Cl 2 The solution is collected and the gas is collected through a gas collection bag.

[0016] Furthermore, after the pyrolysis treatment in step 3, the produced melanin is fixed by the biochar in a nitrogen-containing form to form an aromatic heterocyclic structure of the biochar.

[0017] The beneficial effects of the present invention are:

[0018] 1. Thermal hydrolysis promotes the collapse of the internal structure of sludge, loosening of the surface, and retention of inorganic minerals in the solid phase, providing an effective way to reorganize the spatial configuration of derived biochar. Melanoids, as an important intermediate byproduct of the liquid phase of thermal hydrolysis of sludge, are a class of highly reactive unsaturated heterocyclic nitrogen-containing substances, which further migrate from the liquid phase to the solid phase and bind to the solid phase proteins, polysaccharides and other components of the sludge in the form of non-covalent bonds. After thermal decomposition, melanoids are fixed by biochar in a nitrogen-containing form to form the aromatic heterocyclic structure of biochar.

[0019] 2. Melanoids further combine with endogenous metals in biochar to enhance the catalytic activity of biochar reaction. The volatiles precipitated from the special pore structure of biochar are further cracked to generate bio-oil. The dissolution, hydrolysis and denitrification during the thermal hydrolysis process promote the formation of aliphatic hydrocarbons and acids / esters in bio-oil, and reduce nitrogen- and sulfur-containing compounds. Among them, pyrolysis oil contains unsaturated heterocyclic Maillard products (pyrrole, pyridine, etc.) in the form of nitrogen, which is a typical melanoid stable nitrogen structure. Therefore, since melanoids are fixed by biochar, the volatilization of biochar is promoted and cracked into low-nitrogen high-quality bio-oil.

[0020] 3. The present invention utilizes the superior catalytic activity of melanin and its ability to bind to endogenous metals in sludge to prepare high-quality biochar bio-oil, and the bio-oil is further cracked and reorganized to generate high-grade synthetic gas. In addition, the negative effects of melanin are eliminated.

[0021] 4. The hot water hydrolysis coupled with pyrolysis treatment of the present invention is a feasible strategy to solve the negative effects of the sludge organic matter efficient recovery and difficult-to-degrade melanin. On the one hand, the solid-phase organic matter of the sludge blocked by melanin is rapidly pyrolyzed to generate resource-based high-value products. On the other hand, the electronegative melanin and the Maillard reaction intermediates are combined with cationic metals through coagulation, which can effectively inhibit the further browning of melanin. Therefore, the hot water hydrolysis coupled with pyrolysis treatment provides a new idea for the efficient value-added and recycling of sludge resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a thermal hydrolysis-thermal decomposition coupling process flow chart of the present invention;

[0023] Figure 2 is a diagram of the pore structure types of biochar in the present invention;

[0024] Figure 3 It is the biochar-derived dissolved organic matter of the present invention. DETAILED DESCRIPTION

[0025] Example 1

[0026] See the process flow chart of thermal hydrolysis-thermal decomposition coupling of wet organic solid waste Figure 1 The powder samples were pyrolyzed in a fixed bed pyrolysis reactor. The pyrolysis chamber was purged with nitrogen at a flow rate of 150 mL per minute for 10 minutes. Then, a certain amount of sludge powder samples were pyrolyzed at 500°C and 700°C for 20 minutes at a nitrogen flow rate of 100 mL / min and a heating rate of 20°C / min. Finally, the solid residue was biochar, and the tar was heated in an ice water bath with CH 2 Cl 2 The solution is collected and the gas is collected through a gas collection bag.

[0027] Example 2

[0028] In order to analyze the pore characteristics of biochar, a physical and chemical adsorption instrument (AGILENT7890A, USA) was used. The pore structure types of biochar are shown in Figure 2 .

[0029] Thermal hydrolysis sludge-derived carbon exhibited type IV and H3 hysteresis loops, a mesoporous structure with larger hysteresis loops, and an increase of 1.20 times and 0.99 times in total surface area and total pore volume, respectively. Thermal hydrolysis also formed a microporous structure, which promoted a 1.21-fold increase in micropore area and 1.11-fold increase in micropore volume at 500°C. Therefore, thermal hydrolysis effectively improved the pore structure of pyrolytic biochar by promoting the collapse of the internal structure of sludge. The above results confirmed that thermal hydrolysis effectively improved the pore structure of pyrolytic biochar by promoting the collapse of the internal structure of sludge. In this biochar configuration, the larger pore distribution has a significant advantage in the pyrolysis reactivity of volatiles.

[0030] Example 3

[0031] The extraction of dissolved organic matter from thermal hydrolysis sludge-derived charcoal was carried out in three steps.

[0032] 1. Disperse 0.25 mg of biochar in 25 mL of ultrapure water in a centrifuge tube and place it in a shaker (room temperature, 150 rpm) for 2 h.

[0033] 2. After centrifugation, the supernatant was filtered through a 0.22 μm membrane for analysis.

[0034] 3. The fluorescence intensity of dissolved organic matter components was measured using a fluorescence spectrometer (FL 6500, USA) at an emission wavelength of 200-600 nm and an excitation wavelength, and the organic matter partition (I-V) and fluorescence response percentage were further calculated.

[0035] like Figure 3 As shown in Figure 2, the potential relationship between biochar structure and organic matter composition was investigated by biochar-derived dissolved organic matter analysis. Under thermal hydrolysis conditions, the fluorescence intensities of peak A (degradable components) and peak B (refractory components) were greatly weakened, respectively. This result indicates that the reduction of degradable components directly leads to the formation of refractory aromatic components. However, the content of refractory humic acid in the Maillard reaction remained almost unchanged, indicating that the stable biochar structure effectively mitigated the reactivity of melanin-like substances.

[0036] Based on the published patent (CN 108423959A), the thermal hydrolysis-thermal decomposition coupling process proposed in the present invention is suitable for high-water-content solid waste. The byproduct melanin is used as the key factor to solve the obstruction of melanin on the solid phase decomposition and volatilization analysis of thermal hydrolysis sludge. At the same time, melanin has a significant promoting effect on the solid phase derived carbon, bio-oil and high-value gas of thermal hydrolysis sludge.

[0037] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for resource disposal of organic solid waste based on thermal hydrolysis-thermal decomposition coupling process, characterized in that: The method comprises the following steps: Step 1 Sludge pretreatment: Collect the sludge, sieve it and let it stand for 24 hours to obtain concentrated sludge; Step 2: Thermal hydrolysis treatment: The concentrated sludge is subjected to hydrothermal treatment under high temperature and high pressure conditions in a thermal hydrolysis reactor, cooled after the reaction is completed, and centrifuged to obtain a solid phase product, and the solid phase product is freeze-dried and ground to obtain a sludge powder sample; Step 3 Pyrolysis treatment: The sludge powder sample obtained in step 2 is subjected to pyrolysis treatment by passing through a pyrolysis reactor.

2. The method for resource disposal of organic solid waste based on thermal hydrolysis-thermal decomposition coupling process according to claim 1 is characterized in that: In step 1, the original sludge is sieved through a 20-mesh sieve to remove large particles of impurities, and is allowed to stand at 4°C for 24 hours. After obvious stratification occurs at the mud-water interface, the supernatant is slowly poured off to obtain concentrated sludge.

3. The method for resource disposal of organic solid waste based on thermal hydrolysis-thermal decomposition coupling process according to claim 1 is characterized in that: In step 2, the thermal hydrolysis process is as follows: the thermal hydrolysis temperature is 70-90°C at low temperature, 160-180°C at high temperature, and the pressure is 50×10 3 -600×10 3 Pa, reaction time is 1h; The centrifugal treatment process is: the rotation speed is 10000rpm, and the centrifugal time is 10min; The freeze-drying temperature of the solid phase product is -55°C, and the freezing time is 24 hours.

4. The method for resource disposal of organic solid waste based on thermal hydrolysis-thermal decomposition coupling process according to claim 1 is characterized in that: During the pyrolysis treatment process, nitrogen is purged in the pyrolysis chamber at a flow rate of 150 mL / min for 10 minutes to maintain an oxygen-free environment; the pyrolysis treatment temperature is 500° C.-700° C., the heating rate is 20° C. / min, and the pyrolysis time is 20 minutes.

5. The method for resource disposal of organic solid waste based on thermal hydrolysis-thermal decomposition coupling process according to claim 4 is characterized in that: The biochar, tar and gas produced by the pyrolysis treatment in step 3 are collected separately. The biochar is directly collected as a solid residue; the tar is collected by using a CH2Cl2 solution in an ice water bath; and the gas is collected by a gas collection bag.

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