A method for resource disposal of organic solid waste based on a thermal hydrolysis-pyrolysis coupling process

Abstract

The application discloses a kind of based on thermal hydrolysis-pyrolysis coupling process organic solid waste resource disposal method, the present application is to solve the bottleneck problem of low sludge organic matter conversion efficiency and poor quality of resource product under the stress of melanin-like by-product, propose pyrolysis treatment to thermal hydrolysis sludge solid phase product, to improve pyrolysis reaction activity, improve the pore structure of biochar, inhibit the strategy of melanin-like.By low temperature, high temperature treatment after thermal hydrolysis sludge derived carbon has larger hysteresis ring, and it is mesoporous structure, total surface area, total pore volume significantly increases, so as to promote the development process of biochar pore structure volatile matter pyrolysis reaction activity.In addition, biochar derived dissolved organic matter can be degraded component is split, forms aromatic component, increases the aromaticity of biochar.At the same time, humic acid component in melanin-like is effectively fixed by biochar, and finally eliminates the inhibitory effect of melanin-like.The present application provides an effective strategy for high-quality product recovery in organic solid waste thermal hydrolysis-pyrolysis practical engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic solid waste resource recycling, and particularly relates to an organic solid waste resource treatment method based on a thermal hydrolysis-pyrolysis coupling process. BACKGROUND

[0002] Sludge, as a representative degradable organic solid waste, is continuously released and accumulated from wastewater treatment plants, which has threatened the global environmental ecosystem. Sludge is a typical complex heterogeneous system composed of water, ash, volatile matter, intracellular / extracellular polymers, etc. Due to the convergence of C, N, P and other nutrient substrates, the organic content of sludge reaches 30-60%, and it is rich in about 250-300 mg C / g total solid components, which is a promising energy recovery raw material. However, only 6.25% of the total sludge output is used for energy recovery every year. As the final "sink and source" of many exogenous pollutants (emerging persistent / difficult-to-degrade pollutants, PPCPs, etc.), sludge has potential exposure risks of pollution release and environmental toxicity. Sludge has large output, multiple media, complex structure and composition, and has both pollution and resource dual attributes. Therefore, how to choose sludge treatment strategies and resource recycling paths has become a top priority.

[0003] At present, the mainstream process of sludge disposal represented by "thermal hydrolysis + anaerobic digestion" is widely studied. Studies have shown that thermal hydrolysis induces sludge cell lysis and intracellular and extracellular organic matter release, providing available dissolved organic waste for anaerobic digestion, thereby significantly improving the efficiency of sludge organic matter anaerobic conversion and the potential for high-value product (CH4, H2, polymeric fatty acids, etc.) recovery. Thermal hydrolysis breaks through the bottleneck problem of long reaction period (> 30d) and low organic component conversion rate (40-50%) of sludge anaerobic digestion. Compared with low-temperature thermal hydrolysis, high-temperature conditions have more significant advantages due to more dissolved organic substrates and biodegradability. However, Maillard reaction occurs between reducing sugar carbonyl and amino acid, peptide, protein, amine, etc. components carrying amino groups, which generates dark brown macromolecular refractory substance melanoidin through a series of reactions such as cyclization, dehydration, transaldolization, isomerization, and condensation. The biological toxicity of refractory melanoidin 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 as a new emerging technology for efficient and low-carbon sludge disposal has attracted widespread attention. Under anaerobic high-temperature (~ 1000℃) conditions, pyrolysis effectively destroys the structure of recalcitrant refractory compounds through a rapid gradient heating mechanism, which can remove more than 90% of macromolecular refractory substances within a few hours, while producing biochar, bio-oil, gas and other multi-form high-value products. Related studies have found that melanoidin can be effectively decomposed into biochar, bio-oil, gas and other products at a hydrothermal liquefaction temperature of 200℃ or above, but the negative impact of toxic gas ammonia release cannot be avoided. SUMMARY

[0005] The present application aims at the bottleneck problem of low sludge organic matter conversion efficiency and poor quality of by-product under melanin-like by-product stress, and further provides an organic solid waste resource disposal method based on a hydrothermal-hydrolysis coupling process, so as to realize the regulation of sludge organic matter efficient conversion limitation and the recovery of multi-form high-value products.

[0006] The technical scheme adopted by the present application to solve the above problems is:

[0007] The organic solid waste resource disposal method based on the hydrothermal-hydrolysis coupling process comprises the following steps:

[0008] Step 1, the raw sludge is collected from the secondary sedimentation tank of a sewage treatment plant, the sludge is sieved using a 20-mesh sieve to remove large-particle inorganic matter and impurities, and the sieved sludge is placed at 4℃ for 24 hours, after obvious stratification appears at the sludge-water interface, the supernatant is slowly poured off to obtain concentrated sludge;

[0009] Step 2, the concentrated sludge is subjected to hydrothermal treatment in a hydrothermal reactor under high temperature and high pressure conditions, after the reactor is cooled, a hydrothermal sludge sample is taken out for centrifugal treatment to obtain a solid-phase product, the solid-phase product is freeze-dried and ground to obtain a sludge powder sample;

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

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

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

[0013] Step 3, the sludge powder sample obtained in step 2 is subjected to pyrolysis treatment by a pyrolysis reactor.

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

[0015] Finally, the produced biochar, tar and gas are collected respectively, the solid residue is biochar which can be directly collected, the tar is collected in an ice water bath with CH2Cl2 solution, and the gas is collected by a gas collection bag.

[0016] Further, after step 3 pyrolysis treatment, the melanoidin produced is fixed by biochar in the form of nitrogen, forming the aromatic heterocyclic structure of biochar.

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

[0018] 1. Thermal hydrolysis promotes the collapse of the internal structure of sludge, the loosening of the surface, and the retention of inorganic minerals in the solid phase, providing an effective way for the spatial reorganization of biochar. Melanoidin, as an important intermediate by-product produced in the liquid phase of sludge thermal hydrolysis, is a class of highly reactive unsaturated heterocyclic nitrogen-containing substances that further migrate from the liquid phase to the solid phase and combine with sludge solid-phase proteins, polysaccharides, and other components in the form of non-covalent bonds. After pyrolysis treatment, melanoidin is fixed by biochar in the form of nitrogen, forming the aromatic heterocyclic structure of biochar.

[0019] 2. Melanoidin further combines with endogenous metals in biochar, strengthening the catalytic activity of biochar, and the special pore structure of biochar releases volatile matter to further crack and generate bio-oil. The dissolution, hydrolysis, and denitrification during thermal hydrolysis promote the formation of fatty hydrocarbons, acids / esters in bio-oil, and reduce nitrogen and sulfur compounds. Among them, the thermal oil contains unsaturated heterocyclic Maillard products (pyrrole, pyridine, etc.) in the form of nitrogen, which is a typical stable nitrogen structure of melanoidin. Therefore, due to the fixation of melanoidin by biochar, the volatilization of biochar is promoted and cracked into low-nitrogen high-quality bio-oil.

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

[0021] 4. The thermal hydrolysis coupled with pyrolysis treatment in the present application is a feasible strategy to solve the efficient recovery of sludge organic matter and the negative effects of recalcitrant melanoidin. On the one hand, the sludge solid-phase retained organic matter hindered by melanoidin is generated through rapid thermal cracking to produce resourceful high-value products. On the other hand, the melanoidin with electronegativity and the cationic metals in the Maillard reaction are combined through coagulation, which can effectively inhibit the further browning of melanoidin. Therefore, the thermal hydrolysis coupled with pyrolysis treatment provides a new idea for the efficient value-added and recycling of sludge resources. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the thermal hydrolysis-pyrolysis coupling process flowchart of the present application;

[0023] Figure 2 is the biochar pore structure type chart in the present application;

[0024] Figure 3 is the biochar-derived dissolved organic matter in the present application. DETAILED DESCRIPTION

[0025] Example 1

[0026] The process flow diagram of wet organic solid waste hydrothermal- pyrolysis coupling is shown in Figure 1. Figure 1 The powder sample was pyrolyzed by a fixed-bed pyrolysis reactor. The pyrolysis chamber was purged with nitrogen at a flow rate of 150 mL / min for 10 min. Then, a certain amount of sludge powder sample was pyrolyzed at 500℃ and 700℃, respectively, with a nitrogen flow rate of 100 mL / min and a heating rate of 20℃ / min for 20 min. Finally, the solid residue was biochar, the tar was collected in an ice water bath with CH2Cl2solution, and the gas was collected by a gas bag.

[0027] Example 2

[0028] In order to analyze the pore characteristics of biochar, a physical and chemical adsorption instrument (AGILENT 7890A, USA) was used, and the biochar pore structure type is shown in Figure 2. Figure 2 .

[0029] The hydrothermally pyrolyzed sludge-derived carbon showed type IV and H3 hysteresis loops, with a mesoporous structure of large hysteresis loops, and the total surface area and total pore volume increased by 1.20 times and 0.99 times, respectively. Hydrothermal pyrolysis also formed microporous structure, which promoted 1.21 times of micropore area and 1.11 times of micropore volume increase at 500℃. Therefore, hydrothermal pyrolysis effectively improved the pore structure of pyrolytic biochar by promoting the collapse of the internal structure of sludge. The above results confirmed that hydrothermal pyrolysis 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 had a significant advantage in terms of volatile matter pyrolysis reactivity.

[0030] Example 3

[0031] The extraction of dissolved organic matter from hydrothermally pyrolyzed sludge-derived carbon was carried out in three steps.

[0032] 1. 0.25 mg of biochar was dispersed in 25 mL of ultrapure water in a centrifuge tube, and then placed in a shaker (room temperature, 150 rpm) for 2 hours.

[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 further calculation of organic matter partition (I-V) and fluorescence response percentage.

[0035] As Figure 3The potential relationship between biochar structure and organic matter composition was investigated by biochar-derived dissolved organic matter analysis. Under the condition of thermal hydrolysis, the fluorescence intensity of peak A (degradable component) and peak B (refractory component) was greatly weakened. This result indicates that the decrease of degradable component directly leads to the formation of refractory aromatic component. However, the content of refractory humic acid in Maillard reaction remains almost unchanged, indicating that the stable biochar structure effectively reduces the reactivity of melanoidins.

[0036] Based on the published patent (CN 108423959A), the thermal hydrolysis-pyrolysis coupling process proposed by the present application is suitable for high-moisture solid waste. With the by-product melanoidin as the key factor, the hindering effect of melanoidin on the decomposition of solid phase and the volatilization of sludge in thermal hydrolysis is solved. At the same time, melanoidin has a significant promoting effect on the derived carbon, bio-oil and high-value gas of thermal hydrolysis sludge solid phase.

[0037] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent replacement and improvement of the above embodiments within the scope of the technical solution of the present application, according to the technical essence of the present application, within the spirit and principles of the present application, are all within the protection scope of the present application.

Claims

1. A method for resourceful disposal of organic solid waste based on a hydrothermal-pyrolysis coupled process, characterized in that, The method comprises the following steps: Step 1: sludge pretreatment: Collecting sludge, screening the sludge and standing for 24 h to obtain concentrated sludge; Step 2: thermal hydrolysis treatment: The concentrated sludge is subjected to hydrothermal treatment in a thermal hydrolysis reactor under high temperature and high pressure conditions, and after the reaction is completed, it is cooled and subjected to centrifugal treatment to obtain a solid phase product, which is freeze-dried and ground to obtain a sludge powder sample; The thermal hydrolysis treatment process is as follows: the thermal hydrolysis temperature is low temperature 70-90 ℃ and high temperature 160-180 ℃, Step 3: pyrolysis treatment: The sludge powder sample obtained in step 2 is subjected to pyrolysis treatment by a pyrolysis reactor, and the pyrolysis treatment temperature is 500 ℃; After pyrolysis treatment, the melanoid-like substance is fixed in the form of nitrogen in the biochar, forming the aromatic heterocyclic structure of the biochar, and being cracked into low-nitrogen high-quality bio-oil.

2. The method for resourceful disposal of organic solid waste based on the coupling process of thermal hydrolysis and pyrolysis according to claim 1, characterized in that, In step 1, the raw sludge is screened through a 20-mesh screen to remove large particle impurities, and is then stood at 4 ℃ for 24 h; after obvious stratification appears at the sludge-water interface, the supernatant is slowly poured off to obtain concentrated sludge.

3. The method according to claim 1, wherein the method is characterized in that, In step 2, the pressure was 50 x 10 3 -600 x 10 3 Pa for 1 h; The centrifugal treatment process is as follows: the rotation speed is 10000 rpm, and the centrifugal time is 10 min; The freeze-drying temperature of the solid phase product is -55 ℃, and the freezing time is 24 hours.

4. The method according to claim 1, wherein the method is characterized in that, During the pyrolysis treatment, the pyrolysis chamber is purged with nitrogen at a flow rate of 150 mL / min for 10 minutes to maintain an oxygen-free environment; the heating rate is 20 ℃ / min, and the pyrolysis time is 20 minutes.

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

Images