Method for grading recovery of waste heat in production of organic solid waste hydrothermal carbonization

Abstract

The application discloses a kind of organic solid waste hydrothermal carbonization production waste heat grading recovery method, belong to organic solid waste processing technical field, including primary energy recovery and utilization unit and secondary energy recovery and utilization unit, in primary energy recovery and utilization unit, high-grade heat in material is recovered by adopting heat conducting oil medium indirect heat exchange, return hydrothermal carbonization system;In secondary energy recovery and utilization unit, low-grade heat in material is recovered by adopting water medium indirect heat exchange, and is used for the drying of biochar.The application adopts two-stage waste heat recovery and utilization unit to recover and utilize high-grade heat and low-grade heat respectively, primary waste heat recovery and utilization high-grade heat and return to hydrothermal carbonization system, reduce system processing energy consumption;Secondary waste heat recovery and utilization low-grade heat, for the drying of biochar, further reduce the moisture content of biochar.The application can make full use of the waste heat of organic solid waste hydrothermal carbonization system, reduce processing energy consumption and production cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic solid waste treatment, and particularly relates to a method for grading recovery of waste heat in hydrothermal carbonization production of organic solid waste. BACKGROUND

[0002] The hydrothermal carbonization (HTC) technology is generated on the basis of the high-pressure chemical theory proposed by Friedrich Bergius, a German chemist who won the Nobel Prize in Chemistry in 1931. The method simulates the process of the generation of coal, petroleum and natural gas in nature, and reproduces the reaction process which takes millions of years in nature within a few hours under appropriate temperature, pressure and pH conditions. The HTC reaction is the carbonization of organic materials (such as biological waste or sludge) into HTC biochar within a few hours under the conditions of excluding air and adding catalysts at a temperature of 180-200℃ and a pressure of 20-35 bar. The method is carried out in a water-containing environment, so it does not need to dry the input materials, and the method is particularly suitable for water-rich biological organic waste and sludge. After dehydration of the HTC product, the HTC biochar has a low water content, and due to its high calorific value, it can be used for climate-friendly power generation in coal-fired power plants, or as a substitute for fossil fuels in cement plants or waste incineration plants.

[0003] The industrialization of the hydrothermal carbonization system can adopt batch production or continuous production. The batch production is to send the materials into the reaction kettle in batches, heat in a closed environment, and the materials undergo the hydrothermal carbonization reaction under fixed temperature and pressure. After the reaction time, the reaction product is discharged, and the next batch is processed, and the cycle is repeated. The continuous production is that the materials continuously enter the reaction system, stay in the reactor for a fixed time, and then continuously discharge. The batch production is generally only used for research and small-scale production application due to low efficiency, and is not adopted by industrial large-scale production. The continuous production is suitable for industrial large-scale production application. At present, there are few cases of continuous hydrothermal carbonization production, mainly because the process is complex, the heat recovery efficiency is not high, especially the low-grade waste heat recovery utilization efficiency is not high, resulting in high energy consumption and high treatment cost of hydrothermal carbonization. SUMMARY

[0004] The purpose of the present application is to provide a method for grading recovery of waste heat in hydrothermal carbonization production of organic solid waste, which aims to solve the technical problems of complex process, low heat recovery efficiency, high energy consumption and high treatment cost in continuous hydrothermal carbonization production in the prior art.

[0005] To solve the above technical problems, the technical solution adopted by the present application is:

[0006] A method for grading recovery of waste heat in the production of organic solid waste hydrothermal carbonization, comprising a primary energy recovery and utilization unit and a secondary energy recovery and utilization unit,

[0007] In the primary energy recovery and utilization unit, high-grade heat in the material is recovered by indirect heat exchange with heat conducting oil medium, and returned to the hydrothermal carbonization system; in the secondary energy recovery and utilization unit, low-grade heat in the material is recovered by indirect heat exchange with water medium, and used for drying of biochar.

[0008] Preferably, the primary energy recovery and utilization unit comprises a hydrothermal carbonization system and a heat conducting oil heat exchanger, the material in the hydrothermal carbonization system is transferred to the heat conducting oil heat exchanger for cooling, and the material is transferred from high temperature to low temperature; the heat conducting oil is used as heat exchange medium, the transfer direction of the heat conducting oil in the heat conducting oil heat exchanger is opposite to that of the material, the heat conducting oil is used to reduce the temperature of the material to recover heat, the heat conducting oil is transferred from low temperature to high temperature, and then returned to the hydrothermal carbonization system for recycling.

[0009] Preferably, the hydrothermal carbonization system comprises a material storage bin, a booster feed pump, a front-end preheating pipe and a reaction kettle with a stirrer, the organic solid waste in the material storage bin is delivered to the front-end preheating pipe by the booster feed pump for preheating, and the preheated material is then introduced into the reaction kettle for hydrothermal carbonization reaction.

[0010] Preferably, the secondary energy recovery and utilization unit comprises a water tank, a water pump, a water heat exchanger, a biochar slurry storage tank, a solid-liquid separator, a biochar cake crusher, a dryer and a dried material storage bin, the biochar slurry discharged from the heat conducting oil heat exchanger is introduced into the water heat exchanger, then discharged to the biochar slurry buffer tank by a pressure relief discharge pump, and then introduced into the solid-liquid separator for solid-liquid separation, the separated biochar cake is crushed by the biochar cake crusher, the crushed biochar is introduced into the dryer for evaporation of water, and the dried material is introduced into the dried material storage bin;

[0011] The biochar slurry is transferred to the water heat exchanger for further cooling after being cooled in the primary energy recovery and utilization unit, water is delivered from the water tank to the water heat exchanger by the water pump as heat exchange medium, the transfer direction of the water and the biochar slurry in the water heat exchanger is opposite, the water is used to recover heat and then delivered to the dryer as heat supply medium, the transfer direction of the heat supply medium water in the dryer is consistent with that of the material, and finally the medium water output from the dryer is returned to the water tank for recycling; the dryer is provided with a vacuum pump for vacuumizing and discharging steam.

[0012] Preferably, the input temperature of the heat conducting oil in the heat conducting oil heat exchanger of the primary energy recovery and utilization unit is 60-100℃, and the output temperature is 140-190℃; the input temperature of the biochar slurry is 160-210℃, and the output temperature is 80-120℃.

[0013] Preferably, the input temperature of water in the water heat exchanger of the secondary energy recovery unit is 20-40℃, and the output temperature is 60-100℃; the input temperature of biochar slurry is 80-120℃, and the output temperature is 20-40℃; the input temperature of water medium in the heat exchange jacket of the dryer is 60-100℃, and the input temperature of broken biochar is 20-40℃.

[0014] Preferably, the working pressure of the dryer is 10-50kPa.

[0015] Preferably, the moisture content of the biochar cake separated by the solid-liquid separator is 20-40%, and the moisture content of the output material of the dryer is 5-15%.

[0016] Preferably, the particle size of the biochar cake after being broken by the biochar cake breaker is 0.01-1cm.

[0017] Preferably, the organic solid waste refers to dewatered sludge, plant straw or livestock and poultry manure.

[0018] The beneficial effects produced by the above technical solution are that, compared with the prior art, the present application recovers and utilizes high-grade heat and low-grade heat respectively by adopting two-stage waste heat recovery units, the recovery and utilization of the first-stage waste heat is high-grade heat recovery, the heat oil is recovered and directly used for the water heat carbonization system to supplement the heat for the water heat carbonization reaction and reduce the system processing energy consumption; the recovery and utilization of the second-stage waste heat is to recover low-grade heat by water and use it for drying biochar to further reduce the moisture content of biochar. The present application can fully utilize the waste heat of the organic solid waste water heat carbonization system, reduce the processing energy consumption and production cost. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0020] Figure 1 is a flowchart of the method for grading recovery of waste heat in the production of organic solid waste water heat carbonization provided by the embodiment of the present application;

[0021] Figure 2 is a structural schematic diagram of the first-stage energy recovery unit and the second-stage energy recovery unit in the embodiment of the present application;

[0022] Figure 3 is a structural schematic diagram of the water heat carbonization system in the embodiment of the present application;

[0023] In the figure: 1-material storage bin; 2-pressurized feeding pump; 3-front end preheating pipe; 4-reaction kettle; 5-stirrer; 6-heat conducting oil heat exchanger; 7-water heat exchanger; 8-water tank; 9-water pump; 10-biochar slurry; 11-pressure relief discharging pump; 12-biochar slurry buffer tank; 13-solid-liquid separator; 14-biochar cake crusher; 15-dryer; 16-heat exchange jacket; 17-vacuum pump; 18-dry material storage bin; 19-water heat carbonization system; 20-first stage waste heat recycling unit; 21-second stage waste heat recycling unit. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0025] Referring to Figure 1 , the present application provides a kind of organic solid waste water heat carbonization production waste heat grading recovery method, including first stage energy recycling unit 20 and second stage energy recycling unit 21,

[0026] In first stage energy recycling unit 20, high-grade heat in the material is recovered by indirect heat exchange of heat conducting oil medium, and returned to water heat carbonization system 19; in second stage energy recycling unit 21, low-grade heat in the material is recovered by indirect heat exchange of water medium, and used for drying of biochar.

[0027] In one specific embodiment of the present application, as Figure 2 shown, the first stage energy recycling unit 20 includes water heat carbonization system 19 and heat conducting oil heat exchanger 6, the material in the water heat carbonization system 19 is transferred to the heat conducting oil heat exchanger 6 for cooling, and the material is transferred from high temperature to low temperature; the heat conducting oil is used as heat exchange medium, and the transfer direction of the heat conducting oil in the heat conducting oil heat exchanger 6 is opposite to the transfer direction of the material, the heat conducting oil is used to reduce the temperature of the material to recover heat, the heat conducting oil is transferred from low temperature to high temperature, and then returned to the water heat carbonization system 19 for recycling.

[0028] As Figure 3As shown in the figure, the hydrothermal carbonization system 19 includes a material storage bin 1, a booster feed pump 2, a front-end preheating pipe 3 and a reaction kettle 4 with a stirrer 5, the organic solid waste in the material storage bin 1 is delivered to the front-end preheating pipe 3 by the booster feed pump 2 for preheating, and the preheated material is then subjected to hydrothermal carbonization reaction in the reaction kettle 4, which can reduce energy consumption and improve the reaction efficiency of the hydrothermal carbonization system. The reaction kettle is externally provided with a heat-conducting oil heating jacket, a heat-conducting oil heater is connected to the heat-conducting oil heating jacket through a heat-conducting oil pump for heating the reaction kettle, and the heat-conducting oil of the heat-conducting oil heat exchanger is communicated with the heat-conducting oil heating jacket through a heat-conducting oil pipe to supplement heat to the reaction kettle. The organic solid waste is subjected to hydrothermal carbonization reaction in the hydrothermal carbonization system, realizing wet carbonization reaction of organic matter under high temperature and high pressure environment, simulating the coal formation process in nature, and converting the organic matter into biochar in a few hours.

[0029] In one specific embodiment of the present application, as shown in the figure, Figure 2 As shown in the figure, the secondary energy recovery and utilization unit 21 includes a water tank 8, a water pump 9, a hydrothermal heat exchanger 7, a biochar slurry storage tank 12, a solid-liquid separator 13, a biochar cake crusher 14, a dryer 15 and a dried material storage bin 18, the biochar slurry discharged from the heat-conducting oil heat exchanger 6 enters the hydrothermal heat exchanger 7, is then discharged to the biochar slurry buffer tank 12 through a pressure relief discharge pump 11, is subjected to solid-liquid separation in the solid-liquid separator 13, the separated biochar cake enters the biochar cake crusher 14 for crushing, the crushed biochar enters the dryer 15 for evaporation of water, and the dried material enters the dried material storage bin 18. The heat transfer process is as shown in the figure, Figure 1 The water medium and the material transfer process are as follows:

[0030] The biochar slurry is transferred to the hydrothermal heat exchanger 7 for further cooling after being cooled in the primary energy recovery and utilization unit 20, water is delivered to the hydrothermal heat exchanger 7 from the water tank 8 through the water pump 9, the water and the biochar slurry are transferred in opposite directions in the hydrothermal heat exchanger 7, the water recovers heat and is delivered to the dryer 15 as a heat supply medium, the heat supply medium water and the material are transferred in the same direction in the dryer 15, and finally the medium water output from the dryer 15 is returned to the water tank 8 for recycling; the dryer is externally provided with a heat exchange jacket 16, the water medium output from the hydrothermal heat exchanger 7 flows through the heat exchange jacket 16 to exchange heat with the internal material, and the material is dried.

[0031] Since the heat value of biochar increases with the decrease of water content, further reducing the water content is an effective way to improve the heat value of biochar. The force between organic solid waste and water is relatively large, and the form of water is relatively complex. Taking municipal sludge as an example, there are bound water, mechanically bound water and free water. For sludge with a water content of less than 40%, water mainly exists in the form of bound water, and water molecules are not easy to escape. At present, the energy required for thermal drying and evaporation of sludge water includes four types: the energy required for water molecules to overcome chemical bonds, the energy required for water molecules to overcome the intermolecular physical force of sludge floc, the energy required for water molecules to overcome capillary force, and the energy required for water phase change. Compared with HTC biochar, the force between water and biochar is relatively small, the form of water is relatively simple, and the water molecules are relatively easy to escape. Therefore, the water in the thermal drying biochar is easier to remove than the water in the organic solid waste, and the energy consumption of biochar is significantly reduced.

[0032] In one embodiment of the present application, the input temperature of the heat transfer oil in the heat transfer oil heat exchanger 6 of the primary energy recovery unit 20 is 60-100℃, and the output temperature is 140-190℃; the material in the heat transfer oil heat exchanger 6 is biochar slurry, the input temperature of the biochar slurry is 160-210℃, and the output temperature is 80-120℃; the input temperature of the water in the water heat exchanger 7 of the secondary energy recovery unit 21 is 20-40℃, and the output temperature is 60-100℃; similarly, the material in the water heat exchanger 7 is biochar slurry, the input temperature of the biochar slurry is 80-120℃, and the output temperature is 20-40℃; the input temperature of the water medium in the heat exchange jacket 16 of the dryer 15 is 60-100℃, and the input temperature of the crushed biochar is 20-40℃. At the same time, the working pressure of the dryer 15 is 10-50kPa.

[0033] After the above treatment, the biochar cake separated by the solid-liquid separator 13 has a water content of 20-40%, and the particle size of the biochar cake after being crushed by the biochar cake crusher is 0.01-1cm. The dried material output by the vacuum dryer 15 has a water content of 5-15%, and the water content of the biochar can be reduced to below 10% according to actual needs.

[0034] The organic solid waste treated by the present application refers to dewatered sludge, plant straw, livestock and poultry manure, etc.

[0035] In summary, the present application is directed to the recovery and utilization of waste heat from hydrothermal carbonization, especially the recovery and utilization of low-grade heat. In combination with the characteristic that HTC biochar water molecules are easy to escape, the low-grade heat is used for low-temperature vacuum drying of HTC biochar, further reducing the moisture content of biochar and increasing the calorific value. The high-grade heat is directly recovered for the hydrothermal carbonization reaction system, reducing the energy consumption of the hydrothermal carbonization system. The present application can realize the reduction, harmlessness and stabilization of organic solid waste in one station, is conducive to resource utilization, and has low energy consumption and carbon emission.

[0036] In the above description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in other ways that are different from those described herein without departing from the spirit and scope of the present application, and those skilled in the art can make similar extensions without departing from the concept of the present application. Therefore, the present application is not limited to the above disclosed specific embodiments.

Claims

1. A method for grading recovery of waste heat produced by hydrothermal carbonization of organic solid waste, characterized in that: The energy recovery unit comprises a first energy recovery unit and a second energy recovery unit, In the first energy recovery unit, high-grade heat in the material is recovered by indirect heat exchange of the heat conducting oil medium, and returned to the hydrothermal carbonization system; in the second energy recovery unit, low-grade heat in the material is recovered by indirect heat exchange of the water medium, and used for drying the biochar; The first energy recovery unit comprises a hydrothermal carbonization system and a heat conducting oil heat exchanger, the material in the hydrothermal carbonization system is transferred to the heat conducting oil heat exchanger for cooling, and the material is transferred from high temperature to low temperature; the heat conducting oil is used as a heat exchange medium, the transfer direction of the heat conducting oil in the heat conducting oil heat exchanger is opposite to the transfer direction of the material, the heat conducting oil is used to reduce the temperature of the material to recover heat, the heat conducting oil is transferred from low temperature to high temperature, and then returned to the hydrothermal carbonization system for recycling; The hydrothermal carbonization system comprises a material storage bin, a booster feed pump, a front-end preheating pipe and a reaction kettle with a stirrer, the organic solid waste in the material storage bin is conveyed to the front-end preheating pipe by the booster feed pump for preheating, and the preheated material is then introduced into the reaction kettle for hydrothermal carbonization reaction; The input temperature of the heat conducting oil in the heat conducting oil heat exchanger of the first energy recovery unit is 60-100℃, and the output temperature is 140-190℃; the input temperature of the biochar slurry is 160-210℃, and the output temperature is 80-120℃; The second energy recovery unit comprises a water tank, a water pump, a water heat exchanger, a biochar slurry storage tank, a solid-liquid separator, a biochar cake crusher, a dryer and a dried material storage bin, the biochar slurry discharged from the heat conducting oil heat exchanger is introduced into the water heat exchanger, then discharged to the biochar slurry buffer tank through a pressure relief discharge pump, and then introduced into the solid-liquid separator for solid-liquid separation, the separated biochar cake is introduced into the biochar cake crusher for crushing, the crushed biochar is introduced into the dryer for evaporation of water, and the dried material is introduced into the dried material storage bin; The biochar cake separated by the solid-liquid separator has a water content of 20-40%, and the dried material output from the dryer has a water content of 5-15%; The biochar slurry is transferred to the water heat exchanger for further cooling after being cooled in the first energy recovery unit, water is conveyed from the water tank to the water heat exchanger by the water pump, the transfer direction of the water and the biochar slurry in the water heat exchanger is opposite, the water is used as a heat exchange medium, the water is conveyed to the dryer for heat supply after recovering heat, the transfer direction of the heat supply medium water in the dryer is consistent with the transfer direction of the material, and finally the medium water output from the dryer is returned to the water tank for recycling; the dryer is provided with a vacuum pump for vacuumizing and discharging steam; The input temperature of the water in the water heat exchanger of the second energy recovery unit is 20-40℃, and the output temperature is 60-100℃; the input temperature of the biochar slurry is 80-120℃, and the output temperature is 20-40℃; the input temperature of the water medium in the heat exchange jacket of the dryer is 60-100℃, and the input temperature of the crushed biochar is 20-40℃.

2. The method for grading recovery of waste heat from organic solid waste hydrochar production according to claim 1, characterized in that: The working pressure of the dryer is 10-50kPa.

3. The method for grading recovery of waste heat from organic solid waste hydrochar production according to claim 1, characterized in that: The particle size of the biochar cake crushed by the biochar cake crusher is 0.01-1cm.

4. The method for grading recovery of waste heat from production of organic solid waste hydrochar according to any one of claims 1-3, characterized in that: The organic solid waste refers to dewatered sludge, plant straw or livestock and poultry manure.

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