Urban organic waste ultrahigh-temperature biological drying treatment method assisted by flue gas waste heat

Abstract

The invention relates to a flue gas waste heat assisted ultra-high-temperature biological drying treatment method for urban organic garbage. On the basis of acclimatized inoculation materials rich in extreme thermophilic flora, high-temperature flue gas is used as an external heat source to assist and synergistically reinforce garbage biological drying treatment with the extreme thermophilic flora, organic garbage is promoted to be cracked / hydrolyzed under the dual effects of biological ultra-high temperature and hydrolase, and water and carbon sources in the garbage are released; and meanwhile, air volume regulation and control are conducted in combination with temperature feedback, heat and mass transfer of the system is enhanced, negative influences of ventilation and heat dissipation are weakened synchronously, migration and removal of garbage water are accelerated, and the drying period is remarkably shortened. According to the method, extreme thermophilic bacteria are used for improving a system flora structure, an external heat source is combined for exciting biodegradation potential, the temperature and metabolism limitations of a traditional system are broken through, the purpose of coupling synergy is achieved, sludge degradation and moisture removal are accelerated, pollutants such as SO2 and NOX contained in high-temperature flue gas are removed, and the environmental protection effect is achieved. The method can be used as an effective way for reduction and resource utilization of urban organic garbage.

Description

Technical Field

[0001] The present invention belongs to the field of urban organic waste treatment, and relates to an energy-saving and efficient method for drying waste with high moisture content. The method uses flue gas waste heat as a heat source, stimulates the metabolic activity of extreme thermophilic bacteria through external heat assistance, forms a biological ultra-high temperature environment (>70°C), promotes the stabilization of organic waste and the in-situ removal of moisture, and removes SO2 and NO contained in the flue gas at the same time. X It can be used as an effective way to reduce urban organic waste and recycle it into resources. Background Art

[0002] With the advancement of urbanization in my country, the output of urban organic waste (such as food waste, urban sludge, etc.) has increased year by year, causing great pressure on my country's ecological environment. In view of the characteristics of urban organic waste, tapping its resource potential, promoting waste energy recycling, and realizing its harmless disposal have become urgent needs of my country's waste treatment industry. However, high water content is a bottleneck problem restricting the energy utilization of urban organic waste. Traditional thermal drying technology mainly relies on non-renewable energy, has high energy consumption, and low energy efficiency. Therefore, in order to meet the urgent needs of reducing the amount of urban organic waste and utilizing it for energy, it is urgent to seek an energy-saving, efficient, and environmentally friendly drying pretreatment technology.

[0003] Biodrying uses endogenous biological metabolic heat to drive water evaporation and promotes water vapor removal with the help of ventilation. It is considered to be a zero-secondary pollution, clean technology with good environmental benefits and application prospects. For example, patent 202010584395.X discloses a method of accelerating biodrying through segmented aeration, formulating different aeration amounts according to different stages to maximize the role of microbial heat production in removing moisture. However, due to the relatively low temperature of the traditional biological drying system, the treatment cycle is still relatively long (12-15d), and the moisture content of the product is still high (30%-35%), which cannot meet the needs of combustion utilization.

[0004] Thermophilic bacteria are the core of metabolic heat production in the biological drying system. Thermophilic bacteria in conventional fermentation systems are mostly facultative or obligate thermophiles, and have certain temperature limitations (<70°C). As a special type of thermophilic bacteria, extreme thermophiles have high metabolic activity and strong heat production performance, and have attracted widespread attention in the field of ultra-high temperature fermentation of garbage. For example, patent 201710786427.2 discloses an ultra-high temperature composting method for treating vegetable waste. By inoculating a composting composite bacterial agent, a maximum compost temperature of more than 70°C is achieved, potential pathogens are inactivated, and the humus conversion of vegetable waste is completed at the same time. However, the microorganisms in the ultra-high temperature fermentation system are self-regulated by heat, and the bacterial community structure constantly evolves during the fermentation process, which cannot maintain a stable supply of heat production in the system, resulting in a shorter high temperature period in the treatment process.

[0005] The inventors' previous studies have found that external heat source assistance can effectively enhance the heat production of carbon source metabolism in the biological drying system (Chemosphere, 2021, 272: 129875; Waste Management, 2018, 80: 327-338). External heat sources can stabilize the structure of functional bacterial communities, stimulate biodegradation potential, enhance the synergistic metabolism of system flora, achieve heat production efficiency enhancement of carbon source degradation, maintain stable high-temperature operation of the system, maintain bioheat dominance to promote water evaporation in the system, and significantly shorten the biological drying cycle. However, the energy consumption of external heat assistance through electric heating is high, the heat exchanger can recover waste heat, and the heating is carried out through the reactor heat conduction method, and the heat transfer efficiency between materials is low. Therefore, in order to achieve rapid startup of the biological drying system, it is still necessary to seek an energy-saving and efficient heat assistance method.

[0006] Incinerators or boilers in waste incineration plants, coal-fired power plants, etc. will emit a large amount of high-temperature flue gas during combustion. After heat exchange and dust removal, the flue gas temperature can still reach 150-200°C, which has a certain heat recovery potential. At the same time, the flue gas contains a large amount of SO2, NO X Pollutants such as sulfur dioxide and nitrogen dioxide need to be removed and denitrated later, and the cost of flue gas purification is relatively high. Studies have found that pollutants in flue gas can be effectively removed through a biological aerobic fermentation system (Chen Feng, Research and Application of High-Temperature Aerobic Biological Drying Technology for Domestic Waste, South China University of Technology), which can remove odorous pollutants in garbage without causing harm to the surrounding environment. It can be seen that the waste heat of high-temperature flue gas can not only provide a suitable survival temperature for thermophilic bacteria in the biological drying process, drive water evaporation in situ, but also further purify pollutants in flue gas through biological metabolism.

[0007] In view of the good metabolic potential of extreme thermophiles in the biological drying system and the energy-saving advantages of utilizing the waste heat of high-temperature flue gas, the inventors proposed using high-temperature flue gas to assist in heating, stimulate the metabolism and heat production of thermophilic bacteria, extend the high-temperature period of biological drying, promote garbage drying through biological ultra-high temperature, give full play to the respective advantages of biological drying and hot air drying technology, and provide a new strategy for efficient and energy-saving drying of urban organic waste. Summary of the invention

[0008] The present invention provides a method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat. Based on the domesticated inoculated material rich in extreme thermophilic bacteria, the flue gas waste heat is used as an external heat source to stimulate the metabolic activity of the thermophilic bacteria, promote the degradation and heat production of the garbage carbon source, and combine the temperature feedback mechanism to compound the flue gas and air and control the air volume. The biological ultra-high temperature (≥70°C) is used to promote the evaporation and removal of water, which is expected to achieve the purpose of coupling the external heat assistance with the thermophilic bacteria and achieve excellent garbage drying effect. At the same time, SO2 and NO contained in the high-temperature exhaust gas are removed. X It can remove pollutants such as pollutants and realize high-temperature flue gas purification and efficient utilization of waste heat.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A flue gas waste heat-assisted ultra-high temperature biological drying method for urban organic waste, the specific steps are as follows:

[0011] (1) Flue gas heat assistance

[0012] The high-temperature flue gas after dust removal is mixed with fresh air. The temperature and oxygen concentration of the mixed gas are regulated by adjusting the mixing ratio. The mixed gas is passed into the bio-drying reactor to provide auxiliary heat, oxygen required for metabolism, and remove evaporated water.

[0013] Further, the temperature of the high-temperature flue gas after dust removal is 150-200°C, and the high-temperature flue gas after dust removal is mixed with fresh air in a volume ratio of 1:4-1:3;

[0014] Furthermore, the temperature of the mixed gas is adjusted to 50-80°C for use in the biological drying reaction, the auxiliary temperature is adjusted according to demand at different stages, and the oxygen concentration is maintained above 15%;

[0015] (2) Acclimation and enrichment of thermophilic bacteria

[0016] Add biomass conditioners to urban garbage, adjust the initial moisture content of the material to 55%-65% and the porosity to >60%, and inoculate the mixed material with ultra-high temperature compost products or DY high temperature bacteria. The initial auxiliary temperature is set to 50°C and increased to 70°C at a rate of 5°C / 12h. The flue gas ventilation volume during the acclimation process is set to 20-30L / (h·kg). When the material temperature exceeds 80°C and the oxygen consumption rate exceeds 40mg / (g VS·h), the acclimated material is obtained, which can be used for subsequent biological drying inoculation to achieve the acclimation and enrichment of the desired thermophilic bacteria.

[0017] Furthermore, the biomass conditioning agent is agricultural and garden waste;

[0018] Further, the ratio of the amount of urban waste to the amount of biomass conditioning agent added is 3 to 5:1;

[0019] Furthermore, the ultra-high temperature composting product is derived from the composting product of a composting plant in normal operation; the amount of the ultra-high temperature composting product added accounts for 20-30% of the total mass of the material in the biological drying reactor;

[0020] Furthermore, the time for acclimation and enrichment of the thermophilic bacteria is 3-4 days.

[0021] (3) Efficient biological hydrolysis / decomposition of organic waste

[0022] The urban organic waste and the conditioning agent are mixed evenly according to the method described in step (2). During the first fermentation start-up process, the domesticated material obtained in step (2) is inoculated at a mass ratio of 10%-30%. The subsequent fermentation start-up uses the ultra-high temperature stage material obtained after the previous round of fermentation, and the inoculation amount is 20%-30%. The auxiliary temperature is set at 70-80°C, and the ventilation volume is controlled at 30-60L·h -1 kg -1 , so that the temperature of the pile needs to be maintained above 80℃ for 1 day.

[0023] For urban organic waste treatment, this stage can promote the hydrolysis of carbon sources and form a carbon source that is easily degradable by biological flora; for urban sludge treatment, this stage can achieve the rapid decomposition of extracellular polymers and cells in sludge flocs through the dual effects of biological ultra-high temperature and extracellular hydrolases, promote the release of water and easily degradable organic matter inside the flocs, and facilitate the subsequent biological metabolism heat generation and water removal;

[0024] (4) Ultra-high temperature biological drying of organic waste

[0025] After hydrolysis / cracking, the material is turned over and bio-drying is continued. During this stage, the auxiliary temperature is set at 60-70℃ and the ventilation volume is controlled at 40-80L·h -1 kg -1 The residence time is 2-3 days, and the compost is turned and mixed twice a day. During the drying process, the ventilation volume is adjusted by material temperature feedback to maintain the material temperature in the biological drying reactor at 70-90℃. For every 5℃ increase in material temperature, the ventilation volume is increased by 10L·h -1 kg -1 When the temperature drops, the ventilation volume also decreases at the same gradient.

[0026] High material temperature combined with high ventilation volume can ensure oxygen supply and promote rapid transfer of evaporated water in the pores of the pile. Low temperature combined with low ventilation volume can slow down the heat dissipation of the pile, thereby balancing the heat storage and mass transfer of the system and ensuring efficient evaporation and removal of water.

[0027] (5) Flue gas SO2, NO X Synchronous removal

[0028] Waste incineration or coal combustion flue gas usually contains a certain amount of NO X (200-300mg / m 3 ) and SO2 (80-100 mg / m 3 ), the biological drying system degrades organic matter such as protein to produce ammonia nitrogen substances, making the material alkaline (pH>7), which is conducive to the absorption of such acidic gases; at the same time, the nitrifying bacteria and denitrifying bacteria in the biological flora can use the organic matter in the urban organic waste to provide electron donors, which can convert NO in the flue gas XReduced to N2, releasing a large amount of heat. In addition, the nitrogen and sulfur substances absorbed in the material can also be converted into stable NO3 through biological enzyme oxidation and reduction. - and SO4 2- etc., are absorbed and utilized by microorganisms. Therefore, NO in the exhaust gas x (<30mg / m 3 ) and SO2(<10mg / m 3 ) concentration decreased significantly.

[0029] The beneficial effects of the present invention are: through the assistance of flue gas waste heat and the coordinated regulation of extreme thermophilic bacteria, the bacterial community structure of the system is improved and stabilized, the biodegradation potential is stimulated, the temperature limitation of the traditional system is broken, and the dual effects of biological ultra-high temperature and biological enzyme hydrolysis are used to achieve rapid hydrolysis / cracking of organic waste, and improve the biological utilization effectiveness and water activity of carbon sources in the waste; at the same time, the ventilation volume is regulated based on temperature feedback, the heat and mass transfer of the system is strengthened, and the negative effects of ventilation and heat dissipation are simultaneously weakened, the migration and removal of sludge moisture are accelerated, and the sludge biological drying cycle is significantly shortened. In addition, the biological metabolic process of the system realizes the removal of SO2 and NO in flue gas. X Removal of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of the ultra-high temperature biological drying treatment method for urban organic waste assisted by flue gas waste heat. DETAILED DESCRIPTION

[0031] The operation process of the flue gas waste heat-assisted ultra-high temperature biological drying method for urban organic waste is as follows:

[0032] 1) High-temperature flue gas thermal assistance: High-temperature flue gas (150-200°C) is mixed with fresh air in a volume ratio of about 1:4-1:3 through a gas mixing device, and the temperature of the mixed gas is adjusted to 50-80°C, and the oxygen content is above 15%. The mixed gas is introduced into the bio-drying reactor, and the ventilation volume is adjusted according to the needs of the stage.

[0033] 2) Extreme thermophilic bacteria acclimatization: organic waste and sawdust (5-10 mm) were mixed at a ratio of 4:1, the initial moisture content of the material was adjusted to 65% and the porosity was about 60%, and 20% of ultra-high temperature compost product (obtained from Shenyang Dongyuan Environmental Technology Co., Ltd.) was inoculated into the mixture. The initial auxiliary temperature was set at 50°C and increased to 70°C at a rate of 5°C / 12h, and the ventilation volume was controlled at 25L·h -1 kg -1 After about 4 days of acclimatization, when the material temperature reaches 85°C and the oxygen consumption rate reaches 60 mg / (g VS·h), acclimatization is stopped and the acclimatized material can be used for subsequent biological drying inoculation;

[0034] 3) High-efficiency biological decomposition / hydrolysis of garbage: Mix organic garbage with sawdust to adjust the initial moisture content to 65%, porosity to about 60%, and inoculate the above domesticated materials at a ratio of 30% during the first fermentation start-up process. The auxiliary temperature is set at 70℃ and the ventilation volume is controlled at 40L·h -1 kg -1 , the residence time is 1 day. In this stage, the temperature of the pile is maintained above 80℃ for 14 hours, and the sludge cracking rate exceeds 80%;

[0035] 4) Ultra-high temperature biological drying: After the cracking treatment, the material is turned over and then continues to be biologically dried. The auxiliary temperature in this stage is set to 60°C, the residence time is 3 days, and the pile is turned and mixed twice a day. During the drying process, the ventilation volume is adjusted by material temperature feedback, and the ventilation volume is controlled at 40-80L·h -1 kg -1 Range, 5℃ corresponds to 10L·h -1 kg -1 Gradient control is performed to maintain the material temperature of the drying system at 70-90°C and the NO in the exhaust gas x (<30mg / m 3 ) and SO2(<10mg / m 3 ) concentration decreased significantly.

[0036] The ultra-high temperature stage material (inoculated 30%) obtained in the previous step 4) was subsequently used to start the garbage fermentation, and the treatment process ran stably. The results showed that the moisture content of the material could be reduced to below 25% after 3 days of ultra-high temperature biological drying, and the energy consumption of water removal was still dominated by bioheat (>85%), and the calorific value of the product was increased by 120%, effectively improving the energy utilization performance of high-water content organic waste.

Claims

1. A flue gas waste heat-assisted ultra-high temperature biological drying method for urban organic waste, characterized in that: The specific steps are as follows: (1) Flue gas heat assistance The high-temperature flue gas after dust removal is mixed with fresh air. The temperature and oxygen concentration of the mixed gas are regulated by adjusting the mixing ratio. The mixed gas is passed into the bio-drying reactor to provide auxiliary heat, oxygen required for metabolism, and remove evaporated water. (2) Acclimation and enrichment of thermophilic bacteria Add biomass conditioner to urban garbage, adjust the initial moisture content of the material to 55%-65% and the porosity to >60%, and inoculate the mixed material with ultra-high temperature compost product or DY high temperature bacterial agent; the initial auxiliary temperature is set to 50°C, and increased to 70°C at a rate of 5°C / 12h, and the flue gas ventilation volume during the acclimation process is set to 20-30L / (h·kg); when the material temperature exceeds 80°C and the oxygen consumption rate exceeds 40mg / (g VS·h), the acclimated material is obtained, and the acclimated material can be used for subsequent biological drying inoculation to achieve the acclimation and enrichment of the desired thermophilic bacteria; (3) Efficient biological hydrolysis / decomposition of organic waste The urban organic waste and the conditioning agent are mixed uniformly according to the method described in step (2); the domesticated material obtained in step (2) is inoculated at a mass ratio of 10%-30% during the first fermentation start-up process; the ultra-high temperature stage material obtained after the previous round of fermentation is used for subsequent fermentation start-up, and the inoculation amount is 20%-30%; the auxiliary temperature is set to 70-80°C, and the ventilation volume is controlled at 30-60L·h -1 kg -1 , so that the temperature of the pile needs to be maintained above 80℃ for 1 day; (4) Ultra-high temperature biological drying of organic waste After hydrolysis / cracking, the material is turned over and bio-drying is continued. During this stage, the auxiliary temperature is set at 60-70℃ and the ventilation volume is controlled at 40-80L·h -1 kg -1 The residence time is 2-3 days, and the compost is turned and mixed twice a day. During the drying process, the ventilation volume is adjusted by material temperature feedback to maintain the material temperature in the biological drying reactor at 70-90℃. For every 5℃ increase in material temperature, the ventilation volume is increased by 10L·h -1 kg -1 , when the temperature drops, the ventilation volume also decreases at the same gradient; (5) Flue gas SO2, NO X Synchronous removal Waste incineration or coal combustion flue gas usually contains a certain amount of NO X The biological drying system degrades organic matter such as protein to produce ammonia nitrogen, making the material alkaline, which is conducive to the absorption of such acidic gases; at the same time, the nitrifying bacteria and denitrifying bacteria in the biological flora can use the organic matter in the urban organic waste to provide electron donors, which can convert NO in the flue gas into X Reduced to N2, releasing a large amount of heat; in addition, the nitrogen and sulfur substances absorbed in the material can also be converted into stable NO3 through biological enzyme oxidation and reduction - and SO4 2- etc., are absorbed and utilized by microorganisms; NO in the exhaust gas x And SO2 concentration decreased significantly.

2. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (1), the temperature of the high-temperature flue gas after dust removal is 150-200° C., and the high-temperature flue gas after dust removal is mixed with fresh air in a volume ratio of 1:4-1:

3.

3. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (1), the temperature of the mixed gas is adjusted to 50-80°C for use in the biological drying reaction, the auxiliary temperature is adjusted according to demand at different stages, and the oxygen concentration is maintained at above 15%.

4. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (2), the biomass conditioning agent is agricultural and garden waste.

5. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (2), the ratio of the amount of urban garbage added to the amount of biomass conditioning agent added is 3 to 5:

1.

6. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (2), the ultra-high temperature composting product comes from the composting product of a normally operating composting plant; the amount of ultra-high temperature composting product added accounts for 20-30% of the total mass of the material in the biological drying reactor.

7. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (2), the time for acclimation and enrichment of the thermophilic bacteria is 3-4 days.

8. The method for ultra-high temperature biological drying of urban organic waste assisted by flue gas waste heat according to claim 1, characterized in that: In step (5), the flue gas contains NO X and SO2 content are 200-300mg / m 3 and 80–100 mg / m 3 ; NO in the exhaust gas after biological drying reaction X and SO2 content are <30mg / m 3 and < 10 mg / m 3 .

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