Method for completely energy self-sufficient treatment and utilization of waste from processing of chinese chestnut

Abstract

The invention provides a method for completely energy self-sufficient treatment and utilization of Chinese chestnut processing wastewater and waste, which mixes Chinese chestnut processing wastewater and Chinese chestnut shell as feed, sends into a premixing agitator kettle for stirring, dispersion and preheating, then sends into a hydrothermal reaction kettle, seals the kettle body, heats, keeps warm for a certain time, then sends into a flash tank for flashing, sends the solid-liquid mixture after flashing into a multiple circular plate dewatering machine for dewatering, sends the solid after dewatering into a superheated steam dryer for drying, obtains bio-based carbon after drying, and sends into a burner as fuel for combustion; part of the steam obtained after flashing is sent into the premixing agitator kettle shell side for preheating feed, and the other part is sent into the superheated steam dryer as drying medium for drying the solid after dewatering; the liquid obtained after dewatering of the multiple circular plate dewatering machine is sent into an anaerobic fermentation tank for fermentation, obtains biogas, sends the biogas into the burner for combustion with the bio-based carbon, heats the heat conducting oil, part of which provides the required heat for the HTC reaction kettle, and part of which is used for external heat users or provided for Chinese chestnut processing.

Description

Technical Field

[0001] This invention relates to the field of effective treatment and utilization of chestnut processing wastewater and waste, and in particular to a method for the complete energy self-sufficiency treatment and utilization of chestnut processing wastewater and waste. Background Technology

[0002] Chestnut processing generates a large number of byproducts, and their resource utilization is of great significance for current agricultural product processing and environmental protection. Chestnut processing wastewater mainly originates from wet processes such as washing, steaming, and shelling. Its water quality exhibits typical characteristics of grain processing wastewater: high chemical oxygen demand (COD), with main pollutants being easily biodegradable organic matter such as starch, sugars, and proteins, and containing a certain amount of suspended solids. Direct discharge would cause water pollution. Solid waste mainly consists of chestnut shells and chestnut husks, with a huge annual production. Traditional disposal methods such as incineration and stockpiling easily lead to resource waste and secondary pollution.

[0003] Currently, chestnut processing wastewater is typically treated using screens and grit chambers to remove large particles such as chestnut shells and silt. Oil and grease are separated from the wastewater through oil separation and flotation. Further treatment utilizes microorganisms to degrade organic matter and remove pollutants such as COD, nitrogen, and phosphorus. However, research on chestnut shells has shifted from harmless disposal to high-value utilization, converting them into adsorbents, feed, and cultivation media. However, wastewater treatment systems in these systems are complex and unstable, and processing chestnut shells into adsorbents is costly, making large-scale treatment difficult. Summary of the Invention

[0004] Technical Objective: Addressing the shortcomings of existing technologies, this invention discloses a method for the complete energy self-sufficiency of chestnut processing wastewater and waste. Based on the concept of treating waste with waste, it extends the chestnut processing industry chain and improves overall industry efficiency. By combining hydrothermal treatment technology with flash evaporation and fermentation technologies, the method fully utilizes hydrothermal technology to simultaneously treat chestnut processing wastewater and chestnut shells. This allows for the synergistic cross-linking and degradation of organic matter in the wastewater and chestnut shells. The liquid products after hydrothermal treatment are fermented to produce biogas, while the solid products are used as fuel. The entire process requires no additional energy consumption, achieving complete energy self-sufficiency. This method enables the simultaneous harmless and resource-based treatment of chestnut processing wastewater and wastewater, resulting in significant economic and environmental benefits and possessing broad application prospects and social value.

[0005] Technical solution: To achieve the above technical objectives, the present invention adopts the following technical solution.

[0006] A method for the complete energy self-sufficiency of chestnut processing wastewater and waste, the method comprising the following steps: Step 1: Mix chestnut processing wastewater and chestnut shells in a certain proportion as feed, and send them to a premixing tank for stirring, dispersion and preheating. Then send them to a hydrothermal reactor, seal the tank, heat and keep warm for a certain time. The solid-liquid mixture is then sent to a flash evaporation system for flash evaporation. After flash evaporation and concentration, it is sent to a multi-plate dehydrator for dehydration. The solid obtained after dehydration is sent to a superheated steam dryer for drying. After drying, bio-based char is obtained and sent to a burner for combustion as fuel. Step 2: Send part of the steam obtained after flash evaporation in Step 1 into a premixing reactor for preheating and feeding, and send the other part into a superheated steam dryer as a drying medium to dry the dehydrated solids. Step 3: The liquid obtained after dehydration by the multi-plate dehydrator is sent to the anaerobic fermentation tank for fermentation to obtain biogas. The biogas is then sent to the burner to burn with bio-based charcoal to heat the heat transfer oil. Part of the heat is provided to the hydrothermal reactor and part is used for external heat users.

[0007] Furthermore, in step one, the dry weight ratio of chestnut processing wastewater to chestnut shells is 5~20:1, the preheating temperature is 90℃, and the rotation speed of the premixing reactor is 50r / min~90r / min.

[0008] Furthermore, in step one, the heating temperature range of the hydrothermal reactor is 240℃~300℃, and the reaction time range is 4h~6h.

[0009] Furthermore, in step one, the solid moisture content after dehydration by the multi-plate dehydrator is 50%, and the temperature is 80℃.

[0010] Furthermore, in step one, the drying temperature of the dryer is 120℃, and the moisture content of the bio-based char after drying is 15%.

[0011] Furthermore, in step two, the flash evaporation system is an Alfa Laval plate flash evaporation system with a flash evaporation temperature of 150°C.

[0012] Furthermore, in step two, the heat required for preheating the feed on the shell side of the premixed mixing vessel and drying the solids in the dryer is entirely provided by flash steam, with the remaining steam supplied to external heat users.

[0013] Beneficial effects: (1) This invention provides a method for the complete energy self-sufficiency treatment and utilization of chestnut processing wastewater and waste. It utilizes hydrothermal treatment combined with flash evaporation and fermentation technology. The reaction conditions are mild, the process is simple, the cost is low, and the process is completely energy self-sufficient, realizing the simultaneous harmless and resource-based treatment of chestnut processing wastewater and wastewater. (2) Based on the principle of energy cascade utilization, the present invention uses flash steam to preheat feed and as a drying medium, and can also provide the remaining steam to heat users. Compared with no flash steam, it has higher energy efficiency. (3) The present invention treats chestnut processing wastewater and chestnut shells together, effectively fixing heavy metals lead and chromium in the wastewater and preventing their migration and transformation. After combustion treatment, the residual amount of lead and chromium in the ash is more than 98%.

[0014] (4) By adjusting the hydrothermal treatment parameters, the product drying is made entirely by the system’s own steam, resulting in extremely low energy consumption. At the same time, the liquid after dehydration of the disc has its own temperature, so no external heat is required during fermentation. The obtained methane and bio-based char can be used as fuel, which has significant application prospects. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the method of the present invention; Figure 2 This is a schematic diagram of product mass distribution and methane production when the dry basis mass ratio of chestnut processing wastewater and chestnut shells is 10:1 and the reaction temperature of the HTC reactor is 240~300℃, according to an embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the utilization of flash steam when the dry weight ratio of chestnut processing wastewater to chestnut shells is 10:1 and the reaction temperature of the HTC reactor is 240~300℃, according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the system output energy, total energy consumption, and energy efficiency when the mass ratio of chestnut processing wastewater to dried chestnut shells is 10:1 and the reaction temperature of the HTC reactor is 240~300℃, according to an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating the utilization of flash steam when the reaction temperature of the HTC reactor in this embodiment of the invention is 240°C and the dry basis mass ratio of chestnut processing wastewater to chestnut shells is 5~20:1. Figure 6 This is a schematic diagram of the system energy efficiency when the reaction temperature of the HTC reactor in this embodiment of the invention is 240°C and the dry basis mass ratio of chestnut processing wastewater to chestnut shells is 5~20:1. Detailed Implementation

[0016] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application. Example

[0017] This invention provides a method for the complete energy self-sufficiency treatment and utilization of chestnut processing wastewater and waste, comprising the following steps: Step 1: Mix chestnut processing wastewater and chestnut shells in a certain proportion as feed, and send them to a premixing tank for stirring, dispersion and preheating. Then send them to a hydrothermal reactor, seal the tank, heat and keep warm for a certain time. The solid-liquid mixture is then sent to a flash evaporation system for flash evaporation. After flash evaporation and concentration, it is sent to a multi-plate dehydrator for dehydration. The solid obtained after dehydration is sent to a superheated steam dryer for drying. After drying, bio-based char is obtained and sent to a burner for combustion as fuel. The dry weight ratio of chestnut processing wastewater to chestnut shells is 5-20:1; the preheating temperature is 90℃; the stirring speed of the premixing kettle ranges from 50 r / min to 90 r / min; the hydrothermal reactor, also known as the HTC reactor, has a heating temperature range of 240℃-300℃ and a reaction time range of 4-6 hours. After dewatering by the multi-plate dewatering machine, the solid moisture content is 50% at 80℃; the drying temperature is 120℃; and the moisture content of the dried bio-based char is 15%. The energy consumption for dewatering a unit mass of slurry by the multi-plate dewatering machine is 6.9 KJ / Kg.

[0018] Step 2: Send part of the steam obtained after flash evaporation in Step 1 into a premixing reactor for preheating and feeding, and send the other part into a superheated steam dryer as a drying medium to dry the dehydrated solids. The flash evaporation system is an Alfa Laval plate flash evaporation system with a flash temperature of 150°C. The heat required for preheating the feed on the shell side of the premixed reactor and drying the solids in the dryer is entirely provided by the flash steam, and the remaining steam can be used by external heat users.

[0019] Step 3: The liquid obtained after dehydration by the multi-plate dehydrator is sent to the anaerobic fermentation tank for fermentation to obtain biogas. The biogas is then sent to the burner to burn with bio-based charcoal to heat the heat transfer oil. Part of the heat is provided to the hydrothermal reactor and part is used for external heat users.

[0020] In steps two and three, the temperature of the heat transfer oil heated by the combustion of bio-based charcoal and biogas is controlled by the required temperature of the reactor, and the remaining heat can be used by external heat users or for chestnut processing.

[0021] The method of this invention belongs to a semi-continuous process. The system mainly includes seven components: a premixing stirring tank, a hydrothermal reaction tank, a flash evaporation system, a multi-plate dehydrator, a dryer, an anaerobic fermenter, and a burner, such as... Figure 1As shown. Taking a processing capacity of 4 hours to process 500 kg of mixed slurry as an example, the dry basis mass ratio of wastewater and chestnut shells is 5~20:1, the processing temperature range is 240℃~300℃, the reaction time range is 4h~6h, after the system is running stably, the temperature of the premixing tank is 90℃, the flash temperature of the flash tank is 150℃, the solid moisture content after dewatering by the multi-plate dewatering machine is 50% and the temperature is 80℃, the drying temperature of the dryer is 120℃, the moisture content of the dried bio-based carbon is 15%, the specific heat of the dried bio-based carbon is 1.45 kJ / (kg·℃), the energy consumption of the multi-plate dewatering machine per unit mass of slurry is 6.9 KJ / Kg, the fermentation temperature in the anaerobic digester is 55℃, activated sludge is inoculated, the conversion rate of the liquid product of the anaerobic digester to methane is 0.32, the heat dissipation coefficient of the hydrothermal reactor is 0.032kW / K, and the specific heat of the dry sludge is 1.7 kJ / (kg·℃). System energy gains EB Defined using energy ratio, the calculation is as follows: EB =( E out - E IN ) / E IN In the case where flash steam is not recovered at all, E out It is the sum of the heat released by hydrothermal carbon combustion and the heat released by methane combustion; E in This is the sum of the energy consumption of all parts of the system; during flash steam recovery and utilization, E out It also includes the heat release relative to the environment of the remaining flash steam after preheating and drying, E in This is the sum of the energy consumption of the HTC reactor and the mechanical multi-plate dehydrator.

[0022] The method described in this invention enables complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste, and can provide steam and heat to external heat users. The system also purifies wastewater.

[0023] The specific steps of the method of this invention are as follows: chestnut processing wastewater and chestnut shells are mixed in a certain proportion as feed and fed into a premixing stirring tank for stirring, dispersion, and preheating. Then, the mixture is fed into a hydrothermal (HTC) reactor, the reactor body is sealed, and the mixture is heated and kept at a certain temperature for a certain period of time. The solid-liquid mixture is then fed into a flash evaporation system for flash evaporation. After flash evaporation and concentration, the mixture is fed into a multi-plate dehydrator for dehydration. The dehydrated solid is then fed into a superheated steam dryer for drying. After drying, bio-based char is obtained and fed into a burner for combustion as fuel. Part of the steam obtained after flash evaporation is fed into a feed preheater to preheat the feed, and the other part is fed into a dryer to dry the dehydrated solid. The liquid obtained after dehydration by the multi-plate dehydrator is fed into an anaerobic digester for fermentation to obtain biogas. The biogas is then fed into a burner to burn with the bio-based char to heat the heat transfer oil. Part of the biogas provides the heat required by the HTC reactor, and part of it is used for external heat users or for chestnut processing.

[0024] In one embodiment of the present invention, the mass ratio of chestnut processing wastewater to chestnut shell dry basis is 5:1. The premixing mixer rotates at 50 r / min, and the mixture is stirred, dispersed, and preheated at 90°C. The mixture is then fed into a hydrothermal reactor at 240°C for 4 hours. After the reaction, the solid and liquid mixture is simultaneously fed into a flash evaporation system at 150°C. After flash concentration, the mixture is dehydrated using a multi-plate dehydrator, resulting in a solid moisture content of 50%. The liquid enters a fermenter, where activated sludge is inoculated. The fermentation temperature is 55°C. Biogas, mainly methane, is collected after fermentation and burned in a burner. The solid with a moisture content of 50% is then dried in a superheated steam dryer at 120°C, resulting in bio-based char with a moisture content of 15%, which is then burned in a burner. After the entire process is running stably, part of the flash steam is supplied to the premixing mixer for preheating, part is supplied to the superheated steam dryer as a drying medium, and the remaining steam is supplied to heat users.

[0025] According to inductively coupled plasma mass spectrometry, the residual rates of lead and chromium in the ash residue before and after combustion of bio-based charcoal in the burner were 98.1% and 98.2%, respectively.

[0026] In another embodiment of the invention, the mass ratio of chestnut processing wastewater to chestnut shell dry basis is 20:1. The premixing mixer rotates at 90 r / min, and the mixture is stirred, dispersed, and preheated at 90°C. The mixture is then fed into a hydrothermal reactor at 300°C for 6 hours. After the reaction, the solid and liquid mixture is simultaneously fed into a flash evaporation system at 150°C. After flash concentration, the mixture is dehydrated using a multi-plate dehydrator, resulting in a solid moisture content of 50%. The liquid enters a fermenter, where activated sludge is inoculated. The fermentation temperature is 55°C. Biogas, mainly methane, is collected after fermentation and burned in a burner. The solid with a moisture content of 50% is then dried in a superheated steam dryer at 120°C, resulting in bio-based char with a moisture content of 15%, which is then burned in a burner. Once the entire process is running stably, part of the flash steam is supplied to the premixing mixer for preheating, part is supplied to the superheated steam dryer as a drying medium, and the remaining steam is supplied to heat users.

[0027] According to inductively coupled plasma mass spectrometry (ICP-MS), the residual rates of lead and chromium in the ash residue of bio-based charcoal before and after combustion in the burner were 98.3% and 98.1%, respectively.

[0028] In another embodiment of the invention, the mass ratio of chestnut processing wastewater to chestnut shell dry basis is 10:1. The premixing mixer rotates at 90 r / min, and the mixture is stirred, dispersed, and preheated at 90°C. The mixture is then fed into a hydrothermal reactor at 280°C for 5 hours. After the reaction, the solid and liquid mixture is simultaneously fed into a flash evaporation system at 150°C. After flash concentration, the mixture is dehydrated using a multi-plate dehydrator, resulting in a solid moisture content of 50%. The liquid enters a fermenter, where activated sludge is inoculated. The fermentation temperature is 55°C. Biogas, mainly methane, is collected after fermentation and burned in a burner. The solid with a moisture content of 50% is then dried in a superheated steam dryer at 120°C, resulting in bio-based char with a moisture content of 15%, which is then burned in a burner. Once the entire process is running stably, part of the flash steam is supplied to the premixing mixer for preheating, part is supplied to the superheated steam dryer as a drying medium, and the remaining steam is supplied to heat users.

[0029] According to inductively coupled plasma mass spectrometry, the residual rates of lead and chromium in the ash residue before and after combustion of bio-based charcoal in the burner were 98.4% and 98.2%, respectively.

[0030] As attached Figure 2 To be continued Figure 6 As shown, Figures 2 to 4In this study, the dry weight ratio of chestnut processing wastewater to chestnut shells was 10:1, with a total treatment capacity of 500 kg. When the HTC reactor temperature was between 240℃ and 300℃, the flash steam production increased from 86.02 kg to 143.90 kg. However, the dehydration of the round plates and the moisture content of the dried product both decreased. The dehydration amount decreased from 370.24 kg at 240℃ to 318.64 kg at 300℃, and the moisture content of the dried product decreased from 16.07 kg to 13.33 kg. The yield of bio-based char after drying decreased with increasing HTC temperature, with 22.95 kg of bio-based char obtained at 240℃ and 19.04 kg at 300℃. Methane production initially increased and then decreased with increasing HTC temperature, reaching 5.27 kg at 240℃, 5.33 kg at 270℃, and 5.14 kg at 300℃. At HTC reactor temperatures of 240℃, 270℃, and 300℃, the flash steam quantities were 86.02 kg, 114.96 kg, and 143.90 kg, respectively, sufficient to meet all energy consumption for system preheating and drying, with a surplus. The surplus steam accounted for 16.21%, 38.92%, and 52.02% of the flash steam mass, respectively. The system's energy consumption was primarily concentrated in the HTC reactor section, and increased significantly with increasing reaction temperature, reaching 296.41 MJ, 355.69 MJ, and 414.97 MJ, respectively. When using flash steam for preheating and drying, the total system energy consumption was lowest at 240℃ (299.23 MJ) and highest at 300℃ (417.39 MJ). This indicates that the energy obtained from burning the hydrothermal carbon and methane products obtained by the system is sufficient to meet the system's energy consumption, with a surplus. As shown in the figure, after meeting the system's energy consumption requirements, the system's net energy output is highest at 240℃ (494.27 MJ) and lowest at 300℃ (319.15 MJ). This means that considering energy recovery and product utilization, the system can achieve both waste treatment and energy gain. When recovering and utilizing flash steam energy, the system's energy efficiency is consistently above 1.2, reaching its highest at 240℃ (1.77).

[0031] Figures 5 to 6With the HTC reactor temperature at 240℃, a total processing capacity of 500 kg, and a dry weight ratio of chestnut processing wastewater to chestnut shells of 5-20:1, the preheating flash steam increased from 41.07 kg to 44.61 kg; while the drying flash steam decreased from 28.10 kg to 7.09 kg. Since the total flash steam volume did not vary significantly under different liquid-to-solid ratios, the remaining flash steam increased from 4.03 kg to 26.00 kg with increasing chestnut processing wastewater to chestnut shell weight ratio, meaning the remaining flash steam increased from 6% to 34% of the total flash steam. This indicates that at a flash temperature of 150℃ and the selected operating parameters, the steam obtained from flash evaporation is sufficient for system preheating and drying, with a surplus. When the energy of flash steam is not utilized at all, the energy efficiency decreases from 2.02 to -0.07, which corresponds to the net energy output. This indicates that when the mass ratio of chestnut processing wastewater to chestnut shells is 20, if flash steam is not utilized, the system needs to supplement energy from the outside and there is no energy income. When flash steam is utilized, the energy efficiency decreases from 4.07 to 0.62, both of which are greater than 0. Moreover, when the mass ratio of chestnut processing wastewater to chestnut shells is low, there is a considerable energy efficiency.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the complete energy self-sufficiency treatment and utilization of chestnut processing wastewater and waste, characterized in that, The method includes the following steps: Step 1: Mix chestnut processing wastewater and chestnut shells in a certain proportion as feed, and send them to a premixing tank for stirring, dispersion and preheating. Then send them to a hydrothermal reactor, seal the tank, heat and keep warm for a certain time. The solid-liquid mixture is then sent to a flash evaporation system for flash evaporation. After flash evaporation and concentration, it is sent to a multi-plate dehydrator for dehydration. The solid obtained after dehydration is sent to a superheated steam dryer for drying. After drying, bio-based char is obtained and sent to a burner for combustion as fuel. Step 2: Send part of the steam obtained after flash evaporation in Step 1 into a premixing reactor for preheating and feeding, and send the other part into a superheated steam dryer as a drying medium to dry the dehydrated solids. Step 3: The liquid obtained after dehydration by the multi-plate dehydrator is sent to the anaerobic fermentation tank for fermentation to obtain biogas. The biogas is then sent to the burner to burn with bio-based charcoal to heat the heat transfer oil. Part of the heat is provided to the hydrothermal reactor and part is used for external heat users.

2. The method for complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste according to claim 1, characterized in that: In step one, the dry weight ratio of chestnut processing wastewater to chestnut shells is 5~20:1, the preheating temperature is 90℃, and the rotation speed of the premixing reactor is 50r / min~90r / min.

3. The method for complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste according to claim 1, characterized in that: In step one, the heating temperature range of the hydrothermal reactor is 240℃~300℃, and the reaction time range is 4h~6h.

4. The method for complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste according to claim 1, characterized in that: In step one, the solid moisture content after dehydration by the multi-plate dehydrator is 50% and the temperature is 80℃.

5. The method for complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste according to claim 1, characterized in that: In step one, the drying temperature of the dryer is 120℃, and the moisture content of the bio-based char after drying is 15%.

6. The method for complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste according to claim 1, characterized in that: In step two, the flash evaporation system is an Alfa Laval plate flash evaporation system with a flash evaporation temperature of 150℃.

7. The method for complete energy self-sufficiency in the treatment and utilization of chestnut processing wastewater and waste according to claim 1, characterized in that: In step two, the heat required for preheating the feed on the shell side of the premixed mixing vessel and drying the solids in the dryer is entirely provided by flash steam, and the remaining steam is supplied to external heat users.

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