Condensed waste water reduction system using drying treatment of anaerobic digestate emitted anaerobic disgestion tank

Abstract

The present invention relates to a system that can minimize downstream wastewater treatment facilities by reducing the amount of wastewater finally discharged by anaerobic digestion of food waste in a digester and then drying the digestate discharged from the digester in a dryer. The present invention provides a wastewater reduction system utilizing the drying treatment of digestate discharged from a digester, which can drastically reduce the total amount of wastewater discharged from the system by implementing a new system in which wastewater discharged during the food waste pretreatment process is introduced into a digester for anaerobic digestion treatment, the biogas produced in the digester is used as fuel for a deodorizing incineration boiler and city gas, and the digestate discharged from the digester is dried in a dryer. This allows for a significant reduction in the total amount of wastewater discharged from the system, thereby reducing the cost of external outsourcing treatment and minimizing downstream wastewater treatment facilities, thereby increasing the efficiency of facility operation. Furthermore, by implementing a system in which condensed wastewater discharged through a dryer and condenser is reused as process water for the facility after undergoing a comprehensive wastewater treatment process, the system can drastically reduce water supply costs associated with system operation.

Description

Technology Field

[0001] The present invention relates to a wastewater reduction system using a drying treatment of the digestate discharged from a digester, and more specifically, to a system that can minimize downstream wastewater treatment facilities by reducing the amount of wastewater finally discharged by anaerobic digestion of food waste in a digester and then drying the digestate discharged from the digester in a dryer. Background Technology

[0003] Modern society, characterized by mass production and mass consumption, is causing serious environmental pollution problems due to mass waste. Representative environmental pollution issues include soil and water pollution caused by mass waste and air pollution resulting from the mass consumption of energy.

[0004] Therefore, recently, drying methods for utilizing organic waste, such as food waste, as a renewable energy resource have been attracting attention, and by drying organic waste to reduce its moisture content, excellent solid fuel with a calorific value of 3,000 to 4,000 kcal / kg or more can be obtained.

[0005] Common equipment for drying organic waste includes direct and indirect drying dryers that use hot air and steam, and electromagnetic drying dryers that use microwaves.

[0006] In the drying process using these facilities, high-concentration condensed gas containing a large amount of moisture and oil is inevitably generated, and to treat the generated condensed gas, a condenser is installed in the discharge line of the dryer, and the high-concentration oil contained in the condensed gas is removed using the installed condenser.

[0007] The gas emitted during the drying process of organic waste is sent to a condenser for condensation treatment, and the condensed gas generated after condensation is incinerated in a subsequent deodorizing combustion furnace, while the high-concentration wastewater is transported externally and purified at a wastewater treatment plant.

[0008] However, there is a significant financial burden because the entire amount of high-concentration food waste leachate generated during the drying process of organic waste is transported externally and entrusted to a wastewater treatment plant for processing.

[0009] In other words, there is a problem of increased outsourcing treatment costs because the wastewater discharged during the typical food waste pretreatment process is not only high in concentration but also large in volume.

[0010] For example, the large amount of wastewater generated during the pretreatment of organic waste, such as food waste, is currently mostly outsourced for external treatment after oil is removed in a three-phase separator.

[0011] These food wastes contain large amounts of high concentrations of organic matter (BOD, COD), organic acids, and SS components. When the treated water undergoes anaerobic treatment and is subsequently treated aerobically (biologically), the TN and TD concentrations in the treated water are high, making it costly and difficult to re-treat it to meet discharge standards.

[0012] Furthermore, even if a wastewater treatment facility is installed to purify the significant amount of wastewater generated during the drying process of organic waste, not only does the scale of the facility increase, but there are also disadvantages in terms of facility investment costs and operating costs. Prior art literature

[0014] Published Patent Application No. 10-2019-0050474 Published Patent Application No. 102019-0050477 Registered Patent Application No. 10-1751502 Registered Patent Application No. 101845457 The problem to be solved

[0015] Accordingly, the present invention has been devised in consideration of these points, and aims to provide a wastewater reduction system utilizing the drying treatment of digestate discharged from a digester, which can increase the efficiency of facility operation by drastically reducing the amount of wastewater discharged from the system by implementing a new system in which the wastewater discharged during the food waste pretreatment process is introduced into a digester for anaerobic digestion treatment, the biogas produced in the digester is used as fuel for a deodorizing incineration boiler and city gas, and the digestate discharged from the digester is dried in a dryer, thereby drastically reducing the total amount of wastewater discharged from the system, thereby reducing the cost of external outsourcing treatment, and minimizing downstream wastewater treatment facilities.

[0016] In addition, another objective of the present invention is to provide a wastewater reduction system utilizing the drying treatment of digestate discharged from a digester, which can significantly reduce water supply costs related to system operation by implementing a system that reuses condensed wastewater discharged through a dryer and a condenser as process water for the facility after undergoing a comprehensive wastewater treatment process. means of solving the problem

[0018] To achieve the above objective, the wastewater reduction system using the drying treatment of the digestate discharged from the digester provided in the present invention has the following features.

[0019] The wastewater reduction system using the drying treatment of the digestate discharged from the digester comprises a digester that anaerobically digests the food waste leachate discharged during the food waste pretreatment process, a dryer that dries the digestate discharged from the digester, and a deodorizing incineration boiler that incinerates the waste gas discharged from the dryer. The system is characterized by the fact that after anaerobic digestion of the food waste leachate in the digester, the digestate discharged from the digester is dried in the dryer to reduce the amount of wastewater finally discharged.

[0020] A wastewater reduction system utilizing the drying treatment of digestate discharged from such a digester may further include a maturation tank installed between the digester and the dryer to mature the digestate and digested sludge discharged from the digester, in which a portion of the digestate is fed into the dryer, a portion of the digestate is sent to a wastewater treatment plant or entrusted for external treatment, and the digested sludge is returned to the digester.

[0021] Here, the dryer can use steam supplied from the deodorizing incineration boiler as a heat source, and the deodorizing incineration boiler can use steam condensate supplied from the dryer as boiler feed water.

[0022] In addition, the wastewater reduction system using the drying treatment of the digester discharged from the above digester is a facility for the pretreatment of food waste and may further include a crushing separator, a dehydrator, a low-speed separator, and a three-phase separator. The food waste discharged from the three-phase separator can be fed into the digester, and the oil can be sold externally, and the sludge discharged from the dehydrator and the three-phase separator can be fed into a dryer for drying treatment.

[0023] In a preferred embodiment, the biogas produced in the digester can be partially used as fuel for a deodorizing incineration boiler and partially sold as city gas after passing through a biogas storage tank and a biogas pretreatment unit.

[0024] A wastewater reduction system utilizing the drying treatment of the digestate discharged from such a digester may further include a condenser installed downstream of the dryer, and the condensed wastewater discharged from the condenser may be purified after passing through a condensed wastewater tank, a heat exchange condenser, and a wastewater treatment unit, and then used as reusable water for the facility. Effects of the invention

[0026] The wastewater reduction system using the drying treatment of the digestate discharged from the digester provided in the present invention has the following effects.

[0027] 1) By introducing the wastewater discharged during the pretreatment process into a digester for anaerobic digestion and using the biogas produced in the digester as fuel for deodorizing incineration boilers and city gas, and by drying the digestate discharged from the digester in a dryer, the total amount of wastewater discharged from the system is drastically reduced. This significantly reduces the amount of wastewater discharged, thereby reducing the cost of outsourced treatment and minimizing downstream wastewater treatment facilities, thereby increasing the efficiency of facility operation.

[0028] 2) By reusing the condensed wastewater discharged through the dryer and condenser as process water, such as makeup water for the cooling tower, through a comprehensive wastewater treatment process, it is possible to significantly reduce water supply costs related to system operation.

[0029] 3) By converting the final dried material into solid fuel and compost, waste treatment costs can be reduced through resource recycling, and the production volume of dried organic waste products can be increased. Additionally, by increasing the self-treatment and recycling of wastewater generated in the facility's processes, the amount of pollutants discharged, such as wastewater, can be reduced. This contributes to the government's waste reduction policy and resource circulation policy. Brief explanation of the drawing

[0031] FIG. 1 is a process diagram showing a wastewater reduction system using drying treatment of digestate discharged from a digester according to an embodiment of the present invention. Specific details for implementing the invention

[0032] The present invention will be described in detail below with reference to the attached drawings.

[0033] FIG. 1 is a process diagram showing a wastewater reduction system using a digestion liquid drying treatment discharged from a digester according to one embodiment of the present invention.

[0034] As illustrated in FIG. 1, the wastewater reduction system using the drying treatment of the digester discharged from the digester is a facility for the pretreatment of food waste and includes a crushing separator (14), a dehydrator (15), a low-speed separator (16), and a three-phase separator (17) arranged sequentially to process food waste.

[0035] The crushing and sorting machine (14) serves to crush and sort food waste that is clumped together in lumps, etc., and the dehydrator (15) serves to dehydrate the moisture in the food waste. The low-speed separator (16) and the three-phase separator (17) serve to remove foreign substances contained in the food waste, as well as to extract oil from the food waste.

[0036] Accordingly, food waste brought in from the outside is passed through a crusher (15), a dehydrator (15), a low-speed separator (16), and a three-phase separator (17) in sequence, and through this process, the food waste is finely crushed and sorted, and at the same time, moisture and oil contained in the food waste can be separated.

[0037] And, the dehydrated sludge (cake) discharged from the dehydrator (15) and the three-phase separator (17) is sent to a dryer (11) for drying treatment, the wastewater discharged from the three-phase separator (17) is sent to a digester (10) for anaerobic digestion treatment, and the oil extracted from the three-phase separator (17) is sold externally after undergoing a purification process.

[0038] In addition, the wastewater reduction system using the drying treatment of the digester discharged from the digester includes a digester (10) as a means to produce biogas by anaerobic digestion of the food waste flowing in from the three-phase separator (17) as well as the digested sludge returned from the maturation tank (13).

[0039] The above digester (10) is a digester in which the internal temperature is maintained at approximately 37 to 42°C, and this digester (10) anaerobically digests not only the high concentration organic wastewater from which oil has been removed supplied from the three-phase separator (17) side, but also the digested sludge returned from the aging tank (13) side.

[0040] For example, when high concentrations of organic wastewater and digested sludge are introduced into the digester (10), the high concentrations of organic wastewater and digested sludge are retained in the digester for a period of about 25 to 35 days and the pH is maintained at 7.0 to 7.6. The biogas generated through this retention and fermentation process is collected at the top of the digester, the digested liquid is collected at the upper layer of the water level inside the digester, and the heavy digested sludge is collected at the lower layer inside the digester, and continuous internal circulation and stirring is carried out together with the digested sludge returned from the maturation tank (13).

[0041] Here, the biogas discharged from the digester (10) is sent to the biogas storage tank (18) for storage and is also sent to the biogas pretreatment unit (19) to undergo treatment such as dust removal, dehumidification, and desulfurization. A portion of the biogas produced through this process is used as fuel for the deodorizing incineration boiler (12), and a portion is sold as city gas.

[0042] And, the digested sludge and wastewater (digestion liquid) discharged from the digester (10) are sent to the aging tank (13) for aging treatment.

[0043] In addition, the wastewater reduction system using the drying treatment of the digester discharged from the above digester includes a maturation tank (13) as a means of circulating the digester (10) and the digester sludge while maturing the digester treatment water (digester) and digester sludge discharged from the digester (10).

[0044] The above-mentioned aging tank (13) serves to perform the fermentation aging process and solid-liquid separation process while retaining the wastewater and digested sludge discharged from the digester (10) for a while.

[0045] And, between the above-mentioned aging tank (13) and the digestion tank (10), the digested sludge is continuously circulated and undergoes fermentation and aging processes, and eventually, through these repeated fermentation and aging processes, biogas production can be maximized.

[0046] After undergoing the aging process in the aging tank (13), the digestate discharged is sent to a dryer (11) for drying treatment, and some of the digestate is sent to a wastewater treatment unit (23) or can be entrusted to an external treatment facility.

[0047] In this way, by adopting a method of sending most of the wastewater discharged after digestion treatment, that is, the wastewater discharged after passing through the aging tank (13) after being discharged from the digestion tank (10), to a dryer (11) for drying treatment, the amount of final wastewater discharged from the system can be reduced as much as possible, and ultimately, through the reduction of wastewater, not only can the wastewater treatment facility be minimized, but the efficiency of system operation can also be improved.

[0048] Additionally, the wastewater reduction system using the drying treatment of the digestate discharged from the above digester includes a dryer (11) as a means of drying the digestate discharged from the aging tank (13) and the dehydrated sludge discharged from the dehydrator (15) and the three-phase separator (17).

[0049] The above dryer (11) is a dryer that dries digestion liquid and dehydrated sludge, and is operated using steam supplied from the deodorizing incineration boiler (12) as a heat source.

[0050] The dried material, after being dried in this dryer (11), passes through a cooling sorter (24), a grinder (25), and a sorter (26) in sequence, and can then be sold as feed, compost, solid fuel, etc.

[0051] Then, the waste gas discharged from the above dryer (11), that is, the waste gas containing high concentration N2 gas, passes through a cyclone (27) and a trap (28), and in this process, foreign substances and oil in the waste gas are filtered out, and the waste gas passing through the trap (28) is sent to the condenser (20) to be cooled and then sent to the deodorizing incineration boiler (12) to be deodorized and incinerated, and then discharged into the atmosphere through a dust collector (not shown), a stack (not shown), etc.

[0052] In a preferred embodiment, the steam condensate discharged from the dryer (11) can be stored in a condensate tank (29) and then used as boiler supply water for the deodorizing incineration boiler (12).

[0053] In addition, the wastewater reduction system using the drying treatment of the digester discharged from the above digester includes a deodorizing incineration boiler (12) as a means for incinerating waste gas containing malodorous gas.

[0054] The above deodorizing incineration boiler (12) is installed on the exhaust gas discharge line of the dryer (11), that is, installed at the rear end of the condenser (20), and serves to incinerate the exhaust gas discharged through the condenser (20).

[0055] The exhaust gas incinerated in this deodorizing incineration boiler (12) is purified by passing through a dust collector (not shown) and a stack (not shown) and then released into the atmosphere.

[0056] As a preferred embodiment, the present invention provides a system that can utilize biogas produced in a digester (10) as fuel required for operating the facility.

[0057] To this end, a line for gas transfer is connected between the digester (10) and the deodorizing incineration boiler (12), and accordingly, the biogas discharged from the digester (10) passes through the biogas storage tank (18) and the biogas pretreatment unit (19) before being supplied to the deodorizing incineration boiler (12) and used as fuel.

[0058] At this time, the deodorizing incineration boiler (12) may use city gas or diesel fuel as auxiliary fuel.

[0059] In this way, energy costs can be significantly reduced by utilizing biogas produced in-house in the digester (10) as fuel for operating the facility.

[0060] And, a line for steam transfer is connected between the deodorizing incineration boiler (12) and the dryer (11), and through this line, steam produced in the deodorizing incineration boiler (12) is supplied to the dryer (11) and used as a heat source for the dryer.

[0061] In addition, the wastewater reduction system using the drying treatment of the digestion liquid discharged from the above digestion tank includes a condenser (20) as a means for condensing the waste gas discharged from the dryer (11).

[0062] The above condenser (20) is a condenser that condenses waste gas discharged from the dryer (11), substantially waste gas that has passed through the cyclone (27) and trap (28), and plays the role of condensing high-temperature waste gas using low-temperature circulating water, and at this time, the condenser (20) can be a condenser used in general dryer equipment.

[0063] These condensers (20) include a circulating water cooling tower (not shown), a circulating water tank (not shown), and a pump (not shown) as means for supplying circulating water.

[0064] Accordingly, when the pump is operated, the circulating water in the circulating water tank is supplied into the interior of the condenser (20) and simultaneously undergoes heat exchange with the waste gas inside the condenser (20). After completing the heat exchange, the circulating water is cooled by passing through the circulating water cooling tower and then flows back into the circulating water tank. Through this circulation process of the circulating water, the waste gas can be condensed inside the condenser (20).

[0065] And, the high-temperature condensed wastewater discharged from the condenser (20) is stored in the condensed wastewater tank (21), and the high-temperature (70℃±5℃) condensed wastewater inside the condensed wastewater tank (21) is sent to the heat exchange condenser (22), and the condensed wastewater (39℃±3℃) that has passed through the heat exchange condenser (22) for cooling the condensed wastewater is supplied to the auxiliary digester (30) so that it can be anaerobic digested.

[0066] In addition, the wastewater reduction system using the digestion liquid drying treatment discharged from the above digestion tank includes a condensed wastewater tank (21), a heat exchange condenser (22), and a wastewater treatment unit (23) as means to anaerobic digest the condensed wastewater discharged after heat exchange in the condenser (20) and to comprehensively treat the wastewater so that it can be utilized as process water in the facility.

[0067] The above condensate wastewater tank (21) serves to store condensate wastewater discharged from the condenser (20), that is, condensate wastewater whose temperature has been lowered through heat exchange.

[0068] The above heat exchange condenser (22) serves to lower the temperature of the condensed wastewater discharged from the condensed wastewater tank (21).

[0069] That is, the heat exchange condenser (22) serves to lower the temperature to an appropriate level (39℃±3℃) to facilitate the digestion reaction of the condensed wastewater.

[0070] The above wastewater treatment unit (23) plays the role of converting the condensed wastewater discharged from the condenser (20), substantially the condensed wastewater discharged from the contact oxidation tank (31), into process water that can be used in the system through a comprehensive wastewater treatment process.

[0071] To this end, the wastewater treatment unit (23) includes an auxiliary digestion tank (30), a contact oxidation tank (31), a primary sedimentation tank (32), a reaction tank (33), a secondary sedimentation tank (34), a filtration tank (35), and a treated water tank (36) arranged sequentially.

[0072] Here, the auxiliary digester (30) serves to anaerobic digest the condensed wastewater discharged from the heat exchange condenser (22).

[0073] And, the contact oxidation tank (31) is a facility that oxidizes the condensed wastewater, i.e., the digestion liquid, discharged from the auxiliary digestion tank (30), and plays a role in improving the quality of the treated water by oxidizing the condensed wastewater containing various organic and inorganic pollutants, and then utilizing it as the final treated water for production process water.

[0074] In addition, the primary sedimentation tank (32), reaction tank (33), secondary sedimentation tank (34), filtration tank (35), and treatment tank (36) are identical to general wastewater treatment facilities, so a detailed description will be omitted.

[0075] Accordingly, the condensed wastewater discharged from the condenser (20) passes through the condensed wastewater tank (21) → heat exchange condenser (22) → auxiliary digestion tank (30) → contact oxidation tank (31) → primary sedimentation tank (32) → reaction tank (33) → secondary sedimentation tank (34) → filtration tank (35) in sequence and is stored in the treated water tank (36), and when the pump is operated, the treated water in the treated water tank (36) can be reused as system process water, such as cooling tower makeup water.

[0076] The operating status of the wastewater reduction system utilizing the drying treatment of the digestate discharged from the digester configured in this manner is as follows.

[0077] First, the food waste brought in from the outside is sequentially passed through a crushing sorter (14), a dehydrator (15), a low-speed separator (16), and a three-phase separator (17). Through this process, the food waste is broken into small pieces, and moisture contained in the food waste is removed, along with oil contained in the food waste.

[0078] Next, the dewatered sludge discharged from the dewatering machine (15) and the three-phase separator (17) is fed into a dryer (11) for drying treatment, and the wastewater discharged from the three-phase separator (17) is fed into a digestion tank (10), while the oil discharged from the three-phase separator (17) is sold externally after passing through a purification facility, etc.

[0079] Next, anaerobic digestion of the wastewater is performed in the digester (10) to produce biogas, and the biogas is then used as fuel for a deodorizing incineration boiler (12) or sold as city gas, etc. after passing through a biogas storage tank (18) and a biogas pretreatment unit (19).

[0080] Next, the digestion sludge and digestion liquid discharged from the digestion tank (10) are sent to the maturation tank (13) for maturation, and the digestion liquid discharged from the maturation tank (13) is fed into the dryer (11) for drying treatment, and some of the digestion liquid can be entrusted to an external treatment. In addition, the digestion sludge discharged from the maturation tank (13) is fed back into the digestion tank (10) and activated, thereby contributing to an increase in biogas production.

[0081] Next, the above dryer (11) dries the digestion liquid supplied from the aging tank (13) and the dehydrated sludge supplied from the dehydrator (15) and the three-phase separator (17). The dried material discharged from the dryer (11) is sold as feed or compost, and the waste gas discharged from the dryer (11) passes through a condenser (20), etc., and is then sent to a deodorizing incineration boiler (12) to be incinerated at a high temperature, thereby removing odors and other substances, and is released into the atmosphere.

[0082] Next, the condensed wastewater discharged through the condensation process in the condenser (20) is sent to the wastewater treatment unit (23) and, after being purified, is used as system process water.

[0083] In this way, the present invention provides a system that anaerobic digests the wastewater discharged during the food waste pretreatment process and then dries the digestate discharged from the digester in a dryer, thereby drastically reducing the total amount of wastewater discharged from the system, reducing the cost of entrusting wastewater treatment to an external facility, and increasing the efficiency of system operation, such as minimizing the wastewater treatment facility at the downstream end of the system for wastewater purification treatment. Explanation of the symbols

[0085] 10: Digester 11 : Dryer 12 : Deodorizing Incineration Boiler 13 : Aging tank 14 : Crusher / Sorter 15 : Dehydrator 16 : Low-speed separator 17: Three-phase separator 18: Biogas storage tank 19 : Biogas Pretreatment Unit 20 : Capacitor 21: Condensed wastewater tank 22 : Heat exchange condenser 23 : Wastewater Treatment Department 24 : Cooling separator 25 : Grinder 26 : Sorter 27 : Cyclone 28 : Trap 29 : Condensate tank 30: Auxiliary digester 31: Contact Oxidation Tank 32 : Primary sedimentation tank 33: Reactor 34 : Secondary sedimentation tank 35 : Filtration tank 36 : Treatment tank

Claims

Claim 1 A wastewater reduction system utilizing drying treatment of digestate discharged from a digester, comprising a digester (10) for anaerobic digestion of wastewater discharged during a food waste pretreatment process, a dryer (11) for drying treatment of digestate discharged from the digester (10), and a deodorizing incineration boiler (12) for incinerating waste gas discharged from the dryer (11), wherein after anaerobic digestion of wastewater in the digester (10), the digestate discharged from the digester (10) is dried in the dryer (11) to reduce the amount of wastewater finally discharged. Claim 2 A wastewater reduction system using drying treatment of digestate discharged from a digester, characterized in that, in claim 1, it further comprises a maturation tank (13) connected and installed between the digester (10) and the dryer (11) to mature the digestate and digested sludge discharged from the digester (10), wherein a portion of the digestate is fed into the dryer (11), a portion of the digestate is sent to a wastewater treatment plant or entrusted to an external treatment facility, and the digested sludge is returned to the digester (10). Claim 3 A wastewater reduction system using drying treatment of digestate discharged from a digester, characterized in that, in claim 1, the dryer (11) uses steam supplied from a deodorizing incineration boiler (12) as a heat source, and the deodorizing incineration boiler (12) uses steam condensate supplied from the dryer (11) as boiler feed water. Claim 4 A wastewater reduction system using drying treatment of digestate discharged from a digester, characterized in that, in claim 1, the equipment for pre-treating the food waste further comprises a crushing sorter (14), a dehydrator (15), a low-speed separator (16), and a three-phase separator (17), wherein the food waste discharged from the three-phase separator (17) is fed into a digester (10) and the oil is sold externally, and the sludge discharged from the dehydrator (15) and the three-phase separator (17) is fed into a dryer (11) for drying treatment. Claim 5 A wastewater reduction system using a drying treatment of digestate discharged from a digester, characterized in that, in claim 1, the biogas produced in the digester (10) passes through a biogas storage tank (18) and a biogas pretreatment unit (19), after which some of it is used as fuel for a deodorizing incineration boiler (12) and some is sold as city gas. Claim 6 A wastewater reduction system using a digestion liquid drying treatment discharged from a digestion tank, characterized in that, in claim 1, it further includes a condenser (20) installed at the rear end of the dryer (11), and the condensed wastewater discharged from the condenser (20) is purified after passing through a condensed wastewater tank (21), a heat exchange condenser (22), and a wastewater treatment unit (23) and is used as reusable water for the facility.

Images