Method for purifying kitchen wastewater and retaining organic components

Abstract

The invention belongs to the technical field of kitchen waste treatment methods, and provides a method for purifying kitchen waste water and retaining organic components, which combines a heat pump technology and a film evaporation technology, firstly utilizes the heat pump evaporation technology to evaporate and remove water from the kitchen waste water, and then further concentrates the kitchen waste water in a film evaporator. Tests prove that the heat pump technology and thin film evaporation are combined to concentrate the kitchen wastewater, the COD concentration of discharged sewage is smaller than 500 mg / L, and the concentrated solution can well retain organic nutrients in the concentrated solution and can be used for breeding hermetia illucens. According to the invention, the problem that kitchen wastewater is difficult to treat is effectively solved, organic nutrients in the concentrate are retained, the purposes of wastewater purification and resource reutilization are achieved, and the method has good economic and social benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of kitchen waste treatment methods, and in particular relates to a method for purifying kitchen wastewater and retaining organic components. Background Art

[0002] Kitchen waste is organic waste generated in daily life, and its treatment is of great significance to the environment and human health. If kitchen waste is discharged directly without treatment, it will cause serious pollution to the environment. Among them, waste grease, food residues, etc. are prone to cause foul odors and damage environmental hygiene; organic matter in leftover food will decompose into greenhouse gases such as methane and carbon dioxide under the action of microorganisms, exacerbating global climate change. Untreated kitchen waste is a breeding ground for bacteria and viruses, and it is very likely to cause public health problems. By treating kitchen waste, the spread of pathogens can be effectively reduced, the incidence of diseases can be reduced, and public health can be protected. Therefore, treating kitchen waste is a necessary measure to protect the environment.

[0003] A large amount of wastewater will be generated during the treatment of food waste, and there are many difficulties in its treatment process. Food wastewater is a complex organic wastewater, which contains a large amount of protein, starch, oil, salt and other organic components. These components are easy to condense into agglomerates during the treatment process, and the COD content is very high, which increases the difficulty of biochemical treatment. Common food wastewater treatment processes include biological methods, chemical methods, physical methods, and comprehensive methods. These treatment methods all have certain shortcomings; Take the biochemical method as an example: Biochemical treatment is a method that uses the metabolic process of microorganisms to convert organic matter in wastewater into stable inorganic matter. First, large particles in the water are separated by sedimentation and flotation, and then the organic matter is converted into methane, carbon dioxide and water through anaerobic and aerobic biological treatment. The advantages of this method are good treatment effect and low operating cost. The disadvantages are that nutrients are decomposed, the treatment time is long, the area occupied is large, and the one-time investment cost is high.

[0004] To this end, it has become a current and future technical need to develop a professional food waste wastewater treatment device and method that is energy-saving, efficient, occupies a small area, requires little investment, does not produce secondary pollution, and effectively reuses the organic components of wastewater in food waste in conjunction with food waste treatment technology. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for purifying restaurant wastewater and retaining organic components, which has the advantages of energy saving, high efficiency, small footprint, and no secondary pollution, and solves the current technical difficulties in restaurant wastewater treatment.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for purifying kitchen wastewater and retaining organic components according to the present invention comprises the following steps: In the first step, the raw liquid passes through the raw liquid feed pump and exchanges heat with the condensed water and the concentrated liquid through the condensed water heat exchanger and the concentrated liquid heat exchanger respectively. After the raw liquid passes through the non-condensing steam condenser, it exchanges heat with the non-condensable steam of the evaporator, and then enters the scraper filter together with the dense phase residue of the evaporator; In the second step, the clear liquid filtered out by the scraper filter enters the evaporator through the evaporation feed pump, and the concentrated liquid filtered out by the scraper filter enters the filter screen filter through the scraper filter extraction pump, and then enters the thin film evaporator for further evaporation and concentration; In the third step, the concentrate is heated to 105-120°C by fresh steam in the thin film evaporator. The evaporated water vapor provides heat for the evaporator. The concentrate enters the concentrate collecting tank and is exchanged with the original liquid through the concentrate heat exchanger through the concentrate extraction pump. The concentrate after heat exchange enters the reuse process. In the fourth step, the clear liquid from the scraper filter enters the evaporator through the evaporation feed pump for evaporation, directly exchanges heat with the hot steam through the feed nozzle, and then indirectly exchanges heat with the compressed steam in the tube side, so that the temperature in the evaporator is maintained at 101-105°C. The insufficient heat is supplemented by fresh steam, and the evaporated water vapor enters the centrifugal steam compressor. After compression by the centrifugal steam compressor and the release of latent heat, the water vapor temperature is increased to 107°C-115°C, and enters the tube side of the evaporator to exchange heat with the material in the evaporator; In the fifth step, the condensate in the tube side of the evaporator enters the condensate collecting tank, and the non-condensable gas in the tube side of the evaporator exchanges heat with the original liquid through the non-condensing steam condenser, condenses a small amount of condensate and enters the condensate collecting tank; the condensate is pumped out by the condensate pump and then exchanges heat with the original liquid through the condensed water heat exchanger to form a evaporated liquid and is discharged, and the non-condensable gas is cooled by the non-condensing steam condenser and enters the condensate collecting tank.

[0007] Furthermore, the centrifugal steam compressor is replaced by a Roots compressor.

[0008] Furthermore, the evaporator, the scraper filter and the evaporation feed pump form a forced circulation evaporation.

[0009] Furthermore, the centrifugal steam compressor includes a condensate separation tank and a feeding system. The condensate in the centrifugal steam compressor is separated in the condensate separation tank, the steam enters the evaporator as a heat source, and the condensate and the distilled condensate are recycled after heat exchange.

[0010] The present invention uses filtration and evaporation concentration, and the distilled wastewater contains only low-component substances, impurities are basically removed, and COD is significantly reduced. The water vapor evaporated by the thin film evaporator is reused, and the heat pump utilizes the latent heat, that is, the temperature is increased by a centrifugal steam compressor, which greatly reduces energy consumption. The organic nutrients in the concentrate are basically retained, laying a good foundation for the reuse of the concentrate; while the traditional filtration and biochemical reaction treatment method, the impurities filtered out are used as solid waste, which may cause secondary pollution; the biochemical reaction decomposes the organic matter to decompose methane and carbon dioxide. If it cannot be effectively recovered, it will not only be a waste, but also cause environmental pollution and aggravate the greenhouse effect; the biochemical treatment method has a slow reaction and a long reaction time, and requires a large reaction pool or reaction tank, which occupies a large area and has a high investment cost.

[0011] The whole reaction process of the present invention has high processing efficiency, small floor space, simple process, energy-saving and environmentally friendly production process, and well retains organic nutrients. Through multiple filtration and evaporation by scraper filter, filter screen filter, evaporator, and thin film evaporator, suspended matter and solids in sewage are effectively removed, making the treated sewage clearer. Separating the concentrated liquid can well retain organic nutrients, laying a foundation for further effective utilization; at the same time, by utilizing the evaporation process and the heat exchange of compressed steam, the use of fresh steam is reduced, the utilization rate of energy is improved, and the processing cost is reduced, which has good economic and social benefits.

[0012] The present invention applies evaporation technology to sewage treatment, and combines heat pump technology with thin film evaporation technology to retain organic nutrients in the wastewater during treatment, thereby achieving the purpose of resource recycling. The thick material is filtered out using a scraper filter and a filter screen, and then most of the water is evaporated in a thin film evaporator and a forced circulation evaporation process. Experiments have shown that the COD of the condensate evaporated using evaporation technology can be reduced to below 500 mg / L, and can meet the emission standards after simple biochemical treatment, or be used as a nutritious feed for breeding black soldier flies.

[0013] The method of purifying kitchen wastewater and retaining organic components of the present invention can also be extended and applied to other aspects, such as slaughtering wastewater, fruit processing wastewater, etc., and has a good effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the process flow of the present invention; In the figure: 1-raw liquid feed pump, 2-condensate heat exchanger, 3-concentrate heat exchanger, 4-non-condensing condenser, 5-scraper filter, 6-evaporation feed pump, 7-evaporator, 8-centrifugal steam compressor, 9-condensate collecting tank, 10-condensate extraction pump, 11-filtration extraction pump, 12-screen filter, 13-thin film evaporator, 14-concentrate collecting tank, 15-concentrate extraction pump. DETAILED DESCRIPTION

[0015] The present invention is described in more detail below through specific embodiments to facilitate understanding by those skilled in the art.

[0016] The equipment used in the present invention is as follows: A device for purifying kitchen wastewater and retaining organic components, comprising a collection and heat exchange system, a filtration system, and an evaporation system; The collection and heat exchange system comprises a raw liquid feed pump 1, a condensate heat exchanger 2, a concentrate heat exchanger 3, a non-condensable gas condenser 4, a condensate collection tank 9, a condensate extraction pump 10, a concentrate collection tank 14, and a concentrate extraction pump 15; wherein the condensate heat exchanger 2 and the concentrate heat exchanger 3 are both plate heat exchangers; in this technical scheme, the raw liquid passes through the raw liquid feed pump 1 and exchanges heat with the condensate and the concentrate in two plate heat exchangers respectively, and after heat exchange, enters the non-condensable gas condenser 4 tube pass, and the non-condensable gas in the evaporator 7 tube pass enters the non-condensable gas condenser 4 tube pass. The shell side of the condensate condenser 4 cools a small amount of water vapor carried therein, and the non-condensable gas condensed by the non-condensable gas condenser 4 is discharged into the next deodorization process. The condensate condensed in the tube side of the evaporator 7 enters the condensate collecting tank 9 together with the cooling liquid of the non-condensable gas condenser 4. The water vapor in the condensate collecting tank 9 enters the evaporation chamber of the evaporator 7, and the condensate in the condensate collecting tank 9 is reused by the condensate extraction pump 10; the concentrated liquid condensed by the thin film evaporator 13 enters the concentrated liquid collecting tank 14, and the concentrated liquid is extracted by the concentrated liquid extraction pump 15 for reuse.

[0017] The filtration system includes a scraper filter 5, a filter extraction pump 11, and a screen filter 12; the original liquid enters the scraper filter 5 after heat exchange, and the filtered clear liquid is pumped into the horizontal evaporator 7 through the evaporation feed pump 6. The thick liquid filtered by the scraper filter 5 enters the screen filter 12 for filtration through the scraper filter extraction pump 11, and then enters the thin film evaporator 13.

[0018] The evaporation system includes a fresh steam pipeline, an evaporation feed pump 6, an evaporator 7, a thin film evaporator 13, and a centrifugal steam compressor 8; the water vapor evaporated from the thin film evaporator 7 enters the evaporation chamber 13 together with the fresh steam for evaporation, the evaporated steam enters the centrifugal steam compressor 8, and after being compressed by the centrifugal steam compressor 8, it enters the evaporator 7 pipe side as heating steam, the material at the bottom of the evaporation chamber enters the scraper filter 5, and the clear liquid after filtration enters the evaporator 7 again through the evaporation feed pump 6, and the scraper filter 5, the evaporation feed pump 6, and the evaporator 7 form a forced circulation evaporation.

[0019] The raw liquid feed pump 1 is connected to the condensate heat exchanger 2 and the concentrated liquid heat exchanger 3 at the same time. One side of the condensate heat exchanger 2 is connected to the condensate extraction pump 10 and the condensate outlet pipeline, and one side is connected to the non-condensing steam cooler 4 and the raw liquid feed pump 1; one side of the concentrated liquid heat exchanger 3 is connected to the concentrated liquid extraction pump 15 and the concentrated liquid outlet pipeline, and one side is connected to the raw liquid feed pump 1 and the non-condensing steam cooler 4; the non-condensing steam cooler 4 pipe side is connected to the condensate heat exchanger 2, the concentrated liquid heat exchanger 3 and the scraper filter 5, the shell side is connected to the non-condensing steam outlet and the non-condensing steam outlet pipeline of the evaporator 7, the shell side is connected to the condensate collection tank 9, and is connected to the condensate heat exchanger 2 through the condensate extraction pump 10; the scraper filter 5 inlet is connected to the evaporator 7 The bottom of the scraper filter 5 is connected to the evaporator feed pump 6 Then it leads to the feed port of evaporator 7, and the concentrated liquid outlet is connected to the filter 12 and then leads to the feed port of thin film evaporator 13; the evaporation chamber of evaporator 7 is connected to the fresh steam pipeline and the free gas outlet of condensate collecting tank 9, the top of evaporation chamber 7 is connected to the inlet of centrifugal steam compressor 8, the outlet of centrifugal steam compressor 8 is connected to the air inlet of evaporator 7 tube side, the non-condensing steam outlet of evaporator 7 tube side is connected to the non-condensing steam cooler 4, and the liquid outlet of evaporator 7 shell side is connected to the condensate collecting tank 9; the shell side of thin film evaporator 13 is connected to the fresh steam pipeline, the condensate is connected to the evaporator 7 tube side, the gas phase outlet of thin film evaporator 13 enters the evaporation chamber of evaporator 7, the concentrated liquid outlet is connected to the concentrated liquid collecting tank 14, and leads to the concentrated liquid heat exchanger 3 through the concentrated liquid extraction pump 15; the centrifugal steam compressor 8 can also use a Roots compressor.

[0020] Among them, centrifugal steam compressor 8: select a centrifugal steam compressor, controlled by a frequency converter, with an inlet temperature of 101-105°C, an outlet temperature of 107-115°C, a rotation speed of 8000 rpm, and a power configured according to production capacity.

[0021] Evaporator 7: Select a tube-and-tube evaporator. The evaporation area of ​​the evaporator is selected according to the production capacity, i.e. the feed volume flow rate.

[0022] Non-condensing steam condenser 4: Choose ordinary shell and tube condenser. The heat exchange area of ​​condenser is selected according to production capacity, i.e. feed volume flow rate.

[0023] Condensate heat exchanger 2, concentrate heat exchanger 3: ordinary shell and tube heat exchanger or plate heat exchanger is used, and the model depends on the designed capacity.

[0024] Scraper filter 5: Self-cleaning filter is used, and the production capacity is equipped with feed flow.

[0025] Filter mesh filter 12: Use stainless steel filter mesh filter, filtering capacity feed flow configuration.

[0026] Thin film evaporator 13: A scraped thin film evaporator is used, and the heating area is selected according to the output.

[0027] Condensate extraction pump 10, filter extraction pump 11, concentrate extraction pump 15: corrosion-resistant centrifugal pumps are selected, and the model is determined according to the designed production capacity.

[0028] The stock solution and heating steam used in the present invention are as follows: Raw wastewater: clarified wastewater after kitchen waste is squeezed, crushed and separated from oil, with a COD of 8000mg / L, oil content of less than 0.5%, and impurities of less than 2%.

[0029] Heating steam: saturated water vapor with a temperature greater than 170°C.

[0030] The method for purifying kitchen wastewater and retaining organic components of the present invention comprises the following steps: The first step, heat exchange: The raw liquid passes through the raw liquid feed pump 1 and the condensed water heat exchanger 2 and the concentrated liquid heat exchanger 3 to exchange heat with the condensed water and the concentrated liquid respectively. After passing through the non-condensing steam condenser 4, the raw liquid exchanges heat with the non-condensable steam of the evaporator 7, and then enters the scraper filter 5 together with the dense phase residue of the evaporator 7; Step 2, filtering: The clear liquid filtered out by the scraper filter 5 enters the evaporator 7 through the evaporation feed pump 6, and the concentrated liquid filtered out by the scraper filter 5 enters the screen filter 12 through the scraper filter extraction pump 11, and then enters the thin film evaporator 13 for further evaporation and concentration; Step 3: Concentration: The concentrate is heated to 105-120° C. by fresh steam in the thin film evaporator 13, and the evaporated water vapor provides heat for the evaporator 7. The concentrate enters the concentrate collecting tank 14, and is heat-exchanged with the original liquid by the concentrate heat exchanger 3 through the concentrate extraction pump 10. The concentrate after heat exchange enters the recycling process, i.e., as a nutritious feed for breeding black soldier flies; Step 4: Evaporation: The clear liquid from the scraper filter 5 enters the evaporator 7 for evaporation through the evaporation feed pump 6, and directly exchanges heat with the hot steam through the feed nozzle. The liquid then indirectly exchanges heat with the compressed steam in the tube side, so that the temperature in the evaporator 7 is maintained at 101-105°C. The insufficient heat is supplemented by fresh steam. The evaporated water vapor enters the centrifugal steam compressor 8. After compression by the centrifugal steam compressor 8 and the release of latent heat, the water vapor temperature is increased to 107°C-115°C, and enters the tube side of the evaporator 7 to exchange heat with the material in the evaporator 7. Step 5: Condensation The condensate in the tube side of the evaporator 7 enters the condensate collecting tank 9, and the non-condensable gas in the evaporator tube side is condensed into a small amount of condensate after heat exchange with the original liquid through the non-condensing steam condenser 4, and enters the condensate collecting tank 9; the condensate is pumped out by the condensate pump 10 and then passes through the condensed water heat exchanger 2 to form a evaporated liquid and is discharged, and the non-condensable gas is cooled by the non-condensing steam condenser 4 and enters the condensate collecting tank 9.

[0031] Furthermore, the centrifugal steam compressor 8 is replaced by a Roots compressor.

[0032] Furthermore, the evaporator 7 , the scraper filter 5 and the evaporation feed pump 6 form a forced circulation evaporation.

[0033] Furthermore, the centrifugal steam compressor 8 includes a condensate separation tank 9 and a feeding system. The condensate in the centrifugal steam compressor 8 is separated in the condensate separation tank 9, and the steam enters the evaporator as a heat source. The condensate and the distilled condensate are then recovered after heat exchange. The feeding system includes an oil tank, an oil supply pump, and an oil supply filter. The oil tank provides lubricating oil to the centrifugal steam compressor. The lubricating oil flows into the centrifugal steam compressor through the oil supply pump and the oil supply filter, and then returns to the oil tank from the oil outlet of the centrifugal steam compressor.

[0034] In the above process, through filtration and evaporation concentration, the impurity removal rate in the sewage is greater than 98%, and the COD is reduced to below 500 mg / L.

[0035] The present invention uses filtration and evaporation concentration, and the distilled wastewater contains only low-component substances, impurities are basically removed, and COD is significantly reduced. The water vapor evaporated by the thin film evaporator 13 is reused, and the heat pump uses latent heat, which greatly reduces energy consumption. The organic nutrients in the concentrate are basically retained, laying a good foundation for the reuse of the concentrate; the traditional filtration and biochemical reaction treatment method, the impurities filtered out are used as solid waste, which may cause secondary pollution; the biochemical reaction decomposes the organic matter to decompose methane and carbon dioxide. If it cannot be effectively recovered, it will not only be a waste, but also cause environmental pollution and aggravate the greenhouse effect; the biochemical treatment method has a slow reaction and a long reaction time, and requires a large reaction pool or reaction tank, which occupies a large area and has a high investment cost.

[0036] The method for treating kitchen wastewater of the present invention has obvious energy-saving effect, high treatment efficiency, low investment cost, small footprint, high resource recycling rate, and will not cause secondary pollution to the environment.

[0037] To facilitate the understanding of those skilled in the art, the following conventional treatment method is used as a comparative example to compare with the method of the present invention: Comparative Example 1: The conventional method for treating kitchen wastewater is adopted, and the specific steps include: The first step is wastewater pretreatment: The bulky matter is removed from the original wastewater by filtration and sedimentation; Step 2: flotation: After the first step is completed, flocculants are added to the wastewater and stirred to form large flocs. The flocs float on the water surface under the action of the air pump and are then separated by the scraper. The third step, biochemical treatment: After the first and second steps of separation, the wastewater enters the anaerobic and aerobic sections respectively; anaerobic biological treatment is to convert organic matter into methane and carbon dioxide through the action of anaerobic microorganisms under anaerobic conditions; aerobic biological treatment is to convert organic matter into carbon dioxide and water through the action of aerobic microorganisms under aerobic conditions; Step 4: Secondary precipitation and filtration: The wastewater after biochemical treatment is filtered through volcanic rock or sand to filter out clean water for discharge; In the second step of biochemical treatment, anaerobic reaction is slow and requires anaerobic bacteria to decompose organic matter in an oxygen-free environment, which takes a long time and the corresponding reaction container needs to be large. Aerobic reaction requires full contact with air and uses aerobic bacteria to decompose organic matter, which requires a large area and a long period of time. Compared with the prior art, it can be seen that: The organic application components of the present invention are well preserved, which is very important for the reuse of resources; Biochemical reactions have slow biological decomposition and take a long time, resulting in large reaction vessels, large floor space, and high investment costs.

[0038] The present invention combines heat pump technology with thin film evaporation technology. First, the heat pump evaporation technology is used to evaporate and dehydrate the kitchen wastewater, and then it is further concentrated in a thin film evaporator. Experiments have shown that the COD of the discharged sewage is less than 500 mg / L by combining heat pump technology with thin film evaporation to concentrate the kitchen wastewater. The concentrated liquid can well retain the organic nutrients therein and can be used for black soldier fly breeding or for organic fertilizer production. The present invention effectively solves the problem of difficult treatment of kitchen wastewater, retains the organic nutrients in the concentrate, achieves the purpose of wastewater purification and resource recycling, and has good economic and social benefits.

Claims

1. A method for purifying kitchen wastewater and retaining organic components, characterized in that: The following steps are involved: In the first step, the raw liquid passes through the raw liquid feed pump (1) and the condensed water heat exchanger (2) and the concentrated liquid heat exchanger (3) to exchange heat with the condensed water and the concentrated liquid respectively. The raw liquid passes through the non-condensing steam condenser (4) and exchanges heat with the non-condensable steam of the evaporator (7). Then, the raw liquid and the dense phase residue of the evaporator (7) enter the scraper filter (5). In the second step, the clear liquid filtered out by the scraper filter (5) enters the evaporator (7) through the evaporation feed pump (6), and the concentrated liquid filtered out by the scraper filter (5) enters the filter screen filter (12) through the scraper filter extraction pump (11), and then enters the thin film evaporator (13) for further evaporation and concentration; In the third step, the concentrate is heated to 105-120° C. by fresh steam in a thin film evaporator (13), and the evaporated water vapor is used to provide heat for the evaporator (7). The concentrate enters the concentrate collecting tank (14), and is heat-exchanged with the original liquid by a concentrate heat exchanger (3) through a concentrate extraction pump (11). The concentrate after heat exchange enters the recycling process; In the fourth step, the clear liquid from the scraper filter (5) enters the evaporator (7) for evaporation through the evaporation feed pump (6), directly exchanges heat with the hot steam through the feed nozzle, and then indirectly exchanges heat with the compressed steam in the tube side, so that the temperature in the evaporator is maintained at 101-105° C. Insufficient heat is supplemented by fresh steam, and the evaporated water vapor enters the centrifugal steam compressor 8. After compression by the centrifugal steam compressor 8 and release of latent heat, the water vapor temperature is increased to 107° C.-115° C., and then enters the tube side of the evaporator (7) for heat exchange with the material in the evaporator (7); In the fifth step, the condensate in the tube side of the evaporator (7) enters the condensate collecting tank (9), and the non-condensable gas in the tube side of the evaporator (7) is condensed into a small amount of condensate after heat exchange with the original liquid through the non-condensable steam condenser (4) and enters the condensate collecting tank (9); the condensate is pumped out through the condensate pump (10) and then passes through the condensate water heat exchanger (2) to form a evaporated liquid and is discharged; the non-condensable gas is cooled by the non-condensable steam condenser (4) and enters the condensate collecting tank (9).

2. A method for purifying kitchen wastewater and retaining organic components as claimed in claim 1, characterized in that: The centrifugal steam compressor (8) is replaced by a Roots compressor.

3. A method for purifying kitchen wastewater and retaining organic components as claimed in claim 1, characterized in that: The evaporator (7), the scraper filter (5) and the evaporation feed pump (6) form a forced circulation evaporation.

4. A method for purifying kitchen wastewater and retaining organic components as claimed in claim 1, characterized in that: The centrifugal steam compressor (8) comprises a condensate separation tank (9) and a feeding system. The condensate in the centrifugal steam compressor (8) is separated in the condensate separation tank (9), the steam enters the evaporator (7) as a heat source, and the condensate and the distilled condensate are recovered after heat exchange.

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