Leachate treatment based on combined falling film and forced circulation evaporators

Abstract

Leachate, seepage, and seepage are the result of a series of physical, chemical, and biological changes within waste landfills, which have very high levels of pollution and, if discharged into the environment, can pose a serious threat to human health and the environment. In view of this, here is a waste leachate treatment system presented as a combination of horizontal and vertical falling film and forced circulation evaporators, which consists of: A leachate inlet tank, at least one vertical falling film heat exchanger of the shell and tube type that receives leachate from the leachate inlet tank, a separator assembly that receives leachate and vapor from the leachate from the vertical falling film heat exchanger and the horizontal forced circulation heat exchanger, a horizontal forced circulation heat exchanger that receives condensed leachate from the separator after the vertical falling film heat exchanger, a steam boiler that supplies steam to the horizontal forced circulation heat exchanger, a condenser that condenses the vapor from the heat exchangers The vertical falling film and horizontal forced circulation heat exchanger receive, a cooling tower that receives the heat from the condenser, a recovery water tank that receives the water discharged from the condenser and separators, a filtration that filters the concentrated leachate in the horizontal forced circulation heat exchanger after passing through the separator, a pump set that circulates the water and leachate between the various components, and a pipe set that provides communication between the components. In this system, steam is used as the only heat source.

Description

Description of the invention Title of the invention Leachate treatment based on combined falling film and forced circulation evaporators The technical background of Astronomy The present achievement is generally in the field of landfill leachate treatment using an evaporation method based on combined falling film and forced circulation evaporators, and specifically, leachate treatment without the use of coagulants, without secondary pollution, and the separation of leachate impurities in the form of a wet cake. The technical problem of the invention's objectives Leachate is the result of a series of physical, chemical, and biological changes within landfills, which are highly polluted and, if discharged into the environment, can pose a serious threat to human health and the environment (groundwater, soil, and bird and animal communities). Currently, leachate from landfills and its improper management is recognized as the largest environmental problem related to the operation of landfills.Many research and implementation projects have been designed and implemented worldwide to treat wastewater generated from landfills using various treatment methods, including biological, physicochemical, recirculation and evaporation ponds, oxidation, and filtration. The results of the above implementation methods should lead to a reduction in the pollution of wastewater quality parameters, including Total Solids (TS), Total Dissolved Solids (TDS), Electrical Conductivity (EC), Total Hardness (TH), Turbidity, Biological Oxygen Demand (BOD), Escherichia coli / E. Coli Coliform, and chloride, to levels acceptable to competent authorities, including the country's Environmental Organization. Unfortunately, none of these methods can treat leachate according to standards, but they also have other disadvantages, including the production of secondary pollutants such as chemical sludge, low efficiency, high operating costs, odor emissions, the penetration of pollutants into underground layers, and increased soil salinity.Also, today, in some foreign countries, common evaporation methods such as forced circulation evaporators, thin film evaporators, or common vertical falling film evaporators are used in single or multi-stage for leachate treatment. These processes are such that for leachate treatment, both new and old leachate, additional treatment (pre- and post-treatment) is required, which increases economic costs and increases the number of equipment. Also, the amount of sedimentation and high energy consumption are high in them. Also, in these types of evaporators, a vacuum pump is used for fluid circulation, which itself has high costs and requires high care and maintenance. In addition to purifying landfill leachate, this achievement prevents pollution and environmental degradation. It also prevents water waste (due to water problems and shortages) by recycling water in this project. All leachate impurities are returned to the landfill in the form of a wet and completely dewatered cake.In this designed process, young leachate is purified without the need for post / pre-treatment or any additional treatment, without the use of any chemicals, and without the production of secondary pollutants such as chemical sludge. Finally, water is recovered with high efficiency and in accordance with environmental standards. By implementing a new leachate purification process based on evaporation (a combined method of falling film evaporators and forced circulation in at least three effects); leachate pollutant parameters including TDS, EC, COD, BOD, and chloride are reduced, which is in accordance with environmental standards and even beyond them, and is a revolution in the waste leachate purification industry in the country. Description of the state of the art and history of advances related to the invention of the common law. In some countries, evaporation methods are used as supplementary treatment in addition to conventional treatment methods for leachate treatment. For example, in the patent number CN202898170U in 2012, coagulation and flocculation, denitrification, vaporizer (evaporator) and incinerator are used for leachate treatment. Such evaporators require supplementary treatment and are expensive due to their high energy consumption and are not effective alone in removing pollutants and standardizing leachate. In 2019, the patent CN201920207774U disclosed a device for evaporating concentrated landfill leachate solution by burning biogas in a landfill, which includes a low-temperature leachate evaporation cylinder, a high-temperature leachate evaporation cylinder and a combustion chamber. This evaporation device has the advantages over previous inventions that two evaporation chambers are used for evaporation at different temperatures, so that the evaporation of organic matter is completely reduced and the condensate can meet the discharge requirement. However, these systems require a lot of energy to evaporate the leachate, are costly, and require supplementary treatment. In patent number CN202020210648U in 2020, a two-stage forced circulation evaporator evaporation system is used. In addition to the need for pre-treatment systems, the main disadvantage of these types of evaporators is the high pumping cost. The heat transfer resistance is on the liquid side and the energy consumption is high. In patent number CN202011513668A in 2021, a pre-treatment system (coagulation and flocculation) and a forced circulation thermal evaporator system are used for leachate treatment, but due to reasons such as pumping cost, the heat transfer resistance of this type of evaporator is not suitable for leachate treatment. In patent CN202223113540U in 2011, a thin film evaporator is used to evaporate and purify the leachate. This type of evaporator requires overhead space, is not suitable for leachate desalination and high pollutant removal, and requires recirculation, resulting in increased energy consumption. In the patent number CN201520221325U and CN201520277310U in 2015, a horizontal falling film evaporator (including a concentrate plate heat exchanger, a distilled water plate heat exchanger, an evaporation body, a steam compressor, a storage tank, and a steam generator) pre-treatment system (flocculation and coagulation) and secondary treatment were used for leachate treatment. This method is costly due to the use of pre- and post-treatment systems and also the energy consumption in the single-stage evaporator type used. Also, this process has other disadvantages due to the use of a plate heat exchanger in the evaporator used, including poor flexibility and easy leakage, very high sedimentation, pressure limitation, inefficiency for fluids containing suspended solids, and high resistance to flow. So far, no project has been carried out in Iran to treat waste leachate using thermal evaporators. According to studies and research on landfill leachate treatment, most treatment methods either use coagulants and chemical treatment, which are inefficient and costly, and without standardization. On the other hand, such treatments produce a large volume of sludge, which is problematic to remove. In some landfills, biological and membrane treatment are used. These methods are not only inefficient and cannot reduce toxic leachate pollution and remove heavy metals, they also produce a lot of sludge and are also faced with membrane clogging and high operating costs in connection with membrane processes. Also, common treatment processes require a lot of energy for pumping and aeration. Currently, no effective operations are carried out for leachate management in Iran, and ultimately the leachate is placed in large earthen ponds to evaporate.This practice not only poses environmental hazards and odors, but also has a high probability of leachate seeping into groundwater and water bodies. This method itself acts as a source of windborne pollution for birds and wildlife, thereby spreading pollution widely. In this method, a large volume of water is lost due to water scarcity. In some foreign companies and also articles, thermal evaporator methods such as vertical falling film or forced circulation in single or multi-stage, regardless of whether the leachate is new or old, are used as supplementary treatment along with other common treatment methods, which not only increases the cost and the number of equipment, but also has problems such as sedimentation in the thermal system. Also, in this type of evaporator, a vacuum pump is used for fluid circulation, which itself is high in cost and requires high care and maintenance.In all evaporation systems, a vacuum pump is used to separate steam (water) from the fluid at low temperatures and with the aim of reducing energy consumption, so that separation can take place at low temperatures. Therefore, the pumps of the entire system in the circulation and feeding section must be vacuum pumps, which are foreign technology and are expensive. However, in the present achievement, in order to solve the problem and eliminate foreign technological dependence and reduce costs, by using elevation to the suction points of the pumps, ordinary pumps (centrifuges) are used. The present process, relying on technical knowledge, has been designed with the evaporation method in the form of a combination of vertical falling film evaporators and horizontal forced circulation in three or four stages in such a way that it not only does not have the disadvantages of common purification methods, but it can also purify young leachate from waste landfills in one step without any additional purification, without the use of chemicals, and without producing secondary pollution.Ultimately, the water from the leachate is recovered with high efficiency, without the use of chemicals, without the production of chemical sludge, and in accordance with environmental standards. Providing a solution to an existing technical problem accompanied by an accurate, sufficient, and integrated invention Except for the concepts specifically defined in the text of the present invention, all technical and scientific terms used shall have the same meaning as understood by persons knowledgeable or skilled in this field (the field covered by the present invention). An attempt has been made here to mention the most preferred materials, tools and methods for describing the apparatus, systems and processes, although many similar materials, tools and methods can be used to describe the present invention and / or perform the processes of this achievement. Various aspects and embodiments of the present invention are presented below with respect to the figures provided in the "Technical Drawing" file. It should be noted that these aspects and embodiments merely indicate a representative of the present invention, and therefore the present achievement is not specifically limited to any of these cases. The present application includes a general aspect, a specific aspect and a set of various embodiments.The general aspect relates to a waste leachate treatment system, and the specific aspect relates to a waste leachate treatment system in the form of a combination of falling film and forced circulation evaporators, and the set of various embodiments relates to these two general and specific aspects. The present achievement, regardless of the various embodiments it may have, relates to a waste leachate treatment system as a combination of falling film evaporators and forced circulation. In view of what was said in the technical problem, according to Figure 1, a schematic of a waste leachate treatment system 1000 is disclosed as a combination of horizontal and vertical falling film and forced circulation evaporators. The waste leachate treatment system 100 as a combination of horizontal and vertical falling film and forced circulation evaporators consists of: a leachate inlet tank 100, at least one vertical falling film heat exchanger 200 of the shell-and-tube type that receives leachate from the leachate inlet tank 100, a separator assembly 300 that receives leachate and vapor from the leachate from the vertical falling film heat exchanger 200 and the horizontal forced circulation heat exchanger 400, a horizontal forced circulation heat exchanger 400 that receives condensed leachate from the separator 300 after the vertical falling film heat exchanger 200, a steam boiler 500 that supplies steam to the horizontal forced circulation heat exchanger 400. a condenser 600 that receives the exhaust steam from the vertical falling film heat exchangers 200 and the horizontal forced circulation heat exchanger 400, a cooling tower 700 that receives the heat from the condenser 600, a recovery water tank 800 that receives the exhaust water from the condenser 600, andIt receives separators 300, a filtration 900 that receives and stores the concentrated leachate from the separator 300 after the horizontal forced circulation heat exchanger 400; a pump assembly 110 that circulates water and leachate between the various components, and a pipe assembly 120 that provides communication between the components. As shown in Figure 2, a zoomed-in view of the upper part of the vertical falling film heat exchanger 200, the aforementioned waste leachate treatment system 1000 is such that the steam exiting the horizontal forced circulation heat exchanger 400 and the leachate from the leachate inlet tank 100 enters the vertical falling film heat exchanger 200, and then the heated leachate together with the generated steam enters the separator 300, and the outlet of the vertical falling film heat exchanger 200 enters the next vertical falling film heat exchanger 200, and finally the condensed leachate enters the horizontal forced circulation heat exchanger 400, and at each stage, the water vapor and the leachate are separated in the separators 300 after each heat exchanger 200 and 400. The steam from the steam boiler 500 is used as the only heating source, and the steam generated from the steam boiler 500 first enters the horizontal forced circulation heat exchanger 400 andAfter heat transfer, it enters the vertical falling film heat exchanger 200, where it moves around the tubes and inside the shell of the tube-shell exchanger. In the vertical falling film heat exchanger 200, the leachate from the leachate inlet tank 100 simultaneously enters the tubes of the vertical falling film heat exchanger, and heat is continuously transferred from the steam to the leachate. The temperature and pressure of the leachate in the leachate inlet tank 100 are equal to the ambient temperature and pressure. Heat transfer occurs through indirect contact of the leachate with the steam, causing the water in the leachate to evaporate and condense the leachate. After heating in each vertical falling film heat exchanger 200, the leachate enters the separator 300, and the heated leachate falls from top to bottom. As shown in Figure 3, the nozzle 310 inside the separator 300 for spraying water is also sprayed from top to bottom by the nozzles 310 with a separate pipeline so that foam is not formed during the separation of steam from the leachate. The steam produced from the leachate and the leachate are separated in the separators 300 and the steam produced from the leachate and the thermal energy of the steam produced from the leachate are used as an energy source for the converter.The vertical falling film heat exchanger 200 is used. The leachate enters the vertical falling film heat exchanger 200 at least twice and then enters the separator 200. The concentrated leachate, along with the steam produced from it, enters the horizontal forced circulation heat exchanger 400 after the last stage and then enters the final separator 300. The leachate exiting the horizontal forced circulation heat exchanger 400, which has the maximum concentration, enters the filtration 900 after passing through the separator 300, and after filtering the solids and impurities, it is returned to the landfill in the form of a cake. After filtration 900, the leachate returns to the leachate inlet tank 100. The water vapor obtained from the steps entered the condenser 600 and, by losing heat, turns into water. The water obtained from the condenser 600 is stored in the extracted water tank 800. The reason for using the last exchanger as a horizontal forced circulation is to prevent the formation of deposits. In fact, in order to reduce deposits and increase the system cleaning time (CIP) and reduce the consumption of materials for CIP and easy operation, several measures have been taken, one of which is the selection of a horizontal exchanger for heating the concentrated leachate, which in the horizontal exchanger both the minimum speed to prevent deposits is easily achieved and the steam and evaporator control operation is easy because the leachate clogs the tubes of the vertical falling film heat exchangers 200 and falling film due to excessive evaporation and concentration. For this reason, the last heat exchanger is considered as a horizontal forced circulation heat exchanger 400 so that the concentrated leachate circulates within the tubes of the horizontal forced circulation heat exchanger 400 due to the centrifugal pump and the amount of deposits and, as a result, CIP washing is minimized. Also, in order to reduce energy consumption, the leachate flow is used in the opposite direction of the steam flow. Diluted leachate enters from the first vertical exchanger and steam enters from the horizontal forced circulation heat exchanger.Because in the first exchanger, the steam has a better ability to evaporate the concentrated leachate due to its higher heat. In such a way that live steam is given to the concentrated leachate solution so that the efficiency of the system is kept high. In other words, steam and leachate are not compatible. As shown in Figure 4, the leachate and water characteristics tables obtained from the treatment by the Waste Leachate Treatment System 1000, the quality of the water obtained from the leachate is quite suitable for agriculture. This example of the constructed model of the proposed system is evidence of its good and high-quality performance. Explanation of shapes, patterns, and patterns Figure 1: Schematic of the 1000 waste leachate treatment system, combining falling film evaporators and forced circulation horizontally and vertically. Figure 2: Zoom in on the top of the vertical falling film heat exchanger 200 Figure 3: Nozzle 310 inside separator 300 for water spray Figure 4: Leachate and water characteristics tables obtained from treatment by the Waste Leachate Treatment System 1000 A clear and precise statement of the advantages of the claimed invention over prior inventions. The present achievement process is such that it causes 100% water extraction from young landfill leachate with environmental standards without pre-treatment and supplementary treatment, which results in zero consumption of any chemicals and a reduction in operating costs. It also does not produce secondary pollution (sludge resulting from pre-treatment and supplementary treatment operations). In this type of evaporator, a vacuum pump is not used for fluid circulation due to its high initial cost and high maintenance cost, and no mechanical separation system is used as pre-treatment, which significantly reduces maintenance and initial cost.Also, in this achievement, due to the design of the fluid circulation and the type of flow, no sedimentation occurs in the exchanger, and the device itself performs self-washing and descaling during use due to the turbulence of the flow and the simultaneous cleaning of the device walls. In addition to preventing and preventing sedimentation, this action minimizes the need for CIP in this system, and also results in a long life of the device, higher efficiency, 24-hour operation of the device, less consumption of acidic and alkaline materials for CIP, and more comfortable operation. In other similar systems, the volume of circulation and the type of fluid are not given importance, and sedimentation and clogging are reduced by using magnetic descaling or daily CIPs, which are expensive and require very laborious operators. In the present achievement, no chemicals are used and finally the leachate is first evaporated and then the resulting vapors are condensed and converted into distilled water and can be used as green space irrigation according to environmental standards. All impurities in the leachate are removed from the device in concentrated form, which can ultimately be dewatered in a sand bed or mechanical evaporation (such as a vacuum filter) and turned into a wet cake and sent to a landfill according to environmental regulations. Also, due to the use of the opposite flow direction of steaming and leachate in the system (steam entering from the direction of the concentrated leachate flow), energy consumption is reduced compared to other similar foreign processes. Also, the transfer of leachate into the separator in the horizontal exchanger is by forced flow, accompanied by flow spraying, and with this, the steam flushing level is increased several times compared to external processes at this stage and the efficiency of the system is increased without any additional energy consumption. Unlike similar foreign examples in which the heated leachate enters the separator plate as a horizontal flow, in this innovation, the heated effluent in the horizontal exchanger enters the separator as a spray and from above, which leads to a several-fold increase in efficiency in steam separation. Also, to prevent foam formation in Separator 300, unlike similar systems, in the steam separation chambers (Separator 300), foam formation is prevented by using a self-fluid flow and a separate line in the form of a spray. This reduces costs and increases the quality efficiency of the system due to the lack of use of chemicals (anti-foaming agents). In addition, by preventing foam formation and preventing the exit of foam along with the separated steam in the separator, it also increases the quality of the extracted water. Also, a vacuum pump is not used for circulation and feeding, unlike similar foreign systems. In all evaporation systems, a vacuum pump is used to separate steam (water) from the fluid at low temperatures and with the aim of reducing energy consumption, so that the separation can take place at low temperatures. Therefore, the pumps of the entire system in the circulation and feeding sections must be vacuum pumps, which are foreign technology and expensive. However, in the present method, in order to solve the problem, eliminate foreign technological dependence, and reduce costs, ordinary (centrifuge) pumps are used by raising the suction points of the pumps. A description of the minimum steps required to implement the invention. Initially, freshly extracted leachate from the Qazvin landfill with a capacity of 15 cubic meters per day at an initial ambient temperature and a pressure of one atmosphere is fed into the tubes of the first vertical falling film heat exchanger 200 from above in the same amount, and at the same time, live steam enters the horizontal forced circulation exchanger 400 from the opposite direction of the leachate flow. After heating and indirect heat transfer in the first vertical falling film heat exchanger 200, the leachate, along with the steam exiting from the horizontal forced circulation exchanger 400, enters the separator chamber 300 (steam / water separator) and the steam and leachate are separated. Then, the condensed leachate re-enters the next vertical falling film heat exchanger 200, and the same process is repeated until the last exchanger (horizontal forced circulation exchanger 400). The transfer of leachate into the separator belongs to the horizontal forced flow exchanger with flow spraying. Finally, the steam is released as water by losing heat through the condenser 600 and enters the final purified water tank 800.Finally, 14 cubic meters of water is obtained from the leachate according to the specifications in Figure 3, which can be used for irrigation of green spaces, and 1 cubic meter of concentrated leachate is obtained, which, after being dewatered and dried by the drum filter, is buried in a landfill as a cake according to environmental regulations, and the resulting leachate is added back to the raw leachate container for purification. Express mention of the industrial application of the invention The present achievement can be implemented in all waste landfills throughout the country, all of which have the problem of leachate production and its pollution. In general, the present achievement is used to separate water from waste and is used wherever waste leads to leachate production. �

Claims

Claims What is claimed: Claim 1) A waste leachate treatment system in the form of a combination of horizontal and vertical falling film and forced circulation evaporators, comprising: a leachate inlet tank; at least one vertical falling film heat exchanger of the shell-and-tube type that receives leachate from the leachate inlet tank; a separator assembly that receives leachate and vapor from the leachate from the vertical falling film heat exchanger; a nozzle assembly that sprays water fluid into the separator; a horizontal forced circulation heat exchanger that receives condensed leachate from the separator after the vertical falling film heat exchanger and also provides the leachate and vapor produced to the separator; a steam boiler that supplies steam to the horizontal forced circulation heat exchanger; a condenser that receives exhaust steam from the vertical falling film heat exchangers and the horizontal forced circulation heat exchanger; a cooling tower that receives heat from the condenser; A recovery water tank that receives the water discharged from the condenser and separators; a filtration that receives and filters the concentrated leachate from the separator after the horizontal forced circulation heat exchanger.a pump assembly that circulates water and leachate between the various components; and a pipe assembly that provides communication between the components; wherein the said waste leachate treatment system is such that the steam exiting the horizontal forced circulation heat exchanger and the leachate from the leachate inlet tank enters the vertical falling film heat exchanger, and then the heated leachate enters the separator along with the steam produced, and the outlet of the vertical falling film heat exchanger enters the next vertical falling film heat exchanger, and finally the condensed leachate enters the horizontal forced circulation heat exchanger, and at each stage the water vapor and leachate are separated in the separators. Claim 2) The waste leachate treatment system of claim 1, in such a way that it uses steam from the boiler as a heating source, and the steam produced from the boiler first enters the horizontal forced circulation heat exchanger and, after heat transfer, enters the vertical falling film heat exchanger, where it moves around the tubes and inside the shell of the tube-shell exchanger. Claim 3) The waste leachate treatment system of claim 1, wherein in the vertical falling film heat exchanger, leachate from the leachate inlet tank simultaneously enters the tubes of the vertical falling film heat exchanger and heat is continuously transferred from the steam to the leachate. Claim 4) The waste leachate treatment system of claim 1, wherein the temperature and pressure of the leachate within the leachate inlet tank are equal to the ambient temperature and pressure, and under conditions where the ambient temperature is between 10 and 60 degrees Celsius and the ambient pressure is between 0.8 and 1.2 atmospheres. Claim 5) The waste leachate treatment system of claim 1, wherein heat transfer occurs through indirect contact of the leachate with steam, causing evaporation of water within the leachate and condensation of the leachate. Claim 6) The waste leachate treatment system of claim 1, wherein the leachate enters the separator after heating in each vertical falling film heat exchanger and horizontal forced circulation heat exchanger, and the heated leachate falls from top to bottom, and a stream of water fluid with a separate pipeline is also sprayed from top to bottom by nozzles. Claim 7) The waste leachate treatment system of claim 1, wherein the steam generated from the leachate and the leachate are separated in separators, and the steam generated from the leachate and the thermal energy of the steam generated from the leachate are used as an energy source for a subsequent vertical falling film heat exchanger. Claim 8) The waste leachate treatment system of claim 1, wherein the leachate enters the vertical falling film heat exchanger at least twice and then enters the separator. Claim 9) The waste leachate treatment system of claim 1, wherein the condensed leachate, along with the steam produced therefrom, enters the horizontal forced circulation heat exchanger after the last stage and then enters the final separator. Claim 10) The waste leachate treatment system of claim 1, wherein the leachate exiting the horizontal forced circulation heat exchanger having the maximum concentration enters the filtration. Claim 11) The waste leachate treatment system of claim 1, wherein the concentrated leachate, after passing through filtration, is separated into a wet cake and leachate, and the leachate is returned to the leachate inlet tank. Claim 12) The waste leachate treatment system of claim 1, wherein the water vapor obtained from the steps taken enters the condenser and is converted into water by losing heat. Claim 13) The waste leachate treatment system of claim 1, wherein the water obtained from the condenser is stored within the extracted water tank.

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