Urea desorption waste liquid ammonia nitrogen emission reduction and wastewater recycling equipment and use method

Abstract

The invention provides a urea desorption waste liquid ammonia nitrogen emission reduction and waste water reuse equipment and a use method. The equipment comprises a multi-media catalytic adsorption filter, a circulating water tank, a first water pump, a second water pump, a separator, a chlorination reactor, an ejector, a gas separator and a dosing box; the multi-media catalytic adsorption filter, the circulating water tank, the first water pump, the ejector and the separator are connected in sequence; the inlet end of the separator is connected to the circulating water tank through a pipeline, and the output end of the separator is connected to the input end of the chlorination reactor through a pipeline; the output end of the chlorination reactor is connected to the input end of the ejector; the input end and the output end of the dosing box are respectively connected to the output end of the gas separator and the second water pump.

Description

Technical Field

[0001] The invention relates to the field of fertilizer wastewater treatment, and in particular to a urea desorption waste liquid ammonia nitrogen emission reduction and wastewater recycling device and a use method. Background Art

[0002] During the production process of urea, water will be generated by reaction. In addition to the water and water vapor introduced from the outside, all of this water will eventually be brought into the evaporation section for evaporation and condensation to become analytical wastewater. The waste liquid contains some urea, ammonia, carbon dioxide, biuret and other substances. If it is directly discharged, the ammonia nitrogen in the waste liquid will cause serious pollution to the water environment, which has always been a key governance project for fertilizer companies. The waste liquid generated during the production of urea will pollute the environment, and the metal ions and oxides contained in it will cause fouling and corrosion to the equipment in the subsequent process, high energy consumption in the production process, and low urea recovery and utilization rate.

[0003] In recent years, the urea wastewater treatment process has been continuously improved. Initially, the hydrolysis process was used, which could only treat 20 m 3 / h of wastewater, but it cannot decompose the urea in the process wastewater. The treated wastewater cannot be used directly and needs to be treated again. In 2011, the hydrolysis and steam stripping process was used, and its processing capacity was 25 m 3 / h. In 2012, the treatment process was further improved by adopting a carbon dioxide stripping process urea unit, which uses 2.5 MP of hydrolysis to analyze the waste liquid, and the unit's treatment capacity has been increased to 35 m 3 / h (Hu Jie, 2019). However, these processes all have the disadvantages of high energy consumption, high construction costs and low processing capacity. To this end, the present invention aims to provide a low-energy consumption, economical and applicable urea desorption waste liquid ammonia nitrogen reduction and wastewater reuse method and equipment. Summary of the invention

[0004] In order to solve the ammonia nitrogen load of urea desorption liquid directly entering the environment, reduce the carbon-nitrogen ratio of the comprehensive wastewater, and the high ammonia nitrogen content, the present invention provides a urea desorption waste liquid ammonia nitrogen emission reduction and wastewater reuse equipment, which can effectively reduce the ammonia nitrogen load, and the treated wastewater can be reused as circulating water replenishment.

[0005] The present invention is achieved by at least one of the following technical solutions.

[0006] A urea desorption waste liquid ammonia nitrogen emission reduction and waste water reuse equipment, comprising a multi-media catalytic adsorption filter, a circulating water tank, a first water pump, a second water pump, a separator, a chlorination reactor, an ejector, a gas separator and a dosing tank;

[0007] The multi-media catalytic adsorption filter, the circulating water tank, the first water pump, the ejector, and the separator are connected in sequence;

[0008] The input end of the separator is connected to the circulating water tank through a pipeline, and the output end of the separator is connected to the input end of the chlorination reactor through a pipeline; the output end of the chlorination reactor is connected to the input end of the ejector;

[0009] The input end and the output end of the medicine adding box are connected to the output end of the gas separator and the second water pump respectively.

[0010] Preferably, the input ends of the multi-media catalytic adsorption filter, the circulating water tank and the gas separator all have cooling water input.

[0011] Preferably, the water pump needs to regulate the concentration of urea, ammonia and NH3 and CO2 in the steam phase in the circulating water tank so that the concentration in the liquid phase is greater than that in the gas phase. A high concentration is conducive to faster decomposition of NH3 and CO2. The farther away from the equilibrium point, the greater the driving force, which is more conducive to hydrolysis and decomposition.

[0012] Preferably, the output end of the circulating water tank is connected to the input end of the first water pump, and an output end of the first water pump is connected to the input end of the multi-media catalytic adsorption filter to perform adsorption catalysis again to improve the adsorption catalytic efficiency.

[0013] Preferably, the chlorination reactor adopts the breakpoint chlorination method to control the chlorine input to oxidize NH3-N in the wastewater into N2, thereby reducing the chromaticity of the waste liquid, removing odor, reducing the organic matter content in the waste liquid, and improving the coagulation effect.

[0014] Preferably, the dosing box uses a dispersing interfering agent to adjust the water quality composition of the boiler water in the jacket to prevent the generation of difficult-to-remove biuret or triuret in the jacket, and at the same time, a treatment agent is added to the dosing box for comprehensive treatment of iron removal, catalysis, oxygen reduction, hardness reduction and corrosion inhibition.

[0015] According to the method for using the urea desorption waste liquid ammonia nitrogen reduction and wastewater reuse equipment, the following steps are included:

[0016] 1) Urea desorption waste liquid enters the water pump through the multi-media catalytic adsorption filter and the circulating water tank, a part of the urea desorption waste liquid re-enters the multi-media catalytic adsorption filter for another catalytic adsorption, and a part of the urea desorption waste liquid enters the gas separator through the ejector;

[0017] 2) Cooling water enters the gas separator from the input end of the gas separator, and its function is to adjust the temperature and pressure of the water body, which is conducive to improving the speed and depth of urea hydrolysis; the second water pump is connected to the output end of the gas separator and the dosing box, and its function is to adjust the mixing ratio of the active agent and the wastewater, which is conducive to the full mixing of the agent;

[0018] 3) The nitrogen-containing wastewater in the circulating water tank enters the chlorination reactor from the output end of the separator. The chlorination reactor controls the input amount of chlorine through the inflection point chlorination method to oxidize the NH3-N in the wastewater into N2, and then enters the gas separator through the ejector;

[0019] 4) The waste liquid in the gas separator is passed through the dosing box to add dispersing interfering agents and adjust the water quality components of the boiler water in the jacket. At the same time, treatment agents are added to remove iron, catalyze, reduce oxygen, reduce hardness and inhibit corrosion.

[0020] Preferably, the treatment agent is a vapor phase corrosion inhibitor, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid (HEDP) or a flocculant (TS-609).

[0021] In the present invention, after the urea desorption waste liquid passes through the set of recovery and treatment equipment, the average concentration of ammonia nitrogen in the waste liquid is reduced from 834.4 mg / L to 158.9 mg / L; the average concentration of COD (chemical oxygen demand) is reduced from 3308.2 mg / L to 1324.4 mg / L, reducing the COD load of the sewage station; and the average carbon-nitrogen ratio is increased from 4.29 to 11.52.

[0022] The present invention has the following advantages and effects compared with the prior art:

[0023] After the iron ions and oxygen in the urea desorption waste liquid are removed in the present invention, the waste liquid is directly reused as circulating water for replenishing the jacket and the waste heat boiler, thereby reducing the production cost and improving the economic benefit. The present invention reduces the consumption of desalted water for gasification and recovers the low-level thermal energy in the waste liquid. On the other hand, the amount of sewage generated is effectively reduced, the concentration of ammonia nitrogen in the raw water entering the sewage station is reduced, the carbon-nitrogen ratio of the waste water is effectively improved, and suitable conditions are created for the subsequent denitrification treatment of the waste water. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of a urea desorption waste liquid ammonia nitrogen reduction and waste water reuse equipment in this embodiment;

[0025] Figure 2 This is a graph showing the COD concentration change of the comprehensive sewage entering the recovery and treatment equipment in the 60-day period before and after the start of the urea desorption waste liquid ammonia nitrogen reduction and wastewater reuse equipment in this embodiment;

[0026] Figure 3 This is a graph showing changes in ammonia nitrogen concentration in the comprehensive wastewater entering the recovery and treatment equipment in the 60-day period before and after the start of a urea desorption waste liquid ammonia nitrogen reduction and wastewater reuse equipment in this embodiment;

[0027] Figure 4 This is a graph showing changes in the comprehensive wastewater carbon-nitrogen ratio of wastewater entering a recovery and treatment device within a period of 60 days before and after the start of a urea desorption waste liquid ammonia nitrogen reduction and wastewater reuse device in this embodiment. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the embodiments do not limit the scope of protection claimed for the present invention.

[0029] like Figure 1 The urea desorption waste liquid ammonia nitrogen emission reduction and waste water reuse equipment shown includes a multi-media catalytic adsorption filter 1, a circulating water tank 2, a first water pump 3-1, a second water pump 3-2, a separator 4, a chlorination reactor 5, an ejector 6, a gas separator 7 and a dosing box 8;

[0030] The multi-media catalytic adsorption filter 1, the circulating water tank 2, the first water pump 3-1, the ejector 6, and the separator 7 are connected in sequence;

[0031] The output end of the circulating water tank 2 is connected to the input end of the first water pump 3-1, and one output end of the first water pump 3-1 is connected to the input end of the multi-media catalytic adsorption filter 1, so that a part of the urea desorption waste liquid re-enters the multi-media catalytic adsorption filter 1 for another catalytic adsorption, thereby improving the adsorption catalytic efficiency;

[0032] The inlet end of the separator 4 is connected to the circulating water tank 2 through a pipeline, the output end of the separator 4 is connected to the input end of the chlorination reactor 5 through a pipeline, and the output end of the chlorination reactor 5 is connected to the input end of the ejector 6;

[0033] The input end and the output end of the dosing box 8 are connected to the output end of the gas separator 7 and the second water pump 3 - 2 respectively.

[0034] The multi-media catalytic adsorption filter 1, the circulating water tank 2 and the input end of the gas separator 7 are all supplied with cooling water. The cooling water enters the gas separator 7 from the input end of the gas separator 7, and its function is to adjust the temperature and pressure of the water body, which is beneficial to improve the speed and depth of urea hydrolysis;

[0035] The multi-media catalytic adsorption filter 1 not only effectively removes suspended impurities to clarify the waste liquid and prevent subsequent blockage in the process, but also its filter material coated with the catalyst is also conducive to accelerating the hydrolysis rate.

[0036] Adjust the flow rate of the first water pump 3-1 to keep the concentrations of urea, ammonia in the water of the circulating water tank 2 and NH3 and CO2 in the steam phase at appropriate levels, and make the concentration in the liquid phase greater than that in the gas phase. A high concentration is conducive to faster decomposition of NH3 and CO2. The farther away from the equilibrium point, the greater the driving force, which is more conducive to hydrolysis and decomposition.

[0037] The chlorination reactor 5 adopts the breakpoint chlorination method to control the chlorine input to oxidize NH3-N in the wastewater into N2, thereby reducing the chromaticity of the waste liquid, removing odor, reducing the organic matter content in the waste liquid, and improving the coagulation effect.

[0038] The method for using the urea desorption waste liquid ammonia nitrogen reduction and wastewater recycling equipment comprises the following steps:

[0039] 1) Urea desorption waste liquid passes through the multi-media catalytic adsorption filter 1 and the circulating water tank 2 and enters the first water pump 3-1. A part of it re-enters the multi-media catalytic adsorption filter 1 for another catalytic adsorption, and a part of it enters the gas separator 7 through the ejector 6. Because the components of the urea desorption waste liquid have an impact on the rear-end urea hydrolysis reaction, when the ammonia and carbon dioxide content in the solution is high, it is not conducive to the hydrolysis reaction and the goal of reducing the ammonia nitrogen content cannot be achieved. After the urea analysis waste liquid is processed by the multi-media catalytic adsorption filter 1 and the circulating water tank 2, its component content can effectively improve the efficiency of the rear-end urea deep hydrolysis. Cooling water is added to the circulating water tank 2 to ensure that the operating temperature is stable within the range of 230-236°C;

[0040] 2) Cooling water enters the gas separator 7 from the input end of the gas separator 7, and its function is to adjust the temperature and pressure of the water body, which is conducive to improving the speed and depth of urea hydrolysis; the second water pump 3-2 is connected to the output end of the gas separator 7 and the dosing box 8, and its function is to adjust the mixing ratio of the active agent and the wastewater, which is conducive to the full mixing of the agent;

[0041] 3) The nitrogen-containing wastewater in the circulating water tank 2 enters the chlorination reactor 5 from the output end of the separator 4, and the chlorine input is controlled by the breakpoint chlorination method to oxidize the NH3-N in the wastewater into N2, thereby greatly reducing the color of the waste liquid, removing the odor, reducing the organic content in the waste liquid, and improving the coagulation effect, and then enters the gas separator 7 through the ejector 6;

[0042] 4) The waste liquid in the gas separator 7 is passed through the dosing box 8 to add a dispersing interfering agent and adjust the water quality components of the boiler water in the jacket to prevent the generation of diurea (or triurea) that is difficult to remove in the jacket. At the same time, treatment agents (phosphates such as sodium hexametaphosphate) are added to carry out comprehensive treatment such as iron removal, catalysis, oxygen reduction, hardness reduction and corrosion inhibition. The equipment and method reasonably utilize heat, recover low-level heat energy in the waste liquid, reduce the load of the circulating water system, and at the same time ensure the water quality of the boiler water, greatly reducing the emission of ammonia nitrogen.

[0043] After desorption treatment of fertilizer production wastewater, the original average COD concentration of urea desorption wastewater is 3308 mg / L, the average concentration of ammonia nitrogen is 1324 mg / L, the average carbon-nitrogen ratio is 4.29, the iron ion content is 0.51 mg / L, the oxygen content is 3 mg / L, and the urea content is about 1%. The urea analysis wastewater first enters the multi-media catalytic adsorption filter to effectively remove suspended impurities to clarify the wastewater and prevent subsequent blockage of the process. The clarified wastewater enters the separator after deep hydrolysis in the circulating water tank to separate the ammonia nitrogen wastewater. The separated ammonia nitrogen wastewater enters the chlorine reactor and is subjected to the ammonia removal process by the breakpoint chlorination method. Then it enters the gas separator through the ejector, and is subjected to comprehensive treatment such as iron removal, catalysis, oxygen reduction, hardness reduction and corrosion inhibition by dosing, and then is pumped to the jacket and waste heat boiler for reuse.

[0044] This embodiment adopts a multi-media catalytic adsorption-deep hydrolysis-breakpoint chlorination-treatment and reuse process. The urea analysis waste liquid first enters the three-stage multi-media catalytic adsorption filter to effectively remove suspended impurities to clarify the waste liquid and prevent subsequent blockage of the process. The clarified waste liquid enters the separator after deep hydrolysis in the circulating water tank to separate the ammonia nitrogen wastewater. The separated ammonia nitrogen wastewater enters the chlorine reactor and is subjected to the ammonia removal process by the breakpoint chlorination method.

[0045] from Figure 2 , Figure 3 and Figure 4 It can be known that: under normal production conditions, the original average COD concentration of urea desorption waste liquid is 3308.2mg / L, and the average concentration of ammonia nitrogen is 834.4 mg / L. After being treated by the equipment, the COD concentration has been greatly reduced compared with before, reduced to 1324.4mg / L, and the average concentration of wastewater ammonia nitrogen has also been greatly reduced to 158.92mg / L. The reduction of ammonia nitrogen concentration is mainly due to the recycling of urea desorption waste liquid produced by the urea production workshop, and the average carbon-nitrogen ratio is increased from 4.29 to 11.52, which is conducive to providing sufficient carbon source for denitrification and denitrification. After treatment, the iron ion and oxygen content are both lower than 0.2mg / L. The iron and oxygen content in the urea desorption waste liquid are reduced, so that the carbon steel equipment can be protected, the problem of being unable to be directly sent to the gasification jacket for recovery and discharge is solved, the operating cost of the sewage treatment plant is reduced, the situation of reducing the external discharge of hot water is reduced, and the economic benefit is improved.

[0046] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A urea desorption waste liquid ammonia nitrogen reduction and waste water recycling equipment, characterized by: It comprises a multi-media catalytic adsorption filter (1), a circulating water tank (2), a first water pump (3-1), a second water pump (3-2), a separator (4), a chlorination reactor (5), an ejector (6), a gas separator (7) and a drug adding tank (8); The multi-media catalytic adsorption filter (1), the circulating water tank (2), the first water pump (3-1), the ejector (6), and the gas separator (7) are connected in sequence; The input end of the separator (4) is connected to the circulating water tank (2) through a pipeline, and the output end of the separator (4) is connected to the input end of the chlorination reactor (5) through a pipeline; the output end of the chlorination reactor (5) is connected to the input end of the ejector (6); The dosing box (8) uses a dispersing interfering agent to adjust the water quality components of the boiler water in the jacket to prevent the generation of difficult-to-remove biuret or triuret in the jacket. At the same time, a treatment agent is added to the dosing box (8) to perform comprehensive treatments such as iron removal, catalysis, oxygen reduction, hardness reduction and corrosion inhibition. The method for using the urea desorption waste liquid ammonia nitrogen reduction and wastewater reuse equipment comprises the following steps: 1) The urea desorption waste liquid passes through the multi-media catalytic adsorption filter (1) and the circulating water tank (2) and enters the first water pump (3-1); a portion of the urea desorption waste liquid re-enters the multi-media catalytic adsorption filter (1) for another catalytic adsorption; a portion of the urea desorption waste liquid passes through the ejector (6) and enters the gas separator (7); 2) Cooling water enters the gas separator (7) from the input end of the gas separator (7), and its function is to adjust the temperature and pressure of the water body, which is conducive to increasing the speed and depth of urea hydrolysis; the second water pump (3-2) is connected to the output end of the gas separator (7) and the dosing box (8), and its function is to adjust the mixing ratio of the reagent and the urea desorption waste liquid, which is conducive to the full mixing of the reagent; 3) The urea desorption waste liquid in the circulating water tank (2) enters the chlorination reactor (5) from the output end of the separator (4). The chlorination reactor (5) controls the input amount of chlorine gas through the breakpoint chlorination method to oxidize NH3-N in the urea desorption waste liquid into N2, and then enters the gas separator (7) through the ejector (6); 4) The waste liquid in the gas separator (7) is passed through the dosing box (8) to adjust the water quality of the boiler water in the jacket by adding a dispersing interfering agent, and at the same time, a treatment agent is added to remove iron, catalyze, reduce oxygen, reduce hardness and inhibit corrosion; The first water pump (3-1) regulates the concentration of urea and ammonia in the liquid phase of the circulating water tank (2) and the concentration of NH3 and CO2 in the steam gas phase, so that the liquid phase concentration is greater than the gas phase concentration. A high liquid phase concentration is conducive to the decomposition of NH3 and CO2.

2. The urea desorption waste liquid ammonia nitrogen reduction and waste water reuse equipment according to claim 1, characterized in that: The input ends of the multi-media catalytic adsorption filter (1), the circulating water tank (2) and the gas separator (7) are all supplied with cooling water.

3. The urea desorption waste liquid ammonia nitrogen reduction and waste water reuse equipment according to claim 1 is characterized by: The output end of the circulating water tank (2) is connected to the input end of the first water pump (3-1), and an output end of the first water pump (3-1) is connected to the input end of the multi-media catalytic adsorption filter (1) to perform adsorption catalysis again, thereby improving the adsorption catalytic efficiency.

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