A system for producing purified concentrated ammonium sulfate using a membrane contactor

Abstract

The application discloses a system for producing pure concentrated ammonium sulfate by using a membrane contactor, which comprises a degassing unit and an absorption unit; the degassing unit comprises a degassing membrane contactor, an ammonia-nitrogen wastewater inlet channel connected with a wastewater inlet of the degassing membrane contactor, and a gas extraction pipeline connected with a gas phase outlet of the degassing membrane contactor; the ammonia-nitrogen wastewater inlet channel is connected with an ammonia-nitrogen wastewater tank; the absorption unit comprises an absorption membrane contactor, a waste sulfuric acid inlet channel connected with a waste sulfuric acid inlet of the absorption membrane contactor, and an ammonium sulfate production pipeline connected with a production outlet of the absorption membrane contactor; the waste sulfuric acid inlet channel is connected with a sulfuric acid circulating tank; the gas extraction pipeline is connected with an ammonia gas inlet of the absorption membrane contactor; and the ammonium sulfate production pipeline of the absorption membrane contactor produces ammonium sulfate. The system is simple and reliable, convenient to operate, can treat waste sulfuric acid and ammonia-nitrogen wastewater to generate usable pure ammonium sulfate, does not cause secondary pollution, has high concentration ratio, has high wastewater recycling rate, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a system for producing pure concentrated ammonium sulfate based on the recovery of ammonia nitrogen wastewater and waste sulfuric acid and the use of a membrane contactor. Background Technology

[0002] Ammonium sulfate is an inorganic compound used as fertilizer, an excellent nitrogen fertilizer suitable for various soils and crops, and also used in textiles, leather, and medicine. Ammonium sulfate also has many biological applications, primarily in protein purification processes. Because ammonium sulfate is inert, it does not readily react with other bioactive substances, thus maximizing the protection of protein activity during purification. Furthermore, its excellent solubility allows it to create a high-salt environment, preparing the protein for precipitation and subsequent high-salt purification.

[0003] One method for producing ammonium sulfate involves the direct neutralization reaction of ammonia and sulfuric acid. This method is less common and is mainly used for absorbing byproducts or waste gases from industrial production with sulfuric acid or ammonia water (e.g., sulfuric acid absorbing ammonia from coke oven gas, ammonia water absorbing sulfur dioxide from smelter flue gas, ammonia from caprolactam production, or sulfuric acid waste liquid from the sulfuric acid process for titanium dioxide production). Another method is the gypsum process, which primarily uses natural gypsum or phosphogypsum, ammonia, and carbon dioxide as raw materials to produce ammonium sulfate. Traditional tail gas recovery methods have the following problems: large volume of spray towers, high operational difficulty, high risk, high investment, limited efficiency, waste of ammonia, and high internal ammonia concentrations that can harm operators.

[0004] The production of concentrated ammonium sulfate generally adopts the evaporation concentration method. The concentration rate of ammonium sulfate is affected by factors such as pH value, temperature, and concentration. Furthermore, there are problems such as ammonia evaporation waste and high energy consumption. Moreover, evaporation concentration crystallization is generally only suitable for wastewater with very high ammonia nitrogen concentration, and the concentration ratio is limited.

[0005] Currently, membrane contactors can effectively increase the concentration ratio of ammonium sulfate. However, after long-term use, due to the service life and structural reasons, the surface hydrophobicity of the membrane fibers will gradually disappear, allowing a small amount of ammonia nitrogen wastewater to enter the concentrated ammonium sulfate. If there are different ions in the wastewater, it will cause the concentrated ammonium sulfate to be contaminated, reduce its purity, and have a negative impact on the reuse of ammonia nitrogen. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a system for producing pure concentrated ammonium sulfate using a membrane contactor. This system is simple, reliable, and easy to operate. It can treat waste sulfuric acid and ammonia nitrogen wastewater to generate usable pure ammonium sulfate without causing secondary pollution. Furthermore, it has a high concentration ratio and a high wastewater recycling rate, and has broad application prospects.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0008] A system for producing pure concentrated ammonium sulfate using a membrane contactor includes a degassing unit for removing ammonia from ammonia nitrogen wastewater and an absorption unit for absorbing ammonia.

[0009] The degassing unit includes a degassing membrane contactor, an ammonia nitrogen wastewater inlet connected to the wastewater inlet of the degassing membrane contactor, and an extraction pipeline connected to the gas phase outlet of the degassing membrane contactor; the ammonia nitrogen wastewater inlet is connected to the ammonia nitrogen wastewater tank.

[0010] The absorption unit includes an absorption membrane contactor, a waste sulfuric acid inlet connected to the waste acid inlet of the absorption membrane contactor, and an ammonium sulfate production pipeline connected to the production outlet of the absorption membrane contactor; the waste sulfuric acid inlet is connected to the sulfuric acid circulation tank.

[0011] The degassing unit's extraction pipeline is connected to the ammonia inlet of the absorption membrane contactor of the absorption unit; the ammonium sulfate output pipeline of the absorption membrane contactor outputs the ammonium sulfate generated by the absorption of ammonia by waste sulfuric acid.

[0012] Furthermore, the extraction pipeline is equipped with a vacuum pump and a gas-liquid separator; the gas-liquid separator can separate the gas-liquid mixture at the outlet of the vacuum pump, so that the gas outlet of the gas-liquid separator outputs pure ammonia.

[0013] Furthermore, the gas phase outlet of the degassing membrane contactor is connected to a leakage return pipeline, which is equipped with a leakage return buffer tank, a leakage return buffer valve, a leakage return tank, and a leakage return valve; the leakage return pipeline is connected to the ammonia nitrogen wastewater tank.

[0014] Furthermore, the degassing membrane contactor also has a water outlet, which is connected to an ammonia nitrogen-removed water production pipeline.

[0015] Furthermore, the degassing membrane contactor is connected to an ammonia nitrogen wastewater circulation pipeline at its water outlet; the ammonia nitrogen wastewater circulation pipeline is equipped with an ammonia nitrogen wastewater circulation valve and an ammonia nitrogen wastewater check valve; the ammonia nitrogen wastewater circulation pipeline is connected to the ammonia nitrogen wastewater tank.

[0016] Furthermore, the outlet of the absorber membrane contactor is also connected to a waste sulfuric acid circulation pipeline; the waste sulfuric acid circulation pipeline is equipped with a waste sulfuric acid circulation valve and a waste sulfuric acid check valve; the waste sulfuric acid circulation pipeline is connected to the sulfuric acid circulation tank.

[0017] Furthermore, the gas phase outlet of the absorber membrane contactor is connected to an ammonia circuit, which is equipped with a gas delivery pump; the ammonia circuit is connected to the inlet of the degassing membrane contactor. Excess ammonia flowing out of the gas phase outlet of the absorber membrane contactor can be used as purge gas to enter the degassing membrane contactor for gas purging, thereby improving the efficiency of the degassing membrane contactor.

[0018] Furthermore, the ammonia nitrogen wastewater inlet line is equipped with an ammonia nitrogen wastewater inlet valve, an ammonia nitrogen wastewater pump, an ammonia nitrogen wastewater flow regulating valve, an ammonia nitrogen wastewater safety filter, an ammonia nitrogen wastewater flow meter, and a liquid phase maintenance valve; the waste sulfuric acid inlet line is equipped with an acid inlet valve, an acid circulation pump, an acid flow regulating valve, an acid safety filter, and an acid flow meter.

[0019] Furthermore, the vacuum pump is also connected to a cooling circulation pipeline, which is connected to the waste sulfuric acid inlet, so that the waste sulfuric acid can be used as a cooling medium to cool the vacuum pump.

[0020] Furthermore, the waste sulfuric acid circulation pipeline is also equipped with a heat exchanger, which is connected to a second cooling circulation pipeline, which can cool and reduce the temperature of the liquid in the waste sulfuric acid circulation pipeline.

[0021] Furthermore, online ammonia nitrogen concentration sensors are connected to both the product inlet of the degassing membrane contactor and the product outlet of the absorption membrane contactor.

[0022] The beneficial effects of this invention are:

[0023] The system uses a degassing membrane contactor to treat ammonia nitrogen wastewater and a gas-liquid separator to separate it to obtain pure ammonia gas. It also uses an absorption membrane contactor to treat waste sulfuric acid, allowing the waste sulfuric acid to react with the ammonia gas provided by the degassing membrane contactor to produce pure ammonium sulfate.

[0024] In the degassing unit, the system is equipped with a leakage return buffer tank and a leakage return tank at the gas phase outlet of the degassing membrane contactor. This allows the leaked ammonia nitrogen wastewater to flow into the leakage return buffer tank and the leakage return tank due to gravity, and then flow back to the ammonia nitrogen wastewater tank. This minimizes the leakage of ammonia nitrogen wastewater, reduces the generation of by-products, and improves the purity of the final ammonium sulfate product.

[0025] In the absorption unit, the waste sulfuric acid side of the absorption membrane contactor can continuously absorb pure ammonia gas to generate pure ammonium sulfate.

[0026] The system of this invention utilizes two membrane contactors to treat ammonia nitrogen wastewater and waste sulfuric acid, which not only improves the treatment efficiency and effect of ammonia nitrogen wastewater and waste sulfuric acid, but also obtains relatively pure ammonium sulfate.

[0027] Using this system, waste sulfuric acid and ammonia nitrogen wastewater can be recycled, which can effectively reduce the discharge of sulfuric acid wastewater and ammonia nitrogen wastewater and reduce the impact on the environment.

[0028] This system can safely and quickly treat and recycle waste sulfuric acid and ammonia nitrogen wastewater simultaneously, producing pure concentrated ammonium sulfate. This greatly reduces the production cost of ammonium sulfate, improves production efficiency, reduces operational difficulty and conditions, significantly reduces the emission of sulfuric acid and ammonia nitrogen, and produces no secondary pollutants, thus reducing environmental harm.

[0029] The system of the present invention is simple to operate, safe and reliable, easy to maintain, has a long service life, low operating cost, high economic benefits, and broad application prospects. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the system for producing pure concentrated ammonium sulfate using a membrane contactor according to the present invention;

[0031] In the diagram, 101: Degassing membrane contactor; 102: Ammonia nitrogen wastewater inlet; 103: Exhaust pipe; 104: Ammonia nitrogen wastewater tank; 105: Ammonia nitrogen wastewater inlet valve; 106: Ammonia nitrogen wastewater pump; 107: Ammonia nitrogen wastewater flow regulating valve; 108: Ammonia nitrogen wastewater safety filter; 109: Ammonia nitrogen wastewater flow meter; 110: Liquid phase maintenance valve; 111: Vacuum pump; 112: Gas-liquid separator; 113: Vacuum regulating valve; 114: Ammonia gas flow regulating valve; 115: Ammonia gas flow meter; 116: Needle valve; 117: Separation reflux pipe; 118: Separation reflux buffer tank; 11 9: Separation reflux buffer valve; 120: Separation reflux tank; 121: Separation reflux valve; 122: Leakage reflux pipeline; 123: Leakage reflux buffer tank; 124: Leakage reflux buffer valve; 125: Leakage reflux tank; 126: Leakage reflux valve; 127: Ammonia nitrogen removal water production pipeline; 128: Production water valve; 129: Ammonia nitrogen wastewater circulation pipeline; 130: Ammonia nitrogen wastewater circulation valve; 131: Ammonia nitrogen wastewater check valve; 132: Air supply pipeline; 133: Air inlet valve; 134: Air volume regulating valve; 135: Ammonia nitrogen wastewater supply valve; 136: Ammonia nitrogen wastewater supply pipeline;

[0032] 201: Absorption membrane contactor; 202: Waste sulfuric acid inlet; 203: Ammonium sulfate production pipeline; 204: Sulfuric acid circulation tank; 205: Acid inlet valve; 206: Acid circulation pump; 207: Acid flow regulating valve; 208: Acid security filter; 209: Acid flow meter; 210: Waste sulfuric acid circulation pipeline; 211: Waste sulfuric acid circulation valve; 212: Waste sulfuric acid check valve; 213: Product valve; 214: Ammonia circuit; 215: Gas transfer pump; 216: Purge gas volume regulating valve; 217: Purge gas flow meter; 218: Heat exchanger; 219: Sulfuric acid supply valve; 220: Sulfuric acid supply pipeline;

[0033] 301: Cooling circulation pipe one; 302: Cooling circulation pipe two. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0035] like Figure 1 The system shown is for producing pure concentrated ammonium sulfate using a membrane contactor, comprising a degassing unit for removing ammonia from ammonia nitrogen wastewater and an absorption unit for absorbing ammonia.

[0036] The degassing unit includes a degassing membrane contactor 101, an ammonia nitrogen wastewater inlet 102 connected to the wastewater inlet of the degassing membrane contactor 101, and an extraction pipeline 103 connected to the gas phase outlet of the degassing membrane contactor 101; the ammonia nitrogen wastewater inlet 102 is connected to the ammonia nitrogen wastewater tank 104.

[0037] The absorption unit includes an absorption membrane contactor 201, a waste sulfuric acid inlet 202 connected to the waste acid inlet of the absorption membrane contactor 201, and an ammonium sulfate production pipeline 203 connected to the production outlet of the absorption membrane contactor 201; the waste sulfuric acid inlet 202 is connected to the sulfuric acid circulation tank 204.

[0038] The degassing unit's extraction pipeline 103 is connected to the ammonia inlet of the absorption membrane contactor 201 of the absorption unit; the ammonium sulfate production pipeline 203 of the absorption membrane contactor 201 produces ammonium sulfate generated by the absorption of ammonia by waste sulfuric acid.

[0039] The ammonia nitrogen wastewater inlet 102 in the degassing unit is equipped with an ammonia nitrogen wastewater inlet valve 105, an ammonia nitrogen wastewater pump 106, an ammonia nitrogen wastewater flow regulating valve 107, an ammonia nitrogen wastewater security filter 108, an ammonia nitrogen wastewater flow meter 109, and a liquid phase maintenance valve 110.

[0040] The extraction pipeline 103 is connected to the ammonia inlet of the absorption membrane contactor 201 of the absorption unit. The extraction pipeline 103 is equipped with a vacuum pump 111 and a gas-liquid separator 112; the gas-liquid separator 112 can separate ammonia from liquid (sulfuric acid wastewater), so that the gas outlet of the gas-liquid separator 112 outputs pure ammonia. In addition, the extraction pipeline 103 is also equipped with a vacuum regulating valve 113, an ammonia flow regulating valve 114, an ammonia flow meter 115, and a needle valve 116; the vacuum regulating valve 113 can adjust the vacuum level.

[0041] The outlet of the gas-liquid separator 112 is connected to the separation reflux pipeline 117; the separation reflux pipeline 117 is equipped with a separation reflux buffer tank 118, a separation reflux buffer valve 119, a separation reflux tank 120, and a separation reflux valve 121. The separation reflux pipeline 117 is connected to the sulfuric acid circulation tank.

[0042] The gas phase outlet of the degassing membrane contactor 101 is also connected to a leakage return pipeline 122, which is equipped with a leakage return buffer tank 123, a leakage return buffer valve 124, a leakage return tank 125, and a leakage return valve 126; the leakage return pipeline 122 is connected to the ammonia nitrogen wastewater tank 104.

[0043] The degassing membrane contactor 101 also has a water outlet, which is connected to an ammonia nitrogen removal water output pipeline 127. A water output valve 128 is installed on the ammonia nitrogen removal water output pipeline 127. An ammonia nitrogen wastewater circulation pipeline 129 is also connected to the water outlet of the degassing membrane contactor 101; this ammonia nitrogen wastewater circulation pipeline 129 is equipped with an ammonia nitrogen wastewater circulation valve 130 and an ammonia nitrogen wastewater check valve 131; this ammonia nitrogen wastewater circulation pipeline 129 is connected to the ammonia nitrogen wastewater tank 104.

[0044] The waste sulfuric acid inlet 202 in the absorption unit is equipped with an acid inlet valve 205, an acid circulation pump 206, an acid flow regulating valve 207, an acid safety filter 208, and an acid flow meter 209.

[0045] The outlet of the absorber membrane contactor 201 is also connected to a waste sulfuric acid circulation pipeline 210; the waste sulfuric acid circulation pipeline 210 is equipped with a waste sulfuric acid circulation valve 211 and a waste sulfuric acid check valve 212; the waste sulfuric acid circulation pipeline 210 is connected to the sulfuric acid circulation tank 204. The ammonium sulfate production pipeline 203, which is connected to the outlet of the absorber membrane contactor 201, is equipped with a product valve 213.

[0046] The gas phase outlet of the absorber membrane contactor 201 is connected to an ammonia circuit 214, which is equipped with a gas delivery pump 215. The ammonia circuit 214 is connected to the inlet of the degassing membrane contactor 101. Excess ammonia flowing out of the gas phase outlet of the absorber membrane contactor 201 can be used as purge gas to enter the degassing membrane contactor 101 for gas purging, thereby improving the efficiency of the degassing membrane contactor. In addition, the ammonia circuit 214 is also equipped with a purge gas flow regulating valve 216 and a purge gas flow meter 217.

[0047] To regulate the vacuum level and ensure the amount of purge air entering the degassing membrane contactor, the system is also equipped with an air supply pipeline 132; the air supply pipeline 132 is equipped with an air inlet valve 133; and the air supply pipeline is divided into two supply branches, one of which is connected to the extraction pipeline 103, and the other supply branch is connected to the ammonia circuit 214; both supply branches are equipped with air volume regulating valves 134.

[0048] The vacuum pump 111 is also connected to a cooling circulation pipeline 301, which is connected to the waste sulfuric acid inlet 202. Waste sulfuric acid can be used as a cooling medium to cool the vacuum pump 111.

[0049] The waste sulfuric acid circulation pipeline 210 is also equipped with a heat exchanger 218, which is connected to a cooling circulation pipeline 302. A cooling medium is used to cool the liquid in the waste sulfuric acid circulation pipeline 210. When the temperature of the ammonia nitrogen wastewater does not exceed the maximum tolerance temperature set by the membrane contactor, the cooling medium is ammonia nitrogen wastewater; when the temperature of the ammonia nitrogen wastewater exceeds the maximum tolerance temperature set by the membrane contactor, the cooling medium is cold water.

[0050] Online ammonia nitrogen concentration sensors are connected to the product water inlet of the degassing membrane contactor 101 and the product outlet of the absorption membrane contactor 201 to detect the ammonia nitrogen concentration online.

[0051] Pressure gauges and pH meters are installed on both the ammonia nitrogen wastewater inlet 102 and the waste sulfuric acid inlet 202; pressure gauges and pH meters are also installed on the pipeline at the product water outlet of the degassing membrane contactor 101 and the product outlet of the absorption membrane contactor 201. Pressure gauges are also installed on the ammonia gas circuit 214 and the extraction pipeline 103. The pressure gauges can detect the pressure in each pipeline, and the pH meters can detect the pH of the liquid in the pipeline.

[0052] Both the ammonia nitrogen wastewater tank 104 and the sulfuric acid circulation tank 204 are equipped with low liquid level alarms and high liquid level alarms to detect and warn of liquid levels.

[0053] In addition, the ammonia nitrogen wastewater tank 104 is also connected to the ammonia nitrogen wastewater supply pipeline 136 via the ammonia nitrogen wastewater supply valve 135; the sulfuric acid circulation tank 204 is also connected to the waste sulfuric acid supply pipeline 220 via the sulfuric acid supply valve 219.

[0054] In this system, the membrane fibers in the degassing membrane contactor 101 and the absorption membrane contactor 201 are both treated with a hydrophobic surface, making them breathable, i.e., breathable but not water-permeable.

[0055] The system's operation process:

[0056] After adjusting the pH of the ammonia nitrogen wastewater to 11-12, the ammonia nitrogen wastewater is fed into the ammonia nitrogen wastewater tank 104 through the ammonia nitrogen wastewater supply valve 135 and the ammonia nitrogen wastewater supply pipeline 136. Under the action of the ammonia nitrogen wastewater pump 106, the ammonia nitrogen wastewater passes through the ammonia nitrogen wastewater security filter 108 and enters the degassing membrane contactor 101. By controlling the vacuum pump 111 on the extraction pipeline 103 to generate negative pressure, the ammonia gas escaping from the ammonia nitrogen wastewater is extracted. At the same time, the positive pressure at the outlet of the vacuum pump is used to send the ammonia gas into the gas-liquid separator 112. The gas-liquid separator 112 performs gas-liquid separation to obtain pure ammonia gas, which then enters the absorption membrane contactor 201 for absorption.

[0057] Only ammonia gas and other dissolved gases in the ammonia nitrogen wastewater can be drawn away through the micropores on the surface of the membrane fibers of the degassing membrane contactor 101. However, due to the degradation of the hydrophobicity and permeability of the membrane fibers over time, leakage may occur in the degassing membrane contactor 101, resulting in a small amount of ammonia nitrogen wastewater passing through the membrane fibers. At this time, the leaked ammonia nitrogen wastewater will enter the leakage return buffer tank 123 for temporary storage due to gravity. After the leakage return buffer tank 123 is full, the leaked ammonia nitrogen wastewater enters the leakage return tank 125 through the leakage return buffer valve 124. When the leakage return tank 125 is full, the leakage return valve 126 is opened, and the leaked ammonia nitrogen wastewater enters the ammonia nitrogen wastewater tank 104 for further treatment. After gas-liquid separation by gas-liquid separator 112, the separated liquid passes sequentially through separation reflux buffer tank 118, separation reflux buffer valve 119, separation reflux tank 120 and separation reflux valve 121, and enters sulfuric acid circulation tank 204 for processing.

[0058] The online ammonia nitrogen concentration sensor N-1 installed at the outlet of the degassing membrane contactor 101 determines whether the ammonia nitrogen concentration in the ammonia nitrogen wastewater meets the standard. If it does not meet the standard, the product water valve 128 on the ammonia nitrogen removal water production pipeline 127 is closed, and the ammonia nitrogen wastewater circulation valve 130 on the ammonia nitrogen wastewater circulation pipeline 129 is opened. The wastewater flowing out of the outlet of the degassing membrane contactor 101 returns to the ammonia nitrogen wastewater tank 104 for further treatment. The online ammonia nitrogen concentration sensor N-1 at the outlet of the degassing membrane contactor is continuously observed to determine whether the ammonia nitrogen concentration meets the standard. If it meets the standard, the ammonia nitrogen wastewater circulation valve 130 is closed, and the product water valve 128 is opened. At this time, it is in the production water mode, and the ammonia nitrogen removal water is discharged through the ammonia nitrogen removal water production pipeline 127.

[0059] Pay attention to the pH values ​​of pH-1 at the ammonia nitrogen wastewater inlet 102 and pH-2 at the product outlet of the degassing membrane contactor 101. These values ​​should always be greater than 11 and less than 12. If the value is less than 10.5, add alkali to the ammonia nitrogen wastewater tank 104 to increase the pH value. Pressure gauges PI-1 at the ammonia nitrogen wastewater inlet 102 and PI-2 at the product outlet of the degassing membrane contactor 101 serve as indicators for adjusting the ammonia nitrogen wastewater flow meter 109. If either pressure exceeds the limit, reduce the flow rate as soon as possible to prevent excessive leakage from the degassing membrane contactor into the gas phase outlet. Pressure gauge PI-3 on the extraction pipeline 103 is a vacuum gauge; observe its reading and adjust the vacuum level using the vacuum regulating valve 113 and the air flow regulating valve 134. The cooling medium in the vacuum pump 111 is waste sulfuric acid filtered in the absorption unit. The waste sulfuric acid is returned through the cooling circulation pipeline 301 to further reduce ammonia leakage. The gas-liquid separator 112 ensures that only pure gas enters the absorption unit. The low-level alarm LAL-1 on the ammonia nitrogen wastewater tank 104 prevents the wastewater pump from running dry and being damaged due to low liquid levels, while the high-level alarm LAH-1 prevents wastewater overflow due to high liquid levels in the tank 104. The ammonia nitrogen wastewater check valve 131 prevents ammonia nitrogen wastewater from being directly discharged without being treated by the degassing membrane contactor 101.

[0060] Waste sulfuric acid is fed into the sulfuric acid circulation tank 204 through the waste sulfuric acid supply pipeline 220. Under the action of the acid circulation pump 206, the waste sulfuric acid is filtered through the acid safety filter 208 and then enters the absorption membrane contactor 201 to absorb the pure ammonia gas released from the degassing unit. The pure ammonia gas released from the degassing unit enters the absorption membrane contactor 201 and reacts with the waste sulfuric acid to generate ammonium sulfate. The mixed solution of ammonium sulfate and waste sulfuric acid can be circulated back to the sulfuric acid circulation tank 204 through the waste sulfuric acid circulation pipeline 210. When the ammonia nitrogen concentration reaches the standard, the product valve 213 is opened, and the ammonium sulfate solution will be discharged through the ammonium sulfate production pipeline 203 for the reuse of pure concentrated ammonium sulfate. A heat exchanger 218 is installed on the waste sulfuric acid circulation pipeline 210 to prevent the solution temperature from rising due to the absorption reaction. The cooling medium in the heat exchanger 218 is the circulating ammonia nitrogen wastewater that has undergone degassing treatment in the degassing unit. Moreover, the waste heat from the absorption unit can be used during the heat exchange process to further increase the inlet water temperature of the degassing unit, thereby improving the overall efficiency of the system and reducing energy consumption such as electric heating. Furthermore, when the temperature of the ammonia nitrogen wastewater exceeds the maximum tolerance temperature set by the membrane contactor, cold water can be used as the cooling medium for the heat exchanger.

[0061] After passing through the absorption membrane contactor 201, excess ammonia gas is re-entered into the degassing membrane contactor 101 via the gas transfer pump 215 for gas purging, thereby improving the efficiency of the degassing unit.

[0062] The ammonia nitrogen concentration is checked by monitoring the online ammonia nitrogen sensor N-2 at the outlet of the absorption membrane contactor 201 to determine if it meets the standard. The presence of pH-4 at the outlet of the absorption membrane contactor 201 and pH-3 on the waste sulfuric acid inlet 202 is also monitored to determine if waste sulfuric acid needs to be added or discharged. If the pH value is less than 2 and the online ammonia nitrogen sensor N-2 does not meet expectations, the product valve 213 is closed and the waste sulfuric acid circulation valve 211 is opened, entering circulation mode. The online ammonia nitrogen sensor N-2 and pH-4 are continuously monitored to assess the absorption of sulfuric acid wastewater. When the pH-4 value is greater than 2, the sulfuric acid supply valve 219 is opened to replenish acid until it is less than 2, continuing the circulation process. When the online ammonia nitrogen sensor N-2 indicates that the ammonia nitrogen concentration meets the standard, the waste sulfuric acid circulation valve 211 is closed and the product valve 213 is opened to discharge ammonium sulfate, entering product water mode.

[0063] Note that the pH value of the sulfuric acid wastewater should be less than 4 for absorption. If it is too high, add waste sulfuric acid to the sulfuric acid circulation tank. Pressure gauge PI-4 on the extraction pipeline 103 and pressure gauges PI-5 and PI-6 on the ammonia circuit 214 serve as indicators for adjusting the purge gas flow meter. If any pressure exceeds the limit, the flow rate should be reduced as quickly as possible through the purge gas flow regulating valve 216 to avoid excessive system load and potential danger. Furthermore, an air inlet is added before the gas delivery pump 215 on the ammonia circuit 214, using the air supply pipeline 132 to supplement air. The air intake is controlled by the purge gas flow regulating valve 216 at the gas delivery pump 215 to ensure sufficient purge gas for gas purging in the degassing unit. Pressure gauge PI-7 on the waste sulfuric acid inlet 202 and pressure gauge PI-8 at the outlet of the absorption membrane contactor 201 serve as indicators for adjusting the acid flow meter 209. The low-level alarm LAL-2 on the sulfuric acid circulation tank 204 prevents the acid circulation pump from running dry and being damaged due to a low liquid level in the tank. The high-level alarm LAH-2 on the sulfuric acid circulation tank 204 prevents liquid overflow due to a high liquid level in the tank. The waste sulfuric acid check valve 212 prevents sulfuric acid wastewater from directly entering the ammonium sulfate production pipeline 203 without being treated by the absorption membrane contactor 201.

[0064] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A system for producing pure concentrated ammonium sulfate using a membrane contactor, characterized in that: It includes a degassing unit for removing ammonia from ammonia nitrogen wastewater and an absorption unit for absorbing ammonia. The degassing unit includes a degassing membrane contactor, an ammonia nitrogen wastewater inlet connected to the wastewater inlet of the degassing membrane contactor, and an extraction pipeline connected to the gas phase outlet of the degassing membrane contactor; the ammonia nitrogen wastewater inlet is connected to the ammonia nitrogen wastewater tank. The absorption unit includes an absorption membrane contactor, a waste sulfuric acid inlet connected to the waste acid inlet of the absorption membrane contactor, and an ammonium sulfate production pipeline connected to the production outlet of the absorption membrane contactor; the waste sulfuric acid inlet is connected to the sulfuric acid circulation tank. The degassing unit's extraction pipeline is connected to the ammonia inlet of the absorption membrane contactor of the absorption unit; the ammonium sulfate output pipeline of the absorption membrane contactor outputs the ammonium sulfate generated by the absorption of ammonia by waste sulfuric acid; The gas phase outlet of the degassing membrane contactor is connected to a leakage return pipeline, which is equipped with a leakage return buffer tank, a leakage return buffer valve, a leakage return tank, and a leakage return valve; the leakage return pipeline is connected to the ammonia nitrogen wastewater tank.

2. The system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 1, characterized in that: The extraction pipeline is equipped with a vacuum pump and a gas-liquid separator; the outlet of the gas-liquid separator outputs pure ammonia gas.

3. The system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 1, characterized in that: The degassing membrane contactor also has a water outlet, which is connected to an ammonia nitrogen-removed water output pipeline.

4. The system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 3, characterized in that: The degassing membrane contactor is also connected to an ammonia nitrogen wastewater circulation pipeline at its water outlet; the ammonia nitrogen wastewater circulation pipeline is equipped with an ammonia nitrogen wastewater circulation valve and an ammonia nitrogen wastewater check valve; the ammonia nitrogen wastewater circulation pipeline is connected to the ammonia nitrogen wastewater tank.

5. A system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 1, characterized in that: The outlet of the absorber membrane contactor is also connected to a waste sulfuric acid circulation pipeline; the waste sulfuric acid circulation pipeline is equipped with a waste sulfuric acid circulation valve and a waste sulfuric acid check valve; the waste sulfuric acid circulation pipeline is connected to the sulfuric acid circulation tank.

6. A system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 1, characterized in that: The gas phase outlet of the absorber membrane contactor is connected to an ammonia circuit, which is equipped with a gas delivery pump; the ammonia circuit is connected to the air inlet of the degassing membrane contactor.

7. A system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 1, characterized in that: The ammonia nitrogen wastewater inlet line is equipped with an ammonia nitrogen wastewater inlet valve, an ammonia nitrogen wastewater pump, an ammonia nitrogen wastewater flow regulating valve, an ammonia nitrogen wastewater safety filter, an ammonia nitrogen wastewater flow meter, and a liquid phase maintenance valve; the waste sulfuric acid inlet line is equipped with an acid inlet valve, an acid circulation pump, an acid flow regulating valve, an acid safety filter, and an acid flow meter.

8. A system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 2, characterized in that: The vacuum pump is also connected to a cooling circulation pipeline, which is connected to the waste sulfuric acid inlet.

9. A system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 5, characterized in that: The waste sulfuric acid circulation pipeline is also equipped with a heat exchanger, which is also connected to a second cooling circulation pipeline.

10. A system for producing pure concentrated ammonium sulfate using a membrane contactor according to claim 3, characterized in that: Online ammonia nitrogen concentration sensors are connected to both the product water inlet of the degassing membrane contactor and the product outlet of the absorption membrane contactor.

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