Ammonia degassing device and resource recovery type high-concentration wastewater treatment system using the same

Abstract

To provide an ammonia degassing device and a resource recovery type high-concentration wastewater treatment system using the same.SOLUTION: There is provided a resource recovery type high-concentration wastewater treatment system in which raw water is made by removing solids from high-concentration sewage wastewater, and pH, temperature and pressure conditions in a reduced pressure reactor are optimized, and ammonia is degassed with high efficiency using vacuum degassing or a combination of vacuum and ultrasonic degassing, and the ammonia mixed gas recovered by the degassing process is selectively purified and recovered in an ammonia gas phase without phase change by a separation membrane process in which the ammonia mixed gas is passed through a polymer gas separation membrane. Thereby, the recovered ammonia can be used as a resource for producing urea water, as a raw material for green hydrogen, and for co-combustion power generation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an ammonia degassing device and a resource recovery type high-concentration wastewater treatment system using the same. More specifically, the present invention targets raw water obtained by collecting high-concentration wastewater and removing solids, optimizes the pH, temperature, and pressure conditions in a vacuum reactor, and removes ammonia with high efficiency through an ammonia degassing step using vacuum degassing or a combination of vacuum and ultrasonic degassing. The ammonia mixed gas recovered by the degassing step is selectively purified and recovered in the gas phase with high purity without phase change by a separation membrane step of passing through a polymer gas separation membrane. The present invention relates to a resource recovery type high-concentration wastewater treatment system that performs a process of recycling the recovered high-purity ammonia.

Background Art

[0002] With the increase in the number of livestock, the amount of livestock manure generated is continuously increasing, and livestock manure is mainly recycled as compost or liquid manure and returned to agricultural land.

[0003] However, while the amount of livestock manure generated is expected to increase in the future due to the increase in the number of livestock, the area of agricultural land consuming the recycled compost and liquid manure is expected to continuously decrease. Therefore, it has been pointed out that it is difficult to secure demand destinations for compost and liquid manure.

[0004] Therefore, there are limitations in the utilization of compost and liquid manure as resources, and alternative solutions for resource utilization are needed. Specifically, in addition to the resource utilization of compost and liquid manure, alternatives for fertilizer resource utilization are required through the energy conversion and solid fuel conversion of biogas.

[0005] Therefore, it is necessary to establish strategies for bioenergy, advanced livestock wastewater treatment, and high-value-added resource recovery other than simple compost based on the enlargement of pig farms.

[0006] Regarding the resource utilization of livestock manure, in the case of Chinese enterprises, the pig manure generated on farms is completely converted into biogas and utilized as power generation and heat sources, achieving zero discharge of wastewater and minimizing odor generation. In particular, the realization of carbon neutrality is in progress with a target date of 2050.

[0007] The realization of carbon neutrality is a very challenging goal, but the international community may demand even higher goals. To achieve greenhouse gas reduction through innovation under strengthened environmental regulations, investment is emphasized to support the development and early commercialization of forward-looking energy technologies. At this time, ammonia for accelerating greenhouse gas reduction is regarded as a type of hydrogen energy, with the difference that the produced hydrogen is transported and utilized in the form of ammonia. If a global hydrogen economy arrives, the production, transportation, and utilization destinations of ammonia as a hydrogen carrier should increase, so the ammonia industry is expected to grow together with the hydrogen industry.

[0008] Currently, as a process for recovering nitrogen from wastewater and waste with high nitrogen concentration, the stripping process that extracts ammonium ions contained in the wastewater in gas form and then recovers the extracted ammonia using a sulfuric acid solution is most widely used.

[0009] Generally, in the stripping process, to increase the recovery rate of ammonia gas, the proportion in the form of ammonia gas must be high. So, after raising the pH to about 9.5 - 11.5, air is injected into the stripping column to recover ammonia gas, and the recovered air is injected into the absorption column with sulfuric acid solution to combine sulfuric acid and ammonia gas and convert it to ammonium sulfate ((NH4)2SO4) while finally recovering ammonia. At this time, the nitrogen contained in the wastewater flowing into the stripping process is ammonia gas (NH3) and ammonium ions (NH4 +They exist in the form of + , but the occupancy rates of these two substances have different characteristics depending on the pH of the wastewater. Specifically, under conditions where the pH is higher than 9.25, the proportion of NH3 increases, and under lower conditions, the proportion of NH4

[0010] Also, when performing the stripping process, since the solubility of ammonia gas decreases at high temperatures, in order to increase the ammonia removal efficiency in the influent water, stripping is applied under high temperature conditions of 70 °C or higher. However, the high treatment temperature not only increases the energy requirement, but also promotes the organic matter decomposition rate and causes the pH of the influent water to decrease rapidly, resulting in an increase in the amount of alkaline chemicals added to maintain the pH during the treatment.

[0011] To date, nitrogen recovery processes based on stripping technology have been utilized both domestically and internationally, but they face difficulties in commercialization due to high chemical costs, high nitrogen recovery costs, and the generation of low-grade final by-products.

[0012] As part of solving such problems, Patent Document 1 increases the degassing efficiency of carbon dioxide by increasing the insolubility of the gas at a high temperature (45 °C) in the carbon dioxide degassing tower, raises the pH to 8.5 - 9.0 to remove alkalinity and reduce the usage amount of the subsequent pH adjuster, maintains the pH at 10 or higher in the pH adjustment tank to improve the ammonia degassing efficiency, degasses the ammonia ions in the water in the form of ammonia gas in the degassing tower, and after absorbing the ammonia gas at a pH of 5 or lower in the absorption tower, injects phosphoric acid (H3PO4) to recover valuable resources in the form of liquid fertilizer ((NH4)2H2PO4).

[0013] However, in order to reduce chemical costs, the pH of the influent water was applied below 10, but the nitrogen removal efficiency decreased significantly. To overcome this problem, the carbon dioxide degassing process was applied, but not only ammonia loss occurred during the degassing process, but also a large amount of malodor was discharged.

[0014] Patent Document 2 relates to an invention of a system for removing and recovering high-concentration nitrogen and phosphorus using ammonia degassing, and discloses an apparatus that can recover or remove high-concentration nitrogen and phosphorus in wastewater by coordinating an ammonia stripping tank, a biological water treatment section, an ammonia gas recovery process, and a phosphorus recovery process.

[0015] In the ammonia degassing and biological water treatment section, after effectively degassing ammonia gas with high-concentration ammoniacal nitrogen contained in the anaerobic digestion desorption liquid or wastewater, the adsorbent is used to adsorb and desorb ammonia to recover ammonia gas.

[0016] However, the invention develops an adsorbent and applies it to a pressure swing adsorption system to recover ammonia. It is expected that this consumes more energy than the separation membrane process, and the ammonia obtained through this process is in the form of low-concentration ammonia gas or ammonia water.

[0017] Patent Document 3 relates to a membrane distillation system capable of recovering valuable resources. Using livestock manure anaerobic digestion desorption liquid, which is wastewater containing high-concentration nitrogen and phosphorus, nitrogen and phosphorus are removed and simultaneously recovered as valuable resources (fertilizers). The wastewater from which nitrogen and phosphorus have been removed is used to produce treated water at a level that can be used as agricultural water by using a membrane distillation (MD) process.

[0018] However, since the above invention was advanced for the purpose of removing nitrogen and phosphorus and using the wastewater as agricultural water, no detailed research has been conducted on the recovery of nitrogen. In this process, ammonia was obtained in the form of ammonia water by the absorption method, and no method for recovering it with high purity has been advanced.

[0019] In the case of the conventional ammonia recovery technology as described above, for the application of the degassing process, a high pH and a high temperature of about 50 to 60 °C are used. When using other ion exchange and reverse osmosis membrane processes, there is a risk of fouling, and ammonia is recovered in the form of ammonium sulphate, MAP, DAP, etc., and its utilization range is limited to only fertilizers, which are low-added-value products. The conventional technology has problems such as the absence of a process for removing carbon dioxide or the use of air to degas carbon dioxide from wastewater, resulting in an increase in exhaust gas containing carbon dioxide.

[0020] Also, in the case of the process of recovering ammonia using the absorption method, it is recovered as low-added-value ammonia water, and when ammonia is recovered in the gas phase by adsorption, it has a limitation in that the concentration is low.

[0021] Therefore, as a result of intensive research on a method for highly pure recovery of ammonia from wastewater, the inventors collected high-concentration wastewater and removed solids, and then degassed ammonia with high efficiency using a vacuum reactor for the raw water. By passing the degassed ammonia through a separation membrane process using a polymer gas separation membrane to purify and selectively recover the degassed ammonia in the gas phase without a phase change, the present invention has been completed.

Prior Art Documents

Patent Documents

[0022]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0023] The present invention is made to solve the above-described problems, and an object thereof is to provide an ammonia degassing apparatus using a vacuum-type reactor for raw water from which solid matter has been removed by collecting wastewater at a high concentration.

[0024] Another object of the present invention is to provide a resource recovery type high-concentration wastewater treatment system capable of selectively purifying and recovering ammonia at a high purity through a polymer gas separation membrane from the ammonia degassed by the ammonia degassing apparatus.

Means for Solving the Problems

[0025] To achieve the above object, the present invention provides a vacuum-type reactor in which an ammonia degassing step is performed under conditions where the pressure of raw water flowing in after pretreatment from high-concentration wastewater is controlled, a heat exchanger through which ammonia flowing in from the vacuum-type reactor passes through a heat dissipation passage, a cooler that provides water to the heat dissipation passage to maintain a constant temperature of the heat exchanger, a trap that recovers water condensed from the heat exchanger, and a degassed gas collection unit that recovers ammonia that has passed through the trap, and provides an ammonia degassing apparatus.

[0026] The high-concentration wastewater of the present invention is applied to any one selected from the group consisting of anaerobic digestion effluent of sewage sludge, anaerobic digestion liquid of sewage sludge, slurry-type livestock manure containing pig manure or cow manure slurry, livestock manure digestion liquid, combined digestion supernatant of pig manure and food.

[0027] The pH during the vacuum degassing process is preferably 8.8 to 11, and a basic substance can be further added and adjusted to maintain the concentration.

[0028] The vacuum-type reactor is carried out under conditions where it is continuously operated at a pressure condition of 0.5 to 2 bar and is optimized for a temperature condition of 35 to 60°C.

[0029] In addition, an ultrasonic generator can be installed in the vacuum-type reactor to enhance the degassing efficiency by combining vacuum degassing with vacuum and ultrasonic degassing.

[0030] The present invention also provides a resource recovery type high-concentration wastewater treatment system, which includes an ammonia degassing step in which vacuum degassing or a combination of vacuum and ultrasonic degassing is performed by the ammonia degassing device, a separation membrane step in which the ammonia mixed gas recovered by the degassing step is passed through a polymer gas separation membrane, and a step of recycling the highly concentrated ammonia selectively recovered by the separation membrane step.

[0031] In the resource recovery type high-concentration wastewater treatment system of the present invention, the ammonia degassing step is a low-energy type separation step in which vacuum degassing is performed by a vacuum-type reactor or an ultrasonic generator is further installed to combine vacuum degassing and ultrasonic degassing to remove ammonia.

[0032] In the resource recovery type high-concentration wastewater treatment system of the present invention, the separation membrane step of passing the ammonia mixed gas recovered by the degassing step through a polymer gas separation membrane is continuously performed.

[0033] The polymer gas separation membrane is a non-porous polymer membrane in which gas is dissolved on the polymer surface and diffused through the free volume of the polymer to permeate the gas. In particular, it is a separation step with excellent selectivity for NH3 / N2 mixed gas.

[0034] A desirable polymer gas separation membrane uses a material made of a perfluorinated sulfonic acid polymer or a polyamide-imide or co-polyimide polymer. The polymer gas separation membrane is a flat membrane or a hollow fiber membrane, and is provided in the form of a membrane module composed of the flat membrane or the hollow fiber membrane.

[0035] Preferably, the polymer gas separation membrane is a hollow fiber membrane made of a polyimide-based polymer, and the hollow fiber membrane has an outer diameter of 400 to 500 μm and a membrane thickness of 70 to 100 μm.

[0036] Furthermore, a separation membrane step in which the thermal stability of the hollow fiber membrane is improved by chemical cross-linking can be performed.

[0037] In the resource recovery type high-concentration wastewater treatment system of the present invention, in the separation membrane step, the ammonia mixed gas recovered by the deaeration step flows into the polymer gas separation membrane through a pressure control stage, and the ammonia gas selectively permeated through the polymer gas separation membrane is recovered or collected with high purity through a component analysis stage after a pressure adjustment and flow rate measurement stage.

[0038] Also, the ammonia mixed gas recovered by the deaeration step flows into the polymer gas separation membrane through a pressure control stage, the remaining gas is discarded through a pressure measurement, pressure relief adjustment and flow rate measurement stage, and is characterized by passing through an ammonia neutralization stage immediately before the discard.

Effects of the Invention

[0039] By removing ammonia with high deaeration efficiency by combining vacuum deaeration by a vacuum type reactor and vacuum and ultrasonic deaeration from high-concentration wastewater by the ammonia deaeration device of the present invention, a low-energy type separation process that does not require a conventional air injection stage and separate chemical addition for maintaining a high pH can be provided.

[0040] In addition, a resource recovery type high-concentration wastewater treatment system can be provided in which the ammonia mixed gas recovered by the ammonia deaeration device is selectively purified and recovered in the ammonia gas phase without a phase change in a separation membrane step of passing through a polymer gas separation membrane.

[0041] With the above-described resource recovery type high-concentration wastewater treatment system, ammonia can be recovered from high-concentration wastewater such as anaerobic digestion effluent of sewage sludge, anaerobic digestion liquid of sewage sludge, slurry-type livestock manure containing pig manure or cow dung slurry, livestock manure digestion liquid, pig manure, and combined digestion supernatant of food at a recovery rate of 90% or more and with a high purity of 99%, and can be utilized as a resource.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0043] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0044] FIG. 1 is a schematic diagram of the ammonia degassing apparatus of the present invention, which includes a vacuum reactor 10 in which the raw water flowing in after pretreatment from high-concentration sewage is subjected to an ammonia degassing process under pressure-controlled conditions, a heat exchanger 20 through which ammonia flowing from the vacuum reactor passes through a heat dissipation passage, a cooler 50 that provides water to the heat dissipation passage to maintain a constant temperature of the heat exchanger, a trap 30 that recovers the water condensed from the heat exchanger, and a degassed gas collection unit 60 that recovers the ammonia passing through the trap. An ammonia degassing apparatus is provided.

[0045] The high-concentration sewage of the present invention is any one selected from the group consisting of anaerobic digestion effluent of sewage sludge, anaerobic digestion liquid of sewage sludge, slurry-type livestock manure containing pig manure or cow manure slurry, livestock manure digestion liquid, combined digestion supernatant of pig manure and food, and the raw water obtained by collecting the high-concentration sewage and removing solids is targeted. At this time, the higher the ammonia concentration in the solids, the higher the recoverable ammonia concentration. Therefore, in the examples of the present invention, TN 3,500 mg / L, NH4 + -N 2,500 mg / L, TP 300 mg / L, PO4 3 -P 100 mg / L concentration is described by way of limitation, but is not limited thereto.

[0046] Also, in the ammonia degassing process by the vacuum reactor, if the pH is maintained constant during the vacuum degassing process, the reaction time for degassing can be further reduced or the final ammonia concentration can be maintained lower. At this time, the pH during the vacuum degassing process is preferably 8.8 to 11, and any one basic substance selected from the group consisting of NaOH, CaO, and Ca(OH)2 can be further added and adjusted to maintain a high concentration.

[0047] Conventional ammonia degassing methods are carried out under the condition that the pH of sewage is 11 or more for ammonium ions (NH4 +) is switched to ammonia (NH3) and removed in the gas phase. At this time, slaked lime and sodium hydroxide are mainly used to increase the pH, and the phosphorus component is simultaneously removed through the aggregation and precipitation of phosphorus. However, the conventional ammonia degassing method removes ammonia by setting high pH conditions to make most of the ammonia exist in the gas phase and then stripping it, which has the advantage of high nitrogen recovery rate. However, it is pointed out that long-term air-blowing is required for the atmospheric discharge of supersaturated ammonia, and excessive amounts of high temperature, high pH conditions, and chemicals for maintaining pH are required.

[0048] In contrast, the ammonia degassing device using the vacuum reactor of the present invention can continuously operate the inflowing raw water under certain vacuum conditions to confirm the ammonia degassing phenomenon and pH reduction.

[0049] At this time, the implementation conditions in the vacuum reactor of the present invention can optimize the pH, temperature, and pressure conditions to be driven with low energy by ensuring the results that affect ammonia degassing according to the conditions of pH, temperature, and pressure changes.

[0050] The desirable vacuum condition is carried out at 0.5~2 bar. In the examples of the present invention, the condition is fixed at 1 bar to present the results of ammonia degassing phenomenon and pH reduction, but the pressure condition is not limited to this.

[0051] Also, under the above pressure condition, when the pH is 8.8~11, and more desirably, when the pH condition is 9.5~10, it can be confirmed that the ammonia concentration is reduced to the level of 90~95% compared with the initial concentration of 2,500 mg / L along with the shortening of the reaction time. At this time, when the pH condition exceeds 11, the reduction of the reaction time and the increase effect of ammonia removal efficiency due to the increase of pH are negligible, so the cost-effectiveness for maintaining a high pH is low.

[0052] Also, the desirable temperature condition is 35 to 60°C, more desirably 35 to 50°C. As the temperature increases, the ammonia removal efficiency increases. However, when the temperature exceeds 60°C, the increase in the ammonia removal efficiency is negligible compared to the cost required to raise the reactor temperature.

[0053] To enhance the ammonia degassing efficiency, the ammonia degassing device of the present invention can be implemented by installing an ultrasonic generator in a vacuum reactor and combining vacuum degassing and ultrasonic degassing.

[0054] When ultrasonic waves are oscillated in the raw water that has flowed in after pretreatment from high-concentration wastewater, bubbles are generated at the moment of dropping from high pressure to low pressure, and the bubbles grow when they drop to low pressure. When the bubbles are formed and grow, ammonia gas is collected in the bubbles. By removing the bubbles that are instantaneously generated in large quantities by such ultrasonic oscillation using a vacuum degassing device, the degassing efficiency can be increased.

[0055] By generating sound waves of 20 kHz or more from the ultrasonic generator and performing a degassing process by mechanical vibration, the efficiency of the vacuum degassing device can be increased.

[0056] Figure 2 shows the process sequence of the resource recovery type high-concentration wastewater treatment system of the present invention. A resource recovery type high-concentration wastewater treatment system is provided, which includes an ammonia degassing process in which vacuum degassing or combined vacuum and ultrasonic degassing by the ammonia degassing device is used for the raw water obtained by collecting high-concentration wastewater and removing solids, a separation membrane process in which the degassed ammonia passes through a polymer gas separation membrane, and a process of recycling the high-concentration ammonia selectively recovered by the separation membrane process.

[0057] In the resource recovery type high-concentration wastewater treatment system of the present invention, high-concentration wastewater can be collected and pretreated processes such as screening, coagulation and sedimentation, sludge, flotation, and electrolysis can be performed after removing solids, and known processes necessary for pretreatment can be applied.

[0058] After the pretreatment, the resource recovery type high-concentration wastewater treatment system of the present invention performs an ammonia degassing step of removing ammonia from the raw water by a vacuum type reactor.

[0059] Conventionally, the ammonia degassing method performed for the same purpose switches ammonium ions (NH4 + ) to ammonia (NH3) under the condition that the pH of the wastewater is 11 or more and removes it in the gas phase. At this time, mainly slaked lime and sodium hydroxide are used to increase the pH, and the phosphorus component is simultaneously removed by the aggregation and precipitation of phosphorus. However, the conventional ammonia degassing method removes ammonia by setting high pH conditions so that most of the ammonia exists in the gas phase and then stripping, which has the advantage of high nitrogen recovery rate. However, it is pointed out that long-term air-blowing for the atmospheric discharge of supersaturated ammonia is required, and excessive amounts of high temperature, high pH conditions, and chemicals for maintaining the pH are required.

[0060] On the other hand, in the ammonia degassing step using the vacuum type reactor of the present invention, the inflowing raw water can be continuously operated under constant reduced pressure conditions to confirm the ammonia degassing phenomenon and the decrease in pH.

[0061] In addition, by attaching an ultrasonic generator at an arbitrary position in the vacuum type reactor and performing combined vacuum degassing and ultrasonic degassing, the degassing efficiency can be improved.

[0062] The resource recovery type high-concentration wastewater treatment system of the present invention performs a separation membrane step of passing the ammonia mixed gas recovered by the degassing step through a polymer gas separation membrane.

[0063] The polymer gas separation membrane is a non-porous polymer membrane in which gas is dissolved on the polymer surface and diffused by the free volume of the polymer to permeate the gas. At this time, the gas permeability is calculated by the product of the diffusion coefficient and the solubility according to the dissolution / diffusion model.

[0064] Figure 3 shows the physical properties of the main gases to be separated in the resource recovery type high-concentration wastewater treatment system of the present invention. In the cases of NH3 / O2 and NH3 / N2, since the difference in solubility and the difference in molecular size (diffusivity) are large, it is expected that the permeation selectivity is high. Therefore, the polymer gas separation membrane of the present invention is an ammonia highly permeable selective separation membrane that is particularly excellent in selectivity for NH3 / N2 mixed gas.

[0065] The polymer separation membrane having separation characteristics for the above-mentioned NH3 / O2 or NH3 / N2 (occupying the largest specific gravity), NH3 / CO2 (with a small difference in solubility), NH3 / He or NH3 / H2 (with a small difference in diffusivity) is selected in consideration of solvent solubility, processability, ease of synthesis, etc., and a perfluorinated sulfonic acid polymer or a polyamide-imide, co-polyimide material is desirable.

[0066] The perfluorinated sulfonic acid polymer has a fluorinated main chain and is physically and chemically stable, and has a high NH3 permeability due to the high affinity between the sulfonic acid group in the side chain and NH3.

[0067] In addition, the polyamide-imide, co-polyimide has advantages of high fire resistance and excellent heat resistance, and high possibility of introducing and modifying various chemical structures.

[0068] Figure 4 is a desirable example of the polymer gas separation membrane used in the separation membrane process of the resource recovery type high-concentration wastewater treatment system of the present invention, and is the SEM photograph result of the cross section and thickness of the polyimide hollow fiber membrane. The hollow fiber membrane has an outer diameter of 400 to 500 μm and a membrane thickness of 70 to 100 μm.

[0069] By thinning the thickness of the separation membrane material, the ammonia permeability can be maximized.

[0070] In addition, the polymer gas separation membrane can be applied to a flat membrane or a hollow fiber membrane, and is provided in a membrane module composed of the flat membrane or the hollow fiber membrane.

[0071] Figure 5 shows the membrane module process of the polyimide hollow fiber membrane in Figure 4. After being manufactured in the form of a hollow fiber membrane and then modularized into a tube type for use, the hollow fiber membrane module can have a higher effective area per unit volume compared to a flat membrane type module, and is more desirable because of its excellent ease of process coupling and operation.

[0072] In addition, in order to withstand a harsh environment up to the high-concentration ammonia recovery process, a polyimide hollow fiber membrane having thermal stability up to 200°C was supported in a crosslinking agent (p-xylenediamine) - containing solution for 10 minutes and then dried after crosslinking. As a result, by confirming remarkable thermal stability, the performance of the membrane can be improved by a stable crosslinking reaction.

[0073] Figure 6 shows the thermal analysis results before and after crosslinking of a membrane modified by a chemical crosslinking reaction on a polyimide hollow fiber membrane, and the thermal stability can be confirmed compared to before crosslinking.

[0074] Figure 7 is a flowchart of the separation membrane process in the resource recovery type high-concentration wastewater treatment system of the present invention. The ammonia mixed gas recovered by the deaeration process flows into the polymer gas separation membrane through a pressure control stage, and the ammonia gas selectively permeated through the polymer gas separation membrane is recovered with high purity after passing through a pressure adjustment and flow measurement stage and then a component analysis stage.

[0075] In addition, the ammonia mixed gas recovered by the degassing step flows into the polymer gas separation membrane through a pressure control stage, and the gas remaining through the polymer gas separation membrane is discarded through pressure measurement, back pressure regulator (BPR), and flow rate measurement stages, and passes through an ammonia neutralization stage immediately before the discard.

[0076] The resource recovery process of the resource recovery type high-concentration wastewater treatment system of the present invention selectively purifies and recovers ammonia with high purity through the low-power ammonia degassing step and the separation membrane step passing through the polymer gas separation membrane described above, and can be utilized for urea water production, green hydrogen raw materials, ammonia co-firing power generation in coal-fired power plants, etc.

[0077] Hereinafter, the present invention will be described in more detail through examples.

[0078] This example is for more specifically explaining the present invention, and the scope of the present invention is not limited to these examples. 1. Evaluation of Ammonia Degassing Step Using Vacuum Type Reactor

[0079] <Example 1> A 2L sample of the effluent from the anaerobic digester of sewage sludge collected at the water regeneration center was prepared, and the sample was analyzed to have a TN concentration of 7,800 - 10,700 mg / L and an ammonia concentration of 1,700 - 9,600 mg / L by the process test method.

[0080] The initial concentration of NH3 in the stripping liquid was adjusted to 2,500 mg / L, and a vacuum type reactor was used. The pH was set to 9.5 and carried out under temperature conditions of 35°C and 50°C. At this time, the vacuum condition was fixed at a gauge pressure of 1.0 bar.

[0081] The results of the NH3-N concentration and change rate by temperature according to the vacuum time under the pH 9.5 condition are shown in Table 1 below. However, the following results are those without artificially adjusting the decrease in pH due to degassing after fixing the initial pH to 9.5.

[0082] [Table 1]

[0083] As a result of experimenting with a vacuum reactor under the condition of pH 9.5, the time required for a reduction of 50% or more compared to the initial ammonia concentration was about 170 minutes at 35°C and about 100 minutes at 50°C. The final ammonia concentration in the vacuum reactor decreased by about 73% and 84% respectively compared to the initial concentration under the temperature conditions of 35°C and 50°C after 300 minutes of operation. That is, a high ammonia degassing efficiency was shown at 50°C.

[0084] Since the above experimental values are the results of not artificially adjusting the decrease in pH due to degassing after fixing the initial pH to 9.5, when maintaining the pH at 9.5 constantly during the vacuum degassing process, the reaction time for degassing will decrease, or the final ammonia concentration can be maintained lower.

[0085] <Example 2> The experiment was carried out in the same manner as in Example 1 except that the condition was changed to pH 10. The results of the NH3-N concentration and the change rate by temperature according to the vacuum time under the condition of pH 10 are shown in Table 2 below.

[0086] [Table 2]

[0087] As can be seen from Table 2 above, in the case of pH 10, the time required for a reduction of 50% or more compared to the initial ammonia concentration was about 75 minutes under the condition of 35°C and about 60 minutes at 50°C. The final ammonia concentration in the vacuum reactor decreased by about 94% (35°C) and 97% (50°C) respectively compared to the initial concentration under each temperature condition after 300 minutes of operation. It was also confirmed that the degassing test under the condition of pH 10 had excellent degassing efficiency under the condition of 50°C.

[0088] As can be seen from Table 2 above, despite no artificial pH adjustment during the reaction time under the condition of pH 10, the final ammonia concentrations after 300 minutes of reaction time were 156 mg / L and 74 mg / L under the conditions of 35 °C and 50 °C respectively, and it was confirmed that about 94% and 97% decreased compared to the initial concentration.

[0089] <Example 3> The procedure was carried out in the same manner as in Example 1 except that the condition was changed to pH 11.5. The results of the NH3-N concentration and the change rate according to temperature under the condition of pH 11.5 during the depressurization time are shown in Table 3 below.

[0090]

Table 3

[0091] As can be seen from Table 3 above, the time required for a decrease of 50% or more compared to the initial ammonia concentration at pH 11.5 was about 100 minutes under the condition of 35 °C and about 75 minutes in the case of 50 °C. The final ammonia concentrations in the reactor after 360 minutes of operation decreased by about 93% (35 °C) and 96% (50 °C) respectively compared to the initial concentration under each temperature condition.

[0092] That is, unlike the conditions of pH 9.5 and pH 10, it was confirmed that the effect of reducing the reaction time and increasing the removal efficiency with the increase in pH was negligible when pH was 10.0 or higher, as the ammonia degassing efficiency was achieved to be similar depending on the temperature.

[0093] Also, the ammonia concentration after 300 minutes of reaction time under the condition of pH 10 or higher decreased to the level of 90 - 95% compared to the initial concentration of 2,500 mg / L.

[0094] These experimental results confirm that when the initial pH was set to 9.5, 10, and 11.5 respectively, and despite no further chemical addition for maintaining a constant pH between the reactors, the ammonia concentration decreased. Therefore, when maintaining a constant pH condition, it should be possible to shorten the reaction time and reduce the final ammonia concentration.

[0095] However, after setting the ammonia recovery target amount, since the concentration of ammonia gas can be reduced under temperature and time conditions, it becomes unnecessary to add chemicals to maintain a constant pH, which is useful for low-energy and greenhouse gas reduction type resource recovery.

[0096] <Experimental Example 1> Evaluation of Operating Factors of Vacuum Reactor The ammonia concentration and removal efficiency depending on the pH and temperature in the vacuum reactor were measured and shown in Table 4 below, and the results under vacuum conditions were shown in Table 5.

[0097]

Table 4

[0098]

Table 5

[0099] As can be seen from Table 5 above, in the pump operation stop experiment result, the ammonia removal rate did not even reach 30%, while in the continuous pump operation, the ammonia removal rate was confirmed to be up to 64% at maximum. In the cases of No.5 and No.8, it was confirmed that even under the same pH conditions, the temperature had a great influence on the ammonia removal rate.

[0100] 2. Evaluation of Separation Membrane Process Using Polymer Gas Separation Membrane

[0101] <Example 4> Production of Polyimide Hollow Fiber Membrane A dope solution was prepared at a weight ratio of polyimide blend (P84, Torlon) and NMP solvent of 27 to 73, and a hollow fiber membrane was produced by utilizing the phase transition phenomenon in the dry / wet method of the process of radiation through a nozzle and phase separation in a coagulation bath. The solvent was washed and dried with a winder and modularized.

[0102] <Experimental Example 2> Morphology of Polymer Gas Separation Membrane Cross-sectional SEM imaging was performed to observe the structural characteristics of the manufactured polyimide hollow fiber membrane, and the results are shown in Figure 4. As a result, it was confirmed that the outer diameter and inner diameter of the hollow fiber membrane were approximately 550 and 400 μm, respectively, and the membrane thickness was approximately 70 - 80 μm. In addition, as a result of observing the cross-section of the separation membrane at a magnification of 2,000 times, it was confirmed that the surface of the membrane was very thin and had a dense structure (selective layer), and a finger structure formed while the solvent quickly penetrated inside was observed, indicating that the hollow fiber membrane was well manufactured.

[0103] <Experimental Example 3> Evaluation of the Permeation Performance of a Polymer Gas Separation Membrane Module To confirm the separation performance of the gas separation membrane through an NH3 / N2 mixed gas, the manufactured polyimide hollow fiber membrane was modularized as shown in Figure 5. For the Nafion hollow fiber membrane, multiple fibers were bundled together into one module. Each hollow fiber membrane module was composed of 20 fibers with an effective length of 34 cm and 53 fibers with an effective length of 17 cm in a 1 / 2-inch SUS tube.

[0104] The mixed gas used in the separation test of the NH3 / N2 mixed gas was ordered and used according to different concentrations (mol% NH3 / mol% N2: 10 / 90, 30 / 70, 50 / 50, 70 / 30, 88 / 12).

[0105] The pressure of the supply gas was adjusted by a regulator installed on the gas cylinder, and the operating temperature was adjusted by installing the permeation cell containing the separation membrane in a temperature chamber. The flow rate was adjusted by an MFC (Mass Flow Controller), the pressure on the residue side was adjusted by a BPR (Back Pressure Regulator) to maintain the same as the supply pressure, and the gas that permeated through the separation membrane was sent to a GC (Gas Chromatography) through an MFM (Mass Flow Meter) to analyze the flow rate and composition. As a result, the results using the polyimide hollow fiber membrane module are shown in Table 6 below, and the results of the Nafion hollow fiber membrane module are shown in Table 7.

[0106]

Table 6

[0107]

Table 7

[0108] From the results of Table 6 and Table 7 above, it was confirmed that when the ammonia concentration in the supplied mixed gas was supplied at 30 mol% or more, the concentration of ammonia permeated through the polymer gas separation membrane was recovered at 95 mol% or more, more desirably 99 mol% or more.

[0109] Also, the permeation flow rate increased significantly compared to the increase in the ammonia concentration of the supply gas, and the ammonia recovery rate increased.

[0110] <Experimental Example 4> Evaluation of the Stability of the Polymer Gas Separation Membrane Module To evaluate the thermal stability of the polyimide hollow fiber membrane, TGA analysis was performed, and the results of thermal analysis before and after crosslinking of the membrane modified by chemical crosslinking reaction on the polyimide hollow fiber membrane are shown in Fig. 6.

[0111] As a result, it was confirmed that the polyimide hollow fiber membrane was thermally stable up to 200 °C, while the thermal stability was confirmed at about 600 °C after crosslinking, and it was confirmed that the performance of the membrane could be improved by a stable crosslinking reaction.

[0112] As described above, only the specific examples described in the present invention have been described in detail, but it is obvious to those skilled in the art that various modifications and corrections are possible within the technical idea scope of the present invention, and such modifications and corrections belong to the appended claims.

Explanation of Signs

[0113] 10 Vacuum reactor 20 Heat exchanger 30 Steam trap (WATER TRAP) 40 Vacuum pump 50 Cooler 60 Degassing gas collection section 1 Ammonia degassing device

Claims

1. a reduced pressure reactor in which the raw water that flows in after pretreatment from the high concentration sewage wastewater is subjected to an ammonia degassing process under pressure-controlled conditions; a heat exchanger through which the ammonia flowing from the reduced pressure reactor passes through a heat dissipation passage; a cooler for providing water to the heat dissipation passage to maintain a constant temperature of the heat exchanger; a trap for collecting condensed water from the heat exchanger; and a degassed gas collection section in which the ammonia that has passed through the trap is collected.

1. An ammonia degassing apparatus comprising:

2. The raw water has a pH of 8.8 to 11.

2. The ammonia degassing apparatus of claim 1.

3. The pressure of the vacuum reactor is controlled to 0.5 to 2 bar and is operated continuously.

2. The ammonia degassing apparatus of claim 1.

4. The reaction is carried out under the pressure condition of the reduced pressure reactor and at a temperature of 35 to 60°C.

4. The ammonia degassing apparatus of claim 3.

5. An ultrasonic generator is installed in the decompression reactor.

2. The ammonia degassing apparatus of claim 1.

6. An ammonia degassing step in which vacuum degassing or a combination of vacuum and ultrasonic degassing is performed using the ammonia degassing apparatus according to any one of claims 1 to 5; a separation membrane process in which the ammonia mixed gas recovered by the degassing process is passed through a polymer gas separation membrane; and a process for recycling the high-concentration ammonia selectively recovered from the separation membrane process. A resource recovery-type high-concentration wastewater treatment system.

7. The polymer gas separation membrane is made of a perfluorinated sulfonic acid polymer or a polyimide-imide or co-polyimide. The resource recovery type high-concentration wastewater treatment system according to claim 6.

8. The polymer gas separation membrane is a hollow fiber membrane made of a polyimide-based polymer. The resource recovery type high-concentration wastewater treatment system according to claim 6.

9. The hollow fiber membrane is chemically cross-linked to ensure thermal stability. The resource recovery type high-concentration wastewater treatment system according to claim 8.

10. The ammonia mixed gas recovered from the degassing process is passed through a pressure control step and flows into a polymer gas separation membrane, and the ammonia gas selectively permeated through the polymer gas separation membrane is recovered in high purity through a pressure control step, a flow rate measurement step, and a component analysis step. The resource recovery type high-concentration wastewater treatment system according to claim 6.

11. The ammonia mixed gas recovered by the degassing process is passed through a pressure control step and flows into a polymer gas separation membrane, and the gas remaining through the polymer gas separation membrane is discharged through a pressure measurement step, a back pressure adjustment step and a flow rate measurement step. The resource recovery type high-concentration wastewater treatment system according to claim 6.

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