A phenol ammonia wastewater pretreatment system and method in a coal pyrolysis upgrading production process

Abstract

The present application relates to the technical field of coal chemical industry, and particularly relates to a phenol-ammonia wastewater pretreatment system and method in a coal pyrolysis upgrading production process, which comprises an oil-water separation unit and a front extraction and recovery unit; the oil-water separation unit comprises a first-stage oil-water separation device, a second-stage oil-water separation device and a third-stage oil-water separation device connected in sequence; wherein the first-stage oil-water separation device is internally provided with coalescence material with super oil-wetting and water-repellent characteristics, which is used for separating and removing floating oil and part of dispersed oil; the second-stage oil-water separation device is internally provided with a space fiber mesh structure with super oil-wetting and water-repellent characteristics, which is used for separating and removing dispersed oil. The coal tar separated and recovered from the wastewater can be directly resourceized and utilized, and direct economic benefits are generated; meanwhile, the extract recovered by the front extraction unit can be reused in an ammonia stripping and phenol removal system, and the recovery efficiency of phenolic resources is further improved, so that the dual goals of "pollution treatment" and "resourceization" are achieved.

Description

Technical Field

[0001] This invention relates to the field of coal chemical technology, and in particular to a pretreatment system and method for phenol and ammonia wastewater during the coal pyrolysis and upgrading process. Background Technology

[0002] Phenolic and ammonia wastewater is generated during the low-to-medium temperature pyrolysis of coal. It contains high concentrations of recalcitrant organic pollutants such as coal tar, phenol, and ammonia, making it difficult to treat. Conventional phenolic and ammonia wastewater treatment processes include: oil removal pretreatment, ammonia stripping and phenol removal, and biological treatment. Pretreatment of phenolic and ammonia wastewater from coal pyrolysis and upgrading not only affects the normal operation of the downstream biological treatment system but also plays a crucial role in the recovery of resources such as coal tar, phenol, and ammonia.

[0003] Currently, the pretreatment process for phenol and ammonia wastewater from coal pyrolysis and upgrading adopts a combination of conventional oil-water separation and ammonia stripping for phenol removal. This process aims to remove and recover coal tar, phenol, and ammonia from the wastewater. However, the combination of conventional oil-water separation and ammonia stripping for phenol removal has a series of significant technical drawbacks, environmental and economic issues.

[0004] Conventional oil-water separation processes cannot separate and remove coal tar from phenol-ammonia wastewater, resulting in difficult oil-water separation and poor separation efficiency.

[0005] The reasons are as follows: 1. The densities of light tar and heavy tar in phenol and ammonia wastewater are between 0.96-0.99 g / cm³ and 1.02-1.05 g / cm³, respectively, which are very close to the density of water (1.0 g / cm³). Oil droplets with larger particle sizes separate relatively quickly, while oil droplets with smaller particle sizes (such as dispersed oil and some emulsified oil) cannot be effectively separated. 2. Conventional oil-water separation processes use equipment such as air flotation, large tanks, and inclined plate settling tanks. The design of their equipment structure, selection of packing materials, and process combination are only suitable for oils with large density differences between oil and water, such as refined oil and chemical oil. In phenol and ammonia wastewater, the density difference between light tar, heavy tar, and water is very small. Conventional oil-water separation technology is not specific to the use of phenol and ammonia wastewater, has poor applicability, and poor treatment effect. As a result, coal tar is not recovered and enters the downstream treatment process, which not only wastes resources but also seriously affects the stable operation of the downstream system. 3. Light oily substances are very easy to contaminate and reduce the purity of MIBK extractant in the ammonia stripping and phenol removal system. Once the purity is lower than 90%, the extractant cannot be used and fresh extractant needs to be added to the ammonia stripping and phenol removal system to improve its purity. The annual on-site extractant operating cost caused by the decrease in purity due to extractant contamination is high.

[0006] For ammonia stripping and phenol removal systems, especially those using pulverized coal as raw material, the phenol and ammonia wastewater has a high dust content. The pulverized coal dust, along with tar, enters the ammonia stripping tower for acid removal. This often leads to blockage of the ammonia stripping tower trays and the extraction feed heat exchanger, resulting in reduced heat exchange efficiency and high pressure in the extraction system. Consequently, the COD of the effluent fails to meet standards, and the biochemical system cannot operate stably. The reason is that the oil and dust in the phenol and ammonia wastewater, due to temperature changes such as the temperature rise in the deacidification tower and the temperature drop before entering the extraction system, cause the dust to mix with the coal tar and form solid blockages, resulting in blockage of the ammonia stripping tower trays and the cooling heat exchanger, thus increasing the operating cost of the ammonia stripping and phenol removal system.

[0007] The "conventional oil-water separation process + ammonia stripping and phenol removal system" did not select an appropriate oil-water separation process based on the inherent characteristics of phenol and ammonia wastewater. This resulted in difficulties in oil-water separation, wasted coal tar resources, and caused operational hazards to subsequent processes. The presence of oil and dust in the phenol and ammonia wastewater also created serious difficulties for the long-term stable operation of the ammonia stripping and phenol removal system.

[0008] To address the problems existing in the aforementioned "conventional oil-water separation process + ammonia stripping and phenol removal system", this invention provides a phenol and ammonia wastewater pretreatment system and method in the coal pyrolysis upgrading process to solve the above-mentioned technical and production challenges. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing a pneumatic control valve for dental machine systems.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A pretreatment system for phenol and ammonia wastewater during coal pyrolysis and upgrading process includes an oil-water separation unit and a pre-extraction and recovery unit; The oil-water separation unit includes a primary oil-water separation device, a secondary oil-water separation device, and a tertiary oil-water separation device connected in series. The primary oil-water separation equipment is equipped with a coalescing material with super oleophilic and hydrophobic properties, which is used to separate and remove floating oil and some dispersed oil. The two-stage oil-water separation equipment is equipped with a spatial fiber mesh structure with super oleophilic and hydrophobic properties for separating and removing dispersed oil; The three-stage oil-water separation equipment is equipped with a polymer organic composite membrane material, which is an asymmetric superwetting composite fiber membrane formed by the organic combination of superhydrophilic modified composite fiber membrane and superhydrophobic modified composite fiber membrane, used to separate and remove residual dispersed oil and part of emulsified oil. Furthermore, the separation materials in each level of oil-water separation equipment are organically combined and coordinated with the special flow channel design inside the equipment to synergistically increase the residence time of phenolic ammonia wastewater in the equipment and enhance the oil-water separation effect. The pre-extraction and recovery unit includes a pipeline extractor, a separation tank, a solvent recovery tower, a solvent recovery tower top condenser, a solvent recovery tower separator, and a washing tower; The outlet of the pipeline extractor is connected to the inlet of the separation tank; The outlet of the separation tank is connected to the inlet of the solvent recovery tower; The top vapor outlet of the solvent recovery tower is sequentially connected to the top condenser of the solvent recovery tower and the liquid separator of the solvent recovery tower; The aqueous phase outlet of the solvent recovery tower separator is connected to the top reflux port of the solvent recovery tower; The gas phase outlet of the solvent recovery tower separator is connected to the washing tower.

[0011] As a preferred embodiment of this application, a solvent recovery tower inlet and outlet heat exchanger is also provided at the top of the solvent recovery tower, and the outlet of the separation tank is connected to the inlet of the solvent recovery tower via the solvent recovery tower inlet and outlet heat exchanger.

[0012] A method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading processes, characterized by comprising the following steps: Step S1: The phenol and ammonia wastewater is sequentially fed into a primary oil-water separation device, a secondary oil-water separation device, and a tertiary oil-water separation device for rapid three-stage oil-water separation. The floating oil, dispersed oil, and some emulsified oil in the wastewater are removed step by step to obtain oil-removed phenol and ammonia wastewater. Step S2: The de-oiled phenol and ammonia wastewater obtained in step S1 is fed into a pipeline extractor and mixed with the extract from the top of the extraction tower in the ammonia stripping and phenol removal system or fresh extractant for extraction. The mixture after extraction enters a separation tank to separate the extract and the aqueous phase after extraction. Step S3: The aqueous phase obtained from the extraction in step S2 is fed into the solvent recovery tower. After heat exchange in the inlet and outlet heat exchangers of the solvent recovery tower, it is fed into the solvent recovery tower for solvent recovery. The gas phase at the top of the solvent recovery tower is cooled by the condenser at the top of the solvent recovery tower and then enters the separatory tank of the solvent recovery tower. The aqueous phase at the bottom of the separatory tank is returned to the top of the solvent recovery tower, the lower oil phase enters the solvent circulation tank, and the top gas phase enters the washing tower. After being washed with purified water, it is discharged.

[0013] As a preferred technical solution of this application, the extraction ratio of the degreased phenolic ammonia wastewater to the extract or fresh extractant in step S2 is 1.5:10.

[0014] As a preferred technical solution of this application, the aqueous phase after extraction in step S3 is heated to 105°C by the inlet and outlet heat exchanger of the solvent recovery tower and then enters the solvent recovery tower. The heat source for the bottom of the solvent recovery tower is 0.72MPa low-pressure steam.

[0015] As a preferred technical solution of this application, through the processing of the oil-water separation unit and the pre-extraction and recovery unit, the replenishment frequency of fresh MIBK extractant in the phenol-ammonia extraction system is extended from once per month to once every two months.

[0016] As a preferred technical solution of this application, the extract obtained in step S2 enters the extract tank and is used to be recycled to the extraction tower of the ammonia stripping and phenol removal system.

[0017] As a preferred technical solution of this application, the liquid phase in the bottom of the washing tower in step S3 is returned to the solvent recovery tower after being pressurized.

[0018] The beneficial effects of this invention are as follows: 1. Through the oil-water separation unit and the pre-extraction and recovery unit, light and heavy coal tar, phenols and acidic gases in the coal pyrolysis upgrading phenol and ammonia wastewater are effectively removed, and oil and dust substances entering the ammonia stripping tower are effectively removed, which effectively extends the operating cycle of the ammonia stripping and phenol removal system, reduces the operating cost of the ammonia stripping and phenol removal system, reduces the frequency of tower blockage and heat exchanger blockage in the ammonia stripping and phenol removal system, and promotes stable system operation. 2. Wastewater treated by the phenol and ammonia wastewater pretreatment system and method achieves a COD removal rate of 90%, an oil removal rate of 98%, a phenol removal efficiency of 97%, and an NH3-N removal efficiency of over 95%. 3. Through the processing of the oil-water separation unit and the pre-extraction and recovery unit, the frequency of replenishing fresh extractant in the MIBK phenol-amine extraction system is extended from once per month to once every two months, effectively reducing the cost of replenishing fresh extractant and resulting in significant economic benefits. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of a phenol and ammonia wastewater pretreatment system and method for coal pyrolysis upgrading production proposed in this invention; Figure 2 This is a flow chart of a traditional ammonia stripping and phenol removal process.

[0020] In the diagram: 1. Primary oil-water separation equipment; 2. Secondary oil-water separation equipment; 3. Tertiary oil-water separation equipment; 4. Pipeline extractor; 5. Separation tank; 6. Inlet and outlet heat exchangers of solvent recovery tower; 7. Solvent recovery tower; 8. Top condenser of solvent recovery tower; 9. Separator of solvent recovery tower; 10. Washing tower. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Reference Figure 1A pretreatment system for phenol and ammonia wastewater during coal pyrolysis and upgrading process includes an oil-water separation unit and a pre-extraction and recovery unit. The oil-water separation unit includes a primary oil-water separator 1, a secondary oil-water separator 2, and a tertiary oil-water separator 3 connected in series. Among them, the first-stage oil-water separation device 1 is equipped with a coalescing material with super oleophilic and hydrophobic properties, which is used to separate and remove floating oil and part of the dispersed oil; The secondary oil-water separation device 2 is equipped with a spatial fiber network structure with super oleophilic and hydrophobic properties for separating and removing dispersed oil; The three-stage oil-water separation equipment 3 is equipped with a high-molecular organic composite membrane material. This material is an asymmetric superwetting composite fiber membrane formed by the organic combination of a superhydrophilic modified composite fiber membrane and a superhydrophobic modified composite fiber membrane. It is used to separate and remove residual dispersed oil and part of the emulsified oil. Furthermore, the separation materials in each level of oil-water separation equipment are organically combined and coordinated with the special flow channel design inside the equipment to synergistically increase the residence time of phenolic ammonia wastewater in the equipment and enhance the oil-water separation effect. The pre-extraction and recovery unit includes a pipeline extractor 4, a separation tank 5, a solvent recovery tower 7, a solvent recovery tower top condenser 8, a solvent recovery tower separator 9, and a washing tower 10. The outlet of the pipeline extractor 4 is connected to the inlet of the separation tank 5; The outlet of the separation tank 5 is connected to the inlet of the solvent recovery tower 7; The top vapor outlet of the solvent recovery tower 7 is sequentially connected to the top condenser 8 of the solvent recovery tower and the liquid separator 9 of the solvent recovery tower; The aqueous phase outlet of the solvent recovery tower separator 9 is connected to the top reflux port of the solvent recovery tower 7; The gas phase outlet of the solvent recovery tower separator 9 is connected to the washing tower 10.

[0023] Furthermore, a solvent recovery tower inlet and outlet heat exchanger 6 is also provided at the top of the solvent recovery tower 7, and the outlet of the separation tank 5 is connected to the inlet of the solvent recovery tower 7 through the solvent recovery tower inlet and outlet heat exchanger 6.

[0024] A method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading includes the following steps: Step S1: The phenol and ammonia wastewater is sequentially fed into the primary oil-water separator 1, the secondary oil-water separator 2, and the tertiary oil-water separator 3 for rapid three-stage oil-water separation. The floating oil, dispersed oil, and some emulsified oil in the wastewater are removed step by step to obtain the oil-removed phenol and ammonia wastewater. Step S2: The de-oiled phenol and ammonia wastewater obtained in step S1 is fed into the pipeline extractor 4 and mixed with the extract from the top of the extraction tower in the ammonia stripping and phenol removal system or fresh extractant for extraction. The mixture after extraction enters the separation tank 5 to separate the extract and the aqueous phase after extraction. Step S3: The aqueous phase obtained from the extraction in step S2 is fed into the solvent recovery tower 7. After heat exchange in the inlet and outlet heat exchanger 6, it enters the solvent recovery tower 7 for solvent recovery. The gas phase at the top of the solvent recovery tower 7 is cooled by the condenser 8 at the top of the solvent recovery tower and then enters the separatory tank 9. The aqueous phase at the bottom of the separatory tank 9 is returned to the top of the solvent recovery tower 7, the lower oil phase enters the solvent circulation tank, and the top gas phase enters the washing tower 10. After being washed with purified water, it is discharged.

[0025] Furthermore, in step S2, the extraction ratio of the degreased phenol-ammonia wastewater to the extract or fresh extractant is 1.5:10.

[0026] Furthermore, the aqueous phase extracted in step S3 is heated to 105°C by the inlet and outlet heat exchanger 6 of the solvent recovery tower and the bottom of the solvent recovery tower 7 before entering the solvent recovery tower 7. The heat source for the bottom of the solvent recovery tower 7 is 0.72MPa low-pressure steam.

[0027] Furthermore, through the processing of the oil-water separation unit and the pre-extraction and recovery unit, the replenishment frequency of fresh MIBK extractant in the phenol-ammonia extraction system is extended from once per month to once every two months.

[0028] Furthermore, the extract obtained in step S2 enters the extract tank and is reused in the extraction tower of the ammonia stripping and phenol removal system.

[0029] Furthermore, in step S3, the liquid phase in the bottom of the washing tower 10 is pressurized and returned to the solvent recovery tower 7.

[0030] like Figure 1 As shown, the specific treatment steps of the phenol and ammonia wastewater pretreatment system and method in the coal pyrolysis and upgrading process are as follows: Before oil removal and ammonia stripping treatment, the phenol and ammonia wastewater generated during the coal pyrolysis upgrading process has the following parameters: COD: 50000 mg / L; oil: 3000 mg / L; total phenol: 15000 mg / L; NH3-N: 6000 mg / L; pH value: 11.

[0031] The phenol-ammonia wastewater is first treated by a three-stage series oil-water rapid separation system. Specifically, the phenol-ammonia wastewater sequentially enters the first-stage oil-water separation unit 1, the second-stage oil-water separation unit 2, and the third-stage oil-water separation unit 3. The first-stage oil-water separation unit 1 contains a super-oleophilic and hydrophobic coalescing material, which uses wetting and collisional coalescing to separate and remove floating oil and some dispersed oil from the wastewater. The second-stage oil-water separation unit 2 contains a super-oleophilic and hydrophobic spatial fiber network structure to further promote oil droplet coalescence and separate and remove dispersed oil. The third-stage oil-water separation unit 3 contains a high-molecular organic composite membrane material, which is an asymmetric superwetting composite fiber membrane formed by the organic combination of super-hydrophilic modified composite fiber membrane and super-hydrophobic modified composite fiber membrane. It has a multi-level structure, high porosity, large specific surface area, and is not easily contaminated by oil. It effectively treats the emulsified oil in the phenol-ammonia wastewater, separating and removing residual dispersed oil and some emulsified oil. The three-stage oil-water separation units are arranged in series, with each stage progressively increasing in treatment precision, and each stage providing operational protection for the next.

[0032] The effluent from the three-stage oil-water separator passes through the pipeline extractor 4 and is mixed with the extractant from the top of the extraction tower in the ammonia stripping and phenol removal system at an extraction ratio of 1.5:10. After being mixed evenly, the mixture enters the separation tank 5, where the extractant and the separated water are separated. The separated extractant is returned to the extractant tank, while the separated water enters the solvent recovery tower 7. Phenolic wastewater from the separator enters solvent recovery tower 7. After heat exchange with the bottom of the solvent recovery tower via inlet / outlet heat exchanger 6, it reaches 105°C and then enters solvent recovery tower 7. The gas phase at the top of solvent recovery tower 7 is condensed by solvent recovery tower top condenser 8 and then enters solvent recovery tower separator 9. The aqueous phase at the bottom of separator 9 is pressurized by a reflux pump and then flows back to the top of solvent recovery tower 7. The oil phase at the bottom of separator 9 enters solvent circulation tank. The acidic gas phase at the top of separator 9 enters the lower part of washing tower 10. After being washed with purified water, the gas phase exits the device. The liquid phase at the bottom of washing tower is pressurized and then enters solvent recovery tower 7. The heat source for the bottom of solvent recovery tower 7 is 0.72MPa low-pressure steam.

[0033] The liquid phase from the bottom of solvent recovery tower 7 is heated to 125°C via a primary condenser and a phenol-water heat exchanger and then used as hot feed to the deacidification tower. The bottom of the deacidification tower utilizes the heat required for stripping provided by the reboiler, controlling the bottom temperature to approximately 160°C. The gas phase at the top of the tower, being acidic, is sent to the scrubber, where it comes into countercurrent contact with the spray water entering from the top of the scrubber, further absorbing the solvent from the acidic gas. The acidic gas is then discharged from the boundary area from the top of the scrubber. The upper layer of the liquid phase, consisting of solvent, overflows into the solvent overflow tank and then into the solvent circulation tank. The lower aqueous phase is sent back to the deacidification tower as top reflux by the deacidification tower top reflux pump. The purified water from the bottom of the deacidification tower is pressurized by the phenol-water pump at the bottom of the deacidification tower and then sent to the deammoniation tower.

[0034] Before adopting the pretreatment technology of this invention, the frequency of replenishing fresh MIBK extractant in the phenol-ammonia extraction system was once a month. After adopting the pretreatment technology of this invention, the frequency of replenishing fresh MIBK extractant in the phenol-ammonia extraction system is once every two months, effectively reducing the cost incurred due to replenishing fresh extractant.

[0035] After treatment involving oil removal, pre-extraction, and ammonia stripping to remove phenols, the wastewater from the coal pyrolysis upgrading process has the following parameters: COD: 5000 mg / L; oil: 50 mg / L; total phenols: 500 mg / L; NH3-N: 300 mg / L; pH: 11. The COD removal rate is 90%, the oil removal rate is 98%, the phenol removal efficiency is 97%, and the NH3-N removal efficiency is greater than 95%.

[0036] After further treatment by the subsequent biochemical system, the wastewater parameters are as follows: COD: 150 mg / L; oil: not detected; total phenols: 5 mg / L; NH3-N: 25 mg / L; pH value: 11.

[0037] Finally, it should be noted that in the description of this invention, the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pretreatment system for phenol and ammonia wastewater during coal pyrolysis and upgrading production, characterized in that, Includes an oil-water separation unit and a pre-extraction and recovery unit; The oil-water separation unit includes a primary oil-water separation device (1), a secondary oil-water separation device (2), and a tertiary oil-water separation device (3) connected in series. Among them, the first-stage oil-water separation equipment (1) is equipped with a coalescing material with super oleophilic and hydrophobic properties, which is used to separate and remove floating oil and part of the dispersed oil; The secondary oil-water separation equipment (2) is equipped with a spatial fiber mesh structure with super oleophilic and hydrophobic properties for separating and removing dispersed oil; The three-stage oil-water separation equipment (3) is equipped with a polymer organic composite membrane material, which is an asymmetric superwetting composite fiber membrane formed by the organic combination of superhydrophilic modified composite fiber membrane and superhydrophobic modified composite fiber membrane, used to separate and remove residual dispersed oil and part of emulsified oil. Furthermore, the separation materials in each level of oil-water separation equipment are organically combined and coordinated with the special flow channel design inside the equipment to synergistically increase the residence time of phenolic ammonia wastewater in the equipment and enhance the oil-water separation effect. The pre-extraction and recovery unit includes a pipeline extractor (4), a separation tank (5), a solvent recovery tower (7), a solvent recovery tower top condenser (8), a solvent recovery tower separator (9), and a washing tower (10). The outlet of the pipeline extractor (4) is connected to the inlet of the separation tank (5); The outlet of the separator (5) is connected to the inlet of the solvent recovery tower (7); The top gas phase outlet of the solvent recovery tower (7) is sequentially connected to the top condenser (8) of the solvent recovery tower and the liquid separator (9) of the solvent recovery tower. The aqueous phase outlet of the solvent recovery tower separator (9) is connected to the top reflux port of the solvent recovery tower (7); The gas phase outlet of the solvent recovery tower separator (9) is connected to the scrubbing tower (10).

2. The method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading production according to claim 1, characterized in that, The solvent recovery tower (7) is also equipped with a solvent recovery tower inlet and outlet heat exchanger (6) at the top. The outlet of the separation tank (5) is connected to the inlet of the solvent recovery tower (7) through the solvent recovery tower inlet and outlet heat exchanger (6).

3. A method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading as described in claim 1, characterized in that, Includes the following steps: Step S1: The phenol and ammonia wastewater is sequentially fed into the primary oil-water separation device (1), the secondary oil-water separation device (2) and the tertiary oil-water separation device (3) to perform rapid oil-water separation in three stages in series, removing floating oil, dispersed oil and part of emulsified oil from the wastewater step by step, and obtaining oil-removed phenol and ammonia wastewater; Step S2: The de-oiled phenol and ammonia wastewater obtained in step S1 is fed into the pipeline extractor (4) and mixed with the extract from the top of the extraction tower in the ammonia stripping and phenol removal system or fresh extractant. The mixture after extraction enters the separation tank (5) to separate the extract and the aqueous phase after extraction. Step S3: The aqueous phase obtained from the extraction in step S2 is fed into the solvent recovery tower (7). After heat exchange in the inlet and outlet heat exchanger (6), it is fed into the solvent recovery tower (7) for solvent recovery. The gas phase at the top of the solvent recovery tower (7) is cooled by the condenser (8) at the top of the solvent recovery tower and then enters the separator (9) of the solvent recovery tower. The aqueous phase at the bottom of the separator (9) is returned to the top of the solvent recovery tower (7), the lower oil phase enters the solvent circulation tank, and the top gas phase enters the washing tower (10). After being washed with purified water, it is discharged.

4. The method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading production according to claim 3, characterized in that, In step S2, the extraction ratio of the degreased phenol-ammonia wastewater to the extract or fresh extractant is 1.5:

10.

5. The method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading production according to claim 3, characterized in that, The aqueous phase after extraction in step S3 is heated to 105°C by the inlet and outlet heat exchanger (6) of the solvent recovery tower and the bottom of the solvent recovery tower (7). The heat source for the bottom of the solvent recovery tower (7) is 0.72MPa low-pressure steam.

6. The method for pretreatment of phenol and ammonia wastewater during coal pyrolysis upgrading process according to claim 3, characterized in that, Through the processing of the oil-water separation unit and the pre-extraction and recovery unit, the frequency of replenishing fresh MIBK extractant in the phenol-ammonia extraction system is extended from once per month to once every two months.

7. The method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading production according to claim 3, characterized in that, The extract obtained in step S2 enters the extract tank and is used to be recycled to the extraction tower of the ammonia stripping and phenol removal system.

8. The method for pretreatment of phenol and ammonia wastewater during coal pyrolysis and upgrading production according to claim 3, characterized in that, The liquid phase in the bottom of the washing tower (10) described in step S3 is returned to the solvent recovery tower (7) after being pressurized.

Images