A new process combination for the evaporation treatment of semi-coke wastewater

Abstract

The present application relates to a kind of new process combination for coke wastewater evaporation treatment, and the present application discloses a kind of new process combination for coke wastewater evaporation treatment.The process is first to coke wastewater for deacidification, ammonia evaporation pretreatment, after adding liquid alkali and inhibitor, in turn into one effect, two effect falling film evaporation system and three effect double-heater forced circulation evaporation system, each effect separator is equipped with demister to strengthen gas-liquid separation, to prevent mist entrainment.Three effect concentrated liquid is separated by centrifugal desalting, mother liquor is recovered with carbon dioxide decomposition process, and the clear liquid is recycled;Each effect condensate is uniformly collected and can be directly introduced into biochemical treatment, and the water quality is stable and up to standard.The present application solves the problems of easy scaling, corrosion, high energy consumption and unstable effluent in traditional process by using heat energy cascade utilization, anti-fouling structure and corrosion-resistant material, and has the advantages of stable operation, energy saving, high resource utilization rate and long-term continuous operation, and is suitable for efficient treatment and resource recovery of high-salt and high-phenol coke wastewater.

Description

Technical Field

[0001] This invention relates to the field of semi-coke wastewater treatment technology, specifically a new process combination for the evaporation treatment of semi-coke wastewater. Background Technology

[0002] Semi-coke wastewater is mainly generated in coal chemical production processes such as low-temperature coal dry distillation and coal tar hydrogenation. It is characterized by high COD, high total phenols, high ammonia nitrogen, high oil, and high salt content. It is a typical industrial wastewater that is difficult to degrade. If discharged directly, it will cause serious pollution to water bodies and soil. It must be treated in a harmless and resource-based manner.

[0003] Currently, the mainstream treatment process for semi-coke wastewater is extraction combined with phenol extraction and biochemical treatment. However, this process suffers from problems such as long process duration, high reagent consumption, high operating costs, and large fluctuations in effluent quality. The triple-effect evaporation process can achieve wastewater concentration, salt separation, and reclaimed water reuse, representing an important technological direction for semi-coke wastewater treatment.

[0004] The existing triple-effect evaporation technology for semi-coke wastewater generally has the following drawbacks:

[0005] 1. The wastewater has a high salt content, and after adding alkali, it is easy for scale to form on the inner wall of the heater, which leads to a decrease in heat exchange efficiency, equipment blockage, and short operating cycle;

[0006] 2. The equipment has insufficient corrosion resistance; ordinary materials are easily corroded and damaged in high-salt, high-phenol, and high-alkali environments.

[0007] 3. Poor gas-liquid separation, severe steam mist entrainment, unstable condensate quality, and difficulty in directly entering the biological system;

[0008] 4. Insufficient utilization of thermal energy, high steam consumption, and persistently high operating costs;

[0009] 5. Incomplete salt separation in the concentrate prevents effective circulation of the mother liquor, affecting the continuous and stable operation of the system.

[0010] Therefore, a new process combination for the evaporation treatment of semi-coke wastewater is proposed to solve the above problems. Summary of the Invention

[0011] (a) Technical problems to be solved

[0012] To address the shortcomings of existing technologies, this invention provides a novel process combination for the evaporation treatment of semi-coke wastewater, which has advantages such as corrosion resistance, scale prevention, high thermal energy utilization, stable effluent quality, and continuous long-term operation. It solves the problems of easy scaling, easy corrosion, poor gas-liquid separation, high energy consumption, and unstable effluent quality in the evaporation treatment of semi-coke wastewater in existing technologies.

[0013] (II) Technical Solution

[0014] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A new process combination for the evaporation treatment of semi-coke wastewater, comprising the following steps in sequence:

[0015] S1: The semi-coke wastewater, which has undergone deacidification and ammonia stripping pretreatment, is fed into a single-effect evaporation system by adding liquid alkali and inhibitor at the feed end.

[0016] S2: The first-effect evaporation system uses falling film heating and circulating evaporation. The generated secondary steam is used as the heating source for the second-effect evaporation system. The first-effect concentrate is transported to the second-effect evaporation system via the first-effect transfer pump.

[0017] S3: The double-effect evaporation system uses falling film heating and circulating evaporation. The generated secondary steam is used as the heating source for the triple-effect evaporation system. The double-effect concentrate is transported to the triple-effect evaporation system via the double-effect transfer pump.

[0018] S4: The triple-effect evaporation system uses dual heaters and a triple-effect circulating pump to force circulation evaporation, achieving deep concentration of wastewater. The first, second, and third effect evaporation processes all use a built-in demister in the separator to separate gas and liquid, preventing mist entrainment.

[0019] S5: The triple-effect concentrate is sent to the centrifugal separation process to remove impurities and salts via the triple-effect discharge pump. The centrifugal mother liquor is sent to the carbon dioxide decomposition process to recover crude phenol and liquid alkali. The clear liquid enters the mother liquor tank and is then pumped to the mother liquor storage tank or recycled.

[0020] S6: The condensate from the primary and secondary steam after heat exchange, along with the condensate from the tertiary secondary steam, is collected and discharged by a negative pressure drainage pump as influent for biochemical treatment.

[0021] As a preferred technical solution of the present invention:

[0022] The first and second effects use falling film heaters, while the third effect uses a dual-heater forced circulation structure.

[0023] The heating tubes of the single-effect and double-effect falling film heaters are made of 2507 duplex stainless steel, and the shell is made of 20# steel with an anti-corrosion lining.

[0024] A dedicated demister is installed at the top of the first-effect, second-effect, and third-effect separators to enhance gas-liquid separation.

[0025] The condensate from each effect is collected into the negative pressure drain tank and discharged by the negative pressure drain pump.

[0026] Concentrated sodium phenolate solution can be recovered from crude phenol and liquid alkali using a mature carbon dioxide decomposition process.

[0027] The beneficial effects of this invention are:

[0028] 1) This new process combination for the evaporation treatment of semi-coke wastewater significantly reduces salt crystallization and scaling by adding liquid alkali and inhibitors, combined with a triple-effect forced circulation structure. The heating tube is made of 2507 duplex stainless steel, and the shell is lined with anti-corrosion material, which significantly improves the corrosion resistance of the equipment and enables long-term stable operation. It has the advantages of anti-scaling, anti-corrosion, and long operating cycle.

[0029] 2) This new process combination for the evaporation treatment of semi-coke wastewater uses live steam for heating in the first effect, and the second and third effects utilize the secondary steam from the previous effect in sequence. It has a high thermal energy utilization rate, significantly reduces steam consumption, and has obvious energy-saving effect. It has the advantages of cascade utilization of thermal energy and low energy consumption.

[0030] 3) This new process combination for the evaporation treatment of semi-coke wastewater is equipped with a demister in each separator, which effectively eliminates mist entrainment. The condensate water quality can reach stable indicators and can be directly entered into the biological treatment, eliminating the need for a subsequent dual-membrane system, reducing investment and operating costs, and has the advantages of good gas-liquid separation effect and stable effluent quality.

[0031] 4) This new process combination for the evaporation treatment of semi-coke wastewater involves the triple-effect concentrate being desalted by a centrifuge, and the mother liquor being recycled and concentrated to achieve continuous salt separation. The system is free from salt accumulation and clogging, with a simplified treatment process, a high degree of automation, and the advantages of thorough salt extraction and continuous system operation.

[0032] 5) This new process combination for the evaporation treatment of semi-coke wastewater can recover crude phenol and liquid alkali by decomposing concentrated sodium phenolate with carbon dioxide, and achieve water reuse after biochemical treatment of condensate. It has both environmental and economic benefits and has the advantage of high resource utilization. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the present invention;

[0034] Figure 2 This is a process flow diagram of the present invention.

[0035] In the diagram: 1. First-effect circulating pump; 2. First-effect falling film heater; 3. First-effect separator; 4. First-effect demister; 5. First-effect transfer pump; 6. Second-effect circulating pump; 7. Second-effect falling film heater; 8. Second-effect separator; 9. Second-effect demister; 10. Second-effect transfer pump; 11. Third-effect heater B; 12. Third-effect heater A; 13. Third-effect separator; 14. Third-effect circulating pump; 15. Third-effect discharge pump; 16. Third-effect demister; 17. Mother liquor tank; 18. Mother liquor pump; 19. First-effect transfer regulating valve; 20. Second-effect transfer regulating valve; 21. Third-effect cooler; 22. Negative pressure drain tank; 23. Negative pressure drain pump. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1, by Figure 1-2 A novel process combination for the evaporation treatment of semi-coke wastewater is presented, comprising the following steps in sequence:

[0038] S1: The semi-coke wastewater, which has undergone deacidification and ammonia stripping pretreatment, is fed into a single-effect evaporation system by adding liquid alkali and inhibitor at the feed end.

[0039] S2: The first-effect evaporation system uses falling film heating and circulating evaporation. The generated secondary steam is used as the heating source for the second-effect evaporation system. The first-effect concentrate is transported to the second-effect evaporation system via the first-effect transfer pump 5.

[0040] S3: The second-effect evaporation system uses falling film heating and circulating evaporation. The generated secondary steam is used as the heating source for the third-effect evaporation system. The second-effect concentrate is transported to the third-effect evaporation system via the second-effect transfer pump 10.

[0041] S4: The triple-effect evaporation system uses dual heaters and a triple-effect circulating pump 14 to force circulation evaporation, achieving deep concentration of wastewater. The first, second, and third effect evaporation processes all use a built-in demister in the separator to separate gas and liquid, preventing mist entrainment.

[0042] S5: The triple-effect concentrate is sent to the centrifugal separation process by the triple-effect discharge pump 15 to remove impurities and salts. The centrifugal mother liquor is sent to the carbon dioxide decomposition process to recover crude phenol and liquid alkali. The clear liquid enters the mother liquor tank 17 and is sent to the mother liquor storage tank or refluxed by the mother liquor pump 18.

[0043] S6: The condensate produced by the heat exchange of the primary and secondary steam and the condensate of the secondary steam from the tertiary effect are collected and discharged by the negative pressure drain pump 23 as influent for biochemical treatment.

[0044] In Example 2, based on Example 1, the first-effect evaporation system consists of a first-effect circulating pump 1, a first-effect falling film heater 2, a first-effect separator 3, a first-effect demister 4, and a first-effect material transfer regulating valve 19, forming a circulating evaporation and material transfer path; the second-effect evaporation system consists of a second-effect circulating pump 6, a second-effect falling film heater 7, a second-effect separator 8, a second-effect demister 9, and a second-effect material transfer regulating valve 20, forming a circulating evaporation and material transfer path.

[0045] The triple-effect evaporation system consists of a triple-effect circulating pump 14, a triple-effect heater A12, a triple-effect heater B11, a triple-effect separator 13, and a triple-effect demister 16, forming a series forced circulation evaporation path.

[0046] The bottom outlet of the triple-effect separator is connected to the centrifuge inlet via the triple-effect discharge pump 15, enabling continuous discharge of the concentrate.

[0047] The top outlet of the first-effect separator 3 is connected to the shell-side inlet of the second-effect falling film heater, and the top outlet of the second-effect separator 8 is connected to the shell-side inlet of the third-effect heater A12 and the third-effect heater B11, so as to realize the cascade utilization of thermal energy.

[0048] The heating tubes of the single-effect falling film heater and the double-effect falling film heater are made of 2507 duplex stainless steel, and the heater shell is made of 20# steel with anti-corrosion lining.

[0049] The condensate produced by the heat exchange of the primary and secondary steam and the condensate of the tertiary cooler 21 are all collected into the negative pressure drain tank 22 and discharged by the negative pressure drain pump 23.

[0050] After centrifugation, the mother liquor enters the mother liquor tank 17 and is then returned to the triple-effect evaporation system via the mother liquor pump 18 for continued circulation, concentration, and salt extraction.

[0051] The discharged condensate meets the following water quality requirements: COD < 3000 mg / L, total phenols < 800 mg / L, and total oil < 500 mg / L. It can be directly treated by biological processes.

[0052] The concentrated sodium phenolate solution obtained by triple-effect evaporation is treated by carbon dioxide decomposition to recover crude phenol and liquid alkali.

[0053] Working principle:

[0054] Implementation steps for the first innovation point:

[0055] Step 1: Continuously add liquid alkali and inhibitors to the feed end of the semi-coke wastewater after deacidification and ammonia stripping to stabilize water quality and inhibit salt crystallization and scaling;

[0056] Step 2: The first and second effect evaporation systems use falling film evaporation, and the third effect evaporation system uses dual heaters for forced circulation evaporation to reduce the risk of crystal adhesion on the pipe wall;

[0057] Step 3: The heating tubes of the first-effect falling film heater 2 and the second-effect falling film heater 7 are made of 2507 duplex stainless steel, and the shell is made of 20# steel with anti-corrosion lining to improve corrosion resistance in high-salt and high-phenol environments.

[0058] Implementation steps for the second innovation point:

[0059] Step 1: The first-effect falling film heater 2 uses live steam as a heat source, and the generated secondary steam is sent to the shell side of the second-effect falling film heater 7;

[0060] Step 2: The double-effect evaporation system uses the secondary steam from the first effect for heating, and the generated secondary steam is sent to the shell side of the triple-effect heater A12 and the triple-effect heater B11.

[0061] Step 3: Second and third effects do not consume additional live steam, realizing the gradual utilization of thermal energy and significantly reducing steam consumption and operating costs.

[0062] The third innovation point implementation steps:

[0063] Step 1: Install dedicated first-effect, second-effect, and third-effect demisters 4, 9, and 16 on the top of the first-effect, second-effect, and third-effect separators 3, 8, and 13;

[0064] Step 2: The steam generated by evaporation is demisted to remove droplets and mist, preventing the entrainment of pollutants;

[0065] Step 3: Once the condensate water quality stabilizes to COD < 3000 mg / L, total phenols < 800 mg / L, and total oil < 500 mg / L, it can be directly introduced into the biological system.

[0066] The fourth innovation point implementation steps:

[0067] Step 1: The triple-effect concentrate is sent to a centrifuge via triple-effect discharge pump 15 to remove impurities and salts;

[0068] Step 2: The centrifuged mother liquor enters the carbon dioxide decomposition system to decompose sodium phenolate into crude phenol and liquid alkali and recover them;

[0069] Step 3: The clear liquid is returned to the triple-effect system for circulation and concentration, so as to achieve continuous salt separation and prevent salt accumulation and blockage in the system.

[0070] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A novel process combination for the evaporation treatment of semi-coke wastewater, characterized in that, The steps are as follows: S1: The semi-coke wastewater, which has undergone deacidification and ammonia stripping pretreatment, is fed into a single-effect evaporation system by adding liquid alkali and inhibitor at the feed end. S2: The first-effect evaporation system adopts falling film heating and circulating evaporation, and the generated secondary steam is used as the heating source of the second-effect evaporation system. The first-effect concentrate is transported to the second-effect evaporation system by the first-effect transfer pump (5). S3: The two-effect evaporation system adopts falling film heating and circulating evaporation, and the generated secondary steam is used as the heating source of the three-effect evaporation system. The two-effect concentrate is transported to the three-effect evaporation system by the two-effect transfer pump (10). S4: The triple-effect evaporation system uses dual heaters to force evaporation through a triple-effect circulating pump (14) to achieve deep concentration of wastewater. The first, second and third effect evaporation processes are all separated by a built-in demister in the separator to prevent mist entrainment. S5: The triple-effect concentrate is sent to the centrifugal separator via the triple-effect discharge pump (15) to remove impurities and salts. The centrifugal mother liquor is sent to the carbon dioxide decomposition process to recover crude phenol and liquid alkali. The clear liquid enters the mother liquor tank 17 and is sent to the mother liquor storage tank or refluxed by the mother liquor pump 18. S6: The condensate generated by the secondary steam from the first and second effects after heat exchange is collected with the condensate from the secondary steam from the third effect and discharged by the negative pressure drainage pump (23) as influent for biochemical treatment.

2. The novel process combination for evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The single-effect evaporation system consists of a single-effect circulating pump (1), a single-effect falling film heater (2), a single-effect separator (3), a single-effect demister (4), and a single-effect material transfer regulating valve (19), forming a circulating evaporation and material transfer path; the double-effect evaporation system consists of a double-effect circulating pump (6), a double-effect falling film heater (7), a double-effect separator (8), a double-effect demister (9), and a double-effect material transfer regulating valve (20), forming a circulating evaporation and material transfer path.

3. The novel process combination for evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The triple-effect evaporation system consists of a triple-effect circulating pump (14), a triple-effect heater A (12), a triple-effect heater B (11), a triple-effect separator (13), and a triple-effect demister (16), forming a series forced circulation evaporation path.

4. The novel process combination for evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The bottom outlet of the triple-effect separator is connected to the centrifuge inlet via a triple-effect discharge pump (15) to achieve continuous discharge of the concentrate.

5. A novel process combination for the evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The top outlet of the first-effect separator (3) is connected to the shell-side inlet of the second-effect falling film heater, and the top outlet of the second-effect separator (8) is connected to the shell-side inlet of the third-effect heater A (12) and the third-effect heater B (11), so as to realize the cascade utilization of thermal energy.

6. A novel process combination for the evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The heating tubes of the single-effect falling film heater and the double-effect falling film heater are made of 2507 duplex stainless steel, and the heater shell is made of 20# steel with anti-corrosion lining.

7. A novel process combination for the evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The condensate generated by the heat exchange of the first and second effect secondary steam and the condensate of the third effect cooler (21) are all collected into the negative pressure drain tank (22) and discharged by the negative pressure drain pump (23).

8. A novel process combination for the evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: After centrifugation, the mother liquor enters the mother liquor tank (17) and is returned to the triple-effect evaporation system via the mother liquor pump (18) to continue circulating, concentrating, and extracting salt.

9. A novel process combination for the evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The discharged condensate meets the following water quality requirements: COD < 3000 mg / L, total phenols < 800 mg / L, and total oil < 500 mg / L. It can be directly treated by biological processes.

10. A novel process combination for the evaporation treatment of semi-coke wastewater according to claim 1, characterized in that: The concentrated sodium phenolate solution obtained by triple-effect evaporation is treated by carbon dioxide decomposition to recover crude phenol and liquid alkali.

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