Vacuum flash evaporation treatment method for coal gasification low-pressure black water

Abstract

The invention relates to the technical field of coal gasification, and discloses a vacuum flash evaporation treatment method of coal gasification low-pressure black water, which comprises the following steps: S1, adding a flocculating agent into the coal gasification low-pressure black water, carrying out flocculation precipitation treatment, and removing suspended particulate matters in the black water, the flocculated black water is filtered through a sand filter, and the filtering speed is 5-10 m / h; s2, black water is heated through an efficient heat exchanger, and steam condensation heat is used for heating the black water to 90-120 DEG C; s3, the heated black water is sent to a multi-stage vacuum flash tower, and evaporation is carried out under the conditions that the pressure is 0.05 MPa, the pressure is 0.02 MPa and the pressure is 0.01 MPa. According to the method, moisture and volatile organic compounds in black water are rapidly evaporated under the low-pressure condition through a vacuum flash evaporation treatment method, the volume of the black water is effectively reduced, most moisture in the black water is evaporated through heating and multi-stage vacuum treatment, the volume of the concentrated black water is reduced, the follow-up treatment burden is reduced, and the treatment efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of coal gasification, in particular to a vacuum flash evaporation treatment method for low-pressure black water from coal gasification. Background Art

[0002] Coal gasification technology is the process of converting coal into synthesis gas under high temperature and high pressure. It is widely used in energy, chemical and other industries. However, black water is produced as a by-product during the gasification process. The black water has the characteristics of high pollution, high salt content and high organic matter concentration. The main components of black water include suspended solids, soluble inorganic salts, phenolic compounds, cyanide and other difficult-to-degrade organic matter. If not properly treated, the discharge of black water will cause serious pollution to the environment.

[0003] Traditional methods for treating coal gasification black water mainly include physical, chemical and biological treatment methods. However, the above treatment technologies have many limitations when treating coal gasification black water:

[0004] Traditional treatment technologies such as physical sedimentation and filtration can only remove some suspended matter and solid particles, but have limited effects on the removal of dissolved organic matter and inorganic salts, resulting in the black water after treatment still containing a large amount of pollutants;

[0005] The high temperature and high salt content of black water make the traditional evaporation concentration method extremely energy-intensive and prone to equipment scaling under high temperature conditions, increasing maintenance difficulty and cost.

[0006] The non-volatile organic matter in coal gasification black water is not easy to remove by ordinary treatment methods, resulting in the effluent quality being difficult to meet the discharge standards;

[0007] Due to the high content of inorganic salts in black water, traditional thermal treatment equipment is prone to scaling, the equipment operation and maintenance costs are high, and frequent shutdowns for cleaning affect the sustainability of treatment.

[0008] Therefore, how to reduce energy consumption, improve pollutant removal effects, and alleviate equipment scaling problems while ensuring treatment efficiency has become a technical difficulty and research focus in coal gasification black water treatment.

[0009] Therefore, those skilled in the art provide a vacuum flash treatment method for low-pressure black water from coal gasification to solve the problems raised in the above background technology. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention provides a vacuum flash treatment method for low-pressure black water from coal gasification. The technical problem solved is to reduce treatment energy consumption, improve the efficiency of pollutant removal in black water, prevent equipment scaling, reduce the burden of subsequent treatment, and realize resource recycling by combining vacuum flash treatment with multi-effect evaporation, heat recovery and advanced oxidation technology.

[0011] To achieve the above objectives, the present invention is implemented through the following technical scheme: A vacuum flash treatment method for coal gasification low-pressure black water, comprising the following steps: S1, adding a flocculant to the coal gasification low-pressure black water, performing flocculation and precipitation treatment to remove suspended particles in the black water, wherein the flocculant is polyacrylamide, and the dosage is 60 mg / L-120 mg / L, and the flocculated black water is filtered through a sand filter at a filtration rate of 5 m / h-10 m / h;

[0012] S2. Heat the black water through a high-efficiency heat exchanger, and use the steam condensation heat to heat the black water to 90℃-120℃. The heat exchange capacity of the heat exchanger is calculated by the following formula:

[0013] Q=UAΔT m ,

[0014] Among them, Q is the heat transfer amount, U is the heat transfer coefficient, A is the heat transfer area, ΔT m is the logarithmic mean temperature difference;

[0015] S3. Send the heated black water to a multi-stage vacuum flash tower and evaporate it under pressures of 0.05MPa, 0.02MPa and 0.01MPa. The evaporation amount is calculated according to the following formula:

[0016]

[0017] in, is the mass flow rate of evaporating water vapor, Q 蒸发 is the heat of evaporation, h fg is the latent heat of vaporization of water;

[0018] S4, condensing the water vapor generated by vacuum flash evaporation through a condenser, and recovering clean water for circulation in the system;

[0019] S5. The concentrated liquid after vacuum flash evaporation is subjected to deep treatment, first, by ozone oxidation treatment, and then further oxidized by Fenton oxidation reaction, wherein the Fenton reaction follows the following formula:

[0020] Fe 2+ +H2O2→Fe 3+ +OH - +OH·;

[0021] S6. Separate organic matter and inorganic salts in the concentrate by nanofiltration and reverse osmosis membranes. The permeability is calculated by the formula:

[0022] Among them, J w is the water flux, ΔP is the operating pressure, Δπ is the osmotic pressure difference, and R is the membrane resistance.

[0023] Preferably, during the flocculation and sedimentation treatment, the dosage of the flocculant is dynamically adjusted according to the concentration of suspended matter in the black water, the stirring speed is 200rpm-300rpm, and the sedimentation time is 30min-60min.

[0024] Preferably, the preheating of the black water is achieved by a multiple-effect evaporator, and the steam generated by each stage of multiple-effect evaporation is used to heat the black water of the next stage, and the heat energy recovery rate can reach 60%-80%.

[0025] Preferably, the heat pump system is used to recover the waste heat of low-grade steam after multi-effect evaporation, and the coefficient of performance COP of the heat pump is calculated according to the following formula:

[0026]

[0027] Among them, Q 供热 is the heat supplied by the heat pump, and W is the electrical energy consumption of the heat pump.

[0028] Preferably, the pressure in the vacuum flash tower is automatically adjusted by an intelligent control system, and the evaporation amount is optimized in real time according to the actual operating state. The relationship between the vacuum degree and the evaporation rate is as follows:

[0029]

[0030] Among them, C v is the evaporation constant, P1 and P2 are the pressures of black water when it enters and leaves the flash tower.

[0031] Preferably, the ozone oxidation treatment is carried out before the black water enters the vacuum flash evaporation system, the ozone dosage is in the range of 1.2 to 1.5 times the chemical oxygen demand in the black water, and the reaction time is in the range of 30 min to 60 min.

[0032] Preferably, the Fenton oxidation treatment is used for deep treatment of concentrated liquid, the concentration range of hydrogen peroxide is 50 mg / L-100 mg / L, and the reaction time range is 30 min-60 min.

[0033] Preferably, the permeate produced after the concentrated liquid is separated by membrane is recycled and used as pretreatment or process water in the system.

[0034] Preferably, the inner surface of the vacuum flash tower is coated with an anti-scaling coating, and the coating material is a fluoride or ceramic coating, which is used to reduce the deposition and scaling of inorganic salts.

[0035] Preferably, the device is equipped with an ultrasonic self-cleaning device, and the ultrasonic vibration frequency range is 20kHz-40kHz, which is used to remove scale inside the device, and the vibration power is calculated by the following formula:

[0036]

[0037] Among them, P is the vibration power, ρ is the black water density, ρ is the vibration velocity, and A is the effective area of ​​the equipment.

[0038] The present invention provides a vacuum flash treatment method for low-pressure black water from coal gasification. It has the following beneficial effects:

[0039] 1. The present invention uses a vacuum flash evaporation treatment method to quickly evaporate the water and volatile organic matter in the black water under low pressure conditions, effectively reducing the volume of the black water. The method evaporates most of the water in the black water through heating and multi-stage vacuum treatment, and the volume of the concentrated black water is reduced, thereby reducing the burden of subsequent treatment and improving the treatment efficiency.

[0040] 2. The present invention realizes the step-by-step recovery and efficient utilization of thermal energy through the combination of multi-effect evaporation and heat pump technology. In the vacuum flash evaporation process, the steam generated by evaporation is used to preheat black water, reducing the demand for external energy, while the heat pump technology effectively recovers the low-temperature waste heat generated in the condensation process, further reducing the total energy consumption of the system. Therefore, while maintaining high processing efficiency, energy consumption is greatly reduced.

[0041] 3. The present invention can deeply treat stubborn organic pollutants in black water by introducing advanced oxidation technologies such as ozone oxidation and Fenton oxidation, significantly improve the removal rate of COD indicators, and ensure that the treated black water can meet the discharge standards or reuse requirements.

[0042] 4. The present invention effectively reduces the deposition of inorganic salts in black water and prevents the occurrence of scaling by coating the anti-scaling coating on the inner surface of the equipment. In addition, the application of the ultrasonic self-cleaning system can regularly remove the scaling formed on the surface of the equipment during operation, thereby extending the service life of the equipment and reducing the frequency of shutdown maintenance.

[0043] 5. The present invention effectively utilizes water resources. The recovered condensed water can be recycled and reused in the coal gasification process or further processed to meet the emission standards. Its recycling method reduces the waste of water resources and improves the overall economy and environmental benefits of the system.

[0044] 6. The present invention can further process the concentrated liquid after vacuum flash evaporation to remove organic matter and inorganic salts in the black water, and the permeate water after membrane separation can be recycled or discharged, reducing the amount of wastewater discharged and the difficulty of processing the final concentrated liquid. Its multiple processing methods enable this method to adapt to the treatment needs of coal gasification black water of different compositions and concentrations, and enhance the environmental performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0046] In order to make the technical personnel in the technical field understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in combination with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a partial embodiment of the present invention, not a complete embodiment. Based on the embodiment of the present invention, other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present invention.

[0047] The present invention is described in detail below in conjunction with the accompanying drawings:

[0048] Example:

[0049] Please see attached Figure 1 The embodiment of the present invention provides a vacuum flash treatment method for coal gasification low-pressure black water, comprising the following steps: S1, adding a flocculant to the coal gasification low-pressure black water to perform flocculation and precipitation treatment to remove suspended particles in the black water, the flocculant is polyacrylamide, the dosage is 60 mg / L-120 mg / L, and the flocculated black water is filtered through a sand filter at a filtration rate of 5 m / h-10 m / h;

[0050] S2. Heat the black water through a high-efficiency heat exchanger, and use the steam condensation heat to heat the black water to 90℃-120℃. The heat exchange capacity of the heat exchanger is calculated by the following formula:

[0051] Q=UAΔT m ,

[0052] Among them, Q is the heat transfer amount, U is the heat transfer coefficient, A is the heat transfer area, ΔT m is the logarithmic mean temperature difference;

[0053] S3. Send the heated black water to a multi-stage vacuum flash tower and evaporate it under pressures of 0.05MPa, 0.02MPa and 0.01MPa. The evaporation amount is calculated according to the following formula:

[0054]

[0055] in, is the mass flow rate of evaporating water vapor, Q 蒸发 is the heat of evaporation, h fg is the latent heat of vaporization of water;

[0056] S4, condensing the water vapor generated by vacuum flash evaporation through a condenser, and recovering clean water for circulation in the system;

[0057] S5. The concentrated liquid after vacuum flash evaporation is subjected to deep treatment, first, by ozone oxidation treatment, and then further oxidized by Fenton oxidation reaction, wherein the Fenton reaction follows the following formula:

[0058] Fe2+ +H2O2→Fe 3+ +OH - +OH·;

[0059] S6. Separate organic matter and inorganic salts in the concentrate by nanofiltration and reverse osmosis membranes. The permeability is calculated by the formula:

[0060] Among them, J w is the water flux, ΔP is the operating pressure, Δπ is the osmotic pressure difference, and R is the membrane resistance.

[0061] Benefits of S1: Through flocculation, sedimentation and filtration, suspended particles in black water can be effectively removed, reducing the particle burden in subsequent treatment. The black water after filtration has high purity, which can avoid wear and tear on equipment after entering the heater and vacuum flash tower, extend the service life of the equipment and reduce maintenance costs.

[0062] Benefits of S2: Through high-efficiency heat exchangers and waste heat recovery, the consumption of external energy is reduced, the heat generated by condensed steam is utilized to the maximum extent, and the heat exchange formula is used to calculate the reasonable heat exchange area to ensure that the black water can be evenly heated to the required temperature, improve the thermal energy utilization rate during the heating process, and reduce energy waste. The temperature range in the heat exchanger is controlled to ensure that the black water is at the optimal temperature during the subsequent vacuum flash evaporation process;

[0063] The heat exchange calculation formula of the heat exchanger can accurately calculate the heat exchange amount, determine the optimal heat exchange area of ​​the heat exchanger, ensure that the black water reaches the target temperature, ensure the effective transfer of energy, and reduce unnecessary heat loss;

[0064] The benefits of S3 are that through multi-stage vacuum flash evaporation, substances with different boiling points can be evaporated under different pressure conditions, effectively reducing energy consumption. At the same time, it ensures that the water in the black water can be fully evaporated. Under vacuum conditions, the evaporation temperature of water and volatile organic compounds is low, which reduces energy consumption during the heating process and improves the economy of the overall process.

[0065] The function of the evaporation calculation algorithm formula is to calculate the mass flow rate of evaporated water, help design and optimize the capacity and operating parameters of the evaporation tower, ensure that the water in the black water is fully evaporated, achieve the best energy efficiency ratio, and reduce unnecessary steam waste;

[0066] Benefits of S4: The water vapor produced by condensation can be recycled as clean water, which can be used for recycling in industrial processes and can meet emission standards after further treatment, thus reducing wastewater discharge. At the same time, through the recycling of water, the dependence on external water sources is reduced, the utilization rate of water resources is improved, and the economy and environmental performance of the system are enhanced;

[0067] Benefits of S5: It effectively removes stubborn organic pollutants in black water, especially difficult-to-degrade compounds such as phenols and cyanides, so that the organic content of the concentrated liquid after treatment is reduced. Through advanced oxidation reactions, the chemical oxygen demand in black water is significantly reduced, ensuring that the discharged water quality meets environmental protection requirements or reuse standards after further treatment.

[0068] The role of the Fenton reaction formula guides the actual operating parameters of the oxidation reaction, including the control of reaction time and reagent dosage, thereby improving the oxidation efficiency and ensuring that organic matter is completely degraded;

[0069] The benefits of S6 are that it can effectively remove organic matter and inorganic salts from the concentrate. The separated permeate can be recycled or discharged, which reduces pollution emissions while reducing water resource consumption. It can adapt to the treatment needs of black water of different concentrations and components, and increase the flexibility and adaptability of the system.

[0070] The function of the permeability algorithm formula is to determine the flow rate and pressure gradient of the permeate during the separation process, ensure that the membrane separation system can operate stably and achieve the most efficient water recovery, help design the operating conditions of membrane separation, ensure that the pressure, osmotic pressure difference and resistance are controlled within a reasonable range, and achieve efficient separation and long-term stable operation.

[0071] During the flocculation and sedimentation treatment process, the dosage of flocculant is dynamically adjusted according to the concentration of suspended matter in the black water, the stirring speed is 200rpm-300rpm, and the sedimentation time is 30min-60min.

[0072] The dosage of flocculant is dynamically adjusted according to the concentration of suspended matter in black water to ensure that the suspended particles in black water can be fully flocculated to form particle flocs that are easy to settle. The specific dosage depends on the actual content of suspended matter in black water. When the concentration of suspended matter is high, the dosage of flocculant is increased, and when the concentration of suspended matter is low, the dosage of flocculant is reduced to avoid waste;

[0073] Dynamically adjust the flocculant dosage to ensure the best flocculation effect, which can effectively aggregate the suspended particles in the black water into flocs, facilitating sedimentation and separation; dynamically adjust the dosage according to the actual suspended matter concentration to avoid the use of more or less agents, reduce the waste of flocculants, and reduce operating costs; by accurately controlling the flocculant dosage, the stable operation of the black water pretreatment process can be maintained, ensuring that the processing burden of the downstream treatment unit is reduced and improving the efficiency of the overall system;

[0074] The function of stirring is to make the flocculant fully contact with the suspended matter in the black water and promote the flocculation reaction. When the stirring speed is 200rpm-300rpm, it can ensure the uniform mixing of the flocculant and the suspended matter without destroying the formed floccules.

[0075] Appropriate stirring speed can ensure that the flocculant is evenly distributed in the black water, increase the contact opportunity of the flocculation reaction, and enhance the flocculation effect; rapid stirring will destroy the formed particle flocs and reduce the sedimentation efficiency, while the stirring speed of 200rpm-300rpm can effectively control the reaction rate, avoid the breakage of flocs, and ensure a good sedimentation effect. Controlling the stirring speed within an appropriate range can reduce energy consumption and ensure that energy efficiency is optimized while maintaining the flocculation effect;

[0076] Sedimentation time refers to the time required for floccules to settle to the bottom of the container under the action of gravity. Within the range of 30min-60min, the floccules in the black water can fully settle and the supernatant can be separated;

[0077] Appropriate sedimentation time can ensure that the flocculants are fully settled in the sedimentation tank or sedimentation equipment, reduce the residual suspended matter in the supernatant, and further improve the water quality; controlling the sedimentation time at 30min-60min can improve the treatment efficiency while ensuring the sedimentation of particles, and avoid long waiting times that lead to a decrease in treatment capacity; by optimizing the sedimentation time, the concentration of suspended matter in the black water can be effectively reduced, reducing the load on subsequent filtration or heating equipment, and avoiding equipment blockage or wear due to accumulation of particles.

[0078] The preheating of black water is achieved through a multi-effect evaporator. The steam generated by each stage of multi-effect evaporation is used to heat the black water of the next stage, and the heat energy recovery rate can reach 60%-80%.

[0079] Multi-effect evaporation is an efficient way of utilizing heat energy to treat black water by cascade evaporation through the pressure and temperature difference of different effect sections. The preheating of black water is achieved through a multi-effect evaporation device. The specific process is as follows: black water generates steam when it evaporates in the first effect, and the generated steam is used as the heat source of the second effect to heat the black water in the second effect. By analogy, through the cascade utilization of heat energy, the steam generated at each stage is used to heat the black water of the next stage, realizing the repeated use and efficient recovery of heat energy, and reducing the total energy consumption of the system;

[0080] Multi-effect evaporation technology can make full use of the heat generated by evaporation: the steam generated at each stage is used as the heating source for the next stage, reducing the demand for external heat sources. Since the steam is used in stages at each stage, the benefits of each unit of energy can be maximized. Multi-effect evaporation technology achieves efficient heat transfer and reuse through step cooling and pressure control, significantly reducing the energy consumption of the system. The steam at each stage provides heat for the black water of the next stage, which can reduce the demand for external steam or other heating means, reduce the use of energy, and reduce operating costs. The reuse of steam heat energy at each stage reduces the total energy consumption of the system. Compared with single-effect evaporation, multi-effect evaporation can achieve the same heating effect, reduce energy consumption, and have significant energy-saving effects. The multi-effect evaporation system enables black water to reach the optimal heating temperature before entering the vacuum flash evaporation process, ensuring the efficient operation of the vacuum flash evaporation process. Effective preheating improves the subsequent evaporation efficiency and reduces the energy consumption required in the flash evaporation process. With the improvement of heat recovery rate, the system can process more black water without significantly increasing external energy consumption. Therefore, multi-effect evaporation improves the overall processing capacity of the black water treatment device and improves the processing efficiency.

[0081] The heat pump system is used to recover the waste heat of low-grade steam after multi-effect evaporation. The coefficient of performance (COP) of the heat pump is calculated according to the following formula:

[0082]

[0083] Among them, Q 供热 is the heat supplied by the heat pump, and W is the electrical energy consumption of the heat pump.

[0084] COP is an important parameter for evaluating the operating efficiency of a heat pump system. Through this formula, COP can accurately measure the efficiency of a heat pump system in converting electrical energy into thermal energy. 供热 and W, can directly calculate the actual heat supply and power consumption of the heat pump under specific conditions, helping engineers determine whether the heat pump can meet the system's demand for heat and optimize operating parameters;

[0085] Help evaluate the performance of heat pumps under different operating conditions. Engineers can improve the COP value by adjusting the operating conditions of the heat pump, thereby improving the operating efficiency of the system and reducing energy consumption;

[0086] Through the calculation of COP, designers can be guided to determine the most suitable heat pump specifications and equipment models to ensure that the equipment is used in the black water treatment system to achieve the best efficiency. At the same time, data support can be provided during the system commissioning process to help optimize the overall process flow.

[0087] The main benefit of the heat pump system is that it can recover the low-grade waste heat generated in the multi-effect evaporation process, which is usually wasted in traditional systems. By recovering the thermal energy of low-grade steam, the heat pump converts it into usable heat and uses it again to preheat black water, greatly reducing the demand for external energy and improving the overall energy efficiency.

[0088] The introduction of the heat pump system significantly reduces the external energy consumption required by the system. For example, the system does not require additional steam to heat black water, but relies on recovered waste heat, reducing fuel consumption and electricity use, which can significantly reduce the operating costs of the system;

[0089] Heat pump technology reduces energy waste in industrial production and reduces environmental impact by recovering waste heat. Reducing dependence on fossil fuels means reducing greenhouse gas emissions and enhancing the environmental performance of the system.

[0090] The pressure in the vacuum flash tower is automatically adjusted by the intelligent control system, and the evaporation capacity is optimized in real time according to the actual operating status. The relationship between the vacuum degree and the evaporation rate is as follows:

[0091]

[0092] Among them, C v is the evaporation constant, P1 and P2 are the pressures of black water when it enters and leaves the flash tower.

[0093] It is used to calculate the mass flow rate of evaporated water vapor during the flash evaporation process. By controlling the pressure of black water entering and leaving the flash tower, the evaporation amount at each moment can be accurately calculated. The intelligent control system automatically adjusts the pressure in the flash tower according to the actual operating conditions to optimize the evaporation rate. By adjusting the vacuum degree, the evaporation effect can be optimized in real time to ensure that the water and volatile organic matter in the black water evaporate at the optimal rate.

[0094] The formula is combined with the intelligent control system to automatically adjust the vacuum degree inside the flash tower according to the changes in black water, realizing dynamic optimization of evaporation. The algorithm can instantly calculate the evaporation rate, thus achieving efficient and stable operation and reducing manual intervention.

[0095] Using this formula, the intelligent control system can automatically adjust the pressure of the vacuum flash tower according to the flow and temperature of the black water, ensuring the optimal evaporation effect at each operation stage. By controlling P1 and P2, the system can accurately adjust the evaporation rate to ensure that the water in the black water evaporates quickly and improve the processing efficiency.

[0096] The vacuum degree is directly related to the evaporation rate. A high vacuum degree will lead to energy consumption, while a low vacuum degree will lead to low evaporation efficiency. Since the formula can automatically adjust the vacuum degree according to the actual operating conditions, the system can maintain stable operation under different black water compositions or operating conditions, and the evaporation process can be effectively controlled to ensure the stability and efficiency of the system.

[0097] Traditional vacuum flash evaporation operations require manual monitoring and adjustment of the working status of the vacuum pump, automatically adjusting the vacuum degree according to the pressure difference, simplifying the operation process, reducing manual intervention, and improving the system's automation level and operational convenience; by controlling the evaporation rate, it can accelerate the evaporation process of water and volatile organic matter in black water, reduce the volume of black water, concentrate pollutants, and thereby improve treatment efficiency.

[0098] Ozone oxidation treatment is carried out before the black water enters the vacuum flash evaporation system. The ozone dosage is 1.2 to 1.5 times the chemical oxygen demand in the black water, and the reaction time is controlled in the range of 30 min to 60 min.

[0099] Ozone is a strong oxidant that can quickly react with organic pollutants in black water and decompose them into molecular substances that are easier to handle. The strong oxidizing effect of ozone can destroy the complex and difficult-to-degrade molecular structure of organic matter in black water, especially difficult-to-handle phenolic compounds, cyanide and other toxic and harmful substances;

[0100] Ozone oxidation treatment is carried out before the black water enters the vacuum flash evaporation system. It degrades the organic pollutants in the black water in advance, which can significantly reduce the organic load and the concentration of pollutants, making the subsequent vacuum flash evaporation treatment more efficient and reducing the impact of organic matter on the equipment during the evaporation process.

[0101] Ozone oxidation can effectively oxidize volatile organic compounds in black water, such as benzene and toluene, to reduce the release of volatile compounds in subsequent treatment steps and avoid secondary pollution. Through oxidation, ozone can reduce odor and harmful gases in black water.

[0102] Ozone oxidation treatment can significantly improve the removal rate of COD in black water. The ozone dosage is set to 1.2-1.5 times the chemical oxygen demand in black water to ensure that the oxidant is used to degrade organic matter, ensure that the oxidation reaction is thorough, and reduce the content of organic pollutants in black water.

[0103] Through ozone pretreatment, the stubborn organic matter in the black water has been partially oxidized and decomposed before entering the vacuum flash evaporation system, thereby reducing the organic matter load entering the evaporation system, improving the evaporation efficiency, reducing scaling and equipment pollution in the flash tower, extending the service life of the equipment, and reducing the maintenance cost of the equipment;

[0104] Ozone oxidation can efficiently degrade toxic and harmful organic pollutants, while reducing the emission of volatile organic compounds, effectively reducing secondary pollution to the environment during black water treatment.

[0105] Fenton oxidation treatment is used for deep treatment of concentrated liquid. The concentration range of hydrogen peroxide is 50mg / L-100mg / L, and the reaction time range is 30min-60min.

[0106] Fenton oxidation is an advanced oxidation technology based on the reaction of hydrogen peroxide and ferrous ions to generate strong oxidants, hydroxyl radicals. Hydroxyl radicals have a very strong oxidizing ability and can effectively degrade stubborn organic substances in black water concentrate that are difficult to treat, such as phenolic compounds, cyanide and other toxic organic substances. The Fenton reaction can effectively destroy the molecular structure of organic pollutants and decompose them into harmless or easily biodegradable molecular substances.

[0107] Concentrate is the high-concentration waste liquid left after black water is vacuum flashed, which still contains hard-to-degrade organic pollutants and other impurities. Fenton oxidation treatment is used to deeply treat the concentrate, further decompose the pollutants, reduce their concentration and harmfulness, and ensure that the treated liquid can meet higher discharge standards or facilitate further treatment;

[0108] The hydroxyl radical generated by the Fenton oxidation reaction is one of the most powerful free radicals known to date. It can react quickly with organic pollutants, break the molecular bonds of organic matter, and degrade complex organic molecules into molecules or even inorganic matter, ensuring that there is sufficient oxidant in the concentrate to degrade difficult-to-treat organic pollutants and achieve a high organic matter removal rate.

[0109] Fenton oxidation can significantly reduce the chemical oxygen demand and total organic carbon in the concentrate, ensuring that the treated concentrate meets the discharge or reuse standards. This process helps solve the problem of residual refractory organic matter in the concentrate and lays the foundation for subsequent processes.

[0110] The concentrate usually contains high concentrations of toxic and harmful substances, such as phenols, cyanide, etc. Through Fenton oxidation, toxic organic matter is quickly oxidized and decomposed, reducing its toxicity and environmental hazards, reducing the residual harmful substances in the concentrate, and ensuring that the final discharged wastewater meets environmental protection standards.

[0111] The permeate produced after the concentrate is separated by membrane is recycled for system pretreatment or process water;

[0112] The inner surface of the vacuum flash tower is coated with an anti-scaling coating, the coating material is a fluoride or ceramic coating, which is used to reduce the deposition and scaling of inorganic salts.

[0113] Membrane separation technology separates organic matter and inorganic salts in the concentrate through nanofiltration or reverse osmosis to produce permeate and concentrate;

[0114] The permeate after membrane separation is used in the pretreatment stage of black water, replacing part of the external water demand and saving water resources. At the same time, the permeate can be used as cooling water, flushing water, etc. in other process units to optimize the use of process water.

[0115] By recycling the permeate after membrane separation back into the system, the demand for external water resources is greatly reduced, the water consumption of the enterprise is reduced, the operating cost is reduced, and the sustainability of the system is enhanced; the reuse of permeate saves water costs, reduces the pressure of external water source treatment, and optimizes the economic benefits of the overall water cycle; the reuse of permeate reduces the final wastewater discharge of the system, which helps the enterprise meet more stringent environmental protection requirements and reduce the impact on the environment; the permeate after membrane separation has high water quality and is used for system pretreatment or process flow to maintain the stability and quality of process water and avoid the impact of external water source fluctuations on the production system;

[0116] The vacuum flash tower operates under high temperature and high pressure conditions. The inorganic salts in the black water are easily deposited on the surface of the equipment under these conditions to form scale. To avoid this, the inner surface of the equipment is coated with an anti-scaling coating, such as fluoride or ceramic coating. This coating can significantly reduce the adhesion of inorganic salts and avoid scale formation; the fluoride coating has excellent anti-adhesion properties and can effectively reduce the deposition tendency of inorganic salts at high temperatures; the ceramic coating has excellent corrosion resistance and anti-scaling properties, can operate stably for a long time, and reduce the impact of scaling on the equipment;

[0117] The anti-scaling coating can effectively prevent the inorganic salts in the black water from being deposited on the inner wall of the vacuum flash tower, reduce the formation of scale, reduce the cleaning and maintenance frequency of the equipment after scaling, avoid the damage of scaling to the heat transfer efficiency of the equipment, and extend the service life of the equipment; scaling will affect the heat transfer efficiency and fluid flow of the equipment, resulting in increased energy consumption and decreased processing efficiency. The anti-scaling coating reduces the formation of scale, ensures that the vacuum flash tower is always in an efficient operating state, maintains a stable processing capacity, and reduces operating costs;

[0118] Traditional vacuum flash towers are prone to scaling after long-term operation and require regular shutdown for cleaning and maintenance. Through anti-scaling coatings, the cleaning and maintenance cycle of the equipment is greatly extended, reducing downtime caused by scaling problems and improving system continuity and production efficiency.

[0119] The equipment is equipped with an ultrasonic self-cleaning device with an ultrasonic vibration frequency range of 20kHz-40kHz, which is used to remove scale inside the equipment. The vibration power is calculated by the following formula:

[0120]

[0121] Among them, P is the vibration power, ρ is the black water density, ρ is the vibration velocity, and A is the effective area of ​​the equipment.

[0122] The role of ultrasonic self-cleaning device: When treating black water with high salt content and pollution load, inorganic salts and organic matter are easily deposited inside the equipment, forming scale, which leads to a decrease in equipment operation efficiency. The ultrasonic self-cleaning device generates high-frequency vibrations to induce vibrations on the internal surface of the equipment to prevent dirt and scale from adhering. At the same time, it has a cleaning effect on existing scales. Ultrasonic vibrations can destroy the adhesion of scales and make them fall off.

[0123] Ultrasonic self-cleaning technology can realize automatic equipment cleaning to avoid the accumulation of scale and the impact on equipment performance. The equipment does not need to be shut down during the cleaning process, and the vibration frequency runs automatically, effectively reducing the frequency of shutdown for cleaning and maintaining continuous and efficient operation of the system.

[0124] The ultrasonic self-cleaning device effectively destroys the adhesion between the sediment and the equipment surface through high-frequency vibration, prevents the formation of scale, and removes existing scale to ensure that the equipment surface remains clean;

[0125] Scaling will accelerate the wear of equipment, cause the heat transfer performance of equipment to deteriorate, and cause pipeline blockage and other problems. Ultrasonic self-cleaning technology can continuously remove scaling, avoid frequent shutdown and cleaning of equipment due to scaling problems, reduce equipment loss and downtime, and extend the service life of equipment;

[0126] Traditional equipment needs to be shut down and cleaned regularly when it is scaled, which affects the equipment's processing capacity and increases maintenance costs. Ultrasonic self-cleaning devices prevent scale formation through continuous vibration, eliminating the need for frequent shutdowns for cleaning, greatly reducing maintenance frequency and downtime losses, and lowering operating costs.

[0127] Scaling affects the operation of the equipment, hinders the heat transfer efficiency of the equipment, and increases energy consumption. The ultrasonic self-cleaning device ensures that the inside of the equipment remains clean and the heat transfer surface of the equipment remains in the best condition for a long time, ensuring that the heat exchange process is carried out efficiently, reducing energy consumption and improving the overall energy efficiency of the system.

[0128] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A vacuum flash treatment method for low-pressure black water from coal gasification, characterized in that: The method comprises the following steps: S1, adding a flocculant to the coal gasification low-pressure black water to perform flocculation and sedimentation treatment to remove suspended particles in the black water, wherein the flocculant is polyacrylamide, and the dosage is 60 mg / L-120 mg / L, and the flocculated black water is filtered through a sand filter at a filtration rate of 5 m / h-10 m / h; S2. Heat the black water through a high-efficiency heat exchanger, and use the steam condensation heat to heat the black water to 90℃-120℃. The heat exchange capacity of the heat exchanger is calculated by the following formula: Q=UAΔT m , Among them, Q is the heat transfer amount, U is the heat transfer coefficient, A is the heat transfer area, ΔT m is the logarithmic mean temperature difference; S3. Send the heated black water to a multi-stage vacuum flash tower and evaporate it under pressures of 0.05MPa, 0.02MPa and 0.01MPa. The evaporation amount is calculated according to the following formula: in, is the mass flow rate of evaporating water vapor, Q 蒸发 is the heat of evaporation, h fg is the latent heat of vaporization of water; S4, condensing the water vapor generated by vacuum flash evaporation through a condenser, and recovering clean water for circulation in the system; S5. The concentrated liquid after vacuum flash evaporation is subjected to deep treatment, first, by ozone oxidation treatment, and then further oxidized by Fenton oxidation reaction, wherein the Fenton reaction follows the following formula: Fe 2+ +H2O2→Fe 3+ +OH - +OH·; S6. Separate organic matter and inorganic salts in the concentrate by nanofiltration and reverse osmosis membranes. The permeability is calculated by the formula: Among them, J w is the water flux, ΔP is the operating pressure, Δπ is the osmotic pressure difference, and R is the membrane resistance.

2. The vacuum flash treatment method for coal gasification low-pressure black water according to claim 1, characterized in that: During the flocculation and sedimentation treatment process, the dosage of the flocculant is dynamically adjusted according to the concentration of suspended matter in the black water, the stirring speed is 200rpm-300rpm, and the sedimentation time is 30min-60min.

3. A vacuum flash treatment method for coal gasification low-pressure black water according to claim 1 or 2, characterized in that: The preheating of the black water is achieved through a multiple-effect evaporation device, and the steam generated by each stage of multiple-effect evaporation is used to heat the black water of the next stage, and the heat energy recovery rate can reach 60%-80%.

4. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 3, characterized in that: The heat pump system is used to recover the waste heat of low-grade steam after multi-effect evaporation. The coefficient of performance (COP) of the heat pump is calculated according to the following formula: Among them, Q 供热 is the heat supplied by the heat pump, and W is the electrical energy consumption of the heat pump.

5. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 4, characterized in that: The pressure in the vacuum flash tower is automatically adjusted by an intelligent control system, and the evaporation capacity is optimized in real time according to the actual operating status. The relationship between the vacuum degree and the evaporation rate is as follows: Among them, C v is the evaporation constant, P1 and P2 are the pressures of black water when it enters and leaves the flash tower.

6. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 5, characterized in that: The ozone oxidation treatment is carried out before the black water enters the vacuum flash evaporation system, the ozone dosage is 1.2-1.5 times of the chemical oxygen demand in the black water, and the reaction time is controlled within a range of 30 min-60 min.

7. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 6, characterized in that: The Fenton oxidation treatment is used for deep treatment of concentrated liquid, the concentration range of hydrogen peroxide is 50 mg / L-100 mg / L, and the reaction time range is 30 min-60 min.

8. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 7, characterized in that: The permeate produced after the concentrated liquid is separated by the membrane is recycled and used as pretreatment or process water in the system.

9. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 8, characterized in that: The inner surface of the vacuum flash tower is coated with an anti-scaling coating, the coating material is a fluoride or ceramic coating, which is used to reduce the deposition and scaling of inorganic salts.

10. A vacuum flash treatment method for coal gasification low-pressure black water according to any one of claims 1 to 9, characterized in that: The equipment is equipped with an ultrasonic self-cleaning device, and the ultrasonic vibration frequency range is 20kHz-40kHz, which is used to remove the scale inside the equipment. The vibration power is calculated by the following formula: Among them, P is the vibration power, ρ is the black water density, ρ is the vibration velocity, and A is the effective area of ​​the equipment.

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