A method and system for high-temperature purification and reuse of fixed drainage of a boiler of a waste incineration power plant

Abstract

The present application relates to a kind of waste incineration power plant boiler fixed discharge water high-temperature purification reuse method and system, the method includes the following steps: S1, fixed discharge water is sent into high-temperature buffer regulating and storing unit and is balanced water quantity fluctuation and preliminary sedimentation;S2, fixed discharge water in high-temperature buffer regulating and storing unit is sent into high-temperature iron removal filter unit and is iron removal filtration;S3, the fixed discharge water after filtering of high-temperature iron removal filter unit is sent into waste heat recovery cooling unit and is heat exchange, waste heat recovery cooling unit cold side feedwater heat exchange after being sent into boiler deaerator and / or feedwater system;S4, the fixed discharge water after heat exchange is sent into intermediate storage unit to balance water quantity fluctuation;S5, the fixed discharge water in intermediate storage unit is sent into depth desalination unit and is depth desalination, and the water production of depth desalination unit is sent into boiler and / or directly into boiler deaerator after being treated by chemical water treatment.The present application can realize the high-temperature iron removal of fixed discharge water, waste heat recovery, depth desalination and same level reuse.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and resource reuse technology. More specifically, this invention relates to a method and system for high-temperature purification and reuse of boiler wastewater from a waste-to-energy plant. Background Technology

[0002] During the operation of a waste-to-energy plant, regular boiler blowdown (referred to as "regular blowdown") is an important operation to ensure the quality of boiler steam and water and prevent excessive concentration of boiler water. Regular blowdown comes from boiler water, which is essentially demineralized water (or softened water) that has undergone deep treatment. The purity of the water is much higher than that of industrial fresh water or circulating cooling water, and the temperature is usually between 90℃ and 100℃.

[0003] In traditional power plant designs, this portion of high-temperature wastewater is directly discharged into a cooling pond, where its temperature is lowered to below 40°C by mixing it with a large amount of ambient-temperature industrial fresh water before being discharged. This process involves significant energy and resource waste: on the one hand, the thermal energy of the high-temperature water is not effectively recovered; on the other hand, the high-quality demineralized water, after being mixed with the industrial fresh water, becomes low-quality wastewater that is discharged, requiring the water treatment plant to produce an additional amount of demineralized water to supplement the boiler system, increasing water treatment costs, chemical consumption, and corresponding energy consumption.

[0004] Although boiler wastewater has the potential for high-quality reuse, effective recycling has long been hindered by water quality deterioration. Corrosion is inevitable in boiler systems during operation, resulting in iron corrosion products (primarily Fe2O3 and Fe3O4) in the boiler water, existing in suspended or colloidal states. If this iron is directly reused in the boiler system without effective removal, it will deposit as scale on the heating surfaces, severely impacting heat transfer efficiency and potentially leading to tube rupture. Furthermore, some power plants have high silicon compound content in their boiler water. Improper reclaimed water quality control can cause silicon dioxide to be carried by steam and deposited on turbine blades, affecting unit efficiency and safe operation.

[0005] Currently, there have been some exploratory attempts in the industry, such as using the wastewater from the boiler feedwater system for dilution in urea production systems, or using the water cooled in the cooling pool for slag cooling or fly ash solidification. However, these solutions are all downgraded uses and fail to achieve same-level reuse (i.e., reuse in the boiler feedwater system), thus failing to fundamentally solve the problem of high-quality working fluid loss. True "purification and reuse," treating the wastewater to meet boiler feedwater standards and returning it to the water treatment workshop or directly feeding it into the deaerator, is a gap in the industry.

[0006] Therefore, given the long-term waste of high-temperature wastewater from waste incineration power plants, it is necessary to develop a system that can purify and reuse this wastewater. Summary of the Invention

[0007] The purpose of this invention is to address the technical problems of waste of heat energy in constant-flow wastewater, loss of high-quality desalinated water, and substandard quality of reclaimed water in the prior art. It provides a method and system for high-temperature purification and reuse of constant-flow wastewater from waste-to-energy plant boilers, achieving high-temperature iron removal, waste heat recovery, deep desalination, and same-level reuse of constant-flow wastewater.

[0008] To achieve these objectives and other advantages according to the present invention, a method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant is provided, comprising the following steps:

[0009] S1. The constant drainage is sent into the high-temperature buffer storage unit to balance water volume fluctuations and perform preliminary sedimentation.

[0010] S2. The constant drainage in the high temperature buffer storage unit is sent to the high temperature iron removal and filtration unit for iron removal and filtration.

[0011] S3. The constant water flow filtered by the high temperature iron removal filter unit is sent to the waste heat recovery and cooling unit for heat exchange. The cold side feedwater of the waste heat recovery and cooling unit is sent to the boiler deaerator and / or feedwater system after heat exchange.

[0012] S4. The heat-exchanged wastewater is sent to the intermediate storage unit to balance water volume fluctuations.

[0013] S5. The constant water discharge in the intermediate storage unit is sent to the deep desalination unit for deep desalination. The water produced by the deep desalination unit is then sent to the boiler and / or directly to the boiler deaerator after water treatment.

[0014] Furthermore, in the aforementioned method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant, the effective volume of the high-temperature buffer storage unit in S1 is 2-3 times the maximum single-time wastewater discharge of the boiler. When the boiler wastewater discharge exceeds the effective volume of the high-temperature buffer storage unit, the high-temperature buffer storage unit discharges part of the wastewater into the cooling pool through a bypass discharge pipe.

[0015] Furthermore, in the aforementioned method for high-temperature purification and reuse of waste-to-energy plant boiler wastewater, the filtration accuracy of the high-temperature iron removal filter unit in S2 is 5-10 μm, and the iron content in the effluent does not exceed 0.1 mg / L.

[0016] Furthermore, in the aforementioned method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant, the deep desalination unit in S5 adopts a two-stage reverse osmosis process. The first-stage reverse osmosis permeate enters the second-stage reverse osmosis for further desalination, and the first-stage reverse osmosis concentrate is returned to the intermediate storage unit and / or discharged to the cooling pool. The second-stage reverse osmosis permeate is treated with water treatment and then sent to the boiler and / or directly to the boiler deaerator. The second-stage reverse osmosis concentrate is discharged to the cooling pool and / or wastewater treatment equipment.

[0017] Furthermore, in the aforementioned method for high-temperature purification and reuse of waste-to-energy plant boiler wastewater, the wastewater in the intermediate storage unit is filtered by a security filter with a filtration accuracy of 5μm before being sent to the deep desalination unit.

[0018] Furthermore, in the aforementioned method for high-temperature purification and reuse of waste-to-energy boiler wastewater, the temperature of the wastewater fed into the waste heat recovery and cooling unit is 90-100℃, the temperature of the waste heat recovery and cooling unit discharged into the intermediate storage unit is 45-55℃, and the temperature of the cold-side feedwater after heat exchange in the waste heat recovery and cooling unit is 60-80℃.

[0019] Furthermore, in the aforementioned method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant, the conductivity of the water produced by the deep desalination unit in S5 does not exceed 5 μS / cm and the silica content does not exceed 20 μg / L.

[0020] Furthermore, the method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant also includes:

[0021] The following data are obtained through the online monitoring unit: the temperature and iron content of the constant discharge water from the high temperature buffer storage unit, the iron content of the constant discharge water after filtration by the high temperature iron removal filtration unit, the temperature of the constant discharge water after heat exchange by the waste heat recovery cooling unit, and the conductivity and silicon content of the water produced by the deep desalination unit.

[0022] When the temperature of the constant drainage discharged from the high-temperature buffer storage unit is greater than the first temperature threshold, the constant drainage in the high-temperature buffer storage unit is discharged into the cooling pool through a bypass.

[0023] When the iron content of the wastewater discharged from the high-temperature buffer storage unit exceeds the first iron content threshold, and the wastewater filtered by the high-temperature iron removal filter unit exceeds the second iron content threshold, the backwashing cycle of the high-temperature iron removal filter unit shall be shortened and / or the power of the high-temperature iron removal filter unit shall be increased.

[0024] When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit deviates from the preset temperature range, adjust the opening of the cold side flow regulating valve of the waste heat recovery and cooling unit to bring the temperature of the wastewater after heat exchange back to the preset temperature range.

[0025] When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit exceeds the second temperature threshold, and the conductivity of the permeate from the deep desalination unit exceeds the conductivity threshold, the waste heat recovery and cooling unit stops working and issues a membrane heat decay alarm.

[0026] When the silicon content of the water produced by the deep desalination unit exceeds the silicon content threshold, a scale inhibitor is added to the pipeline between the intermediate storage unit and the deep desalination unit.

[0027] This invention also provides a high-temperature purification and reuse system for boiler wastewater from a waste incineration power plant, comprising:

[0028] The high-temperature buffer storage unit has its inlet connected to the boiler's fixed discharge header.

[0029] The inlet of the high-temperature iron removal filtration unit is connected to the outlet of the high-temperature buffer storage unit.

[0030] The waste heat recovery and cooling unit has its hot side inlet connected to the outlet of the high-temperature iron removal and filtration unit, and its cold side outlet connected to the boiler deaerator and / or feedwater system.

[0031] The intermediate storage unit has its water inlet connected to the hot-side outlet of the waste heat recovery and cooling unit.

[0032] The deep desalination unit has its inlet connected to the outlet of the intermediate storage unit, and its product outlet connected to the boiler's water treatment equipment and / or deaerator.

[0033] Furthermore, the aforementioned waste-to-energy plant boiler wastewater high-temperature purification and reuse system also includes an online monitoring unit, which comprises:

[0034] The first temperature detection device is installed at the outlet of the high-temperature buffer storage unit.

[0035] The first iron content detection device is installed at the outlet of the high-temperature buffer storage unit.

[0036] The second temperature detection device is installed at the outlet of the high-temperature iron removal filter unit.

[0037] The second iron content detection device is installed at the outlet of the waste heat recovery and cooling unit.

[0038] The conductivity detection device is installed at the product water outlet of the deep desalination unit;

[0039] The silicon content detection device is installed at the product water outlet of the deep desalination unit.

[0040] The beneficial effects of this invention are:

[0041] 1. Achieving same-level reuse and filling an industry gap: This invention is the first to achieve the purification and reuse of boiler feedwater from waste incineration power plants. The high-quality demineralized water that was originally discharged into the cooling pool is treated to meet the boiler feedwater standards and then returned to the water treatment workshop or directly entered the deaerator. This fundamentally solves the problem of loss of high-quality working fluid and fills a technological gap in the industry.

[0042] 2. High-temperature direct iron removal, breaking through technical bottlenecks: Targeting the high-temperature characteristics (90℃~100℃) of constant drainage, this invention adopts a high-temperature resistant iron removal filter, realizing direct high-temperature iron removal without pre-cooling conditions. This avoids the energy loss caused by the pre-cooling required in traditional iron removal processes, while effectively removing suspended and colloidal iron corrosion products, ensuring the safety of reclaimed water quality.

[0043] 3. High-efficiency waste heat recovery and significant energy saving and consumption reduction: The waste heat of high-temperature constant flow drainage is used to preheat feedwater through plate heat exchangers. The recovered heat can be directly used in the boiler feedwater system, reducing steam consumption in the deaerator or feedwater heating process and realizing the cascade utilization of energy.

[0044] 4. Composite iron removal process to ensure water quality meets standards: The composite iron removal process of "high temperature iron removal filter + electromagnetic iron removal" is adopted to remove iron corrosion products of different forms in a coordinated manner, ensuring that the iron content of the effluent meets the boiler feedwater standard (≤0.1mg / L, or even ≤0.05mg / L), effectively preventing iron scale deposition on the heating surface.

[0045] 5. Intelligent monitoring ensures system reliability: Through the coordinated operation of online monitoring units and intelligent control units, the system's operating status is monitored in real time and automatically adjusted to ensure stable operation under complex conditions such as high temperature, variable flow rate, and variable water quality. It also has an automatic bypass protection function for faults.

[0046] 6. Significant economic benefits and short investment payback period: This system achieves a wastewater recovery rate of ≥90%, significantly reducing the cost of demineralized water production and chemical reagent consumption, while also recovering waste heat to reduce energy consumption. Calculations show that the system's investment payback period can be controlled within 2 years, demonstrating good commercialization potential.

[0047] 7. Outstanding environmental benefits and support for refined operation: It reduces the discharge of high-temperature wastewater and the use of fresh industrial water, reduces thermal pollution and water consumption in the plant area, and meets the development needs of waste incineration power plants in the "operation is king" stage of energy conservation, carbon reduction and tapping into the value of existing assets.

[0048] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the structure of the waste-to-energy plant boiler constant-flow high-temperature purification and reuse system described in this invention.

[0050] Figure 2 This is a flowchart of the method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant, as described in this invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application, so that those skilled in the art can implement them based on the description. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0052] In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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.

[0053] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0054] Example 1

[0055] like Figure 1 As shown, the present invention also provides a high-temperature purification and reuse system for boiler wastewater from a waste incineration power plant, comprising:

[0056] The high-temperature buffer storage unit has its inlet connected to the boiler's fixed discharge header.

[0057] The inlet of the high-temperature iron removal filtration unit is connected to the outlet of the high-temperature buffer storage unit.

[0058] The waste heat recovery and cooling unit has its hot side inlet connected to the outlet of the high-temperature iron removal and filtration unit, and its cold side outlet connected to the boiler deaerator and / or feedwater system.

[0059] The intermediate storage unit has its water inlet connected to the hot-side outlet of the waste heat recovery and cooling unit.

[0060] The deep desalination unit has its inlet connected to the outlet of the intermediate storage unit, and its product outlet connected to the boiler's water treatment equipment and / or deaerator.

[0061] In this embodiment, the high-temperature buffer storage unit uses a high-temperature buffer tank. The inlet of the high-temperature buffer tank is connected to the boiler's scheduled wastewater discharge main pipe via a pipeline to receive scheduled wastewater from the boiler. The effective volume of the high-temperature buffer tank is designed to be 2.5 times the maximum scheduled wastewater discharge volume of the waste-to-energy plant. For example, if the maximum scheduled wastewater discharge volume is 20 m³, then the effective volume of the high-temperature buffer tank is designed to be 50 m³. Multiple layers of baffles are installed inside the tank to extend the water flow path, promote the initial sedimentation of large particles, and balance the water volume fluctuations caused by intermittent scheduled wastewater discharge. The high-temperature buffer tank has an exhaust port at the top, a drain port at the bottom, and a level gauge on the side. The high-temperature buffer tank also has a bypass discharge pipe connected to the existing cooling pool in the plant area. When the scheduled wastewater discharge volume exceeds the system's design capacity or during system maintenance, the scheduled wastewater can directly enter the cooling pool through the bypass discharge pipe, ensuring the safe operation of boiler blowdown.

[0062] The high-temperature iron removal filtration unit employs a high-temperature iron removal filter with a 316L stainless steel shell, designed to withstand temperatures up to 120℃ and pressures up to 1.0MPa. The internal filter elements utilize high-temperature resistant wound glass fiber filter media with a filtration accuracy of 5μm. The single-unit processing capacity is determined based on the average flow rate of the constant drainage. The high-temperature iron removal filter is equipped with a differential pressure sensor to monitor filter element clogging. When the inlet and outlet pressure difference reaches a set value (e.g., 0.05MPa), an automatic backwashing program is triggered. Backwashing uses filtered high-temperature water, and the backwash drainage is discharged into a cooling tank. The inlet of the high-temperature iron removal filter is connected to the outlet of the high-temperature buffer tank via a pipeline, and the outlet is connected to the waste heat recovery cooling unit.

[0063] The waste heat recovery and cooling unit includes a plate heat exchanger. This plate heat exchanger is a fully welded, wide-channel plate heat exchanger made of 316L stainless steel, designed to withstand temperatures up to 120℃. It can effectively handle high-temperature liquids containing trace amounts of suspended solids, reducing the risk of flow channel blockage. The hot-side inlet of the plate heat exchanger is connected to the outlet of the high-temperature iron removal filter, and the hot-side outlet is connected to the intermediate storage unit. The cold-side inlet is connected to the boiler makeup water or condensate to be heated, and the cold-side outlet is connected to the deaerator inlet. Under typical operating conditions, the hot side cools the high-temperature constant-flow wastewater (90℃-100℃) to approximately 45-55℃, while the cold side preheats the makeup water (at room temperature, approximately 25℃) to approximately 60-80℃. The preheated water directly enters the deaerator, reducing the steam heating load on the deaerator.

[0064] As a preferred embodiment, the high-temperature iron removal filtration unit also includes an electromagnetic iron removal device, which is positioned between the plate heat exchanger and the high-temperature iron removal filter. The electromagnetic iron removal device utilizes high-frequency electromagnetic field technology to further remove dissolved iron ions or fine particulate iron remaining after filtration, stably controlling the iron content in the effluent to below 0.05 mg / L. The magnetic field strength and processing flow rate of the electromagnetic iron removal device can be adjusted according to the iron content of the influent.

[0065] The intermediate storage unit uses an intermediate water tank to temporarily store the cooled wastewater, balancing the continuous operation requirements of the reverse osmosis unit with the intermittent discharge of wastewater. The effective volume of the intermediate water tank is designed based on the processing capacity of the reverse osmosis unit for 2-4 hours.

[0066] The deep desalination unit comprises a security filter, a high-pressure pump, and a reverse osmosis unit connected in sequence. The security filter has a filtration accuracy of 5μm and is used to protect the reverse osmosis membrane from potential damage by microparticles. The reverse osmosis unit employs a two-stage reverse osmosis process; the first stage uses anti-fouling reverse osmosis membrane elements, and the second stage uses low-pressure, high-desalination-rate reverse osmosis membrane elements. The permeate from the first stage enters the second stage for further desalination, while part of the concentrate from the first stage is recycled to the intermediate water tank to improve the system recovery rate, and part is discharged to the cooling pool. The permeate outlet of the reverse osmosis unit 53 is connected to the demineralized water tank in the water treatment workshop or directly to the deaerator. The permeate water quality is controlled with conductivity ≤5μS / cm, silica ≤20μg / L, and iron content ≤0.05mg / L, fully meeting the boiler feedwater standards in GB / T 12145-2016 "Water and Steam Quality of Thermal Power Generating Units and Steam Power Equipment". The concentrate outlet is connected to the cooling pool or the plant wastewater treatment system.

[0067] Furthermore, the aforementioned waste-to-energy plant boiler wastewater high-temperature purification and reuse system also includes an online monitoring unit, which comprises:

[0068] The first temperature detection device is installed at the outlet of the high-temperature buffer storage unit.

[0069] The first iron content detection device is installed at the outlet of the high-temperature buffer storage unit.

[0070] The second temperature detection device is installed at the outlet of the high-temperature iron removal filter unit.

[0071] The second iron content detection device is installed at the outlet of the waste heat recovery and cooling unit.

[0072] The conductivity detection device is installed at the product water outlet of the deep desalination unit;

[0073] The silicon content detection device is installed at the product water outlet of the deep desalination unit.

[0074] The temperature and iron content of the constant drainage discharged from the high-temperature buffer storage unit are obtained by the first temperature detection device and the first iron content detection device, respectively. The iron content of the constant drainage filtered by the high-temperature iron removal filtration unit is obtained by the second temperature detection device. The temperature of the constant drainage after heat exchange by the waste heat recovery cooling unit is obtained by the second iron content detection device. The conductivity and silicon content of the water produced by the deep desalination unit are obtained by the conductivity detection device and the silicon content detection device, respectively.

[0075] When the temperature of the constant-flow wastewater discharged from the high-temperature buffer storage unit exceeds the first temperature threshold, the wastewater from the high-temperature buffer storage unit is discharged into the cooling pool via a bypass. By setting the first temperature threshold, when the boiler's constant-flow wastewater temperature is too high, the wastewater is directly discharged into the cooling pool, preventing excessively hot wastewater from entering the high-temperature iron removal filter unit and causing damage to the unit.

[0076] If the iron content of the wastewater discharged from the high-temperature buffer storage unit exceeds the first iron content threshold, and the wastewater filtered by the high-temperature iron removal filter unit exceeds the second iron content threshold, the backwashing cycle of the high-temperature iron removal filter unit should be shortened and / or its power increased. If the first iron content threshold is greater than the second iron content threshold, the difference in iron content between the wastewater discharged from the high-temperature buffer storage unit and the wastewater filtered by the high-temperature iron removal filter unit represents the filtration effect of the high-temperature iron removal filter unit. The first iron content threshold is set as the upper limit of the designed influent iron content; exceeding this value indicates abnormal deterioration of the influent water quality, and the high-temperature iron removal filter unit may not be able to withstand it. The second iron content threshold is set as the upper limit of the iron content allowed by the process for subsequent units (e.g., waste heat recovery, membrane system iron requirements); exceeding this value is considered filtration failure.

[0077] When the iron content of the wastewater discharged from the high-temperature buffer storage unit does not exceed the first iron content threshold, and the wastewater filtered by the high-temperature iron removal filter unit does not exceed the second iron content threshold, it indicates normal operation and backwashing according to the normal cycle.

[0078] When the iron content of the constant drainage discharged from the high-temperature buffer storage unit exceeds the first iron content threshold, and the constant drainage filtered by the high-temperature iron removal filter unit does not exceed the second iron content threshold, it indicates an influent shock, but the filter unit can still cope. In this case, the backwashing cycle should be shortened and preventive cleaning should be carried out.

[0079] When the iron content in the wastewater discharged from the high-temperature iron removal filter unit exceeds the second iron content threshold, it indicates that the filter unit itself has failed. In this case, the filtration power should be increased and the backwashing cycle shortened. Simultaneously, if the iron content in the wastewater discharged from the high-temperature buffer storage unit exceeds the first iron content threshold, it indicates a severely excessive iron content. In this case, the high-temperature iron removal filter unit should be stopped and repaired. Alternatively, a backup high-temperature iron removal filter can be installed and activated promptly.

[0080] When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit deviates from the preset temperature range, adjust the opening of the cold-side flow regulating valve of the waste heat recovery and cooling unit to bring the temperature of the wastewater back to the preset temperature range. Taking a wastewater temperature of 45-55℃ as an example, when the temperature is below 45℃, decrease the opening of the cold-side flow regulating valve. When the temperature is above 55℃, increase the opening of the cold-side flow regulating valve.

[0081] When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit exceeds the second temperature threshold, and the conductivity of the permeate from the deep desalination unit exceeds the conductivity threshold, the reverse osmosis membrane of the deep desalination unit may have been damaged due to high temperature. At this time, the waste heat recovery and cooling unit will stop working and issue a membrane heat decay alarm message.

[0082] When the silicon content of the water produced by the deep desalination unit exceeds the silicon content threshold, a scale inhibitor is added to the pipeline between the intermediate storage unit and the deep desalination unit to focus on controlling silicon scale.

[0083] Example 2

[0084] This embodiment provides a method for high-temperature purification and reuse of boiler wastewater from a waste-to-energy plant using the above-described system. The specific steps are as follows:

[0085] Step S1: High-temperature buffering and storage:

[0086] A waste-to-energy plant has a 600t / d incinerator equipped with a waste heat boiler. The average periodic wastewater discharge is 8 m³ / h, intermittent, with a maximum single discharge of 15 m³ at a temperature of 95℃. The wastewater first enters a 40 m³ high-temperature buffer tank, where large particles are temporarily stored and preliminarily settled. The effluent from the high-temperature buffer tank is then pumped to subsequent treatment units. During abnormally large-scale boiler wastewater discharges or system maintenance, the wastewater is discharged directly into a cooling pool via a bypass pipe.

[0087] Step S2: High-temperature iron removal filtration:

[0088] The effluent from the high-temperature buffer tank directly enters the high-temperature iron removal filter at 95℃. The filter uses a 5μm wound filter element with a designed flow rate of 10m³ / h. Testing revealed that the iron content in the influent was approximately 0.8mg / L (calculated as Fe), primarily in suspended and colloidal states. After treatment by the high-temperature iron removal filter, the iron content in the effluent decreased to 0.08mg / L. To further ensure water quality, the effluent enters an electromagnetic iron removal device. After treatment with a high-frequency electromagnetic field, the iron content in the effluent further decreased to 0.03mg / L, meeting the stringent requirements for iron content in boiler feedwater (≤0.1mg / L).

[0089] Step S3: Waste heat recovery and cooling:

[0090] The high-temperature water (approximately 95°C) after iron removal enters a plate heat exchanger, where it exchanges heat with ambient-temperature makeup water (approximately 20°C) at a flow rate of 20 m³ / h. After heat exchange, the set discharge temperature drops to 50°C, and the makeup water temperature rises to 72°C before directly entering the deaerator. Calculations show that this waste heat recovery is equivalent to saving approximately 0.5 tons of steam per hour.

[0091] Step S4: Intermediate storage:

[0092] After cooling, the constant flow (50℃) enters the intermediate water tank for temporary storage. The effective volume of the intermediate water tank is 30m³, which can meet the continuous operation requirements of the reverse osmosis unit for 4 hours.

[0093] Step S5: Deep desalination:

[0094] Water from the intermediate tank is filtered through a 5μm security filter and then pressurized by a high-pressure pump before entering the two-stage reverse osmosis unit. The first stage operates at a pressure of 1.5MPa, and the second stage at 1.2MPa. The product water flow rate is 7.2 m³ / h, with a conductivity of 3.2 μS / cm, a silica content of 15 μg / L, and an iron content of 0.02 mg / L, fully meeting the boiler feedwater standards. The concentrate flow rate is 0.8 m³ / h and is discharged into the cooling tank. The overall water recovery rate of the system reaches 90%.

[0095] Through this embodiment, the waste incineration power plant achieves high-quality reuse of wastewater, recovering approximately 63,000 tons of demineralized water annually, saving approximately 630,000 yuan in water production costs; the recovered waste heat is equivalent to saving approximately 4,300 tons of steam per year, saving approximately 860,000 yuan in costs; after deducting system operating power consumption, membrane replacement and other expenses, the annual net income is approximately 1.2 million yuan, the total system investment is approximately 2 million yuan, and the investment payback period is approximately 1.7 years.

[0096] Example 3

[0097] like Figure 2 As shown, an embodiment of the present invention provides a method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant, comprising the following steps:

[0098] S1. The constant drainage is sent into the high-temperature buffer storage unit to balance water volume fluctuations and perform preliminary sedimentation.

[0099] S2. The constant drainage in the high temperature buffer storage unit is sent to the high temperature iron removal and filtration unit for iron removal and filtration.

[0100] S3. The constant water flow filtered by the high temperature iron removal filter unit is sent to the waste heat recovery and cooling unit for heat exchange. The cold side feedwater of the waste heat recovery and cooling unit is sent to the boiler deaerator and / or feedwater system after heat exchange.

[0101] S4. The heat-exchanged wastewater is sent to the intermediate storage unit to balance water volume fluctuations.

[0102] S5. The constant water discharge in the intermediate storage unit is sent to the deep desalination unit for deep desalination. The water produced by the deep desalination unit is then sent to the boiler and / or directly to the boiler deaerator after water treatment.

[0103] In the aforementioned method for high-temperature purification and reuse of waste-to-energy plant boiler wastewater, the wastewater in the intermediate storage unit is filtered by a security filter with a filtration accuracy of 5μm before being sent to the deep desalination unit.

[0104] In the aforementioned method for high-temperature purification and reuse of waste-to-energy plant boiler wastewater, the temperature of the wastewater fed into the waste heat recovery and cooling unit is 90-100℃, the temperature of the waste heat recovery and cooling unit discharged into the intermediate storage unit is 45-55℃, and the temperature of the cold-side feedwater after heat exchange in the waste heat recovery and cooling unit is 60-80℃.

[0105] In the method for high-temperature purification and reuse of waste-to-energy plant boiler wastewater, the conductivity of the water produced by the deep desalination unit in S5 does not exceed 5 μS / cm and the silica content does not exceed 20 μg / L.

[0106] The method for high-temperature purification and reuse of boiler wastewater from waste incineration power plants also includes:

[0107] The following data are obtained through the online monitoring unit: the temperature and iron content of the constant discharge water from the high temperature buffer storage unit, the iron content of the constant discharge water after filtration by the high temperature iron removal filtration unit, the temperature of the constant discharge water after heat exchange by the waste heat recovery cooling unit, and the conductivity and silicon content of the water produced by the deep desalination unit.

[0108] When the temperature of the constant drainage discharged from the high-temperature buffer storage unit is greater than the first temperature threshold, the constant drainage in the high-temperature buffer storage unit is discharged into the cooling pool through a bypass.

[0109] When the iron content of the wastewater discharged from the high-temperature buffer storage unit exceeds the first iron content threshold, and the wastewater filtered by the high-temperature iron removal filter unit exceeds the second iron content threshold, the backwashing cycle of the high-temperature iron removal filter unit shall be shortened and / or the power of the high-temperature iron removal filter unit shall be increased.

[0110] When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit deviates from the preset temperature range, adjust the opening of the cold side flow regulating valve of the waste heat recovery and cooling unit to bring the temperature of the wastewater after heat exchange back to the preset temperature range.

[0111] When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit exceeds the second temperature threshold, and the conductivity of the permeate from the deep desalination unit exceeds the conductivity threshold, the waste heat recovery and cooling unit stops working and issues a membrane heat decay alarm.

[0112] When the silicon content of the water produced by the deep desalination unit exceeds the silicon content threshold, a scale inhibitor is added to the pipeline between the intermediate storage unit and the deep desalination unit.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application, and should all be covered within the scope of the claims of this application.

Claims

1. A method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant, characterized in that, Includes the following steps: S1. The constant drainage is sent into the high-temperature buffer storage unit to balance water volume fluctuations and perform preliminary sedimentation. S2. The constant drainage in the high temperature buffer storage unit is sent to the high temperature iron removal and filtration unit for iron removal and filtration. S3. The constant water flow filtered by the high temperature iron removal filter unit is sent to the waste heat recovery and cooling unit for heat exchange. The cold side feedwater of the waste heat recovery and cooling unit is sent to the boiler deaerator and / or feedwater system after heat exchange. S4. The heat-exchanged wastewater is sent to the intermediate storage unit to balance water volume fluctuations. S5. The constant water discharge in the intermediate storage unit is sent to the deep desalination unit for deep desalination. The water produced by the deep desalination unit is then sent to the boiler and / or directly to the boiler deaerator after water treatment.

2. The method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 1, characterized in that, The effective volume of the high-temperature buffer storage unit in S1 is 2-3 times the maximum constant discharge volume of the boiler. When the constant discharge volume of the boiler exceeds the effective volume of the high-temperature buffer storage unit, the high-temperature buffer storage unit discharges part of the constant discharge into the cooling pool through the bypass discharge pipe.

3. The method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 1, characterized in that, The S2 high-temperature iron removal filter unit has a filtration accuracy of 5-10μm, and the iron content in the effluent does not exceed 0.1mg / L.

4. A method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 3, characterized in that, The S5 medium-desalination unit adopts a two-stage reverse osmosis process. The first-stage reverse osmosis permeate enters the second-stage reverse osmosis for further desalination. The first-stage reverse osmosis concentrate is returned to the intermediate storage unit and / or discharged to the cooling pool. The second-stage reverse osmosis permeate is sent to the boiler and / or directly to the boiler deaerator after water treatment. The second-stage reverse osmosis concentrate is discharged to the cooling pool and / or wastewater treatment equipment.

5. A method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 3, characterized in that, Before the constant drainage in the intermediate storage unit is sent to the deep desalination unit, it is filtered by a security filter with a filtration accuracy of 5μm.

6. A method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 1, characterized in that, The temperature of the constant drainage water sent into the waste heat recovery and cooling unit is 90-100℃, the temperature of the waste heat recovery and cooling unit discharged into the intermediate storage unit is 45-55℃, and the temperature of the cold side feedwater after heat exchange in the waste heat recovery and cooling unit is 60-80℃.

7. A method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 1, characterized in that, The conductivity of the permeate from the deep desalination unit in S5 does not exceed 5 μS / cm and the silica content does not exceed 20 μg / L.

8. A method for high-temperature purification and reuse of boiler wastewater from a waste incineration power plant as described in claim 1, characterized in that, Also includes: The following data are obtained through the online monitoring unit: the temperature and iron content of the constant discharge water from the high temperature buffer storage unit, the iron content of the constant discharge water after filtration by the high temperature iron removal filtration unit, the temperature of the constant discharge water after heat exchange by the waste heat recovery cooling unit, and the conductivity and silicon content of the water produced by the deep desalination unit. When the temperature of the constant drainage discharged from the high-temperature buffer storage unit is greater than the first temperature threshold, the constant drainage in the high-temperature buffer storage unit is discharged into the cooling pool through a bypass. When the iron content of the wastewater discharged from the high-temperature buffer storage unit exceeds the first iron content threshold, and the wastewater filtered by the high-temperature iron removal filter unit exceeds the second iron content threshold, the backwashing cycle of the high-temperature iron removal filter unit shall be shortened and / or the power of the high-temperature iron removal filter unit shall be increased. When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit deviates from the preset temperature range, adjust the opening of the cold side flow regulating valve of the waste heat recovery and cooling unit to bring the temperature of the wastewater after heat exchange back to the preset temperature range. When the temperature of the wastewater after heat exchange in the waste heat recovery and cooling unit exceeds the second temperature threshold, and the conductivity of the permeate from the deep desalination unit exceeds the conductivity threshold, the waste heat recovery and cooling unit stops working and issues a membrane heat decay alarm. When the silicon content of the water produced by the deep desalination unit exceeds the silicon content threshold, a scale inhibitor is added to the pipeline between the intermediate storage unit and the deep desalination unit.

9. A high-temperature purification and reuse system for boiler wastewater from a waste incineration power plant, characterized in that, include: The high-temperature buffer storage unit has its inlet connected to the boiler's fixed discharge header. The inlet of the high-temperature iron removal filtration unit is connected to the outlet of the high-temperature buffer storage unit. The waste heat recovery and cooling unit has its hot side inlet connected to the outlet of the high-temperature iron removal and filtration unit, and its cold side outlet connected to the boiler deaerator and / or feedwater system. The intermediate storage unit has its water inlet connected to the hot-side outlet of the waste heat recovery and cooling unit. The deep desalination unit has its inlet connected to the outlet of the intermediate storage unit, and its product outlet connected to the boiler's water treatment equipment and / or deaerator.

10. A high-temperature purification and reuse system for boiler wastewater from a waste incineration power plant as described in claim 9, characterized in that, It also includes an online monitoring unit, which comprises: The first temperature detection device is installed at the outlet of the high-temperature buffer storage unit. The first iron content detection device is installed at the outlet of the high-temperature buffer storage unit. The second temperature detection device is installed at the outlet of the high-temperature iron removal filter unit. The second iron content detection device is installed at the outlet of the waste heat recovery and cooling unit. The conductivity detection device is installed at the product water outlet of the deep desalination unit; The silicon content detection device is installed at the product water outlet of the deep desalination unit.

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