A clarifying process for desulfurization wastewater of thermal power plant based on silicon carbide membrane ultrafiltration technology

Abstract

The present application relates to the filter cleaning process of the silicon carbide membrane of the clarification of the desulfurization wastewater of the thermal power plant, the automatic process of the backwashing process is improved, the quantitative backwashing process starting point and the stop point are set, and the backwashing process is accurately controlled; The process further introduces an acid tank and a descaling cleaning tank, the acid tank and the descaling cleaning tank are connected to a cleaning regeneration pump, the outlet end of the cleaning regeneration pump is connected to the inlet end of the silicon carbide membrane filter circulating pump, and the accumulated sludge on the filter membrane can be removed together, so that the regeneration of the filter membrane can be quickly realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flue gas wet desulfurization wastewater treatment in thermal power plants, and relates to a desulfurization wastewater clarification process based on silicon carbide membrane ultrafiltration technology in thermal power plants. BACKGROUND

[0002] China is a country with coal as the main energy source, and coal-fired power generation is one of the most important ways of coal utilization in China. Among the many air pollutants emitted by coal-fired power plants, SO2 is more harmful to the environment and is the main pollutant to be controlled. At present, the existing flue gas desulfurization technologies include wet desulfurization and dry desulfurization, etc. Among them, the wet desulfurization technology is the most widely used. However, during the operation of the wet flue gas desulfurization, desulfurization wastewater containing a large amount of gypsum slurry and salt, as well as a small amount of carbon black, tar, mercury, lead, nickel, arsenic and chromium and other heavy metal ions will be generated, and direct discharge will cause great harm to the environment.

[0003] With the increasing prominence of environmental problems and the increasingly stringent emission standards, the deep treatment and reuse of desulfurization wastewater in thermal power plants will be paid more and more attention. Desulfurization wastewater should be treated by lime treatment, coagulation, clarification, neutralization and other processes before being reused. The use of flue gas evaporation drying or evaporation crystallization and other treatment processes is encouraged to achieve non-discharge of desulfurization wastewater. However, the use of conventional treatment processes such as flocculation sedimentation and clarification separation has high reagent cost, long process, large equipment area, relies on manpower and low automation level. The existing evaporation crystallization and other thermal processes for concentrating and solidifying dissolved salts have complex systems, mainly rely on boiler tail heat flue gas evaporation and rely on boiler flue gas waste heat, have high energy consumption, large maintenance amount and low process reliability. The reason is that the desulfurization wastewater mainly contains a large amount of supersaturated sulfite, sulfate, suspended solids and trace heavy metals. These ions are mixed together, have high suspended solids, high scaling tendency, mixed solution of multiple ions and large variation of components, and must be subjected to appropriate pretreatment and clarification before being subjected to further treatment or recycling. Therefore, how to solve the desulfurization wastewater clarification process has become a problem to be solved for the comprehensive utilization of desulfurization wastewater.

[0004] Thermal power is a large user of water and drainage, and water use accounts for 20% of the total industrial water use. From the perspectives of economic operation and environmental protection, it is of great significance to save water for power generation, improve the reuse rate of circulating water and realize zero discharge of wastewater in thermal power plants. Traditional wastewater treatment in power plants can easily implement various levels of cascade application, and various wastewaters can be solved by traditional mature processes. However, the most concentrated, complex and difficult to treat wastewater is desulfurization wastewater, and its treatment has become a key factor restricting the zero discharge of wastewater in thermal power plants. The demand for zero discharge of desulfurization wastewater in thermal power enterprises is becoming more and more urgent, and it will become an inevitable trend in the future.

[0005] Most of the power plant desulfurization wastewater treatment uses the traditional triple box chemical treatment process, which is highly dependent on chemical agents, has high construction, operation and maintenance costs, and occupies a large area. In this context, in order to solve the problems of high suspended solids in desulfurization wastewater and difficult to precipitate, it is necessary to develop a physical filtration device to abandon the chemical agent treatment process, reduce the construction and operation cost and the load of subsequent wastewater treatment equipment, and realize the stable operation of desulfurization wastewater. SUMMARY

[0006] The purpose of the present application is to provide a silicon carbide membrane filter device for clarifying desulfurization wastewater in thermal power plants, which is used for filtering and removing solid particulate impurities in desulfurization wastewater, and reducing the solid content and turbidity in desulfurization wastewater.

[0007] The first aspect of the present application provides a desulfurization wastewater clarification process for thermal power plants based on silicon carbide membrane ultrafiltration technology, which specifically comprises the following steps:

[0008] Step 1, after the wastewater generated by the desulfurization system is transported to the feed buffer tank, it is pre-filtered through the pre-filter;

[0009] Step 2, the filtrate pre-filtered in step 1 is filtered by a first silicon carbide diaphragm filter through a first membrane filtration circulating pump;

[0010] Step 3, the sludge separated after filtration in step 2 is sent to the sludge pool, and the filtrate through the membrane is filtered again by a second silicon carbide filter membrane filter through a second membrane filtration circulating pump;

[0011] Step 4, the filtrate through the membrane in step 3 is sent to the clear liquid collection tank, and the separated sludge is sent to the sludge pool,

[0012] The above process further comprises a backflushing step, wherein the backflushing step is:

[0013] The pressure difference between the upstream pipe pressure value P1 and the downstream pipe pressure value P2 of the membrane into which the filtrate of step 2 or step 3 enters is ΔP%=(P1-P2) / P1*100%,

[0014] When the value of ΔP% is 30-40%, the clear liquid backflushing pump is opened, and the backflushing step is operated;

[0015] When the value of ΔP% is 25% or less, the clear liquid backflushing pump is closed, and the backflushing step is stopped;

[0016] The backflushing step is carried out in the first or second silicon carbide filter membrane filter.

[0017] In some preferred embodiments, when the backflushing step is operated, the silicon carbide filter membrane filter stops working.

[0018] In some preferred embodiments, the silicon carbide filter membrane filter starts working when the backwashing step stops.

[0019] In some preferred embodiments, the liquid used by the clear liquid backwashing pump comes from the circulating clear liquid collection tank.

[0020] In some preferred embodiments, the liquid used by the clear liquid backwashing pump contains third-party clear liquid outside the process.

[0021] In some preferred embodiments, the liquid used by the clear liquid backwashing pump enters the first or second silicon carbide filter membrane filter for the backwashing step via the cleaning pipeline I.

[0022] In some preferred embodiments, an acid liquid tank is further introduced, which is connected to the cleaning and regeneration pump.

[0023] In some preferred embodiments, a descaling cleaning tank is further introduced, which is connected to the cleaning and regeneration pump.

[0024] In some preferred embodiments, the cleaning and regeneration pump is connected to the cleaning pipeline II, which enters the first or second silicon carbide filter membrane filter for the backwashing step.

[0025] In some preferred embodiments, the flow of the clear liquid backwashing pump is 25-40 m 3 / h, and the head is 50-100 water columns.

[0026] The beneficial effects of the present application are:

[0027] The present application is a silicon carbide membrane filtration and cleaning process that can be used for clarifying desulfurization wastewater in thermal power plants, an optimized automatic process of backwashing, setting quantitative backwashing process starting and stopping points, and precise control of backwashing process.

[0028] The present application also ingeniously uses the pressure difference before and after the filter membrane as a reference for the start and stop of the backwashing process, which is simple but has a practical effect.

[0029] At the same time, the process further introduces an acid liquid tank and a descaling cleaning tank, which are connected to a cleaning and regeneration pump, and the outlet end of the cleaning and regeneration pump is connected to the inlet end of the silicon carbide membrane filtration circulating pump, which can cooperatively remove the accumulated sludge on the filter membrane and quickly regenerate the filter membrane.

[0030] The silicon carbide membrane filtering and cleaning process for clarifying desulfurization wastewater of a thermal power plant has simple device structure, scientific and reasonable setting, good filtering effect, can effectively filter and remove solid particle impurities in the desulfurization wastewater; after the cleaning process is operated, the solid content in the desulfurization wastewater slurry can be reduced, the subsequent water treatment load can be reduced or direct reuse can be achieved; through actual test, after the thermal power unit of 600 MW is put into use, the turbidity of the desulfurization wastewater is effectively reduced, no chemical agent is used in the operation process, the automation degree is high, the operation and maintenance cost of personnel is low, the operation cost and maintenance cost are saved, and the process has popularization and application value. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a process schematic diagram of the desulfurization wastewater clarification process of the thermal power plant based on the silicon carbide membrane ultrafiltration technology.

[0032] Figure 2 is a filtering process of the desulfurization wastewater clarification process of the thermal power plant based on the silicon carbide membrane ultrafiltration technology. DETAILED DESCRIPTION

[0033] The application will be described in detail below with reference to the drawings and specific embodiments.

[0034] The embodiments of the application are described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals represent the same or similar modules or modules with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application.

[0035] In the description of the present specification, the description referring to the terms "one embodiment", "another embodiment" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment are contained in at least one embodiment of the application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0036] Fgd wastewater of thermal power plant

[0037] The application relates to a desulfurization wastewater clarification process based on a silicon carbide membrane ultrafiltration technology.

[0038] Silicon carbide membrane ultrafiltration technology

[0039] The silicon carbide ceramic membrane used in the application is a new type of non-oxide inorganic membrane, has the characteristics of high mechanical strength, concentrated pore size distribution, good thermal shock resistance and long service life, and has outstanding advantages in membrane flux, high-temperature stability and strong acid and strong alkali resistance, and has a wide prospect when used in the treatment of heavy-polluted thermal power plant wastewater. The silicon carbide (SiC) ceramic membrane separation technology is considered to be one of the most rapidly developed membrane separation new technologies in recent years.

[0040] In the application, the silicon carbide ceramic membrane has the following advantages: good chemical stability, strong acid and strong alkali resistance and resistance to all organic solvents; good thermal stability and resistance to thermal shock; high open porosity and large flux; good hydrophilicity and oil repellency; high membrane bonding strength and good wear resistance.

[0041] The silicon carbide ceramic membrane (SIC) in the application can be formed by high-temperature sintering through recrystallization technology, the separation layer, the transition layer and the porous support layer are all SiC materials, and the filtering precision is mostly microfiltration and ultrafiltration. According to the different membrane structures, the silicon carbide ceramic membrane is generally divided into a tubular membrane and a flat plate membrane. The tubular membrane is composed of a separation layer, a transition layer and a support layer, and the flat plate membrane is composed of a separation layer and a support layer.

[0042] In the process, the maximum advantage of the silicon carbide membrane is that no pretreatment is needed, and the flux is large, so that the desulfurization wastewater can be directly purified, the process flow is greatly shortened, the dependence of the desulfurization wastewater treatment on chemical drugs is fundamentally avoided, various hidden dangers caused by the use of chemical drugs on health and environment are eliminated, and the cost generated thereby is also avoided; the scheme of the application is a pure physical purification process, and the advancement is incomparable to other processes.

[0043] Silicon carbide membrane filtration device

[0044] The carbonized silicon membrane filter device used in the clarification process of the flue gas desulfurization wastewater of the power plant of the silicon carbide membrane ultrafiltration technology of the present application can refer to the structure described in the specific embodiments of the utility model patent CN214570924U. As shown in the utility model CN214570924U Figure 1 The two carbonized silicon membrane filtration circulating pumps 1 are arranged side by side, the desulfurization wastewater inlet pipeline is connected to the inlet pipeline of the carbonized silicon membrane filtration circulating pump 1, the carbonized silicon membrane filter 2 is arranged on the outlet pipeline of the carbonized silicon membrane filtration circulating pump 1, and the two carbonized silicon membrane filtration circulating pumps 1 are connected in parallel.

[0045] The outlet ends of the two carbonized silicon membrane filtration circulating pumps 1 are respectively connected with the carbonized silicon membrane filter 2, and the carbonized silicon membrane filter 2 is shown in CN214570924U Figure 1 According to the processing capacity and medium parameters, the carbonized silicon membrane filter device is designed with two sets of carbonized silicon membrane filters 2 operating in parallel and arranged symmetrically; each set of carbonized silicon membrane filter 2 corresponds to one carbonized silicon membrane filtration circulating pump 1;

[0046] The carbonized silicon membrane shell 5 is the main component of the carbonized silicon membrane filter 2, and each carbonized silicon membrane filter 2 includes three carbonized silicon membrane shells 5. The three carbonized silicon membrane shells 5 are vertically installed on the horizontally placed parallel mother pipe, and the three carbonized silicon membrane shells are arranged side by side on the parallel mother pipe. The carbonized silicon membrane shells 5 maintain a fixed transverse distance and a fixed longitudinal distance, a valve is installed at the bottom of the parallel mother pipe for emptying or discharging the concentrated liquid; the three carbonized silicon membrane shells 5 are connected through the top communication pipe and operate in series, and rubber expansion joints are installed at the bottom of the carbonized silicon membrane shells 5 for reducing vibration; as shown in CN214570924U Figure 1 The desulfurization wastewater is transported to the first set of parallel mother pipes and carbonized silicon membrane shells 5 by the carbonized silicon membrane filtration circulating pump 1, enters the second set of carbonized silicon membrane shells 5 and parallel mother pipes through the top communication pipeline, and is jointly discharged into the inlet of the carbonized silicon membrane filtration circulating pump 1 with the desulfurization wastewater inlet to form a closed circulation;

[0047] A drain port is further arranged at the top of the side surface of the carbonized silicon membrane shell 5, the clear liquid filtered by the carbonized silicon membrane is output through the drain port at the upper part of the side surface of the carbonized silicon membrane shell 5, the drain port is connected with the clear liquid collecting tank 4, a drain port A is arranged at the lower part of the side surface of the carbonized silicon membrane shell 5 for emptying the water in the membrane shell, the drain port A is connected with the outlet end of the clear liquid backflushing pump 3 for backflushing of the carbonized silicon membrane, and an exhaust pipeline is installed on the top communication pipe of the carbonized silicon membrane shell 5, and the exhaust port of the exhaust pipeline is higher than the communication pipe;

[0048] The device also comprises an acid liquid tank 6 and a descaling cleaning tank 7, which are connected to a cleaning and regenerating pump 8, the outlet end of the cleaning and regenerating pump 8 is connected to the inlet end of the silicon carbide membrane filter circulating pump 1; the two sets of silicon carbide filters 2 share one cleaning and regenerating pump 8, and the flushing sequence is controlled by valves; it also comprises a clear liquid backflushing pump 3, the inlet end of the clear liquid backflushing pump 3 is connected to the clear liquid collecting pipe 4, and the outlet end of the clear liquid backflushing pump 3 is connected to the silicon carbide membrane filter 2; the acid liquid tank 6, the descaling cleaning tank 7 and the clear liquid collecting tank 4 are all cylindrical closed containers.

[0049] The silicon carbide membrane filter device is designed to handle 2×12.5m 3 / h of desulfurization wastewater, the solid content concentration of the incoming desulfurization wastewater is 5-10%; two sets of silicon carbide membrane filters 2 are designed to operate in parallel, and the design handling capacity of each set of silicon carbide membrane filter 2 is 12.5m 3 / h; in actual operation, one set of silicon carbide membrane filter 2 can be started according to needs or two sets of silicon carbide membrane filters 2 can be operated simultaneously;

[0050] The flow rate of the silicon carbide membrane filter circulating pump 1 is 120m 3 / h, and the head is 40m of water column; the flow rate of the cleaning and regenerating pump 8 is 25m 3 / h, and the head is 20m of water column; the flow rate of the clear liquid backflushing pump 3 is 25m 3 / h, and the head is 50m of water column;

[0051] The overall size of the silicon carbide membrane filter device is 8387mm×6238mm×3453mm, and the size of each rack is 3477mm×560mm×2485mm; the silicon carbide membrane filter 2 is composed of two groups of silicon carbide membrane shells 5, three silicon carbide membrane shells 5 in each group, which are installed side by side on the parallel mother pipe with a spacing of 500mm; each parallel mother pipe has a size of DN200×1670mm, is placed horizontally, has one end for feeding and one end for plugging, and there are four of them; DN50 emptying pipes and valves are installed at the bottom of each parallel mother pipe;

[0052] The silicon carbide membrane shells 5 are all installed vertically, each membrane shell has a size of DN200×1050mm, the silicon carbide membrane shell 5 is connected to the inlet and outlet pipes by flanges, the size of the flange is DN100, and a DN100 rubber expansion joint is installed between the bottom of each silicon carbide membrane shell 5 and the parallel mother pipe;

[0053] The clear liquid of the silicon carbide membrane filter 2 after clarification is discharged from the side of the silicon carbide membrane shell 5, one DN40 water outlet is arranged on the side of each silicon carbide membrane shell 5, the distance from the upper flange of the silicon carbide membrane shell 5 is 50mm, and one DN40 water outlet is arranged at the lower part of the side of each silicon carbide membrane shell 5 for emptying, the distance from the lower flange of the silicon carbide membrane shell 5 is 50mm. The clear liquid is finally collected in the clear liquid collecting tank 4;

[0054] Each of the top communication pipes of the silicon carbide membrane shell 5 is provided with a DN50 exhaust pipe, and the exhaust port of the exhaust main pipe is 3453mm high, which is 711mm higher than the center line of the communication pipe;

[0055] The desulfurization wastewater inlet pipe D65x3450mm is connected to the DN200x820mm inlet pipe of the silicon carbide membrane filter circulating pump 1, and the outlet pipe of the silicon carbide membrane filter circulating pump 1 is a inverted U-shaped pipe, which is provided with a DN80 rubber expansion joint at the bottom, and the parameters are DN80x660mm. The pipe between the outlet of the silicon carbide membrane filter circulating pump 1 and the first group of silicon carbide membrane shells 5 is provided with a pressure transmitter.

[0056] After the desulfurization wastewater is evenly distributed and enters the bottom of the silicon carbide membrane shell 5, it is output from the top of the silicon carbide membrane shell 5, and after passing through the second group of silicon carbide membrane shells 5, it is collected into the second group of exhaust main pipes and enters the inlet pipe of the silicon carbide membrane filter circulating pump 1. The distance between the center lines of the two exhaust main pipes is 946mm. The exhaust main pipe of the inlet of the silicon carbide membrane filter circulating pump 1 is on the same center line as the silicon carbide membrane filter circulating pump 1.

[0057] The acid tank 6, the descaling cleaning tank 7 and the clear liquid collection tank 4 are all cylindrical closed containers with a volume of 1 cubic meter.

[0058] The cleaning process equipment of the present application also has the following characteristics:

[0059] The inlet of the silicon carbide membrane filter circulating pump is also connected to an exhaust main pipe for receiving desulfurization wastewater, and the exhaust main pipe is on the same center line as the silicon carbide membrane filter circulating pump.

[0060] The two silicon carbide membrane filters each include three silicon carbide membrane shells, which are vertically installed on the horizontally placed exhaust main pipe, and the three silicon carbide membrane shells are arranged side by side on the exhaust main pipe. The bottom of the exhaust main pipe is provided with a valve for emptying or discharging the concentrated liquid; the three silicon carbide membrane shells are connected by top communication pipes and operate in series;

[0061] The bottom of each silicon carbide membrane shell is provided with a rubber expansion joint for reducing vibration;

[0062] The top of the side surface of the silicon carbide membrane shell is also provided with a drain port, which is connected to the clear liquid collection tank, and the lower part of the side surface of the silicon carbide membrane shell is provided with a drain port A, which is connected to the outlet end of the clear liquid backflushing pump;

[0063] An exhaust pipe is installed on the top communication pipe of the silicon carbide membrane shell, and the exhaust port of the exhaust pipe is higher than the communication pipe;

[0064] The acid tank, the descaling cleaning tank and the clear liquid collection tank are all cylindrical closed containers.

[0065] Working mode of backflushing process in clarification process of fgd wastewater of thermal power plant

[0066] The present application is based on the clarification process of the desulfurization wastewater of the thermal power plant using the silicon carbide membrane ultrafiltration technology. Another improvement of the prior art is the setting of the clear liquid backwash process. In the prior art, the backwash process is also used in the ultrafiltration system, but there are some deficiencies, such as non-automation, unclear starting point and ending point of the backwash process, etc.

[0067] In the process of purifying water quality, the continuously running clarification process makes the filter layer continuously intercept the pollutants in the water. As the amount of intercepted pollutants increases, the pollutants accumulated on the system membrane of the silicon carbide membrane group will increase, causing the gap to be blocked, and then the filtered water volume decreases, and the filtration efficiency and effect become poor.

[0068] In the clarification process of the desulfurization wastewater of the thermal power plant using the silicon carbide membrane ultrafiltration technology, the pressure difference before and after the water of the silicon carbide membrane in the ultrafiltration system is monitored, and then the backwash process is accurately controlled.

[0069] The specific principle is that after the silicon carbide membrane works for a long time, the thickness of the deposited filter material accumulated on the membrane increases. The increase of the deposit will cause the increase of the pressure difference between the two ends of the membrane. Because the more serious the membrane is blocked, the more pressure the fluid needs to accumulate when passing through the membrane. Therefore, in order to prevent the pressure difference between the two ends of the membrane from being too large and causing damage to the filter membrane, the present application designs to timely dredge the deposit on the membrane to reduce the accumulated pressure difference.

[0070] The present application sets pressure gauges between the upstream pipe and the downstream pipe of the fluid entering the membrane, and monitors the values of the two pressure gauges. The difference between the values of the two pressure gauges is the pressure difference of the fluid entering and exiting the two ends of the membrane.

[0071] The pressure gauges of the present application are preferably connected to the centralized control system for intelligent monitoring and control of filtration.

[0072] When the pressure difference rises to a set degree, the wastewater pump will stop working. Then the clear liquid backwash pump is opened, and the backwash starts to run. The backwash fluid enters the ultrafiltration membrane system to perform backwash. When the pressure difference returns to a set degree, the backwash is completed. The backwash fluid is closed again, the filtrate outlet valve is opened again, and the wastewater pump starts to work again to restore filtration. The whole process of backwash repair will be automatically operated.

[0073] The value of the upstream pipe pressure gauge of the fluid entering the membrane is denoted as P1, the value of the downstream pipe pressure gauge is denoted as P2, and the pressure difference of the fluid is ΔP=(P1-P2). In the present application, the relative percentage of the pressure difference ΔP%=ΔP / P1*100% is used to represent the relative value of the pressure difference when calculating the start time of the backwash pump.

[0074] The opening and closing of the start-up time is tested by the relative percentage of the pressure difference of the present application, and the accuracy and effectiveness of the precise control method under the condition of ensuring that the membrane is not damaged are tested. As shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] Through the above experiments, in the clarification process of the desulfurization wastewater of the thermal power plant based on the silicon carbide membrane ultrafiltration technology of the present application, the point value of ΔP% when the backflushing pump is opened is between 30-40%, and is preferably 35%.

[0079] It is worth noting that during the period when the backflushing pump is opened, since the cleaning of the blockage accumulated on the membrane is a balanced flushing process, it also takes a certain time to clean and transport these deposits, so the value of ΔP% will remain unchanged for a long period of time. Therefore, in order to ensure complete cleaning, the point value of ΔP% when the backflushing pump is closed is set to be below 25%, and is preferably below 20%.

[0080] At the same time, the cleaning process of the present application further adds cleaning of the deposits accumulated on the filter membrane, and further introduces an acid tank and a descaling cleaning tank, which are connected with a cleaning regenerating pump, and enter the first or second silicon carbide filter membrane filter through the cleaning pipeline II for an auxiliary backflushing step. Embodiment

[0082] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference signs represent the same or similar modules or modules with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0083] In the description of the present specification, the description of the terms "one embodiment", "another embodiment", and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0084] As shown in the accompanying drawings of the present application, Figures 1-2 As shown in the accompanying drawings of the present application, Figure 1is a flow chart of the clarifying process of the desulfurization wastewater of the thermal power plant based on the silicon carbide membrane ultrafiltration technology of the present application; Figure 2 is the filtration flow of the clarifying process of the desulfurization wastewater of the thermal power plant based on the silicon carbide membrane ultrafiltration technology of the present application.

[0085] In particular, the clarifying process of the desulfurization wastewater of the thermal power plant based on the silicon carbide membrane ultrafiltration technology comprises the following steps:

[0086] Step 1, the wastewater generated by the desulfurization system is transported to the feed buffer tank 110, then passes through the pre-filter 112 to complete the pre-filtration.

[0087] Step 2, the filtrate of the pre-filter 112 of step 1 is filtered by the first membrane filtration circulating pump 114 through the first silicon carbide diaphragm filter 116.

[0088] Step 3, the separated sludge after filtration in step 2 is sent to the sludge tank, and the filtrate passing through the membrane is filtered again by the second membrane filtration circulating pump 118 through the second silicon carbide filter membrane filter 120.

[0089] Step 4, the filtrate passing through the membrane in step 3 is sent to the clear liquid collection tank 210, and the separated sludge is sent to the sludge tank,

[0090] The above process further comprises a backwashing step, wherein the backwashing step is:

[0091] The pressure difference between the upstream pipe pressure value P1 and the downstream pipe pressure value P2 of the filtrate entering the membrane in step 2 or step 3 is ΔP%=(P1-P2) / P1*100%,

[0092] When the value of ΔP% is 30%, the clear liquid backwashing pump 208 is opened, and the backwashing step is operated;

[0093] When the value of ΔP% is 25, the clear liquid backwashing pump 208 is closed, and the backwashing step is stopped.

[0094] The backwashing step is carried out in the first or second silicon carbide filter membrane filter 116, 120.

[0095] When the backwashing step is operated, the silicon carbide filter membrane filter stops working; when the backwashing step is stopped, the silicon carbide filter membrane filter starts working; the liquid used by the clear liquid backwashing pump comes from the circulating clear liquid collection tank 210.

[0096] The liquid used by the clear liquid backwashing pump 208 enters the first or second silicon carbide filter membrane filter 116, 120 through the cleaning pipe I to carry out the backwashing step.

[0097] In another bypass, an acid tank 218 is introduced, connected to the cleaning and regeneration pump 216 and to the descaling and cleaning tank 214, connected to the cleaning and regeneration pump 216. The cleaning and regeneration pump is connected to the cleaning conduit II, entering the first or second silicon carbide filter membrane filter 116, 120 for the backflushing step.

[0098] wherein 220 is a process external third party clear liquid, which can be selected from industrial tap water, which can be used as a complementary cleaning liquid to the backflushing.

[0099] Although the embodiments of the present application have been shown and described above, it is to be understood that the above-described embodiments are merely exemplary, and that the present application is not to be limited to the above-described embodiments, and that one skilled in the art can make changes, modifications, substitutions and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for clarifying desulfurization wastewater in a thermal power plant based on silicon carbide membrane ultrafiltration technology, the method being used in a silicon carbide membrane filtration device, the silicon carbide membrane filtration device comprising a buffer tank, a pre-filter, a first membrane filtration circulating pump, a first silicon carbide diaphragm filter, a second membrane filtration circulating pump, a second silicon carbide diaphragm filter, a sludge tank, a clear liquid collection tank, a clear liquid backflushing pump, a cleaning and regenerating pump, an acid liquid tank, a descaling cleaning tank, the acid liquid tank and the descaling cleaning tank being connected to the cleaning and regenerating pump respectively; an outlet end of the clear liquid backflushing pump being connected to the first silicon carbide diaphragm filter and the second silicon carbide diaphragm filter; an outlet end of the cleaning and regenerating pump being connected to an inlet end of the first membrane filtration circulating pump and the second membrane filtration circulating pump; the method comprising the following steps: Step 1: after the wastewater generated by a desulfurization system is transported to the buffer tank, pre-filtration is completed through the pre-filter; the wastewater contains solid content with a concentration of 5-10%; Step 2: the filtrate obtained by pre-filtration in Step 1 is filtered by the first silicon carbide diaphragm filter through the first membrane filtration circulating pump; Step 3: the sludge separated after filtration in Step 2 is sent to the sludge tank, and the filtrate through the membrane is filtered again by the second silicon carbide diaphragm filter through the second membrane filtration circulating pump; Step 4: the filtrate through the membrane in Step 3 is sent to the clear liquid collection tank, and the separated sludge is sent to the sludge tank, wherein the method further comprises a backflushing step, the backflushing step being: determining a pressure difference ΔP% of an upstream pipeline pressure value P1 and a downstream pipeline pressure value P2 of the first silicon carbide diaphragm filter into which the filtrate in Step 2 enters, ΔP% = (P1-P2) / P1*100%; when the value of ΔP% is 30-40%, the clear liquid backflushing pump is started, and the backflushing step is run; when the value of ΔP% is 25% or less, the clear liquid backflushing pump is stopped, and the backflushing step is stopped; the backflushing step is performed in the first silicon carbide diaphragm filter; the liquid used by the clear liquid backflushing pump enters the first silicon carbide diaphragm filter through a cleaning pipeline I to perform the backflushing step; the cleaning and regenerating pump is connected to a cleaning pipeline II to enter the first silicon carbide diaphragm filter to perform an auxiliary backflushing step; alternatively, determining a pressure difference ΔP% of an upstream pipeline pressure value P1 and a downstream pipeline pressure value P2 of the second silicon carbide diaphragm filter into which the filtrate in Step 3 enters, ΔP% = (P1-P2) / P1*100%; when the value of ΔP% is 30-40%, the clear liquid backflushing pump is started, and the backflushing step is run; when the value of ΔP% is 25% or less, the clear liquid backflushing pump is stopped, and the backflushing step is stopped; the backflushing step is performed in the second silicon carbide diaphragm filter; the liquid used by the clear liquid backflushing pump enters the second silicon carbide diaphragm filter through a cleaning pipeline I to perform the backflushing step; the cleaning and regenerating pump is connected to a cleaning pipeline II to enter the second silicon carbide diaphragm filter to perform an auxiliary backflushing step; wherein the liquid used by the clear liquid backflushing pump comes from the circulating clear liquid collection tank.

2. The clarification process of claim 1, wherein the silicon carbide membrane filter is inoperative when the backflush step is in operation; and the silicon carbide membrane filter is operative when the backflush step is inoperative.

3. The clarification process of claim 1, wherein the liquid used by the clear backflush pump comprises third party clear liquid that is outside of the process.

4. The clarification process of claim 1, the flow rate of the clear supernatant backflush pump is 25-40 m 3 / h, and the head is 50-100 water column.

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