Dehydration system for limestone-gypsum wet desulphurization wastewater

Abstract

The utility model discloses a dehydration system for limestone-gypsum wet desulphurization wastewater, which comprises a gypsum cyclone, a filtrate tank, a dehydrator and an inclined plate concentrator, and a top flow outlet of the cyclone is connected with an inlet of the inclined plate concentrator and the filtrate tank; an underflow outlet of the cyclone is connected with the dehydrator; a top flow outlet of the inclined plate concentrator is connected with a filtrate tank and a pipeline for connecting a wastewater treatment system; and an underflow outlet of the inclined plate concentrator is connected with the filtrate tank and the dehydrator. According to the utility model, the inclined plate concentrator is adopted to treat the slurry of the gypsum cyclone, and the top fluid solid content can be further reduced after multiple times of concentration treatment to meet the subsequent process treatment requirements.

Description

TECHNICAL FIELD

[0001] The utility model relates to wastewater treatment technology, concretely relates to a limestone - gypsum wet desulphurization wastewater dewatering treatment system. BACKGROUND

[0002] The flue gas desulfurization system of the coal-fired power plant mainly comprises an absorption tower system for removing SO2, a dewatering system for dewatering gypsum slurry, an oxidation air system for oxidizing the gypsum slurry, a slurry preparation system of limestone slurry and a wastewater system for treating final wastewater.

[0003] The dewatering system is used for dewatering the oxidized gypsum slurry, and the existing dewatering process adopts a gypsum cyclone for dewatering.

[0004] In actual operation, the above process is affected by factors such as insufficient oxidation of the slurry and insufficient output of the gypsum cyclone in the dewatering system, so that the top flow of the gypsum cyclone and the wastewater cyclone cannot reach the designed solid content, thereby causing the solid content of the wastewater entering the wastewater treatment system to exceed the standard, which seriously affects the operation of the wastewater system. UTILITY MODEL CONTENT

[0005] In view of the defects or deficiencies of the prior art, the utility model provides a dewatering system of limestone - gypsum wet desulphurization wastewater.

[0006] Therefore, the dewatering system of limestone - gypsum wet desulphurization wastewater provided by the utility model comprises a gypsum cyclone, a filtrate tank, an inclined plate thickener and a dewatering machine, the gypsum cyclone is provided with a gypsum slurry inlet, the top of the gypsum cyclone is provided with a top flow outlet, and the bottom of the gypsum cyclone is provided with a bottom flow outlet, the inclined plate thickener is provided with an inlet, the top of the inclined plate thickener is provided with a top flow discharge outlet, and the bottom of the inclined plate thickener is provided with a bottom flow discharge outlet.

[0007] The top flow outlet is connected with the inclined plate thickener inlet and the filtrate tank, the bottom flow outlet is connected with the dewatering machine, the top flow discharge outlet is connected with the filtrate tank and a pipeline for connecting the wastewater treatment system, and the bottom flow discharge outlet is connected with the filtrate tank and the dewatering machine.

[0008] In the preferred scheme, the gypsum cyclone is located above the inclined plate thickener, and the inclined plate thickener is located above the filtrate tank, the dewatering machine and the wastewater treatment system.

[0009] In an alternative aspect, the system further comprises a top stream collection tank, the top stream outlet is connected to an inlet of the top stream collection tank, an outlet of the top stream collection tank is connected to the inclined plate concentrator inlet and the filtrate tank. The system further comprises a bottom stream collection tank, the bottom stream outlet is connected to an inlet of the bottom stream collection tank, an outlet of the bottom stream collection tank is connected to the dewatering machine. The dewatering machine is a belt dewatering machine.

[0010] In some aspects, the system comprises at least two sets of parallel gypsum cyclones.

[0011] The gypsum cyclone slurry is treated by the inclined plate concentrator, the top stream solid content is further reduced after multiple dewatering and concentration treatment, and the subsequent process treatment requirements are met. In the preferred aspect, the inclined plate concentrator is arranged between the gypsum cyclone and the filtrate tank in terms of height, a slurry pump is not required, and energy consumption is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The figure is a system structure schematic diagram of the utility model. In the figure: 1-gypsum cyclone, 101-cyclone, 1011-top stream outlet, 1012-bottom stream outlet, 102-top stream collection tank, 103-bottom stream collection tank, 2-inclined plate concentrator, 201-inlet, 202-top stream outlet, 203-bottom stream outlet, 3-filtrate tank, 4-wastewater treatment system, 5-dewatering machine, 6-absorption tower. DETAILED DESCRIPTION

[0013] Unless otherwise specified, the scientific and technical terms in this document are understood according to the understanding of ordinary skilled in the art.

[0014] The top, bottom, upper, lower and other directional or positional terms described in this document are consistent with the related directions or positions in the drawings of the specification, and it should be noted that the drawings of the specification are intended to explain the utility model, and the solutions obtained by equivalent changes based on the disclosure in this document by those skilled in the art are within the disclosure range of the utility model.

[0015] The structures and working principles of the gypsum cyclone, the dewatering machine, the inclined plate concentrator and the wastewater treatment system involved in this document are all based on the existing related devices and working processes.

[0016] Reference is made to Figure 1As shown, the dewatering system of the utility model includes gypsum cyclone 1, inclined plate thickener 2, filtrate tank 3 and dewatering machine 5 (such as belt dewatering machine); the gypsum cyclone 1 in it adopts existing gypsum cyclone, mainly including cyclone 101, the side wall of cyclone 101 is equipped with gypsum slurry inlet, the top is equipped with top flow outlet 1101, the bottom is equipped with bottom flow outlet 1012; the inclined plate thickener 2 adopts existing inclined plate thickener, the top is equipped with inlet 201 and top flow discharge outlet 202, the bottom is equipped with bottom flow discharge outlet 203; wherein, the top flow outlet is connected with the inclined plate thickener inlet and the filtrate tank; the bottom flow outlet is connected with the dewatering machine; the top flow discharge outlet is connected with the filtrate tank and the pipeline for connecting the wastewater treatment system; the bottom flow discharge outlet is connected with the filtrate tank and the dewatering machine. In the specific scheme, valves are arranged on each connecting pipeline to control the system to realize the following process dewatering process.

[0017] When dewatering by the above system, the gypsum slurry containing gypsum crystals (generally with solid content of about 15% wt) from the desulfurization absorption tower 6 enters the cyclone, and a high-speed rotating flow field is formed in the cyclone; the gypsum crystals with higher density in the slurry move downward along the axial direction while moving outward along the radial direction under the action of the flow field; when the gypsum crystals reach the cone section of the cyclone, they move downward along the cone wall to form the bottom flow (such as with solid content of about 50% wt); the liquid with smaller density in the slurry moves toward the central axis and moves upward along the central axis to form the top flow (such as with solid content of about 3% wt);

[0018] When the chloride ion content in the cyclone top flow exceeds the threshold value (such as the threshold value of chloride ion content is 20000 ppm, and equal to or greater than the threshold value is over-standard), the top flow outlet is controlled to communicate with the inclined plate thickener inlet (the passage between the top flow outlet and the filtrate tank 3 is closed), and the cyclone top flow enters the inclined plate thickener, overflows upward between the inclined plates, the solid particles with higher concentration fall to the surface of the inclined plate and slide to the lower part of the inclined plate thickener 2 under the action of gravity, and the clarified filtrate flows out from the top of the inclined plate thickener 2 through the holes of the perforated plate, thereby generating the bottom flow and the top flow (the solid content of the top flow is about 1% wt, and the solid content of the bottom flow is higher, about 8-10% wt); when the chloride ion content in the cyclone top flow is within the threshold value (such as less than 20000 ppm), the top flow outlet is controlled to communicate with the filtrate tank 3 (the passage between the top flow outlet and the inclined plate thickener inlet is closed), and the cyclone top flow enters the filtrate tank 3;

[0019] The cyclone bottom flow enters the dewatering machine to produce gypsum and dewatering filtrate after dewatering, the gypsum is recovered, and the dewatering filtrate is recovered to the filtrate tank or directly sent into the SO2 removal absorption tower as system makeup water;

[0020] When the chloride ion content in the top stream of the inclined plate concentrator exceeds the threshold (e.g., less than 20000 ppm), the connecting pipeline between the top stream outlet and the wastewater treatment system 4 is opened (the passage between the top stream outlet and the filtrate tank 3 is closed), and the top stream of the inclined plate concentrator enters the wastewater treatment system for subsequent purification treatment; when the chloride ion content in the top stream of the inclined plate concentrator is within the threshold (e.g., less than 20000 ppm), the passage between the top stream outlet and the filtrate tank 3 is opened (the passage between the top stream outlet and the wastewater treatment system 4 is closed), and the top stream of the inclined plate concentrator is recovered to the filtrate tank.

[0021] When the inert content in the bottom stream of the inclined plate concentrator exceeds the threshold (e.g., greater than or equal to 10% wt), the connecting pipeline between the bottom stream outlet and the dewatering machine 5 is opened (the passage between the bottom stream outlet and the filtrate tank 3 is closed), and the bottom stream of the inclined plate concentrator enters the dewatering machine for dewatering treatment; when the inert content in the bottom stream of the inclined plate concentrator is within the threshold (e.g., less than 10% wt), the passage between the bottom stream outlet and the filtrate tank 3 is opened (the passage between the bottom stream outlet and the dewatering machine 5 is closed), and the bottom stream of the inclined plate concentrator is recovered to the filtrate tank.

[0022] In the above scheme, the dewatered filtrate recovered to the filtrate tank 3 can be returned to the SO2 removal absorption tower as system makeup water.

[0023] In the above scheme, the common wastewater treatment system includes a triple tank and a plate and frame filter press. After the wastewater passes through the triple tank, supernatant and lower suspension are generated. After the lower suspension passes through the plate and frame filter press, the sludge and water are separated, and the sludge is discharged alone, and the water is mixed with the supernatant of the triple tank and then discharged. The triple tank generally includes a neutralization tank, a reaction tank and a flocculation tank, and adjacent tanks are connected through overflow ports at the top. Lime milk or sodium hydroxide is added to the neutralization tank, and rapid stirring makes the originally acidic wastewater alkaline. During this process, most heavy metals form slightly soluble hydroxides and precipitate from the wastewater. The effluent from the neutralization tank flows into the reaction tank. Organic sulfur and coagulant are added to the reaction tank to remove residual heavy metals in the form of sulfide precipitate. The effluent from the reaction tank enters the flocculation tank, where coagulant aid is added. Under low-speed stirring, flocculation reaction is carried out to promote the further growth of the floc.

[0024] In the preferred scheme, the functional unit devices are arranged in an upper and lower position in space. Specifically, the inclined plate concentrator is arranged between the cyclone and the filtrate tank, dewatering machine and wastewater treatment system, i.e., as shown in Figure 1 the cyclone is located at the uppermost position, the inclined plate concentrator is located below the cyclone, and the filtrate tank, dewatering machine and wastewater treatment system are located below the inclined plate concentrator. In this way, the fluid inside the system can flow by gravity, reducing or eliminating the use of a liquid pump.

[0025] In further aspects, referring to Figure 1 The system further comprises a top flow collection tank 102 or / and a bottom flow collection tank 103, wherein the top flow outlet is connected to the inlet of the top flow collection tank, and the outlet of the top flow collection tank is connected to the inlet of the inclined plate thickener and the filtrate tank. The bottom flow outlet is connected to the inlet of the bottom flow collection tank, and the outlet of the bottom flow collection tank is connected to the dewatering machine.

[0026] To increase the processing efficiency of the system, multiple gypsum cyclones can be arranged in parallel in the entire system, and multiple sets of cyclones are alternately or simultaneously operated according to the actual wastewater processing amount. For example, Figure 1 Two are arranged as shown in

[0027] In a certain thermal power "up big and down small" 2x350MW new project environmental protection facility EPC project, the desulfurization system adopts limestone-gypsum wet single-tower single-cycle desulfurization process, the inlet SO2 concentration is 4000mg / m 3 , and the desulfurization device efficiency is not less than 99.3% for design. The gypsum slurry pumped by the gypsum discharge pump is transported to Figure 1 The gypsum cyclone installed on the top of the gypsum dewatering workshop as shown in the figure, the slurry is concentrated for the first time to about 48-50%wt of the bottom flow and about 3%wt of the top flow, the bottom flow slurry flows to the dewatering machine for dewatering; the chloride ion content in the top flow slurry exceeds the threshold value of 20000ppm, and is subsequently sent to the inclined plate thickener below;

[0028] After the inclined plate thickener treatment, the solid content in the top flow generated by the inclined plate thickener is 0.5-0.9%wt, the solid content in the bottom flow is 8-10%wt, and the chloride ion content in the top flow exceeds the threshold value of 20000ppm, and is subsequently sent to the wastewater treatment system for further purification treatment; the content of inert substances in the bottom flow of the inclined plate thickener exceeds 10%wt, and the bottom flow is subsequently sent to the dewatering machine for dewatering treatment.

[0029] In the above scheme, the solid content determination, chloride ion content determination, and inert substance content determination methods are as follows:

[0030] Solid content (or solid content rate) determination:

[0031] Take a fast qualitative filter paper and weigh its mass A (accurate to 10mg), use the filter paper to vacuum filter V (mL) of slurry, and rinse the filter residue with ethanol; then dry the filter residue at 45-50℃ to constant weight, and weigh its mass B (accurate to 10mg); the solid content X of the slurry is calculated by the formula: X=(B-A) / V; the solid content rate x (%) of the slurry, i.e. the concentration (mass percentage) of solids in the slurry, is: x=100% x X / ρ, where ρ is the absorption tower slurry density.

[0032] Chloride ion content determination:

[0033] The water sample is injected into a carbonate-bicarbonate solution and flows through a series of ion exchange resins. Based on the different relative affinities of the anions to be measured for the low-capacity strong basic anion resin (separation column), the anions are separated from each other. The separated anions, when flowing through the strong acid cation resin (suppression column) chamber, are converted into high-conductivity acid types, and the carbonate-bicarbonate is converted into weak-conductivity carbonic acid (eliminates background conductivity). The anions converted into the corresponding acid types are measured by a conductivity detector, compared with the standard, and qualitatively determined according to the retention time, and quantitatively determined according to the peak height or peak area.

[0034] Inert matter content determination

[0035] About 0.5 g of the sample (m1) is weighed to 0.000 lg, placed in a 250 mL beaker, wetted with water, covered with a watch glass, 40 mL of hydrochloric acid (1 part of 36%-38% HCI + 5 parts of distilled water) is added, after the reaction stops, the watch glass and the cup wall are washed with water and diluted to about 75 mL, heated and boiled for 3-4 min, filtered with slow filter paper, washed with hot water until no chloride ions are detected (no turbidity with silver nitrate titration); the residue and filter paper are moved together into an already burned, constant-volume porcelain crucible, ashed, burned at a temperature of 950-1000°C for 20 min, taken out, placed in a desiccator, cooled to room temperature, weighed; the burning, cooling and weighing are repeated until constant (m2).

[0036] The mass fraction of acid-insoluble matter (inert matter content) Y is calculated as follows: Y = m2 / m1 x 100%; wherein m2 is the mass of the residue after burning, g; and m1 is the mass of the sample, g.

Claims

1. A dewatering system for limestone-gypsum wet desulfurization wastewater, comprising a gypsum cyclone, a filtrate tank and a dewatering machine, the gypsum cyclone being provided with a gypsum slurry inlet, a top flow outlet at the top and a bottom flow outlet at the bottom, characterized in that, it further comprises an inclined plate thickener provided with an inlet, a top flow discharge outlet at the top and a bottom flow discharge outlet at the bottom; the top flow outlet is connected with the inlet of the inclined plate thickener and the filtrate tank; the bottom flow outlet is connected with the dewatering machine; the top flow discharge outlet is connected with the filtrate tank and a pipeline for connecting a wastewater treatment system; the bottom flow discharge outlet is connected with the filtrate tank and the dewatering machine.

2. The limestone-gypsum wet desulfurization wastewater dewatering system according to claim 1, characterized in that, The gypsum cyclone is located above the inclined plate thickener, and the inclined plate thickener is located above the filtrate tank, the dewatering machine and the wastewater treatment system.

3. The limestone-gypsum wet FGD wastewater dewatering system according to claim 1, characterized by, The system further comprises a top flow collection tank, the top flow outlet is connected with the inlet of the top flow collection tank, and the outlet of the top flow collection tank is connected with the inlet of the inclined plate thickener and the filtrate tank.

4. The limestone-gypsum wet FGD wastewater dewatering system according to claim 1, characterized by, The system further comprises a bottom flow collection tank, the bottom flow outlet is connected with the inlet of the bottom flow collection tank, and the outlet of the bottom flow collection tank is connected with the dewatering machine.

5. The limestone-gypsum wet FGD wastewater dewatering system according to claim 1, characterized by, The dewatering machine is a belt dewatering machine.

6. The limestone-gypsum wet FGD wastewater dewatering system according to claim 1, characterized by, The system comprises at least two sets of parallel gypsum cyclones.

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