Dehydration system for flue gas desulfurization gypsum of power plant

Abstract

A dehydration system for flue gas desulfurization gypsum of a power plant belongs to the technical field of flue gas desulfurization and comprises an absorption tower, a heating kettle, a primary preparation assembly and a secondary preparation assembly, and the absorption tower is provided with a spraying mechanism and a liquid phase outlet; an inlet of the heating kettle is connected with the liquid phase outlet, and the heating kettle is provided with a first clear liquid area and a first turbid liquid area; an inlet of the first-stage preparation assembly is connected with an outlet of the first turbid liquid area, and the first-stage preparation assembly is provided with a second clear liquid area and a second turbid liquid area; an inlet of the second-stage preparation assembly is connected with an outlet of the second turbid liquid area, an outlet of the second-stage preparation assembly is connected with a gypsum finished product box, the separation amount of calcium sulfate is increased by heating slurry in the reaction kettle, and the temperature of the slurry in the subsequent water removal step is high, so that the calcium sulfate can be better separated out and precipitated; therefore, the utilization rate of calcium sulfate in the slurry is improved, and calcium sulfate in supernatant liquid in the slurry is prevented from being wasted; the water content of the slurry in the turbid liquid area can be better removed, and the water removal efficiency is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of flue gas desulfurization, and in particular to a dehydration system for flue gas desulfurization gypsum in a power plant. Background Art

[0002] At present, the wet limestone-gypsum desulfurization process is the dominant process for flue gas desulfurization in thermal power plants in my country, and the absorption tower is the core equipment of the wet desulfurization device. The limestone slurry washes the flue gas in the absorption tower in countercurrent, and the limestone slurry droplets sprayed from the atomizing nozzle react with the sulfur dioxide in the flue gas to generate soluble calcium sulfite and calcium bisulfite, which flow into the slurry pool in the form of small particles. The oxidation fan sprays the oxidizing air into the slurry pool. Under the action of the agitator, the calcium sulfite and calcium bisulfite are almost completely oxidized to generate gypsum crystals. The slurry is discharged by a gypsum discharge pump and sent to a gypsum cyclone for concentration and particle classification, and finally gypsum is obtained.

[0003] For example, the invention patent with publication number "CN201920839059.8" discloses a wet flue gas desulfurization wastewater discharge system that can adapt to large changes in limestone quality, including a gypsum dehydration recovery unit, a recovered water collection unit, a wastewater recovery unit and a wastewater discharge unit. The absorption tower slurry storage unit, the gypsum dehydration recovery unit and the recovered water collection unit are connected in sequence, and the desulfurized gypsum slurry is collected by the absorption tower slurry storage unit. The gypsum dehydration recovery unit is used to perform solid-liquid separation on the gypsum slurry and obtain recovered water and gypsum by-products to solve the problem of high gypsum moisture content.

[0004] The above-mentioned invention patent uses a gypsum cyclone to remove water from the slurry in the absorption tower for the first time, and then directly discharges the discharged clear liquid into the recycled water collection unit. However, at this time, the clear liquid discharged from the gypsum cyclone contains a large amount of calcium sulfate, thereby causing a waste of calcium sulfate (raw material for preparing gypsum). Summary of the invention

[0005] In view of this, it is necessary to provide a method for solving the problem of low utilization rate of calcium sulfate in the slurry discharged from the liquid phase outlet of the absorption tower.

[0006] The solution of this application to solve the technical problem is:

[0007] A dehydration system for flue gas desulfurization gypsum in a power plant, comprising:

[0008] An absorption tower, wherein the absorption tower is provided with a spray mechanism and a liquid phase outlet;

[0009] A heating kettle, wherein the inlet of the heating kettle is connected to the liquid phase outlet, and the heating kettle is provided with a first clear liquid area and a first turbid liquid area;

[0010] A primary preparation component, the inlet of the primary preparation component is connected to the outlet of the first turbid liquid area, and the primary preparation component is provided with a second clear liquid area and a second turbid liquid area;

[0011] A secondary preparation component, the inlet of which is connected to the outlet of the second turbid liquid zone, and the outlet of which is connected to the gypsum finished product box.

[0012] Preferably, the heating kettle is provided with a reflux pipe, and the outlet of the reflux pipe is connected to the inlet of the spray mechanism.

[0013] Preferably, the heating kettle is provided with a steam outlet, a reflux piece and a reflux port, the inlet of the reflux piece is connected to the steam outlet, and the reflux port is connected to the outlet of the reflux piece.

[0014] Preferably, the reflux component includes a condenser and a reflux tank, the inlet of the condenser is connected to the steam outlet, the outlet of the condenser is connected to the inlet of the reflux tank, and the outlet of the reflux tank is connected to the reflux port.

[0015] Preferably, the primary preparation component is a decanter centrifuge.

[0016] Preferably, the secondary preparation component is one of a membrane filter press and a vacuum filter.

[0017] Preferably, it further comprises a clear liquid recovery tank, and the clear liquid recovery tank is connected to the first clear liquid area.

[0018] Preferably, the clear liquid recovery tank is connected to the second clear liquid area, and the outlet of the clear liquid recovery tank is connected to the inlet of the spray mechanism.

[0019] This application adopts a technical solution of a dehydration system for flue gas desulfurization gypsum in a power plant to achieve the following beneficial effects:

[0020] The precipitation amount of calcium sulfate is increased by heating the slurry in the reaction kettle, and the temperature of the slurry is relatively high in the subsequent dewatering step, so that the calcium sulfate can be better precipitated and precipitated, thereby improving the utilization rate of the calcium sulfate in the slurry and avoiding the waste of the calcium sulfate in the upper clear liquid of the slurry; at the same time, the primary preparation component and the secondary preparation component can better remove the water content of the slurry in the first turbid liquid area and the second turbid liquid area, thereby improving the dewatering efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the dehydration system of flue gas desulfurization gypsum in the power plant in this application.

[0022] In the figure: absorption tower 10, spray mechanism 101, liquid phase outlet 102, heating kettle 20, first clear liquid zone 201, first turbid liquid zone 202, reflux pipe 203, steam outlet 204, reflux piece 205, condenser 2051, reflux tank 2052, reflux port 206, primary preparation component 30, second clear liquid zone 301, second turbid liquid zone 302, secondary preparation component 40, clear liquid recovery box 50, gypsum finished product box 60. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Please see Figure 1 A dehydration system for flue gas desulfurization gypsum in a power plant comprises an absorption tower 10, a heating kettle 20, a primary preparation component 30 and a secondary preparation component 40, wherein the absorption tower 10 is provided with a spray mechanism 101 and a liquid phase outlet 102; the inlet of the heating kettle 20 is connected to the liquid phase outlet 102, and the heating kettle 20 is provided with a first clear liquid area 201 and a first turbid liquid area 202; the inlet of the primary preparation component 30 is connected to the outlet of the first turbid liquid area 202, and the primary preparation component 30 is provided with a second clear liquid area 301 and a second turbid liquid area 302; the inlet of the secondary preparation component 40 is connected to the outlet of the second turbid liquid area 302, and the outlet of the secondary preparation component 40 is connected to a gypsum finished product box 60.

[0025] The slurry discharged from the absorption tower 10 is used to prepare gypsum. In this process, the gypsum needs to be dehydrated. Gypsum is prepared by drying, centrifugal dehydration and vacuum dehydration. The clear liquid separated in this process is directly recovered or discharged without any recovery treatment, resulting in a waste of calcium sulfate in the upper clear liquid in the slurry.

[0026] Working process: Flow path of the slurry: the liquid phase outlet 102 of the absorption tower 10 is discharged into the heating kettle 20, and then the first turbid liquid area 202 of the heating kettle 20 is discharged into the first-level preparation component 30, and finally the second turbid liquid area 302 of the first-level preparation component 30 is discharged into the second-level preparation component 40.

[0027] At the same time, the absorption tower 10 sprays limestone solution or carbide slag solution through the spray mechanism 101 to absorb sulfur dioxide in the flue gas to form a slurry containing calcium sulfate (raw material for preparing gypsum). At this time, this part of the slurry is discharged from the liquid phase outlet 102 into the heating kettle 20, and the slurry is heated in the heating kettle 20. According to the physical properties of calcium sulfate, the solubility of calcium sulfate decreases with the increase of temperature, but when the temperature is about 1200°C, it decomposes into calcium oxide. At this time, the temperature of the heating kettle 20 is set to 80°C to 150°C. At this temperature, calcium sulfate precipitates in large quantities. At this time, the slurry in the first turbid liquid area 202 is passed into the first turbid liquid area 202. In the first preparation component 30, preliminary water removal is carried out, and then the slurry in the second turbid liquid area 302 is passed into the second preparation component 40. In the process again, it should be clear that the temperature is gradually reduced. In this process, the slurry is precipitated for the first time in the heating kettle 20, precipitated for the second time in the first preparation component 30, and precipitated for the third time in the second preparation component 40. During these three precipitation processes, the calcium sulfate contained in the first clear liquid area 201 and the second clear liquid area 301 is precipitated to reduce the content of calcium sulfate in the first clear liquid area 201 and the second clear liquid area 301. At this time, the precipitated calcium sulfate enters the first turbid liquid area 202 and the second turbid liquid area 302, reducing the loss of calcium sulfate in the slurry. Reasons for reducing the loss: the clear liquid in the first clear liquid area 201 and the second clear liquid area 301 is directly discharged from the dehydration system of the flue gas desulfurization gypsum of the power plant. At this time, the calcium sulfate in the first clear liquid area 201 and the second clear liquid area 301 is also discharged, resulting in a waste of calcium sulfate.

[0028] Beneficial effect: By changing the temperature of the slurry through the heating kettle 20, the calcium sulfate in the first clear liquid area 201 and the second clear liquid area 301 is precipitated into the first turbid liquid area 202 and the second turbid liquid area 302, thereby avoiding the waste of calcium sulfate in the first clear liquid area 201 and the second clear liquid area 301, thereby improving the utilization rate of calcium sulfate in the slurry.

[0029] Furthermore, the heating kettle 20 is provided with a reflux pipe 203 , and the outlet of the reflux pipe 203 is connected to the inlet of the spray mechanism 101 .

[0030] The reflux pipe 203 returns the slurry in the first clear liquid zone 201 in the heating kettle 20 to the spray mechanism 101. This is because the slurry in the first clear liquid zone 201 contains limestone or carbide slag, light calcium sulfite and calcium carbonate that have not reacted with sulfur dioxide. At this time, these substances react with sulfur dioxide to generate calcium sulfate, thereby increasing the content of calcium sulfate in the slurry.

[0031] In a preferred embodiment, the heating kettle 20 is provided with a steam outlet 204 , a reflux piece 205 and a reflux port 206 , the inlet of the reflux piece 205 is connected to the steam outlet 204 , and the reflux port 206 is connected to the outlet of the reflux piece 205 .

[0032] Since the temperature in the heating kettle 20 is relatively high, the water in the slurry will be gasified at this temperature to form steam, and the steam will enter the reflux part 205 from the steam outlet 204, and will be cooled and the substances (including calcium sulfate) will be separated in the reflux part 205. The separated water can be used as cooling water for other process steps, and the separated substances will flow back to the heating kettle 20 through the reflux port 206 to avoid the waste of calcium sulfate.

[0033] In a preferred embodiment, the reflux component 205 includes a condenser 2051 and a reflux tank 2052 , the inlet of the condenser 2051 is connected to the steam outlet 204 , the outlet of the condenser 2051 is connected to the inlet of the reflux tank 2052 , and the outlet of the reflux tank 2052 is connected to the reflux port 206 .

[0034] The material at the steam outlet 204 is condensed in the condenser 2051 , and then the condensed material is separated by using the reflux drum 2052 , that is, water and the material containing calcium sulfate are separated.

[0035] Specifically, the first-stage preparation component 30 is a sedimentation centrifuge.

[0036] The first-stage preparation component 30 is used to remove moisture in the first turbid liquid area 202, which can be done by centrifugation or sedimentation. In this case, a sedimentation centrifuge is used. The sedimentation centrifuge is a new type of horizontal spiral unloading centrifuge. Its working principle is to utilize the solid-liquid specific gravity difference and rely on the centrifugal field to expand it by thousands of times. The solid phase is precipitated under the action of centrifugal force, thereby realizing solid-liquid separation, and is discharged from the body separately under the action of a special mechanism; and the entire feeding and separation process is completed continuously, closed, and automatically.

[0037] Specifically, the secondary preparation component 40 is one of a membrane filter press and a vacuum filter.

[0038] In the secondary preparation component 40, the slurry in the second turbid liquid area 302 is dehydrated. At this time, the dehydrated slurry becomes a cake-shaped gypsum and a separated liquid. In this process, a diaphragm filter press is selected, that is, a diaphragm filter press, which is a filter press with an elastic membrane installed between the filter plate and the filter cloth. During use, when the feeding is completed, a high-pressure fluid or gas medium can be injected into the diaphragm plate. At this time, the entire diaphragm will swell and compress the filter cake, thereby achieving further dehydration of the filter cake, and it is also convenient to remove the filter cake (cake-shaped gypsum) on the diaphragm filter press; or a vacuum filter can be used.

[0039] In a preferred embodiment, a clear liquid recovery tank 50 is further included, and the clear liquid recovery tank 50 is connected to the first clear liquid area 201 .

[0040] The clear liquid recovery box 50 is used to recover the slurry in the first clear liquid collection. Because this part of the slurry contains calcium sulfate, the slurry in the first clear liquid collection is collected, and the calcium sulfate is collected in a disguised form. The clear liquid recovery box 50 is connected to the second clear liquid area 301, and the second clear liquid collection is also collected. The collected clear liquid is then used to compound limestone or carbide slag, thereby increasing the utilization rate of calcium sulfate in the slurry and avoiding waste of calcium sulfate in the slurry.

[0041] What is disclosed above is only a preferred embodiment of the present application, and it certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A dehydration system for flue gas desulfurization gypsum in a power plant, characterized in that: It includes an absorption tower, wherein the absorption tower is provided with a spray mechanism and a liquid phase outlet; A heating kettle, wherein the inlet of the heating kettle is connected to the liquid phase outlet, and the heating kettle is provided with a first clear liquid area and a first turbid liquid area; A primary preparation component, the inlet of the primary preparation component is connected to the outlet of the first turbid liquid area, and the primary preparation component is provided with a second clear liquid area and a second turbid liquid area; A secondary preparation component, the inlet of which is connected to the outlet of the second turbid liquid zone, and the outlet of which is connected to the gypsum finished product box.

2. The dehydration system for flue gas desulfurization gypsum of power plant according to claim 1, characterized in that: The heating kettle is provided with a reflux pipeline, and the outlet of the reflux pipeline is connected to the inlet of the spray mechanism.

3. The dehydration system of flue gas desulfurization gypsum in power plant according to claim 1, characterized in that: The heating kettle is provided with a steam outlet, a reflux piece and a reflux port. The inlet of the reflux piece is connected to the steam outlet, and the reflux port is connected to the outlet of the reflux piece.

4. The dehydration system of flue gas desulfurization gypsum in power plant according to claim 3, characterized in that: The reflux component includes a condenser and a reflux tank, the inlet of the condenser is connected to the steam outlet, the outlet of the condenser is connected to the inlet of the reflux tank, and the outlet of the reflux tank is connected to the reflux port.

5. The dehydration system of flue gas desulfurization gypsum in power plant according to claim 1, characterized in that: The first-stage preparation component is a sedimentation centrifuge.

6. The dehydration system of flue gas desulfurization gypsum in power plant according to claim 1, characterized in that: The secondary preparation component is one of a membrane filter press and a vacuum filter.

7. The dehydration system of flue gas desulfurization gypsum in power plant according to claim 1, characterized in that: It also includes a clear liquid recovery tank, which is connected to the first clear liquid area.

8. The dehydration system of flue gas desulfurization gypsum in power plant according to claim 7, characterized in that: The clean liquid recovery tank is connected to the second clean liquid area, and the outlet of the clean liquid recovery tank is connected to the inlet of the spray mechanism.

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