Method and equipment for treating desulfurized fly ash in semi-dry flue gas desulfurization process

Abstract

The invention discloses a method and equipment for treating desulfurized fly ash in a semi-dry flue gas desulfurization process, and relates to the technical field of environmental engineering. The method comprises the following steps: mixing desulfurized fly ash of a semi-dry desulfurization system with water in a reaction container to prepare desulfurized fly ash slurry; a path of flue gas is led out from the front of a semi-dry desulfurization absorption tower and introduced into the slurry, the amount of the flue gas is adjusted so that the oxidation temperature of the slurry can meet the requirement, and in the oxidation process, water is supplemented into a reaction container so that the concentration of the slurry can be maintained, and an oxidation auxiliary agent is added to control the oxidation time so that the oxidation time can be matched with the ash discharging period of a semi-dry desulfurization system; after oxidation is completed, the flue gas amount is increased, and desulfurized fly ash slurry is dried into powder; transferring and storing the dried product into an ash silo; the method provided by the invention is simple in process, only needs to respectively lead out pipelines from the front flue and the inlet section of the semi-dry desulfurization absorption tower for connection, is low in cost, utilizes the flue gas to carry out oxidation and drying processes, is convenient to transfer and store, and is beneficial for realizing continuous large-scale production by matching with the ash discharge period of the system.

Description

Technical Field

[0001] The invention relates to the technical field of environmental engineering, and in particular to a method and equipment for treating desulfurization ash in a semi-dry flue gas desulfurization process. Background Art

[0002] Desulfurization ash is a byproduct collected by the dust removal system after desulfurization in the semi-dry flue gas desulfurization process. Its main components include calcium sulfate (CaSO4), calcium sulfite (CaSO3), unreacted desulfurizer Ca(OH)2, etc., of which calcium sulfate generally accounts for only 30-50%. Due to the unstable chemical properties of calcium sulfite, the high calcium sulfite content seriously limits the comprehensive utilization of desulfurization ash, resulting in secondary pollution; at the same time, the presence of unreacted desulfurizer Ca(OH)2 makes the desulfurizer utilization efficiency low and the desulfurization ash composition complex.

[0003] There are generally different methods for the treatment of calcium sulfite in desulfurized ash, such as high-temperature oxidation and low-temperature oxidation. For example, patent CN114409290A discloses a device and method for modifying desulfurized ash based on blast furnace gas heating. Blast furnace gas is used as a heat source fuel to heat the desulfurized ash to 300-450°C for oxidation. Although the oxidation temperature of this method is lower than the decomposition temperature, it still needs to consume high calorific value fuel, the system is complex, the floor space is large, and the economy is poor. Another example is a method and device for preparing calcium sulfate from desulfurized ash disclosed in patent CN109455752A. The desulfurized ash is reacted with a strong oxidant in a solution state to achieve low-temperature oxidation. However, this method requires adjusting the pH value, and after oxidation, filter pressing and drying are required. The operation is complicated, and wastewater is generated, forming secondary pollution. Another example is the system and method for preparing high-purity gypsum from semi-dry flue gas desulfurization ash disclosed in patent CN112875740B, which uses a wet desulfurization system to convert calcium oxide and calcium sulfite in the semi-dry desulfurization ash into gypsum. Although this method uses the existing wet desulfurization system to dispose of desulfurization ash, there is still the problem of transporting the semi-dry desulfurization ash, and a wet desulfurization system needs to be built within the transport distance. In summary, a semi-dry flue gas desulfurization process desulfurization ash treatment method and equipment are urgently needed to solve these problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method and equipment for treating desulfurization ash in a semi-dry flue gas desulfurization process, so as to solve the problems of high energy consumption, easy generation of secondary pollution such as wastewater, and insufficient simplicity of the existing semi-dry desulfurization ash treatment.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for treating desulfurization ash in a semi-dry flue gas desulfurization process, comprising the following specific contents:

[0006] Mixing desulfurization ash from a semi-dry desulfurization system with water in a reaction container to prepare a desulfurization ash slurry;

[0007] A flue gas is drawn out from the front of the semi-dry desulfurization absorption tower and introduced into the prepared desulfurization ash slurry in the reaction vessel. The flue gas volume is adjusted to maintain the slurry oxidation temperature to meet the requirements. During the oxidation process, water is added to the reaction vessel to maintain the slurry concentration, and an oxidizing agent is added to control the oxidation time to match the ash unloading cycle of the semi-dry desulfurization system.

[0008] After the oxidation of the desulfurized ash slurry is completed, the water and oxidizing agent are stopped from being added, the amount of flue gas introduced into the slurry is increased, and the desulfurized ash slurry is dried until it is in a dry powder state;

[0009] The flue gas escaping from the reaction vessel is returned to the inlet section of the semi-dry desulfurization absorption tower after dust removal, and the dust collected by the dust removal is returned to the reactor;

[0010] After oxidation and drying reactions, the dry powdered desulfurization ash is transported and stored in the ash storage, and the next batch of desulfurization ash slurry preparation begins in the reaction container.

[0011] Preferably, the concentration of the desulfurized ash slurry is 5-30%, and the slurry oxidation temperature is 70-90°C.

[0012] Another technical solution provided by the present invention is: a desulfurization ash treatment equipment for a semi-dry flue gas desulfurization process, which is used to implement the above method, comprising an oxidation fan, an oxidation reactor, and a dust collector, wherein the oxidation fan inlet is connected to the flue in front of the semi-dry desulfurization absorption tower, and the dust collector outlet is connected to the inlet section of the semi-dry desulfurization absorption tower; the oxidation reactor is provided with a feed port, a discharge port, an air inlet, an air outlet, a return port, a water inlet, and an oxidation aid inlet; the feed port of the oxidation reactor is connected to the desulfurization ash discharge port of the semi-dry desulfurization system, the discharge port is connected to the desulfurization ash storage through an ash discharge device, the air inlet is connected to the oxidation fan outlet, the air outlet is connected to the dust collector inlet, and the return port is connected to the ash discharge port of the dust collector.

[0013] Preferably, the oxidation fan is a variable frequency regulated fan and is provided with an adjustable damper.

[0014] Preferably, the oxidizing agent inlet of the oxidation reactor is connected to an external oxidizing agent supply device.

[0015] Preferably, a stirring device is provided inside the oxidation reactor.

[0016] Preferably, the feed inlet, air inlet, water inlet and oxidation aid inlet of the oxidation reactor are all provided with flow metering instruments and control valves.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The desulfurization ash treatment method and equipment of the semi-dry flue gas desulfurization process have a simple and reasonable structure and can be directly modified on the basis of the traditional semi-dry desulfurization system. It only needs to lead out pipelines from the flue in front of the semi-dry desulfurization absorption tower and the inlet section respectively, without the need for off-site disposal, and can achieve "no solid waste leaving the factory", with low investment cost.

[0019] 2. The desulfurization ash treatment method and equipment of the semi-dry flue gas desulfurization process utilize the oxygen and temperature of the semi-dry flue gas to be treated to oxidize and dry the semi-dry desulfurization ash, without the need for additional heat sources, and with low operating costs.

[0020] 3. The desulfurization ash treatment method and equipment of the semi-dry flue gas desulfurization process fully react SO2 in the flue gas with the unreacted desulfurizer Ca(OH)2 in the desulfurization ash, which indirectly improves the utilization efficiency of the desulfurizer and further reduces the operating cost.

[0021] 4. The desulfurization ash treatment method and equipment of the semi-dry flue gas desulfurization process, the water added during the treatment process is converted into water vapor during the oxidation and drying process, and is returned to the original semi-dry desulfurization system with the flue gas, without generating secondary pollution such as wastewater. The desulfurization ash after treatment is in a dry powder state, which is convenient for storage and subsequent secondary utilization.

[0022] 5. The desulfurization ash treatment method and equipment of the semi-dry flue gas desulfurization process is an online disposal system. The oxidation time of the desulfurization ash can be controlled by adjusting the amount of oxidized flue gas and the amount of oxidizing agent added. By adjusting the time, it can be matched with the ash unloading cycle of the original semi-dry desulfurization system. It has high oxidation efficiency, flexible control means, and can realize continuous large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the system of the present invention;

[0024] Figure 2 It is a schematic structural diagram of the oxidation reactor of the present invention.

[0025] In the figure: 1- oxidation fan; 2- oxidation reactor; 201- feed inlet; 202- discharge port; 203- air inlet; 204- air outlet; 205- return port; 206- water inlet; 207- oxidation aid inlet; 3- dust collector; 4- ash unloading device; 5- desulfurization ash storage. DETAILED DESCRIPTION

[0026] The semi-dry flue gas desulfurization process desulfurization ash treatment method of the present invention includes pulping, oxidation, drying and ash discharge, etc. Specifically:

[0027] Mixing desulfurization ash from a semi-dry desulfurization system with water in a reaction container to prepare a desulfurization ash slurry;

[0028] A flue gas is drawn out from the front of the semi-dry desulfurization absorption tower and introduced into the prepared desulfurization ash slurry in the reaction vessel. The flue gas volume is adjusted to maintain the slurry oxidation temperature to meet the requirements, generally 70-90°C. During the oxidation process, water is added to the reaction vessel to maintain the slurry concentration, which can be specifically controlled at 5-30%. Oxidation aids are added to control the oxidation time to match the ash unloading cycle of the semi-dry desulfurization system.

[0029] After the oxidation of the desulfurized ash slurry is completed, the water and oxidizing agent are stopped from being added, the amount of flue gas introduced into the slurry is increased, and the desulfurized ash slurry is dried until it is in a dry powder state;

[0030] The flue gas escaping from the reaction vessel is returned to the inlet section of the semi-dry desulfurization absorption tower after dust removal, and the dust collected by the dust removal is returned to the reactor;

[0031] After oxidation and drying reactions, the dry powdered desulfurization ash is transported and stored in the ash storage, and the next batch of desulfurization ash slurry preparation begins in the reaction container.

[0032] To implement the above method, the present invention also provides a semi-dry flue gas desulfurization process desulfurization ash treatment equipment, see Figure 1 and Figure 2 , including an oxidation fan 1, an oxidation reactor 2, and a dust collector 3. The inlet of the oxidation fan 1 is connected to the flue before the semi-dry desulfurization absorption tower, and the outlet of the dust collector 3 is connected to the inlet section of the semi-dry desulfurization absorption tower; the oxidation reactor 2 is provided with a feed port 201, a discharge port 202, an air inlet 203, an air outlet 204, a return port 205, a water inlet 206, and an oxidation aid inlet 207, wherein the air inlet 203 is generally preferably connected to the lower part of the oxidation reactor 2 to increase the contact time between the flue gas and the internal slurry, and the air outlet 204 is preferably connected to the It is connected to the upper end of the oxidation reactor 2; the feed port 201 of the oxidation reactor 2 is connected to the desulfurization ash discharge port of the semi-dry desulfurization system, the discharge port 202 is connected to the desulfurization ash storage 5 through the ash discharge device 4, the air inlet 203 is connected to the outlet of the oxidation fan 1, the air outlet 204 is connected to the inlet of the dust collector 3, and the return port 205 is connected to the ash discharge port of the dust collector 3. The ash discharge port is usually provided with a valve to cooperate with the ash discharge cycle of the semi-dry desulfurization system. The collected dust ash is added to the oxidation reactor 2 for slurrying by opening the valve in the next batch.

[0033] In a preferred embodiment, the oxidation fan 1 adopts a variable frequency regulation fan and is provided with an adjustable damper for adjusting the flue gas intake volume of the oxidation reactor 2 .

[0034] In addition, the oxidizing agent inlet 207 of the oxidation reactor 2 can be connected to an external oxidizing agent supply device, such as a storage tank and a pumping pipeline. The oxidizing agent is generally hydrogen peroxide, ozone, waste sulfuric acid, etc.

[0035] In order to make the desulfurized ash contact with the flue gas more complete and the temperature more uniform, a stirring device can be provided inside the oxidation reactor 2. For details, please refer to Figure 2 The stirring motor is fixedly mounted on the upper end of the oxidation reactor 2, the stirring shaft passes through the outer wall, and the stirring head is suspended in the oxidation reactor 2. Other conventional stirring methods may also be used.

[0036] If the system needs to be controlled more accurately, flow meters and control valves may be provided at the feed inlet 201, air inlet 203, water inlet 206 and oxidation aid inlet 207 of the oxidation reactor 2 to adjust the flow rates respectively.

[0037] For reference, the use process and principle of the above-mentioned disposal system can be as follows: the desulfurized ash from the desulfurized ash discharge port of the semi-dry desulfurization system (generally the ash discharge port of the bag filter) enters the oxidation reactor 2 through the feed port 201, and is mixed with the water sprayed through the water inlet 206 to form a desulfurized ash slurry with a concentration of 5 to 30%; the oxidation fan 1 draws out a flue gas from the front of the semi-dry desulfurization absorption tower, and enters the oxidation reactor 2 through the air inlet 203, and adjusts the operating frequency and air door opening of the oxidation fan 1 so that the flue gas volume meets the requirement of maintaining the slurry oxidation temperature range of 70 to 90°C, and the SO2 in the flue gas reacts with the CaOH2 in the desulfurized ash slurry to generate CaSO4 and CaSO3, and at the same time, the oxygen in the flue gas will desulfurize. CaSO3 in the desulfurized ash slurry is oxidized to CaSO4; during the oxidation process, water is added through the water inlet 206 to maintain the slurry concentration, and an oxidizing agent is added through the oxidizing agent inlet 207 to control the oxidation time; after the oxidation of the desulfurized ash slurry is completed, the water inlet 206 and the oxidizing agent inlet 207 valves are closed, the operating frequency of the oxidation fan 1 is increased, the amount of flue gas introduced is increased, and the desulfurized ash slurry is dried to a dry powder state; the dried flue gas enters the dust collector 3 through the oxidation reactor 2, and the desulfurized ash carried is collected by the dust collector 3 and returned to the oxidation reactor 2; after oxidation and drying reactions, the dry powder desulfurized ash is collected in the desulfurized ash storage 5 through the discharge port 202 of the oxidation reactor 2 and the ash unloading device 4;

[0038] Among them Figure 1 As shown, the ash unloading device 4 can be a screw conveyor or the like. Usually, the discharge port 202 should be provided with a switch valve. To prevent blockage, a pipeline crusher can also be installed in the pipeline connected to the ash unloading device 4.

[0039] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0040] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for treating desulfurization ash in a semi-dry flue gas desulfurization process, characterized in that: The specific contents include: Mixing desulfurization ash from a semi-dry desulfurization system with water in a reaction container to prepare a desulfurization ash slurry; A flue gas is drawn out from the front of the semi-dry desulfurization absorption tower and introduced into the prepared desulfurization ash slurry in the reaction vessel. The flue gas volume is adjusted to maintain the slurry oxidation temperature to meet the requirements. During the oxidation process, water is added to the reaction vessel to maintain the slurry concentration, and an oxidizing agent is added to control the oxidation time to match the ash unloading cycle of the semi-dry desulfurization system. After the oxidation of the desulfurized ash slurry is completed, the water and oxidizing agent are stopped from being added, the amount of flue gas introduced into the slurry is increased, and the desulfurized ash slurry is dried until it is in a dry powder state; The flue gas escaping from the reaction vessel is returned to the inlet section of the semi-dry desulfurization absorption tower after dust removal, and the dust collected by the dust removal is returned to the reactor; After oxidation and drying reactions, the dry powdered desulfurization ash is transported and stored in the ash storage, and the next batch of desulfurization ash slurry preparation begins in the reaction container.

2. The method according to claim 1, characterized in that: The concentration of the desulfurized ash slurry is 5-30%, and the slurry oxidation temperature is 70-90°C.

3. A semi-dry flue gas desulfurization process desulfurization ash treatment equipment, used to implement the method of claim 1 or 2, characterized in that: The invention comprises an oxidation fan (1), an oxidation reactor (2) and a dust collector (3); the inlet of the oxidation fan (1) is connected to the flue before the semi-dry desulfurization absorption tower, and the outlet of the dust collector (3) is connected to the inlet section of the semi-dry desulfurization absorption tower; the oxidation reactor (2) is provided with a feed port (201), a discharge port (202), an air inlet (203), an air outlet (204), a return port (205), a water inlet (206) and an oxidation aid inlet (207); the feed port (201) of the oxidation reactor (2) is connected to the desulfurization ash discharge port of the semi-dry desulfurization system, the discharge port (202) is connected to the desulfurization ash storage (5) through an ash discharge device (4), the air inlet (203) is connected to the outlet of the oxidation fan (1), the air outlet (204) is connected to the inlet of the dust collector (3), and the return port (205) is connected to the ash discharge port of the dust collector (3).

4. The desulfurization ash treatment equipment of the semi-dry flue gas desulfurization process according to claim 3 is characterized in that: The oxidation fan (1) is a variable frequency adjustable fan and is provided with an adjustable damper.

5. The desulfurization ash treatment equipment of the semi-dry flue gas desulfurization process according to claim 3 is characterized by: The oxidation aid inlet (207) of the oxidation reactor (2) is connected to an external oxidation aid supply device.

6. The desulfurization ash treatment equipment of the semi-dry flue gas desulfurization process according to claim 3 is characterized by: A stirring device is provided inside the oxidation reactor (2).

7. The desulfurization ash treatment equipment of the semi-dry flue gas desulfurization process according to claim 3 is characterized by: The feed inlet (201), air inlet (203), water inlet (206) and oxidation aid inlet (207) of the oxidation reactor (2) are all provided with flow metering instruments and control valves.

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