A desulfurization and dust removal ash recycling system

Abstract

The present application relates to a kind of desulfurization dust removal ash recycling system, belong to flue gas desulfurization technical field.The system includes ash collection unit, return unit, fresh reactant dosing unit, detection unit and control unit.Ash collection unit is communicated with desulfurization dust removal equipment, for collecting the ash containing calcium content 20% or more;Return unit sprays the collected ash into furnace again to participate in the reaction;Detection unit obtains the parameters such as flue gas sulfur dioxide concentration or ash calcium content in real time;Control unit dynamically adjusts ash return flow according to detection parameters, and synchronously reversely adjusts fresh reactant dosage.The present application uses high calcium ash as secondary reactant, reduces the calcium content of final ash to about 10%, realizes solid waste reduction and resource utilization;At the same time, through intelligent collaborative control, it significantly saves fresh reactant consumption while ensuring stable desulfurization efficiency, with significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, specifically a desulfurization, dust removal, and ash recycling system. Background Technology

[0002] Circulating fluidized bed boilers are widely used in industrial production due to their wide fuel adaptability and high combustion efficiency. To achieve ultra-low sulfur dioxide emissions, in-furnace calcium injection desulfurization technology is commonly used. This involves injecting calcium-based reactants such as limestone powder into the furnace, where they decompose at high temperatures to generate calcium oxide. This calcium oxide reacts with sulfur dioxide in the flue gas to form calcium sulfate, thus achieving desulfurization. Part of the solid products generated from the reaction are discharged with the slag, while the majority are collected by subsequent dust removal equipment along with the flue gas, forming the desulfurization, dust removal, and ash discharge. With increasingly stringent environmental standards, the dosage of desulfurization reactants is constantly increasing, leading to a corresponding increase in the amount of desulfurization, dust removal, and ash discharge. How to effectively handle this ash discharge has become a practical problem for enterprises.

[0003] In existing technologies, desulfurization and dust removal ash is usually treated as solid waste and directly transported off-site for disposal, or simply landfilled. However, actual testing has revealed that these ash ash ash often contains a large amount of incompletely reacted calcium-based reactants, with calcium content reaching over 20%. Direct discharge not only wastes reactant resources and increases the company's reagent procurement costs, but also exacerbates the environmental burden of solid waste disposal. Although some studies have attempted to return the ash ash to the furnace for reuse, existing solutions mostly adopt a simple direct return method, lacking coordinated control of the return flow rate and the amount of fresh reactant added. This makes it difficult to optimize the reactant dosage while ensuring desulfurization efficiency, and it cannot be dynamically adjusted according to different operating conditions, resulting in persistent problems of system instability or reagent waste. Summary of the Invention

[0004] In order to solve the problems of the prior art, the present invention provides a desulfurization, dust removal, ash discharge and recycling system.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: Firstly, a desulfurization, dust removal, and ash removal recycling system is applied to a furnace and desulfurization and dust removal equipment connected thereto, comprising: The ash collection unit has its inlet connected to the ash discharge port of the desulfurization and dust removal equipment, and is used to collect calcium-containing ash. The return unit has its inlet connected to the outlet of the ash collection unit and its outlet connected to the return material injection inlet of the furnace, forming an ash discharge circulation loop. A fresh reactant dosing unit is used to add fresh reactants to the furnace or desulfurization system; The detection unit is used to acquire parameters related to the desulfurization effect in real time or intermittently; The control unit is communicatively connected to the return unit, the fresh reactant dosing unit, and the detection unit, respectively. The control unit is configured as follows: Based on the parameters obtained by the detection unit, the flow rate of the return unit injecting calcium-containing ash into the furnace is adjusted. Furthermore, the amount of fresh reactant added is adjusted according to the return flow rate of the calcium-containing ash discharge unit to maintain desulfurization efficiency and reduce the consumption of fresh reactant.

[0006] In one specific embodiment of the first aspect, the detection unit includes an online monitoring instrument for detecting the concentration of sulfur dioxide in the flue gas after desulfurization, or an analyzer for detecting the calcium content in the ash discharged from the ash collection unit.

[0007] In one specific embodiment of the first aspect, the return unit includes a pneumatic conveying pipeline and a flow regulating valve disposed on the pipeline, the flow regulating valve being controlled by the control unit.

[0008] Secondly, a method for desulfurization, dust removal, and ash recycling includes the following steps: S1, collects calcium-containing ash discharged from the desulfurization and dust removal equipment; S2, the collected calcium-containing ash is injected into the furnace through the return unit, so that the residual calcium-containing components can participate in the reaction again at high temperature; S3 monitors the operating parameters of the desulfurization system in real time through the detection unit; S4, the control unit dynamically adjusts the return flow rate of the calcium-containing ash discharge according to the operating parameters obtained in S3; S5, the control unit adjusts the amount of fresh reactant added synchronously and in reverse according to the return flow rate determined in S4; S6 discharges the ash residue with reduced calcium content produced after the second reaction from the system.

[0009] In one specific embodiment of the second aspect, the initial calcium content of the calcium-containing ash during collection is above 20%, and after being reacted again in the furnace, the calcium content of the discharged ash is reduced to below 10%.

[0010] In one specific implementation of the second aspect, the "synchronous and reverse adjustment" in step S5 specifically means: when the return flow increases, the control unit reduces the amount of fresh reactant added by the fresh reactant addition unit; when the return flow decreases, the control unit increases the amount of fresh reactant added by the fresh reactant addition unit.

[0011] In one specific embodiment of the second aspect, the operating parameters in step S3 include at least one of the following: sulfur dioxide concentration at the flue gas outlet, furnace temperature, or calcium content in the discharged ash.

[0012] The beneficial effects of this invention are as follows: 1. By constructing an ash recycling loop, the high-calcium ash discharged from desulfurization and dust removal equipment is collected and re-injected into the furnace to participate in the reaction, achieving solid waste reduction and deep utilization of residual reactants. Specifically, the initial calcium content of the calcium-containing ash discharged from desulfurization and dust removal equipment is usually above 20%, containing a large amount of unreacted calcium-based reactants. Direct discharge not only wastes resources but also increases solid waste treatment costs. This invention uses a return unit to quantitatively inject these high-calcium ash into the high-temperature zone of the furnace, allowing the residual calcium oxide or calcium hydroxide to react again with sulfur dioxide in the flue gas to generate calcium sulfate, thereby reducing the calcium content of the final discharged ash to about 10%. This technology not only significantly reduces the amount of final ash generated and achieves waste resource utilization, but also improves the overall utilization rate of calcium-based reactants by extending the residence time of the reactants in the system, reducing the solid load entering the desulfurization and dust removal equipment from the source.

[0013] 2. This invention further constructs an intelligent collaborative adjustment mechanism based on real-time operating parameters by introducing a detection unit and a control unit. The detection unit acquires key parameters such as flue gas sulfur dioxide concentration, calcium content in ash discharge, or furnace temperature in real time. The control unit dynamically adjusts the return flow rate of calcium-containing ash discharge based on these parameters and simultaneously adjusts the dosage of fresh reactant in the reverse direction. When the return flow rate increases, the control unit correspondingly reduces the dosage of fresh reactant; when the return flow rate decreases, the dosage of fresh reactant increases. This closed-loop control logic ensures that the total effective calcium content in the system always matches the desulfurization load, maximizing the conservation of fresh desulfurization reactant consumption while maintaining a stable and compliant sulfur dioxide concentration in the emitted flue gas. Simultaneously, since the returned ash has been pre-treated by the dust removal system, the particles are fine and uniformly distributed. After being injected into the furnace, it can quickly disperse and fully contact the flue gas, further enhancing the gas-solid reaction efficiency. Therefore, it achieves multiple technical effects overall, including improved desulfurization efficiency, reduced reactant consumption, and reduced solid waste emissions. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the desulfurization, dust removal, and ash recycling system of the present invention.

[0015] Figure 2 This is a schematic diagram of the desulfurization, dust removal, ash discharge, and recycling method of the present invention. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figures 1 to 2 The above describes a desulfurization, dust removal, and ash recycling system.

[0018] Example 1: System Structure Example Figure 1 This is a schematic diagram of the desulfurization, dust removal, and ash recycling system provided in an embodiment of the present invention. Figure 1 As shown, the system is applied to a circulating fluidized bed boiler (hereinafter referred to as the furnace) 101 and a desulfurization and dust removal device 102 connected thereto.

[0019] The system mainly includes: ash collection unit 200, return unit 300, fresh reactant addition unit 400, detection unit 500, and control unit 600.

[0020] The ash collection unit 200 is used to collect calcium-containing ash discharged from the desulfurization and dust removal equipment 102. In one specific embodiment, the desulfurization and dust removal equipment 102 can be a bag filter or an electrostatic precipitator / bag filter hybrid dust collector, and its ash hopper outlet is connected to the inlet of the ash collection unit 200 through a pipe. Specifically, the ash collection unit 200 can be an intermediate ash silo. A silo top dust collector can be installed at the top of the silo to prevent secondary dust generation, and a discharge device, such as a rotary valve or a gate valve, is provided at the bottom to control the ash discharge output. The initially collected calcium-containing ash typically has a calcium content of over 20%, for example, reaching 25%-30%. This portion of the ash still contains a large amount of unreacted calcium-based reactants.

[0021] The return unit 300 is used to transport calcium-containing ash from the ash collection unit 200 back to the furnace 101 to participate in the reaction again. The inlet of the return unit 300 is connected to the outlet of the ash collection unit 200 (such as below the rotary valve), and the outlet is connected to the return material inlet of the furnace 101, thus forming a complete ash discharge circulation loop. The return unit 300 may specifically include a pneumatic conveying pipe 301 and a flow regulating valve 302 installed on the pipe. The pneumatic conveying uses compressed air as a power source to blow the calcium-containing ash into the furnace 101 through the pipe. The flow regulating valve 302 can be an electric regulating valve or a pneumatic regulating valve, and its opening degree is controlled by the control unit 600 to precisely regulate the amount of ash returned to the furnace per unit time. To ensure smooth conveying, wear-resistant elbows can be installed at pipe bends.

[0022] The fresh reactant dosing unit 400 is used to add fresh reactants, such as limestone powder or hydrated lime, to the furnace 101 or desulfurization system. This unit typically includes a reactant storage silo 401, a feeder 402 (such as a screw feeder or rotary feeder valve), and associated conveying pipelines. The rotational speed or feeding frequency of the feeder 402 is controlled by a control unit 600, thereby regulating the amount of fresh reactant added.

[0023] The detection unit 500 is used to acquire parameters related to the desulfurization effect in real time or intermittently, providing feedback signals to the control unit. In this embodiment, the detection unit 500 may include various instruments: Flue gas online monitoring instrument 501: installed on the flue downstream of the desulfurization and dust removal equipment 102, used to detect the concentration of sulfur dioxide (SO2) in the emitted flue gas in real time.

[0024] Calcium content analyzer 502: Installed on the ash collection unit 200 or its outlet pipe, it is used to detect the residual calcium content of the collected ash in real time or at regular intervals. This analyzer can employ online detection equipment such as X-ray fluorescence analyzer or laser-induced breakdown spectroscopy analyzer.

[0025] Temperature sensor 503: Installed inside furnace 101, used to monitor the temperature of the reaction zone.

[0026] The control unit 600 is the core of this system. The control unit 600 can be a distributed control system (DCS) or a programmable logic controller (PLC). The control unit 600 is connected to the flow regulating valve 302 of the return unit 300, the feeder 402 of the fresh reactant addition unit 400, and the various instruments (501, 502, 503) of the detection unit 500 via signal cables.

[0027] Control unit 600 is configured to execute the following core control logic: The receiver detects real-time parameters acquired by the receiver 500, such as flue gas SO2 concentration, calcium content in ash discharge, or furnace temperature.

[0028] Based on the preset desulfurization efficiency target value (e.g., SO2 emission concentration below 35 mg / Nm³), 3 Based on the current parameters, the system automatically calculates and adjusts the opening of the flow regulating valve 302 using a PID control algorithm or a feedforward-feedback composite control algorithm, thereby controlling the return flow of calcium-containing ash discharge.

[0029] Simultaneously, the control unit 600 dynamically calculates the required amount of fresh reactant based on the current return flow rate and the real-time calcium content of the discharged ash (if the detection unit includes a calcium content analyzer), and adjusts the speed of the feeder 402 accordingly. The core adjustment logic is: when the return flow rate of calcium-containing discharged ash increases, the control unit 600 instructs the feeder 402 to reduce its speed, decreasing the amount of fresh reactant added; conversely, when the return flow rate decreases, the amount of fresh reactant added increases. This maintains a relatively stable total effective calcium content entering the system, ensuring desulfurization efficiency while maximizing the conservation of fresh reactant.

[0030] Example 2: Method Example This embodiment describes a method for recycling desulfurization, dust removal, and ash discharge based on the above system. The method includes the following steps: S1, collect calcium-containing ash.

[0031] The unloading device of the ash collection unit 200 is activated to collect the calcium-containing ash deposited in the ash hopper of the desulfurization and dust removal equipment 102 into the intermediate ash silo. Testing revealed that the initial calcium content of this ash was 22%.

[0032] S2, return ash discharge into the furnace.

[0033] The pneumatic conveying system of the return unit 300 is activated, and the initial return flow rate is set via the control unit 600. Calcium-containing ash is injected through pipe 301 from the return inlet of furnace 101 (e.g., located in the reduction zone or at the return feeder in the middle of the furnace), mixing with the high-temperature flue gas inside the furnace. The residual CaO or Ca(OH)2 in the ash reacts again with SO2 at a high temperature of 850℃-950℃ to generate CaSO4, thus realizing the secondary utilization of residual calcium in the ash.

[0034] S3 monitors operating parameters in real time.

[0035] During system operation, the detection unit 500 operates continuously. The flue gas online monitoring instrument 501 sends SO2 emission concentration data to the control unit 600 in real time. At the same time, the calcium content analyzer 502 also periodically feeds back the calcium content data of the ash and slag in the ash collection unit 200 to the control unit 600.

[0036] S4 dynamically adjusts the return traffic.

[0037] The control unit 600 received an SO2 emission concentration of 28 mg / Nm³. 3 Slightly higher than the set target value of 25 mg / Nm 3 Meanwhile, the calcium content of the discharged ash was displayed as 18%. According to the preset control program (for example, when the SO2 emission concentration increases, the return flow of circulating ash is increased first), the control unit 600 issued a command to increase the opening of the flow regulating valve 302 from the current 40% to 50%, thereby increasing the return flow of calcium-containing discharged ash.

[0038] S5, synchronously adjust the amount of fresh reactant added.

[0039] While increasing the return flow rate, the control unit 600 immediately calculates the amount of fresh reactant that should be reduced based on a pre-established material balance model (considering the return ash flow rate and calcium content, as well as the purity of the fresh reactant), and issues a command to reduce the speed of the feeder 402, reducing the limestone powder dosage from 1.2 tons / hour to 1.0 tons / hour. This process is automatic, synchronous, and reverse-biased.

[0040] S6, discharge the final ash residue.

[0041] The calcium content of the ash residue after the second reaction has been reduced from the initial 22% to 9%, and it is finally discharged through the ash removal system of the desulfurization and dust removal equipment 102, achieving waste reduction and resource utilization. Throughout the process, the SO2 emission concentration remains stable at 25 mg / Nm³. 3 The following have met the requirements for low-emission retrofitting.

[0042] Other embodiments Based on the above embodiments, various modifications can be made.

[0043] For example, the detection unit 500 may only include the online flue gas monitor 501. In this case, the adjustment logic of the control unit 600 can be simplified as follows: based primarily on the SO2 emission concentration. When the SO2 concentration is higher than the upper limit, the return flow rate is increased first until it reaches the preset maximum value; if the SO2 concentration still does not meet the standard, then the addition of fresh reactant is considered. When the SO2 concentration is lower than the lower limit, the amount of fresh reactant added is reduced first until it reaches the minimum safe addition amount; if the SO2 concentration is still too low, then the return flow rate is considered to be reduced.

[0044] For example, the return unit 300 can also use a mechanical conveying method, such as a bucket elevator combined with a screw conveyor, to lift the ash and slag from the ash collection unit 200 and transport it to the feed port at the top of the furnace, where it falls into the furnace by gravity. In this case, flow rate regulation is achieved by controlling the operating speed of the mechanical conveying equipment.

[0045] In summary, this invention constructs a closed-loop system that includes ash collection, return, detection, and automatic control, reusing the high-calcium ash generated during desulfurization and dust removal as a secondary reactant. This not only significantly reduces the calcium content of the final ash residue (from over 20% to around 10%), achieving solid waste reduction, but more importantly, through intelligent coordinated control, it greatly saves the amount of fresh desulfurization reactant used, resulting in significant economic and environmental benefits.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A desulfurization, dust removal, and ash recycling system, applied to a furnace and connected desulfurization and dust removal equipment, characterized in that, include: The ash collection unit has its inlet connected to the ash discharge port of the desulfurization and dust removal equipment, and is used to collect calcium-containing ash. The return unit has its inlet connected to the outlet of the ash collection unit and its outlet connected to the return material injection inlet of the furnace, forming an ash discharge circulation loop. A fresh reactant dosing unit is used to add fresh reactant to the furnace or desulfurization system; The detection unit is used to acquire parameters related to the desulfurization effect in real time or intermittently; The control unit is communicatively connected to the return unit, the fresh reactant dosing unit, and the detection unit, respectively. The control unit is configured as follows: Based on the parameters obtained by the detection unit, the flow rate of the return unit injecting calcium-containing ash into the furnace is adjusted. Furthermore, the amount of fresh reactant added is adjusted according to the return flow rate of the calcium-containing ash discharge unit to maintain desulfurization efficiency and reduce the consumption of fresh reactant.

2. The desulfurization, dust removal, and ash recycling system according to claim 1, characterized in that, The detection unit includes an online monitoring instrument for detecting the sulfur dioxide concentration in the flue gas after desulfurization, or an analyzer for detecting the calcium content in the ash discharged from the ash collection unit.

3. The desulfurization, dust removal, and ash recycling system according to claim 1, characterized in that, The return unit includes a pneumatic conveying pipeline and a flow regulating valve installed on the pipeline, the flow regulating valve being controlled by the control unit.

4. A method for desulfurization, dust removal, and ash recycling, characterized in that, Includes the following steps: S1, collects calcium-containing ash discharged from the desulfurization and dust removal equipment; S2, the collected calcium-containing ash is injected into the furnace through the return unit, so that the residual calcium-containing components can participate in the reaction again at high temperature; S3 monitors the operating parameters of the desulfurization system in real time through the detection unit; S4, the control unit dynamically adjusts the return flow rate of the calcium-containing ash discharge according to the operating parameters obtained in S3; S5, the control unit adjusts the amount of fresh reactant added synchronously and in reverse according to the return flow rate determined in S4; S6 discharges the ash residue with reduced calcium content produced after the second reaction from the system.

5. The method according to claim 4, characterized in that, The calcium-containing ash has an initial calcium content of over 20% when collected, and after being reacted again in the furnace, the calcium content of the discharged ash is reduced to below 10%.

6. The method according to claim 4, characterized in that, The "synchronous and reverse adjustment" mentioned in step S5 specifically means: when the return flow rate increases, the control unit reduces the amount of fresh reactant added by the fresh reactant addition unit; when the return flow rate decreases, the control unit increases the amount of fresh reactant added by the fresh reactant addition unit.

7. The method according to claim 4, characterized in that, The operating parameters mentioned in step S3 include at least one of the following: sulfur dioxide concentration at the flue gas outlet, furnace temperature, or calcium content in the discharged ash.

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