System for removing calcium from papermaking wastewater by using boiler tail gas and use method of system

Abstract

The invention provides a system for removing calcium from papermaking wastewater by using boiler tail gas and a use method of the system. The system comprises a calcium removal reaction tank, a sedimentation tank, a pre-acidification tank, an anaerobic reactor, a biogas pressure stabilizing cabinet, a biogas boiler and a booster fan which are connected in sequence, the system is also provided with an intelligent monitoring module, and the intelligent monitoring module is used for carrying out online real-time monitoring on the system. A central controller is further arranged and used for controlling all the modules to be regulated and controlled to operate. The method provided by the invention realizes treatment of wastes with wastes, effectively reduces the hardness of calcium in wastewater, prevents calcification of the anaerobic reactor, has the advantages of low operation cost and high treatment efficiency, reduces greenhouse gas emission, and has significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and resource utilization technology, and in particular to a system and method for removing calcium from papermaking wastewater using boiler exhaust gas. Background Technology

[0002] Wastewater from the paper industry typically contains high concentrations of calcium ions, primarily originating from calcium carbonate fillers, raw materials, and water used in the papermaking process. When this high-calcium wastewater enters an anaerobic biological treatment system, the calcium ions combine with carbonate ions within the anaerobic reactor to form calcium carbonate precipitates. This leads to calcification of the anaerobic sludge, a reduction in the effective reactor volume, and a decrease in treatment efficiency; in severe cases, it can paralyze the entire anaerobic system.

[0003] Paper mill wastewater contains a large amount of calcium ions, mainly from calcium carbonate filler and production water. High-calcium wastewater entering anaerobic systems easily leads to problems such as sludge calcification, pipe scaling, and reactor blockage, severely impacting treatment efficiency. While traditional chemical precipitation methods can remove calcium, they are costly and generate large amounts of sludge.

[0004] Meanwhile, the anaerobic treatment of papermaking wastewater generates a large amount of biogas, which is usually utilized through boiler combustion. The exhaust gas contains approximately high concentrations of carbon dioxide. Direct emissions not only waste carbon resources but also exacerbate the greenhouse effect.

[0005] Therefore, there is an urgent need for an integrated system and method that can both efficiently remove calcium and achieve carbon resource recycling. Summary of the Invention

[0006] This invention provides a system and method for removing calcium from papermaking wastewater using boiler exhaust gas. By technically modifying existing wastewater treatment devices, it solves the problems of high operating costs and insufficient energy efficiency and environmental friendliness of existing wastewater treatment equipment.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A system for removing calcium from papermaking wastewater using boiler exhaust gas includes a calcium removal reaction tank, a sedimentation tank, a pre-acidification tank, an anaerobic reactor, a biogas pressure stabilizing cabinet, a biogas boiler, and a booster fan connected in sequence. The outlet of the calcium removal reaction tank is connected to the inlet of the sedimentation tank, the supernatant outlet of the sedimentation tank is connected to the inlet of the pre-acidification tank, and the outlet of the pre-acidification tank is connected to the anaerobic reactor via an anaerobic feed pump. The biogas outlet of the anaerobic reactor is sequentially connected to a biogas gas-liquid separator, a biogas pressure stabilizing cabinet, and a biogas boiler; the tail gas outlet of the biogas boiler is sequentially connected to a bag filter and a booster fan, and the outlet of the booster fan is connected to a calcium removal reaction tank for reuse. It also includes a pipeline mixer installed at the inlet of the calcium removal reaction tank, and a dosing unit is connected to the outside of the pipeline mixer; It is also equipped with an intelligent monitoring module, which is used to monitor the system online in real time; It is also equipped with a central controller. The calcium removal reaction tank, sedimentation tank, pre-acidification tank, anaerobic reactor, biogas pressure stabilizing cabinet, biogas boiler, booster fan and intelligent monitoring module are all connected to the central controller and are controlled by the central controller.

[0008] Preferably, the intelligent monitoring module includes an online pH monitor installed in the dosing unit, a sludge concentration sensor installed at the bottom of the sedimentation tank, and a C sensor installed at the outlet of the booster blower. Online concentration analyzer.

[0009] Preferably, the dosing unit includes a dosing tank, a dosing agitator, a dosing metering pump, a dosing check valve, a tap water pipe, and an online pH monitor. The dosing agitator is installed inside the dosing tank. The inlet of the dosing metering pump is connected to the dosing tank, and the outlet of the dosing metering pump is connected to the inlet of the pipeline mixer. The dosing check valve is installed on the outlet pipe of the dosing metering pump. The pH online monitoring instrument is installed in the calcium removal reaction tank and is connected to the dosing pump for automatic adjustment of the dosing amount according to the pH value. The pH online monitoring instrument and the dosing pump are electrically connected to the central controller.

[0010] Preferably, the agent added by the dosing unit is either sodium hydroxide or sodium carbonate.

[0011] Preferably, a cyclone aerator is provided at the bottom of the calcium removal reaction tank, and the outlet of the booster blower is used to introduce exhaust gas into the tank through the cyclone aerator. The cyclone aerator is provided with a flange connection structure and a ball valve connected to the gas supply pipeline at the outlet of the booster blower. The air flow rate of the cyclone aerator is 0.4 to 1.0 m³ / min, the service area is 3 to 12 m² / unit, and the material is 304 stainless steel.

[0012] Preferably, the sedimentation tank is equipped with a sludge discharge pipe at the bottom and a sludge concentration sensor is installed above the sedimentation tank. The sludge discharge pipe is also connected to a seed return system for returning part of the sludge to the calcium removal reaction tank.

[0013] Preferably, the seed reflux system includes a seed reflux pump and a seed reflux pipe. The sludge discharge pipe is connected to the calcium removal reaction tank through the seed reflux pump and the seed reflux pipe. The seed reflux pump is electrically connected to the sludge concentration sensor and the central controller. The seed reflux system automatically adjusts the flow rate of the seed reflux pump by receiving feedback from the sludge concentration sensor through the central controller.

[0014] Preferably, the sludge discharge pipe is also equipped with a backwash pipe for flushing the sludge discharge pipe, and the backwash pipe is connected to an external high-pressure water source.

[0015] Preferably, the exhaust pipe is also equipped with an emergency exhaust valve, and the booster fan outlet is equipped with a C... Online concentration analyzer, the C Electrical connection settings between the online concentration analyzer and the system's central controller.

[0016] The above-mentioned system for removing calcium from papermaking wastewater using boiler exhaust gas includes the following steps: S1. Wastewater containing high concentrations of calcium ions is introduced into a calcium removal reaction tank, while simultaneously being supplied with biogas boiler exhaust gas. The reaction conditions are controlled to ensure that calcium ions react with C... The reaction produces calcium carbonate precipitate; S2. After the reaction, the wastewater enters the sedimentation tank for solid-liquid separation. S3. The supernatant from the sedimentation tank enters the pre-acidification tank to adjust the acidity, and then enters the anaerobic reactor for anaerobic treatment. S4. The biogas produced by the anaerobic reactor is separated into gas and liquid by a biogas gas-liquid separator. After gas-liquid separation, the tail gas enters the biogas pressure stabilizing cabinet for pressure stabilization. S5. After pressure stabilization, it is sent to the biogas boiler for combustion. S6, the carbon-rich substances produced after exhaust combustion After the exhaust gas is removed by the bag filter, it is pressurized by the booster fan and sent to the cyclone aerator at the bottom of the calcium removal reaction tank for reuse.

[0017] The beneficial effects of this invention are as follows: This application effectively utilizes the exhaust gas from biogas combustion as a calcium removal agent, reducing the calcium hardness of wastewater while simultaneously realizing the resource utilization of carbon dioxide in the exhaust gas, significantly reducing carbon emission intensity. It not only reduces the consumption cost of traditional calcium removal agents but also provides a practical and feasible technical path to promote carbon reduction and contribute to the industry's carbon neutrality goals through a "waste-to-waste" circular model.

[0018] 1. Waste-to-waste treatment and resource recycling: This application achieves "waste-to-waste treatment" by recycling exhaust gas C As a calcium remover, it reduces the cost of the pharmaceutical agent; 2. Effectively prevents calcification: This application removes calcium ions before anaerobic digestion, effectively preventing calcification and scaling in the anaerobic system; 3. High mixing efficiency: This application is equipped with a pipeline mixer and a cyclone aerator at the inlet of the calcium removal reaction tank to achieve efficient mixing in the reaction tank; 4. Anti-clogging and durable: The cyclone aerator installed in this application is made of 304 stainless steel and flange connection, which is corrosion resistant and easy to clean; 5. High level of intelligence: This application is equipped with an intelligent monitoring module, which monitors pH, sludge concentration, and C. Concentration monitoring enables automatic system optimization; 6. High degree of resource utilization; This application is equipped with a seed crystal reflux system, which can improve the quality of calcium carbonate crystallization and facilitate recycling. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the present invention; Figure 2 This is a process flow diagram of the present invention; The reference numerals are: calcium removal reaction tank (1-1), pipeline mixer (1-2), and swirl aerator (1-3). Sedimentation tank (2-1), sludge concentration sensor (2-2), sludge discharge pipe (2-3), backwash pipe (2-4), seed crystal return pump (2-5), seed crystal return pipe (2-6); Pre-acidification tank (3-1), anaerobic feed pump (3-2); Anaerobic reactor (4-1), biogas gas-liquid separator (4-2); Biogas pressure stabilizing unit (5-1); Biogas boiler (6-1), tail gas discharge pipe (6-2), emergency exhaust valve (6-3); Booster fan (7-1), bag filter (7-2), C Online concentration analyzer (7-3); Chemical dosing tank (8-1), chemical dosing agitator (8-2), chemical dosing metering pump (8-3), chemical dosing check valve (8-4), tap water pipe (8-5), pH online monitor (8-6). Detailed Implementation

[0020] The specific content of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0021] Please see Figure 1-2As shown, the present invention provides a system and method for removing calcium from papermaking wastewater using boiler exhaust gas, comprising a calcium removal reaction tank (1-1), a sedimentation tank (2-1), a pre-acidification tank (3-1), an anaerobic reactor (4-1), a biogas pressure stabilizing cabinet (5-1), a biogas boiler (6-1), and a booster fan (7-1) connected in sequence. The outlet of the calcium removal reaction tank (1-1) is connected to the inlet of the sedimentation tank (2-1), the supernatant outlet of the sedimentation tank (2-1) is connected to the inlet of the pre-acidification tank (3-1), and the outlet of the pre-acidification tank (3-1) is connected to the anaerobic reactor (4-1) through the anaerobic feed pump (3-2). The biogas outlet of the anaerobic reactor (4-1) is sequentially connected to the biogas gas-liquid separator (4-2), the biogas pressure stabilizing cabinet (5-1), and the biogas boiler (6-1); the tail gas outlet of the biogas boiler (6-1) is sequentially connected to the bag filter (7-2) and the booster fan (7-1), and the outlet of the booster fan (7-1) is connected to the calcium removal reaction tank (1-1) for reuse; It also includes a pipeline mixer (1-2) installed at the inlet end of the calcium removal reaction tank (1-1), and a dosing unit is also connected to the outside of the pipeline mixer (1-2); It is also equipped with an intelligent monitoring module, which is used to monitor the system online in real time; It is also equipped with a central controller. The calcium removal reaction tank (1-1), sedimentation tank (2-1), pre-acidification tank (3-1), anaerobic reactor (4-1), biogas pressure stabilizing cabinet (5-1), biogas boiler (6-1), booster fan (7-1) and intelligent monitoring module are all connected to the central controller and are controlled by the central controller.

[0022] Furthermore, in order to enable real-time monitoring of the system, the intelligent monitoring module includes an online pH monitor (8-6) installed in the dosing unit, a sludge concentration sensor installed at the bottom of the sedimentation tank (2-1), and a C sensor installed at the outlet of the booster blower (7-1). Online concentration analyzer (7-3).

[0023] Furthermore, in order to achieve intelligent control, real-time regulation of dosing, and reduce operating costs, the dosing unit includes a dosing tank (8-1), a dosing agitator (8-2), a dosing metering pump (8-3), a dosing check valve (8-4), a tap water pipe (8-5), and a pH online monitor (8-6). The dosing agitator (8-2) is installed inside the dosing tank (8-1). The inlet of the dosing metering pump (8-3) is connected to the dosing tank (8-1), and the outlet of the dosing metering pump (8-3) is connected to the inlet of the pipeline mixer (1-2). The dosing check valve (8-4) is installed on the outlet pipe of the dosing metering pump (8-3). The pH online monitoring instrument (8-6) is installed in the calcium removal reaction tank (1-1) and is connected to the dosing metering pump (8-3) for automatically adjusting the dosing amount according to the pH value. The pH online monitoring instrument (8-6) and the dosing metering pump (8-3) are electrically connected to the central controller.

[0024] Furthermore, the agent added by the dosing unit is either sodium hydroxide or sodium carbonate.

[0025] Furthermore, a cyclone aerator (1-3) is provided at the bottom of the calcium removal reaction tank (1-1). The outlet of the booster blower (7-1) is used to introduce tail gas into the tank through the cyclone aerator (1-3). The cyclone aerator (1-3) is provided with a flange connection structure and a ball valve connected to the gas supply pipeline at the outlet of the booster blower (7-1). The swirl aerator (1-3) has an air flow rate of 0.4–1.0 m³ / min, a service area of ​​3–12 m² / unit, and is made of 304 stainless steel. The swirl aerator (1-3) generates strong swirling bubbles, providing the necessary carbon dioxide for the reaction. This also ensures thorough mixing of the fluids within the reaction tank. Regularly cleaning the cyclone aerator (1-3) with a 5%~10% hydrochloric acid solution (e.g., once a month) can effectively remove scale.

[0026] Furthermore, a sludge discharge pipe (2-3) is provided at the bottom of the sedimentation tank (2-1), a sludge concentration sensor (2-2) is provided above the sedimentation tank (2-1), and a seed return system for returning part of the sludge to the calcium removal reaction tank (1-1) is also connected to the sludge discharge pipe (2-3).

[0027] Furthermore, the seed reflux system includes a seed reflux pump (2-5) and a seed reflux pipe (2-6). The sludge discharge pipe (2-3) is connected to the calcium removal reaction tank (1-1) through the seed reflux pump (2-5) and the seed reflux pipe (2-6). The seed reflux pump (2-5) and the sludge concentration sensor (2-2) are electrically connected to the central controller. The seed reflux system automatically adjusts the flow rate of the seed reflux pump (2-5) by receiving feedback from the sludge concentration sensor (2-2) through the central controller.

[0028] Furthermore, in order to flush the sludge discharge pipe (2-3) and prevent blockage, a backwash pipe (2-4) for flushing the sludge discharge pipe (2-3) is also installed on the sludge discharge pipe (2-3), and the backwash pipe (2-4) is connected to an external high-pressure water source.

[0029] Furthermore, an emergency exhaust valve (6-3) is also installed on the exhaust pipe (6-2), and a C-type exhaust valve is installed at the outlet of the booster fan (7-1). Online concentration analyzer (7-3), the C The concentration online analyzer (7-3) is electrically connected to the system's central controller.

[0030] The above-mentioned system for removing calcium from papermaking wastewater using boiler exhaust gas includes the following steps: S1. Wastewater containing high concentrations of calcium ions is introduced into the calcium removal reaction tank (1-1), while simultaneously introducing tail gas from the biogas boiler (6-1). The reaction conditions are controlled to allow calcium ions to react with C. The reaction produces calcium carbonate precipitate; S2. After the reaction, the wastewater enters the sedimentation tank (2-1) for solid-liquid separation; S3. The supernatant from the sedimentation tank (2-1) enters the pre-acidification tank (3-1) to adjust the water quality, and then enters the anaerobic reactor (4-1) for anaerobic treatment; S4. The biogas produced by the anaerobic reactor (4-1) is separated into gas and liquid by the biogas gas-liquid separator (4-2). After gas-liquid separation, the tail gas enters the biogas pressure stabilizing cabinet (5-1) for pressure stabilization. S5. After pressure stabilization, it is sent to the biogas boiler (6-1) for combustion treatment; S6, the carbon-rich substances produced after exhaust combustion After the exhaust gas is removed by the bag filter (7-2), it is pressurized by the booster fan (7-1) and transported to the cyclone aerator (1-3) at the bottom of the calcium removal reaction tank (1-1) for reuse.

[0031] Specifically, in use: wastewater containing high concentrations of calcium ions first enters the pipeline mixer (1-2), where it mixes with the alkaline reagent added by the dosing unit before entering the calcium removal reaction tank (1-1). A swirl aerator (1-3) is installed at the bottom of the tank, through which carbon-rich gas from the biogas boiler (6-1) is introduced. Exhaust gas promotes Ca With C The reaction produces CaC precipitation.

[0032] After the reaction, the wastewater enters the sedimentation tank (2-1) for solid-liquid separation. The sedimentation tank (2-1) is equipped with a sludge concentration sensor (2-2) and a seed crystal return system. Part of the sludge is returned to the calcium removal reaction tank (1-1) as seed crystals to improve crystallization efficiency. A backwash pipe (2-4) is installed on the sludge discharge pipe (2-3) to prevent clogging.

[0033] The effluent from the sedimentation tank (2-1) enters the pre-acidification tank (3-1) to adjust the pH and acidification degree, and then is sent to the anaerobic reactor (4-1) for anaerobic treatment via the anaerobic feed pump (3-2). The biogas produced is purified by the gas-liquid separator (4-2) and then enters the biogas pressure stabilizing cabinet (5-1), and then sent to the biogas boiler (6-1) for combustion.

[0034] After the combustion exhaust gas is filtered by the bag filter (7-2), it is pressurized by the booster fan (7-1) and then passes through C After monitoring by the online concentration analyzer (7-3), the solution is recycled back to the calcium removal reaction tank (1-1), forming a closed-loop resource cycle.

[0035] The dosing unit automatically adjusts the dosage based on feedback from the online pH monitor (8-6), prioritizing the use of wastewater alkalinity, and adding NaOH or N2 when necessary. C .

[0036] This application effectively utilizes the exhaust gas from biogas combustion as a calcium removal agent, reducing the calcium hardness of wastewater while simultaneously realizing the resource utilization of carbon dioxide in the exhaust gas, significantly reducing carbon emission intensity. It not only reduces the consumption cost of traditional calcium removal agents but also provides a practical and feasible technical path to promote carbon reduction and contribute to the industry's carbon neutrality goals through a "waste-to-waste" circular model.

[0037] 1. Waste-to-waste treatment and resource recycling: This application achieves "waste-to-waste treatment" by recycling exhaust gas C As a calcium remover, it reduces the cost of the pharmaceutical agent; 2. Effectively prevents calcification: This application removes calcium ions before anaerobic digestion, effectively preventing calcification and scaling in the anaerobic system; 3. High mixing efficiency: This application has a pipeline mixer (1-2) and a swirl aerator (1-3) installed at the inlet end of the calcium removal reaction tank (1-1) to achieve efficient mixing in the reaction tank; 4. Anti-clogging and durable: The cyclone aerators (1-3) provided in this application are made of 304 stainless steel and connected by flanges, which are corrosion resistant and easy to clean; 5. High level of intelligence: This application is equipped with an intelligent monitoring module, which monitors pH, sludge concentration, and C. Concentration monitoring enables automatic system optimization; 6. High degree of resource utilization; This application is equipped with a seed crystal reflux system, which can improve the quality of calcium carbonate crystallization and facilitate recycling.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0039] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art. In addition, the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0040] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or a connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A system for removing calcium from papermaking wastewater using boiler exhaust gas, characterized by, A system for removing calcium from papermaking wastewater by using boiler tail gas and a method for using the same, comprising a calcium removal reaction tank, a sedimentation tank, a pre-acidification tank, an anaerobic reactor, a biogas pressure stabilizing tank, a biogas boiler and a booster fan connected in sequence; The outlet of the calcium removal reaction tank is connected to the inlet of the sedimentation tank, the supernatant outlet of the sedimentation tank is connected to the inlet of the pre-acidification tank, and the outlet of the pre-acidification tank is connected to the anaerobic reactor through an anaerobic feeding pump; The biogas outlet of the anaerobic reactor is connected to a biogas gas-liquid separator, a biogas pressure stabilizing tank and a biogas boiler in sequence; the tail gas outlet of the biogas boiler is connected to a bag-type dust collector and a booster fan in sequence, and the outlet of the booster fan is connected to the calcium removal reaction tank for reuse; A pipeline mixer is further arranged at the water inlet end of the calcium removal reaction tank, and a dosing unit is further arranged outside the pipeline mixer; An intelligent monitoring module is further arranged for online real-time monitoring of the system; A central controller is further arranged, and the calcium removal reaction tank, the sedimentation tank, the pre-acidification tank, the anaerobic reactor, the biogas pressure stabilizing tank, the biogas boiler, the booster fan and the intelligent monitoring module are connected to the central controller and are controlled and operated by the central controller.

2. The system for removing calcium from papermaking wastewater using boiler exhaust gas according to claim 1, characterized by, The intelligent monitoring module comprises a pH on-line monitor arranged at the dosing unit, a sludge concentration sensor arranged at the bottom of the sedimentation tank, and a C on-line analyzer arranged at the outlet of the booster fan.

3. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, characterized in that, The dosing unit comprises a dosing tank, a dosing stirrer, a dosing metering pump, a dosing check valve, a tap water pipe and a pH online monitor; the dosing stirrer is arranged in the dosing tank; the inlet of the dosing metering pump is connected to the dosing tank; the outlet of the dosing metering pump is connected to the inlet end of the pipeline mixer; and the dosing check valve is arranged on the outlet pipeline of the dosing metering pump. The pH online monitor is arranged in the calcium removal reaction tank and is signal-connected to the dosing metering pump, so as to automatically adjust the dosing amount according to the pH value; and the pH online monitor and the dosing metering pump are electrically connected to the central controller.

4. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, characterized in that, The dosing agent of the dosing unit is any one of sodium hydroxide or sodium carbonate.

5. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, wherein A cyclone aerator is arranged at the bottom of the calcium removal reaction tank; the outlet of the booster fan is connected to the cyclone aerator to introduce tail gas into the tank; and the cyclone aerator is provided with a flange connection structure and a ball valve which are connected to the gas supply pipeline of the outlet of the booster fan. The aeration capacity of the cyclone aerator is 0.4-1.0 m³ / min, the service area is 3-12 m² per unit, and the material is 304 stainless steel.

6. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, wherein A sludge discharge pipe is arranged at the bottom of the sedimentation tank, and a sludge concentration sensor is arranged above the sedimentation tank; a seed backflow system for backflowing part of the sludge to the calcium removal reaction tank is further arranged on the sludge discharge pipe.

7. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, wherein The seed backflow system comprises a seed backflow pump and a seed backflow pipe; the sludge discharge pipe is connected to the calcium removal reaction tank through the seed backflow pump and the seed backflow pipe; the seed backflow pump and the sludge concentration sensor are electrically connected to the central controller; and the seed backflow system automatically adjusts the flow of the seed backflow pump by receiving the feedback of the sludge concentration sensor through the central controller.

8. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, wherein A backwashing pipe for flushing the sludge discharge pipe is further arranged on the sludge discharge pipe and is connected to an external high-pressure water source.

9. The system for removing calcium from papermaking wastewater using boiler exhaust according to claim 1, wherein The tail gas exhaust pipe is further provided with an emergency exhaust valve, and the outlet of the booster fan is provided with a C Concentration on-line analyzer, the C The concentration on-line analyzer is electrically connected with the central controller of the system.

10. A method of using a system for removing calcium from papermaking wastewater using boiler exhaust gas according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: S1, the wastewater containing high concentration of calcium ions is introduced into a calcium removal reaction tank, while the tail gas of a biogas boiler is introduced, and the reaction conditions are controlled to make calcium ions react with C to generate calcium carbonate precipitate; S2, after the reaction, the wastewater enters the sedimentation tank for solid-liquid separation; S3, the supernatant of the sedimentation tank enters a pre-acidification tank to adjust the acidification degree, and then enters an anaerobic reactor for anaerobic treatment; S4, the biogas generated by the anaerobic reactor is subjected to gas-liquid separation by a biogas gas-liquid separator, and the tail gas after the gas-liquid separation enters a biogas pressure stabilizing tank for pressure stabilization; S5, after the pressure stabilization, it is sent to a biogas boiler for combustion treatment; S6, the tail gas combustion of rich C The tail gas after dust removal by bag filter is pressurized by booster fan and delivered to the cyclone aerator at the bottom of calcium removal reaction tank for reuse.

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