System for removing calcium from papermaking wastewater by using biogas boiler tail gas

Abstract

The utility model provides a kind of biogas boiler tail gas for papermaking wastewater calcium removal system, including calcium removal reaction pool, sedimentation tank, pre-acidification pool, anaerobic reactor, biogas pressure regulating tank, biogas boiler and booster fan connected in turn;The effluent of calcium removal reaction pool is connected with the influent of sedimentation tank, and the supernatant outlet of sedimentation tank is connected with the influent of pre-acidification pool, and the effluent of pre-acidification pool is connected with anaerobic reactor by anaerobic feeding pump, and the biogas outlet of anaerobic reactor is connected biogas gas-liquid separator, biogas pressure regulating tank and biogas boiler in turn, and the tail gas outlet of biogas boiler is connected bag-type dust collector and booster fan in turn, and the outlet of booster fan is connected to calcium removal reaction pool for reuse.The utility model realizes waste treatment with waste, effectively reduces wastewater calcium hardness, prevents anaerobic reactor calcification, with the advantages of low operating cost, high processing efficiency, while reducing greenhouse gas emissions, with significant economic and environmental benefits.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a system for using biogas boiler exhaust gas to remove calcium from papermaking wastewater. 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] Currently, the main method for treating high-calcium wastewater is chemical precipitation, which involves adding chemical agents such as sodium carbonate or sodium hydroxide to precipitate calcium ions as calcium carbonate. While effective, this method is costly to operate and produces large amounts of chemical sludge. Anaerobic treatment of papermaking wastewater generates significant amounts of biogas, which is typically utilized through biogas boilers. The exhaust gas produced after biogas combustion contains high concentrations of carbon dioxide; direct emission of this gas would contribute to greenhouse gas emissions.

[0004] Therefore, developing a technical solution that can utilize carbon dioxide from biogas boiler exhaust gas to treat high-calcium wastewater and simplify the system structure has significant economic and environmental value. Utility Model Content

[0005] This invention provides a system for using biogas boiler exhaust gas to remove calcium from papermaking wastewater. By technically modifying existing wastewater treatment devices, it solves the problems of high cost and carbon dioxide emissions associated with existing wastewater treatment methods.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A system for using biogas boiler exhaust gas to remove calcium from papermaking wastewater 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.

[0007] Preferably, it also includes a pipeline mixer installed at the inlet end of the calcium removal reaction tank, and a dosing unit is also connected to the outside of the pipeline mixer.

[0008] 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 located 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 pipe mixer. The dosing check valve is located on the outlet pipe of the dosing metering pump. The online pH monitor is located inside the calcium removal reaction tank and is signal-connected to the dosing metering pump. A tap water pipe for water supply is also connected to the dosing tank.

[0009] Preferably, the agent added by the dosing unit is either sodium hydroxide or sodium carbonate.

[0010] Preferably, a cyclone aerator is installed at the bottom of the calcium removal reaction tank, and the CO2 tail gas delivered by the outlet of the booster blower is output to the calcium removal reaction tank through the cyclone aerator.

[0011] Preferably, the cyclone aerator has an air flow rate of 0.4 to 1.0 m³ / min, a service area of ​​3 to 12 m² / unit, is made of 304 stainless steel, and is equipped with a flange connection structure and a ball valve connected to the air supply pipeline at the outlet of the booster fan.

[0012] Preferably, the sedimentation tank is equipped with a sludge discharge pipe at the bottom, and a sludge concentration sensor is also installed inside 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 reflux ratio of the seed reflux system is 5%~15%, and the flow rate of the seed reflux pump is automatically adjusted based on the feedback from the sludge concentration sensor.

[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, an emergency exhaust valve is also provided on the exhaust pipe, and an online CO2 concentration analyzer is provided at the outlet of the booster fan. The online CO2 concentration analyzer is electrically connected to the central controller of the system.

[0016] The beneficial effects of this utility model are as follows: 1. This application can treat waste with waste, using CO2 from exhaust gas as a calcium removal agent, reducing the cost of the agent, and using CO2 from biogas combustion exhaust gas as a calcium removal agent, thus realizing the resource utilization of waste, which is more energy-saving and environmentally friendly. 2. This application removes calcium ions before the wastewater enters the anaerobic system, which can prevent calcification in the anaerobic reactor; 3. The pipeline mixer installed in this application can ensure that the reagent and wastewater are premixed, and then the mixture is efficiently stirred in the calcium removal reaction tank by the cyclone aerator, resulting in higher mixing efficiency; 4. This application also includes a cyclone aerator in the calcium removal reaction tank. The cyclone aerator is made of 304 stainless steel and connected by flanges. It is anti-clogging, durable, corrosion-resistant, and easy to clean. 5. This application is equipped with an online pH monitor, a sludge concentration sensor, and an online CO2 concentration analyzer. Through pH monitoring, sludge concentration monitoring, and CO2 concentration monitoring, the system can be automatically optimized. 6. This application is equipped with a seed crystal reflux system, which can recycle sludge back into the calcium removal reaction tank. Seed crystal reflux improves the quality of calcium carbonate crystallization and facilitates recycling. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the system connection structure of this utility model; 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), online CO2 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

[0018] The specific content of this utility model will be described in detail below with reference to the accompanying drawings and embodiments.

[0019] Please see Figure 1As shown, this utility model provides a system for using biogas boiler exhaust gas to remove calcium from papermaking wastewater, including 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.

[0020] Furthermore, in order to add chemicals to the calcium removal reaction tank (1-1), a pipeline mixer (1-2) is also included, which is installed at the inlet end of the calcium removal reaction tank (1-1). A dosing unit is also connected to the outside of the pipeline mixer (1-2).

[0021] In actual operation, the high-calcium papermaking wastewater is first thoroughly mixed with the reagents added by the dosing unit in a pipeline mixer (1-2). The pipeline mixer (1-2) adopts a static mixer design with 4-6 spiral blades inside to ensure rapid and uniform mixing of the reagents and wastewater. The mixed wastewater then enters the calcium removal reaction tank (1-1).

[0022] Furthermore, 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 water supply pipe (8-5), and an online pH monitor (8-6). The dosing agitator (8-2) is installed inside the dosing tank (8-1), and the inlet of the dosing metering pump (8-3) is connected to the dosing tank (8-6). -1) Connection: The outlet of the dosing 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 pipeline of the dosing 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 pump (8-3) via a signal connection. A tap water pipe (8-5) for water supply is also connected to the dosing storage tank (8-1). This application includes a dosing mixer (8-2) to maintain uniform mixing of the reagents, a dosing check valve (8-4) to prevent wastewater backflow, and a pH online monitoring instrument (8-6) to send detection information. The system's central controller controls the dosing pump (8-3) to regulate the dosing dosage, resulting in a higher level of intelligence.

[0023] Furthermore, the agent added by the dosing unit is either sodium hydroxide or sodium carbonate.

[0024] Furthermore, a swirl aerator (1-3) is installed at the bottom of the calcium removal reaction tank (1-1), and the CO2 tail gas delivered from the outlet of the booster fan (7-1) is output to the calcium removal reaction tank (1-1) through the swirl aerator (1-3).

[0025] Furthermore, the cyclone aerator (1-3) has an air flow rate of 0.4–1.0 m³ / min, a service area of ​​3–12 m² / unit, is made of 304 stainless steel, and is equipped with a flange connection structure and a ball valve for connection to the outlet air supply pipeline of the booster blower (7-1). The cyclone aerator (1-3) can generate strong swirling bubbles, which not only provides the CO2 required for the reaction but also achieves thorough mixing of the fluids in 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), and a sludge concentration sensor (2-2) is also provided in the sedimentation tank. 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), and 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).

[0028] The reflux ratio of the seed crystal reflux system is 5%~15%, and the flow rate of the seed crystal reflux pump (2-5) is automatically adjusted based on the feedback from the sludge concentration sensor (2-2).

[0029] Furthermore, 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.

[0030] Furthermore, an emergency exhaust valve (6-3) is also installed on the exhaust pipe (6-2), and an online CO2 concentration analyzer is installed at the outlet of the booster fan (7-1). The online CO2 concentration analyzer is electrically connected to the central controller of the system. This application also includes an online CO2 concentration analyzer (7-3) for real-time monitoring, and uses the emergency exhaust valve (6-3) to control the airflow input to provide safety assurance.

[0031] The workflow for this application is as follows: S1. The high-calcium wastewater is first thoroughly mixed with the reagents added by the dosing unit in the pipeline mixer (1-2), and then enters the calcium removal reaction tank (1-1) to react with the CO2-rich tail gas input through the cyclone aerator (1-3); S2. The wastewater after the reaction enters the sedimentation tank (2-1) for solid-liquid separation; S3. The effluent from the sedimentation tank (2-1) enters the pre-acidification tank (3-1) to adjust the acidification degree. The pre-acidified wastewater is then sent to the anaerobic reactor (4-1) through the anaerobic feed pump (3-2) for anaerobic treatment. S4. The biogas produced by the anaerobic reactor (4-1) is separated by the biogas gas-liquid separator (4-2) and then enters the biogas pressure stabilizing cabinet (5-1). S5. After pressure stabilization, the exhaust gas is sent to the biogas boiler (6-1) for combustion and utilization. S6. The CO2-rich exhaust gas produced after the combustion of the exhaust gas is removed by the bag filter (7-2), and then 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.

[0032] This utility model has the following features: 1. This application can treat waste with waste, using CO2 from exhaust gas as a calcium removal agent, reducing the cost of the agent, and using CO2 from biogas combustion exhaust gas as a calcium removal agent, thus realizing the resource utilization of waste, which is more energy-saving and environmentally friendly. 2. This application removes calcium ions before the wastewater enters the anaerobic system, which can prevent calcification in the anaerobic reactor; 3. The pipeline mixer installed in this application can ensure that the reagent and wastewater are premixed, and then the mixture is efficiently stirred in the calcium removal reaction tank by the cyclone aerator, resulting in higher mixing efficiency; 4. This application also includes a cyclone aerator in the calcium removal reaction tank. The cyclone aerator is made of 304 stainless steel and connected by flanges. It is anti-clogging, durable, corrosion-resistant, and easy to clean. 5. This application is equipped with an online pH monitor, a sludge concentration sensor, and an online CO2 concentration analyzer. Through pH monitoring, sludge concentration monitoring, and CO2 concentration monitoring, the system can be automatically optimized. 6. This application is equipped with a seed crystal reflux system, which can recycle sludge back into the calcium removal reaction tank. Seed crystal reflux improves the quality of calcium carbonate crystallization and facilitates recycling.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model 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 this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

[0034] All standard parts used in this utility model 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.

[0035] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," 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 utility model based on the specific circumstances.

Claims

1. A system for using biogas boiler exhaust gas to remove calcium from papermaking wastewater, characterized in that, It 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.

2. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 1, characterized in that, 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.

3. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 2, characterized in that, 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 located 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 pipe mixer. The dosing check valve is located on the outlet pipe of the dosing metering pump. The online pH monitor is located inside the calcium removal reaction tank and is connected to the dosing metering pump. A tap water pipe for water supply is also connected to the dosing tank.

4. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 3, characterized in that, The dosing unit administers either sodium hydroxide or sodium carbonate.

5. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 1, characterized in that, A cyclone aerator is installed at the bottom of the calcium removal reaction tank, and the CO2 tail gas delivered by the outlet of the booster blower is output to the calcium removal reaction tank through the cyclone aerator.

6. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 5, characterized in that, The cyclone aerator has an air flow rate of 0.4 to 1.0 m³ / min, a service area of ​​3 to 12 m² / unit, is made of 304 stainless steel, and is equipped with a flange connection structure and a ball valve for connecting to the air supply pipeline at the outlet of the booster fan.

7. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 1, characterized in that, The sedimentation tank is equipped with a sludge discharge pipe and a sludge concentration sensor at the bottom. The sludge discharge pipe is also connected to a seed return system for returning part of the sludge to the calcium removal reaction tank.

8. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 7, characterized in that, 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.

9. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 7, characterized in that, 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.

10. A system for using biogas boiler tail gas to remove calcium from papermaking wastewater according to claim 1, characterized in that, The biogas boiler is connected to a tail gas discharge pipe at its tail gas outlet. An emergency exhaust valve is also installed on the tail gas discharge pipe. An online CO2 concentration analyzer is installed at the outlet of the booster fan. The online CO2 concentration analyzer is electrically connected to the central controller of the system.

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