Venturi wet dust collector: a practical equipment for flue gas control in boilers and power plants

Boilers and generator sets will produce dusty flue gas during the fuel combustion process, which may contain fly ash, smoke dust and some acidic pollutants. If it is not effectively treated, it will not only affect the surrounding environment, but also increase the operating load of the flue, fans and subsequent purification equipment.

The Venturi wet dust collector uses high-speed airflow to fully contact the spray liquid, so that the particles in the flue gas are wetted, collided, condensed and separated from the airflow. It is suitable for cooling and pretreatment of some high-temperature and high-concentration dusty flue gases.

1. Working principle of Venturi wet dust collector

After the boiler flue gas enters the Venturi tube, it is rapidly accelerated in the throat area. The spray liquid is broken into fine droplets under the action of high-speed airflow, and undergoes inertial collision, interception and agglomeration with the dust particles in the flue gas.

Smaller particles combine with liquid droplets to form larger dust-containing droplets, which then enter the gas-liquid separation device. Under the action of centrifugal force, gravity or mist removal structure, dust-containing droplets are separated from the air flow and flow into the circulating water tank or sedimentation area.

After the treated flue gas passes through the mist removal device to remove entrained water droplets, it is discharged from the equipment outlet or enters the subsequent flue gas treatment system.

2. Main applications in boiler power plants

1. Boiler smoke pretreatment: reduce the concentration of fly ash and particulate matter in the flue gas.

2. High-temperature flue gas cooling: Use the spray liquid to absorb part of the heat to create suitable operating conditions for subsequent equipment.

3. Fine particle capture: High-speed airflow can increase the probability of collision between droplets and fine particles.

4. Wet pretreatment: It can be used as a pretreatment unit at the front end of desulfurization, defogging or other flue gas treatment equipment.

5. Reduce secondary dust: After the collected dust enters the liquid phase, it is difficult to re-suspend.

3. Main components of the equipment

1. Venturi tube: including a contraction section, a throat and a diffusion section, used to increase the air flow speed and strengthen gas-liquid contact.

2. Spray system: It consists of a circulating water pump, pipelines and nozzles, used to spray cleaning liquid into the flue gas.

3. Gas-liquid separation device: separates dust-containing droplets in flue gas.

4. Mist eliminator: Reduce water droplets discharged with smoke.

5. Circulating water tank: stores and circulates washing liquid, and collects dust and sediment.

6. Fan and control system: Provide flue gas transportation power and monitor the operating status of the equipment.

IV. Main features of the Venturi wet dust collector

1. Suitable for handling high-concentration smoke and dust: It has strong adaptability to some high-load dust-laden flue gases.

2. Can capture some fine particles: improve the aggregation and separation effect of particles through high-speed gas-liquid contact.

3. Able to cool down at the same time: suitable for cooling and wet pretreatment of high-temperature flue gas.

4. Reduce the secondary diffusion of dust: dust entering the liquid phase facilitates centralized treatment.

5. The structure can be adjusted according to working conditions: the pipe size, spray volume, material and gas-liquid separation structure can be designed according to flue gas conditions.

5. Instructions for the treatment of sulfur dioxide and nitrogen oxides

The main function of the Venturi wet dust collector is to capture particulate matter. If a suitable alkaline absorbent is added to the circulating liquid, part of the sulfur dioxide can be absorbed and neutralized, but the actual desulfurization effect is related to the liquid formula, gas-liquid ratio, contact time and pollutant concentration.

For nitrogen oxides, especially nitric oxide that is poorly soluble in water, the removal effect of ordinary water washing is usually limited, and selective catalytic reduction, selective non-catalytic reduction or other dedicated denitrification processes need to be configured.

6. Impact on boiler operating efficiency

The Venturi wet dust collector is mainly responsible for flue gas purification and cooling, and cannot directly improve the combustion efficiency of the boiler. After the equipment is installed, there will be a certain amount of system resistance, which requires a fan to provide power.

Rational design of equipment and flue systems can reduce the impact of dust accumulation on subsequent equipment and create conditions for the entire flue gas treatment system to maintain stable operation. However, the dust removal effect cannot be equated with an increase in power generation efficiency.

7. Comprehensive assessment of operating energy consumption is required

Venturi wet dust collectors usually have a high pressure drop, and their operating energy consumption mainly comes from induced draft fans and circulating water pumps. Higher throat velocities generally provide greater particle capture capabilities, but system resistance and fan energy consumption may also increase.

Equipment design should strike a balance between dust removal efficiency, system resistance, circulating water volume and operating costs. We cannot simply assume that wet dust removal equipment must be low-energy consumption equipment.

8. Circulating water and sludge treatment

Wet dust removal will transfer the dust in the flue gas to the circulating liquid, so sedimentation, filtration, sewage discharge and sludge treatment systems must be set up simultaneously.

1. Clean the circulating water tank and sedimentation area regularly.

2. Drain the sewage in time according to the turbidity and pollution level of the circulating fluid.

3. Monitor the pH value of circulating fluid containing acidic components and add medication appropriately.

4. Dispose of collected fly ash and sludge in a standardized manner.

5. Set up a water replenishment device to keep the liquid level in the circulating water tank stable.

9. Parameters required for equipment selection

1. Boiler type, fuel type and rated load.

2. Actual flue gas volume and daily operating time.

3. Flue gas inlet temperature, humidity and corrosiveness.

4. Dust concentration, particle size and fly ash properties.

5. Concentrations of sulfur dioxide, nitrogen oxides and other pollutants.

6. Allowable system resistance and fan configurations.

7. Discharge requirements and conditions for circulating water, wastewater and sludge treatment.

10. Routine operation and maintenance

1. Regularly check whether the nozzles, throats and pipelines are blocked or worn.

2. Check whether the circulating water pump, fan and valve are operating normally.

3. Clean the mist eliminator regularly to reduce water droplets entrained in the flue gas.

4. Monitor equipment pressure difference, flue gas volume and circulating fluid level.

5. Regularly check the wear of equipment linings and high flow areas.

6. Timely replenish water, add medicine, filter and discharge sewage according to the status of circulating fluid.

The Venturi wet dust collector is suitable for particle capture, cooling and wet pretreatment in boiler flue gas, but it cannot alone replace a complete desulfurization, denitrification and deep flue gas purification system. The actual equipment should be specially designed based on flue gas composition, treatment air volume, emission requirements and operating costs.