What Equipment Can Be Used for Flue Gas Decolorization?

What equipment can be used for flue gas decolorization?

Direct Contact Heat Exchanger

This type of equipment achieves heat and moisture exchange through direct contact between flue gas and a spray liquid (usually water). Its core function is to rapidly cool and remove some moisture, without the need for fins.

1. Spray Tower (Spray Scrubber)

Working Principle: High-temperature, high-humidity flue gas enters the tower from the bottom and comes into countercurrent contact with ambient or low-temperature circulating water sprayed from the top. Heat in the flue gas is absorbed by the water, rapidly cooling it. The water vapor condenses into water and is then discharged along with the spray liquid.

Applicable Applications: Suitable for applications with high flue gas dust content that require simultaneous desulfurization and denitrification (agents can be added to the spray water), such as coal-fired boilers and waste incineration plants.

Advantages and Disadvantages: Simple structure, low cost, and simultaneous dust removal and purification; however, water consumption is high, and subsequent wastewater treatment containing pollutants is required. 2. Venturi Scrubber

Working Principle: Utilizing the "throat" structure of the Venturi tube, the flue gas flows through at high speed, mixing thoroughly with the atomized spray liquid, creating a strong disturbance that rapidly cools, dehumidifies, and removes dust.

Applicable Applications: Suitable for industrial applications with high flue gas flow rates and the need for efficient dust removal, such as high-temperature exhaust gas treatment in the metallurgical and chemical industries.

Advantages and Disadvantages: High heat transfer efficiency and excellent dust removal; however, the system has high resistance, requires a high-pressure blower, and consumes relatively high energy.

Indirect Heat Exchanger

This type of equipment achieves heat exchange between the flue gas and the heat transfer medium through a solid wall, avoiding direct contact.

1. Shell and Tube Heat Exchanger (Smooth Tube)

Working Principle: Composed of a shell and tube bundle, the flue gas flows through the tube side or shell side, while the heat transfer medium (such as cooling water or thermal oil) flows through the other side. Heat is transferred through the tube wall, cooling or heating the flue gas. Unlike finned tubes, the tube wall of this type does not have fins. Applicable Applications: Suitable for applications requiring high flue gas cleanliness and no significant ash accumulation, such as exhaust gas treatment from gas and biomass boilers.

Advantages and Disadvantages: Stable structure, easy maintenance, and resistant to clogging; however, the heat exchange area is smaller than that of a fin-tube heat exchanger of the same volume, resulting in relatively lower heat exchange efficiency and a larger device size.

2. Plate Heat Exchanger

Working Principle: Composed of multiple stacked corrugated metal plates, the flue gas and heat transfer medium flow through the flow channels of adjacent plates, transferring heat through the plates to achieve temperature control.

Applicable Applications: Suitable for heat exchange of medium- and low-temperature flue gases (temperatures < 200°C), such as process exhaust from the chemical industry and decolorization of hot and humid waste gas from printing and dyeing plants.

Advantages and Disadvantages: Higher heat exchange efficiency than bare tube heat exchangers, compact size, and lightweight; however, the narrow flow channels between the plates can easily become clogged by dust or sticky materials in the flue gas, making it unsuitable for high-dust flue gases.

Multifunctional White Smoke Removal Equipment

This type of equipment integrates multiple functions. Besides cooling and dehumidifying, it can also simultaneously remove pollutants or recover energy, eliminating the need for separate devices.

1. Wet Electrostatic Precipitator (with White Smoke Removal)

Operating Principle: Its core function is to remove fine dust and droplets from the flue gas. Simultaneously, the flue gas contacts the sprayed water film in the electric field, which has a certain cooling and dehumidifying effect, indirectly reducing the generation of "white smoke." Some wet electrostatic precipitators are equipped with additional heat exchange modules to enhance the white smoke removal effect.

Applicable Applications: Applications requiring deep dust removal and high smoke plume visual quality, such as ultra-low emission retrofits in power plants and steel mills.

Advantages and Disadvantages: It provides integrated "dust removal and white smoke removal" functionality, resulting in high smoke plume transparency; however, the equipment investment and operating costs are high, and the electrodes and water film require regular cleaning. 2. MGGH (Flue Gas Heat Exchanger)

Working Principle: Essentially an indirect heat exchange device, it consists of a "cooling section" and a "heating section." It utilizes untreated, high-temperature raw flue gas to heat low-temperature clean flue gas after desulfurization and dehumidification. This eliminates the need for additional energy (such as steam or electricity), achieving energy recovery and whitening.

Applicable Applications: Large coal-fired power plants, heating boilers, and other locations with large quantities of high-temperature raw flue gas. It is currently a mainstream device for ultra-low emission retrofits.

Advantages and Disadvantages: Significant energy savings and low operating costs; however, the system is complex, requires a large footprint, and requires regular cleaning of dust and scale deposits on the heat exchange surfaces.