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How To Choose Right Flue Gas Cleaning System For Your Factory?

In category Industrial News
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Flue gas cleaning or flue gas treatment become hot around the world. As we all know, flue gas cleaning system is needed in many industries, such as steel plant, cement plant, power plant, chemical plant, etc. At the same time, there are various types of flue gas treatment technology and systems on the market, for owners of the factory we mentioned above, some of them are confused about the flue gas cleaning system.

As a professional equipment supplier in the industry, Ruichang has plenty of experience in flue gas cleaning systems and technology, we own over 50 national patents covering low NOx process burners, high temperature, super large CO incinerators, RT anti-wear ceramic nozzles, SRU burners, and flare equipment. We are certified by ISO9001, ISO14001, ASME U & U2.

Today we will help you get an overall understanding of the flue gas cleaning systems and clarify how to choose the right flue gas cleaning system.

Why flue gas cleaning system is important?

With the continuous improvement of environmental protection requirements and the continuous progress of flue gas treatment technology, the wet flue gas treatment market will continue to maintain a growth trend. The increase in investment in environmental protection by enterprises, the continuous implementation of government support policies, and the improvement of public environmental awareness will all promote the widespread application of wet flue gas treatment technology in more fields. The demand for wet flue gas treatment, especially in developing countries and emerging market countries, will rapidly increase globally, bringing broad market prospects to related industries.

After wet flue gas desulfurization treatment, when the saturated wet flue gas discharged from the chimney comes into contact with lower-temperature air, during the process of flue gas cooling, the water vapor in the flue gas becomes supersaturated and condenses. The condensed water droplets refract and scatter light, resulting in white or gray smoke plumes, which are called “wet flue gas” (also known as “colored smoke plumes”). When wet flue gas is discharged, the lifting height of the “smoke plume” will be reduced, and the diffusion effect will be relatively poor. The landing concentration of pollutants near the chimney will increase, which has a certain impact on the surrounding environment.

The severity of colored flue gas is significantly related to environmental temperature and humidity. The lower the environmental temperature and the higher the air humidity, the more difficult it is to control colored flue gas.

Flue gas cleaning system application

Wet flue gas treatment technology should be applied in the following fields, which can not only effectively reduce pollutants in smoke and environmental pollution, but also meet national and local emission standards, and promote green and sustainable development in various industries.

  • Electricity industry: thermal power plants generate a large amount of flue gas containing pollutants such as sulfides, nitrogen oxides, and particulate matter during the coal and fuel combustion process. Wet desulfurization and wet dust removal technologies are widely used in the treatment of these flue gases.
  • Steel industry: equipment such as blast furnaces, converters, and electric furnaces in the steel production process emits a large amount of flue gas. Wet flue gas treatment technology is commonly used to treat pollutants such as sulfur dioxide and particulate matter in these flue gases.
  • Cement industry: cement kilns generate a large amount of high-temperature flue gas during the production process. Wet flue gas desulfurization technology can effectively remove sulfur dioxide from the flue gas and reduce environmental pollution.
  • Chemical industry: the smoke emitted during the chemical production process usually contains various harmful gases, such as ammonia, chlorine, sulfur dioxide, etc. Wet flue gas treatment technology can effectively treat these harmful gases.
  • Paper industry: the flue gas generated in the papermaking production process contains a large amount of sulfur dioxide and particulate matter, and wet desulfurization and wet dust removal technologies are widely used to treat these flue gases.
  • Garbage incineration: the smoke generated during garbage incineration contains various harmful substances, including dioxins, heavy metals, acidic gases, etc. Wet flue gas treatment technology can effectively treat these pollutants.
  • Nonferrous metal smelting: the flue gas generated during the non-ferrous metal smelting process contains a large amount of acidic gases and particulate matter, and wet flue gas treatment technology is commonly used to remove harmful substances from these flue gases.
  • Petroleum Refining: the flue gas generated during the petroleum refining process contains harmful gases such as sulfides and nitrogen oxides. Wet flue gas treatment technology is used to remove these pollutants and improve emission quality.

3 flue gas treatment technology

The wet flue gas treatment technology can be classified into three categories: heating, condensation, and condensation reheating.

Based on the mechanism of formation and dissipation of wet flue gas, the existing technologies that have effective treatment effects on wet flue gas, can be summarized as flue gas heating technology, flue gas condensation technology, and flue gas condensation reheating technology.

As a Chinese national high-tech enterprise, Ruichang has studied the characteristics of various technologies and their adaptability in wet flue gas treatment, and explored the applicability of three types of technologies under different environmental temperature and humidity conditions, combined with the formation and dissipation mechanisms of wet flue gas.

Flue gas heating technology

The flue gas heating technology is to heat the wet saturated flue gas at the desulfurization outlet, so that the relative humidity of the flue gas is far away from the saturation humidity curve. The initial state of wet smoke is located at point A. After heating, it is heated according to AB and then mixed and cooled along BC to environmental state point C. The entire process of ABC change does not intersect with the saturation humidity curve, so no wet flue gas are generated.

The current heating technologies in service can be divided into two categories based on heat exchange methods: indirect heat exchange and direct heat exchange. The main representative technologies of indirect heat exchange include rotary GGH, tubular GGH, heat pipe GGH, MGGH, steam heater, etc. The main representative technologies of direct heat exchange include mixed heating of hot secondary air, direct heating of gas, and mixed heating of hot air. If the same technical indicators are used to achieve wet plume treatment for each heating technology.

Although direct heating technology has a lower initial investment, its operating cost is too high due to its heat source not utilizing the waste heat of flue gas. The cost of wet flue gas treatment technology is too high, and there are very few cases in practical application. In indirect heating technology, both rotary GGH and tubular GGH have varying degrees of air leakage. In the ultra-low emission environment of coal-fired power plants in China, their application as a wet plume control method is also limited. After the large-scale production of heat pipe GGH, it will be difficult to arrange the soot blower and increase the footprint, so it is not currently applied in large units. The steam heating method also consumes too much energy due to heat source issues. Therefore, considering the current requirements for ultra-low smoke emissions and energy conservation, MGGH has the widest application prospects as one of the means of wet flue gas treatment.

Flue gas condensation technology

The flue gas condensation technology cools the wet saturated flue gas at the desulfurization outlet, causing the flue gas to cool down along the saturation humidity curve, resulting in a significant decrease in moisture content during the cooling process. The initial state of wet flue gas is located at point A. After cooling, it condenses according to AF, and then mixes and cools along Fc to the environmental state point C. The FC change process does not intersect with the saturation humidity curve, so no wet flue gas is generated.

Condensation technology can be mainly divided into two categories based on heat exchange methods: indirect heat exchange and direct heat exchange. Direct heat exchange mainly uses newly built spray towers as heat exchange equipment, which have certain land requirements. The refrigerant and clean flue gas come into direct contact, resulting in high heat exchange efficiency. However, the refrigerant water system needs to be supplemented with chemicals to control the pH value, making the system more complex. Indirect heat exchange often uses tube heat exchangers as heat exchange equipment, and the refrigerant does not directly contact the clean flue gas, making the system simpler.

wet flue gas treatment
wet flue gas treatment system of Ruichang

According to the different condensation techniques of cold sources, they can be divided into water cooling sources, air cooling sources, and other artificial cooling sources. The circulating water system composed of water-cooled sources is the simplest, only equipped with pumps and circulating pipelines, usually open circulation. The lowest operating cost and small footprint. Systems that use air cooling sources usually require cooling towers in the circulating water system, which are more complex and occupy a larger area than water cooling. The newly added cooling towers will become a new source of white smoke near the ground. Other artificial cooling sources, such as heat pumps, have a large footprint and high energy consumption (taking the steam lithium bromide heat pump as an example, it requires 0.7MJ of steam to exchange 1MJ of heat). The quality of the cold source in a system that uses ambient air, rivers, and seawater as its cold source is significantly affected by the season. Taking the East China region as an example, the temperature difference between winter and summer environments is 20-30 degrees, so the condensation effect of the same system will vary significantly in different seasons.

The flue gas condensation technology cools the wet flue gas after desulfurization, causing a large amount of gaseous water in the flue gas to condense into liquid droplets. During this process, it can capture various pollutants such as fine particles and SO. Therefore, as a means of treating wet smoke plumes, flue gas condensation technology can not only have a good effect on eliminating white smoke, but also achieve the joint removal of multiple pollutants from flue gas. The condensate water can be used as desulfurization water supplement.

The REGLASS industrial wet flue gas condensation treatment technology adopts a non-heating condensation method, using ambient air as a cold source, to perform condensation phase change heat transfer treatment on wet flue gas, achieving the effect of eliminating colored flue gas. This technology has significant water-saving and emission reduction characteristics. While condensing and collecting moisture in wet flue gas, it condenses water-soluble salts, ultrafine particles, and acidic gases in the flue gas with the condensate water. REGLASS® glass plate heat exchanger and metal plate heat exchanger are mainly used for flue gas cleaning system.

Flue gas condensation and reheating technology

The flue gas condensation and reheating technology is a combination of the aforementioned two methods. The initial state of wet smoke is located at point A. After cooling, it condenses according to AD, then heats along DE, and then mixes and cools along EC to the environmental state point C. The process of EC change does not intersect with the saturation humidity curve, so no wet flue gas are generated. The dissipation mechanism of wet flue gas shows that environmental humidity and temperature have a significant impact on the formation and scale of wet flue gas. In theory, under given environmental temperature and humidity conditions, regardless of cost, both heating and condensation technologies can achieve the elimination of wet flue gas (heating temperature is high enough, condensation temperature is low enough). However, based on the actual situation of coal-fired power plants, from an economic perspective, both simple heating and condensation methods have their own limitations. Heating is limited by the original flue gas temperature conditions, while condensation is limited by the ambient air and water temperatures. If condensation reheating technology is adopted under these conditions, combining heating and condensation can expand the adaptability range of the wet flue gas treatment system to environmental temperature and humidity.

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