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Eliminating "white smoke" from chimneys is not worth the candle


Recently, some articles attribute the cause of the smog pollution to the wet flue gas emitted from  thermal power plants, and further advocate " eliminating white smoke", to recommend and promote the corresponding technology or company. These articles have the following prominent features: first, pretending to be experts, simply blaming the complex smog pollution problem on "white smoke". Second, defiling China's achievements in pollution control of coal-fired power plants, accusing the government of poor management. Third, to oppose China‘s pollution control technology for thermal power plants with developed countries, creating the illusion that China's technology is inferior to that of foreign countries. Last, to recommend technical equipment, and claim to have achieved "brilliant" performance, which results in the illusion that the claimed environmental protection technology is exclusive. As an industry insider working on power industry environmental protection for several decades, I need to clarify some problems to avoid misunderstanding of the public.


First, the formation and influence of wet plume are poorly understood, and the criteria are lack of preciseness. Wet plumes produced by thermal power plants undergo slight changes in color due to the background color of the sky, sky lighting, and viewing angles. They usually appear white, gray (white), or blue. Among them, "white plume" is more common. For ultra-low emission units with qualified treatment facilities, the main components are water mist and the concentration of pollutants is very low, which has no direct impact on the environmental quality and is a visual pollution.


Different local authorities of environmental protection have different views and management requirements for wet smoke plumes. Some experts collectively refer to "white smoke plume", "grey smoke plume" and "blue smoke plume" as "colored smoke plumes", while others believe that the treatment of wet plumes is only aimed at " eliminating white smoke". Due to inconsistencies in cognition, different judgments based on the "observation method" and "exhaust temperature method" are lack of preciseness.


Second, the treatment measures & their effect and the environmental quality disjointed. The current wet plume treatment measures implemented by current thermal power companies essentially change the condensation of water vapor after it is discharged into the environment by adjusting the temperature and humidity of the flue gas, and the main purpose is to eliminate the visual impact of "white plume". Among them, the method of flue gas heating cannot reduce the emission of existing pollutants in the flue gas. On the contrary, the heating of flue gas will increase energy consumption, which means that pollutant emissions are generally increased. The treatment of wet smoke plumes in thermal power plants is essentially not related to improving environmental quality. From the perspective of policy objectives, regulatory requirements and treatment measures, it can only play a role in eliminating visual impact.


Third is, the wet plume treatment measures affect the original equipment or system, increasing the potential risks of system operation and maintenance. According to the power plants that have completed the technical transformation, the stability of wet plume treatment technology and equipment is poor, and it affects production equipment and systems in many aspects, including the water balance of the desulfurization system, the leakage problem, the difficulty of eliminating the failure after the leakage, the problem that affects the normal operation of the desulfurization system equipment, and the desulfurization efficiency.


Fourth, the treatment of wet smoke plume requires  considerable investment with high operating costs, while the technical economy and environmental benefits are poor. According to calculations by electric power enterprises, the biggest factor influencing the economics of the wet plume reconstruction project is the unit utilization hours, followed by the static investment in the project, and the electricity and water prices also have a certain impact. With the increasing proportion of renewable energy power generation, the flexibility transformation of thermal power plants will continue moving on, thus the utilization hours of coal power will be hard to rebound, and the cost of " eliminating white smoke " will further increase. From the perspective of the whole society, these large amounts of investment will inevitably be transmitted to the whole society and become the cost of it. The removal of wet plume on the basis of ultra-low emission of coal-fired power plants is blind and not worth the candle.


Fifth, the policy of wet smoke plume is arbitrary, which conflicts with legal requirements. Regarding the management of wet plume, without adequate scientific justification, it is not appropriate to set requirements for enterprises at will and implement such requirements on a large scale. What's more important is that the license to an enterprise should be based on the effect to be achieved, rather than directly specifying the measures that the enterprise should take. Obviously, the relevant regulatory requirements for eliminating wet plumes are inconsistent with legal requirements.


Policy recommendations


First, understand the basic concept of wet plume scientifically. The basic issue of the impact of wet plume on the environment should be a matter of known, and individual technical issues cannot be enlarged into social problems;


Second, well operate the existing environmental protection facilities to reduce the generation of secondary pollutants; From the basic situation of the existing technology and equipment, as long as the ammonia escape is controlled and the demister is operated according to the technical requirements, white or colored plumes will not be the cause of smog formation, nor will it cause unacceptable environmental impact.


Third, carry out assessment and law enforcement inspection. For the typical power plants that have completed the technical transformation of wet plume, a comprehensive evaluation conclusion should be put forward considering the environmental, technical and economic factors. Law enforcement inspections should not only focus on the implementation of laws by enterprises, but also on the legality of the relevant requirements of local governments.


Fourth, consider appropriate policy compensation to the power generation enterprises that have piloted the treatment of wet plume. The wet plume treatment policy is the change to the existing environmental protection administrative license of thermal power enterprises. According to relevant laws and regulations, economic compensation should be given to power generation enterprises by the local government.


Fifth, strengthen publicity and improve the public's awareness of the treatment of pollutants in thermal power plants. With the prevalence of some misleading information, many people believe that the emissions from the power plant chimney (including "white smoke") are pollution, even without distinguishing the water vapor from chimneys and water-cooling towers. Power industry organizations and government departments should strengthen the popularization of science and technology on the environmental protection effectiveness of thermal power plants, and improve the public's awareness of pollution control of thermal power plants.

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