At present, the common VOCs terminal treatment processes include regenerative combustion (RTO), catalytic combustion (RCO), direct combustion (TO), activated carbon adsorption and desorption, low-temperature plasma, etc.
However, due to the complex composition of VOCs exhaust gas, which is usually a variety of flammable and explosive mixed organic gases, the technical process selection in the early stage is not in place or the use of these devices is not professionally managed and controlled, which often brings new safety hazards. For example, corona discharge ignition of low-temperature plasma device, low-temperature plasma dust explosion, RTO device explosion, activated carbon device spontaneous combustion, and hazardous waste treatment problems. In recent years, there have been some safety accidents and emission substandard phenomena in the organic waste gas combustion treatment facilities of enterprises in many places.
At the recent meeting on energy saving and consumption reduction technology exchange of organic waste gas combustion treatment facilities and the unveiling ceremony of the environmental safety training base of Wuxi Ecological Environment Comprehensive Administrative Law Enforcement Bureau, Professor Yang Huizhong, director of the Combustion Technology and Equipment Research Center of Wuxi Institute of Applied Technology of Tsinghua University, introduced that the reason behind this is the lack of standards for how to operate, manage, maintain and supervise combustion waste gas treatment facilities in the current industry;
"These factors have also led to a variety of problems such as dilapidated and leaky pipes, occasional excessive exhaust emissions, and inadequate equipment safety protection measures for high-efficiency combustion equipment. At the same time, in the case of limited regulatory power, it also makes supervision more difficult. Yang Huizhong said.
How to better open up the regulatory model?
The Wuxi Municipal Bureau of Ecology and Environment of Jiangsu Province and the Wuxi Municipal Emergency Management Bureau jointly commissioned the Wuxi Institute of Applied Technology of Tsinghua University to establish the Combustion Technology and Equipment Research Center (hereinafter referred to as the Research Center), and innovatively explored a new regulatory model.
According to reports, the research center mainly monitors and provides technical guidance to the RTO/RCO/TO/CO and other combustion waste gas treatment equipment of Wuxi enterprises offline, and gives full play to the advantages of data resources online, through the collection of real-time operation data of the treatment facilities of key waste gas treatment enterprises in Wuxi, and the use of big data analysis, artificial intelligence and other technologies to effectively monitor the temperature, pressure, exhaust gas concentration and total VOCs of these equipment in real time, so as to effectively help the supervision of precise policies. In addition, it can provide government functional departments with the total carbon emissions of enterprises, carry out supervision and inspection, and carry out immediate early warning and disposal of emergencies such as illegal discharge, over-discharge, and fire alarms.
According to Yang Huizhong, the research center began research in April 2023, and as of July 7, 2023, it has visited 349 enterprises that have investigated and investigated waste gas treatment by combustion method, with a total of 509 organic waste gas combustion treatment equipment, including 238 CO, 165 RTOs, 33 RCOs, and 73 TOs.
In view of the problems existing in the facilities, the research center sent an expert team to sort out the list of problems and rectification opinions of the combustion waste gas treatment facilities of various enterprises, and sorted out and compiled the "Wuxi Organic Waste Gas Combustion Treatment Equipment Operation Management Specification" in response to the problems. In addition, the research center is also responsible for the energy efficiency evaluation of related equipment, and the research and development and upgrading of combustion technology and equipment, so as to improve the thermal efficiency of combustion equipment and help enterprises save energy and reduce emissions.
Can prevention be strengthened at the source?
Different from strengthening the end supervision, Professor Xie Qiang of the School of Chemical and Environmental Engineering of China University of Mining and Technology proposed that potential safety hazards should be prevented from the source, and an intrinsically safe VOCs treatment project should be constructed. He pointed out that based on the principle of "changing post-treatment to pre-prevention", in the design stage of VOCs treatment project, the safety evaluation system of VOCs treatment project should be constructed through applied research, and the VOCs treatment project with the characteristics of "intrinsic safety" should be designed.
"After the statistics and analysis of VOCs treatment engineering accidents, we found that nearly 70% of the accidents were issued by human error. Xie Qiang pointed out that at the same time, the current engineering specifications that can be based on do not cover all VOCs treatment technologies, and some enterprises that lack professionals in the management and operation and maintenance of VOCs treatment facilities are difficult to require their manual operation to never make mistakes.
Therefore, Xie Qiang suggested that the idea should be changed, and the "post-treatment" should be changed to "pre-prevention", and in the design stage of VOCs treatment engineering, the safety evaluation system of VOCs treatment engineering constructed by application research should be designed to develop equipment, facilities or production technology, and its contained, intrinsic, and fundamental functions that can fundamentally prevent accidents. It allows the operator to be injured or other accidents even if the operator makes a mistake, and can temporarily maintain normal operation or automatically change to a safe state when equipment, facilities or production technology fails.
During the meeting, the All-China Environmental Protection Federation and the China Society of Technology and Economics jointly issued the standard text of the organic waste gas disposal group standard - "Quality Classification and "Leader" Evaluation Requirements Regenerative Incineration Device (RTO)" and solicited opinions.
Weng Lulu, the relevant person in charge of Wuxi Edvance Technology Co., Ltd., one of the drafting units of the standard, interpreted the new highlights of the group standard. He said, "The standard uses the indicator of 'energy efficiency' instead of the previous 'temperature' index to evaluate the treatment effect, which can scientifically measure the treatment effect." Weng Lulu said that the idea of the new indicator is to collect the heat generated during the combustion treatment of volatile organic compounds and "recycle" it for organic waste gas treatment, so as to achieve low-carbon environmental protection.
According to rough calculations, for a 24-hour regenerative incineration unit (RTO), if the relevant indicators can be increased by 5%, it can save more than 100 yuan for a unit a year, and the original cost needs to purchase the corresponding cubic meters of natural gas to treat organic waste gas, which has the dual benefits of energy saving, carbon reduction and cost saving.