Compared with the 200 1 version of the standard, the revised draft of Pollution Control Standard for Domestic Waste Incineration, which was reviewed and approved in principle by the Standing Committee of the Ministry of Environmental Protection, not only greatly tightened the emission limits of conventional pollutants such as sulfur dioxide, nitrogen oxides and particulate matter, but also increased the working condition control indicators such as carbon monoxide. At the same time, the waste entering the furnace and the monitoring requirements were revised accordingly.
Compared with GB 18485-200 1, GB 18485-20 14 is more practical, stricter and more scientific. In particular, the newly added working condition control index has moved pollution control from the end to the process, which is an active exploration in the formulation of environmental standards in China.
Pollutant discharge restrictions have been greatly tightened.
The emission concentration limit of major pollutants is basically the same as that of the EU, while dioxin is tightened from 1.0ngTEQ/m3 to 0. 1ngTEQ/m? .
In the new standard, the emission limits of particulate matter, heavy metals (mercury, cadmium, thallium, lead and others), HCl, SO2, nitrogen oxides and dioxins are greatly tightened. For example, the new standard stipulates that particulate matter is 80mg/Nm? Tighten to 20mg/Nm? (daily average), the mercury content varies from 0.2mg/Nm? Tighten to 0.05mg/Nm? , dioxins from 1ngTEQ/m? Tighten to 0. 1ngTEQ/m? , in line with EU standards.
It is the general trend to tighten the emission limit of pollutants from waste incineration, which is not only related to the environmental situation and the increasing emission standards of other industries, but also related to the continuous improvement of the technical level and incineration scale of waste incineration industry.
At the beginning of this century, there were only 36 garbage incineration facilities in China, which were small in scale, with a daily processing capacity of only 6520 tons (200 1), and the pollutants discharged were very small compared with industrial emissions. But this number has been multiplied several times. The Statistical Yearbook of Urban Construction in China shows that in 20 12 years, the number of garbage incineration plants in China has reached 138, and the daily incineration capacity has exceeded 120,000 tons, and the annual incineration capacity is nearly 40 million tons, which is 15 times higher than that of 10 years ago. At the same time, the proportion of incineration capacity in garbage harmless treatment has also increased from less than 3% of 200 1 to nearly 30%, and it is still increasing rapidly.
According to relevant calculations, with the increase of waste incineration, the pollutant emissions also increase accordingly. Taking nitrogen oxides as an example, GB 18485-200 1 stipulates (400mg/m? ), 20 1 1 year, the total emission of nitrogen oxides from flue gas in China is 24.043 million tons, and the emission of nitrogen oxides from domestic garbage incineration is between 55,000 tons and 96,000 tons, accounting for 0.23%~0.40%. If the new standard is implemented (250mg/m per day? ), the emission of nitrogen oxides from domestic waste incineration in that year was reduced by 1/4 compared with the implementation of the current standards, which was equivalent to about 0. 1% of the national nitrogen oxide emission reduction in 201year, accounting for about 1% of the total nitrogen oxide emission reduction target in the Twelfth Five-Year Plan.
The situation of sulfur dioxide is similar to that of nitrogen oxides. As for dioxins, all the new large-scale waste incineration projects in China have reached the EU standard, that is, 0. 1ngTEQ/m? . "
According to the new standard, the average value of dioxins in sludge produced by domestic sewage treatment facilities and general industrial solid waste incinerators with a single boiler of less than 50 tons/day is 1.0ngTEQ/m? ; The average value of dioxin determination in incinerators with a scale of 50 tons/day to 100 tons/day should be 0.5ngTEQ/m? ; The incinerator with the scale of100t/day is 0. 1ngTEQ/m? .
Compared with domestic waste incinerators, incinerators for treating sludge and general industrial solid waste generated by domestic sewage treatment facilities are very small, so it is difficult to achieve stable combustion during incineration, and the dioxin emission level is difficult to reach 0. 1ngTEQ/m3.
Compared with Japanese grading control, China's new standards are more stringent. For example, the corresponding standards in Japan stipulate that the furnace type with the scale of 2 tons/hour to 4 tons/hour should meet the requirements of 1ngTEQ/m3; The furnace type with a scale of less than 2 tons/hour shall meet the requirements of 5.0ngTEQ/m3.
In addition to hydrogen chloride, cadmium thallium, lead, etc., the emission concentration limit of other pollutants GB 18485-20 14 has been equivalent to that of the European Union.
Dioxins mostly exist in solid form at room temperature, so dioxins in flue gas are mostly attached to particulate matter, and the improvement of dust removal efficiency means the improvement of dioxin removal rate. Therefore, the new standard requires that the flue gas dust removal facilities of waste incineration plants must adopt the bag dust removal technology with the highest dust removal efficiency.
The new standard greatly improves the emission limit of particulate matter in flue gas, and also improves the emission control requirements of dioxins and heavy metals. All countries in the world adopt this level of emission quota allocation.
From terminal control to process control
By controlling the concentration of carbon monoxide, the production conditions of dioxins are controlled; For the first time, the pollution control limit value combining "hourly average value" and "daily average value" was adopted.
The transition from terminal control to process control is a main feature of the new standard.
The trace dioxin in flue gas can not be monitored online in real time, but the dioxin emission can be inferred from some online monitoring data. The contents of carbon monoxide and soot in flue gas are closely related to combustion efficiency and dust removal efficiency, and are also important factors affecting dioxin content.
The revised new standard takes the concentration of carbon monoxide as the process control index, which is precisely to control the concentration of carbon monoxide and the production conditions of dioxins, so as to control the mass production of dioxins.
Improving the combustion efficiency of incinerator can effectively burn dioxin-like substances contained in domestic garbage and precursor substances that may be synthesized in flue gas, and reduce the chance of synthesis of dioxin-like substances.
The research shows that when the concentration of carbon monoxide in the flue gas of incinerator is reduced to 100mg/Nm? When the following conditions are met, the concentration of dioxin-like substances in the flue gas will be greatly reduced, which will greatly reduce the pressure on the subsequent dioxin-like substance removal facilities and provide a good foundation for ensuring the standard. This value is adopted as the control index of incinerator operation condition by standards all over the world.
The newly revised standard stipulates that domestic waste incineration plants should set up on-line monitoring devices for the operating conditions of incinerators, and the monitoring results should be publicized through electronic display boards and networked with the monitoring centers of local environmental protection departments. On-line monitoring indicators of incinerator working conditions should at least include carbon monoxide concentration in flue gas, oxygen concentration in the furnace and incineration temperature.
In addition, based on the characteristics of domestic waste itself, its moisture content and composition will change irregularly with the change of time and region. This brings great trouble to the working condition and pollution control of garbage incinerator. Irregular changes in operating parameters and flue gas emission concentration often lead to enterprises exceeding the standard and being punished.
In order to maximize the feasibility and operability of the standard and encourage enterprises to abide by the law in good faith, the new standard refers to the international common practice, adopts the pollution control limit value combining "hourly average value" and "daily average value", and sets the control standard in different periods.
For example, during the start-up, stop and accident stages, the concentration of pollutants in flue gas increases significantly, and the environmental impact at this stage is inevitable. Among them, dioxins, which have the greatest impact on human health, are mainly emitted in the form of accumulation on smoke particles. Therefore, during the driving, parking and accident stages, the emission concentration of particulate matter is mainly controlled, and the emission of dioxin-like substances is indirectly controlled. According to the requirements of EU standards, the particle concentration at these stages should be 150mg/m? limit value
Medical waste and leachate have a home.
The new incineration standard allows the treated medical waste to be incinerated in the domestic waste incinerator, which can make full use of the high calorific value characteristics of medical waste and reduce the risk of environmental pollution; Treat landfill leachate and incineration leachate differently.
GB 18485-200 1 stipulates that "hazardous wastes are not allowed to enter the domestic waste incineration plant for treatment", which shuts out all medical wastes and hazardous wastes, but it has caused more environmental hazards invisibly.
The new standard allows the treated medical waste to be incinerated in the domestic waste incinerator, which can make full use of the resource characteristics of high calorific value of medical waste and greatly reduce the risk of environmental pollution.
Medical waste disposal facilities are being built in cities, and the most commonly used disposal technology is incineration. However, the scale of special incinerators for medical wastes is small, generally ranging from 10 ton/day to 30 ton/day, and small incinerators smaller than 10 ton/day are also common.
It is difficult to control the pollution of small stoves. Most medical wastes contain high chlorine content, and dioxin-like substances are easily produced during incineration, which causes very high environmental risks. In view of this, some cities have built non-incineration treatment facilities such as high-temperature cooking and disinfection to treat medical waste, but the destination of the treated waste has become a new problem.
The nonstandard treatment of landfill leachate has caused many environmental pollution incidents, and the new standard also has clear and feasible provisions on landfill leachate treatment.
Because most domestic waste incineration plants are close to landfills or have close cooperative relations, the new standard stipulates that domestic waste leachate and vehicle cleaning wastewater should be collected and treated in domestic waste incineration plants or sent to leachate treatment facilities of domestic waste landfills for treatment. After treatment, it can be directly discharged after reaching the corresponding requirements of Pollution Control Standard for Domestic Waste Landfill (GB 16889), or it can be sent to the second stage through sewage pipe network or closed transportation under certain conditions.
This requirement of the new standard is quite different from GB 16889. Because of the requirements of GB 16889, all landfill sites must treat landfill leachate by themselves. For this difference, Wang Qi explained: "There is a difference between landfill leachate and landfill leachate." The former is not only large in quantity, but also fluctuates greatly with seasons and water quality; The latter is relatively stable and small in scale. Considering the needs of technology, economy, environment and social management, sewage treatment plant can be used for treatment.
In addition to the above contents, compared with the current standards, the scope of application of the new standards is also different. The new standard stipulates that the sludge pollution control standards produced by domestic sewage treatment facilities and general industrial solid waste incineration facilities refer to the domestic waste incineration pollution control standards.
For the collaborative disposal of domestic waste by industrial kilns, referring to the experience of foreign countries, especially the United States, if the mass of domestic waste burned does not exceed 30% of the total mass of materials entering the kiln, the corresponding pollution control standards for industrial kilns shall be implemented; This standard shall be implemented when the mass of mixed domestic garbage exceeds 30% of the total mass of materials fed into the furnace (kiln).
In order to make the public feel more at ease about incineration facilities and strengthen supervision, the new standard also increases the requirements for online monitoring of operating conditions and flue gas emissions. The flue gas purification system of the facility shall be equipped with on-line monitoring equipment, which can detect and record the furnace temperature, operating conditions such as O2 and CO, and emission data of pollutants such as particulate matter, HCl, SO2 and NOX in the flue gas at any time. And set up a public notice board outside the factory to display the test data immediately and accept public supervision. At the same time, the system is networked with the monitoring center of the local environmental protection administrative department and subject to the supervision and management of law enforcement departments. In addition, the frequency of self-monitoring and supervision and monitoring is also required.