This paper analyzed the feasibility of the organic waste gas treatment method adopted by a material packaging enterprise in Jiangsu Province, and focused on the practical operation effect of RTO (regenerative waste gas oxidation device) combined with comprehensive energy-saving technology of waste heat utilization of flue gas to treat volatile organic waste gas. Field operation data show that the emission limits of non-methane hydrocarbons meet the second level of Table 2 in the Comprehensive Emission Standards for Atmospheric Pollutants (GB16297-1996). The total investment of RTO system totals 1.6 million yuan. By installing the waste heat recovery device of flue gas, the economic benefit will be about 410,000 yuan per year. The use of this equipment not only greatly reduces VOCs emissions, but also has good social, environmental and economic benefits.

Volatile Organic Compounds (VOCs) are the most common atmospheric pollutants, including halogenated hydrocarbons, aliphatic hydrocarbons, aromatic hydrocarbons, organic acids and sulfur hydrocarbons. These organic exhaust gases can cause great direct harm to animal and plant production, human health and environmental quality. Under sunlight, VOCs react with nitrogen oxides and hydrocarbons in the atmosphere, causing a series of environmental problems, such as photochemical smog, acid rain, haze and climate change. The suspension and convergence of these volatile organic wastes in the air is also one of the reasons for the rising values of PM2.5 and PM10. Cutting down these volatile pollutants is crucial.

China is a big printing country. According to statistics, there are more than 80,000 large-scale enterprises. Most of the ink and coating industries use oily paint as coating solution, which results in the annual emission of organic waste gas as high as hundreds of thousands of tons. These VOCs not only cause great harm to people's health, but also cause a great waste of raw material resources, which leads to the rise of production costs and the decline of economic benefits. According to the production and discharge characteristics of VOCs-containing waste gas from a material packaging enterprise in Jiangsu Province, this paper adopts the "three-compartment RTO + heat recovery" process to treat the end of the waste gas of the enterprise, and achieves good economic, environmental and social benefits.

1 pollution producing links

The main products of the company include PET ordinary cigarette bag transfer film, OPP laser anti-counterfeiting transfer film, PET laser anti-counterfeiting transfer film and so on. The coating and drying sections of the project are operated on the coating machine, which consists of unwinding, pre-unwinding tension, deviation correction system, coating head, drying oven (oven), cooling system, post-winding deviation correction, tension system and winding system.

The applicator consists of coated roller, back roller (pressure roller), scraper and scraper adjusting mechanism. The coating head is the core part of the coater, and the technical ability of the coating machine depends on the coating head. The heating is made by 5 stage electric heating, GSN hot air circulation, and the highest temperature is 140 C. The base film (thickness 12-18um) placed on the unwinding device is automatically rectified and then enters the floating roller tension system. After adjusting the pre-unwinding tension, it enters the coating head. The prepared coatings are continuously coated according to the setting of the coating system. After coating, the wet film enters the drying box (oven) and is dried by hot air. After drying, the plastic film with information coating is coated. After the cold roll of the cooling system is finalized, the tension of the system is controlled well, and the winding speed (80-100m/min) is controlled well, so that it can synchronize with the coating speed. The film after cooling is automatically rectified by the rectifying system to keep it in the central position and winded by the winding device.

In the production process, there will be the mixing of waste gas, coating waste gas, drying waste gas, mainly containing ethyl acetate, n-butyl acetate, butanone, propylene glycol methyl ether and other organic pollutants. In the scheme, regenerative thermal oxidation furnace is used to treat the organic waste gas in the production process, and combined with waste heat recovery equipment, an environmental protection and energy saving treatment process route is developed for enterprises.

2 design points

2.1 air volume design

The exhaust hood is used to collect local ventilation in the workshop allocation area. The exhaust hood is set above the pollutants. According to the formula, the calculation is Q=kphvx; in the formula, the circumference of the open surface of the P-exhaust hood is m; the distance between the H-exhaust hood and the pollution source is m; the edge of the vx-pollutant is used to control the wind speed; and the k-safety factor is generally taken as 1.4. The final emission Q1 is 1200m3/h.

The project is to seal the coating machine head area and adopt full ventilation. The total ventilation volume can be determined according to the number of ventilation, that is, Q = nV, type: n-ventilation frequency, 1/h; V-ventilation room volume, m3. Because the cleanliness level of the workshop space is 7, according to GB50073-2001, the ventilation times are 15-25 times, the scheme is chosen n=20, and the emission Q2 is 2400m3/h.

The oven is equipped with hot air circulation system and exhaust device. The rated air volume of the exhaust fan is Q=5000m3/h, so the total air volume of the two production lines is Q 3=10000m3/h.

To sum up, Q total =Q1+Q2+Q3=13600m3/h. Considering that the operating margin of the treatment system is 10%, the waste gas handling capacity Q = 15 000 m3/h is determined.

2.2 waste heat recovery system

According to the actual operation of the project, the main pollutant of the waste gas collected is ethyl acetate solvent, whose concentration is 4000mg/m3. Calorific value of the waste gas is 365640 kcal/h, and the energy required to maintain the self-operation of RTO equipment is 176023 kcal/h. Therefore, the waste heat after VOC oxidation can be recovered by heat exchanger for coating. The heat balance equation is as follows:

The other formulas for calculating the economic benefits of heat recovery are as follows:

189617 (rich waste heat)*0.7 (comprehensive utilization ratio of the system)*24 (h/d)*300 (d/a)/8500 (calorific value of natural gas)=112432 (m3/a);

112432 (m3/a) x 3.65 (yuan /m3) =41 (10000 yuan /a)

In the above calculation, the benefit will vary with the actual working hours of the production line (the base of year).

Figure 1RTO