Waste gas purification and environmental protection equipment requirements: 4+1 (Yin Yiguo)

Exhaust gas purification and environmental protection equipment requirements: 4+1

Yin Yiguo

Since the promulgation of the Law of the People's Republic of China on Cleaner Production Promotion, our metal packaging industry has to implement clean production according to law, improve resource utilization, reduce and avoid the generation of pollutants, protect and improve the environment, and the time is tight and the situation is grim. On the one hand, the state is stepping up enforcement of environmental protection regulations. On the other hand, many of our printing and iron enterprises have indeed produced exhaust gas that has not been effectively purified. Under the current conditions, it is a good solution for the printing and ironing enterprises to install exhaust gas purification and environmental protection equipment in the coating drying room. However, because they need to consume more energy and some manufacturers' product performance has yet to be confirmed, many enterprises have various doubts and view. I would like to introduce to you the requirements and relevant data on the installation of exhaust gas purification and environmental protection equipment at home and abroad in recent years. The exhaust gas purification and environmental protection equipment that can achieve the "double effect of environmental protection and energy conservation" is the most ideal and successful. To this end, I proposed the technical target of “4+1” exhaust gas purification and environmental protection equipment for your reference.

First, "4+1" content

4 is:

1. The exhaust gas purification effect reaches the national environmental protection standard of QB/6270-1996 in the case of smokeless and odorless.

2. The heat discharged from the exhaust gas purification and environmental protection equipment should be recycled and fully utilized.

3. The heat discharged by environmental protection equipment should be controllable when used for printing iron and coating drying room. The general accuracy is ±3 °C.

4. Does not affect product quality.

+1 is:

The operating system of the waste gas treatment environmental protection equipment and the operating system of the drying room are independent and mutually controllable, which is conducive to the normal operation of production scheduling and drying room.

It should be noted that after the discharge of the waste gas purification and environmental protection equipment of the coating production line is recovered, the heat exchanger system can supply heat to the other drying room, and the remaining amount can provide heat source to another printing iron drying room, which can reduce the heat source consumption of the printing iron baking room, and even It can completely shut down its heating system, commonly known as "one for two".

Second, the type and principle of waste gas purification and environmental protection equipment

The effective method for purifying exhaust gas in the printing and iron industry at home and abroad is the combustion method. Among them are flame combustion (direct combustion), thermal combustion, catalytic combustion and other types. Due to the low concentration of paint exhaust gas in the printing iron industry, there is no self-made fuel purification. Therefore, only the combustion methods of the latter two can be introduced.

Thermal combustion (also known as incineration)

It relies on the heat generated by the combustion of the auxiliary fuel (burner) to raise the temperature of the exhaust gas and vaporize the hydrocarbon-containing components in the exhaust gas. Decomposition turns into harmless carbon dioxide and water vapor. For the printing iron industry, in order to achieve the desired purification effect, it is necessary to design an incinerator that meets the capacity of the drying room, the baking process, and the circulating air volume, that is, to achieve the heat. Three T" conditions: The reaction temperature in the furnace is about 760 ° C. The exhaust gas residence time (Time) at this temperature, the exhaust gas and the well-mixed (Turbulence) can fully purify the exhaust gas. Therefore, for different specifications of the drying room, different coating varieties must have a reasonable plan, although thermal combustion is the most thorough method to purify waste, but because it is purified at 760 ° C high temperature, it is necessary to use this method to purify the exhaust gas. Recycling of heat can reflect the practicality and economy of environmental protection equipment.

Catalytic combustion

The catalyst is used in the combustion of the exhaust gas to accelerate the reaction speed of the decomposition of the exhaust gas, so that when the exhaust gas passes through the catalyst layer, only the temperature of 250 to 400 ° C is required to purify the exhaust gas, which is obviously economical. Therefore, the design of the catalytic combustion method must be matched with different drying ovens and coatings to make the high-efficiency catalysts match the concentration of the exhaust gas in the variety and amount of the catalytic chamber, so as to fully purify the exhaust gas. Generally, the catalyst composition is divided into three parts: the active component, the cocatalyst and the carrier, wherein the active component is the main body of the catalyst, and the catalytic reaction cannot be completed without it. The most preferable active component is a noble metal such as platinum or palladium, and again nickel. Transitional non-precious metals such as cobalt. They have a long service life, high activity, and do not have the required activity when the cocatalyst is present alone. However, when it coexists with the former, the activity of the active component can be increased. The carrier supports the above catalyst, and the catalyst has a suitable shape and particle size, and has a large specific surface area, which is favorable for reaction, heat transfer and dilution. Extend the life of the catalyst. The carrier may be in the form of a sheet, a honeycomb, a pellet, a column or the like. Therefore, the choice and arrangement of the catalyst is crucial, but in the process of purifying the exhaust gas, the activity of the catalyst is always gradually decreasing over time, that is, we call the catalyst aging or poisoning because the catalyst is at a high temperature. Long-term use will cause grain growth, sintering phenomenon will occur, and the specific surface area will eventually fail. Therefore, the use of this method will reduce the catalyst, and the catalyst replacement will always occur.

Third, the comparison of combustion method and catalytic combustion method

These two methods are currently the most concerned and commonly used methods in the ironworks.

Incineration method: simple structure, convenient management, and a complete burning method. It is the most thorough method for purifying exhaust gas, and is widely used at home and abroad. However, since the method purifies exhaust gas at a high temperature of 750-800 ° C, the heat is added and utilized. It is the key to the technology, otherwise it will lose its practical value. At present, domestic incinerators have been able to recycle heat for production, achieving the goal of one to two (the original two ovens are closed for use), depending on the specific conditions of each printing plant.

Catalytic combustion method: The purification temperature of the exhaust gas can be reduced by 250 to 400 ° C through the catalytic layer, which is more energy efficient than the incineration method. However, if heat recovery is not carried out, the energy consumption of the catalytic furnace plus the energy consumption of the two combustion chambers of the original paint drying room will of course increase the production cost for the printing iron factory. At present, there are catalyzed environmentally friendly furnaces that can carry out one-to-one heat recovery (the two combustion chambers in the paint drying room are stopped), which is a welcome phenomenon. If the life of the catalyst can be extended to more than two years, it is more practical. In addition, strengthening the management of catalytic environmental protection furnaces and avoiding catalyst exposure to substances such as sulfur and iron are important measures to prolong the life of the catalyst.

The above two combustion methods have one thing in common, that is, to fully utilize the heat generated by the exhaust gas during oxidative decomposition to provide the temperature requirement of the combustion chamber. Therefore, the concentration of the exhaust gas is conducive to saving energy. It is hoped that the various iron works in the printing iron production line will be the best condition.

Fourth, the relevant data

The energy consumption of the 33-meter-long paint drying room is 35-400,000 kcal/hour;

The energy consumption of the 27-meter-long printing iron oven is 25-300,000 kcal/hour;

If kerosene is used as fuel, the calorific value of kerosene is 10,000 kcal/kg, then the kerosene consumption in two drying rooms is 60-70 kg/h;

Therefore, in the case of “one for two”, the exhaust gas purification and environmental protection equipment is an ideal environmental protection equipment with an energy consumption of 700,000 kcal/hour, achieving the dual effects of environmental protection.

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