Since the promulgation of the "Cleaner Production Promotion Law of the People's Republic of China", our metal packaging industry has to implement cleaner production according to law, improve resource utilization, reduce and avoid the generation of pollutants, and protect and improve the environment. The time is pressing and the situation is severe. On the one hand, the state is increasing the enforcement of environmental laws and regulations. On the other hand, many of our printing companies do produce waste gas that has not yet been effectively purified. Under current conditions, Indian iron companies install waste gas purification and environmental protection equipment in the coating drying room is a better solution, but because they need to consume more energy and some manufacturers' product performance remains to be confirmed, many companies have various concerns and view. I would like to use this article to introduce the requirements and related 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 saving†is the most ideal and successful. To this end, I propose the technical goal of “4+1†exhaust gas purification and environmental protection equipment for your reference.
I. "4+1" content
4 is:
1. The effect of exhaust gas purification reaches the QB/6270-1996 national environmental protection standard in the absence of smoke and odorless.
2. Exhaust gas purification The heat discharged from environmental protection equipment should be recovered and fully utilized.
3. The heat emitted by the environmental protection equipment is to be controllable when using the printing iron and coating drying room. The general accuracy is ±3°C.
4, does not affect product quality.
+1 is:
The operating system of exhaust 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 exhaust gas purification and environmental protection equipment of the coating production line recovers the amount of heat discharged by the heat exchanger system and supplies the self-heating room, the remaining amount can provide another heat source for the Indian iron drying house, which can reduce the heat source consumption of the printing iron drying room, even Can completely shut down its heating system, commonly known as "one for two."
II. Introduction to types and principles of exhaust gas purification and environmental protection equipment
The effective method of purifying the exhaust gas in the domestic and international printing iron industry is the combustion method. Among them are flame combustion (direct combustion), thermal combustion, catalytic combustion and other types. Due to the low concentration of coating exhaust gas in the printing industry, it is not possible to purify the fuel by itself. Therefore, only the latter two combustion methods can be introduced.
Thermal combustion (also known as incineration)
It is based on the heat generated by the combustion of the auxiliary fuel (burner) to increase the exhaust gas temperature and vaporize the hydrocarbon-containing components in the exhaust gas. The decomposition is transformed into harmless carbon dioxide and water vapor. For the printing industry, in order to achieve the desired purification effect, it is necessary to design an incinerator that meets the requirements of drying room capacity, baking process, and circulating air volume, that is, to achieve thermal performance. Three-T" condition: The reaction temperature in the furnace is about 760°C. The exhaust gas residence time (Time) at this temperature, and the exhaust gas and the oxidizing mixture (Turbulence) can fully purify the exhaust gas. Therefore, for different types of drying rooms, different paint types must have a reasonable solution. Although thermal combustion is the most thorough way to clean waste, it is necessary to use this method to purify the exhaust gas because the exhaust gas is purified at a high temperature of 760°C. Heat recycling can reflect the practicality and economy of environmental protection equipment.
Catalytic combustion
The use of catalysts in the combustion of exhaust gas accelerates the reaction rate of 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 has significant economical efficiency. Therefore, the catalytic combustion method must be designed for different drying rooms and paints to make high-performance catalyst in the variety, the amount and the catalytic indoor air volume exhaust gas mutual support in order to fully purify the exhaust gas. The general catalyst composition is divided into three parts: the active component, the cocatalyst and the carrier. The active component is the main body of the catalyst. Without it, the catalytic reaction cannot be completed. The most ideal active components are precious metals such as platinum and palladium, and nickel again. , cobalt and other non-precious metals transition. They have long life, high activity, and do not have the required activity when the cocatalyst alone is present. However, when it coexists with the former, it can increase the activity of the active component. The carrier supports the above catalyst, so that the catalyst has a suitable shape and particle size, has a large specific surface area, is favorable for the 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 catalysts is crucial, but in the process of purifying exhaust gas, the activity of the catalyst is always decreasing with time, namely: we call the catalyst aging or poisoning, because the catalyst is at high temperature The long-term use will cause the growth of crystal grains. The sintering phenomenon will occur and the specific surface area will eventually fail. Therefore, the use of this method to convert the exhaust gas will always result in the replacement of the catalyst.
Third, the combustion method and catalytic combustion method comparison
These two methods are the most concerned and commonly used methods at the Indian Iron Works.
Incineration method: simple structure, easy management, and one-hundred burning, is the most thorough method for purifying exhaust gas. It is widely used at home and abroad, but because this method purifies the exhaust gas at a high temperature of 750-800°C, the use of heat is increased. It is a key technology, otherwise it will lose its practical value. At present, domestic incinerators have been able to recycle heat to production, reaching the goal of one to two (the original two drying rooms with four combustion chambers ceased to be used), depending on the specific conditions of the ironworks.
Catalytic combustion method: Through the catalyst layer, the purification temperature of exhaust gas can be as low as 250 to 400°C, which is more energy-efficient than incineration. However, if heat recovery is not performed, the energy consumption of the catalytic converter plus the energy consumption of the two combustion chambers of the original paint drying room will, of course, increase the production costs for the Indian Iron Works. At present, there has been a catalytic environmental protection furnace capable of one-to-one heat recovery (stopping the use of the two combustion chambers of the coating drying room). This is a promising phenomenon, and if the catalyst life can be extended to more than two years, it is more practical. In addition, strengthening the management of catalytic environmental protection furnaces and avoiding catalysts in contact with sulfur, iron and other substances are important measures to extend the life of the catalyst.
Both of the above two combustion methods have one thing in common: they fully utilize the heat emitted by the exhaust gas during the oxidative decomposition to provide the temperature requirements of the combustion chamber. Therefore, large exhaust gas concentration is conducive to saving energy consumption. It is hoped that each Indian Iron Works will be able to achieve the best conditions for the full implementation of the coating iron production line.
Fourth, relevant data
33 meters of paint drying room energy consumption to 35 ~ 400,000 kcal / hour;
The energy consumption of the 27-meter long iron drying room is 250-300,000 kcal/hour;
If kerosene is used as fuel, the calorific value of kerosene is 10,000 kcal/kg, then the two kerosene-consuming kerosene is 60 to 70 kg/hour;
Therefore, exhaust gas purification and environmental protection equipment in the "one for two" case, the energy consumption is 700,000 kcal / hour is the ideal environmental protection equipment, to achieve the dual effect of environmental protection performance.
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