The development of international low nitrogen incineration technology has experienced three generations. In the first generation, the combustion system has been greatly modified; in the second generation, the combustion system is characterized by an air staged incinerator; in the third generation, the combustion system (or incinerator) is implemented simultaneously in the furnace.
The first generation of low NOx incineration technology
This generation of technology does not require large-scale modification of the incineration system, but only mediation or improvement of the operation method or one-sided operation method of the incineration assembly. It is simple and easy to be used in the active assembly, but the low range of NOx is very limited. It is important to experience the following methods to complete the low NOx emission concentration.
(1) operation with low and excessive atmosphere coefficient.
This is a simple skill of burning and reducing NO x production. It does not need to arrange the incineration assembly, and the operation with too low gas coefficient can restrain the production of NO x, which is related to the fuel variety, incineration method and slag discharge method. Too much atmosphere coefficient of steam boiler in power station can not be adjusted by a large margin. As for coal-fired boiler, too low atmosphere coefficient will lead to fouling and erosion of heating surface, change of steam temperature characteristics and economic decline due to increase of fly ash combustibles. As for the gas and oil boiler, the key limitation is that the CO concentration exceeds the standard.
(2) low preheating temperature of combustion supporting atmosphere.
The preheating temperature of low combustion supporting atmosphere can reduce the peak temperature in the flame zone, thus reducing the production of thermal NOx. This mistake should not be used in coal-fired or oil fired boiler. As for gas-fired boiler, there is low No. The results of the emissions.
(3) thick and thin incineration technology.
This technique is to make one-sided fuel burn under the condition that the atmosphere is not enough, i.e. the fuel is too thick; the other one-sided fuel burn under the condition that the atmosphere is redundant, i.e. the fuel is too thin. No matter it is over concentrated incineration or over light incineration, its excess atmosphere coefficient α is not 1. The former is α & lt; 1, and the latter is α & gt; 1, so it is also called non chemical equivalent incineration or error incineration. In the process of dense and lean incineration, the fuel is too rich because the oxygen is not enough and the incineration temperature is not high, so the fuel type NO x and thermal type NO x are both reduced. Because of the large amount of atmosphere and low combustion temperature, the thermal NOx production is also reduced. The total consequence is that NO x production is lower than that of conventional incineration.
(4) flue gas in furnace is recycled.
Mixing flue gas into combustion supporting atmosphere and lowering the oxygen concentration of combustion supporting atmosphere is a kind of low-level coal-fired liquid slag extractor, especially the NO x emission technique of gas and oil fired boiler. Usually, the flue gas is discharged from the outlet of the economizer into the secondary air or primary air. When entering the secondary air, there is no influence in the middle of the flame. Its sole purpose is to lower the flame temperature, which is beneficial to reduce the production of thermal NOx. For the solid-state slag removal boiler, about 80% of NO x is produced by fuel nitrogen, and the application of this technique is the most limited.
As for the non graded incinerator, the result of mixing fire and gas in the primary air is better, but the burning condition near the incinerator will be changed, so it is necessary to mediate the burning process.
(5) the one-sided incinerator is out of operation.
This technique is suitable for multi-layer power plant boiler with incinerator. The detailed method is to stop the fuel supply of the top layer or several layers of incinerator and only send the atmosphere. In this way, all the fuel is fed into the furnace from the bottom incinerator, the bottom incinerator area is burned with rich fuel, and the atmosphere of sending people from the surface causes graded air supply. This technique is especially suitable for gas and oil boiler, and it is unnecessary to carry out a huge innovation on the fuel delivery system. This technique has been used in large lignite units in Germany with good results.
The second generation of low NOx incineration technology
The feature of this generation technology is that the combustion supporting atmosphere is sent to people for incineration assembly in stages, so as to reduce the oxygen concentration in the initial incineration area (also known as the primary area) and the peak temperature of the flame in response. There are many kinds of low NO x atmosphere staged incinerators which are widely used in power plant steam boiler. For example, abb-ce's integrated furnace atmosphere graded DC incinerator and coaxial incineration system (CFS
I, CFS 11), low NO x co axial incineration system (lncfs) and its various variation modes, tfs2000 incineration system, dual regulation cyclone incinerator (DRB, drb-xcl) of B & W company, various cyclone incinerators of steinmuller company and Babcock company of Germany, etc.
——Author：ebico