Product Description
1. Process introduction
SCR (Selective Catalytic Reduction) is a selective catalytic reduction technology, which has developed rapidly in recent years and has been widely used in Western Europe and Japan. At present, the ammonia catalytic reduction method is the most applied technology. In the presence of oxygen, NH3 preferentially undergoes reduction and removal reactions with NOx to produce nitrogen and water without oxidizing with oxygen in the flue gas. The main reaction formula is:
4NO + 4NH3 + O2 → 4N2 + 6H2O (1)
2NO2 + 4NH3 + O2 → 3N2 + 6H2O (2)
In the absence of a catalyst, the above chemical reaction is only carried out in a very narrow temperature range (about 980 ℃). When using a catalyst, the reaction temperature can be controlled at 300-400 ℃, which is equivalent to the boiler economizer and air pre-treatment. The temperature of the flue gas between the heaters is an exothermic reaction. Since the concentration of NOx in the flue gas is low, the increase in the catalyst temperature caused by the reaction is negligible. SCR selective catalytic reduction denitration technology is currently the most widely used flue gas denitration technology in the world. It is basically used in most power plants in Japan, Europe, the United States and other countries and regions. It has no by-products and does not form secondary Pollution, simple device structure, and high removal efficiency (up to 90%), reliable operation, easy maintenance and other advantages. The principle of SCR technology is: under the action of a catalyst, ammonia is injected into the flue gas at a temperature of about 280 to 420 ℃ to reduce NOX to N2 and H2O.
Two; schematic diagram
NH3 and flue gas are evenly mixed and passed through a reactor filled with catalyst (such as V2O5-TiO2), where NOx and NH3 undergo a reduction reaction to produce N2 and H2O. The catalyst in the reactor is placed in multiple layers (generally 3-4 layers) in order.
The method has the following problems: the aging of the catalyst and the residual ammonia in the flue gas. In order to increase the activity of the catalyst, a college dust collector should be added before the SCR. Residual ammonia reacts with SO2 to produce (NH4) 2SO4. NH4HSO4 easily sticks to the air preheater and has a great influence on the air preheater. At the position where the SCR is arranged, we should consider the problem in many ways.
2. A brief introduction to the catalyst
It can be seen from the volume comparison that the contact area of the honeycomb catalyst is large, and the total volume required is nearly 30% smaller than other catalysts under the same design conditions. Choosing a honeycomb catalyst can reduce the size of the reactor and reduce the initial investment cost for an enterprise to increase the SCR device. From the point of view of the performance of the catalyst itself, the uniform structure of the honeycomb catalyst has a stronger ability to resist various poisoning, so the life is longer. Economical. From the safety point of view, the main accident is generally caused by the burning of dust. The honeycomb catalyst is made of active materials and will not support combustion; if it has a metal structure, a fire will not cause the destruction of the entire catalyst. From the analysis of actual working conditions, the ash content and properties and the conditions of flue gas parameters are completely within the scope of our company's experience database, and the choice of honeycomb coal contact can be fully competent.
Catalyst specifications
Item Specification
Type Honeycomb
Material TiO2, V2O5, WO3
Catalyst unit pitch 5.9mm
Catalyst unit arrangement 25 holes x 25 holes
Catalyst monomer size ((width × length × height) 150mm × 150mm × 960mm
Catalyst module size (width × length × height) 960mm × 1900mm × 1220mm
Before our company installs the catalyst, the catalyst volume meets the requirements of the performance guarantee regarding the denitration efficiency and ammonia escape rate. The design of the catalyst module can effectively prevent the short circuit of the flue gas, and the life of the sealing device is not less than the life of the catalyst. The module specifications of each layer of the catalyst are uniform and interchangeable. See below.
According to the provided flue gas parameters and the required denitration efficiency, our company can propose a denitration reactor arrangement.
3. Schematic diagram of SCR flue gas denitration process
