Low nitrogen incineration technology
1、 Air staged incineration
Air staged incineration technology is one of the low NOx incineration technologies widely used in China. Shanxi blue sky environmental protection equipment Co., Ltd. Lang Feng'e explained.
1. The basic principle is that the atmosphere required for fuel incineration is divided into two or more stages and sent to the furnace, so that the combustion process of coal can be realized in stages on the basis of connecting all the bases with fixed excessive atmosphere coefficient:
1) * the stage is fuel rich incineration, making α < 1. 70-80% of the total space required for incineration is sent from the main incineration area to ensure that the fuel is burned under the condition of lack of oxygen, build a restorative atmosphere and restrain the production of fuel type NOx;
2) The second stage is oxygen enriched incineration, which transfers the surplus atmosphere (burnout air) from the burnout area above the main incineration area to the furnace to realize the burnout process of pulverized coal. Although there is a large amount of empty space in the burn out area, one side NOx will be produced again, but the NOx production in the furnace will be reduced.
2. Components affecting the result of NOx reduction by staged combustion in atmosphere:
1) Excessive atmosphere coefficient distribution of two-stage incineration;
2) Incineration temperature;
3) Pause time, etc;
* air staged incineration shall prevent slagging and erosion in fuel rich incineration area
Two flue gas recycling
1. Principle: extract a one-sided burned flue gas from the air preheater and simply supply it to the furnace. It is probably sent to the air box and mixed with the hot air before it is supplied to the furnace to reduce the incineration temperature and oxygen concentration, so as to reduce the NOx production;
Flue gas rebirth rate = (rebirth smoke volume) / (smoke volume without rebirth) × 100%
2. The results of NOx reduction by flue gas re cycling method are related to fuel variety and re cycling rate, and the NOx reduction rate increases with the increase of re cycling rate.
3. When the recycle rate is 15-25%, the NOx emission concentration of pulverized coal boiler can be reduced to 25%.
4. The rate of common reincarnation is 10-20%;
5. The higher the incineration temperature (e.g. the liquid slag extractor), the greater the effect of the recycling rate on the NOx depression;
* to receive flue gas reincarnation, it is necessary to install reincarnation fans, flue, etc., which increases investment and complicates the system. Therefore, it is necessary to hold a relative determination of technology and economy.
3、 Staged combustion of fuel
1. Fuel staged incineration is also known as reburning technology. It is important to exercise the principle of hydrocarbon recovery and NOx destruction. All incineration areas are divided into three parts. Lang Feng'e explained as follows:
1) Main combustion area: 80-85% of the fuel is sent to grade * incineration area, which is burned and produces NOx on the premise of > 1;
2) Reburning zone: the other 15-20% fuel is sent to the secondary incineration zone at the upper part of the main incineration zone. Under the premise of 1, a strong restorative atmosphere is created to recover NOx to N2.
3) Burn out area: located above the reburning area, send the burn out wind to burn out the products that are not completely burned
2. In the reburning zone, the components that affect the low NOx value are:
1) Type of secondary fuel;
2) Proportion of secondary fuel;
3) Excessive atmosphere coefficient in reburning zone;
4) Temperature of reburning zone;
5) The pause time of flue gas in the reburning area.
* accept the technical requirements of reburning to measure the overall height of the boiler and ensure the burn out rate of fuel in the reburning area.
In addition, the current foreign low nitrogen incineration technology of upflow also includes: dense light incineration, excessive atmosphere in low main incineration area, low NOx incinerator, etc,
——Author：ebico