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At present, the technology of NOx control in cement kiln mainly includes low NOx burner, staged combustion, non-selective catalytic reduction (SNCR), selective catalytic reduction (SCR), etc. The low NOx burner has been widely used in China, but its effect is greatly influenced by the kiln condition. Generally, the emission of NOx cannot achieve the desired effect, or the effect is not obvious. SCR has the advantage of high denitrification efficiency and is widely used in power plant boiler denitrification. However, due to the special requirements of SCR operating temperature window (300 ~ 400 ℃), the denitrification technology is rarely used in cement plants at home and abroad. The main reasons are as follows: (1) The flue gas coming out of C1 is typically used for generating power from its waste heat, the flue gas temperature of waste heat generating system can't satisfy the requirement of SCR temperature. (2) there is basically no space for SCR catalyst frame to be arranged around the kiln inlet. (3) the high concentration of dust and its harmful elements in the flue gas of C1 can easily cause the catalyst to be damaged and failed. (4) The disposable investment is large. The resistance of flue gas through catalyst increases resistance of kiln system. (5) the catalyst needs to be replaced every three years, and the operation cost is high. SNCR has been applied in European cement industry for more than 20 years with good effect. The comparison of technical performance parameters and economic indicators of staged combustion and SNCR denitrification technology in Sinoma is shown in table 1. You can choose different NOx control technology or combine the two NOx control technology according to raw material, fuel, equipment and different emission requirements in cement plant.

Table 1 the comparison of NOx control technology

Note: before nitrogen removal, the NOx emission value of 900mg/Nm3(with NO2 and 10% O2) is the general level of cement kilns.

Technique Source

The research achievements of the "cement kiln reducing NOx technology and equipment development project" funded by the state and provincial ministries, and the scientific research achievements and patented technology of Sinoma International for more than ten years.

Technique characteristic

The denitrification integration technology of staged combustion and SNCR at kiln inlet , denitrification efficiency was 60%~80%, NOx<300mg/Nm3;The operation cost can be effectively controlled, it can both take the advantage of low operating cost of staged combustion and the advantaged of high nitrogen removal efficiency of SNCR.

Technique principle

Staged combustion——In the reduction atmosphere, NOx is reduced to N2 by the generated CO, CH_i, H₂, HCN, NH₃, Char and so on. Coal burning in hypoxic environment can also reduce the conversion rate of N in the fuel (that is, reducing the amount of NOx produced in the decomposition furnace).

Ammonia – spraying denitrification of SNCR——Ammonia (mass concentration 20% ~ 25%) is directly sprayed into appropriate temperature zone (900 ~ 980 ℃)in decomposing furnace by atomization injection system. Then, spraying ammonia and NOx (NO, NO2, etc) occur selective non-catalytic reduction reaction. NOx were converted to non-polluting N2. If the reaction temperature is too low ,the reaction efficiency will decrease; If the reaction temperature is too high, ammonia will be oxidized directly to N2 and NO.

Sinoma denitrification integration demonstration

①         With fuel-staged combustion technology and selective non-catalytic reduction technology of low NOx decomposition furnace, it can realize the continuous control of nitrogen oxide emissions from 200 to 500 mg/m3 according to different denitrification cost, and meet the persistent adaptation requirements of environmental standards at different stages.

②         With fuel-staged combustion technology of low NOx decomposition furnace, it can reduce nitrogen oxide emissions at 30% ~ 40%, no matter using anthracite or bituminous coal, without any increase in the cement kiln operation cost, and influence of normal production of cement kiln.

③         With Ammonia – spraying selective non-catalytic reduction technology, it can reduce nitrogen oxide emissions at 50% ~ 60%. Ammonia escape concentration is 3~5 mg/m3 at large.

④         With fuel-staged combustion technology and selective non-catalytic reduction technology, it can reduce nitrogen oxide emissions at 60% ~ 80%. Ammonia escape concentration is 1~3 mg/m3 at large.

Achievements appraisal

 

Engineering service for denitrification technology of Sinoma

1.Field calibration (temperature, oxygen content, NOx determination)

2. Analysis of the kiln inlet structure and searching for suitable injection points.

3. Scheme resolution , searching for suitable injection points and to control wind velocity with numerical simulation.

4. Design of system integration and equipment supply.

5. Civil construction and equipment installation.

6. Debugging optimization and technical consultation.

7. Operation personnel training of nitrogen removal system.

8. Operation of nitrogen removal system and maintenance manual.