No. 036
Classification of Technology:
Air Pollution Control
Type of Industry:
Chemical; Petrochemical
Subject:
Decrease of NOx in Boiler Exhaust Gas by Ammonia Catalytic Reduction Method
1. Purpose
According to the prefectural regulation, NOx discharged from chimney stack is to be reduced from 200ppm to 60ppm.
2. Applied Technology and the Time
When installing the coal boiler in 1990, the flue gas denigration system by the dry ammonia catalytic reduction method was introduced to prevent NOx exhaust from exceeding the existing value.
3. Principle
4NO + 4NH3 + O2 -> 4N2 + 6H2O
Ammonia is injected as the reducing agent in the exhaust gas of 300 ~ 400°C to break down nitrogen oxides into harmless nitrogen and steam by the above reaction under the existence of the denigration catalyst. The process flow is described on the next page.
4. Effect and Achievement
This was installed initially from the time of new installation of a 190 t/h coal boiler and has operated stably under load changes with an achievement of under 50ppm compared with an estimated N0x value of 180ppm in the furnace denigration alone ( using low NOx burner ).
5. Future Subject
If the catalyst deteriorate, unreacted leak ammonia will increase and if the leakage exceed 5ppm, it will generate ammonium sulfate, and cause the clogging of the air preheater element. It is difficult to carry out high accuracy life analysis of deciding the replacement period of the denigration catalyst.
Implementing company:
Japan Synthetic Rubber Co., Ltd. Yokkaichi Plant
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