Our Business / Thermal Power StationsAir Pollution Countermeasures
When fuel burns in the boiler, the sulfur content in the fuel becomes sulfur oxides (SOx). In addition, nitrogen in the air combines with oxygen to generate nitrogen oxides (NOx), as well as soot. Restrictions on these air-polluting substances are stipulated by emission standards, etc., according to environmental preservation agreements concluded by laws and in environmental municipalities.
At our power stations, we take various measures to make sure that these standards not to be exceeded.
This device removes SOx in exhaust gas by reacting this with limestone.
This exhaust gas denitrator injects ammonia into the exhaust gas containing NOx from the boiler, a chemical reaction is promoted by the action of the catalyst to reduce NOx, then the gas decomposes into N2 and H2O.
All thermal power stations, excluding gas-dedicated thermal power stations emitting no soot, install high-performance electric precipitators. Soot passing between the high voltage discharging electrodes is electrified to be collected by electric force in the direction of the dust collecting electrodes.
An electric collects dust by attracting electrically charged dust to the dust-collecting electrode that discharges at high voltage.
We suppress the generation of NOx by controlling of the combustion temperature inside the boiler, gas turbine combustor, and so on. Specifically, we use a combination of the following methods to strive to suppress NOx.
〇 Methods to Improve Combustion for the Boilers
- Method for slow combustion, where exhaust gas is partially mixed into the combustion air and the concentration of oxygen is lowered in the combustion air (exhaust-gas-mixing method)
- Method for slow combustion, where the combustion gas is led into the boiler in 2 stages (2 stage combustion method)
- Method where a burner suppressing high-temperature combustion zone is used (low NOx burner)
〇 Method to Improve Combustion for the Gas Turbine
- Method for uniform and stable combustion, where the fuel and air are pre-mixed prior to combustion (pre-mixed combustion method)