In order to realize high-efficiency and low-cost mercury emission control

a fly ash modifier was added to a supercritical 1 000 MW coal-fired boiler for fly ash real time modification. The influence of fly ash modification on mercury emission and migration were studied at different loads. The results showed that

the addition of the fly ash modifier promoted oxidation of mercury and significantly improved the mercury adsorption by fly ash. The finer the fly ash particle

the stronger the mercury adsorption capacity of the fly ash. At 900 MW

after adding the fly ash modifier

the ratio of the mercury removed by fly ash to the total mercury greatly increased from 34.5% to 93.9%～97.9%

and the ratio of the mercury entering gypsum and desulphurized waste water to the total mercury was less than 1%

so the secondary release of mercury during gypsum utilization can be prevented effectively. When the addition amount of the fly ash modifier was 40 mL/t

the mass concentration of the mercury emitted from flue gas decreased to 0.14～0.20 μg/m~3

and the overall mercury removal rate of the unit reached 95.1%～98.1%

indicating the mercury removal effect was good. At 500 MW

the effect of fly ash modifier showed to be reduced moderately

which might be related to the less fly ash cracking

larger particle size and smaller specific surface area under lower load conditions.