Estimate of arsenic emission amount from the coal power stations in china

Abstract

To study the amount of arsenic emission from the coal power stations (mainly Permo-Carboniferous coal) in China in different combustion conditions, the arsenic content of the coal, the fly ash and the cinder in high-temperature power stations as well as mid-low temperature power stations have been analyzed. This note provides a rough estimate of the total amount of arsenic emission as well as emission ratio from steam coal combustion in China. The results show that by combustion of 1 t of Permo-Carboniferous coal (containing roughly 5 mg/kg arsenic), high-temperature power stations emit roughly 0.40 g arsenic into the atmosphere and the arsenic emission rate is about 7.70%; mid-low power stations emit roughly 0.15 g arsenic into the atmosphere and the arsenic emission rate is about 2.97%. A total of 600 million tons coal is burnt annually in China power stations, and the coal comes mainly from Permo-Carboniferous depositing in the North China Plate and northwest China coal mines. Taking the average arsenic content of the coal used at the value of 5 mg/kg, the total annual arsenic emission from steam coal combustion into the atmosphere is about 195.0 t. Most of the arsenic in coal can be released in the process of coal combustion, and the most of the released arsenic can be seized by the fly ash and then both of them are seized by the dust catcher of power station, so the arsenic emission ratio to the atmosphere is declined; in addition, research on the arsenic emission amount and emission rules from the coal power stations in China should go on the coal power stations with the dry-process dust catchers by the experiments results. In the wet process of dust catcher, 20% of the arsenic in the fly ash is dissolved in the water of sedimentation tank in high-temperature power station; in the mid-low temperature power station there are 70% of the arsenic in the fly ash dissolved in the water of sedimentation tank, this is an important source of arsenic pollution in environment and should not be overlooked. The arsenic emission rate in the process of coal cineration in the laboratory is higher than the actual arsenic emission rate of power station.