Semi-dry desulphurization and defoaming agent for a long time, so as to control the liquid level in the tower, eliminate the bubble caused by the virtual high liquid level, prevent the slurry overflow, alleviate the foam caused by the heat exchanger (GGH) scaling and blocking problem. It is widely used in desulfurization industry.[usage] :1. Before use, tests should be conducted to determine the applicability;2. Stir gently before use;3. Calculation of dosage: generally, the dosage of defoamer is 1 ~ 5‰. The specific amount of dosage is based on the actual experiment. For the first time, the product should be added by one time impact, and then every 24 hours, but the actual amount of added is determined by the composition of foaming liquid, fume volume, coal composition and combustion conditions, absorbent, sulfur dioxide content. The unit of use can determine the amount of input according to the actual situation.4. In the process of continuous addition, the addition can be calculated by pump and added once in the intermittent process.