Method for reducing hydrogen chloride emissions from air-blown asphalt

摘要

In a method for reducing hydrogen chloride emissions from an asphalt air-blowing process, an asphalt is subjected to an air-blowing process where air is bubbled through hot asphalt to raise the softening point of the asphalt. The fumes from the air-blowing process are bubbled through a liquid seal in a knockout tank before going to an incinerator and finally being emitted to the atmosphere. The knockout tank normally operates to condense oil in the fume stream, and the liquid seal is composed of this oil, as well as some of the water evolved in the air-blowing process. When using ferric chloride or ferrous chloride as a catalyst in the air-blowing process, the fume stream contains significant levels of hydrogen chloride. In this invention, a chemical modifier is added to the process oil and water seal in the knockout tank prior to the start of the process in order to reduce the amount of hydrogen chloride in the emitted fume stream by at least 25% by weight compared to the same process without the addition of the chemical modifier.