Abstract: 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.

Abstract: In a method for reducing hydrogen chloride emissions from an asphalt blowing process, ferric chloride and/or ferrous chloride are added to the asphalt. A chemical modifier is also added to the asphalt. The asphalt is subjected to a blowing process which produces hydrogen chloride emissions. The addition of the chemical modifier reduces the hydrogen chloride emissions by at least 25% compared to the same process without the addition of the chemical modifier. The addition of the ferric chloride and/or ferrous chloride provides beneficial effects such as increased blowing rate and increased final penetration of the asphalt. Preferably, the addition of the chemical modifier does not significantly reduce these beneficial effects.