The main purpose of adding refractory cement or refractory brick is to avoid the sulfur in coal in the combustion process of corroding metal, especially under the conditions of high water content and low temperature of flue gas. If use natural gas after desulfurization, without considering the life circumstances, can not be adopted, but the carbon steel pipe is unsuitable for what you said, safety first! Earnestly!
I think it shouldn't. There is no refractories used for circulation pipe inside the boiler, and there is how long distance between pipe and coal fire
