Questions under current technology regarding whether boilers and their chimneys constitute open flames or sources of sparks
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Hello, teachers! Building codes already define locations for open flames and spark generation. However, the flue gas from coal-fired boilers, after going through wet dust removal, desulfurization, and denitration processes, is emitted into chimneys. Can such chimneys still be considered sources of sparks? Speaking of gas boilers, their tanks are generally well insulated; only the front and rear viewing ports as well as the manhole covers have higher temperatures. So, can gas boilers still be considered open-flame sources? The chimney of a gas boiler is, in my opinion, merely an exhaust pipe for the combustion gases; these combustion gases as well as the boiler water undergo heat exchange to cool down. Can this chimney still be considered a source of sparks?
Hello, I have the same question: does this chimney count as a source of open flame? If so, is there a requirement for a 15-meter distance between it and the urea plant used for denitration? Should the safety distance from a chimney be measured from its center or its edge?
Isn’t a boiler also considered an open flame? Can your boiler be isolated from the outside?
Note that, according to building codes, an open flame is defined as one with exposed flames or a red-hot surface. An exposed flame is easy to understand; a red-hot surface – I assume it refers to a surface that is burning red and extremely hot. In modern gas boilers, the gas burns inside the furnace, and the insulation of the furnace body is very good. Upon on-site inspection, it was found that only the covers of the access holes at the front and back were relatively warm; noticeable radiant heat could be felt near them, but it certainly wasn’t hot enough to be considered scorching hot. Therefore, I wonder whether gas boilers are considered to be sources of open flames, and whether the chimneys through which their exhaust gases are released (which I believe are essentially the exhaust pipes for the combustion gases) are regarded as places where sparks may be generated. This is because no flying sparks were observed, and moreover, the combustion gases have already cooled down after exchanging heat with the soft water entering the boiler. Another issue is whether the chimneys of coal-fired boilers, from which emissions are released after wet dust removal, desulfurization, and denitration processes, should be considered as locations where sparks may be generated. In my opinion, after these processes, it is no longer possible for sparks to fly, so it cannot be considered a location where sparks are generated.
In building codes, open flames or red-hot surfaces refer to those that can ignite combustible gases or vapors, thereby causing backfire; therefore, if the air intake system of a gas boiler is able to draw in combustible gases, ignition can occur； And if it exceeds the ignition temperature of the combustible gas, and can be ignited upon contact with the gas, it should be considered a red-hot surface. Insulation does not prevent gas from seeping in, especially after several years of use.
Are there any quantified temperature data for red-hot surfaces?