Problems with the front arch of small boilers
Thread Content
One of our units has a 4-ton steam boiler, and before the New Year, a large piece of insulation material fell off from the front arch area. Due to the intense production demands in the workshop, it wasn’t possible to stop work for repairs at that time. After the New Year, it was found that the area of the refractory material that has fallen off is getting larger and larger. Are there anyone who is familiar with the structure of this type of boiler? Could you give some advice on how to carry out the repairs? It would be best to explain in detail whether the front arch is entirely cast from refractory material, or whether bricks are used inside with refractory material applied on the outside It would be great to have a structure diagram. Thank you here; I hope Haiyou can be of some help.
Is yours a chain furnace? Boilers that typically have front and rear arches are probably coal-fired chain boilers. Our boilers are larger than yours, but the structure should be the same; the front and rear arches are arranged together to form a throat in the furnace, thereby creating turbulence in the gases inside the furnace. The front arch is designed to absorb radiant heat and re-emit it to accelerate the combustion of new coal, while also protecting the coal gates from high-temperature radiation. The function of the rear arch is mainly to direct the flue gas toward the combustion center and prolong its residence time in the furnace, thereby ensuring complete combustion of the fuel. The front arch of the boiler in our facility was formed by pouring refractory material directly; I think it should be poured in that way anyway, as it makes it stronger. Larger boilers are probably also constructed in this manner (ours has a capacity of 75 t/h). It would be best for you to shut down the boiler and check it to see the exact situation. The flame deflection corner at the upper part of the rear arch of the boiler in our facility once collapsed (the rear arch was cast, while the flame deflection corner was built with bricks; perlite insulation material was poured on top of it, but it deformed and collapsed due to heat). In the end, aluminum silicate insulation blankets were used to address the issue.
The front arch is formed by the direct casting of refractory materials
Since the front arch design makes it difficult to lay bricks and results in poor stability, as well as making it hard to ensure flatness and proper brick joints, it is recommended to replace the front arch with a structure cast from refractory concrete.
After the furnace is shut down, simply break off the refractory bricks of the front arch, and then pour the material on-site.
Our unit’s 4-ton steam boiler has a front arch that is constructed from 9 sections made of refractory material, with refractory material applied on the outside as well.
Our unit uses a 10-ton quick-install chain furnace. The front arch is cast from refractory materials. Based on your situation. I think it would be necessary to consult the manufacturer and use the boiler drawings as a reference to shape the temporary refractory bricks. A decision will be made during the shutdown for major repairs.