A new approach to reducing slagging based on laser modification of heating surfaces: Field tests and mathematical modeling

[Display omitted] •Ash deposition on metal surfaces was tested at an operating boiler house and during modeling.•Laser-textured surfaces are less prone to slagging than ground ones.•Microchannel texture allows reducing the slagging intensity by up to 60%.•Laser modification increases the efficiency of heat exchange equipment up to 2.7 times. The article presents the results of field tests of a new approach to reducing slagging of a boiler furnace. The approach involves laser radiation treatment of metal surfaces to obtain a coating with a high degree of passivation and a special texture (microchannel or anisotropic). Due to the texture and formation of the oxide layer, the resistance of the heating surfaces to adhesion of hydrocarbon fuel combustion products, including slag, is increased. Field tests were conducted over 60 days in an operating boiler burning brown coal, the combustion products of which form solid ferrous and sulfate–calcium deposits. The study used scanning microscopy, X-ray fluorescence spectral analysis and mass analysis of slag deposits. The results showed that steel samples with the Microchannels texture formed by laser radiation are characterized by increased resistance to adhesion of brown coal slag. Using the original software code, a mathematical model has been developed to describe the slag deposition process on heat exchange surfaces modified by laser radiation. A numerical simulation was performed under conditions of dynamic change in the thickness of the slag layer on the surface of the heat exchanger pipe to assess the heat transfer characteristics in the “hot flue gases – slag layer – pipe wall – liquid coolant” system. The results showed that the steel surface modified by laser radiation, compared to the untreated surface, is resistant to slagging at the initial stages of interaction with molten ash from different types of fuel. The use of laser-modified surfaces in boiler furnaces will increase the intervals between procedures for cleaning the furnace from slag by up to 64 %. Also, due to the increase in absorbed heat per unit area by 1.6–2.2 times, the use of laser-modified surfaces increases the efficiency of energy production.