YLM thermal fluid heater is square coil horizontal chain grate shop-assembled heater, chain grate and heater proper are transferred separately. It adapts chain grate to realize mechanical feeding coal, mechanical venting by blower and induced draft fan, and mechanical discharging by slag machine. Fuel falls on the grate from coal bucket during operating and burning, high temperature smoke enters furnace by passing combustion arch, after radiation heat exchange, smoke enters convection heating surface for convection heat exchange, then goes to waste heat boiler and air heater, at last enters dust collector then is vented into the atmosphere through chimney by induced draft fan.