Reliability. Therefore, the selection of design parameters first considers the unit to operate reliably.   
Economical. Under the premise of reliable operation, the heat transfer temperature difference is increased as much as possible, the volume and weight of the heat exchange surface are reduced, and equipment investment is reduced. On the basis of technical and economic comparison, the reasonable design of the smoke temperature reduction is not lower than 20 °C. If the temperature of the flue gas is excessively reduced, in addition to the limitation of the head volume of the fan, the energy saving of the unit temperature drop will rapidly decrease, and the payback period will be greatly extended.   
Reasonable optimization. The highest level of energy is required to recover heat. Through the reasonable coupling between the boiler system and the steam turbine system, the position of the water intake and return water points of the low-temperature economizer can be reasonably optimized.   
Safety. Reasonably control the temperature of the metal wall on the heated surface and avoid the dew point of the smoke. This is a prerequisite for ensuring that the heated surface does not leak, so the solution must first satisfy this condition.
Using H-type as the heat exchange element, the heat transfer efficiency is high, the structure is compact, the ash accumulation is small, the wear resistance is good, the overall steel is strong, and the exhaust heat recovery effect is good. There is maintenance and maintenance clearance (usually 500-600mm) between the high temperature section and the low temperature section to facilitate maintenance. The low-temperature section of the contact part with the flue gas is made of sulfuric acid-resistant steel to ensure the operating life of the whole machine is ≥10 years. The flue gas inlet adopts a baffle and an anti-wear tube structure, and the smoke is evenly distributed, thereby effectively reducing wear.