The atmospheric pressure furnace is one of the important equipments of the atmospheric and vacuum distillation unit of the refinery. The high-power heat pipe radiator is also the main energy-consuming equipment of the installation, and its energy consumption accounts for more than 50% of the total energy consumption of the atmospheric and vacuum distillation unit. The design pressure of the atmospheric and vacuum distillation unit of Luoyang Petrochemical Complex is 27.9MW, and the actual operating load is 34.9MW. Under the current full-load operating conditions. The flue gas exhausting temperature from the convection chamber of the atmospheric furnace is about 350 °C, the flow rate is 67 dma3/h, and the heat carrying capacity is 6.98 MW. This heat accounts for 20% of the load of the atmospheric pressure furnace and accounts for 15% of the total energy consumption of the device. This part of the calorific value is considerable, and whether it can be effectively recovered is essential for the atmospheric and vacuum distillation unit to meet the standards and energy conservation and consumption reduction work.

>>>>◆ There is a problem with the preheater of the waste heat recovery system before the transformation

>>>> The original design waste heat recovery system uses a rotary air preheater, which has the following problems:

>>>> First, the amount of air leakage is large. Due to the gap between the rotating surface and the fixed surface of the rotary preheater, and the large pressure difference between the air side and the flue gas side, the air is easily "short-circuited" at the rotor and is generated due to long-cycle operation. Deformation wear and corrosion often cause the actual air leakage coefficient to be much larger than the design air leakage coefficient. The maximum air leakage can reach about 30%, which causes unnecessary energy waste.

>>>> Second, the failure rate is high. Due to the large number of rotating parts of the rotary preheater, such as the rotor, gear oil pump, reducer, gear box, etc., in order to maintain the normal operation of these rotating parts, a complicated lubrication piping system is also required. During the actual operation, the rotor loses the dynamic balance due to the accumulation of ash, or the heat storage sheet falls off, causing the drive motor to trip, the lubrication pipeline leaks, and the rotor bearing failures often occur, such as the 1997 preheater. The class of faults reached 12 times and the abnormal outage time was 52 days, which seriously affected the safe and stable production of the device and became a hidden danger to the safe production of the device.

>>>> Third, the pressure drop is large. The multi-layer corrugated shape accumulating sheets are superimposed on each other to form the heat transfer body of the rotary preheater. The corrugated shape of the regenerator sheet obviously increases the heat transfer area and heat transfer coefficient, but also increases the pressure drop of the preheater. And because the fuel oil contains a large amount of metal salt impurities (such as Fe, Ni, Na, Ca, Mg, V, etc.) and floating dust, after combustion, it is adsorbed on a large amount of carbon particles in the high-temperature flue gas, and reaches the air preheater. When the flow rate is lowered and the temperature is lowered, it is condensed and adsorbed on the heat storage sheet, and gradually accumulates to generate ash scale. Due to the corrugated shape of the heat storage sheet and the strong ash viscosity, the general soot blowing method is difficult to remove the ash scale, thereby causing the flow passage blockage, increasing the pressure drop of the preheater and reducing the thermal conductivity. At the same time, these gray scales adhere to the heat storage sheet, which is prone to corrosion under the scale, causing the heat storage sheet to fall off and affect the safe operation of the preheater.

>>>> Four, dew point corrosion. The dew point temperature of the normal furnace flue gas of the plant is generally 140~150 °C, and the regenerator of the regenerative rotor of the rotary air preheater continuously moves to the air (cold end 0~100 °C) and flue gas (hot end) Between 180~350 °C), the heat storage sheet will be subjected to two dew point corrosions every lap during continuous heating and cooling. Often, the heat storage sheet has been corroded for one year and must be replaced as a whole. Therefore, dew point corrosion is an Achilles heel that is difficult for a rotary air preheater to escape.

>>>> Due to the above reasons, the heat recovery rate of the rotary air preheater is low, and the actual heat recovery rate of the rotary air preheater is only 4% to 5%, which is lower than the design heat of 6% to 8%. The recovery rate is also lower than the heat recovery rate of 7%~10% of the general waste heat recovery system.