Boiler flue heat recovery technology
Boiler flue heat recovery is an energy-saving and environmentally friendly product developed, designed, and manufactured by our company in collaboration with key universities. Boiler flue heat recovery is a safe and reliable energy-saving product, mainly manifested in:
Technical features:
1: Significantly reduce the exhaust temperature; Fundamentally solve low-temperature corrosion.
2: Recovering medium and low temperature heat energy, safely and stably significantly reducing exhaust gas temperature; Usually, it can stabilize the exhaust temperature of coal-fired boilers to 105-115 ℃;
3: While reducing the exhaust temperature, it fundamentally avoids the occurrence of condensation corrosion and ash blockage, greatly reducing the maintenance cost of the equipment.
working principle:
At present, in the domestic boiler industry in China, due to the presence of S in fuels such as coal, oil, and natural gas, SO2 and SO3 are usually produced during combustion. SO2 and SO3 combine with H2O to form sulfurous acid or sulfuric acid vapor. When the temperature of the metal wall of the heating surface at the tail of the boiler is lower than the condensation point of sulfuric acid vapor (called the acid dew point), liquid sulfuric acid will form on its surface (called condensation).
For a long time, corrosion of the tail heating surface of air preheaters caused by condensation has occurred frequently and is difficult to avoid. So much so that currently in boiler design, it is necessary to alleviate the occurrence of condensation and corrosion by increasing the exhaust gas temperature or using non-metallic materials with extremely poor heat transfer (such as enamel pipes), without fundamentally solving the problem. Simply increasing the exhaust temperature will inevitably result in a significant waste of low-temperature energy, which cannot be further recovered. However, air preheaters often experience corrosion and eventually perforation after running for a period of time. This is a global challenge.
At present, most small and medium-sized boilers use tubular air preheaters, and the designed exhaust gas temperature remains high. In the early 1990s, heat pipe heat exchangers were once promoted in the renovation of air preheaters. Although they reduced the exhaust temperature to a certain extent, the low wall temperature of the tail heating surface was still lower than the acid dew point temperature, which could not avoid corrosion caused by condensation. Moreover, heat pipes generally produced and accumulated non condensable gases, gradually aging, resulting in a sharp decrease in heat transfer efficiency. As its shortcomings continue to be exposed, people have taken a cautious attitude towards the application of heat pipe heat exchangers.
The commonly used heat exchanger is a tubular heat exchanger, where the low wall temperature of the metal heating surface and the discharge temperature of the hot fluid are roughly in a multiple relationship, that is, when the exhaust temperature is 140 ℃, the corresponding low wall temperature is only about 70 ℃. For heat pipe heat exchangers, if the wall temperature of the metal heating surface is required to be no lower than 77.8 ℃, the exhaust temperature should usually not be lower than 155 ℃, otherwise it will inevitably cause low-temperature condensation corrosion "(see Gu Weizao et al.," Enhanced Heat Transfer ", Science Press); The wall temperature of the above-mentioned heat exchanger can only be used as the verification temperature, which means that when the operating conditions need to be adjusted due to operational needs, even if it is known that low-temperature corrosion will inevitably occur, it cannot be avoided, and there is no way to directly adjust and control the wall temperature.
The self-control combined heat exchange technology is a brand new heat exchange technology. Our company constantly innovates during the construction process. Two energy-saving products for waste heat recovery based on different principles have been developed.
Actual plan:
Option 1: Targeting lower smoke temperatures, but with lower levels of corrosive gases in the smoke.
Option 2: Directly retrofit the boiler economizer and air preheater;
Option 3: Heat the desalinated water (increase the water temperature entering the deaerator);
Option 4: Increase the inlet air temperature while heating the desalinated water;
Plan 5: Internal circulation to increase the steam production per ton of coal;
Plan 6: Generate high-temperature hot water;
Option 7: As a waste heat boiler, produce low-pressure steam;
