Necessity and feasibility
The heat loss of exhaust gas is one of the largest heat loss for industrial natural gas boiler
, generally about 5%~12%, accounting for 60%~70% of boiler heat loss. Main factors affecting the exhaust gas heat loss is the exhaust gas temperature, under normal circumstances, each timethe exhaust gas temperature is increased by 10℃, the heat loss of exhaust gas is increased by 0.6% ~I.0%, which is equal toextra 1.2% ~2.4% coal consumption. Therefore, reducing exhaust gas temperature has an important practical significanceto save fuels and reduce pollution.
As we all know, there are many industrial natural gas steam boiler technique transformation solutions for the purpose of reducing the exhaust gastemperature of boiler, however, considering that most of boiler tail flue space is small and it has high requirement of abrasion resistance and corrosion resistance, so we adopt the low pressure economizer byutilizing low pressure water feeding to recover boiler
exhaust heat, heating surface form utilizes the spiral ribbed composite extended surface serpentuator, nickel-chromium infiltration layer zero-gap resistance heat exchange tube in order to achieve in a limited space to minimize the exhaust gas temperature and ensure the reliable operation. Using this solution, the temperature of hot air entering into the furnace will notbe affected, in addition, the exhaust gas temperature can be adjusted according to the season and coal quality.
According to the use of boiler that is equipped with low pressure economizer, the following feasible conclusions are obtained which are based on thermodynamic calculation as well as technical and economic comparison:
1) the rear flue space of theindustrial steam boiler
can be arranged withfull open low pressure economizer heating surfaces.
the thermodynamic system and parameters of the steam turbine are suitable for the retrofit of the low pressure economizer;
3) the equipment has the advantages of investment-saving, short recovery period, feasibletechnical economy;
4) surface extending manufacturing process and quality are qualified.
To sum up, retrofitting the boiler with low pressure economizer to reduce the exhaust gas temperature is not only necessary, urgent, but also feasible.
Technical characteristics for low pressure economizer
1. the water flow of low pressure economizer can be adjusted
2. In order to improve the safety and reliability of the system, there is no need to add the pump for the water side of low pressure economizer
. The flow resistance is overcome by the pressure drop between the two stages, in this way, the required low water flow can be obtained.
The wall temperature of low pressure economizer can be controlled , which can ensure that the wall temperature is slightly higher than the flue gasdew point, low temperature corrosion will not occur easily.
3. In currentoperation, there is not too much allowance for the general boiler fan under full load, it has strict requirement to new low flow resistance even taking the exhaust gas temperature decreaseinto account. The transformation takes various measures to reduce the flue gas pressure
drop, so as to meet the requirements of boiler fan operation.
The abrasion problem of coal economizer in
4. Economizer abrasion is still one of the most important problems at home and abroad. It is also one of the key technical points to be considered in this retrofit. A number of measures are taken to improve the wear status of low pressure economizer and ensure that the life span of low pressure economizer is not less than 8~10 years
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