There are two main factors that affect the steam temperature of the steam generator: one is the flue gas side; the other is the steam side.
The main influencing factors on the flue gas side are: 1) Changes in fuel properties. 2) Changes in air volume and distribution. 3) Changes in ash formation on the heating surface. 4) Changes in furnace temperature. 5) Adjust the furnace negative pressure within the normal range.
The main influencing factors on the steam side are: 1) Changes in steam generator load. 2) Changes in saturated steam temperature. 3) Changes in feed water temperature.
There is no doubt that the steam generator steam temperature is one of the main parameters for the safe and economical operation of the steam generator. The steam generator steam temperature directly affects the safety and economy of the unit. Excessively high steam temperature may cause the heating surface to overheat and burst the pipe, causing additional thermal stress in the steam pipe and the high-pressure part of the steam turbine, thereby shortening the service life of the equipment. On the other hand, too low steam temperature will reduce the economic efficiency of the unit, and in severe cases, water may be generated. impact.
The factors that affect the steam temperature of the steam generator mainly include the following three aspects:
1. Changes in main steam pressure
The influence of main steam pressure on superheated steam temperature is realized through the distribution of working medium enthalpy rise and the change of steam specific heat capacity. The specific heat capacity of superheated steam is greatly affected by pressure. The difference between rated steam temperature and saturation temperature increases at low pressure, and the total superheated steam The enthalpy rise will decrease.
2. Influence of feed water temperature
When the feed water temperature is lowered, such as when high heating is withdrawn, when the steam generator output remains unchanged, the low feed water temperature will inevitably lead to an increase in the amount of fuel, resulting in an increase in the total radiant heat in the furnace and the temperature difference between the furnace outlet smoke and radiant overheating. The steam temperature at the outlet of the convection superheater will increase; on the other hand, the increase in the flue gas volume and heat transfer temperature difference of the convection superheater will increase the outlet steam temperature. The sum of the two changes will cause the superheated steam temperature to increase significantly. This increase has a greater impact than simply increasing the load of the steam generator while keeping the feed water temperature unchanged. On the contrary, when the feed water temperature increases, the steam temperature will decrease.
3. Influence of the center position of the furnace flame
As the center position of the furnace flame moves upward, the furnace outlet smoke temperature will increase. Since the heat absorbed by the radiant superheater and the convection superheater increases and the steam temperature rises, the flame center position has a great influence on the superheated steam temperature.
The factors that affect the reheat steam temperature and superheat steam temperature are basically the same. However, the pressure of reheated steam is low and the average steam temperature is high. Therefore, its specific heat capacity is smaller than that of superheated steam. Therefore, when the same amount of steam obtains the same heat, the temperature change of reheated steam is larger than that of superheated steam. In short, the steam temperature of the steam generator is an important aspect of operation, but because there are many factors that affect the steam temperature, the adjustment process is difficult. This requires that steam temperature adjustment should be frequently analyzed and observed, and the idea of advance adjustment should be established.
When the temperature changes, we should strengthen the monitoring and adjustment of steam temperature, analyze the relationship between its influencing factors and changes, and explore some experience in steam temperature adjustment to guide our adjustment operations.
Post time: Nov-03-2023
