Guide: During the start-up process of the unit's pressure method and sliding parameters, the boiler side generally does not use water spray to reduce temperature to adjust the steam temperature before the steam turbine impulses.
During the start-up process of the pressure method of the unit, the boiler side generally does not use water spray desuperheating to adjust the steam temperature before the steam turbine impulses, but when the desuperheating water needs to be used in the subsequent process, it should be based on the layout characteristics of the desuperheater In accordance with the characteristics of the parameters under different conditions, rational use of primary and secondary desuperheaters can ensure the safety of the superheater and the steady rise of the main steam temperature.
For example, in the case of a low boiler thermal load, although the steam flow rate is small, the steam temperature required by the steam turbine is also low. Generally, it will not cause excessively high wall temperature of the panel superheater. At this time, if a first-stage desuperheater is used When the steam temperature is controlled and adjusted, the steam flow after the desuperheating water is sprayed is long and the flow velocity is very low. The boiler outlet steam temperature reaction is very slow and pure, which is easy to cause low steam temperature and may form a water plug in some of the serpentine tubes. Therefore, a secondary desuperheater arranged near the steam outlet should be used at this time to spray water with a small amount to finely adjust the steam temperature.
When the boiler thermal load gradually increases (such as above 30% of the rated load), the increase in the steam flow rate of the panel superheater will not be sufficient to cool the tube wall, which often makes the tube wall temperature higher or even over-temperature. At this time, the steam temperature adjustment should try to use a first-level desuperheater, which can reduce the inlet temperature of the panel superheater, and increase the flow rate between it and its subsequent heating surface, so that the safety factor of the panel superheater is improved.
However, regardless of whether the primary or secondary desuperheater is used, the phenomenon of large changes in the amount of spray water should be avoided, and attention should be paid to monitoring the change of the outlet temperature of the desuperheater.