ALLOWABLE RATE OF TEMPERATURE CHANGES DURING START-UP OF THE STEAM BOILER

In this paper the problem of the dynamics of boiler evaporator was presented. An expression for the heat flow rate from the furnace to the evaporator, as a function of change of the pressure in the boiler drum was derived from the conservation equations of mass and energy. First, the allowable rate of the steam temperature change in the boiler drum was determined with respect to the total stresses on the edge of the drum - down corner intersection using the TRD-301 boiler regulations. Later, after solving the differential equation, the temperature and pressure changes in the boiler drum, with reference to time function have been established. Knowing the pressure changes in the boiler drum, the heat flux, which shall be delivered to the boiler evaporator, was determined. On the basis of the calculations of the furnace chamber, the changes of the fuel flow, assuring the pressure changes in the boiler evaporator most comparable to the assumed ones, were determined. The fuel consumption was also determined during the start up of the boiler for the case of the maximum allowable change of the temperature of the work medium. The results specified in this paper can be used for designing boilers and for the automation of the boiler start up processes.