Valves in action -
Pressure reducing valve DM 401
Pressure regulation of superheated steam for cleaning boilers in a coal-fired power plant
Industrial combustion processes and conventional fossil fuel energy generation produce unwanted residues in the incineration plant. Hence, all types of heat exchangers or reaction surfaces in residue incineration plants, waste incineration plants, in steel works or many petrochemical sectors must be regularly freed from soot, ashes or other deposits. If such production residues are not removed, they will impair the heat transfer and may lead to heavy malfunctions of the plant.
Especially in fossil fuel power stations, the boilers are affected by process-related heavy contaminations. In coal-fired steam generating plants, soot blowing by means of high pressure superheated steam is part of the normal operation and has proven efficient as a standard procedure for cleaning the heat exchange surfaces.
The soot blowing intervals depend on the condition of the heat exchange surfaces and are determined in accordance with the pollution index. Account should be taken in this regard of the quality of the supplied coal and/or other combustibles that may strongly vary. Consequently, the volume of the combustion residues may increase correspondingly.
In an East German coal-fired plant, the boilers on the exhaust gas side are cleaned once a day. For this purpose sootblower lances are installed on two sides in seven layers which are pushed into the boiler in sets during the blowing procedure thus aiming the steam directly towards the stains.
Two self-acting pressure reducing valves of the Mankenberg DM 401 type per boiler supply heated steam of a temperature of 450 to 470 °C to the sootblowers. The pressure reducing valves DM 401 reduce the inlet pressure of 48 bar to an outlet pressure of 28 bar at a flow rate of 8,000 and/or 15,000 kg/h, respectively.
The sturdy pressure reducing valve DM 401 has been designed for very high flow rates, high temperatures and high pressure diffe- rences and is, therefore, especially suitable for this case of application. It has been additionally fitted with a damping device that compensates for system-related pressure variations. Heat-resistant steel has been used to meet specific requirements with regards to pressure and temperature.
