Once-through steam generator

A method, comprising:

• operating a once-through steam generator comprising:
• a burning chamber of substantially rectangular cross section, the burning chamber walls of which comprise substantially vertically arranged evaporator tubes of the once-through steam generator which are connected to one another in a gastight manner via tube webs and are flowed through by a flow medium from the bottom to the top, wherein the evaporator tubes of the burning chamber walls are combined in accordance with their degree of heating by inlet headers which are arranged upstream in each case to form more heated tube groups and less heated tube groups, and wherein the respective inlet headers are assigned a feed water supply;
• at least one control valve provided in the region of the feed water supply for the controlled throttling of the mass flow of the flow medium in the evaporator tubes;
• and
• temperature measuring devices for measuring outlet temperatures of the flow medium from the evaporator tubes located in the region of outlet headers which are arranged downstream in order to determine a control variable for the at least one control valve;
• wherein each of the more heated tube groups and less heated tube groups are assigned in each case to one of the inlet headers and an outlet header,
• wherein each of the outlet headers has one of the temperature measuring devices, and
• wherein the less heated tube groups being corner wall regions of the substantially rectangular burning chamber, and wherein each of the four corner wall regions has a dedicated feed water supply line with in each case one control valve;
• and
• reducing the feed water supply of the less heated tube groups by throttling of the at least one control valve to such an extent that outlet temperatures of the more heated tube groups are equalized to those of the less heated tube groups.

A once-through steam generator, comprising:

• a burning chamber of substantially rectangular cross section and comprising burning chamber walls which comprise substantially vertically arranged evaporator tubes connected to one another in a gastight manner via tube webs and which conduct a flow medium from the bottom to the top of the burning chamber, wherein the evaporator tubes are combined to form more heated tube groups in middle wall regions of the burning chamber and less heated tube groups in corner wall regions of the burning chamber;
• a dedicated inlet header and a dedicated outlet header for each tube group;
• a dedicated feedwater supply line in fluid communication with each inlet header of the less heated tube groups;
• a control valve in the feedwater supply line for controlling a mass flow of the mass flow medium;
• a temperature measuring device for measuring outlet temperatures of the flow medium;
• a controller in signal communication with the temperature measuring device and the control valve and configured to control the mass flow rate of the flow medium in the dedicated feedwater supply line independent of a mass flow rate of the flow medium in the more heated tube groups in order to homogenize an outlet temperature of the flow medium of the less heated tube groups with an outlet temperature of the flow medium of the more heated tube groups.