Abstract: The releasing temperature of safety valves on the top of hot low pressure separator is about 360 ℃, but the design temperature of flare pipes is usually bellow 260 ℃. Available methods are needed to decrease the releasing temperature from 360 ℃ to 260 ℃. The HTRI software is used to simulate several cooling schemes, which are compared and analyzed in economy and feasibility. We may draw conclusions that the scheme of embedding the cooling exchangers inside the flare drum of unit is preferred and the schemes of fin pipes and double pipes are fit for installing on flare pipes outside unit.

Key words: HTRI, residuum hydrotreating, hot low pressure separator, pressure drop, cooling