Abstract: Thermal decoking of cracking gas coolers which operate with low gas pressure is accomplished by controlling the temperature of a cleaning gas delivered to the cooler. The temperature control is achieved by mixing a cleaning gas, which has been heated in a cracking oven, with a stream of relatively cool cleaning gas upstream of the cooler.

Abstract: A quench cooler or transferline heat exchanger for quenching the effluent from a hydrocracking furnace has an inlet coupling between the cracking furnace tubes and the tubes of the quench cooler which splits the flow into a plurality of branches. The flow passages are configured to initially decelerate and then re-accelerate the gas. This involves a conical diverging diffuser section and then a tapered and branched converging section. The cross sectional transitions are smooth to avoid dead spaces and minimize pressure loss.

Abstract: In a process for the mechanical cleaning of heat exchange surfaces of an evaporator or superheater of a steam generator, a dust-laden hot waste gas being passed through the steam generator, the formation of adhesive deposits on the heat exchange surface is prevented by lowering surface temperature at least at the beginning of a cleaning cycle. The surface temperature will be reduced to below the softening temperature of the material being deposited whereby such material forms hard deposits which may be loosened from the surfaces by mechanical means such as vibration.

Abstract: A heat exchanger for cooling a hot process waste gas has an interior gas-flow pipe which is surrounded by a cooling jacket defined by a plurality of parallel pipe segments which are spaced from another and from the gas flow pipe. The pipe segments, through which a coolant flows, are mechanically and thermally interconnected to one another and to the gas flow pipe by means of a body of material having a thermal conductivity which is greater than that of the material from which the pipe segments are fabricated.