Add an external cooler for the medium-pressure absorption tower so as to reduce the heat load of absorption tower and the addition amount of reflux ammonia.

Calculation was made for liquid phase components of the first stage absorption external cooler in urea unit with water solution full circulation, the operating status of traditional medium pressure absorption system was introduced, the optimal operation method of medium pressure absorption system under high load condition was raised, and the applied situation of actual production was summarized.

Extermal cooling technology is one of the key technology to realize fast-cast-rolling pro cess of a-lu mini um,that is through compulsive cooling on the outside surface of rollers to improve the cooling abili-ty of system during cast-rolling,so the interface heat transfer coefficient is the important factor for the ex ternal cooling tech nology under varied external cooling conditions.

The problems on great heating and high temperature were solved perfectly through double water outer cooling technology.

Through the introduction of formulating standard and the use of external iron chill in cast steel, the paper pointed out a way for saving cost, simplifying working processes and improving quality.