Pyrogas cooling block in the EP-300 unit. Modernization at Salavatnefteorgsintez OJSC

Abstract

The output of the EP-300 unit for production of ethylene is a function of the operation of the compressor that pumps over dry gas to a significant degree. The output of the compressor in turn is determined by the temperature of the gas entering it. According to the design, this temperature must be no higher than 40°C, but it is actually 50°C and higher in the summer. This is due to insufficiently effective cooling of the pyrogas in the air and water cooling systems, so that the unit's output in the summer drops 10-15%.The following was proposed to solve this problem:• • using the cold stream from the separation block for cooling circulating water in the pyrogas cooling block [1];• • • • • scrubber T-1A equipped with structured packing was also installed for cooling pyrogas by direct contact with circulating water cooled to 15°C in a supplementary heat exchanger.A diagram of the modernized pyrogas cooling block is shown in Fig. 1. Pyrogas from the primary fractionation tower goes through the air cooler and water-cooling heat exchanger at a temperature of 50°C down to scrubber T-1A equipped with structured packing. Previously cooled water with a temperature of 15°C is fed through a nozzle distributor at the top to the packing. After contact with the water, the pyrogas goes out of the scrubber at a temperature below 40°C and enters the compressor through the separator.The condensed water vapors and hydrocarbons at the bottom of the scrubber enter the settling tank,where water is separated from the hydrocarbons. The water is partially evacuated from the unit and partially sent to heat exchangers 9 and 8, where it is successively cooled with recirculating water and the ethylene-propylene fraction taken from the still of methane tower T-10 is cooled. The ethylene-propylene fraction is heated, partially evaporated, and enters deethanizer T-11 (not shown in Fig. 1) for separation.By using the still stream from the demethanizer for cooling the circulating water, two problems can simultaneously be solved: the circulating water temperature decreases significantly and the unit power consumption for separation in deethanizer T-11 decrease significantly due to heating of the feedstock and a decrease in consumption of the steam fed to the thermosiphons.