Process integration and operation optimization of Absorption-Stabilization System

More emission of high-value C₃/C₃⁺ components and higher energy consumption has been troubling the Absorption-Stabilization System in an oil refinery. In this paper, a brand-new process and operation case has been suggested based on the process integration, resulting significant energy save and C₃/C₃⁺ recovery. Where, the condensed oil tank to be operated in higher temperature; the stripper to be fed in full cold feed and equipped with a middle re-boiler; a side light gasoline to be drawn from the stabilizer column and then used as supplement absorbent; absorption column to be run in a lower temperature. The practical application shows the new process and operation success with a drop of both 17% energy consumption and 41.85% lose of C₃/C₃⁺.

I. Introduction

The Absorption-stabilization System, mainly including rich gas compressor, condensed oil tank, absorption column, stripper and re-absorption column as well as gasoline stabilizer, is widely used in Fluid Catalytic Cracking Unit (FCCU), Delayed Cracker and Hydrocracking Unit in petroleum refining industry [1]–[3]. Where, rich gas and crude naphtha from the upstream sections of the reaction and fractionation are separated into stabilized gasoline, liquefied petroleum gas (LPG) and dry gas (usually, the quality control system asks that the concentration of C₃/C₃⁺ is less than 2% in dry gas) by means of absorption and fractional processes. However, two major problems have been troubling the existing system. Firstly more high-value components such as propylene and butylene are contained in dry gas and then used as low-value fuel, resulting less productive rate of LPG; Secondly more low-pressure steam(LP) graded 1000Kpa is consumed in the stripper re-boiler, increasing the running cost [4]–[6]. This paper will aim at settling them by process integration.