Optimization of Technological Scheme for Unstable Hydrocarbon Condensates Demethanization

The modern technological process allowing to achieve high recovery of C2+ components is low-temperature gas rectification, including demethanization stage of unstable hydrocarbon condensates. Demethanization is based on separation of gas-liquid mixture by low-temperature rectification. The yield and quality of the target gas separation products depend on the demethanizer operation. In this connection it is important to arrange the demethanization unit operation so as to preserve the separation quality in the column and minimize ethane losses with commercial gas. One of the methods of process optimization is the use of technological techniques aimed at reducing the flow rate of gas supplied to the column.This article presents a brief overview of the demethanization process, considers the features of demethanizer operation. Technological solutions of the leading engineering company Linde are analyzed and bottlenecks in the technological scheme are revealed: low depth of ethane recovery, which is associated with high losses of ethane with dry stripped gas; large diameter of the upper part of the demethanizer, which is associated with high loads of the column on the vapor phase. In this connection the optimized technology of the process developed by Research and Design Institute «PEGAZ» LLC is offered. It is shown that application of three-stage separation of gas-liquid streams before their feeding into the demethanizer leads to unexpected results: prevention of possible ethane entrainment, reducing ethane losses, reduction of vapor phase load in the upper part of the demethanizer due to feeding only separation residues into the column as a feed stream. Implementation of such a modified scheme allows increasing the degree of ethane recovery, reducing ethane losses, reducing the mass and dimensional characteristics of the column and its cost.