AM-14-44 Capital Project Breakpoints for Recovering Light Hydrocarbons and Hydrogen from Refinery Fuel Gas

Description:

The typical refinery fuel gas system has become a repository for collecting and burning purge streams and vent gases from process units to avoid flaring. Burning these light gases in refinery furnaces can lower purchased natural gas volumes to less than 50% of the total fuel demand. With abundant production of natural gas from shale deposits in the US and consequent fall in its price, increased profitability may be achieved by recovering hydrogen and valuable light hydrocarbon gases and replacing the fuel requirement with purchased natural gas. Since the US refining industry has suffered from flat product demand, uncertainties in crude and product pricing, and increasingly stringent environmental pressures, optimizing recovery of fuel gas system components can be a key element of increased profitability. Refinery fuel gas system complexity and difficulty of developing and analyzing study options have limited implementation of optimized natural gas liquids, hydrogen and light olefins recovery projects. This paper summarizes a comprehensive analytical study methodology which merges process technical skills, conceptual cost estimating and stepwise scope reduction techniques (experience-based reductions in equipment, process stream selection and product recovery targets) to produce a road map of potential candidate projects for capital project implementation. Selecting the optimal refinery off-gas improvement project can be difficult due to trade-offs of product recoveries versus capital and operating costs. This paper describes a simple and effective approach to evaluate project economic breakpoints focusing on the major equipment, operating costs and recovery product values. Since high recovery of lower boiling products affects both cryogenic system pressure and refrigeration system capacity, proper evaluation of breakpoints is essential to making good decisions.