(142a) Integration of Hydrogen and Light Ends Recovery in Oil Refineries

Off-gases from hydroprocessors are typically rich in both hydrogen and valuable light hydrocarbons, such as propane and butanes. Due to high hydrogen production cost, hydrogen recovery from various hydrogen-rich off-gas streams is of critical importance to improve hydrogen utilisation in oil refineries and, therefore, a key subject in Refinery Hydrogen Management. Due to its economic benefit, light ends recovery from off-gas is another key area of interest in the refining industry, which is mainly dealt with in refinery gas plants. There are evident synergies between hydrogen recovery and light ends recovery. Recovering one component will make other components more concentrated and, thus, easier to recover. However, even though hydrogen and light hydrocarbon recovery have been deeply investigated as separate topics in the past, there is a lack of systematic approach and investigation of the integration of between hydrogen and light ends recovery in the refining industry.

Absorption is commonly adopted as the procedure for light ends recovery. In theory, absorption can then be integrated with various hydrogen recovery schemes, such as membrane and PSA. In this work, a process for absorption-based light ends recovery is developed and incorporated into the modelling and optimisation framework for refinery hydrogen management, in order to quantitatively analyse and optimise various integrated recovery schemes.

A retrofit study in a 10 mt/y Chinese refinery has been carried out using this integrated procedure. Compared with isolated recovery schemes, the optimal integrated scheme for hydrogen and light ends recovery shows significant economic benefits, with a reduction in the operating costs of 20 mUS$/y, and payback time of just over 3 months. This case study illustrates the importance of the integrated procedure considering hydrogen and light ends recovery simultaneously as well as demonstrates the effectiveness of the developed modelling and optimisation methodology.