Challenges In Using Refinery Fuel Gas Feedstock for Steam Reforming Based Hydrogen Plants

Peter V Broadhurst & Graham Hinton

(Johnson Matthey Catalysts, PO Box 1, Belasis Avenue, Billingham, Cleveland TS23 1LB, UK)

ABSTRACT

Operators of steam reforming based hydrogen plants are seeking feedstock options to minimise operating costs and maximise operational flexibility. One option being considered increasingly by hydrogen plant operators associated with oil refineries is the refinery fuel gas (RFG) pool. RFG usually has a low value compared to other hydrogen plant feed options and so represents a particularly attractive feedstock option where there is excess RFG available.

RFG is a combination of refinery unit waste or by-product gases, often referred to as off gases. Off gases are sent to the RFG pool because these are difficult to process elsewhere in the refinery. Accordingly, incorporation of RFG into the hydrogen plant feed slate is not straightforward in terms of plant design and operation. The challenges may comprise

• high olefin levels;
• significant sulphur levels;
• substantial levels of higher hydrocarbons which may include naphthenes and/or aromatics;
• less usual trace and minor components;
• variability in the RFG composition as the blend of off gases changes with fluctuating operation of the contributing unit operations.

These factors impact substantially upon the design, catalyst and absorbent selection, and operation of the front end purification and the steam reforming section of the hydrogen plant. This is complicated further where the RFG is part of a complex multiple feed slate for the plant.

This paper will review the challenges presented by the use of RFG feed and the design and catalytic solutions which are available to allow the successful processing of an RFG feed.