Petroleum Refinery Catalytic Reforming -- Cutting High Energy Costs

Abstract

Hydrocarbon reforming involves a variety of chemical reactions at high temperatures and pressures in the presence of suitable catalysts. The conversion of naptha to high octane aromatics requires high energy to initiate and sustain the reaction at temperatures of 850-950oF. Hydrogen - rich off - gases are fired in combinations of process furnaces. Heat is transferred to hydrocarbon fluids by radiation, principally. Feed or return stream temperatures determine the need for convection sections. It is essential that the operation and maintenance of these furnaces be optimized to minimize production costs. This paper describes the performance testing and evaluation of a set of ten refinery furnaces used to thermally drive several reforming reactors and to regenerate catalysts. Firing rates provide an input of 216.2 x 106 Btu/hr. to the furnaces, at $1.90 per 106 Btu. The units are fitted with multiple natural draft burners. There is insufficient turbulence and swirl in the burners. Operators manually set up the burners with excessive airflows for normal, full-load firing. These furnaces represent production limits. Products of combustion exhaust at high thermal levels - the range is from 985-1700oF. The mixed gases flow through a "waste heat" boiler, or they bypass the boiler and enter a single stack. Steam generation at 150 psig averages 38,200 lb/hr. Heat is wasted via the bypass at a rate of 41.1x106 Btu /hr. at 1240oF. When airflows are reduced (to 15% excess air) the loss will be 18.7x106 Btu/hr. at 1180oF. Installation of a second, parallel waste heat boiler will result in a saving of l3.4x106 Btu/hr. Energy savings at this furnace complex will be equivalent to $628,700 per year. Investment costs were estimated to be less than $250,000 for the proposed heat trap addition.