Waste Heat Recovery Using a Circulating Heat Medium Loop

Abstract

As energy costs continue to increase, one must be willing to accept greater complexities in heat recovery systems. The days of being satisfied with only simple hot product to cold feed exchange, restricted to the plot boundaries of each unit, are a thing of the past. This paper presents results of a refinery-wide survey to identify potential high temperature heat sources that are not being recovered and low temperature systems that consume fuel. The best candidates in each category were connected by a circulating heat medium loop where waste heat is recovered for useful purposes. The heat medium chosen is turbine fuel. It is pumped around the refinery to pick up heat at the crude distilling unit, the hydrocracker, the catalytic cracker, and the coker; the heat is used to reboil a butylenes splitter column and to preheat boiler feed Water. The heat that is recovered is equivalent to some 660 B/D of fuel: at an illustrative fuel value of say $30 per barrel, the value of the recovered heat is $20,000 per day.

An energy conservation project at Shell's Norco (Louisiana) Manufacturing Complex involves several processing units and recovers heat that was previously lost to air or cooling water. The recovered heat is used to reboil a butylenes splitter column and to preheat boiler feed water. Essentially, the system consists of a circulating heat medium that transfers waste heat to heat consumers. The heat medium picks up heat from multiple donors and transfers it to multiple consumers.