Hydrocracking Waste Heat Recovery
Figure 3300-6 illustrates the principle of power recovery in a Hydrocracker. The 2500 PSIG process streams would have to be let-down through a control valve to lower pressure at three locations. The 3300 kW recovered from the three units shown represents about 7% of the total electric load for the complex. At 8.6 cents/kWH, it is valued at $2,300,000/year. Also shown are the investments, annual savings, and before-tax payouts.
Figure 3300-7 shows how air preheaters can be used in a plant to recover waste heat after all the economic steam production has been accomplished. The three fired heaters in this graphic reduce the stack temperatures to the 350°F to 500°F range while preheating ambient combustion air to the 400°F to 800°F range. Shown are the investments, annual savings, and before-tax payouts, in years, for air preheaters on the three fired heaters.