Brayton Cycle Heat Pump for VOC Control

Abstract

The first full size continuous operation Brayton Cycle Heat Pump (1)(2)(3) application for VOC recovery occurred in 1988. The mixed solvent recovery system was designed and supplied by NUCON for the 3M facility in Weatherford, OK (4). This first full size plant was designed to be convertible to a conventional steam regenerable unit, if the Brayton cycle regeneration was unsuitable. The successful demonstration of the Weatherford facility lead to optimization studies and the construction of mobile and portable energy efficient direct condensation and sorbent concentrated indirect condensation (BRAYCYCLE R) systems. The energy efficiency of these units is better than that of the state of the art conventional solvent recovery systems. The capital cost, even after a limited application of this technology, is competitive with conventional systems. The VOC recovery efficiency is very high (~99%) and the recovered solvent is free of water. The continued development of the application of the Brayton Cycle Heat Pumps in VOC control is discussed on the basis of energy use per unit weight solvent and capital cost per 1000 CFM contaminated air. The evolution of the P&IDs, thermohydraulics and the equipment sizes are presented. The application of this technology is particularly suitable for recovery of CFCs, water miscible solvents, and halogenated hydrocarbons. The process can be directly or indirectly coupled to various adsorbent based solvent concentrators.