(426b) Heat-Integrated Work Exchange Network Design

Energy loss in the manufacturing sectors is very high (~50% of the total consumption in 2010, according to a DOE report). While thermal energy efficiency has been greatly improved through adopting effective heat integration technologies over the past decade, the improvement of mechanical energy efficiency is yet to be fully investigated. Mechanical energy, often characterized by process pressure change as the driving force, is more difficult to recover; this is especially true as the pressurization/depressurization involves temperature change, which makes the process non-isothermal. Thus, effective mechanical energy recovery should be coupled with heat integration. Mechanical energy recovery can be realized using work exchangers that are currently used in industrial scale for desalination. The concept and fundamentals of this type of unit, as well as a thermodynamic analysis method for identifying the maximum amount of recoverable mechanical energy from a process system under isothermal condition has been investigated by us previously.

In this paper, a thermodynamic analysis on mechanical energy recovery under non-isothermal condition is described, and a process synthesis methodology for designing a heat-integrated work exchange network is introduced. The methodological efficacy is illustrated by two examples, where both mechanical and thermal energy efficiencies as well as economic feasibility analysis are provided. Furthermore, certain key dynamic performance of the system is analyzed, which is valuable for developing operational strategies for the integrated system.

Reference:

Energetics Incorporated, Manufacturing Energy and Carbon Footprint, Prepared for the Industrial Technologies Program (ITP), DOE, 2010.