Case Study- Steam System Improvements at Dupont Automotive Marshall Laboratory

Abstract

Dupont's Marshall Laboratory is an automotive paint research and development facility in Philadelphia, Pennsylvania. The campus is comprised of several buildings that are served by Trigen-Philadelphia Energy Corporation's district steam loop. In 1996 Dupont management announced that it was considering moving the facility out of Philadelphia primarily due to the high operating cost compared to where they were considering relocating. The city officials responded by bringing the local electric and gas utilities to the table to negotiate better rates for Dupont. Trigen also requested the opportunity to propose energy savings opportunities, and dedicated a team of engineers to review Dupont's steam system to determine if energy savings could be realized within the steam system infrastructure. As part of a proposal to help Dupont reduce energy costs while continuing to use Trigen's steam, Trigen recommended modifications to increase energy efficiency, reduce steam system maintenance costs and implement small scale cogeneration. These recommendations included reducing the medium pressure steam distribution to low pressure, eliminating the medium pressure to low pressure reducing stations, installing a back pressure steam turbine generator, and preheating the domestic hot water with the condensate. Dupont engineers evaluated these recommended modifications and chose to implement most of them. An analysis of Dupont's past steam consumption revealed that the steam distribution system sizing was acceptable if the steam pressure was reduced from medium to low. After a test of the system and a few modifications, Dupont reduced the steam distribution system to low pressure. Energy efficiency is improved since the heat transfer losses at the low pressure are less than at the medium pressure distribution. Additionally, steam system maintenance will be significantly reduced since 12 pressure reducing stations are eliminated. With the steam pressure reduction now occurring at one location, the opportunity existed to install a backpressure turbine generator adjacent to the primary pressure reducing station. The analysis of Dupont's steam and electric load profiles demonstrated that cost savings could be realized with the installation of 150 kW of self-generation. There were a few obstacles, including meeting the utility's parallel operation requirements, that made this installation challenging. Over two years have passed since the modifications were implemented, and although cost savings are difficult to quantify since process steam use has increased, the comparison of steam consumption to heating degree days shows a reducing trend. Dupont's willingness to tackle energy conservation projects without adversely affecting their process conditions can be an example to other industrial steam users.