Two bulk conveyors prove better than one
An energy assessment at Dow Chemical’s St. Charles Operations in Hahnville, La., has led to a 272,000-million-Btu/yr reduction in natural gas use, providing $1.9 million in annual savings; costs to improve operations were paid back in about six weeks. The U.S. Department of Energy (DOE) has named the petrochemical complex a 2007 Energy Champion Plant, an honor awarded only to the top energy savers in the country.
The 2,000-acre St. Charles facility, which has been in operation since 1966, produces more than 40 different products that go into a variety of consumer goods, and relies heavily on steam — for electricity generation and process duties. Dow has an active energy-management program which includes the corporate 2015 sustainability goal of reducing energy intensity by 25% from 2005 baseline, therefore we took advantage of a “Save Energy Now” assessment sponsored by DOE’s Industrial Technologies Program to gain insights on potential energy saving opportunities. A specialist qualified on DOE’s Steam System Assessment Tool (SSAT), Riyaz Papar of Hudson Technologies came to the site and worked with an empowered team comprised of plant operators and engineers. Once SSAT was installed on their computers, the team members modeled the facility and investigated a variety of what-if scenarios for energy savings.
This led to the identification of both near- and medium-term opportunities, based on payback periods. Implementing all of these could result in a more than $5 million annual savings.
With the help of SSAT, the team pinpointed four efforts to undertake first:
- Implementing a steam-trap repair project. An audit performed before the assessment had identified all failed steam traps. SSAT enabled us to quantify the value of implementing a repair program — annual savings exceeding 112,000 million Btu of natural gas and $880,000 in costs.
- Upgrading the steam-leak management program. Initial estimates from the assessment proved overly optimistic due to inaccurate measurements taken during data gathering. However, upon verifying the measurement system and performing quantitative analysis, the revised figures still pointed to savings greater than steam trap repair alone.
Improving insulation. Inspection revealed that several areas of the steam distribution network lacked sufficient insulation per Dow standards. Using 3EPlus, DOE’s insulation calculation program, the team estimated insulation losses to be about 1%, Reducing such losses to 0.1% promised savings in gas of more than 3,000 million Btu and $25,000 in costs.
Figure 1. Adding insulation, stopping leaks and repairing steam traps played key roles.
- Boosting condensate recovery. At the time of the assessment, Dow was recovering about half of the low pressure condensate. The SSAT indicated that a site-wide recovery rate of 75% was possible. This would cut gas use by nearly 88,000 million Btu and costs by almost $650,000.