Project No: SC0004499
Performer: Reaction Engineering International
Jenny Tennant Gasification Systems Technology Manager National Energy Technology Laboratory 3610 Collins Ferry Road P.O. Box 880 Morgantown, WV 26507-0880 304-285-4830 firstname.lastname@example.org Robert Romanosky Crosscutting Research Technology Manager National Energy Technology Laboratory 3610 Collins Ferry Road P.O. Box 880 Morgantown, WV 26507-0880 304-285-4721 email@example.com Steven Seachman Project Manager National Energy Technology Laboratory 3610 Collins Ferry Road P.O. Box 880 PO3B Morgantown, WV 26507-0880 304-285-5255 firstname.lastname@example.org Mike Bockelie Principal Investigator Reaction Engineering International 77 West 200 South Salt Lake City, Utah 84101 801-364-6925 email@example.com
DOE Share: $1,098,895.00
Performer Share: $0.00
Total Award Value: $1,098,895.00
Performer website: Reaction Engineering International - http://www.reaction-eng.com
While fouling of the syngas cooler probably cannot be completely eliminated, it can be better managed. REI is pursuing mitigation technologies that include (a) periodic in situ tube cleaning with targeted soot blowing and (b) surface coatings that inhibit buildup of deposit material and provide easier removal of deposits. These technologies are being tailored for the conditions that exist in the convective syngas cooler used at coal gasification plants. The project team will acquire a new and improved understanding of the mechanisms governing fouling to form the basis for mitigation technologies.
Program Background and Project Benefits
Coal gasification, in conjunction with integrated gasification combined cycle (IGCC) power production, is under development to increase efficiency and reduce greenhouse gas emissions associated with coal-based power production. However, coal gasification plants have not achieved their full potential for superior performance and economics due to challenges with reliability and availability. In particular, performance of the syngas cooler located downstream of the gasifier has been an issue. The syngas cooler is a fire tube heat exchanger located between the gasifier and the gas turbine. The purpose of the syngas cooler is to cool the raw syngas from the gasifier and recover heat. Although it offers high efficiency, the reliability of the syngas cooler has generally been lower than that of other process equipment in the gasification island. Fouling of the syngas cooler can lead to poor performance, reduced equipment life, and increased maintenance costs. The fouling mechanism in the syngas cooler is not sufficiently understood to allow equipment vendors to develop a solution. Fouling is caused by vaporized and very fine solid ash from the gasifier depositing on the fireside surfaces in the syngas cooler. The fouling deposits occur in regions where the temperatures are lower than traditional sticking temperatures for coal-fired boilers. The Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) has partnered with Reaction Engineering International (REI) to develop technology to mitigate syngas cooler fouling. The target application for the soot blower technology developed in this project is for coal gasification plants producing syngas for power generation and for refinery and chemical production applications. If successful, the soot blower technology will improve the reliability and availability of coal gasification plants, thereby reducing the United States’ dependence on foreign energy sources and decreasing greenhouse gas emissions.
Goal and Objectives
The goal of this project is to develop technology to mitigate the fouling that occurs in the gasifier syngas cooler. In support of this goal, a combination of laboratory experiments, analyses of syngas cooler deposits, modeling, and guidance from industry will be used to (a) acquire a better understanding of fouling mechanisms and (b) develop and evaluate strategies to mitigate syngas cooler fouling, thereby improving the performance of the syngas cooler.
REI has completed analysis of gasifier feed and samples of fouling deposits taken from the syngas cooler of an IGCC plant. REI researchers, with support from the University of Utah and collaborators from the gasification industry, have conducted laboratory tests on the samples to characterize gasifier feed composition and deposit composition and morphology. The deposits are quite different from deposits that occur in coalfired boilers. The syngas cooler deposits are enriched in specific metals from the ash contained in the gasifier fuel. The deposits contain a substantial amount of fine (sub-micron) particulate, with the average particle size being about one micron and nearly all particulate is less than five microns. Layering and large char particles (~10 microns) are rarely observed in the deposits. Data collected supports the hypothesis that the deposits are not the result of surface condensation but rather are formed by aerosols generated when vaporized materials pass through cooler regions upstream of the syngas cooler.
REI has created a computational fluid dynamics (CFD) model for a "generic" syngas cooler. The model simulates a transition duct, tube sheet face, and tube bank. Deposition in the CSC was predicted using an advanced version of the REI deposition model, a mechanistic model that includes the impacts of (1) ash properties (individual particle composition, particle size, temperature, density and viscosity), (2) local conditions (gas composition, temperature, heat flux to surfaces), and (3) properties of deposits (composition, temperature, density, viscosity). The model provides predictions for the properties of particles exiting the furnace in suspension, deposition rate (growth rate) and the impacts of fouling on overall heat transfer. Model results indicate that most of the deposition occurs on uncooled surfaces upstream of the syngas cooler and on the tube sheet face of the syngas cooler. Little if any deposition occurs on the tubes themselves after the tube entrance region; this is in agreement with behavior reported by plant operators.