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Operational experience leading to knowledge about gasification is available in a variety of sources. There are some main issues which came up repeatedly in the early years of the first generation of gasification plants, despite the wide range of feedstocks, products, and process decisions.
Most of the issues with newly built gasification plants are related to the integration of the different pieces of process equipment with one another. This is typically the boundary between one manufacturer’s responsibility and another's. These issues have been addressed increasingly as the operational knowledge base has expanded over the past 15 to 20 years.
Examples of this integration issue between the air separation unit (ASU), the gas turbine and the gasifier, have occurred in the European integrated gasification combined cycle (IGCC) plants (ELCOGAS and Nuon). Availability is highly vulnerable to an outage of any one of these systems, in particular, at facilities which require long restart periods. In fact, another lesson that was quickly learned in this first generation of plants was that the control systems for the plants should allow for the gasifiers to perform a "hot restart" when a less serious issue has triggered an emergency alarm. This avoids long restart procedural cycles in the event of a less serious upset condition or "nuisance alarm".
Other points of concern are coal preparation and the feeding system. A lot of kinks have emerged with these pre-gasification systems as gasification experience has grown that have required attention. Most of the gasification plants experienced at least minor mechanical problems in the feed system that needed to be addressed.
Particulate removal from the product syngas was also a reoccurring issue. Modifications to system piping or the types of filters needed to be adjusted to the specific application in order to remove enough particulates to prevent adverse effects in downstream processes.
Finally, issues were encountered in adapting the gas turbines to run on either syngas exclusively or a combination of syngas and natural gas. Gas turbines employed in IGCC facilities were designed based on principles from previous natural gas fired turbine experience. Inevitably, issues arose due to the unique burning characteristics of syngas versus natural gas which required modifications including redesign of the fuel nozzles to eliminate overheating.
Information about individual projects can be found on the page dealing with that facility by following the links below:
Issues with a variety of existing facilities through the first several years of operation have been reported by Phillips (2007) in an EPRI publication. The report provides plant descriptions and operating histories of the following IGCC plants:
The report also provides similar descriptions and operating history information for other gasification plants including:
The final sections of the report present an overview of findings from all the IGCC plants, broken down by process, along with a summary and conclusion. The conclusion provides analysis on which pieces of equipment lead to disruptions in operation, providing direction for future improvement of gasification technology systems.
Another report that provided information regarding past gasification experience was produced by the U.S. Department of Energy's Office of Fossil Energy (2006). The report includes a discussion of each process detailing the initial design, the encountered issues and how they were addressed, and considerations for future designs. Following discussion of the plant processes, are sections covering the diversification of the plant products, including capturing carbon dioxide (CO2) to sell via pipeline for enhanced oil recovery efforts. It also includes a look into the pre-operational phase of the project and a critique of that process.
For example, see the presentation given by EPRI, in 2004.
References/Further Reading
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