September 14, 2016

Balancing Air/Fuel Ratio with Gas Chromatography – A Glass Manufacturing Example

 

Hi. I’m Bonnie Crossland, Rosemount product manager for gas chromatograph (GC) technology and I’ll be your analytic expert today. I recently had an opportunity to write an article for InTech magazine and I’d like to share with you some of the ideas from that article.

mj-2016_web-exclusive-storyYou may be aware that glass production is one of the most energy intensive industries, with energy costs topping 14% of total production costs. The bulk of energy consumed comes from natural gas combustion for heating furnaces to melt raw materials, which are then transformed into glass. Additionally, glass manufacturing is sensitive to the combustion processes, which can affect the quality of the glass and shorten the lifespan of the melting tanks if not managed properly. Historically, the composition of natural gas has been relatively stable. However, dramatic changes in the supply of natural gas (including shale gas and liquefied natural gas imports) are causing end users to experience rapid and pronounced fluctuations in gas quality.

You may not have anything to do with glass manufacturing, however, this application is an excellent example of the impact of the combustion process on energy consumption in any industry – and the best ways to measure and control that process. Many companies in a wide range of industries faced with the problems of inconsistent quality in natural gas may not have considered gas chromatography as a viable solution for balancing air/fuel ratio due to the traditional complexities of the measurement. It’s time to look again. New developments in gas chromatography technology may make this approach the first choice for improving energy efficiency, and ultimately, process quality.

The efficiency of the furnace can be optimized for the air/fuel ratio when the composition of the incoming gas changes. This can significantly reduce energy consumption and provide substantial savings to the business in product quality and equipment life. Optimizing the furnace efficiency has traditionally been complex and costly. Next-generation gas chromatography, however, is changing that paradigm, providing a cost-effective, task-focused methodology that can be carried out by less technically proficient personnel than were traditionally required.

A major glass company in the southeastern U.S. is a heavy user of natural gas. However, the gas comes from multiple locations, causing a constant fluctuation of the BTU value. Because gas flow is adjusted based on the BTU value, knowing the precise measurement is essential. In addition, because gases with the same BTU operate differently through a burner, knowing the Wobbe Index is critical to quality.

mj-2016_we-fig-1When the company began employing a gas chromatograph to optimize its fuel quality, it found the traditional intricacies of gas chromatographs inappropriate for its application. Despite repeated training, its staff was unable to calibrate the instrument. New GC technologies designed specifically for natural gas optimization significantly reduced the complexity of operation. In new designs, all of the complex analytical functions of the gas chromatograph may be contained in a replaceable module, greatly simplifying maintenance. Features like auto-calibration make operation easier and more accurate, even for novice users. And unlike other analyzers that change the air/fuel ratio based on feedback after combustion, the GC offers a feed-forward control, where the air/fuel ratio can be changed based on the composition before combustion occurs in the flue. This can help stay in emission compliance and maintain energy efficiency with the GC.

The InTech article has a lot of other details on the need and process of optimizing combustion and the effectiveness of new generation GCs in meeting those needs. Gas chromatographs are used throughout the natural gas chain of custody (from wellhead to burner tip) to determine the gas composition for quality monitoring and energy content. For pipeline quality natural gas, the industry standard is the C6+ measurement method. If your company is a user of natural gas, you may already have GCs involved in your process. Using them to ensure the efficiency of your combustion and the ultimate quality of the product is just another vital addition. If you aren’t currently using GCs, let me know if you have any questions, or would like a demonstration, by leaving a comment HERE, or emailing me HERE.

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