Improved combustion analysis techniques reduce energy consumption

While energy prices continue to fluctuate, energy remains the second leading cost pressure (behind only raw materials) currently affecting most manufacturers.

Some of the biggest culprits are incinerators, crackers, process heaters and other energy-intensive combustion-based equipment.

The harsh operating conditions associated with combustion analysis applications can eat up a sensor in no time, resulting in inaccurate and unreliable sensor measurements. This can make it nearly impossible to control these processes adequately.

However, new analysis techniques, such as tuneable diode laser spectroscopy (TDLS), can improve efficiency, maximise throughput, reduce emissions and improve safety in combustion analysis applications.

ABB, Siemens, Vaisala and Yokogawa all currently offer TDLS technology for process measurements. Most energy-intensive operations, such as those found in a refinery or chemical plant, experience considerable variability in energy consumption due to changing operating conditions, equipment degradation, fluctuating market conditions, and inefficient control strategies.

As a result, plants consume more energy than necessary, yet are unable to improve efficiency due to the inability to collect and analyse real-time performance data. Frequently, the goals of optimising efficiency and maximising throughput are at odds with the need to reduce emissions and ensure plant and personnel safety.

Effective energy management is essential for a "triple bottom line" business strategy that addresses social, economic, and environmental concerns. TDLS contributes to a triple bottom line strategy by helping increase throughput and reduce energy costs, while supporting safe and environmentally responsible operations.

Advanced process control systems require sensitive and accurate process measurements in real time, ornear-real time. APC reduces process variability and inefficiency, improves product quality and provides for more stable operations.

With few exceptions, current process analytical techniques lack the speed, accuracy, and sensitivity to provide reliable measurements for APC. Online optimisation goes beyond advanced control to optimise a process based on an economic objective function.

This is becoming more important in applications where profitability depends upon improving quality, while maximising material utilisation and minimising energy usage.

Features and benefits of TDLS technology.

Features and benefits of TDLS technology.

Historically, obtaining reliable quality measurements in time to impact control has been an issue in combustion control applications. The current best practice utilises a Zirconia sensor for point measurement of oxygen.

In applications requiring multiple measurements, point measurement cannot provide a representative sample, making it both error-prone and potentially dangerous. Process oxygen measurement requires samples to be extracted and then transported to an analyser for conditioning and analysis. This slows response time, adds cost, and degrades measurement accuracy.

Inefficient combustion can be attributed to the air/fuel ratio. Too much excess air (air rich) results in loss of efficiency and increased NOx emissions, while too little excess air (fuel rich) is downright dangerous. Carbon monoxide measurement provides an indication of fuel-rich conditions, while oxygen measurement indicate air-rich conditions.

The optimum control point is the lowest possible excess air value thatdoes not cause the system to enter into an unsafe condition or violate emissions limits. Tuneable diode laser technology is an innovative measurement technique that utilises semiconductor lasers to detect a variety of gases at trace levels in the part-per-million (ppm) or part-per-billion (ppb) range.

Tuneable lasers, which enable miniaturisation of transmission and receiving units, provide highly sensitive, quantitative measurements with fast response times without the need for recalibration. The lasers can be tuned to detect specific constituents independent of process gas concentrations.

TDLS enables high-performance measurements in real time, even in challenging process environments. Exact performance specifications may vary somewhat according to supplier; however, the benefits are universal.

To date, the most widely reported application of TDLS has been for combustion control. However, the technology potentially offers much wider applicability. In refineries, it can monitor CO, CH4, and O2 in burner flameout applications, and identify process tube leaks.

Energy can be the largest component of a manufacturer’s cost structure. Despite the recent drop in energy prices, costs are expected to trend upward over the long term.

A willingness to apply state-of-the-art technologies can have a significant impact on the success of energy management programs. Technologies, such as TDLS, that can improve performance and provide quick ROI can have a significant impact on the bottom line.

Improved combustion analysis techniques reduce energy consumption, writes Paula Hollywood.Paula Hollywood is Senior Analyst, ARC Advisory Group.

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