Improved analytical techniques to boost plant performance

Paul Boughton

Being able to accurately measure mercury levels in crude oil is vital to ensuring that a plant is operating as safely as possible. However, mercury levels differ from crude to crude, depending on their source. And the analysis process, being laboratory based, takes time.

Now, however, there is a faster solution to the problem. Developed by ABLE Instruments and Controls, the Jerome 431-XE mercury analyser is a portable, hand-held unit that can easily be carried to locations where mercury might be present.

It uses a patented gold film sensor for accurate detection and measurement and is ideal for applications such as industrial hygiene monitoring, mercury spill clean up and mercury exclusion testing. Simple, push-button operation allows users to measure mercury levels from 0.003 to 0.999mg/m3 in just seconds.

The gold film sensor is inherently stable and selective to mercury, eliminating interferences common to ultraviolet analysers, such as water vapour and hydrocarbons. When the sample cycle is activated, the internal pump in the 431-XE draws a precise volume of air over the sensor. Mercury in the sample is absorbed and integrated by the sensor, registering it as proportional change in electrical resistance. The instrument computes the concentration of mercury in milligrams per cubic metre or nanograms, and displays the final result in the LCD readout. An improved film regeneration circuit in the
431-XE makes for increased sensor longevity.

Innovene called upon ABLE Instruments and Controls to assist in the detection of mercury contamination in crude oil streams at its Grangemouth site in England (Fig.1).
A Jerome analyser is now used around the Grangemouth site, within many of the different plants, to measure the mercury vapour levels in oil pipelines and storage vessels.

The main importance of mercury measurement is to protect employees’ health. There are certain strict limits to which we adhere. The Jerome is used because the analysis is almost instant.

Combustion control has always been an important aspect of plant management, both in terms of process efficiency and environmental impact.

As a result, the US-based Electric Power Research Institute (EPRI) has been carrying out trials to verify the suitability of analysers for analysing oxygen and carbon monoxide in a flue gas in order to achieve efficient combustion control.

The EPRI compared the performance of three oxygen and carbon monoxide flue gas analysers from different manufacturers. According to Servomex, its 2700 analyser ‘demonstrated outstanding results’.

Throughout the six-month duration of the test the Servomex analyser operated reliably. No further calibration was performed after initial start up. Even after an unplanned power down during the tests, the analyser restarted and after warm up continued its analysis without any significant change.

The results of regular checks carried out during the test period indicate that the oxygen sensor only needs to be calibrated on a yearly basis. Similarly, the results also indicated that the combustibles sensor should only need a span calibration every year with a zero calibration every two months. The results were also used to predict seven years as the expected lifetime of the oxygen sensor and five years as the expected lifetime of the combustibles sensor. 

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