Greg Wainhouse, UK Water Segment manager at Bürkert, looks at some examples of where process optimisation, involving the effective use of data, delivers application improvements and reduces costs


he control of industrial processes can be a complex operation involving

multiple valves, sensors and controllers which means there are many considerations when looking for opportunities for process optimisation. Using best practice and ensuring control protocols are updated when process changes are implemented however, ensures the process remains efficient and effective. Process control engineers are constantly

aiming for perfection while all the time tackling the challenges that stand in their way. From variable inputs to changing conditions and complex infrastructure, there is always another obstacle to overcome, but by taking advantage of expertise within the industry, it is possible to make practical improvements.

WASTE WATER PROCESSING One of the major challenges in the water treatment sector involves the sludge dewatering process, which in many cases involves high speed centrifuges that separate the solid and liquid fractions. To assist this process, a polymer is added to the sludge to help bind the solid particles together. The goal is to produce a final product that has the right consistency that makes transport efficient, without moving excess water to the fields, where it is spread as agricultural soil enhancer. The process has a number of variables,

including the percentage solids of the raw sludge, the flowrate of the sludge, the amount of polymer being added and the speed of the centrifuge. Of these, the solid content of the sludge is crucial to determine the settings for the rest of the process. There are several ways in which this can

be determined, including a process where a sludge sample is placed in a petri dish, and the water is evaporated off to obtain the mass of the solids. This is not a very efficient process and can take 45 minutes to complete. Once the results are available, the centrifuge and polymer settings can be adjusted and an improvement in the consistency of the dewatered sludge should be apparent. However, changes in the solids content

can occur frequently, which makes this process quite ineffective and labour intensive. In addition, it is a reactive process, more often used when the consistency of the dried sludge doesn’t


meet expectations. During the time taken to observe the change, complete the test and alter the settings, the centrifuge has continued to discharge a sub-standard end product. In the first instance, assessing the

percentage of solids using a turbidity sensor located on the intake to the centrifuge will increase the response time to any changes. These sensors look at refracted light to provide an approximation of the solids loading of the incoming sludge, but they can suffer from fouling problems, and the calibration process can be interpreted differently by various operators. By constantly monitoring the inlet of the

process, adjustments can be made quickly and the amount of processed sludge that falls below the required standard is minimised. Further improvements can be made by adding a flowmeter, or better still a device that provides a mass flow measurement. By creating a pro-active system that

makes adjustments based on data from the inlet, as opposed to a reactive system, means process engineers will be following best practice. This setup also reduces the amount of operator intervention and delivers a more stable output.

BREWING QUALITY An important part of the brewing process is adding oxygen to the wort to allow the yeast to thrive and create the alcohol and carbon dioxide. After the boiled wort has been chilled to fermentation temperature, oxygen is used to start the fermentation process.

By taking advantage of expertise within the process control industry, it is possible to make practical improvements

If air, which contains 20% oxygen, is

added, then the process can only achieve an O2 concentration of eight parts per million (ppm). For higher levels, around 10 ppm, typically used by commercial breweries for higher strength beers, pure oxygen is required. However, the ability of the wort to absorb

oxygen is affected by its specific gravity, which is measured on the Plato gravity scale. This measures the concentration of dissolved solids in the wort. Furthermore, each yeast strain has an optimum oxygen level and if this is not achieved precisely, the optimum fermentation rate will not be reached. Some of the most important flavour

contributors to beer are fermentation products such as esters, higher alcohols and sulphur compounds. The concentrations of these flavour compounds will be altered if the growth characteristics of the yeast are less than perfect. Achieving the optimum O2 level in the

Oxygen levels can be accurately controlled during fermentation to ensure optimum product quality

wort for each beer is essential to maintain quality. Using a mass flow sensor to establish the concentration of dissolved solids, and total volume, coupled with a mass flow controller to deliver the gas, is an efficient starting point. To improve the accuracy of the system

even more, the signal from a dissolved oxygen (DO) probe in the fermenter vessel can provide feedback to adjust the setpoint and obtain the exact level of dissolved oxygen required.

INTERPRETATION & ANALYSIS Ultimately, improving data collection, interpretation and analysis can offer many advantages. Working with experienced process control manufacturers, such as Bürkert, can yield benefits across the board. From designing new installations to improving the efficiency of existing equipment, getting the right sensor in the right place will have a significant impact.

Bürkert Fluid Control Systems


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