Membrane cleaning and its impact on plant operations and economics in food and biotech industry

• Membrane cleaning is an integrated part of the daily membrane plant operation in the food and biotech industry. However, the impact of membrane cleaning on the plant operations and economics are often neglected parameters in the development of new applications despite the fact that the cost for membrane cleaning is a dominating membrane operating expenditure apart from electricity. The aim of this paper is to provide some insights on the importance of membrane cleaning and how it can be optimised from an operating and economical point of view and to give an outlook how membrane cleaning can be further improved by moving from empirical understanding of cleaning to a more fundamental approach. Membrane cleaning and plant operationAlready during the test on lab and pilot scale cleaning has to be considered and if possible optimised. In the food and biotech industry a 4-hour-per-day-cleaning consisting of: flushing – caustic cleaning – flushing – acid cleaning – flushing – caustic cleaning – flushing is often standard. Reducing or combining steps - e.g. replacing two chemical steps by one enzymatic step - does not only reduce the amount of water and chemicals used but also the plant downtime and thus increases the daily plant capacity. Furthermore, cleaning at the appropriate time is another important factor to maximise plant capacity by replacing one cleaning cycle of four hours per day with two cleaning cycles of two hours per day. Additional, the impact of plant design, in particular continuous operations with sequential cleaning versus conventional cleaning of the complete plant will be discussed. Membrane cleaning and plant economics Membrane cleaning has a significant impact on operational (OPEX) and capital (CAPEX) expenditures of membrane plants. The key factors influencing the OPEX are costs for cleaning chemicals, rinsing water and wastewater. Furthermore, the length and frequency of cleaning has also an impact on the membrane life cycle and plant productivity, e.g. excessive cleaning can reduce the membrane life cycle significantly, while insufficient cleaning lead to lower average flux in the plant and thus a reduction of plant capacity. Optimising the cleaning cycles and cleaning frequency and will boost the average flux and increase the plant capacity. Consequently, optimising the cleaning protocol during the lab and pilot tests before the design of the plant can reduce the CAPEX of the plant and can thus have a significant impact on the overall process economics. Different approaches to improve membrane cleaning with regard to plant operations and economics will be demonstrated with application studies related to the food and biotech industry, i.e. for starch and protein applications. Outlook and conclusionsMost of the approaches to optimise membrane cleaning are currently of empirical nature. In order to overcome this, a deeper and more fundamental understanding of membrane cleaning is required using e.g. real time monitoring technologies such as ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D) and confocal laser scanning microscopy (CLSM) combined with cleaning models. Overall, this paper will demonstrate the importance of membrane cleaning in the food and biotech industry and will provide an insight into how membrane cleaning can be optimised with regard to plant operation and economics.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)

Nyckelord

Membrane filtration

Fouling

Cleaning

Food industry

Biotech industry

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