Characterising the cleaning behaviour of brewery foulants - to minimise the cost of cleaning in place operations.

Goode, Kylee Rebecca (2012). Characterising the cleaning behaviour of brewery foulants - to minimise the cost of cleaning in place operations. University of Birmingham. Eng.D.


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Industry operations require a clean plant to make safe, quality products consistently. As well as product quality, the environmental impact of processes has become increasingly important to industry and consumers. Cleaning In Place (CIP) is the ubiquitous method used to ensure plant cleanliness and hygiene. It is therefore vital the system is optimal and efficient. I.e. the correct cleaning agent is delivered to the fouled surface at the right time, temperature, flow rate and concentration. This cannot be assured without effective online measurement technologies.

Fryer and Asteriadou (2009) describe how the nature of a fouling deposit can be related to the cost of cleaning. The evolution of three key deposit types has also enabled current fouling and cleaning literature to be easily classified. In the brewery there are many types of soil that need to be cleaned of which the cost of cleaning was unknown. The cost of fermenter CIP in one brewery was found to be £106 k per year. Effective fouling methods for yeast and caramel; and the relationship between flow, temperature, and caustic concentration in the removal of yeast and caramel soils seen in industry has been done. This work has helped determine effective cleaning methods for these soils from stainless steel coupons and pipes.

Fermentation vessels have been found by Goode et al., (2010) to have two types of soil: A – fouling above the beer resulting from the act of fermentation, and B – fouling below the beer resulting from emptying the fermenter. The type B fouling below the beer was found to be a type 1 soil that could be removed with water. An increase in flow velocity and Reynolds number decreased cleaning time. An increase in temperature did not decrease cleaning time significantly at higher flow velocities, 0.5 m s-1. Fouling above the beer occurs when material is transported to and stick on to the wall during fermentation foaming. This happens initially and as a result the fouling has a long aging time. This yeast film represents a type 2 deposit, removed in part by water and in part by chemical. Most of the deposit could be removed by rinsing with warm water. At 50°C the greatest amount of deposit was removed in the shortest time. A visually clean surface could be achieved at all temperatures, 20, 30, 50 and 70°C, using both 2 and 0.2 wt % Advantis 210 (1 and 0.1 wt % NaOH respectively). A visually clean surface was achieved quicker at higher detergent temperatures rather than rinsing at higher flow velocity or concentration. This finding suggests most deposit can be removed with warm water and cleaned with lower detergent concentrations. Currently in the brewery 2 % NaOH is used at 70°C.

Caramel represents a type 3 soil. When heated it sticks to stainless steel and requires chemical action for removal. Confectionary caramel was cooked onto pipes and coupons and the effect of flow velocity, temperature and concentration on removal determined. At high flow velocity most of the deposit could be removed from the pipe using water. There was no significant difference in the mass of caramel removed by the water however. A visually clean surface was achieved by rinsing at 80°C with 2.5% Advantis. A visually clean surface could not be achieved at lower temperatures at higher concentration, 5% Advantis, or at higher flow velocity.

The measurement of online conductivity and flow rate values was invaluable during each experiment. Turbidity values did indicate the removal of yeast and caramel from pipes however offline measurements were required to confirm removal. Caramel removal could be wholly quantified by mass when cleaning pipes. The integration of the turbidity values measured during each rinse correlated well with the mass of deposit removed in most cases. Coupon cleaning was wholly quantified by area . A cost saving of £69 k can be made by optimising fermenter CIP to warm pre-rinsing followed by ambient caustic circulation. An £8 k saving can be made by optimising yeast tank CIP to pre-rinsing only and acid sanitisation. Industry must ensure effective online CIP measurements are made throughout cleaning to describe the process effectively and enable optimisation. It is crucial to have cleaning measurement information to hand because that is how we ensure our customers they are buying a quality product. Also you cannot optimise what you do not measure effectively.

Type of Work: Thesis (Doctorates > Eng.D.)
Award Type: Doctorates > Eng.D.
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Chemical Engineering
Funders: None/not applicable
Subjects: T Technology > TP Chemical technology


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