Novel Strategies for Cleaning-in-Place Operations

Abstract

Cleaning-in-place (CIP) is a widely used technique in food and pharmaceutical industries. The execution of CIP is critical for food safety and public health. Since the introduction of CIP, various studies have been performed in order to reduce the cleaning costs without compromising the cleaning quality.The starting point for this thesis was a mapping study at the world-leading brewery, Carlsberg Danmark A/S (Fredericia), in which the most time- and resource-consuming CIP operations were identified. The suggestions for improving the existing CIP systems in the brewery are representative for the processes where similar CIP systems are utilized in other fields. The findings from the mapping study led to the topics explored in thisPh.D study.The objective of this thesis is to investigate different approaches for reducing the resourceconsumption and cleaning costs during CIP operations. A number of parallel projectswere defined and conducted for this purpose. All of these projects can stand alone whenreading this thesis. Firstly, a study based on the cleaning of an industrial brewery fermenter demonstrateshow to analyse historical cleaning data to improve cleaning operations in the future. The proposed analysis approach detects anomalies in a CIP system online and offline. A trouble-shooting process is advised to guide the operators to diagnose the likely anomalyor fault. Secondly, Computational Fluid Dynamics (CFD) was used to simulate the displacement of cleaning agent by water during the intermediate and final rinses of pipe systems. The results obtained include the identification of dead zones and the calculation of rinsing time, minimum water consumption, minimum generation of waste water, and pressure drop, etc. The cross-comparison of different pipe geometries indicates the key factors that determine the cleanability of various pipe elements. CFD proves to be an effective tool for the hygienic design of pipe systems and the optimization of pipe rinsing. Thirdly, burst cleaning technique to clean the tank surfaces soiled by egg yolk was studied. The experimental observations were compared with the conventional cleaning method using continuous flows. Different cleaning parameters were investigated and optimised for removing the soil material at the lowest cleaning costs. The primary findings from pilot-scale studies were then examined in scale-up tests. Fourthly, a three-stage measurement-based partial recovery CIP system was designed. The purpose of the design was to prolong the lifetime of cleaning liquid by only recycling the clear liquid from the CIP outlet. The proposed approach was compared with other cleaning scenarios for economic analysis. Lastly, the cleaning of toothpaste soil from vessel surfaces by impinging liquid jet andfalling film was studied. The properties of the soil material and the removal force were investigated. The adhesive removal model presented by other researchers was applied to describe the experimental results. This study is the first work to integrate the effect of soil soaking and the cleaning by falling film into the existing model.