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Quantification of Fouling during UHT Processing in an Indirect Tubular Heat Exchanger
Quantification of Fouling during UHT Processing in an Indirect Tubular Heat Exchanger
- Publication Year :
- 2016
-
Abstract
- Fouling is a ubiquitous and financially burdensome problem in the food industry, with the potential to affect the safety and quality of products. The impacts of fouling include increased pressure drop, along with reductions in heat transfer and process efficiency. Ultimately, build-up of fouling requires system shutdown for cleaning, leading to reduced product throughput. The overall objective of this research was to investigate the ultra-high temperature (UHT) processing conditions (time and temperature) needed to reduce the rate of fouling and extend run time. Ten kilograms of 20% (w/w) reconstituted nonfat dry milk (NFDM) was processed at 127C, 132C, and 138C, and recirculated for 5 run times ranging from 3min to 60min. Flow rate was constant at 3L/min (NRe,Hold Tube˜3000). Following a water rinse, 0.5% (w/w) sodium hydroxide cleaning solution was recirculated for 30min to remove protein-based fouling from an indirect MicroThermics UHT/HTSTLab-25HV tubular system. Samples of the sodium hydroxide cleaning solution containing fouling were collected and analyzed for protein concentration using Bicinchoninic Acid and Bradford Assays, free hydroxyl group level by active alkali titration and electrical conductivity (EC) meter, and brown color by spectrophotometry at 420nm. These assays were used as indicators of fouling during processing. Results from this research indicated that protein concentration and brown color increased with run time at a given process temperature. In addition, active alkali and EC levels decreased with run time. These measurements became indicators of the rate of fouling at a constant temperature, and the changes were described by a first order model. The first order rate constants at each process temperature (127C, 132C, and 138C) were used to determine activation energy coefficients. First-order rate constants for fouling based on protein concentration were 0.0860min-1, 0.1169min-1, and 0.2053min-1, at 127C, 132C, and 138C, respectively. Based on the analysis, run times could be extended by 8% for each 1C of decrease in process temperature.
Details
- Language :
- English
- Database :
- OpenDissertations
- Publication Type :
- Dissertation/ Thesis
- Accession number :
- ddu.oai.etd.ohiolink.edu.osu1469172226