Analysis of Heat Transfer Fouling by Thin Stillage From Dry Grind Corn Processing Facilities
Wilkins, Mark Robert
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https://hdl.handle.net/2142/86057
Description
Title
Analysis of Heat Transfer Fouling by Thin Stillage From Dry Grind Corn Processing Facilities
Author(s)
Wilkins, Mark Robert
Issue Date
2004
Doctoral Committee Chair(s)
Rausch, Kent D.
Department of Study
Agricultural Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Language
eng
Abstract
This study determined the effect of pH, type of acid used to adjust pH and Reynolds number on fouling by thin stillage from a commercial dry grind corn (DGC) process used to produce ethanol from corn. Thin stillage is a DGC process stream consisting primarily of unfermented dissolved solids that are concentrated by evaporators to produce an animal food. Evaporator fouling is costly in DGC processes. An annular fouling probe was used to evaluate fouling behavior of DGC thin stillage, and all tests used 30 L of thin stillage. Four 90 L thin stillage batches were used to measure the variability of fouling rates within batches using the fouling probe. Variability of fouling rate within thin stillage batches was similar to other fouling probe studies (COV < 7.1%). Three 90 L batches were obtained to study effect of pH on fouling. Samples were adjusted with 5% (w/v) NaOH or 37.5% (w/v) HCl to one of three pH levels (3.5, 4.0 or 4.5). Induction period, amount of time between the start of a fouling test and the time fouling is observed, was greater for pH 4.0 and 4.5 samples than for pH 3.5 samples. Protein content decreased and ash content increased in fouling deposits as pH increased. One 180 L batch was collected to observe the effect of acid type on fouling. Three samples were adjusted to pH 3.5 with 37.5% (w/v) HCl and three samples were adjusted to pH 3.5 with 95.9% (w/v) H2SO4. No differences in induction periods were observed. An increase in fouling after 4.5 hr was observed during some tests using HCl, but not during tests using H2SO 4. Three 120 L batches were used to study the effect of Reynolds number (Re) on fouling. Tests at Re = 440 had shorter induction periods and faster fouling rates than tests at Re = 880. Protein contents of fouling deposits from tests at both Re were similar, but ash contents of fouling deposits from tests at Re = 440 were less than ash contents from tests at Re = 880.
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