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Size Modulation Operations
Published in Susanta Kumar Das, Madhusweta Das, Fundamentals and Operations in Food Process Engineering, 2019
Susanta Kumar Das, Madhusweta Das
Colloid mill is called a high-shear homogenizer. It is used for homogenization of fluid and making emulsion and fine dispersion of solids into liquid. In this mill, feed is pumped through a narrow gap (0.1–1.0 mm) between a high-speed rotor disc and the stator (casing) (vide Figure 7.15). The rotor is made of inert synthetic material or stainless steel (smooth or grooved or abrasive surface), and rotates at very high speed (3,000–15,000 rpm). This action results in a high degree of shear to form a thin film of material that continuously passes through the gap. Absorbed energy is sufficient to reduce the dispersed phase of size much less than the gap (Coulson et al., 1998). High power consumption in colloid mill could be reduced considerably with prior reduction in feed size. Capacity and power requirement in colloid mill are inversely proportional to each other for homogenizing highly viscous products like making of mayonnaise (Saravacos & Kostaropoulos, 2002). Numerous modified designs are available for different applications. Colloid mills are more effective than pressure homogenization for high-viscosity foods (μ > 1 Pa s). Cooling arrangement is provided for viscous foods.
Mixing and Separation Processes
Published in C. Anandharamakrishnan, S. Padma Ishwarya, Essentials and Applications of Food Engineering, 2019
C. Anandharamakrishnan, S. Padma Ishwarya
A colloid mill is more appropriate for high-viscosity liquids, as it creates high shear than pressure homogenizers (Figure 12.19). It is a vertical disk mill with a narrow gap (0.05–1.3 mm) between the stationary and rotating disks that rotate at 3000–15000 rpm. Different designs of the disk are available for varied applications: flat, corrugated, and conical-shaped and those made up of carborundum (silicon carbide). The colloid mills require cooling due to the greater friction created during the size reduction of high-viscosity liquid foods. Cooling is achieved by the water that circulates in the jacketed layer of the mill.
Validation of Oral/Topical Liquids and Semi-Solids
Published in James Agalloco, Phil DeSantis, Anthony Grilli, Anthony Pavell, Handbook of Validation in Pharmaceutical Processes, 2021
There are two principal types of homogenizers, the valve type and the rotor–stator type. The latter, while capable of achieving homogenization, is better classified as a disperser or colloid mill. The valve type usually has two stages, consisting of two valves in series, to prevent clustering of lipid globules after the first stage. The manufactures frequently encountered are the Cherry-Burrell and the older Gifford-Wood. The mechanism by which homogenization is achieved is not definitively known, although there are three prevailing theories, any one of which may dominate for a particular material and viscosity. These theories are based upon the generation of turbulent velocity arising from high pressure. The three mechanisms are as follows: shearing between globules, shattering of globules from impact with the valve surface, and the formation of pits or cavitations following passage through the valves resulting in the condensation of small vapor bubbles. There is an increase in viscosity following homogenization of oil-in-water formulations caused by the increase of surface area of the oil globules. This provides a convenient physical test to confirm the success of the operation. Microscopic examination is also often necessary to confirm homogeneity. Additional testing consists of particle sizing (Coulter Counter) and light scattering. Homogenization is a process where examination of the resultant product, especially upon standing, determines the adequacy of the machine settings. Manufacturing procedures may specify some variability in machine setting to accommodate for variations in input materials, especially natural products. Typical first stage pressures are 2,000 psig, while second stage pressures are near 500 psig, with valve clearance around 500 microns. Positive displacement pumps are used and in many cases are an integral part of the homogenizers. These ranges are provided because validation personnel are often required to verify setting adequacy. In one instance, a homogenization process was transferred to another location after the sale of the particular product and equipment to another manufacturer. The original process consisted of eight homogenizers connected in parallel to accommodate the desired production volume. The new manufacturer hard-piped the homogenizers in series and then proceeded to apply the maximum pressure to both stages of all the homogenizers to try to achieve homogenization, which was never accomplished. When the author pointed out that the oil-water percentage was the same as ice cream mix and that appropriate homogenizer settings were widely available in the literature, the new manufacture still would not change the process and homogenizer configuration and attempted to validate the process, which included a 10% reject rate upon visual inspection.
Effects of waterborne epoxy resin on the fatigue performance of bitumen emulsion
Published in Road Materials and Pavement Design, 2023
Rui Li, Zhen Leng, Hui Li, Hongzhou Zhu, Lingyun Kong, Xiong Xu
A base bitumen with a penetration grade of 60/70 (Pen 60/70), commonly used in Hong Kong, was used in this study. Table 1 demonstrates the basic properties of the bitumen. The cationic slow setting emulsifier was kindly provided by Ingevity under the trade name of INDULIN® W-5. Bitumen emulsion with a solid content of 60% was first prepared with a laboratory colloid mill. Waterborne epoxy resin was then prepared following the procedure detailed in previous studies (Li et al., 2019; Li, Shen, et al., 2022). The waterborne epoxy resin was subsequently mixed with bitumen emulsion at three mass percentages, 1, 3, and 5 wt%. At last, the waterborne epoxy resin modified bitumen emulsions were conditioned at ambient room temperature for three days, followed by 24 h of oven conditioning at 60°C. This procedure ensures the fully curing of the waterborne epoxy resin, and the cured WEBERs were then obtained, denoted as WEBER-1, WEBER-3, and WEBER-5. The bitumen emulsion residue without waterborne epoxy resin was used as control and denoted as WEBER-0.
Laboratory and field performances of grave emulsion manufactured using nanocellulose crystals as an asphalt-emulsion emulsifier
Published in Road Materials and Pavement Design, 2023
A.R. Pasandín, I. Pérez, F.J. Prego, A. Miguens
The required amount of heated (120 °C) B160/200 cells is weighed to manufacture the bitumen emulsion. Then, the dispersing phase (water and emulsifier agent including CNC) is decided. To this end, the required amount of water and emulsifier are weighed and mixed at 60 °C with a magnetic stirrer at 500 rpm. Then, the pH is adjusted by adding hydrochloric acid (HCl) until a pH lower than 7 is obtained. Subsequently, the colloid mill is conditioned at 80 °C. Once everything is acclimatised to the working temperature, the dispersing phase is introduced into the colloidal mill, which operates at 3,000 rpm. Next, heated bitumen is added gradually so that the thickness of the flow did not exceed 6 mm in diameter during this operation. Finally, the outlet valve of the mill is opened to allow the bituminous emulsion to flow through the colloid mill once the asphalt emulsion is manufactured.
Alternative bio-based emulsifiers for road materials
Published in Road Materials and Pavement Design, 2023
Fanny Lévenard, Vincent Gaudefroy, Isabelle Capron, Cédric Petiteau, Emmanuel Chailleux, Bruno Bujoli
The main conclusions of this study are the following: First emulsification tests using the ultra-turrax disperser showed that biopolymer E1 was acceptable.Non-modified particles E2 led to a very viscous emulsion, thus E2 particles were not used to manufacture emulsions with the colloid mill. However, using the same particle modified in the surface to facilitate compatibility (HE2) allowed producing a promising formula.For the two selected emulsifiers, E1 and HE2, the colloid mill allowed to obtain bitumen-in-water emulsions with a bitumen content of 60%. The emulsions presented different droplet size distributions, with droplets larger than the ones of the reference Em-CS, but were all stable over at least 50 days.The test specimens of GE-E1 showed a significant water recovery, likely due to the ability of the polymer to swell with water. It led to very high water sensitivity.GE-HE2b test specimens, with the modified particles, showed similar water recovery to the specimens of the reference GE-CS. Although the results did not reach the standard required values, water recovery and sensitivity were improved.