Roller mill design Flashcards
(14 cards)
What is the primary function of a roller mill?
To comminute grain by passing it between two or more pairs of rollers through compression and shear forces
Comminution involves breaking down the grain into smaller particles.
What are the two main forces involved in the operation of a roller mill?
Compression and shear
Compression deforms the grain until it fractures, while shear tears the grain apart.
How is grain fed into a roller mill in large breweries?
Via a conveyor that brings cleaned and screened malt to a hopper above the mill
In smaller breweries, malt is manually tipped into the hopper.
What role does the feed roller play in a roller mill?
It helps distribute and orientate the grain correctly for milling
The feed roller can be grooved or fluted to catch malt grains.
What is the ideal way for grains to enter the rollers in a roller mill?
Tip first
This orientation allows the grains to be split longitudinally.
What is the typical diameter of modern mill rollers?
Around 250 mm
This size is optimal for working with typical grain sizes.
How does roller diameter affect the nip zone in a roller mill?
A lower roller diameter means a smaller nip zone and a lower rate of throughput
The nip zone is crucial for grabbing and processing grain.
What factors determine the throughput of a pair of rollers?
Speed of rotation, size of the mill gap, and length of the rollers
The slowest, shortest, and smallest gap rollers in multi-set mills determine overall throughput.
What is the typical length of mills designed for small versus large breweries?
Less than 400 mm for small breweries and up to 1.5 m for large breweries
This length affects the milling capacity.
What is fluting in the context of roller mills?
Grooves milled into the rollers to increase the coefficient of friction and shear on the grain
Fluting enhances the milling efficiency.
How many flutes per cm of circumference are typically found on a fluted roller?
6.5-10 flutes per cm
The design of the flutes contributes to effective grain processing.
What is the purpose of the twisting of flutes on the rollers?
To increase the shearing action as the grain passes through
The twisting aids in effective crushing and processing of the grain.
What types of edges can be arranged in roller sets for milling?
Cutting edges vs. rear edges, cutting edges vs. cutting edges, or rear edges vs. rear edges
Different arrangements are used depending on the type of grain being processed.
True or False: Smaller diameter rollers provide a larger area to crush the grain than correctly sized rollers.
False
Smaller diameter rollers crush the grain less completely.
