Milling

The milling process industry comprises all manufacturers involved in process technology that is used for breaking down, separating, sizing, or classifying bulk materials. Milling processes can also remove contamination or water/moisture from bulk materials to produce dry particles before transport.

Milling allows you to control the particle size of your product in the manufacturing process. Particle size consistency enhances product flow rate and reduces the size, which can assist in the downstream process, depending on the product goals.

A milling process refers to the complete process of cleaning, grading, breaking down, sizing, separating, or classifying dry bulk materials. The actual milling process involves the mill that is used to break solid bulk materials into smaller pieces by grinding, cutting, or crushing.

Types of mills

There are a variety of mills that can be used to process bulk materials. Specific mills can grind powders and solids as small as single-digit microns to any specification.

Here is a list of the most common types of mills:

Jet mill
Air classifying mill
Hammermill
Ball mill
Impact mill
Pulverizing mill

The grinding of solid materials occurs through mechanical forces that break up the structure.

After the grinding, the state of the solid is changed: the particle size, the particle size disposition, and the particle shape.

Purposes of the milling process in engineering:

Pulping: Converting the bulk materials into pulp
An increase in the surface area of a solid
Manufacturing of a solid with a desired particle size

Dry milling vs wet milling

Dry grinding creates much dust that results in the need for proper filtering systems. This can be of specific importance during the grinding of substances whose dust can result in explosive mixtures when mixed with aerial oxygen. Elaborate technical solutions such as systems for dust removal and inert gas overlay are often necessary to achieve the required level of safety. The cost for these filtration machines often significantly exceeds the actual mill’s.

Wet milling, also called wet media milling, is a process in which particles are dispersed in a liquid by shearing, impact or crushing, or attrition. Wet milling can be more intensive, but it can reduce a bulk product into more components and finer particles in the micron & submicron (or nanometer) particle size range.

Corn milling process

Corn wet and dry milling are the most important methods of processing corn, and each method produces distinct co-products. The corn wet-milling process is designed to extract the highest use and value from each component of the corn kernel. Wet milling involves soaking or steeping whole corn to soften the grains, after which further processing separates features used in a variety of products. In general, ethanol is not the primary focus for wet milling processors.

The corn dry-milling process is a less versatile, less capital-intensive process that focuses primarily on grain ethanol production. In this process, the corn kernels are hammer milled into a medium-to-fine grind meal for adding to the ethanol production process.

Wheat milling process

The wheat milling process is how cereal grains are ground into flour.

The overall aims of the miller are to produce:

A consistent product
A range of flours suitable for a variety of functions
Flours with predictable performance

Waste from wheat milling is often used on agricultural land as fertilizer.

Bulk solids milling is applied to improve the flowability, dissolvability, or volume reduction of blocky, abrasive, or hard-to-process bulk materials to the exact desired finished particle size.

It is imperative to understand which performance can be achieved by a particular type of mill and which type of bulk solids. It will allow the process engineer to properly select a mill type for a new process or troubleshoot an existing process.

The global milling industry is driven by responding to customer and consumer trends and needs. It is challenging to find a source covering all aspects of the milling process.

Many milling process innovations and new technologies are available in the global processing industries. Some current small developments in available machine models, some present agricultural innovations, and some present revolutionary technologies.

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