Pre-grind refers to the storage of individual raw materials after grinding which are held in bins before weighing and mixing in their specific formulation. With post grind, the raw materials are weighed out in batches as required from their main storage bins before each batch is ground prior to mixing.
Both systems have their own advantages & disadvantages as mentioned:
Few Advantages of Pre –Grind Systems
1. Machine down Time: In a pre-grinding system as the grinding process is independent & not an integral part of the complete process; in case of repair and maintenance of hammer mill, there would not be a direct effect on the production output.
2. Ease In operation: As the process is continuous and not depends upon batching time; there is less idle time, more uniform load on hammer mill, most of the time at single product hammer mill runs on the single setting. Frequent change of products affects the hammer mill performance in post-grinding systems.
3. Energy consumption: As there is no idle time and it is unnecessary for the milling to take place at the same time as the remaining production process which in some cases allows the use of the cheaper energy tariffs.
4. Selection of screen as per product: we can use: As we grind the material one by one we can use the screen size matching the raw material initial particle size and grinding required.
Post –Grind Systems –Advantages
1. Less Operational expenses: in post grinding system no extra intake section for powder ingredients are required, which results in lower investment and operation costs. Also, no separate operators are required for the grinding process as grinding operation is an integrated part of the total feed preparation.
While in the pre-grind system we need extra material handling equipment for powder ingredients which increases the project & running cost.
2. Bins Capacity: As ground material occupies more space; high volume of storage bins are required for the same storage capacity in case of the pre-grind system. Hence space utilization of bins is maximum in post grind system.
3. Grinding of fibrous material: Maize and some high-density grains help other low-density fibrous material ( less in percentage ) to come out through screen; that would not be possible in the pre-grinding system as for low-density fibrous materials required to be pulverized.
4. Life of storage bins: In Pre Grind system, the top layer of ground material in storage bin releases moisture which leads to corrosion/wearing of bin walls & top sheet.
5. Flowability of Ingredients: Storing ground ingredients for a longer period of time causes flowability issues; complicate and precise design of batching feeders, weight fluctuation while batching.
6. Flexibility in required grinding texture: The fineness of grinding can be adjusted per batch. This is very important when different types of feed are to be produced in one feed mill, e.g. coarse feed for layers, fine feed for broilers and extra-fine feed for fish, mash concentrate feed. Sometimes clients asked for different grinding textures.
Both systems have been used in the feed milling industry for many years, whereby the choice between one and the other was sometimes purely a matter of personal preference.
The increase in the number of raw materials, the variable physical properties as well as the increase of the number of formulas has led to the introduction of the post-grinding system. Considering all factors mentioned above post grinding system nowadays is a more prevalent and optimum solution for better results.
The above information is based on data collected from our existing customers & internet sources and is only for your reference. As expertise in feed mill engineering only, Lark Engineering will not be responsible for any type of loss occur due to above stated information.