Calcium is an important dietary supplement and is necessary for many normal bodily functions, especially bone formation and maintenance.
Calcium is an additive used in human and pet food products for Calcium fortification. The minimum recommended requirement for an adult is 1000 milligrams of elemental calcium each day. Calcium fortified foods include milk, soymilk, yogurt, cereals, snack foods, and breakfast bars. Calcium Carbonate has the highest level of elemental calcium at 40%. Another use of calcium is as an antacid, as Calcium is an effective acid neutralizer. Calcium supplements are available in many forms, including soft chews, tablets, and liquids.
Depending on the use of the calcium supplement, a range of particle sizes are required. Final particle size is dependent upon the functional requirements of the end-product. Dissolution rate, bio-availability, texture, and smoothness are considerations in the determination of the final particle size. Finer grades of Calcium Carbonate are manufactured using a precipitation process and is called Precipitated Calcium Carbonate or PCC. Calcium Carbonate is also mechanically ground, and is called Ground Calcium Carbonate or GCC. Both types of Calcium Carbonate are milled for specific applications. The most common type of impact mill for producing GCC is an Air Classifying Mill .
An Air Classifying Mill system works by performing impact milling and air classification in one step. Air provides the motive force to convey material to the mill, classify the product into fine and coarse fractions, convey the fine material out of the mill, and then return the coarse material fraction to the grinding zone of the mill for further size reduction. This process is repeated on a continuous basis during the operation of the milling system. The unique feature of the ACM mill is that the classification step takes place inside the mill and is not a separate or external operation. This design allows these mills to be relatively compact in size, requiring less floor space and less equipment to clean for the relatively high production rates they can achieve.
With a change in operating parameters, many different end-product particle size distributions can be achieved. By maintaining all other operating parameters and increasing the classifier speed from 2500 rpm to 4000 rpm on this model mill, we can achieve a reduction in particle size as seen here from 38 microns down to 25 microns. The resultant finer product which requires longer residence time in the mill will cause a reduction in overall capacity of the system.
Another common form of Calcium, used as a food supplement, is Tri-Calcium Citrate. Tri-Calcium Citrate is the Calcium salt of Citric Acid and has a relatively high Calcium content of 21% with excellent bio-availability. Tri-Calcium Citrate is used as a food additive to prevent and to treat calcium deficiencies. Common food applications include:
Tri-Calcium Citrate, as an additive, enriches calcium content and adjusts PH. In addition to health benefits, it improves consistency and reduces caking in food products.
Tri-Calcium citrate used as a food supplement needs to be a relatively fine powder. The required particle size distribution normally has a top size of fewer than 15 microns. The ACM Air Classifying Mill can produce a product with a top size of 12 microns.
To achieve a particle size of fewer than 10 microns a fluidized bed jet mill is required. While a finer particle size is achievable, the additional energy required to run a jet mill system will substantially increase the system operating costs, compared to the air classifying mill system. If you compare the two technologies the relative cost for producing the less than 10 micron product is about four times that of an ACM system.