Animal Feed Ingredients

Calcium and phosphorous cannot be synthesized by the body and must be provided at adequate levels in the daily diet of animals. Their primary function is to provide structural support for the body (i.e., bones and teeth). Typical natural animal feeds have a relatively low content of these minerals. Therefore, animal feed supplements are often utilized to meet this deficiency.

Due to low cost, one type of animal feed supplement that has been used historically is recycled animal parts. However, as has been highly publicized, this practice is suspected of transmitting "Mad-Cow" disease by sub-viral prions that are not destroyed in normal sanitization techniques. These prions pose a threat to humans as well. Animal feed supplements from phosphate rock, however, have a high biological availability and nutrient content that can safely enhance feed formulations without the risk of prion transmission.

The main types of animal feed ingredients are shown below:

Properties	MCP	DCP	DFP
P total	21.0%	18.5%	18%
Ca total	15 to 18 %	20 to 24%	31%
Ca : P	0.8 : 1	1.2 : 1	1.8 : 1
P : F	100:1
Size	97% -12 + 65 mesh

Monocalcium phosphate (MCP) and dicalcium phosphate (DCP)

The production of minigranular MCP/DCP can be divided into several operations:

• preparation of defluorinated phosphoric acid by dilution with scrubbing liquid from the Reactor,
• production of minigranular MCP/DCP in the Reactor using a metered flow of ground limestone, diluted phosphoric acid and recycled solids,
• drying and classification,
• treatment and recovery of the gas flow from the reactor and the dryer before being released to the atmosphere.

 The SPINDENTM Reactor

A key feature of the process is the SPINDEN Reactor. The SPINDEN is used to agglomerate solid raw materials with a minimum amount of liquid phase - resulting in a very low recycle ratio. It has been used in five animal feed plants to produce minigranular MCP and DCP.

Phosacid Defluorination

Phosphoric acid defluorination can be carried out by precipitation, air stripping, steam stripping, or in the evaporation process. Precipitation has a high chemical cost and produces a solid waste stream. Steam stripping and evaporation have a considerably higher steam requirement than air stripping. KEMWorks offers a simple low-cost air-stripping technology.
Phosphoric acid is defluorinated in an air-stripping process by adding a silica source (e.g. diatomaceous earth) and vaporizing SIF4 by spraying heated phosphoric acid in a stream of air. This process is very energy efficient using only 25% of the steam used in the conventional steam stripping process.

Defluorinated Phosphate Rock (DFP)

Defluorinated Phosphate (DFP), also known as Tricalcium Phosphate (TCP), is produced from phosphate rock, phosphoric acid, and soda ash. This process can be broken down into three sections:

• Feed preparation / mixing,
• Defluorination (by calcining), and
• Product sizing
  

The chemical reactions of this process occur in two stages; the first at low temperature being a neutralization of the acids and alkalis, the second at high temperature being a complex thermal decomposition and evolution of gaseous molecules from solids, substitution and recombination of molecules, as well as phase change.

The first stage reactions take place in the feed preparation area. The phosphate rock, phosphoric acid, and soda ash are brought into the plant and blended in correct proportions in a batch or continuous mixer/reactor. The mixer product is conveyed to a screening system that excludes oversize material that is milled and recycled. The product from the screen is sent to storage prior to feeding into the defluorination system. The mixer/reactor is vented through a fairly simple scrubber system.

The second stage reactions takes place in a large kiln (or fluidized bed) where the material is heated to approximately 2800° F. The hot DFP product from the kiln is discharged through a cooler and cooled by air. The kiln is vented to a scrubber system that must handle a large load of fluoride vapors.

Material from the cooler is transferred to the product sizing area where screens, mills, and hoppers are used to classify and store the product prior to shipping.