Development Of Pellet Quality
In response to demand for better quality pellets, engineering process technology has responded by applying greater amounts of electrical energy per ton of pelleted feed -- more so for ruminant and pig than for poultry. Graph 1 and 2/3 show, over a 20 year period, how pellet quality has improved in relation to electrical energy input at the pelleting plant (excluding steam, cooler and conveyors). Thus, we can see that pellet quality is relative to energy input and we can use this criteria when trouble shooting. Fundamental Requirements For Good Pellet Quality And Production Rate There are just two! That is, assuming adequate grinding and conditioning.
1. A good feed formulation.
2. Sufficient Specific Energy (kWh/ton) used by the pellet press motor.
These are the first two stages of investigation used that are recommended to investigate when troubleshooting either Pellet Quality or Production Rate problems.
Stage 1
Determination Of The Formulation’s "Feed Pellet Quality Factor" (FPQF)
The first step to take when trouble shooting is to calculate FPQF. If it is higher than your level of acceptability, then you know the problem is in the feedmill. If it is lower, then discuss it with your nutritionist or feed formulator.
Determination of FPQF can be used:
A. as a formulating tool to predict pellet quality!
B. as a production tool to maximize production rate!
A. Let us first take a look at feed raw materials and their influence on physical pellet quality. Knowing that some raw materials pellet well, wheat for example, and some are very difficult e.g., grain screenings, it should be possible from experience to given each raw material a Pellet Quality Factor; 0 for bad, 10 for good. I say from experience because pelleting each raw material as a "straight" and ascribing a value to it in order to calculate the pelletability of a mixture, does not always work out correctly. There is, without doubt, a synergy between raw materials which we do not yet fully understand.
The values listed for various raw materials are given in the table on page 40 of "The Pelleting Handbook" , published by Borregaard Ligno Tech. Clearly, if a feed formulation can be identified as potentially difficult before it gets into production, then a great deal of time and money can be saved. However, it should be stressed that the results from calculations should only be used as guidelines.
As an example, Tables 1, 2, 3 and 4, show the FPQF calculation of a ruminant, pig, duck and Tilapia feed formulation, respectively. The process of calculating the Feed Pellet Quality Factor (FPQF) for any given formulation is straightforward. List the raw materials used in the formulation with their respective % inclusion and Pellet Quality Factor (taken from The Pelleting Handbook or your own modified version). Then, multiply the PQF by the % inclusion of the raw material e.g., Wheat meal: PQF 8: Inclusion 30%. Therefore, its contribution to the overall FPQF = 8 x 30% = 2.4. Add all the FPQF’s together and their total represents the Feed Pellet Quality Factor for that particular feed formulation.
When using a conventional pelleting line with no expander, if the result is below 5, there could be a pellet quality problem, if it is below 4.7, then the probability of a problem is very high. The tolerance between 4.7 and 5 takes into account the effectiveness and pelleting technique of the feed mill, some mills need to be "5" or over to make good pellets, while others could tolerate a lower level. It is suggested, therefore, that producers of pelleted feeds set their own FPQF level based on nutritional production circumstances and raw materials in relation to the level of pellet quality acceptability. When using an Expander, lower FPQF’s can be tolerated.
B. Calculating FPQF also provides a means of deciding production strategy. If FPQF is 5 or over, it generally indicates that the formulation will be easy to condition, therefore more steam can be added. It also indicates that Pellet Quality should be good, therefore, production rate can be maximized.