Herentals (Belgium) – There are still additional ways to increase profitability in feed production. That was the collective focus of feed engineering experts, assembled by Kemin, at the 2nd International Feed Engineering Summit.
The key is to focus on feed processing to further improve feed mill efficiency and profitability by minimizing ingredient segregation, eliminating shrinkage, reducing production process variability, assuring product quality, improving nutrient and feed utilization by the animals, savings in energy use and increased production rate.
‘There is a clear demand for this kind of sessions,’ said Tom Verleyen, marketing director for Kemin Industries animal nutrition and health EMENA division. ‘Typically the attention is on animal nutrition and health. Very few symposia provide in depth discussions on the actual process of feed production. That’s why we brought together feed engineering experts to share their expertise and tools.’
Dr. Ing. Janine Bohlmann, Research Institute of Feed Technology, Germany, discussed the need to start with good pellet quality because of the benefits gained such as compaction, which reduces the volume of the feed, saving transport and storage capacity. Good pellets have a homogeneous shape and are stable in transport and storage which reduces loss from dust or fines. Good heat transfer during steam conditioning is a valuable tool for feed hygiene, and improves nutrient digestibility.
An important requirement for pelleting feed is that the various particles in a feed mixture adhere or stick together. Adherence is generally caused by the capillary force between moist surfaces and involves Van der Waal’s forces, moisture bridges, physical adhesion and solid state bridges. The ability to convert a feed mixture into homogeneous stable pellets is also influenced by the physical and chemical properties of the feed mixture.
The two things to focus on are the physical properties of bulk density and particle size distribution, and the chemical properties of fat, protein, fiber, starch, molasses, ash and moisture.
Dr. Bohlmann shared that pellet durability will generally decline exponentially with increasing fat content when fat is added as a separate ingredient. In contrast to fat, high protein contents of approximately 25 percent, gives more solid pellets. Crude fiber contents above 10 percent increase friction in the die and makes the pellets more solid.
Crude fiber levels change the pressing behavior of feed mixtures more than increasing starch or protein. It is preferable that starch modification or gelatinization should take place during conditioning of the feed mixture and not during compacting in the die as this can reduce pellet quality. Inorganic feed ingredients such as minerals, which contribute to the ash content, can result in harder pellets, increased energy demand and increased die wear.
Use of steam
There are several important processing parameters which influence the feed pelleting process, of which steam is a critical one. Steam is widely used in many industries including animal feed manufacturing and various grades and quality of steam are available.
Mr. Peter De Cneudt, Spirax Sarco, of Belgium strongly emphasized that for the feed industry saturated steam used as superheated steam is not appropriate. With saturated steam there is a direct connection between temperature and pressure. If you know the temperature you know the pressure and vice versa, regardless of the dryness fraction. For the feed industry, the major quality criterion for steam is to keep the variance of the dryness fraction as low as possible. Steam for conditioning can take up to as much as 20 percent of energy costs in feed manufacture so careful monitoring of steam use is important.
Mr. Peter Sillen, Geelen Counterflow, of The Netherlands explained the theory of cooling, essentially a process of heat and moisture transfer from the product to the air. In a feed mill, air flow is used to achieve an evaporative cooling of feed pellets and also to reduce the moisture content in the pellets. Air flow rate and temperature are important parameters of cooling. The air flow rate must be sufficiently high to avoid the air becoming saturated with moisture or condensation will occur. Cold air holds less water than warm air and the air moisture content can be measured using a relative humidity sensor. High air flow rates will give more cooling by heat transfer but less evaporation and therefore will take out less water whereas long retention times will remove more water.
Energy consumption needs to be reduced as part of a sustainability program. Ir. Oriane Guerin, Zetadec, of The Netherlands has investigated feed manufacturing in relation to energy use. It is recognized that there are possibilities to decrease variability in the pelleting process by understanding the factors contributing to the energy impact of the feed production process.
Results of a study were presented where the energy consumption of the pelleting process from three feed factories was compared, two of which were medium-sized companies and the third was a large producer. In general, when capacity increased, the net Specific Mechanical Energy (SME) decreased. This requires online measurements to optimize capacity, temperature and the various machines in use. The objective being to reduce variability in the manufacturing process – as this in turn leads to reduced energy consumption.
The process of preparing the feed mixture for effective processing through steam conditioning, pressing, and cooling is key. Preconditioning will result in the optimum production, both in physical characteristics of pellet quality, as well as feed production efficiency. In order to reach consistent moisture targets in the mixer through preconditioning practices it is crucial to reach moisture targets at each step of feed processing. Dr. Luis Conchello, Kemin product manager, explained the Millsmart preconditioning program to effectively prepare the feedstuff for optimum conditioning, compacting and cooling.
The Millsmart program is designed to operate before steam conditioning and ensures the feed mixture has the optimum conditions for effective steam conditioning, pelleting and cooling.
Millsmart uses a preconditioning solution based on powerful surface-active agents that provide uniform dispersion and penetration of the preconditioning solution. Special nozzle technology reduces droplet size in the applicator before spraying. Lower surface tension further reduces drop size during the spraying phase. The smaller drops cover a greater feed surface, which improves dispersion. The preconditioning solution has a low contact angle, ensuring the drops spread widely on the feed particle surface with better penetration and thereby improving the efficacy of the preconditioning treatment. The quantity of the preconditioning solution can be adjusted according to the desired target levels through on-line moisture management. Pelleting under these conditions has a positive impact on energy consumption of the pellet press and reduces wear on the dies. The preconditioning solution increases the moisture level, requiring a longer cooling time, which is beneficial for pellet durability characteristics.
The goal during a batch process is to limit moisture variability within a batch (and between batches) to ensure feed pellets have uniform quality with little variability. A sophisticated online process management supports the Millsmart program. Mr. Raf Snoekx, Kemin product application manager, explained how Kemin has developed engineering systems that use their own software and hardware to manage feed moisture content during the production process. These allow real time correction of the actual moisture level in the mixer and ensures more consistent process.