It seems that all exotic raw materials have one thing in common: they have a negative effect on the pelleting process. Typically, they reduce pellet quality and pellet mill capacity while increasing energy consumption, costly wear and tear on machinery and overall operating costs. Because raw materials are by far the biggest share of feed costs (up to 85%), using lower-cost alternative raw materials will easily make up for increased production expenditures. That means that the pellet mill operator is left in a painful position and needs a better solution to produce the required daily feed amounts and quality.
Segment Manager – Feed & Oilseeds
CPM Europe
Every feed miller knows what is good for their pellet mill: A formulation consisting of a nice mix of maize, wheat and soya without too much fat. This mix is ideal for making good quality pellets at a high capacity, especially when an appropriate die specification and dry steam are used. However, with a growing world population, protein sources are becoming more scarce, making feed production more costly. On top of this the opinion exists that materials which can consumed by humans are not to be fed to animals. To make the feed industry more sustainable, we need to explore other raw material sources. Creating a circular feed industry is the first step. For many years, residues from other industries have been used in the feed industry, but we are and need to be even more creative in finding alternative protein sources.
It seems that all exotic raw materials have one thing in common: they have a negative effect on the pelleting process. Typically, they reduce pellet quality and pellet mill capacity while increasing energy consumption, costly wear and tear on machinery and overall operating costs. Because raw materials are by far the biggest share of feed costs (up to 85%), using lower-cost alternative raw materials will easily make up for increased production expenditures. That means that the pellet mill operator is left in a painful position and needs a better solution to produce the required daily feed amounts and quality.
Traditionally feed millers have only sought cost savings in the pelleting process. But this single-minded approach risks making them “penny wise and pound foolish”. The real cost saving is in the alternative lower cost ingredients. This creates openings to invest in the pelleting process. But for this we need to analyze the characteristics of the ingredients end recipes first, because “one size fits all” unfortunately doesn’t exist.
LESS ABSORPTION
Most alternative ingredients have lower absorption capabilities than traditional ingredients. This means that the retention time in the conditioner needs to be increased.
To help solve this problem, California Pellet Mill (CPM) brought a new conditioning technology to the market when they introduced a revolutionary shaft and paddle design in combination with shaft speed regulation. This innovation makes it possible to fill the conditioner up to 70% while providing full contact mixing of product particles with liquids and steam. The improved conditioning allows for the higher temperatures that achieve better quality pellets with lower energy and operational costs. This conditioner also provides excellent blending with molasses and other added liquids. The design principle is based on the fact that the material is moving forwards and backwards through the conditioner, and is “rubbing” itself what is increasing liquid and steam absorption.
LESS DENSITY
The lower density of some exotic ingredients also negatively affects processing. Conditioners can hold less mass of the product, while generally a longer retention time is required due to the ingredient’s lower absorption capabilities. Since the pelleting process is volumetric, less density means fewer tons can be produced.
LESS BINDING
Another characteristic of alternative ingredients is that they have weaker binding properties. This means that the pellet needs to be produced more mechanically. With traditional ingredients, pellet binding is enhanced by the heat and moisture from the added steam, but pellets made from alternative ingredients must be formed with brute force in a thicker pellet mill die. Thick dies are the pellet mill operator’s curse. They make the pellet mill more sensitive to roll slip and the surface of the die is more easily damaged, which adds to the instability of the overall process. Sometimes it is so difficult to add the required energy in the pelleting process that capacity is reduced just to maintain pellet quality. Even when quality is not negatively affected by the higher capacity, using more mechanical energy still reduces capacity because the pellet mill motor becomes a limiting factor.
Variations in raw materials also means variation in how they influence the pelleting process. One day a “good” formulation can make the pellet mill operate smoothly while on the next day it won’t move at all. This creates a headache for the planner because the output demand on the factory doesn’t take into account the pellet mill behavior.
DOUBLE PELLETING
If pelleting is harder to do in one big step, a simple solution is breaking it into two smaller ones that allow for thinner dies, increased flexibility, lower-cost raw materials and lower production costs. This pelleting principle is extremely successful with cheaper high-fiber formulations that have replaced grains and soya.
The effect is shown in the next tables. In the first dairy formulation, beet pulp is replaced by coconut meal. This is a lower cost formulation, but pellet quality drops from 60 to 43. By using double pelleting, the low-cost formulation can be produced with a quality of 62, which is slightly higher than the original formulation. The second example shows the effect of a high-energy formulation on the pelleting process. When 3.2% of tapioca meal is replaced by fat, quality drops from 40 to 27. However, double pelleting enables the high-energy formulation to reach the same quality as the lower energy formulation produced with single pelleting. A major benefit of the double pelleting process is that the capacity is much more stable compared to the single pelleting process. This reduces headaches and ensures that the required quantities can be produced daily.
EXPANDER PELLETING
For very high fat and liquid formulations that make it harder to supply enough energy to produce good pellet quality the Expander can be a solution. It enables control over the energy consumption by adjusting the cone, pressure, kneading intensity and product heating.
At high fat and liquid formulations where it is hard to get energy in, the Expander improves pellet quality. However, it uses a lot more energy. Running the expander on lower fat and liquid formulations results in much higher energy usage and wear costs, as well as a less controllable and user-friendly process. We see the same outcome if we compare the double pelleting process with Expander pelleting. This reinforces that there is no single solution that works in all cases.
Finding the optimal process depends on the properties of the raw materials and the desired pellet quality. When formulations use fewer traditional ingredients, especially newer ones, it is important that the pelleting process is flexible enough to adapt to variable characteristics. When considering investments in machinery and process configurations, producers should carefully consider potential problems these ingredients can create. The pellet mill size that is currently sufficient to meet required capacities simply won’t be able to do the job in the future. Feed millers should consider larger machines now, and especially those that help optimize the conditioning process. And, when selecting pre-compacting machines, it is essential to carefully consider which solution is most suited for your specific situation. A sub-optimal choice may result in purchasing costly machines which have a negative impact on the production process.
FLEXIBILITY
The key is incorporating flexibility into the pelleting process. That starts with using reliable and energy-efficient machines equipped with useful pelleting tools like remote roll adjustment and roll speed measurement.
Mechanical energy is added in the pellet mill die. However, the optimal amount of mechanical energy varies depending on the processed formulation. It is therefore necessary to be able to adjust the amount of mechanical energy. This can be done with remote roll gap adjustment. By increasing the distance between the die and rolls, more electrical energy is consumed by the pellet mill what increases pellet quality. If pellet quality allows, the roll gap can be decreased, which saves energy. The remote control of the roll gap provides an increased safety level and reduces downtime. It’s important to recognize that during pellet mill start-up, mill roll distance must be limited to prevent roll slippage. However, once it’s up and running, the gap can be increased. This reduces steel to steel contact between die and roll and extends die life. The longer the die stays in shape, the greater the energy savings and capacity gains.
To find the find the maximum allowable roll gap is always a challenge. The roll slip will increase with the roll distance till a pellet mill choke occurs. CPM has introduced a roll slip measurement system that makes the pellet mill operate exactly at its optimal working point. What’s more, the system prevents pellet mill chokes, reducing downtime and increasing effective production capacity. The roll slip measurement system can determine the exact “zero” position of the rollers and, with that, prevent steel to steel contact with the die. This results in reduced wear costs, ensuring optimal productivity under changing circumstances.
To remain profitable in volatile market conditions, our industry must keep searching for alternative protein sources. We simply cannot keep doing what has “worked before”. We must find new ways to adapt our technologies and production processes to accommodate changes. Longer term visions that invest in and implement innovative technologies will help take us there.
About Arthur vom Hofe
Arthur vom Hofe is CPM Europe’s Segment Manager for Feed & Oilseeds. Since the early nineties, he has been at the front line representing the company’s pelleting and particle size-reduction equipment. Throughout this time, he has gained valuable experience with feed production processes across the world.
