Poultry feed production
Jan. 19, 2011
by Andreas Schultz
Hygienizing and grinding by roller mills is an ideal approach for the production of animal feeds. In order to maximize the feed quality, it is necessary to give consideration to several criteria in selecting the number of rolls and their corrugations (fluting).
Like any other markets and industries, the feed manufacturing industry is subject to continuous changes. Customer needs, market changes, new legislation, and striving for optimization are constantly keeping plant suppliers in motion.
CONSUMER BEHAVIOR CHANGES
Various scandals that have attracted attention in the food processing industry over the past few years have led to an increasingly critical consumer behavior. The world of politics has also responded to these incidents. It has issued new regulations and directives and defined targets for the feed markets or stiffened existing ones such as open declarations, separate production lines, a ban on different raw ingredients in feeds, etc.
Legislators’ responses have triggered innovation and capital investments in the field of animal feed production which were long overdue.
Numerous production managers and company operators have seized this opportunity to launch new and improved products. For example, no major poultry producers today will think of feeding anything but hygienized feed to their animals. Today, hygienizing is no longer achieved by brief heating of the poultry feed during a few seconds, but by carefully elaborated complete solutions.
THE RIGHT COMBINATION
In the assessment of poultry feed quality, it is not only the design of the hygienizing system that plays a role; the feed texture is also crucial. Poultry producers prefer a feed meal with the coarsest texture possible but still fine enough to allow a good pellet to be produced. In practice, the best poultry feed qualities obtained today use a combination of grinding by roller mills to satisfy the specific needs of poultry and stateof-the-art hygienizing solutions.
When taking a closer look at the success factors involved, you will find that it is important to assess the overall concept applied and not merely a small section of the process. You can only speed across the countryside in your Ferrari if you master the vehicle and the roads are unobstructed and in a good condition. Exactly the same is true for a feed production plant. What is required is the correct process, the right equipment, properly trained personnel, and a carefully maintained and intact plant. These requirements are essential in order to master the challenges of the future.
GOALS DETERMINE THE CONCEPT
What are the requirements that must be satisfied to achieve the defined quality targets? First of all, a business idea is needed on which to base one’s goals. The goals pursued by individual feed producers may vary widely. Some aim at achieving price leadership, others at producing niche products, and yet others at manufacturing premium segment feeds, and so on. Another option is to target a specialized feed market.
Let’s assume that your customer operates a feed manufacturing plant which produces a high proportion of poultry feeds. Let’s further assume that this market is to remain the strongest pillar in the company’s strategy for the future and is therefore to be expanded.
These targets give rise to the following questions:
• Does the feed texture meet the needs of the market, or can you further improve it in the interest of your customers?
• What can you do to improve the feed conversion rate by the animal?
• Does your poultry feed satisfy the increasingly stringent sanitation requirements of the market and consequently of the trade chains?
• If your plant produces different feeds, has it been designed to allow a clear separation of the individual production lines, including the loadout section?
FROM HAMMERMILLS TO ROLLER MILLS
From the list of possible improvements, let’s focus on the grinding process. A lot has changed over the past 10 years, especially in this area. Indeed, you might even almost say: from the conventional hammermill via the vertical hammermill to the roller mill.
That’s not to say the roller mill is a new technology. But using rolls for size reduction is undergoing something of a renaissance in feed production plants. This is because of the following benefits:
• low specific energy consumption;
• high particle size flexibility through automatic roll gap adjustment and the use of double or even triple roller mills;
• compact design including bypass system;
• low maintenance requirements;
• production of a good feed texture, with hardly any fines thanks to narrower particle size distribution than that achieved by hammer mill grinding;
• lower moisture loss than by hammer mill grinding; and
• suitable for both pre-grinding and post-grinding applications.
Today, either double or triple roller mills are used, depending on the required processing capacity and the grinding method (pre-grinding or post-grinding). In a triple roller mill, the sole function of the first roll pair is to reduce large particles such as sugar beet slices or soy extraction meal. The second and third roll pairs then produce the desired product texture.
CORRUGATIONS AND CONDITION OF THE ROLLS
The product texture is greatly determined by the roll corrugations (fluting). What’s important is not only the configuration and geometry, but also the condition of the individual corrugations. Differences undoubtedly exist depending on whether operation is based on “sharp to sharp,” “with or without spiral,” or some entirely different combination. This may lead to discussions similar to those that you know today from the determination of roller shells of pellet mills. Here, too, the discussion continues unabated as to whether it is preferable to use dimpled or corrugated (fluted) rolls. It is therefore understandable that many production managers rely on their own experience when making related decisions.
What is more important than the selection of the “right” corrugations is their condition. The better the condition of the flutes, the better also the particle size distribution, and therefore the lower the content of fines of the feed. A well-maintained roller mill will allow up to 40,000 tonnes of material to be ground before its rolls need to be recorrugated (refluted) or — after two or three refluting cycles — exchanged. Of course, this also greatly depends on the raw materials that are ground. Different raw materials and the pre-cleaning process applied may have a major impact on the wear to which the corrugations are exposed — both in the positive and in the negative sense.
The selection of the raw materials is usually dictated by global market prices. Production managers rarely have a chance to influence this factor. On the other hand, a good production manager or maintenance manager has direct control over the condition of the production equipment. They can decisively reduce plant downtimes by careful, preventive maintenance.
Practice teaches that the fineness of feeds does not say anything about the product quality. “The finer, the better!” has ceased to apply. In other words, it does not matter whether a feed is pelletized after its particles have been reduced or whether it is processed into feed meal. What does matter is careful processing in the roller mill.
Needless to say, certain physical principles must be taken into account. Thus, it is not possible to reduce a feed to a particle size of three millimeters and then to process it into pellets of the same size. This would result in a very high breakage rate and thus in high pellet abrasion.
In selecting and specifying a roller mill, the following questions must be answered:
• What hourly grinding rate is necessary?
• What particle size (mean particle size, particle size distribution) has to be obtained?
• What product formulations are to be produced?
• Is a final screening stage required?
• Will the pre-grinding or postgrinding process be applied?
• Will a double or triple roller mill be used?
• Might a combined grinding system — that is, a roller mill in conjunction with an intermediate screening stage and a hammer mill — be the best solution?
Before any capital investment is made, a number of additional questions must also be answered. The installation situation is usually no problem. If an existing conventional hammermill is to be replaced, the space available for accommodating a roller mill will normally be adequate.
Once a careful prior analysis has been conducted of the current condition of an existing grinding system, and once the goals have been clearly defined, success will be all but inevitable after a rebuild.
Andreas Schultz is head of center of competence for Buhler’s Feed & Biomass unit, Braunschweig, Germany. He may be contacted at