Feed weighing systems
by Lukas Bruijnel and Tim Broeke, KSE Process Technology
he design of a premix, compound feed or petfood production facility has one main goal: how to get all the raw materials into the end product(s); of course in an accurate, time- and costefficient and flexible fashion with the desired capacity and footprint, while respecting any contamination groups. And last but not least, within budget. So there’s of course a lot more than just the one goal while designing the ideal process. That always makes for an interesting discussion on how to approach the design, since everyone in the production process has his or her own approach and requirements. Perhaps the three most important are nutritionist requirements, production requirements, and (of course) commercial requirements.
Nutritionists need a wide variety of raw materials to be available 24/7 to dose a large selection of recipes automatically – of course with minimum manual interferences and maximum accuracy. This allows the nutritionist to produce specialised formulas without manual dosing, and a lot of different materials readily available. Developments in nutritional science are producing more efficient compound feed and feed additives (premixes). They are also however increasing the demand for faster, more accurate and cleaner dosing, transport and mixing equipment. Generally speaking, there are nowadays more ingredients and often small doses.
Process requirements depend strongly on the type of production facility. Whereas a compound feed facility may focus on output and efficiency, a dedicated premix facility might focus on maximum flexibility in exotic or customer-specific premix production to serve demanding (niche) markets. This may allow longer batch times, but require more ingredients per dosing installation, and the ability to dose small and large components from a single silo. Flow characteristics of ingredients are often poor, and hygroscopic materials need to be treated carefully. This indicates different design parameters for storage and dosing equipment. Additionally, these ingredients often are considered difficult for health and safety and should be handled with much care. Minimal operator contact is therefore another issue to face when design a best in class plant. 56 | August 2016 - Milling and Grain
Many larger compound feed facilities are adding a dedicated premix line, bringing the supply of the most popular premixes in house and thus creating flexibility for themselves. That not only shortens lead time, it also provides a significant economic advantage. Depending on demand, in-house production can also dose in-line, dosing the various additives directly into the mixer. Some plants find it more efficient to create larger quantities of premixed additives and carriers in one go. Doing so allows larger dosing sizes, and the production of premix when time is available (not inside the batch time of the main process). Additional storage might provide a challenge here, but again each different process and facility will have to prove which way works best.
Commercial requirements include delivering a range of products with as short a lead time as possible, with low capital and operating costs, and without compromising quality. In our experience, the best starting points for a process design or redesign are a thorough analysis of (realistic) wishes, with a good balance of nice-to-have features and future-proof design. Don’t overdo the nice-to-have and future-proof parts, though. The optional extras might tick all the boxes, but blow up your budget all the same.
It appears that also the design of a weighing construction needs much attention in this process. It still happens frequently that not all the products end up directly on the scale, but (partly) on a funnel to the weigher. This gives false measurements and product mix up in the process. The weighed product should be dosed directly on the scale, and in such a way that there will be no ‘leverage effect’. Leverage