Feed & Additive Magazine Issue 2 March 2021

ARTICLE 74 FEED & ADDITIVE MAGAZINE March 2021 maintain a more regular final shape. In contrast, less plastic or ductile material will shatter into finer and irregular shards like particles. The elasticity of the material is defined by its wa- ter content: therefore, by controlling the moisture of the material, it is possible to determine the ener- gy consumption of the process, the final size of the powder particles, and the product yield and loss. For these reasons, the initial moisture of many food materials is the most important element to reg- ulate before the grinding process. TRANSPORT AND FLOWABILITY After the grinding process, the moisture remains very important as it determines the flowability of the particles as the bonds between water molecules affect the stickiness and caking effect of the powder. PELLETISING Pelletising is the process of extruding the for- mulation into cylindric shapes that are more easily consumed by animals. The content of the mix is ex- tremely variable between the various applications and recipes. However, even in this process and after all the other steps, the water content is still an important factor to measure the quality of pellets. Additionally, the pellets may need to be dried for storage. CONTROL AND SENSORS In summary, the moisture affects the costs and the quality of the products. Knowing and subsequently controlling the water content of the material in every step of the process is necessary to improve efficiency, to reduce carbon footprint, and to save money. To achieve these results, sampling the material is not enough because the samples may not be repre- sentative of the full batch and the speed of the feed- back process is not adequate. It is possible to achieve real-time control in the process with inline sensors. As water content is an indirect measurement, this means the value is attainable only by calculating it from another measured characteristic; therefore, it is necessary to keep as constant as possible all other variables such: • Material composition (mix recipe) • Particles size • Pressure on the sensor • Flow speed For this reason, it is key to calibrate the sensors for each recipe or formulation, only after the system in- stallation. The calibration must be realized by accurate lab tests, calibrating any sensor with another different sensor can cause a sum of errors resulting in incorrect calibrations, defeating the initial objective completely. Independently from the method used in the process, whilst calibrating any sensor, during the lab test it is critical to completely “cook” away the moisture of the sample to reach the dry weight, as this is what will be used to define the moisture reported by the sensor. There are many moisture sensors available on the market, and we can summarise the different technology used in five categories: Disturbed by: Type of Technology NIR/lnfrared Resistive Capacitive Microwave Analogue Hydronix Digital Nuclear Maintenance High Medium Medium Medium Very low Very high Temp • • • • Note Only surface reading Unreliable Unreliable Unreliable For flowing materials Only huge quantity Salts • • • Density • • • • Dust • Colour •