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WHY SHOULD I CARE ABOUT MOISTURE?

21 September 20208 min reading

Alessandro Mario Technical Sales Engineer Hydronix

As it is well known in the agricultural, feed, and related industries; moisture is a determining factor in every process. Let us take a few steps back and have a brief overview of all the steps where it is possible to increase profits and efficiency by controlling the moisture.

Imagine a world where moisture does not matter… a world where you can harvest when you want, where mould and toxins do not affect stored products, where mills operate always at maximum efficiency and final products are perfect.

It sounds fabulous … but as it is well known in the agricultural, feed, and related industries; moisture is a determining factor in every process.

Let us take a few steps back and have a brief overview of all the steps where it is possible to increase profits and efficiency by controlling the moisture.

HARVESTING AND THRESHING Harvesting is the procedure where ripe crops are cut and picked up to then proceed with the extraction of the grains by another mechanical process called threshing.

Depending on the destination of the yield, the crops need to be harvested at precise moisture.

For example, harvesting and threshing grains when it is too dry (water content below 20% - 25%) can lead to loss, waste, and breakage of material.

Contrary to that, if crops are too wet, it is possible to get mechanical issues requiring additional adjustment of the harvesting equipment. Wet crops will also limit the weight capacity of the machinery and cause problems with the threshing action.

The water content of the yield can be measured inline directly inside the combine harvester to calculate the dry weight as well as provide additional information about spatial variability in the field.

Depending on the location and the weather, the first 48h are crucial for the yield, as moulds and toxins can contaminate the product before the storage and drying operations, therefore knowing the moisture during the harvest will also allow the farmer to plan easily ahead.

STORAGE AND DRYING After the previous operations, the yield needs to be stored and preserved accordingly to prevent mould, spoilage, or heat spots. These often give problems that are directly related to the moisture contents of the yield.

Monitoring moisture during storage is fundamental to be able to regulate the storage operations and to react timely to problems.

Drying is a common practice to safely store grains, and it is a delicate process to reach the perfect moisture. By missing the target, the yield is still prone to mould and spoilage, on the other hand, over-drying is not just an expansive waste of energy but can cause damage and breakage to the grain’s skin, making it prone to moulds and insect attacks. Excessive drying can also cause the grains to shrink in size causing yield loss.

The material entering the drier has variable water content and this makes it difficult to regulate the amount of time the material needs to be exposed to the heat or to regulate the temperature.

In this process, the inline moisture control is used to automate the dryer to save money and improve the quality.

CONDITIONING After drying, depending on the material and system requirements, it may be necessary to reintroduce water into the product by conditioning.

This process can be done before the grinding mill and before pelleting operations.

Depending on the final application the conditioning can also heat the material to kill germs, to cook ingredients, and to gelatinate starch.

In the same way that moisture control enhances the drying phase, it also improves the conditioning process by monitoring the target moisture to react timely to changes in the input material.

GRINDING Grinding is one of the most energy-consuming transformations in many food processes. Through mechanical action, it reduces the size of food materials such as grains, seeds, fruits, and many more to achieve different chemical and microbiological stability.

The results vary based on what machines and methods are used as well as the toughness and moisture of the material processed.

The toughness is the ability of a material to resist breakage; therefore, tougher material will need more mechanical energy to be reduced in size.

The plasticity or ductility of a material determines the amount of energy absorbed before breaking down as well as the final size. More plastic or ductile material will need more energy to break, but it will maintain a more regular final shape, while a less plastic or ductile material will shatter into finer and irregular shards like particles.

The elasticity of the material is defined by its water content: therefore, by controlling the moisture of the material it is possible to determine the energy 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 regulate 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 formulation into cylindric shapes that are more easily consumed by animals. The content of the mix is extremely variable between the various applications and recipes, but even in this process, after all the other steps, the water content is still an important factor to measure the quality of pellets. Moreover, the pellets may need to be dried for storage.

CONTROL AND SENSORS Summarising, 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 representative of the full batch and the speed of the feedback 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 installation. 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 completely the initial objective.

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:

An essential, often overlooked, difference in the microwave technology is the linearity and stability of the output.

Sensors with digital measurement technique have a linear output, so that signal and water content are directly and proportionally related, allowing systems to achieve optimal calibration with a few points (In theory with a linear system it is possible to achieve calibration with only two points).

We had a brief journey from harvesting to the final product and we observed the importance of water content control and automation.

It is now possible to define the ideal requirements of this system.

• In line with multiple readings per second providing quick feedback for the control to adjust and stay on the target moisture. • Robust, made with high-quality materials to withstand tough industry conditions • Linear output stable in time, accurate in every condition and easy to calibrate • Store multiple calibrations for multiple recipes • Self-contained and easy to integrate into a pre-existing system • Low maintenance and cost-effective • Able to monitor from any device for full connectivity and remote analysis • High temperature resistance may also be required • Some applications could also require ATEX or IECEx certificate

Thanks to the expert research and development team at Hydronix you can find all the above characteristics in the XT series of sensors with unique digital microwave technology.

Hydronix is driven by the belief that by helping your success, we help to build a more sustainable future for our children and the generations to come.

For these reasons, Hydronix, with its 38 years of passion and expertise, provides the best digital microwave moisture sensor technology.

Hydronix is present in over 65 countries around the globe, providing a network of expert engineers on the field speaking your language.

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