Dry beans are considered an important field crop in South Africa as a relatively low-cost high protein source and its range of nutritional benefits. Many farmers are recognizing the value of dry beans, as despite the labour-intensive production requirements involved, they can deliver good returns.
Adding value to these highly sought-after products is achieved with a specialized Dry Bean Processing Plant, which removes around 95% of impurities, leaving the product ready to sell to the market or for further preparation processing. With the inclusion of an additional electronic sorting equipment, this figure can be increased to as high as 99% clean. In this article, we highlight briefly how we achieve this process.
Cleaning after harvesting
Like most grains and pulses, dry beans need to be cleaned once harvested in order to remove dirt, impurities and other foreign particles. Dry beans are generally very dirty post-harvest, and the process of cleaning beans typically requires pre-cleaning and fine cleaning before the product can be stored. A Grain Cleaner is used for both pre-cleaning and fine cleaning and works using a system of vibrating screens combined with aspiration to remove impurities.
The pre-cleaning or pre-separating process involves separating by particles based on size, removing the larger impurities such as pods, sticks and leaves from the beans that are smaller in size. It is important to note that although pre-cleaning separates out the larger impurities, there is still a significant amount of foreign matter that will pass through during this stage.
For best results it is recommended that fine cleaning then follows. This involves the separation and removal of smaller impurities such as dust, sand and other small particles, referred to as ‘fines’. Bean splits are also removed during this process.
Once the beans have undergone the fine cleaning process, the product is relatively clean. However, the beans will not yet be ready for bagging as some impurities will still be present, including stones and underdeveloped grains that are similar in size and weight as the dry beans.
In farming regions where stones are prevalent, Destoners are a critical component in bean processing. These machines are highly effective in separating product based on density – so stones, kernels or fragments of metal similar in size but heavier will easily be removed.
GENTLE CONVEYING BETWEEN PROCESSES
Dry beans are considered quite fragile and during processing often incur breakage and splits. It is for this reason that gentle handling and conveying is required to minimize damage to the product.
Gentle handling is vital to maintain product integrity and minimize breakage wherever possible. To this end, the our Swing Tray Elevator, or pivoting bucket elevator has been designed to do exactly that. Tubular belt conveyors are another example of gentle handling conveyors, that gently transport grains and beans with minimal impact on the product.
Product Grading and sorting
Grading and sorting of dry beans is an important step in the process to ensure uniformity in the quality of the final product. This is where a Gravity Table or Densimetric Table comes in. The main function of a gravity table is to efficiently separate out high quality product from poor quality product (this includes damaged, immature, half grains) and any debris that may have passed through previous processes.
Separating by colour is the final step in the sorting process. Electronic Colour Sorters separate product based on colour differences and are usually found near the end of the processing line, after mechanical separations have removed the impurities of similar size and density. Colour sorters detect the colour or optical properties of a product, and with the use of pneumatic ejection drives, separate out the product with colour that does not fall within the acceptable colour range required.
Proper sorting by size, weight and colour enables the producer to effectively grade the dry beans and affords the opportunity to then sell the higher-grade product for a higher price. Once sorting and grading are complete, the beans can then be bagged and stored for additional processing that may take place further down the value chain.
If you are looking to set up a Dry Bean or Grain Processing Plant, Contact Us directly to discuss your product handling and process capacity requirements.