How to get the best debranning
The introduction of the debranning fase has brought extraordinary benefits for the milling industry: the bran is well removed, obtaining a high quality product and a substantial increase in the yield of the mill.
The setting of the decorticators in a mill is usually entrusted to the experience of the miller or technologist. What are the variables to set in a decorticator? Is it easy to find the best setpoint for each individual machine? What are the consequences of an incorrect setpoint? What is the correct percentage of bran? When to change the decorticator setpoint?
In this article we will try to answer these questions.
How is wheat grain made?
The wheat grain is composed of several bran layers that surround the endosperm and the germ. However, in this article we want to simplify the discussion by dividing the grain into 3 logical blocks: bran, endosperm and aleurone layer.
The bran is the external coating, such as the peel of the grain. The endosperm is located at the core of the grain and is the part that, appropriately separated from the bran, produces the semolina (in the case of durum wheat) or the white flour (in the case of soft wheat). The aleurone layer acts like a glue between bran and endosperm.
Separating the endosperm from the bran depends on both the characteristics of the grain and how it is debranned. In general, this is not a simple operation; however, the durum wheat, for the production of semolina, allows a simpler separation than the soft grains, for the production of all types of flour 1.
In order to obtain a good quality semolina or flour, it is necessary to separate the bran from the endosperm with the maximum efficiency at the lowest energy consumption possible. The decortication is one of the most recent technologies that allows that separation before the final milling.
In technologically older mills, which do not use decortication, yields are generally between 65% and 72%: this result is not excellent because part of the bran remains attached to the endosperm, increasing the amount of waste and reducing the yield in semolina or flour.
In mills equipped with decorticators, most of the bran is removed before the wheat grains enter the first breaking mill. This brings an increase of the yields, typically in the range of 76% -80%, and to a whiter flour (in the case of processing of soft wheat), since most of the bran contaminating the flour and increasing its color points, is no longer present 2.
Set-up of the decorticator
This is the hardest part of the process: what are the techniques to adjust the decorticator to obtain the maximum extraction rate of the bran at the lowest energy consumption, in order to reach the maximum yield? This delicate task is usually assigned to the experience of the miller or technologist and to the characteristics of the decorticators.
When there are several debranning steps, the setting of the machines is not easy at all; the miller’s five senses are no longer enough and the continuous change of wheat mix leads to a continuous change of the decorticators’ setpoint, without any objective counter-evidence.
Types of debranning: (a) ideal, (b) hypo-debranning, (c) hyper-debranning.
A bad configuration of the decorticator does not allow a correct separation of the bran from the endosperm; in fact, it reduces the beneficial effects.
In the most serious cases, where the configuration of the decorticator is completely wrong, two phenomena can be observed:
- hypo-debranning (figure b), in which the machine does not remove all the bran, increasing the probability of polluting the product with a consequent reduction in yield;
- hyper-debranning (figure c), in which the machine, in addition to removing the bran, also removes part of the endosperm, increasing the probability of finding broken grains in the bran and in the wheat in the first break, with a consequent reduction in yield.
Many are the parameters of the decorticator where you can intervene to improve your performance; however, we identify 4 as the most important affecting the yield: (a) instant power rotation of the machine, (b) angle of the mechanical beater and distance from the wheels, (c) grinding technology, (d) waste flow.
It is expressed in kW and is the amount of energy supplied to the decorticators in order to move the wheels that scratche the wheat grain. The amount of energy supplied to the machines depends on the type of grinding wheels, the volume of processed wheat (flow) and the type of wheat.
Angle of the mechanical beater
The mechanical beater is an part that contrasts with the grinding wheel and serves to prevent the grain from following a perfectly circular trajectory during decortication. The mechanical beater is a spoiler that mixes the wheat, ensuring greater homogeneity of the peeled grains.
The wheels are very hard abrasive stones and traditionally they are made of Silicon Carbide, a material that leads to excessive heating of the debranned grains.
For some years now, diamond wheels have been proposed on the market, which should guarantee a longer life compared to traditional ones, a lower consumption of electricity and a substantial decrease in the temperature of the debranned grain.
At the moment there is no tool that makes objective the goodness of a material with respect to the other.
Today the decortication is normally set in order that it varies in a range between 8-12% of extracted bran. This value changes according to the installed machine and the number of steps of decorticators.
Most incident parameters in a decorticator set-up: (a) machine rotation power, (b) angle of the mechanical beater and its distance from the grinding wheels, (c) grinding wheel technology, (d) wastes flow rate.
Hydra: the solution
On the market there are no tools to identify the optimal setpoint for a decorticator and keep it constant over time.
Caronte Consulting solved this problem by designing and creating Hydra, an innovative device able to identify and correct the decorticator’s setpoint in real time.
The principle on which Hydra is based is very simple: the device continuously analyzes the scrap decortication and modifies the parameters of the machine until it reaches the optimal separation between starch and bran, creating a beneficial domino effect on the whole milling process, with a consequent increase of yield.
Ashes and proteins
The correction of the debranning in real time allows to constantly have a final product with very low ash percentage. In this way it will be possible to add to the final product the flours coming from the processing of the aleuronic layer, which has a high concentration of ash, but also a high concentration of proteins.
The separation of the bran from the endosperm is perfected in order to increase yield. The correct energy dosage made by Hydra obtains a low temperature debranned wheat, minimizing the presence of small fragments of broken wheat in the wastes.
With Hydra we deepen the knowledge of the production process, the millers can use always the best setpoints and objectively validate their changes into the plant.
This causes a stabilization of the entire production process and increase the yield.
The results of the application of Hydra are visible in a few weeks and are unequivocal: with the same mix of milled wheat, it will be possible to see an average yield increase of 2.7-3%. This increase gives the possibility to amortize the investment immediately, with excellent results in the medium and long term.
Stabilization of the ashes in the finished product is the direct consequence of a perfectly balanced debranning, with a significant reduction of non-standard products.
Reduction of wastes, optimization of the separation of bran and endosperm, cooling of debranned wheat.
The realtime calibration of the machines leads to an increase of the yield.
Hydra is installed in line with two possible configurations:
- on each decorticator (recommended solution);
- on each debranning step.
Hydra‘s devices are connected to each other (IoT) communicating the different settings to easily identify the optimal configuration for each single mix of processed grain (Industry 4.0).
By installing Hydra on each decorticator, you can observe a very interesting phenomenon: each single hull will take a set of parameters, as well as the type of mix to be debranned, even the physical conditions of the machine such as the level of wear of the wheels, the type of grain of the wheels, the inaccuracies in the regulation of the mechanical beaters, etc.
Hydra‘s installation on each decorticator will allow to have:
- very fine and precise debranning;
- maximum increase of yield;
- decorticators with different degree of wear of the wheels (lengthening of the life of the wheels);
- diagnostic for the planning of maintenance activities.