Sugarcane harvest losses

Among the visible losses in the sugarcane harvest, the rotation speed of the primary exhaust fan has a great influence, especially considering losses due to chips. 

Currently, Brazil is the world's largest producer of sugar cane, followed by India and China, respectively, with the first two having a share of world production above 50%. In national territory, according to the National Supply Company (Conab - 2013), the state of São Paulo is the largest producer of the crop, responsible for approximately 52% of the planted area, followed by the states of Minas Gerais and Goiás.

Sugarcane harvesting must be carried out at the stage when it has the greatest accumulation of sugars (fructose and sucrose) in its stalks, which is extremely important for maintaining the quality of the sugarcane field, as it is renewed after long periods of extraction of plant material.

Carrying out the harvesting process, seeking high quality, is essential, considering that harvesting is responsible for up to 35% of the sugarcane production cost and it is extremely important to carry out this task aiming at the quality of the process, combining this factor with operational performance.

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The primary extractor is one of the main components of the sugarcane harvester's cleaning and unloading system, which also consists of a topper, side cutting disc and primary and secondary extractors. Studies carried out by Voltarelli indicate that it is responsible for cleaning in the first instance up to 80% of the harvested material, removing mineral and vegetable impurities out of the machine, with this cleaning process being carried out after splitting the stalks.

Losses obtained during the harvesting process can be classified as visible and invisible. Visible losses are associated with the characteristics of the area to be harvested and also with the harvesting operation itself - which involves training of professionals, speed of the harvester compatible with the conditions of the sugarcane field and in synchronization with the transshipment or truck, situation of the harvester equipment , mainly base cutting knives and the stalk chopper roller, speed of the harvester's primary exhaust fan, load height, base cutting height, equipment maintenance, trimming, harvest time, load height, among others -, being that they are classified into: stumps - which are pieces of thatch that are adhered to the sugarcane stump, being smaller than 20cm; tip cane - piece of cane that is attached to the pointer, and its removal is done by breaking it at the point of least resistance manually; whole cane - represented by those with proportions equal to or greater than 2/3 of the normal size of sugar cane; stalks - are those that can or cannot be crushed with the chopping knife; splinters - are completely torn fragments.

Invisible losses are those that are difficult to visualize and quantify in the field, and can occur through the quality and service conditions of the cutting disc knives, the type of blade being used, and the speed of both extractors. These can be classified as broth, sawdust and shrapnel.

Researchers from the Mechanized Harvest Study Group (Gecom), linked to Fatec “Shunji Nishimura” Pompeia (SP), developed work that aimed to evaluate the influence of two rotations of the primary exhaust fan on visible losses occurring during mechanized sugarcane harvesting. -of sugar.

For the development of this work, the evaluations were carried out in a plot of 35,8 hectares at Fazenda Santa Tereza, with an average altitude of 520 meters and a slope of around 8%, located in the municipality of Duartina, in the interior of the state of São Paulo. .

The sugarcane variety that was being harvested in the area for the experiment was RB86-7515. This variety is not demanding regarding soil characteristics, good adaptation to mechanized harvesting, good sprouting with the presence of straw, in addition to drought tolerance.

For harvesting, a Case IH harvester, model 8800, manufactured in 2012/2013, was used. The sugarcane field was in its third cut and was classified as bedded (Figure 1), due to the presence of strong winds that hit the region in previous days, potentially aggravating losses during harvest.

The methodology developed by the sugarcane technology center was used to carry out biometrics, where manual harvesting was carried out, collecting all the sugarcane present in a five meter line, carrying out four repetitions within the area, always seeking to collect at representative points of the sugarcane field to obtain an average productivity.

For the experiment, two treatments were carried out at random points in the area. In treatment 1 (T1) the harvest was carried out with the rotation of the primary exhaust fan at 800rpm and in treatment 2 (T2) the harvest was carried out with the rotation of the primary exhaust fan at 1.100rpm. Each sampled point had an area of ​​10m² (3,33m x 3m), performing four replications for each treatment.

The location for collecting visible losses from the variation of the primary exhaust fan was demarcated using string and stakes in predetermined dimensions.

All plant material present within the area was piled up, then the straw was separated from the material of interest to classify and quantify losses.

For this assessment, a work developed by the sugarcane technology center was used as a reference, where it defines losses at three levels, being low: from 0% to 2,5%, medium: from 2,5% to 4,5, 4,5%, and high: above XNUMX%.

The biometric analysis carried out on site identified an average productivity of 88,7t/ha, meaning the machine's feed rate was 17,95kg/s. The sugarcane field was found to have fairly uniform productivity conditions from the biometric analysis, as in the four replications carried out the productivity values ​​found were very close, varying only 6,1t/ha from the lowest to the highest value.

According to Table 1, it is evident that in the 800rpm treatment, where the exhaust fan rotation was lower, the losses were also lower, obtaining an average value of 0,330t/ha, equivalent to 0,37% losses, and in the 1.100rpm treatment the average weight of losses due to chips was 0,500t/ha, equivalent to 0,56% of losses, resulting in a higher loss rate when compared to the 800rpm treatment.

 Using the data shown in Figure 5, using as a reference the loss classification method developed by the sugarcane technology center, it is possible to classify both treatments with low loss levels, as total losses are below the values of 2,5%.

However, the purpose of the work was to evaluate the influence of the rotation speed of the primary exhaust fan on visible losses, and considering that the loss due to chips is directly influenced by this component of the machine, it can be considered that the rotation of 800rpm was the most appropriate. for offering a 0,37% lower amount of losses when compared to the 1.100rpm rotation which resulted in a loss of 0,56%.

It must be considered that with the rotation variation from 800rpm to 1.100rpm, there was an increase in chip losses of 51,35%, as it is influenced by this factor. Therefore, it can be concluded that the variation in rotation of the primary exhaust fan in sugarcane harvesters has an influence on losses classified as visible, especially chip losses.

Danilo Tedesco de Oliveira, Rafael de Graaf Correa, FCAV/Unesp; Edson Massao Tanaka, Bruno Kawamoto, Rafael Fachini Mamoni, Fatec “Shunji Nishimura”

Article published in issue 172 of Cultivar Máquina