Design, development and evaluation of a dust separation system for wheat straw combine

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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
In northern India, wheat straw is the main and major feed source for domestic milch animals and has huge demand and economic value. During straw combining operation a lot of dust and foreign materials goes into collector which comes from settled dirt on straw lying in the field, the undulations on the field which cause the cutter bar to hit them during operation, very low height of cut with the intention to retrieve more straw and also due to bunds and rodent burrows in the field. Excessive dirt intake may lower feed intake, disrupt digestion and may have adverse impact on animal health. The design and development of an integral dust separation system for straw combine is the need of the farmers particularly in Punjab, so as to obtain the quality straw. An integral dust separation system for wheat straw combine was designed and developed to reduce the soil entrainment into the bruised straw. A perforated sheet of 2050×425 mm effective size with 7 mm diameter hole size, was provided at a distance of 130 mm behind the cutter bar and under the straw conveying unit. To remove soil clods, which goes along the cut straw while straw being pushed towards the bruising unit, a clod trapper was made of rectangular metal sheet of size 1415×180×3 mm hinged vertically and inclined with the lower body of the machine by helical spring. A bruising drum (1450×740 mm) consisting of serrated tooth M type blades (204 blades) for bruising the wheat straw was developed. The width of concave was 1435 mm with peripheral length of 920 mm. A counter cutter (3 rows and 53 blades) for effective size reduction of straw was provided adjacent to concave, under the bruising drum with a cleaning sieve of 5.0 mm diameter hole size placed below it. A centrifugal blower having 762 mm diameter was used for the blowing of bruised wheat straw. The bruised straw was collected into the wire meshed trailer, hooked behind the machine by means of a maneuverable duct. The dust separation was evaluated in the laboratory using sieve setup. During laboratory evaluation of the dust separation system, the independent parameters viz sieve opening size (S), sieve oscillations (O) and straw load (L) had significant effect on the straw quality parameters like ash content, acid insoluble ash and dust concentration. From the laboratory study S3O3 (sieve opening size 5.0 mm and sieve oscillations 400 stroke/min) as operational parameter was selected for field evaluation. The independent parameters for field evaluation were forward speed (2.0, 2.5 and 3.0 km/h), clod/stone trapper mechanism opening (32.5 and 25.0 mm) and wheat variety (HD 3086 and HD 2967). The dependent parameters for field study were straw size, ash content, acid insoluble ash, dust concentration, fuel consumption, and actual field capacity. From field evaluation the best suited performance combination of independent parameters was found at forward speed F1 (2.0 km/h) and clod trapping mechanism opening T1 (23.5 mm) in terms of minimum ash content (8.82 and 8.89 %), minimum acid insoluble ash (4.98 and 5.01%), minimum dust concentration (6.64 and 6.67 %), minimum fuel consumption (6.20 and 6.25 l/h) and desired range of straw size (19.71 and 18.20 mm), respectively for both varieties. The field capacity of wheat straw combine having developed integral dust separation system at forward speed 2.0 km/h was 0.36 ha/h, whereas, it was 0.34 ha/h for commercial wheat straw combine. The ash content, acid insoluble ash, dust concentration and straw size of bruised straw obtained from straw combine with integral dust separation system were 4.68 %, 1.72 %, 4.61 % and 20.86 % lesser compared to straw obtained from commercial straw combine (control). The cost of operation of the improved machine was calculated to be Rs 890/h.
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