FAIR-CT95-0069 Innovative Harvesting and Sugar-Juice Separating Machine for Sweet Sorghum and Fibre Sorghum

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Crops for Liquid Biofuels and Biogas : Crops for Solid Biofuels : Electricity : FAIR Area 1.1 - Biomass and Bioenergy Chain : Fibre : Liquid Biofuels and Biogas : Separation/Fractionation : Solid Biofuels : Sugar

	Proposal No:	FAIR-CT95-0069
	Date Prepared:	September 1999
	Source:	Final report November 1997

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Final report November 1997

Summary

During the last part of the project, the functionality and operation of the machine developed was tested in the field, with special attention paid to the sorghum used which was cultivated especially for this purpose. The on-the-field testing was carried out in connection with four different partial processes, as follows: cutting of the stalks; conveying of the stalks towards the squeezing system; squeezing of the stalks; removal of the cut stalks, after the squeezing system.

Cutting The testing of the cutting operation was made after dismounting the other operating part of the machine. After a number of tests, the system proved to operate properly as speed was increased up to about 3 km/hour. Only with thick sorghum plants some inadequacy of the system was experienced. This was overcome by applying a higher rotational speed to the blades together with the use of less powerful hydraulic motors. Results were as good with partially flattened crop. However, the test was restricted to small areas with very limited slope.

The bundling problems experienced were limited to those areas where the sorghum was particularly thick and vigorous and when the speed was raised to around 5 km/hour. With a speed of around 10 km/hour performances was good, so long as plants were planted in rows and each plant had only one stalk. The cut was very clean and sharp.

By means of mechanical artifices it was possible to verify that the machine is capable of operating correctly at 10 km/hour, even with several stalks per plant if the stalks are quickly moved away from the cutting area.

Stalk conveyor To test the stalk conveyor, a group of corrugated chains was re-mounted on the machine. The advancing speed was increased by increments, going from the lowest to the highest speed. The test proved that a higher number of stalks per plant may result in an irregular falling, of the cut stalks, making the removal of the cut stalks from the cutting area more difficult and consequently increasing the possibility of system clogging. Large foliage also can increase the size of the stalk bundle, so that it is difficult to transport by the chains.

The geometrical dimensions of the stalks are important since they reflect the mass of the stalks which in turn determines the power that has to be applied to transfer them to the next process step. In order for the transport chains to operate properly an advance speed of around 3 km/hour is required.

Complete machine The final test was carried out with the complete machine, with all parts mounted. Under these conditions, the number of enforced stops over a given time period was noted, regardless of their cause. At the same time the efficiency of the overall extraction system was also noted. At the end of the test it was clear that the best result could be obtained with a higher pressing time, together with an even squeezing, which means that progression through the field has to be constant and steady. The more this is achieved, the better the results obtained.

In order to assess the operating performance of the machine it was decided to count the number of stops in one hour on a basis of 10 successive stops. This means that the periods in which the first 10 stops take place are added. The sum of these periods, divided by 10, gives the mean time between two consecutive stops. Finally, the number of times this period is contained in one hour gives us the hourly occurrence of machine stops.

This was done at various advancing speeds, when it was found that the hourly occurrence (mean number of machine stops, due to whatever cause, in units per hour) increased as follows:

Speed of advance km/h	Number of stops (rounded off)
0.5	4
1.0	9
1.5	17
2	29
3	127

It must be considered, however, that if the same tests were made in uniformly cultivated areas the above-mentioned values can be reduced by 60%. This indicated the great importance of field conditions of the sorghum if a good machine performance was to be achieved.

Juice extraction The juice extraction tests were carried out by starting with the mass of the squeezed sorghum and measuring the percentage ratio between the mass of juice obtained and the original mass. The testing was carried attempting constant pressure in the control circuit (although the uneven distribution of sorghum on the ground did not always allow this), at variable speeds up to 2 km/hour. The same testing was repeated with the passage for the sorghum ranging from 10 mm to 2 mm. For each weighing the mass of juice obtained from the squeezing was correlated with the original mass, evaluated by correspondence to a similar length of row. Each measurement was expressed as the arithmetic mean of at least three observations, at advancement speeds between 0.5 km/hour an d 2 km /hour, with 0.5 km/hour intervals. The following table summarises the results obtained:

Passage width mm	10	8	6	4	2
Speed (km/h) 0.5	27	39	42	45	47
1.0	25	28	37	38	39
1.5	22	25	26	27	28
2.0	14	20	21	23	24

These results taken on the field considerably different from those expected. It is believed that values closer to those originally proposed can be reached if the cultivation result in sorghum plants in more homogeneous rows with few stalks per plant, regular dimensions of the stalks and consistent foliage. This would make the harvesting of the sorghum as reproducible and steady in time as possible. In fact, the machine showed a big improvement as far as functionality and operation was concerned in those parts of the trial where these ideal conditions were met. However, the information obtained will enable possible solutions and adjustments to be made.

Expelling spent stalks A last series of observations concerned the expelling of the squeezed stalks to the ground. Treating these through a lateral outlet enabled them to fall in a more ordered way, allowing the stalks to be gathered and formed into round bales. Under these conditions the machine does not pass over the stalks and this facilitates the gathering work of the picker, that can thus follow the sorghum harvester machine closely.

During these trials a series of adjustments were made on the machine, both to reassemble the different operating part of the machine and to improve mechanical operations and make repairs. These were necessary, for example, to replace some broken cutting blades, to repair the fairings of the blade operation motors, to repair whole cutting systems, to repair the corrugated chains, broken hydraulic pipes and other.

Other activities These included production of documents providing general data on the characteristics of sorghum, of the composition of the juice, of the chemical composition of the badges and of the photosynthesis efficiency; together with an estimate of the amount of energy obtainable from each field unit cultivated with sweet sorghum.

When operations are improved, the potential market for this machine would be between 400 and 500 machine /year over a production period of 10 years can be considered.