* Published as Paper No. 179 in the Journal Series of the Experiment Station, Hawaiian Sugar Planters' Association.

Transcription

1 ASSAYNG CANE DELVERES'BY CORE SAMPLNG AND DRECT ANALYSS* John H. Payne and L. J. Rhodes Experiment Station, Hawaiian Stgar Planters' Association, Honolul.u, Hawaii, U.S.A. NTRODUCTlON Mechanically harvested cane as delivered to the factory contains variable amounts of extraneous matter referred to as trash. As the relative quantity of trash increases, the problem of assessing the quality of the cane becomes increasingly difficult, *and the reliability of traditional stripping tests reaches the point of diminishing returns. Net cane weights incur possible errors of as much as 50%. This situation in Hawaii, where trash percent cane delivered to the factory averages 35%, has led to the opment of the method herein described of assaying cane. The procedure in mechanical sampling of the cane while in the delivery vehicle by ineans of coring, mechanical subsampling followed by direct analysis tl~rougl~ use of the Pol Ratio Method. This paper compares the estimated yield as obtained by this method with the actual yield based upon inixed juice weight and analysis. PROCEDURE B Cpne Weighing, Sampling and Analysis Weighing - The gross weigllt of cane is determined by direct weighing on the transport unit. Core Sam9ling - Cane on the delivery vehicle is sampled by taking a core. Two types of coring machines are currently in use in Hawaii. Both of these were designed in basic form by the Field Engineering Department of the Experiment Station, HSPA. The first type consists of a 10-inch diameter rotating sampling tube with a serrated cutting edge at its end which bores horizontally through the inid portion of the cane load. The second type has an 8-inch sampling tube which is pivoted to enter at a so0 angle through the top of the load (Fig. ). S.uBsam$ling - Cores from the 10-inch machine average close to 30 pounds; those from the 8-inch machine are somewllat heavier due to packing. These are subsampled mechanically to give approximately 0.5 pound. The core is l~ydraulically discharged onto a belt conveyor which delivers it to a size reducing machine (Rietz Prebrealter). The final sample is obtained from the discharge from this machine by means of a disc-type subsampler. A view of the sample handling equipment is shown in Fig. 2. The sample is placed in a plastic container and frozen prior to delivery to the laboratory. -- * Published as Paper No. 179 in the Journal Series of the Experiment Station, Hawaiian Sugar Planters' Association.

2 J. H. PAYNE, L. H. RHODES Fig.. Core sampler. Fig. 2. Sainple handling equipment.

3 554 ENGNEERNG TABLE ANALYSS OF DUPLCATE SAMPLES WTHN A TRANSPORT UNT Duplicates Ref. Pol Purity Fiber Duplicates Ref. Pol Purity Fiber D~~ ~ i ~ solids l d %cane %cane D~~ ~ i ~ solids l d %cane %cane %cane %cane Aveyage 'f Odd 9.61 j ; 16.7 Even ,oo Paivs

4 J. H. PAYNE, L. H. RHODES 555 TABLE 2 c COMPARSON OF POL % CANE ANALYSES ON COMPOSTES O$ ONE CORE FROM EACH OF FOUR TRANS- PORTS Pairs Pol Pairs Pol Pa~rs Pol -- Day Field % cane Day. Field % cane Day Field % cane 6/ Analysis - n the laboratory the samples are analyzed directly for pol, refractometer solids, and fiber by the Pol-Ratio procedure (Mahon, 1953; Payne et al., 1956; Darroch et al., 1959). Disintegration was accomplished in 15 min with a Rietz Varigrator. Other types of disintegrators may be used (Waddell, 1953; Foster, 1956; Wiggins, 1956; Deike, 1959; Harris et al., 1959). Refractometer solids were determined on centrifiged juice samples in order to eliminate the error due to the effect of insoluble solids. A Dietert Moisture Teller was used for drying the fiber in most instances, although oven drying was used at times. Mixed Juice Weighing, Sanzpling, alzd Analysis Weiglzing: Mixed Juice is weighed on automatic beam scales. Saeling: Samples of mixed juice are obtained continuously. " Analysis: n the laboratory the samples are analysed for pol, refractometer solids, and insoluble solids according to the Official Methods of the Hawaiian Sugar Tecl~nologists.

5 155~ ENGNEERNG CALCULATONS The core samples represent the cane as delivered to the factory. The weight of the cane has been obtained. Analysis determines pol, refractometer solids, and purity. Application of the s-j-m formula gives the percentage pol available. From this the weight of pol available which was delivered may be calculated, assuming no losses except in final molasses. This is the basis for establishing the equity in the sugar produced by the factory in a given period. The weight of mixed juice, with its analysis, enables the calculation of the weight of pol availj~ble at this point, again if the only loss is in final molasses. This value, however, reflects all losses which have occurred between the weighing of the cane and the weighing of the mixed juice. These include those inherent in cane handling, cleaning, and milling. The weight of pol available in mixed juice is calculated at the end of a period of segregation when all the cane of record has been ground. From these figures a preliminary distribution of sugar may be made using the equities established. These preliminary figures are adjusted at the end of the stoclstaking periods when actual sugar manufactured figures are available. TABLE 3 RESULTS The results reported here include data from four fields studied during 1963 at Paau\1aup Sugar Company. n Table are shown the analyses of duplicate core samples from a given trans. port unit. Table 2 givesmthe results of pol analyses on several pairs of composite samples comprising one core from each of four transports. DALY ANALYTCAL DATA BY FELDS Field 26 Field 27 Strata B B B B Totals A None None B C C and averages Fzeld Cane, tons Ref.solids,tons Pol, tons Ref. solids, % pol, % Purity s-j-na Recovery Available, % Available, tons MixedJuzce,tons Ref.solids,tons Pol, tons Ref. solids, % pol, % o.zz1o.oz Purity s- j-na Recovery Available, % Available, tons Mixed Juzce Avazlable Pol % Field cane available pol 75.9

6 (1 J. H. PAYNE, L. H. RHODES 557 n the calculation of yields, daily data are given from three fields in Table 3. A comparison of these preliminary figures with those obtained by the routine plantation procedure is shown in Table 4. The routine procedure utilizes the weight and analysis of mixed juice. TABLE 4 COMPARSON OF PRELMNARY YELDS BY DRECT ANALYSS WTH THOSE OF ROUTNE PROCEDURE Field Tons 96 DA Sugar Routine method Direct analysis method DSCUSSON The variation between duplicate cores within transport units provides an estimate of the sampling precision which is summarized in Table V. Although the sampling error between cores appears high for refractometer solids and pol, it must be viewed from the standpoint of the sampling rate. Since the transports averaged 28 tons of cane, each core samples only 0.05% of the total weight, which is a very low rate. At agricultural sampling rates of 2.5 to O.O%, sampling errors of 5% are considered acceptable. TABLE 3 Field 28 C C Totals None None None None None A A B Totals Totals and and and averages aver- averages ages All fields G i ~ ,

7 155~ ENGNEERNG Sampling error is reduced as a result of extracting four cores and running one analysis on a composite sample. This is shown in the pol results given in Table 5. n these the sampling error was Z.T% which is close to half that found between duplicate cores. The variation is less between cores within transports than between transports within days or between days within fields. Thus it is better to sample more transports and composite the samples for analyses.!! 1 Field Distvibution There was a good agreement between the actual yield of sugar and that calculated from the weight a,nd analysis of field cane through.use of the core sampling procedure (Table 4). This h;~s led to the routine use of this system in the distribution of sugar and molasses to lots of cane delivered to the factory. The major consideration in the application of the system is the precision desired, which determines the frequency of sampling. Use of the method has shown it to be preferred over other methods because the ' sampling and subsampling are performed mechanically, thus eliminating errors arising from individual judgment. Acceptance has been favorable because the method is direct and involves the use of no arbitrary factors such as Java Ratio or Normal Juice Factor. Labor requirements have proven to be less than those involving classic'al methods of stripping to obtain clean cane for juice quality analysis. One man is required on the core sampler. n the laboratory one analyst can run 20 complete analyses per 8-h shift. f fibers are not run, then 30 samples can be completed. TABLE 5 ANALYSES OF VARANCE N DUPLCATE CORFS Source of variation d.f. Variance (mean square) for Ref. solids Pol Purity Fiber % cane % cane % cane Between fields 3 Between days within fields 9 Between transports within days 45 Between cores within transports 58 General mean Sainpllng error between cores (% of mean) ACRNOWLEDGMENTS The writers appreciate the assistance of the staffs of the Pauhau Sugar Company and C. Brewer & Company for their assistance in the tests.

8

9 1560 ENGNEERNG ing on the sampler before constructing it and applying it. Could you tell us how did you go about that? PAYNE : The experimental work that lead to the development of the core sampler, was reported a few years ago in the proceedings of the Hawaiian Sugar Technologists. t was the usual procedure of talring various size tubes and seeing what happened mechanically. They went through the normal procedure of taking a truck and a little experimental unit and seeing what they could draw through it and what speeds were required. We have core samplers now being used that range in diameter from three inches to ten inches. The three inches diameter sampler is used outin the field, for sampling bundles of cane. That worlcs very well too. PUR (ndia): t appeared from the last slide that the results of the core sampling were consistently lower than those by the conventional sampling. f that observation is correct, is there an explanation? PAYNE : Yes. n those three fields, the distribution of sugar was less. Of course, we don't know which method is correct. They are probably both wrong. CHARMAN: Any further question? Well, gentlemen, we have just completed another very interesting paper. would lilre to thanlr you, Dr. Payne, for that paper. This completes the Engineering session this morning41 think we would all agree that we have had the pleasure of listening to three ~nteresting papers afld participating in some real debate on them.