Cane: - Determine % Pol in Open Cells Sampling and Sub-sampling
The difficulty of obtaining representative samples is the biggest hurdle to be overcome in direct cane analyses. EXTREME CARE AND DILIGENCE must be exercised in collecting and preparing samples, as, loss of juice and fibre particles is a common source of error and must be kept at a minimum.
The prepared cane taken from the carrier chute just before #1 mill is the most suitable sampling point. The sample should be from the entire width of the carrier in one motion.
Apparatus Bagasse Disintegrator 3 gallon tumbler 400 mm Polariscope tube Conical flasks 250 ml Beakers 500 ml Reagent Home's dry lead Procedure
1. Sample approximately 25 lbs prepared cane from chute to # 1 mill.
2. Chop any large pieces of cane present in sample cleanly with sharp blade into 2 in.
— 3 in. lengths and include in sample.
3. Cone and quarter sample carefully and divide into two (2) portions.
4. Treat each portion as follows:
Portion I
1. Weigh 1000 gms of prepared cane into container of wet disintegrator.
2. Add three (3) litres of water.
3. Disintegrate for 45 minutes.
4a. Pour off approximately 240 mls of extract through a fine wire mesh sieve into a 250 ml conical flask.
4b. Cool sample in water bath to room temperature.
5. Clarify with a minimum quantity of dry lead acetate and filter.
6. Discard the first 20 mls of filtrate, then rinse 400 mm tube three times with portions of filtrate; then fill and take Polariscope reading.
7. Take average of three readings (A)
Portion II
1. Weigh 1000 gms of prepared cane and place in tumbler.
2. Add four (4) litres of water.
3. Roll for ten (10) minutes.
4. Pour off approximately 240 mls of extract through a fine wire mesh sieve into a 250 ml conical flask.
5. Clarify with a minimum quantity of dry lead acetate and filter.
6. Discard the first 20 mls of filtrate, then rinse 400 mm tube three times with portions of filtrate; then fill and take Polariscope reading.
7. Take average of three readings. (B) Calculations
i) Derived ratio R = B A
ii) Determine % fibre in cane (F) on sample used for wet disintegration (i.e. Portion I at stage (4)), unless otherwise known.
% Cell Breakage = 400 R
4 - R - (1.25F/100)(1 - R ) Cane: - Determination of Stateness
Apparatus:
100 ml measuring cylinder 100 ml beaker Filter funnel Reagents - 96% alcohol Procedure
1. Obtain a sample of mixed juice
2. Filter and place 50 ml in a 100 measuring cylinder.
3. Fill to the mark with 96% alcohol.
4. Shake vigorously and allow to settle for 30 minutes.
Results
This causes precipitation of gums and polysaccharides produced by staling of the cane.
If the percentage sediment is less than - 10% — cane is fresh.
- 10 — 20% - cane is becoming stale.
- Over 20% - cane is over 5 days old.
IT IS NECESSARY TO ADJUST THIS FORMULA TO YOUR LOCAL CONDITIONS.
Evaporator Cleaning Solutions
For efficient running, Evaporators and Vacuum Pans have to be cleaned at regular intervals either chemically or mechanically. An important factor in good cleaning tech- niques is the monitoring of strengths of the solutions used; Regular checks have to be made to ensure that weakened solutions are brought back to strength. The following analyses are set out for this purpose.
A. ACID (Determination of Strength)
Commercial hydrochloric (muriatic) acid (1.16 sp.gr & HC1) Apparatus
50 ml Burette 20 ml Pipette Reagents
I. N Sodium Hydroxide solution Phenolphthalein indicator Procedure
1. Pipette 20 mls of the acid solution into a 250 ml conical (Erlenmeyer) flask and add 100 ml of distilled water.
NOTE: More than 20 mls of acid will be needed if less than 2% solution.
2. Add three drops of phenolpthalein and titrate with I.N. NaOH solution until pink colour just appears.
Calculation and Example
One (I) ml I.N. NaOH is equivalent to 0.03647 gm HC1.
Titration readings 10.6 mls.
20 mls of acid solution required 10.6 mls of I.N. NaOH 10.6 x 0.03647 = 0.3866 gm of HCl in 20 mls solution.
i.e. 0.3866 x 100 = 1.93 gms HC1 per 100 mls solution 20
B. ALKALINE (determination of strength)
The approximate concentration of a freshly prepared solution may be determined from the density (or brix) by referring to Table IX, however, used solutions CANNOT be treated likewise due to accumulation of soluble materials from the scale.
The method set out below is designed to determine Total Alkalinity since a mixture of Caustic Soda (NaOH) and Soda Ash (Na2 CO3) is normally used.
Apparatus 5 ml Pipette Hot Plate
100 ml Graduated cylinder 50 ml Burette
500 ml Conical (Erlenmeyer) flasks Reagents
I.N. Sulphuric Acid solution Barium Chloride Solution Methyl Orange Indicator Phenolphthalein Indicator Procedure
1. Pipette 5 ml of cleaning solution into each of two 500 ml conical flasks and and approximately 200 ml of freshly boiled and cooled distilled water to each.
2. Add three drops of methyl orange and titrate rapidly against I.N. Sulphuric Acid solution until colour change occurs (green to orange). Take burette reading.
3. Using second flask add one ml of sulphuric acid less than required for step 2 (do not add indicator).
4. Cover flask and heat the contents on hot plate to boiling. Continue boiling gently for five minutes.
5. Cool to room temperature, add three drops of methyl orange and titrate to the exact end point, stirring well, add acid dropwise to achieve sharp colour change.
Calculation and Example
Total alkalinity is expressed in terms of Na20 one ml of I.N. Sulphuric acid is equivalent to 0.031 gm Na20.
Titration reading 41.6 ml.
Total alkalinity = 41.6x0.031 = 1.290 gm in 5 ml sample.
C. Steam Side Cleaning
The solutions and method set out below is designed to clean the steam side of calandria during the out of crop. Keeping the steam side clean is as important as cleaning the juice side (though it is not done as often).
i) Factories using steam engines extensively can soak steam side of calandria with diesel oil for entire out of crop,
ii) For other factories, the following is recommended.
Reagents Caustic Soda (NaOH) Potassium Permanganate (KMn O4) Muriatic Acid (1.16 sp. gr HC1) Ferrous Sulphate (Fe SO4) NOTE: All industrial grade reagents.
Procedure
1. Prepare solutions of 72 lbs NaOH and 72 lbs KMn O4 per 1000 gallons water and heat to 60°C (140°F).
2. Fill calandria to be cleaned and heat with steam to 100°C (212°F) for at least 24 hours.
3. Discard solution and rinse calandria thoroughly.
4. Mix with cold water and inject into calandria solution of six carbouys of muriatic acid and 60 lbs of Ferrous Sulphate in 1000 gallons of water.
5. Heat (in calandria) with steam to 94°C (200°F) for 45 minutes.
6. Run out solution and rinse thoroughly with clean cold water.
This cleaning is recommended periodically, but a well regulated factory once per year is too often.
FLUE GAS ANALYSES Excess Air
For the complete combustion of boiler fuels (crude oil and or bagasse) to carbon dioxide (CO2) and water (H2O), more air is required than theoretical considerations indicate. The quantity needed above the theoretical is called EXCESS AIR. All flue gases thus contain "excess air" but, this must be carefully controlled at the minimum which contains that quantity of oxygen (O2) required for complete combustion. This is important for efficient boiler operations as excess of air passing through the furnace absorbs heat which is lost in flue gasses. On the other hand insufficient "excess air"
results in incomplete combustion with the appearance of carbon monoxide (CO) and very often smoke in the flue gas.
Theoretical air is the calculated quantity containing just sufficient oxygen to combine with the carbon, net hydrogen and sulphur of the fuel to form carbon dioxide, water vapour and sulphur dioxide (fuel oil).
The results of the analyses described below based on ORSAT or equivalent apparatus and their interpretation are based on the quantity of carbon dioxide (CO2) present in flue gas. More modern apparatus (e.g. Zirconium oxide cells) analyses oxygen (O2) present in flue gasses continuously and control damper settings automatically.
NOTE: Such equipment analyses on a wet basis and is sensitive to water vapour in flue gasses. Allowance must be made for this if the unit is used on bagasse fired boilers.
Apparatus
Orsat or Equivalent (See chapter III) Reagents
Potassium hydroxide (KOH) 20% solution Alkali solution of pyrogallic acid Acid solution of cuprous chloride (See chapter VIII)
Procedure
1. Fill absorption pipette (to point "A") with freshly prepared reagents, after ensuring that all needle valves and rubber hoses and connections are free of leaks.
2. Fill the measuring burette with more than 100 units of flue gas by lowering the levelling bottle and placing the sample pipe suitable in flue duct.
3. Expell the excess flue gas through the three way petcock leaving exactly 100 units in measuring burette at atmospheric pressure, then close petcock.
4. Force the entire volume of air info the #1 (CO2) absorption pipette by (a) opening the needle valve and raising the levelling bottle, then allow to stand for half minute.
5. By lowering the levelling bottle allow the reagent in #1 absorption pipette to return to the original level (mark "A"). Hold levelling bottle so that water level is equal to that in measuring pipette. Take reading. The quantity of CO2 absorbed, is the difference between the original volume (i.e. 100 units) and the reading at the end of step 5.
6. Repeat steps 4 and 5 until a constant reading is obtained.
7. The flue gas sample remaining is now forced into #2 absorption pipette (O2) as in step 4 and step 5.
8. Repeat step 7 until a constant reading is obtained. The reading on the measuring burette is now the sum of the percentage of CO2 and the percentage of O2 in original flue gas. The O2 percentage is found by subtraction.
9. The remainder of the flue gas sample is now forced into #3 absorption pipette (CO) as in step 4 and 5 and the quantity of CO in original flue determined.
The remaining flue gas after all determination is assumed to be nitrogen (N2).
10. To ensure that the analyses have been correctly done the flue gas is expelled and the oxygen (O2) contained in a 100 unit volume of air is carried out. CARE MUST BE TAKEN TO KEEP SAMPLING PIPE AWAY FROM CARBON DIOXIDE (CO2) and or CARBON MONOXIDE (CO) sources. Result should be 21%. If this is off by more than ½%, check solutions and apparatus and repeat analyses. The results obtained are in % by volume on a dry basis. The flue gas sample is saturated with water vapour at all times, but the water jacket surrounding the measuring burette keeps the sample at a constant (room) temperature during the analyses. While there is always water vapour present, when the sample volume decreases the volume of water vapour also decreases to maintain the same partial pressure of water vapour. Thus the water vapour bas no effect on the analyses and the results are exactly as if dry gas analyses had been done.
Excess Air Calculations
If CO2 is the % carbon dioxide determined in flue gas by gas analyses the excess air is calculated by the formula.
Excess = 20.3 x 100 - 100 CO2 (determined)
Example: If analyses gives CO2 is 16% by volume
Excess air = (20.3 x 100 ) - 100 = 126.9 - 100 ( 1 6 )
= approx. 27%
% C02 to % Excess Air Based on Flue gas at 500°F and 50% bagasse moisture.
%CO
2 20.3 17 16 15 14 13 12 11 10% Excess Air 0 19 27 35 44 56 68 84 102
Oxygen Nitrogen
Composition of Air (dry)
% by Weight % by Volume 23.15
76.85
20.84 79.16
Heat Value per Pound of Bagasse, Flue gas at 500°F
% Bagasse Moisture
45 46 47 48 49 50 51 52 53 54
Theoretical Air required 3326 3241 3160 3077 2993 2910 2829 2744 2664 2582
50%
3169 3087 3007 2928 2851 2767 2689 2607 2528 2450
Excess Air 100%
3012 2933 2856 2779 2700 2624 2548 2469 2393 2319
150%
2854 2778 2704 2631 2557 2481 2416 2332 2259 2188
2 0 0 % 2692 2624 2553 2482 2409 2338 2275 2194 2124 2057
HYDRATED LIME - DETERMINATION OF AVAILABLE CaO The quality of lime supplied to factories is an important but often neglected factor in the clarification process. Apart from the economic aspect, the use of substandard quality lime can introduce significant quantities of undesirable impurities into process.
Apparatus Analytical balance Hot Plate
Conical flask 250 ml
Filter paper. Whatman #1 or equivalent Pipette - 25 ml
Burette - 50 ml Reagents Granulated sugar Phenol phthalein solution Sulphuric acid, 0.357N Procedure
1. Weight 5.0 g of the finely powdered lime sample.
2. Transfer to a 250 ml conical flask with 75—90 ml freshly boiled and cooled distilled water.
3. Boil gently on a hot plate for three minutes, shaking with a rotary motion to break up any lumps.
4. Cool the flask and contents to room temperature.
5. Dissolve 40 g of granulated white sugar in 40 ml of freshly boiled and cooled distilled water. Add this to the flask with the lime.
6. Shake for 30 minutes with a rotary motion of the flask, keeping the lime in suspension.
7. Complete to volume with freshly boiled and cooled distilled water and shake well.
8. Filter and discard the first 25-50 ml of filtrate.
9. Kpette 25 ml of the filtrate into a clean 250 ml conical flask.
10. Add 5 drops phenolphthalein solution and titrate with 0.375N sulphuric acid until the pink colour just disappears.
Calculation
Available CaO% = ml of 0.375N sulphuric acid multiplied by 2.
Example
Titration reading = 31.6 ml Available CaO = 31.6 x 2 = 63.2%
MIXED JUICE - DETERMINATION OF SULPHATED ASH Apparatus
Analytical balance
Platinum dish (100-125 ml capacity) Hot Plate (or bunsen burner) Muffle furnace Desiccator Water bath
Graduated cylinder (50 ml capacity) Reagents
Concentrated sulphuric acid in a dropping bottle. Paraffin liquid.
Procedure
1. Heat dish to redness in oven or over a bunsen burner.
2. Cool in desiccator and weigh
3. Transfer 50 ml of filtrated juice to the dish and weigh.
4. Add 5 drops of concentrated sulphuric acid and mix by gently rocking the dish.
5. Heat on a water bath and evaporate to the consistency of final molasses.
6. Heat on a hot plate (bunsen burner) until completely charred. Start hot plate on low heat and gradually increase heat to prevent spattering of the sample.
If there is any tendency of the mixture to foam, add a few drops of liquid paraffin.
This operation must be watched and cannot be hurried or the material will swell and overflow.
7. Transfer to the furnace and heat at 550° for 4 hours.
8. Cool first in air then in a desiccator and weigh to constant weight. Generally, heating at 800°C for a further 30 minutes will be sufficient to arrive at a condition of constant weight.
Calculation
Weight of dish + juice = 99.527 g Weight of dish = 45.585 g Weight of juice = 53.942 g Weight of dish + ash = 45.994 g Weight of ash = .409 g
%sulphatedash = 0.409 x 100 53.942
0.76%
MIXED JUICE - DETERMINATION OF % EXTRANEOUS MATTER
Apparatus
1 litre measuring cylinder Reagents
Procedure
1. Place a 1000 ml of mixed juice in a 1000 ml cylinder.
2. Allow to settle for 2 hours and read off the percentage of sediment in the bottom of the cylinder. - 50 ml - 5% — good clarification.
6 0 - 150 ml 6 - 12% Fair
More than 120 ml - 12% clarification problems These results are for an average factory. The percentage sedimentation may be slightly different for your factory juice. Carry out the procedure on juice of known quality in your laboratory and use the results as your reference standards.
MIXED JUICE - DETERMINATION OF PHOSPHATE
Phosphate analyses are usually made to determine the clarification characteristics of juices.
Apparatus
Nessler tubes and Lovibond Comparator with a disc No. 3/51 covering the range 10-400 of phosphate. OR
Colorimeter
Volumetric (graduated) flasked - 50 ml, 100 ml.
Pipettes - 10 ml, 5 ml graduated Timer
Beaker Watch glass Reagents
Ammonium molybdate reagent Ascorbic acid powder IN Sulphuric Acid
Standard phosphate solution containing 25 ppm.
Procedure - Prepare 10 ppm phosphate solution as follows:-
1. Pipette 10 ml standard phosphate solution into a 100 ml graduated flask and make up to mark with distilled water - THIS SOLUTION NOW CONTAINS 10 ppm PHOSPHATE.
2. Pipette 25 ml of this solution into a beaker and add 15 ml distilled water and 4 ml Ammonium molybdate reagent and mix thoroughly.
3. Add 0.1 gm Ascorbic acid, cover the beaker with a watch glass and heat to boiling point for one minute. A BLUE COLOUR WILL NOW DEVELOP.
4. Cool the contents rapidly and transfer to a 50 ml volumetric flask. Wash beaker with distilled water and transfer washings to flask. Make up to 50 ml with distilled water and transfer washings to flask. Make up to 50 ml with distilled water.
5. Prepare a blank by Procedure 2-4 substituting water for phosphate solution in procedure 2. i.e. 40 mls water, 4 mls Ammonium molybdate etc.
6. Prepare Juice sample as follows: -
A. Pipette 5 ml juice into a 200 ml flask. If sample is alkaline neutralise with IN sulphuric acid.
B. Dilute to 200 ml with distilled water.
C. Proceed as in 2-4 above, substituting juice for phosphate solution in pro- cedure 2.
7. A. Read 10 ppm phosphate standard and sample on instrument, (colorimeter, 640-740, set at zero with blank).
OR
B. Compare standard and sample in Comparator/Nessler tubes.
Calculation
A. Reading of 10 ppm standard phosphate = 0.45 Reading of sample 0.36
.'. ppm phosphate in original juice sample = 0.36 x 10 x 200 = 320ppm.
0.45 5
= 320 ppm
B. Multiply ppm concentration obtained by 40.
MIXED JUICE - DETERMINATION OF % MUD VOLUME OF LIMED AND HEATED JUICE
Apparatus Hotwater bath Boiling Tube 10 ins x 1 in.
Hot plate
Centimetre (or inch) rule Alarm Clock (or Interval Timer) Reagents
Procedure
1. Ensure that water in bath is at boiling point. Adjust with rheostat control if available.
2. Heat random sample of hot limed juice to boiling on a hot plate.
3. Fill boiling tube with sample of hot limed juice, and measure height of liquid in the boiling tube = Hcm (ins).
4. Insert boiling tube in water bath, ensuring that level of water in bath is higher than that of the hot limed juice. Set alarm clock to go off after one hour.
5. After one hour measure height of mud in the boiling tube = h cm (ins).
6. Calculate % mud volume of the limed and heated juice as follows:
Calculations
Height of liquid in boiling tube = H cms (ins).
Height of mud in boiling tube = h cms (ins).
% mud volume of limed and heated juice = h x 100 H
SUGAR - DETERMINATION IN EFFLUENTS
Appreciable amounts of sugar may be lost from a factory, carried away by entrain- ment and pass undetected in the large volume of water used in condensers etc., and which continually leave the plant. All such effluents e.g. condensates, condenser tail pipe water, should therefore be tested regularly and at short intervals.
Tests should be made on fresh or recently obtained samples only, as sugar content of samples several hours old will be greatly reduced due to bacterial decomposition.
A. Qualitative Test Apparatus
Test tube - approx. 100 mm.
Burette Reagents
Alpha Naphthol solution Concentrated sulphuric acid.
Procedure
1. Make certain that all glassware and sample containers are free from any trace of sugar.
2. Cool a portion of the sample to room temperature.
3. Rinse a 100 mm test tube with a portion of the sample and half fill the tube with the sample.
4. Add 5 drops of alpha - naphthol solution to the test tube and mix thoroughly.
5. Hold the test tube in an inclined position with the tip of the burette contain- ing concentrated sulphuric acid, touching the tube.
Allow about 2 ml of acid to run into the tube so that it flows to the bottom forming a distinct layer.
Hold the tube upright - do not mix contents.
7. A lilac or purple ring at the interception of the two layers indicates sugar. If no purple or lilac ring appears after 15 seconds, the test is reported negative.
The test is very sensitive and 100 ppm of sucrose gives a black ring due to a charing of the sugar by the acid.
8. A positive test for sugar should be checked by running a blank test with distilled water to ensure that the alpha naphthol has not been contaminated with sugar.
B. Quantitative Test Apparatus
Pyrex Test tubes, approximately 150 x 20 mm, Comparator such as Lovibond or similar
Reagents
Alpha naphthol — concentrated sulphuric acid — reagent.
Procedure
1. Pour 2.5 ml of sample * into a glass stoppered test tube. Pipette 5 ml of sulphuric acid reagent down the side of the tube.
2. Stopper tube and mix gently by inverting two or three times, holding stopper firmly in position. **
3. Allow mixture to stand for exactly ten minutes with the stopper removed.
4. Replace the stopper and match with colour standards.
5. Read off amount of sugar in ppm in the indicator recess.
* Concentrations of more than 100 ppm may be determined by dilution.
** Considerable heat is evolved on addition of the acid solution and the stopper should be removed each time the tube has been inverted.
Hold the tube away from the face when inverting the tube and always handle the acid with great caution.