CONTROL CALCULATIONS FOR FACTORIES PRODUCING BOTH SUGAR AND ALCOHOL.

Transcription

1 CONTROL CALCULATIONS FOR FACTORIES PRODUCING BOTH SUGAR AND ALCOHOL By P.G. WRIGHT 1, A.C. FERNANDES 2 and FLORENAL ZARPELON 3 1 PGW ProSuTech (Australia), 2 GAtec (Brazil), 3 STAB (Brazil) peterwright@internode.on.net KEYWORDS: Sugar, Alcohol, Balance, TRS, Chemical Control. Abstract FOLLOWING the lead of the sugar industry in Brazil and the realities of the oil markets, the sugar industry in Australia may soon be moving to the large scale production of anhydrous ethanol fuels from substrates other than final molasses. This paper introduces some of the concepts involved in the analyses and factory balances for total reducing sugars (TRS), and details the calculations of TRS equivalents for the various sugar and ethanol grades which may be produced. The approved conversion constants for ethanol density, theoretical yields of sugar and ethanol and for other relevant relationships are presented. All such material is taken from the 2003 edition of the STAB (Brazil) publication by Antonio Carlos Fernandes. The formulations and equations given there are based on experience acquired during 27 years of work in the Brazilian Centre of Technology, Copersucar. The paper is presented in the hope that it will make a contribution to the development of the sugar/ethanol sector in Australia, in the way that the referenced STAB publication has done in Brazil. Introduction The present trends in oil markets are leading to high costs of petroleum-derived fuels and to problems in energy security in respect to fueling the large motor vehicle fleet. Following the lead of the sugar industry in Brazil, the sugar industry in Australia may soon be moving to the large scale production of anhydrous ethanol fuels from substrates other than final molasses. This will involve sugar factories in diverting part of their molasses, juice and syrup streams, in addition to the traditional use of final molasses for fermentation to ethanol. The techniques of chemical accounting for sugar-ethanol factories have been worked out by Brazilian technologists over the three decades since the ethanol program was introduced in Brazil. It is of interest to adapt their techniques to traditional Australian methods for analyses and payment in order to present a system which might best suit local factories now moving to ethanol production This paper introduces some of the concepts involved in the analyses and factory balances for total reducing sugars (TRS), drawing on the 2 nd edition of the STAB (Brazil) publication by Antonio Carlos Fernandes (Fernandes, 2003). The formulations and equations given there are based on experience acquired during 27 years of work in the Centre of Technology, Copersucar. 1

2 The paper summarises the calculations of TRS equivalents for the various sugar and ethanol grades which may be produced. Approved conversion constants for ethanol density, theoretical yields of sugar and ethanol and for other relevant relationships are presented. Definitions and terminology The terminology of the traditional sugar factory has to be extended when alcohol manufacture is included. The definitions in the Australian Laboratory Manuals (Anon., 1984, 1991) updated in each past edition to follow new analytical methods and equipment, have now to include a number of new terms to cover the introduction of annex ethanol facilities. These are listed in Appendix 1. Conversion factors and tables Each molecule of inverted sugar or reducing sugar is fermented for the conversion to two molecules of ethanol and two of carbon dioxide. Thus, g of inverted sugar produce g (2*46.07) of ethanol, and each 100 kg of TRS corresponds to kg of ethanol, which when divided by the specific mass of ethanol at 20 o C (789.3 kg/m 3 ), results in L ethanol per kg TRS. This result is called stoichiometric efficiency of the fermentation, the volume in litres of ethanol that can be produced by a kilogram of TRS with efficiency of 100% fermentation. For other types of alcohol, such as hydrous or anhydrous, or alcohol of different grades, the recommended procedure is first to calculate the corresponding volume of each type of alcohol as pure 100% alcohol, and then adjust it according to the grade (% w/w ) of each type of alcohol. This way, the volumes of the diverse types of alcohol can be added and the result divided by to get the stoichiometric equivalent in TRS. Theoretical factors for the conversion of sucrose and TRS to four grades of ethanol are given in Table 1. These have been taken from Fernandes (2003, p 44, Table 4), modified with data from Perry & Green, (1984). Table 1 Factors for the theoretical conversion of sucrose and TRS to four grades of ethanol. ITEM Pure ethanol Anhydrous alcohol Hydrous alcohol Hydrous alcohol (2) Grade, % w/w Grade o GL, % v/v Density, kg/m 3 at 20 o C Yield of alcohol on TRS, L kg 1 TRS Yield of alcohol on sucrose, L kg 1 sucrose The maximum practical yield (the fermentation efficiency) is ~94.6% of the theoretical yield because some of the sugars are consumed in the side reactions necessary for ethanol synthesis. Fermentation efficiencies between 88% and 92% are considered good in practice, with the higher value easier to obtain with high purity fermentation feed. 2

3 The distillation efficiency is the ratio of the mass of ethanol in the final product to the mass of ethanol in the feed (wine) to the distillery. The losses of ethanol in distillation are small and distillation efficiencies are usually in the order of %. The overall ethanol yield is on a mass basis, the product of the yield for fermentation and the distillation efficiency. Laverack (2003) outlines a range of methods used in day-to-day operations for specifying ethanol yields. However, the method favoured in Brazil appears to be the yield as anhydrous alcohol per unit of TRS (Fernandes, 2003, p 177). It is seen in Table 1 that the maximum theoretical yield of anhydrous alcohol is , its density is kg/m 3, and it has 99.3% w/w content of pure ethanol. Table 2 lists fermentation and overall efficiency yields for anhydrous alcohol. It assumes the distillation efficiency is 99.0%. Table 2 Yields of anhydrous alcohol from total reducing sugars, TRS. Overall yield Efficiency Efficiency Anhydrous alcohol Fermentation Overall* Tonne/tonne L/tonne *Assuming distillation efficiency as 99.0%. Analyses of and first expressed juice Analysis of The analyses of by first expressed juice (FEJ) analyses and direct fibre analysis (eg by the SRI can fibre apparatus) can give in ( ), brix in (Bx ), and fibre in (Fib ). The basic assumption of the Australian CCS is that the recoverable sugar, by an idealised standard sugar factory is given by the sucrose in less half the quantity of impurity entering in, as in Equation (1). CCS # sucrose " 0.5! impurity # # 1.5! " 0.5! ( Bx " 0.5! Bx " For practical reasons there is an approximation of to sucrose and dry substance to Brix. As well, the analysis of is often not done directly but is estimated from the and brix measured in first expressed juice (FEJ). The analysis estimate is made by the 3 & 5 formula, with the following relationships: = po1 FEJ x (100 - (Fib + 5) / 100) (2) Bx = Bx FEJ x (100 - (Fib + 3) / 100) (3) Analysis of reducing sugars in For control of factories producing alcohol it is necessary to add analyses of the reducing sugars in FEJ (RS FEJ ) and in (RS ). Fernandes (2003, p 57 58) 3 ) (1)

4 describes the estimation of RS in juice by Lane-Eynon titration. Assuming that the sequestration of the reducing sugars by the fibre in the follows the same 5 formula relationship as does the, we can estimate the reducing sugars in (RS ) from its value in first expressed juice as equation 4, [or, taking a Brazilian regression (Fernandes, 2003, p 75), from its value in mixed juice, as in equation 5]: RS = RS FEJ x (1 (Fib + 5) / 100) (4) RS = RS MJ ( x Fib ) x ( x Fib ) (5) However, where a reducing sugars titration is not available, Fernandes (2003) has used a simple expression (equation 6), a function of the apparent purity of mixed juice P MJ, to estimate the value of reducing sugars in mixed juice, and then (using equation 5). RS MJ = x P MJ (6) Total reducing sugars, TRS (Brazilian ART) In Brazil practice, the total reducing sugars (the TRS available for fermentation) per 100 is commonly estimated 1 by the simple expression: TRS = ( / 0.95) + RS (7) This is because, in the process of inversion of sucrose each molecule of sucrose takes up one molecule of water to form two molecules of monosaccharides, increasing the mass by the factor 360/342, or 1/0.95. Theoretical yield of sugar and alcohol from in the conventional process The calculations of the theoretical yield of sugar and of alcohol can be made with reference to a general diagram of the principal processing phases from to sugar and alcohol, as shown in Figure 1. This shows the processing steps and loss areas, with diversion of juice (preferentially second mill juice of lower concentration and purity) to the fermentation, as well as the diversion of molasses (varying in purity from that of normal final molasses to B and A molasses, or even a higher purity stream such as partly exhausted syrup). Knowing the technological quality of the sugar and fixing the parameters of losses and efficiencies of the industrial unit, the theoretical incomes of sugar and alcohol can be calculated. The calculation can be made, as for the CCS assumptions, through deducting the losses of the processes, and then multiplying for a chosen industrial efficiency. Such theoretical estimates of the yield of sugar and alcohol can be used: $ For planning the estimative harvest norms of the production of sugar and alcohol. $ To calculate the price received for ton of sugar. $ For the simulation of yields from alternative investments. $ For the calculation of the relative industrial efficiency. In estimating the sugar and alcohol yields, many characteristics of the raw material that may influence the results and theoretical incomes have to be ignored. Some of these factors are: 1 It might well be argued that some of the original reducing sugars may not be fully fermentable by yeasts, and that a small fraction of the other organic matter in the (or juice) might be fermentable. The Brazil practice, however, is to ignore these details, reasoning that the two effects cancel each other out, and to use the simpler assumption given here. 4

5 $ The ysaccharides resulting from deterioration after cutting/burning. These include the ysaccharide dextran, proteins, starch, organic acids, oligisaccharides and phenolic compounds. $ Sugar of low moisture content. $ Impurities derived from the mechanised loading or mechanised harvest. $ Field soil and trash. Raw material Cane plus extraneous matter Weighing Sampling Cleaning Milling/extraction Bagasse Primary juice Secondary juice Filtrates Clarification for sugar Clarified juice Clarification for alcohol Fs Multi-effect evaporation (1-Fs) Sugar losses by deterioration Sugar losses in cleaning Sugar losses in final bagasse Sugar losses in filter cake Sugar losses undetermined Syrup TRS to distillery Sugar boiling & Centrifuging Molasses (1- FSJM) Fermentation TRS losses in fermentation FSJM Distillation & Dehydration Losses of alcohol & TRS in vinasse Sugar product Alcohol product Fig. 1 Diagram of the principal phase of the processing from to sugar, with diversions for alcohol production. (after Fernandes, 2003, Fig. 18). 5

6 Those sugars that pass through the initial phases of processing can be used in different proportions for production of sugar and of alcohol (Figure 2). Here the factor FS approximately indicates the amount of raw material used for fabrication of sugar. 1.0 t POL = x10 (kg) Sugar losses in cleaning bagasse, filter cake, undetermined POL recovered to syrup RECOVERY EFFICIENCY 1.0 t RS = RS x10 (kg) RS losses in cleaning bagasse, filter cake, undetermined RS in, recovered to syrup Factor FS 1 - FS TRS diverted to distillery Sugar boiling & centrifuging RECOVERY SJM FORMULA TRS entering the distillery 1-FSJM TRS diverted from molasses Factor FSJM SUGAR PRODUCT EFFICIENCY of FERMENTATION & DISTILLATION Fermentation & Distillation ALCOHOL PRODUCT Fig. 2 Simplified scheme for calculation of the theoretical yield of sugar and alcohol from a sugar factory with an annexed distillery. In Figure 2 it is supposed, for illustrative purposes, that the POL and RS enter the mill in separate streams. The TRS is the sum of the POL (as inverted sugar) and RS. It is seen that the distillery will receive: $ The POL flow in (as recovered after the losses in bagasse, filter cake and undetermined) multiplied by the factor (1 FS). $ The POL (sucrose) retained in molasses (depending on molasses purity or (1 F SJM ). $ The RS flow in recovered after the losses in bagasse, filter cake and undetermined. The sugar product will come from: $ The POL flow in (as recovered after the losses in bagasse, filter cake and undetermined) multiplied by the factor FS; less $ The POL (sucrose) retained in the molasses stream. 6

7 Estimation of benchmark sugar yield in a factory Yield for a fully exhausted final molasses using the RCS formula For a fully exhausted final molasses, the sugar yield (per 100 ) can be the factor FS multiplied by the RCS, where RCS is the benchmark sugar recovery, based on the % and the apparent purity of the mixed raw juice (P MJ ) (Wright, 2005). The RCS value is given here in equation 8: RCS # 0.945!!! 1.50 " sugar P MJ Yield for a partially exhausted molasses or syrup using the SJM formula For a partially exhausted molasses of purity P molasses, the sugar yield can be the factor FS times the sugar recovery, based on the % [less the sum of the losses (in per 100 in units) in bagasse, filter cake and undetermined], and on the traditional SJM formula factor for the fraction sugar recovered. The SJM factor (F SJM ) is based on the apparent purity of the clarified juice (P CJ ), sugar (P sugar ) and molasses (P molasses ) as in equations 9 and 10. The sugar yield Y sugar (in kg/ t units) can then be estimated by equation 11. F losses # 0.01! (100 " loss bagasse " loss filter _ cake " loss und ) Psugar P CJ " Pmolasses F SJM %! PCJ Psugar " Pmolasses 100 Y sugar % 10!! FS! F SJM! F losses! Estimation of benchmark alcohol yield in a factory For a factory fermenting all the final molasses, and, as well, diverting a fraction FS of the juice/syrup flow to the distillery, the benchmark alcohol yield is calculated from the sum of: 1. The invert sugar (per 100 ) equivalent of the fraction diverted directly for fermentation, % 0.95!(1 " FS )! F 2. The original reducing sugars in the, RS, multiplied by the fraction of recovery of sucrose and reducing sugars, estimated as the ratio F losses ; % RS! F losses losses 3. The estimate of the invert sugar (per 100 ) equivalent of the retained in molasses. This is approximated by: sugar (8) (9) (10) (11) (12) (13) % 0.95! FS! F losses!(1 " F SJM ) (14) 7

8 The sum of the above three elements gives the total reducing sugars (TRS ferment, per 100 ) available to be fermented to alcohol, as in equation 15. TRS ferment % F losses!! SJM 0.95 & 1" & F! FS ''( RS (15) This TRS ferment value can be used to calculate the yield of the distillery (Y AA ), usually expressed in litres of anhydrous alcohol per t. The multiplier value used for the yield of alcohol from TRS depends on both the theoretical yield and the efficiency of the fermentation and distillation. Some values for anhydrous ethanol (99.3% w/w ) were shown in Table 2. In equation 16, it is calculated from the combined fermentation/distillation efficiency E F&D and then this value is used to estimate the distillery yield Y AA. The combined efficiency E F&D value can range from 88 to 92%, being higher for a high purity feed stock to the fermentation. Y AA = 0.10 x TRS ferment x x E F&D (16) Another estimation of the theoretical alcohol yield expressed the yield in terms of pure ethanol, Y E100. For this the constant in equation 16 above is altered to Y E100 = 0.10 x TRS ferment x x E F&D (17) Calculation of the amount of TRS from the recorded yields of sugar and alcohol The amount of TRS required for the production of the recorded yields of sugar and alcohol, TRS THP (kg/t ) is given by Fernandes (2003, p 178) as in equation 18. Here the sugar yield Y S100 is as its equivalent of pure sucrose (kg/t ) and the alcohol yield Y E100 as pure ethanol or Y AA as anhydrous alcohol (in L/t ). Y S100 Y Y 100 sugar E sugar Y AA TRS THP % ( %! ( (18) The percentage ratio of the TRS THP value to that of the estimated TRS value is the Theoretical Industrial Efficiency. Where product yields are directly recorded, the equivalent TRS in the actual products, TRS ACP, can be calculated from equation 18, and the percentage ratio of the TRS ACP value to that of the estimated TRS in TRS is the Relative Industrial Efficiency. The spreadsheet coding presented in Table 3 is an example of the use of the relationships presented to estimate yields of sugar and alcohol. Table 3 addresses the special case where (a) all the lowest purity molasses is used in the fermentation and, (b) where the split of streams between sugar and alcohol takes place on the clear juice or evaporator syrup stream. The split streams are of therefore equal purity. In practice, however, the most economical split directed to the fermentation has a preferential inclusion of second mill juice and filtrate, both of which are of a lower purity (and lower quality) than the clarified first mill juice. The balance in this case require additional inputs of 1 st mill extraction, overall extraction, and uses appropriate factors to determine the quality differences between the 1 st and 2 nd mill juice streams. Spreadsheets have been formulated to cover these aspects, and these will be explored in the future. 8

9 Table 3 Example of spreadsheet coding for combined sugar and ethanol production balances. Sugar properties Label Value Pol %, Vr Entered value Purity of first expressed juice, P 1EJ Vr Entered value Fibre %, Fib Vr Entered value RS % first expressed juice, R FEJ Vr Entered value Efficiencies and losses Sum of bagasse, filter cake, undet. losses, per 100 -in Vr Entered value Fermentation efficiency, E F, % Vr Entered value Distillation efficiency, E D,% Vr Entered value Product specifications Purity of sugar product, P sugar Vr Entered value Pol of sugar product, sugar Vr Entered value Purity of molasses, P molasses Vr Entered value Alcohol Grade, (% w/w ) Vr Entered value Recorded yields Recorded yield sugar at specification quality, Y sugar, kg/t Recorded yield anhydrous. 99.3% w/w, L/t Adjustment of factor FS, controlling the fraction split to sugar Entered diversion split factor FS Vr12 Vr13 Calculated factors Label Value Value of FS that best corresponds to the balance of products Density of alcohol, kg/m 3 Theoretical Yield of anhydrous alcohol from TRS, L/kg Entered value Entered value Vr Entered value Vr =(Vr12*100/Vr9)/((10-Vr5/10)*Vr1*Vr24) Vr = *Vr11^ *Vr Vr =2*46.07/180.16*1000/Vr21*100/Vr11 Factor for the losses in process, F losses Vr =(100-Vr5)/100 Factor SJM recovery to sugar, F SJM Vr =Vr8*(Vr26-Vr10)/Vr26/(Vr8-Vr10) Calculated values Entered 1st expressed juice Purity Vr Estimated clarified juice Purity Vr =Vr RS % (estimated from RS FEJ using CCS 5 Factor) Vr27 =if(vr2=0,( *Vr1^ *Vr ), Vr2) =Vr4*(100-(Vr3+5))/100 9

10 Sugar properties Label Value Combined fermentation and distillation efficiency, E F&D, % Anhydrous alcohol yield corrected for distillery efficiency, L/kg TRS Vr28 Flows of TRS, POL Label Value TRS in, kg/t TRS in juice after losses, kg/t Flow of POL, kg/t Flow of POL in syrup, kg/t Flow of POL into the pan station, kg/t Yield of sugar =100*Vr6/100*Vr7/100 Vr =Vr22*Vr28/100 Vr =10*(Vr1/0.95+Vr27) Vr =Vr30*Vr23 Vr =10*Vr1 Vr =Vr32*Vr23 Vr =Vr33*Vr14 Sugar yield at 100, kg/t Vr =Vr34*Vr24 Sugar yield at specification, kg/t Sugar, per 100, as 100% Sugar, per 100, at specification Noted sugar yield (as entered), kg/t Difference between calculated and recorded sugar yields, % Yield of TRS & Alcohol Vr =Vr35*100/Vr9 Vr =Vr35/10 Vr =Vr36/10 Vr39 Vr =Vr12 RS in, kg/t Vr =10*Vr27 RS (from ) in molasses, kg/t POL diverted from pan station to fermenters, kg/t RS from invert POL diverted syrup/juice to fermenters, kg/t RS from inverted in molasses, kg/t =IF(Vr39>0,100*(Vr36/Vr39-1),0) Vr =Vr41*Vr23 Vr43 Vr44 TRS in fermenter feed, kg/t Vr46 Total TRS as calculated, kg/t =Vr33*(1-Vr14) =Vr43/0.95 Vr =Vr34*(1-Vr24)/ =Vr44+Vr45+Vr42 Vr =Vr35/0.95+Vr46*Vr28/100 Total TRS as recorded, kg/t Vr =(Vr12*Vr9/100)/0.95+Vr13/Vr22 TRS ferment, per 100 Vr =Vr23*(Vr1/0.95*(1-Vr24*Vr14)+Vr27) Yield of Alcohol at specified Grade, per 100 Yield of Alcohol at specified Grade, L/t Vr50 Vr =Vr49*Vr22*Vr28/100*Vr21/ =0.10*Vr49*Vr22*Vr28 10

11 Sugar properties Label Value Actual yield (as recorded), L/t Difference between calculated and recorded alcohol yields, % Industrial efficiency values Vr52 Y S100, kg pure sucrose/t Vr =Vr13 Vr =IF(Vr52>0,100*(Vr51/Vr52-1),0) =10*Vr37 Y E100, L pure ethanol/t Vr =10*Vr50*Vr11/100*1000/ Y AA, L anhydrous_alcohol/t Vr =10*Vr50*1000/Vr21 TRS, per 100 Vr =Vr30/10 TRS ACP, per 100 Vr =Vr48/10 TRS THP, kg/t Vr =Vr54/0.95+Vr56/Vr22 TRS THP, per 100 Vr =Vr59/10 Theoretical Industrial Efficiency, % Relative Industrial Efficiency, % Vr61 Vr =100*Vr60/Vr =100*Vr58/Vr57 Discussion and conclusions This paper has used material from a recent Brazilian publication (Fernandes, 2003) and applied some of the concepts involved to outline the analyses and factory balances required for Australian sugar factories which may become involved in the co-production of sugar and alcohol in sugar factories. Equations and relationships are presented to assist in the chemical control of sugar/alcohol factories, and an illustration of their application to a simple case of process stream diversion to alcohol production is presented. Their adaptation to the more complex scenarios of preferential diversion of second mill juice and filtrate to the fermentation will be given in another paper. The authors hope that this work will make a contribution to the future development of the sugar/ethanol sector in Australia. REFERENCES Anon. (1984). Laboratory Manual for Australian Sugar Mills. Vol. 1. BSES Publications. Brisbane. Anon. (1991). Laboratory Manual for Australian Sugar Mills. Vol. 2. (Analytical Methods and Tables). BSES Publications. Brisbane. Fernandes, A.C. (2003). Cálculos na Agroindústria da Cana-de-açúcar. 2 nd Ed., Sociedade dos Technicos Acucareiros e Alcooleiros do Brasil (STAB), 240 p. Laverack, B.P. (2003). Estimates of ethanol production from sugar feedstock. Proc. Aust. Soc. Sugar Cane Technol., 25: CD-ROM. Perry, R.H. and Green, D. (1984). Perry s Chemical Engineers Handbook, 6 th Ed., McGraw-Hill, New York, Table 3 112, Wright, P.G. (2005). Process benchmarking in sugar factories. Proc. Aust. Soc. Sugar Cane Technol., 27:

12 Symbols: Bx P Fib RS TRS loss FS Table of Symbols Sucrose concentration, w/w, having the same optical rotation as the solution. Sucrose concentration, w/w, having the same density as the solution. The apparent purity of the solution, the percentage ratio of to Bx The dry, water-insoluble matter in the. The concentration, w/w, of the reducing sugars (mainly glucose and fructose). The total reducing sugars content, the sum of the invert equivalent of the sucrose and the reducing sugars. The loss of sucrose (or, or RS) The split factor, the fraction of the clear juice or syrup remaining in the pan stage feed stream. E Efficiency, % F Factor Y Yield, kg/ t or L/t POL Flow of RS Flow of RS TRS Flow of TRS Subscripts: FEJ the first expressed juice MJ the extracted juice (preferably taken without admixing of recycled streams from the process) CJ the clarified juice molasses the lowest purity product from the pan-centrifugal station bagasse milled bagasse filter_cake filter cake or mud byproduct und undetermined stream (of losses) losses Sum of losses in bagasse, filter_cake and undetermined loss SJM the SJM formula method of estimating sugar recovery from a stream of known purity ferment The fermentation process using yeasts AA Anhydrous alcohol 99.3% w/w E100 F&D sugar S100 THP ACP Pure 100% Ethanol Combined fermentation and distillation processes Sugar at the quality specification produced. Sugar at 100% and purity Theoretical yields of sugar and alcohol Actual recorded yield of sugar and alcohol 12

13 APPENDIX 1 DEFINITIONS Sugars and total reducing sugars Some extra terms are necessary to describe the flows and mass balance of total sugars when alcohol is being produced in the sugar factory. $ Total Reducing Sugars: The total reducing sugars (TRS) represent all sugars of the sugar in the reducing or inverted form. After acid (or enzymic) inversion of any sucrose, TRS can be determined analytically by oxireduction methods, by colorimetric methods, or by chromatography. It is estimated by the addition of the reducing sugars (glucose and fructose) to sucrose in the inverted form of sugars (POL/0.95). Besides glucose, fructose and inverted sucrose, other reducing substances in the sugar juice may be included in the determination. $ Purity of TRS: The percentage of total sugars contained in the brix. Used in the same way as the normal Apparent Purity to express the quality of the broth for fermentation. $ Total sugars recovered: The Brazilian term ATR constitutes one of the parameters of the system of payment of sugar in Sao Paulo, Brazil, and represents the amount of TRS recovered from the sugar into sugar and syrup, and is the result of difference between the TRS of the sugar and the losses in the washing of sugar, final bagasse, filter cake and the undetermined losses and after applying a factor for the average standard efficiency. Grades of Alcohol In the sugar/alcohol sector of Brazil, there are diverse denominations related to alcohol. $ Ethyl alcohol or ethanol: the chemically pure product is mentioned of formula C 2 H 6 O. $ Absolute Alcohol: Alcohol which is highly purified and contains only traces of water, otherwise the same as chemically pure ethanol. $ Grade of alcohol: indicates the percentage of ethanol in a water-ethanol mixture. o Grade Gay Lussac ( GL): the percentage (volume /volume) of ethanol in an ethanol-water mixture at 15 C. For example, 95 GL indicates an alcohol with 95 ml of ethanol for 100 ml of the mixture at 15 C. o Grade, or Grade INPM ( INPM): The relative mass /mass of ethanol in an ethanol-water mixture. The grade INPM is the official measure of the alcohol grade in Brazil. o Anhydrous alcohol: Alcohol with a minimum ethanol content of Grade 99.3 % w/w, containing 99.3 kg of ethanol and 0.7 kg of water for 100 kg of anhydrous alcohol. o Hydrous alcohol: Alcohol with alcoholic grade in the range 92.6% to 93.8% w/w, containing on average some 93.2 kg of ethanol for 100 kg of hydrous alcohol. 13