Code of Technical Standards for the Professional Practice of Chemical Engineering in the Sugar Boiling Processes and Operations
PRC Board of Chemical Engineering Resolution No. 004(B)-14

August 13, 2014



WHEREAS, Section 6 (f) of

WHEREAS, Section 6 (i) of the same law mandates the Board to adopt a Code of Technical Standards for the practice of chemical engineering;

WHEREAS, the unit processes and operations leading to the production of raw sugar and refined sugar involve the application and demonstration of chemical engineering principles and concepts;

WHEREAS, there is a need to prescribe a Code of Technical Standards for the practice of chemical engineering in the sugar boiling processes and operations to ensure the competent and effective provision of professional services of chemical engineers in this industry;

WHEREAS, in the development and finalization of this Code of Technical Standards, the Board has consulted the stakeholders of the Philippine sugar industry such as, but not limited to the Philippine Sugar Technologists Association, Inc. (Philsutech), Philippine Sugar Millers Association, Inc., (PSMAI), Philippine Sugar Research Institute (Philsurin), and the Philippine Institute of Chemical Engineers (PIChE), its Accredited Professional Organization (APO).

WHEREAS, violation of any provision of this Code of Technical Standards shall give rise to liabilities under

NOW THEREFORE, the Board RESOLVES, as it is hereby RESOLVED, to adopt and promulgate, with the approval of the Commission, the Code of Technical Standards for the Professional Practice of Chemical Engineering in the Sugar Boiling Processes and Operations, which is hereby made an integral part of this Resolution as Annex A.

This Resolution and Annex A, entitled, "Code of Technical Standards for the Professional Practice of Chemical Engineering in the Sugar Boiling Processes and Operations", shall take effect after fifteen (15) days following its full and complete publication in the Official Gazette or in any newspaper of general circulation in the Philippines. TSIaAc

Let copies of this Resolution and its annex be transmitted to the UP Law Center, Philippine Sugar Technologists Association, Inc. (Philsutech), Philippine Sugar Millers Association, Inc., (PSMAI), Philippine Sugar Research Institute (Philsurin), and the Philippine Institute of Chemical Engineers (PIChE) for dissemination to all concerned.

DONE in the City of Manila this 13th day of August, 2014.

Professional Regulation Commission

Professional Regulation Commission

Professional Regulation Commission


Office of the Secretary to the Professional Regulatory Boards


Professional Regulation Commission

Professional Regulation Commission

Professional Regulation Commission


Philippine Chemical Engineering Standard
PChES 901:2011

PChES 901:2011 Code of Technical Standards for the Practice of Chemical Engineering: Sugar Boiling

1 Scope

This Philippine Chemical Engineering Standard (PChES) establishes guiding principles for the development and use of code of technical standards for the practice of chemical engineering in sugar boiling. It is intended that other applicable standards in the PChES series shall be used in conjunction with this Philippine Chemical Engineering Standard.

This Philippine Chemical Engineering Standard is intended for use as a specification for certification and registration purposes.

2 Normative References

The following referenced documents are indispensable to the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

Professional Regulation Commission,

3 Definition of Terms

For purposes of this document, the following terms and definitions shall apply.

3.1 Sugar Boiling

Sugar Boiling the collection of unit processes and unit operations implemented in sequence to produce raw sugar.

3.2 Specific Unit Operations

Cane Preparation the process of reducing the cane fed to the mill into small pieces suitable for the subsequent extraction process. TICAcD

Centrifugal Separation processing the massecuite in a machine which spins at high speed to separate sugar from mother liquor.

Clarification the process of purification of juices by defecation, sulphitation, phosphatation or carbonation and subsequent subsidation, decantation and filtration to remove the maximum quantity of impurities at the earliest possible stage of sugar manufacturing process.

Crystallization the process of nucleation and growth of crystals from a sugar solution.

Evaporation the process of removing the greatest amount of water that goes with the clarified juice in order to yield syrup of 65 Bx before crystallization process.

Filtration the process step in juice clarification in which a liquid pass through a medium which retains certain undissolved solids.

Heating the process step in juice clarification where the juice is being heated up to a temperature a few degrees above boiling point just before the clarifier.

Juice Extraction the process to separate the sucrose-containing juice from the remainder of the cane, which comprises mainly of fiber.

Liming the process step in juice clarification in which lime is introduced into the sugar juice in the form of milk of lime or lime saccharate solution.

3.3 Specific Unit Processes

Boiling scheme any of the different methods of crystallization of sugar in a vacuum pan.

Carbonatation a process in which gas that is high in CO2 is added to the limed and heated cane juice.

Graining charge the charge of syrup drawn into the vacuum pan at the beginning of the batch massecuite boiling.

Metastable zone region of super-saturation in which crystals already formed will grow, but new crystal formation will not occur.

Seeding supplying crystal nuclei to the graining charge after the later has been concentrated to the metastable zone of supersaturation.

Strike a batch of finished massecuite in a sugar boiling process.

Sulphitation the process of treating the cane juice with SO2.

Sugar boiling transformation of syrup into a mixture of crystals and mother liquor by simultaneous evaporation and crystallization.

3.4 Other Operations/Processes

Imbibition the process in which water or dilute juice is applied to the bagasse to mix with and dilute the juice present in the latter to enhance extraction. The water so used is termed imbibitions water.

Juice extraction the percentage by weight of mixed juice in cane. Also called dilute extraction, dilute juice extraction, mill extraction, juice extraction % cane or mixed juice % cane.

Maceration the process in which bagasse is steeped in an excess of water or light juice, generally imbibitions. The water so used is termed maceration water. HCTaAS

Mill is used to extract juice from sugarcane by pressure, and consists of three grooved horizontal rollers, two below and one on top. It is driven through a gear train.

3.5 Allied Profession

3.6 Others

Bagasse the fibrous part of cane, left after juice has been extracted.

Brix the percentage by weight of dissolved solids in sugar solutions; identical to gravity solids but generally accepted to represent the apparent solids in sugar solution as determined by the brix hydrometer or other densimetric measurement converted to brix scale.

Calandria heating element used in a certain type of evaporator bodies and vacuum pans, consisting of a drum or lens-shaped body traversed by vertical tubes with steam or heating vapor in the space surrounding the tubes.

Cane sugar cane, a giant grass belonging to genus Saccharum; the raw material delivered to the factory.

Gross cane the raw material entering the milling plant including clean cane, field trash and adhering water.

Net cane gross cane minus field trash.

Prepared cane the harvested material after preparation for extraction including field trash not removed and adhering water.

Cane knives blades attached in a central shaft driven by a motor or steam turbine and rotate at 600 r.p.m.

Centrifugal (batch) a basket with perforation, suspended by a spindle and lined with screens, in which massecuite is spun, and where the liquid phase is separated from crystals by centrifugal force.

Clarifier a round large-diameter tank used for settling suspended matter and for thickening settled mud obtained from limed and heated cane juice.

Clarity the degree of clearness of a sugar solution.

Condensate water obtained by condensation of steam or vapor in surface condensers or in the steam or vapor chests of heating or evaporating vessels.

Continuous centrifugal conical perforated basket driven by an electrical motor through pulley and V-belts at the bottom. The basket rotates continuously and is charged with a low-grade massecuite. The sugar separated from mother liquor by centrifugal force climbs the wall of the basket and is thrown overboard, while the liquid phase is filtered out through a special type of screen.

Crystallizer apparatus for continuing the crystallization of sugar in massecuite after its discharged from the vacuum pan, by providing retention time, stirring and cooling at a controlled rate.

Evaporator effect evaporator body or group of bodies working as one of the series-connected units in a multiple-effect evaporator.

Fiber the dry water-insoluble matter in cane.

Filter cake material retained on the filter screens and discharged from the filters after filtering clarifier mud.

Filtrate liquid passed through the screens of the filter.

Floc the fluffy precipitate of suspension formed in sugar solution by the action of lime/heat or flocculants in the filtration process, the destruction of which impedes its settling and causes poor clarification and filtration.

Grain aggregate of the crystals in the massecuite.

Inversion the hydrolysis or decomposition of sucrose into its component monosaccharide: glucose (dextrose) and fructose (levulose). CcEHaI

LKg a unit bag of 50 kilograms sugar.

Magma (seed) a mechanical mixture of sugar crystals and liquor (syrup, sometimes clarified juice or high-grade molasses), used as seed or footing in boiling massecuite.

Massecuite the mixture of sugar crystals and mother liquor resulting from crystallization process. Massecuites are classified according to purity as A, B, or C massecuites.

Moisture the loss in weight due to drying under specific conditions, expressed as percentage of the total weight.

Molasses the mother liquor separated from sugar crystals in the massecuite. A, B, or C molasses is derived from the corresponding massecuites.

Final molasses the liquid residue from low-grade or C massecuite where no more sugar can be recovered economically.

High-grade molasses the molasses removed by centrifuging high-grade or A and B massecuite.

Mud concentrated settlings in a clarifier from limed and heated cane juice.

Multiple-effect evaporator series of evaporator effects operating at successive reduced vapor and gradually increased vacuum. The evaporators are so connected that the first effect is heated by exhaust steam, the second by vapors generated by first effect, and so on.

Polarization the value obtained by direct or single polarization of the normal weight of a sugar product in a saccharimeter. The term is used in calculation as if it were a real substance.

Purity the percentage of a cane sugar in dissolved solids.

Raw juice juice obtained from the cane extraction process. Also referred to as mixed juice or cane juice.

Recovery the percentage of sucrose (pol) produced at the end of the process in the sucrose (pol) of the original material.

Remelt a syrup made from centrifuged low-grade sugar which is dissolved or remelted and returned to the high-grade boiling.

Shredder a hammer mill with swinging hammer, or combination of knives or hammer. The purpose of the shredder is to disintegrate the cane and to open the maximum number of cells.

Slurry liquid suspension of finely-divided sugar used for seeding.

Sucrose the dissacharide, alpha-D glucopyranosyl, Beta-D Furanoside (C12 H22 O11).

Sugar the crystals, including any adhering molasses, recovered from the massecuite after centrifuging.

Low-grade sugar sugar from low grade or C massecuite.

Raw sugar (commercial or centrifugal) sugar obtained from high-grade massecuite.

Syrup the concentrated juice from evaporators before crystallization begins.

Suspended solids the solids not in solution in the juice or other liquids and removable by mechanical means.

Trash all the extraneous materials delivered to the mill as part of the cane load, consisting of leaves, tops, dead stalks, roots, soil, etc.

Turbidity the light scattering resulting from the difference between refraction indices of suspended materials and sugar solution. cDAISC

Vacuum pan apparatus in which crystallization of sugar is achieved under vacuum by evaporation.

Vapor steam derived from boiling juice or syrup, as differentiated from steam originating in boilers.

Yield generally means commercial sugar percent cane. It is the reciprocal of tonnes cane per tonne commercial sugar.

4 Sugar Boiling Processes and Operations

4.1.0. Sugarcane Milling

4.1.1. Cane Preparation

The first step in the manufacture of raw sugar from sugarcane is to prepare the cane thoroughly by cutting and shredding the stalks in heavy preparation equipment so as to disintegrate the material.

The cane is received from trucks or rail cars and mechanically unloaded and feed to the cane carrier. As the cane carrier moves, the cane kicker evens out cane load in the cane carrier and then two sets of revolving knives cut the cane into small pieces. Shredders, crushers, or combination of these processes further reduces the cane into fibrous material and rupture the juice cells. These shredded canes then, pass through different mills and the juice is extracted.

4.1.2. Juice Extraction

Juice extraction is done by grinding or milling of the shredded cane. Multiple sets of three-roller mills are most commonly used for juice extraction. Some mills consist of four, five, or six rollers in multiple sets. Conveyors transport the crushed cane from one mill to the next. Water or juice is applied to the crushed cane to enhance the extraction of the juice. This is called the imbibition process. The imbibition water is introduced into the last mill and transferred from mill to mill towards the second mill. Meanwhile, the crushed cane travels from the first mill to the last mill in opposite direction to the imbibition water. The juice from the first and second mill is collected and strained to remove large particles. This is now called the mixed juice and ready for clarification at the Boiling House. The crushed cane exiting the last mill is called bagasse and is used as fuel for the boilers for seam generation. Steam Generation. The boiler generates steam using bagasse as fuel. It provides nearly all of the steam requirements of the mills and electricity generator turbines. Other mills use high-pressure boilers for co-generation purposes. The feed water for these high-pressure boilers is continuously monitored as to the parameters such as hardness, pH, and Total Dissolved Solids (TDS). Exhaust steam from turbines is used in juice heaters, evaporators and vacuum pans at the boiling house. Power Generation. Some of the high pressure steam generated by the boiler is utilized for the production of power by the turbo-alternators. The power produced is used for factory requirements and the surplus power can be exported to the power grid. AaITCS

4.2.0. Sugar Boiling

4.2.1. Clarification

Mixed juice from the mills contains fine bagasse ("bagacillo") and other impurities. For the purposes of factory performance control, it is necessary to measure the quantity of sucrose entering the system, thus enabling an estimate of recovery and losses to be made. The first step for sugar boiling is clarification, and is done by treating the mixed juice first before pumping to the clarifier. Heating and liming of mixed juice are the two main process of treatment and are performed in several different variations. The treated juice is allowed to settle in order to separate the clear juice from the settled mud at the bottom, and the settling is carried out in continuous settler called clarifiers. The settled mud is taken to a rotary vacuum filter to recover the juices that went with the mud. The recovered juice is returned to the juice heating system. Heating. The juice extracted by the mills is heated up to the temperature just above its boiling point. The heated juice is then flashed in a flash tank so that the juice temperature to the clarifier is always constant and entrained has is removed. Juice heating is generally done in two or more stages, making use of lower pressure vapors generated by multiple effect evaporators to improve steam economy. In a two stage heating setup, primary heating is done with the vapor from second or third bodies of the multiple-effect evaporators. The secondary or final heating is done with vapor from first body of evaporator or exhaust steam. Heaters are usually shell and tube heat exchangers or sometimes called tubular heaters. Other types of heaters like the plate and frame (plate heaters) and direct contact heaters are finding increasing use. Liming. There are many variants of the simple defecation (clarification) process used throughout the sugar milling industry. Treatment with milk of lime remains the basic method of clarification. Lime is added to neutralize the acidic juice and to precipitate tricalcium phosphate and all other impurities to produce a clear juice of low turbidity and color.

Lime can be added in the form of milk of lime, lime-juice mixture, or lime-syrup saccharate. Milk of lime gives the densest floc and mud but with poorest turbidity. Mixtures of lime with juice or syrup give lighter, slower settling floc with better turbidity.

Juice from the mill is generally at a pH of 5.5. Lime is added to increase pH to a range of 7.8-8.0. It can be applied to cold, warm or hot juice. In a cold liming process, lime is added to the cold juice having a temperature of 50 C. The limed juice is then pumped to the heaters to bring the temperature to just above its boiling point of 105 C.

Lime addition to a warm juice is termed intermediate liming. First, the cold juice is heated to 75 C and is then pumped to a warm juice tank. Addition of lime is done before the warm juice is heated again to just above its boiling point.

In hot liming, the lime is added just before the flash tank. The cold juice is heated to just above its boiling point before the lime is added.

Fractional liming with double heating process is a newer practice in the sugar milling industry. In this process, the cold juice is pre-limed to a pH of 6.2-6.5. The juice is then pumped to a primary heater to raise its temperature to 70-80 C. After pre-heating the juice is limed again to a pH of 7.8-8.0 and is finally heated to just above its boiling point. Clarifier. Type of clarifier is either a multi-tray type or single tray rapid clarifier. Multi-tray type clarifiers are generally divided into several compartments to increase the area for settling with juice residences of up to 2 hours. Single tray rapid clarifier was designed to provide optimum conditions for removing the maximum amount of impurities from the treated juice while producing clear juice free of suspended solids. It is simpler and considerably cheaper than the multi-tray type for the same juice throughout. The low residence time of 30-45 minutes will lead to minimal pH drop, low lime usage and improved clarified juice quality. Clear juice from clarifier is taken to evaporator for evaporating its water content. CHcTIA Filtration. The vacuum filter separates the filter cake from the filtrate. The filter cake is used as fertilizer and soil conditioner on cane farms. Rotary drum vacuum filter is a widely used equipment for the treatment of cane mud. The washing and dewatering process in the vacuum filter reduces the pol of the filter cake. Fine bagasse particles known as bagacillo is commonly used as filter aid and added to the mud before filtration as a filtration aid.

Figure 4.1 Fractional Liming


4.2.2. Evaporation

The juice from the clarifier is concentrated in the evaporator to a concentration of about 65-68% sucrose by weight. As the juice is concentrated, the material is now called a syrup. Evaporation is a key unit operation in sugar milling and is the principal factor that determines the energy efficiency of the whole factory. It consists essentially of a tubular calandria serving as a heat exchanger and the bulk of evaporation of water is done by this means. Since the evaporator is the major user of steam, the way it is configured determines the amount of steam the factory requires.

A multiple effect evaporator consists typically of a series of four or five evaporators to enable the steam requirement to be reduced. Exhaust steam from mill and power generator turbines is used to heat the first evaporator body and its vapor obtained is used to heat the second body. This heat transfer process continues all through the remaining effects. The juice travels from the first body to another because of the gradual increase of vacuum across the evaporator cells. As the temperature decreases from the first body to the last body, the pressure also decreases which allows the juice to boil at low temperature. This will avoid caramelization and sugar loss during the evaporation process. Some vapor in the first three evaporators is used as a heating medium for juice heaters and vacuum pans. This is called vapor bleeding. The last effect is equipped with a direct contact condenser and a vacuum equipment to condense vapor. A vacuum of 25-27 inches mercury is maintained to reduce entrainment problems and possibility of inversion. The total water evaporated in the evaporator is 75-80 percent.

Figure 4.2 Quadruple Effect Evaporator


4.2.3. Crystallization

The syrup from the evaporators is further evaporated in a single effect evaporator called the vacuum pan. The syrup is boiled under vacuum to form a heavy mixture of sugar crystals (formed as the syrup approaches the super saturation point) and syrup. This is now called the massecuite.

The common types of vacuum pan used in the cane sugar milling is the regular calandria type and the continuous horizontal vacuum pan. A standard calandria vacuum pan is a tubular calandria similar to that of an evaporator but the tubes are shorter and of larger diameter. The continuous horizontal vacuum pan is a fully automatic vacuum pan and consists of multiple compartments. The massecuite moves continuously from one compartment to another and is withdrawn from the last compartment by a lobe pump. cEAaIS Sugar Boiling Schemes. Maximum recovery of sucrose by crystallization cannot be achieved in one step. The massecuite from purely syrup material is called A-Massecuite. The A-Massecuite is centrifuged to separate the crystal sugar from the exhausted syrup (molasses). The molasses produced still contains sucrose and it is again boiled to yield sugar crystals. The boiling process is repeated usually twice to achieve the optimal sucrose recovery. The purity of the massecuite decreases with each successive stage as more sucrose is crystallized.

Various crystallization schemes may be employed to suit the purity of the syrup and the quality of sugar to be produced. The three-boiling scheme, two-boiling scheme and the double magma scheme are commonly used crystallization schemes to produce raw sugar. Three-Boiling Scheme. The scheme most commonly used is the three-boiling scheme. The A-massecuite is made by boiling pure syrup and a seed magma consisting of C-sugar in water. This A-massecuite is centrifuged in a high speed batch centrifugal machine in which the A-molasses is separated from the A-sugar. B-massecuite is crystallized from A molasses and syrup, using the same C-sugar magma as the starting grain. The B-massecuite, the same with A-massecuite is centrifuged using the high speed batch centrifugal. Boiling of C-massecuite consists of a mixture of A-molasses and syrup as initial footing. The liquor is concentrated until the metastable zone is reached. Crystallization is initiated by adding some very fine seed in the form of slurry, which provide the nuclei to start crystallization. B-molasses will then be added to attain good molasses exhaustion. C-massecuite is centrifuged in a continuous centrifugal to yield C-sugar as magma and final molasses.

Figure 4.3 Three-Boiling Scheme

image Two-Boiling Scheme. In the two-boiling scheme, only A-massecuite and C-massecuite are boiled. The A-massecuite is crystallized from C-sugar magma as footing and syrup as feed. The C-massecuite boiling is the same with the three-boiling procedure except that A-molasses is used as feed instead of B-molasses. The main advantage of this scheme as compared to the three-boiling is a simplification of the equipment needed by eliminating the B-sugar stage. The scheme is better suited to low purity syrup.

Figure 4.4 Two-Boiling Scheme

image Double Magma Scheme. In the double-magma scheme, the three-stage crystallization scheme is still used. However only one product, the A-sugar is produced. C-sugar magma is the nucleus for B-sugar in B-massacuite boiling and the B-sugar magma is the nucleus for A-sugar in A-massecuite. The advantage of this scheme is the production of consistently good quality sugar.

Figure 4.5 Double Magma Scheme

image Crystallizer. The massecuite leaving a vacuum pan can still achieve additional exhaustion in a crystallizer prior to centrifuging. As the hot and supersaturated massecuite is cooled and stirred at sufficient retention time, it will achieve the additional crystallization desired. Cooling crystallizer should be provided for C massecuites in order to reduce final molasses purities to a minimum and thereby contain the sugar loss in molasses to a minimum. An A massecuite crystallizer is often provided to ensure good exhaustion and augmenting the work in the vacuum pan. Usually, no crystallizer needs to be provided in B massecuite other than strike receiver. The only situation requiring the installation of B massecuite crystallizer is in the case of a B molasses purity too high to achieve the required C massecuite purity. aAEHCI

4.2.4. Centrifugal Separation

After crystallization, the sugar crystals are separated from the massecuite by centrifuging. Centrifugation is done either with continuous or batch centrifugal baskets. Once the mother liquor has been exhausted to the practical limit for the strike concerned, it remains only to separate the crystals in order to obtain the sugar in the commercial form. This operation is carried out in the centrifugal machines. Batch Centrifugal. It consists of a cylindrical basket attached on a vertical shaft which is driven from its upper end by a motor. The basket is a drum with numerous holes to allow the molasses to escape. The basket is fitted with a fine screen which retains the crystals and also with a backing screen to assist the molasses to pass through. It is open at the top to allow the massecuite to be fed into it, and a bottom opening the sugar to be discharged. While the machine is running, this discharge is generally closed by a cone of thin sheet metal. It is surrounded by a casing designed to catch the molasses separated and to protect the operator from the running parts. Continuous Centrifugal. Continuous centrifugals are used for processing C massecuites and also for B massecuites in factories where B sugar is not a product sugar, like factories adopting the Double Magma Scheme in the crystallization process. The massecuite is fed into the center bottom of the rotating basket continuously through a stationary tube. The basket with an angle of 30 degree is driven from the bottom by a set of V belts attached to a motor. It is also fitted with a fine screen and with a backing screen. It is also surrounded by a 2 layered casing designed to collect the crystals that moves from the bottom and discharges at the top of the basket. The other casing is designed to catch the molasses separated.

4.2.5. Storage

The commercial sugar leaving the centrifugals is delivered into the bulk storage by a rubber belt conveyor and generally has a moisture content of 0.5-2.0%. Moisture is very detrimental to keeping qualities of the sugar, when it exceeds a certain limit, and particularly when it rises above 1.0%. It is necessary that the sugar should be dry and not too hot. The sugar will harden at a temperature above 38.0 C. It would be of advantage to maintain the humidity in the sugar storage as uniform and as low as possible. It should not rise above 65.0%. The storage calculation may be based on a bulk density of sugar of 800-900 kg/cu. meter. The angle of repose of dry sugar is about 33-35 degree. It may increase as far as 50-53 degree when the sugar is moist.

4.3.0. Process Flow Diagram


5. Practice of Chemical Engineering in Sugar Boiling

5.1 General requirements

Sugar boiling processes and operations shall require the services of a chemical engineer. A chemical engineer shall ensure that the raw juice accepted from the Mill is either fit for human consumption or will be made fit for human consumption by the sugar boiling activities. A chemical engineer shall ensure that nothing added to or made to come in contact with the process materials shall render it unfit for human consumption. A chemical engineer shall ensure that the environmental impacts of the sugar boiling activities are taken care of.

5.2 Practice of chemical engineering in sugar boiling.

The following processes and operations in sugar boiling shall require the services of a chemical engineer:







Centrifugal Separation

6 Certificate of Compliance of Sugar Boiling

All sugar mills, as defined as industrial plants in

7 Act Not Affecting Other Professions

The Code shall not be construed to affect or prevent the practice of any lawfully recognized profession.

Published in the Official Gazette, Vol. 110, No. 50, Page 7655 on December 15, 2014.