Question

Can crystallization process be used to separate sugar from molasses?

Answer 1

NO IT CANNOT BE SEPARATED BOTH SUBSTANCE IT CAN BE DONE WITH THE HELP OF CENTRIFUGATION PROCESS


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Answer 2

. The A molasses is concentrated to yield a B strike, and the low-grade B molasses is concentrated to yield C sugar and final molasses, or blackstrap. Blackstrap contains approximately 25 percent sucrose and 20 percent invert (glucose and fructose); at these levels the sugar cannot be removed economically by crystallization.

Crystal separation and drying

Crystals and mother liquor are separated in basket-type centrifuges. Continuous machines are used for C and sometimes B sugars, but batch machines are best for A sugars because of the crystal breakage that takes place in continuous centrifuges. Mother liquor is spun off the crystals, and a fine jet of water is sprayed on the sugar pressed against the wall of the centrifugal basket, reducing the syrup coating on each crystal. In modern factories, the washing process is quite extensive in an effort to produce high-purity raw sugar. Overall recovery of sugar from cane juice averages between 70 and 80 percent.

Raw sugar products

Open pan sugar

In industrial sugarcaneprocessing, crystallization is conducted under vacuum in order to lower operating temperatures, but some sugar is produced in the tropics by “open pan” processes. In these processes, crudely clarified juices are boiled down in open containers until a sludgy mass of crystals can be transferred to molds. The hardened brown product is sold as panela or piloncilloin Latin America and as guror khansari in Asia.

Plantation white sugar

Plantation white, or mill white, sugar is a white sugar commonly produced for local consumption in sugarcane-growing countries. It is produced at the factory without remelting and refining of the raw sugar. Instead, sulfur dioxide gas (produced by burning sulfur in air) is injected into extracted juice, where it bleaches juice colorants, is oxidized to sulfate, and then is neutralized by the addition of lime. (Sulfite salts are sometimes substituted for sulfur dioxide.) A white sugar results that is suitable for table use but not for food processing, because it contains all the nonsugars (including bleached or reduced colorant) present in raw sugar.

Higher grades of plantation white are produced by a carbonatation purification process, in which carbon dioxide gas (scrubbed flue gas) is injected into juice and reacted with lime to form calcium carbonate, which absorbs and adsorbs nonsugars and is filtered off. Powdered vegetable carbon is sometimes added to increase decolorization.

As demand for high-quality white sugars increases among food processors and beverage manufacturers in tropical areas, the processes described above are being improved and replaced by “Blanco Directo” processes, in which colour-precipitating reagents remove colorants instead of temporarily bleaching them.

Sugar refining

Sugar refining is the production of high-quality sugars from remelted raw cane sugars. (“Refining” is also used in beet sugar factories to describe the remelting and recrystallization processes by which high-quality white sugars are made from lower-grade beet syrups; see below Beet sugar.) About 35 percent of cane sugar is refined; the remainder is consumed as plantation white or as raw sugar. In tropical regions, small “white end” refineries are often built to refine the raw sugar produced by cane-processing plants. Raw sugar factories produce their own steam by burning bagasse, and a reasonably efficient plant has as much as 20 percent excess bagasse.


Clarification and decolorization

Melt syrup is clarified either by phosphatation, in which phosphoric acid and lime are added to form calcium phosphates, which are removed by surface scraping in a flotation clarifier, or by carbonatation, in which carbon dioxide gas and lime form calcium carbonate, which is filtered off. Colour precipitants are added to each process.

The carbonatated liquors are filtered in pressure leaf filters with the use of diatomaceous earth, a filter aid invented for sugar processing. The resultant yellow to light brown liquor is further decolorized by carbon adsorbents, such as granular activated carbon or bone charcoal, or by ion-exchange resins of acrylic or styrenic materials. Decolorization is conducted in columns in various serial or parallel conformations.

Crystallization

Fine clarified liquor is boiled to white sugar in a series of vacuum pans similar to those used in sugarcane processing. The boiling system is complicated because the purity of the fine liquor is more than 98 percent, and at least six or seven stages of boiling are necessary before the molasses is exhausted. The first three or four strikes are blended to make commercial white sugar. Special large-grain sugar (for bakery and confectionery) is boiled separately. Fine grains (sanding or fruit sugars) are usually made by sieving products of mixed grain size.




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