Sugar Production and Relative Humidity

The sugar market worldwide

Sugar is one of the most important raw materials traded on the worldwide markets.

Top 5 sugar producing companies

1. Suedzucker AG,

2. Cosan SA Industria & Comercio

3. British Sugar PLC

4. Tereos Internacional SA

5. Mitr Phol Sugar Corp.

In the 18th century only a few countries were producing sugar. However, these days over 100 nations process different base materials into sucrose. Remarkably India, China, Brazil & the European Union alone deliver 50% of the global demand.

Sugar Facts:

– Worldwide 170 million tons of raw sugar were produced in 2011/2012

– Brazil, India, China & EU are the most important sugar producing nations

– With an annual consumption of more than 24 million tons India, is the world’s largest market for raw sugar

Raw materials & processing

In temperate regions such as West, Central & Eastern Europe, the United States, China and Japan raw sugar is produced from sugar beet. However in the tropics and subtropics sugar is extracted from sugar cane.

800px-cut_sugarcane

Sugar cane & Sugar Beet

Processing

The processing of these two raw materials only differs in the first few steps. The main goal is to extract the juice, containing the sugar,  as efficiently as possible.

Extracting the sugar

Sugar cane is cut into small pieces during the harvest. It is then put through an industrial press to squeeze out the sweet sap.
Sugar beet has to be processed in extraction towers, where the plants release their sugar during a hot water treatment at 70°C.

Evaporation

After filtering the juice the water is extracted by passing through different stages of evaporators until only a thick syrup is left consisting of around 70% sugar.

Crystallisation

The syrup is then boiled until sugar crystals are formed. These crystals are then cleaned through centrifugation. To further improve purity this process is repeated twice.

Cooling & drying

Now the sugar has to be dried. One option is in large scale drum dryers at a temperature of 60°C. after drying, the sugar is cooled down on fluidized-bed coolers before heading to the warehouse or packed for shipping.

Trommel2_400_219_01

Inside a drum dryer.

Storage & logistics

Sugar belongs to the group of hygroscopic goods with an extremely low water content – below 1.5%. Basically sugar is a robust material but vulnerable to high humidity and temperature changes.
Generally it is recommended to store and transport sugar at a temperature of 20-25°C and 25-60% relative humidity.

By taking a closer look at the adsorption curve of sugar it is easy to see that over a long range of relative humidity the product quality is not affected. But as soon as the humidity level rises to 75% sugar starts to clump and above 80% relative humidity even dissolves .

Storage

Immediately after production the refined sugar is stored in humidity controlled sugar terminals or ventilated silos connected to dehumidifiers.

6.2.4. Sugar Terminal 5086

Sugar in a storage terminal

Logistics

Large quantities are trans-ported in silo trucks or train wagons. When sent by ship sugar is packed in double-walled bags made of natural fibre and plastic. If sealed like this, temperature is the crucial parameter which can affect the quality of the sugar. Due to big differences in temperature water vapour left inside the bags may cause clumping and even liquefaction.
The finer the sugar, the higher the risk of clumping.

Caking-dark-brown-sugar

Sugar clumping

Why the need to measure humidity?

As seen above, temperature and humidity measurements are crucial parameters in the sugar industry. Due to its hygroscopic behavior sugar can resist small changes in humidity, and slight temperature variations are not a major problem. But as soon as relative humidity rises above 80% or temperature changes significantly, the product can be destroyed as it clumps or even turns liquid.
During the process of evaporation, crystallisation, drying and cooling temperature and humidity play a huge role.

Philip Robinson                                                                                                        Rotronic UK

 

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