3.6 Decolourisation

Typical arrangement of PAC system for decolourisation of sugar syrup

The process flow diagram illustrates a typical industrial process using activated carbon to remove colour bodies from a recycled glucose intermediary prior to use in the production of confectionery. The glucose containing the colour taint is heated to a temperature of approximately 70oC, so that the normally solid product becomes less viscous and easier to transport hydraulically. The syrup is pumped through high efficiency mechanical filters to remove any entrained particulate or crystallised sugar which may have formed during the heating process.

The filtered syrup is then either passed through columns containing granular activated carbon using a high residence time, or powdered activated carbon is added. It is during these stages that the colour bodies are physically adsorbed by the highly porous activated carbon. When the additon of PAC is undertaken the heated syrup is agitated for a period of time. Following stirring in a heated vessel, the syrup then undergoes mechanical filtration to remove the PAC prior to the glucose being used to manufacture the confectionery. The reprocessing of waste in this way allows it to be suitable for re-use as a saleable product after further processing. This technique is similarly used in diverse applications such as pharmaceutical processes, chemical intermediaries manufacture and soft drink production. CPL Carbon Link manufactures a range of Granular Activated Carbon (GAC) and Powdered Activated Carbons (PAC) products for decolorisation applications.

Powdered activated carbon (PAC) dosing from IBC containers

The key features of these product are;

• Granular coal and powdered wood enable optimum product selection
• Highly macroporous pore size distributions provide an effective removal of colour bodies
• High filterability PAC products to ensure maximum removal of adsorbent during mechanical filtration

Typical Product Properties