March 2007 – Product of the Month

Moisture Analysers for the Sugar Processing Industry

Measurement of Moisture in Raw and Refined Sugar is critical to the sugar process and impacts greatly on the quality of the final product.

Raw sugar is usually manufactured in batches and in the newer factories has been automated to be a continuous process. The syrup from the cane is boiled and sugar crystals form, this is put through a centrifuge to take out impurities and then the remaining material is dried to moisture of around 0.3 to 0.5%

Refined sugar is raw sugar that is processed further. Typically the raw sugar is returned to the liquid state, this liquid is then passed through a number of refining processes including CO2 purification and Charcoal filtering. The refined liquid is then boiled and the sugar crystals passed through a centrifuge. The remaining material is then dried down to moisture of around 0.03%.

The MoistTech Model IR3000 Sensors, supplied in Australasia by JW Industrial Instruments Pty Ltd, can be located pre and post dryer for process optimization and closed loop process control.

Measurement of POL or the polymerization level in the sugar is also an important parameter in the Raw and Refined sugar process. The POL of the sugar directly relates to the clarity or purity of the sugar. An IR3000 gauge set up for moisture and POL, can be used in this process and provide additional payback with the simultaneous POL analysis.

Moisture Analysis in Bagasse:

A significant drawback of using bagasse for fuel is its variable moisture content and moisture control in bagasse has always been a critical element in the Sugarcane Industry. The measurement of moisture in bagasse is more important because it affects the performance of the milling and boiler operation. If the moisture is not controlled and the materials become too wet, it takes longer time to ignite and does not burn properly. To compensate this, extra fuel must be added. If the material is too dry, the feed rate must be slowed or the fire will burn too hot which will result in producing too much steam, which is then wasted.

Traditional methods of obtaining bagasse Moisture Analysis by manual sampling and oven drying are labor intensive and time consuming. By the time one grabs the sample from the line and obtains the moisture result from the laboratory the information is too old to be adjusted to a dryer due to variations in the process. Automatic control is virtually impossible utilizing offline manual sampling. In recent years many Sugarcane mills, worldwide have been able to operate their process more efficiently and economically by utilizing continuous Online NIR moisture analyser.

NIR Moisture Sensors are typically located on a screw or belt conveyor at the entrance or exit of the dryer. The percentage moisture signal is displayed on an operator interface or display, which gives instantaneous and continuous moisture readings. Furthermore automatic control may be achieved by transmitting the output signal from the moisture analyser to the PLC, DCS or PID controller.

MoistTech pioneered the use of NIR technology for Process moisture monitoring and manufacturing analysers considering the sugar mill conditions such us hot, dusty, or hazardous environment, non-technical operators and variable sample presentation.

The model IR3000 series gauges utilise the industry proven and patented optical system. The measurement technique, based on Near Infrared (NIR) light absorption, is non-contacting, non-destructive and non-hazardous.

MoistTech sensors measure moisture by shining light of a known NIR wavelength of which the water or other measured constituent absorbs. The light reflected back to the sensor is inversely proportional to the amount of water or other constituent in product. The more present, the greater the absorption of the light energy. NIR analysers are secondary measurement instruments and as a result they must be calibrated by comparison with a laboratory method (Typically oven drying or Chemical Titration) to give the accurate measurements.

MoistTech IR3000 analysers are the fastest on the market providing, accurate, precise and reliable method for online NIR analysis in industrial process. Their speed, accuracy and reliability make them ideally suited for use in monitoring or close loop control. Use in closed loop control can improve quality by maintaining the product tightly within the specification and can also yield savings by lower energy cost by allowing moisture to be more tightly controlled to the target value.

JW Industrial Instruments Pty Ltd specialise in sales and service of Process Analytical Instrumentation. With an experienced team of people with a wide range of knowledge, they cover all aspects of Process Control using instrumentation. Their range of services includes supply of process equipment, installation, commissioning, training on aspects of instrumentation and repair and calibration.

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