Parboiled paddy should be dried to 14% moisture for safe storage or milling. Parboiled paddy is more difficult to dry and requires more energy than field paddy because its moisture content is much higher. However, higher air temperatures help reduce the drying time. If drying is done too fast, internal stresses develop in the grain and cause breakage during milling. After drying is completed, the paddy should be allowed to stand for at least several hours - preferably for 1 or 2 days - before it is milled, to permit internal moisture differences and stresses to equalize.

Moisture reduction takes place rapidly during the first part of drying from 36 to 18% moisture level, but is slow from 18 to 14%. The drying process should be stopped at about 18% moisture to allow the paddy to temper or equalize for several hours before continuing the drying to 14%.

Most parboiled paddy is sun-dried on large drying floors close to the rice mill. A large number of workers is needed to constantly turn and mix the paddy to achieve rapid, uniform drying. For best results, paddy should be spread about 2.5 cm thick over the floor. At this thickness 500 square meters of drying floor can handle 6 tons of paddy. Depending on drying air temperature and relative humidity, sun-drying usually takes 1 or 2 days.

Sun-drying paddy from 36% to 14% moisture in a single stages causes considerable damage to its milled quality. The problem is overcome by dividing the drying periods and tempering the paddy in between.

Mechanical equipment for drying parboiled paddy is the same as for drying field paddy. But the operation of the equipment differs. The continuous-flow dryer (LSU type) is used as a recirculating batch dryer. Wet paddy is recirculated in the dryer until it reaches 14% moisture.

In contrast with field paddy, parboiled paddy requires air temperatures of up to 100°C during the first drying period. During the second period air temperature should be kept below 75°C. Maintaining higher air temperature will not decrease the drying time but will result in increased drying cost and more damage to milled rice quality. The first drying period takes about 3 hours including dryer loading and unloading time. After tempering, the second drying period takes about 2 hours.

Continuous-flow dryers are available in many sizes to match the capacity of the parboiling system. A 24-5/day parboiling plant needs an 8-ton (holding capacity) dryer. In some cases, rotary dryers are used to pre-dry parboiled paddy before it is loaded into the continuous-flow dryer. That removes large quantities of surface moisture quickly.

Many parboiling plants use husk-fired boilers to supply steam and hot water for parboiling. These same boilers can supply steam to heat exchangers that are used to supply the heated air for drying. In some cases, oil-fired burners and direct husk-fired furnaces have supplied the heated air for drying.

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