Rotary Dryer for Biomass Drying

When using biomass as a raw material for wood pellet and wood briquette production, the level of dryness of the biomass must be dry enough so that it can be compacted in the form of the pellet or briquette. Biomass raw materials in the form of wood or agricultural wastes are often still wet, so the drying process needs to be done first. As a tropical country the sun's rays will continue to shine throughout the year, but relying on drying in the sun under the hot sun will take a long time, large space and inefficient handling. Based on these conditions, the drying carried out with certain equipment needs to be done. The characteristic of the dryer in the industry is that it can dry out large capacities in a short time and economical.

Rotary dryer or drum dryer is a type of dryer that is most widely used in the pellet and briquette industry. That is because the rotary dryer has a simple construction, easy to operate and also maintenance. The use of a rotary dryer is not only for drying biomass but also in other fields such as minerals, fertilizers and a number of aggregates. The use of rotary dryers in a number of fields with various types of material also has consequences for a number of supporting devices, for example the use of cyclones, scrubbers, bag houses to induced drafts (ID) fans. Meanwhile, from the operational side it also varies according to the characteristics of the dried raw material such as counter current or co-current drying flow, and the use of indirect drying or direct drying.

Each dryer also has its own characteristics and is suitable for certain types of material. Selection of the type of dryer that is not suitable results in the drying goal not being achieved, for example a rotary dryer is suitable for drying materials that are not broken or damaged when dropped from above, while the type of dryer fluidized dryer is suitable for materials that are lightweight and break easily or are damaged when dropped. Biomass especially in small particle size is material that is not damaged or broken when dropped, so the use of a rotary dryer is more appropriate. In addition to more expensive investment costs, operational and maintenance fluidized dryers are also more expensive compared to rotary dryers. The choice of material for manufacturing rotary dryers is also important. Metal material that is not suitable is feared that it will make the quality of the drying product not meet the target besides the shorter service life.

In biomass materials with small particle sizes, a rotary dryer is the most commonly used dryer. For drying flow using cocurrent, not counter current based on a number of considerations. In large capacity wood pellet and briquette plants, the rotary dryer usually operates 24 hours a day, so the performance of the rotary dryer becomes very important. Inadequate installation makes the performance of the rotary dryer is not optimal and the service life. The occurrence of many vibrations and unbalanced rotation indicates that the rotary dryer installation is inadequate and makes the performance not optimal and the service life of the rotary dryer shorter.

Improving Dryer Efficiency At Wood Pellet And Wood Briquette Factories

Rotary dryer or drum dryer is a common type of dryer used in the biomass industry namely wood pellet and woodbriquette factories. The advantages of rotary dryer due to the construction is simple, easy in operation and the drying capacity is quite large. There are two important points to consider in the use of a rotary dryer dryer: 1. Heat flow pattern, single pass or triple pass drum; 2. Type of equipment for emission control, such as multiple cyclone systems or other types. Both of these will affect the dryer efficiency as well as the environmental aspects. In practice in Indonesia almost all rotary dryers use single pass with a co-current with material to be dried. Multi-cyclone with cyclone also serves as a temporary storage is also widely encountered.

Side of other efficiencies that can be improved that is on the heating media. This is because the fuel consumption for drying is costly. Currently the rotary or drum dryer drying process that operates by direct-contact between the flue gas heat with the dried material such as sawdust. The flue gas usually comes from burning wood waste as well. If the plant site contains bulk materials such as rice husks, peanut shells, palm shells, cashew shells and so on, improve efficiency with gasification technology can be done. The trick is to replace the flue gas burning furnace with gasifier or from the beginning has designed a rotary dryer with a gasifier as a heat generator. An increase of efficiency by 20% can be achieved by using the gasifier.

Heat gasifier type downdraft and work continuously will be suitable for the heat source. This is because the heat gasifier does not require a complicated syngas cleaning unit and with the downdraft type syngas will be cleaner because the resulting tar is much less than the updraft type.