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.

Utilization of Air Pressure For Biomass Drying

In the process of production of wood pellet and wood briquette, dryer has an important role due to regulate the moisture content before compacted (densification). Almost all wood pellet and wood briquette factories also use a dryer to keep the quality and quantity of the production. Today most of the drying of biomass using heat from combustion flue gas directly (direct heating) and a fraction using the heat of combustion indirectly (indirect heating). Of course the main concern is the issue of effectiveness and economics. Drum dryer or a rotary dryer is the most common type of dryer and popular because it proved capable of drying a large scale economically. Several types of dryers are also widely available and developed at this time with a variety of characteristics. The availability of a number of options also allow users or the industry to make their choice if they wish to withdraw and not fixated on one option only.

One type of dryer that started appearing on the market that take advantage of the heat of compression dryer (heat of compression type dryer). When the compressed air, more energy is converted into heat which is then stored in pressurized air (compressed air) and normally the heat is simply discharged in a cooler (cooler). At dryers that utilize hot air compression, the energy used to regenerate the desiccant, thereby eliminating the need for heating or heat is utilized directly in the drying. This type of dryer is also energy efficient than refrigerated air dryer type while the dew point is also much better than refrigerated type air dryer.