Drying Palm Kernel Shells (PKS) by Utilizing Waste Heat from Palm Oil Mills and POME Biogas Units

The need for palm kernel shells or PKS is getting bigger because its use is increasing and diversifying. PKS can be used as boiler fuel in industry and in power plants. In addition, it can also be used as a raw material for activated carbon whose needs are also increasing, for more details, read here. The global trend to decarbonize or replace fossil fuels with renewable energy including biomass fuels, especially PKS is the main driving force for the increasing demand for PKS. Even oil-rich countries with economies driven from oil (petrodollars) are also gradually implementing the decarbonization program.

To be used as fuel or further processed into a number of derivative products such as torrified PKS, PKSC or palm kernel shell charcoal and activated carbon, the PKS must be dried first. The process of drying or reducing the moisture content to a certain level requires energy. PKS, which are palm oil mill waste, are generally just piled up in the backyard of the palm oil mill, so they are usually dirty and wet, resulting in a low selling price. If the palm oil mill can dry and clean its PKS, the selling price will also increase, so that there is added value as well as additional income for the palm oil mill. A number of energy sources from waste heat from palm oil mills can be used for the drying process.

Heat is an energy source that can be used for various purposes, either heat generated directly from the combustion process or from waste heat which is the residual heat from the combustion or other sources such as electricity and so on. In palm oil mill operations there is a certain amount of waste heat that can be extracted or harvested or recovered as a heat source for drying such as heat from combustion in the boiler, heat from steam turbine and heat from the FFB sterilization process. If the palm oil mill also processes its liquid waste for electricity production, the waste heat from burning biogas in the generator can also be used as a heat source for drying the PKS. A number of heat sources which are waste heat when integrated, the amount is large so that it can be sufficient for drying the PKS.

In addition to producing CPO (Crude Palm Oil) as the main product, palm oil mills generally also produce palm kernel. Currently, there are still a few palm oil mills (CPO mills) that also have PKO (Palm Kernel Oil) mills , meaning that there are palm oil mills that process fiber for CPO production and palm kernel for PKO production. The palm kernel is produced from the separation of palm kernel with its shell (PKS). Separation is done by breaking the palm kernel shell in a nut cracker drum, then it can be separated between the palm kernel shell and the kernel or core based on differences in specific gravity. If the palm oil mill wants to get added value from its palm kernel shells (PKS), then as soon as it leaves the palm oil mill it goes straight into the dryer (with waste heat as the heat source) after which it is cleaned with a sieve (screening) so that it becomes the final product in the form of dry and clean PKS, so that higher sale value. The size of the shell and fibers that pass the sieve (undersize), can also be used as boiler fuel. Palm oil mill boilers currently operate using fiber fuel (mesocarp fiber) and part of the palm kernel shell (PKS). The rejected material in the form of undersize can be used as boiler fuel so that less PKS are used.