PKS for FBC Powerplant Part 2

Between the two variants of fluidized bed combustion (FBC) technology, the type of CFBC (circulating fluidized bed combustion) is more widely used for power generation than BFBC (bubbling fluidized bed combustion). That is because the level of efficiency is higher, the use of large capacity and the amount of flue gas produced is less. Stoichiometric air requirements for CFBC (1.1 - 1.2) are less than BFBC (1.2 - 1.3), this also results in less flue gas produced at CFBC compared to BFBC. The main difference between CFBC and BFBC is that there is a circulation of the use of bed material in CFBC and CFBC using air velocity greater than BFBC.

The fuel used for CFBC has a smaller particle size compared to BFBC so it will require higher preparation / pretreatment costs. This is one of the drawbacks of CFBC. The usual preparation is foreign material control and size reduction. Fuels used like coal must be cleaned of a number of impurities such as metals. Magnetic separator is a equipment commonly used to separate the impurities of these metals. The metals that pollute the coal apart from damaging the screen on the crusher (if using a hammer mill type crusher) it is also possible to cover the perforated plate at the bottom of the fluidized bed furnace. The closure of these pores causes disruption of air circulation which will certainly affect the output of the unit.

PKS or palm kernel shell is a biomass fuel that are widely available in Indonesia and have characteristics close to wood pellets. The PKS can be used for CFBC fuel both for cofiring and fullfiring (100% PKS). Regarding the preparation or pre-treatment of fuel before it is fed or used in CFBC, it also needs to be done for PKS. PKS measuring 2-5 cm need to be cleaned from a number of impurities and size reduction before use. In cofiring, when equipments for coal preparation can also be used for PKS, it means no new line is needed for that. But if it can't, a new line needs to be made. Some power plants in Japan even use 100% PKS as fuel with the CFBC technology and especially in the framework of environmental and climate change solutions supported by the government.

CFBC biomass power plants in Japan with 49 MW capacity
which has been operating since 2015 with PKS

The use of fluidized bed combustion (FBC) technology has actually been carried out since the 1960s, which at that time was mainly used to treat municipal and industrial waste. At present it is estimated that more than 300 FBC units are installed and operating throughout the world. PKS as palm oil mill solid waste (CPO mill) is available in abundance in Indonesia which is estimated to reach more than 10 million tons / year and in Malaysia is estimated to be more than 5 million tons / year. This is so that the use of PKS on FBC is very possible because the volume and availability is sufficient. Economic factors are especially limiting the use of the PKS, although in terms of the environment and climate change, it is strongly supported. The location of the palm oil mills which is in the middle of the plantation commonly in very remote locations also makes logistical costs expensive so it affects the selling price of the PKS.