Case Study: Technical Considerations to Optimize Rice Husk Burning in a Boiler to Retain a High Solubility of the Silica in Rice Husk Ash

Aims: Optimal conditions were investigated for the operation of a boiler using rice husks as fuel. Superior operation resulted in the production of high quality ash as well as heat recovery. Good quality ash is a useful resource that can bring profits to a local community.

Study Design: Rice husks were burned in a boiler and the boiler operation was evaluated by measuring the ash solubility in an alkali solution. The operational factors influencing the performance were determined.

Location and Duration of Study: The study was located at the local Imizuno Agricultural Association (IAA) in Imizu, Japan, the location of Toyama Prefectural University. Data were collected from June 2011 to March 2016.

Methodology: The quality of ash was evaluated by examining its solubility. The NaOH method and Testing Method 4.4.1.c were employed to measure solubility. The operational factors of temperature control, maximum temperature setting, air flow capacity, and fire grate movement pattern were chosen to determine the optimal boiler performance.

Results: The following was determined for temperature control: Do not use the AUTO setting at the beginning of the process but engage the AUTO setting once the boiler has finished idling. The optimal maximum temperature was found to be 500ºC; the air flow capacity was 30 Hz; and the fire grate moving pattern was 5-5-6.

Conclusion: For boiler burning or an exothermal reaction, two phases were needed to produce a better quality of ash: An exothermal reaction for the first phase and an endothermic reaction for the second phase. Also, there may be additional factors that contribute to a superior operation.