Rice Hull-Fired Furnace for Batch Recirculating Dryers
Farmers and ricemillers can save at least P5,900 every time they use their batch recirculating dryers by retrofitting it with rice hull-fired furnace.
This was demonstrated in a study conducted by BPRE agricultural engineers led by Engr. Edgar D. Flores. Other collaborators in the study were engineers Nestor T. Asuncion, Wryan Quiet Z. Viloria, Robelyn E. Daquila, Romualdo C. Martinez, and Ruben E. Manalabe.
Batch recirculating dryers were originally designed to use kerosene as a source of heat for drying. However, their utilization has become minimal as a result of spiraling prices of fossil fuel like kerosene.
This is because these mechanical dryers typically require about 0.75 liter of kerosene per bag of wet palay, constituting about 80 percent of the total operating cost of batch recirculating dryers.
Flores and his co-workers earlier thought that the cost of drying could be substantially reduced if a cheaper fuel is used as source of heating.
As a result, they successfully developed a rice hull-fed furnace that can be retrofitted to presently installed batch recirculating rice dryers. The furnace has an automatic feeding mechanism synchronized with ash removal, thereby facilitating continuous combustion. It also has a temperature controller, which regulates and maintains uniform drying air temperature throughout the drying operation.
Likewise, the furnace has a heat exchanger that delivers clean air to the products being dried. Moreover, it has fly ash scrubber that controls the emission of fly ash.
The heating efficiency of this rice hull-fed furnace meets the required PSAE standard for indirect fired furnace. The emission of fly ash from this furnace (15.1 mg/NCM) is very much below the maximum limit set by the Department of Environment and Natural Resources, which is 200 mg/normal cubic meter (NCM).
Amazingly, the BPRE rice hull-fed furnace can be retrofitted to two adjacent batch recirculating rice dryers and operated simultaneously. With this scheme, about 160 to 180 liters of kerosene costing about P5,920 to P6,660 can be saved per batch of drying. This means that if two batches of drying is done in one day, the savings would be P35,520 to P39,960 every week or P142.080 to P159,840 a month.