Comparison of rotary fertilizer dryer efficiency using electrical generator waste heat and liquefied petroleum gas as a heat source

Abstract

This research compared rotary dryer efficiency using waste heat from an electrical generator and liquefied petroleum gas (LPG) as a heat source. A fertilizer drying experiment was conducted using residues from bio-gas production with a 3-ton/day capacity fertilizer dryer. Flow drying and drying efficiency was tested concurrently and measured together with water evaporation, energy consumption, and an economic analysis of data was conducted. Two heat sources were applied at the rates of 10, 15, and 20 rpm, drying cylinder with inclination angles of 1°, 3°, and 5°, and hot gas flow rates of 60, 120, and 180 m3/h. The tests showed that dryer inclination of 1°, heat flow rate of 180 m3/h, and dryer rotation speed at 10 rpm were the most optimal drying conditions. When waste heat from the electrical generator was applied, thermal efficiency was 79.19%, while the fertilizer's moisture content could be reduced from 57.84% dry weight standard to 12.45%, with an evaporation rate of 56.93 kg/h. The energy consumption was 23.78 kW h/1 ton of fertilizer. LPG drying yielded a heat efficiency of 72.69%, while moisture content went from 56.16% to 12.77%. Water evaporation from the fertilizer was 54.24 kg/h, and heat consumption was 986.33 kW h per 1 ton of fertilizer. Analysis revealed that fertilizer drying by waste heat from an electrical generator yields better efficiency and saves more energy than using LPG as the heat source. The cost of drying is also approximately 3.14 times lower.