Installation design of on-line near infrared spectroscopy for the production of compound fertilizer

Abstract

Low-analysis fertilizer composition highly poses risk to soil infertility, crop yield and farmer livelihood. Fertilizer testing via traditional laboratory methods is a tool for quality control but with the significantly high cost of investment and maintenance in the long run. Physiochemical data from vibrational spectra obtained from the near-infrared reflectance (NIR) analyzer shows successful installation design for real-time quality monitoring of compound fertilizer production in this study overcoming exhaustive laboratory methods offering competitive advantages to the fertilizer industry becoming a great tool for product development and lower the risk of farmers buying the low-analysis fertilizer. The NIR analyzer was designed for on-line analysis of nutrient contents of the fertilizer before bagging. Total nitrogen (TN%), available phosphorus (available P2O5%), water-soluble potassium (water-soluble K2O%), total organic matter (TOM%), moisture content (TMC%) including pH were required to be monitored to ensure final product release being within limits legislatively established. Spectral variations across different times of measurement over a day of the production was investigated in the condition of on-line system instead of a controlled condition to confirm the measurement will be reliable and in good reproducibility. Calibration models were developed using Partial Least Squares (PLS) regression with a series of data pretreatments on individual model per nutrient. Precision and accuracy figures of NIR results were obtained considerably good enough to the manufacturing practice. NIR prediction results were later designed for threshold and feed-back to the process control.