Monitoring Temperature and Humidity in Biomass Gasification Using Arduino Technology

Abstract

Gasification of biomass can be done with pure oxygen or with ambient air. We have chosen gasification with ambient air in our project for costs considerations. Relative humidity (RH) of the air we used with a downdraft co-current gasifier is monitored in this paper. RH sensor used in this paper presents a capacitor which depends on the amount of water contained in the gaseous mixture. That RH, behaving as a variable capacitor is inserted in serial with the RC circuit of an astable multivibrator. Frequency of the oscillator is dependent of the resistance and the capacity which depends on the RH. We have inserted the RH sensor as a variable capacitor in the RC circuit of a NE555 oscillator. From the RH sensor datasheet, a mathematical model has been developed and the equation giving RH found to be $$Rh=496,23 * ( {1.44*T \over (R_4+2R_2 )* C_55}) -443,26.$$ The frequency of the oscillator is calculated with Arduino and the RH is deduced. Temperature can be measured with a K type thermocouple from 25 to 1024C with accuracy of +/-1.5C.The effect of temperature on the RH is also taken into account. Using Arduino Uno3 as a computer, we have calculated corrected RH respective to temperature and displayed both ambient and real RH on 20 columns with 4 lines LCD display. Arduino has also enabled us to save measured data in an Excel sheet, allowing us to analyses measured temperature and RH and plot different curves from it. The same circuit is also used to monitor RH of produced synthesis gas. Results of the Arduino temperature and monitoring system shows that visual observation of air and human feeling can be very misleading in respect to the air RH.