Development of a Dual-Chamber Pyrolizer for Biochar Production from Agricultural Waste in Sri Lanka

Abstract

This study investigates the design and development of a pyrolysis reactor for batch-type biochar production from rice husks. The main objective is to develop an appropriate technology to regulate pyrolysis temperature and biomass residence time that can be easily operated under field and household conditions with minimal operational and technical requirements. The designed novel dual-chamber reactor comprises two concentrical metal cylinders and a syngas circulation system. The outer cylinder is for energy generation and the inner one is for pyrolysis. Temperature profiles, energy exchanges, syngas production, and the physicochemical characteristics of biochar were obtained to determine the performance of the reactor. Different trials were carried out to obtain different pyrolysis temperatures under constant amounts of feedstock and fuel. The temperature was monitored continuously at three predetermined reactor heights, the temperature profile varied from 380 °C to 1000 °C. The biochar yield was 49% with an average production rate of 1.8 ± 0.2 kg h−1. The reactor consumed 11 ± 0.1 kg of rice husk as feedstock and 6 ± 1 kg h−1 of wood as fuel. The gaseous products from the pyrolysis were CH4, CO2, H2, CO, and CnHm, which contributed 23.3 ± 2.3 MJ m−3 of energy as fuel for the pyrolysis process. The specific surface area of the biochar was 182 m2 g−1. The achieved operational capacity and thermal efficiency of the reactor show biochar production is a suitable option to convert discarded biomass into a value-added product that can potentially be used in several environmental applications.