A Kinetic Study of Marginal Soil Energy Plant Helianthus annuus Stalk Pyrolysis

The pyrolytic characteristics and kinetics of new marginal soil energy plant Helianthus annuus stalk were investigated using thermogravimetric (TG) method from 50 to 800°C in an inert argon atmosphere at different heating rates of 5, 10, 20, and 30°C min？1. The kinetic parameters of activation energy and pre-exponential factor were deduced by Popescu, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods, respectively. The results showed that three stages appeared in the thermal degradation process. The primary devolatilization stage of H. annuus stalk can be described by the Avrami-Erofeev function . The average activation energy of H. annuus stalk was only 142.9？kJ？mol？1. There were minor kinetic compensation effects between the pre-exponential factor and the activation energy. The results suggest that H. annuus stalk is suitable for pyrolysis, and more importantly, the experimental results and kinetic parameters provided useful information for the design of pyrolytic processing system using H. annuus stalk as feedstock. 1. Introduction As potential “next generation” biofuel feedstock, marginal soil plants have attracted considerable attention because of their advantages, such as high photosynthetic efficiency, maximum biomass production, fast growing, high conversion rate, ease of harvesting, and lack of arable soil requirements. Helianthus annuus can grow well in barren marginal lands and has good resistance to adverse situations. Moreover, it does not compete with grain crops for arable lands, which is significant for one populous country lack of arable land as China. The agriculture is producing huge amount of H. annuus stalks as by-products of seeds every year in China. It has been reported that the stalk yield was ranging between 5 and 14 tons per hectare. H. annuus has an excellent adaptability, and the growth cycle is only about 100 days. These characteristics of H. annuus suggest that it can be used as a good potential energy source and should be further studied as a good biofuel feedstock candidate [1–8]. Biomass pyrolysis has demonstrated itself to be a kind of biomass-energy utilization technology which transforms low-energy density biomass materials into high-energy density liquid products which can be utilized more efficiently in an environment-friendly manner. A thorough knowledge of the thermal behavior and pyrolysis kinetics of biomass are required for the proper design and operation of the pyrolysis conversion systems. Thermogravimetry (TG) analysis method was selected to investigate the thermal decomposition process.