Pyrolysis of biomass including palm shell, palm kernel, and cassava pulp residue was studied in a laboratory free-fall reactor with three separated hot zones. The effects of pyrolysis temperature (250-1050 ∘ C) and particle size (0.18-1.55 mm) on the distribution and properties of pyrolysis products were investigated. A higher pyrolysis temperature and smaller particle size increased the gas yield but decreased the char yield. Cassava pulp residue gave more volatiles and less char than those of palm kernel and palm shell. The derived solid product (char) gave a high calorific value of 29.87 MJ/kg and a reasonably high BET surface area of 200 m 2 /g. The biooil from palm shell is less attractive to use as a direct fuel, due to its high water contents, low calorific value, and high acidity. On gas composition, carbon monoxide was the dominant component in the gas product. A pyrolysis model for biomass pyrolysis in the free-fall reactor was developed, based on solving the proposed two-parallel reactions kinetic model and equations of particle motion, which gave excellent prediction of char yields for all biomass precursors under all pyrolysis conditions studied.

Effect of KOH, reaction temperature and time, and introduced carbonization step on the amount and composition of syngas as well as porous properties of the carbon products for CO2gasification of coconut shell at low temperatures (300–700°C) was investigated. Results showed that the presence of potassium hydroxide and gasification temperature had a significant effect on the amount and composition of syngas product and facilitated the rate of hydrogen and carbon monoxide formation. It was also found that carbonization step could promote the generation of hydrogen gas as well as increasing the gas heating value per kg of gas. Furthermore, the porosity development of carbon product was found to be influenced by the chemical ratio and gasification temperature. The optimal conditions for achieving high hydrogen composition and specific surface area were to gasify coconut shell under CO2at 600°C for 60 min with carbonization step and with chemical weight ratio of 3.0. This condition gave the hydrogen composition as high as 29.70 %weight of produced syngas with heating value of 41.4 MJ/kg of gas and specific surface area of 2650 m2/g of the carbon product.

The commercial COCO simulation program was used to mimic the experimental slow pyrolysis process of five different biomasses based on thermodynamic consideration. The program generated the optimum set of reaction kinetic parameters and reaction stoichiometric numbers that best described the experimental yields of solid, liquid and gas products. It was found that the simulation scheme could predict the product yields over the temperature range from 300 to 800 • C with reasonable accuracy of less than 10% average error. An attempt was made to generalize the biomass pyrolysis behavior by dividing the five biomasses into two groups based on the single-peak and two-peak characteristics of the DTG (derivative thermogravimetry) curves. It was found that this approximate approach was able to predict the product yields reasonably well. The proposed simulation method was extended to the analysis of slow pyrolysis results derived from previous investigations. The results obtained showed that the prediction errors of product yields were relatively large, being 12.3%, 10.6%, and 27.5% for the solid, liquid, and gas products, respectively, possibly caused by differing pyrolysis conditions from those used in the simulation. The prediction of gas product compositions by the simulation program was reasonably satisfactory, but was less accurate for predicting the compositions of liquid products analyzed in forms of hydrocarbons, aromatics and oxygenated fractions. In addition, information on the kinetics of thermal decomposition of biomass in terms of the variation of fractional conversion with time was also derived as a function of temperature and biomass type.Processes 2019, 7, 775 2 of 20 applications without substantial pretreatment. As an energy source, biomass can be generally converted to biofuels by two possible routes, namely, fermentation and thermal decomposition. Based on the end-products required, thermal decomposition can be classified into direct combustion, gasification and pyrolysis [1][2][3].Pyrolysis is the thermal degradation of biomass by heat in the absence of oxygen that results in the production of charcoal (solid), bio-oil (liquid) and gas products comprising mainly of CO 2 , CO, H 2 and CH 4 . Generally, pyrolysis process operates in the temperatures ranging from 280 to 850 • C with different heating rates and residence times and can be classified into three subclasses: Conventional pyrolysis, fast pyrolysis, and flash pyrolysis.Conventional pyrolysis may also be termed "slow pyrolysis". This type of pyrolysis has been mainly used for the production of charcoal. Slow pyrolysis is characterized by the slow heating rate (less than 10 • C/s) and long residence times of gas and solids with the temperature being around 450 • C [1]. The release of vapor products does not occur as rapidly as in the fast pyrolysis. Thus, components in the vapor phase continue to react with each other, resulting in the formation of char and additional liquids.Fast pyrolysis is a high-temperature process in which biomass is rapidly...