Assessment of biomass energy potential for SRC willow woodchips in a pilot scale bubbling fluidized bed gasifier

The current study investigates the short rotation coppice (SRC) gasification in a bubbling fluidized bed gasifier (BFBG) with air as gasifying medium. The thermochemical processes during combustion were studied to get better control over the air gasification and to improve its effectiveness. The combustion process of SRC was studied by different thermo-analytical techniques. The thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) were performed to examine the thermal degradation and heat flow rates. The product gas composition (CO, CO2, CH4 and H2) produced during gasification was analyzed systematically by using an online gas analyzer and an offline GC analyzer. The influence of different equivalence ratios on product gas composition and temperature profile was investigated during SRC gasification. TG/DTG results showed degradation occur in four stages; drying, devolatilization, char combustion and ash formation. Maximum mass loss ~70% was observed in devolatilization stage and two sharp peaks at 315–500 °C in TG/DSC curves indicate the exothermic reactions. The temperature of gasifier was increased in the range of 650–850 °C along with the height of the reactor with increasing equivalent ratio (ER) from 0.25 to 0.32. The experimental results showed that with an increment in ER from 0.25 to 0.32, the average gas composition of H2, CO, CH4 decreased in the range of 9–6%, 16–12%, 4–3% and CO2 concentration increased from 17 to 19% respectively. The gasifier performance parameters showed a maximum high heating value (HHV) of 4.70 MJ/m3, Low heating value (LHV) of 4.37 MJ/m3 and cold gas efficiency (CGE) of 49.63% at 0.25 ER. The ER displayed direct effect on carbon conversion efficiency (CCE) of 95.76% at 0.32 ER and tar yield reduced from 16.78 to 7.24 g/m3 with increasing ER from 0.25 to 0.32. All parametric results confirmed the reliability of the gasification process and showed a positive impact of ER on CCE and tar yield

Biomass Torrefaction and CO2 Gasification: Exergy Analysis and Kinetic Study

In this study, rice husk pellet (RHP) and Crymptomeria Japonica (CJ) have been used as feedstock in gasification process. The feedstock has been torrefied at 250 °C and 350 °C in 1 hour. before performing gasification in bubbling fluidized bed (BFB) gasifier and thermogravimetric analyzer to determine exergy efficiency and kinetic characteristics respectively. To evaluate exergy efficiency of combined torrefaction and gasification, the exergy analysis was performed in the BFB gasification process using raw and torrefied RHP. The gasification was conducted in a 30 kWth bubbling fluidized bed. The effects of air equivalence ratio (ER) and torrefaction temperature on overall exergy efficiency were examined. Results of experiments showed that torrefaction process may enhance chemical energy (exergy) of RHP due to lower values of O/C and H/C. However, the overall energy (exergy) efficiency decreases due to the energy loss in volatile gas and electric energy input during the combined torrefaction-gasification process. The efficiency decrease was more severe in the case of torrefaction at 350 °C. The overall exergy efficiencies of the torrefied RHP at 250 °C and 350 °C are 30% and 21%, respectively. To study the gasification reactivity of the raw and torrefied biomass, the CJ was used in the kinetic analysis of non-isothermal) and isothermal gasification in CO2 environment. For non-isothermal process, thermal decomposition occurred in three different stages, including dehydration, hemicellulose-cellulose and lignin decomposition on 30.2-102.6 oC, 222.6-422.1 oC and 426-847.2 oC respectively. A linear model was proposed in this paper, and this model fits the experimental data quite well. In main decomposition stage, the activation energy of raw CJ, CJ-250 and CJ-350 are 77, 114.3 and 49.9 kJ/mol respectively. The highest activation energy of CJ-250 is found due to the higher quantity of cellulose in the sample compared with other two samples. The activation energy of CJ-350 shows the lowest value because most of volatile in hemicellulose-cellulose zone are expelled during the torrefaction process. Rising heating rate leads to shift the mass loss curve towards higher temperature, increase activation energy and pre-exponential factor. For isothermal process, three gasification temperature of 750°C, 800°C, and 850°C were conducted to evaluate the kinetic parameters of Arrhenius form with proposed models. Homogeneous model (HM), shrinking core model (SCM) and linear model (LM) were used and the predicted results obtained from these models were compared with experimental data. The reaction rate of gasification was enhanced as the temperature was raised, and a correlation of kinetic parameters with temperature was obtained. The simulated results of linear model (LM) fit well with experimental data.ABSTRACT i TABLE OF CONTENTS iii LIST OF TABLES vi LIST OF FIGURES vii CHAPTER 1 Introduction 1 1.1 Background 1 1.2 Biomass as an energy resource 1 1.3 Biomass conversions 2 1.2.1 Combustion 3 1.2.2 Pyrolysis 3 1.2.3 Gasification 4 1.2.4 Torrefaction 4 1.2.5 Liquefaction 4 1.3 Problem statement 4 1.4 Objectives 5 1.5 Organization of thesis 5 CHAPTER 2 Literature reviews 7 2.1 Introduction 7 2.2 Exergy analysis of torrefied biomass in gasification 7 2.2.1 Biomass components 7 2.2.2 Biomass torrefaction 8 2.2.3 Torrefaction and gasification 8 2.2.4 Thermodynamics analysis on gasification 9 2.3 CO2 gasification 15 2.3.1 Non-isothermal gasification of biomass 15 2.3.2 Isothermal gasification of biomass 16 CHAPTER 3 Experimental set-up and procedures 27 3.1 Introduction 27 3.2 Biomass Characteristics 27 3.3 Torrefaction process 28 3.4 Gasification process 31 CHAPTER 4 Exergy analysis of torrefied biomass in BFB gasification 33 4.1 Introduction 33 4.2 Exergy analysis 33 4.2.1 Torrefactor 34 4.2.2 Gasifier 37 4.3 Results and Discussion 41 4.3.1 Torrefactor 41 4.3.2 Gasifier 43 CHAPTER 5 Non-isothermal kinetics of torrefied biomass in CO2 gasification 50 5.1 Introduction 50 5.2 Non-isothermal gasification 50 5.3 Experimental 51 5.4 Decomposition characteristics of the raw and torrefied biomass 52 5.5 Kinetic analysis 57 5.6 Results and discussion 59 5.7 Effect of heating rate 63 CHAPTER 6 Isothermal kinetics of torrefied biomass in CO2 gasification 68 6.1 Introduction 68 6.2 Kinetic modelling 68 6.3 Experimental 70 6.4 Results and Discussion 71 CHAPTER 7 Conclusions and recommendations 82 7.1 Conclusions 82 7.1.1 Exergy analysis of torrefied biomass in BFB gasification 82 7.1.2 Non-isothermal kinetics of torrefied biomass in CO2 gasification 82 7.1.3 Isothermal kinetics of torrefied biomass in CO2 gasification 83 7.2 Recommendations 83 REFERENCES 85 APPENDIX 89 1. Exergy analysis calculation for torrefactor-gasifier 90 1.1 Torrefactor at RHP-250 at 60 mins 90 1.2 Gasifier 91 2. Pictures of torrefactor-gasifier in real experiment 95 2.1 Torrefactor 95 2.2 Gasification system 96 2.3 Thermogravimetric analyzer 97 CV 98 List of Publications 9

Co-combustion Characteristics and Kinetics Behavior of Torrefied Sugarcane Bagasse and Lignite

The co-combustion characteristics and kinetics of torrefied sugarcane bagasse (TB), lignite (L), and their blended samples were experimentally investigated using thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG)based on the Coats-Redfern method for kinetic estimation.Their physicochemical properties were also investigated.Raw bagasse was thermally treated in a laboratory-scale torrefactor at 275 °C with a torrefaction time of 60 min under an inert nitrogen environment.Then, the torrefied bagasse was blended with Thai lignite as a co-fuel at ratios of 50:50 (TB50L50), 70;30(TB70L30), and 90:10 (TB90L10), respectively. Torrefaction improved the fuel properties and heating value of the raw bagasse as well as reducing the O/C and H/C ratios.In addition, the blending of torrefied bagasse with lignite improved the combustion behavior.The TGA and DTG results indicated that the ignition and burnout temperatures stepped downwards with different increasing ratios of torrefied bagasse.The co-combustion behavior at the maximum burning rate showed that the burnout temperatures of TB50L50, TB70L30, and TB90L10 were 532, 529, and 528 °C, respectively, indicating a slight decrease with an increasing torrefied bagasse blending ratio.These results were sufficient to provide comprehensive guidelines in terms of the design and operation of the combustion system for adding torrefied bagasse into the co-firing process

Optimization of gasification process parameters for COVID-19 medical masks using response surface methodology

Due to the COVID-19 pandemic, large amounts of medical wastes have been produced and their disposal has resulted in environmental and human health problems. This medical waste may include face masks, gloves, face shields, goggles, coverall suits, and other related wastes, such as hand sanitizer and disinfectant containers. To address this issue, the effect was investigated of gasification process parameters (type of COVID-19 medical mask based on the polypropylene ratio, pressure, steam ratio, and temperature) on hydrogen syngas and cold gas efficiency. The gasification model was developed using process modeling based on the Aspen Plus software. Response surface methodology with a 3k statistical factorial design was used to optimize the process aiming for the highest hydrogen yield and cold gas efficiency. Analysis of variance showed that both the steam ratio and temperature were significant parameters regarding the hydrogen yield and cold gas efficiency. Proposed models were constructed with very high accuracy based on their coefficient of determination (R2) values being greater than 0.97. The optimum conditions were: 65 % polypropylene in the mixture, a pressure of 1 bar, a steam ratio of 0.38, and a temperature of 900 °C, producing a maximum hydrogen yield of 40.61 % and cold gas efficiency of 81.43 %. These results supported the efficacy of the primary design for steam gasification using a mixture of plastic wastes as feedstock. The hydrogen could be utilized in chemical applications, whereas the efficiency could be used as a basis for further development of the process

Co-torrefaction of rice straw and waste medium density fiberboard: A process optimization study using response surface methodology

Co-torrefaction is a flexible way of improving the properties of various kinds of waste biomass for utilization as a clean solid fuel. Rice straw (RS) and medium density fiberboard (MDF) were used as feedstock for the torrefaction. Three input parameters were evaluated to determine the optimum conditions: rice straw ratio (RSR), torrefaction temperature and residence time. A response surface method based on a Box-Benhken design was used to achieve the optimum conditions (maximizing torrefied heating value and energy yield). Main and interaction effects for the independent variables on the responses were investigated based on analysis of variance (ANOVA). The findings revealed that temperature was the main effect and that there was no interaction effect between the inputs. Thus, a lower temperature optimized co-torrefaction. The optimum conditions for maximizing the heating value (22.13 MJ/kg) and energy yield (99.60%) were an RSR of 25%, a temperature of 208.10 °C and a residence time of 50 min. The experimental values were in good agreement with the corresponding predicted values. These findings should provide guidelines for the thermal pretreatment of mixed waste material for co-firing or co-gasification

Porous Biochar Supported Transition Metal Phosphide Catalysts for Hydrocracking of Palm Oil to Bio-Jet Fuel

The upgrading of plant-based oils to liquid transportation fuels through the hydrotreating process has become the most attractive and promising technical pathway for producing biofuels. This work produced bio-jet fuel (C9–C14 hydrocarbons) from palm olein oil through hydrocracking over varied metal phosphide supported on porous biochar catalysts. Relative metal phosphide catalysts were investigated for the highest performance for bio-jet fuel production. The palm oil’s fiber-derived porous biochar (PFC) revealed its high potential as a catalyst supporter. A series of PFC-supported cobalt, nickel, iron, and molybdenum metal phosphides (Co-P/PFC, Ni-P/PFC, Fe-P/PFC, and Mo-P/PFC) catalysts with a metal-loading content of 10 wt.% were synthesized by wet-impregnation and a reduction process. The performance of the prepared catalysts was tested for palm oil hydrocracking in a trickle-bed continuous flow reactor under fixed conditions; a reaction temperature of 420 °C, LHSV of 1 h−1, and H2 pressure of 50 bar was found. The Fe-P/PFC catalyst represented the highest hydrocracking performance based on 100% conversion with 94.6% bio-jet selectivity due to its higher active phase dispersion along with high acidity, which is higher than other synthesized catalysts. Moreover, the Fe-P/PFC catalyst was found to be the most selective to C9 (35.4%) and C10 (37.6%) hydrocarbons

Enhancing performance of polymer-based microchannel heat exchanger with nanofluid: A computational fluid dynamics-artificial neural network approach

Polymer-based heat exchangers can offer a promising solution for environmental sustainability due to their low energy consumption. The incorporation of microchannels and nanofluids further enhances the heat transfer performance of these heat exchangersIn this study, a polymer-based microchannel heat exchanger combined with nanofluid is simulated through the integration of an artificial neural network predictive model and a three-dimensional computational fluid dynamics model. This study unveils an advanced calculation that integrates artificial intelligence and readily-available computational software provided as the advanced calculation system. A statistical mathematics response surface method which data is used for correlating the calculation model  is applied to obtain the design parameters between operating conditions and for optimal performance. The optimized results reveal that polymer-based microchannel heat exchanger combined with nanofluid is a promising innovation. The heat transfer improvement achieved a 12 % increase in the overall heat transfer coefficient by using TiO2/Water compared to Water. Moreover, a 1.03 performance index is obtained when CuO/Water nanofluid is used, a 66 horizontal parallel connecting of the polymer-based microchannel heat exchanger shows that the equipment can afford the same heat transfer performance of the metal-based microchannel heat exchanger in TiO2/Water nanofluid usage and implying a balance between heat transfer enhancement and energy consumption