Performance evaluation and modelling of a small-scale biomass gasifier

Many parts of the World have remained underdeveloped due to the lack of access to electricity. Developing and promoting alternative energy sources from renewable materials would assist to mitigate the energy crisis in many parts especially in the World. This research examined the possibility of using a 10KW power pallet as a sustainable energy generation system especially for energy poor areas. This was achieved through the gasification of woodchips at varying moisture content, varying gasification times and at varying electrical loads while investigating the numerous changes in the major factors affecting gasification such as temperature, fuel consumption rate, equivalence ratio (ER), quality of the producer gas, heating value, carbon conversion efficiency as well as the cold gasification efficiency of the gasifier. Experimental data was analysed and interpreted by one way Analysis of Variance (Anova) to establish a relationship on the effect of the major factors affecting gasification as investigated in this study. It was discovered that the gasifier is an autothermal system that maintains a steady state of thermodynamic equilibrium for longer hours as long as the gasifier is constantly supplied with a drier fuel. The gasifier stably and optimally operates with woodchips of moisture content less than 10% to produce an energy rich gas for gasification times longer than six hours to yield a gas rich in Hydrogen (H2), Carbon monoxide (CO) and methane (CH4) at a respective concentration of up to 18.1%, 25.3% and 2.2% with a corresponding Higher Heating Value (HHV), Cold Gas Efficiency (CGE) and gas production rate of 6.4MJ/m3, 75.8% and 2.34m3/kg respectively. The reactor takes longer time to attain thermodynamic equilibrium once operated with woodchips of moisture content above 15%. This subsequently affects the quality of producer gas yielding a gas of low calorific value that would even clog the engine. The moisture content of the wood chips was found to play a very significant role in determining the values of temperatures attained and subsequently determining the quality of producer gas. The gasifier was found to produce the required energy up to the design capacity of 10KW required for several industrial applications. Increasing the engine throttle valve increased the frequency of the engine and subsequently the voltage. The designed energy output of up to 10KW could only be produced if the engine frequency was 60HZ and could be lower if the engine operated at a lower frequency. A thermodynamic equilibrium model was further developed to predict the composition of producer gas going to the engine. The thermodynamic equilibrium model yielded a gas composition of 25.99%, 23.92%, and 0.42% for CO, H2 and CH4 respectively that was in good agreement with the experimental results at 850 ºC and ER of 0.27. Similarly, the modelled gasification temperature of 870.85ºC corresponds with a minor deviation of 2.5% with the experimental gasification temperature of 850ºC. The exhaust stream composition contained Carbondioxide (CO2) of upto 20% which is on the higher side because air was used as the gasifying agent and the gasifier was completely autothermal. Such CO2 concentration ought to be lowered if the gasifier is to be adopted as a sustainable renewable energy system. The gasifier was found to operate better with wood chips in the size range between 1.3cm – 4.0cm as very fine wood chips would block the flow of air hence compromising on the sustainability of the exothermic reactions and bigger wood chip particles would not be easily broken down by the auger hence resisting the flow of the woodchips into the reactor. Operating the gasifier at optimal conditions yields a gas of high calorific value good enough to make it a reliable standalone system that could be integrated into sustainable bioenergy systems

Gasification of biochar from empty fruit bunch in a fluidized bed reactor

A biochar produced from empty fruit bunches (EFB) was gasified in a fluidized bed using air to determine gas yield, overall carbon conversion, gas quality, and composition as a function of temperature. The experiment was conducted in the temperature range of 500–850 °C. It was observed that biochar has the potential to replace coal as a gasification agent in power plants. Hydrogen gas from biochar was also optimized during the experiment. High temperatures favor H2 and CO formation. There was an increase of H2 over the temperature range from 500–850 °C from 5.53% to 27.97% (v/v), with a heating value of 30 kJ/g. The C conversion in the same temperature range increased from 76% to 84%. Therefore, there are great prospects for the use of biochar from EFB as an alternative fuel in power plants, as a renewable energy providing an alternative path to biofuels. Results from this work enable us to better understand syn gas production under high treatment temperatures

Performance evaluation and modelling of a small-scale biomass gasifier

Many parts of the World have remained underdeveloped due to the lack of access to electricity. Developing and promoting alternative energy sources from renewable materials would assist to mitigate the energy crisis in many parts especially in the World. This research examined the possibility of using a 10KW power pallet as a sustainable energy generation system especially for energy poor areas. This was achieved through the gasification of woodchips at varying moisture content, varying gasification times and at varying electrical loads while investigating the numerous changes in the major factors affecting gasification such as temperature, fuel consumption rate, equivalence ratio (ER), quality of the producer gas, heating value, carbon conversion efficiency as well as the cold gasification efficiency of the gasifier. Experimental data was analysed and interpreted by one way Analysis of Variance (Anova) to establish a relationship on the effect of the major factors affecting gasification as investigated in this study. It was discovered that the gasifier is an autothermal system that maintains a steady state of thermodynamic equilibrium for longer hours as long as the gasifier is constantly supplied with a drier fuel. The gasifier stably and optimally operates with woodchips of moisture content less than 10% to produce an energy rich gas for gasification times longer than six hours to yield a gas rich in Hydrogen (H2), Carbon monoxide (CO) and methane (CH4) at a respective concentration of up to 18.1%, 25.3% and 2.2% with a corresponding Higher Heating Value (HHV), Cold Gas Efficiency (CGE) and gas production rate of 6.4MJ/m3, 75.8% and 2.34m3/kg respectively. The reactor takes longer time to attain thermodynamic equilibrium once operated with woodchips of moisture content above 15%. This subsequently affects the quality of producer gas yielding a gas of low calorific value that would even clog the engine. The moisture content of the wood chips was found to play a very significant role in determining the values of temperatures attained and subsequently determining the quality of producer gas. The gasifier was found to produce the required energy up to the design capacity of 10KW required for several industrial applications. Increasing the engine throttle valve increased the frequency of the engine and subsequently the voltage. The designed energy output of up to 10KW could only be produced if the engine frequency was 60HZ and could be lower if the engine operated at a lower frequency. A thermodynamic equilibrium model was further developed to predict the composition of producer gas going to the engine. The thermodynamic equilibrium model yielded a gas composition of 25.99%, 23.92%, and 0.42% for CO, H2 and CH4 respectively that was in good agreement with the experimental results at 850 ºC and ER of 0.27. Similarly, the modelled gasification temperature of 870.85ºC corresponds with a minor deviation of 2.5% with the experimental gasification temperature of 850ºC. The exhaust stream composition contained Carbondioxide (CO2) of upto 20% which is on the higher side because air was used as the gasifying agent and the gasifier was completely autothermal. Such CO2 concentration ought to be lowered if the gasifier is to be adopted as a sustainable renewable energy system. The gasifier was found to operate better with wood chips in the size range between 1.3cm – 4.0cm as very fine wood chips would block the flow of air hence compromising on the sustainability of the exothermic reactions and bigger wood chip particles would not be easily broken down by the auger hence resisting the flow of the woodchips into the reactor. Operating the gasifier at optimal conditions yields a gas of high calorific value good enough to make it a reliable standalone system that could be integrated into sustainable bioenergy systems

Designing and Performance Evaluation of Biochar Production in a Top-Lit Updraft Upscaled Gasifier

The Original Belonio Rice Husk Gasifier (OBRHG), initially of height of 0.6 m, diameter of 0.15 m and thickness of 0.025 m was tested for biochar production through air gasification of rice husk (RH) and the design was upscaled to height of 1.65 m, diameter of 0.85 m and thickness of 0.16 m. A total of 27 experiments were conducted to monitor the gasifier performance and the system can operate with the centrifugal blower operating at a power input of 155 W and a maximum flow rate of 1450 m3/hr regulated according to the air requirement. Building the UBRHG is simple and inexpensive to fabricate and with the fairly satisfactory performance and ease of construction along with the convenience of operation, the UBRHG with RH as feed would find abundant avenues of applications in a rural setting for biochar production alongside thermal, mechanical and electrical energy delivery.publishedVersio

Effect of wettability on oil recovery and breakthrough time for immiscible gas flooding

The effect of wettability on oil recovery at higher water saturation is still not fully understood, especially in the case of mixed wettability. This study was conducted to examine the effects of wettability on oil recovery and breakthrough time through experiments for two wettability conditions (water-wet and mixed-wet) and three water saturations (20%, 40%, and 60%). Clashach sandstone core with a porosity of 12.8% and a permeability of 75 md was utilized as the porous media. Immiscible gas flooding was performed by injecting nitrogen gas into the core at room temperature and pressure. The results showed 54.3% and 48.8% of the initial oil in place (IOIP) as the ultimate oil recovery at 40% water saturation from mixed-wet core and water-wet core respectively. In contrast, the water-wet core displayed better results (32.6% of the IOIP) in terms of breakthrough time compared to the results of water-wet core (10.6% of the IOIP) at the same water saturation. In conclusion, oil recovery was found highly dependent on water saturation while breakthrough time was mainly affected by the wettability of the cores

Performance of polyethylene and polypropylene beads towards drill cuttings transportation in horizontal wellbore

Drilled cuttings removal is critical in drilling operations, especially in horizontal wells. These cuttings are postulated to be among the possible causes of many costly complications, such as mechanical pipe sticking, bore hole instability, drag and torque. This study proposes a new approach that uses polymer beads as a mud additive to improve cutting transportation. In this study, the effect of the concentration of polyethylene (PE) and polypropylene (PP) polymer beads on cuttings transport efficiency (CTE) in water-based mud in a horizontal wellbore was investigated. Experiments were conducted in a lab-scale flow loop equipped with a 13-ft (3.96 m) test section consisting of a concentric annulus acrylic outer casing (2 in. ID) and a static inner PVC drill string (0.79 in. OD). A total of 150 tests were conducted using 10 ppg water based mud (WBM) with 1%–5% by vol. Concentrations of polymer beads (PE and PP) were added at a range of 8–9.5 cp. Six different sizes of drilled cuttings ranging from 0.5 to 4.0 mm were used as samples to determine the CTE at a constant 0.69 m/s average annular fluid velocity. The results revealed that CTE increased with the increase of polymer bead concentrations and that PP is better compared to PE overall due to its low density. The highest CTE was recorded at a 5% concentration of water-based mud polypropylene (WBMPP), which is approximately 96% for cutting sizes of 0.50mm–0.99 mm