Master of Science

thesisCoal gasification temperature distribution in the gasifier is one of the important issues. High temperature may increase the risk of corrosion of the gasifier wall or it may cause an increase in the amount of volatile compounds. At the same time, gasification temperature is a dominant factor for high conversion of products and completing the reactions during coal gasification in a short time. In the light of this information it can be said that temperature is one of key parameters of coal gasification to enhance the production of high heating value syngas and maximize refractory longevity. This study aims to predict the adiabatic flame temperatures of Australian bituminous coal and Indonesian roto coal in an entrained flow gasifier using different operating conditions with the ChemCAD simulation and design program. To achieve these objectives, two types of gasification parameters were carried out using simulation of a vertical entrained flow reactor: (1) oxygen-to-coal feed ratio by kg/kg and pressure and (2 ) steam-to-coal feed ratio by kg/kg and pressure. In the first part of study the adiabatic flame temperatures, coal gasification products and other coal characteristics of two types of coals were determined using ChemCAD software. During all simulations, coal feed rate, coal particle size, initial temperature of coal, water and oxygen were kept constant. The relationships between flame temperature, coal gasification products and operating parameters were fundamentally investigated. The second part of this study addresses the modeling of the flame temperature relation to methane production and other input parameters used previous chapter. The scope of this work was to establish a reasonable model in order to estimate flame temperature without any theoretical calculation. Finally, sensitivity analysis was performed after getting some basic correlations between temperature and input variables. According to the results, oxygen-to-coal feed ratio has the most influential effect on adiabatic flame temperature

Economic Rationale for Safety Investment in Integrated Gasification Combined-Cycle Gas Turbine Membrane Reactor Modules

A detailed Net Present Value (NPV) model has been developed to evaluate the economic viability of an Integrated Gasification Combined Cycle – Membrane Reactor (IGCC-MR) power plant intended to provide an electricity generating and pure H2 (hydrogen) producing technology option with significantly lower air pollutants and CO2 (carbon dioxide) emission levels, where the membrane reactor module design conforms also to basic inherent safety principles. Sources of irreducible uncertainty (market, regulatory and technological) are explicitly recognized, such as the power plant capacity factor, Pd (palladium) price, membrane life-time and CO2 prices (taxes) due to future regulatory action/policies. The effect of the above uncertainty drivers on the project’s/plant’s value is elucidated using a Monte-Carlo simulation technique that enables the propagation of the above uncertain inputs through the NPV-model, and therefore, generate a more realistic distribution of the plant’s value rather than a single-point/estimate that overlooks these uncertainties. The simulation results derived suggest that in the presence of (operational, economic and regulatory) uncertainties, inherently safe membrane reactor technology options integrated into IGCC plants could become economically viable even in the absence of any valuation being placed on human life or quality of life by considering only equipment damage and interruption of business/lost production cost. Comparatively more attractive NPV distribution profiles are obtained when concrete safety risk-reducing measures are taken into account through pre-investment in process safety (equipment) in a pro-active manner, giving further credence to the thesis that process safety investments may result in enhanced economic performance in the presence of irreducible uncertainties.Process economic analysi

Comparison of Biomass to Bio-oils Reactor Systems: Direct Conversion vs. Companion Coal Gasification

It is well known that the United States’ dependence on crude-oil negatively affects its economy, safety, and environment. To alleviate these negative consequences, a more economical and environmentally-friendly source of fuel, such as biomass, should be explored. The conversion of biomass to bio-oils involves the pyrolysis of biomass at about 500°C, thus requiring a great deal of heat. This heat source could be the excess waste heat from a coal gasifier. As such, this report specifies the design of an industrial plant that produces bio-oils from biomass by using the waste heat from a coal gasifier. It is designed to produce 2.24×108 kg/yr of bio-oil that can be sold at $0.79/kg. This plant involves coal and biomass solids handling, a coal gasification reactor, a biomass pyrolysis reactor, and a series of separation units to remove waste products from the syngas and isolate the bio-oil. The syngas contains methane, hydrogen, and carbon monoxide and is sold as a by-product credit. The plant is expected to run on feeds of 1.5x1011 kg/yr of coal and 5.4 x108 kg/yr of raw biomass. The coal gasification reactor was sized based on the heating duty of steam at 273000 kJ/s and the biomass pyrolysis reactor was sized based on a heating duty of 7026 kJ/s. The plant’s operating factor (POF) is 0.9 at 7884 hrs/yr running 24 hrs/day and 328.5 days/yr. The total bare module equipment cost, including all pumps, heat exchangers, grinders, separators, absorber, and reactors is$93 million. The total capital investment of the plant is $173 million. The DCFRR and NRR are 12.59Given that selling price of bio-oil ($0.79/kg) associated with this plant is about six times more expensive that the average cost of bio-oil ($0.13/kg), it is not recommended that a Class – 1 Estimate be conducted. Before a Class – 1 Estimate can be conducted, the unnecessary costs associated with this proposed plant must be addressed and reduced. Specific attention must be paid to the following two heat exchangers, E-127 and E-129. Additionally, attention should be given to discover a cheaper source of industrial, liquid oxygen

Torrefaction of Oil Palm Wastes for Improvement of Gasification Process

The project studies the biomass characteristic and the hidden problems behind it from become the main source of energy for this world. The use of gasification process as a technique to produce syngas which itself called fuels have certainly broaden the choice of using renewable energy as a replacement to current fossil fuels. The degradation of fuel storage in the whole world helps significantly to promote biomass as an alternative energy and at the same time, the need to find a suitable replacement. Therefore, gasification of biomass is seen as a future technology that can replace the current fossil fuels. However, the exploitation of this fuel sources through gasification does have drawbacks that need to be solved. Thus, this report, the torrefaction for Oil Palm Wastes for the improvement of gasification process was studied in order to improve its properties. Subsequently, it will enable biomass to be a much better fuel quality for combustion and gasification applications. For this study, palm wastes such as Palm Frond, Fiber and Kernel Shell are used to produce torrefied material and the factors affecting the process are investigated. The factors were the reactor temperature and the particle size. To analyze the characteristic of the biomass and to make comparison with the torrefied material, several analysis have been made. Thermal Gravimetric Analyzer(TGA) were used for proximate analysis where the decomposition regime was exhibited. The entire sample were analyzed for four main regions which are moisture content, volatile matter, fixed carbon content and ash content. The Ultimate Analysis were done using CHNS Analyzer were all the samples shows that the carbon content contributes to the major componenet. Halogen Moisture Analyzer(HMA) were used to analyze the moisture content of every samples and lastly, Bomb Calorimeter as a tool to determined the calorific value. Overall, the comparison was made to justify the improvement made by torrefaction process. It is found and suggested that for an optimum condition of torrefaction was at 280°C and particle size of 250 μm. Thus it is believed that with the improvements that were made to the biomass, it is viable to be promoted in the scale up production

Thermochemical conversion of non‐woody biomass: upgrading cotton gin waste into solid fuel

Non-woody biomass is a common waste material found in agriculture. Despite its abundance, the waste is not widely utilised due to unfavorable physical properties (bulkiness, irregular size and varied composition) and low energy content. The aim of this research is to study the solid fuel properties of a non-woody biomass in order to improve their qualities. Cotton gin waste (CGW), a source of non-woody biomass from the processing of cotton, was selected. Methods of densification and blending of biochar were proposed and evaluated for transforming CGW into pellets in order to create a fuel with high density and energy content, as well as uniform physical properties. The development of CGW pellets was achieved by using a small scale pellet mill. CGW was blended with 5 to 20 percent weights of biochar. The developed CGW pellets were accordingly defined as CGW100, CGW95, CGW90, CGW85 and CGW80 pellets, implying the weight percentages of CGW as much as 100%, 95%, 90%, 85% and 80% in pellets, respectively. It has been found that pelleting the CGW increases the bulk density from 112 kg/m3 to 600 kg/m3. The biochar blends upgraded the heating values of CGW pellets from 14 MJ/kg of CGW100 to 18 MJ/kg of CGW80. In the process of stabilisation, the blended pellets slightly shrank, while the pure CGW pellet marginally expanded. In contrast to the pellet durability, the hardness was significantly influenced by the biochar addition. The biochar in the pellets diminished the rancid smell of raw CGW. It has also been found that CGW95 and CGW90 behaviours in the thermogravimetric (TGA) combustion were almost identical with CGW100 combustion. In addition, CGW95 pellets had the highest conversion rate and resulted in the least residual ash. On the contrary, CGW85 and CGW80 pellets were slow in conversion and burn out at closer to the biochar ignition temperature. From the examination of ash content and activation of energies, all the blended pellets show a synergism in co-combustion. Similar to combustion, the TGA pyrolysis using inert gas also resulted in a slightly higher conversion for CGW95. Other biochar blended pellets show a lower and more linear conversion as a function of biochar content. A CFD model has been developed using ANSYS Fluent 17.2 software. The approaches are the discrete phase and non-premix combustion models. The model shows an accurate prediction of the gasifier temperature and resulting gas composition. The simulation also predicts that CGW95 will have a higher CO yield than CGW90. The gasification of CGW95 pellets with air to fuel ratio of 1.3 v/w results in a gas composition of CO, CO2, H2 and CH4 gas of 19.8%, 11.6%, 14.2% and 0.2%, v/v respectively. The estimated gas heating values are in the range of 3.9-5.1 MJ/m3. It has been found that 30% energy produced from CGW pellet gasification is sufficient to cover the energy need for pellet production. The costs of energy in the ginning house can be reduced by 20-40% from the use of produced gas. The GHG emission is also lowered. Overall, it can be concluded that upgrading the non-woody biomass into pellets and applying it in a co-gasification could potentially provide an effective alternative fuel source to achieve agricultural energy self-sufficiency and off-grid operation

Techno-economic assessment of two novel feeding systems for a dry-feed gasifier in an IGCC plant with Pd-membranes for CO2 capture

This study focuses on the application of Pd-based membranes for CO[subscript 2] capture in coal fueled power plants. In particular, membranes are applied to Integrated Gasification Combined Cycle with two innovative feeding systems. In the first feeding system investigated, CO[subscript 2] is used both as fuel carrier and back-flushing gas for the candle filters, while in the second case N[subscript 2] is the fuel carrier, and CO[subscript 2] the back-flushing gas. The latter is investigated because current dry feed technology vents about half of the fuel carrier, which is detrimental for the CO[subscript 2] avoidance in the CO[subscript 2] case. The hydrogen separation is performed in membrane modules arranged in series; consistently with the IGCC plant layout, most of the hydrogen is separated at the pressure required to fuel the gas turbine. Furthermore, about 10% of the overall hydrogen permeated is separated at ambient pressure and used to post-fire the heat recovery steam generator. This layout significantly reduces membrane surface area while keeping low efficiency penalties. The resulting net electric efficiency is higher for both feeding systems, about 39%, compared to 36% of the reference Selexol-based capture plant. The CO[subscript 2] avoidance depends on the type of feeding system adopted, and its amount of vented gas; it ranges from 60% to 98%. From the economic point of view, membrane costs are significant and shares about 20% of the overall plant cost. This leads in the more optimistic case to a CO[subscript 2] avoidance cost of 35 €/t[subscript CO2], which is slightly lower than the reference case.Seventh Framework Programme (European Commission) (Grant agreement no. 241342

Modeling and Optimization of Hydrogen Production from Gasification of Waste Polyethylene

Due to the energy crisis and environmental concern of fossil fuel usage, hydrogen has emerged as an alternative source of fuel. Hydrogen which is the major component of syngas, can be produced through gasification of waste polyethylene (PE). PE is a very sustainable source with a global production of 67 million tons in 2010. Waste PE catalytic steam gasification with in-situ carbon dioxide capture using CaO provides good prospects for the production of hydrogen rich gas. This work focuses on the process modeling and optimization for hydrogen production from waste PE using MATLAB. The model incorporates the reaction kinetics calculations of the steam gasification of waste PE with in-situ CO2 capture, as well as mass balances calculations. The developed model is used to investigate the effect of temperature, type of catalyst and steam/PE ratio on the hydrogen purity and hydrogen yield. Based on the results, hydrogen purity of 35 mol% can be achieved. The maximum hydrogen yield predicted at the outlet of gasifier is 125gH2/kg PE. It is also found that the increased in temperature and steam/PE ratio will enhance the hydrogen production. In conclusion, this work provided meaningful resources that can be used as a basis for more detail work for gasification of waste PE

Coal conversion processes and analysis methodologies for synthetic fuels production

Information to identify viable coal gasification and utilization technologies is presented. Analysis capabilities required to support design and implementation of coal based synthetic fuels complexes are identified. The potential market in the Southeast United States for coal based synthetic fuels is investigated. A requirements analysis to identify the types of modeling and analysis capabilities required to conduct and monitor coal gasification project designs is discussed. Models and methodologies to satisfy these requirements are identified and evaluated, and recommendations are developed. Requirements for development of technology and data needed to improve gasification feasibility and economies are examined

Effects of intraparticle heat and mass transfer during devolatilization of a single coal particle

The objective of the present work is to elucidate the influence of intraparticle mass and heat transfer phenomena on the overall rate and product yields during devolatilization of a single coal particle in an inert atmosphere. To this end a mathematical model has been formulated which covers transient devolatilization kinetics and intraparticle mass and heat transport. Secondary deposition reactions of tarry volatiles also are included. These specific features of the model allow a quantitative assessment to be made of the impact of major process conditions such as the coal particle size, the ambient pressure and the heating rate on the tar, gas and total volatile yield during devolatilization. Model predictions are compared to a limited number of experimental results, both from the present work and from various literature sources

Simulation and economic evaluation of coal gasification with SETS reforming process for power production

Increasing natural gas prices have raised interest in alternate energy resources. Popular belief in the connection between carbon dioxide emissions and global warming has motivated the search for a technique to isolate carbon dioxide from combustion stack gases. Coal gasification with SETS reforming has been proposed as a solution to both of these issues in that it provides an alternate energy source and 100% carbon dioxide sequestration. The purpose of this research is to simulate this process using AspenPlus to perform the rigorous material and energy balances. The results of this simulation are used to carry out a complete economic evaluation of the process and estimate the overall cost of energy production (in 2003 dollars). Certain design parameters are modified from literature values. The simulations and economic evaluations are repeated for each case to study its effect on energy production cost. The final results of this study are compared with the current cost of electricity and the costs of other energy production methods