Tar and trace element measurements in synthesis gas from a pressurized black liquor gasifier.

One of the strategies to improve environmentally friendly energy harvesting can be realized by using biomass as a primary energy source for generating electricity and H2. In addition, high energy efficiency can be achieved by minimizing the exergy loss through process integration and exergy recovery. As an implementation, this study proposes a cogeneration system for black liquor (BL) to co-produce electricity and H2. The system primarily comprises of BL drying, circulating fluidized bed gasification, syngas chemical looping (SCL), and power generation. The Aspen Plus V8.8 software package is used for modelling and performing calculations of the proposed integrated system. Furthermore, thermodynamic analysis of gasification is performed by employing Gibbs energy minimization. The effects of target solid content on the required total work and compressor outlet pressure during drying and gasification with different steam-to-fuel ratios are evaluated. Moreover, the SCL process adopts three reactors, namely, the reducer, oxidizer, and combustor. Compared to the conventional processes, the integrated drying-gasification-SCL processes are significantly cleaner and more energy efficient. The proposed integrated system can achieve a net energy efficiency of about 70 %, with almost 100 % carbon capture.

Experimental and Thermo-Economic Analysis of Catalytic Gasification and Fuel Cell Power Systems

The use of biomass as a CO2-neutral renewable fuel and the only carbon containing renewable energy source is becoming more important due to the decreasing resources of fossil fuels and their effect on global warming. The projections made for the Renewable Energy Road Map [1] suggested that in the EU, the use of biomass can be expected to double, to contribute around half of the total effort for reaching the 20 % renewable energy target in 2020 [2]. To achieve this goal, efficient processes to convert biomass are required. At the Karlsruhe Institute of Technology (KIT), Germany, a two-stage process called bioliq [3], for the conversion of biomass into synthetic fuel, is being developed. In this process, straw or other abundant lignocellulosic agricultural by-products are converted to syngas through fast pyrolysis and subsequent entrained flow gasification. After gas cleaning and conditioning, the syngas is converted into different chemicals via known processes such as direct methanol synthesis or Fischer-Tropsch synthesis. The prime goal of this thesis was the modeling and simulation of the gasification of biomass-based pyrolysis oil-char slurries in an entrained flow gasifier, which is an important step of the bioliq process. Computational Fluid Dynamics (CFD), as a powerful tool for modeling and simulation of fluid flow processes, was utilized in this thesis. A lab scale entrained flow gasifier, located at KIT, was simulated using the CFD code ANSYS FLUENT 12.0. Due to the turbulent nature of the flow, the realizable k-epsilon model was used to model the turbulence. The discrete phase model (DPM) was employed to describe the fluid phase, consisting of char particles suspended in ethylene glycol. Ethylene glycol served as non-toxic model fuel for pyrolysis oil, mainly because of its similar C/H/O-ratio and its similar physical properties to biomass derived liquid pyrolysis products. A detailed reaction mechanism for high temperature oxidation of ethylene glycol was implemented in the CFD code. The mechanism comprised of 43 chemical species and 629 elementary reactions. The use of detailed chemistry enables one to have a deeper insight into the gasification process. Turbulence-chemistry interactions were modeled with the eddy dissipation concept (EDC). The in-situ adaptive tabulation (ISAT) procedure was employed to dynamically tabulate the chemistry mappings and reduce computer time for the simulation. The effect of the thermal radiation was taken into account by using the discrete ordinates model (DOM). The radiative properties of the gas were described with the weighted sum of gray gases model (WSGGM). The simulation results were compared with the experimental measurements wherever possible, with good agreement. The simulations depicted the importance of the recirculation zone in entrained flow gasification. Furthermore, the main reaction path of ethylene glycol gasification could be observed and analyzed. In order to study the effect of boundary conditions on the gasification process, a series of simulations were done to perform sensitivity analysis. Four parameters were varied, namely: oxidizer and fuel inlet temperatures, the oxidizer composition, the air-fuel ratio and the operating pressure of the gasifier. Effects of the parameter variations on the gasification efficiency and the composition of the product gas were studied. Three different chemistry models (i.e. equilibrium chemistry, flamelet model and EDC) were studied in this thesis. Their relative advantages and disadvantages for the simulation of gasification processes were examined. The EDC model proved to be the better choice for entrained flow gasifiers with recirculation zones. The slurry gasification simulations were performed to study the effects of the mass fractions of the char particles on the process. With the aid of the detailed chemistry model, sub-processes could be analyzed and suggestions for the improvement could be made. The simulations performed in this work help to better understand the gasification process inside entrained flow gasifiers and considerably reduce the number of experiments needed to characterize the system. The simulations produced spatial and temporal profiles of different system variables that are sometimes impossible to measure or are accessible only by expensive experiments. However, more experimental measurements help to validate and optimize the CFD model. The sensitivity analyses performed in this study are considered as a basis to find optimized operating conditions and assist the successful scale-up of entrained flow gasifiers.

Pyrolysis of dried pulverized BL was carried out using a microwave. Microwave method offers several advantages such as volumetric heating, rapid turnover as well as efficient energy conversion. The objectives this works were to study microwave heating pyrolysis technique and resulting products as well as conversion efficiency. Weak BL used in this experiment was taken from soda and kraft pulping process from local pulp mill which was then dried and sieved. Pyrolysis was performed in quartz reactor heated in microwave using silicon carbide as microwave receptor. It was found that the reaction temperature may reach 545-1120°C within 10 min by employing microwave heating depending on the amount of dried BL used. The obtained gas products were quantified by gas analyzer. Char and tar were collectively analyzed by weight measuring. Results indicated that optimum operating conditions were pyrolysis of BL achieved at microwave power of 625 W (1120oC), BL 10 g., silicon carbide ratio 1:1 and residence time 6 min where high fuel gases (H2, CO, CH4, and CO2) were 25.9, 20.0, 1.6 and 0.4 vol.%, respectively. The syngas (H2 and CO) increased from 17.62 %vol and 12.20 %vol to 25.90 %vol and 20.00 %vol, respectively when increasing of temperature from 830°C to 1120°C. It was observed that yields of gas product increased, while the yield of solid char decreased. Comparison of the results suggested that microwave heating had obvious advantages over conversional heating in terms of more valuable products and energy efficiency.

This is the first ever study assessing the possibility of dimethyl ether (DME) production through gasification of Victorian brown coal. This project involves gasification of Victorian brown coal and catalyst development for syngas to DME conversion process. Victoria has large reserves of brown coal, 430 billion tonnes at current estimate. Use of Victorian brown coal is currently limited mostly to mine-mouth power generation because of high moisture content of the as-mined coal and high reactivity of the dried coal; both these properties make Victorian brown coal, raw or dried, unexportable. Gasification based alternative processing paths can provide export market for brown coal derived products, and more energy efficient application of brown coal. Syngas from Victorian brown coal can be catalytically converted into DME with higher energy efficiency and at potentially lower CO₂ emission. DME is a non-toxic, non-carcinogenic and non-corrosive compound. In addition, it has wide application as a fuel in cars, gas turbines, fuel cells and household applications. A process simulation for as-mined Victorian brown coal to DME was performed using ASPEN Plus. The simulation study shaped the experimental matrix as it provided a realistic range of operating conditions (e.g. gasification temperature and syngas H₂ to CO ratio). CO₂ Gasification kinetics for raw parent coal as well as demineralised and catalyst-loaded (Ca, Fe) coals were studied using a thermogravimetric analyser. Pyrolysis and gasification of the coal was performed in an entrained flow reactor (EFR) and the solid, liquid and gaseous products were characterised. DME synthesis experiments were performed in a high pressure fixed-bed reactor, using commercial and developed catalysts, and synthetic syngas consisting H₂ and CO. A 3² factorial experimental design was used to optimise catalyst composition and syngas ratio (H₂ to CO). The developed catalysts were prepared based on the information generated from preliminary experiments with commercial catalysts. Physical mixing and coprecipitation-impregnation methods were used for the preparation of bi-functional DME synthesis catalysts. Performance (CO conversion, DME yield and DME selectivity) of the developed catalysts was compared with that of commercial catalysts. Effects of sulphur poisoning on CO-conversion, DME yield and DME selectivity were also studied. Process simulation using ASPEN plus showed that the low temperature gasification at 900 °C can produce syngas with appropriate H₂ to CO ratio. The ratio was found to be 0.81 at the gasifier outlet (before the recycle stream) and 1.41 at the DME reactor inlet (after the recycle stream). The overall process efficiency was found to be ∼ 32% after considering the energy penalty for CO₂ separation, higher than the power generation efficiency of 28% (without CO₂ separation). Two kinetic models (Grain model and random pore model) were used to find the intrinsic CO₂ gasification kinetics. Random pore model predicted the experimental results better than the grain model. The activation energy for char-CO₂ gasification was ∼189 kJ/mol. Ca-loaded coal char showed better gasification reactivity. However, addition of iron did not show any improvement. The results indicate that the effect of minerals become insignificant at 1000 °C or above and catalytic gasification showed be carried out below this temperature. EFR studies showed that the tar yield rapidly decreased as the gasification temperature was increased. The residence time and gasification temperature in the EFR were not enough for complete carbon conversion. In situ synchrotron radiation X-ray diffraction on methanol and DME synthesis catalysts showed rapid catalyst deactivation at temperatures above 300 °C, resulted from phase mobility and thermal sintering. The extent of deactivation was higher for the bi-functional DME catalyst compared to the methanol synthesis catalyst. Regression analysis on the yield data, obtained using commercial catalysts, showed that a H₂ to CO ratio of 1.45 and a catalyst consisting 58% methanol synthesis component results maximum DME yield. Among the four developed catalysts (DSC-1, DSC-2, DSC-M, DSC-1-PRE), three catalysts (except DSC-1-PRE) showed performance similar or better than the commercial catalyst mixture M1A1. CO conversion was between 67-70% for the DSC-1 catalyst, best among the developed catalysts, compared to 58-60% conversion for the M1A1 catalyst. DME yield was 36-40% and 35-38% for the DSC-1 and M1A1, respectively. A 10 hour exposure of the catalyst to 103 ppm H₂S showed at least 12% reduction in conversion and yield, indicating rapid deactivation in the catalyst activity. All the results were at least duplicated, and triplicated in most of the cases. The obtained results positively indicate that the conversion of syngas from Victorian brown coal to DME is a feasible option.

In this study, Cascabela thevetia seed shell (CTSS), maize corn cob (MCC) and black liquor (BL) are used for the production of cylindrical fuel briquettes in various mixing proportions at different pressures; 60, 70, 80, 90 MPa under room temperature conditions. Briquette properties such as compressed density, relaxed density, relaxation ratio and shattering index were evaluated. The mathematical regression equations between independent variables (applied pressure and mixing proportion) and briquette properties were developed using SPSS statistical software and briquette property values obtained from mathematical equations compared with experimental values. The results showed that the addition of BL could significantly enhance the briquette properties at all pressures, and briquette produced with a mixing proportion of CTSS:MCC:BL = 60:25:15 at 90 MPa gives better briquette properties. Thus, combustion characteristics of a briquette produced with a mixing proportion of CTSS:MCC:BL = 60:25:15 at 90 MPa were evaluated and compared with other briquettes. The results showed that combustion characteristics were eco-friendly and comparable with other briquettes.

This review of the literature from 2004 and 2005 concerning secondary ion mass spectrometry (SIMS) highlights the contribution the technique has made in the fields of petrology, geochronology, cosmochemistry and material sciences. In petrology, much research was devoted to the measurement of stable isotopes and trace elements by developments in multicollection acquisition, with emphasis on low atomic mass number elements. Elements studied in particular were S (in sulfides), O (in garnets), C (in sedimentary organic matter), Cl (in glasses) and Si. Novel applications of SIMS to geochronology have included the measurement of young zircon grains by the U‐Pb and U‐Th decay methods. An increasing number of studies have combined U‐Pb geochronology with the measurement of trace elements or stable isotopes in zircon.

In Thailand, the ministry of energy needs to increase the use of renewable energies, especially biodiesel and syngas, more than 25%. However, blending biodiesel more than 10% provided lower engine performance significantly. Therefore, this research aims to present about the investigating performance and emissions of a turbocharging diesel engine using the diesel blended to 10% biodiesel (B10) compared with the use of B10 and syngas on dual fuel. Syngas was generated from a downdraft gasifier by using the charcoal, and it was increased the gas flow rate from 76 to 125 lpm by using a supercharger. Results of using B10 compared with diesel show that the fuel properties of B10 were similar to diesel. Engine performance was decreased slightly, but emissions, such as carbon monoxide, hydrocarbon, and black smoke, were also reduced. Results of engine test using the dual fuel between B10 and increasing syngas quantity (B10+SG) indicate that the use of B10+SG at 85 lpm had similar engine performance to using diesel only. Use of B10+SG at 125 lpm was the best because of higher engine performance and more fuel saving as compared with using B10 and diesel only. On the other hand, the use of B10+SG compared with using both oils only show that various emissions were enormously increased while the syngas quantity was increased to 125 lpm. Keywords: B10, syngas, diesel engine, performance, emissions

PILOT SCALE GASIFICATION: DEVELOPMENT OF A SIMULATION TOOL TO AID THE EXPERIMENTAL ACTIVITIES

NON-CONVENTIONAL WASTE-DERIVED FUELS FOR MOLTEN CARBONATE FUEL CELLS

Chemical looping combustion of Victorian brown coal using Fe-based oxygen carriers

Elucidating the mechanism underpinning ultra-clean coal production from Victorian brown coal and its application as a gasification fuel

Research has been conducted to find out the percentation of lignin in delignification process, rate of delignification, and order or reaction from the coconut fiber with peroxide alkali. Three experiments were done in this study : 1) optimalized of pH to find out highest lignin percentation from black liquor; 2) simple characterized of lignin by spectrophotometer IR; and 3) graphical interpretation of the percentation of lignin with cooking time to find out the order of reaction of delignification. The lignins were isolated by acid process. The obtained of lignin precipitation was filtrated, washed and rinsed with water until free from acid, and then heated at 105 o C for 1 hours. The cooking time were varied as: 1 hour, 1,5 hours, 2 hours, 2,5 hours, 3 hours, 3,5 hours and 4 hours. The result of the experiments indicated that the highest lignin percentation were gotten in pH = 2, and from the IR spectra of lignin after was compared with standard lignin spectra, it can be seen that this sample is realy lignin. Than, according to graphical interpretation indicated that the order of reaction from coconut fiber delignification by peroxide alkali process followed first order. Key words : Black liquor, Delignification, peroxide alkali.

Utilising biomass for thermal generation purpose is one of the ways to reduce CO2 emissions. For that reason, the biomass gasification process is used to produce rich heating value fuel which is known as syngas. Because of the complicated nature of this field, the research should comprise both conducting experimental investigation on actual facilities and developing a numerical model. This study compared the affection of two kinds of gasification agents, the air and the air-steam mixture, on the composition of syngas and cumulative CO. The ratio of steam for the best quality of syngas was then determined. The two-dimensional Computational Fluid Dynamics (CFD) was developed for determining the suitable kinetics model. The parameters of geometry were taken from practical pilot plant gasifier. The validation process for this simulation was carried out by comparing the simulation data with experimental data which was measured by online gas analyser-TESTO 350XL. The results illustrate the influence of air-steam mixture on the composition of CO and H2 in syngas, H2/CO ratio, and the advantage of using the stream in gasification on both experimental and simulation results.

This paper deals with an important point for biomass gasification processes: the measurement of tars. The well known tar protocol technique is reliable but not very simple to implement in different points of a process and it is not precise for low concentrations of tars (<100 mg/Nm3). Tests were performed using a pilot scale fluidized bed producing a real syngas. Tar were measured in a wide range of concentration from mg to g/ Nm3. Tar protocol has been compared with µGC analysis (for benzene and toluene) and with SPA (Solid Phase Adsorption) technique. SPA probes are analyzed using thermo desorption coupled with GC/FID technique. Results show that tar protocol and µGC are in good agreement. SPA provides also consistent results for benzene and toluene. SPA values obtained for naphtalene are more scattered for high concentration and over estimated for low concentration. It appears that SPA is a simple and convenient method for tar measurement but it is necessary to be very conscientious during the sampling allowing a representative sample and avoiding pollution of probes.