I den här rapporten utvärderas det nya konceptet Power & Biomass to Liquid (PBtL). PBtL är ett alternativ till den tidigare och mer etablerade Biomass to Liquid (BtL) processen. Med PBtL förbättras utbytet av kol jämfört med BtL genom att elektricitet läggs till i processen. Elektriciteten används för att producera H2, som används för att höja H2/CO förhållandet istället för att använda WGS som i vanlig BtL process. Rapporten är en del i ett större PBtL projekt som bedrivits vid Institutt for kjemisk prosessteknologi vid NTNU och på SINTEF. Utvärderingen utfördes genom flera simuleringar av lågtemperaturs Fischer-Tropsch reaktorer i simuleringsprogrammet Aspen Plus. Omvandling och katalytiska reaktorer utvecklades och togs fram i programmet. Produktfördelningen i omvandlingsreaktorn modellerades med ASF distribution theory tillsammans med en metod för sammanslagning av högre kolväten. Fördelningen av paraffiner, olefiner och oxygenater baserades på experimentella resultat från Shafer et al. som studerade en slurryreaktor under liknande förhållanden. Den kinetiska reaktorn modellerades med en variant av ASF fördelningsteori kallad ”consorted vinylene mechanism” från Rytter och Holmen. Reaktorerna adderades till förgasningsprocess, som utvecklats tidigare av PBtL gruppen, I förgasningsprocessen förgasas biomassa till syntesgas, dvs H2 och CO. För att möjliggöra en utvärdering av det efterföljande steget med separering av vax, mellandestillat och lättare kolväten så antogs en väl fungerande separation av Fischer-Tropsch produkterna. En enklare separation av med flash förångning gjordes också, dels för fortsättningen av PBtL processen och för att kunna studera tailgasrecirkulering. Ett mindre bidrag var studier av en torkningsprocess för biomassa innan inloppet till förgasningsprocessen. PBtL konceptet diskuterades även ur ett praktiskt perspektiv.  Resultaten visar att vid driftbetingelser på 210 °C, 25 bar och H2/CO = 1,95 så gav omvandlingsreaktorn en kolselektivitet för CH4 respektive C5+ på 14,77 respektive 75,40 mol% C. Högre temperatur, tryck och H2/CO förhållande i reaktorn resulterar i en högre kolselektivitet mot lägre kolväten. Vid samma driftbetingelser gav den katalysreaktorn en kolselektivitet för CH4 respektive C5+ på 7,612 respektive 86,00 mol% C. Resultaten visar att C8-C16 produktionen var högre än C17+ med avseende på molflöde men lägre beträffande massflöde för katalysreaktorn. Generellt så ökar kolselektiviteten med ökande kolnummer till ett maximum runt 13 för att sedan minska. / In this report, the new Power & Biomass to Liquid (PBtL) concept was evaluated. The PBtL concept is a new alternative to the more well-established Biomass to Liquid (BtL) concept where electricity is added to the process. The main purpose for developing the PBtL is that the BtL process exhibits poor carbon efficiency compared to the PBtL process. The electricity here is used to produce H2 in electrolysis. The report is part of a larger PBtL project pursued for several years at the Department of Chemical Engineering at NTNU and SINTEF. The evaluation was done by simulating different types of low temperature Fischer-Tropsch reactors in simulation software Aspen Plus. A conversion reactor and a kinetic reactor was developed. A conversion reactor based on the result from the kinetic reactor was also developed.  The conversion-based reactor was modeled with the ASF distribution theory which describes the distribution of products formed in Fischer-Tropsch synthesis along with a method of lumping higher hydrocarbons. The distribution between paraffins, olefins and oxygenates was based on experimental data from Shafer et al. with similar operating condition with a Slurry reactor. The kinetic-based reactor was modeled with ASF distribution theory with a consorted vinylene mechanism previously described in Rytter and Holmen. The reactors were added to a process for which the biomass gasification section had previously been developed by the PBtL group. The Fischer-Tropsch products were as well separated in order to evaluate the subsequent step of separation of waxes, middle distillate and lighter hydrocarbons. This enabled the option of recycling of tail gas to the Fischer-Tropsch reactor to be evaluated. A smaller contribution included addition of a biomass dryer prior the biomass gasification section. The PBtL concept is also shortly discussed from a practical point-of-view.  It was found that for the operating condition of 210 °C, 25 bar and H2/CO = 1.95 for the conversion-based reactor yielded a carbon selectivity towards CH4 and C5+ of 14.77 and 75.40 mol C% respectively. For the same operating condition, the kinetic-based reactor yield a carbon selectivity towards CH4 and C5+ of 7.612 and 86.00 mol C% respectively. It could be seen from the conversion-based reactor that elevating temperature, pressure and H2/CO (to a certain extent) results in higher carbon selectivity towards lower hydrocarbons. From the product separation with the kinetic reactor, it was observed that C8-C16 production was higher than the C17+ production in terms of mole flow but lower in terms of mass flow. For both models, carbon selectivity increases with carbon number and peaks around carbon number 13 and then starts to decrease.

Revised; Originally published: 2006 / 5 pp. / Recent events in the forests of the Southwest, and across western North America, have prompted scientists to consider the role of climate variability in insect and disease cycles. Studies focusing on Arizona and other southwestern states point to multiple, interacting climate-related mechanisms that increase the propensity for forest mortality. Effects of insects on forests are complex, and species and site dependent. Many influences, such as drought, decreased precipitation, increased temperature, increased vapor pressure deficit, and increased stand density, combined in nonlinear and overlapping ways to create the recent and devastating pine bark beetle outbreaks in Arizona forests. Climate clearly plays a role in many, but not all, Southwest insect cycles. It is important that educators demonstrate the complexity of all of the interplaying issues, in order to communicate no false impressions of an “easy” or “one-size- fits-all” solution” for land managers.

In recent years, there is a rapid growing interest in the use of biomethane for the transport sector. A new method of combining anaerobic digestion and biomass gasification is proposed.The feasibility study shows that more biomethane can be produced; resulting in an increase in the revenue compared to individual biogas plants. The GoBiGas project,which is initiated by Göteborg Energi, adopted another method based on gasification, water gas shift and methanation to enable biomethane production from forest residue. The aim of the present study is to investigate the economic viability of the new method when compared with the GoBiGas (Gothenburg Biomass Gasification) process. For this study, a model of GoBiGas process was developed in Aspen Plus to perform the technical analysis, in which the overall efficiency and exergy efficiency were calculated at different moisture contents of biomass. For the economic analysis, the annual revenue was also estimated during the study. The results show that the overall efficiency of the new method is higher than the efficiency of the GoBiGas process and there is more production of biomethane from the new process.

This work includes wetted wall column experiments that measure the CO₂ equilibrium partial pressure and liquid film mass transfer coefficient (kg') in 7, 9, 11, and 13 m MEA and 2, 5, 8, and 12 m PZ solutions. A 7 m MEA/2 m PZ blend was also examined. Absorption and desorption experiments were performed at 40, 60, 80, and 100°C over a range of CO₂ loading. Diaphragm diffusion cell experiments were performed with CO₂ loaded MEA and PZ solutions to characterize diffusion behavior. All experimental results have been compared to available literature data and match well. MEA and PZ spreadsheet models were created to explain observed rate behavior using the wetted wall column rate data and available literature data. The resulting liquid film mass transfer coefficient expressions use termolecular (base catalysis) kinetics and activity-based rate expressions. The kg' expressions accurately represent rate behavior over the very wide range of experimental conditions. The models fully explain rate effects with changes in amine concentration, temperature, and CO₂ loading. These models allow for rate behavior to be predicted at any set of conditions as long as the parameters in the kg' expressions can be accurately estimated. An Aspen Plus® RateSep™ model for MEA was created to model CO₂ flux in the wetted wall column. The model accurately calculated CO₂ flux over the wide range of experimental conditions but included a systematic error with MEA concentration. The systematic error resulted from an inability to represent the activity coefficient of MEA properly. Due to this limitation, the RateSep™ model will be most accurate when finetuned to one specific amine concentration. This Aspen Plus® RateSep™ model allows for scale up to industrial conditions to examine absorber or stripper performance. / text

4 pp. / This is part of a series on climate variability and forested ecosystems / Recent events in the forests of the Southwest have prompted scientists to consider the role of climate variability in insect and disease cycles. Over 70 million pine trees along with millions of other conifers died in 2002-03. Average temperature increases of 3°C enabled the MPB at those high elevations to achieve univoltine (having one generation per year) reproduction leading to previously unheard of outbreaks in white bark pine at high elevation sites in Idaho.Aspen defoliation in Arizona and New Mexico averaged ~ 20,375 acres from 1990 to 1997. A series of events has contributed to the decline of aspen since 1997.

This thesis focuses on enhancing knowledge on co-firing oxy-combustion cycles to boost development of this valuable technology towards the aim of it becoming an integral part of the energy mix. For this goal, the present work has addressed the engineering issues with regards to operating a retrofitted multi-fuel combustor pilot plant, as well as the development of a rate-based simulation model designed using Aspen Plus®. This model can estimate the gas composition and adiabatic flame temperatures achieved in the oxy-combustion process using coal, biomass, and coal-biomass blends. The fuels used for this study have been Daw Mill coal, El Cerrejon coal and cereal co-product. A parametric study has been performed using the pilot-scale 100kWth oxy-combustor at Cranfield University and varying the percentage of recycle flue gas, the type of recycle flue gas (wet or dry), and the excess oxygen supplied to the burner under oxy-firing conditions. Experimental trials using co-firing with air were carried out as well in order to establish the reference cases. From these tests, experimental data on gas composition (including SO3 measurement), temperatures along the rig, heat flux in the radiative zone, ash deposits characterisation (using ESEM/EDX and XRD techniques), carbon in fly ash, and acid dew point in the recycle path (using an electrochemical noise probe), were obtained. It was clearly shown during the three experimental campaigns carried out, that a critical parameter was that of minimising the air ingress into the process as it was shown to change markedly the chemistry inside the oxy-combustor. Finally, part of the experimental data collected (related to gas composition and temperatures) has been used to validate the kinetic simulation model developed in Aspen Plus®. For this validation, a parametric study considering the factor that most affect the oxy-combustion process (the above mentioned excess amount of air ingress) was varied. The model was found to be in a very good agreement with the empirical results regarding the gas composition.

A dissertation submitted to the faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science in Engineering. 21 November 2016 / In this work a comprehensive exergy analysis and heat integration study was carried out on a coal based oxy-combustion power plant simulated using ASPEN plus. This is an extension on the work of Fu and Gundersen (2013). Several of the assumptions made in their work have been relaxed here. Their impact was found to be negligible with the results here matching closely with those in the original work. The thermal efficiency penalty was found to be 9.24% whilst that in the original work was 9.4%. The theoretical minimum efficiency penalty was determined to be 3% whilst that in the original work was 3.4%. Integrating the compression processes and the steam cycle was determined to have the potential to increase net thermal efficiency by 0.679%. This was close to the 0.72% potential reported in the original work for the same action. / MT2017

Accurate modeling of mixed solvent electrolyte systems is difficult and is not readily available in property modeling software such as Aspen Plus. Support for modeling these systems requires the knowledge and input of parameters specific to the compounds in question. The need for these parameters is particularly relevant in simulating new designs based upon recent developments in a concept known as pass-through distillation (PTD). In support of a specific application of PTD, this work determines and validates with existing experimental data, accurate user-parameters for the eNRTL property model in the ternary system of ethanol, water, and lithium bromide. Furthermore, this work creates the foundation for simulating this new PTD process by modeling the removal of bioethanol from a fermentation broth using low temperature evaporation in conjunction with absorption and stripping units to omit the need of a condenser requiring refrigeration. This will enable future investigations into the applications of PTD as well as provide a foundation for modeling the ternary system of ethanol, water and lithium bromide.

Submitted by Cássio da Cruz Nogueira (cassionogueirakk@gmail.com) on 2017-02-13T14:55:17Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ModelagemSimulacaoProcessos.pdf: 2691666 bytes, checksum: 7d7b152f8bdd96c51cda9787a6d9a5e0 (MD5) / Approved for entry into archive by Edisangela Bastos (edisangela@ufpa.br) on 2017-02-15T15:00:28Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ModelagemSimulacaoProcessos.pdf: 2691666 bytes, checksum: 7d7b152f8bdd96c51cda9787a6d9a5e0 (MD5) / Made available in DSpace on 2017-02-15T15:00:28Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ModelagemSimulacaoProcessos.pdf: 2691666 bytes, checksum: 7d7b152f8bdd96c51cda9787a6d9a5e0 (MD5) Previous issue date: 2014 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho, foi elaborada uma base de dados de parâmetros de interação binária de diferentes regras de mistura, para as equações de estado de Soave-Redlich-Kwong (SRK) e Peng-Robinson (PR), a partir de dados experimentais de sistemas binários e multicomponentes de hidrocarbonetos, N2, CO2, água, β-caroteno, etanol, acetona e metanol, com objetivo de aplicar em simulações com o Aspen Hysys aos processos de fracionamento do gás natural em um processo de turbo-expansão simplificado; de fracionamento de óleo, gás e água, em separador trifásico, de extração com CO2 supercrítico de acetona de uma solução aquosa e de β-caroteno de uma solução aquosa, em coluna de multiestágios em contracorrente. De modo geral, não ocorreram diferenças significativas na predição do equilibro de fases dos sistemas binários estudados, para ambas as equações, com as regras de mistura quadrática, Mathias-Klotz-Prausnitz (MKP) com dois e três parâmetros. Cabe destacar que a regra de mistura MKP com 3 parâmetros de interação binária apresentou os menores erros absolutos para os sistemas binários de hidrocarbonetos e CO2/ hidrocarbonetos. Para os ajustes de dados de equilíbrio dos sistemas multicomponentes de hidrocarbonetos, a equação de SRK combinada com a regra de mistura quadrática com 2 parâmetros de interação binária, foi a que apresentou os menores erros médios para os sistemas ternários e para o sistema com 5 componentes em ambas as fases. No estudo de caso do separador trifásico a equação de SRK com a regra de mistura RK-Aspen foi a que apresentou a maior separação da fase aquosa de todas as simulações (285,68 kg/h) contra 256,88 kg/h para a equação SRK, 249,81 kg/h para a equação PR e 152,90 kg/h para a equação PRSV, confirmando a grande influência do uso da matriz de parâmetros de interação binária determinada neste trabalho, com destaque para os parâmetros que representam as interações entre os hidrocarbonetos com a água. Os resultados das simulações com a planta simplificada de turbo-expansão estão de acordo com a análise descrita na literatura, apresentando as seguintes taxas de recuperação de etano: 84,045% para PRSV, 84,042% para SRK, 84,039% para TST e PR e 83,98% para RKAspen. O produto final da simulação publicada na literatura para o fracionamento de uma solução aquosa de acetona utilizando o processo de extração com CO2 supercrítico consistiu na corrente de saída do fundo da coluna de destilação a 65 atm (6586 kPa), com uma composição de 67,67 % de CO2 (74,3 kg/h), 31,11% de acetona (34,15 kg/h) e 1,21% (1,33 kg/h) de água em base mássica. Na simulação com o Aspen Hysys a corrente de saída da coluna de destilação foi submetida a um conjunto de separadores flash para a separação do CO2 atingindo a recuperação de 27 kg/h de acetona em três correntes (11,14 e 15) com menos de 5 kg/h residuais de CO2 e 0,8 kg/h de água. O fracionamento da solução aquosa de β- caroteno foi simulado com o Aspen Hysys, com uma coluna de múltiplos estágios em contracorrente e um separador flash vertical para a separação do CO2. As simulações convergiram com, no mínimo, cinco estágios. Foi obtida uma corrente de fundo (produto) do separador flash com 97,83% de β-caroteno contra 89,95% em massa, para a simulação de um extrator de um único estágio publicada na literatura. / The purpose of this work was to elaborate a database of binary interaction parameters of different mixing rules, for the Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) equations of state, using experimental data of binary and multicomponent systems of hydrocarbons, N2, CO2, water, β-carotene, ethanol, acetone and methanol, in order to apply in simulations with the Aspen Hysys fractionation processes, of natural gas into a simplified turbo-expansion process; fractionation of oil, gas and water, in three-phase separator, supercritical CO2 extraction of acetone from an aqueous solution and β-carotene from an aqueous solution in multistage countercurrent column. In general, there were no significant differences, to both equations, in the phase equilibrium prediction of the binary systems studied, between the quadratic and Mathias-Klotz-Prausnitz (MKP) mixing rules with two and three parameters. It is worth mentioning that the MKP mixing rule with 3 binary interaction parameters presented the smallest absolute errors for hydrocarbon binary systems and CO2/hydrocarbons systems. For the settings of hydrocarbons phase equilibrium multicomponent systems data, the SRK equation combined with quadratic mixture rule with 2 binary interaction parameters, was presented the lowest average errors for ternary systems and for system with 5 components in both phases. In the case study of three-phase separator the SRK equation with the mixing rule RK-Aspen was the one that presented the greater separation of the aqueous phase of all simulations (285.68 kg/h) against 256.88 kg/h to the SRK equation, 249.81 kg/h for the PR equation and 152.90 kg/h to PRSV equation, confirming the great influence of the use the binary interaction parameters matrix determined in this work, with emphasis on the parameters that represent the interactions between the hydrocarbons with water. The results of the simulations with the simplified plant turboexpansion are according to the analysis described in the literature showing the following recovery rates of ethane: 84.045% to PRSV, 84.042% for SRK, 84.039% for TST and PR and 83.98% for RK-Aspen. The final product of the simulation published in the literature for the fractionation of an aqueous solution of acetone by using supercritical CO2 extraction process consisted in the output current from the bottom of the distillation column at 65 atm (6586 kPa), with a composition of 67.67% CO2 (74.3 kg/h), 31.11% of acetone (34.15 kg/h) and 1.21% (1.33 kg/h) of water in mass base. In the simulation with Aspen Hysys the output current of the distillation column was subjected to a set of flash separators for separation of CO2 reaching the recovery of 27 kg/h of acetone in three currents (11.14 and 15) with less than 5 kg/h CO2 waste and 0.8 kg/h of water. The fractionation of aqueous solution of β- carotene was simulated with the Aspen Hysys, with a multistage countercurrent column and a vertical flash separator for separation of CO2. The simulations have converged with a minimum of five stages. It was retrieved from an underflow (product) flash separator with 97.83% of β-carotene against 89.95% by mass for the simulation of an extractor of a single stage published in the literature.

In western North America, quaking aspen (Populus tremuloides Michx.) is the most common hardwood in montane landscapes. Fire suppression, grazing, wildlife management practices, and climate patterns of the past century are some of the threats to aspen coverage in this region. Researchers are concerned that aspen-dependent species may be losing habitat, thereby threatening their long-term local and regional viability. Though lichens have a rich history as air pollution indicators, I believe that they may also be useful as a metric of community diversity associated with habitat change. To date, few studies have specifically examined the status of aspen's epiphytic lichen community in the Rocky Mountains. A preliminary study was conducted using 10 transect-based plots to assess lichen species substrate preferences between aspen and various conifer species and to gain basic knowledge of species diversity. Following this work, I established 47 plots in the Bear River Range of northern Utah and southern Idaho to evaluate the effects of forest succession on epiphytic macrolichen communities. Plots were located in a narrow elevational belt (2,134-2,438 m) to minimize the known covariant effects of elevation and moisture on lichen communities. Results show increasing lichen diversity and a decrease in aspen-dependent species as aspen forests succeed to conifer cover types. The interactive roles of stand aspect, basal area and cover of dominant trees, stand age, aspen bark scars, and recent tree damage were examined in relation to these trends. An aspen index score was developed based on lichens showing an affinity for aspen habitat. I present a landscape-level multivariate analysis of short and long-term factors influencing epiphytic lichen communities in aspen forests. Nonrnetric multidimensional scaling (NMS) ordination stressed the importance of succession and local air pollution sources in shaping lichen communities. I also investigated the role of historic human intrusions and climate on aspen forests and aspen dependent epiphytic lichens at the landscape-level. Implications of this work include 1) realization of nitrogen impacts on ecosystems, 2) the potential for using lichens as bioindicators for monitoring aspen stand health, and 3) suggestions for working with natural disturbance regimes to minimize human impacts on aspen and associated species.