Generation of synthesis gas for fuels and chemicals production

Many scientists believe that the oil production will peak in the near future, if the peak has not already occurred. Peak oil theories and uncertain future oil deliveries have stimulated interest in alternative sources of fuel and chemicals. This interest has been enhanced by concerns about energy security and about the climate change caused by emissions of carbon dioxide. The result has been increased interest in substituting fossil fuels with renewable energy sources such as wind, solar and biomass. However, this has proved particularly difficult in the transportation sector. The most likely source of renewable hydrocarbon fuels for transportation is biomass. It comes in many forms, none of which are suitable for direct use in internal combustion engines and gas turbines. Thus the biomass has to be refined to convert its energy into a more usable form. The most versatile conversion of biomass is thermochemical conversion via gasification and downstream synthesis, which allows the production of both fuels and chemicals. In the biomass gasification process, a gasifier converts the solid biomass into a gaseous product known as producer gas. The producer gas contains the desired components carbon monoxide and hydrogen, but it also contains water, carbon dioxide, lower hydrocarbons, tars and impurities that need to be removed from the gas. Reforming the tars and hydrocarbons in producer gas is difficult because of the amount of sulphur present. This thesis investigates the use of reverse-flow reactors to reform the tars and hydrocarbons in biomass generated producer gas.. Reverse-flow reactors operate by periodically reversing the direction of flow to enable high levels of heat recovery. The high heat recovery enables non-catalytic reformers to be operated at efficiencies near that of catalytic reformers. The operation of reverse-flow reactors is investigated experimentally in a tar-cracking reactor using dolomite as bed material and also theoretically using computer models. The investigations show that reverse-flow reactors have great potential, offering a chemically robust alternative to conventional reformers when operating on sulphur-containing biomass-generated producer gas. Furthermore, operation of reverse-flow tar crackers using dolomite as bed material is an efficient and viable solution for tar removal and syngas boosting. The producer gas also contains ammonia in varying amounts depending on the gasifier’s operating parameters and feedstock. Ammonia can be a poison for catalysts and, if the producer gas is burnt, will produce elevated levels of NOX in the flue gas. The selective catalytic oxidation of ammonia in synthesis gas was thus also investigated by experiments on a model synthesis gas. This thesis also covers mass and energy balance calculations to determine the efficiency and economics of synthetic fuels and chemicals plants. Several possible plant configurations were investigated, both stand-alone and integrated. The integration of a pulp and paper mill with a fuel synthesis plant is a very likely scenario as the biomass logistics are already located on-site. Another possible integration scenario involves steel plants, where large quantities of energy-rich gases are handled as off-gases in coke production. Utilisation of this off-gas coupled with biomass gasification was also investigated. In the stand-alone plants, the difference between reverse-flow reformers and conventional non-catalytic reformers was investigated as front-ends to well-head gas upgrading to produce crude oil via the Fischer-Tropsch synthesis. Furthermore a well-to-wheel comparison of synthetic natural gas, methanol, ethanol, dimethyl ether, Fischer-Tropsch diesel and synthetic gasoline was performed. The comparison used woody biomass as feedstock and computed mass and energy balances for complete plants from gasifier to fuel as well as for lignocellulosic ethanol production by fermentation. Efficiency in regard to feedstock to travel distance (Well-to-Wheel) and the cost of transportation was also investigated. Ammonia is one of the most valuable chemicals for modern agriculture. Current production is almost entirely based on fossil fuels. Thus small-scale production of ammonia from renewable feedstocks was also investigated

Techno-Economic Aspects of Production, Storage and Distribution of Ammonia

The cost of green ammonia is determined primarily by its production cost, but it is also influenced by the cost of distribution and storage. Production costs are a function of plant location, size, and whether the plant is islanded or semi-islanded, that is whether the power source is variable renewable energy (VRE) or grid electricity. Capital costs for a green ammonia plant consist of equipment for the production of hydrogen (electrolyzer) and nitrogen (air separation), ammonia synthesis (Haber–Bosch, compressors and separators) and storage. Operating costs are mainly due to power consumption. The electrolyzer dominates both capital and operating costs in the manufacture of green ammonia. Ammonia is stored in either pressurized or refrigerated vessels with the latter preferred for large scale storage. Distribution of ammonia may involve several transport modes depending on the location of the production and consumption sites. Inland transport can involve pipelines, trains, and trucks, and offshore shipping is generally done with medium, large or very large gas carrier vessels with refrigerated tanks. A case study to supply a fleet of 36 ultralarge container vessels (ULCVs) operating between the ports of Shanghai and Rotterdam is used to exemplify the combination of production, storage and transportation costs

Reproductive factors and risk of mortality in the European Prospective Investigation into Cancer and Nutrition; a cohort study

Background: Reproductive events are associated with important physiologic changes, yet little is known about how reproductive factors influence long-term health in women. Our objective was to assess the relation of reproductive characteristics with all-cause and cause-specific mortality risk. Methods: The analysis was performed within the European Investigation into Cancer and Nutrition prospective cohort study, which enrolled > 500,000 women and men from 1992 to 2000, who were residing in a given town/geographic area in 10 European countries. The current analysis included 322,972 eligible women aged 25-70 years with 99 % complete follow-up for vital status. We assessed reproductive characteristics reported at the study baseline including parity, age at the first birth, breastfeeding, infertility, oral contraceptive use, age at menarche and menopause, total ovulatory years, and history of oophorectomy/hysterectomy. Hazard ratios (HRs) and 95 % confidence intervals (CIs) for mortality were determined using Cox proportional hazards regression models adjusted for menopausal status, body mass index, physical activity, education level, and smoking status/intensity and duration. Results: During a mean follow-up of 12.9 years, 14,383 deaths occurred. The HR (95 % CI) for risk of all-cause mortality was lower in parous versus nulliparous women (0.80; 0.76-0.84), in women who had ever versus never breastfed (0.92; 0.87-0.97), in ever versus never users of oral contraceptives (among non-smokers; 0.90; 0.86-0.95), and in women reporting a later age at menarche (>= 15 years versus < 12; 0.90; 0.85-0.96; P for trend = 0.038). Conclusions: Childbirth, breastfeeding, oral contraceptive use, and a later age at menarche were associated with better health outcomes. These findings may contribute to the development of improved strategies to promote better long-term health in women

Adherence to the World Cancer Research Fund/American Institute for Cancer Research cancer prevention recommendations and risk of in situ breast cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.

BACKGROUND: Even though in situ breast cancer (BCIS) accounts for a large proportion of the breast cancers diagnosed, few studies have investigated potential risk factors for BCIS. Their results suggest that some established risk factors for invasive breast cancer have a similar impact on BCIS risk, but large population-based studies on lifestyle factors and BCIS risk are lacking. Thus, we investigated the association between lifestyle and BCIS risk within the European Prospective Investigation into Cancer and Nutrition cohort. METHODS: Lifestyle was operationalized by a score reflecting the adherence to the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) cancer prevention recommendations. The recommendations utilized in these analyses were the ones pertinent to healthy body weight, physical activity, consumption of plant-based foods, energy-dense foods, red and processed meat, and sugary drinks and alcohol, as well as the recommendation on breastfeeding. Cox proportional hazards regression was used to assess the association between lifestyle score and BCIS risk. The results were presented as hazard ratios (HR) and corresponding 95% confidence intervals (CI). RESULTS: After an overall median follow-up time of 14.9 years, 1277 BCIS cases were diagnosed. Greater adherence to the WCRF/AICR cancer prevention recommendations was not associated with BCIS risk (HR = 0.98, 95% CI 0.93-1.03; per one unit of increase; multivariable model). An inverse association between the lifestyle score and BCIS risk was observed in study centers, where participants were recruited mainly via mammographic screening and attended additional screening throughout follow-up (HR = 0.85, 95% CI 0.73-0.99), but not in the remaining ones (HR = 0.99, 95% CI 0.94-1.05). CONCLUSIONS: While we did not observe an overall association between lifestyle and BCIS risk, our results indicate that lifestyle is associated with BCIS risk among women recruited via screening programs and with regular screening participation. This suggests that a true inverse association between lifestyle habits and BCIS risk in the overall cohort may have been masked by a lack of information on screening attendance. The potential inverse association between lifestyle and BCIS risk in our analyses is consistent with the inverse associations between lifestyle scores and breast cancer risk reported from previous studies

Numerical Analysis of Condensation and Frost in Rotary Heat Exchangers

In this thesis, a three-dimensional mathematical model is developed and implemented using COMSOL Multiphysics - a platform for physics-based modeling and simulation. The numerical model solves a conjugated heat transfer problem for the air stream and heat exchange media with only wheel data and inlet flow properties needed as input. The model was validated using previously established effectiveness correlations for a comparable regenerative heat exchanger but needs further validation. Proper scaling analysis was performed to establish the simultaneously developing Nusselt numbers in the entrance region from incomplete tabular data sources, and a new local peripheral Nusselt number function was defined from the flow geometry to take into account the variable local heat flux around the periphery. Results indicate that the local properties at any cross-section may differ significantly from the bulk properties, suggesting that condensation may be present locally in pockets of near-stagnant regions for a considerable length of the wheel

Woody biomass-based transportation fuels – A comparative techno-economic study

Production of synthetic vehicle fuels from biomass is a hot topic. There are several alternative fuels to consider when evaluating properties such as cost of production and energy efficiency to both product and final use in a road vehicle. Thermochemical conversion via gasification and downstream synthesis of fuels as well as biochemical conversion of woody biomass to ethanol is considered in this paper. The vehicle fuels considered in this paper include methanol, ethanol, synthetic natural gas, Fischer–Tropsch diesel, dimethyl ether and synthetic gasoline from the methanol-to-gasoline process. The aim of the study is to evaluate all the different fuels on the same basis. The production cost of the various fuels is estimated as well as the overall investment cost. Well-to-wheel energy efficiency calculations were performed to evaluate how far a vehicle can travel on the fuel produced from a specific amount of feedstock. The production cost of the fuel as a function of distance travelled is also presented. Of the fuels considered in this study, dimethyl ether manages the highest efficiency from feedstock to travelled distance and manages to do so at the lowest cost. Ethanol produced from woody biomass is the most inefficient and expensive fuel, when considering biomass harvesting and transport, the production and road use (ignoring fuel distribution), in this study due to low yields in fuel production. Total investment cost for ethanol is considerably lower at MM$281 compared to the thermochemical fuels that ranges from MM$ 580 to MM$760. The production costs of the various fuels range from$79.9/MW h for synthetic natural gas to 139.6 $/MW h for Fischer–Tropsch diesel. The production cost translates to a travel cost ranging from$4.98/100 km for dimethyl ether to $8.51/100 km for ethano

A new process for well-head gas upgrading

As oil-prices and environmental concerns are increasing, it is of interest to better use the well-head gas. This light fraction co-produced with petroleum is generally flared and in this paper a method for upgrading and returning the co-product to the petroleum stream is suggested. The method is based on a conversion of the gas to synthesis gas and upgrading this synthesis gas into liquid hydrocarbons. But as the placement of such systems would be remote, the design has been performed using the following criteria. First of all the system has to be robust in design and secondly it has to be self-sustaining in that no additional feedstocks or chemicals are required for its operation and thirdly, the product should be crude oil compatible. In the paper, the system has been outlined, the major unit operations designed and heat and mass balances have been determined. Six cases have been compared, differing in reforming and oxygen generation technology. The comparison has been made on both a technical and production economic premises. In each case the investment cost has been determined and from this, and the calculated produced hydrocarbons, a production cost per barrel has been determined. The production of hydrocarbons well-head gas is a viable route and the production cost for the hydrocarbons vary between $71 and$156 a barrel, with the lower cost being quite attractive with the crude prices of recent years (around $100 a barrel). The production cost is however heavily influenced by the investment cost and the fact that the stranded natural gas is considered free. The production of an alternative, upgraded fuel would be a possibility; this however warrants additional investment in both production equipment and infrastructure