Comparison of Chemical Absorbents Used for CO2 Capture in Coal-Fired Power Plants.

Climate change conference was hold in Copenhagen in 2009, global warming became the worldwide focus once again. China as a developing country has paid more attention for this environmental problem. In China, a large part of carbon dioxide is emitted to the atmosphere from combustion of fossil fuels in power plants. How to control emission of the greenhouse gas into atmosphere is becoming an urgent concern. Among numerous methods, CO2 capture is the hope to limit the amount of CO2 emitted into the air. The well-established method for CO2 capture is to remove CO2 by absorption into solutions in conventional equipment. Absorbents used for CO2 and H2S capture are important choice for CO2 capture technology. It is related to the cost and efficiency of plant directly and is essential to investigate the proposed CO2 and H2S absorbents.

Safety assessment of underground vehicles passing over highly resilient straight tracks in the presence of a broken rail

In this paper, vehicle-track interaction for a new slab track design, conceived to reduce noise and vibration levels has been analyzed, assessing the derailment risk for trains running on curved track when encountering a broken rail. Two different types of rail fastening systems with different elasticities have been analysed and compared. Numerical methods were used in order to simulate the dynamic behaviour of the train-track interaction. Multibody system (MBS) modelling techniques were combined with techniques based on the finite element method (FEM). MBS modelling was used for modelling the vehicle and FEM for simulating the elastic track. The simulation model was validated by comparing simulated results to experimental data obtained in field testing. During the simulations various safety indices, characteristic of derailment risk, were analysed. The simulations realised at the maximum running velocity of 110 km/h showed a similar behaviour for several track types. When reducing the running speed, the safety indices worsened for both cases. Although the worst behaviour was observed for the track with a greater elasticity, in none of the simulations did a derailment occur when running over the broken rail.

Safety assessment of underground vehicles passing over highly resilient curved tracks in the presence of a broken rail

Vehicle–track interaction for a new resilient slab track designed to reduce noise and vibration levels was analysed, in order to assess the derailment risk on a curved track when encountering a broken rail. Sensitivity of the rail support spacing of the relative position of the rail breakage between two adjacent rail supports and of running speed were analysed for two different elasticities of the rail fastening system. In none of the cases analysed was observed an appreciable difference between either of the elastic systems. As was expected, the most unfavourable situations were those with greater rail support spacing and those with greater distance from the breakage to the nearest rail support, although in none of the simulations performed did a derailment occur when running over the broken rail. When varying the running speed, the most favourable condition was obtained for an intermediate speed, due to the superposition of two antagonistic effects.

Improved design of an overhead rail current conductor for application in underground lines

Overhead rail current collector systems for railway traction offer certain features, such as low installation height and reduced maintenance, which make them predominantly suitable for use in underground train infrastructures. Due to the increased demands of modern catenary systems and higher running speeds of new vehicles, a more capable design of the conductor rail is needed. A new overhead conductor rail has been developed and its design has been patented [13]. Modern simulation and modelling techniques were used in the development approach. The new conductor rail profile has a dynamic behaviour superior to that of the system currently in use. Its innovative design permits either an increase of catenary support spacing or a higher vehicle running speed. Both options ensure savings in installation or operating costs. The simulation model used to optimise the existing conductor rail profile included both a finite element model of the catenary and a three-dimensional multi-body system model of the pantograph. The contact force that appears between pantograph and catenary was obtained in simulation. A sensitivity analysis of the key parameters that influence in catenary dynamics was carried out, finally leading to the improved design.

Comparison of vibration and rolling noise emission of resilient and solid monobloc railway wheels in underground lines

Flat or worn wheels rolling on rough or corrugated tracks can provoke airborne noise and ground-borne vibration, which can be a serious concern for nearby neighbours of urban rail transit lines. Among the various treatments used to reduce vibration and noise, resilient wheels play an important role. In conventional resilient wheels, a slightly prestressed V­shaped rubber ring is mounted between the steel wheel centre and tyre. The elastic layer enhances rolling noise and vibration suppression, as well as impact reduction on the track. In this paper the effectiveness of resilient wheels in underground lines, in comparison to monobloc ones, is assessed. The analysed resilient wheel is able to carry greater loads than standard resilient wheels used for light vehicles. It also presents a greater radial resiliency and a higher axial stiffness than conventional V­wheels. The finite element method was used in this study. A quarter car model was defined, in which the wheelset was modelled as an elastic body. Several simulations were performed in order to assess the vibrational behaviour of elastic wheels, including modal, harmonic and random vibration analysis, the latter allowing the introduction of realistic vertical track irregularities, as well as the influence of the running speed. Due to numerical problems some simplifications were needed. Parametric variations were also performed, in which the sensitivity of the whole system to variations of rubber prestress and Poisson’s ratio of the elastic material was assessed.Results are presented in the frequency domain, showing a better performance of the resilient wheels for frequencies over 200 Hz. This result reveals the ability of the analyzed design to mitigate rolling noise, but not structural vibrations, which are primarily found in the lower frequency range.

Comparison of CO2 from coal captureprocesses and valorisation technologies

Coal is the most plentiful and evenly distributed fossil fuel worldwide. Based on current production, it is estimated that the reserves will last approximately 130 years. Its use worldwide has been increasing, mainly due to consumption by emerging countries. CO2 emissions generated by combustion and the repercussions of such on climate change support the view that it could no longer be used. CO2 capture may be the solution to continue using it, which would cater for the growing energy demand worldwide. The aim of this study is to compare different processes concerning CO2 capture that may be economically viable, ultimately showing that coal, a fossil energy source widely distributed around the world, can, as a result of using different CO2 capture processes, be used as a clean source of electricity. Hence, in places where geological hurdles may render the costs of CO2 storage considerably higher, since it might have to travel far, coal may be used for other purposes, thus valorizing CO2 within the industrial sector. This research is focused on the technical and economic comparison of the most relevant CO2 capture projects designed in Spain using different existing technologies. The oxyfuel project in Ciuden (Leon, Spain), the IGCC Elcogas, precombustion CO2-capture project (Puertollano, Spain) and the postcombustion project in Carboneras (Almeria, Spain) will be analyzed in order to assess the options available to valorizecaptured CO2. Valorizing captured CO2 may be an adequate solution in areas where, although CO2 capture is still possible, storage is not equally so, thus generating a further benefit. The possible uses of CO2 will be assessed in vegetable growing greenhouses, harnessing CO2 in vegetable life cycles. This will also be used in growing algae for subsequent biodiesel production. Both CO2capture and valorizing will eventually lead to the clean use of coal, which will thus enhance the level of self-supply, aiding the development of electric vehicles, which require large amounts of electricity, as well as improve the level of energy autonomy in countries around the world. Another type of fuel, biodiesel, will also be obtained, without this affecting international food prices.

Estudio energético comparativo de diferentes configuraciones de ciclo combinado

El objetivo del presente proyecto consiste en la modelización y optimización de una planta de gasificación integrada en ciclo combinado de 400 MW de potencia neta, mediante el uso del programa Cycle-Tempo, desarrollado por la Universidad de Delft. Para la modelización de la planta, se ha dividido en sus dos unidades principales: la isla de gasificación y el ciclo combinado. Para la validación del modelo de la isla de gasificación, se ha utilizado una composición de referencia de un combustible gasificable y se ha obtenido la composición del gas de síntesis esperada. Se han modelado y optimizado varias configuraciones de ciclo combinado, variando los parámetros característicos de la caldera de recuperación de calor. Se ha realizado la integración de las dos unidades para maximizar la potencia entregada por la planta. Finalmente, se ha estimado el balance anual de energía del ciclo combinado alimentado con gas natural y con el gas de síntesis, con el fin de comparar las rentabilidades económicas obtenidas. Mediante el estudio realizado, se deduce que la forma más eficiente de producir energía, a partir del uso del carbón, es la tecnología de gasificación integrada en ciclo combinado, pese a que su rendimiento sea inferior al ciclo combinado alimentado con gas natural. ABSTRACT The aim of this project is the modeling and optimization of an integrated gasification combined cycle plant of 400 MW net power, using the Cycle-Tempo program, developed by the University of Delft. For the modeling of the plant, it has been divided into its two main units: the island of gasification and the combined cycle. For the model validation of the gasification island, a reference composition of a gasifiable fuel has been used and the expected synthesis gas composition was obtained. Several configurations of combined cycle have been modeled and optimized by varying the characteristic parameters of the heat recovery steam generator. It has made the integration of the two units to reach maximum optimization of power, which has been delivered by the plant. Finally, it has been estimated the annual energy balance for the combined cycle plant fueled with natural gas and with syngas, in order to compare the profitability obtained with each one. Through the study, it is deduced that the most efficient way to produce energy from the use of coal, is the integrated gasification combined cycle technology, although their performance is lower than that obtained from the combined cycle fueled with natural gas.

Underground parking structure built with deep foundations and vault precast elements in Spain

In many cases the only places available for the construction of a new car park are the existing streets or roads. These streets may also have important or historic buildings very close to the structure, which means that they cannot be disturbed in any way during the construction of the parking structure. In many cases the only places available for the construction of a new car park are the existing streets or roads. These streets may also have important or historic buildings very close to the structure, which means that they cannot be disturbed in any way during the construction of the parking structure.

AFBC of coal with tyre rubber. Influence of the co-combustion variables on the mineral matter of solid by-products and on Zn lixiviation

The study focuses on the generation and distribution of mineral species in fly and bottom ashes. These were formed during a fluidised co-combustion of a fossil fuel (coal) and a non-fossil fuel (tyre rubber) in a small fluidised bed combustor (7cm x 70cm). The pilot plant had continuous fuel feed using varying ratios of coal and rubber. The study also focuses on the lixiviation behaviour of metallic elements with the assessement of zinc recovering.

Coal purchase optimization: a review from Spain

The study addresses the need to manage the risk of the purchase price of coal in a power company by changing the management model of the purchasing department. It eliminates the risk of price reduces the cost of buying coal and optimizing the performance of all electricity generation plants belonging to the company. You get more flexibility and optionallity to gain additional benefits both economic and efficiency in the supply to our generation fleet. The tools to achieve the above purpose will be financial derivatives that will be used as elements of management and not as mere speculation in the markets.

Natural ventilation in underground wine cellars

The main objective of this research is to promote passive thermal design techniques in the construction of wineries. Natural ventilation in underground cellars is analyzed, focusing on the entrance tunnel, the ventilation chimney and the cave. A monitoring system was designed in order to detect changes in the indoor conditions and outdoor air infiltration. Monitoring process was carried out during one year. Results show the influence of outside temperature, ventilation chimney and access tunnel on the conditions inside the underground cellar. During hot periods, natural ventilation has a negligible influence on the indoor ambience, despite the permanently open vents in the door and chimney. The tunnel and ventilation chimney work as a temperature regulator, dampening outside fluctuations. Forced ventilation is necessary when a high air exchange ratio is needed. During cold periods, there is greater instability as a result of increased natural ventilation. The temperature differences along the tunnel are reduced, reflecting a homogenization and mixing of the air. The ventilation flow is sufficient to modify the temperature and relative humidity of the cave. Forced ventilation is not necessary in this period. During the intermediate periods --autumn and spring-- occurs different behaviors based on time of day.

Characterization of underground cellars in the Duero Basin by GNSS, LIDAR and GPR techniques

The underground cellars of the Duero River basin are part of spread and damaged agricultural landscape which is in danger of disappearing. These architectural complexes are allocated next to small towns. Constructions are mostly dug in the ground with a gallery down or "barrel" strait through which you access the cave or cellar. This wider space is used to make and store wine. Observation and detection of the winery both on the outside and underground is essential to make an inventory of the rural heritage. Geodetection is a non-invasive technique, suitable to determinate with precision buried structures in the ground. The undertaken works include LIDAR survey techniques, GNSS and GPR obtained data. The results are used to identify with centimetric precision construction elements forming the winery. Graphic and cartographic obtained documents allow optimum visualization of the studied field and can be used in the reconstruction of the place.

Sewage sludge gasification. Dolomite performance under different operating conditions

Gasification is a technology that can replace traditional management alternatives used up to date to deal with this waste (landfilling, composting and incineration) and which fulfils the social, environmental and legislative requirements. The main products of sewage sludge gasification are permanent gases (useful to generate energy or to be used as raw material in chemical synthesis processes), liquids (tars) and char. One of the main problems to be solved in gasification is tar production. Tars are organic impurities which can condense at relatively high temperatures making impossible to use the produced gases for most applications. This work deals with the effect of some primary tar removal processes (performed inside the gasifier) on sewage sludge gasification products. For this purpose, analysis of the gas composition, tar production, cold gas efficiency and carbon conversion were carried out. The tests were performed with air in a laboratory scale plant consisting mainly of a bubbling bed gasifier. No catalyzed and catalyzed (10% wt of dolomite in the bed and in the feeding) tests were carried out at different temperatures (750ºC, 800ºC and 850ºC) in order to know the effect of these parameters in the gasification products. As far as tars were concerned, qualitative and quantitative tar composition was determined. In all tests the Equivalence Ratio (ER) was kept at 0.3. Temperature is one of the most influential variables in sewage sludge gasification. Higher temperatures favoured hydrogen and CO production while CO2 content decreased, which might be partially explained by the effect of the cracking, Boudouard and CO2 reforming reactions. At 850ºC, cold gas efficiency and carbon conversion reached 49% and 76%, respectively. The presence of dolomite as catalyst increased the production of H2 reaching contents of 15.5% by volume at 850 °C. Similar behaviour was found for CO whereas CO2 and CnHm (light hydrocarbons) production decreased. In the presence of dolomite, a tar reduction of up to 51% was reached in comparison with no catalyzed tests, as well as improvements on cold gas efficiency and carbon conversion. Several assays were developed in order to test catalyst performance under more rough gasification conditions. For this purpose, the throughput value (TR), defined as kg sludge “as received” fed to the gasifier per hour and per m2 of cross sectional area of the gasifier, was modified. Specifically, the TR values used were 110 (reference value), 215 and 322 kg/h·m2. When TR increased, the H2, CO and CH4 production decreased while the CO2 and the CnHm production increased. Tar production increased drastically with TR during no catalysed tests what is related to the lower residence time of the gas inside the reactor. Nevertheless, even at TR=322 kg/h·m2, tar production decreased by nearly 50% with in-bed use of dolomite in comparison with no catalyzed assays under the same operating conditions. Regarding relative tar composition, there was an increase in benzene and naphthalene content when temperature increased while the content of the rest of compounds decreased. The dolomite seemed to be effective all over the range of molecular weight studied showing tar removal efficiencies between 35-55% in most cases. High values of the TR caused a significant increase in tar production but a slight effect on tar composition.

Underground dwellings in the Tajuña valley, Madrid, Spain and their bioclimatic adaptation

Underground dwellings are the maximum example of the vernacular architecture adaptation to the climatic conditions in areas with high annual and daily thermal fluctuations. This paper summarizes the systematic research about the energy performance of this popular architecture and their adaptation to the outdoor conditions in the case of the low area of the River Tajuña and its surroundings. Some considerations on their maintenance and renovation arise from the research.