Biomass fast pyrolysis energy balance of a 1kg/h test rig

The present paper offers a methodological approach towards the estimation and definition of enthalpies constituting an energy balance around a fast pyrolysis experiment conducted in a laboratory scale fluid bed with a capacity of 1 kg/ h. Pure N2 was used as fluidization medium at atmospheric pressure and the operating temperature (∼500°C) was adjusted with electrical resistors. The biomass feedstock type that was used was beech wood. An effort was made to achieve a satisfying 92.5% retrieval of products (dry basis mass balance) with the differences mainly attributed to loss of some bio-oil constituents into the quenching medium, ISOPAR™. The chemical enthalpy recovery for bio-oil, char and permanent gases is calculated 64.6%, 14.5% and 7.1%, respectively. All the energy losses from the experimental unit into the environment, namely the pyrolyser, cooling unit etc. are discussed and compared to the heat of fast pyrolysis that was calculated at 1123.5 kJ per kg of beech wood. This only represents 2.4% of the biomass total enthalpy or 6.5% its HHV basis. For the estimation of some important thermo-physical properties such as heat capacity and density, it was found that using data based on the identified compounds from the GC/MS analysis is very close to the reference values despite the small fraction of the bio-oil components detected. The methodology and results can help as a starting point for the proper design of fast pyrolysis experiments, pilot and/or industrial scale plants

Process analysis and comparative assessment of advanced thermochemical pathways for e-kerosene production

Climate change and energy supply are major driving forces for the promotion of sustainable fuels production. In the aviation sector, due to inherent difficulties to adopt electrification methods for long distance flights, the successful implementation of sustainable aviation fuel (SAF) is crucial for the achievement of greenhouse gas emissions mitigation strategies. This study presents four different pathways for the valorization of captured CO2 into synthetic kerosene using renewable hydrogen and demonstrates the comparative assessment in terms of various technical and aspects such as hydrogen consumption, thermal energetic efficiency and produced e-kerosene quality. Two are based on the production of Low Temperature Fischer-Tropsch synthesis based on CO (LTFT) or CO2 conversion to fuels, while the other two are based on the valorization and upgrading of light alcohols (methanol and ethanol) derived from CO2 hydrogenation. The process models were developed in Aspen Plus. Simulation results revealed that the LTFT pathway is the most efficient pathway to maximize the jet fuel yield with the lower energy and exergy losses. Indicatively for that case, 90.7% of the initial carbon is utilized for kerosene fraction synthesis, the overall thermal efficiency reaches up to 70.9% whereas the plant exergetic efficiency is 72.6%. The basic properties of the produced e-kerosene at all cases meet with the required Jet-A1 specifications or are close to them

Technoeconomic and Environmental Assessment of Biomass Chemical Looping Gasification for Advanced Biofuel Production

Chemical looping gasification is a promising biomass conversion technology that could produce sustainable liquid transportation fuels on a large scale to reduce fossil fuel dependency. The current paper examines the technical, economic, and environmental performance of a biomass-to-liquid (BtL) process based on chemical looping gasification and Fischer-Tropsch synthesis. Two biomass feedstocks, i.e., pine forest residues and wheat straw, are selected for assessing the complete BtL production chain. The results of process simulations showed that both biomass types are suitable gasification feedstocks, with an overall energy efficiency of 53% and 52% for pine residues and wheat straw, respectively. The economic results show that the breakeven selling prices (BESP) are €816 and €781 per m3 for the pine forest residues and wheat straw pellets, respectively. However, if low-grade excess heat valorisation and CO2 credits are considered, the BESPs could meet or become lower than the target value of €700 per m3, making the BtL plant competitive with other biofuel plants. The CO2 avoidance cost is estimated at €74.4/tCO2 for pine residues and €61.3/tCO2 for wheat straw, when replacing fossil fuels. The results of the life cycle assessment study showed that the produced biofuels fulfil the requirements of the EU Renewable Energy Directive II, achieving the reduction in greenhouse gases emissions of up to 79% without carbon capture and storage (CCS) and up to 264% with CCS compared to fossil fuels

SmartWall

Following the need of urban areas to maintain the existing building stock and simultaneously upgrade the overall energy performance, the renovation down-to-nZEB state has already become a necessity. In this regard, a vast range of prefabricated solutions have been developed lately. The main objective of such solutions would be not only to constitute an effective system to tackle building energy consumption but also to be versatile in terms of implementation and economic viability. In this regard, an adaptable off-site prefabricated envelope solution with an embodied HVAC system called “SmartWall” has been developed. The SmartWall can minimise thermal losses through the well-insulated envelope while, at the same time, its integrated HVAC system efficiently maintains indoor thermal comfort conditions. This study examines the virtual implementation of the SmartWall as a “Plug-n-Play” renovation solution to reach the nZEB state of a typical apartment in a multi-family residence in Athens. The analysis considers two SmartWall alternatives using conventional and eco-friendly materials. The results indicate a reduction of 88% in primary energy consumption without affecting thermal comfort conditions and highlighting that the nZEB state can be ensured if the SmartWall application is enhanced with photovoltaic modules

Chemical Looping Gasification for Sustainable Production of Biofuels – The CLARA Project

Within the scope of the Horizon 2020 project CLARA, a novel biomassto-biofuel process chain is being developed. The fuel production plant consists of a chemical looping gasifier for the production of a raw syngas, a gas treatment train to provide the required syngas composition for the subsequent synthesis, and a FischerTropsch (FT) reactor to covert the syngas into liquid FT-crude. This crude can then be purified and upgraded to ready-to-use second generation drop-in biofuels in existing state-of-the-art refineries. So far, various oxygen carrier materials were evaluated through lab-scale test regarding their suitability for chemical looping gasification. Ilmenite proved to be the most promising candidate and was therefore selected for further investigations. Successful test campaigns in a small CLG pilot unit supported the findings made in lab-scale units. A novel pre-treatment concept of wheat straw based on pelleting and additivation was developed, which allows for an economic decentralized production and avoids bed agglomeration in a chemical looping gasifier. Furthermore, a novel sour gas separation concept, allowing for an efficient removal of H2S from sour gases, was successfully tested at lab-scale. Based on the underlying technologies, the project partners derived an optimized process layout of the entire biomass-to-liquid chain, achieving competitive figures for the most important key performance indicators, such as attaining negative CO2 emissions and achieving an energetic fuel efficiency of 55 % for the entire process chain. The full process chain has been demonstrated within four weeks of pilot testing at the Technical University of Darmstadt. Currently, the full-chain BtL concept is being assessed by means of risk studies as well as techno-economic and environmental considerations

NUMERICAL INVESTIGATION OF THE EFFECT OF VACUUM INSULATION PANELS ON THE THERMAL BRIDGES OF A LIGHTWEIGHT DRYWALL ENVELOPE

This paper addresses the thermal bridges issues of a two storey lightweight steel framed envelope in which the VIPs are placed in an inner “protected” layer of the external walls. This configuration provides “protection” for the VIPs, allows flexibility in installation of façade elements and at the same time permits interventions and modifications (e.g. drilling, installation of appliances) on the internal side of the wall. The envelope is extensively analyzed in terms of all the different types of thermal bridges utilizing commercial computational tools and standardized methodologies and their effect on the overall thermal performance is evaluated. A total improvement of 33% on the heat transfer coefficient of the building is estimated. Results indicate the junctions between the external and internal walls, the external walls and the ceiling, the internal walls and the roof and the internal walls and the floor, respectively, as the most crucial thermal bridges. Different design modifications and solutions are assumed in order to further reduce the impact of the most crucial thermal bridges. The implementation of the modifications resulted to a further reduction of the overall thermal losses by 27.5%, leading to an overall thermal loss reduction by 60.5% when compared to the reference building

Thermodynamic analysis and comparison of retrofitting pre-drying concepts at existing lignite power plants

Lignite is considered as a domestic and abundant energy source for several countries. However, its high ash and moisture content have a negative effect on power plant efficiency, on cost of electricity (COE) and consequently on CO2 emissions. The aim of the present work is the investigation and optimization of existing lignite pre-drying concepts and their improvement in terms of overall plant efficiency and integration. The main process parameters examined are the heat source for drying and the respective drying medium. In the conventional lignite drying process, hot recirculating flue gas is used as a heating medium, while in the current state-of-the art pre-drying concepts, a fluidized bed drying system is considered. Different concepts are also examined including a) the utilization of preheated air as heating medium and b) the optimized integration of a heat pump as a heat source for the drying process. Based on the performed thermal cycle calculations, the plant efficiency increase is evaluated. The results of the study indicate that higher plant efficiency is expected, when focussing on the optimized pre-drying process scheme and its integration with the overall steam

Off-site prefabricated hybrid façade systems

The residential sector is responsible for the largest share of global energy consumption, while the existing building stock in Europe is relatively old. This issue, in combination with the low rate of new constructions, highlights the necessity for deep renovation of existing buildings to reach NZEB standards. At the same time, in the last decades, off-site prefabricated solutions have gained popularity in the building market, allowing the reliable and effective integration of diverse components and reducing the total renovation cost and occupants’ disturbance. The current study describes three all-in-one “Plug & Play” prefab renovation solutions and their assessment in terms of thermal, static, acoustic, and fire performance. The assessing performance is selected depending on their incorporated element as well as the national regulations of the country where the renovation solution is going to be installed. The assessment aims to ensure their characteristics’ satisfaction with the European and national requirements. In parallel, the assessment identifies the accurate behaviour of prefab façade systems both in passive and active mode and improves/optimises any possible design drawbacks

Process integration of a Calcium-looping process with a natural gas combined cycle power plant for CO2 capture and its improvement by exhaust gas recirculation

AbstractIn this study, it was sought to find an efficient way to integrate a Ca-looping process with a Natural Gas Combined Cycle (NGCC) power plant for its post-combustion CO2 capture. Compared to its application to coal combustion flue gas, Ca-looping would incur augmented energy penalty when integrated with a NGCC of which the flue gas contains only 4.0mol% CO2. The reduced CO2 concentration in the feed requires the carbonator to operate at a lower temperature and more solids to circulate between carbonator and calciner for keeping up the carbon capture efficiency at 90%. However, this study demonstrated that such negative effects could be alleviated greatly by implementing 40% exhaust gas recirculation to the NGCC with the CO2 concentration in the flue gas increasing up to 6.8%. Accordingly, the resulting net power efficiency increased notably 1.6% points in comparison to its equivalent non-EGR NGCC case and it was only 0.9% points less than amine capture case. This study exhibited that exhaust gas recirculation would be crucial in decarbonising a NGCC power plant by Ca-looping