Specific CO2 Emissions Research Articles

Effects of road slope on emission characteristics for a heavy-duty diesel vehicle based on engine-in-the-loop methodology

A dump truck with a maximum designed total mass of 24500 kg was selected to measure the emission characteristics of pollutants and carbon dioxide (CO2) under fully-loaded and unloaded conditions at the same simulated road with different road slope, same driver and vehicle model by using the engine-inthe- loop methodology. The results show that driving at gradient road will result in an increase in power and total emissions. The brake specific emissions of gaseous pollutant and CO2 are lower at gradient road, while the brake emission of particle number are higher at gradient road. Road slope affects exhaust temperature so as to affect nitrogen oxide (NOx) emissions. Under unloaded conditions, long-slope conditions are more likely to cause an increase in NOx emissions.

Pollutant emission and CO2 emission at various vehicle loading for a heavy-duty commercial vehicle by EIL methodology

Pollutants and carbon dioxide (CO2) under different vehicle loading were investigated on a dump truck with a maximum designed total mass of 18000 kg. An engine-in-the-loop (EIL) methodology was applied to achieve the test consistency because EIL can use the same road, driver and vehicle model. The results show that the total CO2 emission increases while the brake specific CO2 emission decrease as the vehicle loading increases. Both the total and specific emissions of PN increase when vehicle loading increases. The effect regularity of increasing vehicle loading on NOx, THC and CO is not significant. It is necessary to comprehensively consider the changes in the raw exhaust due to the engine operation points changes and in the SCR catalytic efficiency derived from the SCR inlet temperature variation. The DPF generation is also need to be concerned because the CO2, PN and NOx emissions will rapidly increase during this period.

DATABASE OF CERTIFICATES OF ENERGY EFFICIENCY OF BUILDINGS IN UKRAINE: ANALYSIS FOR NEW CONSTRUCTION


 
 
 Ukraine is an energy dependent country. The largest energy consumer in Ukraine is the household sector and industry. The technical characteristics of most existing serial buildings in Ukraine do not meet modern requirements for energy consumption. One of the tools to influence the reduction of consumption of construction resources is the introduction into the regulatory framework of requirements for improving energy efficiency. With the entry into force of the Law of Ukraine "On Energy Certification of Buildings", the development of an energy certificate has become mandatory for new buildings, state-owned buildings, local government buildings and in case of attracting public funds for thermal modernization of buildings. The energy certificate is developed by a certified energy auditor and entered into an open database in the Unified State System in the field of construction. The energy certificate contains an energy efficiency class determined by calculation according to the methodology of the national standard, which is developed taking into account European approaches to the calculation of energy
 
 
 
 consumption for different needs of buildings. The generalized analysis of the data from the available certificates is of considerable interest for estimating the characteristics of enclosing structures, engineering systems and equipment and the actual and estimated specific energy consumption of different types of buildings. In this study, the authors focused on the energy efficiency of new buildings (starting in 2019). The following indicators of residential and public buildings were analyzed: heat transfer resistance of external walls and translucent structures, specific energy consumption, primary energy, specific CO2 emissions, energy efficiency class. It was determined that the potential for energy savings compared to similar buildings in the European Union is significant, so improving the energy efficiency of the construction sector is an extremely important issue in Ukraine.
 
 
 
 
 

CCGT unit with a carbonation system for CO2 capture

The paper considers the issues of creating energy-efficient and environmentally friendly resource-saving energy generation technologies based on fossil fuels, solid waste and materials. A natural gas CCGT with a MSW ash carbonation unit was chosen as the research object. The prototype of the CCGT unit is the CCGT “Akademicheskaya” with an installed capacity of 230 MW. For the carbonation of MSW ash, a direct semi-dry route is used. In the calculation of the CCGT, the power and efficiency of the cycle are determined, as well as the parameters of the flue gas, which are transferred to the calculation of carbonation. As a result of calculations, it was found that this specific CO2 emissions from the power plant using carbonation can be reduced by almost 20% from 403 to 329 g kWh-1, however, a large amount of required MSW (2.6-6.7 kg per kg of flue gases) causes certain difficulties for the implementation of the project.

Utilization of Low-Rank Coals for Producing Syngas to Meet the Future Energy Needs: Technical and Economic Analysis

Increased energy demand in recent decades has resulted in both an energy crisis and carbon emissions. As a result, the development of cleaner fuels has been under the research spotlight. Low-rank coals are geographically dispersed, abundant, and cheap but are not utilized in conventional processes. Syngas can be produced from coal-using gasification which can be used in various chemical engineering applications. In this study, the process model for syngas production from low-rank coal is developed and the effects of various process parameters on syngas composition are evaluated, followed by a technical and economic evaluation. The syngas production rate for the low-rank coal has been evaluated as 25.5 kg/s, and the contribution to H2 and CO production is estimated as 1.59 kg/s and 23.93 kg/s, respectively. The overall syngas production and energy consumed in the process was evaluated as 27.68 kg/GJ, and the CO2 specific emissions were calculated as 0.20 (mol basis) for each unit of syngas production. The results revealed that the syngas production efficiency for low-rank coals can be as high as 50.86%. Furthermore, the economic analysis revealed that the investment and minimum selling prices per tonne of syngas production are EUR 163.92 and EUR 180.31, respectively.

Heat-pump-assisted reactive distillation for direct hydration of cyclohexene to cyclohexanol: a sustainable alternative

As an important raw material to produce many useful chemicals, cyclohexanol production attracts much attention to obtain high purity product, leading to high energy consumption. Traditional technologies include three routes: oxidation of cyclohexane, hydrogenation of phenol and direct hydration of cyclohexene. Without the risk of explosion and having a low price of raw material, the direct hydration of the cyclohexene route is selected in this paper. Four processes with different phase-refluxed or with/without a stripper configuration for the direct hydration of cyclohexene are investigated, including aqueous-phase-refluxed conventional reactive distillation (ACRD), an organic-phase-refluxed conventional reactive distillation (OCRD), an aqueous-phase-refluxed reactive distillation with a stripper (ARDS), and an Organic-phase-refluxed reactive distillation with a stripper (ORDS). The results show that the conventional reactive distillation (ACRD and OCRD) has a relatively low capital cost but has high operating costs due to high energy consumption, while the ARDS and ORDS show better performance than the OCRD and ACRD, but still have considerably high energy consumption. The ORDS shows better performance due to a slightly higher conversion of cyclohexene to cyclohexanol and the potential to achieve the better performance in terms of energy and economic considerations. Integration of a novel confirmation with heat pump assisted reactive distillation (HPRD) is investigated to further improve the energy efficiency and thereby reduce CO2 emission. The results show that the HPRD process realizes a significant energy saving of 58% and achieves 62% and 24% reductions in specific CO2 emission and total annualized cost, respectively, compared to ORDS, demonstrating high feasibility and environmental sustainability.

Techno-economic comparison of technology options for deep decarbonization and electrification of residential heating.

This study aims to provide detailed information on the key technologies that utilize renewables for decarbonization and electrification of the residential heating sector. To contextualize and compare the economics of the technologies, a levelized cost model is employed to perform a comparative analysis for a dense urban area in Switzerland. The outcome shows that decarbonization of the heat supply with a dominant share of renewables is feasible, but it is challenged by the high cost of some options. In the given context (current energy and CO2 prices, no coercive measures), the rapid shift from conventional boilers to electrification via decentralized heat pumps and/or the introduction of targeted small-scale thermal energy networks utilizing cheap local resources like industrial excess heat is the most viable option. The replacement of natural gas boilers with electrification technologies also is recommendable because it would result in a sixfold reduction in specific CO2 emissions. Wide-scale application of heat pumps may require significant electricity grid reinforcement which ultimately may escalate the costs. Large-scale district heating systems are currently relatively expensive due to the high network costs and require a sustainable financing mechanism. To speed up the energy transition, policy interventions by the government are urgently needed.

Climate assessment of single flights: Deduction of route specific equivalent CO2 emissions

Climate impact of anthropogenic activities is more and more of public concern. But while CO2 emissions are accounted in emissions trading and mitigation plans, emissions of non-CO2 components contributing to climate change receive much less attention. One of the anthropogenic emission sectors, where non-CO2 effects play an important part, is aviation. Hence, for a quantitative estimate of total aviation climate impact, assessments need to comprise both CO2 and non-CO2 effects (e.g., water vapor, nitrogen dioxide, and contrails), instead of calculating and providing only CO2 impacts. However, while a calculation of CO2 effects relies directly on fuel consumption, for non-CO2 effects detailed information on aircraft trajectory, engine emissions, and ambient atmospheric conditions are required. As often such comprehensive information is not available for all aircraft movements, a simplified calculation method is required to calculate non-CO2 impacts. In our study, we introduce a simple calculation method which allows quantifying climate assessment relying on mission parameters, involving distance and geographic flight region. We present a systematic analysis of simulated climate impact from more than 1000 city pairs with an Airbus A330-200 aircraft depending on the flight distance and flight region to derive simplified but still realistic representation of the non-CO2 climate effects. These new formulas much better represent the climate impact of non-CO2 effects compared to a constant CO2 multiplier. The mean square error decrease from 1.18 for a constant factor down to 0.24 for distance dependent factors and can be reduced even further to 0.19 for a distance and latitude dependent factor.

Techno-economic and environmental assessment of staged oxy-co-firing of biomass-derived syngas and natural gas

The utilisation of biomass is regarded as a promising technology as a negative CO2 resource and is widely under investigation. Although being a developing technology predominantly used as the axillary fuel, the interest in biomass gasification has increased since the last decade due to increased attention in sustainable bioenergy. Therefore, in this study, a novel process of biomass-derived syngas and natural gas oxy-co-firing is being investigated. Aspen Plus® is employed to develop the staged oxy-co-firing of biomass-based syngas and the natural gas cycle. The results revealed that the net power efficiencies are in the range of 42.6% and 45.5%. Furthermore, the economic assessment reveals that the LCOE increases with the increment of biomass flowrate with the highest cost of €79.6/MWh for 7 kg/s biomass mass flow rate. The effect of different biomass prices on LCOE is also investigated. It proved that the implementation of biomass with the price of €80/tdry results in the competitive LCOE to the state-of-the-art power cycles without carbon capture system (€62.9/MWh). On the other hand, the environmental analysis reveals that in order to have a negative CO2 emission power cycle, the minimum biomass flowrate should be at 7 kg/s which results in specific negative CO2 emission and total life cycle of CO2 emission of 195.5 and 168.5 kg CO2/MWh, respectively.

Decarbonization of Fossil Energy-intensive Industrial Processes Using Innovative Calcium Looping Technology

Mitigation of fossil carbon dioxide emissions from the main industrial sectors is a key element in the fight against global warming and climate change. In this respect, the main fossil energy-intensive processes (e.g., heat and power generation, cement, iron and steel, chemical applications etc.) are to be decarbonized for the future low-carbon economy. This paper is evaluating the post-combustion carbon capture based on innovative Calcium Looping (CaL) technology to be applied for decarbonization of various fossil-based industrial applications e.g., power generation, cement, iron and steel production. As illustrative cases, relevant industrial size systems are considered (e.g., 1,000 MW power plants, 4 Mt/year steel mills, 1 Mt/year cement plants). As benchmarks, similar processes without carbon capture as well as ones using chemical gas-liquid absorption for carbon capture are considered to assess the energy penalty for decarbonization. The decarbonized systems have 90 % carbon capture rate. As assessment tools a wide range of process systems engineering elements are used as follow: mathematical modelling and simulation using ChemCAD software, model validation based on experimental data, thermal integration analysis using pinch method for optimization of overall energy efficiency, technical and environmental evaluation to quantify the key performance indicators. As the results show, the innovative calcium looping technology for post-combustion carbon capture has significant advantages in comparison to the chemical gas-liquid absorption in term of higher overall plant energy efficiency (by about 2 net energy efficiency percentage points), lower CO2 capture energy penalty (7 - 8 vs. 10 net energy efficiency percentage points), reduced specific CO2 emissions etc.

The Study of the Faba Bean Waste and Potato Peels Recycling for Pellet Production and Usage for Energy Conversion

The article presents the results of a study on the preparation and use of faba bean waste and potato peel pellets for energy purposes. Physical and mechanical characteristics (moisture, density, ash content) of faba bean waste and potato peel pellets were investigated. The largest fraction of flour was formed on a sieve with 1 mm holes: faba bean waste—28.2 ± 2.02 g, potato peels—29.09 ± 0.73 g. For this experiment, samples were taken by mixing faba bean waste (four variants) and potato peel in the ratio of 1:1; 1:2; 1:3; 1:4 by volume (12 samples). It was found in this study that the density of pellets (DM) ranged from 1226.22 ± 13.88 kgm−3 to 1349.79 ± 6.79 kgm−3. The pellet moisture ranged from 6.70 ± 0.04% to 3.64 ± 0.13%. The lower calorific value of dry fuel pellets ranged from 15.27 ± 0.43 MJkg−1 to 16.02 ± 0.50 MJkg−1. The ash content of the pellets ranged from 8.05 ± 0.57% to 14.21 ± 0.05%. The ST temperature of the experimentally measured mixture of faba bean waste and potato peel pellets ranged from 924 to 969 °C; the DT temperature ranged from 944 to 983 °C; the HT temperature ranged from 1073 to 1202 °C, and a change in FT temperature from 1174 to 1234 °C was observed. The temperatures were sufficiently high to melt the ash. Specific emissions of CO2, CO, NOx and CxHy did not exceed the maximum levels allowed. In summary, from the results of the study of the physical properties, combustion, and emissions of waste beans and potato peel pellets (all samples), it is evident that they are used for biofuels. The combustion process of this type of pellet is characterized by efficient combustion and minimal emissions to the atmosphere.

Conceptual design, exergoeconomic analysis and multi-objective optimization for a novel integration of biomass-fueled power plant with MCFC-cryogenic CO2 separation unit for low-carbon power production

In the present study, the low-Carbon power production concept is proposed to introduce a novel integration. In the Bio-Energy Carbon Capture and Storage framework, Municipal Solid Waste is regarded as the main fuel for the system. To administer the analysis, a combination of a downdraft gasifier, a directly fired-gas turbine, Molten Carbonate Fuel Cell, Organic Rankine Cycle, and cryogenic CO2 separation unit is considered. The proposed integration is investigated from themodynamic, exergoeconomic, and environmental points of view. The multi-objective optimization is also conducted to minimize the CO2 emission and cost of electricity besides maximizing the overall exergy efficiency. By applying the optimum values for decision parameters, exergetic and economic results indicate that the combustion chamber and downdraft gasifier are identified as the component with maximum exergy destruction rate (17.44% and 14.59% of the total, respectively) due to high combustion and chemical reactions inefficiencies. Also, the net energy and exergy efficiency, cost of electricity, and specific CO2 emission result as 51.65%, 45.98%, 80.59 USD/MWh, and 101.20 kgCO2/kWh for the proposed system, respectively. The optimization results reveal that the CO2 emission was reduced by 33%. However, the exergy efficiency and cost of electricity will increase by 3% and 1.6%, respectively.

A research on the determination of energy consumption and carbon dioxide emissions in corn production in Harran plain

Due to global climate change, greenhouse gas (GHG) analyzes for agricultural production systems are becoming more common with energy analyzes. In this study, carbon dioxide (CO2) emissions in the Harran Plain due to fuel consumption in first crop seed corn production were evaluated. A total of 100 face-to-face surveys were conducted with a total of 100 producers in the Harran Plain and data were collected on fuel consumption in production processes. The calculations to determine the CO2 emissions released as a result of corn production are based on the proposed method of calculation of the fuel-based CO2 emissions in the Intergovernmental Panel on Climate Change (IPCC). The total fuel and oil consumption per unit production area (ha) for different field applications in corn production is 98 l/ha in the Harran Plain. The total fuel and oil consumption in unit production corresponds to 3645.89 MJ/ha of energy consumption, resulting in a total of 269.6 kg CO2 emissions per hectare. The specific fuel consumption, the specific energy productivity, the specific CO2 emission, the specific fuel efficiency, the specific energy consumption and the specific CO2 efficiency in seed corn production in the Harran Plain were determined to be 8.91 l/t, 3.02 kg/MJ, 24.51 kgCO2/t, 112.22 kg/l, 331.44 MJ/t and 40.80 kg/kgCO2, respectively.

Economic and environmental impacts of a proposed ‘Carbon adder' on New York’s energy market

ABSTRACT The New York Independent System Operator (NYISO) has developed a carbon-pricing proposal to reduce carbon intensive electricity generation in anticipation of future clean energy goals in the state. The proposed measure is a so-called ‘carbon adder’ on CO2 emissions from the power sector that targets the social cost of carbon amidst existing overlapping policies. The carbon adder is set as the difference between the targeted social cost of carbon and the prevailing RGGI price for CO2 emission allowances. We investigate the economic and environmental impacts from the imposition of a carbon adder on New York’s power sector. Our analysis indicates that the carbon adder gives the ‘right’ price signal for New York’s power generation to turn into a greener one and is shown to be more cost-effective than clean energy standards. Requirements for permit price floors in the RGGI market induces carbon permit retirements across RGGI states leading to small reductions in region- and country-wide emissions levels.The proposed border carbon adjustments on electricity trade are shown to further mitigate emission leakage. Key policy insights NYISO’s proposed carbon adder provides strong incentives for decarbonization and renewable power generation in the New York region. The carbon adder is shown to be more cost-effective than New York's clean energy standard measures in achieving an equivalent level of emissions reductions. This is because the carbon adder targets energy carriers by their specific CO2 emissions while the clean energy standard implicitly targets energy carriers by their specific CO2 emissions while the clean energy standard implicitly provides a uniform subsidy to all clean energy carriers. The existing RGGI price floor mechanism assures that NYISO’s unilateral use of carbon adder is environmentally effective by generating overall emission reductions in the RGGI region in order to maintain the existing price floor. Border carbon adjustments on the embodied carbon of electricity imports to New York, and an emission containment reserve, which dynamically adjusts RGGI cap as a response to RGGI price change, will likely mitigate leakage further and improve competitiveness of the New York’s energy sector.

Coal Gasification: At the Crossroad. Technological Factors

The article presents results from analyzing the state of the art achieved in the coal gasification technologies developed around the world and the demand for them. It is shown that such technologies have presently arrived at a crossroad in their development. Their future will be determined by the development prospects of coal energy as a whole. Coal still continues to play the most important role in the world energy. In recent years, external factors have become extremely negative for the development of coal energy. Among other fuels, coal produces the largest specific emissions of CO2 during its combustion, in view of which it may become the first victim of the unfolding energy decarbonization policy. Under such conditions, there is a need to diversify the coal utilization fields, primarily through manufacturing a wide range of chemical products with a high added value. This generates the need to develop the appropriate technologies, and, first of all, gasification technologies, the use of which opens the possibility of making almost the entire range of products from coal that are obtained from petroleum and natural gas. It has been determined that gasification technologies have already reached a high level of technical maturity, and a large number of gasifier designs have been proposed. It has been determined that the majority of operating coal gasification plants are presently used for manufacturing various chemical products, first of all, natural gas substitute (which is then forwarded to gas networks) and also methanol and ammonia. It is pointed out that only a few integrated gasification combined cycle plants have been implemented and planned for construction, which means that the private sector shows little interest in this technology. At the same time, such plants have quite a high potential for being used in low-carbon energy, of course, provided that the problem of disposing the captured CO2 is solved. It is shown that a large number of gasifier equipment manufacturers are available around the world. However, gasifiers are produced in single units or in a small series, which unavoidably leads to the high cost of this equipment. For the further innovative development of the gasification technology, combined efforts should be taken by the private sector and the state.

Understanding the Potential of Bio-Carbon Capture and Storage from Biomass Power Plant in Indonesia

Indonesia is currently experiencing a significant increase in population, industrialization and energy demand. As the energy demand increases, so does the production of climate-altering CO2 emission. Biomass power plants have emerged as a low carbon power generation alternative, utilizing agricultural and industrial waste. Biomass power plants have the potential of being a carbon-negative power generation technology in the near future by integrating carbon and capture storage (bio-CCS). The objective of this paper is to analyze and map potential CO2 emission in the processes of biomass power plants from gasification and firing or co-firing technology, then recommend suitable carbon capture technology based on the biomass power plant characteristics in Indonesia. The CO2 emission to be captured in the gasification process is 11-15% of the producer gas, while in co-firing it is 7-24% of the flue gas stream. Using biomass instead of coal in power plants reduces the electric efficiency and increases the plant’s in-house emission, but when analyzed in a wider boundary system it is apparent that the net GWP and CO2 emission of biomass power plants are way smaller than coal power plant, moreover when equipped with carbon capture unit. Biomass power plant that uses firing technology can reduce CO2 emission by 148% compared to typical coal power plant. Installing carbon capture unit in biomass firing power plants can further reduce the specific CO2 emission by 262%. If carbon capture technology is implemented to all existing biomass power plants in Indonesia, it could reduce the greenhouse gas emission up to 2.2 million tonnes CO2 equivalent annually. It is found that there are 3 significant designs for gasification technology: NREL design, Rhodes & Keith design and IGBCC+DeCO2 design. The first two designs are not suitable to be retrofitted into existing biomass power plants in Indonesia since they are based on a specific BCL/FERCO gasifier. While IGBCC+DeCO2 design still needs further study regarding its feasibility. While for firing, the most promising technology to be applied in the near future is solvent-based absorption because it is already on commercial scale for coal-based power plants and can be implemented for other source, e.g. biomass power plant. Bio-CCS in existing biomass power plant with firing technology is likely to be implemented in the near future compared to the gasification, because it applies the post combustion capture as an “end-of-pipe” technology which is generally seen as a more viable option to be retrofitted to existing power plants, resulting in potentially less expensive transition.

Process Improvements for Direct Reduced Iron Melting in the Electric Arc Furnace with Emphasis on Slag Operation

Steelmaking based on direct reduced iron (DRI, and its compacted derivative hot briquetted iron, HBI) is an anticipated important global alternative to current steel production based on FeOx reduction in blast furnaces due to its lower specific CO2 emission. The majority of DRI is melted and refined in the electric arc furnace with different process conditions compared to the melting of steel scrap due to its raw material composition being rather different. We provide data and analysis of slag composition of DRI charges vs. steel scrap charges for 16 industrial electric arc furnaces (EAFs). Suggestions for optimized slag operation and resulting process improvements of DRI melting in the EAF are given. A dynamic mass and energy model of the DRI melting in the EAF is introduced to illustrate the implications of the adapted slag operation on the EAF process with DRI charges.

CO2 Capture for Dry Reforming of Natural Gas: Performance and Process Modeling of Calcium Carbonate Looping Using Acid Based CaCO3 Sorbent

Several industrial activities often result in the emissions of greenhouse gases such as carbon dioxide and methane (a principal component of natural gas). In order to mitigate the effects of these greenhouse gases, CO2 can be captured, stored and utilized for the dry reforming of methane. Various CO2 capture techniques have been investigated in the past decades. This study investigated the performance and process modeling of CO2 capture through calcium carbonate looping (CCL) using local (Malaysia) limestone as the sorbent. The original limestone was compared with two types of oxalic acid-treated limestone, with and without aluminum oxide (Al2O3) as supporting material. The comparison was in terms of CO2 uptake capacity and performance in a fluidized bed reactor system. From the results, it was shown that the oxalic acid-treated limestone without Al2O3 had the largest surface area, highest CO2 uptake capacity and highest mass attrition resistance, compared with other sorbents. The sorbent kinetic study was used to design, using an Aspen Plus simulator, a CCL process that was integrated with a 700 MWe coal-fired power plant from Malaysia. The findings showed that, with added capital and operation costs due to the CCL process, the specific CO2 emission of the existing plant was significantly reduced from 909 to 99.7 kg/MWh.

Optimization of solvent free ohmic-assisted heating as a promising esterification tool for ethyl butyrate synthesis

Solvent free ohmic-assisted esterification (OAE) was investigated as a promising tool for ethyl butyrate (pineapple flavor) synthesis. To this end, Amberlyst 15 dry was used as an ion exchange catalyst to promote the esterification reaction between ethanol and butyric acid. Solubility, electrical conductivity, and heating rate of the reaction mixture as affected by different salt types and concentrations were studied. Then, the OAE operation parameters (i.e., electrical field, catalyst concentration, and mole ratio of ethanol:butyric acid) were optimized. The highest ethyl butyrate yield (63%) was achieved after 90 min in presence of 1% LiCl, 2% Amberlyst 15 dry using field strength of 25 V/cm and an ethanol:butyric acid mole ratio of 1:1. Optimum conditions of OAE were also compared with microwave- and magnetic stirrer-assisted esterification methods. OAE provided the highest yield (61.20%) at a shorter time with the lowest specific energy consumption (0.04 kWh/g ethyl butyrate) and specific CO2 emission (0.03 kg CO2/g ethyl butyrate). The micrographs of scanning electron microscopy showed less structural damages in the catalyst structure using OAE compared to other esterification methods. Therefore, OAE can be proposed as a cost-effective and environmentally friendly technology for the synthesis of flavor esters in the food industry.

A Technical Analysis of Oil Shale Firing Power Units Retrofitting for Carbon Capture and Storage (CCS)

In Estonia the significant part of power generation is still based on firing oil shale fuel in thermal power plants despite of the growth of the share of the green energy in recent years. Electricity generation is based on power units utilizing different combustion technologies. A significant part still comprises old units with capacity 185-195 MWe commissioned in early 70s of last century. These pulverized combustion (PC) based units utilize oil shale as a fuel and are operating with subcritical steam parameters, characterizing by relatively low efficiency 26 - 30% (net, LHV based). Due to their low performance, operational issues (intensive fouling of heating surfaces), and remarkable environmental impact, these units were decommissioned or retrofitted with boilers implementing circulating fluidized bed combustion (CFBC) technology in 2004-2005. Implementation of CFBC technology for oil shale combustion significantly reduced both operational issues and environmental impact. With some additional modifications in turbine island allowing to increase rated capacity up to 215 MWe and after increasing steam parameters, the net efficiency of up to 37% was achieved. Consequently, the specific CO2 emissions in the range of 0.99 – 1.05 t/MWhe depending on quality of oil-shale used, was achieved. Recently, the new 300 MWe CFBC based power unit was commissioned. It is operating with subcritical steam parameters: live steam temperature 565 °C and pressure 17 MPa. Net efficiency (LHV based) of that unit is 40 % and specific CO2 emissions up to 0.9 t/MWhe in case of firing only oil shale. In this study the technical viability of retrofitting oil shale based power generation units with CC is described. In the analysis two CC methods were considered: post-combustion (assuming conventional amine process) and oxy-fuel combustion. Among other CC technologies these processes are at the present time characterized by higher technical readiness level, can be applied for existing units with minimal modifications and are applicable for oil shale fuel with it specifics. Besides power generation, Estonia has for almost 100 years of experience in production of shale oil through thermal decomposition of oil shale kerogen in retorts. Currently, solid heat carrier (SHC) method is the main method used for producing shale oil. In this method, direct CO2 emission comes from the preparation of SHC by combustion of solid retorting residue (semi-coke). Mainly two combustion methods are presently applied: lift pipe combustion and CFBC which was recently successfully integrated into shale oil production process. The possibility of utilizing CC technologies in shale oil production units and their technical analysis is described in this study.