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Pyrolysis of defatted Euglena gracilis was investigated in this study to maximize energy recovery from algal biomass after lipid extraction. Prior to pyrolysis of defatted E. gracilis, the growth rate of E. gracilis was monitored to determine its potential as an initial carbonaceous feedstock for pyrolysis. This study revealed that the cell density of E. gracilis linearly increased for the first 5 days, during which the cell density reached 6.06 ± 0.82 g L−1, demonstrating that defatted E. gracilis is a promising feedstock for pyrolysis. To increase the thermal efficiency of defatted E. gracilis pyrolysis, CO2 was employed as a reactive gas medium. CO levels were increased by 45% following pyrolysis of defatted E. gracilis in a CO2 environment compared to in an N2 environment. Considering that CO is a highly combustible permanent gas, the use of CO2 in pyrolysis may result in the production of more fuel-range gaseous chemicals. Additionally, CO2 utilization increased the gaseous product yield compared to N2-pyrolysis for treating the defatted algal biomass while decreasing tar yield.

In this work, the concept of biomass direct (air) gasification was demonstrated in a pilot-scale bubbling fluidized bed and the influence of in-situ application of low-cost catalytic materials on the produced gas characteristics and gasifier performance was analyzed. Three different low-cost catalysts were tested: bottom bed ashes resulting from combustion of residual forest biomass derived from eucalyptus, char particles resulting from wood pellets direct (air) gasification, and synthetic fayalite (Fe2SiO4). Without using catalysts, the produced gas composition was 7.7–16.9%v CO, 3.2–8.3%v H2, 0.5–3.4%v CH4 and 9.5–14.6%v CO2, with 2.4–4.3 MJ/Nm3 lower heating value, specific dry gas production between 1.0 and 1.8 Nm3 dry gas/kg biomass (dry basis), cold gas efficiency between 13.7 and 30.5% and carbon conversion efficiency between 30.7 and 50.9%. With the use of catalysts, the produced gas composition was 14.2–37.6%v CO, 9.5–14.7%v H2, 2.6–3.5%v CH4 and 3.6–14.8%v CO2, with 3.9–6.3 MJ/Nm3 lower heating value, specific dry gas production between 1.4 and 2.0 Nm3 dry gas/kg biomass (dry basis), cold gas efficiency between 38.1 and 66.3% and carbon conversion efficiency between 56.8 and 86.6%. The highest increase in H2 concentration (352% increase) was observed on experiments using wood pellets char as catalyst while the highest increase in CO (305% increase), lower heating value (123% increase), specific dry gas production (62% increase), cold gas efficiency (262% increase) and carbon conversion efficiency (174% increase), was observed on experiments using synthetic Fe2SiO4 as catalyst.

In this study, experimental and mathematical studies were carried out to investigate heavy oil production performance using the carbon dioxide (CO2) huff-n-puff process, as well as the potential of CO2 storage in abundant reservoirs. Five experiments were conducted under different injection pressures and different pressure depletion rates. The components in the produced heavy oil were measured using a gas chromatography-mass spectrometry system to investigate the influence of CO2 extraction under different injection pressures in different cycles. The experimental results indicate that (a) heavy oil recovery factor increases with increasing injection pressure. (b) CO2 extraction of the light/medium components in heavy oil affect heavy oil production. (c) With different pressure depletion rates, an optimized pressure depletion rate can be identified as 4 kPa/min. And (d) the relationship between heavy oil and gas production can be predicted using the developed equation with high agreements. Mathematically, the potential of CO2 storage and CO2 capacity were calculated, and the investigations show that the most significant influences on CO2 capacity are CO2 stored in the available space and dissolving into the remaining heavy oil. An objective function was developed to optimize the heavy oil recovery factor and the CO2 storage factor in the CO2 huff-n-puff process. The influences of weights between heavy oil production and CO2 storage were investigated, and the optimized case with the same weight (0.5) was studied.

Biomass combustion in the oxy-fuel circulating fluidized bed is a promising technology to maximize the negative carbon dioxide emission and reduce pollutants emission in power plants. However, biomass ash related behaviors under oxy-combustion with kaolin additives still lack sufficient information. In this study, kaolin was used as an additive to manage ash problems during oxy-biomass combustion in a 0.1 MWth circulating fluidized bed combustion facility. Kaolin was fed at ratios of kaolin/wood pellet (wt./wt.): 0.21 and 0.25 by separately feeding or pre-mixing, respectively. The sampled ashes were characterized using X-ray fluorescence and X-ray diffraction analysis. Additionally, the potassium capture performance, slagging and fouling indices, attrition characteristics, and strength were also evaluated. The results revealed that potassium capture performance was improved by up to 24% at the ratio of kaolin/wood pellet (0.25) and kalsilite (KAlSiO4) within ash increased by adsorption on the metakaolin surface of gaseous potassium. The fouling formation decreased from 0.43 without kaolin to 0.07–0.15 with kaolin. In terms of oxy-fuel operation, SO2 emission was decreased when kaolin used, performing a high CO2 concentration of over 93 vol% and combustion efficiency of over 99%.

Over recent years there has been a significant increase in the amount of technology contributing to lower emissions of carbon dioxide. The aim of this paper is to provide a comparison between two technologies for methanol production, both of which use carbon dioxide and hydrogen as initial raw materials. The first methanol production technology includes direct synthesis of methanol from CO2, and the second has two steps. During the first step CO2 is converted into CO via RWGS (reverse water gas shift) reaction, and methanol is produced during the second step. A comparison between these two methods was achieved in terms of economical and energy-efficiency bases. The price of electricity had the greatest impact from the economical point of view as hydrogen is produced via the electrolysis of water. Furthermore, both the cost of CO2 capture and the amounts of carbon taxes were taken into consideration. Energy-efficiency comparison is based on cold gas efficiency, while economic feasibility is compared using net present value. Even though the mentioned processes are similar, it was shown that direct methanol synthesis has higher energy and economic efficiency.

This study investigates the CO2 influence on thermal decomposition of sugarcane bagasse and a low-rank coal. Experiments at low and high heating rates were performed under different ratios of CO2/O2/N2 atmospheres to evaluate devolatilization, char combustion, burnout, SO2, NO and CO emissions. When N2 was replaced by CO2, the coal combustion was enhanced and the kinetic study presented lower initial activation energy, the devolatilization yield was higher and the CO2-char presented higher reactivity compared to N2-char. The results obtained for sugarcane bagasse presented opposite behavior, and lower conversions and char reactivity were observed. The kinetic study showed a negative influence on sugarcane bagasse devolatilization and the activation energy was significantly higher under CO2 than under N2 (189 kJ mol−1 and 86 kJ mol−1, respectively). The difference between the fuels can be attributed to the higher volatiles content of the sugarcane bagasse, in which the suppression caused by CO2 partial pressure under 80% CO2 atmosphere was more pronounced for biomass than for coal, confirmed during devolatilization in the DTA results. Regarding the pollutant emissions, the NO formation decreased and the CO formation increased when N2 was replaced by CO2. No conclusive trend was observed for the SO2 species.

In this study, the techno-economic, energy consumption (EC), and environmental performances of biomass-to-hydrogen (BTH) production with/without methane tri-reforming (MTR) from corn straw were studied. The techno-economic analysis includes an assessment of the energy efficiency, MTR operating conditions, total capital investment (TCI), production cost (PC), and payback period. The BTH energy efficiency with MTR is 17.08% higher than that without MTR. The Claus unit is the largest contribution unit of energy loss. The reaction temperature and operating pressure of one MTR unit are 800 °C and 0.1 MPa, respectively. Compared with BTH without MTR, the TCI of BTH with MTR increased by 10.97%, and the PC decreased by 10.12%. The static payback period of BTH with MTR is approximately 4.72 yr. BTH without MTR exhibits 3.09% less EC and 7.85% greenhouse gas emissions than that of BTH with MTR. The life cycle analysis of the BTH process illustrates that the BTH with MTR can realize negative carbon dioxide (CO2) emissions when considering the natural carbon cycle. The evaluation method combines a thermodynamic analysis with a life cycle assessment, which is significant for the development of clean hydrogen production technology with low carbon and high energy savings.

Oxy-combustion with a circulating fluidized bed (Oxy-CFBC) can facilitate the separation of high CO2 concentration and reduce emissions by biomass co-firing. This study investigated Oxy-CFBC characteristics such as temperature, solid hold-up, flue gas concentrations including CO2, pollutant emissions (SO2, NO, and CO), combustion efficiency and ash properties (slagging, fouling index) with increasing input oxygen levels (21–29 vol%), and biomass co-firing ratios (50, 70, and 100 wt% with domestic wood pellet). The possibility of bio-energy carbon capture and storage for negative CO2 emission was also evaluated using a 0.1 MWth Oxy-CFBC test-rig. The results show that combustion stably achieved with at least 90 vol% CO2 in the flue gas. Compared to air-firing, oxy-firing (with 24 vol% oxygen) reduced pollutant emissions to 29.4% NO, 31.9% SO2 and 18.5% CO. Increasing the biomass co-firing from 50 to 100 wt% decreased the NO, SO2 and CO content from 19.2 mg/MJ to 16.1 mg/MJ, 92.8 mg/MJ to 25.0 mg/MJ, and 7.5 mg/MJ to 5.5 mg/MJ, respectively. In contrast to blends of sub-bituminous coal and lignite, negative CO2 emission (approximately −647 g/kWth) was predicted for oxy-combustion only biomass.

Growth of the hydrogen market has motivated increased study of hydrogen production. Understanding how biomass is converted to hydrogen gas can help in evaluating opportunities for reducing the environmental impact of petroleum-based fuels. Using an atmospheric-pressure microwave plasma reactor coupled with species-selective analysis, experiments are conducted at microwave power levels of 800, 900 and 1000 W, a reactant flow rate of 12 slm, and 1 g of dry Spirulina algae in nitrogen. At the absorbed microwave power levels used in this experiment, hydrogen gas produced is in the range of 36.75–45.13% volume fraction, 13.42–15.48 mg per minute, and 12.37–31.46 mg per gram of Spirulina algae consumed. Moreover, the selection of power levels demonstrates that 20.62–52.43% hydrogen atom mass content in dry algae is converted to hydrogen gas. In general, the effect of reaction temperatures on the gas product formation is qualitatively consistent with those produced from other biomass materials reported in literature. Overall, these results will help to expand our knowledge concerning Spirulina algae and hydrogen yield on the basis of microwave-assisted pyrolysis and reaction temperatures, which will inform the study and design of hydrogen production technologies.

Aircraft performance degradation causes higher fuel consumption. This results in higher emission and it is an important factor when the complete life cycle is analyzed. Current research in the field doesn’t quantify degradation emissions in the life cycle of an aircraft. The objective of this paper is to suggest a methodology for determining carbon dioxide emission during the life cycle of turbofan aircraft. Special attention is given to degradation and the importance of proper and timely maintenance as a way of controlling these emissions. Degradation plays a significant role in the carbon dioxide emission of turbo fan aircraft. The life cycle was modeled by eight sequences. In this paper a new mathematical interpretation is suggested for following life sequences: use and repair. In the use cycle, emission caused by aerodynamic structure degradation and engine degradation is calculated separately. The proposed methodology was implemented on four and tested on eight turbofan aircraft. Results show that more than 99% of carbon dioxide emission occurs in the use sequence. The emission caused by degradation (aerodynamic structure and engine) makes up between 3.6% and 6.4% of total carbon dioxide emission. A novel methodology for reducing emission caused by degradation is proposed by the authors.

The paper deals with cold recovery during LNG regasification. The applications analyzed pertain to the use in deep freezing agro food industry and in space air conditioning facilities in commercial sector (Supermarkets and Hypermarkets) of cold recovered from the regasification process. A modular LNG regasification unit is proposed having the regasification capacity of 2 billion standard cubic meters/year of gas and it is based on use of a Power Cycle working with Ethane, this unit allows operation of cold energy transfer, contained in LNG to be regasified, in a range of temperatures suitable for multipurpose use of cold, reducing regasification process irreversibility. Some electric energy is produced by the Power Cycle, but the purpose of the modular unit is to deliver cold suitable for industrial and commercial use in the proper temperature range utilizing Carbon dioxide as secondary fluid to transfer cold from regasification site to far end users. The subject is divided in two papers: this paper deals with facilities delivering cold released during LNG regasification and related pipeline facilities to transfer cold at far end-users while the other paper pertains to analysis of end users applications. Results of a detailed thermodynamic and economic analysis demonstrate the suitability of the proposal.

The paper deals with waste gasification as a technology allowing for indirect co-firing of large quantities of biodegradable wastes in coal-fired power boilers. In contrast to common landfilling and direct co-firing, gasification of wastes presents a number of advantages. Problematic species in original feedstocks can be partly safely incinerated in the furnace and partly retained in the gasification residues. The paper focuses on the impact of indirect co-firing on basic boiler parameters and performance. The work carried out was in the form of a case study for co-firing LCV gas in a 230 t/h dual fuel pulverized coal-gas fired boiler. Thermal shares of 10, 20 and 40% have been investigated for two extreme LCV gas qualities represented in the calculations by its calorific value of 2.0 and 8.5 MJ/m3n respectively, thus six calculation cases are given. The results of the study reveal that even high thermal shares of LCV gas may be achieved for co-firing of better quality gas without significant effects on boiler operation. For lower quality gas, even a 10% thermal share influenced boiler operation to a great extent. This paper also gives consideration in relation to avoided CO2 emissions accomplished via indirect co-firing.

Asia has become a major emitter of carbon emissions. To better achieve emission reduction targets, it is necessary to study the characteristics of carbon dioxide emissions in Asia and their emission reduction potential. Firstly, the gravity movement of Asia's carbon dioxide emissions and its leading forces are explored. Then, the Logarithmic Mean Divisia Index method is applied to find the driving factors governing carbon dioxide emissions. Furthermore, this paper establishes a theoretical model of carbon dioxide emission reduction. At last, the influencing factors are utilized to construct a decoupling index, which is used to describe the dependence of economic development on carbon dioxide emissions. The gravity center for Asia's carbon dioxide emissions was an overall movement towards southwest. However, the gravity center for carbon dioxide emissions per capita was an overall movement towards the southeast. The energy intensity effect was the most factor decreasing Asia's carbon dioxide emissions. Only five countries achieved theoretical reduction of carbon dioxide emissions over 2000–2015. However, three countries were failed to achieve the theoretical reduction of carbon dioxide emissions in this period. The economic development in most east Asia and southeast Asia countries was less dependent on energy-related carbon dioxide emissions over the period 2000–2015.

Within this paper, investigations to convert softwood with four different types of bed materials in the 100 kWth dual fluidized bed steam gasification pilot plant at TU Wien are presented and discussed. The results of ten different experiments were compared. Quartz, olivine and feldspar were mixed with limestone in mass ratios of 100/0, 90/10, 50/50 and 0/100. Limestone was used due to its catalytic activity at high temperatures as CaO and thus enhanced tar, char and water conversion of quartz, olivine and feldspar. The admixture of limestone to quartz, olivine and feldspar shifted the product gas compositions towards higher hydrogen and carbon dioxide and lower carbon monoxide contents. By using 100 wt.-% limestone as bed material a hydrogen content of 47.4 vol.-% could be generated. Additionally, the tar concentrations as well as the tar dew points decreased and especially the heavy tar compounds could be reduced. Already small amounts of limestone (

This paper presents a thermochemical regenerative heat recovery process for utilizing the waste heat of oxy-fuel furnaces, with three significant modifications compared to current state-of-the-art reforming concepts. (I) Experimental tests with a reformer test rig were performed, in order to investigate the bi-reforming of methane into syngas by using water and carbon dioxide with a steam-to-carbon ratio of 0.5. The measured syngas concentrations were compared to calculated equilibrium values and carbon deposits were determined. A methane conversion rate of 95.3% was achieved. (II) Carbon deposits in a regenerator bed are usually burned with purge gases. In contrast to this procedure, oxygen was added to the fuel/exhaust gas mixture in order to cause tri-reforming of methane with a steam-to-carbon ratio of 0.4. The syngas concentrations were compared to equilibrium values and it was found, that tri-reforming significantly reduces carbon formation. A methane conversion rate of 96.7% was achieved. (III) Furthermore, reforming and regeneration cycles were coupled and it was found that the temperature profile within the TCR regenerator bed material varies greatly from that of a common regenerator. Regeneration with water and carbon dioxide was sufficient to eliminate all carbon deposits.

Complex fluid-rock interactions can occur during the injection of carbon dioxide (CO2) into saline aquifers for sequestration, which may affect CO2 injectivity and storage capacity. In this paper, a comprehensive reactive transport model is established to analyze salt precipitation, CO2-water-rock geochemical reactions, and their effects on reservoir physical properties and injectivity. In addition, sensitivity analyses are conducted to investigate the main factors that affect fluid-rock interactions and injectivity with relevance for site selection for CO2 storage. Results show that the back flow of formation water not only affects the salt precipitation but also affects the CO2-water-rock geochemical reactions, resulting in salt and calcite precipitations mainly occurring in the dry-out zone. However, most of the mineral dissolution/precipitation caused by CO2-water-rock reaction occurs in the two-phase and aqueous-phase zones, and their effect on reservoir porosity and permeability are small. A considerable amount of sodium chloride precipitates in the dry-out zone as brine is drawn by capillary action into this zone, with significant consequences for porosity, permeability and injectivity. The injection rate, salinity, capillary pressure–saturation relationships, and reservoir permeability strongly affect the distribution of salt precipitation. Moderate injection rates, salinities, capillary pressures, and permeabilities all lead to favorable CO2 injectivity.

The paper addresses the production of urea from carbon dioxide and nitrogen in the flue gas of the power plants as an alternative to other proposed and suggested processes. The conventional separation process of CO2 from flue gases has been so far directed to the methanol synthesis, while nitrogen, as the main part of the combustion product, is ignored. Carelessness about and lack of use of this byproduct is led to the techno-economical failure of the process and cause environmental problems. In this research, to the best of our knowledge, for the first time, the synthesis of urea and ammonia from the combustion of oxy-fuel was investigated and the appropriate and green process was designed and proposed. To enhance economic justification, the process design was carried out using all three main components of the flue gas (CO2, N2, and H2O), along with efficiency increment of the combustion units. Considering of 2036 kg/hr oxy-fuel combustion products, direct removal of 1700 kg/hr CO2 from the carbon cycle and production of 2856 kg/hr molten urea is estimated, which the latter product worth about 3.5 × 106 US$/year.

International audience; One of the best low-cost approaches for capturing carbon dioxide from the combustion of solid fuels is chemical looping combustion (CLC) technology, where the processes of fuel oxidation and extraction of oxygen from the air are split in two separate reactors. In order to model the petroleum coke (petcoke) conversion in a CLC method, detailed knowledge about the reactions of pet-coke with O2, CO2, and H2O at temperatures between 750 and 1100 °C is required. Due to the lack of sufficient literature data, in this paper, the reactivity of these reactions is investigated in a custom-built test rig that enabled measurements of the mass loss of the fuel sample and the composition of the released gases. The Avrami, Random Pore, Shrinking Core, and Hybrid models were applied to the experimental results to determine the kinetic parameters of petcoke gasification. At temperatures up to 1000 °C, the reaction with CO2 was found to be negligibly slow. An activation energy of 103.91 kJ/mol was obtained for petcoke gasification in 10–40 vol% of H2O, while a value of 15.87 kJ/mol was found for oxidation in 2–4 vol% O2, as described by best-fitting models, i.e. Hybrid and Random Pore models, respectively.

In this paper the driving factors of carbon dioxide emissions from electricity generation in the European Union are examined for the years 2000–2018, separated into three time periods using decomposition analysis, and particularly LMDI-I. Seven driving factors are examined, namely the economic activity effect, the population effect, the electricity intensity effect, the electricity trade effect, the energy intensity effect, the generation structure effect, and the emissions factor effect. The results showed that the main driving factor leading to increased carbon dioxide emissions is the economic activity effect counterbalanced mainly by the contribution of the generation structure effect. Moreover, a decoupling analysis between economic growth and carbon dioxide emissions was carried out aiming to identify the state of each country for each period. In the third examined period (2013–2018) most countries in the EU-27 are in a state of strong decoupling.

Propane (C3H8) is being considered as an alternative refrigerant, besides being used as an alternative fuel, because of its low Global Warming Potential and zero Ozone Depletion Potential. Using blends of C3H8 with CO2 as refrigerants, diminishes the fire safety concerns in case of accidental leak of this flammable substance in refrigeration applications. This paper reports on the effects of CO2 on laminar burning speed and flame instability of C3H8/air blends at elevated temperatures and pressures. The flame structures were investigated in a Schlieren system. The laminar burning speeds of C3H8/CO2/air mixtures were measured in a spherical chamber and were fitted by a power-law mathematical correlation. The one-dimensional flame code from Cantera with kinetic model was also used to predict laminar burning speed. The high-speed photography showed that CO2 inhibits the flame instability because of its hydrodynamic and diffusional-thermal effects. Results showed that the laminar burning speed decreased with increasing CO2 mole fraction in the mixtures and that CO2 promotes the flame stability. The high temperature C3H8 oxidation was governed by the reaction of H + O 2 = O + OH . The effects of CO2 on laminar burning speed were mainly determined by the reaction of CO 2 + H = CO + OH and the high energy capacity (specific heat) of CO2.

Carbon dioxide ( C O 2 ) sequestration is considered to be one of the most effective technologies of mitigating greenhouse gas emissions. In this technology, single phase supercritical C O 2 is injected into an underground geological formation such as a deep saline aquifer. Existing sequestration projects demonstrate that successful implementations are possible; however, significant uncertainties associated with the risks of leakage remain an obstacle for broader use of this technology. The security of underground disposal could be considerably increased by dissolving the C O 2 in a brine produced from the aquifer, then re-injecting the mixture underground. The dissolution process occurs before the mixture reaches the aquifer; this significantly reduces or completely eliminates the risks of C O 2 leakage. This technique can drastically extend the amount of worldwide aquifers available for carbon sequestration. As was previously shown, complete dissolution could be achieved in a surface pipeline operating under the pressure of a target aquifer, where C O 2 is injected. In this paper, a comprehensive model of C O 2 droplet dissolution in a vertical injection well is presented. The model accounts for droplet breakup, coalescence, and dissolution processes as well as temperature and pressure variations over well depth. Feasibility and results are discussed and compared with surface dissolution options.

Increasing energy demand triggered by industrialization has led to high carbon dioxide (CO2) emission into the environment, causes rise in earth temperature resulting in global warming. Therefore, there is urgent need to develop a cost effective methods and materials for its sequestration from point source and reduce its impact on the environment. This paper reviewed the recent development in functionalized composites for CO2 capture. The composites can help to develop more efficient technologies and cost effective materials for CO2 capture in view of the exponential growing demand for energy. Myriad of researchers have focused interest on the development of novel materials to trap CO2 using solid sorbents that appear promising. The composite adsorbents have superficial properties in terms of surface area, pore characteristic, adsorption capacity and stability at high temperature. The superior properties can be achieved by surface modification via activation or functionalization. The study revealed that functionalized composites provides superficial properties in terms of surface area, microporosity and high adsorption capacity for CO2 sequestration. However, the development of carbon based composite derived from lignocellulose biomass and understanding the mechanism and kinetics of CO2 onto functionalized composite have been graced with few research and needs to be explored further.

This study focuses on the mechanistic understanding of effects of CO2 on pyrolysis of peat. To do this, three pyrolytic products (i.e., syngas: H2 and CO, pyrolytic oil (tar), and biochar) were characterized. Thermal cracking of volatile organic carbons (VOCs) generated from pyrolysis of peat was enhanced in the presence of CO2. Besides the enhanced thermal cracking of VOCs, unknown reaction between CO2 and VOCs was also identified. Accordingly, CO2 played a role in enhancing syngas production and in reducing tar formation in pyrolysis of peat. This study also reveals that peat-biochar produced in CO2 exhibited a larger surface area than that produced in N2. The results shown in this paper would be used for various applications such as energy recovery from peat using a potent greenhouse gas (for example, CO2).

Carbon dioxide emissions from the chimneys of thermal power plants create major environmental risks. Therefore, an important step toward reducing the emissions in these power plants can be the carbon dioxide pre-combustion capture process. In this paper, a 150 MW thermal steam cycle power plant fueled by bagasse was studied. The power plant has an efficiency of 32.74%, and emits 246.52 t/h carbon dioxide. First, the design and simulation of a suggested pre-combustion carbon dioxide capture process was outperformed. In this process, the amount of carbon dioxide separation and capture using mono ethanol amine (MEA) 30 wt% as solvent is 90%. In this condition, the mass flow of bagasse was increased about 60% to keep the plant efficiency constant. At the same time, the energy loss as a result of the addition of the carbon dioxide recovery unit was around 11%. The process was optimized through Pinch Analysis to reduce energy waste and fuel flow. Moreover, it was indicated that power plant efficiency could be increased around 8% by integrating the hot exhaust gases from the gasification unit with power plant boiler using a heat recovery steam generation (HRSG) unit. With this modification, bagasse consumption was decreased by 23%.

Carbon dioxide due to its chemical and physical properties can be successfully used in the wide range of surface cleaning an pre-treatment applications. One of the main carbon dioxide cleaning application is the dry-ice blasting, which seems to be a promising method of industrial devices cleaning. In the method the solid carbon dioxide particles supplied by the pressurized dry air are speed up to supersonic velocities in the convergent-divergent nozzle to finally reach the cleaning surface. Then via cooling and sublimation, causing in the rapid volume growth the pollution is crashed and removed with the air flow. Main cleaning mechanisms of dry-ice blasting are described in the paper. The crucial part of the system is the nozzle. The article covers the operational parameters impact on the nozzle performance. The authors present the methodology allowing the dry-ice blasting system assessment and provided the bench tests of the convergent-divergent supersonic nozzle in the field of nozzle’s efficiency, cleaning speed and operational costs. Impact of inlet air pressure, nozzle outlet-surface distance, cleaning angle, surface type and crushing sieve implementation was determined and analysed.

Complex factors can affect carbon dioxide (CO2) geological storage efficiency and capacity. In this paper, a three-dimensional (3D) conceptual model of the Shiqianfeng formation in the Ordos basin was established (a total of 16 sets of schemes) to study the influence of injection temperature on CO2 storage efficiency and migration safety in the sloping formation with a fault. In addition, storage capacity is investigated for CO2 storage site selection. The results show that injection temperature and formation slope have a significant effect on CO2 storage efficiency. Faulting provides a possible channel for CO2 leakage. High injection temperature is more likely to cause CO2 leakage in the sloping formation. When the injection temperatures are 11, 31.5, 51 and 71 °C in the 15° slope formation, the time points of CO2 leakage are 200, 170, 150 and 140 years, respectively. The lower injection temperature results in a higher CO2 concentration near the injection well and a closer migration distance of dissolved CO2. The larger the formation slope is, the farther the dissolved CO2 migration distance will be. The higher injection temperature results in a greater gas phase, dissolved phase, and total CO2 storage amount in the whole formation. The larger the formation slope is, the smaller the CO2 storage capacity will be for CO2 injected over 20 years. However, the larger formation slope resulted in a smaller gas phase and larger storage amount of the dissolved phase CO2 for CO2 migration after 140 years. The influence of the formation slope on the dissolved CO2 migration safety is more obvious than that of injection temperature. However, the influence of the injection temperature on CO2 storage capacity is more obvious than that of the formation slope.

In this paper, the effects of carbon dioxide on the upper flammability limits of oxy-methane were investigated. Firstly, the upper flammability limits of oxy-methane were measured under normal pressure and temperature. Then, the chemical effect of CO2 on the upper flammability was studied using the kinetic simulation. Finally, the thermal and radiative effects of CO2 on the upper flammability limits were discussed using energy balance analysis. The experimental upper flammability limits of CH4/O2/CO2 are from 9.5% to 33.25% in the condition of increasing oxygen concentrations from 15% to 50%. The analysis shows that the upper flammability limits of methane are mainly determined by the thermal property of CO2 and not significantly changed by the chemical and radiative effects.

With recent surge in the number of vehicles, particularly private vehicles, the transport sector has significantly contributed to the increase in energy consumption and carbon dioxide emissions in China. Most of the existing researches utilized time series data to investigate the factors influencing transport sector's carbon dioxide emission at the national level while neglecting the level of regional differences. This paper adopts provincial panel data from 2000 to 2012 and panel data models to examine the key driving forces of carbon dioxide emissions in the transport sector at the regional level in China. The estimation results show that the impacts of urbanization on carbon dioxide emissions in the transport sector vary across regions and decline continuously from the western region to the eastern and central regions. Private vehicles are more important than cargo turnover in emission reduction because of its relatively inefficient and excessive growth. The role of energy efficiency improvement in mitigating carbon dioxide emissions in the three regions varies due to significant differences in research and development investment and management efficiency. Hence, in order to effectively achieve emission reduction, local governments should consider all these factors as well as regional heterogeneity in developing appropriate mitigation policies.

This paper presents an analysis of the thermal cycle of a supercritical 900 MWe condensing power plant which meets the “capture ready” requirements. The CO2 separation method selected for the analysis is chemical absorption using MEA (monoethanolamine) or ammonia as sorbent. The indispensable scope of the turbine system upgrade necessitated by the incorporation of the carbon dioxide separation installation is proposed. The change in indices of the power unit operation after integration with the capture installation is presented for different variants of the retrofit. If MEA is used for carbon dioxide separation, the smallest drop in electric power can be observed in the case of hard coal for added stages at the intermediate pressure part outlet. In the case of lignite, the most favourable upgrade solution in terms of the smallest drop in electric power is elimination of one low pressure part and a backpressure turbine is added at the same time. If ammonia is used as sorbent, the best upgrade solution in terms of the smallest drop in electric power is the variant with more stages added at the IP part outlet, regardless of the type of fuel. An economic analysis is conducted for the proposed variants.

This paper focuses on the feasibilities of energy, economic and environment of a method to enhance an ORC (organic Rankine cycle) efficiency by CCHP (combined cooling heating and power) generation from an absorption system for reducing the ORC condenser temperature. A projection of a 25 kWe R245fa ORC integrated with a 20 kW LiBr-water absorption unit was considered. The experimental data of both units were generated as performance curves and used to find out the suitable operating conditions. It could be found that the ORC with the absorption system gave higher total efficiency compared with the normal ORC. The ORC efficiency could be increased around 7%, with 15 °C of cooled water temperature supplied from the absorption system. But, in term of the economic result, a LEC (levelized electricity cost) of the modified system was around 0.0891 USD/kWh, which was higher than that of the normal system at around 0.0669 USD/kWh. In term of the environmental impact, a released carbon dioxide intensity of the new unit was lower than the normal unit at around 0.203 and 0.216 kg CO2 eq/kWh, respectively.

The separation of carbon dioxide (CO2) by hydrate-based technology has attracted much attention due to its low energy consumption and simple process. In view of the problems of slow hydrate formation and low gas consumption the factors influencing the hydrate-based separation of CO2 from integrated gasification conbined cycle (IGCC) syngas in the presence of cyclopentane (CP) are systematically studied in this paper. The results show that CP helps to promote the formation of CP-CO2 binary hydrate, and the gas consumption is affected by hydrate formation mode and hydrate density. The denser the hydrate phase is, the lower the gas consumption is. At the optimum condition of 275.65 K and 4.45 MPa with CP of 5v%, the highest gas consumption of 0.0128 mol/mol is obtained. The gas-hydrate contact is an important factor affecting gas consumption. In the hydrate formation system, the liquid often exists between gas and hydrate, limiting the full contact of gas and hydrate. Therefore, in the process of hydrate formation, making the hydrate fully contact with the gas without being covered by the liquid is a way to improve the gas consumption.

The indoor air quality in schools is very important for health and learning abilities of children. The primary indoor CO2 source in classrooms is the respiration of school building occupants. Also, CO2 comes from outside as a result of fossil fuels combustion. CO2 concentration depends on a ventilation rate, size of the classroom, number of occupants and their activity and time they spend in school building. Unfortunately, ventilation rates in schools were not often measured, even in cases when inadequate ventilation caused pupils health problems and their absence from school. The increase in indoor CO2 concentration above the outdoor concentration is considered as a good surrogate for the indoor concentrations of bio effluents. This paper presents the research of ventilation rates in five naturally ventilated schools in urban and rural areas in Serbia during the heating season. CO2 concentrations were measured outdoor and in three classrooms for five working days, continually. Ventilation rates are calculated based on measured concentrations of CO2. The results have shown that classrooms in Serbian schools have inadequate ventilation during the heating period. Mean value of carbon dioxide concentration has often been exceeding 1000 ppm. (C) 2014 Elsevier Ltd. All rights reserved.

This paper presents a novel approach to recover energy from mineral carbonation process, one of the CCS (carbon capture and storage) technologies, to reduce its additional energy demand and reports the feasibility of integrating a carbonation process with an existing power plant for reducing CO2 (carbon dioxide) emission. A thermodynamic mass and energy flow model of the carbonation process is developed using Matlab/Simulink software for a range of carbonation temperatures using two naturally available feedstocks, namely serpentine and olivine. The CO2 emissions are reduced if a carbonation system is implemented in the power plant, though the power generation efficiency and net power output are reduced too due to the large amount of extra energy required for the grinding of feedstock and the compression of CO2. The existing power plant efficiency was found to be 36.1%. If a carbonation system is incorporated, the plant efficiency reduces to 22% and 24% using serpentine and olivine feedstocks respectively. However, a significant amount of heat energy can be recovered from exothermic reaction of carbonation and carbonated products. The power plant efficiency can be increased to 35% and 34% again, respectively, when energy from carbonation reaction and carbonated products can be recovered appropriately.

The paper reports the preliminary design and the economic evaluation of an innovative carbon dioxide removal process from biogas, characterized by the capture and storage of the removed carbon dioxide. The studied process uses industrial residues for carbon dioxide capture and storage, through an accelerated carbonation process. The considered industrial residues are APC (air pollution control) residues from waste-to-energy plants, which are characterized by a high content of alkaline earth metals, calcium in particular, in the form of hydroxides, oxides or silicates. The carbon dioxide is removed from the biogas by alkali solution absorption. The spent solution, containing carbonate and bicarbonate ions is regenerated through reaction with calcium contained in the APC residues, forming calcium carbonate (APC carbonation) and reproducing – at least in part – the original alkali compound. A technical feasibility assessment of the method was carried out, based on pilot plant operation results, highlighting some constraints on the possibility of operating at very large scale, due to the high amount of required residues. Then a preliminary economic assessment of the method was carried out, with the aim of estimating the specific cost of treatment on appropriate industrial scale and comparing it with the costs of commercial methods.

This paper explores the importance of differential output growth across regions within a country in reducing the country's total carbon dioxide emissions from the combustion of fossil fuels. It proposes a framework that decomposes changes in emissions into sources attributable to 1) national growth rate of gross domestic product (GDP), 2) differential GDP growth across regions, 3) changes in energy intensity, and 4) changes in CO 2 emission coefficient of energy. Data for China (1995–2009) and the United States (1990–2009) are analyzed. Uneven growth across regions reduced carbon dioxide emissions in both countries.

This paper investigated the short-run causal relationships and the long-run equilibrium relationships among carbon dioxide emissions, economic growth, technical efficiency, and industrial structure for three African countries. Using Bounds cointegration approach the result showed evidence of multiple long-run equilibrium relationships for Ghana and Senegal but a one-way long-run equilibrium relationship for Morocco. The result from the Toda and Yomamoto granger causality test showed a mix of bidirectional, unidirectional, and neutral relationships for all countries. Whilst in Senegal carbon dioxide emission was not found to be a limiting factor to economic growth; it was found to act as a limiting factor to economic growth in Morocco and Ghana. Lastly, the result from the variance decomposition analysis revealed that economic growth contributes largely to changes in future carbon dioxide emissions in Senegal and Morocco whilst in Ghana technical efficiency contributes largely to changes in future variations in carbon dioxide emissions. These results have important policy implications for these countries' energy efficiency systems.

This paper describes a staged carbonation process for magnesium silicate mineral carbonation. This carbon dioxide capture and storage (CCS) alternative involves the production of magnesium hydroxide, followed by its carbonation in a pressurised fluidised bed (PFB) reactor. The goal is to utilise the heat of the carbonation reaction to drive the Mg(OH) 2 production step. The results show that Mg(OH) 2 can be produced successfully (up to 78% Mg extraction extent achieved so far) and efficiently from different serpentinite minerals from locations worldwide (Finland, Lithuania, Australia, Portugal…). From the extraction step, ammonium sulphate is recovered while iron oxides (from the mineral) are obtained as by-products. The carbonation step, while still being developed, resulted in >50%-wt conversion in 10 min (500 °C, 20 bar) for > 300 μm serpentinite-derived Mg(OH) 2 particles. Thus the reaction rate achieved so far is much faster than what is currently being considered fast in the field of mineral carbonation.

Permeability has been identified as one of the foremost factors that determine the effectiveness of CO 2 sequestration in deep coalbeds. Coal matrix swelling can cause a remarkable decrease in the permeability of a coalbed reservoir during the carbon dioxide injection process. The main aim of this paper is to correlate the diametrical swelling percentage with coal permeability. This experimental program further attempts to investigate the effect of gas flow properties in coal due to CO 2 sorption. Furthermore, the applicability of using a laboratory-made reconstituted coal specimen for permeability testing has been comprehensively investigated. A laboratory-based experimental program has been carried out using a high pressure triaxial experimental set-up. In this study, the effect of swelling on coal permeability has been investigated using two types of specimens. An intact brown coal specimen cored from a natural coal block and a reconstituted brown coal specimen made by compacting coal dust in a mould has been subjected to testing. Tests have been carried out under different gas injection and confining pressures. CO 2 and N 2 gases have been used as injection media. Gas injection has been carried out with two stages of N 2 injection, prior to and after CO 2 injection. Diametrical swelling of the two specimens has been compared with the permeability data. A good correlation was observed between permeability and coal swelling. The coal swelling percentage increased on exposure to carbon dioxide compared to exposure to N 2 . This effect increased as gas injection pressure increased. Exposure of the coal specimens to CO 2 has contributed to a detrimental effect on permeability. This was clearly evident during the second injection of N 2 gas.

This paper examines non-isothermal effects during carbon dioxide injection into a depleted gas reservoir for storage and EGR (enhanced gas recovery). We illustrate Joule–Thomson behavior with VHD (viscous heat dissipation) effects during reservoir repressurization. The equations of state for density (empirically extended ideal gas equation) and dynamic viscosity of the real gaseous mixture are tested with numerical and experimental data. We consider the real behavior of the mixture by using energy and distance parameters. The energy conservation equation is solved to account for gas expansion with convection and conduction processes. Additionally, we present temperature profiles of the reservoir column during gas expansion and discover that the Joule–Thomson process and VHD decrease reservoir temperature, with a decrement in temperature of the reservoir depending strongly on medium porosity. Isothermal pressure and temperature calculations are compared with existing one-dimensional analytical solutions for model verification.

Numerous coal gasification studies have been found in the literature those employed various kinds of gasifying agents such as steam and carbon dioxide. These studies are featured with wide variations in the parametric conditions and the usage of equipments. Steam is frequently employed as a gasifying agent, however, in several studies carbon dioxide has also been used as a gasifying agent either pure or in combination with other gasifying agents (H2O, O2, CO, H2). This paper is a brief review of the coal gasification with CO2 as a diluent. Different factors were studied over the coal gasification with CO2 such as coal rank, pressure, temperature, gas composition, catalyst and the minerals present inside the coal, heating rate, particle size, and diverse reactor types. It also deals with the application of the gas–solid models developed in the literature and the combustion and gasification mechanisms for O2/CO2 streams. Moreover, it reviews the kinetics and the reaction rate equations (Arrhenius and Langmuir–Hinshelwood types) for coal-char gasification both in the reaction kinetic control region (low temperature) and the diffusion control region (high temperature) and at both low and high pressures.

Knowledge of influencing factors of industrial carbon emissions (ICE) is crucial to the efforts of reducing anthropogenic greenhouse gas emissions. In this paper, main factors responsible for the ICE in Shanghai between 1996 and 2007 were identified and quantitatively analyzed using the Log-Mean Divisia Index method. It was found that the industrial output was the main driving force of ICE. The decline in energy intensity and the adjustment of energy and industrial structure are major determinants for reduction of ICE, with the former alone accounting for 90% of the reduction. To better investigate the relative contribution of different industrial sectors and their changes over time, we divided the study period into two equal time intervals and analyzed some high-carbon emission sectors. The results suggested that the intensity of energy use should be reduced further, for it was far higher than the world average. Adjustment of industrial structure by developing low-carbon emission industries is more crucial than energy mix.

Air-to-water heat pumps using CO2 as a natural refrigerant have been developed and commercialized. They are expected to contribute to energy saving in residential hot water supply. The objective of the research is to analyze the performance of a water heating system composed of a CO2 heat pump and a hot water storage tank by numerical simulation. In this paper, the system performance is analyzed under a daily change in a standardized hot water demand, and some features of the temperature distribution in the storage tank and the system performance criteria such as coefficient of performance, storage and system efficiencies, and volumes of stored and unused hot water are investigated. It turns out that the daily change in the hot water demand does not significantly affect the daily averages of the COP, and storage and system efficiencies, while it significantly affects not only the daily change in the volume of hot water unused after the tapping mode, but also that in the volume of hot water stored after the charging mode. The influence of the daily change in the hot water demand on the volumes of stored and unused hot water is clarified quantitatively.

The paper presents synergy effects found during the co-firing of wooden biomass with Bosnian coal types in an experimental reactor. The co-firing tests used spruce sawdust in combination with Kakanj brown coal and a lignite blend of Dubrave lignite and Sikulje lignite. Coal/biomass mixtures at 93:7 and 80:20 wt% were fired in a 20 kW pulverized fuel (PF) entrained flow reactor. Over 20 test trials were performed to investigate ash deposition behavior and emissions under different conditions, varying the process temperature, excess air ratio, and air distribution. During the tests, the temperature in the experimental facility varied between 880 and 1550 °C, while the excess air ratio varied between 0.95 and 1.4. There was sufficient combustion efficiency under all co-firing regimes, with burning out at 96.5–99.5% for brown coal–sawdust co-firing. Synergy effects were detected for all co-firing regimes with regard to SO 2 emission, as well for slagging at the process temperature suitable for the slag tap furnace. CO 2 emissions were also calculated for the blends tested and significant reductions of CO 2 found, due to the very low ranking of Bosnian coals.

This paper presents results from a total of 27 projects from the Finnish CLIMTECH technology program. These were used to investigate the prospects of greenhouse gas-mitigation technologies under Finnish conditions, including all emissions sources and all Kyoto gases. The estimated impacts of climate change on the energy system were also taken into account in the analysis. Systematic investments in technology development were found to yield substantial benefits in the long term by decreasing emissions reduction costs and by facilitating more ambitious reduction targets. Advanced biofuel production and utilization technologies, as well as offshore wind power, have proved to have the largest potential by the 2030s. Results also indicated a clear relationship between technological development and national emissions-trading patterns.

An ocean sequestration method to dispose of a large amount of CO 2 gas has been developed to mitigate global warming. This system is called the gas lift advanced dissolution (GLAD) system. This system works by dissolving CO 2 gas into seawater at a depth of 200–300. The CO 2 -rich seawater is then transported to a depth greater than 1000 m. This system is composed of short riser pipes for gas-lift and CO 2 dissolution, a tank for separating indissoluble gas ingredients from seawater, and long down-comers for transporting CO 2 -rich seawater to great depths. For the system to function optimally, the riser pipe needs to be long and wide enough to dissolve CO 2 thoroughly. Also the down-comer has to be long enough to transport the CO 2 -rich seawater to great depths and sufficiently large in diameter to enable transportation of large quantities of seawater. The most important aspect for disposal of CO 2 into the ocean is minimizing the environmental impact, especially its influence on marine life. The CO 2 concentration of seawater, therefore, must be limited below a certain value in order to minimize the environmental impact. This paper describes a mathematical model of GLAD's internal flow, which was derived to optimize the system specifications, and the correlations among the design factors of GLAD system derived by using this mathematical model.

In this paper, a comparative study is performed for the transcritical carbon dioxide refrigeration cycles with a throttling valve and with an expander, based on the first and second laws of thermodynamics. The effects of evaporating temperature and outlet temperature of gas cooler on the optimal heat rejection pressure, the coefficients of performance (COP), the exergy losses, and the exergy efficiencies are investigated. In order to identify the amounts and locations of irreversibility within the two cycles, exergy analysis is employed to study the thermodynamics process in each component. It is found that in the throttling valve cycle, the largest exergy loss occurs in the throttling valve, about 38% of the total cycle irreversibility. In the expander cycle, the irreversibility mainly comes from the gas cooler and the compressor, approximately 38% and 35%, respectively. The COP and exergy efficiency of the expander cycle are on average 33% and 30% higher than those of the throttling valve cycle, respectively. It is also concluded that an optimal heat rejection pressure can be obtained for all the operating conditions to maximize the COP. The analysis results are of significance to provide theoretical basis for optimization design and operation control of the transcritical carbon dioxide cycle with an expander.

This study focuses on waste paper gasification in carbon dioxide atmosphere with molten alkali carbonates including potassium, sodium, lithium carbonate or their intermixtures as catalyst. The molten catalysts is capable of facilitating a desired reaction (C+CO2→2CO), which was hardly feasible even at a high temperature of 973 K if catalyst absences. It is that the catalysts which provides a gas–liquid interface between carbon and carbon dioxide, replacing original gas–solid, then allows the two reactants contact each other effectively. Further experimental results demonstrate that the intermixture carbonates exhibit strongly enhancement on catalytic activity than any carbonate salts in the form of single. The reaction rate depends on temperature evaluating manners, a rapid heating processes is favorable to the aimed reaction. With respect to recycling of carbon dioxide, the process provides a conversion in 30%.

Chemical recuperation of heat is the most considerable method of increasing the efficiency of combined-cycle plants, but plants with chemical recuperation are not in application yet. In this paper, the causes of this phenomenon have been examined and the thermodynamic basis of using chemical recuperation of heat has been given. The energy efficiency of a combined cycle plant with chemical recuperation has reached 80–90% and more and it increases with lower reforming pressure. Additionally, chemical recuperation has raised the amount of gas fuel used in energy and chemical industries and has decreased the amount of waste carbon dioxide ejected into the environment by nearly 20%. The energy efficiency of a power plant with chemical recuperation must be calculated with registration of the methane which does not undergo a reaction in the reformer.

This paper describes experiments comparing a commercially available R410A heat pump and prototype R744 (carbon dioxide) system in heating mode. The R744 system utilizes aluminum microchannel heat exchangers and a prototype semi-hermetic compressor. System performance is compared for two configurations: first, when the R744 compressor speed is set to match the baseline system’s heating capacity at 8.2 °C outdoors and 21.1 °C indoors; and second, when the air conditioning capacity is matched at 35 °C outdoors and 26.5 °C indoors. The R744 system operates with a slightly lower heating COP, but its higher capacity at lower outdoor temperatures reduces the need for less efficient supplementary heating capacity.

This paper describes our most recent analysis of U.S. manufacturing energy consumption and extends our previous efforts in two important ways. We have acquired new data that enable us to extend our previous period of study and thus examine three distinct time periods, two with stable energy prices (1958–1973 and 1985–1991) and one in which energy prices rose significantly (1973–1985). We have also adapted our method to examine the historical trends of carbon emissions associated with manufacturing.