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The waste biomass has immense opportunities and plenty of potentials to be an efficient source of renewable energy. Initially, native unripe coconut husk (NCH) was used as raw material for fluidized bed gasification. Then NCH was treated with paper and pulp waste water to impregnate metals present in it for getting enhanced H2 yield in fuel gas. Humidified air was used as gasifying medium, which served the purpose of introducing water vapour to take part in the gasification process. Then after, gasification medium was retrofitted with CO2, which enhanced both the higher heating value (HHV), and CO and H2 content in the fuel gas. This research serves the dual benefit of energy generation and waste minimization. HHV of unripe coconut husk was investigated and found to be 20.95 MJ/kg. H2 yield and HHV from impregnated coconut husk (ICH) were obtained as 55.55 vol % and 5.24 MJ/Nm3, respectively at HER 0.1 and gasification temperature of 850 °C in case of fluidized bed gasification. The GC-MS analysis of fuel oil obtained from ICH gasification was done to get the information about high yield of fuel gas as promise product of fluidized bed gasification.

A novel two-stage gasifier, consisting of a fluidized bed gasifier and a swirl-melting furnace, was proposed and built to gasify biomass with low ash melting temperatures into clean fuel gas. Improvements of the two-stage gasification in gas upgrading, tar removal and ash separation were confirmed by characteristic analysis of gas, tar, ash and slag. Influence of equivalence ratio (ER), oxygen distribution and gasifying agent were assessed for process optimization. Refined gas with a LHV up to 11.1 MJ/Nm3 and a tar content lower than 1 g/Nm3 was produced. Ash was completely vitrified with a high conversion of fixed carbon and volatile, resulting in a cold gas energy fraction of approximately 80%. Increasing ER promoted gas production but limited energy conversion efficiency and gas LHV. Proper oxygen distribution among the two stages was beneficial to decrease energy loss and increase gas quality. Increasing oxygen percentage of gasifying agent enhanced combustible gas content and improved overall gasification efficiency.

The flame front stabilization of low calorific fuel gas (LCFG) combustion with preheated air was investigated numerically in a burner filled with Al2O3 ceramic foams. A two-dimensional model was implemented to simulate the flame propagation process of methane–preheated air combustion at an extra-low equivalence ratio. In addition to the wall heat loss, the effects of the preheated air temperature were analyzed by focusing on the flame front inclination and propagation velocity. The flame front instability for room temperature air agreed well with the results of the corresponding experiments. The results show that an increase in the preheated air temperature helps to improve the flame stabilization, such as inhibiting flame front inclination, decreasing its propagation velocity, and increasing the maximum combustion temperature. A stable combustion flame can be realized for LCFG by preheating the air to a critical temperature, which decreases with increase in the equivalence ratio and decrease in the inlet velocity. The wall heat loss promotes the flame front inclination, whereas it has little effect on its propagation velocity for stable combustion. The results are conducive to clean combustion of LCFG in porous media, and helpful for the design and operation of porous burners.

In this study, a diesel engine was modified to operate in dual fuel mode with natural gas as the main fuel and a novel fuel mixture of biodiesel and glycerol triacetate additive as pilot fuel. Regarding to experimental tests results, engine emissions were modeled using a combination of artificial neural network and genetic algorithm to determine the appropriate ratio of pilot fuel to gaseous fuel, biodiesel and additive to reduce engine emissions. The algorithm inputs were engine torque, pilot fuel and natural gas consumption, biodiesel and additive proportions in pilot fuel, while outputs were exhaust emissions including NOx, PM, CO, and UHC. Overall, the results of the modeling were consistent well with experimental data. Simulations were performed for a variety of biodiesel and additive compositions and it was accordingly concluded that by using biodiesel and additive, NOx and CO emissions were reduced by up to 63% and 42%, respectively, while PM was reduced substantially by 27 times in comparison with neat diesel fuel in the diesel operation mode. In the dual fuel mode, 24% reduction in NOx emission. However, under these circumstances, UHC emission was 10% higher than that of the diesel operation mode.

The development of modern energy technology made more demands for the performance of the gas turbine, and more attention was paid to the engine's stability, efficiency and cleanliness. The technical level of combustor played an important role in the engine's efficiency and emissions issues. In order to broaden the stable working range and reduce emissions of the combustor, the fuel concentration distribution and combustion characteristics of trapped vortex combustor was numerically and experimentally analyzed in this study. The influences of swirl field and fuel injection mode were studied, and the research was conducted under the non-reaction condition and the reaction condition, respectively. Based on the numerical simulation results of fuel concentration distribution, a new type of trapped vortex combustor with centrifugal nozzles was designed, and the combustion characteristics of the combustor were experimentally evaluated. The results showed that a vertical double vortex structure could be formed in the cavity under various conditions. The air velocity of cavity inlet, the spray cone angle, and Sauter mean diameter of kerosene droplets had different effects on the liquid and gaseous fuel concentrations. High efficiency and low emissions combustion could be achieved, which was beneficial to improve gas turbine efficiency and reduce pollution emissions.

This study explores the impact of natural gas (NG) enrichment with high H2 concentrations (20, 30, 40 and 50 by v %) on combustion characteristics, engine performance, exhaust emissions and knock in a compression ignition engine running in dual fuel (DF) mode. Results indicated that H2 addition to NG contributes to enhance gaseous fuel combustion that corresponds to an increased heat release rate (HRR) during the premixed phase of gaseous fuel that also causes an increase in the pressure peak, particularly at high loads. The maximum pressure peak and HRR correspond to 50% H2 addition. The combustion duration is shortened for all H2 mixtures. Regarding engine performance, an important benefit in terms of brake thermal efficiency is noted for all H2 blends; it increases with increasing enrichment rate and reaches approximately 16% increase for the 50% H2 mixture relative to pure NG case. Moreover, enriching NG with H2 is an effective solution for reducing unburned hydrocarbons and carbon monoxide at moderate to high engine loads. However, for NOx emissions, the addition of H2 to NG is only attractive at low and moderate loads. In addition, over 80% engine load, NG enrichment with H2 generates knock, which rapidly reaches high intensities.

As an effective means to improve the efficient use of energy, multi-energy coupled systems have indicated the important direction for the development of Energy Internet in the foreseeable future. However, the uncertainties that exist in various energy networks present severe challenges to the implementation of this innovative system. In this regard, this paper proposed a multi-stage robust optimization model for the coordinated operation of an electricity-gas-transportation coupled system, which simultaneously considered the uncertainties of traffic demands, wind power, and gas fuel consumption by gas-fired units. To conform to the non-anticipative sequential decision-making process for power system scheduling, the multi-stage robust unit commitment (UC) problem was established and considered as the master problem, which was solved by introducing a linear affine rule and the robust counterpart method. The gas network operation feasibility checks in each period were then addressed as the subproblems, and the generalized benders decomposition-based decoupling-coordination strategy was developed to solve the above master-subproblems iteratively. Simulation results demonstrate that the proposed multi-stage robust UC model can achieve a scheduling solution with superior economic performance and reduced conservativeness compared to the two-stage robust UC model. Furthermore, the effectiveness of the decoupling-coordination solving strategy was verified for the multi-energy coupled system.

The rapid growth of natural gas fuel consumption by gas-fired generators and the new emerging power-to-gas technology have intensified interdependency of electric power and natural gas systems. Consequently, such interdependency, together with heterogeneous uncertainties of the power system (e.g., power loads and renewable energy) and the gas system (e.g., gas loads), has brought new challenges to energy system operators for the secure and economic operation of interdependent power and gas systems. Specifically, uncertainties from one infrastructure could easily spread to the other, which consequently increase vulnerability and eventually lead to cascading outages of both systems. This paper proposes a two-stage adjustable robust model to study day-ahead coordinated optimal scheduling of the interdependent power and gas systems. Dual-fuel generating units are also considered for shaving gas fuel consumptions and ensuring the security of both systems during peak gas demand hours. Moreover, Weymouth gas flow constraints are linearized via Taylor series expansion, which facilitates the implementation of column-and-constraint generation algorithm to effectively solve the proposed two-stage adjustable robust model with nonlinear gas flow constraints in the second stage. Numerical case studies illustrate that dual-fuel units can enhance the secure and economical operation of interdependent power and gas systems, especially when natural gas demands present upward uncertainties. It is also demonstrated that power-to-gas facilities can facilitate a deeper penetration of volatile renewable energy by effectively converting excessive renewable generation into natural gas.

This paper proposes an LNG fuel gas supply system in which the compressors are used for multiple purposes. Referred to as the compressor-assisted fuel gas supply system (CA-FGSS), the proposed system uses its compressors to both manage the boil-off gas (BOG) in the LNG fuel tank and generate a pressure differential for drawing LNG from the tank. The feasibility of the defined operation sequence of the CA-FGSS was verified by dynamic process simulations in which the system was applied to two-stroke dual-fuel engines that required medium and high fuel gas injection pressures (16 and 300 bar), respectively. An availability analysis revealed 99% system availability of the CA-FGSS, which has a lower number of redundant equipment compared to a conventional pump-based fuel gas supply system (PB-FGSS). This is because the CA-FGSS does not use components with high failure rates and long maintenance times, such as in-tank pumps in the LNG fuel tank. These findings demonstrate the economic feasibility of the CA-FGSS, which also has a 10% lower capital expenditure compared to a PB-FGSS. A sensitivity analysis of the entire propulsion system of the CA-FGSS further showed that it was operationally more economical than a PB-FGSS for the same gas supply pressure. Moreover, a high-pressure propulsion system that utilizes the CA-FGSS was found to be more economical than a medium-pressure propulsion system for a high LNG price.

Due to the growing increase in fuel price, a significant part of costs of power plants is expended on obtaining high-quality fuels. The change of fuel type from the natural gas to the liquid in the winter due to the increase in natural gas consumption is the main reason for this research. The goal is to select the appropriate fuel type from the Energy, Exergy, Exergy-economic, and Environmental (4E) aspects. The topic of this paper is an irreversible comparison of combined cycle power plant (CCPP) components by changing fuel type from natural gas to liquid fuels with different APIs. The costs resulting from the pollution of normalized air with fuel change were compared. The results were validated by the data from the largest CCPP in Iran. Multi-objective optimization of the CCPP was implemented by objective functions of the price of the power produced, exergy efficiency and normalized production amount of CO2. The results showed that decrease in API˚ led to proper exergy efficiency and cost but exposed very high environmental impacts compared with gas fuel. Results of changing objective functions demonstrated that propagation rate of CO2 in gas fuel was much lower than that of liquid fuel.

Exergy analysis as well as energy analysis is applied to Chinese comprehensive utilization system, in which oil shale is firstly introduced to fluidized bed (FB) retort for obtaining oil and resulting semicoke is fed to circulating fluidized bed (CFB) reactor for further utilization. During the calculation, linear programming helps optimize the efficiency of FB retort in the system. In the light of the results, the process flow diagram of the whole system is redrawn. Also, this paper discusses how three operating parameters (the retorting temperature, the mass of burned fuel gas and the temperature of circulating ash) influence the system, especially exergy efficiency. With the retorting temperature increasing, the exergy efficiency first increase and then decrease, and the highest exergy efficiency is in the temperature range 460–490 °C. Compared with retorting temperature, the mass of burned fuel gas and circulating ash temperature have less effect on the exergy efficiency of the whole system. But it is a good strategy for stable operation of the system to burn more fuel gas to provide more energy and exergy to FB retorting unit. This work could give further detailed suggestions and more reference data to operate the system stably and efficiently.

Experimental investigations of the effects of a new gaseous fuel injector on the performance of a micro gas turbine combustor have been conducted. The new injector which is called swirl injector exerts a swirl-like motion on the fuel flow to increase air-fuel mixing in the combustor. The results, including temperature distribution in the secondary zone of the combustor, NOx, CO, and CO2 emissions, thermal power, and pattern factor are compared with the conical injector configuration. The results show that the temperature distribution is more uniform, both at the secondary zone and outlet section of the combustor in the swirl injector configuration, and the pattern factor of the combustor is reduced by a factor of two. Moreover, the mean outlet temperature of the combustor is higher in the swirl injector configuration which leads to increased thermal power and combustion efficiency up to 12%. Analysis of the emission of the combustor reveals that the CO emission can reduce to half in the swirl configuration at high fuel flow rates. NO emission, however, is two times higher in the new configuration at low fuel flow rates, but at higher flow rates the NO emission is equal to the conical injector configuration.

In this paper, a fast and effective dynamic model was developed to predict and investigate the performance of liquefied natural gas (LNG) fuel tank pressurization under marine conditions. An extended sloshing Nusselt number was defined to quantitatively evaluate the heat transfer enhancement in horizontal tanks under resonant sloshing. The validity of the model was confirmed by the corresponding experimental data. The pre-pressurization process, the fuel gas supply process, and the cryogenic liquid sloshing were investigated for two types of LNG fueled ships. Parametric studies, including the tank size, the filling level, the rated power, the engine load, and the sloshing intensity were conducted. The results showed that the heat transfer between the vapor and tank wall dominates the pressurization process, while the vapor condensation at the liquid-vapor interface dominates the holding period and the sloshing process. Moreover, the sloshing has a severe impact on the tank pressure, especially when the resonance condition of the tank is met, which can cause the shut-down of gas engines in extreme situations.

This paper presents theoretical study of the concept of a small-scale combined cycle system composed of natural gas fired microturbine and Organic Rankine Cycle, integrated with thermal gasification of biomass. A conventional natural gas fired microturbine engine is applied within the system. Gaseous fuel from an updraught biomass gasification reactor is burned in duct burners located in the exhaust gas stream downstream of the turbine. Enthalpy of the combustion gases is used in the ORC cycle. The only product of the system is electric energy. Mathematical modelling of the system gives estimated values of achievable power and energy efficiency of the proposed setup. The plant can be considered as a robust technology for utilization of scattered biomass resources located in places where a natural gas network is available. The main issues addressed in the paper are: configuration of the ORC technology and allocation of generated electricity between natural gas and biomass. Energy and exergy allocation keys are demonstrated. An initial cash flow calculations are presented in order to assess financial performance of the plant.

The performance of a natural iron ore originated from Mentes mine (Kayseri-Turkey) as an oxygen carrier in the CLC process was assessed in this study. A laboratory scale, alternating atmosphere fluidized bed set-up was used in order to simulate the CLC conditions. The oxygen carrier material was stable until the end of tests, and it exhibited more than 90% gas yield during the tests when fueled with pure CO (flow rates between 130 and 200 W-th) at 800 degrees C (1073 K). On the other hand, the syngas yield was approximately 83% at almost the same test conditions (flow rates between 120 and 180 W-th). It was determined that test temperature had almost no effect on fuel gas yield. (C) 2017 Elsevier Ltd. All rights reserved.

Biomass-steam gasification is an efficient unitization technology of biomass to produce gas fuel for a combined cooling, heating and power (CCHP) system. The aim of this paper is to modify the exergoeconomic method and analyze the cost allocations of multi-products from CCHP system. Firstly, two integrated CCHP schemes with biomass-steam gasification are designed. The difference lies in the gasification endothermic process driven by electricity and thermal energy from the product gas, respectively. The thermodynamic models are presented and validated. Then, a modified exergoeconomic method based on energy level is proposed to accord with the principle of high quality and high price. Finally, a case study is presented to analyze the thermodynamic performances of two CCHP schemes and the production cost allocations including electricity, chilled water for cooling (hot water for heating) and domestic hot water in different operation modes. Compared with the previous exergoeconomic method, the unit exergy cost of electricity with higher energy level increases 0.09 Yuan/kWh while the cost of other products with lower energy level decrease. The results show that the modified exergoeconomic method is more reasonable and efficient.

Hydrogen-rich industrial by-products, such as coke oven gas (COG) and synthetic ammonia exhaust tail gas, are often simply utilized as fuel gas, or even not utilized at all in many cases. An innovative and efficient utilization method is proposed and investigated in this paper. Aiming to coproduce liquid hydrogen and liquefied natural gas (LNG), three helium reverse Brayton cycles are constructed, optimized, analyzed and compared. The LN-He-1 process is constructed with reference to conventional industrial hydrogen liquefaction processes, but with different feedstock gas. The LN-He-2 and N–He processes, which are an improvement on the basis of LN-He-1. A combination of distillation and flash is utilized to reduce the separation load. Analysis of load variation, power consumption, exergy, heat transfer and turbomachinery efficiencies are carried out. For different feedstock gas compositions, the specific power consumptions of LN-He-1, LN-He-2 and N–He processes are within 26.45–54.78 kWh/kmol (feedstock gas), 26.32–53.78 kWh/kmol (feedstock gas) and 21.94–50.42 kWh/kmol (feedstock gas), respectively. The exergy efficiencies are between 13.0% and 66.5%.

The direct carbon solid oxide fuel cell (DC-SOFC) is a green and efficient energy conversion device with all-solid-state structure, which can convert carbon fuel into electricity directly. Recently, using biomasses as fuels for DC-SOFC has become fascinating due to their abundance and renewable property. However, it usually provides inferior performance compared to that with gas fuel feeding (hydrogen). Here, we report a promising and high-performing tubular segmented-in-series YSZ electrolyte-supported DC-SOFC stack. Thereinto, the YSZ electrolyte supports are fabricated by dip-coating and both pure walnut shell biochar and Fe-loaded biochar are used as fuels. The single cell can achieve a maximum power density of 147 mW cm−2 at 800 °C and it is improved to 205 mW cm−2 as FenOm catalyst is loaded on the biochar fuel. Furthermore, a two-cell-stack of DC-SOFC operated with Fe-loaded walnut shell char is assembled and tested. It delivers an outstanding performance, with an OCV of 1.98 V, an output power of 1.11 W and a maximum volumetric power density of 505 mW cm−3 at 800 °C, indicating high potentials for developing into a high performance battery for portable or distributed applications.

Scrap tires are a burdensome and common kind of waste. Almost 1.5 billion tires are produced each year and each tire produced will eventually join the waste stream. According to European Union regulations, the disposal of waste tires is prohibited; as an alternative they should be recovered and recycled. Pyrolysis allows the dissolution of the waste and it also produces useful by-products. In this process gas, liquid and solid phases are formed. Pyrolytic gases have high heating value, about 30–40 MJ/Nm3. The energy obtained from combustion of the pyrolytic gas is enough not only to perform the pyrolysis process but it can also be utilized for other applications. However, there is a big challenge: the concentration of SO2 in the flue gases is greater than regulatory limits. Similar situations could also arise with HCl, NOX and heavy metals. In order to meet regulatory requirements and maintain optimum pyrolysis, gas cleaning methods will be needed in order to remove those substances from the exhaust gases formed during waste tire pyrolysis. The main aim of this article is to review the properties of pyrolysis gas for energy recovery because it is a good gaseous fuel. In addition, possible implications will be identified.

This article reports and discusses the application of an analysis of reservoir greenhouse gas (GHG) emission using the net emission approach (difference between post-impoundment and pre-impoundment emissions) to assessments of GHG emissions from hydropower reservoirs compared with GHG emissions from thermal plants producing electrical energy. Reservoirs were chosen from a representative set of different Brazilian biomes and climatic regimes. A field campaign program was performed between 2011 and 2013 to estimate net GHGs emissions from 8 Brazilian representative hydropower plants. Four field campaigns to each hydropower plant were scheduled within two-month intervals to measure CH 4 , CO 2 and N 2 O diffusive fluxes on air-water interfaces (reservoir surface area and downstream river, CH 4 and CO 2 ebullitive fluxes on the air-water interfaces of the reservoir and degassing rates at powerhouse turbines). Permanent carbon burial rates were also measured in the reservoirs. Statistical analyses of the data were representative of post-impoundment annual values for GHG emissions for each pathway and for permanent carbon burial rates. Values for pre-impoundment representative annual GHG emission were calculated taking into account previous land cover mapping data from the period of the creation of the reservoir, and reference GHG flux values established by the literature for each land cover class. To compare with thermopower generation, annual values obtained were expressed as GHG intensity in g of CO 2 eq.kWh −1 considering a Global Warming Potential value for 100 years; the factor 44/12 was considered as the permanent carbon burial rate necessary to transform carbon into carbon dioxide; and production of plant firm energy was also considered. Annual net GHG emissions estimates were expressed as GHG intensity in g of CO 2 eq kWh −1 . In all cases analyzed, hydroelectric plants emit less greenhouse gases than natural gas and coal-fired thermoelectric plants. The exception was the Balbina hydroelectric dam, which has a low annual power generation and a very large reservoir: it emits more gas per unit of energy than the two thermoelectric plants abovementioned.

A gas and steam mixture cycle (GSMC) is presented with a mixture of LNG/O2 (liquid natural gas/oxygen) combustion product and feedwater as working medium, integrating features of high efficiency power generation, peak shaving, energy storage and CO2 capture. The liquefied oxygen is produced during off-peak hours. During the operation hours, the cryogenic liquids of both LNG and oxygen are pumped to a high pressure and preheated before entering the combustors through the burners. The combustion product heats and mixes with the atomized feedwater to form supercritical H2O/CO2 mixture vapor for power generation in a turbine unit. The CO2 vapor is separated from condensate water in the condenser and liquefied by the cryogenic liquids of both LNG and oxygen after being compressed to a higher pressure. The circulation feedwater is injected to the annular channel between flame tube and shell cylinder of modular combustor via feedwater heating system. The results show that under the conditions of turbine inlet parameters of 40 MPa/800 °C and condensation temperature of 30 °C, the output power efficiency based on the thermal value of LNG fuel is 49.2% and the equivalent net efficiency is 46.4%, which accounts for 1/4 off-peak electricity consumption for liquid O2 production.

This paper presents an exergy and environmental assessment of a 1000 metric t/day ammonia production plant based on the steam methane reforming (SMR) process, including the syngas production, purification (CO 2 capture) and compression units, as well as the ammonia synthesis and purge gas treatment. An integrated heat recovery system produces power and steam at three pressure levels, besides exporting hot water, CO 2 and fuel gas, with no additional heat or power consumption being required. Two configurations for ammonia refrigeration process (−20 °C) are compared in terms of power consumption. Exergy cost data for upstream processing stages of natural gas is used to calculate the extended exergy cost of the products of the plant, namely ammonia, CO 2 and fuel gas. Moreover, an appropriated methodology is employed to properly allocate the renewable and non-renewable exergy costs, as well as the CO 2 emissions of the reforming, shift and furnace stack among the products of the plant. By considering that the cost reduction of the combustion gases is a linear function of the exergy flow rate reduction in each component of the heat recovery system, an improved allocation of the CO 2 emission cost along the convection train is performed. A breakdown of the total exergy destruction rate of the plant (136.5 MW) shows that about 59% corresponds to the reforming process followed far behind by the ammonia synthesis and condensation (18.3%) and the gas purification units (13.2%). The overall exergy efficiency of the ammonia plant is calculated as 66.36%, which is enhanced by recovering the hydrogen-rich and fuel gases in the purge gas treatment process. The total and non-renewable exergy costs and CO 2 emission cost of the ammonia produced are calculated as 1.7950 kJ/kJ and 0.0881 kg CO2 /MJ, respectively. In addition, a rational exergy cost of 1.6370 kJ/kJ and CO 2 emission cost of 0.0821 kg CO2 /MJ are allocated to the CO 2 gas, which can be supplied as feedstock to an associated chemical plant (urea, methanol, polymers, etc.).

A pressurized oxy-fuel combustion system is a technology for carbon capture and storage with a low efficiency penalty. In this study, the characteristics of combustion, heat transfer, and NOx/SOx emissions at various pressures were investigated using a lab-scale pressurized oxy-fuel combustion system. A gaseous fuel, composed of CO and H2, and pure oxygen were considered. The internal flue gas recirculation was induced by the inner wall to control the high oxy-flame temperature. The total heat recovery rate determined using the water jacket is 3% higher at 10 barg compared with atmospheric conditions, although the combustion temperature is lower. The heat flow rate increased by a higher H2O fraction in flue gas because the emissivity of H2O is higher than that of CO2. Under the condition of low H2O in flue gas, NOx and SOx simultaneously decreased, by approximately 50% and 63% at 10 barg, respectively. The concentrations of NOx and SOx with a higher H2O contents condition in flue gas decreased by 87% and 93% respectively at 10 barg, compared with atmospheric conditions. The effects of H radicals and the H2O fraction on the NOx and SOx oxidation and decrease were identified.

The regulations of the international maritime organization (IMO) on ship emission are becoming increasingly strict. Liquefied natural gas (LNG) is an ideal alternative fuel for vessels, considering its environmental and economic advantages. In this paper, comparative life cycle cost (LCC) analysis of low pressure fuel gas supply systems (FGSS) for LNG fueled ships was performed. Nine cases with different ship scale and FGSS configurations were compared and analyzed, in which the BOG was handled by gas combustion units (GCU), auxiliary engines or reliquefaction devices. The variation of utility cost of FGSS during different stages of voyage was particularly considered. Moreover, sensitivity analysis was performed to investigate the influences of sailing time index, LNG price and lifetime on LCC. The study revealed that the LCC of FGSS depends strongly on ship scale, LNG fuel price and ship operation. BOG reliquefaction onboard is a feasible solution when the sailing time index is low and LNG price is high, especially for large scale ship. On the contrary, when the sailing time index is high and LNG price is low, it is more economic to supply the BOG to auxiliary engines after compression.

Pilot ignited direct injection natural gas engines have the potential to obtain both high efficiency and low emissions, thus, are considered as promising alternations for diesel engines. In order to assess the effects of gaseous fuel composition on this type of engines, a three-dimensional model was constructed based on a new mechanism developed for the high-precision prediction of soot precursors. The numerical results showed that thermal efficiency could be improved by increasing nitrogen proportion at medium and high loads as well as increasing propane proportion at low load. Regarding emissions, it was found that ethane addition will lead to deteriorated NOx and CO emissions at high and medium loads along with increases in soot emissions at all loads. When propane is blended, though notable increased NOx emissions and higher soot emissions could be observed at all loads, improved CO emissions are revealed at high load with small blending ratios and at low load with all blending ratios. In contrast to ethane and propane addition, nitrogen addition is favorable for NOx control at all engine loads and is beneficial for soot control at high and medium loads. CO emissions, however, will suffer from nitrogen addition at high and low loads.

Ceiling thermal impingement fire spread induced by indoor uncontrollable energy combustion occurred frequently and caused many casualties and property damage. The sub-atmospheric pressure environment has a great impact on uncontrollable energy combustion characteristics of hazardous combustible gaseous fuel fire. China west high-altitude cities develop rapidly due to the economic development, and fire accidents frequently occur. This paper focused on experimentally studying the ceiling fire impingement hazard characteristics induced by wall-attached fires under sub-atmospheric pressures, the various sub-atmospheric pressures (from 55 kPa to 100 kPa), energy heat release rates (from 0.25 kW to 2.5 kW), and source-ceiling heights (0.475 m, 0.38 m, 0.285 m, 0.19 m and 0.095 m) were selected as an variable. The ceiling flame extension lengths of facing and lateral directions were measured and analyzed. Result showed that, the dimensionless ceiling flame extension area is higher in sub-atmospheric pressures. There are many differences between them due to the lower buoyancy in various sub-atmospheric pressures. By accounting for the air entrainment change characterization, it is found that the air entrainment of wall-attached propane jet fire is weaker in sub-atmospheric pressures. The influence of pressure on the flame expansion area is related to the 4/5 power of the ratio of the entrainment coefficient ( ( α / α 100 ) 4 / 5 ). And a new model was finally obtained to correlate ceiling flame extension area induced by wall-attached fires with various sub-atmospheric pressures. This work provides can help understand ceiling impingement flow and hazard characteristics under various sub-atmospheric pressures.

EGR (Enhanced natural gas recovery) with CO2 sequestration offers the prospect of significant environmental and economic benefits by increasing gas recovery while simultaneously sequestering the greenhouse gas. Field-scale deployment is currently limited as the risks of contamination of the produced gas by injected CO2 are poorly understood. Reservoir simulations offer a method to quantify the risk but only if sufficiently accurate. For the first time, finite element simulations are presented for several EGR scenarios that incorporate the most accurate models available for fluid mixture and rock properties. Specifically, the GERG-2008 EOS (equation of state) is utilised to describe the supercritical fluid mixture's density, as are reference correlations linked to the most accurate experimental data available for diffusivity and viscosity. Realistic values for rock dispersivity and tortuosity determined from high-accuracy core-flooding and NMR (nuclear magnetic resonance) experiments were also integrated. The relative impacts of these properties were investigated for a benchmark layered reservoir with a quarter 5-spot well pattern. Recovery efficiency at different CO2 injection rates was also investigated and was determined to be the dominant consideration: a 100-fold rate increase improved recovery from 53% to 69% while CO2 breakthrough time decreased by less than expected. Collectively, these results emphasise the importance of accurate reservoir simulations for EGR.

The high price of crude oil, strict environmental regulations and ever-increasing demand for energy have made refineries adopt a more holistic approach to integrating energy, economics and environment in their design and operation. Gas flaring is a major factor for the wastage of energy in oil and gas industries that could be better utilized and even generates revenue. Integration and use of wasted and flared gases with fuel gas network (FGN) is an effective approach for reducing GHG emissions as well as conserving energy in refineries. In this paper, current FGN model introduced by Hassan et al. was modified and also a novel methodology was presented for grass-root and retrofit design of FGNs using integration of flare gas streams. GHG emission concept is added to the base model as new constraint to control and minimize the flaring. A FGN proposed for a refinery case study with integration of flare gas streams indicated a 12% reduction in natural gas consumption compared to the non-integrated flare gas stream case and a 27.7% reduction compared to the base case with no FGN. In the retrofit case, results suggested that the maximum utilization of flare gas streams can be the most profitable solution.

This paper describes an original and innovative technical solution for exploiting low-temperature energy sources from cogeneration gas reciprocating engines installed within district heating systems. This solution is suitable for those systems in which the heat is generated by the use of reciprocating engines powered by gaseous fuel for combined heat and power production. This new technical solution utilizes low-temperature energy sources from a reciprocating gas engine which is used for a combined production of heat and power. During the operation of the cogeneration system low-temperature heat is released, which can be raised to as much as 85 °C with the use of a high-temperature heat-pump, thus enabling a high-temperature regime for heating commercial buildings, district heating or in industrial processes. In order to demonstrate the efficiency of utilizing low-temperature heat sources in the cogeneration system, an economic calculation is included which proves the effectiveness and rationality of integrating high-temperature heat-pumps into new or existing systems for combined heat and power production with reciprocating gas engines.

This study proposes a new boosting system that is capable of increasing the pressure of a low-temperature liquid such as LNG (liquefied natural gas) and supplying it continuously to a ship engine without using cryogenic pumps. The system consists of two boosters, each of which is equipped with a mini-vaporizer and regulating valves. The two boosters operate alternately to ensure a continuous supply of the low-temperature pressurized liquid. The operating philosophy is that the mini-vaporizer of the first booster increases the internal pressure and supplies the pressurized liquid to the engine while the other booster is filled with the low-pressure fresh liquid, waiting for its turn to supply the liquid to the engine. This boosting system is applied to an LNG fuel gas supply system. Dynamic process simulation is conducted to demonstrate its operational feasibility. Assessment of operation availability and life-cycle cost analysis are also conducted to show that the proposed system offers better reliability and cost-effectiveness than the conventional pump system.

In this study, a fixed bed of pulverized coal particles was employed to enhance the precombustion CO 2 capture from fuel gas (40 mol% CO 2 /H 2 ). The performance of the HAHF (hybrid adsorption-hydrate formation) process occurred in the fixed bed was evaluated at different liquid saturations and operation pressures. The experiments were carried out at 274.2 K with the pressure varying from 3.0 MPa to 6.0 MPa. 1.0 mol% THF (tetrahydrofuran) solution instead of liquid water was used to saturate the fixed bed and reduce the hydrate phase equilibrium conditions. The results indicated that gas hydrate nucleation in the fixed bed was quickly induced by gas adsorption in coal particles. The HAHF process was dominated by hydrate formation as the fixed bed saturation increased, and the CO 2 recovery and separation factor were increased. Gas consumption during the HAHF process was promoted with the increase of operation pressure, but the CO 2 recovery and separation factor decreased. In the fixed bed of coal particles saturated by 1.0 mol% THF solution the highest gas uptake obtained was 51.9 mmol of gas/mol of water, which was comparable with that obtained in the fixed bed of silica sand in the presence of 5.53 mol% THF. Therefore, compared with the hydrate based gas separation process, the hybrid adsorption-hydrate formation process proposed in this study could be a viable option for CO 2 capture from fuel gas.

Using the Bakken shale play as a case study, the previous part of this two-part series demonstrated how small-scale mobile plants could be used to monetize associated or stranded gas effectively. Here, we address the issue of uncertainty in future supply, demand and price conditions. To this end, we modified our multi-period optimization framework to a stochastic programming framework to account for various scenarios with different parameter realizations in the future. The maximum ENPV (expected net present value) obtained was $2.01 billion, higher than the NPV obtained in the previous part. In addition, the value of the stochastic solution was 0.11% of the optimal ENPV, indicating that the flexible nature of mobile plants affords them a great advantage when dealing with uncertainty.

THF (Tetrahydrofuran) is the most commonly employed promoter for the gas hydrate formation pertaining to applications like carbon dioxide capture and energy storage (for natural gas and hydrogen). In this work, THF was investigated as a promoter for pre-combustion capture of carbon dioxide (CO 2 ) from fuel gas mixture (CO 2 /H 2 ) in a systematic manner. 0.5, 1.0, 3.0 and 5.56 mol% THF solution were employed with different driving force conditions to study the effect of pressure, temperature and composition of gases in hydrate. The kinetic performance of the CO 2 /H 2 /THF gas hydrate system was evaluated by reviewing the IT (induction time), normalized gas uptake, normalized rate of hydrate formation and the hydrate phase composition. The optimum operating conditions and optimum THF concentration in this study was found to be 6.0 MPa, 282.2 K, and 5.56 mol% THF respectively. 5.56 mol% THF solution yielded an average gas uptake of 13.9 mmol of gas/mol of water for hydrate growth and an average normalized rate of hydrate formation of 1679.8 mmol s −1 m −3 .

This paper deals with a furnace which its fuel (gas oil) is replaced by natural gas in such a way that the flue gas temperature and the rate of heat removal from the furnace are remained unchanged. The question now is: what are the benefits due to replacement of the fuel of the furnace? The objective of this work is to answer this question. Modeling the furnace similar to a continuous flow stirred-tank reactor, the computational results show that the production of NO for equivalent natural gas is considerably less than that for gas oil. It is also obtained that the production rates of CO2 for both gas oil and natural gas are approximately close together. Considerable cost reduction is obtained by using natural gas in gas oil furnaces.

The solar pyrolysis of beech wood was investigated with the objective of determining the optimal pyrolysis parameters for maximizing the LHVs (lower heating values) of the gas products because they can be further utilized as fuel gas for power generation, heat and production of transportable fuels. The investigated variables were the pyrolysis temperature (600–2000 °C), heating rate (5–450 °C/s), argon flow rate (6–12 NL/min) and pressure (0.44–1.14 bar). The results indicate that the product yields (liquid, char and gas), gas composition (H2, CH4, CO, CO2 and C2H6) and LHV are strongly influenced by the pyrolysis parameters. The total gas LHV greatly increases with increasing temperature (from 600 to 1200 °C) and increasing heating rate (from 5 to 50 °C/s), which is mainly due to increases in the CO and H2 yields. The variation in the gas LHV with pressure and argon flow rate is slight. A maximum gas production of 62% with a LHV of 10 376 ± 218 (kJ/kg of wood) is obtained under solar pyrolysis conditions of 1200 °C, 50 °C/s, 0.85 bar and 12 NL/min. This heating value is almost identical to that of the initial beech wood, thus confirming that valuable combustible gases can be produced via the solar pyrolysis of beech wood.

In order to enhance energy recovery efficiency from MSW (municipal solid waste), an in-situ steam gasification method for hydrogen production where CaO was used as CO2 sorbent and catalyst in the process was proposed. The effects of moisture content, the molar ratio of CaO to carbon in wet MSW ([Ca]/[C]) and reactor temperature on H2 yield and gas composition were investigated. The results showed that maximum hydrogen volumetric concentration (49.42 vol%) and hydrogen yield (277.67 ml/g MSW) were obtained at 40 wt.% moisture content at gasification temperature of 750 °C and [Ca]/[C] ratio of 0.7. The proposed direct gasification of wet MSW with in situ CO2 capture process may be a promising route to produce hydrogen rich fuel gas using MSW.

SOFCs (solid oxide fuel cells) are a promising technology for electric power generation, because of their high efficiency and fuel flexibility. Relative to more mature technologies, they appear very competitive starting from small-scale applications. The aim of this study is to map SOFC performances varying fuel composition, reproducing gases of technical interest (biomass air and oxy-gasification, water and carbon dioxide co-electrolysis, steam methane reforming) and to provide a forecasting tool to predict performance upon the fuel composition occurring in any application. Therefore, at first commercial SOFC are tested using several fuel gas mixtures produced by means of the chosen technologies (H2, CO, CH4 molar fractions ranges are respectively 8–50%, 0–42%, 1–8%). Secondly, experimental data are used to build a mathematical tool to predict SOFC characteristic curve from the fuel composition. This result is interesting from the point of view of system-level modelling, because it allows characterizing commercial SOFCs performances in many technical applications. Forecast error is less than 1%. Because of its accuracy, the model can be implemented to assess properly SOFC performance as a consequence of any particular hybridization, whereas fuel composition falls into the range already defined.

Pipeline companies deploy a series of pipeline resource optimal configurations and efficiency enhancement strategies with the purpose of improving financial benefits. Thus far, pipeline owners and stakeholders have usually focused on efficiency evaluation processes based on the technological aspects of transmission. In this context, here we derive a pipeline efficiency evaluation method from the perspective of the pipeline energy input–output by monitoring the energy and transmission amount changes along the pipeline. The parameter of volumetric work, which is defined as the energy consumption required for transporting a certain amount of gas over a certain distance along the pipeline, measures the energy change except for the intrinsic energy and mechanical pressure energy. With no distribution stations being taken into consideration, the gas amount change due to the pipeline's self-energy consumption is regarded as the equivalent fuel gas while also considering the volumetric work change caused by gas consumption. Upon accounting for all factors via volumetric work and pressure energy, we utilise the input–output variation to develop a data envelopment analysis (DEA) model, which affords the relative efficiency via calculation and evaluation of the operating efficiency of the pipeline and related facilities. Subsequently, analytic hierarchy process (AHP) is introduced to determine the impact from different facilities. Our result, which presents the difference between the ideal objective efficiency and current efficiency based on the measured volumetric work can aid in identifying the most efficient situation. Here, we note that owing to factors such as the inlet pressure and equipment configuration, the first station usually exhibits lower efficiency than the other stations. In terms of energy for the whole pipeline, the efficiency (unit consumption) grows in inverse proportion to the transmission amount. In the final phase of the study, we consider an actual pipeline case study in our analysis and verify the practical utility of this method. Our results also indicate that the transmission efficiency and economic efficiency exhibit a trade-off relationship.

The present paper briefly elaborates the influence of inlet valve masking (IVM) and nozzle hole configuration on performance, emission and combustion behaviour of a single cylinder water cooled turbo-charged engine fuelled with Calophyllum inophyllum as injected fuel and babul wood chip generated producer gas from a downdraft gasifier as inducted fuel with modified mask angle and nozzle hole configuration keeping compression ratio, speed, injection parameters constant. Experimental results depicted a lower brake thermal efficiency of (2.1%↓ and 3.3%↓) and exhaust gas temperature of (50.3%↓ and 49.6%↓) with increased specific fuel consumption by (3.7%↑ and 4.3%↑) for IVM-90 and 4-hole nozzle. Considering emission characteristics, smoke opacity and nitric oxide were reduced by (42.7%↓ and 48.1%↓) for IVM-90 and (32.4%↓ and 41.7%↓) for 4-hole nozzle, with a marginal increment in carbon monoxide and hydrocarbon by (16.6%↑ and 4.5%↑) for IVM-90, while (16.7%↑ and 6.7%↑) for 4-hole nozzle. Moreover, heat release rate and cylinder pressure were on higher side in contrast to diesel injected single fuel mode. Hence, introduction of valve mask and modified nozzle hole with inducted gaseous fuel in dual fuel mode has proven to be effective in enhancing engine performance and combustion characteristics, thereby reducing emission levels.

A plastic waste containing polyvinyl chloride was gasified in a two-stage gasifier consisting of a fluidized bed reactor and tar-cracking zone to produce a hydrogen-rich producer gas with low tar and HCl contents. In particular, this study investigated the effects of calcined Ca-based additives, especially oyster shells, and a Ni-loaded activated carbon on the chlorine and tar removal. Additionally, a ∼3 h gasification of the plastic waste was performed using a distributor with a large hole size to confirm the gasification stability. In the experiments, where 900 g activated carbon was applied, all the producer gases were free of tar. The maximum H 2 content (30 vol.%) in the producer gas was obtained with 900 g of Ni-loaded activated carbon. Chlorine in the feed material was mainly distributed in char and condensate liquid. The HCl contents in the producer gases obtained with the calcined Ca-based additives including oyster shells were under 1 ppm. The ∼3 h gasification revealed that the gasification was stable in terms of tar content in producer gas and producer gas composition.

In this work, a systematic review of the literature work done so far on the use of hydrate crystallization as a basis to develop data for the hydrate based gas separation (HBGS) process for the capture of CO2 from fuel gas mixtures is presented. Such a gas mixture may arise in integrated gasification combined cycle (IGCC) power plants. A thorough assessment of the thermodynamic, kinetic factors and economic aspects of the HBGS process and critical comments are presented. Compared with competing technologies, high CO2 capacity and the use of water as a solvent are key advantages for the HBGS process for CO2 capture. Furthermore, in this review, a snapshot of the current state-of-the-art is presented and further research and development opportunities and pathways for commercializing the HBGS process for pre-combustion capture of CO2 from IGCC power plants are discussed.

The present study demonstrates the potential of hydrogen (H2)-doped ammonia (NH3) as a carbon-free fuel. The extinction limits, flame temperature and morphology of the counterflow nonpremixed NH3–H2/air flames at elevated temperatures and normal pressure are experimentally determined. Also, the detailed flame structure and the extinction limits are computed using a detailed kinetic mechanism. Results show that the blow-off limits, the concentration of radicals H, OH and O and the maximum flame temperature are enhanced with H2 substitution in NH3/air flames. This supports the potential of H2 as an additive for improving the reactivity and ignition of nonpremixed NH3/air flames and thus the potential of H2-doped NH3 as a carbon-free fuel. Meanwhile, the extinction limits (in terms of the mole fraction of NH3 in the fuel gas) and the maximum flame temperature are reduced with increasing strain rates, indicating that flames can sustain more NH3 at low strain rates. Also, it is observed that the blow-off limits and the maximum flame temperature are enhanced with increasing air temperature. Measured and predicted tendencies of the extinction limits and temperature for various conditions show encouraging agreement, but quantitative discrepancies among the measurements and predictions merit additional consideration in boundary condition modeling and the reaction mechanism.

In order to accomplish significant primary energy saving and GHG (greenhouse gas) emissions reduction, CHP (combined heat and power) technology can be adopted largely for industrial and civil sectors. Waiting for the cutting-edge appliances (i.e. Fuel Cell) wide deployment, ICEs (internal combustion engines) fuelled with an environmentally-friendly fuel, such as H2NG (hydrogen-natural gas mixtures) could represent the bridge technology towards the forthcoming pure hydrogen economy. This paper deals with the results of an experimental campaign carried out on a Single Cylinder ICE, fuelled with NG (natural gas) and H2NG @ 15% vol. In detail, energy performances were assessed at rated and partial loads. From data analysis, it emerged that the electrical efficiency increased up to 2.28%, at the expense of the heat recovery one, having added hydrogen. Additionally, due to the higher water content in exhaust gas when H2NG is burned, it was investigated on how heat recovery efficiency has been affected by condensing operating conditions. Finally, to estimate this benefit, an expeditious procedure was developed building three maps for H2NG blends condensing properties from 0% up to 30% vol. of H2. Their outputs provided the condensation efficiency value and the absolute gain of heat recovery one with varying exhaust gas temperatures and hydrogen fraction in the mixture.

In this work, an experimental study of the gasification of lignite with various particle sizes was carried out in a pilot-scale (10 kWe) downdraft type fixed bed gasifier. The main objective of the study was to investigate the feasibility of the lignite as a fuel for downdraft gasifier and to evaluate the effect of the particle size on gasifier performance. The influence of the particle size on fuel consumption rate, temperature profile in various zone, gas yield, gas composition and cold gas efficiency was studied. Six different particle sizes viz. 13–16 mm, 16–19 mm, 19–22 mm, 22–25 mm, 25–28 mm, 28–31 mm were selected for experimental work. With the increase in particle size, the reduction in fuel consumption rate was observed, whereas the producer gas production rate had increased. The heating value of the gas increased as particle size increased from 13–16 mm to 22–25 mm and then same had decreased with increase in particle size. Higher temperature in reduction zone resulted in higher H 2 and CO contents in producer gas. Under the experiment conditions, the fuel consumption rate, gas yields, LHV (Lower heating value) of gas fuel and cold gas efficiency varied in the range of 9.58–10.67 kg/hr, 2.43–2.63 Nm 3 /kg, 3.33–4.17 MJ/Nm 3 and 51.5%–65.7% respectively. The experimental results showed that the gasification performance was better with lignite particle size of 22–25 mm.

The progressive reduction of high-quality-easy-to-extract energy is a widely recognized and already ongoing process. Although depletion studies for individual fuels are relatively abundant, few of them offer a global perspective of all energy sources and their potential future developments, and even fewer include the demand of the socio-economic system. This paper presents an Economy-Energy-Environment model based on System Dynamics which integrates all those aspects: the physical restrictions (with peak estimations for oil, gas, coal and uranium), the techno-sustainable potential of renewable energy estimated by a novel top-down methodology, the socio-economic energy demands, the development of alternative technologies and the net CO 2 emissions. We confront our model with the basic assumptions of previous Global Environmental Assessment (GEA) studies. The results show that demand-driven evolution, as performed in the past, might be unfeasible: strong energy-supply scarcity is found in the next two decades, especially in the transportation sector before 2020. Electricity generation is unable to fulfill its demand in 2025–2040, and a large expansion of electric renewable energies move us close to their limits. In order to find achievable scenarios, we are obliged to set hypotheses which are hardly used in GEA scenarios, such as zero or negative economic growth.

Polygeneration system for chemical and power co-production has been regarded as one of the promising technologies for fossil fuel sustainable utilization. In this paper, a new polygeneration system with carbon capture is integrated, based on coal gas and coke oven gas inputs for methanol and power co-production. New system can achieve more than 5% of primary energy saving ratio, and more than 50% of exergy efficiency. Exergy balance and Energy Utilization Diagrams (EUDs) are applied to show the performance improvement. In the system, pressure swing adsorption process is used to remove hydrogen from coke oven gas to enhance methane concentration, which reduces energy consumption and exergy destruction of reforming process. And for the methane reforming process, thermal energy for reforming is sensible thermal energy of syngas out of gasifier instead of fuel gas combustion. Furthermore, fresh syngas for methanol synthesis is the mixed gas of reformed coke oven gas and coal gas, which means that syngas components are adjusted without energy consumption. Lastly, CO2 is recovered during chemical energy discharge and at the highest concentration resulting in less energy penalty. All of these energy integrating characteristics result in good thermal performance, which supplies a new direction for clean energy technology.

In this work, we present enhanced kinetics of hydrate formation for the clathrate process in the presence of two liquid promoters namely THF (tetrahydrofuran) and TBAB (tetra-n-butyl ammonium bromide) in a FBR (fixed bed reactor) for pre-combustion capture of CO 2 . Silica sand was used as a medium to capture CO 2 from CO 2 /H 2 gas mixture by hydrate crystallisation. Experiments were performed at different temperatures (274.2 K and 279.2 K) and 6.0 MPa to determine the total gas uptake, induction time and rate of hydrate formation. The observed trends indicated that higher driving force resulted in higher gas consumption and significantly reduced induction time. For the same driving force, higher gas consumption and shorter induction time was achieved by THF as compared to TBAB. 5.53 mol% THF attained higher gas consumption than 1.0 mol% THF whereas 3.0 mol% TBAB attained lower gas consumption than 0.3 mol% TBAB. A highest gas uptake of 51.95 (±5.183) mmol of gas/mol of water and a highest rate of 51.21(±8.91) mol.min −1 .m −3 were obtained for 5.53 mol% THF at 6.0 MPa and 279.2 K. Overall, this study indicated better hydrate formation kinetics with the use of THF in an FBR configuration for CO 2 capture from a fuel gas mixture.

An exergetic analysis has been performed on a gasification-based bio-hydrogen generation system consisting of an ASU (air separation unit), a gasifier and a water gas shift reactor. The biomass feed in the system is rice straw. The influences of oxygen percentage in the gasifying agent (in the range 85–99%) and gasifier equivalence ratio (in the range 2–4) on the system exergetic efficiency have been studied. The analysis also investigates the effect of the above mentioned operating parameters on the hydrogen yield and cold gas efficiency. It is observed that, with 95% oxygen in the gasifying agent and with gasifier equivalence ratio of 4.0, the process generates 107.8 g hydrogen per kg of dry biomass (on ash free basis) with a cold gas efficiency of 70%. An increase in gasifier equivalence ratio is found to increase the exergetic efficiency of the system. However, the exergetic efficiency remains almost immune to the change in oxygen percentage in the gasifying agent. The maximum destruction of exergy, in quantitative term, is found to be in the gasifier due to the irreversible chemical reactions occurring there. However, in terms of percentage of exergy input, the highest exergy destruction and exergy loss are observed to occur in the ASU.

Limited crude oil resources and growing environmental awareness have raised a huge led to a huge motivation to seek new fuel alternatives for combustion engines. In this study the goal was to research the potential of ethanol as a compression ignition engine fuel utilizing dual-fuel combustion technology. In the studied DF (dual-fuel) concept, the primary fuel is injected into the intake manifold and it is ignited by injecting diesel fuel into the cylinder near the TDC (top-dead centre). A similar concept has been widely used in natural gas dual-fuel engines. By using ethanol as a primary fuel instead of gaseous fuel, the dual-fuel concept could be a true alternative for on-road and off-road heavy-duty vehicles without the obstacles of energy density and fuel distribution challenges of the gaseous fuels. The research engine in this study was a high speed heavy duty diesel engine modified for dual fuel combustion. The engine was equipped with a common-rail diesel injection system, which gave flexibility to modify the diesel injection to control the combustion. Especially the relationship between pilot and main diesel injection was investigated. The gathered results were promising. A maximum ethanol/diesel mass ratio of around 90% was achieved at high load conditions.