Thermochemical recovery of heat contained in exhaust gases of internal combustion engines (A general approach to the problem of recovery of heat contained in exhaust gases)

The concept of the use of heat contained in exhaust gases of internal combustion engines in order to increase the degree of utilization of the energy contained in engine fuels has been examined. It has been suggested to use heat recovered in such a way for carrying out endothermic reactions of the conversion of alternative fuels. Calculated estimations of the thermal effects of possible reactions and the thermodynamic efficiency of the thermochemical recovery of heat contained in exhaust gases for a reversible thermal power-producing cycle have been performed. A comparison between the effectiveness of the thermal power-producing cycle without the implementation of the stage of thermochemical recovery of heat contained in exhaust gases and that with its implementation has been made. It has been concluded that continuing the research effort in this direction would be appropriate.     

Combined Decarbonization of Electrical Energy Generation and Production of Synthetic Fuels by Renewable Energies and Fossil Fuels

Power generation from renewable energy sources and fossil fuels are integrated into one system. A combination of technologies in the form of a carbon capture utilization (CCU)-combined power station is proposed. The technology is based on energy generation from fossil fuels by a coal power plant with CO₂ recovery from exhaust gases, and pyrolysis of natural gas to hydrogen and carbon, completed by reverse water-gas shift for the conversion of CO₂ to CO, which will react with hydrogen in a Fischer-Tropsch synthesis for synthetic diesel. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered. This technology offers significant CO₂ savings compared to the current state of technology and makes an environmentally friendly use of fossil fuels for electricity and fuel sectors possible.     

Komplementäre Dekarbonisierung der Erzeugung von Elektroenergie und Gewinnung synthetischer Kraftstoffe durch Erneuerbare Energien und fossile Energieträger

The concept of complementary decarbonisation of power generation from renewable energy sources and fossil fuels consists of their integration in one system. A technology network in the form of a CCU‐combined power plant is proposed for the energy generation from fossil fuels by a coal power plant with CO₂ recovery from the exhaust gases and a pyrolysis of natural gas to hydrogen and carbon as a basic technology. This technology network is completed by a reverse water‐gas shift reaction for the conversion of the CO₂ to CO, which will react with the hydrogen in a Fischer‐Tropsch synthesis for synthetic diesel. The recovered energy from the exothermic Fischer‐Tropsch synthesis meets the energy needs of CO₂ scrubbing. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered.     

Coproduction of liquid transportation fuels and C6_C8 aromatics from biomass and natural gas

The coproduction of liquid transportation fuels and C₆?C₈ aromatics from the thermochemical conversion of biomass and natural gas (BGTL+C₆_C₈) is investigated in this article. An optimization‐based process synthesis framework incorporating multiple synthesis gas conversion technologies, such as Fischer–Tropsch synthesis or methanol conversion, is described. Production of aromatics can proceed through several technologies, such as naphtha reforming and aromatization of hydrocarbons via a metal‐promoted H‐ZSM‐5 catalyst. This is the first article in the literature to incorporate an aromatics complex for the coproduction of liquid fuels and C₆?C₈ petrochemicals within a rigorous process synthesis and deterministic global optimization framework. The optimal process topologies across several case studies are discussed and the results indicate that the coproduction of aromatics with liquid fuels can significantly increase the profitability of these refineries. © 2015 American Institute of Chemical Engineers AIChE J, 2015 2014 American Institute of Chemical Engineers AIChE J, 61: 831–856, 2015     

低阶固体燃料热化学转化过程中挥发分与半焦相互作用的基本原理

挥发分-半焦相互作用是低阶含碳固体燃料热化学转化过程中普遍存在的一种重要现象。挥发分-半焦相互作用可以影响低阶燃料热化学转化过程的各个方面:促进碱金属/碱土金属(AAEM)的挥发、抑制气化、催化焦油分解、碳-碳结构重排及稳定化(抑制气化)、促进半焦上N的迁移等。回顾了低阶燃料热化学转化过程中的挥发分-半焦相互作用的最新研究进展,为更好的利用低阶固体燃料提供理论指导。     

Methane Pyrolysis for CO2-Free H2 Production: A Green Process to Overcome Renewable Energies Unsteadiness

The Carbon2Chem® project aims to convert exhaust gases from the steel industry into chemicals such as methanol to reduce CO₂ emissions. Here, H₂ is required for the conversion of CO₂ into methanol. Although much effort is put to produce H₂ from renewables, the use of fossil fuels, especially natural gas, seems to be fundamental in the short term. For this reason, the development of clean technologies for the processing of natural gas with a low environmental impact has become a topic of utmost importance. In this context, methane pyrolysis has received special attention to produce CO₂-free H₂.     

Low-temperature catalytic conversion of lignite: 3. Tar reforming using the supported potassium carbonate

Alumina-supported K₂CO₃–LaMn_0.8Cu_0.2O₃ was investigated for the catalytic conversion of tar, produced from lignite, into syngas under inert and steam-reforming conditions. A double-bubble fluidized bed reactor system, equipped with a micro gas chromatograph and a collecting system to analyze permanent gases and condensable species, was developed to screen the catalytic conversion of tar components below 700 °C. The redox properties of catalysts, estimated by hydrogen temperature programmed reduction analyses, were correlated with their catalytic performance in tar conversion. The synthesized catalyst effectively converted tars into hydrogen-rich syngas and also improved tar reforming by inhibiting coke deposition.     

A target‐oriented solid‐gas thermochemical sorption heat transformer for integrated energy storage and energy upgrade

An innovative target‐oriented solid‐gas thermochemical sorption heat transformer is developed for the integrated energy storage and energy upgrade of low‐grade thermal energy. The operating principle of the proposed energy storage system is based on the reversible solid‐gas chemical reaction whereby thermal energy is stored in form of chemical bonds with thermochemical sorption process. A novel thermochemical sorption cycle is proposed to upgrade the stored thermal energy by using a pressure‐reducing desorption method during energy storage process and a temperature‐lift adsorption technique during energy release process. Theoretical analysis showed that the proposed target‐oriented thermochemical sorption heat transformer is effective for the integrated energy storage and energy upgrade, and the low‐grade thermal energy can be upgraded from 87 to 171^°C using a group of sorption working pair MnCl₂‐CaCl₂‐NH₃. Moreover, it can give the flexibility of deciding the temperature magnitude of energy upgrade by choosing appropriate sorption working pairs. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1334–1347, 2013     

Effect of the composition of an oxide coating and the preparation method of block catalysts on their activity in the deep oxidation of methane

Deep methane oxidation catalysts containing 3d metal (Mn, Co), rare-earth (La) and alkali-earth (Ba, Sr) oxides in the porous matrices of secondary supports (Al₂O₃, ZrO₂, and their binary composition) formed on honeycomb blocks (cordierite, kaolin-aerosil) are studied by means of X-ray powder diffraction, the thermal desorption of nitrogen, and temperature-programmed reduction with hydrogen. It is shown that the activity and stability of the catalysts depend on the method for their preparation and the nature of the active components and secondary and block supports. After life cycle tests, the proposed catalysts with 80–100% conversion of methane into CO₂ at temperatures of 650–750°C can be recommended for use in systems for the catalytic purification of gases containing hydrocarbon admixtures (methane and C₂–C₄ homologues) and the combustion of hydrocarbon fuels in industrial and household catalytic heat generators.     

Lean NO x Reduction with Various Bio-Diesels as Reducing Agents

Commercial Cu-ZSM-5- and Ag/Al₂O₃-based lean NO _x catalysts were evaluated in a synthetic exhaust gas bench with the fuels RME, B30, B15, Agrodiesel 15, GTL, NExBTL, and MK1 as reducing agents. The influence of reductant was larger for Ag/Al₂O₃, albeit moderate, whereas the Cu-zeolite showed the highest NO _x conversion at lower temperature for all alternative fuels tested.     

Greenhouse gas emissions of bioenergy from agriculture compared to fossil energy for heat and electricity supply

Increasing the use of bioenergy is one promising option to reduce greenhouse gas emissions. Hence it is important to know the greenhouse gas emissions of bioenergy systems in comparison to fossil fuel systems. A life cycle analyses of biomass and fossil fuel energy systems is made to compare the overall greenhouse gas emission of both systems for heat and electricity supply. Different bioenergy systems to supply electricity and heat from agriculture are analysed for the Austrian situation in 2000. Total emissions of greenhouse gases (CO₂, N₂O, CH₄) along the fuel chain, including land use change and by-products, are calculated. The systems taken into consideration are different conversion technologies and different fuels from agriculture. The methodology was developed within the International Energy Agency (IEA) Bioenergy Task 25 on `Greenhouse Gas Balances of Bioenergy Systems'. In this paper the results of selected bioenergy systems for heat supply and combined supply of electricity and heat shown as emission of CO₂-equivalents per kWh for bioenergy systems in comparison to fossil fuel systems, and as a percentage of CO₂-equivalent reduction. The results demonstrate that some of the bioenergy systems reduce greenhouse gas emission already because of avoided emissions of the reference biomass use and/or because of certain substitution effects of by-products. In general the greenhouse gas emissions of bioenergy systems are lower compared to the fossil systems. Therefore a significant reduction of greenhouse gases is possible by replacing fossil energy systems with bioenergy systems. This comparison should help policy makers, utilities and industry to identify effective agricultural biomass options in order to reach emission reduction targets. This revised version was published online in August 2006 with corrections to the Cover Date.     

On the temperature control in a microstructured packed bed reactor for methanation of CO/CO2 mixtures

Microreactor technology is widely used for process intensification and is essential for fast and strongly exothermic reactions exhibiting mass and heat transfer limitations. In the scope of the MINERVE Power‐to‐Gas project, sponsored by KIC InnoEnergy from 2012 to 2015, a micro packed bed reactor was developed for conversion of syngas containing CO₂ into methane. This work focuses on heat removal and temperature control in a manufactured device using syngas throughputs less than 1.4 Nm³/h (10% CO, 7% CO₂, H₂/C = 4) while examining the cooling potential of different cooling fluids, e.g., air, steam and water. © 2016 American Institute of Chemical Engineers AIChE J, 63: 120–129, 2017     

Experimental investigation of mineral diesel fuel, GTL fuel, RME and neat soybean and rapeseed oil combustion in a heavy duty on-road engine with exhaust gas aftertreatment

The effects of mineral diesel fuel, gas-to-liquid fuel, rapeseed methyl ester, neat soybean and neat rapeseed oil on injection, combustion, efficiency and pollutant emissions have been studied on a compression ignition heavy duty engine operated near full load and equipped with a combined exhaust gas aftertreatment system (oxidation catalyst, particle filter, selective catalytic NO_x reduction). In a first step, the engine calibration was kept constant for all fuels which led to differences in engine torque for the different fuels. In a second step, the injection duration was modified so that all fuels led to the same engine torque. In a third step, the engine was recalibrated in order to keep the NO_x emissions at an equal level for all fuels (injection pressure, injection timing, EGR rate). The experiments show that the critical NO_x emissions were higher (even behind the exhaust gas aftertreatment systems) for oxygenated fuels in case of the engine not being recalibrated for the fuel. GTL and the oxygenated fuels show lower emissions for some pollutants and higher efficiency after recalibration to equal NO_x levels.     

On the Efficiency of NH3–SCR Catalysts for Heavy Duty Vehicles Running on Compressed Natural Gas in Synthetic Gas Bench Scale

This work aims to study the effectiveness of NH₃–SCR after-treatment systems, initially developed for a Diesel application, on Heavy duty natural gas engines working in lean conditions for exhaust gas pollutants abatement. Commercial oxidation and NH₃–SCR catalysts were investigated for respectively CH₄, CO oxidation and NO_X reduction. In this study, we showed that the NH₃–SCR coupled with an oxidation catalyst lead to significant conversion of CH₄, CO and NO_X, and can be used as after-treatment system for pollutants providing from CNG lean burn engines.     

Computational Fluid Dynamics Modeling of Combustion of Synthetic Fuel of Thermochemical Heat Recuperation Systems

CFD modeling of the combustion of synthetic fuel formed in the systems of thermochemical recuperation of waste flue gas heat due to steam methane reforming was performed using the ANSYS Fluent software. Scientific justification and validation of the physicomathematical approaches involved the ANSYS Fluent for the problems of modeling the combustion of multicomponent hydrogen-containing gas mixtures. Numerical results were validated against experimental data. A visual comparison of the flame contours obtained by burning syngas at Reynolds numbers of 600, 800, and 1000 was performed. In all cases there is obvious convergence of the results. Change in the temperature of the fuel–air mixture at the entrance to the combustion chamber was found to have no significant effect on the temperature of the combustion products. The obtained results are of practical importance for the design of burner units of high-temperature plants with thermochemical heat recuperation.     

Synthesis of augmented biofuel processes using solar energy

A method for synthesizing augmented biofuel processes, which improve biomass carbon conversion to liquid fuel (η_carbon) using supplemental solar energy as heat, H₂, and electricity is presented. For a target η_carbon, our method identifies augmented processes requiring the least solar energy input. A nonconvex mixed integer nonlinear programming model allowing for simultaneous mass, heat, and power integration, is built over a process superstructure and solved using global optimization tools. As a case study, biomass thermochemical conversion via gasification/Fischer–Tropsch synthesis and fast‐hydropyrolysis/hydrodeoxygenation (HDO) is considered. The optimal process configurations can be categorized either as standalone (η_carbon ≤ 54%), augmented using solar heat (54% ≤ η_carbon ≤ 74%), or augmented using solar heat and H₂ (74 ≤ η_carbon ≤ 95%). Importantly, the process H₂ consumption is found to be close to the derived theoretical minimum values. To accommodate for the intermittency of solar heat/H₂, we suggest processes that can operate at low and high η_carbon. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2533–2545, 2014     

Auto‐thermal combustion of lean gaseous fuels utilizing a recuperative annular double‐layer catalytic converter

The results of the investigations on the auto‐thermal combustion of lean gaseous fuels in a recuperative annular double‐layer catalytic converter were reported in the current contribution. Several modifications were proposed to improve the stationary and transient behaviour of the converters. The miniaturized recuperative converter exhibited reduced resistances to the mass and heat transfer and attractive bifurcation changes of a very low combustible content, that is, the histeresis for T_in and C_in and isola for mf_in and h_g. It was revealed that the utilization of an adiabatic recuperative converter led to an autothermal operation for T_in = 300 K and C_in = 177 ppmv of propane. The inlet fuel mass flow rate range to apply was wider than earlier reported in the literature, that is, 0.63–2.94 × 10^?6 kg s^?1 for C_in = 200 ppmv. Transient experiments showed that recuperative converter was able to transfer short‐time inlet disturbances of parameters due to the energy accumulation and temporal reversed recuperation counteracting to extinction or to destructive overheating of the catalysts. Stability analysis was performed showing location of folds, stable and unstable branches of solutions for the different parameters of the recuperative converter. A two‐dimensional process model was developed.     

Auto-cyclic reactor: Design and evaluation for the removal of unburned methane from emissions of natural gas engines

A non-adiabatic fixed bed auto-cyclic reactor (ACR) consisting of two counter-current concentric compartments was designed and built for removing low concentrations of methane from exhaust gases from natural gas engines. The length was based on simulations by a simple heterogeneous one dimensional model using literature parameters and kinetic data, while the diameter was selected to assure a linear fluid velocity between 0.5 and 2 m/s. Its innovative design consists of a judicious combination of 14 longitudinal fins welded to the outlet part of inner reactor compartment to maximize the heat transfer to the inlet section and highly active pellet type catalyst filling the space between fins to lower the ignition temperature.The experimental ACR pilot unit was loaded by a combination of highly active laboratory prepared catalysts: palladium/alumina pellets and palladium/alumina coated cordierite monoliths. The efficiency of methane removal from air and from synthetic exhaust gas containing 7 vol% CO₂ and 14 vol% H₂O was evaluated under a wide range of operating conditions: temperature from 290 to 500 °C, methane concentration between 500 and 3800 ppm. The reactor performance was monitored in terms of axial temperature profiles and methane conversion both in transient and steady state conditions.Reproducible performance of the ACR was observed even after 1200 h of cumulative operation and complete methane removal was obtained at relatively low temperatures.To simulate the obtained experimental data, a heterogeneous one-dimensional model was developed to suit the final reactor configuration using actual laboratory determined kinetic data. The model described adequately the experimental temperature profiles and methane conversion when heat transfer between the reactor compartments and heat loss were taken into account.     

Solid fuels in chemical-looping combustion using oxide scale and unprocessed iron ore as oxygen carriers

Chemical-looping combustion (CLC) is a novel technology that can be used to meet demands on energy production without CO₂ emissions. The CLC-process includes two reactors, an air and a fuel reactor. Between these two reactors oxygen is transported by an oxygen carrier, which most often is a metal oxide. This arrangement prevents mixing of N₂ from the air with CO₂ from the combustion. The combustion gases consist almost entirely of CO₂ and H₂O. Therefore, the technique reduces the energy penalty that normally arises from the separation of CO₂ from other flue gases, hence, CLC may make capture of CO₂ cheaper.Iron ore and oxide scale from steel production were tested as oxygen carriers in CLC batch experiments with solid fuels. Petroleum coke, charcoal, lignite and two bituminous coals were used as fuels.The experiments were carried out in a laboratory fluidized-bed reactor that was operating cyclically with alternating oxidation and reduction phases. The exhaust gases were led to an analyzer where the contents of CO₂, CO, CH₄ and O₂ were measured. Gas samples collected in bags were used to analyze the content of hydrogen in a gas chromatograph.The results showed that both the iron ore and the oxide scale worked well as oxygen carrier and both oxygen carriers increased their reactivity with time.     

Combustion of Lithium Particles: Optical Measurement Methodology and Initial Results

Combustion examinations on the single‐grain level were carried out in order to get further fundamental insight into the ignition and combustion of lithium particles. Combustion of solid lithium particles in a defined size fraction was analyzed in a laminar‐flow reactor. The exhaust gases of a methane‐air flame provided the reactants O₂, CO₂, N₂, and H₂O for the lithium conversion. Two different atmospheres at various temperatures were investigated. A high‐speed camera system measured size and radiation intensity of burning particles. The results indicate that two different combustion phenomena occurred in lithium combustion. The first was identified as a homogeneously enveloping flame around the lithium particle and the second as a reaction zone next to the particle surface.