Thermochemical Recuperation Research Articles

Performance and emissions of a direct injection internal combustion engine devised for joint operation with a high-pressure thermochemical recuperation system

This paper presents the results of an experimental study on performance and pollutant emissions of a direct-injection spark-ignition engine devised for joint operation with a high-pressure thermochemical recuperation system based on methanol steam reforming. A comparison with gasoline and ethanol decomposition is performed. Engine feeding with methanol steam reforming products shows an 18%–39% increase in the indicated efficiency and a reduction of 73–94%, 90–96%, 85–97%, and 10–25% in NOx, CO, HC and CO2 emissions, respectively, compared to gasoline within a wide power range. Efficiency improvement and emissions reductions are obtained compared to ethanol decomposition products as well. The possibility of an unthrottled engine operating with a substantially lower cycle-to-cycle variation compared to both gasoline and ethanol decomposition is demonstrated. At high loads, the injector flow area was insufficient for a low injection pressure of 40 bar, leading to late injection and reduced engine efficiency for methanol steam reforming products. In the case of ethanol decomposition, the problem was less severe due to the higher energy content of ethanol decomposition products per mole. The concept of a direct-injection internal combustion engine with high-pressure methanol steam reforming shows good potential, while additional research on injection strategies and gaseous reformate combustion is required.

Моделирование энергосберегающих промышленных установок с термохимической регенерацией

The article explains importance of elaborating scientific and technical solutions aimed at creating energy-saving and environmentally friendly technologies based on thermochemical recovery (TCR) of the heat of natural gas combustion products. To address this challenge, the authors propose to use the SCAN (Steam Conversion Analyzer) software package, a computation system based on the results from numerical investigation of the processes that occur during thermochemical heat recovery and intended for providing the necessary information support to specialists in charge for developing process flow diagrams involving the use of TCR. A characteristic feature of the above-mentioned software system is that it combines mathematical models intended for calculating process flow diagrams (represented by lumped-parameter or system models) and models for calculating hydrodynamic and heat-and-mass transfer processes accompanied by chemical reactions in the apparatuses included in the composition of process flow diagrams (represented by distributed-parameter or detailed models). The SCAN package allows the user to select packages and subroutines that make it possible to minimize the computation time and resources required to perform the computation. In addition, the system includes features for tracking how the values of sought characteristics depend on the degree of detail (accuracy) of the model describing the process under study. The SCAN software system includes a library module containing the process flow diagrams of installations and individual apparatuses within their composition. Each example is supplemented with recommendations for modeling and arranging the processes, which were obtained as a result of numerical calculations. Two examples of using the SCAN software system for elaborating circuit solutions and simulating the processes involving TCR are given. The first example is devoted to the scheme for analyzing the TCR of the heat of gas turbine exhaust gases, and the second one is devoted to modeling the processes according to an algorithm combining system and detailed calculations. It is pointed out that the SCAN software system offers the possibility to study the effect the design features of apparatuses (including the design of reaction elements that make up the conversion reactor) and the process operating parameters have on the conversion completeness degree. It also allows the user to evaluate the saving of fuel in a production process or in generating electricity.

Study of particulate matter and gaseous emissions in gasoline direct injection engine using on-board exhaust gas fuel reforming

Gasoline Direct Injection (GDI) engines provide advantages over preceding spark ignition engine technologies in terms of reduced fuel consumption, increased power output and CO2 depletion. However, the main drawback is the increased level of Particulate Matter (PM) emissions, which is associated with the adverse effects on human health and the environment.GDI engine’s fuel economy can further be enhanced by exhaust gas fuel reforming, a thermochemical recovery technique, which utilizes the engine exhaust gas heat, CO2 and H2O to produce a hydrogen-rich gas named reformate. Furthermore, additional benefits in gaseous emissions can be achieved through the combustion of reformate. In this investigation, a prototype on-board fuel reformer has been employed in a GDI engine to study the effects of reformate combustion as a supplementary fuel to gasoline on PM and gaseous emissions. Between 5% and 6% reduction in the engine fuel consumption was achieved by using the fuel reformer. The different effects (i.e. dilution, thermal, chemical, etc.) of the reformate combustion on the PM nature and gaseous emissions has been identified. It was found that the reformate combustion can decrease notably the engine PM emissions, however, the reduction is dependent on the PM nature. Reformate combustion was found to remove soot cores more efficiently than the volatile PM. The study has shown that the three-way catalytic converter (TWC) can reduce PM emissions. The possible interactions between the reformate and the TWC operation have also been analyzed. For the studied conditions, fuel reforming technology has not shown significant detrimental influence on the TWC operation.

Internal combustion engine with thermochemical recuperation fed by ethanol steam reforming products - feasibility study

This research analyses the performance of a spark ignition engine fueled by ethanol steam reforming products. The basic concept involves the use of the internal combustion engine's (ICE) waste heat to promote onboard reforming of ethanol. The reformer and the engine performance were simulated and analyzed using GT-Suite, Chem CAD and Matlab software. The engine performance with different compositions of ethanol reforming products was analyzed, in order to find the optimal working conditions of the ICE - reformer system. The analysis performed demonstrated the capability to sustain the endothermic reactions in the reformer and to reform the liquid ethanol to hydrogen-rich gaseous fuel using the heat of the exhaust gases. However, the required reformer's size is quite large: 39 x 89 x 73 cm, which makes a feasibility of its mounting on board a vehicle questionable. A comparison with ICE fed by gasoline or liquid ethanol doesn't show a potential of efficiency improvement, but can be considered as a tool of additional emissions reduction.

Вплив режимних параметрів та нерівноважності конверсії на показники термохімічної регенерації теплоти відпрацьованих газів високотемпературних установок

We have performed the calculations of thermodynamic of parameters of thermochemical recuperation (TCR) of the heat of exhaust gas of industrial furnaces and internal combustion engine (ICE), which burn natural gas. TCR is based on the conversion of the mixtures natural gas with products of its combustion. We have established that, in performing the TCR of the heat of an industrial furnace with the distribution of the flow of exhaust gases between the reactor and air heater, one can compensate the negative action non-equilibrium character of conversion by a decrease in the fraction of the flow fed to the reactor. We have shown that an increase in fraction of reaction mixture fed to the high-temperature reactor of ICE and the corresponding decrease in the flow to the low-temperature enhance both the economy of primary fuel and the efficiency of its use. To reduce influence of non-equilibrium generation character of conversion on the parameters of recuperation of the heat of an ICE. One should provide conditions under which the non-equilibrium character of reacting mixture in the low-temperature reactor will be minimal.

Використання ентальпії охолодження високотемпературних елементів теплових установок методом термохімічної регенерації (термохімічний захист)

Використання ентальпії охолодження високотемпературних елементів теплових установок методом термохімічної регенерації (термохімічний захист)

Визначення оптимальних умов реалізації процесу термохімічної регенерації для використання теплоти відпрацьованих газів газотурбінної установки

The problem of the use of thermal secondary energy resources, being formed in gas-turbine plants working on natural gas, is important from the viewpoint of energy saving. The most efficient way of its solution is connected with the technology of thermochemical recuperation, based on fuel reforming with exhaust gases. We have developed 4 schemes of thermochemical recuperation for using the heat of exhaust gases and carried out thermodynamic calculations of their efficiency. We have established that the highest efficiency can be obtained by using scheme G4, where the process of fuel reforming as well as the heating of air spent for fuel combustion and ballast (a certain part of exhaust gases), providing the cooling of the working medium after combustion chamber to an acceptable temperature, are realized in the reactor-heat exchanger. We have revealed and explained a paradoxical, on the face of it, dependence of the efficiencies of different schemes on the initial pressure. We have found the optimal conditions of the scheme G4, under which its efficiency reaches 60 %. In addition to fuel economy, this scheme enables one to decrease the emission of harmful substances to the atmosphere.

Energy efficiency of a direct-injection internal combustion engine with high-pressure methanol steam reforming

This article discusses the concept of a direct-injection ICE (internal combustion engine) with thermo-chemical recuperation realized through SRM (steam reforming of methanol). It is shown that the energy required to compress the reformate gas prior to its injection into the cylinder is substantial and has to be accounted for. Results of the analysis prove that the method of reformate direct-injection is unviable when the reforming is carried-out under atmospheric pressure. To reduce the energy penalty resulted from the gas compression, it is suggested to implement a high-pressure reforming process. Effects of the injection timing and the injector's flow area on the ICE-SRM system's fuel conversion efficiency are studied. The significance of cooling the reforming products prior to their injection into the engine-cylinder is demonstrated. We show that a direct-injection ICE with high-pressure SRM is feasible and provides a potential for significant efficiency improvement. Development of injectors with greater flow area shall contribute to further efficiency improvements.

Thermochemical recovery technology for improved modern engine fuel economy – part 1: analysis of a prototype exhaust gas fuel reformer

Exhaust gas fuel reforming has the potential to improve the thermal efficiency of internal combustion engines, as well as simultaneously reduce gaseous and particulate emissions.

Heavy metal removal and speciation transformation through the calcination treatment of phosphorus-enriched sewage sludge ash

On the basis of the heavy metal (Cd, As, Pb, Zn, Cu, Cr, and Ni) control problem during the thermochemical recovery of phosphorus (P) from sewage sludge (SS), P-enriched sewage sludge ash (PSSA) was calcined at 1100°C. The effect of organic chlorinating agent (PVC) and inorganic chlorinating agent (MgCl2) on the fixed rate of P removal and the speciation transformation of heavy metal was studied. The removal of heavy metals Cd, Pb, As, Zn, and Cr exhibited an increasing tendency with the addition of chlorinating agent (PVC). However, an obvious peak under 100gCl/kg of PSSA appeared for Cu, owing to the presence of carbon and hydrogen in PVC. MgCl2 was found to be more effective than PVC in the removal of most heavy metals, such that up to 98.9% of Cu and 97.3% of Zn was effectively removed. Analyses of heavy metal forms showed that Pb and Zn occurred in the residue fraction after calcination. Meanwhile, the residue fraction of Cr, Ni, Cd, and Cu exhibited a decreasing tendency with the increase in the added chlorinating agent (MgCl2). Losses of P from PSSA were around 16.6% without the addition of chlorinating agent, which were greatly reduced to around 7.7% (PVC) and to only 1.7% (MgCl2).

Thermo-Chemical Recuperation as an Efficient Way of Engine's Waste Heat Recovery

It is known that about 30% of fuel energy introduced to an internal combustion engine (ICE) is wasted with engine exhaust gases. One of the promising ways of waste heat recovery is thermo-chemical recuperation (TCR). For the purpose of TCR realization, in principle any fuel may be used. However, utilization of renewable bio-alcohols, especially ethanol or methanol is the most favorable. The advantages of TCR over turbocharging are in the fact that its energy transfer is not limited by isentropic expansion and that the reforming process improves the fuel properties. A comprehensive theoretical analysis of the ICE with TCR was carried out using the developed model for simulation of the joint operation of ICE with alcohol reformer, when the ICE is fed by the alcohol reforming products and the energy of the exhaust gases is utilized to sustain endothermic reforming reactions. Simulation results show that it is possible to sustain endothermic reforming reactions with a reasonable reactor size. Modeling results point out a possibility of engine's efficiency improvement by up to 13% in comparison with ICE feeding by gasoline together with achievement of zero-impact pollutant emissions.

Modeling Internal Combustion Engine with Thermo-Chemical Recuperation of the Waste Heat by Methanol Steam Reforming

Modeling Internal Combustion Engine with Thermo-Chemical Recuperation of the Waste Heat by Methanol Steam Reforming

Thermochemical conversion of fuels into hydrogen-containing gas using recuperative heat of internal combustion engines

The problem of the thermochemical recuperation of heat from the exhaust gases of internal com� bustion engines (ICEs) as a method of increasing of the efficiency of fuels has been considered. The thermo� dynamic analysis of thermochemical recuperation conditions was performed, and maximum efficiency con� ditions were determined. Catalysts for the steam conversion of oxygencontaining fuels into syngas were developed, and the Co-Mn/Al2O3 catalyst was shown to be the most promising. The model of a thermo� chemical heat recuperation system was developed and manufactured, and its bench tests in the conversion of alcohols were performed using the simulated exhaust gases from a heating device. Mathematical models for calculating units of the heat recuperation system were developed. A recuperation system was manufactured and tested in the ICEfree and ICEintegrated variants. Based on the test results, the equivalent fuel con� sumption characteristics of a recuperative ICE was revealed to decrease by 11-22% depending on its load with a decrease in the concentration of hazardous emissions by 8-12 times for CO, 2-3.5 times for CH, and 18-25 times for NO x .

Thermochemical recovery of heat contained in flue gases by means of bioethanol conversion

In the present paper consideration is being given to the use of bioethanol in the schemes of thermochemical recovery of heat contained in exit flue gases. Schematic diagrams illustrate the realization of thermochemical heat recovery by implementing ethanol steam conversion and conversion of ethanol by means of products of its complete combustion. The feasibility of attaining a high degree of recovery of heat contained in flue gases at the moderate temperature (up to 450°C) of combustion components is demonstrated in the example of the energy balance of the system for thermochemical heat recovery. The simplified thermodynamic analysis of the process of ethanol steam conversion was carried out in order to determine possible ranges of variation of process variables (temperature, pressure, composition) of a reaction mixture providing the efficient heat utilization. It was found that at the temperature above 600 K the degree of ethanol conversion is near unity. The equilibrium composition of products of reaction of ethanol steam conversion has been identified for different temperatures at which the process occurs at the ratio H2O/EtOH = 1 and at the pressure of 0.1 MPa. The obtained results of calculation agree well with the experimental data.

Biogas upgrade to syngas through thermochemical recovery using exhaust gas reforming

Exhaust gas fuel reforming has been examined as a process for upgrading biogas into hydrogen enriched gaseous fuel for use in transportation. The effect of different O2/CH4 mole ratios and space velocities on the reformer product has been studied. In addition, 20% volume fraction of exhaust gas recirculation (EGR) has been introduced into the engine system to investigate the effect of engine-out exhaust composition on the reforming process. Our results imply that fuel reforming process efficiencies of up to 95% (based on the energy content of the reformate produced compared to the energy content of the biogas used) can be achieved at optimum biogas and engine exhaust gas ratios for the different engine conditions. Furthermore, the total carbon dioxide content is reduced by reforming biogas to form better quality fuel.

Thermodynamic Analysis of Alternative Approaches to Chemical Looping Combustion

In this article, we review and clarify some of the points made by previous authors(1, 2) regarding chemical looping combustion (CLC). Although much of the recent interest in chemical looping combustion has been associated with carbon sequestration, our primary interest here is its potential to increase the thermodynamic efficiency of converting fuel chemical energy into useful work. We expand on several points about the details of CLC that we feel have not previously been sufficiently explored and suggest alternative (and possibly more practical) approaches that exploit some of the same thermodynamic concepts. We illustrate our key points with first and second law analyses of ideal conceptual processes, which, in addition to CLC, also include isothermal, nonequilibrium, preheated combustion and combustion with thermochemical recuperation. Our results suggest that a significant portion of the potential efficiency benefit of CLC might be achieved without the need to handle and transport large quantities of ...

Study of the Theoretical Potential of Thermochemical Exhaust Heat Recuperation for Internal Combustion Engines

A detailed thermodynamic analysis of thermochemical recuperation (TCR) applied to an idealized internal combustion engine with single-stage work extraction is presented. Results for several different fuels are included. For a stoichiometric mixture of methanol and air, TCR can increase the estimated ideal engine second law efficiency by about 3% for constant pressure reforming and over 5% for constant volume reforming. For ethanol and isooctane, the estimated second law efficiency increases for constant volume reforming are 9 and 11%, respectively. The second law efficiency improvements from TCR result primarily from the higher intrinsic exergy of the reformed fuel and pressure boost associated with the gas mole increase. Reduced combustion irreversibility may also yield benefits for future implementations of combined cycle work extraction.

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.

Numerical Analysis for Chemical Recuperated Gas Turbine System (CRGT) Fuelled by Bio-Ethanol

Chemically recuperated Gas Turbine (CRGT) that recovers exhaust heat by endothermic reaction converting fuel to reforming gas is one of candidates for effective utilization of ethanol from biomass fermentation. Bio-ethanol can easily be applied to steam reforming process for hydrogen-rich gas production, because the moisture in bio-ethanol is included about 80% after the fermentation process. The chemical composition in reformer was evaluated according to chemical equilibrium equations. This numerical analysis reports a performance comparison with simple cycle gas turbine. Thermochemical recuperation in the ethanol was allowed to achieve a significant change in power output, and the maximum increase in thermal efficiency was 16% compared with simple cycle at 8.0 in steam/fuel molar ratio and 600 deg. C in reforming temperature.

Energy-Recuperative Coal-Integrated Gasification/Gas Turbine Power Generation System

Coal-integrated gasification/gas turbine (CIG/GT) based power plants are well known for achieving electricity more efficient and at a lower cost than direct combustion based power plants. Since the gasification is an endothermic, thermochemical conversion process, it requires heat to proceed. In general, this heat is furnished by internal combustion taking place in the gasifier by virtue of oxygen-blown or air-blown gasification. However, the direct combustion of the solid fuel is seen to be inefficient because of the large amount of exergy destruction posed during the combustion, especially at relatively low temperatures like gasification temperatures. This causes the overall performance deterioration of the CIG/GT system. Therefore, a decrease in the destruction of exergy during the combustion can contribute to improve overall system efficiency. In this paper, an innovative concept of energy-recuperative gasification was proposed and incorporated in the CIG/GT system. The idea is to make use of the waste heat from the gas turbine exhaust as the reaction heat for the gasification instead of the internal combustion. This type of energy recuperation is also called thermochemical recuperation. In addition, the proposed CIG/GT incorporates other effective energy recuperation, including heat and steam recuperation, in order to maximize the generation efficiency. The feasibility of the concept implementation and the system improvement were preliminarily examined and discussed.