Modeling of single coal particle combustion in O2/N2 and O2/CO2 atmospheres under fluidized bed condition

A one-dimensional transient single coal particle combustion model was proposed to investigate the characteristics of single coal particle combustion in both O₂/N₂ and O₂/CO₂ atmospheres under the fluidized bed combustion condition. The model accounted for the fuel devolatilization, moisture evaporation, heterogeneous reaction as well as homogeneous reactions integrated with the heat and mass transfer from the fluidized bed environment to the coal particle. This model was validated by comparing the model prediction with the experimental results in the literature, and a satisfactory agreement between modeling and experiments proved the reliability of the model. The modeling results demonstrated that the carbon conversion rate of a single coal particle (diameter 6 to 8 mm) under fluidized bed conditions (bed temperature 1088 K) in an O₂/CO₂ (30:70) atmosphere was promoted by the gasification reaction, which was considerably greater than that in the O₂/N₂ (30:70) atmosphere. In addition, the surface and center temperatures of the particle evolved similarly, no matter it is under the O₂/N₂ condition or the O₂/CO₂ condition. A further analysis indicated that similar trends of the temperature evolution under different atmospheres were caused by the fact that the strong heat transfer under the fluidized bed condition overwhelmingly dominated the temperature evolution rather than the heat release of the chemical reaction.     

Thermochemical hydrogen production from a two-step solar-driven water-splitting cycle based on cerium oxides

A new thermochemical cycle for H₂ production based on CeO₂/Ce₂O₃ oxides has been successfully demonstrated. It consists of two chemical steps: (1) reduction, 2CeO₂ → Ce₂O₃ + 0.5O₂; (2) hydrolysis, Ce₂O₃ + H₂O → 2CeO₂ + H₂. The thermal reduction of Ce(IV) to Ce(III) (endothermic step) is performed in a solar reactor featuring a controlled inert atmosphere. The feasibility of this first step has been demonstrated and the operating conditions have been defined (T = 2000 °C, P = 100–200 mbar). The hydrogen generation step (water-splitting with Ce(III) oxide) is studied in a fixed bed reactor and the reaction is complete with a fast kinetic in the studied temperature range 400–600 °C. The recovered Ce(IV) oxide is then recycled in first step. In this process, water is the only material input and heat is the only energy input. The only outputs are hydrogen and oxygen, and these two gases are obtained in different steps avoiding a high temperature energy consuming gas-phase separation. Furthermore, pure hydrogen is produced (it is not contaminated by carbon products like CO, CO₂), thus it can be used directly in fuel cells. The results have shown that the cerium oxide two-step thermochemical cycle is a promising process for hydrogen production.     

Characterisation of oils from the fluidised bed pyrolysis of biomass with zeolite catalyst upgrading

Biomass in the form of pine wood was pyrolysed in an externally heated 7.5 cm diameter, 100 cm high fluidised bed pyrolysis reactor with nitrogen as the fluidising gas. A section of the freeboard of the reactor was packed with zeolite ZSM-5 catalyst. The pyrolysis oils before and after catalysis were collected in a series of condensers and cold traps. In addition, gases were analysed off-line by packed column gas chromatography. The compositions of the oils and gases were determined in relation to the primary fluidised bed and after catalysis at increasing catalyst bed temperatures from 400° to 550°C. The oils were analysed by a number of techniques to determine composition, including liquid chromatography, gas chromatography/mass spectrometry. Fourier transform infrared spectroscopy and size exclusion chromatography. The results showed that the oils before catalysis were highly oxygenated; after catalysis the oils were markedly reduced in oxygenated species with an increase in aromatic and polycyclic aromatic species.

The gases evolved from the fluidised bed pyrolysis of biomass were CO₂, CO, H₂, CH₄, C₂H₄, C₃H₆ and minor concentrations of other hydrocarbon gases. After catalysis the concentrations of CO₂ and CO were increased. The conversion of oxygenated compounds was mainly to H₂O at lower catalyst temperatures and CO₂ and CO at high catalyst temperatures. Detailed analysis of the oils showed that there were high concentrations of biologically active polycyclic aromatic species in the catalysed oil which increased with increasing catalyst temperature. The oxygenated compounds in the uncatalysed oil were mainly phenols and carboxylic acids. After catalysis these decreased in concentration with increasing catalyst temperature     

Fuel saving, carbon dioxide emission avoidance, and syngas production by tri-reforming of flue gases from coal- and gas-fired power stations, and by the carbothermic reduction of iron oxide

Flue gases from coal, gas, or oil-fired power stations, as well as from several heavy industries, such as the production of iron, lime and cement, are major anthropogenic sources of global CO₂ emissions. The newly proposed process for syngas production based on the tri-reforming of such flue gases with natural gas could be an important route for CO₂ emission avoidance. In addition, by combining the carbothermic reduction of iron oxide with the partial oxidation of the carbon source, an overall thermoneutral process can be designed for the co-production of iron and syngas rich in CO. Water-gas shift (WGS) of CO to H₂ enables the production of useful syngas. The reaction process heat, or the conditions for thermoneutrality, are derived by thermochemical equilibrium calculations. The thermodynamic constraints are determined for the production of syngas suitable for methanol, hydrogen, or ammonia synthesis. The environmental and economic consequences are assessed for large-scale commercial production of these chemical commodities. Preliminary evaluations with natural gas, coke, or coal as carbon source indicate that such combined processes should be economically competitive, as well as promising significant fuel saving and CO₂ emission avoidance. The production of ammonia in the above processes seems particularly attractive, as it consumes the nitrogen in the flue gases.     

How to make the production of methanol/DME “GREENER”—Integration of wind power with modern coal chemical industry—

The urgency and necessity of alternative fuels give an impetus to the development of modern coal chemical industry. Coal-based methanol/DME is the key element of this industry. Wind power, whose installed capacity increased at a rate of more than 100% in recent years, has the most developed technologies in renewable energy. However, there still exist many unsolved problems in wind power for on-grid utilization. A new integrated system which combines coal-based methanol/DME production with wind power is proposed in this paper. In this system, wind power is used to electrolyze water to produce H₂ and O₂. The O₂ is fed to the gasifier as gasification agent. The H₂ is mixed with the CO-rich gas to adjust the H₂/CO to an appropriate ratio for methanol synthesis. In comparison with conventional coal-based methanol/DME system, the proposed system omits the expensive and energy-consuming ASU and greatly reduces the water gas shift process, which brings both advantages in the utilization of all raw materials and significant mitigation of CO₂ emission. This system will be attractive in the regions of China which have abundant wind and coal resources.     

Fuel production from a brewery residue

A laboratory feasibility study was undertaken to evaluate the bioconversion of draff, a residue from the industrial conversion of malt in brewery, into a valuable fuel. Reaction rates up to 0.194 m³ gas/m³ digester/day and an overall yield of 35 m³ gas/dry ton substrate were observed at ambient temperature. Orsat analysis showed the biogas composition to be (in %): CH₄, 61; CO₂, 38; O₂, 0.40; H₂S, 0.20. Its energy content is 24.5 MJ/m³. The latent period was shortened to 24 hrs by seeding the reactor with active microorganisms from a well-operating anaerobic digester charged with horse's manure. A conversion-factor chart is constructed which compares the product biogas to other common fuels. Experimental tests were also performed on the same bench-scale equipment to evaluate the bioconversion of bovine and horse manures under similar conditions. The draff is shown to be a valuable potential fuel source.     

Coal conversion submodels for design applications at elevated pressures. Part II. Char gasification

This paper surveys the database on char gasification at elevated pressures, first, to identify the tendencies that are essential to rational design of coal utilization technology, and second, to validate a gasification mechanism for quantitative design calculations. Four hundred and fifty-three independent tests with 28 different coals characterized pressures from 0.02 to 3.0 MPa, CO₂ and steam mole percentages from 0 to 100%, CO and H₂ levels to 50%, gas temperatures from 800 to 1500 °C, and most of coal rank spectrum. Only a handful of cases characterized inhibition by CO and H₂, and only a single dataset represented the complex mixtures of H₂O, CO₂, CO, and H₂ that arise in practical applications. With uniform gas composition, gasification rates increase for progressively higher pressures, especially at lower pressures. Whereas the pressure effect saturates at the higher pressures with bituminous chars, no saturation is evident with low-rank chars. With fixed partial pressures of the gasification agents, the pressure effect is much weaker. Gasification rates increase for progressively higher gas temperatures. In general, gasification rates diminish for coals of progressively higher rank, but the data exhibit this tendency only for ranks of hv bituminous and higher.

These tendencies are interpreted with CBK/G, a comprehensive gasification mechanism based on the Carbon Burnout Kinetics Model. CBK/G incorporates three surface reactions for char oxidation plus four reactions for gasification by CO₂, H₂O, CO and H₂. Based on a one-point calibration of rate parameters for each coal in the database, CBK/G predicted extents of char conversion within ±11.4 daf wt% and gasification rates within ±22.7%. The predicted pressure, temperature, and concentration dependencies and the predicted inhibiting effects of CO and H₂ were generally confirmed in the data evaluations. The combination of the annealing mechanism and the random pore model imparts the correct form to the predicted rate reductions with conversion. CBK/G in conjunction with equilibrated gas compositions accurately described the lone dataset on complex mixtures with all the most important gasification agents, but many more such datasets are needed for stringent model evaluations.

Practical implications are illustrated with single-particle simulations of various coals, and a 1D gasifier simulation for realistic O₂ and steam stoichiometries. The rank dependence of gasification rates is the determining factor for predicted extents of char conversion at the gasifier outlet. But soot gasification kinetics will determine the unburned carbon emissions for all but the highest rank fuels. Only gasification kinetics for gas mixtures with widely variable levels of H₂O, H₂, and CO are directly relevant to gasifier performance evaluations.     

Emissions of nitrous oxide from combustion sources

Nitrous oxide (N₂0) has recently become the subject of intense research and debate, because of its increasing concentrations in the atmosphere and its known ability to deplete the ozone layer and also to contribute to the greenhouse effect. There are both natural and anthropogenic sources for N₂O; however, the man-made sources are increasing at a much higher rate than natural ones. Until very recently it was believed that the combustion of fossil fuels, especially coal, was the major contributing factor to these anthropogenic sources. For example, 30% of all N₂0 released into the atmosphere was once attributed to combustion sources, with 83% of the combustion sources coming from coal combustion. Correction of a recently discovered sampling artifact, whereby SO₂, H₂O and NO in combustion gases react in a sampling vessel to produce N₂O, has revealed that, in fact, less than 5 ppm of N₂0 are found in most product gases from combustion systems. Fluidized bed coal combustors are the exception, though, yielding N₂O levels of ca. 50ppm in their off-gases.

The gas-phase reactions of N₂0 in flames are reviewed first. It is clear that in most cases N₂0 is a very reactive intermediate, which is quickly destroyed before being emitted from a flame. The important homogeneous reactions removing N₂0 are thermal decomposition to N₂ and O₂ and also radical attack in e.g. N₂O + H → N₂ + OH. Nitrous oxide is formed from nitrogen-containing species by NO reacting with a radical derived from either HCN or NH₃; the reactions are NCO + NO → N₂0 + CO and NH + NO → N₂0 + H. The levels of N₂O observed are a balance betwen its rates of formation and destruction. It turns out that HCN is a more efficient precursor than NH₃ at producing N₂0. The removal of N₂O is fastest at high temperatures and in fuel-rich systems, where free hydrogen atoms are present in relatively large amounts.

When coal burns in a fluidized bed, most of the N₂O detected is produced during devolatilization, rather than in the subsequent stage of char combustion. It is clear that HCN and NH₃ are produced from nitrogenous material released during devolatilization; these two compounds give N₂0 when the volatiles burn. The burning of char, on the other hand, involves the chemi-sorption of O₂ on to sites containing carbon or nitrogen atoms, followed by surface reaction, with one of the products being N₂0, in addition to CO, CO₂ and NO. Fluidized coal combustors have temperatures around 900°C, which is low enough for the thermal decomposition of N₂O to be relatively slow. In addition, the presence of the solid phase provides a large area for radical recombination, which in turn reduces the rate of removal of N₂O by free radicals. Parametric studies of fluidized bed combustors have shown that factors such as: temperature, amount of excess air, carbon content and O/N ratio of the coal, all have a significant effect on N₂O emissions. It is important to note that heterogeneous reactions with solids, such as CaO and char, can cause large decreases in the amount of N₂O produced during the combustion of coal in a fluidized bed. In fact, there are several methods available for lowering the yields of N₂O from fluidized bed combustors generally. Areas of uncertainty in the factors affecting N₂O emissions from fluidized bed combustors are identified.     

下吸式固定床的生物质O2/CO2分段气化流程模拟

建立干桦木屑在下吸式固定床气化炉中的Aspen Plus气化模型,该模型预测煤气组成和煤气热值,与文献试验结果吻合良好。利用灵敏度分析模块模拟了氧碳比、CO₂/C对气化结果的影响,并提出O₂/CO₂分段气化流程,对比常规的CO₂气化特征,分析了CO₂/C对气化结果的影响。结果表明,纯氧气化时可获得高H₂和CO浓度的气化气,但其净CO₂排放量较高,氧碳比增加使碳转化率逐渐增加、冷煤气效率先增加后降低;CO₂作为气化剂时,随着CO₂/C的增加,净CO₂排放量逐渐减少,但碳转化率及冷煤气效率大幅降低;与常规CO₂气化相比,O₂/CO₂分段气化在保持低CO₂排放量的同时,可有效增加气化过程中的碳转化率及冷煤气效率。     

下吸式固定床的生物质H2O/CO2气化数值模拟研究

利用Aspen Plus 软件建立干桦木屑在下吸式固定床气化炉中的气化模型,模拟值与文献实验值吻合良好。利用Aspen Plus的灵敏度分析模块模拟分别以水蒸气（H₂O）和二氧化碳（CO₂）为气化剂时气化剂/生物质碳比（GC值）对气化结果的影响,并结合H₂O、CO₂各自的特点研究其复合气化。结果表明,H₂O气化时可获得富氢煤气,但其净CO₂排放量较高;CO₂气化时碳转化率及冷煤气效率较低,但净CO₂排放量较低;H₂O、CO₂复合气化使碳转化率及冷煤气效率略有降低,但可有效减少气化系统中的净CO₂排放量。     

Hydrogen and oxygen from water—VI. Quenching the effluent from a solar furnace

Numerical integration of a set of rate equations applicable to the hydrogen-oxygen system suggests that it should be possible to recover H₂ and O₂ by rapid cooling of low-pressure equilibrium mixtures from a solar furnace. Using the University of Minnesota 4.2 m solar furnace, we were able to recover explosive mixtures of H₂ and O₂ from water which had been heated to about 2100K. The numerical calculations and the experiment are described.     

Biomass as a reburning fuel: a specialized cofiring application

Reaction Engineering International has performed a series of combustion tests to evaluate the potential for utilizing wood biomass as a reburn fuel for nitrogen oxides (NO_x) control. Reburning is an effective NO_x reduction technology that utilizes fuel injection above the main burner zone. Studies with other hydrocarbon fuels such as coal and natural gas as reburn fuels have shown that NO_x emissions can be reduced by more than 50–60% with about 15% of the heat input coming from the reburn fuel. Two different biomasses, a hardwood and softwood, were evaluated as reburning fuels and compared to coal and natural gas. The use of wood to reduce NO_x is attractive for several reasons. First, wood contains little nitrogen, as compared with coal which is also used as a reburning fuel. This results in lower NO_x production from fuel nitrogen species for wood. In addition, wood contains virtually no sulfur, so sulfur dioxide (SO₂) emissions are reduced in direct proportion to the coal replacement. Wood is a regenerable biofuel; when a fossil fuel is replaced by a biofuel, there is a net reduction in carbon dioxide (CO₂) emissions. Finally, since the reburning fuel is normally 10–20% of the total heat input, large quantities of wood are not necessary. Experimental results showed NO_x reductions of as high as 70% were obtained with approximately 10–15% wood heat input. The stoichiometric ratio in the reburn zone was the single most important variable affecting NO_x reduction. The highest reductions were found at a reburn stoichiometric ratio of 0.85. NO_x reduction fell to about 40–50% at slightly higher stoichiometric ratios (0.9x reduction was strongly dependent on initial NO_x concentration and only slightly dependent upon temperature, where increased temperature increased NO_x reduction. Finally, the experimental results suggest that wood is as effective as natural gas or coal as a reburning fuel. In addition, REI has completed computer simulations of a full-scale boiler to evaluate the conditions that maximize the NO_x reduction efficiency using biomass as the reburn fuel. Computer modeling of the TVA Allen Station Unit 3, a 265 MW_e cyclone-fired boiler, showed that NO_x reductions as high as 50–60% could be achieved within the constraints set by the boiler and operations. The most important parameters affecting final NO_x emissions are the cyclone barrel stoichiometry, residence time in the reburn zone, and mixing in both the reburn and overfire air zones. The combination of computer simulations and experimental programs has provided the engineers with the tools needed to optimize biomass as a reburn fuel to maximize NO_x reduction.     

Factors regulating nitrogenase activity and hydrogen evolution in Azolla-anabaena symbiosis

Nitrogenase activity and H₂ production capacity have been studied in intact Azolla plants. Under aerobic conditions the plants showed a C₂H₂ reduction rate of 6.65 nmoles C₂H₄ mg⁻¹ fresh weight in light at 48h. Considerable activity was also present in the dark. Though H₂ evolution was detected under aerobic conditions there was multifold stimulation under anaerobic conditions. There was no significant change in nitrogenase activity under anaerobic conditions. Increasing concentrations of O₂ inhibited nitrogenase activity but 5% O₂ proved stimulatory for H₂ evolution in light. In the dark, there was a gradual stimulation in H₂ evolution even up to 20% O₂. Addition of combined nitrogen sources, namely NH₄Cl or KNO₃ (10 mM) resulted in complete inhibition of C₂H₂-reduction activity within 48 h, but H₂ evolution was not inhibited. Indeed these combined nitrogen sources stimulated H₂ evolution. Though nitrogenase activity was affected, the heterocyst frequency remained unaltered. Phosphate addition resulted in significant stimulation of nitrogenase and H₂ evolution activity. These results suggest that on nitrogenase and H₂ evolution activity in Azolla are affected by a number of factors which show a differential effect on nitrogenase and H₂ evolution. Furthermore, our results indicate the presence of a soluble reversible hydrogenase in Azolla.     

Effect of Fe on NO release during char combustion in air and O2/CO2

The chemistry of char was probed by studying nitrogen release under the reactions with air and oxy-fuel combustion. The experiments were conducted in a drop tube furnace and a fixed bed flow reactor. NO was observed during those experiments. The results show that the particle size of char generated at 1073 K in CO₂ is larger than that in N₂. However, at 1573 K, it is smaller in CO₂ atmosphere due to particle breaking by gasification of char and CO₂. The Fe addition increases the NO conversion ratio, and the effect of Fe rises steeply with the process going until it becomes stable in the end. The results also indicate that the release of NO increases more significantly with the Fe addition in oxy-fuel environment.     

Characteristics of oxygen-blown gasification for combustible waste in a fixed-bed gasifier

With increasing environmental considerations and stricter regulations, gasification of waste is considered to be a more attractive technology than conventional incineration for energy recovery as well as material recycling. The experiment for combustible waste mixed with plastic and cellulosic materials was performed in a fixed-bed gasifier to investigate the gasification behaviour with the operating conditions. Waste pelletized to a diameter of 2–3 cm and 5 cm length, was gasified in the temperature range 1100–1450 °C. The composition of H₂ was in the range 30–40% and CO 15–30% depending upon the oxygen/waste ratio. Gasification of waste due to the thermoplastic property of the mixed-plastic melting and thermal cracking shows a prominent difference from that of coal or coke. It was desirable to maintain the top temperature at 400 °C to ensure the mass transfer and uniform reaction throughout the packed bed. As the bed height was increased, the formation of H₂ and CO was increased, whilst the CO₂ decreased by the char-CO₂ reaction and plastic cracking. From the experimental results, the cold gas efficiency was around 61% and the heating values of product the gases were in the range of 2800–3200 kcal/Nm³.     

Carbon dioxide emission rates for conventional and synthetic fuels

With rising concern about the increasing atmospheric concentration of CO₂ and its potential impact on global climate, there have been suggestions that the CO₂ emission rates be considered in selecting among fuel-producing technologies. Many previous comparisons have been inadequately drawn. We discuss criteria for carefully drawn comparisons and compute CO₂ emission rates in kgC/10⁹ joules for a variety of conventional or synthetic fuel processes. Although the total CO₂ release per joule is on the order of 1.8 (±0.2) times as much for burning liquid fuels from coal as for liquid fuels from crude oil, useful comparisons among synthetic fuel processes are not easy and the results are subject to changes in boundary conditions of resource availability, plant location, environmental requirements, output slate desired, economics, etc.     

Test of a small domestic boiler using different pellets

This paper presents results from an experimental study performed on a 13 kW_th commercial domestic boiler using pellets as fuel. Four different types of pellets were used and, for each one, the boiler was tested as a function of its capacity and the fan regulation affecting excess air. Measurements were performed for boiler heat load, pellets consumption rate, flue-gas temperature and composition. Mass balances allowed the calculation of the flue-gas flow rate and associated heat losses. Losses from incomplete combustion have also been quantified. Under boiler steady-state conditions the flue-gas O₂ concentration changes with boiler load and ventilation due to the regulation scheme of the boiler. Flue-gas CO shows a minimum for values of O₂ in the flue-gases of about 13%. NO_x emissions are independent of excess air for low values of nitrogen in the fuel whereas, for larger values, NO_x emissions increase with the O₂ present in the combustion products. The fractional conversion of the pellets nitrogen into NO_x is in line with literature data. The boiler start-up was characterised by the temperature evolution inside and above the bed showing the propagation of combustion in the bed during about 10 min. During boiler start-up, a maximum in CO emissions was observed which is associated with the maximum combustion intensity, as typified by the flue-gas O₂ concentration and temperature, regardless the pellets type.     

Effects of increased biomass pellet combustion on ambient air quality in residential areas—a parametric dispersion modeling study

Sweden's goals of contemporaneously reducing CO₂ emissions and phasing out nuclear power will require a maximum utilization of biomass fuels. This would imply a significant shift from electricity and fuel oil to biomass generated heat, but must also be accomplished without a deterioration of the local air quality. The most suitable energy carrier seems to be pelletized biomass fuels with their associated low emissions and considerable residential conversion potential. Using an underlying statistical design, a parametric dispersion modeling study was performed to estimate and illustrate the combined effects of source-specific, meteorological and modeling variables on the ambient air quality in a typical residential area for different conversion scenarios. The work nicely illustrated the benefits of combining statistical designs with model calculations. It further showed that the concentration of combustion related ambient THC was strongly related to conditions affecting the source strength, but only weakly to the dispersion conditions and model variables. Time of year (summer or winter); specific emission performance; extent of conversion from electricity; conversion from wood log combustion; and specific efficiency of the pellet appliances showed significant effects in descending order. The effects of local settings and model variables were relatively small, making the results more generally applicable. To accomplish the desired conversion to renewable energy in an ecologically and sustainable way, the emissions would have to be reduced to a maximum advisable limit of 25±7 mgTHC/MJ_fuel (given as CH₄). Further, the results showed the potential positive influence by conversion from wood log to low emission pellet combustion.     

联合CO2捕集的生物质化学链气化制备合成气系统分析

本文提出以Fe₂O₃为载氧体、以CaO捕集CO₂的生物质化学链气化系统,利用Aspen Plus软件对该系统进行了模拟,以合成气组成（干基）、合成气氢碳比、含碳产物的碳摩尔分布、冷气效率及收率等为系统性能评价指标,重点分析了燃料反应器温度（T_FR）、载氧体Fe₂O₃与生物质碳摩尔比（Fe₂O₃/C）、水蒸气与生物质碳摩尔比（Steam/C）、CaO与生物质碳摩尔比（CaO/C）等系统参数对固体生物质化学链气化系统的影响。结果表明,在T_FR = 825℃、Fe₂O₃/C = 0.5、Steam/C = 0.71和CaO/C = 0.26条件下,合成气制备系统性能较优,合成气中H₂和CO₂含量分别为55.2%和15.4%,氢碳比为1.93,冷气效率为78.2%,被CaCO₃捕集的生物质碳为18.2%,收率（湿气基）为1.95 Nm³/kg_biomass,其中合成气中H₂和CO收率为1.24 Nm³/kg_biomass。     

High-temperature solar chemistry for converting solar heat to chemical fuels

This paper reviews the recent developments on thermochemical conversion of concentrated solar high temperature heat to chemical fuels. The conversion has the advantage of producing long term storable energy carriers from solar energy. This conversion also enables solar energy transportation from the sunbelt to remote population centers. The thermochemical pathway is characterized by a theoretical high efficiency. However, there are solar peculiarities in comparison to conventional thermochemical processes—high thermal flux density and frequent thermal transients because of the fluctuating insolation—, and conventional industrial thermochemical processes are generally not suitable for solar driven processes. Therefore, the adaptation to such peculiarities of solar thermochemical processes has been the important R&D task in this research field. Thermochemical water splitting, steam or CO₂ gasification of coal, steam or CO₂ reforming of methane, and hydrogenetive coupling of methane, are industrially important, endothermic processes to produce useful chemical fuels such as hydrogen, synthesis gas and C₂-hydrocarbons, which have been examined as solar thermochemical processes. The technical developments and feasibilities to conduct these endothermic processes by utilizing concentrated solar radiation as the process heat are discussed here. My recent experimental results to improve the advanced solar thermochemical technologies are also given.