Enhancing the aromatic hydrocarbon yield from the catalytic copyrolysis of xylan and LDPE with a dual-catalytic-stage combined CaO/HZSM-5 catalyst

The high concentration of oxygenated compounds in pyrolytic products prohibits the conversion of hemicellulose to important biofuels and chemicals via fast pyrolysis. Herein CaO and HZSM-5 was developed to convert xylan and LDPE to valuable hydrocarbons by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and elucidate the reaction mechanism were also investigated in detail. The results indicated that xylan/LDPE copyrolysis was more complicated than pyrolysis of the individual components. LDPE hindered the thermal decomposition and aromatic hydrocarbon formation from xylan at temperatures under 350 °C and had a synergistic effect at high temperatures. 50% LDPE was proven to be more beneficial than other percentages for the formation of monocyclic aromatic hydrocarbons. Simultaneously, the addition of CaO/HZSM-5 significantly reduced the reaction Ea and increased the reaction rate. CaO can effectively improve the deoxygenation and aromatization reaction, enhancing the yield and selectivity of aromatics to a certain extent. The maximum yield of hydrocarbons (96.01%), mono-aromatic hydrocarbons (88.53%) and S_BTXE (85.79%) were obtained at a CaO/HZSM-5 ratio of 1:2, a pyrolysis temperature of 450 °C, a catalytic temperature of 550 °C, a catalyst dose of 1:2 and a xylan-to-LDPE ratio of 1:1 via an ex situ process. The system was dominated by toluene, xylene and alkyl benzene. Diels-Alder reactions of furans and hydrocarbon pool mechanism of nonfuranic compounds improved aromatic formation. This study provides a fundamental for recovering energy and chemicals from pyrolysis of hemicellulose.     

H2S effect on dry reforming of biogas for syngas production

The effect of hydrogen sulfide (H₂S) on dry reforming of biogas for syngas production was studied both experimentally and theoretically. In the experimental work, the H₂S effect on Ni‐based catalyst activity was examined for reaction temperatures ranging from 600°C to 800°C. It was found that the presence of H₂S deactivated the Ni‐based catalysts significantly because of sulfur poisoning. Although bimetallic Pt‐Ni catalyst has better performance compared with monometallic Ni catalyst, deactivation was still found. The time‐on‐stream measured data also indicated that sulfur‐poisoned catalyst can be regenerated at high reaction temperatures. In the theoretical work, a thermodynamic equilibrium model was used to analyze the H₂S removal effect in dry reforming of H₂S‐contained biogas. Calcium oxide (CaO) and calcium carbonate (CaCO₃) were used as the H₂S sorbent. The results indicated that H₂S removal depends on the initial H₂S concentration and reaction temperature for both sorbents. Although CO₂ was also removed by CaO, the results from equilibrium analysis indicated that the dry reforming reaction in the presence of CaO was feasible similar to the sorption enhanced water‐gas shift and steam‐methane reforming reactions. The simulation results also indicated that CaO was a more preferable H₂S sorbent than CaCO₃ because syngas with an H₂/CO ratio closer to 2 can be produced and requires lower heat duty.     

Entrained flow gasification of straw- and wood-derived pyrolysis oil in a pressurized oxygen blown gasifier

Fast pyrolysis oil can be used as a feedstock for syngas production. This approach can have certain advantages over direct biomass gasification. Pilot scale tests were performed to investigate the route from biomass via fast pyrolysis and entrained flow gasification to syngas. Wheat straw and clean pine wood were used as feedstocks; both were converted into homogeneous pyrolysis oils with very similar properties using in-situ water removal. These pyrolysis oils were subsequently gasified in a pressurized, oxygen blown entrained flow gasifier using a thermal load of 0.4 MW. At a pressure of 0.4 MPa and a lambda value of 0.4, temperatures around 1250 °C were obtained. Syngas volume fractions of 46% CO, 30% H₂ and 23% CO₂ were obtained for both pyrolysis oils. 2% of CH₄ remained in the product gas, along with 0.1% of both C₂H₂ and C₂H₄. Minor quantities of H₂S (3 vs. 23) cm³ m⁻³, COS (22 vs. 94) cm³ m⁻³ and benzene (310 vs. 532) cm³ m⁻³ were measured for wood- and straw derived pyrolysis oils respectively. A continuous 2-day gasification run with wood derived pyrolysis oil demonstrated full steady state operation. The experimental results show that pyrolysis oils from different biomass feedstocks can be processed in the same gasifier, and issues with ash composition and melting behaviour of the feedstocks are avoided by applying fast pyrolysis pre-treatment.     

The influence of temperature and heating rate on the slow pyrolysis of biomass

The slow pyrolysis of biomass in the form of pine wood was investigated in a static batch reactor at pyrolysis temperatures from 300 to 720°C and heating rates from 5 to 80 K min⁻¹. The compositions and properties of the derived gases, pyrolytic oils and solid char were determined in relation to pyrolysis temperatures and heating rates. In addition, the wood and the major components of the wood—cellulose, hemicellulose and lignin—were pyrolysed in a thermogravimetric analyser (TGA) under the same experimental conditions as in the static batch reactor. The static batch reactor results showed that as the pyrolysis temperature was increased, the percentage mass of solid char decreased, while gas and oil products increased. There was a small effect of heating rate on product yield. The lower temperature regime of decomposition of wood showed that mainly H₂O, CO₂ and CO were evolved and at the higher temperature regime, the main decomposition products were oil, H₂O, H₂, hydrocarbon gases and lower concentrations of CO and CO₂. Fourier transformation infra-red spectroscopy and elemental analysis of the oils showed they were highly oxygenated. The TGA results for wood showed two main regimes of weight loss, the lower temperature regime could be correlated with the decomposition of hemicellulose and the initial stages of cellulose decomposition whilst the upper temperature regime correlated mainly with the later stages of cellulose decomposition. Lignin thermal decomposition occurred throughout the temperature range of pyrolysis.     

Mechanism of wet sewage sludge pyrolysis in a tubular furnace

The main objective of this work was to develop a preliminary mechanistic understanding of wet sewage sludge decomposition from starting constituents to final products, including intermediates formed during the pyrolysis process. Sewage sludge with a moisture content of 84.2 wt% was pyrolyzed at different temperatures in a tubular furnace, the pyrolysis products (hydrogen-rich fuel gas, tar and solid char) were detected by micro-GC, GC-MS, and FTIR, respectively. The high moisture content of wet sewage sludge generated a steam-rich atmosphere at high temperatures, leading to an in situ steam reforming of the volatile compounds and a partial gasification of the solid char, which contributed to the production of hydrogen-rich fuel gas. The pyrolysis process can be divided into two steps: at a relatively low temperature (<600 °C), the breaking of the C-H bonds of alkyl gave rise to the release of CH₄ and C₂ hydrocarbons, and a large amount of CO and CO₂ evolved as the result of CO decreasing, both processes indicated the decomposition of volatile compounds. The increasing absorbance amount of C-O and C-H_aromatic demonstrated the formation of tar. As temperature increased further, the diminishing IR absorbance of C-O and C-H_aromatic was accompanied by a significant reduction of tar yield and an increase of H₂. H₂ was considered as an indicator for the occurrence of tar cracking. The Diels-Alder reaction mechanism followed by dehydrogenation was employed to explain the PAHs formation.     

Pyrolysis-catalytic steam reforming of agricultural biomass wastes and biomass components for production of hydrogen/syngas

The pyrolysis-catalytic steam reforming of six agricultural biomass waste samples as well as the three main components of biomass was investigated in a two stage fixed bed reactor. Pyrolysis of the biomass took place in the first stage followed by catalytic steam reforming of the evolved pyrolysis gases in the second stage catalytic reactor. The waste biomass samples were, rice husk, coconut shell, sugarcane bagasse, palm kernel shell, cotton stalk and wheat straw and the biomass components were, cellulose, hemicellulose (xylan) and lignin. The catalyst used for steam reforming was a 10 wt.% nickel-based alumina catalyst (NiAl₂O₃). In addition, the thermal decomposition characteristics of the biomass wastes and biomass components were also determined using thermogravimetric analysis (TGA). The TGA results showed distinct peaks for the individual biomass components, which were also evident in the biomass waste samples reflecting the existence of the main biomass components in the biomass wastes. The results for the two-stage pyrolysis-catalytic steam reforming showed that introduction of steam and catalyst into the pyrolysis-catalytic steam reforming process significantly increased gas yield and syngas production notably hydrogen. For instance, hydrogen composition increased from 6.62 to 25.35 mmol g^?1 by introducing steam and catalyst into the pyrolysis-catalytic steam reforming of palm kernel shell. Lignin produced the most hydrogen compared to cellulose and hemicellulose at 25.25 mmol g^?1. The highest residual char production was observed with lignin which produced about 45 wt.% char, more than twice that of cellulose and hemicellulose.     

A combined thermodynamic and experimental study on chemical‐looping ethanol reforming with carbon dioxide capture for hydrogen generation

Chemical‐looping ethanol reforming with carbon dioxide capture is proposed. It combines chemical‐looping reforming and carbon dioxide capture for pure hydrogen generation from ethanol with inherent separation of carbon dioxide. A thermal analysis of the process using NiO oxygen carrier is performed by simulating reactions using the Gibbs energy minimization method. The promising systems are investigated further with respect to temperature, NiO/C₂H₅OH molar ratio, CaO/C₂H₅OH molar ratio and pressure changes as well as possible carbon formation in the reformer. Favorable operation conditions in the presence of CaO are: pressures around 3 atm, reactor temperatures around 850 K, NiO/C₂H₅OH molar ratio = 3 and CaO/C₂H₅OH = 3. The H₂ yield and thermal efficiency with CaO addition are higher than that without CaO addition, showing that the addition of a CO₂ sorbent in the process increases the H₂ production. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of calcium promoter on catalytic pyrolysis characteristics of iron-loaded brown coal in a fixed bed reactor

The Fe–Ca catalysts in catalytic pyrolysis of brown coals were studied to investigate the catalytic activity of the Fe–Ca in a fixed-bed reactor. Experimental results showed the maximum yields of the light aromatic hydrocarbons (LAHs) were 5.90 wt% (0.88 wt% of benzene, toluene and xylene ‘BTX’, 4.10 wt% of phenol and cresol ‘PC’ and 0.92 wt% of naphthalene) when the 1.5% Ca was added into 5% Fe-loaded brown coal. The yields of water and gas significantly reduced, the tar yield gradually increased with increasing heating rate. The characterization results indicated that when calcium promoter was impregnated with iron, Ca₂Fe₂O₅, CaO, Fe₂O₃ and α-Fe were formed on the surface of the coal char, Ca₂Fe₂O₅ and α-Fe decomposed polyaromatic tar, CaO and Fe₂O₃ accelerated water gas shift reaction to enhance the H₂ yield, the Fe₂O₃ and Ca₂Fe₂O₅ could be reduced to α-Fe by volatiles (C, CO and H₂) under high temperature catalytic pyrolysis. The synergistic effects between iron and calcium improved brown coal pyrolysis and the volatiles such as free radical fragments were further pyrolyzed, indicating that Fe–Ca catalysts inhibited α-Fe deactivation by tar and carbon deposition, thus promoting brown coal pyrolysis and formation of CO_x, H₂ and LAHs.     

Exergy analysis of biomass staged-gasification for hydrogen-rich syngas

Using Aspen Plus simulations, exergy analyses of hydrogen-rich syngas production via biomass staged-gasification are carried out for three configurations, namely, staged-gasification with pyrolysis gas combustion and char gasification (C-1), staged-gasification with pyrolysis gas reforming and char gasification (C-2), and staged-gasification with pyrolysis gas reforming and char combustion (C-3). The results show that, for the gasification and reforming processes, the exergy loss of pyrolysis gas with tar reforming is less than that of char gasification. As for the system, it is conducive to generating hydrogen by making full use of the hydrogen element (H) in biomass instead of the H in water. The benefits of C-1 are that it removes tar and produces higher yield and concentration of hydrogen. However, C-2 is capable of obtaining higher exergy efficiency and lower exergy loss per mole of H₂ production. C-3 theoretically has greater process performances, but it has disadvantages in tar conversion in practical applications. The appropriate gasification temperature (T_G) are in the range of 700–750 °C and the appropriate mass ratio of steam to biomass (S/B) are in the range of 0.6–0.8 for C-1 and C-3; the corresponding parameters for C-2 are in the ranges of 650–700 °C and 0.7–0.8, respectively.     

Hydrogen from Various Biomass Species via Pyrolysis and Steam Gasification Processes

The aim of this study was to assess the scientific and engineering advancements of producing hydrogen from biomass via two thermochemical processes: (a) conventional pyrolysis followed by reforming of the carbohydrate fraction of the bio-oil and (b) gasification followed by reforming of the syngas (H₂ + CO). The yield from steam gasification increases with increasing water-to-sample ratio. The yields of hydrogen from the pyrolysis and the steam gasification increase with increasing of temperature. In general, the gasification temperature is higher than that of pyrolysis and the yield of hydrogen from the gasification is higher than that of the pyrolysis. The highest yields (% dry and ash free basis) were obtained from the pyrolysis (46%) and steam gasification (55%) of wheat straw while the lowest yields from olive waste. The yield of hydrogen from supercritical water extraction was considerably high (49%) at lower temperatures. The pyrolysis was carried out at the moderate temperatures and steam gasification at the highest temperatures. This study demonstrates that hydrogen can be produced economically from biomass. The pyrolysis-based technology, in particular, because it has coproduct opportunities, has the most favorable economics.     

The effects of Fe2O3 catalyst on the conversion of organic matter and bio-fuel production during pyrolysis of sewage sludge

In this paper, the pyrolysis treatment of sewage sludge is studied in a fixed bed reactor at temperatures range of 400–600 °C. Meanwhile, the catalytic effect of Fe₂O₃ on the characteristics of the resulting gases, bio-oil and bio-char are also investigated. The experimental results indicate that the yields of gases and bio-oil respectively increase from 8.69 wt% and 32.54 wt% to 11.62 wt% and 38.74 wt%, and the char yield decreases from 58.77 wt% to 49.64 wt% during Fe-embedded sewage sludge pyrolysis when Fe₂O₃ is added equal to 5% in the dried sewage sludge. Meanwhile, Fe₂O₃ promotes the CO and H₂ formation and inhibits the CH₄ formation, while it exhibits no significantly effect on the composition of the bio-oil. Moreover, the bio-oil should be direct combustion for power generation due it contains higher oxygenated hydrocarbons. In addition, the bio-char exhibits good desulfurization activity.     

Experimental and theoretical study on propane pyrolysis to produce gas and soot

The pyrolysis gas and soot production characteristics of propane at different temperatures and residence time were studied experimentally. Based on the combustion mechanism of propane proposed by the University of California, San Diego and Appel mechanism, a new mechanism of propane pyrolysis and soot formation, SD-APP_MECH was established. The reaction paths and dominant controlling reactions of propane pyrolysis and soot production were investigated. According to the experimental results, the new mechanism was optimized to predict the processes of propane pyrolysis and soot formation accurately. The optimized mechanism of propane pyrolysis was named as C₃H₈_MECH. The results showed that propane begins to pyrolyse at around 970 K, the main components of the syngas are H₂, CH₄, C₂H₂ and C₂H₄. At the later stage of pyrolysis, C₂H₂ was generated from C₂H₄ dehydrogenation at 1150 K. When the temperature is below 1173 K, little soot was produced. However, the soot formation rate increased obviously when the temperature is higher than 1250 K. The soot diameter increased with the temperature increasing, and the amount of soot formation decreased with the residence time reducing. The mole fraction of dominant products in propane pyrolysis and soot formation rate calculated from the C₃H₈_MECH mechanism agreed well with the experimental values.     

Hydrogen production by biomass gasification in a fluidized-bed reactor promoted by an Fe/CaO catalyst

Biomass gasification for hydrogen production was performed in a continuous-feeding fluidized-bed with the use of Fe/CaO catalysts. The relationship between catalyst properties and biomass gasification efficiencies was studied. The findings indicated that only CaO was involved in the enhancement of char gasification, resulting in an increased hydrogen production. However, CaO was also easily deactivated by biomass tar. The characterization results indicated that when CaO was impregnated with Fe, Ca₂Fe₂O₅ formed on the surface of the support. Ca₂Fe₂O₅ decomposed polyaromatic tar but was not effective in char gasification. The synergistic effects between Fe and CaO that effectively enhanced biomass gasification mainly involved combustion and pyrolysis, and the biomass gasification products, i.e., char and tar, were further gasified, indicating that tailor-made Fe/CaO catalysts prevented CaO deactivation by tar, thus promoting biomass gasification and hydrogen production.     

An overview of solar decarbonization processes,reacting oxide materials,and thermochemical reactors for hydrogen and syngas production

Solar decarbonization processes are related to the different thermochemical conversion pathways of hydrocarbon feedstocks for solar fuels production using concentrated solar energy as the external source of high-temperature process heat. The main investigated routes aim to convert gaseous and solid feedstocks (methane, coal, biomass …) into hydrogen and syngas via solar cracking/pyrolysis, reforming/gasification, and two-step chemical looping processes using metal oxides as oxygen carriers, further associated with thermochemical H₂O/CO₂ splitting cycles. They can also be combined with metallurgical processes for production of energy-intensive metals via solar carbothermal reduction of metal oxides. Syngas can be further converted to liquid fuels while the produced metals can be used as energy storage media or commodities. Overall, such solar-driven processes allow for improvements of conversion yields, elimination of fossil fuel or partial feedstock combustion as heat source and associated CO₂ emissions, and storage of intermittent solar energy in storable and dispatchable chemical fuels, thereby outperforming the conventional processes. The different solar thermochemical pathways for hydrogen and syngas production from gaseous and solid carbonaceous feedstocks are presented, along with their possible combination with chemical looping or metallurgical processes. The considered routes encompass the cracking/pyrolysis (producing solid carbon and hydrogen) and the reforming/gasification (producing syngas). They are further extended to chemical looping processes involving redox materials as well as metallurgical processes when metal production is targeted. This review provides a broad overview of the solar decarbonization pathways based on solid or gaseous hydrocarbons for their conversion into clean hydrogen, syngas or metals. The involved metal oxides and oxygen carrier materials as well as the solar reactors developed to operate each decarbonization route are further described.     

Catalytic reforming of biomass primary tar from pyrolysis over waste steel slag based catalysts

Steel slag (SS) contains high amounts of metal oxides and could be applied as the catalyst or support material for the reforming of biomass derived tar. In this research, steel slag supported nickel catalysts were prepared by impregnation of a small amount of nickel (0–10 wt%) and calcination at 900 °C, and then tested for the catalytic reforming of biomass primary tar from pine sawdust pyrolysis. The steel slag after calcination was mainly composed of Fe₂O₃ and MgFe₂O₄, and granular NiO particles was formed and highly dispersed on the surface of nickel loaded steel slag which lead to a porous structure of the catalysts. The steel slag showed good activity on converting biomass primary tar into syngas, and its performance can be further enhanced by the loading of nickel. The yield of H₂ increased significantly with the increase of nickel loading amount, while excessive nickel loading resulted in the decrease in CO and CH₄ yields and significant increase in CO₂ yield. The presence of steam contributed to enhancing the tar steam reforming as well as reactions between steam and produced gases, while decrease the contact probability between the reactants and the active sites of catalysts, leading to a little decrease in tar conversion efficiency but significant increase in syngas yield. The iron and nickel oxides were reduced by the syngas (CO and H₂) from the biomass pyrolysis, and stable and porous structure was formed on the surface of the nickel loaded catalysts during tar reforming.     

Kinetic characteristics of in-situ char-steam gasification following pyrolysis of a demineralized coal

This study aims to examine the char-steam reactions in-situ, following the pyrolysis process of a demineralized coal in a micro fluidized bed reactor, with particular focuses on gas release and its kinetics characteristics. The main experimental variables were temperatures (925 °C?1075 °C) and steam concentrations (15%–35% H₂O), and the combination of pyrolysis and subsequent gasification in one experiment was achieved switching the atmosphere from pure argon to steam and argon mixture. The results indicate that when temperature was higher than 975 °C, the absolute carbon conversion rate during the char gasification could easily reach 100%. When temperature was 1025 °C and 1075 °C, the carbon conversion rate changed little with steam concentration increasing from 25% to 35%. The activation energy calculated from shrinking core model and random pore model was all between 186 and 194 kJ/mol, and the fitting accuracy of shrinking core model was higher than that of the random pore model in this study. The char reactivity from demineralized coal pyrolysis gradually worsened with decreasing temperature and steam partial pressure. The range of reaction order of steam gasification was 0.49–0.61. Compared to raw coal, the progress of water gas shift reaction (CO + H₂O ? CO₂ + H₂) was hindered during the steam gasification of char obtained from the demineralized coal pyrolysis. Meanwhile, the gas content from the char gasification after the demineralized coal pyrolysis showed a low sensitivity to the change in temperature.     

Ethanol steam reforming on Ni/CaO catalysts for coproduction of hydrogen and carbon nanotubes

Catalytic steam reforming of ethanol is considered as a promising technology for producing H₂ in the modern world. In this study, using a fixed‐bed reactor, steam reforming of ethanol was performed for production of carbon nanotubes (CNTs) and H₂ simultaneously at 600°C on Ni/CaO catalysts. Commercial CaO and a synthetic CaO prepared using sol‐gel were scrutinized for ethanol's catalytic steam reforming. Analysis results of N₂ isothermal adsorption indicate that the CaO synthesized by sol‐gel has more pore volume and surface area in comparison with the commercial CaO. When Ni was loaded, the Ni/CaO catalyst shows an encouraging catalytic property for H₂ production, and an increase in Ni loading could improve H₂ production. The Ni/CaO catalyst with sol‐gel CaO support has presented a higher hydrogen production and better catalytic stability than the catalysts with the commercial CaO support at low Ni loading. The highest hydrogen yield is 76.8% at Ni loading content of 10% for the Ni/sol‐gel CaO catalyst with WHSV of 3.32/h and S/C ratio of 3. The carbon formed after steam reforming primarily consists of filamentous carbons and amorphous carbons, and CNTs are the predominant type of carbon deposition. The deposited extent of carbon on the used Ni/CaO catalyst lessen upon more Ni loading, and the elongated CNTs are desired to be formed at the surface of the Ni/sol‐gel CaO catalyst. Thus, an efficient process and improved economic value is associated with prompt hydrogen production and CNTs from ethanol steam reforming.     

Multifaceted analysis of products from the intermediate co-pyrolysis of biomass with Tetra Pak waste

This study investigates the co-pyrolysis of two types of biomass (pine bark and wheat straw) with Tetra Pak waste (TPW). The experiments were performed using a fixed-bed reactor equipped with an innovative system, where a sample was rapidly heated to 600 °C before being rapidly cooled. The multifaceted analysis included the determination of the i) physical and chemical properties of the feedstocks and chars, ii) aqueous phase, tars, and waxes, iii) char ignition and burnout temperature, iv) chemical composition of gas, and v) distribution of carbon and hydrogen in the obtained products. The results showed that the addition of TPW to the both types of biomass significantly reduced the char mass and aqueous phase, decreased the carbon, hydrogen, and nitrogen contents of the char, and increased the wax and tar yields retained in the water cooler. Different organic compounds such as alkenes, aromatic hydrocarbons, and acids were found in tars and waxes. The chemical composition of the released gases was detected in situ (by a flue-gas analyser) and ex-situ (using gas chromatography). Changes in the concentrations of H₂, CH₄, CO, CO₂, and C2–C4 were observed. The addition of Tetra Pak to the two types of biomass had an evident and positive effect on the hydrogen content of the pyrolysis gas.     

Absorption enhanced reforming of light alcohols (methanol and ethanol) for the production of hydrogen: Thermodynamic modeling

Thermodynamic modeling of the steam reforming of light alcohols using CaO, CaO*MgO, Na₂ZrO₃, Li₂ZrO₃ and Li₄SiO₄ as CO₂ absorbents was carried out to determine promising operating conditions to produce a high hydrogen yield (YH₂)$\left(Y_{{\text{H}}_2}\right)$ and concentration (% H₂). Ethanol and methanol were studied at 300–800 °C and 1 atm. Steam to alcohol (S/COH) feed molar ratio varied from 1:1 (stoichiometric) to 6:1 for methanol and from 3:1 (stoichiometric) to 6:1 for ethanol. Thermodynamic simulations employed the Gibbs free energy minimization technique. Results indicate no carbon formation at S/COH ≤ stoichiometric. For both alcohols reforming at 600 °C and S/COH = 6, using CaO, CaO*MgO, and Na₂ZrO₃ produced optimal YH₂$Y_{{\text{H}}_2}$ and hydrogen purity (% H₂). In both reforming systems most favorable thermodynamics were obtained with CaO, CaO*MgO and Na₂ZrO₃ as absorbents. A Thermal efficiency analysis performed in all system confirmed the superiority of the CO₂ absorption systems against conventional reforming processes.     

Effects of CaO on nitrogen transformation during pyrolysis of soybean protein

To elucidate the effects of CaO on nitrogen transformation during sludge pyrolysis, transformation behavior from char N into NO_x precursors during pyrolysis of soybean protein (SP) with CaO at 600–700°C was investigated. Results showed that CaO inhibited the transformation of pyridine N and quaternary N into HCN and promoted HCN conversion into NH₃ at 600–700°C. CaO inhibited the conversion of protein N and tar N into NH₃ at 600°C but promoted it at 700°C. NO_x precursor yield was the lowest when SP was pyrolyzed with CaO/N of 5.5 at 600°C (reduced by 11.66% compared with raw SP pyrolysis).