Investigation of oxy-fuel combustion for methane and acid gas in a diffusion flame

Co-combustion of methane(CH4)and acid gas(AG)is required to sustain the temperature in Claus reaction furnace.In this study,oxy-fuel combustion of methane and acid gas has been experimentally studied in a diffusion flame.Three equivalence ratios(ER=1.0,1.5,2.0)and CH_(4)-addition ratios(CH_(4)/AG=0.3,0.5,0.7)were examined and the flame was interpreted by analyzing the distributions of the temperature and species concentration along central axial.CH_(4)-AG diffusion flame could be classified into three sections namely initial reaction,oxidation and complex reaction sections.Competitive oxidation of CH_(4)and H_(2)S was noted in the first section wherein H_(2)S was preferred and both were mainly proceeding decomposition and partial oxidation.SO_(2)was formed at oxidation section together with obvious presence of H2 and CO.However,H2 and CO were inclined to be sustained under fuel rich condition in the complex reaction section.Reducing ER and increasing CH4/AG contributed to higher temperature,H_(2)S and CH_(4)oxidation and CO_(2)reactivity.Hence a growing trend for CH_(4)and AG to convert into H_(2),CO and SO_(2)could be witnessed.And this factor enhanced the generation of CS2 and COS in the flame inner core by interactions of CH4 and CO_(2)with sulfur species.COS was formed through the interactions of CO and CO_(2)with sulfur species.The CS_(2)production directly relied on reaction of CH_(4)with sulfur species.The concentration of COS was greater than CS_(2)since CS_(2)was probably inhibited due to the presence of H_(2).COS and CS_(2)could be consumed by further oxidation or other complex reactions.

Comparative study on SO_2 release and removal under air and oxy-fuel combustion in a fluidized bed combustor

SO2 release and removal were studied under both the air and oxy-fuel combustion conditions using an anthracite coal from the Jincheng mine in China on a bench-scale fluidized bed combustor （FBC）. Special attention was paid to the effects of the combustion atmosphere, 02 concentration, bed temperature, and limestone addition. The released amount of SO2 was clearly higher under 30% 02/70% CO2 than that of the air atmosphere. As the O2 concentration in O2/CO2 mixture increased from 21% to 40%, the released amount of SO2 increased significantly, but then it decreased when the 02 concentration increased up to 50%. The bed temperature from 860 to 920 ℃ has no obvious influence on the the SO2 release but shows a strong influence on the desulfurization with limestone in both oxy-fuel and air conditions. The maximum SO2 removal efficiency appears to be at 880 to 900 ℃ for both the air and oxy-fuel combustion conditions.

Transformation of alkali and alkaline-earth metals during coal oxy-fuel combustion in the presence of SO_2 and H_2O

The occurrence modes of alkali and alkaline-earth metals（AAEMs） in coal relate to their release behavior and ash formation during combustion. To better understand the transformation of AAEMs,the release behavior of water-soluble,HCl-soluble,HCl-insoluble AAEMs during Shenmu coal（SM coal） oxy-fuel combustion in the presence of SO2 and H2O in a drop-tube reactor was investigated through serial dissolution using H2O and HCl solutions. The results show that the release rates of AAEMs increase with an increase in temperature under the three atmospheres studied. The high release rates of Mg and Ca from SM coal are dependent on the high content of soluble Mg and Ca in SM coal. SO2 inhibits the release rates of AAEMs,while H2O promotes them. The effects of SO2 and H2O on the Na and K species are more evident than those on Mg and Ca species. All three types of AAEMs in coal can volatilize in the gas phase during coal combustion. The W-type AAEMs release excessively,whereas the release rates of I-type AAEMs are relatively lower. Different types of AAEM may interconvert through different pathways under certain conditions. Both SO2 and H2O promote the transformation reactions. The effect of SO2 was related to sulfate formation and the promotion by H2O occurs because of a decrease in the melting point of the solid as well as the reaction of H2O.

Microstructure and Performances of Glasses Melt under Oxy-fuel Combustion

We prepared a series of glass samples under the different simulated atmosphere.Systematic evaluation about the performances of the glasses fabricated under the different simulated atmosphere indicates that the increase of the H2O：CO2 ratio under the simulated atmosphere will decrease the softening point temperature,microhardness,viscosity,and chemical resistance,while increase the thermal expansion coefficient.Through the analysis of the hydroxyl content and network structure according to the IR transmitting spectra and NMR spectra,the structural origin of the evolution of the performances for the samples fabricated under different simulated atmosphere was elucidated.According to the feedback information from the customers,despite the decrease of some performances,the glass produced under oxy-fuel combustion can also fulfill the requirements of the engineering applications.Therefore,the technique of oxy-fuel combustion is worthy to be promoted in glass industry.

Effect of carbon dioxide on oxy-fuel combustion of hydrogen sulfide:An experimental and kinetic modeling

CO_(2) is an important component in the acid gas and it is necessary to study the effect of CO_(2) presence on the oxy-fuel combustion of H_(2)S with particular focus on the formation of carbonyl sulfide(COS).The oxyfuel combustion of acid gas was conducted in a coaxial jet double channel burner.The distribution of flame temperature and products under stoichiometric condition along axial(R=0.0)and radial at about 3.0 mm(R=0.75)were analyzed,respectively.The Chemkin-Pro software was used to analyze the rate of production(ROP)for gas products and the reaction pathway of acid gas combustion.Both experimental and simulation results showed that acid gas combustion experienced the H2S chemical decomposition,H_(2)S oxidation and accompanied by H_(2) oxidation.The CO_(2) presence reduced the peak flame temperature and triggered the formation of COS in the flame area.COS formation at R=0.0 was mainly through the reaction of CO_(2) and CO with sulfur species,whereas at R=0.75 it was through the reaction of CO with sulfur species.The ROP results indicated that H_(2) was mainly from H_(2)O decomposition in the H_(2)S oxidation stage,and COS was formed by the reaction of CO_(2) with H_(2)S.ROP and other detailed analysis further revealed the role of H,OH and SH radicals in each stage of H_(2)S conversion.This study revealed the COS formation mechanisms with CO_(2) presence in the oxy-fuel combustion of H_(2)S and could offer important insights for pollutant control.

Low Steam Condition Heat Generator Combined with Advanced Oxy-Fuel Combustion LNG Gas Turbine for Power Generation

We propose a novel concept for power generation that involves the combination of a LSCHG （low-steam-condition heat generator）, such as a light water nuclear reactor or a biomass combustion boiler, with an advanced closed-cycle oxy-fuel combustion gas turbine-a type of complex and efficient oxy-fuel gas turbine. In this study, a LSCHG is designed to heat water to saturated steam of a few MPa, to assist in the generation of the main working fluids, instead of a compressor used in the advanced oxy-fuel gas turbine. This saturated steam can have a lower pressure and temperature than those of an existing nuclear power plant or biomass-fired power plant. We estimated plant performances in LHV （lower heating value） basis from a heat balance model based on a conceptual design of a plant for different gas turbine inlet pressures and temperatures of 1,300 ℃ and 1,500 ℃, taking into account the work to produce O2 and capture CO2. While the net power generating efficiencies of a reference plant are estimated to be about 52.0% and 56.0% at 1,300 ℃ and 1,500 ℃, respectively, and conventional LSCHG power plant is assumed to have an efficiency of about 35% or less for pressures of 2.5-6.5 MPa, the proposed hybrid plant achieved 42.8%-44.7% at 1,300 ℃ and 47.8%-49.2% at 1,500 ℃. In the proposed plant, even supposing that the generating efficiency of the LNG system in the proposed plant remains equal to that of the reference plant, the efficiency of LSCHG system can be estimated 37.4% for 6.5 MPa and 33.2% for 2.5 MPa, even though the LSHCG system may be regarded as consisting of fewer plant facilities than a conventional LSCHG power plant.

Gas-phase oxidation of NO at high pressure relevant to sour gas compression purification process for oxy-fuel combustion flue gas

The removal of NO from oxy-fuel combustion is typically incorporated in sour gas compression purification process. This process involves the oxidation of NO to NO2 at a high pressure of 1–3 MPa, followed by absorption of NO2 by water. In this pressure range, the NO conversion rates calculated using the existing kinetic constants are often higher than those obtained experimentally. This study aimed to achieve the regression of kinetic parameters of NO oxidation based on the existing experimental results and theoretical models.Based on three existing NO oxidation mechanisms, first, the expressions for NO conversion against residence time were derived. By minimizing the mean-square errors of NO conversion ratio, the optimum kinetic rate constants were obtained. Without considering the reverse reaction for NO oxidation, similar mean-square errors for NO conversion ratio were calculated. Considering the reverse reaction for NO oxidation based on the termolecular reaction mechanism, the minimum mean-square error for NO conversion ratio was obtained. Thus, the optimum NO oxidation rate in the pressure range 0.1–3 MPa can be expressed as follows:-d[NO]/dt=d[NO2]/dt=0.0026[NO]2[O2]-0.0034[NO2]2 Detailed elementary reactions for N2/NO/NO2/O2 system were established to simulate the NO oxidation rate. A sensitivity analysis showed that the critical elementary reaction is 2 NO + O2? 2 NO2. However, the simulated NO conversions at a high pressure of 10–30 bar are still higher than the experimental values and similar to those obtained from the models without considering the reverse reaction for NO oxidation.

Comparisons of Fly Ash and Deposition Between Air and Oxy-Fuel Combustion in Bench-Scale Fluidized Bed with Limestone Addition

In Oxy-fuel circulating fluidized bed,the residual Ca O particles may react with high concentration of CO2 in flue gas to form bonded deposit on heat transfer surfaces in backpass when limestone is used as a sorbent to capture SO2.In this paper,experiments were designed on ash deposition in a bench-scale fluidized bed under oxy-fuel and air atmosphere. A novel ash deposit sampling probe was used to simulate the tubes of tail surfaces.The chemical composition of fly ash and ash deposit from both air-firing and oxy-fuel firing cases were analyzed by Inductively Coupled Plasma-Atomic Emission Spectrometry( ICP-AES) and Scanning Electron Microscopy( SEM),respectively. The degrees of carbonation reaction of ash deposits were measured by Thermo Gravimetric Analysis. The results showed that there are distinct differences in fly ash deposition rate between oxy-fuel and air firing cases,and oxy-fuel combustion with limestone addition can affect chemical composition of fly ash and ash deposit,especially for elements of Ca,Na,K,and S. However,the carbonation reaction degree of ash deposits is found weak,which is due to the relatively low Ca O content in ash deposit or not long enough of the sampling time.

Effect of Atmosphere on Volatile Emission Characteristic in Oxy-Fuel Combustion

A new type of power supply which was called oxy-fuel combustion power plant was introduced to reduce greenhouse gasses emission. In this paper the volatile emission characteristic of pulverized coal is studied under air atmosphere and oxy-fuel atmosphere. Combustion experiments of Datong bituminous coal were carried out in a wire mesh reactor at heating rates of 1 K/s, 10 K/s and 1000 K/s respectively under air and O2/CO2 atmosphere conditions in order to investigate the volatile emission characteristic. The concentrations of volatile (mainly CO and CH4) emission were on-line measured by infrared gas analyzer. It was indicated that the concentrations of CO and CH4 in O2/CO2 atmosphere were higher than those in air. The direct oxidation of carbon and gasification reaction between carbon and CO2 are the main causes of the increased amount of CO. The higher concentration of CO2 also results in the increased amount of CH4 in O2/CO2 conditions.

Experimental investigation on the NO formation of pulverized coal combustion under high-temperature and low-oxygen environments simulating MILD oxy-fuel combustion conditions

The NO formation experiments simulating moderate and intense low-oxygen dilution(MILD)oxy-coal combustion conditions were conducted on a laminar diffusion flame burner with the coflow temperatures of 1473-1873 K and the oxygen volume fractions of 5%-20%in O_(2)/CO_(2),O_(2)/Ar and O_(2)/N_(2)atmospheres.The flame images of pulverized coal combustion were captured to obtain the ignition delay distances,and the axial species concentrations were measured to obtain the variation of NO formation and reduction.The NO yield in O_(2)/Ar atmosphere decreased by nearly 0.2 when the oxygen volume fraction decreased from 20%to 5%and by about 0.05 when the coflow temperature decreased from 1873 K to 1473 K.The NO yield in O_(2)/CO_(2)atmosphere was 0.1-0.15 lower than that in O_(2)/Ar atmosphere.The optimal kinetic parameters of thermal NO and fuel NO formation rate were obtained by a nonlinear fit of nth-order Arrhenius expression.Finally,the relative contribution rates of thermal NO to total NO(Rth)and NO reduction to fuel NO(Rre)were quantitatively separated.Rth decreases with the increase of oxygen volume fraction,below 6%at 1800 K,25%at 2000 K.Rre is almost unaffected by the coflow temperature and affected by the oxygen volume fraction,reaching 30%at 5%O_(2).

Thermal Analysis and Kinetics of Coal during Oxy-Fuel Combustion

The pyrolysis and oxy-fuel combustion characteristics of Polish bituminous coal were studied us/ng non- isothermal thermogravimetric analysis. Pyrolysis tests showed that the mass loss profiles were almost similar up to 870℃ ha both N2 and CO2 atmospheres, while further mass loss occurred ha CO2 atmosphere at higher temper- atures due to char-CO2 gasification. Replacement of N2 ha the combustion environment by CO2 delayed the com- bustion of bituminous coal. At elevated oxygen levels, TG/DTG profiles shifted through lower temperature zone, ignition and burnout temperatures decreased and mass loss rate significantly increased and complete combustion was achieved at lower temperatures and shorter times. Kinetic analysis for the tested coal was performed using Kissinger-Akahira-Sunose （KAS） method. The activation energies of bituminous coal combustion at the similar oxygen content in oxy-fuel with that of air were higher than that in air atmosphere. The results indicated that, with O2 concentration increasing, the activation energies decreased.

Experimental Study on Oxy-Fuel Combustion and NO Emission in a Spouted-Fluidized Bed with under Bed Feeding

The spouted-fluidized bed is modified from the classical fluidized bed device,which combines the features of spouted and fluidized beds.In the present work,the performance of oxy-fuel spouted-fluidized bed combustion with under bed feeding and its effect on NO emission were systematically investigated.The results revealed that it was feasible to use a spouted-fluidized bed combustor for oxy-fuel combustion with real flue gas recycling.The transition from air combustion to oxy-fuel combustion was smooth and the concentration of CO_(2) in the flue gas could be as high as 90%steadily(dry base).Increasing the reaction temperature exhibited a negative effect on NO emission.Compared with that under the shallow bed,the concentration of NO in the flue gas was lower under the deep bed condition.Besides,the utilization of crush particles was favorable for suppressing NO emission because of the promoted mixing between coal particles and solid bed materials.Furthermore,the addition of limestone was proven to undesirably increase the NO emission during oxy-fuel spouted-fluidized bed combustion.

Integration of LNG Regasification Process in Natural Gas-Fired Power System with Oxy-Fuel Combustion

Oxy-fuel combustion power systems can utilize the cold energy released during the liquefied natural gas(LNG)regasification to reduce the power consumption of CO_(2) capture,but the specific LNG cold energy consumption of CO_(2) capture is still too large.To recover more CO_(2) with the limited LNG cold energy at a low energy cost,a novel natural gas-fired oxy-fuel power system with the cascade utilization of LNG cold energy is proposed in this work,where the LNG cold energy could be sequentially utilized in the air separation unit and the CO_(2) recovery process.The new system is evaluated with the Aspen Plus software.The results show that the net electrical efficiency and the specific primary energy consumption for CO_(2) avoided(SPECCA)of the new system are comparable to those of the chemical looping combustion cycle,and superior to those of the conventional O_(2)/CO_(2) cycles.Moreover,the specific LNG needed for CO_(2) avoided(SLNCC)of the new system is more than 67.2%lower than the existing oxy-fuel power systems utilizing the LNG cold energy.Furthermore,it is found that the O_(2) purity of 97.0 mol.%and the CO_(2) capture ratio of 97.0%are optimal conditions,because the SPECCA,the specific exergy consumption for CO_(2) avoided(SECCA)and the SLNCC are at the minimum of 1.87 GJLHV⋅t_(CO_(2))^(−1),2.60GJ⋅t_(CO_(2))^(−1) and 1.88tLNG⋅t_(CO_(2))^(−1),respectively.Meanwhile,the net electrical efficiency and the exergy efficiency of the new system reach 51.51%and 49.23%,respectively.

Experimental and Modelling Study on Emission of Volatile Nitrogen Derived NO during Pressured Oxy-fuel Combustion under Wet Flue Gas Environment

Pressurised oxy-fuel combustion(POFC)is a clean and efficient combustion technology with great potential.Due to the recycling of flue gas,the concentration of steam in the flue gas is higher than that of conventional combustion,which enriches the free radical pool in the flue gas and thus affects the emission of gaseous pollutants.Therefore,further research into the effect of high steam concentrations on NO_(x)emission mechanisms in POFC is necessary.In this work,a fixed-bed reactor was used to conduct combustion experiments of volatiles and combined with chemical kinetic models to study the NO release characteristics for different pressures and steam concentrations in an O_(2)/CO_(2)atmosphere at 800℃/900℃temperature.The results of the study indicated that the volatile nitrogen comes from the pyrolysis of part of pyrrole,pyridine,and all quaternary nitrogen in coal.The increase in temperature promoted the formation of NO during combustion.Higher pressure affects the main reaction pathway for NO formation,promoting NO consumption by HCCO and C_(2)O groups while enhancing the overall NO reduction.Steam promoted NO consumption by NCO.In addition,steam increased the amount of H/OH groups during the reaction,which affected both NO formation and consumption.However,from the overall effect,the steam still inhibits the emission of NO.

Experimental study on NO_(x)emission characteristics under oxy-fuel combustion

This study focuses on the emission characteristics of NO_(x)under oxy-fuel combustion conditions.A comparative analysis with air combustion was performed.NO_(x)emission,control measures and influence factors under different working conditions were studied.Experiments were carried out on a 3-MWth test platform and a laboratory platform.The‘π’-type furnace was adopted,with the fur-nace width of 2.6 m,depth of 2.0 m and height of 10.5 m for the 3-MWth coal-fired boiler.NO_(x)emissions at different oxygen concen-trations and different air distribution were investigated;the effects of H2O and CO_(2)concentration on denitrification efficiency and SO_(2)/SO_(3)conversion rate were explored.Experiment results suggest that,compared with air combustion,NO concentration(volume basis)at the furnace outlet under oxy-fuel combustion is higher than that of air combustion,but the amount of NO_(x)emissions in the discharged gas significantly decrease compared to the air combustion conditions.In addition,the formation of NO_(x)can be effectively controlled through staged combustion.Furthermore,the selective catalytic reduction(SCR)denitrification efficiency and the con-version rate of SO_(2)to SO_(3)decreases when the CO_(2)concentration and the H2O content increase,indicating that CO_(2)and H2O have an adverse effect on the performance of the catalyst.Additionally,compared with CO_(2)concentration,H2O content has a greater effect on catalyst performance.

Model of limestone calcination / sulfation under oxy-fuel fluidized bed combustion

The characteristics of the simultaneous calcination/ sulfation of limestone under oxy-fuel fluidized bed combustion were studied and compared with those of the sulfation of precalcined CaO. During the calcination stage, SO2 can react with product CaO and slow down the CaCO3 decomposition rate by the covering effect of the CaSO4 product. The sulfation rate of simultaneous calcinatiort/sulfation is slower than that of precalcined CaO, but with a long enough sulfation time, the calcium conversion of simultaneous calcination/sulfation is higher than that of the precalcined CaO. A grain-micrograin model is established to describe the simultaneous calcination, sintering and sulfation of limestone. The graln-micrograln model can reflect the true reaction process of the calcination and sulfation of limestone in oxy-fuel fluidized bed combustion.

Emission characteristics and combustion instabilities in an oxy-fuel swirl-stabilized combustor

This paper presents an experimental study on the emission characteristics and combustion instabilities of oxy-fuel combustions in a swirl-stabilized combustor. Different oxygen concentrations (Xoxy=25%～45%, where Xoxy is oxygen concentra- tion by volume), equivalence ratios (φ=0.75～1.15) and combustion powers (CP=1.08～2.02 kW) were investigated in the oxy-fuel (CH4/CO2/O2) combustions, and reference cases (Xoxy=25%～35%, CH4/N2/O2 flames) were covered. The results show that the oxygen concentration in the oxidant stream significantly affects the combustion delay in the oxy-fuel flames, and the equivalence ratio has a slight effect, whereas the combustion power shows no impact. The temperature levels of the oxy-fuel flames inside the combustion chamber are much higher (up to 38.7%) than those of the reference cases. Carbon monoxide was vastly produced when Xoxy>35% or φ>0.95 in the oxy-fuel flames, while no nitric oxide was found in the exhaust gases because no N2 participates in the combustion process. The combustion instability of the oxy-fuel combustion is very different from those of the reference cases with similar oxygen content. Oxy-fuel combustions excite strong oscillations in all cases studied Xoxy=25%～45%. However, no pressure fluctuations were detected in the reference cases when Xoxy>28.6% accomplished by heavily sooting flames which were not found in the oxy-fuel combustions. Spectrum analysis shows that the frequency of dynamic pressure oscillations exhibits randomness in the range of 50～250 Hz, therefore resulting in a very small resultant amplitude. Temporal oscillations are very strong with amplitudes larger than 200 Pa, even short time fast Fourier transform (FFT) analysis (0.08 s) shows that the pressure amplitude can be larger than 40 Pa.

Unraveling the role of dual Ti/Mg metals on the ignition and combustion behavior of HTPB-boron-based fuel

Metal additives play an essential role in explosive and propellant formulations. Boron(B) is widely used in propellant applications owing to its high energetic content. The addition of B to explosives and propellants increases their energy density, making them more efficient and powerful. Nevertheless, B forms oxide layers on its surface during combustion, slowing down the combustion rate and reducing rocket motor efficiency. To overcome this issue, other metal additives such as aluminum(Al), magnesium(Mg),and titanium(Ti) are revealed to be effective in boosting the combustion rate of propellants. These additives may improve the combustion rate and therefore enhance the rocket motor’s performance. The present study focused on preparing and investigating the ignition and combustion behavior of pure hydroxyl-terminated polybutadiene(HTPB)-B fuel supplemented with nano-titanium and nanomagnesium. The burn rates of HTPB-B fuel samples were evaluated on the opposed flow burner(OFB)under a gaseous oxygen oxidizer, for which the mass flux ranges from 22 kg/(m^(2)·s) to 86 kg/(m^(2)·s). The addition of Ti and Mg exhibited higher regression rates, which were attributed to the improved oxidation reaction of B due to the synergetic metal combustion effect. The possible combustion/oxidation reaction mechanism of B-Mg and B-Ti by heating the fuel samples at 900℃ and 1100℃ was also examined in a Nabertherm burnout furnace under an oxygen atmosphere. The post-combustion products were collected and further subjected to X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM) analyses to inspect the combustion behavior of B-Ti and B-Mg. It has been observed that the B oxide layer at the interface between B-Ti(B-Mg) is removed at lower temperatures, hence facilitating oxygen transfer from the surroundings to the core B. Additionally, Ti and Mg decreased the ignition delay time of B, which improved its combustion performance.

Fabrication and characterization of multi-scale coated boron powders with improved combustion performance:A brief review

Boron has high mass and volume calorific values,but it is difficult to ignite and has low combustion efficiency.This literature review summarizes the strategies that are used to solve the above-mentioned problems,which include coatings of boron by using fluoride compounds,energetic composites,metal fuels,and metal oxides.Coating techniques include recrystallization,dual-solvent,phase transfer,electrospinning,etc.As one of the effective coating agents,the fluorine compounds can react with the oxide shell of boron powder.In comparison,the energetic composites can effectively improve the flame temperature of boron powder and enhance the evaporation efficiency of oxide film as a condensed product.Metals and metal oxides would react with boron powder to form metal borides with a lower ignition point,which could reduce its ignition temperature.

The regulation of ferrocene-based catalysts on heat transfer in highpressure combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum composite propellants

The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors.In this work,the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated,including the burning rate,thermal behavior,the local heat transfer,and temperature profile in the range of 7-28 MPa.The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts(Ce-Fc-MOF),the burning rate inhibitor((Ferrocenylmethyl)trimethylammonium bromide,Fc Br)and the mixture of Fc Br/catocene(GFP).However,the characteristic pressure has increased,and the exponent decreased from 1.14 to 0.66,0.55,and 0.48 when the addition of Ce-FcMOF,Fc Br and Fc Br/GFP in the propellants.In addition,the temperature in the first decomposition stage was increased by 7.50℃ and 11.40℃ for the AP/Fc Br mixture and the AP/Fc Br/GFP mixture,respectively,compared to the pure AP.On the other hand,the temperature in the second decomposition stage decreased by 48.30℃ and 81.70℃ for AP/Fc Br and AP/Fc Br/GFP mixtures,respectively.It was also found that Fc Br might generate ammonia to cover the AP surface.In this case,a reaction between the methyl in Fc Br and perchloric acid caused more ammonia to appear at the AP surface,resulting in the suppression of ammonia desorption.In addition,the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added.In the process,the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF.The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure,rather than 3.6 times of the difference in the blank propellant.Overall,the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.