Isothermal Combustion Research Articles

Investigation of Combustion and NO/SO2 Emission Characteristics during the Co-Combustion Process of Torrefied Biomass and Lignite.

This paper investigates the combustion characteristics and pollutant emission patterns of the mixed combustion of lignite (L) and torrefied pine wood (TPW) under different blending ratios. Isothermal combustion experiments were conducted in a fixed bed reaction system at 800 °C, and pollutant emission concentrations were measured using a flue gas analyzer. Using scanning electron microscopy (SEM) and BET (nitrogen adsorption) experiments, it was found that torrefied pine wood (TPW) has a larger specific surface area and a more developed pore structure, which can facilitate more complete combustion of the sample. The results of the non-isothermal thermogravimetric analysis show that with the TPW blending ratio increase, the entire combustion process advances, and the ignition temperature, maximum peak temperature, and burnout temperature all show a decreasing trend. The kinetic equations of the combustion reaction process of mixed gas were calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic equations. The results show that the blending of TPW reduces the activation energy of the combustion reaction of the mixed fuel. When the TPW blending ratio is 80%, the activation energy values of the mixed fuel are the lowest at 111.32 kJ/mol and 104.87 kJ/mol. The abundant alkali metal ions and porous structure in TPW reduce the conversion rates of N and S elements in the fuel to NO and SO2, thus reducing the pollutant emissions from the mixed fuel.

Effect of NaCl on the migration of heavy metals during the non-isothermal and isothermal combustion of sludge: Static and dynamic analyses

Chlorine has been proven to promote the volatilization of heavy metals during sludge combustion. This work compared the migration of heavy metals with NaCl addition under different combustion modes at 900 ℃. The combustion modes have less effect on the mineral phase of residues, but the volatilization and toxicity reduction of heavy metals were more pronounced under isothermal combustion. The mineral evolution, release of Cl, and migration of metals were dynamically tracked by the continuous sampling at different combustion time under isothermal combustion. It was found that the volatile matter and fixed carbon burned almost simultaneously, and the addition of NaCl promoted them. As combustion proceeded, the minerals gradually crystallized and the heavy metals were volatilized due to the direct and indirect chlorination. Meanwhile, the chlorination and volatilization of Zn was less than that of Pb due to its effective solidification by minerals. The combination of the adsorption by exposed char and solidification by sludge minerals influenced the dynamic leaching behavior of metals. These results will help understand the interactions between heavy metals, inorganic Cl, and Fe-Si-Al minerals during combustion, which will further help optimize the combustion strategy for both stabilization or enrichment of heavy metals when inorganic chlorine exists.

In-situ torrefaction-densification approach for pelletizing of rice hull/rice stalk and the combustion behavior analysis

The utilization of biomass resources could optimize the energy consumption structure and achieve the goal of carbon neutrality. Torrefaction and densification pretreatment could improve the defects of high oxygen content, low energy density, and low bulk density of biomass. In this work, high-density and hardness pellets were prepared by torrefaction coupling densification (in-situ torrefaction-densification without binders). In-situ torrefaction-densification significantly reduced the pressure required for the densification process. In-situ torrefaction-densification lowered the pressure required to prepare RH pellets with a bulk density of 1000 kg/m3 from 88.23 MPa to 30.95 MPa. The effects of the in-situ torrefaction-densification method and pelletizing pressure on the pellet combustion process were investigated by non-isothermal and isothermal combustion. The volatile and carbon of TCDP could be burned intensively during combustion, and the emissions of CO and CxHy were reduced during combustion. The original structural strength of TCDP was still maintained in the combustion process. The alkali metal K in TCDP was difficult to escape, effectively reducing the emission of K in the flue gas. In-situ torrefaction-densification could not only improve the quality of biomass solid fuel but also facilitate the storage and transportation of biomass solid fuel.

Comparison of isothermal and nonisothermal combustion methods when evaluating semicoke for pulverized coal injection of blast furnace

AbstractUsing semicoke instead of anthracite for pulverized coal injection (PCI) in a blast furnace can greatly reduce the cost of iron making, but the combustion performance of semicoke first needs to be accurately predicted. In this study, the combustion performances of different fuels were compared and analyzed in a drop tube furnace (DTF) and under isothermal and nonisothermal conditions. The results showed that semicoke had a better combustion performance than coal in the DTF. Isothermal combustion provided a more consistent performance evaluation of the fuels because the effect of volatiles was eliminated. Nonisothermal combustion significantly differed from the DTF results because of the influence of volatiles; after the fuels received high‐temperature treatment for devolatilization, the combustion performance was consistent with the DTF results. The influencing factors for the fuel combustion performance differed according to the combustion conditions. For the DTF, the burnout rate was correlated with the pore structure and microcrystalline structure, especially the latter. For isothermal combustion, the combustion characteristic parameter and microcrystalline structure d002 and Lc after high‐temperature treatment were strongly correlated. For nonisothermal combustion, the combustion characteristic parameters were strongly correlated with the volatile content. The above results can serve as a reference for evaluating the combustion performance of different fuels in a blast furnace using PCI.

Application of experiments and density function theory on the formation mechanism of NH3 during O2/Ar and O2/H2O combustion process of demineralized coals

Understanding the formation mechanism of NH3 during the pulverized coal combustion process is a feasible approach to reducing NOx emissions. In this study, the emission characteristics of NH3 during the O2/Ar and O2/H2O combustion processes were investigated by the isothermal combustion experiments and the Density Functional Theory (DFT) method. The experimental results demonstrated that H2O accelerated the conversion of HCN to NH3, and the positive effects of H2O were applied to all kinds of coal-based fuels. The DFT calculations deeply revealed the formation mechanism of NH3 through the homogeneous conversion of HCN and the heterogeneous hydrogenation of coal-N. The hydrogenation of coal-N is the primary source of NH3 emissions during O2/Ar combustion. During O2/H2O combustion process, the heterogeneous generation of NH3 was modified by the synergetic effects of O2 and H2O, and the additional H2O strengthened the proportion of the homogeneous reaction. The homogeneous conversion of HCN was the main NH3 formation pathway. This study is prone to coupling the experiments and quantum chemistry to deeply reveal the formation mechanisms of NH3 during O2/Ar and O2/H2O combustion processes, providing a relatively complete pathway for the emissions of NH3.

QUANTITATIVE APPROACH OF CARBONATES, CALCITE AND DOLOMITE FROM THE TARFAYA, Z3 AND Z4 OIL SHALE LAYERS BY ACID ATTACK (MOROCCO)

The carbonates of the oil shale calcite CaCO3 and dolomite CaMg(CO3)2 were the object of this study to determine their percentage inside the oil shales. Work has been carried out in the same context (A.Attaoui and H.Mokhlis:2022) for the Tarfaya shale layers Z0, Z1 and Z2. However, the Z3 and Z4 layers present a migration of matter: the light organic matter is found in the Z3 layer and the heavy one is present in the Z4 layer, and the heavy organic matter consumes more acid in the attack reaction than the light organic matter for the same mass, which is why it is necessary to follow the decomposition of this organic matter isothermally, especially at 500°C. Therefore, by combining the two reactions and by choosing well-defined isotherms (500°C, 600°C, 700°C and 800°C) we were able to approach the percentages of calcite and dolomite in these particular layers showing the phenomenon of in situ pyrolysis. The techniques used are isothermal combustion followed by HCl acid attacks and return dosing of the acid remaining after the attack. The objective of this study, which is done in return dosing using the Tacussel pH meter, is to establish a table of compositions in mass percentages of calcite and dolomite, which are the constituents of the carbonate of the Tarfaya oil shale (Morocco). Calcite CaCO3 is taken as a control; it was used under the same conditions as the oil shale, i.e. combustion in an isothermal regime, followed by acid attack.

Simulation of Prosopis juliflora Air Gasification in Multistage Fluidized Process

A multistage atmospheric fluidized bed gasifier was developed using the Aspen Plus simulation process. The innovative gasification reactor aims to yield a high-quality product gas as it conducts pyrolysis, combustion, and reduction in different zones. In addition, it uses gas as a heat carrier and has a fluidized char bed in the reduction zone to enhance the in-situ tar reduction. In order to study the feasibility of the gasifier, an evaluation of the product gas and the process efficiency is required. The proposed model was based on the reaction rates and hydrodynamic parameters of the bubbling bed. Four different stages were initially considered in the simulation process: decomposition of the feed, partial volatile combustion, char reduction, and gas solid separation. The gasification reactor was operated over a temperature range of 800–1000 °C and an isothermal combustion reactor was operated at 1000 °C. In addition, the air to biomass mass ratio was varied from 0.2 to 0.5. It has been validated and displayed very good agreement with published data. Effects of gasification reactor temperature, air to biomass ratio, and gasifier dimensions on the composition of product gas were investigated Results showed that the principal component is CO and its concentration in the product gas increases with increase in gasifier temperature but decreases with increasing air to biomass ratio. The results also gave a relatively high value of the lowered gas caloric value and acceptable cold gas efficiency which help the sizing of gasifiers and the choice of optimal operating conditions.

Combustion of nickel hyperaccumulator plants investigated by experimental and thermodynamic approaches

This work was undertaken to determine whether thermodynamic calculations can predict the amount and composition of ash produced by combustion of nickel hyperaccumulator (HA) plants in the context of agromining. To this end, three HA plants containing about 1wt% of nickel were submitted to isothermal combustion at 550, 815, 900°C and the solid residues were characterized by complementary techniques (TGA, XRD, ICP-OES, ion chromatography, SEM-EDX), while thermodynamic calculations were performed with the FactSage software using the dry biomass composition as input. We present an in-depth evaluation of inorganics behavior based on the combination and comparison of experimental data and calculations: effect of temperature on ash yield, nature of crystallized phases, ash elemental composition and inorganics volatilization. Our work confirms that equilibrium calculation is a powerful method to evaluate the behavior of inorganic elements during thermal treatment of biomass, despite some lacks in the databases. For the nickel HA plants, an innovative result is that, after combustion, nickel is always in the form of NiO particles, that can mix with MgO to form (Ni,Mg)O solid solutions. These results have direct implications for understanding the combustion process and for better design of the following leaching step aiming at Ni recovery.

Investigation of combustion reactivity and NO emission characteristics of chars obtained from the devolatilization of raw and partially dried lignite

AbstractIn an attempt to achieve the clean and efficient utilization of lignite, drying pre‐treatment was performed in this study before lignite combustion. The combustion reactivity and NO emission characteristics of the partially dried lignite samples in the char combustion stage were investigated by means of TG and isothermal combustion tests, and the reactivity could be summarized as the following order: L1>L0.5>raw>L3>LT>L5 (chars obtained from the devolatilization of the raw and partially dried coals at 378 K for 0.5, 1, 3, 5, and 120 minutes) and the NO conversion ratio of L1 was the lowest. When the moisture content in the coal particles was relatively high (19.68%‐35.84%), the drying treatment could increase the combustion reactivity and inhibit NO emission in the char combustion stage; When the moisture content was within a relatively low range (0.17%‐19.68%), the moisture removal had negative effects on the reactivity and NO emission in the char combustion stage. The surface behaviour and microstructure of the raw coal char and chars derived from the partially dried coals were clarified by temperature programmed desorption/reduction (TPD/TPR) and Raman spectroscopy. The results illustrated that L1 derived from Lc1 (19.68%) was the most reactive sample with the largest amount of C(O) on the particle surface. There were also more reactive aromatic structures in L1 than other samples. Compared with direct combustion or excessive drying treatment, lignite should be dried to a certain degree (19.68%) for optimized lignite combustion.

Structure and Reactivity of Low-Rank Coal Chars Prepared from Fluidized Bed and Moving Bed Pyrolyzers and the Potential for Using Them in Pulverized Coal Injection (PCI)

Utilizing pyrolysis chars as the injection fuel in a blast furnace can reduce the dependence on high-quality pulverized coal injection (PCI) coal. In this study, the physical properties and reaction characteristics of chars prepared from two different industrial-scale pyrolyzers (fluidized bed and moving bed) are investigated. The results reveal remarkable component segregation in the char particles with different particle sizes. The properties of large-size char particles are found to better satisfy the PCI fuel requirement in a blast furnace. Compared with PCI coal, the char particles exhibit a rough surface, well-developed pore structure, and less-ordered chemical structure of carbon. Results from isothermal combustion, isothermal gasification, and drop tube furnace experiments show that both types of chars exhibit a better reactivity than PCI coal. The excellent reactivity of chars is closely related to its high Brunauer–Emmett–Teller surface area and relatively poor chemical ordering during conversion. Based on these characteristics, both fluidized bed char (FBC) and moving bed char (MBC) have a great potential to be used as PCI fuels. The application method of chars for PCI in a blast furnace is proposed finally.

Effects of Reaction Condition on the Emission Characteristics of Fuel-N during the O2/H2O Combustion Process of Demineralized Coal

This research investigated the emission and evolution characteristics of fuel-N during the O2/H2O combustion process of a typical bituminous coal (Shenhua). To avoid the catalytic interference of alkali metal salts, the demineralized coal obtained from the raw coal sample was employed for the investigation in this research. The effects of reaction temperature (Tr) and H2O concentration, which were two vital factors affecting coal combustion characteristics, on the emission characteristics of fuel-N during the combustion process were also taken into consideration. Isothermal combustion tests performed under different O2/H2O conditions (Tr: 1073 and 1473 K; O2: 30%; H2O: 0, 3.5, 8.5, 15, 20, and 30 vol %) indicated that relatively high concentrations of N2O, HCN, and NH3 were measured in the O2/H2O combustion of the coal sample. With the increase of Tr and H2O concentration, more fuel-N would be released in the devolatilization/volatile oxidation stage of the reaction. The X-ray photoelectron spectroscopy r...

Effects of reaction condition on NO emission characteristic, surface behavior and microstructure of demineralized char during O2/H2O combustion process

Surface behavior and structural characteristics of char particles generally play a vital role in affecting char NO emission characteristics during combustion process. A typical bituminous Shenhua from northwest China was employed for demineralization in this research. The demineralized coal without catalytic interference of alkali metal salts was employed as the experimental sample. Moreover, by means of the utilization of isothermal combustion test, Temperature Programmed Desorption (TPD) and Raman spectrometer, the conversion ratio of nitrogen content in char to NO, as well as the evolution of char surface behavior and micro-structure in the process of O2/H2O combustion under different conditions were determined. With the increase of reaction temperature (Tr) and O2 concentration, more surface active sites (Cf), oxygen containing functional groups (C(O)) and small aromatic ring structures generated on char particle surface inhibiting the emission of NO during O2/H2O combustion process. Under identical reaction conditions (Tr, O2 and H2O concentration), the partially oxidized chars with moderate burnout degree (Xc ≈ 0.3) had the largest amount of Cf on particle surface. On the other hand, the amount of Cf and small aromatic ring structures first increased and then decreased as the H2O concentration enhanced. When the Cf amount and the value of I(Gr+VL+Vr)/ID reached the maximum at the H2O concentration of approximately 8.5 vol%, the conversion ratio of char-N to NO reached the minimum value. Meanwhile, the increase of H2O concentration initially accelerated the NO reduction rate and this positive effects gradually diminished when the H2O concentration exceeded the critical value (8.5 vol%). Thus, the optimal combustion condition for char combustion with the lowest NO conversion ratio in this study was: 1473 K, 30% O2 and 8.5 vol% H2O.

Study of co-combustion of dried sewage sludge with coke: Thermogravimetric assessment and gaseous emissions

Co-combustion of urban dried sewage sludge (DSS) and coke in existing infrastructures is potentially an energy efficient sustainable management option. The main objective of the present study was to examine the amount of energy release and the resulting pollutant emissions from co-combustion of coke in the presence of DSS as a cheap and accessible matter, for the first time. To investigate the effects of combustion temperature on gases emissions, the isothermal combustion of five blend samples was carried out in a lab-scale electrically heated tube furnace connected to a gas sensor setup. The combustion of blend samples was characterized in terms of their proximate and ultimate analyses and calorific values. Also, the heating values and thermal characteristics of the samples were analyzed and compared with the results from thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Measurement results showed that a 1-to-4 DSS-coke ratio was optimal because of its similar characteristic and pollution emissions with coke. Therefore, such a blend can be used instead of pure coke in smelting iron ore in a blast furnace. Furthermore, according to the results of the DSC analysis, this sample has a positive effect on the heat value of coke and the amount of released energy was increased by about 40%.

Isothermal combustion characteristics of anthracite and spent coffee grounds briquettes

The isothermal combustion characteristics of anthracite and spent coffee grounds briquettes in a bench-scale fixed-bed furnace were examined by using a macro-thermogravimetric analysis approach between 873 and 1173 K. The combustion performances in terms of the conversion rates, flame evolution, pollutant emissions, ash compositions and ash fusion temperatures of two anthracite/spent coffee grounds blend briquettes with blending ratios of 40% and 60% were also compared with those of their individuals. There was only an obvious peak in DTG profile for every sample at each temperature. At 973 K, the average burning rate of the spent coffee grounds was about 8 times higher than that of the anthracite. The average burning rate of 60% anthracite/40% spent coffee grounds blend at 1173 K increased by about 3 times in comparison with that at 873 K. NO2 emissions for the four samples were much less than other gaseous emissions. The four ash fusion temperatures for the anthracite were higher than 1791 K. The deformation temperature, softening temperature, hemispherical temperature and flow temperature for the spent coffee grounds were 1526, 1626, 1687 and 1791 K. The ash fusion characteristics of the spent coffee grounds were improved by blending the anthracite.

Experimental study of low-temperature combustion characteristics of shale rocks

Relatively low temperature (500 °C) combustion has been applied to shale rocks collected from Lianmuqing, Xinjiang Province, China, to improve the permeability of shale without pore structure change caused by mineral decomposition. The shale rocks were firstly grinded into small particles, then burned in a furnace at a constant temperature of 500 °C for 5 min, 15 min, and 30 min, respectively. A cylindrical shale sample was also subjected to the combustion experiment. It was found that thermal cracking occurred along the height of the shale as combustion propagated from bottom to top. From the low-temperature nitrogen adsorption test, it was found that the pore diameters of shale samples were in the range of 2–50 nm, which were less than the mean free path of an oxygen molecule. Thus, the diffusion of gas inside the shale was Knudsen diffusion and the Knudsen number (Kn) was between 8 and 25. Moreover, the mean diameter of shale pores and the effective diffusion coefficient increased with increasing oxidization time. Whereas the surface area decreased after combustion, the diameter of the shale particles remained constant. So the density of the shale decreased with increase of combustion time. According to the porous media combustion model, the oxidization of shale particles was considered to be in Regime I, which is under kinetic control at isothermal combustion condition (500 °C). Furthermore, the effective diffusion coefficient was in a range of 3 × 10−6–6 × 10−6 m2/s. It increased with increasing combustion duration, especially during the first five minutes. The experiment results showed that low temperature combustion can effectively improve shale permeability to facilitate gas extraction from shale reservoir.

Effect of microwave pretreatment on the combustion behavior of lignite/solid waste briquettes

Lignite is one of common applied fossil fuels worldwide, and solid wastes like biomass as well as sewage sludge are promising alternatives of fossil fuels. The isothermal combustion performances of lignite/solid wastes (eucalyptus bark and sewage sludge) briquettes between 500 °C and 800 °C in a bench-scale fixed bed furnace were examined based on a macro-thermogravimetric analysis approach. Compared with untreated samples, the average combustion rates of lignite and sewage sludge with the microwave treatment decreased, while those for treated eucalyptus bark increased. The drying, devolatilization and char combustion processes overlapped in the isothermal combustion for all samples. The treated lignite had a high aromatic hydrocarbon, while both the treated sewage sludge and eucalyptus bark had high hydroxyl and methyl group (CH3). After the microwave pretreatment, the fuel rank of lignite was prompted, while that for eucalyptus bark and sewage sludge degraded. Through the microwave pretreatment, the activation energies of lignite, sewage sludge, and eucalyptus bark grew from 15.45 to 21.20 kJ mol−1, 18.23–20.77 kJ mol−1, and 13.27–14.22 kJ mol−1. The study can provide some basic data for the energy utilization of lignite and solid wastes.

Combustion characteristics of biodried sewage sludge

In this study, effects of biodrying on the characteristics of sewage sludge and the subsequent combustion behavior were investigated. 7-Day of biodrying removed 49.78% of water and 23.17% of VS initially contained in the sewage sludge and increased lower heating value (LHV) by 37.87%. Meanwhile, mass contents of C and N decreased from 36.25% and 6.12% to 32.06% and 4.82%, respectively. Surface of the biodried sewage sludge (BDSS) appeared granulated and multi-porous, which was thought to facilitate air transfer during combustion. According to thermogravimetric (TG) analysis coupled with mass spectrometer (MS) with a heating rate of 10 °C/min from 35 °C to 1000 °C, thermally-dried sewage sludge (TDSS) and BDSS lost 74.39% and 67.04% of the initial mass, respectively. In addition, combustibility index (S) of BDSS (8.67 × 10−8 min−2 K−3) was higher than TDSS. TG-MS analyses also showed that less nitrogenous gases were generated from BDSS than TDSS. It was again showed that the average CO and NO concentrations in exit gas from isothermal combustion of BDSS were lower than those from TDSS, especially at low temperatures (≤800 °C). Based on these results, it was concluded that biodrying of sewage sludge was an energy-efficient water-removal method with less emission of air pollutants when BDSS was combusted.

Simultaneous volatilization characteristics of arsenic and sulfur during isothermal coal combustion

Six coals that with different rank and sulfur contents were chosen for the isothermal combustion experiments at 900°C and 1300°C. By changing the residence time, the volatilization ratio and rate of arsenic with time were obtained. Effects of residence time, temperature, coal type and sulfur content on arsenic volatilization characteristics were discussed. The emission concentration of SO2 was also obtained through online monitoring by flue gas analyzer. Furthermore, the curves of arsenic volatilization, SO2 emission and mass loss of coal were compared together to study the simultaneous volatilization characteristics of arsenic and sulfur. Results show that coals with higher sulfur content tend to have a larger proportion of sulfide bound arsenic, which could have a positive effect on arsenic volatilization. With the increase of residence time, the volatilization ratio of arsenic increases gradually with various volatilization rate. One volatilization peak of arsenic is observed for all the coals. The volatilization peak of arsenic moves forward with higher temperature and lower coal rank. The peak rate of arsenic increases with higher temperature while varies much in different coals. At 900°C, coals with lower coal rank tend to have a higher peak rate of arsenic, while at 1300°C, coals with larger proportion of sulfide bound arsenic tend to have a higher peak rate of arsenic. As for SO2, all the coals have one emission peak at 900°C while two emission peaks at 1300°C, which is similar to the mass loss characteristics of coals. The simultaneous releasing behavior of arsenic and sulfur is observed at 900°C due to the moderate mass loss of coal and at 1300°C due to the decomposition of As-bearing sulfides.

Pyrolysis of biomass in a batch fluidized bed reactor: Effect of the pyrolysis conditions and the nature of the biomass on the physicochemical properties and the reactivity of char

This work was carried out in order to understand the effect of the pyrolysis operating conditions and the nature of the biomass on the physicochemical properties of the char and its reactivity toward the combustion. The chars were obtained by fast pyrolysis of two types of cylindrical wood particle (beech stick: diameter of 6mm, length of 10mm and beech bark pellet: diameter of 10mm, length of 15mm) under an inert atmosphere of nitrogen in a fluidized bed reactor for three different temperatures (450, 650 and 850°C) and at atmospheric pressure. The ultimate and FTIR analyses revealed that an increase in the pyrolysis temperature led to a raise of the carbon content and a decrease in the oxygen and hydrogen content. At high pyrolysis temperatures, Raman spectroscopy and XRD analyses showed that the char is more and more aromatic with a large size of the aromatic rings. The different chars prepared at a pyrolysis temperature of 850°C exhibited a true density close to the one of graphite. The reactivity of chars was studied by isothermal combustion at 400°C in TGA. The reactivity was found to be highly dependent on the pyrolysis temperature and the nature of the biomass. An increase in the pyrolysis temperature led to a decrease of the reactivity. Besides, char from fast pyrolysis of beech bark pellet is more reactive than char from fast pyrolysis of beech stick.

Removal of NOx and soot over Ce/Zr/K/Me (Me = Fe, Pt, Ru, Au) oxide catalysts

The potentiality of ceria/zirconia based catalysts in the simultaneous removal of particulate matter (soot) and NOx is investigated in this work, and compared with that of a model LNT Pt-K/Al2O3 sample. Ceria-zirconia (molar ratio 75/25) catalysts doped with Pt, Au, Ru or Fe (2% by weight) and containing K (7% by weight) were prepared by a modified citrate method and characterized by X-ray diffraction, surface area and pore volume measurements. The behavior of the catalysts in the soot combustion and NOx removal was separately analyzed by means of temperature programmed oxidation (TPO), isothermal combustion and isothermal NOx adsorption experiments. The results showed that all the ceria/zirconia based catalysts are more active than Pt-K/Al2O3 in soot combustion; the Ru-containing system also showed NOx storage performances comparable to Pt-K/Al2O3. Accordingly the capability of the Ru-based catalyst to accomplish the removal of NOx in the absence and in the presence of soot was further investigated by reactivity experiments and FT-IR spectroscopy to analyze both the gas phase and the catalyst surface species. The data indicate that the Ru-based system is able to simultaneously remove soot and adsorb NOx pointing out higher performances in the soot combustion as compared to the Pt-K/Al2O3 catalyst, and similar behavior in the NOx storage capacity. However the NOx reduction activity results lower than the traditional LNT Pt-based catalyst. Conversely, when the Ru-based catalyst is mixed with the LNT sample (physical mixture) a NOx reduction efficiency similar to Pt-K/Al2O3 is found.