Devolatilization Stage Research Articles

Influence of the fertilizer type in the agronomic and energetic behaviour of the residues coming from oleander, cypress and quinoa

The use of biomass as an alternative energy source is a fact. Apart from the traditional ones, this work aims to carry out an energy and agronomic analysis of three new crops: oleander, cypress and quinoa. In the same sense, fertilizers of different nature (organic and inorganic) were applied to determine the influence on agronomic and thermal behaviour. TGA and characteristic indexes were employed for an oxidative atmosphere. All the crops here analysed had acceptable value as fuels. Organic fertilizer consisting of cow manure was the one that further increased the height and diameter of the plants. Likewise, oleander was the species with better fuel potential together with the lowest gases emission. Devolatilization and ignition weight loss stages were identified in DTG profiles being quinoa stems the raw material with higher DTGmax values (>7%/min). As kinetics concerned, fertilizer application decreased the activation energy values for almost all cases.

(Co-)pyrolytic performances and by-products of textile dyeing sludge and spent mushroom substrate

The (co-)pyrolysis of textile dyeing sludge and spent mushroom substrate was conducted to characterize their thermal behaviors and by-products. The devolatilization of textile dyeing sludge mainly occurred between 150 and 500 °C, while the decomposition of inorganic matter as well as the secondary cracking of coke and tar happened between 500 and 1000 °C. The addition of spent mushroom substrate increased the release rate at the devolatilization stage of textile dyeing sludge and their blends due to its higher volatiles content. The enhanced co-pyrolysis performance occurred mainly at the high temperature. The melting of inorganic matter was enhanced with the temperature rise but weakened with the addition of spent mushroom substrate. Sulfur mainly existed as sulfate in textile dyeing sludge and as organic sulfur in spent mushroom substrate. With the temperature rise, nitrogen-containing compounds formed more stable compounds. Spent mushroom substrate promoted the formation of nitrogen oxides by converting nitrogen to an inactive form. Sulfates were decomposed at high temperatures partially turning into sulfide. 30% spent mushroom substrate increased the relative sulfate content at 800 °C and fixed sulfur into inorganic compounds. The relative contents of aromatics, and nitrogen-containing compounds rose in the bio-oils, whereas alkanes fell with the elevated temperature. Spent mushroom substrate enhanced the formation of aromatics and reduced the yields of nitrogen-containing compounds, and acidic volatiles. The co-pyrolysis appeared to improve the bio-oil quality and the pyrolytic performance of textile dyeing sludge.

Determination of pyrolysis characteristics and thermo-kinetics to assess the bioenergy potential of Phragmites communis

This study systematically investigated the bioenergy potential of Phragmites communis, a large perennial grass found in wetlands. The biofuel physicochemical characteristics of Phragmites were determined and a pyrolysis kinetic study and thermal behaviour analysis were performed. Thermal degradation was investigated by exposing dried and powdered biomass to different heating rates (10, 20, 30, and 40 ℃/min) using TG-FTIR-GC/MS. The pyrolysis process of Phragmites communis occurred in three stages, with maximum mass loss (59.32%) during the main stage of devolatilization in the range of 150–500 ℃. The iso-conversional models of Flynn-Wall-Ozawa method was applied to explain the reaction chemistry, with good statistical confidence (R2 ≥ 0.9). The kinetic reaction mechanism of the three sub-stages predicted by the master-plots is f(α) = 3α2/3; f(α) = 3α3/4; and f(α) = 2 (1 − α)2, respectively. The coupled TG-FTIR-GC/MS analyses allowed identification of the volatile species as the major pyrolytic products, including acids, ketones, furan, phenols, benzene, furan, and alkane. Based on the thermodynamic parameters of Phragmites communis, this material is a promising feedstock for bioenergy production, and this study provides theoretical and practical guidance for effective energy and resource utilization.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass 2. Predicting total yields for torrefied woods

Apparently, no detailed reaction mechanisms for any torrefied biomass have yet been put forward. This study expands bio-FLASHCHAIN® to accurately predict the total volatiles yields from any torrefied wood. Whereas the original reaction mechanism and depolymerization kinetics are retained, the analysis introduces a fuel constitution submodel that uses the carbon aromaticity added during torrefaction to estimate the changes in torrefied woods that are responsible for the impacts on primary devolatilization behavior. Torrefaction replaces bridges with char links within wood macromolecules of both cellulose and lignin and these added char links are entirely responsible for the reductions in volatiles yields. The added char links are estimated without any adjustable parameters, given only an ultimate analysis for the torrefied wood. The primary devolatilization of torrefied woods abides by the same reaction kinetics as the parent raw woods, except that the energy distribution for bridge scission narrows for progressively more severe torrefaction conditions to coarsely represent the elimination of the most reactive components during torrefaction. The predictions are validated with volatiles yields from 13 woods and 22 torrefied woods for heating rates from several hundred to more than 104 °C/s to temperatures from 500 to 1000 °C with contact times from tens of milliseconds through several minutes. According to this interpretation, the most important chemistry to unravel in raw and torrefied woods is the accumulation of furans and benzenoid and condensed aromatics in cellulose throughout all stages of both torrefaction and primary devolatilization.

Experimental study of potassium release during biomass-pellet combustion and its interaction with inhibitive additives

In the present study, two types of biomass were investigated as typical agricultural and woody biomass fuel, i.e., corn straw and poplar. Firstly, laser induced breakdown spectroscopy (LIBS) was employed to investigate the release characteristics of potassium (K) from a burning biomass pellet. In order to further investigate the correlation between K release and the combustion process, combustion parameters including pellet surface temperature and pellet diameter were simultaneously measured with LIBS. A dual-peak trend is observed in the K release history of poplar, but only a single peak is found in that of corn straw. Both biomass samples show the strongest K release during the devolatilization stage in comparison with the subsequent char burnout and ash cooking stages. Similar tendencies are observed between K release and pellet temperature, which suggests that K release is closely related to the combustion process. The K release mechanism can be attributed to temperature rise and therefore breakdown of chemical bonds during combustion. Then the release of different chemical forms of K was investigated by chemical fractionation treatment of the biomass samples. The released amount of H2O-soluble, NH4Ac-soluble and HCl-soluble potassium compounds were obtained. The H2O-soluble potassium is found to be the major released potassium compound. Finally, four kinds of additives (two pure additives, i.e., silica and alumina, and two typical natural mineral additives, i.e., kaolin and mica) were added to the biomass samples to investigate their inhibition effects on K release. The natural sorbent additives show better inhibition effects than the pure ones.

Assessment of biomass energy potential for SRC willow woodchips in a pilot scale bubbling fluidized bed gasifier

The current study investigates the short rotation coppice (SRC) gasification in a bubbling fluidized bed gasifier (BFBG) with air as gasifying medium. The thermochemical processes during combustion were studied to get better control over the air gasification and to improve its effectiveness. The combustion process of SRC was studied by different thermo-analytical techniques. The thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) were performed to examine the thermal degradation and heat flow rates. The product gas composition (CO, CO2, CH4 and H2) produced during gasification was analyzed systematically by using an online gas analyzer and an offline GC analyzer. The influence of different equivalence ratios on product gas composition and temperature profile was investigated during SRC gasification. TG/DTG results showed degradation occur in four stages; drying, devolatilization, char combustion and ash formation. Maximum mass loss ~70% was observed in devolatilization stage and two sharp peaks at 315–500 °C in TG/DSC curves indicate the exothermic reactions. The temperature of gasifier was increased in the range of 650–850 °C along with the height of the reactor with increasing equivalent ratio (ER) from 0.25 to 0.32. The experimental results showed that with an increment in ER from 0.25 to 0.32, the average gas composition of H2, CO, CH4 decreased in the range of 9–6%, 16–12%, 4–3% and CO2 concentration increased from 17 to 19% respectively. The gasifier performance parameters showed a maximum high heating value (HHV) of 4.70 MJ/m3, Low heating value (LHV) of 4.37 MJ/m3 and cold gas efficiency (CGE) of 49.63% at 0.25 ER. The ER displayed direct effect on carbon conversion efficiency (CCE) of 95.76% at 0.32 ER and tar yield reduced from 16.78 to 7.24 g/m3 with increasing ER from 0.25 to 0.32. All parametric results confirmed the reliability of the gasification process and showed a positive impact of ER on CCE and tar yield.

Non-isothermal kinetic analysis of the combustion of argan shell biomass

Abstract Argan shell is one of the main by-products during argan oil production. It is considered as an attractive, cheap and renewable biomass source for sustainable energy utilization. The present paper reports on combustion characteristics of argan shell in order to evaluate their potential for thermochemical conversion. Combustion studies using thermogravimetry (TG) are performed at four different heating rates of 5, 10, 15 and 20 °C·min−1. Kinetic parameters under non-isothermal condition are calculated using FWO (Flynn-Wall-Ozawa method) and KAS (Kissinger-Akahira-Sunose) model free methods. From the results obtained, it was revealed that when the conversion level (α) fluctuates between 0.1 and 0.55, the average activation energy were 154 and 145 KJ/mol for FWO and KAS methods, respectively. Then, it decreases drastically with α ≥ 0.6, reflecting the kinetic complexity of the combustion process characterized by a faster reaction caused by the intense devolatilization stage. Overall, the results highlight the potential use of argan shell as a biomass product for thermal conversion through combustion.

Evaluation of thermal decomposition characteristics and kinetic parameters of melina wood

The evaluation of thermal decomposition characteristics and kinetic parameters of melina wood were investigated. Proximate, ultimate and calorific value analyses of the melina wood were carried out based on standards. Melina wood was subjected to multiple heating rates (5–15 °C/min) in thermogravimetric experiment. Two prominent isoconversional methods (Flynn-Wall-Ozawa and Starink) were adopted to obtain kinetic parameters from the non-isothermal thermogravimetric analysis curves. The ash, volatile matter and carbon contents of the melina were 2.15, 81.42 and 47.05%, respectively, while the calorific value was 18.72 MJ/kg. The main devolatilization stage of melina ranged from 220 °C to 350 °C while 80% weight loss was obtained below 400 °C. The activation energy varied between approximately 15 and 162 kJ/mol as a function of degree of conversion. The pre-exponential factors varied between 1.60E + 2 and 5.67 E + 12/min. The decomposition kinetic mechanism of melina is concluded to be a multi-step reaction.

Energy recovery from high-ash municipal sewage sludge by hydrothermal carbonization: Fuel characteristics of biosolid products

Hydrothermal carbonization (HTC) is a promising approach for the fuel upgrading of moist biomass wastes. However, its effects on high-ash municipal sewage sludge (HA-MSS), which is produced largely in China, are unclear. In this study, HA-MSS was treated at various temperatures from 170 °C to 350 °C. The fuel characteristics of hydrochar products, namely, chemical compositions; heat value; water-holding capacity; mineral components; and chemical bonding forms of carbon, nitrogen, and sulfur, were comprehensively discussed. Low-temperature HTC below 260 °C decreased the amounts but only slightly changed the species of mineral components in HA-MSS. However, temperatures exceeding 290 °C removed some alkali and alkaline earth minerals completely and formed a new species, namely, anorthite (CaAl2Si2O8). In terms of fuel characteristics, 230 °C was determined to be the optimal temperature for the HTC of HA-MSS. At this temperature, the HA-MSS was upgraded to a hydrochar with a large higher heating value and good dewaterability. When the hydrochars were combusted, SO2 and NOx were mainly released during the devolatilization stage of fragile volatiles. With the increase in HTC temperature, the releasing peak of SO2 decreased. However, for hydrochars obtained at HTC temperatures lower than 260 °C, the releasing peaks of NOx showed only a small difference.

Effect of carbonization temperature on the grindability of carbonaceous material produced from different coals

Carbonization experiments were conducted on four kinds of sub‐bituminous coal particles at a temperature range of 450–1200 °C. The effect of treating temperature on the grindability of produced carbonaceous materials was investigated, and its mechanism was analyzed through various means. Results show that the grindability of all coals, whether caking or slightly‐caking, exhibit the same variation trend with an increase in carbonization temperature. Moreover, the entire process can be divided into four stages. (1) After the most intense devolatilization stage, the grindability of carbonaceous material exhibited different degrees of increase compared with that of raw coal because of the development of a pore structure. (2) The first significant decrease in the grindability occurred from the plastic stage to the complete resolidification of the coal matrix. (3) After the aromatic polycondensation stage accompanied by a large amount of H2 release, the coal molecular structure became compact, such that the grindability of semi‐coke considerably decreased again. (4) At high temperatures, the coal matrix underwent graphitization, which changed semi‐coke to coke. The molecular structure of coal became ordered, and the grindability decreased again. The analysis shows that a change in the internal chemical structure of carbonaceous material has a much more pronounced effect on grindability than a change in its pore structure, except in the first stage. The constant compaction and regularization of the coal molecular structure continued happening throughout the entire process and play a decisive role in the change in grindability.

Experimental investigation on temporal release of potassium from biomass pellet combustion by flame emission spectroscopy

The paper presents experimental investigation on temporal release of potassium (K) from single biomass pellet combustion by Flame Emission Spectroscopy (FES). Through the analysis of spontaneous emission spectra and a calibration procedure, the concentration of gas phase potassium, temperature and thermal radiation during the whole process of biomass pellets combustion in a Hencken burner were measured simultaneously. Camphorwood and rice husk with volatile matter 87.93%, 69.12%, respectively, and K2O content from the ash analysis 7.99%, 1.8%, respectively, were used in the experiment. The effects of biomass composition and moisture content in the pellet on the temporal release of K were analyzed. Experimental results showed the three stages (devolatilization, char, and ash stage) of biomass pellets combustion can be distinguished by the changing points of K concentration, temperature and thermal radiation curves obtained by the FES. The volatile content in biomass pellet has effect on the release behavior of K. The change of moisture in biomass pellet may affect significantly the ratio of K release from biomass pellet with low volatile. The experimental investigation proves FES is feasible for on-line monitoring the K release and combustion process of biomass pellet.

Numerical simulation of ignition mode and ignition delay time of pulverized biomass particles

In this paper, numerical simulations were carried out to identify the mode of ignition and ignition delay time of pulverized biomass particles in hot flue gas produced by a methane/air flame. In the experiments, it was observed that for most biomass residues the dominant combustion mode was the staged gas-phase ignition in the surrounding gas followed by surface ignition at the char surface. There were some exceptions to this general trend, e.g. wheat straw particles, which ignited at the surface of the particle under some temperature conditions. Moreover, temporally and spectrally resolved images of the single burning particles were obtained in the experiments and CH* chemiluminescence at different stages of biomass conversion was recorded. In this study, by means of a detailed numerical model for conversion of biomass particles and employing detailed gas chemistry mechanism, the ignition mode and ignition delay time of the particles are studied. The model is able to distinguish between different ignition modes of the particles in agreement with the experimental data. The underlying physics behind shifting ignition mode from homogeneous ignition to heterogeneous ignition for wheat straw are discussed. The ignition delay times for different biomass sources at different conditions are calculated and the results are in good agreement with the experimental data. Apart from the detailed model, CFD simulations are performed to assess the flow and combustion process (temperature, O2 concentration and velocity difference between the ambient gas and the particle) around the particle. The CFD results show similar trends compared with the CH* chemiluminescence from the particle at different times during the devolatilization stage.

Investigation on the interactions among lignocellulosic constituents and minerals of biomass and their influences on co-firing

The influences of biomass constituents, such as lignocellulosic components and minerals, on the combustion of coal/biomass blends are of significant importance in co-firing due to its potential impacts on ignition, flame stability and burnout. In this research, combustion characteristics of pure lignocellulosic elements, Rosewood, Mengxi coal and their blends were studied in detail. The effect of minerals in Rosewood on combustion of biomass/Mengxi coal blends was investigated which revealed reductions in the ignition (≤20 °C), peak (≤12 °C) and burnout temperatures (≤6 °C). The results also demonstrate the existence of interactions between lignocellulosic constituents in the model biomass, which is dominated by the interactions of cellulose-derived products with xylan and lignin respectively which led to ∼8% reduction in char oxidation temperature. The minerals in biomass showed different impacts at different stages of the combustion process, such as inhibition effect during the devolatilization stage, and promotive synergy (mainly due to calcium) on ignition and char oxidation.

Solid Waste as a Renewable Source of Energy: A Comparative Study on Thermal and Kinetic Behavior of Three Organic Solid Wastes

Pyrolytic characteristics of three different organic solid wastes, municipal solid waste (MSW), digested MSW (DMSW), and digested swine manure (SWD), were investigated at heating rates of 10, 15, and 20 °C min–1 in a thermogravimetric analyzer coupled with mass spectrometer. Three stages of devolatilization, dehydration (0–200 °C), decomposition of major structural components (200–500 °C), and decomposition of solid residue (500–800 °C), appeared during the pyrolysis of all the samples. The major devolatilization stage (stage II) is characterized with three peaks at 319, 379, and 438 °C for MSW, two peaks at 339 and 430 for DMSW, and one peak with a shoulder on the right at 332 and 444 °C for SWD, respectively. The evolved gas species were quantified by using a semiquantitative approach, and H2, CO and CO2 were noticed to be predominant gas species in the above-mentioned range. While the evolution of H2 is mostly temperature dependent, the evolution of CO and CO2 occurred all through the run. Isoconversio...

Techno-economic estimation of wastewater phycoremediation and environmental benefits using Scenedesmus obliquus microalgae

This study investigated the dual application of Scenedesmus obliquus for wastewater phycoremediation and biochemical component accumulation in microalgal cells. The microalgae grown in wastewater showed micro-elements uptake and removal efficiencies of 71.2 ± 3.5% COD, 81.9 ± 3.8% NH4+, ∼100.0% NO3−, and 94.1 ± 4.7% PO43−. The growth profile of Scenedesmus obliquus indicated a specific growth rate of 0.42 ± 0.02 1·d−1 and carrying capacity of 0.88 ± 0.04 g L−1. The lipid, protein, and carbohydrate yields (w·w−1 of dry weight) were 26.5 ± 1.5%, 28.5 ± 1.5%, and 27.5 ± 1.6%, respectively. The de-oiled biomass was subjected to biochemical extraction, achieving protein and carbohydrate yields of 25.3 ± 1.4% and 21.4 ± 1.2%, respectively. Fourier transform infrared spectroscopy showed several functional groups (e.g., NH, CH3, CH2, CO, CN, PO, and SiO) on the biomass surface, confirming the accumulation of biochemical elements in microalgae. The thermal analysis of microalgal biomass depicted sequential stages of dehydration (60–190 °C), devolatilization (200–490 °C), and solid residue decomposition (490–600 °C). The cost-benefit analysis of microalgae cultivated in wastewater was derived regarding amortization and operating costs and energy and environmental benefits. The net profit of phycoremediation was 16885 US$·y−1, resulting in a payback period of 14.8 years (i.e., shorter than the project lifetime). Accordingly, the proposed phycoremediation process was economically viable.

Effect of oxygen concentration on oxy-fuel combustion characteristic and interactions of coal gangue and pine sawdust

Coal gangue is an inevitable coal waste from coal mine, which results in serious environmental problems. Oxy-fuel firing of coal waste and biomass waste is an alternative technology for efficient and clean utilization and CO2 reduction of coal waste. In this study, the oxy-fuel combustion characteristics and interactions of coal gangue and pine sawdust were investigated using thermogravimetric analysis, with a focus on the effect of oxygen concentration on interactions between coal gangue and pine sawdust during oxy-fuel combustion. The oxy-fuel combustion of pine sawdust had two obvious stages, including the release of volatile matter and the combustion of the remaining char, which differed from oxy-fuel combustion of coal gangue with one overlapped stage of devolatilization and char oxidation. Moreover, the addition of pine sawdust could improve the oxy-fuel combustion reactivity of coal gangue. The significant deviations between the experimental derivative thermogravimetric curves and theoretical derivative thermogravimetric curves for the blends indicated that interactions between coal gangue and pine sawdust had occurred in the temperature range of 400–600 °C. The interaction mechanism was primarily thermal effect between coal gangue and pine sawdust during oxy-fuel combustion. The oxygen concentration had a significant effect on the interactions between coal gangue and pine sawdust. The increase of oxygen concentration from 20% to 40% could improve interactions between coal gangue and pine sawdust obviously. However, relative small improvement of interactions was detected between coal gangue and pine sawdust when oxygen concentration was further increased from 60% to 80%. This was related to the difference of rate controlling factor for oxy-fuel combustion reaction under various oxygen concentrations.

Pyrolysis and combustion kinetics of lignocellulosic biomass pellets with calcium-rich wastes from agro-forestry residues

The pyrolysis and combustion kinetics of biomass pellets (i.e., rice husk, herb residue, and wood residue) with the calcium-rich wastes (i.e., CaO, CaCO3, and eggshell) from agro-forestry residues were comparatively studied. During pyrolysis or combustion of biomass, the Ca-rich wastes could slightly influence the decomposition rate in the stage of devolatilization at relatively lower temperatures (e.g., <400 °C). However, the lignin decomposition and the char combustion were obviously influenced by the calcium-based catalysis at higher temperatures (>700 °C). Particularly, the eggshell had a lowest activation energy in the stage of char combustion. The presence of alkali and alkaline-earth metals (AAEMs) in the eggshells might have positive effects on volatile and char combustion. During the combustion, the decomposition temperatures of CaCO3 and eggshell were decreased, thereby favoring to uptake CO2. Furthermore, by identifying the small molecular products, it was found that both CaCO3 and CaO can improve the pyrolysis of RH, but CaCO3 showed better performances, especially on CO2 capture at lower temperatures and on the enhancement of CO production.

Pyrolytic kinetics, reaction mechanisms and products of waste tea via TG-FTIR and Py-GC/MS

The present study experimentally quantified the pyrolysis behaviors of waste tea (WT) as a function of four heating rates using thermogravimetric-Fourier transform infrared spectrometry and pyrolysis-gas chromatography-mass spectrometry analyses. The maximum weight loss of WT (66.79%) occurred at the main stage of devolatilization between 187.0 and 536.5 °C. The average activation energy estimates of three sub-stages of devolatilization were slightly higher (161.81, 193.19 and 224.99 kJ/mol, respectively) by the Flynn-Wall-Ozawa than Kissinger-Akahira-Sunose method. Kinetic reaction mechanisms predicted using the master-plots were f (α) = (3/2)(1 − α)2/3[1 − (1 − α)1/3]−1, f (α) = (1 − α)2, and f (α) = (1 − α)2.5 for the three sub-stages, respectively. The prominent volatiles of the WT pyrolysis were CO2 > CO > phenol > CH4 > C O > NH3 > H2O > CO. A total of 33 organic compounds were identified including alkene, acid, benzene, furan, ketone, phenol, nitride, alcohol, aldehyde, alkyl, and ester. This study provides a theoretical and practical guideline to meeting the engineering challenges of introducing WT residues in the bioenergy sector.

Thermogravimetric analysis of combustion characteristics and kinetics of hydrothermally treated and washed empty fruit bunch

This study aims to study the fuel properties, combustion behaviors and kinetics of hydrothermally treated and washed empty fruit bunch (HTW-EFB). For the lab-scale samples, EFB was hydrothermally treated (HT) at 180, 200 or 220 °C for 30 min and washed using water at 60 °C for 15 min to remove alkaline metals. For the commercial-scale sample, EFB was HT at 2 MPa for 30 min and washed with room temperature water using a centrifugal machine. Results indicate that a combination of hydrothermal and washing treatments (HTW) improved fuel properties of EFB significantly, with an increase in calorific value to 2.33 × 104 kJ kg−1 and a reduction in the alkaline contents. Significant shifts in combustion behavior were observed when EFB underwent HTW. The ignition temperature of the hydrochars was 290–296 °C with the burnout temperature at 438–485 °C. From the kinetic study, a first-order reaction and one-dimensional diffusion is the main mechanism in the combustion of volatiles, while one-dimensional diffusion is the main mechanism for the combustion of the fixed carbon of the hydrochars. The activation energy of HTW-EFBs was between 99.96 and 138.26 kJ mol−1 in the devolatilization stage and 10.97–27.56 kJ mol−1 in the char oxidation stage.

Bottom ash characteristics and pollutant emission during the co-combustion of pulverized coal with high mass-percentage sewage sludge

A municipal and a coal-coking industrial sludge (MS and CS) were separately co-combusted with bituminous coal at a sludge mass ratio (SMR) of 10%–50%. Quartz, larnite, gehlenite, mayenite, and calcium sulfate were formed during co-combustion. Slight or medium slagging was predicted to occur when slagging tendency was assessed based on the mineral components and fusion temperature of the ash. The SO2 emission peak at the devolatilization stage increased with increasing SMR of MS but only slightly changed with increasing SMR of CS. SO2 emission at the char combustion stage was suppressed due to the sulfur retention effects of sludge ash. NO, HCN, and N2O were the main emission forms of N-containing gases. With increasing SMRs of MS and CS, HCN emissions became increasingly prominent, whereas NO showed only a slight increase and even decreased. In addition, the volatilization percentages (VP) of Cd, Zn, Cr, and Ni decreased. By contrast, the VP of Pb increased when coal was combusted with CS because Pb was considerably influenced by high Cl. The concentrations of Cd, Cr, Ni, Pb, and Zn in the bottom ashes were determined and satisfied China's threshold limit value for landscaping land application or soil amendment.