In this study, 11 coal mono-combustion tests and four co-combustion tests of coal and tannery sludge were conducted on a 35 kW fluidized-bed combustor. The combustion behavior and emission characteristics of the fuels were investigated on a bubbling fluidized bed (BFB) and a circulating fluidized bed (CFB). The effects of an excess air ratio, primary air rate, secondary air ratio, and fuel type on flue gas emissions were studied. The results showed that the fluidization status and temperature distribution had direct influences on CO emission. Sufficient fluidization and high temperature effectively reduced CO emission. NOx emission was relatively sensitive to the excess air ratio and increased with increasing excess air ratio. By comparing BFB and CFB, we found that CFBs have an advantage in optimizing combustion and controlling emissions by enhancing mixing and increasing freeboard temperatures. The Cr speciation and distribution among different ash types were extensively investigated in four co-combustion tests. The results showed that the distribution modes of Cr in BFBs and CFBs were different and determined by separate fluid dynamics modes of sludge ash particles in the combustor. The extent of Cr oxidation in ash in CFB tests was higher than that in BFB tests, particularly for bottom ash and heat exchanger ash, due to longer residence times in high-temperature regions.

The effect of bituminous coal and pickling sludge co-combustion on the distributions of Cr, Ni, Mn, As, Cu, Sb, Pb, Cd, Zn, and Sn in flue gas, fly ash, and bottom ash were studied in a drop-tube furnace. To simulate combustion conditions in suspension-firing boilers, experiments were carried out at temperatures ranging from 1100 to 1400 °C, with sludge amounts ranging from 0% to 10% by weight. The results show that the 10 selected heavy metals could be divided into three distinct classes according to bottom ash mass percentage, except for Sn, which showed an irregularity. Class I included Cr, Ni, Mn, and As and were identified as less volatile heavy metals because more than 95% was retained in the bottom ash; these heavy metals exhibit high-temperature stability. Class II contained Cu, Sb, Pb, and Cd and were identified as semivolatile heavy metals; nearly 20–40% was distributed among flue gas and fly ash. In addition, the bottom ash heavy metal percentage decreased markedly with increasing temperature. Zn belongs to class III and was identified as a volatile heavy metal; less than 20% was retained in bottom ash under all experimental conditions. Thermodynamic equilibrium calculations were used to forecast heavy metal compounds, and most calculation results were consistent with the actual outcomes. X-ray diffraction results indicated that Cr and Ni mainly reacted with MgO and Fe2O3 to form MgCr2O4 and NiFeO4 in solid phase during the co-combustion process. The heavy metal emissions in flue gas meet the national standard, while the bottom ash leaching results indicate that the bottom ash from bituminous coal and pickling sludge co-combustion cannot be disposed of as common waste through landfill disposal without further treatment.

Combustion is a key process of energy utilization in fluidized beds. To achieve higher efficiency and lower pollution, a fundamental understanding of the complex combustion behavior is required. Mathematical modeling plays important roles in the exploration of the complex process and the prediction of combustion performance. Up to now, many models of the combustion of solid fuel particles have been presented. This study gives a detailed review of the proposed combustion models for common solid fuels, i.e., coal, biomass, and solid waste. The combustion models for coal and biomass have matured. However, models for solid waste have seldom been studied and need to be studied further. Considering the complex compositions of biomass and solid waste, a systematic model library based on many works should be proposed for them in the future. In addition, the transformation behavior of hazardous substance (F, Cl, and heavy metals) in solid waste should also be considered in combustion models in the future. Moreover, advanced measuring methods, such as laser measurements, should be used in future works to better understand the reaction mechanism during combustion and improve the accuracies of the models. An overall and accurate model library for the combustion of various type of solid fuels is expected to be established in the future, which will be helpful in the design, adjustment, and operation of combustion systems.

In this paper, microwave-assisted hydrothermal treatment was performed to stabilize the heavy metals of municipal solid waste incineration (MSWI) fly ashes in a circulating fluidized bed (CFB). Influences of the types of chemical additives, reagent concentration, liquid/solid ratio, reaction temperature, and reaction time were investigated by single and orthogonal experiments. A solid waste extraction procedure for leaching toxicity-acetic acid buffer solution method (HJ/T 300-2007) was adopted to detect the toxicity of raw fly ash and the hydrothermal products. The effect of pH on the leaching test of raw and treated fly ash was also carried out. Characteristics of fly ash were determined by XRF and XRD, and the leaching concentration was determined by ICP-MS. Experimental results revealed that the stabilization of heavy metals in fly ash was facilitated by a microwave-assisted hydrothermal process and, except for Cd, the regulatory limits were achieved when fly ash was treated with 1 mol/L NaOH and a liquid-to-solid ratio of 3.5 mL/g at 125 °C for 20 min of microwave-assisted hydrothermal heating. It was further concluded that the significance of factors was in the order of reagent > concentration ≈ temperature > time > L/S ratio (10–30 mL/g). More zeolites were formed over 20 min, which confirmed the high efficiency of the microwave-assisted hydrothermal treatment. In pH experiments, it was found that the safe pH range of treated fly ash was broadened from 7.5 to 11 to 6.3–13, which led to better environmental adaptability. The microwave-assisted hydrothermal treatment may be applied to harmlessly manage the MSWI fly ash or to recover and utilize MSWI fly ash in a high efficiency, energy saving way compared to traditional hydrothermal treatment.

In this work, a microwave-assisted hydrothermal treatment was investigated to solidify the heavy metals of municipal solid waste incineration fly ash in a circulating fluidized bed. The influences of additive dosage, temperature, liquid/solid (L/S) ratio, and reaction time with addition of NaH2PO4 were investigated. The chemical components, hydrothermal product, and the leaching concentration of fly ash were determined by X-ray fluorescence, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy. Also, pH tests were conducted to assess the environmental adaptability of the treated fly ash. In terms of the solidification effect of heavy metals, the effectiveness of additives was in the order Na2HPO4, NaH2PO4, H3PO4, and FeSO4. Experimental results revealed that heavy metals in fly ash were solidified by a microwave-assisted hydrothermal process, under the optimized conditions of 1.5 mol/kg NaH2PO4, 2 mL/g L/S ratio, 10 min reaction time, and 200 °C, and the heavy metal contents met the standard limitation in GB 16889-2008. In pH tests, it was found that the safety range of the treated fly ash was widened from 7.5–11 to 5–13, which indicated that the properties of environmental stability and acid- and alkali-resistance of fly ash were enhanced. Therefore, hydrothermal treatment with microwave heating is a feasible approach for the solidification of heavy metals in fly ash in just 10 min. The treated fly ash is suitable for safe disposal or even for recovery and reutilization.

Co-combustion tests of pickling sludge with coal were performed in a high-temperature tubular furnace system. The effect of combustion conditions (combustion temperature from 800 to 1500 °C and sludge ratio from 0 to 100% by weight) on the partitioning of Cr, Pb, Ni, Cu, and Mn in flue gas, fly ash, and bottom ash was investigated. The results showed that the largest part of Cr, Ni, and Mn was retained in bottom ash. The content of Pb in fly ash and flue gas was obviously affected by the temperature. No more than 9% of Cu was emitted with flue gas. Increasing the combustion temperature caused a significant increase in the partitioning of Pb and Cu in bottom ash, while the partitioning of Cr, Ni, and Mn in bottom ash remained stable. The thermodynamic equilibrium calculation was carried out to determine the species of selected heavy metals during co-combustion. The results revealed that Cr, Ni, and Mn were enriched in bottom ash mainly combined with a mineral substance, such as SiO2, Al2O3, Fe2O3, and MgO, while Cu and Pb were predicted to report to the gas phase in the form of chlorides and oxides. Additionally, the results of principal component analysis (PCA) indicated that the concentration of Mn in the gas phase was positively correlated with the sludge ratio, while Cr and Ni had a weakly negative correlation with the sludge ratio. The sludge ratio seemed irrelevant to Pb and Cu.

The influence of co-combustion of bituminous coal and pickling sludge on SO2, NOx, HF, HCl and PCDD/Fs emissions was studied in a drop tube furnace. To simulate the combustion condition of suspension firing boilers, the experiment was performed at 1100–1400 °C with the share of sludge in the feed ranging from 0 to 10% by weight. The combustion characteristics of coal and of blended fuels were studied by TG analysis. The results showed that the average combustion efficiency of co-combustion of bituminous coal and pickling sludge in the drop tube furnace is larger than 99%. SO2, NOx and HCl emissions had an increasing tendency with the temperature rising, but HF emissions were not sensitive to temperature. SO2 and HF emissions had a rising trend with increasing share of sludge, while NOx and HCl emissions had an opposite trend. No obvious effect of temperature and the share of sludge on the total TEQ of PCDD/Fs was found, and the emissions of the seventeen congeners were basically stable under different experimental conditions. TG results showed that the combustion characteristics of coal and blended fuels were basically the same. XRD results showed that the ash composition changed significantly with the addition of sludge. Compared to the national standard, when co-combusting of bituminous coal and pickling sludge in commercial power plant, desulphurization and denitrification equipment, activated carbon injection and baghouse should be provided.

In this study, the combustion and emission characteristics of slurry from an Indonesian lignite washery tailing (LWT) and a bituminous coal were studied and compared in both a bubbling fluidized bed (BFB) and a circulating fluidized bed (CFB). The effects of excess air ratio, feeding rate, secondary air ratio, and secondary air location on the flue gas emissions were analyzed to investigate the optimal operating conditions. The results show that it is feasible to directly fire LWT slurry in a CFB. The temperature of the dense-phase bed firing the LWT slurry can reach 800 °C but is lower than that of a normal BFB/CFB firing coal. Both SO2 and NO emissions of bituminous coal are higher than those of LWT slurry, but their emission characteristics are still below the limits for both EU and Chinese regulations. Improved emission characteristics are observed when firing LWT slurry and coal in CFB compared to BFB. Two main differences were found between LWT slurry and coal: (1) Low primary air (PA) flow rates facilitate the defluidization of the FB combustor when firing LWT slurry. (2) High feeding rates of LWT slurry may reduce the temperature along FB instead. These factors should be paid special attention when designing and operating an FB system. Optimal secondary air (SA) ratios were determined for both LWT slurry and coal. The SA should not be located near the distributor. All of the analyses in this study provide useful information for the design and operation of a commercial FB system.

•Analysis method of TG-FTIR and GC/MS were used to investigate pyrolysis.•Bigger particle size put off gas release during sewage sludge pyrolysis.•Reaction of evolving gas with sludge layer was enhanced for bigger particle size.•Smaller particles tended to yield more PAHs due to their incomplete crack.Sewage sludge with different particle sizes (diameters) was pyrolyzed using thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR) to study the dynamic kinetics and gas evolution, while batch scale experiments were conducted in a tubular reactor to study the emission performances of 16 polycyclic-aromatic hydrocarbons (PAHs) characterized by the United States Environmental Protection Agency (USEPA) as priority pollutants. The temperature of the tubular reactor was fixed to 850 °C, and sewage sludge samples with different particle sizes were separately introduced into the reactor at a gas residence time of 10 s (calculated) for pyrolysis. The results showed that sewage sludge with a smaller particle size tended to release water and volatile matter at a lower temperature and higher intensity of FTIR evolution. FTIR analysis further verified the enhancement of the second crack for pyrolysis of sewage sludge with larger particle sizes. The particle size also significantly influenced PAH formation, while the highest amount of PAHs was produced during sewage sludge pyrolysis with particles of 0.075 mm. The effect can be explained by the rapid release of volatile matter from the particle, resulting in a greater possibility of PAH formation under conditions of smaller particle size. The total PAH amount and their toxic equivalents (TEQs), the fractional distribution of the 16 PAH amounts and their TEQs, and the classification of PAHs by ring number were separately displayed to evaluate the influence. The present results may be valuable for the evaluation of sewage sludge thermal treatment and for gaining knowledge of PAH formation during pyrolysis of sewage sludge with different particle sizes.

•Rheological properties and stability of LWTS were studied.•LWTS has good stability and is suitable for long-term storage and transportation.•Rheological properties were studied by rotational viscometer and pipeline system.•The two rheological methods were compared and a rheological model was proposed.•Dispersant NDF has no effect on stability but improves the rheological properties.The rheological properties and stability of lignite washery tailing suspensions (LWTS) were studied as a special type of coal water slurry (CWS). The properties of LWTS in these aspects are all shown to meet the requirement of a CWS. Two test methods, i.e., a rotational viscometer and a pipeline test system, were used to study the rheological properties of the LWTS and to distinguish between theory and practice. Furthermore, a rheological model of LWTS transfer in the pipeline test system was proposed and proved to be suitable and useful in designing commercial pipeline systems. Moreover, the influence of an anionic dispersant NDF (a co-polymer of methylene naphthalene sulfonate, styrene sulfonate and maleate) on the stability and rheological properties of LWTS was studied. The dispersant NDF proved to have no effect on the stability of the LWTS, while it significantly improved the rheological properties of the LWTS.

•The effect of three anionic dispersants on moisture distribution of CWS was studied.•The study is conducted by means of thermal drying and TG–DSC analysis.•A new method for moisture distribution was proposed and proved to be reasonable.•Dispersants affect the moisture distribution of CWS in this order: CLS > NDF > NNO.•The effect of dispersants on water in CWS with physical adsorption is much greater.Coal water slurry (CWS) was prepared from lignite washery tailings. Its moisture content can be subdivided into two forms: free water (surface adsorption water) and bound water, i.e., interparticle, capillary, adhesion and internal adsorption water. The effect on moisture distribution of three distinct dispersants was studied through thermal drying and TG–DSC analysis. A new test method combining thermal drying and bond strength analysis was put forward for a thorough moisture distribution. The new method showed reasonable results and arrives at the same conclusion as the TG–DSC method. The addition of dispersants increased the free water content and decreased the bound water content, in particular those of interparticle and capillary water. Also there was a slight decrease in total moisture, compared to CWS prepared without dispersant. The moisture distribution showed its biggest change with dispersant CLS (calcium lignosulfonate), followed by dispersant NDF (a co-polymer of methylene naphthalene sulfonate, styrene sulfonate and maleate), and ended up with NNO (sodium methylene bis-naphthalene sulfonate).

Pyrolysis of wet sewage sludge with a moisture of 86.47 wt % was conducted using electric heating (conventional pyrolysis, CP) and microwave heating (microwave pyrolysis, MWP) separately on two sets of batch reactors. Sixteen polycyclic aromatic hydrocarbons (PAHs) characterized by United States Environmental Protection Agency (U. S. EPA) as priority pollutants were determined by gas chromatography/mass spectroscopy (GC/MS) in gas, liquid, and solid phases of pyrolysis products to get detailed transmission characteristics of PAHs in sewage sludge pyrolysis. Temperatures of 400–900 °C and microwave power of 400–900 W were investigated. Production yields in MWP and CP behaved similarly for different power in MWP and for different temperatures in CP, whereas liquid yielded more than 75% of the total weight for the high content of water in wet sewage sludge. Liquid yield went through a high peak at 500 W for MWP and 700 °C for CP. Total yield of PAHs had trend of increase in MWP, whereas it peaked at 700 °C in CP. Naphthalene, fluorene, phenanthrene, and anthracene contributed most of the yield change, which can be explained by integration of the secondary pyrolysis of solid, decomposition of PAHs and synthesis of gas in different temperature. CP yielded more PAHs than MWP, which is more obvious in gas fraction than oil fraction. Distillation effect had great influence on PAHs distribution between gas and oil fraction. PAHs yield in solid for MWP decreased with increase of power, which might be attributed to the special effect of microwave on the microscope characteristic of solid, whereas PAHs in solid for CP were even lower and would cause fewer environmental problems. The results also indicated “nonthermal” impacts of microwave on the process.

Biofermenting residue (BR) arising from the production of antibiotics was cogasified in an industrial scale MCSG coal-water slurry gasifier. It released large amounts of volatiles during pyrolysis at low temperature (below 650 °C), as follows from thermogravimetric analysis in an inert gas stream. The main evolved volatiles are light gaseous compounds, such as H2O, CO, CO2, and H2 (monitored by MS analysis), and heavy organics with high oxygen content (monitored by FTIR analysis). During industrial scale experimental tests, BR cogasification had little influence on syngas composition, when compared with straight coal-water slurry gasification. The emissions to air from BR cogasification basically meet the emission limits in China. The solid residues produced meet the Chinese requirements of agricultural sludge. Cogasification in a MCSG coal-water slurry gasifier may be a viable alternative solution for BR treatment. However, further research is needed to apply this in other types of gasifiers or to expand the range of waste/biomass cotreatment.

•Most volatile matters were released before 600 °C in FTIR analysis of pyrolysis of wet sludge.•Distillation effects explained the congener profiles of 17 toxic PCDD/Fs well.•Both CP and MWP of wet sludge had effects of distillation and dechlorination of PCDD/Fs.•CP presented more prominent dechlorination and distillation effects than MWP.TG-FTIR was carried out to investigate gas evolution during pyrolysis of wet sewage sludge from Shanghai, China. Weight lost 85% in the temperature range 25–600 °C while the main volatile matters were released before 600 °C.To get emission characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) during pyrolysis processes, conventional pyrolysis (CP) by electric heating and microwave pyrolysis (MWP) by microwave heating were separately conducted on two set of batch reactors.Both CP and MWP evolved no more than 5% of concentration of 17 toxic PCDD/Fs in untreated sewage sludge while corresponding ratios of International Toxicity Equivalents (I-TEQ) were around 30%. The ratios of difference congeners can be well explained by distillation effect. Homologue profiles of the total PCDD/Fs indicated presence of dechlorination and distillation effects during the two processes while the effects in CP were more prominent than in MWP though the latter got higher temperature. Other to that, MWP produced equivalent quantity of PCDD/Fs compared with CP indicating the absence of “nonthermal” effect in MWP on PCDD/Fs evolution.

Hazardous waste treatment facilities in China are in shortage. Co-firing hazardous waste with coal in industrial and utility boilers would be a near term, low cost, and low risk option. This work presents a thermogravimetric and kinetic analysis based study on bioferment residue (BR, hazardous waste), coal and their blends to understand their cocombustion characteristics at different proportions. Kinetic data are obtained using the Coats-Redfern method. The co-firing ratio for BR/coal in different combustion types is suggested. It is found that BR has a composition that favors combustion, although its combustion properties are not as good as that of coal. Co-firing BR with coal mainly consists of four stages. Reaction mechanisms vary with combustion stage and blending ratio. BR-coal blends present a sum reactivity of their parent component. With increasing BR cofiring ratio, ignition temperature, and combustion rate basically decrease as well as the total energy output. Provided sufficient reaction time, BR, coal and their blends would be completely burnt below a temperature of 750 °C. Co-firing BR in coal fired boilers preferably below percentage of 10.1–42.2% for grate, 90.7–100% for FB, and 3.1–86.3% for PF.

With fast development of industry large quantities of hazardous waste are produced in China. Today, incineration plays an important role in the disposal of hazardous waste. Co-incineration of some types of hazardous wastes with municipal solid waste (MSW) has been suggested in the Proposed Standards for Pollutants for MSW combustors in China, published in 2010. According to this proposal, coincinerated hazardous waste should have similar combustion characteristics with MSW, such as bioferment residue (HW02–276–001–02 in China Hazardous Waste List). In this study, residue from the production of hydrochloride salt spectinomycin, a bioferment process, was studied by thermogravimetric analysis (TGA) coupled with Fourier transform infrared (TG-FTIR) analysis. In TGA, the sample attains its final weight before 800 °C. No gaseous pollutants evolve in large amount during FTIR analysis. During test runs at a MSW incineration plant in Jinhua, Zhejiang Province, bioferment residue was added to MSW at a rate of 24 ton/day and fed to the circulated fluidized bed (CFB) incineration system with capacity of 500 ton/day MSW. The operating parameters and emissions were monitored. The system performance was obviously not affected by addition of bioferment residue to MSW/coal and the pollutant emissions met the Chinese standard, with or without addition of bioferment into feedstock.

Industrial hazardous waste from the fluorine chemical industry sometimes has a high content of fluorine, and incinerating it could be very poisonous if the flue gas is not properly disposed. In this study fluoroborate residue is used to represent a typical waste from the fluorine chemical industry . Thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR analysis) was used to study the evolution characteristics of gaseous products during the pyrolysis of fluoroborate residue. The pyrolysis process of fluoroborate residue could be divided into three stages according to the TG analysis: moisture loss, fast decomposition, and charring. SiF4, BF3, and HF are found as fluorine gas species evolved in the pyrolysis process. The evolution of SiF4 finishes at 600 °C. The evolution of BF3 has two peaks and most of the emission happens before 600 °C. The release of HF could be divided into two stages due to the different existence of F–. In addition, the reforming condition of different fluorine-containing gaseous substances is verified in a thermodynamic equilibrium model and the results could explain the experiment phenomenon well.

Hazardous waste from chemical factories including fluorine and chlorine has rather low fusion temperatures. During incineration in a rotary kiln incinerator, hazardous waste including fluorine and chlorine melts and turns into slag, possibly adhering to the inner wall and leading to unstable operation of the incinerator. Prediction of the melting characteristics of hazardous waste including fluorine and chlorine hence plays an important role in preventing slagging. The effect of various chemical components on fusion temperatures (deformation temperature, DT; softening temperature, ST; hemisphere temperature, HT; and flow temperature, FT) has been investigated experimentally: Na2O and NaF are the most remarkable chemical compounds among those investigated. Correlations between fusion temperatures and chemical components have been investigated; neural networks have been used to predict four characteristic melting temperatures and are verified by tested slag samples of hazardous waste including fluorine and chlorine. Relative errors of fusion temperatures (computed vs. measured) are mostly less than 1.2%.Highlights► Compounds of slag of hazardous wastes are investigated by XRF and aided by FactSage. ► Na2O decreases the fusion temperatures sharply. ► The effect of NaF on the melting characteristics is complex. ► Prediction of fusion temperatures are obtained by neural network. ► The prediction results are verified by testing.

In China, safe disposal of hazardous waste is more and more a necessity, urged by rapid economic development. The pyrolysis and combustion characteristics of a residue from producing monopotassium phosphate (monopotassium phosphate residue), considered as a hazardous waste, were studied using a thermogravimetric, coupled with Fourier transform infrared analyzer (TG-FTIR). Both pyrolysis and combustion runs can be subdivided into three stages: drying, thermal decomposition, and final devolatilization. The average weight loss rate during fast thermal decomposition stage in pyrolysis is higher than combustion. Acetic acid, methane, pentane, (acetyl) cyclopropane, 2,4,6-trichlorophenol, CO, and CO2 were distinguished in the pyrolysis process, while CO2 was the dominant combustion product.

Incineration is considered one of the most readily available techniques for sewage sludge disposal, including tannery sludge, which often contains significant amounts of volatile heavy metals. The combustion characteristics and kinetic analysis of tannery sludge were investigated using thermogravimetric analysis (TGA) at a heating rate of 30 °C/min in 50–950 °C. In addition to confirming that tannery sludge has a high content of volatile material and ash, it was further discovered that almost all the zinc (Zn) in tannery sludge is volatilized at 900 °C. The degree of volatilization for heavy metals at 900 °C followed the order of Zn>Cd>Cu>Mn>Pb>Cr. Moreover, the volatilization of these heavy metals increased with temperature. It is thus concluded that, to avoid heavy metal volatization during incineration disposal, 800 °C is a reasonable incineration temperature.

•Co-combustion experiment of tannery sludge and bituminous was conducted in a 220 t/h commercial fluidized bed boiler.•Pollutants emissions do not have a lot of changes when tannery sludge co-combusted in fraction of 50% by weight.•Addition of TS shifts the partitioning of Cr, Ni from bottom ash to fly ash, especially for Cr.•Cr concentrations in leachates of ashes from co-combustion are remarkably higher than that for coal mono-combustion.Co-combusting hazardous wastes in existing fluidized bed combustors is an alternative to hazardous waste treatment facilities, in shortage in China. Tannery sludge is a kind of hazardous waste, considered fit for co-combusting with coal in fluidized bedboilers. In this work, co-combustion tests of tannery sludge and bituminous coal were conducted in a power plant in Jiaxing, Zhejiang province. Before that, the combustion behavior of tannery sludge and bituminous were studied by thermogravimetric analysis. Tannery sludge presented higher reactivity than bituminous coal. During the co-combustion tests, the emissions of harmful gases were monitored. The results showed that the pollutant emissions met the Chinese standard except for NOx. The Concentrations of seven trace elements (As, Cr, Cd, Ni, Cu, Pb, Mn) in three exit ash flows (bottom ash in bed, fly ash in filter, and submicrometer aerosol in flue gas) were analyzed. The results of mono-combustion of bituminous coal were compared with those of co-combustion with tannery sludge. It was found that chromium enriched in fly ash. At last, the leachability of fly ash and bottom ash was analyzed. The results showed that most species were almost equal to or below the limits except for As in bottom ashes and Cr in the fly ash of co-combustion test. The concentrations of Cr in leachates of co-combustion ashes are markedly higher than that of coal mono-combustion ashes.