Incineration Conditions Research Articles

Ash blended cement composites: Eco-friendly and sustainable option for utilization of corncob ash

Corncob, byproduct of maize crop, is one of the biomass from agricultural waste that is being used as energy source since it has significant energy content. After being burnt, the ash is disposed to landfill sites or ash ponds, locking the useful land. Moreover, corncob ash (CCA) is rich in silica and can be used as pozzolan but this characteristic is linked with temperature and grinding conditions. Hence, we aimed at evaluating the most favorable conditions of incineration and grinding to determine the pozzolanic activity of CCA. At first, the open burnt ash was sieved through #50 and #12 sieves (ashes retained on #12, #50 and pan were denoted as R12, R50 and R00 respectively) to find incineration requirement. It was found that R00 ash having smaller particle size could directly be used as pozzolan whereas R12 and R50 ashes having larger particle sizes needed further incineration. Thereafter, the research was divided into four phases to find optimum incineration (temperature and time) and grinding conditions. In Phase I, R12 ash was incinerated at 400 °C, 500 °C, 600 °C, 700 °C and 800 °C for 2 h to find the optimum incineration temperature. Best results for Chapelle activity (438 mg/g), CaO reduction in Frattini (82.8%) and Pozzolanic activity index (PAI) (97.3%) obtained at 500 °C signified it as optimum incineration temperature. In Phase II, R50 ash was incinerated at optimum temperature i.e. 500 °C for different time intervals (15, 30, 60 and 120 min) to find optimum incineration time and possibly reduce energy requirement. Test results showed that incineration time of 30 min was optimum and hence in comparison to larger particle size (R12 sample), ash having smaller particle size (R50 sample) require less time to achieve required pozzolanic activity. In Phase III, all three sieved ashes (R12, R00 and R50) incinerated at optimum conditions were mixed (to make use of entire corncob ash) and it was found to possess adequate PAI (80.3%). Based on above three phases, it can be concluded that R00 ash as obtained from sieving, R12 ash incinerated at 500 °C for 2 h and R50 ash incinerated at 500 °C for 30 min, provided good results mutually as well as independently. Finally, in Phase IV, the optimum grinding time was determined by grinding ash for 30, 60, 120 and 240 min. Test results showed that the surface area increased with the increase in grinding duration. However, keeping in mind that grinding is energy intensive process, 60 min of grinding showing specific surface area of 4220 cm2/gm, Chapelle activity of 511.05 mg/g and 28 days PAI of 77.6%, was selected as optimum. Thus, corncob ash after optimum conditions of incineration and grinding can successfully be used in cement based composites. Moreover, it would address sustainability issues of ash disposal and natural resources depletion by reducing the amount of cement production.

Development of the regionalised municipal solid waste incineration (RMWI) model and its application to France

Incineration is mainly studied when municipal solid waste (MSW) treatment options are assessed in life cycle assessment case studies. A variety of incineration models have been used to create life cycle inventories (LCIs), but they often do not represent the technology and input waste composition of a given incineration situation. This article describes development of the regionalised municipal solid waste incineration (RMWI) model designed at the city-to-country level and its application to French MSW incineration. RMWI is based on previously published incineration models from the ecoinvent database and Koehler et al. (Environ Sci Technol 45:3487–3495, 2011). Its system boundaries include furnace, gas-treatment steps, transport and management of by-products (e.g. clinkers, residues from cleaning flue gas, scrap). Its first strong point is the ability to adapt input waste composition. Its second strong point is that MSW collection and energy, scrap and clinker recovery options are modelled as stocks. Thus, users may adapt RMWI for the types of waste input and regional outlets for energy and matter recovery. French data were used in the model for MSW input composition, emission limits of some exhaust gases and transport distances of by-products. The method used to the collect these data is described so it can be reproduced for another region. The RMWI model is designed in GaBi 6. Environmental impacts predicted by RMWI for France are assessed to identify hot spots and input parameters with high influence. Chemical production for gas treatments was identified as a major contributor to abiotic depletion, whilst NH3 and NOx emissions were mainly responsible for acidification and eutrophication. In a second approach, the consideration of the recovery of by-products as heat, electricity, clinker, iron and aluminium scraps aims at understanding their contributions to environmental impacts. Sensitivity analyses were performed to determine to what extent RMWI predictions are sensitive to French incineration conditions. Comparison to generic LCI approaches highlighted merits of a regionalised model, especially concerning the type of gas treatment. The RMWI model effectively links input waste composition and environmental impacts. RMW-predicted impacts, representation of stocks, sensitivity analyses and comparison to generic approaches were assessed to examine the model’s relevance, robustness and limits. The model is now available for French incineration but also can be used to assess environmental impacts of an incineration plant or another regional (city-to-country) incineration situation by adapting and calibrating it.

廃棄物焼却における初期熱分解の挙動

In order to incinerate heterogeneous fuel such as waste products completely, high excess air ratio was traditionally applied to the burning zone in the incinerator. However, from viewpoints of heat recovery efficiency and flue gas treatment, low excess air ratio at high temperature has been becoming more popular for the waste incinerator year by year. Meanwhile, technologies for NOx emission control should be stricter since high temperature and flame instability under low excess air incineration conditions intend to extend NOx formation. In this study, initial pyrolysis behaviors of wastes in their incineration processes were analyzed to investigate their contributions to NOx formations.

Hot Corrosion Behavior of Cold-Sprayed Ni-50Cr Coating in an Incinerator Environment at 900 °C

In the present study, 50%Ni-50%Cr coating was developed on Superni 75 superalloy by a novel and facile cold-spray coating deposition technique. Dense, adhered, and oxide-free cold-sprayed coating was obtained in this study. This coating effectively provided corrosion protection to the substrate in real service incinerator conditions at 900 °C. The corrosion rate of the coated alloy was 0.47 mm/year, compared with 1.04 mm/year for bare alloy. This study indicates that the cold-spray process is an effective alternative for depositing high-temperature corrosion-resistant coatings.

Pilot-scale incineration of wastes with high content of chlorinated and non-halogenated organophosphorus flame retardants used as alternatives for PBDEs

Chlorinated and non-halogenated organophosphorus flame retardants (OPFRs) including tris(2-chloroisopropyl) phosphate (TCIPP), diethylene glycol bis(di(2-chloroisopropyl) phosphate) (DEG-BDCIPP), triphenyl phosphate (TPHP), and bisphenol A bis(diphenyl phosphate) (BPA-BDPP) have been used increasingly as alternatives to polybrominated diphenyl ethers and other brominated flame retardants. For this study, five batches of incineration experiments of wastes containing approximately 1% of TCIPP, DEG-BDCIPP, TPHP, and BPA-BDPP were conducted using a pilot-scale incinerator. Destruction and emission behaviors of OPFRs were investigated along with the effects on behaviors of unintentional persistent organic pollutants (POPs) such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (dl-PCBs), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), and pentachlorophenol (PCP). Incineration conditions were chosen according to current regulations for waste incinerators in Japan and UNEP. The OPFRs in the input materials were mainly destroyed in the primary combustion with destruction efficiencies greater than 99.999%. Concentrations of the OPFRs in the exhaust gases and ash were, respectively, <0.01–0.048μgm−3 and <0.5–68μgkg−1. Almost all of the total phosphorus in the input materials was partitioned into the ash, but less into final exit gases, indicating negligible emissions of volatile phosphorus compounds during incineration. Inputs of chlorinated OPFRs did not affect the formation markedly. Destruction and emission behaviors of unintentional POPs were investigated. Emissions of such POPs in exhaust gases and the ash were lower than the Japanese and international standards. Results show that even in wastes with high contents of chlorinated and non-halogenated OPFRs, waste incineration by the current regulations for the waste incinerators can control environmental emissions of OPFRs and unintentional POPs. Incineration is regarded as a best available technology (BAT) for waste management systems.

Study of the heavy metals residual in the incineration slag of textile dyeing sludge

The effects of various incineration conditions on the residual ratios of Cu, Cr, Cd, Pb, Ni and Zn in the slag of textile dyeing sludge were investigated. The results indicated that higher temperatures (1000–1100°C) were conducive to the solidification of Cu, Ni and Zn in the slag and that a lower temperature (700°C) was conducive to the solidification of Cr, Cd and Pb. The residual ratios of Cu, Cr, Cd and Ni exhibited similar tendencies as the residence time increased, but Pb exhibited a negative correlation. The residual ratios of Cu, Cr, Ni and Zn were relatively stable as the moisture increased except for those of Cd and Pb. The residual ratios of Cr, Zn, Pb and Cd increased as the CaO dosage increased, but Cu exhibited a negative correlation. For XRD analysis, a higher temperature and the CaO additive had a positive effect on the crystallization of heavy metals during incineration.

Emission of greenhouse gases from controlled incineration of cattle manure

Greenhouse gas emission is a potential limiting factor in livestock farming development. While incineration is one approach to minimize livestock manure, there are concerns about significant levels of nitrogen and organic compounds in manure as potential sources of greenhouse gas emissions (N 2O and CH 4). In this study, the effects of various incineration conditions, such as the furnace temperature and air ratio on N 2O and CH 4 formation behaviour, of cattle manure (as a representative livestock manure) were investigated in a pilot rotary kiln furnace. The results revealed that N 2O emissions decreased with increasing temperature and decreasing air ratio. In addition, CH 4 emissions tended to be high above 800 °C at a low air ratio. The emission factors for N 2O and CH 4 under the general conditions (combustion temperature of 800–850 °C and air ratio of 1.4) were determined to be 1.9–6.0% g-N 2O -N/g-N and 0.0046–0.26% g-CH 4/g -burning object, respectively. The emission factor for CH 4 differed slightly from the published values between 0.16 and 0.38% g-CH 4/g -burning object. However, the emission factor for N 2O was much higher than the currently accepted value of 0.7% g-N 2O -N/g-N and, therefore, it is necessary to revise the N 2O emission factor for the incineration of livestock manure.

Hydrodynamics of a multistage wet scrubber incineration conditions

The objective of the study was to determine the hydrodynamics of the two stage counter-current cascade wet scrubbers used during incineration of medical waste. The dependence of the hydrodynamics on two main variables was studied: Inlet air flow rate and inlet liquid flow rate. This study introduces a new wet scrubber operating features, which are liquid accumulation, together with a detailed analysis of liquid-to-gas ratio and pressure drops. Liquid accumulation at the base of each scrubber helps to prevent the gas from short circuiting to the scrubber solution feed tanks. It was observed that liquid accumulation increases linearly with inlet scrubbing liquid flow rate beyond 0.2 L/s in the absence of flue gas flow. When flue gas is flowing into multistage wet scrubber the accumulation level increases abruptly starting from inlet scrubbing liquid of 0.45 L/s and stabilizes at accumulation level of 0.1 m beyond 0.75 L/s. Increasing the flue gas flow rate increases the minimum inlet scrubbing liquid flow rate at which initial accumulation was observed. The outlet scrubbing solution flow rate and liquid accumulation in the bottom of the scrubber increase as the inlet liquid flow rate increases. Beyond inlet liquid flow rate of 0.75 L/s, the outlet liquid flow rate does not increase any more, the wet scrubber enters flooding range, whereby, the volume of accumulated liquid increases faster with inlet scrubbing liquid flow rate. The maximum liquid-to-gas ratio was observed to be 1.9 L/m3 and the minimum liquid-to-gas ratio was 0.1 L/m3. Based on liquid accumulation and minimum flooding conditions, the operating liquid-to-gas ratio was recommended to be 0.6 to 1.9 L/m3, while the allowable inlet liquid flow rate ranged between 0.45 and 0.75 L/s, giving a constant accumulation of scrubbing liquid in the wet scrubber. The pressure drop across the wet scrubber remained constant at lower flow rate and increased linearly beyond Ug = 5 m/s. The maximum pressure drop of the multistage wet scrubber was 75 kPa. Key words: Wet scrubber, liquid accumulation, flooding, liquid-to-gas ratio, incineration, pressure drop

Fixation and partitioning of heavy metals in slag after incineration of sewage sludge

Fixation of heavy metals in the slag produced during incineration of sewage sludge will reduce emission of the metals to the atmosphere and make the incineration process more environmentally friendly. The effects of incineration conditions (incineration temperature 500–1100°C, furnace residence time 0–60min, mass fraction of water in the sludge 0–75%) on the fixation rates and species partitioning of Cd, Pb, Cr, Cu, Zn, Mn and Ni in slag were investigated. When the incineration temperature was increased from 500 to 1100°C, the fixation rate of Cd decreased from 87% to 49%, while the fixation rates of Cu and Mn were stable. The maximum fixation rates for Pb and Zn and for Ni and Cr were reached at 900 and 1100°C, respectively. The fixation rates of Cu, Ni, Cd, Cr and Zn decreased as the residence time increased. With a 20min residence time, the fixation rates of Pb and Mn were low. The maximum fixation rates of Ni, Mn, Zn, Cu and Cr were achieved when the mass fraction of water in the sludge was 55%. The fixation rate of Cd decreased as the water mass fraction increased, while the fixation rate of Pb increased. Partitioning analysis of the metals contained in the slag showed that increasing the incineration temperature and residence time promoted complete oxidation of the metals. This reduced the non-residual fractions of the metals, which would lower the bioavailability of the metals. The mass fraction of water in the sludge had little effect on the partitioning of the metals. Correlation analysis indicated that the fixation rates of heavy metals in the sludge and the forms of heavy metals in the incinerator slag could be controlled by optimization of the incineration conditions. These results show how the bioavailability of the metals can be reduced for environmentally friendly disposal of the incinerator slag.

Activity and characterization of Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts for the SCR of NO with CO in the presence of SO 2 and HCl

SO 2 and HCl are major pollutants emitted from waste incineration processes. Both pollutants are difficult to remove completely and can enter the catalytic reactor. In this work, the effects of SO 2 and HCl on the performance of Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts for NO removal were investigated in simulated waste incineration conditions. The characterizations of the catalysts were analyzed by BET, SEM/EDS, XRD, and ESCA. Experimental results indicated the 1%Rh/Al 2O 3 catalyst was significantly deactivated for NO and CO conversions when SO 2 and HCl coexisted in the flue gas. The addition of between 2 and 10 wt.% Na promoted the activity of the 1%Rh/Al 2O 3 catalyst for NO removal, but decreased the CO oxidation and BET surface area. The catalytic activity for NO removal was inhibited by HCl as a result of the formation of RhCl 3. Adding Na to the Rh/Al 2O 3 catalyst decreased the inhibition of SO 2 because of the formation of Na 2SO 4, which was observed in the XRD and ESCA analyses. SEM mapping/EDS showed that more S was residual on the surface of the Rh–Na/Al 2O 3 catalyst than Cl.

Optimum production conditions for reactive rice husk ash

Addition of pozzolanic admixtures generally enhances the performance of concrete and in particular the durability. If rice husk ash (RHA) is incinerated in controlled conditions, it can exhibit high pozzolanicity. Significant amount of work has already been reported on the production methodologies of reactive RHA. However, the optimum conditions which will result in highly reactive amorphous ash with minimum production energy have not yet been established. In the present experimental work, RHA samples are produced under various conditions of incineration using laboratory box furnace. Energy consumption has been examined in this study. Reactivity of ash has been established by various techniques, such as X-ray diffraction (XRD), scanning electron microscopic study (SEM), analytical method and conductometric test. RHA-OPC reactivity has also been studied in this work. Based on the experimental investigations on fineness, amorphous silica content, energy consumption and reactivity of ash, the optimum production conditions of reactive RHA have been identified.

Effects of oxygen and hydrogen chloride on NO removal efficiency by Rh/Al 2O 3 and Rh–Na/Al 2O 3 catalysts

The influences of oxygen, hydrogen chloride, and sodium modification on the activity of the Rh/Al 2O 3 catalyst for NO removal were investigated in simulated waste incineration conditions. The characterizations of the catalysts were analyzed by SEM/EDS, XRD, and ESCA. Experimental results indicated that the Rh/Al 2O 3 catalyst has high stability and activity for NO removal over a range of 0–20% O 2. The addition of Na promoted the activity and N 2 selectivity of the Rh/Al 2O 3 catalyst, but an increase in NO 2 selectivity was observed when oxygen concentration and reaction time increased. The Rh/Al 2O 3 catalyst gradually deactivated on both NO and CO conversions when HCl concentration increased to 500 ppm because of the formation of RhCl 3. The Rh–Na/Al 2O 3 catalyst has a low activity for NO conversion, but 100% CO conversion still remained even though 500 ppm HCl was contained in the feed gas. The Na added to the Rh/Al 2O 3 catalyst can react with HCl to form NaCl, resulting in a suppressed deactivation for Rh active sites. Low HCl concentrations do not affect NO 2 selectivity of the Rh/Al 2O 3 catalyst but do decrease that of the Rh–Na/Al 2O 3 catalyst.

Distribution of heavy metals in an incineration system of solid wastes in the Three-Gorges region of the Yangtze River

On the basis of investigations on the composition and contents of heavy metals in the domestic refuse in the Three-Gorges region of the Yangtze River, in combination with the experimental results, this paper deals with the distribution rule of heavy metals in the various compartments of an incineration system: leachate pool, fly ash and residue. It is concluded that in the leachate pool heavy metals should not be neglectable since about 30% of Pb and 10% of Cr are leached here; in the incineration system, above 74% of Cr, As and Pb exists in residue; above 96% of Hg exists in fly ash and the contents of Cd in fly ash are close to those of residue. It is also concluded that the physical conditions of incineration have a significant influence on the distribution of heavy metals in the incineration system.

Capture of Dioxins by Ionic Liquids

Dioxins are highly toxic compounds that mainly originate from incineration and combustion sources. In this work, a new, simple, and efficient approach for the absorption of dioxins from gaseous streams using thermally stable ionic liquids is proposed. The absorption process of nonchlorinated and chlorinated dibenzo-p-dioxin compounds was studied in the temperature range 100-200 degrees C. Imidazolium-, ammonium-, and guanidinium-based ionic liquids were designed for this specific purpose. It was observed that imidazolium cations having long alkyl side chains exhibit the highest absorption capacities, whereas the anion dicyanoamide [DCA] possesses higher absorption capacity than other anions studied. In a typical experiment, it was found that the ionic liquid 1-n-octyl-3-methyl imidazolium dicyanoamide [C8mim][DCA] can absorb more than 14% by weight of dibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin, and 1,2,3,4-tetrachlorodibenzo-p-dioxin from a gaseous stream. A process for desorption of dioxins from the ionic liquid was tested, revealing that complete desorption can be achieved under a high vacuum. Additionally, the feasibility ofthe process was examined by carrying out experiments under real operating conditions of incineration and combustion processes. The success of the method heavily relies upon the design and selection of specific ionic liquids having enhanced affinity for the aromatic compound functionality present in dioxins and, simultaneously, possessing extremely low volatility and high chemical and thermal stability.

Safe disposal of toxic chrome buffing dust generated from leather industries

The high concentration of trivalent chromium along with organic/inorganic compounds in chrome buffing dust (CBD), the solid waste discharged from leather industries, causes severe groundwater contamination on land co-disposal and chronic air pollution during thermal incineration. In the present investigation, CBD was subjected to starved air incineration (SAI) at 800 °C in a thermal incinerator under different flow rates of oxygen to optimize the oxygen required to incinerate the organic compounds and simultaneously preventing the conversion of Cr 3+ to Cr 6+. The energy audit of SAI of buffing dust under the external supply of oxygen was carried out under different incineration conditions. The bottom ash from SAI was effectively solidified/stabilized using Portland cement and fine aggregate. The solidified blocks were tested for unconfined compressive strength and heavy metal leaching. Unconfined compressive strength of the blocks was in the range of 120–180 kg/cm 2. The stabilization of chromium(III) in the cement gel matrix was confirmed using Scanning Electron Microscopy SEM, Electron Paramagnetic Resonance spectroscopy (EPR) and X-ray diffraction spectroscopy (XRD). Leachability studies through TCLP on solidified blocks were carried out to determine the degree of leaching of chromium and organic compounds (expressed as COD) under standard conditions.

Thermal degradation of fluorotelomer treated articles and related materials

This study reports the first known studies to investigate the thermal degradation of a polyester/cellulose fabric substrate (“article”) treated with a fluorotelomer-based acrylic polymer under laboratory conditions conservatively representing typical combustion conditions of time, temperature, and excess air level in a municipal incinerator, with an average temperature of 1000 °C or greater over approximately 2 s residence time. The results demonstrate that the polyester/cellulose fabric treated with a fluorotelomer-based acrylic polymer is destroyed and no detectable amount of perfluorooctanoic acid (PFOA) is formed under typical municipal incineration conditions. Therefore, textiles and paper treated with such a fluorotelomer-based acrylic polymer disposed of in municipal waste and incinerated are expected to be destroyed and not be a significant source of PFOA in the environment.

NO x formation from ammonia, hydrogen cyanide, pyrrole, and caprolactam under incinerator conditions

The oxidation of NH 3, HCN, pyrrole, and caprolactam has been investigated under incinerator conditions. The residence time resolved measurements have been conducted within a ceramic plug flow reactor built up in semi-technical scale. The experiments cover a temperature range from 1100 to 1350 K, and the air equivalence ratio varies between 0.93 and 1.5. A very important aspect is the presence of H 2O and CH 4 under these conditions. In the temperature range investigated, water and methane have an essential influence on the levels of the important radicals H, O, OH, and HO 2 and, thereby, affect the reaction rates of the reaction system. The measurements for the oxidation of ammonia in the presence of methane show a characteristic conversion of ammonia to hydrogen cyanide of about 10% of the initial NH 3 content, occurring at fuel rich and fuel lean conditions. The only reaction path for the generation of HCN in such an extent proceeds via methylamine arising from the reaction of CH 3 with NH 2. Furthermore, with growing temperature a distinct increase in the NO emissions has been observed, with reaction NO + NH 2 ⇔ N 2 + H 2O playing a key role in the NO removal. The experimental concentration profiles have been simulated using a detailed mechanism from the literature with substantial modifications. The kinetic model is able to predict all characteristics of the experiments very well. The experiments for the decomposition of pyrrole and caprolactam reveal that HCN is formed as intermediate species in very high concentrations. The hydrogen cyanide is then partially oxidized to NO. The destruction of pyrrole has been simulated with the modified mechanism for NH 3 and HCN oxidation, extended by a modified model for pyrrole decomposition from the literature. The agreement of experiments and simulations is very good. For the modelling of the destruction of caprolactam, a new mechanism has been derived that reproduces the experimental results very well.

Characteristics of major dioxin/furan congeners in melted slag of ash from municipal solid waste incinerators

Polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in slag of fly ash from three municipal solid waste (MSW) incinerators were analyzed to observe any changes in characteristics and distribution of their congeners by melting process. Actual concentration and Toxic Equivalent (TEQ) concentration profiles of 17 major congeners of PCDDs/PCDFs for gas, fly ash and melted slag were compared. The distributions of PCDDs/PCDFs in different streams macroscopically showed similarities with the generally known profiles for emission gas from a municipal waste incinerator. The total concentrations of PCDDs/PCDFs in off-gas and fly ash have been known to be a function of incineration conditions and of air pollution control device utilization; however, their normalized distributions were independent of such conditions. The concentrations of PCDDs/PCDFs in the melted slag of fly ash were not related to the concentrations of PCDDs/PCDFs congeners in fly ash but were rather a function of the melting furnace type and operation. The total amount of PCDDs/PCDFs in the melted slag of fly ash contained almost 150–27,000 times less dioxin than that in fly ash, however, the TEQ of dioxin in the slag was reduced by 435–43,500 times, which could enable them to be utilized as recycled construction materials. In normalized TEQ concentration profiles of 17 congeners of PCDDs/PCDFs, the ratio of PCDFs to PCDDs changed from 1.32 to 2.19 by melting, which showed relatively higher portion of furans left in melted slag than those in fly ash. By comparing reduction ratios of different congeners, PCDDs (dioxins) were relatively easier to destruct than PCDFs (furans) during melting process. The most difficult congener to destruct could be octa-chlorinated dibenzofuran (OCDF) among major congeners. For slag cooling methods, dioxin concentration in TEQ of slow cooled slag by air was four times higher than that of fast cooled slag by water. Thus cooling by water is more appropriate with the added beneficial effect of producing granules/particles, which can be utilized as roadbed materials.

Kinetics of HCl emission from inorganic chlorides in simulated municipal wastes incineration conditions

Sulfation of inorganic chlorides (KCl, CaCl 2 and NaCl) of mean particles size 75–125 μ m was done in a lab-scale tubular reactor. The reactor was supplied with a mixed gas consisting of SO 2 :0.3–1.3 vol%, O 2 :2.5–15 vol% and H 2 O:5–20 vol% in the temperature range 623–1123 K. The rates of HCl emission from the particles samples were measured and compared. It was found that at 1023 K, an HCl of about 8000 ppm was emitted from CaCl 2 and this emission concentration was more than 3 times as high as those from NaCl and KCl. The reaction kinetic parameters such as rate constants and reaction orders with respect to SO 2 , O 2 and H 2 O partial pressures were determined for the sulfation of NaCl, KCl and CaCl 2 . The rate of HCl emission from KCl, CaCl 2 and NaCl became increasingly high when the temperature was raised above 923 K and depend on SO 2 , O 2 , and H 2 O partial pressures. It was considered that an increase in the rate of HCl emission from the inorganic chlorides at temperatures above 923 K was caused by a change in the reaction mode from a gas–solid to a gas–liquid and/or a gas phase reaction, owing to a partial melting and/or volatilization of the inorganic chlorides.

Analyses of incinerated ash of paper sludge: comparison with incinerated ash of municipal solid waste

Fourteen paper sludge samples were collected at seven representative pulp and paper mills in Japan, and were analyzed to obtain fundamental data on the reuse of paper sludge-incinerated ash as papermaking material. For comparison, incinerated ashes of municipal solid waste (MSW) were collected at MSW incineration plants in Tokyo, and analyzed by similar methods. Elementary and X-ray diffraction analyses revealed that the predominant elements in paper sludge samples are calcium, silicon, aluminum, and magnesium, which are derived from paper fillers, coating pigments, and coagulants used in papermaking and process effluent treatments. Similar results were also obtained for the MSW-incinerated ashes, indicating that major components in the collected MSW are paper-related materials. Incineration of paper sludge around 800°C is recommended in terms of high brightness of the incinerated ash, which has about 60% brightness. Calcium, silicon, and aluminum components in the paper sludge are fused or sintered by heating. Although paper-sludge-incinerated ashes have irregular shape and large particle size distributions, they may be used as papermaking materials after pulverization using a ball mill. The MSW-incinerated ashes have 5%–30% water-soluble fractions and low brightness, and thus incineration conditions must be changed to reuse the MSW-incinerated ash as a papermaking material.