Mechanical strength changes of combustible municipal solid waste components during their early pyrolysis stage and mechanism analysis.

Implementation of municipal solid waste (MSW) source segregation leads to a more convenient recycle of combustible MSW components. Textiles, plastics and papers are commonly available combustible components in MSW. Their shredding is conducive to resources recovery. But these components usually have high tensile strengths and are difficult to shred. To understand their mechanical strength changes in their early pyrolysis stage will help to address this problem. In this study, a universal electronic testing machine was used to determine the breaking strengths of the materials including cotton towel, polyethylene glycol terephthalate (PET), ivory board (IB), kraft paper (KP) and wool scarf in the temperature range of 30-250°C under N2 atmosphere, and the mechanisms of their strength changes were explored. The reaction force field molecular dynamics (ReaxFF-MD) simulation was used to explain the decomposition behaviours of different sugar groups of hemicellulose in cotton and paper and the change of van der Waals energy of wool during their early pyrolysis stages. The results showed that breaking strengths of all the combustible MSW components reduced as the temperature increased. The breaking strength of PET was found to have the highest descent rate with increasing temperature, then the descent rates of wool and cotton came as the second and third, respectively. Compared with cotton, the breaking strengths of KP and IB decreased more slowly. As the temperature increased, the breaking strength of cotton reduced mainly due to the decomposition of the glucuronic acid in hemicellulose, and the reduction was characterized by CO2 release. The breaking strength reduction of PET was caused by its molecular chain being relaxed. The breaking strength reduction of wool was firstly caused by the decrease in the van der Waals energy between its molecules, and then caused by molecular chain breaking. In addition, in order to understand the influence of material size on the breaking strength change during thermal treatment, the breaking strengths of cotton yarn bundles were correlated with their yarn number and temperature. This study lays the foundation for understanding changes in mechanical strengths of combustible MSW components during their early pyrolysis stage.

Prediction of MSW pyrolysis products based on a deep artificial neural network.

Pyrolysis is a promising method for recovering resources and energy products from municipal solid waste (MSW). Predicting MSW pyrolysis products is crucial for establishing an efficient pyrolysis system for resource recovery. In this study, a database was established based on MySQL to record relevant information on MSW pyrolysis, which includes the MSW ultimate analysis results, proximate analysis results, parameters of pyrolysis operation and yields of pyrolysis products, etc. Based on the database and with help of a deep artificial neural network (ANN) which contains 10 hidden layers, a prediction model was successfully established to predict the yield of char, liquid and gas products from MSW pyrolysis. The results showed that the coefficients of determination for predicting the yields of char, liquid and gas from the MSW pyrolysis are 0.841, 0.84, and 0.85, respectively; these values demonstrate an accuracy comparable to that achieved for product prediction from single biomass, indicating a successful model performance. The results also show that ash content and temperature are the most important input factors influencing the outputs, namely, yields of char, liquid and gas. The results of this study can help to achieve a more efficient design of the pyrolysis system and improve the recovery of the desired pyrolysis products.

Adsorption of pyrolysis oil model compound (phenol) with plasma-modified hydro-chars and mechanism exploration.

Phenol is one of the important ingredients of pyrolysis oil, contributing to the high biotoxicity of pyrolysis oil. To promote the degradation and conversion of phenol during anaerobic digestion, cheap hydro-chars with high phenol adsorption capacity were produced. The phenol adsorption capabilities of the plain hydro-char, plasma modified hydro-char at 25 °C (HC-NH3-P-25) and 500 °C (HC-NH3-P-500) were evaluated, and their adsorption kinetics and thermodynamics were explored. Experimental results indicate that the phenol adsorption capability of HC-NH3-P-500 was the highest. The phenol adsorption kinetics of all samples followed the pseudo-second-order equation and interparticle diffusion model, indicating that the adsorption rate of phenol was controlled by interparticle diffusion and chemistry adsorption simultaneously. By DFT calculations, π-π stacking and hydrogen bond are the main interactions for phenol adsorption. It was observed that an enriched graphite N content decreased the average vertical distance between hydro-chars and phenol in π-π stacking complex, from 3.5120 to 3.4532 Å, causing an increase in the negative adsorption energy between phenol and hydro-char from 13.9330 to 23.4181 kJ/mol. For hydrogen bond complex, the average vertical distance decreased from 3.4885 to 3.3386 Å due to the increase in graphite N content; causing the corresponding negative adsorption energy increased from 19.0233 to 19.9517 kJ/mol. Additionally, the presence of graphite N in the hydro-char created a positive diffusion region and enhanced the electron density between hydro-char and phenol. Analyses suggest that enriched graphite N contributed to the adsorption complex stability, resulting in an improved phenol adsorption capacity.

Numerical simulation of heat transfer properties of large-sized biomass particles during pyrolysis process.

During the pyrolysis process of large particles, the conduction between particles cannot be ignored. In the present work, a numerical simulation model for the pyrolysis of biomass particles was established, which takes into account the conduction within the particles. Based on this model, the temperature distribution inside the particle during the pyrolysis process was determined and the effects of particle size, moisture content, and gas velocity on heat transfer characteristics were analyzed. The results showed that the temperatures at different positions of the particles along the inflow direction were quite different, and the maximum temperature difference inside the particles was about 146.7 K for a particle diameter of 10 mm and a velocity of 0.2 m/s. During the pyrolysis process of biomass particles, there were two peaks of Nusselt number. The increase of moisture content prolonged the pyrolysis time. The pyrolysis. time of particles with moisture content of 15 % was about 1.5 times longer than that of dry particles when the particle diameter was 10 mm. Increasing the particle size decreased the difference between the two peaks and increased the time interval between the two peaks. Increasing the gas velocity can improve the heat transfer, but the effect of too high gas velocity on improving the heat transfer is limited. The present study is of great importance for a detailed understanding of the pyrolysis process of biomass particles.

MSW pyro-gasification using high-temperature CO2 as gasifying agent: Influence of contact mode between CO2, char and volatiles on final products.

The volatiles and char derived from municipal solid waste (MSW) pyrolysis can be catalytically reformed and gasified using high-temperature CO2 (HT-CO2) as gasifying agent and char as a catalyst simultaneously to obtain high quality synthesis gas, but the reactor's design for this purpose is still a question. In this research, the contact configuration between the HT-CO2, the volatile compounds, and the char from MSW pyrolysis were studied to understand the relevant reaction behaviors and to establish guidelines for the reactor's design. Three contact modes were designed, including: M1, where volatiles and HT-CO2 contact first, then contact the char; M2, where volatiles, CO2, and char contact simultaneously at the bottom of the char layer; and M3, where CO2 contacts with the char first, then the volatiles contact in the middle of the char layer. The temperature evolution in the char layer, the yields and properties of the resultant combustible gases, used char, and tar were investigated. Experimental results revealed that the contact mode significantly affected the levels of char gasification and volatiles' reforming. For M1, intense thermal cracking of volatiles occurred and 65.41% of the input heat of HT-CO2 was consumed for thermal cracking, resulting in substantial carbon deposition and limited energy transfer from char to the synthesis gas. While, the char contacting HT-CO2 firstly in M3 improved its catalytic activity, causing 73.33 % of the input heat utilized for gasification and reforming; as a result, the maximum synthesis gas yield of 0.71 Nm3/kgMSW and gas energy ratio of 76.3 % were obtained respectively in M3 with the lowest tar yield of 5.45 %; additionally, the used char corresponded to the highest specific surface area of 10.12 m2/g. Ultimately, M3 is constructive and recommended, and the findings of this study offer helpful guidance for the design of pyro-gasification reactors.

Ecological risk assessment of heavy metals in bottom ashes generated by small-scale thermal treatment furnaces for domestic waste in villages and towns of China.

Small-scale Solid Waste Thermal Treatment (SSWTT) is prevalent in remote Chinese locations. However, the ecological threats associated with heavy metals in resultant bottom ash remain undefined. This research study scrutinized such ash from eight differing sites, assessing heavy metal content, chemical form, and leaching toxicity. Most bottom ash samples met soil contamination standards for development land (GB36600-2018). However, levels of As, Cd, Cr, Cu, Ni, Pb, and Zn in some samples exceeded agricultural land standards GB15618-2018) by 1591%, 64,478%, 1880%, 3886%, 963%, 1110%, and 2011% respectively. Additionally, the As and Cd contents surpassed the construction land control limit value by 383% and 13% respectively. The mean values of the combined oxidizable and residual fraction (F3 + F4) for each heavy metal in all samples exceeded 65%, with Cr, Cu, Ni, and Pb reaching over 95%. All sample leaching concentrations, obtained via the HJ/T 299 procedure, were less than limits set by the identification standards for hazardous wastes (GB5085.3-2007). However, only the leaching concentrations of three samples via the leaching procedure HJ/T 300 met the "Solid Waste Landfill Pollution Control Standard" (GB 16889-2008). The results indicate that the location and type of SSWTT equipment play a crucial role in determining an appropriate solution for bottom ash management.

Atmospheric phthalate esters in a multi-function area of Hangzhou: Temporal variation, gas/particle phase distribution, and population exposure risk.

Phthalate esters (PAEs) are prevalent in both indoor and outdoor environments. However, there are relatively few studies on phthalate contamination in the air of multi-function areas. Experiments were conducted to analyze the concentrations of 14 distinct PAEs in outdoor air in the college town of Hangzhou throughout both the warm and cold seasons. Correlation and principal component analyses were performed to investigate the influence and source factors of PAEs. This study also focused on the relationship between the gas/particle partition coefficient Kp and temperature, as well as the application of the gas/particle partition model. The risk of exposure to PAEs via inhalation was predicted for four groups of the general population: toddlers, adolescents, adults, and older adults. The results indicated that the concentration levels of Σ14PAEs in outdoor air were 1573 ng/m3 in the gaseous phase and 126 ng/m3 in the particulate phase. Additionally, this study indicated three primary sources of PAEs: indoor diffuse sources, industrial emission sources, and building construction sources. The gas/particle partitioning of PAEs also revealed that low-molecular-weight PAEs are more prevalent in gas, whereas high-molecular-weight PAEs are more predominant in the particle phase. A health risk analysis revealed high estimations of daily intakes (EDI) for toddlers and adolescents and high lifetime average daily doses (LADD) for older adults. This study establishes a solid foundation for formulating scientific and effective air pollution control measures by analyzing the characteristics and assessing the health risks of PAEs.

Comparative study of carbon-deNOx process by different sewage sludge chars.

Sewage sludge char (SC) reduces NO to N2 at high temperatures thus acting as a potential reducing agent in flue gas cleaning systems. However, SC needs to be modified to enhance the carbon-deNOx performance. In this study, coal char (CC) and different types of SCs, i.e., original (SC-R), pyrolytic volatiles activated (SC-V) and KOH activated (SC-K), were compared in terms of their carbon-deNOx performance, including NO removal rate and secondary pollution discharged. The results showed that when the oxygen content in the flue gas was 5-6%, the carbon-deNOx efficiency of the three types of SCs was greater than 70%, which was higher than that of the CC. SC-V has lower emissions of CO and gaseous nitrogen-containing compounds (NH3, HNCO, HCN) among the three types of SCs. For the oxygen content of 8-11% in the flue gases, the NO conversion performance was found in the order of SC-K > SC-R > SC-V > CC. The physical and chemical characterization of activated carbon shows that pyrolytic-volatile activation increases the ratio of C-O and C=O functional groups on its surface of SC-V, which not only facilitates the chemisorption of NO but are also easily converted under high oxygen conditions. SC-V is found as a suitable reductant for carbon-deNOx within the temperature range of 300-350 °C.

Preparation of activated carbon from sewage sludge using green activator and its performance on dye wastewater treatment.

The remediation of dyes in wastewater using activated carbon produced from sewage sludge pyrolysis char (PYC) is an environmentally friendly and sustainable process. However, traditional activators can cause corrosion of the processing facility, thereby increasing the costs of waste disposal. Here, activated carbons were prepared from sewage sludge PYC, and the effects of activation conditions (different activators, temperature and time, and char:activator mass ratio) on their specific surface areas and adsorption of iodine and methylene blue (MB; model dye) were studied. The results showed that a value of 952 m2/g could be attained for the specific surface area and values of 882 and 162 mg/g for the adsorption of iodine and MB, respectively, by heating PYC with KHCO3 (PYC- KHCO3: 1:2 w/w) for 60 min at 800 ℃. Compared with activation by KOH, the adsorption of MB using PYC-KHCO3 was slightly lower but the yield was 13.7% higher. Optimization of the activation process using surface response modelling indicated that sensitivity of three key factors to the adsorption of iodine and MB followed the order: Mass ratio > temperature > time. Systematic investigation of the effects of time, pH and temperature on the removal of MB by the activated carbon revealed that adsorption conformed to the Langmuir model and pseudo-second-order kinetics. The proposed mechanisms of MB adsorption involved ion exchange, functional group complexation and physical/π-π interactions. This study provides a basis for the efficient remediation of dyes in wastewater using activated carbon prepared from sustainable sewage sludge PYC and green chemistry.

MSW pyrolysis volatiles' reforming by incineration fly ash for both pyrolysis products upgrading and fly ash stabilization.

The effective disposal of municipal solid wastes (MSW) and its incineration-derived fly ash (IFA), which contains large amounts of heavy metals (HMs) and chlorine (Cl), is an urgent task. In this study, IFA was used to reform MSW pyrolysis volatiles within 500-800 °C. The changes of reformed pyrolysis products, the migration characteristics of HMs and Cl between IFA and pyrolysis products were investigated. The results indicated that the O- and Cl-containing compounds in pyrolysis oil tended to decrease, light hydrocarbons and its calorific value increased accordingly after reforming; more CH4 and H2 gases were produced concurrently. The increase in reforming temperature enhanced these trends. The IFA absorbed Cl from volatiles during reforming, which reduced HCl in the gas product. The toxicity equivalent (TEQ) of PCDD/Fs in IFA decreased dramatically from 0.47 µg/kg to 0.0055 µg/kg after reforming at 500 °C, and it decreased with increasing reforming temperature. Some of the HMs' concentrations in the used IFAs increased, but their leaching capacity all decreased significantly at 800 °C except for Cr. The used IFA at 800 °C (IFA-800) corresponded to the lowest HMs leaching concentrations and could meet the landfill requirements; while the used IFA at 500 °C (IFA-500) corresponded to the maximum carbon deposition of 14.63 wt%, providing the energy source for its melting. Therefore 800 °C was recommended for harmless disposal of IFA, and 500 °C was better for a further melting of IFA., The contamination of pyrolysis liquid caused by inorganic Cl-containing compounds at 500 and 800 °C with much lower levels than the original. This study showed the hazardous properties of IFA can be dampened after interacting with MSW pyrolysis volatiles within the tested temperature range, and provided a good chance for the simultaneous disposal of IFA and recovery of high-quality MSW pyrolysis products.

Promotion of methane production and degradation of pyrolysis oil during its co-anaerobic digestion process via addition of N-doping hydro-chars.

Pyrolysis of wastes usually produces toxic pyrolysis oil (PO), which has complex ingredients, including benzene series and long-chain macromolecule organic pollutants. Co-anaerobic digestion (co-AD) can be an economic and high-efficiency method for PO degradation and recovery of methane simultaneously, but complete degradation of PO has not been achieved yet. Addition of a hydro-char in the process is beneficial to PO degradation and methane production. In this study, to further enhance the effectiveness of the hydro-char, nitrogen (N) was doped into the hydro-char by plasma modification in a NH3 atmosphere; and the effectiveness of the N-doped hydro-chars for promoting PO degradation and methane production during the co-AD process were evaluated. The experimental results indicated that all the hydro-chars can reduce the biotoxicity of the PO, improve its degradation during the co-AD process, and increase the methane yield. Compared with the plain hydro-char (HC), the hydro-chars modified at ambient temperature (HC-NH3-P-25) and at 500 °C (HC-NH3-P-500) can help achieving complete PO degradation and increasing the methane yield more effectively. The anaerobic digestor containing the HC-NH3-P-500 had the highest apparent methane yield (169.03 mLCH4/mLPO) and highest COD removal rate (79.5%). The nitrogen content, specific surface area, and electron transfer capability are found to be the key factors affecting PO degradation and methane yield; and the HC-NH3-P-500 had the highest N-doping, most specific surface area and electron transfer capability, explaining its best performance. The microbial communities of the digestate with the addition of the hydro-chars were founded to be richer with Clostridia and Methanosarcina, which could enhance the electron transfer between different microorganisms and contribute to the PO degradation.

Stabilizing Li-Rich Layered Cathode Materials Using a LiCoMnO4 Spinel Nanolayer for Li-Ion Batteries.

Lithium-rich cathodes have excess lithium in the transition metal layer and exhibit an extremely high specific capacity and good energy density. However, they still have some disadvantages. Here, we propose LiCoMnO4, a new nanolayer coating material with a spinel structure, to modify the surface of lithium cathode oxide (Li7/6Mn1/2Ni1/6Co1/6O2) with a layered structure. The designed cathode with nanolayer spinel coating delivers an excellent reversible capacity, outstanding rate capability, and superior cycling ability whilst exhibiting discharge capacities of 300, 275, 220, and 166 mAh g-1 at rates of 0.1 C at 2.0-4.8 V formation and 0.1, 1, and 5 C, respectively, between 2.0 and 4.6 V. The cycling ability and voltage fading at a high operational voltage of 4.9 V were also investigated, with results showing that the nanolayer spinel coating can depress the surface of the lithium cathode oxide layer, leading to phase transformation that enhances the electrochemical performance.

Municipal solid wastes pyro-gasification using high-temperature flue gas as heating resource and gasifying agent.

With the implementation of municipal solid wastes (MSW) source segregation collection policy, the combustible waste components are suitable for pyrolysis treatment to recover value-added energy such as gas or oil. In this research, the volatile compounds from MSW pyrolysis were reformed by the char obtained from the same process and the high-temperature flue gas (HTFG) of 1200 °C was supplying as heating resource and gasifying agent in a tailor-made experimental set-up. The final yields and properties of the syngas, char, and oil after reforming were investigated. Experimental studies showed that the composition of HTFG had a significant influence on the products. As the HTFG being CO2 and its flowrate increased from 0 to 4 L/min/(kgMSW), the energy share in the gas first increased from 8.29 to 15.1 MJ/(kgMSW) with a higher heat value (HHV) of 19.9 MJ/Nm3, then it decreased slightly with a further increase in the flowrate. However, as the HTFG was H2O or the model flue gas (consisting of CO2, H2O, O2 and N2), the higher flowrate always increased the energy share and cold gasification efficiency (CGE) in the gas products. Both CO2 and H2O participated the volatiles' reforming reactions and enhanced char gasification; while the volatiles' reforming inhibited char gasification. When the flowrate of the model flue gas increased from 0 to 12.04 L/min/(kgMSW), the oil and char yields decreased and the CGE increased to more than 75%, which was much higher than that from direct air gasification of MSW; moreover, the gas products had much higher HHVs. This research provides a guidance for producing high-quality syngas from the MSW.

Modification of hydro-chars by non-thermal plasma to enhance co-anaerobic digestion and degradation of sewage sludge pyrolysis oil.

The pyrolysis oil produced from the sewage sludge pyrolysis process is a complex admixture of organic substances, which is difficult to be degraded in a normal anaerobic digestion (AD) process. In this study, the hydro-chars produced at 200, 240, and 280 °C were modified by non-thermal plasma (NTP) and then they were used to promote pyrolysis oil degradation and biogas production in a co-AD digester. The experimental results revealed that after NTP modification, the specific surface areas of the hydro-chars produced at 200 °C (SW200+P) and 240 °C were increased from 28.0 to 39.3 m2g-1 and from 36.2 to 45.4 m2g-1, respectively. Their pore volumes also increased by more than 10%. The SW200+P hydro-char exhibited the highest chemical oxygen demand (COD) removal rate (60.49%) and the highest CH4 yield, which is 6.3 times of the digester with pyrolysis oil but without hydro-char addition (PO + CC). Additionally, the benzene series in the pyrolysis oil can be completely degraded in all digesters with the hydro-char addition. With addition of the SW200+P hydro-char, the Clostridia increased most significantly to become the predominant bacteria community at the class level, and the Methanosarcina became the predominant archaea community at the genus level, which contributed to the increased CH4 yield. The hydro-char addition also increased Dietzia and Cellulosimicrobium, which promoted the degradation of benzene series in the pyrolysis oil. The investigation results suggest that the NTP modification technique can be a potential solution to effectively utilize the hydro-char and help pyrolysis oil degradation via the co-AD process.

[Application of special acupoints for chronic gastritis in ancient literature of acupuncture and moxibustion].

The application of special acupoints for different primary symptoms of chronic gastritis in ancient literature of acupuncture and moxibustion was analyzed and summarized. With keywords, electronic and manual retrieval of ancient literature being performed to establish a database, the association rules were performed with SPSS Modeler 18. As a result, ① among all the 2243 items included, 109 items mentioned special acupoints (excluding those only mentioned crossing acupoint). The frequency of special acupoints was 2554 (71.7%), and the special acupoints on the spleen meridian, the stomach meridian, the conception vessel were frequently used. The frequency of five-shu point was highest, followed by front-mu points. ② The special acupoints for four main primary symptoms of chronic gastritis, "stomachache" "vomiting and regurgitation" "belching and acid regurgitation" and "epigastric fullness", included Zusanli (ST 36), Neiguan (PC 6), Zhongwan (CV 12), Gongsun (SP 4), Taibai (SP 3). In addition, the back-shu points were also selected to treat the primary symptoms other than "epigastric fullness". Zhangmen (LR 13) was added to treat "belching and acid regurgitation". The combination of Neiguan (PC 6) and Gongsun (SP 4) showed the strongest correlation; due to different primary symptoms, the combination had different emphasis.

Preparation of activated sewage sludge char for low temperature De-NOx and its CO emission inhibition.

Sewage sludge (SS) char can be potentially applied to De-NOx processes but it should be active enough and the relevant CO emissions should be controlled. In this paper activated SS chars have been prepared by using a simple KOH impregnation-carbonisation method and the activated chars are applied to remove NOx from flue gases within temperature range of 100-250 °C, acting as both reductants and catalysts. Special attention is paid to inhibiting CO emission in the process. Four reductive agents are adopted to check the catalytic effect of the activated SS chars. The results show that the activated SS chars (i.e. SC-KOHs) present a higher adsorption-reduction ability with much lower CO emission than that of non-activated SS chars (i.e. SC-Raws). SC-KOH produced at 800 °C (SC-KOH-800) shows obvious chemical adsorption behaviors, its adsorption capacity for NO is higher than 8.06 mg.L-1, superior to the coal-based activated carbon. Hydrazine hydrate is found to enhance De-NOx performance with SC-KOHs acting as catalysts, especially at higher temperatures. However, the De-NOx efficiency decreased when ammonia, urea and urea involved reductants were used. The physicochemical structure of the SS chars was characterized to show that the SC-KOHs are more porous with higher BET areas and pore volumes. Simultaneously, the SC-KOHs are crystallized to much lower extent, less graphitised, but have richer O-containing functional groups and zeolite structure on the surface when compared to the SC-Raws, which contributed to their high activities. Moreover, SC-KOH-800 can be recommended as the suitable adsorbent/catalyst for De-NOx within 100-250 °C.

Sewage sludge pyrolysis coupled with self-supplied steam reforming for high quality syngas production and the influence of initial moisture content.

A technology of sewage sludge (SS) pyrolysis coupled with self-supplied steam reforming of the volatile is developed to utilize the latent heat of the steam vapor released in the SS drying & pyrolysis process. An integrated reactor consisting of a vertical free-falling pyrolysis section and a horizontal screw-moved reforming section is designed for this purpose. The performance of the reactor shows that by changing the moving speed of the char in the reforming section, high quality syngas with an H2/CO ratio of 4.37 and a percentage of H2 + CO up to 66.58 vol% can be obtained at approximately 570-600 °C for the dry SS. There is an optimum moving speed of the screw for producing the highest volume of the syngas. A higher moving speed of the screw also results in a higher concentration of the aromatic compounds in the final pyrolysis oil. When the initial moisture content of SS increases from 0 to 65.50%, the H2/CO ratio and H2/CO2 ratio in the syngas increase from 4.37 to 30.87 and from 2.1 to 2.6 correspondingly, and the final oil yield decreases from 24.03 wt% to 14.16 wt%. Moreover, the total energy recovery efficiency decreases from 88.85% to 61.92%, while the energy portion of syngas shows a peak of 44.18% of the total energy input when the initial moisture content is 41.26%. The integrated reactor also provides a good opportunity for adding a catalyst such as dolomite to make the process more effective. The technology developed in this paper provides an approach to deal with SS with a relatively high moisture content.

Chlorine removal from MSWI fly ash by thermal treatment: Effects of iron/aluminum additives.

The high content of alkali chlorides in municipal solid waste incineration (MSWI) fly ash limit its resource reuse due to the potential environmental risks. In this paper, with superheated steam as the gasifying agent and inducer, chlorides in fly ash were removed by thermal treatment within a moderate temperature range. Thermal treatment experiments were performed under different conditions: temperature (500-800°C), steam addition (mass ratio of steam to fly ash = 0.25-1) and residence time (0.5-3 hr). Iron and aluminum powders were added to fly ash to improve the chlorine removal efficiency. Water-soluble chlorides included NaCl and KCl, and insoluble chlorides mainly included Ca(OH)Cl. The heating process with the addition of water steam was more efficient than that without steam in terms of the removal performance of water-soluble chlorides. The removal efficiency of soluble chlorides reached 75.25% for a mass ratio of 1:1 after 1-hr thermal treatment at 700°C. When the residence time was increased above 1 hr, the total dechlorination efficiency was not increased dramatically. Moreover, adding iron and aluminum powder into the fly ash improved the removal of water-insoluble chlorides, and the total dechlorination efficiency was increased by 11.41%-16.64%.

Upgrading gas and oil products of the municipal solid waste pyrolysis process by exploiting in-situ interactions between the volatile compounds and the char.

The gas and oil product derived from municipal solid waste (MSW) pyrolysis was upgraded by utilizing the interaction between the volatile compounds and the char and the mechanism involved is explored. The influences of operation parameters, including interaction temperature, char/volatiles mass ratio (C/V) and gas hourly space velocity (GHSV) of the volatiles on the distribution and property of the upgraded products were investigated. The results showed that the higher interaction temperature, higher C/V and lower GHSV favored the conversion of condensable volatiles into gas products, thus increasing the gas yield in the outlet stream. The highest gas yield (44.14 wt%) was obtained at 700 °C with the natural C/V ratio (0.8) and GHSV, which was twice of the gas yield in the volatiles. The chemical energy portion of gas increased to 8065 kJ/kgMSW from 3209 kJ/kgMSW at this condition. Syngas with H2/CO molar ratio of around 2 can be obtained at 700 °C with C/V ratio of 0.8 or at 600 °C with higher C/V ratios (C/V = 1.5-2.2). Oxygenates and acidity of the reformed oil products decreased; but monoaromatics and light polyaromatics concentration increased greatly. Heavy polycyclic aromatic hydrocarbons (PAHs) in the liquid products were degraded after volatiles/hot char interaction. Suitable conditions can be varied and recommended for obtaining different desired high-quality products based on this process.

Pyrolysis of the mixture of MSWI fly ash and sewage sludge for co-disposal: Effect of ferrous/ferric sulfate additives.

Co-pyrolysis with sewage sludge was proved to be an efficient pre-treatment for sanitary landfill of municipal solid waste incineration (MSWI) fly ash (FA). In this study, to improve the stabilization effect of heavy metals, mixed ferrous/ferric sulfate was added into the FA/SS mixture before pyrolysis. To examine the feasibility of the landfill of co-pyrolysis char, toxicity characteristic leaching procedure (HJ/T300) was conducted. In addition, physio-chemical characteristics of char were also tested to explain the stability of heavy metals, including the speciation, mineralogical composition and the morphological features of them. The results indicated that within the range that the obtained char could meet the standard for landfill (GB16889-2008), the appropriate addition of mixed ferrous/ferric sulfates benefit to raising the FA ratio in the FA/SS mixture. The maximum ratio of 67 wt% is achieved when the additive was 1.5 wt% of dried SS (based on iron element) and the pyrolysis temperature was 500 °C.