Effect of temperature tuning on the aerosol acoustic aggregation process

Diesel exhaust aerosols（DEAs） can absorb and accumulate toxic metal particulates and bacteria suspended in the atmospheric environment, which impact human health and the environment.The use of acoustic standing waves（ASWs） to aggregate DEA is currently considered to be an efficient particle removal method; however, study of the effect of different temperatures on the acoustic aggregation process is scarce. To explore the method and technology to regulate and optimize the aerosol aggregation process through temperature tuning, an acoustic apparatus integrated with a temperature regulation function was constructed. Using this apparatus, the effect of different characteristic temperatures（CTs） on the aerosol aggregation process was investigated experimentally in the ASW environment. Under constant conditions of acoustic frequency 1.286 kHz, voltage amplitude 17 V and input electric power 16.7 W, the study concentrated on temperature effects on the aggregation process in the CT range of 58–72℃. The DEA opacity was used. The results demonstrate that the aggregation process is quite sensitive to the CT, and that the optimal DEA aggregation can be achieved at 66℃. The aggregated particles of 68.17 μm are composed of small nanoparticles of 13.34–62.15 nm. At CTs higher and lower than 66℃, the apparatus in non-resonance mode reduces the DEA aggregation level. For other instruments, the method for obtaining the optimum temperature for acoustic agglomeration is universal. This preliminary demonstration shows that the use of acoustic technology to regulate the aerosol aggregation process through tuning the operating temperature is feasible and convenient.

Effect of biomass addition on the surface and adsorption characterization of carbon-based adsorbents from sewage sludge

Sewage sludge with the additive corn cob was used as prescusor to prepare sludge-based carbon adsorbents by pyrolysis method. And then, the carbonizated products were activated with potassium hydroxide. The mixing ratio of the corn cob to sewage sludge was investigated. The surface area and pore size distribution, elemental composition, surface chemistry structure and the surface physical morphology were determined and compared. The results demonstrated that the addition of corn cob into the sewage sludge sample could effectively improve the surface area （from 287 to 591 m 2 /g） and the microporosity （from 5% to 48%） of the carbon based adsorbent, thus enhancing the adsorption behavior. The sulfur dioxide adsorption capacity was measured according to breakthrough test. It was found that the sulfur dioxide adsorption capacity of the adsorbents was obviously enhanced after the addition of the corn cob. It is presumed that not only highly porous adsorbents, but also a high metallic content of these materials are required to achieve good performances.

Combustion characteristics and kinetics of bio-oil

The combustion characteristics of bio-oils derived from rice husk and corn were studied by thermogravimetry analysis.According to the thermo-gravimetry(TG),differential thermogravimetry(DTG)and differential thermal analysis(DTA)curves of bio-oils in air and nitrogen atmosphere,we analyzed the combustion characteristics of different kinds of bio-oils in different atmospheres and worked out the combustion kinetics parameters of the bio-oil,providing reliable base data for the burningofbio-oil.Thethermogravimetry indicatedthat the combustion process of bio-oil was divided into three stages.At the same time,the combustion process can be described by different order reaction models,and with the method of Coats-Redfern,the activation energy and frequency factor of different kinds of bio-oils were obtained.

Immigration,transformation,and emission control of sulfur and nitrogen during gasification of MSW:Fundamental and engineering review

This paper proposes a comprehensive summary and analysis of an important issue during municipal solid waste(MSW)gasification-sulfur and nitrogen pollution.It provides an overview of the fundamentals of MSW and the basic aspects of nitrogen and sulfur elements.Their characteristics of immigration,transformation and distribution during gasification with control solutions in realized or potential engineering are also concluded.The analysis indicates that the complete scenario of the occurrence form of sulfur and nitrogen elements in MSW is difficult to obtain,owing to the diverse sources and complicated compositions.However,with the assistance of advanced characterization and quantification methods(XPS,XRD,TG-FTIR,et al.),the common sulfur-and nitrogen-containing compounds in both organic and inorganic states can be detected.Adjustment of gasification conditions can regulate the transformation of these elements for emission control.The multiple pollutants including H_(2)S,SO_(x),COS,NH_(3),HCN and NO_(x)cannot be eliminated by one-step treatment but a combination of adsorption and catalytic treatments may realize the control goal.This research aims to benefit meeting emission standards during MSW gasification and to provide a reference for other processes such as incineration,pyrolysis and other feedstocks like biomass and refuse derived fuel(RDF).

Effects of temperature and composite alumina on pyrolysis of sewage sludge

An interactive dual-circulating fluidized bed system has been proposed in which the pyrolysis of sewage sludge（SS） and incineration of biomass proceed simultaneously, and alumina is used as the bed material and heat carrier. The alumina coated with biomass ash would mix with sewage sludge in the pyrolysis reactor of this device. It is important to know the influence of composite alumina（CA） on the pyrolysis progress. Sewage sludge was pyrolyzed in a fixed bed reactor from 400 to 600°C using CA as catalyst. The effects of temperature and CA additive ratio on the products were investigated. The product yields and component distribution of non-condensable gas were more sensitive to the change of temperature, and the maximum liquid yield of 48.44 wt.% and maximum Useable Energy of Liquid of 3871 k J/kg sludge were observed at 500°C with 1/5 CA/SS（mass ratio）. The gas chromatography–mass spectrometry results showed that the increase of temperature enhanced devolatilization of organic matter and promoted cyclization and aromatization of aliphatics. The presence of CA could strengthen secondary cracking and interaction among primary products from different organic compounds, such as acid–amine condensation,and reduce the content of oxygenated compounds. When the CA additive amount exceeded a certain proportion, the aromatization was clearly strengthened. The effects of CA on decomposition of fatty acids and formation of aromatics were similar to that of temperature. This means that the reaction temperature could be lowered by introducing CA, which has a positive effect on reducing energy consumption.

In-situ catalytic decomposition of emitted ammonia from municipal solid waste gasification by Ni–M bimetallic catalysts supported on sewage sludge-derived biochar

Gasification technology can effectively realize energy recovery from municipal solid waste(MSW)to reduce its negative impact on the environment.However,ammonia,as a pollutant derived from MSW gasification,needs to be treated because its emission is considered harmful to mankind.This work aims to decompose the NH3 pollutant from MSW gasification by an in-situ catalytic method.The MSW sample is composed of rice,paper,polystyrene granules,rubber gloves,textile and wood chips.Ni–M(M=Co,Fe,Zn)bimetallic catalysts supported on sewage sludge-derived biochar(SSC)were prepared by co-impregnation method and further characterized by X-ray diffraction,N2 isothermal adsorption,scanning electron microscopy,transmission electron microscopy and NH3 temperature programmed desorption.Prior to the experiments,the catalysts were first homogeneously mixed with the MSW sample,and then in-situ catalytic tests were conducted in a horizontal fixed-bed reactor.The effect of the second metal(Co,Fe,Zn)on the catalytic performance was compared to screen the best Ni-M dual.It was found that the Ni–Co/SSC catalyst had the best activity toward NH3 decomposition,whose decomposition rate reached 40.21%at 650℃.The best catalytic performance of Ni–Co/SSC can be explained by its smaller Ni particle size that facilitates the dispersion of active sites as well as the addition of Co reducing the energy barrier for the associative decomposition of NH species during the NH3 decomposition process.Besides,the activity of Ni–Co/SSC increased from 450℃to 700℃as the NH3 decomposition reaction was endothermic.