Nakorn Tippayawong

Non-isothermal pyrolysis characteristics of giant sensitive plants using thermogravimetric analysis.

A giant sensitive plant (Mimosa pigra L.) or Mimosa is a fast growing woody weed that poses a major environmental problem in agricultural and wet land areas. It may have potential to be used as a renewable energy source. In this work, thermal behaviour of dried Mimosa was investigated under inert atmosphere in a thermogravimetric analyzer at the heating rates of 10, 30, and 50 degrees C/min from room temperature to 1000 degrees C. Pyrolysis kinetic parameters in terms of apparent activation energy and pre-exponential factor were determined. Two stages of major mass loss occurred during the thermal decomposition process, corresponding to degradation of cellulose and hemicellulose between 200-375 degrees C and decomposition of lignin around 375-700 degrees C. The weed mainly devolatilized around 200-400 degrees C, with total volatile yield of about 60%. The char in final residue was about 20%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. As the heating rates increased, average devolatilization rates were observed to increase while the activation energy decreased.

Thermogravimetric analysis of giant sensitive plants under air atmosphere

The aim of this work is to utilise thermal analysis to study the thermal degradation of giant sensitive plants (Mimosa pigra L.) or Mimosa under oxidative environment. Thermogravimetric method was used under air sweeping in dynamic conditions at the heating rates of 10, 30, and 50 degrees C/min, from room temperature to about 725 degrees C. Starting with dehydration step between 30 and 150 degrees C, the main thermal decomposition process under air showed two distinct degradation zones, corresponding to devolatilisation step between 200 and 375 degrees C and combustion step around 375-500 degrees C. Kinetic parameters in terms of apparent activation energy and pre-exponential factor were determined. Comparison was made against other biomass materials. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. As the heating rates increased, average devolatilisation and combustion rates were observed to increase while the activation energy showed slight increase.

Characterization of ambient aerosols in Northern Thailand and their probable sources

The present study examines variation of ambient aerosol mass and number concentrations in Chiang Mai, Thailand during winter. Aerosol particle samples were collected and measured at four different sites, representative of urban, industrial, residential and rural areas during daytime between December 2003 and January 2004. Average 10 h particulate matter (PM) mass concentrations were found to be in the range of 75–290 ì g/m3, with average value of 149 ± 45 ì g/m3. Urban and industrial areas appeared to have higher PM loading than residential and rural areas. Number concentration and size distribution of particles in the range of 0.3–10.0 ìm did not exhibit any marked variation between sites. Relatively stable number concentrations were reported. Temporal variation of number concentrations was not clearly significant. No short term peak observed during rush hours. During sampling period, the average number concentration for 0.3–0.5, 0.5–1.0, 1.0–5.0 and 5.0–10.0 ìm were 6.60 × 106, 1.18 × 106, 2.11 × 105 and 1.12 × 104/m3, respectively. Particles with diameter smaller than 1.0 ìm accounted for over 90 % of the total number concentration. Concentrations of major metals were determined by atomic absorption spectrophotometer (Pb, Fe, Al, Si, Cr, Cd, Ni, Zn) and flame photometer (K, Na and Ca). Data obtained were used to identify probable sources via a multivariate analysis. Si, Na, Fe, Ca, Al and K were the six dominant elements in the airborne PM. Principle component analysis was carried out and major sources of airborne PM in Chiang Mai were determined, namely, (1) long distance sources such as sea spray, earth soil and industrial combustion, (2) short-distance sources such as crustal re-suspension, vehicular related emissions and vegetation burning, and (3) the unknown distance sources with low influence of traffic emissions.

Design and Evaluation of a High Concentration, High Penetration Unipolar Corona Ionizer for Electrostatic Discharge and Aerosol Charging

The aim of this paper is to design and evaluate a high concentration, high penetration unipolar corona ionizer. The electrostatic characteristics in terms of voltage-current relationships of the present ionizer in the discharge zones for positive and negative coronas were discussed. Using ion current measurement, the concentration and penetration of ions were evaluated at corona voltages across the needle electrodes between 1 and 4 kV, flow rates between 1 and 5 L/min, and an operating pressure of 1 atm. In the discharge zone of the ionizer, the highest ion concentrations were found to be about 1.71×10 14 and 5.09×10 14 ions/m³ for positive and negative coronas, respectively. At the outlet of the ionizer, it was found that the highest ion concentration was about 1.95×10 13 and 1.91×10 13 ions/m³ for positive and negative coronas, respectively. The highest ion penetration for positive and negative coronas through the ionizer was found to be about 98 % and 33 %, respectively. The Nit product for positive and negative coronas was also found to 1.28×10 13 and 7.43×10 13 ions/m³s, respectively. From the findings, this ionizer proved to be particularly useful as an aerosol charger for positive and negative charge before the detector in an electrical aerosol detector.

Yields and Gaseous Composition from Slow Pyrolysis of Refuse-derived Fuels

Abstract Pyrolysis of refuse-derived fuels (RDF) has been experimentally conducted in a laboratory-scale, externally heated tubular reactor at temperatures in the range of 400°C–700°C. Combinations of solid wastes were tested in a batch operation where temperature evolution was recorded. The yields of final pyrolysis products were collected for solid char, liquid, and gas. The collected gaseous component was analyzed using gas chromatography. It was found that both the composition and temperature had a significant effect on yields of pyrolysis products. The yield of solid product was found to decrease from 55 to 49% for the RDF as the pyrolysis temperature was changed from 400°C to 700°C. Liquid product yield was small but found to increase with temperature. A maximum gaseous product yield of 43% was obtained at a pyrolysis temperature of 400°C, which slightly declined with rising temperature. Gaseous composition also proved to vary with sample material and temperature. Percentage of HC showed a peak at 500°C, whereas CO was observed to increase monotonically with increasing temperature.

DEVELOPMENT OF A LABORATORY SCALE AIR PLASMA TORCH AND ITS APPLICATION TO ELECTRONIC WASTE TREATMENT

Expansion in electrical and electronic equipment trade has led to significant increase in electronic waste which should be dealt with special priority due to its potential negative impact to the public health and the environment. Thermal plasma technology offers a very promising alternative of hazardous waste treatment for the near future. In this study, a laboratory scale apparatus for generating high temperature plasma flame was presented. Design of a 20 kW plasma torch system was based on a non transferred direct current arc discharge with air as a medium gas. In this investigation, measurements of temperature distribution were performed. It was shown that high temperature flames can be generated, comparable to those reported in the literature. The gas temperature was found to increase with an increase in power input. The flame temperature was found to further increase from 1210 K to 1480 K when a small amount of added fuel gas. Assessment of electronic waste treatment using the air plasma system in a batch operation was also carried out. It was shown that the system was able to convert the electronic waste into combustible gas and inert solid residues. High mass loss rate of bulk electronic waste was demonstrated.

Particulate Emission Reduction from Biomass Burning in Small Combustion Systems with a Multiple Tubular Electrostatic Precipitator

Biomass utilization via combustion is gaining an increasingly important role worldwide in heat and power production. Emissions of particulate matter from biomass burning have drawn considerable attention because of concern over their possible toxicity and implications for human health. For small-scale applications, it is desirable to employ a simple, compact, and inexpensive solution to avoid air quality problems related to biomass combustion. Electrostatic precipitation is a very reliable method to control particulate emissions from boilers, incinerators, and other industrial processes. It is therefore applied to small combustors. In this work, a simple, compact, and cost-effective multiple tubular electrostatic precipitator was designed and evaluated theoretically and experimentally for removal of particulate matter from a small biomass combustor. The precipitator consisted of a simple array of coaxial discharge electrodes placed along the axis of each cylindrical collection tube. The discharge electrodes were connected to the positive high-voltage supply, while the cylindrical collection tubes were grounded. The positive high-voltage supply was used to produce the corona discharge field between individual discharge electrode and collection tube. The particle-laden exhaust gas flow from the small biomass furnace was directed across the corona discharge field and then charged. The charged particles were deflected outward in a radial direction and deposited on the collection tube wall. The overall collection efficiency of the electrostatic device was evaluated as a mass loading ratio of the difference at inlet and outlet to the particle loading at the inlet of the device. It was found that about 70% overall collection efficiency can be achieved with a relatively simple multiple tubular electrostatic precipitator design. The device appeared to be a promising tool for reduction of particulate matter in flue gas from a small biomass combustion system.

Ethanolysis of soybean oil into biodiesel: process optimization via central composite design

A process for production of ethyl ester for use as biodiesel has been studied. The sodium hydroxide catalyzed transesterification of soybean oil with ethanol was carried out at different molar ratio of alcohol to oil, reaction temperature and catalyst amount for a constant agitation in two hours of reaction time. Central composite design and response surface methodology were used to determine optimum condition for producing biodiesel. It was found that ethanol to oil ratio and catalyst concentration have a positive influence on ester conversion as well as interaction effects between the three factors considered. An empirical model obtained was able to predict conversion as a function of ethanol to oil molar ratio, reaction temperature and catalyst concentration adequately. Optimum condition for soybean ethyl ester production was found to be moderate ethanol to oil ratio (10.5: l), mild temperature range (70°C) and high catalyst concentrations (l.0%wt), with corresponding ester conversion of 93.0%.

Effect of Operating Conditions on Catalytic Gasification of Bamboo in a Fluidized Bed

Catalytic gasification of bamboo in a laboratory-scale, fluidized bed reactor was investigated. Experiments were performed to determine the effects of reactor temperature (400, 500, and 600°C), gasifying medium (air and air/steam), and catalyst to biomass ratio (0 : 1, 1 : 1, and 1.5 : 1) on product gas composition, H2/CO ratio, carbon conversion efficiency, heating value, and tar conversion. From the results obtained, it was shown that at 400°C with air/steam gasification, maximum hydrogen content of 16.5% v/v, carbon conversion efficiency of 98.5%, and tar conversion of 80% were obtained. The presence of catalyst was found to promote the tar reforming reaction and resulted in improvement of heating value, carbon conversion efficiency, and gas yield due to increases in H2, CO, and CH4. The presence of steam and dolomite had an effect on the increasing of tar conversion.

Investigation of a Small Biomass Gasifier–engine System Operation and Its Application to Water Pumping in Rural Thailand

This article reports experimental and developmental studies on a producer gas/diesel dual fuel operation of a small engine for irrigation water pumping. In this work, a biomass gasifier–engine system was designed, built, and tested. Waste woods from the furniture-making industry and charcoal were used as feedstock to produce fuel gas in the downdraft, throat-type, fixed-bed gasifier. The engine performance was evaluated over a fixed load and variable speeds between 1,000–2,000 rpm. Results showed that dual operation was able to produce slightly higher power output than normal diesel operation, with similar thermal efficiency. Producer gas substitution or diesel replacement of about 60–70% by mass was achieved. The producer gas powered water pumpset was later installed at a farm in rural Thailand. Start-up was straight forward and continuous operation was achieved with a water yield at 60% of nominal value. It was successfully demonstrated that biomass gasification could provide clean fuel to a small engine and this renewable energy technology could be a sustainable option for water pumping in rural areas.