Eilhann Kwon

Urban energy mining from municipal solid waste (MSW) via the enhanced thermo–chemical process by carbon dioxide (CO2) as a reaction medium

The enhanced gasification of municipal solid waste (MSW) using carbon dioxide (CO(2)) as the gasification medium was investigated to achieve environmentally benign and energy efficient ways for the disposal of MSW. Two main steps of thermal decomposition of MSW were observed. The first thermal degradation step occurs at temperature between 280 and 350°C and consists of the decomposition of the biomass component into light C(1-3)-hydrocarbons. The second thermal degradation step occurs between 380 and 450°C and is mainly attributed to polymer components, such as plastics and rubber, in MSW. To extend this understanding to a more practical level, MSW samples were tested in a drop tube reactor (DTR) at a temperature range from 500 to 1000°C under various atmospheres with CO(2) concentrations of 0-30%. The release of major chemical species from the DTR has been determined using a micro-GC. For example, CO (≈ 30%), H(2) (≈ 25%) and CH(4) (≈ 10%) were generated.

New candidate for biofuel feedstock beyond terrestrial biomass for thermo-chemical process (pyrolysis/gasification) enhanced by carbon dioxide (CO2).

The enhanced thermo-chemical process (i.e., pyrolysis/gasification) of various macroalgae using carbon dioxide (CO(2)) as a reaction medium was mainly investigated. The enhanced thermo-chemical process was achieved by expediting the thermal cracking of volatile chemical species derived from the thermal degradation of the macroalgae. This process enables the modification of the end products from the thermo-chemical process and significant reduction of the amount of condensable hydrocarbons (i.e., tar, ∼50%), thereby directly increasing the efficiency of the gasification process.

Transforming Municipal Solid Waste (MSW) into Fuel via the Gasification/Pyrolysis Process

Municipal solid waste (MSW) gasification/pyrolysis enhancement using CO2 as gasification medium has been studied to understand the performance under various reaction conditions. MSW gasification/pyrolysis has been characterized thermo-gravimetrically under various atmospheres covering the gasification/pyrolysis process, which has been used as a basis for scale-up experimental work using a flow-through reactor (FTR) and drop tube reactor (DTR) (0.5 g/min of sample, 4–5 sec residence time, 500°C-1000°C). For example, FTR has been used to carry out the fast pyrolysis process having a nominal heating rate of 800°C/min. Oils produced from the FTR have been condensed and analyzed with GC/MS. Among identified chemical species in the pyrolysis sample, the 10 most abundant compounds (benzene, toluene, styrene, limonene, 2,3-dimethyl-1-heptene, benzoic acid, ethylbenzene, indole, xylene, and d-allose) in the pyrolysis oil sample were determined and quantified. These 10 abundant chemical species are substantially reduced in the presence of CO2 . This leads to a substantial increase of C1–5 hydrocarbons in gaseous (non-condensable) products and a reduction of pyrolysis oil (∼20%) as well. In addition, MSW samples have been tested in the DTR at a temperature range from 500°C and 1000°C under various atmospheres with CO2 concentrations of 0% and 30%. The release of all chemical species from the DTR was determined using μ-GC. For example, CO (∼30%), H2 (∼25%), and CH4 (∼10%) under the presence of CO2 were generated and introducing CO2 into the gasification process substantially enhanced syngas production. Finally, steam gasification using different ratios of biomass to polyethylene has been explored to better understand the enhanced steam gasification of MSW that is mostly composed of biomass and polymer. Overall thermal degradation trend is the similar, but steam gasification of MSW needs a relatively long residence time and high temperature as compared to biomass.Copyright

Thermo-Gravimetric Analysis (TGA) of Combustion and Gasification of Styrene-Butadiene Copolymer (SBR)

An investigation has been initiated to determine the effects of various atmospheres (6.9% O2 /N2 , 21% O2 /N2 (air), 30% O2 /N2 , 3% H2 /N2 and pure N2 ) on the efficiency of gasifying or combusting rubber waste to produce synthesis gas or generate steam or power. This paper reports on the findings from a series of TGA experiments at various heating rates on styrene-butadiene copolymer (SBR), which is the main starting component for tire manufacturing. The results indicate that oxygen enhanced atmospheres have a significant effect on increasing combustion efficiency at the tested heating rates. A hydrogen-spiked atmosphere, surprisingly, did not have a significant effect on the gasification rates of SBR at any heating rate; in addition, this atmosphere resulted in a carbon residual that remained in the sample carrier, something that was not observed in the other atmospheres, including pure nitrogen. An unexpected result of the N2 -O2 tests was the development of a plateau in the mass-loss versus temperature curves, at temperatures near 500°C.Copyright

An Investigation Into the Syngas Production From Municipal Solid Waste (MSW) Gasification Under Various Pressures and CO2 Concentration Atmospheres

The Municipal Solid Waste (MSW) gasification process is a promising candidate for both MSW disposal and syngas production. The MSW gasification process has been characterized thermo-gravimetrically under various experimental atmospheres in order to understand syngas production and char burnout. This preliminary data shows that with any concentration of carbon dioxide in the atmosphere the residual char is reduced about 20% of the original mass (in an inert atmosphere) to about 5%, corresponding to a significant amount of carbon monoxide production (0.7% of CO was produced from a 20mg sample with 100ml/min of purge gas at 825°C). Two main steps of thermal degradation have been observed. The first thermal degradation step occurs at temperatures between 280∼350°C and consists mainly of the decomposition of the biomass component into light C1–3 -hydrocarbons. The second thermal degradation step occurs between 380∼450°C and is mainly attributed to polymer components, such as plastics and rubber, in MSW. The polymer component in MSW gave off significant amount of benzene derivatives such as styrene. In order to identify the optimal operating regime for MSW gasification, a series of tests covering a range of temperatures (280∼700°C), pressures (30∼45 Bar), and atmospheres (100% N2, 0∼20%CO2 +Bal. N2 with/without steam) have been done and the results are presented here.Copyright

Experimental Research on Microwave Induced Thermal Decomposition of Printed Circuit Board Wastes

As a result of electronic industry development in China, significant amount of Printed Circuit Board (PCBs) wastes are generated. The thermal decomposition via combustion or pyrolysis/gasification is considered to be a feasible disposal way for PCBs. To understand the consequences of pyrolysis, gasification or combustion in WTE facilities, thermo-gravimetric analysis (TGA) has been carried to characterize the thermal decomposition mechanisms and extract the kinetic parameters in various atmospheres (N2 , CO2 and air) to simulate different regions in WTE applications. TGA tests in N2 atmosphere showed there was only one significant reaction in the low temperature range of 270∼350°C, which was the decomposition of epoxy resin in PCBs. The behavior in CO2 atmosphere was similar with that in N2 . However, the PCBs oxidation process in air atmosphere showed two thermal decomposition steps. One was the thermal decomposition similar to the volatilization in N2 atmosphere and the second step showed oxidation behavior. Some pre-processing was investigated to explore possible benefits in WTE combustion. PCBs waste was pyrolyzed using a microwave tubular furnace. The liquid product were collected and then identified by means of gas chromatography–mass spectrometry (GC–MS). Most of the Br contained in PCBs was released into non-condensable gas in the form of HBr. The liquid product contained a large amount of phenolic compounds, bisphenol A and other aromatic compounds that can be used to produce related chemical products or used in WTE facilities. The experimental results including the thermal kinetic parameters and microwave induced pyrolysis indicate the complex mechanisms that take place during the pyrolysis of PCBs wastes.Copyright

Use of Statistical Entropy and Life Cycle Analysis to Evaluate Global Warming Potential of Waste Management Systems

The statistical entropy (SE) function has been applied to waste treatment systems to account for dilution or concentration effects on metals. We later extended it to account for carbon flows, especially in waste management systems involving thermal treatment. Now, a simple lifecycle “net energy” metric ‐ encompassing the “lost energy” that would have been gained when high-calorific materials are landfilled rather than combusted with energy recovery ‐ is introduced to account for additional influxes of carbon when using landfilling as the primary disposal method. When combining net energy calculations and long terms effects of landfilling, waste to energy (WTE) becomes a more attractive option for dealing with non-recycled municipal solid waste (MSW). A greenhouse gasforcing factor is also introduced to account for the entropy generating effects of methane. When incorporating forcing and lost energy, WTE performs notably better than landfills with respect to entropy generation and carbon.

Investigation of Thermo-Gravimetric Analysis (TGA) on Waste Tires and Chemical Analysis Including Light Hydrocarbons, Substituted Aromatics, and Polycyclic Aromatic Hydrocarbon (PAH)

This investigation has been initiated to characterize the thermal decomposition of waste tires with Thermo-Gravimetric Analysis (TGA) in various atmospheres ranging in oxygen content; 100% N2 , 7%, 21% (air) and 30% O2 . Chemical analysis focusing on light hydrocarbons, substituted aromatics, and polycyclic aromatic hydrocarbon has been done qualitatively and quantitatively to understand the mechanism of thermal degradation of scrap tires and hazardous air pollutants such as PAH. The release of chemicals from scrap tires has been determined experimentally using Gas Chromatography/Mass Spectroscopy (GC/MS) coupled to TGA unit. The identities and absolute concentrations of over 50 major and minor species have been established. Significant volatile organic carbons (VOC) including substituted aromatics and PAH were observed between 300°C and 500°C. In addition, significant black carbon residual was observed in most environments except air and oxygen enhanced atmospheres and suggested not only the potential recovery of black carbon out of feedstock, but also the possibility of combined thermal treatment between combustion and gasification. These measurements supply information on the identities and levels of hazardous air pollutants, and provide useful new data for the development and validation of detailed reaction mechanisms describing their origin and fate. Finally, while high contents of VOC show significant potential to be utilized as an unconventional solid fuel, they also tend to generate hazardous pollutants.Copyright

Polycyclic Aromatic Hydrocarbon (PAH) Formation in Thermal Degradation of Styrene Butadiene Copolymer (SBR)

This study has been initiated to quantify the release of the Polycyclic Aromatic Hydrocarbon (PAH) species from Styrene Butadiene Copolymer (SBR) during gasification. The identification and quantification has been determined experimentally using Gas Chromatography/Mass Spectroscopy (GC/MS) coupled to a Thermo-Gravimetric Analysis (TGA) unit. SBR samples were pyrolysed in a TGA unit in a N2 atmosphere. The identities and absolute concentrations of over 32 major and minor species have been established, including a large number of aromatics, substituted aromatics, and PAHs. The light hydrocarbon species also have been determined simultaneously and identified as H2 , C2 H2 , CH4 , C2 H6 , and C4 H10 with lower concentrations of other hydrocarbon gases. Significant amounts of ethyl benzene, toluene, and styrene were observed between 330°C and 500°C. The largest PAH detected was the family of C24 H14 (molecular weight 302), benzo[ghi]perylene with peak concentrations reaching 0.19 ppmv. The effluent species detected suggest that formation of PAH’s occurs either through hydrocarbon addition reactions or benzene ring re-combination reactions. In addition, the chemical structure of SBR lends itself gas phase release of benzene molecules or radicals, thus facilitating the PAH production route. Preliminary calculations done using MOPAC provided some insight into the energy required to break the benzene ligand bond from the butadiene structure. The measurements supply information on the identities and levels of hazardous air pollutants, and provide useful new data for the development and validation of detailed reaction mechanisms describing their origin and fate.Copyright

An investigation of the thermal degradation mechanisms of a waste tire through chemical analysis including hydrocarbons, benzene derivatives, and Polycyclic Aromatic Hydrocarbons (PAHs) at high temperature

Previous work has focused on a series of fundamental Thermal Gravimetric Analysis (TGA) studies using representative atmospheres found in Waste-to-Energy (WtE) boilers. Those studies were done for waste tires and their major constituents, such as Styrene-Butadiene Copolymer (SBR) and Poly-Isoprene (IR). The outcome has been the elucidation of the likely mechanism responsible for initial decomposition, final product and byproduct formation. To extend that understanding to a more practical level, a flow through apparatus has been used to test waste tire samples in the temperature range of 500°C–800°C. A chemical analysis in this temperature range has been performed to compare the thermal degradation mechanism and air pollutant generation in low temperature regimes. The release of chemicals from a tubular quartz reactor containing a tire sample has been determined experimentally using a GC/MS. Significant Volatile Organic Carbons (VOCs) including benzene derivatives, PAHs, and Hetero-N containing PAHs were observed. This study identifies and quantifies the concentration levels of various hazardous air pollutants, and provides new data for the overall development and validation of detailed reaction mechanisms that can describe the thermal degradation of waste tires. This information will enable the development of mitigation strategies that can address those levels of pollutant species.Copyright