CF_4 Decomposition by Thermal Plasma Processing

Sun, Jong-Woo,Park, Dong-Wha 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.3

Decomposition of CF_4 was investigated by thermal plasma method. Thermal plasma processes applied to environmental problems have the features of high temperature, high activity and rapid decomposition rate, so it can perfectly decompose non-decomposed materials like CF_4 to a high degree. Before the experiment, thermodynamic equilibrium calculations were performed from 300 K to 5,000 K at atmospheric pressure. Based on the thermodynamic equilibrium calculations, the trends in decomposition and recombination of CF_4 were studied. Decomposition was carried out by injecting mixtures of CF_4 bubbled by Ar, with some addition gases, such as H_2 and O_2 at atmospheric pressure. Experiments were performed to determine the effects of additive gas identity, additive gas dilution, input power, etc. on the decomposition ef CF_4. Plasma input power has a slight effect on CF_4 decomposition, and the injection of reacting gas through a torch increased CF_4 decomposition. Supply of H_2 and O_2 as addition gases increased the CF_4 decomposition to 99% for experimental conditions tested.

튜브 반응로에서 HFC 134a 열분해를 위한 수치해석 연구 및 검증

신미수,장동순,하종욱 한국폐기물자원순환학회 2015 한국폐기물자원순환학회지 Vol.32 No.8

Since HFCs does not contain Cl component, they are not harmful to the depletion of Ozone layer but require reduction especially due to the high GWP (global warming potential). The HFC 134a, known as one of typical refrigerant of HFCs is generally shown to be effectively thermally decomposed only above the temperature of 3,000℃. However, giving condition of sufficient water vapor and the temperature more than 800℃ with large heating source like in calcination reactor or blast furnace, the thermal decomposition of HFC 134a will occur easily due the component of H and O contained in water vapor. In order to investigate this phenomenological finding appeared in large scale field test, a series of experimental investigation has been made for the thermal decomposition rate of HFC 134a as a function oxygen and HFC 134a flow rate for a small tubular reactor. In this experiment the wall temperature of tubular reactor was fixed to be 900℃. In order to verify and figure out the finding by experiment, numerical calculation has also been made for the detailed reaction of HFC 134a inside the tubular reactor. The comparison between experiment and numerical calculation are in good agreement each other especially for the rate of thermal destruction at the exit of the reactor. Further, considering the efficient thermal decomposition of HFC 134a in the H2O vapor environment with sufficient heating source, the application of the stoichiometric mixture of hydrogen and oxygen, that is, H2+ 1/2O2, is made numerically in the same tubular reactor, for the thermal decomposition of HFC 134a. The result appears physically acceptable and looks promising for the future method of the HFCs decomposition.

튜브 반응로에서 HFC 134a 열분해를 위한 수치해석 연구 및 검증

신미수,장동순,하종욱 한국폐기물자원순환학회 2015 한국폐기물자원순환학회지 Vol.32 No.8

Since HFCs does not contain Cl component, they are not harmful to the depletion of Ozone layer but require reduction especially due to the high GWP (global warming potential). The HFC 134a, known as one of typical refrigerant of HFCs is generally shown to be effectively thermally decomposed only above the temperature of 3,000oC. However, giving condition of sufficient water vapor and the temperature more than 800oC with large heating source like in calcination reactor or blast furnace, the thermal decomposition of HFC 134a will occur easily due the component of H and O contained in water vapor. In order to investigate this phenomenological finding appeared in large scale field test, a series of experimental investigation has been made for the thermal decomposition rate of HFC 134a as a function oxygen and HFC 134a flow rate for a small tubular reactor. In this experiment the wall temperature of tubular reactor was fixed to be 900oC. In order to verify and figure out the finding by experiment, numerical calculation has also been made for the detailed reaction of HFC 134a inside the tubular reactor. The comparison between experiment and numerical calculation are in good agreement each other especially for the rate of thermal destruction at the exit of the reactor. Further, considering the efficient thermal decomposition of HFC 134a in the H2O vapor environment with sufficient heating source, the application of the stoichiometric mixture of hydrogen and oxygen, that is, H2+ 1/2O2, is made numerically in the same tubular reactor, for the thermal decomposition of HFC 134a. The result appears physically acceptable and looks promising for the future method of the HFCs decomposition.

열분해 반응조건에 따른 염화탄화수소 생성물 분포 특성

김용제(Yong-Je Kim),원양수(Yang-Soo Won) 한국청정기술학회 2010 청정기술 Vol.16 No.3

염화탄화수소 열분해와 생성물분포 특성을 고찰하기 위해 등온 관형 반응기를 이용해 두 가지 실험을 수행하였다. 첫 번째는 반응분위기에 따른 열분해 특성을 파악하기 위해 H2 또는 Ar 반응분위기에서 dichloromethane (CH₂Cl₂) 분해율과 생성물분포 특성을 고찰하였다. Ar 반응분위기(CH₂Cl₂/Ar 반응계)에서 보다 H₂ 반응분위기(CH₂Cl₂/H₂ 반응계)에서 CH₂Cl₂ 분해율이 더 높았다. 이는 반응성 기체인 H₂ 분위기에서 CH₂Cl₂ 분해를 촉진시키며 수소 첨가 탈염소반응을 통해 탈염소화된 탄화수소화합물을 생성시키며, 다환방향족탄화수소(polycyclic aromatic hydrocarbon: PAH)와 soot 생성을 억제하기 때문이다. CH₂Cl₂/H₂ 반응계에서 주요생성물로 탈염소화합물인 CH₃Cl, CH₄, C₂H6, C₂H₄, HCl 등이 생성되었으며, 미량 생성물로 chloroethylene이 검출되었다. CH₂Cl₂/Ar 반응계에서는 탄소물질수지가 낮았으며 특히 반응온도 750 ℃ 이상에서 탄소물질 수지가 더 낮게 나타났다. 주요 생성물로는 chloroethylene과 HCl이 검출되었으며, 미량 생성물로는 CH₃Cl과 C₂H₂이 검출되었다. 고온 Ar 반응분위기에서 CH₄ 주입에 따른 chloroform(CHCl₃) 분해와 생성물분포 특성을 비교 고찰하였다. CHCl₃ 분해율을 비교해 보면 CH₄을 주입할 경우(CHCl₃/CH₄/Ar 반응계)가 CH₄을 주입하지 않았을 경우(CHCl₃/Ar 반응계)보다 분해율이 낮았다. 이는 CHCl₃가 분해되면서 생성되는 활성도가 큰 이중라디칼(diradical)인 :CCl₂가 첨가물로 주입된 CH₄와 반응하여 소모됨으로써 CHCl₃ 분해율이 상대적으로 감소되기 때문이다. Ar 반응분위기에서 CH₄ 첨가 여부에 따라 CHCl₃이 분해되면서 생성되는 생성물 분포는 큰 차이를 나타내고 있었다. 앞에서 고찰된 각 반응계에서 분해율 비교와 생성물 분포특성을 고려하고 열화학이론 및 반응속도론을 기초로 주요 반응경로를 제시하였다. Two sets of thermal reaction experiment for chlorinated hydrocarbons were performed using an isothermal tubular-flow reactor in order to investigate thermal decomposition, including product distribution of chlorinated hydrocarbons. The effects of H₂ or Ar as the reaction atmosphere on the thermal decomposition and product distribution for dichloromethane(CH₂Cl₂) was examined. The experimental results showed that higher conversion of CH₂Cl₂ was obtained under H₂ atmosphere than under Ar atmosphere. This phenomenon indicates that reactive-gas H₂ reaction atmosphere was found to accelerate CH₂Cl₂ decomposition. The H₂ plays a key role in acceleration of CH₂Cl₂ decomposition and formation of dechlorinated light hydrocarbons, while reducing PAH and soot formation through hydrodechlorination process. It was also observed that CH₃Cl, CH4, C₂H6, C₂H₄ and HCl in CH₂Cl₂/H₂ reaction system were the major products with some minor products including chloroethylenes. The CH₂Cl₂/Ar reaction system gives poor carbon material balance above reaction temperature of 750℃. Chloroethylenes and soot were found to be the major products and small amounts of CH₃Cl and C₂H₂ were formed above 750℃ in CH₂Cl₂/Ar. The thermal decomposition reactions of chloroform(CHCl₃) with argon reaction atmosphere in the absence or the presence of CH₄ were carried out using the same tubular flow reactor. The slower CHCl₃ decay occurred when CH₄ was added to CHCl₃/Ar reaction system. This is because :CCl₂ diradicals that had been produced from CHCl₃ unimolecular dissociation reacted with CH₄. It appears that the added CH₄ worked as the :CCl₂ scavenger in the CHCl₃ decomposition process. The product distributions for CHCl₃ pyrolysis under argon bath gas were distinctly different for the two cases: one with CH₄ and the other without CH₄. The important pyrolytic reaction pathways to describe the important features of reagent decay and intermediate product distributions, based upon thermochemistry and kinetic principles, were proposed in this study.

Thermal Analysis Study of Modified Urea-Formaldehyde Resin

Wei Hong,Mianwu Meng,Dingding Gao,Qingye Liu,Caiyan Kang,Siyu Huang,Zhenming Zhou,Chunqiang Chen 한국고분자학회 2016 폴리머 Vol.40 No.5

In this study, the structures and thermal stability of pure urea-formaldehyde resin (PR) and modified urea-formaldehyde (UF) resin are investigated by differential thermal gravity (TG/DTG), and differential scanning calorimetry (DSC) supported by data from Fourier transform infrared spectroscopy. FTIR analysis indicate that the modifiers such as polydimethylsiloxane, dicyclohexylcarbodiimide and phenol have actively participated in the curing reactions. TG/DTG and DSC curve of UF resin show that its pyrolysis process is conducted in three steps: desiccation and dehydration, flash pyrolysis and slow decomposition. Compared with pure urea-formaldehyde resin (PR), modified UF resin exhibited good thermal stability. The activation energy (E) of modified UF resin acquired by Kissinger and Ozawa method was higher than that of PR. ΔH > 0, ΔS > 0 and ΔG > 0 in the thermal decomposition process of UF resin means that the decomposition reaction of UF resin before and after modification is a process of unnatural decalescence and entropy increase.

Preparation of nanostructure CuO/ZnO mixed oxide by sol–gel thermal decomposition of a CuCO3 and ZnCO3: TG, DTG, XRD, FESEM and DRS investigations

Mohammad Hossein Habibi,Bahareh Karimi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.3

Nanostructure CuO/ZnO mixed oxide was systematically prepared via the sol–gel route using zinc andcopper carbonates as precursors (molar ratio of 2:1) under thermal decomposition. The zinc and coppercarbonates precursors have been synthesized by a simple chemical reaction in high yield andcharacterized by its melting point, FT-IR and thermal analysis (TG/DTG). The TG/DTG analysis provedthat the thermal decomposition of zinc and copper carbonates precursors at 255 ℃ and 289 ℃ respectively. Thermo-gravimetric analysis (TG-DTG), X-ray diffraction (XRD), field emission scanningelectron microscopy (FESEM) and diffuse reflectance spectroscopy (DRS) studies were undertaken toinvestigate the thermal properties and electronic structure of the CuO/ZnO mixed oxide catalysts. XRDdata of the samples proved the formation of the nano-crystalline CuO/ZnO mixed oxide. Scanningelectron microscopy (SEM) showed that the spherical-like particles have a diameter in the range 35–45 nm. Optical spectra of the nanostructure show a band peaked at 1.35 eV which is associated to nearband gap transitions of CuO and a band centered at about 3.00 eV related to band gap transitions of ZnOnanostructures.

오스테나이트계 스테인리스강 용접부 델타-페라이트의 열화에 따른 미세조직 변화가 기계적 물성 및 부식 특성에 미치는 영향

박상규,이호중,이종현 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.4

347 austenitic stainless steel weld (ASSW) was thermally aged at 343, 400 and 450 °C up to 20,000 h in this study. Effects of thermal aging induced microstructure evolution on the mechanical properties and corrosion resistance of delta-ferrite in the 347 ASSW were qualitatively and quantitatively assessed by high resolution transmission electron microscopy (0.07 nm) with energy-dispersive spectroscope (EDS) and Fast Fourier Transform (FFT). After thermal aging at 343 °C for 20,000 h and 400 °C over 5,000 h, fluctuation of major alloying elements such as Fe, Cr, and Ni was observed by spinodal decomposition in the delta-ferrite. Meanwhile, a Ni+Si-rich G phase was developed as thermal aging progressed at 400 °C for 20,000 h and 450 °C for 5,000 h in the delta-ferrite. Such microstructure evolutions tended to be accelerated with increasing aging temperature and exposure period, while the G phase was formed at a higher exposure temperature and/ or period compared to spinidal decomposition. These effects increased the tensile strength and decreased the elongation of 347 ASSW at room temperature, compared to the as-welded condition. Moreover, when spinodal decomposition and G phase were observed, the degree of sensitization values of the 347 ASSW in the double loop-electrochemical potentiodynamic reactivation tests were significantly increased, due to localized Cr depletion in the delta-ferrite.

Thermal Decomposition Kinetics of Polyurethane Elastomers Prepared with Different Dianiline Chain Extenders

( Wonsool Ahn ) 한국고무학회 2016 엘라스토머 및 콤포지트 Vol.51 No.2

Thermal decomposition kinetics for two different types of polyurethane elastomers prepared with 2,2``-dichloro- 4,4``-methylenedianiline (MOCA) and 3,5-dimethyl-thiotoluenediamine (Ethacure-300), based on PTMG/TDI isocyanate prepolymer, were studied using non-isothermal thermogravimetric analysis (TGA). Thermograms were obtained and analyzed using Friedman (FR) and Kissinger-Akahira-Sunose (KAS) methods for activation energy, Ea. The results obtained showed that decomposition reaction of both samples was observed similarly to occur through three different stages, i.e., initial stage with vaporization of low molecular weight materials, second stage of urethane linkage decompositions, and later stage of polyol segment decompositions. However, activation energy values at each stage for the sample cured with Ethacure- 300 was much lower than those for the sample with MOCA, exhibiting relatively lower thermal stability for the sample with Ethacure-300 than that with MOCA.

Isothermal Decomposition of Ammonium Molybdate to Molybdenum Trioxide in a Fluidized Bed Reactor

Oh, Chang-Sup,Park, Yong-Ok,Hasolli, Naim,Kim, Hang Goo,Won, Yong Sun,Shin, Su-Been,Kim, Yong-Ha Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.10

The present study prepared molybdenum trioxide ($MoO_3$), the most important intermediate of molybdenum metal, by using a fluidized bed reactor for the thermal decomposition of ammonium molybdate (AM) in the presence of an air flow. During the process of fluidizing the sample inside the reactor, the reaction time and temperature were optimized with a close analysis of the X-ray diffraction (XRD) data and with thermogravimetric analysis (TGA). In particular, the temperature level, at which the AM decomposition is completed, is very important as a primary operating parameter. The analysis of the XRD and TGA data showed that the AM decomposition is almost completed at ${\sim}350^{\circ}C$ with a reaction time of 30 min. A shorter reaction time of 10 min. required a higher reaction temperature of ${\sim}500^{\circ}C$ with the same air flow rate to complete the AM decomposition. A sharp rise in the decomposition efficiency at a temperature ranging between 320 and $350^{\circ}C$ indicated a threshold for the AM decomposition. The operating conditions determined in this study can be used for future scale-ups of the process.

Comparison Study of Thermal Decomposition Characteristics of Wattle & Pine Tannin-based Adhesives

SuminKim,엄영근,김현중,이영규 한국목재공학회 2002 목재공학 Vol.30 No.3

This study investigated the thermogravimetric analysis of two types of cured tannin-based adhesives from wattle and pine, with three hardeners of paraformaldehyde, hexamethylenetetramine and TN (tris(hy- droxyl)nitromethan), at a temperature of 170oC and a heating rate of 5, 10, 20 and 40oC/min for 10 minutes. The 5 minutes cured wattle tannin-based adhesive with each hardener at 170oC was also tested to compare the degree of curing. It was found that thermogravimetric analysis could be used to measure the degree of curing of a thermosetting adhesive. The TG-DTG curves of all the adhesive systems were similar and showed three steps in a similar way to a phenolic resin. This means that each adhesive system is well cross-linked. However, a high thermal decomposition rate was shown at 150 to 400oC in the case of the pine tannin sample with TN (tris(hydroxyl)nitromethan). The Flynn & Wall expression was used to evaluate the activation energy for thermal decomposition. As the level of conversion (α) increased, the activation energy of each system increased. The activation energy of the wattle tannin-based adhesive with paraformaldehyde was higher than the others.