Search Results

You are looking at 1 - 10 of 11 items for :

  • "unburned carbon" x
  • Refine by Access: All Content x
Clear All

Abstract  

The thermal decomposition behavior of hard coal fly ash (HCA2), obtained from the combustion of an Australian hard coal in thermoelectric power plants, in different atmospheres (air, N2 and N2-H2 mixture), was studied using thermogravimetry (TG), infrared-evolved gas analysis (IR-EGA), differential scanning calorimetry (DSC) and thermodilatometry (DIL) techniques. It was found that changing of the applied atmosphere affects the carbon content of the ash which results in different thermal decomposition behaviors. In air, the carbon content was oxidized to carbon dioxide before the decomposition of carbonate. In N2 or in N2-H2 atmospheres, the carbon content acts as a spacer causing a fewer points of contact between calcium carbonate particles, thus increasing the interface area which results in a decrease of the carbonate decomposition temperature. Following the carbonate decomposition, the iron oxide content of the ash undergoes a reductive decomposition reaction with the unburned carbon. This oxidation-reduction reaction was found to be fast and go to completion in presence of the N2-H2 mixture than in the pure nitrogen atmosphere due to the reducing effect of the hydrogen. The kinetics of the carbonate decomposition step, in air and N2-H2 mixture was performed under non-isothermal conditions using different integral methods of analysis. The dynamic TG curves obeyed the Avrami-Erofeev equation (A2) in air, and phase boundary controlled reaction equation (R2) in N2-H2 mixture. The change in the reaction mechanism and the difference in the calculated values of activation parameters with the change of the atmosphere were discussed in view of effect of the atmosphere on the carbon content of the ash.

Restricted access

Abstract  

Three bio-fuels with or without additives and their fly ash samples were characterized using simultaneous Thermogravimetry-Differential Thermal Analysis-Fourier Transform Infrared Spectrometry-Mass Spectrometry (TG-DTA-FTIR-MS), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscopy-Energy Dispersive Spectrometry (SEM-EDS). The results show that the additives increase the reactivity of the bio-fuel during combustion. The additives also significantly decrease the amount of unburned carbon in the fly ash. The additives affect the compounds formed in the fly ash sample, and consequently the thermal behaviour of the fly ash. The fly ash samples are thermally stable in air up to 100C. The fly ash samples contain fine particles with irregular shape, small round particles, and large hollow spherical particles with entrapped gases.

Restricted access

Abstract  

A method has been developed using thermoanalytical techniques for the analysis of residues from coal-burning fluidised bed plant where limestone is used as a sulphur scavenger. This completely eliminates the need for lengthy wet chemical analyses and allows the derivation of parameters necessary for efficient plant operation, such as limestone addition rate, calcium utilisation efficiency and calcium to sulphur mole ratio. The method also gives values for the unburned carbon content and the ratio of coal ash to limestone derivatives in the sample.

Restricted access

°C due to oxidation of unburned carbon. However, the precursor having the composition x = 0.3, although decomposes in a similar way, it loses four N 2 H 4 molecule first at 154.8 °C followed by loss of two N 2 H 4 molecules at 189 °C as seen in

Restricted access

region at 316.4 °C due to oxidative decarboxylation. A marginal mass loss of 0.34% was observed from 320 °C to 900 °C due to oxidation of unburned carbon. Fig. 2 TG-DSC curve of Co 1− x Ni x Fe 2 (C 4 H 2 O

Restricted access

Co-firing of biomass with coals

Part 1. Thermogravimetric kinetic analysis of combustion of fir (abies bornmulleriana) wood

Journal of Thermal Analysis and Calorimetry
Authors: Ahu Gümrah Dumanli, Sinem Taş, and Yuda Yürüm

structure of the wood contained amorphous, the ash was consisted of some prismatic, mainly micron-scale cubical forms of 0.2 μm size. EDS analysis of the wood ash revealed, Table 2 , that the ash contained unburned carbon and in the order of decreasing

Restricted access

Nano-crystalline Mn0.3Ni0.3Zn0.4Fe2O4 obtained by novel fumarato-hydrazinate precursor method

Synthesis, characterization and studies of magnetic and electrical properties

Journal of Thermal Analysis and Calorimetry
Authors: U. B. Gawas, V. M. S. Verenkar, and S. C. Mojumdar

mass loss of 3.45 % in the region 350–420 °C may be due to unburned carbon which is indicated in the DSC by a broad exothermic peak in this region. The complex decomposes autocatalytically at room temperature, once ignited, to give nanocrystalline Mn 0

Restricted access

exothermic peaks in this region with the peak temperature of 180 and 306 °C due to two-step oxidative decarboxylation. A marginal mass loss of 3.8% in the region 350–440 °C may be due to unburned carbon which is indicated on the DSC curve by a broad

Restricted access

due to the oxidation of unburned carbon. Fig. 2 TG–DTA curves of Co 0.6 Ni 0.4 Fe 2 (C 4 H 2 O 4 ) 3 ·6N 2 H 4 Table 2 TG

Restricted access

335 to 900 °C on the TG curve due to the oxidation of unburned carbon. Fig. 2 TG–DSC curves of Co 0.8 Zn 0.2 Fe 2 (C 4 H 2 O 4 ) 3 ·6N 2 H 4 Table 2

Restricted access