Factors influencing precision and accuracy of a carbon-in ash monitor

This research is to enhance the performance of a carbon-in-ash monitor based on the photoacoustic effect. The original instrument was invented at ISU and licensed to Ametek Corporation for commercial manufacture. However, the company encountered problems with precision and accuracy of measurements performed with prototype instruments. The purpose of this study is to investigate factors that influence the precision and accuracy of photoacoustic measurement of carbon in fly ash;Measurements are influenced by both fly ash sampling and preparation procedure and operational features of the instrument. Thermogravimetric analysis (TGA) tests have shown that as-received fly ashes are heterogeneous and need to be ground for the calibration of the carbon-in-ash-monitor. Homogeneity of fly ash is the most important factor to affect the precision and accuracy of the carbon-in-ash monitor. A sample preparation procedure was standardized to control sample density and to eliminate operator-introduced errors. Thermogravimetric analysis tests have also shown that LOI reports high for unburned carbon in fly ash because it accounts the weight loss from the release of compounds decomposed under high temperature. The highest relative error of LOI as a carbon indicator in the seventy fly ash samples collected from four countries is 3040%. Total organic carbon (TOC) measured with TGA was proven to be a correct carbon indicator and was used for the calibration of the carbon-in-ash monitor. It was found that photoacoustic signal saturation existed in the calibration process of carbon-in-ash monitor. Calcium carbonate was used to dilute samples to avoid the photoacoustic signal saturation. Universal calibration of the carbon-in-ash monitor was proven to be impossible but its custom calibration was successful. Redesigned head and LED holder of the carbon-in-ash monitor and increase of power output of excitation sources were evaluated to increase the responsitivity of photoacoustic signal for the improvement of accuracy of instrument calibration. Finally, statistics program was employed to study the effect of ambient temperature on precision and experiments with controlled ambient temperature confirmed the conclusion derived from the output of the statistic program

Reaction Kinetics for a Novel Flue Gas Cleaning Technology

This paper studies the kinetics of the reaction between NaClO3, FeSO4, and NaHSO3, which can potentially be used as an alternative to the conventional lime-limestone process for flue gas desulfurization. The key for the establishment of a kinetic model of the reaction is to find a way to determine concentrations of reactants or products during the reaction. The generation rate of Cl- during the reaction was monitored using a Dionex Series 4000i ion chromatograph. Based on the changes of Cl- concentrations at the designed initial reaction conditions, reaction orders for each reactant were derived. The reaction orders were determined to be 1.1 for NaClO3, 1.1 for FeSO4, and 1.4 for NaHSO3. The global rate coefficients of the reaction at temperatures ranging from 40 to 80 °C were determined. Furthermore, the preexponential factor and the activation energy in the empirical Arrhenius form of the reaction were derived from the relationship between temperature and its corresponding observed global rate coefficient

CO2 capture using nanoporous TiO(OH)2/tetraethylpentamine

In this work, an inorganic-organic CO2 sorbent was prepared by immobilizing tetraethylenepentamine (TEPA) onto nanoporous titanium oxyhydrate (TiO(OH)2). The prepared sorbents were characterized using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analysis. At the optimal TEPA loading of 60 wt.% on TiO(OH)2, its CO2 sorption capacity reached 3.1 mmol CO2/g-sorbent for 1 vol.% CO2 in N2 along with ~1 vol.% H2O at 60°C. Studies of adsorption kinetics and thermodynamics showed that the activation energies for CO2 adsorption and desorption of TiO(OH)2/TEPA are 38.31 kJ/mol and 44.51 kJ/mol, respectively. Its low CO2 desorption activation energy means a high CO2 dsorption rate and thus a low CO2 capture cost. The sorbent has the potential to be used for capturing ultra-dilute CO2 from gas mixtures. Key words: CO2 capture; nanoporous titanium oxyhydrate; sorption; kinetics *Corresponding author’s email address:[email protected] (M. Fan), Tel.: +1 307 766 5633; fax: +1 307 766 6777

Desorption Kinetics of an Alternative Monoethanolamine Based CO2 Capture Process

Supported monoethanolamine (MEA) sorbents are promising materials for CO2 separation due to their low energy demands. Like any other CO2 separation technologies, CO2 desorption from supported MEA sorbents is the most energy-expensive step in the overall CO2 separation process. The presence of water during CO2 desorption process leads to a significant increase in energy consumption. Therefore, CO2 desorption in the absence of water is an important method to reduce energy consumption of CO2 separation using supported MEA, which is determined by several major factors, including desorption kinetics. However, study on CO2 desorption kinetics of supported MEA is lacking. This research was designed to make progress in this area. The CO2 desorption kinetic model of TiO2-supported MEA is experimentally derived with the data collected within water-free desorption environment and theoretically proved by pseudo-steady state theory. The Avrami-Erofeyev mechanism controls the CO2 desorption process, which is first order with respect to [RNH3 +RNHCOO-] or RNH3+ or RNHCOO-. The activation energy of the CO2 desorption process is 80.79 kJ/mol. The kinetic characteristics of the CO2 desorption are much superior to those associated with aqueous MEA based CO2 separation. The energy saving due to the use of supported MEA for CO2 separation not only results from avoiding the use of water, with its high specific-heat capacity and high vaporization enthalpy, but also from the favorable desorption kinetics of the supported MEA based CO2 separation

Supported Monoethanolamine for CO2 Separation

An alternative method for using monoethanolamine (MEA) in CO2 separation is developed from the viewpoints of the MEA-CO2 reaction environment and the process of spent sorbent regeneration. The method could be used to considerably reduce energy consumption compared to conventional aqueous MEA processes. MEA-TiO2 (MT) CO2 sorbent is synthesized using pure MEA and a support material, TiO2. The performance of the MT sorbent on CO2 separation was investigated in tubular reactors under various experimental conditions. The effects of several major factors on CO2 sorption by the MT sorbent were investigated. The sorption capacity of the MT sorbent increased with MEA loading, reaching 48.1 mg-CO2/g-MT at 45 wt% MEA. However, an optimum of 40 wt% MEA loading was chosen for most of the sorption tests conducted in this research. Temperature affected the CO2 sorption capacity considerably, with optimum values of 45°C for adsorption and 90°C for regeneration, while humidity had a small positive effect under initial test conditions. In addition to TiO2, TiO(OH)2 and FeOOH were also tested as potential supports for MEA. TiO(OH)2 appears to be the best support material for MEA, but more evaluation is needed. The MT sorbent is regenerable, with a multi-cycle sorption capacity of ~40 mg-CO2/g-MT under the given experimental conditions

Self-activated, Nanostructured Composite for Improved CaL-CLC technology

The development of bifunctional CaO/CuO matrix composites with both high and stable reactivity is a research priority and key for the development of calcium looping integrated with chemical looping combustion (CaL-CLC), a new CO2 capture technology that eliminates the requirement for pure O2 for the regeneration of CaO-based sorbents. In this work, a simple but effective approach was first used, i.e., solution combustion synthesis (SCS), to produce various nanostructured CaO/CuO matrix composites with homogenous elemental distributions. All CaO/CuO matrix composites possessed increased CO2 uptake in the form of self-activation and excellent cyclically stable O2 carrying capacity over as many as 40 reaction cycles. For instance, the final carbonation conversion of CaO-CuO-1-800-30 was 51.3%, approximately 52.7% higher than that of the original material (33.6%). Here, the self-activation phenomenon have been observed for the first time in contrast to the rapid decay in CO2 uptake capacity previously reported, due mainly to the increase of both specific surface area and pore volume. In-situ X-ray diffraction (in-situ XRD) analysis revealed that no side reactions occurred between CaO/CaCO3 and CuO/Cu during the overall process. All of these results make CaO/CuO matrix composites an attractive candidate for CaL-CLC

Reduction of S02 in Flue Gas and Applications of Fly Ash: A Review

Flue gas and fly ash are the two most important wastes from power plants. This review focuses on technologies for S02 removal from emissions and on properties and applications of fly ash. It predominantly focuses on the non-European situation; in Europe, flue gas desulfurization and ash utilization have been extensively practiced during several decades. Flue gas desulfurization (FGD) technologies are the most commonly used methods in the removal of S02 in flue gas. Factors influencing S02 removal efficiency and optimal operation conditions are considered. Physical and chemical properties of fly ash make it useable in various fields, such as cement production, concrete admixtures, soil amendment, as a low-cost adsorbent of certain types of contaminants in wastewater, and in the production of effective wastewater coagulants