Application of a low pressure economizer for waste heat recovery from the exhaust flue gas in a 600 MW power plant

The corrosion study of the pipeline steel is extremely important for the safety of CO2 pipeline. The present work studied the effect of temperature on the corrosion behaviour of X70 steel in high pressure CO2/SO2/O2/H2O mixtures. Weight loss method was utilised to measure the corrosion rate. Environmental scanning electron microscopy and focused ion beam technology were employed to observe the morphology of product scales. X-ray diffraction was used to analyse the composition of product scales. The porosity of product scales was measured, and the exhaust gas was detected by gas chromatography. Results showed that the corrosion rate increased with the increasing temperature and then started to decline with temperature with the peak corrosion rate at 348 K. Results also showed that there was hydrogen that existed in the exhausted gas, indicating that the hydrogen evolution reaction was contained in the corrosion cathodic process.

Effect of temperature on corrosion behaviour of X70 steel in high pressure CO2/SO2/O2/H2O environments

A mechanistic model was established to predict uniform corrosion rate and investigate the corrosion mechanisms of pipeline steel in supercritical CO 2 –SO 2 –O 2 –H 2 O environments. A six-region division (SIWDES: Supercritical CO 2 , Interface, Water film, Deposition, Electrodic, and Solid) was applied to mathematically describe the model. The modified three-characteristic-parameter correlation model was used to calculate the ion activity coefficients, which calculates the activity coefficients of ions in thin water film with high ionic strength. The model can reasonably predict the corrosion rate of pipeline steel for the primary variables, determine the concentration distribution of each component in the water and product films, and also reflect the impact of corrosion product film on corrosion rate. A comparative analysis between the model and the experimental results showed that the model reasonably predicted the effects of the main factors on corrosion rate.

A mechanistic model for pipeline steel corrosion in supercritical CO2–SO2–O2–H2O environments

Predicting acid dew point with a semi-empirical model

The corrosion of X70 steel and iron in supercritical CO2/SO2/O2/H2O environment were investigated after a 454 h exposure. Optical microscopy was applied to observe the morphology of etch pits and synthesise the three-dimensional morphology. X-ray diffraction and X-ray photoelectron spectroscopy were employed to detect the composition of product scales. Experimental results verified that the localised corrosion occurred on the X70 steel sample under corrosion product deposits. Ferrous sulphate, sulphur and iron sulphide were detected as the corrosion products.

Long term corrosion of X70 steel and iron in humid supercritical CO2 with SO2 and O2 impurities

Acid dew point of flue gas is one of the most important parameters of the design and operation of boilerAt present,there are lots of calculation methods of acid dew point of flue gas,and the results of different methods are quite differentThis paper compares several methods in reference to relevant literatures,analyzes the effect trend of SO_3 concentration and H_2O vapor on acid dew pointThe following results are obtained from the study:AG Okkes formula andИABapahob formula are more precise than the others but formula of acid dew point in the thermal calculation from the former USSR,formula of Japan Electric Power Research Institute and formula of Haase Borgmann have more errorFinally it corrects the formula of acid dew point in the thermal calculation from the former USSR

Comparison and Analysis on the Calculation Methods of Acid Dew Point of Flue Gas

Wet limestone scrubbing is the most common flue gas desulfurization process (FGD) for control of sulfur dioxide emissions from the combustion of fossil fuels. Forced oxidation, which controls the overall reaction of the sulfur dioxide absorption, is the key path of the process. Manganese which comes from the coal is one of the catalysts during the forced oxidation process. In the present work, the two-film theory was used to analyze the sulfite forced oxidation reaction with an image boundary recognition technique, and the oxidation rate was experimentally studied by contacting pure oxygen with a sodium sulfite solution. There was a critical sulfite concentration 0.328 mol/L without catalyst or at a constant catalyst concentration value. The kinetics study focused on the active energy of the reaction and the reaction constant k; furthermore, we obtained the order with respect to the sulfite and Mn2+ concentrations. When the Mn2+ catalyst concentration was kept unchanged, the sulfite oxidation reaction rate was controlled by dual film and the reaction kinetics was first order with respect to sulfite while SO
 3
 2−
 concentration was below 0.328 mol/L; the sulfite oxidation reaction rate was controlled by gas film only and the reaction kinetics was zero order with respect to sulfite while SO
 3
 2−
 concentration over 0.328 mol/L. When SO
 3
 2−
 concentration was kept unchanged, the sulfite oxidation reaction rate depended on gas-liquid mass transfer and the reaction kinetics was different in various stages with respect to Mn2+ concentrations.

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Mass transfer and kinetics study on the sulfite forced oxidation with manganese ion catalyst

This study deals with the simultaneous removal of sulfur dioxide (SO2) and trace selenium dioxide (SeO2) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range, especially the feasibility of simultaneous removal of these two pollutants in a moderate temperature dry flue gas desulfurization (MTD-FGD) reactor. The effect of SO2 presence on selenium capture is studied through the experiments performed on a thermogravimetric analyzer (TGA) and the following conclusions can be obtained. When CaO conversion is relatively low and the reaction rate is controlled by chemical reaction kinetics, the SO2 presence does not affect selenium capture. When CaO conversion is very high and the reaction rate is controlled by product layer diffusion, the SO2 presence and the product layer diffusion resistance jointly reduce selenium capture. Through analyses of some pilot scale MTD-FGD tests, it can be concluded that in the MTD-FGD reactor, the sulfate reaction of sorbent particles is generally kinetically controlled. Therefore, it is feasible that sulfur and trace selenium can be simultaneously removed by Ca-based sorbent in the MTD-FGD reactor.

Feasibility study on simultaneous removal of sulfur and trace selenium in the MTD-FGD reactor

The recent development of coal combustion pollution control technologies in China, including desulphurization, denitrification, particulate matters and heavy metals emission control technologies, have been reviewed. The development histories and the advantages of China’s self-developed technologies have been introduced in detail. The key points of future research and development in coal combustion pollution control, e.g., combined emission control and CO2 emission control technologies, have also been discussed.

Tong Huiling

Papers

Comparison and Analysis on the Calculation Methods of Acid Dew Point of Flue Gas

Mass transfer and kinetics study on the sulfite forced oxidation with manganese ion catalyst

Feasibility study on simultaneous removal of sulfur and trace selenium in the MTD-FGD reactor

The development of pollution control technology in coal combustion in China