High-temperature performance of ferritic steels in fireside corrosion regimes: temperature and deposits

The paper reports high temperature resistance of ferritic steels in fireside corrosion regime in terms of temperature and deposits aggressiveness. Four candidate power plant steels: 15Mo3, T22, T23 and T91 were exposed under simulated air-fired combustion environment for 1000 h. The tests were conducted at 600, 650 and 700 °C according to deposit-recoat test method. Post-exposed samples were examined via dimensional metrology (the main route to quantify metal loss), and mass change data were recorded to perform the study of kinetic behavior at elevated temperatures. Microstructural investigations using ESEM-EDX were performed in order to investigate corrosion degradation and thickness of the scales. The ranking of the steels from most to the least damage was 15Mo3 > T22 > T23 > T91 in all three temperatures. The highest rate of corrosion in all temperatures occurred under the screening deposit

The control characteristic shaping of fluid mass flow adjustment elements

W artykule przedstawiono koncepcję elementów nastawczych: zasuwy, przepustnicy oraz zaworu grzybkowego, które charakteryzują się dobrze założoną zależnością między strumieniem płynu a stopniem ich otwarcia. Przedstawiono ideę algorytmu obliczeń projektowych, w którym wykorzystano metodę charakterystyki odwrotnej, kryterium liniowości oraz uogólnioną, podstawową charakterystykę przepływową.Paper presents a concept of adjustment elements which is characterized by demanded relation between the fluid mass flow and the opening factor. A method suitable for design process is presented in which the method of inverse characteristic, linearization criteria and fluid mass flow characteristic are utilized

Changes in total active centres on particle surfaces during coal pyrolysis, gasification and combustion

In the paper, on the basis of our studies and the available literature data, a model of changes in the number of active centers corresponding to the structure of the reactive coal particle has been developed. A new distribution function that links the specific surface area of a particle with its porosity and reaction degree has been proposed. An equation for estimation of changes in this parameter during the reaction, on the basis of the initial value, has been presented. In the range of our data and the analysis of the literature data, the model, with satisfactory accuracy, describes internal structural changes of coal and coal char particles. The present results may constitute a basis for complex modelling of coal conversion processes. Based on the results it was found that the total active centres are related to the internal surface area and porosity of the particle. For a specific coal type, this value depends on the porosity, true density and size of the particle. Changes in total active centres, when these structural properties during thermal conversion of coal are considered, are described in equations

Effect of annealing on properties of carbonaceous materials. Part II: porosity and pore geometry

The pore structure of carbonaceous materials was studied using image analysis. The effect of annealing on the porosity and pore geometry of cokes, chars, and pyrolyzed coals (laboratory chars) was examined in the temperature range of 973 K to 1773 K (700 C to 1500 C). The porosity of chars and pyrolyzed coals significantly increased during annealing at temperatures below 1373 K (1100 C) due to volatile matter release. Further increasing of the annealing temperature from 1373 K to 1773 K (1100 C to 1500 C) caused marginal porosity evolution. The porosity of cokes was not affected by annealing at temperatures below 1573 K (1300 C) and slightly increased in the temperature range 1573 to 1773 K (1300 C to 1500 C). The increase in the porosity of chars and pyrolyzed coals during annealing at temperatures 1373 K to 1773 K (1100 C to 1500 C), and cokes at 1573 K to 1773 K (1300 C to 1500 C), was a result of reactions with oxides of their mineral phases. Annealing had a marginal effect on the pore shape (Feret ratio) of carbonaceous materials, but enlarged the pore size of chars and pyrolyzed coals and decreased their pore density