A Study of the Prediction of Ammonium Bisulfate Formation Temperature by Artificial Intelligence

Ammonium bisulfate (ABS) is an acidic deposit that can form on the metal elements of air preheaters in power boilers, leading to unit operational issues. As a byproduct of the Selective Catalytic Reduction (SCR) systems for nitrogen oxide (NOx) emissions control, ABS could result in unit efficiency deterioration, even unit outage. ABS formation temperature is an important factor in controlling the issues associated with ABS fouling problems. If the ABS formation temperature could be monitored, the ABS deposition location could be identified. Subsequently, preventative actions could be taken to avoid ABS fouling to develop into a serious operational problem, such as air preheater plugging. This study deals with indirect predictive models of ABS formation temperature. Five models were developed based on data mining technologies, using actual power plant data. Data composed of 14,230 samples, from 49 variables were used in the study. In the modeling, Principal Component Analysis (PCA) and Sensitivity Analysis (SA) were used to reduce the number of variables in the data set. K-Means Clustering (KMC) was also employed to compress training samples. Neural Networks (NN) and Support Vector Machine (SVM) were used for data modeling. Model results were validated with ABS formation temperatures measured with an ABS dew-point probe. A SA was performed to determine the impact of individual variables on the ABS formation process. It was found that four unit variables: SO2 stack concentration, SCR gas outlet temperature, SCR inlet NOx concentration and dilution skid ammonia flow, can provide a good representation of the data set for ABS formation temperature prediction. The most accurate predictive model consists of a sequence of KMC and SVM. This approach can predict ABS formation temperature within a 9% error from the physical measurement

Research on the Disaster-Inducing Mechanism of Coal-Gas Outburst

In China, coal-gas outburst is seriously affecting safety of the coal mine. To improve the safety status of underground coal mining, this work investigated the evolution process and occurrence mechanism of coal-gas outburst under the coupling action of stress and gas. Results show that increasing either gas pressure or in-situ stress can make coal destroy and destabilize, and the contribution of gas pressure to coal failure is twice that of in-situ stress. In ultradeep coal mining, coal-gas outburst may occur even under the condition of low gas pressure due to large in-situ stress. Moreover, the larger the mining depth is, the lower the gas index is required for disaster occurrence. The results have certain guiding significance for coal energy mining and the control of coal-gas outburst in deep coal mining

Formation and autocatalytic nucleation of co-zone {101¯2} deformation twins in polycrystalline Mg: A phase field simulation study

A phase-field model is developed to study the formation and autocatalytic nucleation of twins in polycrystalline Mg. The twins are found to nucleate most favourably in grains with the most negative interaction energy. Within such grains, the energetically most favoured nucleation site is determined by stresses concentrated near the grain boundaries that are related to the elastic anisotropy of the material. Furthermore, in a structure consisting of three lamellar grains with an incoming twin in the central grain, the simulation results show that before autocatalytic nucleation, the incoming twin often has a lenticular shape. The stress field around the tip of the incoming twin plays the major role in the autocatalytic nucleation. After a twin has nucleated in the neighbouring grain, the incoming and the outgoing twins evolve simultaneously, and the shape of the incoming twin gradually changes from lenticular to parallel-sided plate. Under the condition that the crystallographic orientation of the central grain and the applied strain remains unchanged, the driving force for twin nucleation decreases with increasing misorientation (up to 90°) across the grain boundary. It is further derived that the interaction energy values between the pre-existing stress field of the polycrystalline structure and the eigenstrain of the to-be-nucleated twin is mathematically related to the resolved shear stress of twins

A hierarchical porous electrode using a micron-sized honeycomb-like carbon material for high capacity lithium-oxygen batteries

A micron-sized honeycomb-like carbon material (MHC) is prepared in a facile way using nano-CaCO3 as a hard template. A novel electrode for lithium-oxygen batteries is fabricated and displays a superior discharge capacity as high as 5862 mA h g(-1). The higher electrode space utilization is attributed to its hierarchical pore structure, with intrinsic mesopores in the MHC particles for Li2O2 depositions and macropores among them for oxygen transport

Variant selection of primary–secondary extension twin pairs in magnesium: An analytical calculation study

Twining is an important deformation mode in magnesium. In a deformed magnesium sample, an extension twin crystal, i.e., {101̅2} twin, can form inside a {101̅2} primary twin, which is named {101̅2}– {101̅2} secondary twin. These secondary twins often appear at the intersection of two primary twins, and form primary–secondary twin pairs. Experimental observations show that the most frequently observed primary–secondary twin pairs have a unique misorientation, i.e., twin variant selection exists. Such variant selection of the primary-secondary twin pairs is studied in this work. The crystallographic analysis reveals that the twin planes of the primary and secondary twins that form a twin pair have coincident intersection lines with the boundary where the twin pair adjoins. An analytical calculation method based on Eshelby’s inclusion theory is developed, and the calculation results show that only for this unique misorientation, the stress fields concentrated at the rims of the primary and the secondary twins are mutually favoured. The analysis is further extended to the incoming–outgoing twin pairs across ordinary grain boundaries, and compared with the commonly used geometrical compatibility factor m'. It is found that m' only gives good prediction for twin transmission when the shear stress component on the twin plane along the twin shear direction of the incoming twin is the major contributor to the resolved shear stress of the outgoing twin. When other stress components play a dominant role, m' becomes ineffective in prediction, which is the case for the primary-secondary twin pair