A review of chemical leaching of coal by acid and alkali solution

Low rank or low-grade (LRC or LGC) coals are most abundant distribute around the several regions in the world. The contribution of low-rank coal is a significant role in the energy sectors and chemical feedstock to the industries. The hard coal reserves are gradually depleting, and the mining operation at deeper coal seam with greater difficulties as well as the cost of exploration is so high, which has a significant issue for plant economics. Therefore, the low-grade coal can be used as an alternative energy source to minimize these problems. Low-rank coals are usually associated with high mineral matter and moisture content, which exerts substantial impacts on their consumption including pyrolysis, liquefaction, gasification and combustion process. In order to understand the essential treatment of coal for efficient removal of mineral matters and improve coal properties by beneficiation techniques are crucial to developing advanced technologies. The present article provides a comprehensive overview of the various processes concerning demineralization of coal by chemical beneficiation technique. It has been found from the study; the degree of demineralization was greater in chemical beneficiation compared to physical beneficiation. It is because the chemical reagents are attacked to the interior of coal which removes the inorganic materials and finely dispersed minerals from the coal matrix. The chemical methods have separated all types of minerals from the coal matrix. However, the separation of minerals by the physical method depends on the mineral properties. Chemical beneficiation is an appropriate method to reduce both organic and inorganic mineral constituents from the LGC by leaching method. The chemical reagents are diffusing to the interior of coal matrix through the pores and subsequently dissolute the minerals. Throughout the study challenges, the chemical cleaning of low-grade coal has been efficient techniques for reducing the minerals to a minimum level that can be upgraded to high rank coal

Generalized PVO‐based dynamic block reversible data hiding for secure transmission using firefly algorithm

In this paper, we proposed a novel generalized pixel value ordering–based reversible data hiding using firefly algorithm (GPVOFA). The sequence of minimum and maximum number pixels value has been used to embed the secret data while prediction and modification are held on minimum, and the maximum number of pixel blocks is used to embed the secret data into multiple bits. The host image is divided into the size of noncoinciding dynamic blocks on the basis of firefly quadtree partition, whereas rough blocks are divided into a larger size; moreover, providing more embedding capacity used small flat blocks size and optimal location in the block to write the information. Our proposed method becomes able to embed large data into a host image with low distortion. The rich experimental results are better, as compared with related preceding arts

Air Pollution and Its Control

© 2012 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. Chemical and allied process industries emit huge air pollutants and causes severe degradation to the environment. The control option of air pollutants greatly depends on the nature of pollutants and type of sources. There is a tremendous demand for airpollution control in fertilizer, coal-fired thermal power plants, petroleum refinery, cement, steel industries, etc. to meet the stringent demands. The topics covered are air pollution sources, nature, transport, pollution problems encountered, and control technologies usually used with design consideratio

GAS HOLDUP IN A THREE-PHASE FLUIDIZED BED WITH CYLINDRICAL PARTICLES

ABSTRACT The gas holdup characteristics in a cocurrent three-phase fluidized bed with liquid as continuous phase and gas as the discontinuous phase have been studied. Air, water and ceramic raschig rings are used as the gas, liquid and solid phases respectively. The experiments were carried out in a 0.1 m internal diameter, 1.88 m height vertical Plexiglas column. The results indicate that gas holdup increases with increasing gas velocity and decreasing liquid velocity. From the correlation developed for gas holdup it is found that gas holdup is a strong function of modified gas Reynolds number and a weak function of the liquid Reynolds number. The experimental values have been compared with those calculated from the developed correlation and have been found to agree well