Showing papers on "Carbochemistry published in 2010"

Kirk‑Othmer Encyclopedia of Chemical Technology Coal Conversion Processes, Cleaning and

Abstract: An overview of coal cleaning and desulfurization schemes designed to minimize contaminants from coal combustion systems is presented. Coal cleaning can be divided into two basic categories: physical and chemical processes. Physical cleaning involves specific gravity-controlled processes. Surface-force-controlled processes, such as flotation and selective agglomeration, dominate newer developments. Whereas chemical and biological coal cleaning processes have shown potential to produce deep-cleaned coal, most of these processes have yet to be tested at commercial scale.

Enhancing the Steam Gasification Reactivity of Coal by Boosting the Factors Affecting the Gasification Reactions in the Stepwise Coal Conversion

Abstract: Factors affecting the steam gasification reactivity of coal have been reviewed. Studies have been performed on investigating the effects of organo-refining (solvent extraction) using coal-derived solvents, such as anthracene oil and liquid paraffin. The residual coals obtained from the organo-refining of coal were subjected to steam pyrolysis at 650°C to generate active chars. The steam gasification reactivity of original coal, anthracene oil extracted residual coals, anthracene oil–liquid paraffin (successively) extracted residual coals, and their chars were studied first in a laboratory gasifier and then by using thermogravimetric analysis apparatus in steam atmosphere. Nonisothermal kinetic studies revealed that organo-refining and steam pyrolysis are beneficial pretreatments for the steam gasification of coals/chars. These pretreatments leave sufficient residual volatile matter in coals/chars, increase the active surface area, and expose and make available the finely dispersed mineral matter ...

The Steam Gasification of Coal under Milder Low Temperature Conditions—Nonisothermal Kinetics Studies for Reactor Design

Abstract: Advanced systems of power generation, such as integrated gasification combined cycle power generation, are being demonstrated as the next generation of clean coal technology. It is important commercially to exploit the coal in such a way that premium and added value chemicals are recovered from coal before subjecting this to destructive gasification to yield the smallest molecules, such as H2 and CO, from coal macromolecules (C~20–C~240). In the present studies, original Talcher coal was subjected to organo-refining using coal-derived solvents, such as anthracene oil and liquid paraffin. The residual coal obtained from organo-refining was pyrolyzed in steam atmosphere. The kinetics of the low temperature steam gasification of the original coal, residual coal, and their chars was studied. These studies would help in designing the reactor for the steam gasification of coals, residual coals, and chars, thereof. These pretreatments beneficially disrupt the structure of coal by exposing more active si...

The Nature of Coal

Abstract: Coal is used primarily as a fuel, so its most important property is its heat of combustion. Gross calorific value , also known as higher heating value (HHV) , is determined by measuring the heat released when coal is burned in a constant-volume calorimeter, with an intitial oxygen pressure of 2 to 4 MPA, and when the combustion products are cooled to a final temperature between 20 and 35°C. Coal is a porous medium, and these pores, especially in low rank coals, can contain substantial quantities of water even though the coal appears to be dry. In the coalification process, the coal rank increases from lignite to anthracite. Bituminous and subbitumous coals are the primary commercial coals. A relatively small amount of anthracite is available. Some coal, particularly bituminous coal, has the tendency to cake. With increasing temperature, coal particles simultaneously pyrolize and partially melt, causing the coal particles to stick to one another. Some gasification reactors, especially moving bed and fluidized bed gasifiers, are limited to processing coal that does not cake. The melting temperatures of coal ash impose temperature limits for coal gasification. Fluidized bed gasifiers and dry-bottom moving bed gasifiers, such as the Lurgi gasifier, require free-flowing ash. The maximum operating temperature for these gasifiers is the initial deformation temperature.

Washability studies and characterization of cleans of coking coal sample from BCCL, CIL, India

Abstract: Coking coal is an essential prerequisite for production of Iron & Steel through blast furnace route. Systematic R&D studies on the availability of desired quality coking coal from indigenous resources have become imperative to minimize the dependence on imported coals. The Low Volatile Coking Coal (LVCC) constitutes about 50% of the total coking coal reserves in India. These coals are characterized by high ash content and difficult in cleaning potential. The present paper highlights the R&D investigations carried on a typical LVC coal of Bharat Coking Coal Limited. The run-of-mine (ROM) coal was crushed to 75 mm and detailed float and sink tests were carried out on the fraction 75–0.5mm basically to study the cleaning potentiates of the coal on washing. The coal fines were subjected to standard laboratory flotation tests to study the flotation behavior. Combined cleans was generated at 17.5% ash level and characterized for finding its utilization in metallurgical industries. The characterization studies revealed that the coal after suitable beneficiation may be used as a blendable coal for metallurgical purposes.

How the steel industry can get the best out of Indian coal

Abstract: Coal, particularly coking coal is a vital raw material for the steel industry, since coke plays a key role in blast furnace ironmaking. Efforts are always made to reduce the consumption of coke in blast furnaces by injection of non-coking coal through the tuyeres. This automatically imposes severe restrictions on the quality of blast furnace coke. Furthermore, for coal injection to be effective, the injected coal has to be carefully selected so that it does not drastically alter the conditions prevailing in the blast furnace raceway. The quality of blast furnace coke depends on: the properties of the coal blend used, the process used for cokemaking including the technique of pre-carbonisation employed (if any), and to a lesser extent, on post-carbonisation operations. The influence of the properties of coking coal on blast furnace coke and the parameters involved in the choice of non-coking coal for coal injection are discussed in this paper. In India, there is dearth of both coking as well as non-coking coal suitable for the steel industry. Intensive efforts in terms of coal selection, up-gradation by beneficiation, etc. are required to optimise the properties (particularly the ash content) of Indian coal. In addition, in order to produce high grade coke from weakly coking Indian coking coals, blending with low ash imported coal of high rank is essential. The cost incurred on imported coal can be controlled by paying simultaneous attention to the preparation of indigenous coals.

Simulating the generation of products from thermochemical processing of coal

Abstract: A method of calculating the kinetic processes of thermochemical decomposition of coal is proposed by taking Irsha-Borodino coal from the Kansk-Achinsk coal field as an example. Results obtained from calculations of the yield of products from coking the organic mass of coal are presented.

Paper ID : 20100986 Performance comparison of high ash Indian coal under different gasification conditions

Abstract: The increasing demand for clean fuels and climbing crude oil prices are driving oil industries to pursue the route of reducing the bottom of the barrel and alternative energy sources. Among various options available, Gasification finds an important place in the refinery to increase the refining margin as well as meeting the demand for cleaner fuels. Coal, Resid or biomass can be gasified to produce Syngas, which can be used to produce wide spectrum of products such as, clean liquid fuels, power or hydrogen. In particular, India having huge resource of coal receives wider attention. However, Indian coals are difficult to process due to its high ash content. In addition to this, the efficiency of the plant is inversely influenced by the inherent ash content in coal. This leads to the option of co-processing petroleum resids with coal to increase the efficiency of the plant. Simulation models based on basic thermodynamics are useful in analyzing different scenarios, optimization and for carrying out economic analysis for various options. Such steady state models were developed by us using ASPEN Plus for processes such as, gasification, Syngas conditioning, FT liquids production and power generation. These models are useful for studying the effect of Indian coals, petroleum resids, co-processing of various carbonaceous feedstocks, steam to oxidant ratio, process conditions, mode of feeding (dry or slurry), etc on the composition of produced syngas. These models can be used for identifying suitable gasifier configuration for processing high ash coals and can also carry out economic analysis for various co processing options such as co-production of hydrogen and power, co-production of FT liquids and power. In this paper, we present the simulation results with Indian coals for different polygeneration options and compared the efficiencies with low ash coals. The option of processing petcoke along with high ash Indian coals was also studied. Literature on high ash coals is very scarce and not readily available. In this perspective, the approach presented in this paper serves as a tool for selecting a suitable configuration for coal/resid co-processing options.