Methods of Coal Gasification

According to their mechanical technology, i.e. to the method of feeding the coal to the gasifier and to its behaviour in it, coal gasification processes may be classified into 

Going by the way in which the required heat is provided, they may also be grouped into 

In addition to the above two criteria, the processes can also be classified according to the types of product gases, e.g. lean gas, reduction gas, rich gas (methane) and synthesis gas. Among these types, however, only the latter needs to be considered here. 

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There are two possibilities for electrochemical utilization of the chemical energy of coal (1) via prior coal gasification and use of the hydrogen and/or carbon monoxide produced in this process in various fuel cells, and (2) by direct electrochemical oxidation within the fuel cell. Various methods of coal gasification are discussed in Chapter 11. Some attempts to realize the second approach, which is basically a much simpler one-step process, are discussed in the present section. [Note that coal and carbon are somewhat interchangeable terms when... 

At present this method is excluded by a more economical process of methane reforming (considered in Section XIV). The exhaustion of natural gas resources may, however, restore the importance of coal gasification. In addition, reaction (377) is a constituent part of the blast furnace process. Reaction (378) is employed in the production of activated charcoal. 

There are many methods for the desulfurization of nature gas, which can be classified into dry desulfurization, wet desulfurization, and catalytic adsorption. In the dry desulfurization, some solid sorbents, such as iron oxide, zinc oxide, activated carbon (AC), zeolites, and molecular sieves, are used. In wet desulfurization method, liquid-phase chemical/physical solvent absorption systems are usually used for scrubbing H2S amine-based processes are subject to equipment corrosion, foaming, amine-solution degradation, and evaporation, and require extensive wastewater treatment. As a result, this sulfur removal technology is complex and capital intensive,44 although the processes are still employed widely in the industry. The desulfurization of coal gasification gas will be reviewed in detail in Section 5.5. In the catalytic-adsorption method, the sulfur compounds are transformed into H2S by catalytic HDS or into elemental sulfur or SOx by selective catalytic oxidation (SCO), and then, the reformed H2S and SOx are removed by the subsequent adsorption. 

As mentioned above, the chemical process in a large scale gasifier cannot be perfectly explained by kinetics and equilibrium. Composition of gases produced by gasification is a very clear indicator of the chemical state in the gasifier. We propose a stoichiometric method to analyze the reaction process of coal gasification. 

The licensor s basis for sizing has already been discussed and agreed to or changed. For an olefin plant, the number of steam crackers of the licensor s standard size is firm. For a new process, reactor scaleup methods have been agreed to. For a coal gasification plant, gasifier size. 

This section discusses some of the items considered in the start-up costs for a coal gasification project, along with the methods of estimating each item. 

Coal used in power stations has the potential to be partly replaced by fuels derived from pre-treated plastics and paper waste, reducing both dependency on fossil fuels and reliance on landfill. APME reports on a project in the Netherlands which it co-sponsored to develop a substitute fuel from plastics. The environmental assessment of the project compared the environmental impacts of coal substitution with other plastics recovery methods, including gasification in feedstock recycling and energy recovery from plastics waste in cement kilns. The study also compared coal substitution with the generation of power from burning biomass. 

Two-constant equation of state phase behavior calculations for aqueous mixtures often require the use of temperature dependent binary interaction parameters. The methods used for evaluating these parameters for some of the typical aqueous binary pairs found in coal gasification and related process streams are described. Experimental and predicted phase compositions based on these methods are illustrated for aqueous pairs containing CO2. H2S, NH3, and other gases. 

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