Ievgenii Poltavskyi

MASTERS'S THESIS ABSTRACT

           The limited world reserves of oil and natural gas, raising their prices and growing such environmental problems cause transition of the world economy to the new energy sources.Clearly,that the mega coal mining regions as the Donbass, will build its strategy on gradual transition to cleaner energy sources, namely coal-based.At the same time coal as energy source has very significant negative characteristics.All this problems can find a positive solution due to coal gasification.
          This direction of coal utilization is associated with its so-called "non-energy" use. This is processing of coal on to other kindes of fuels (eg, combustible gas, coke, etc.) preceding or concomitant to receipt of a thermal energy. For example, in Germany during World War II technology of coal gasification was actively used for production of motor fuels. In South Africa the SASOL plant is using this technology, the first design of which was also performed in Germany in the 30's and 40's of the XX century, Currently plant produces more than 100 kinds of products from brown coal. (This process of gasification is also known as "method of Lurgi».)
          The most important characteristic of a coal gasification process is the possibility of its widespread use. Uniqueness of the technology is connected the fact that the raw syngas we can receive more than one hundred products for various industries: steel, power, chemicals, petrochemicals, etc.. The syngas is the raw material for alternative fuels, such as synthetic natural gas (SNG), ethanol, diesel, jet fuel, as well as many others, thet the same time are environmentally friendly. In addition, the cost of syngas is lower than natural.In favor of coal gasification, as well as the use of syngas as a whole, says the follow ing:

– coal gasification provides an opportunity to produce energy and products at low cost, which provides competitive advantage in the market of expensive energy;

– Although a major power plant using gas from coal, require large investments(like any other large-scale production), operation costs by installing the gasification of coal will be potentially lower than for conventional coal plants, because the first are more effective and do not require expensive equipment for environmental protection;

– gas from coal could replace increasingly expensive natural gas used as fuel or raw.

          I believe that in a world that need to reduce greenhouse gases, coal gasification will benefit from the economic as well as with environmental point of view.
           Rapid development of coal gasification is projected in the world. Expected to increasing of coal gasification capacity by 70% by 2015, with 80% of this growth occurring in Asia. The reason for this is not only an increase of population, but high prices of oil and natural gas. It leds increased interest to alternative energy sources.
          In my master work, I plan to undertake an analysis of existing brands of the Donbass coal; as the main (basic); and new, dynamically developing, installations for the gasification, thereby identifying the most suitable ratio of coal and brand. During the analysis will cover the following basic schemes gasification:

          Scheme of "Lurgi" gasification technology.

          GasificationAutothermal Gasification under pressure in the sheet reactor with countercurrent movement of coal and steam mixture.This gas generator is used successfully by many enterprises in a wide range of large-scale industrial assemblies. Process established long time ago remains the only large-scale and quite perfect process of gasification under pressure.Despite the fact that many technological stages of the process will still be refined, in technical terms this method is the most deeply developed currently.Productivity of a gasifier contemplates 75000 м³/h.

          Scheme of "Vinkler" gasification technology.

          Autothermal water vapor - gasification with air or oxygen in a fluidized bed under normal pressure. It is known 16 industrial units with 36 gas generators, nominal capacity of which synthesis gas is from 5000 to 60000 м³/h,which corresponds the consumption of coal approximately from 3 to 35 t/h.Nowadays some of these plants still being exploited. A new version of the process involves gasification of dry brown coal with oxygen or direct hot air under pressure (fever heat - Winkler process)

          Scheme of "Kopers-Tottsek" gasification technology.

          Autothermal steam – oxygen Gasification of balanced mixture under normal pressure in a parallel flow mode. Gasifiers with two burners heads have been manufactured predominantly till now.The length of such gas generator is 7,5 м. The inner diameter is up to 3,5 м ,internal volume is approximately 28 м³. The volume of a gas generator with four burners heads is twice more. Consumption of coal contemplates 13,5 t/h for a gas generator with two burners heads, with four - 20,8 t/h.Production of unstripped gas contemplates 21000 м³/h, for a gas generator with two burners heads, with four - 32300 м³/h.

          Scheme of "Teksako" gasification technology.

          Autothermal Gasification of coal under pressure in forward flow of steam and oxygen. In 1978 in the plant Morgantauie (West Virginia) firm Olney Mathieson Chemical Corporation commissioned the industrial installation with gas productivity at the level of 6500 м³/h to obtain synthesis-gas by Texaco technology.This technology does not depend on the type of coal.

          Scheme of "Lurgi-Rur-100" gasification technology.

          Autothermal Gasification in a backflow with a steam – oxygen mixture in layered reactor under pressure of 10 MPa. The gas generator is designed for pressures up to 10 MPa and flow rate of 7.1 t / h clean coal.There are two gazootbornyh channel for pure gas and semi-coking gas, as well as a built-cold water jacket to produce high pressure steam.The generator has two alternately operating coal Gateway, a shaft, which rotates with the distributor of coal and a few agitators, provided due to a tendency of coal to sintering under high pressure. One of the possible targets of gas generator improvement is a change in particle size distribution of coal in the direction of small fractions. In addition, zabalastovany coal should be used. The ultimate goal is to use a wet raw coal.In studies being conducted up to now stone coal was used firstly, then hard-coal enrichment waste with high maintenance of ash and finally gas coal enrichment waste. The gas generator for this process looks the following way:

          The analysis will receive the following data: enthalpy of formation of various grades of coal; assessing the impact of heat of combustion of fuel on the enthalpy of its formation; influence of the enthalpy of formation on the basic parameters of the process of gasification; influence of moisture and ash content of coal on its enthalpy of formation;the influence of enthalpy of formation of coal on the adiabatic temperature and composition of gasification products; the influence of enthalpy of formation of coal on the heat of combustion and output of the generator gas.Next will be a mathematical model of the process of gasification for the selected method and brand of coal. To construct the mathematical models and engineering calculations suffice to consider the total kinetic parameters of reactions of carbon with О₂, СО₂ and Н₂О. The result of calculation should be the most steam / oxygen effective ratio of the mixture and its influence o n the composition of synthesis gas at various temperatures and pressures and possible suggestions for improvement of either the gas generator, or an existing process.
References:

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