Coal liquid fuel

Finally, the considerations developed for the conditions of ignition and the feasibility of combustion may also be applied to the combustion of coal, liquid fuel, etc., due to oxygen in the surrounding medium. In these cases the temperature gradient in the c-phase (in coal or oil) also plays a role in the thermal balance. A number of substantial differences, particularly a different form of the combustion velocity curve as a function of the parameters, makes a special study, inappropriate here, essential. 

The purpose of this program was to define for utility diesel systems what engine and operating condition modifications might be necessary to accommodate the use of coal liquid fuels. 

The low cetane number of coal liquid fuels could lead to poor starting and warm-up characteristics at low ambient temperatures and to engine roughness at part load operation. 

Preparation and Utilization of Pulverized Coal LIQUID FUELS Characteristics... 

Liquid Fuels via Methanol Synthesis and Conversion. Methanol is produced catalyticaHy from synthesis gas. By-products such as ethers, formates, and higher hydrocarbons are formed in side reactions and are found in the cmde methanol product. Whereas for many years methanol was produced from coal, after World War II low cost natural gas and light petroleum fractions replaced coal as the feedstock. 

A. Sass, "The Garrett Research and Development Company Process for the Conversion of Coal iato Liquid Fuels," paper presented at 65th Annual AIChE Meeting New York, Nov. 29, 1972. 

Liquid Fuels. Liquid fuels can be obtained as by-products of low temperature carbonization by pyrolysis, solvent refining, or extraction and gasification followed by catalytic conversion of either the coal or the products from the coal. A continuing iaterest ia Hquid fuels has produced activity ia each of these areas (44—46). However, because cmde oil prices have historically remained below the price at which synthetic fuels can be produced, commercialization awaits an economic reversal. 

The increasing use of carbon-bonded and carbon-impregnated refractories is providing another growing market for refined tars. These vary from a soft pitch to a refined tar of as low as 30°C equiviscous temperature (EVT) (see Refractories). Liquid fuels were formerly important outlets for coal-tar, pitch—oil blends, and topped tar which could not be disposed of more profitably (79). However, as a result of reduced tar suppHes this usage has been phased out. 

In recent years there has been a rapid growth in the number of combined heat and power (CHP) and combined cycle gas turbine (CCGT) plants, driven mainly by gas turbines using natural gas, sometimes with liquid fuel available as stand-by. Governments have encouraged the construction of these plants, as their efficiency is high and they produce less carbon dioxide than conventional coal and oil-burning power stations. However, they present some hazards, as gas turbines are noisy and are therefore usually enclosed. 

Although biomass used directly for heating and cooking is the thermodynamically most efficient use, followed by use for electricity generation, the economics are much more favorable to convert to a liquid fuel. Economic considerations outweigh thermodynamics as an electricity generator, biomass must compete with relatively low-priced coal, but as a liquid fuel the competition is higher-priced oil. 

Liquid fuels for use in internal-combustion engines are extracted and refined from crude oil, with diesel fuels being part of the middle distillate or kerosene fraction. Kerosene was initially derived from coal pyrolysis. The initial main use of this type of distillate was for the kerosene lamp, which had replaced lamps based on whale oil. 

From a practical standpoint, coal, because of its abundance, has received the most attention as a source for synthetic fuels. As early as 1807, a coal-gas system was used to light the streets of London, and until the 1930s, when less expensive and safer natural gas started to flow through newly constructed pipelines, gas piped to homes in the Eastern United States was derived from coal. Kerosene, originally a byproduct from the coking of coal tor metallurgical applications, can be considered the first synthetic lic -uid fuel made in quantity. But once crude oil became cheap and abundant, there was little serious research on synthetic liquid fuels in the industrial world until the Energy Crisis of 1973. The main exceptions to... 

As crude oil reserves dwindle, the marketplace will either transition to the electrifying of the transportation system (electric and fuel-cell vehicles and electric railways), with the electricity being produced by coal, natural gas, nuclear and renewables, or see the development of an industry to produce liquid fuel substitutes from coal, oil shale, and tar sands. It might also turn out to be a combination of both. The transition will vary by nation and will be dictated strongly by the fuels available, the economic and technological efficiencies of competitive systems, the relative environmental impacts of each technology, and the role government takes in the marketplace. 

Regional scarcities of coal initially drove these uses. As petroleum became more abundant and as its price fell, oil became more attractive. In firing boilers, fuel oil possessed only a slight advantage over good-quality coal in Btus per unit volume. But liquid fuels were much easier to handle and store than coal. Competitive pressures kept the prices per Btu of residual oil and coal quite close. 

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