Natural Gas as a Fuel

Natural gas is an excellent fuel which bums cleanly with little or no residue. The main problem with its use is its low energy density—it is not readily stored in sufficient quantities to power a vehicle for the normal distance of 300 00 km. The simplest storage method is as a compressed gas in cylinders. Buses in Vancouver have such storage cylinders on the roof. It has been shown that by filling a cylinder with active carbon, it is possible to double the amount of CH4 which can be stored in the cylinder. However, this still limits the use of compressed natural gas (CNG) to fleet vehicles which can routinely refill the cylinders with compressed gas. Buses mn on natural gas in Vancouver (British Columbia, Canada) during the last 2010 Winter Olympic Games. This is shown in Fig. 6.6. 

Natural gas can be stored in insulated containers as a liquid at — 161°C, and as a liquid fuel, the LNG has sufficient energy density. Its use has been tested in airplanes and locomotives. However, the use of natural gas as an automotive fuel is still limited unless higher densities can be achieved. 

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Direct Reduction. Direct reduction processes are distinguished from other ironmaking processes in that iron oxide is converted to metallic iron without melting. Because this product, called direct reduced iron (DRI), is soHd, it is most suitable for melting in an electric arc furnace (EAF) as a substitute for scrap (see Furnaces, electric). The briquetted form of DRI, hot briquetted iron (HBI) is used when the product is to be transported. Briquetting increases density and chemical stabiUty. The predominant direct reduction processes (MIDREX and HyL III) are based on natural gas as a fuel and reductant source. They are economically attractive in regions where natural gas is cheap and abundant, especially if iron ore is available nearby (see Iron BY DIRECT reduction). ... 

The development of natural gas as a fuel source in the UK has led to reductions in tar acid supplies and this has prompted the petrochemicals industry to make... 

Against this background of the changed economics of plant performance, we consider some of the many new gas turbine plants that have been proposed over the past few years. In this section, we first formulate a list and classify these plants (and the cycles on which they are based), as in Tables 8.1A-D, noting that most but not all use natural gas as a fuel. 

United States, methanol derived from natural gas as a fuel additive is a promising future market. Methanol has neither the environmental problems of methyl-t-butyl ether (MTBE), nor the evaporating qualities of ethanol. 

There are several transportation applications where natural gas storage as CNG provides inadequate range because of limited space and allowable weight for a CNG fuel system. The railroad industry and heavy-duty over-the-road trucks are the two current primary examples of transportation vehicles that as a practical matter must use LNG instead of CNG in order to use natural gas as a fuel. 

Consolidated Edison Co. announced on January 12, 1979 that it will seek federal approval to replace up to 10 million barrels of imported oil per year with domestic natural gas as a fuel in its electric power and steam plants. 

In view of the abundance of natural gas resources found since the 1980s, and natural gas being a considerably cleaner fuel than petroleum or coal for the fuel processors, the main goals of the major worldwide fuel cell programs are to develop fuel cell power plants and portable power sources using natural gas or natural gas-derived fuel cells. A chart of all types of fuel cells, using natural gas as a fuel, is presented in Scheme 9.2 the applications being considered for the different types of fuel... 

The first MCFC was demonstrated by Broers in 1950 [336], and the first MCFC at high pressure was built by Reiser and Schroll [337] in 1980. As shown in Figure 32, at present the MCFC it is the most efficient fuel cell, and this will be discussed in the following. The MCFC, operating at a temperature between 600 and 650°C, is generally considered a second-generation fuel cell [316,338,339], It can be used with coal gas and even more so with natural gas as a fuel. 

Typical examples of the first approach, upgrading or improving the fiiel, are the catalytic removal of sulfur and aromatic compounds in automotive fuels [8,9]. A shift from the use of coal to the use of natural gas as a fuel in many industrial applications has led to reduced emissions, due to the favorable composition of natural gas as compared to coal. However, future developments of combustion processes will most likely include the use of more low-grade fuels, such as heavy fuel oils [10]. The use of coal will increase again, which can be related to its relative abundance. Finally, low-Btu fuels, such as gasified biomass or gasified coal will play an important role [11]. 

The initial phase of experiments will include a mapping of the engine characteristics using natural gas as a fuel. These data will be the basis for comparison and discussion of the results for different gas mixtures. The next step will be to use synthetic producer gas as a fuel as the most extreme low value gaseous fuel. Further experiments will include mixtures of synthetic producer gas and natural gas. 

Gaseous fuel refers to any fuel in the form of a gas state at normal temperature and pressure. Natural gas and, sometimes, synthetic gas are used most often in high-temperature processes. The use of natural gas as a fuel depends on the availability and its economics. In North America and Europe, natural gas is widely used in heating and melting processes. In some regions, however, synthetic gas is more common. In this section, chemical compositions are summarized and basic concepts of gaseous fuel combustion are briefly discussed. 

The oxygen-reforming process was first developed for use with natural gas as a fuel but also has been applied to light oils and heavy bunker-type fuel oils. The flexibility of the process with respect to fuels is particularly attractive since it is possible to establish plants needing hydrogen at locations where neither natural gas nor coal is economically available but to which fuel oils can be easily transported. 

A self-supporting SOFC-based power plant system, HEXIS (Heat Exchanger Integrated Stack), using circular planar elements has been developed by the Sulzer company in Switzerland for natural gas as a fuel and a power of up to 7 kW [26]. Field tests have started in summer 1997 commercialization is planned for the year 2002. The development goal is the construction of small-size systems in the power range of 1 - 200 kW. 

The use of methane or natural gas as a fuel entails some specific requirements. Depending on the nature of the fuel and its origin, some sulfur species may be present in various concentrations. Natural gas may contain a significant amount of sulfur, usually in the form of SO2 or H2S. However, in methane combustion, the S species are present in the form of oxides, due to the excess of oxygen. 

After the discovery of large reserves of natural gas in The Netherlands, coal and oil were rapidly replaced by natural gas as a fuel for production of electricity, heat, energy in industry etc. This resulted in a change in the concentrations of air pollutants. Sulphur dioxide, smoke, grit and polycyclic aromatic hydrocarbons (as far as related to the use of coal and oil as afue.l)went down in concent ration. 

The above mentioned conclusions are found under the special situation in The Netherlands a flat country with high wind velocities, domestic heating with natural gas as a fuel, large contribution of natural gas as a fuel for energy production. 

Hydrogen gas has a higher fuel value than natural gas on a mass basis but not on a volume basis. Thus, hydrogen is not competitive with natural gas as a fuel transported long distances through pipelines. Calculate the heats of combustion of H2 and CH4 (the principal component of natural gas) (a) per mole of each, (b) per gram of each, (c) per cubic meter of each at STP. Assume H20(l) as a product. 

Engineers and scientists are developing new ways to power cars and trucks without using petroleum. Many cars around the world instead use natural gas as a fuel source. Fuel cells, whose only by-product is water, show great promise as a clean power source. New types of batteries also are being developed to power cars that will drive longer distances before they need to be recharged. 

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