Natural gas-fired plants

From an economic standpoint, electricity production from a new natural gas plant versus a newly built coal-fired plant heavily favors natural gas, because natural gas-fired plants are cheaper to build. However, older coal-fired plants built 20 to 30 years ago are often more profitable than newly built gas plants, because — among other reasons — coal is cheaper than natural gas, and the older plants have long since paid for their capital investments through depreciation. 

Chiesa and Con.sonni [1,3] have made detailed studies of how a CO2 tax would affect the economic viability of several of these cycles when a tax and CO2 removal are introduced. Fig. 8.27 shows their results on the cost of electricity for natural gas-fired plants plotted against the level of a carbon tax (in c/kg CO2 produced), for two of the novel cycles studied here, in comparison with an existing CCGT plant with natural gas firing. 

Mimura et al [1] found an effective amine solvent (KS-2) with a long lifetime and reported that the KS-2 solvent system could reduce the energy penalty by 20% compared with a MEA system. The power plant losses based on generator output power were calculated to be 5.4-5.8% for a natural gas-fired plant and 9.0% for a coal-fired plant at CO recovery of 90%. 

If the aggressive case relied on hydrogen produced by electrolysis from natural gas-fired plants, the demand for natural gas would increase 8% by 2030, 31% by 2040, and 43% by 2050. Again, these numbers are significantly higher than those for the reformation of natural gas due to the inefficiency of electrical generation. In terms of new generating facilities, this increased demand is the equivalent of 382 new 1000 MW nuclear or coal-fired plants by 2050. 

The theoretical advantage an IGCC plant has over a conventional coal plant is in the higher system efficiency of the combined cycle, a concept originally developed for natural gas-fired plants and used in many such plants for meeting intermediate and peak loads. 

H2 separation membrane WGS can, of course, also be adopted in natural gas fired plants to treat syngas from a steam reformer however, the benefits are expected to be smaller than those obtained by integrating the reformer and membrane directly. 

Gas turbine-based power plants, particularly natural gas-fired cogeneration and combined-cycle faciUties, have proven to be highly rehable, efficient, and environmentally attractive. Advances in machine design, more efficient plant integration, and optimistic forecasts for the availabiUty of affordable natural gas worldwide have boosted the appeal of these systems for both base-load and peaking service. 

At least two manufacturers have developed and installed machines rated to produce more than 210 MW of electricity in the simple-cycle mode. In both cases, the machines were designed and manufactured through cooperative ventures between two or more international gas turbine developers. One 50-Hz unit, first installed as a peaking power faciUty in France, is rated for a gross output of 212 MW and a net simple-cycle efficiency of 34.2% for natural-gas firing. When integrated into an enhanced three-pressure, combined-cycle with reheat, net plant efficiencies in excess of 54% reportedly can be achieved. 

When optimizing industrial ventilation, the real consequences for the environment due to decisions made are of interest. Therefore, the marginal effect on the whole energy system is what is required. This is of course difficult. Many practitioners use electricity produced from coal processes as marginal, but some use natural-gas-fired power plants. It depends mainly on the area and time frame that is being considered. 

Fig. 8.1 shows a diagram of a chemical absorption process described by Chiesa and Consonni [1], for removal of CO2 from the exhaust of a natural gas-fired combined cycle plant (in op>en or semi-closed versions). The process is favoured by low temp>erature which increases the CO2 solubility, and ensures that the gas is free of contaminants which would impair the solvent properties. 

The capital cost of an IGCC plant for biomass or coal IS in the range of 1,500 to 2,000 per installed kW. A comparable natural gas fire facility costs about 750 to 1,000. The economics of biomass electricity based on IGCC technology depend on the relative cost of natural gas and biomass fuels. Biomass must be lower m cost than gas to pay back the additional capital cost of gas production and cleaning. A 1999 estimate suggestes that the biomass would have to be 3 per million Btiis cheaper than natural gas for biomass to be economical. 

Under such circumstances, companies tend to choose relatively small generating units with low capital investment per unit of capacity, which are quick to build and have a short pay-out. These choices reduce the overall risk of an investment and are today available by choosing combined cycle gas fired plants if natural gas can be obtained at competitive prices. Compared to present nuclear power plants, such units have 1/3 of capital/kw, take two, rather than four to six years to build. Being more acceptable to the public, suitable sites for such plants are also far easier to find. 

The fuel cell system emits much less carbon into the air than a combustion-based power plant. Less than one percent of the amount is produced from generating the same amount of power. The system is more expensive, costing several times as much per kilowatt-hour (kWh) of electricity produced than energy from a new natural gas fired turbine system. 

Table 13.1 summarizes representative NO emission limits for coal-, oil- and natural gas-fired thermal power plants, gas turbines and incinerators in Europe. 

Gas-Zero Emissions Plant (ZEP). Alstom Power s Cas-ZEP project explores methods to capture the CO2 as it is produced in a natural gas-fired power plant without substantial reductions in plant efficiencies. 

Figure 6.10 pictures the case of a natural gas-fired power station. The hot combustion gases drive a combined cycle consisting of a gas turbine and a steam power plant. The power station "cogenerates," or produces, electricity and heat. The produced heat and electricity are used to upgrade the quality... 

A major fire erupted in a nonflammable solvents manufacturing unit in a U.S. Gulf Coast chemical complex. A furnace tube in a natural-gas-fired heater ruptured due to overheating. At least 1,800 gallons (6,800 liters) of a combustible heat transfer fluid spilled and burned intensely. Within about 25 minutes, the intense hot fire damaged four levels of structure and associated process equipment. The plant on-site emergency squad quickly and properly responded. However, the price tag for short-lived incident was over 1.5 million in direct property damage and over 4 million in business interruption (U.S. 1979). Fortunately, there were no injuries. [2]... 

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