Furnace energy efficiency

Energy efficiency of the process. If the process requires a furnace or steam boiler to provide a hot utility, then any excessive use of the hot utility will produce excessive utility waste through excessive generation of CO2, NO, SO, particulates, etc. Improved heat recovery will reduce the overall demand for utilities and hence reduce utility waste. 

Reducing products of combustion from furnaces, steam boilers, and gas turbines by making the process more energy efficient through improved heat recovery. 

The second law can also suggest appropriate corrective action. Eor example, in combustion, preheating the air or firing at high pressure in a gas turbine, as is done for an ethylene (qv) cracking furnace, improves energy efficiency by reducing the lost work of combustion (Eig. 4). 

Flue gas recirculation (FGR) is the rerouting of some of the flue gases back to the furnace. By using the flue gas from the economizer outlet, both the furnace air temperature and the furnace oxygen concentration can be reduced. However, in retrofits FGR can be very expensive. Flue gas recirculation is typically applied to oil- and gas-fired boilers and reduces NO, emissions by 20 to 50%. Modifications to the boiler in the form of ducting and an energy efficiency loss due to the power requirements of the recirculation fans can make the cost of this option higher. 

The U.S. Department ofEnergy develops test procedures for efficiency measurements and sets minimum efficiency standards for furnaces, boilers, and water heaters. Information on energy efficiency of buildings and equipment is available from the DOE. 

Taxpayers who receive incentive payments for installing energy-efficient equipment, such as a high-efficiency furnace, do not have to include the payment in their taxable income. This tax-favored treatment may make consumers more likely to purchase energy-saving equipment, thereby reducing demand for energy. 

Batch-type production processes, particularly those with small batch sizes, have less energy efficiency as compared to continuous processes. A typical example of a batch operation on a relatively small scale is the production of titanium in 1-ton batches of the metal. The energy efficiency of the process is much less than that of continuous methods such as iron being produced in a blast furnace, or even of large-scale batch methods such as basic oxygen steel-making. The heat losses per unit of production are much less in continuous and large-batch processes, and this also enables the waste heat from process streams to be used. 

Energy efficiency of the process. If the process requires a furnace or steam boiler to provide hot utility, then any... 

Gas- or oil-fired melting furnaces, such as are in common use in small foundries, serve well in the present context. These will be suited to on-site fixed facilities or mobile units for individual sludge generators producing up to one cubic yard of filter cake per day. Tiltpouring units can be had for capital costs of between 25,000 and 45,000. The crucibles mounted in the furnace are expendable but if properly chosen should last for 50 to 100 melts. Fuel and crucible costs are very moderate. Small open hearth furnaces are available and these furnaces are more energy efficient. 

In the rotary kiln process, coke is fed to a rotating cylindrical furnace sloped slightly toward the discharge end. Coke flows down the kiln countercurrent to the hot gas flow. Moisture is liberated from the coke in the feed zone, then the coke passes through the combustion zone where VCM is liberated. As coke leaves the kiln, it is discharged to a cooler where it is quenched with water and then cooled with ambient air. Recent designs have incorporated energy efficient features such as air preheat and steam... 

In the proprietary rotary hearth method of calcining coke, green coke is fed to the perimeter of the rotating circular table and gently moved toward the center of the hearth in a circular path by stationary rabbles. A combustion zone above the coke bed, formed by liberated volatiles, supplies the heat necessary for calcination. A rotating hearth furnace can also be equipped with energy efficient features, such as steam generation and air preheat. 

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