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The afterboiler phase Saturated steam leaving the drums of large industrial and utility boilers is commonly directed through superheaters. Superheater tubes have steam on one side and hot combustion gases on the other. Temperatures here are higher than in boiler tubes. The superheated steam can then be used to drive turbines which function to drive some other rotating piece of equipment. The largest turbines are used to drive generators and produce electric power. Once steam is used in the plant, it is condensed and returned to the feedwater system. Condensate re-enters the preboiler, having made one complete pass through the steam generating system. In a system with a properly maintained chemical treatment programme, condensate is high in purity. As mentioned earlier, this reduces the amount of water which must be pretreated before it enters the boiler. In addition, because condensate has a high heat value, less energy is required to heat the feedwater. The more condensate your plant can return to the boiler, the lower your make-up and fuel requirements will be. This results in increased energy efficiency of your boiler. We have now handled the components of an industrial steam generating system. The system consists of three sections. - The preboiler section removes impurities from incoming make up water and raises the temperature of the feedwater before it enters the boiler. The boiler heats the water to boiling and separates steam. - The afterboiler phase superheats the steam to a temperature above boiling and carries it to the plant where it is put to work. If not lost in the system through process consumption or leaks, steam condenses and is recycled in the feedwater. |
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