A Working Example for Generating Steam Balance

For end users that do not have meters for measurement, correlations should be developed to estimate steam flows based on process conditions. The key for developing decent correlations is to identify major operating variables that affect energy use. 

As a guideline, an accuracy of at least 97, 95, and 90% should be maintained for HP, MP, and LP steam headers, respectively. The inaccuracy could be attributed by meter miscalibration, uncertainty in steam losses, and estimates for unmeasured flows. The most difficult task in making the steam balance is to balance the LP header with high accuracy as there are many unmeasured LP flows and losses all over the site, which are not measured. 

However, as a starting point, one should try to make good HP and MP balances. If they are not in good balance, the reasons causing the imbalance should be identified and actions be taken to maintain high accuracy because HP and MP steam are very expensive. 

The purpose is to develop a steam balance for operational supervision as well as for identification of improvement opportunities in the steam system. Models for boilers, turbines, deaerators (DAs), letdown valves, desuperheaters, and steam flash tanks are discussed in the previous chapter. Historian and distributed control system (DCS) data will be coimected to steam balance so that the steam balance is capable of dynamically balancing the steam and power demands due to process variations, units on or off, and weather change. 

The examples below are used to illustrate two different methods and essential steps of developing a steam balance. 

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A WORKING EXAMPLE FOR GENERATING STEAM BALANCE TABLE 16.8. Deaerator Balance... 

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