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#BoilerManual #AirAndGasFlow #Section3 #Page34

SPRAY ATTEMPERATION FOR STEAM TEMPERATURE CONTROL

Gas recirculation is used to control reheat steam temperature. Spray attemperators, located in the fluid path upstream of the secondary superheater, are used to lower main stream temperatures to design.

The normal steam temperatures with gas recirculation and attemperator flows are shown in Figure 30. Notice that gas recirculation (GR) drops

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Alt = Labeled Fig. 29 Gas recirculation requirements -- it has a top title of GAS TEMPERING TO UPPER PORTS GAS RECIRCULATION TO LOWER PORTS-- and in the upper right corner has the notation "Three fans at T-50 2,250,000 lb/hr". the x axis is in terms of Main steam flow - 10 to the 6th power lb/hr, incremented from 0 to 4.4 in .4 increments. The y axis is in terms of recirculated gas weight - M lb/hr; incremented zero to 2400 in increments of 200. It maps out what was covered in detail in the main text.

#BoilerManual #AirAndGasFlow #Section3 #Page34

SPRAY ATTEMPERATION FOR STEAM TEMPERATURE CONTROL

Gas recirculation is used to control reheat steam temperature. Spray attemperators, located in the fluid path upstream of the secondary superheater, are used to lower main stream temperatures to design.

The normal steam temperatures with gas recirculation and attemperator flows are shown in Figure 30. Notice that gas recirculation (GR) drops

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Alt = Labeled Fig. 29 Gas recirculation requirements -- it has a top title of GAS TEMPERING TO UPPER PORTS GAS RECIRCULATION TO LOWER PORTS-- and in the upper right corner has the notation "Three fans at T-50 2,250,000 lb/hr". the x axis is in terms of Main steam flow - 10 to the 6th power lb/hr, incremented from 0 to 4.4 in .4 increments. The y axis is in terms of recirculated gas weight - M lb/hr; incremented zero to 2400 in increments of 200. It maps out what was covered in detail in the main text.

#BoilerManual #FluidCirculation #Section2 #Page34

BOILER FLUID CYCLE

We have now discussed, in some detail, the fluid circulation throughout the boiler, and the effects of pressure, temperature and enthalpy on the generation of steam. Let's back up and examine the specific properties and phase changes that occur in each boiler circuit at Baldwin.

Fluid Cycle at Minimum Feedwater Flow

Flow and pressure are maintained by the feed pumps at approximately 1.4 mlb/hr {million lbs/r?} and 2500 psi respectively. Referring to Figure 26, feedwater enters the economizer at about 375 F, at this point it is saturated water. As flow passes through the economizer tube banks, additional heat energy and temperature are picked up. Still in the form of saturated water, the fluid leaves the economizer and enters the cyclones at about 535 F. Temperature and heat energy increase as flow is directed through the cyclone circuits and feed into the furnace wall headers at about 625 F. Entering the furnace wall tubes and up to a point approximately 1/4 to 1/3 the way up the furnace, the fluid is still in its saturated water state (0% quality), but contains much more heat energy and is about 670 F. At this point, the fluid temperature will level off at about 670 F. The additional heat being absorbed through the remainder of the furnace passes is being expended in the conversion of saturated water (0% quality) into saturated steam (100% quality).

At this point (100% quality), the steam temperature will begin to rise again and become superheated as flow passes through the roof tubes (furnace and convection pass) and to the convection pass enclosure. Superheated steam at a temperature of about 680 F enters the primary superheater and exits at about 765 F. Between the PSH and SSH, the superheated steam is attemperated, thus reducing its temperature and enthalpy below that of the PSH outlet. By the time the steam leaves the SSH, it has been brought up to the desired temperature of 1005 F.

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#BoilerManual #FluidCirculation #Section2 #Page34

BOILER FLUID CYCLE

We have now discussed, in some detail, the fluid circulation throughout the boiler, and the effects of pressure, temperature and enthalpy on the generation of steam. Let's back up and examine the specific properties and phase changes that occur in each boiler circuit at Baldwin.

Fluid Cycle at Minimum Feedwater Flow

Flow and pressure are maintained by the feed pumps at approximately 1.4 mlb/hr {million lbs/r?} and 2500 psi respectively. Referring to Figure 26, feedwater enters the economizer at about 375 F, at this point it is saturated water. As flow passes through the economizer tube banks, additional heat energy and temperature are picked up. Still in the form of saturated water, the fluid leaves the economizer and enters the cyclones at about 535 F. Temperature and heat energy increase as flow is directed through the cyclone circuits and feed into the furnace wall headers at about 625 F. Entering the furnace wall tubes and up to a point approximately 1/4 to 1/3 the way up the furnace, the fluid is still in its saturated water state (0% quality), but contains much more heat energy and is about 670 F. At this point, the fluid temperature will level off at about 670 F. The additional heat being absorbed through the remainder of the furnace passes is being expended in the conversion of saturated water (0% quality) into saturated steam (100% quality).

At this point (100% quality), the steam temperature will begin to rise again and become superheated as flow passes through the roof tubes (furnace and convection pass) and to the convection pass enclosure. Superheated steam at a temperature of about 680 F enters the primary superheater and exits at about 765 F. Between the PSH and SSH, the superheated steam is attemperated, thus reducing its temperature and enthalpy below that of the PSH outlet. By the time the steam leaves the SSH, it has been brought up to the desired temperature of 1005 F.

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