Steam Generation, Distribution, Energy Use, and Recovery

For users unfamiliar with the basics of steam systems or seeking a refresher, read about the four basic parts of steam systems: generation, distribution, end use, and recovery. Also consult the Steam Sourcebook and tip sheets for more.

Steam Generation

Cogeneration applications, boiler controls, and water treatment

Overview and Key Components

Steam generation systems can generally be classified into two principal types: fired boiler systems and waste heat systems. The primary purpose of an effective steam generation system is to produce steam under the conditions - flow rates and pressures- required for the system end-use requirements. It is important to generate the steam at the highest possible generator efficiency. It is equally important that high-quality (dry) steam be produced; transmission of wet steam to the distribution system can lead to water hammer and also to inefficiencies in the end use of the steam produced.

Key components include the boiler itself, boiler system components including controls, valves piping and meters, water treatment equipment, economizers, and deaerators.

Key Inputs and Outputs

Key inputs include boiler feedwater, condensate returned, water treatment chemicals and air/oxygen input. Key outputs include steam mass flowrate, steam pressure, steam quality, combustion gas conditions.

Opportunities for Improvements

Determine the efficiency of your steam generation system (based on steam output/fuel input).

Determine how much steam you use, and how much it costs to generate this steam. Steam generation needs to be measured with accurate, well maintained and calibrated flow measurement devices and reconciled by a rigorous steam balance. The steam balance should be done on a regular basis to confirm that the flow measurements are good.

Optimize excess air in your boiler to increase steam generation efficiency. An often stated rule of thumb is that boiler efficiency can be increased by 1% for each 15% reduction in excess air or 40°F reduction in stack gas temperature. Good measurements of fuel flow and air flows are required to do this as well as good stack gas analysis.

Maintain clean fire-side and water-side boiler heat transfer surfaces. A good deposit control program is necessary to do this. Optimize boiler blowdown to reduce Total Dissolved Solids (TDS) in the boiler system. Work closely with your boiler feed water additives vendor to do this.

Optimize your boiler control system to optimize steam generation efficiency. Before you do this, make sure that the logic diagrams actually reflect what is wired into the system and that all the components of this system make sense and work.

Ensure that an effective water treatment system is in place. Work closely with your boiler feed water additives vendor to do this.

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Steam Distribution

Checking steam leaks, installing insulation and proper steam trap maintenance

Overview and Key Components

The primary purpose of an effective steam distribution system is to link the output of the steam generation system to the steam end use equipment. The distribution system should supply high-quality steam to the end use equipment at the required rate and pressure, and with the minimum heat loss.

Key components include steam distribution piping, valves, and flanges, distribution system insulation, steam traps, air vents, drip legs, and strainers.

Key Inputs and Outputs

Key inputs include steam conditions (pressure and quality) from the generation system. Key outputs include steam distribution outlet mass flow and pressure, distribution outlet steam quality.

Opportunities for Improvements

Properly select, size, and maintain your distribution system steam traps.

Insulate all distribution system pipes, flanges, and valves.

Ensure that steam mains are properly laid out, sized, adequately drained, and adequately air vented.

Ensure that Distribution System piping is correctly sized to produce the appropriate system pressure drops.

Ensure that distribution system piping is adequately supported, guided, and anchored, and that appropriate allowances are made for pipe expansion at operating temperatures.

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Steam End Use

Heat exchanger maintenance

Overview and Key Components

The primary purpose of the steam end use system is to maximize the effective use and heat content of the steam transmitted to the end use equipment.

Key components include a variety of end use equipment, including heat exchangers, unit heaters, and other process-specific steam use equipment. Other key components include steam trap systems to drain condensate from the end use equipment and piping to transmit steam through the end use equipment and condensate out of the end use equipment.

Key Inputs and Outputs

Key inputs include steam conditions (pressure and quality) from the distribution system and process inputs. Key outputs include product produced, steam and condensate resulting from specific end use applications.

Opportunities for Improvements

Understand how much steam is used per unit of product produced. You can use this information to compare with other information–within your company and by your competition–to determine where there might be opportunities for improvement of your steam operations.

Select, size, and maintain steam traps for specific end use applications.

Blowdown of non-condensables from condensing equipment is critical. If non-condensables are not removed from condensing applications, the condensing equipment will quickly cease to function. The rule of thumb is that for every 1% of non-condensables there is in steam, the heat transfer coefficient decreases by 10%.

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Steam Recovery

Condensate return

Overview and Key Components

The primary purpose of an effective condensate recovery system is to make the most effective use of all remaining steam and condensate energy after process use.

Key components include condensate return piping, flash tanks, and condensate pumps.

Key Inputs and Outputs

Key inputs include condensate from the end use system. Key outputs include condensate returned to the generation system and low-pressure steam transmitted to applications that can use it.

The low pressure steam component will consist of flash from the condensate receiver (or steam trap) plus blow-through steam that accompanies the condensate.

Opportunities for Improvements

Identify how much condensate you presently recover and return to the boiler system. Determine if you can increase the amount of condensate that you return – cost savings can result from energy savings and from water treatment cost savings.

Ensure that the condensate piping is adequately sized. Condensate piping has to accommodate two-phase flow B liquid and vapor. The vapor portion of the condensate stream is more voluminous than the liquid portion. In general, condensate piping must be sized to handle the flash and blow-through steam rather than just the liquid portion. Condensate piping that is sized for the liquid portion only will be grossly undersized.

Ensure that your condensate return piping, flanges, and valves are properly insulated.

Identify if it is possible to return hot condensate to a flash recovery system, so that you can use the flash steam to supplement low-pressure steam needs.

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