20 Nov Most attemperation that I am familiar with in this setting is to spray water into the steam line in the boiler, before it gets to the turbine. There are temperature limits . Product – DAM-B Steam Attemperator. DAM-B: Steam AttemperatorAttemperation is the primary technique used for controlling the degree of superheat in a boiler. Spray flow attemperator is used for controlling superheater outlet steam temperature in power house. The attemperator undergoes cyclic thermal load and.

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If you have disturbances affecting your reboiler, then yes, consider using cascade control. If the spray water flow rate to the attemperator is measured, a flow control loop can be implemented as a tertiary inner loop to provide very fast disturbance rejection.

Steam temperature is one of the most challenging control loops in a power plant boiler because it is highly nonlinear and has a long dead time and time lag. Variable-area nozzles offer this capability, fixed-orifice nozzles do not.

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Can you give the that logic which can implemented to reduce this problem? Such issues are the result of project complexity, size, uniqueness and regulation, boiled well as the need for virtual team collaboration.

If there is a strong relationship between e. Unfortunately, turbines and superheater tubes do not like water. Are your measurements and controller outputs ranged exactly the same as they were before the retrofit? Hi All, What are the technical differences between an attemperator and desuperheater. As previously mentioned, the ASME Code now prohibits attemperator arrangements without automatic drain pots on the interconnecting piping. Resources Few production environments have the luxury of ordering new equipment to replace existing machines on their shop floor.


This loop measures the desuperheater outlet temperature and manipulates the control valve position to match the desuperheater outlet temperature to its set point coming from the main steam temperature controller Figure 2. Again, it depends where your disturbances or nonlinearities show up first. Download Now The Architecture, Engineering and Construction AEC industry is constantly looking for process improvements to better manage potential project delays and costs.

An attemporator controls steam temperature while a desuperheater removes whatever superheat there is in steam and reduces the temperature to a point at or nearly at saturation temperature.

I read the article and found it to give an objective assessment on APC in power plants. The disadvantages include the potential for carryover of water into piping and tube bundles harpsand the significant distance of the measured setpoint from the spray-water injection point.

Designing HRSG desuperheaters for performance and reliability

In the few cases where it is necessary to spray to saturation, a simple temperature based limit cannot be used. Changes in steam flow rate will affect the amount of cooling obtained from a given spray water flow rate.

But for secondary atomization to occur, the dynamic forces acting on a droplet must be greater than the viscous forces holding the droplet together and depends on the relative velocity between the steam and water droplet. Because of the changing dead time and lag of the superheater, the integral and derivative times must be scheduled in addition to the controller gain.

The attemperator undergoes cyclic thermal load and pressure and is prone to failures associated with thermal fatigue cracking of its components and welds. If these pipes suffer thermal humping, water will not drain.

To present it in a block diagram, it will look similar as in the figure above, except you will have three function generator or f x blocks, one for each of the tuning settings. The gain of the desuperheater outlet temperature loop will be affected greatly by steam flow rate. The ring design also ensures distribution of spray flow across the entire cross section of steam flow.


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I didnt get the cascade control theory basics…. Anderson next explained how attemperation works and what can go wrong with any desuperheater system, including the following:. Designers must ensure total evaporation ahead of the temperature sensor in the steam outlet pipe refer back to Fig 1. See your Yokogawa user attempefator for how to do it. September 23, at Goal is to create as small a droplet as possible attempsrator of the water spray flow rate.

Difference between attemperator and desuperheater An attemporator controls steam temperature while a desuperheater removes whatever superheat there is in steam and reduces the temperature to a point at or nearly at saturation temperature. Proper atomization and evaporation of the spray water supplied by an attemperation system is necessary both for good temperature control boiiler to prevent water carryover.

The spray pattern was ineffective.


Click Here to join Eng-Tips and talk with other members! Other methods of steam temperature control attempefator flue gas recirculation, flue gas bypass, and tilting the angle at which the burners fire into the furnace. In the plant where I worked, the main and re-heat steam temperature control loop is cascade without feedforward demand.

You can touch upon the integral windup problem frequent in STC.