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Desuperheater Application Best Practices

An ever-increasing need for steam at specific temperatures and pressures exists in many modern plants. Fortunately,

significant improvements have been made to increase operational thermal efficiency and heat rates by the precise, coordinated

control of the temperature, pressure and quality of this steam. But, much of the steam produced in power and process plants

today is not at the required conditions for each application, so conditioning is required, often by a desuperheater system.

The sizing, selection, application, installation and maintenance of the proper desuperheating and steam-conditioning

equipment, including control valves, is therefore critical to optimum performance. This article will discuss superheaters and

associated control valves in detail, but first I will look at common applications and issues in affected industries.

Power Industry

Competing in the modern power market requires a heavy emphasis on the ability to utilize multiple operating strategies.

Increased cyclical operation, daily start-stop and faster ramp rates are required to ensure full-load operation, particularly

at daily peak hours, and to maximize profit and plant availability. Changes resulting from environmental regulations and

economics also are combining to alter the face of power production.

At the same time, these changes are affecting the operation of existing power plants and the design of future plants.

Advanced plant designs include requirements for increased operating temperatures and pressures along with stringent noise

limitations in urban areas. Steam is used throughout power plants in many ways, from driving to turbines to feedwater

heaters.

Hydrocarbon and Petrochemical Industries

Hydrocarbon and petrochemical industries rely on the efficient conversion of low cost feedstock to high profit products.

Hydrocrackers, furnaces, distillation columns, reactors and other process units must be designed to meet a range of

conditions to accommodate various modes of plant operation. Temperature is a critical factor that must be taken into

consideration during the design of each process unit, and it must be controlled precisely to optimize each operation.

Temperature is controlled in many ways in these plants. The most common method is through the use of heat exchangers and

process steam. Process steam must be conditioned to a point near saturation before it is transformed into a medium that is

more efficient for heat transfer. The proper selection of equipment will ensure optimum plant availability, reliability and

profitability.

Other process industries such as mining, pulp and paper, life sciences and food and beverage experience reliability

issues caused by steam-conditioning challenges. These industries also use steam for motive force and heat transfer.

Desuperheater Basics

A schematic of a typical desuperheating system is shown in figure 1. A typical system consists of four main components:

Control valve.

Desuperheater.

Temperature transmitters.

Spray-water strainer.