Desuperheaters for cooling superheated steam and ensuring efficient heat transfer
This tutorial article covers all you need to know about Desuperheaters and the process of reducing the temperature of superheated steam to improve the process of heat transfer in steam applications. Steam control experts Spirax Sarco provide us with invaluable explanations of how different types of Desuperheaters work, as well as introducing the typical applications you will find them in throughout the Process Industry.
What are Desuperheaters?
Desuperheating is the process by which superheated steam is restored to its saturated state, or the superheated temperature is reduced.
Many processes throughout the Process Industry use saturated steam in their steam applications. For efficient heat transfer to occur and for high control over the process of cooling superheated steam, Desuperheaters are used. Desuperheaters reduce the temperature and pressure of superheated steam to near saturation levels, thus improving heat transfer.
How do Desuperheaters work?
Desuperheaters work by mixing finely atomized cooling water droplets into superheated steam flow. These water droplets must remain suspended in downstream pipework for as long as possible, otherwise ‘water droplets fall-out’ occurs, resulting in loss of efficiency in the desuperheating process and possible corrosion.
Spirax Sarco Desuperheaters eliminate water droplet fallout and ensure a reliable, efficient energy transfer. Read on to understand how…
Spirax sarco Desuperheaters:
- Robust, durable design – High quality stainless steel inner that can resist corrosion and options of carbon steel or chrome molybdenum outer to withstand high temperature applications.
- No moving parts – Spirax Sarco’s Desuperheaters are virtually maintenance free and have been designed to reduce plant maintenance.
- Pre-assembled – Spirax Sarco’s Desuperheaters are virtually maintenance free and have been designed to reduce installation times.
- Multiple configuration options – The Desuperheaters can be installed vertically or horizontally to suit application design Saves time on installation and installation costs
- Increase process efficiency – Waste and residual heat can be recovered and recycled
Different types of Desuperheaters
Spirax Sarco’s range of Desuperheaters are comprised of 4 different designs. The type of Desuperheater required will depend on the control required over the downstream temperature. Spirax Sarco engineers will help to specify the correct Desuperheater into your application to help ensure maximum efficiency, control and reliability.
The Spray type and the Spray Nozzle type Desuperheaters are the best solutions for low turn-duties, whereas the Venturi type Desuperheaters are the most popular Desuperheaters and are ideal for most duties. The Steam Atomising type Desuperheater is more specialist and is suited to applications with high turndown duties. Turndown ratio is dependent on a wide variety of factors, such as, installation (horizontal or vertical), amount of residual superheat and piping.
Spray Nozzle Desuperheaters:
Offer a maximum turndown of 5:1
Inserted into the steam line to release a fine spray of water into the flow, these desuperheaters suit retrofitting in existing pipes and are highly cost-effective for large diameter pipes.
Spray Type Desuperheaters:
Offer a maximum turndown of 5:1
A complete pipeline unit incorporates spray nozzle technology with thermal pipeline sleeves reducing water droplet fall out.
Venturi Type Desuperheaters:
Suitable for when tighter control over downstream temperature is needed – offers a possible turndown of 10:1.
A venturi nozzle is used to create extra turbulence resulting in effective steam cooling within the double diffusers. This desuperheater suits most general applications.
Steam Atomising Desuperheaters:
Suitable for when tighter control over downstream temperature is needed – offers a possible turndown of 50:1.
For applications where the load varies considerably, these desuperheaters use a secondary, high-pressure steam supply to atomise the cooling water entering the superheated steam.
Typical Applications for Desuperheaters
Desuperheaters are used in many applications throughout the process industry, but typical applications include Power generation applications, where they are used to reduce the temperature of steam discharged from turbine bypass systems to that required for other parts of the plant. They are used in Process applications as part of a system for reducing the temperature and pressure of steam from boilers to economic levels of operation.
For more applications including Desuperheaters, click here.