Fundamentals of Direct Contact Steam Injection
What is Direct Steam Injection Heating?
Direct steam injection (DSI) heating is a general term that refers to any type of fluid heating that utilizes steam being directly mixed with the utility or process fluid. Several forms of direction steam injection include: spargers, externally and internally modulated heaters and eductor pumps.
There are advantages to using direct steam over indirect heating methods. Directly injecting steam into the process fluid is 100% energy efficient because it uses both the latent and sensible heat available in the steam. Read more about Hydroheater® internal modulation and its advantages.
View and Download "Understanding The Basics of Direct Steam Injection" and "Taking the Direct Approach: DSI for Heating Water Provides Many Benefits" to learn more about heating with direct steam!
Internal Modulation Internally modulated heaters use the full steam pressure available to choke the steam flow through precisely engineered nozzles. Choked flow allows for superior control of the steam flow into the process fluid by adjusting the flow area between steam and working fluid.
» High powered sonic velocity steam 1500 ft/s
» Self cleaning characteristic
» Atomizes steam particles for superior mixing
» Eliminates steam hammer
» Fast response time to changes in set point and process upsets
» Temperature holding to within ±1°F
External Modulation Externally modulated heaters utilize a valve on the steam inlet piping to control the steam pressure. Most in-line direct steam injection heaters use some form of external modulation to adjust the temperature of the process fluid.
» Does not use full steam potential
» Prone to scaling/fouling due to low velocity steam
» Can cause hammer and vibration damage
Sparging A sparger is an early DSI designs which consists of little more than a pipe with holes drilled in it. The pipe is placed directly into a tank of process fluid and steam is pumped through it, being released directly into the tank of fluid.
» Incomplete condensation leads to steam being released to the atmosphere (major energy loss)
» Poor mixing and temperature stratification
Venturi Pumps Venturi pump heaters use a flow restriction to mix in steam and accelerate the flow and pump the fluid.
» Poor mixing and steam condensation
» Lack of temperature control and reaction to process upsets