Direct Superheated Steam Injection 2

[rbel038]

We want to heat between 3~15L/s of water from 10-50°C using direct steam injection of 225°C 14bar.g superheated steam. This is from a site loop off the back of a power plant turbine.

My question is what issues if any arise from the steam being superheated when it is injected rather than saturated? The concept is just to control the rate of steam from through a mixing tee to achieve instantaneous heating of the water. Is there anything to worry about (cavitation, thermal shock)

Your thoughts and ideas are appreciated.
Thanks

 

[SNORGY]

I think this is a steam hammer accident waiting to happen. This would have to be very carefully controlled...not sure how...

I always thought it was never a good idea to hit liquid water with live pressurized steam. My biggest concern would be death.

 

[TD2K]

http://www.pro-sonix.com/waterHeating.asp

I haven't any experience with them but I've seen more than one advertised direct steam injection to give hot water. I don't think superheated steam is an issue, the real issue is when the steam collapses as it condenses.

Hopefully someone else on the site will have some direct experience.

 

[rbel038]

Yes something like the pro-sonix injector we are waiting on for some information. Steam hammer / cavitation is what we are worried about and what failure could happen down the track due to this. My thinking is along the same lines as you TD2K its just extra heating taken up by the cold water stream before the steam hits the saturation temp and begins to collapse, the collapse of vapor to liquid being the source of the problem. Finding anyone with experience of superheated steam is quite hard around here , only really the powerplants seem to make use of it.

The merits of using the super-heated site loop is that its free to us and unlike indirect heating through a desuperheater+condensing HX we dont have any condensate taking heat out of the system . Its consumed in the heating process (more efficient)

 

[TD2K]

I suspect direct steam injection works just fine.

We had on one job to put in a tempered water system to supply safety showers. Our options were an industrial hot water tank with a blend valve to give the desired temperature, in-line electrical heating or direct steam injection. No one on the client's side (or us for that matter) really like the idea of direct injection steam feeding safety showers but they were supposed to have the appropriate ratings (can't remember just what they were, ANSI?). We ended up going with the hot water tank and blend valve skid. I've also seen ads for direct steam injection for wash down stations where you want hot water.

Get some literature, talk to the reps and get the names of some users to talk to.

 

[rmw]

Google "hose station steam" and take it from there. YOu will find a healthy selection between Pick, Sarco, Armstrong, Kadant, and others. None that I saw prohibit superheated steam. In fact, most equipment of this nature would prefer some superheat in the steam to prevent steam cutting of the steam handling equipment due to moist steam.

rmw

 

[SNORGY]

I am going to do some research to bring myself up to speed with this. My first reaction was that this is something I really would not ordinarily want to do. My apologies if I offended anyone, I have just never heard of this before, at least not in a positive light.

 

[EdStainless]

The Russians do this a lot, their power plants don't have feedwater heaters they just inject the bleed steam into the returning feedwater.
I have seen this in food process also, it how they make apple sauce. There is an even longer list than Mike gave us of people that build these systems. I like Pick.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[GHartmann]

The devices cited by "rmw" were specifically created for this application.

Everyone is quite correct that you don't just want to inject steam into a water line through a simple tee or nozzle.

All the different devices have been engineered to avoid the water hammer issue.

I suggest putting together a simple material balance for the system and sending it to one of the vendors suggested.

Good luck.

 

[MJCronin]

Contact the fine people at Pick....I have had good experiences.

http://www.pickheaters.com

However, I caution you to consider both the noise and the vibration that are generated with this kind of heating method.

These are not minor considerations !

 

[bcincotta]

I have 25+ years working with direct steam.

Direct Steam injection is well established for heating a variety of fluids. However, it does need to be done in a controlled manner. The amount of energy being transferred can be quite high.

This question regarding superheat is important as it can have some impact on performance of the injection device. Not all devices handle it equally well. Make sure you communicate the amount of superheat you expect with the vendor.

There is a lot of good technical information available at:

http://www.pro-sonix.com/engineersToolbox.asp#bulletins