Decreasing waters boiling point while under pressure 2

[CraigH88]

I work for a company that uses steam to cure new sewer pipe. In the process condensation builds up in low spots (sags in host pipe) and prevents the material from curing. I'm working on an additive to be injured (liquid or pellets)into the pipe to reduce the boiling point of condensation to return to vapor, prevent condensation, and improve thermal conductivity of the steam and material being cured.

Current consideration is ethanol injection.

Delivery method as a liquid or absorbed into a material that would aid in nucleation of the water to reach a low boiling point of the condensation.

Also considering an exothermic additive.

End goal is remove condensation in sags of pipe while under pressure. To prevent the insulation of condensation build up.

 

[LittleInch]

What's the question?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[CraigH88]

I need to remove the condensation from sags in the pipe.

The process is CIPP lining. We use a temperature activated resin to cure a soft liner that is blown into an existing sewer line. The line is kept at 30 degrees installed with air then brought up to temp with a steam unit that provides 270 degrees steam to bring the line up to a curing temperature of 130 degrees.

The old pipes have sags and fill up with condensation. This creates an insulation between the steam and the liner. I am trying to figure out a chemical solution to remove the water from the sags.

We install a valve at the bottom end of the line to control the pressure and allow for circulation of the steam and remove condensation that flows down the grade of the line. The problem occurs when there are sags in the existing pipe.

 

[georgeverghese]

The ethanol water azeotrope is mostly ethanol, so you need a fairly large amount of ethanol for each quantum of water that condenses.
How about electric or steam tracing of this sewer line while curing this liner? External electric tracing can easily enable the outside surface of this pipe wall to operate at your required temp of 130degC - speak to Thermon for example, and work out control options that will suit your application. From memory, 120degC is the limit for self regulating type tracing, so HPT style tracing may be the one to select. Maintain temp of 130degC is within the capability of the HPT20 type cables.

https://content.thermon.com/pdf/us_pdf_files/TEP0012-D1-HPT-Spec.pdf

 

[CraigH88]

#georgeverghese. Thank you for your feedback. To clarify my Temps were in F. Curing temp of liner is 130F. I'm interested in HTP20 heat cable but I think it would be cost prohibited. Average line length is 400ft sometimes as long as 1500ft. I am definitely going to look into it.

Do you have any suggestions on foaming the water (the line is under pressure and has circulation in the direction from top to bottom) or an exothermic reaction that would be safe for discharging into sanitary sewer. Also safe and following OSHA guidelines.

Acids are off the table

 

[georgeverghese]

Offhand, nothing comes to mind that would trigger an exothermic reaction to boil off this condensed water that wouldnt be corrosive.
I dont see why this exothermic reaction chemical would be the way to go anyway; electric tracing would be the conventional solution.
With 130degF maintain temp, self regulating cables would be better, and is safer than HPT style tracing

https://content.thermon.com/pdf/us_pdf_files/TEP0067-BSX-Spec.pdf

 

[pierreick]

Hi,
What about using hot air to cure the pipe?
Pierre

 

[CraigH88]

There needs to be enough thermal mass to get the reaction to happen in a timely manner.

I'm trying to improve on an existing industrial process CIPP. The host pipe (underground sewer) along with ground water stays at a constant 55F year round and is pulling heat away from the active process. Our steaming unit is 300,000 BTU. Using 200 to 2,000 gal of (water to steam). Lots of variables to why a 10ft section of liner will not reach curing temp in a 500ft line. Sags that hold condensation and running ground water around the pipe are the to main reasons.

I think Azeotropes are a step in the right direction.

The reason I like exothermic idea. It will put the heat specifically when it is needed in a long section of pipe. F.E. 500ft line with a sag at 380ft for 15 feet. 2 hours into a cure 90+ percent of the line is cured and to temp I just need more heat in the sag. Also steam rises and the cold spots are on the bottom.

In large diameter pipe 30"and up we use something like a steam tracer ( 2" perforated lay flat hose rated for steam and pressure). It's time consuming and expensive. It's only affordable on large diameter.

 

[georgeverghese]

Your use of US units has thrown me off.
With water boiling at 212degF at atmospheric pressure, pipe wall temp will have to be some 215degF or so, assuming the pipe pressure is atmospheric during curing. With the steam at 270degF and the pipe wall at 215degF, curing temp at the liner will be somewhere between 215-270degF. Which is a lot higher than your plan to cure at 130degF.
I can see why you are looking at water azeotropes.
The modified procedure then to the electric tracing option is to drop the pressure in the pipe so that boiling water temp is less than 65degF, with a vacuum pump. Operating press in the pipe will have to be less than 0.3psi abs. And the electric heat tracing can be operated at 65degF to keep the pipe walls warmer than the ambient temp of 55degF.
I dont see any water binary pair azeotropes that boil at <65degF. The ethanol - water azeotrope boils at some 172degF,so that doesnt sound suitable either (unless you are okay with curing temp > 172degF).

 

[CraigH88]

This is real world application. I do this every day and my numbers are correct. Part of the problem is delivering enough energy density to the liner before ground water wicks it away. Steam also collapse on itself as it transfers heat (the whole reason we have condensation). The temp of the steam can be 270F but if there is 4"of water that is 10' long. The water insulates from the steam. While the whole time the ground is pulling the heat away from the liner.

Tetrachloroethylene Azeotropes boil at 180 and is used in dry cleaning and manufacture at industrial scale. The tet to water it 30/70 by weight.

Also looking at ternary Azeotropes. I might not be able to get down boil at 130F but any move in the right direction will help. I think

 

[Compositepro]

Your concept is entirely magical thinking with no validity. Heat transfer by steam is almost entirely by condensation. Vaporizing the condensate is a reversal of the heat transfer, causing cooling. Your comments about cost sensitivity are amusing. What do you think your costs will be for the chemicals you are considering?
Sewer lines cannot tolerate vacuum, which would be almost impossible to avoid with pure steam, so your pipe will be filled with steam/air mixture. For heat transfer this will behave like hot air except for the condensate issue. The only practical solution that I an think of is to fill the line with hot water. Steam can be used to heat the water.
Many companies are doing this. There is a common solution already in use. What is it?

 

[georgeverghese]

So you could operate the external heat tracing at 130degF (55degC), keep the sewer line at atmospheric pressure and live with whatever condensation that occurs ?
I dont see any homogenous azeotropes with water at around 50-60 degC normal boiling point which dont require high concentrations of the other component.

 

[LittleInch]

Ok, this is CIPP where there is a liner with epoxy or similar temp cured material.

At your 270F that needs about 45 psi pressure ? Then you open up the drain to get the condensate out but maintain flowing steam.

so the issue is the water / condensate gathering in low points.

How long does this process take?

Can't you just blow down the section on regular basis to sweepout the condensate?

Or pig it with a foam pig to sweep it out?

I can't work out what an additive is going to do for you as once the water / ad mixture condenses, it won't suddenly uncondense / boil off unless you maybe drop pressure every now and then?

Or maybe add some mixture every now and then and lower pressure?

I'm struggling to see how a thin pool of water is going to impact your heating when that water will be at or close to 200F.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[CraigH88]

We do use hot water to cure line.

There are 2 methods to epoxy resin CIPP. Steam cure and water cure. Water is much more time consuming and expensive. You can still have the issue with cold spots when using water. You are all underestimating how much heat the ground( especially when water is present) will pull the heat away.

#Compositepro I am aware that phase changes requires heat. Once the majority of the line is up to temp condensation is much less. So it would be advantageous to remove the water and allow the steam to contact the line. Cost savings is huge in a business. Our business is paid by the foot and we do thousands of feet per week. The solution is going to be a combination of material and processes. Maybe your not as insightful as you think.

I am considering all options. I don't think pigging is an option due to the way we install we only have a 2inch access durring the cooking process. I'm looking into tracer cables but we need to be able to reuse them. Exothermic is the best in my opinion. Using the sag as an advantage by plowing in a pellets that would add heat where needed.

 

[CraigH88]

#LittleInch

The length of time is determined by diameter and length along with temp readings.

8"_15" under 400ft takes 30min to reach temp130F on the low end and an hour or longer on the long end. Then held for 2 hours

24"_36 can require multiple steam units several hours to reach temp and held for 4 or more hours to cure.

We are able to adjust pressure but only after the curing temp is reached. The install pressure is also different depending on diameter and thickness. The pressure is what holds the liner in place till pipe becomes hard/cured. It also keeps the live sewer upstream from getting under the liner.

I have cycled pressure before to get a better temperature reading. With some success but not a definite confirmation

The sag is usually due to a ground water issue that compromised the host pipe. It's a compound issue.

MREs use a chemical to heat water. I'm looking into that.

Please continue with feedback. This has been very helpful

 

[LittleInch]

The heat losses into the ground will be huge not to mention the thermal inertia of the material itself.

Can you not warm up the original pipe before you insert eh liner to get some of the surrounding soil warmed up? I've done analysis before now which says about a day of flow is enough to establish a steady state condition.

Regular blow down would move a lot of the water surely?

how long do you steam the line for? Sorry - your reply was the same time as writing this one.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[3DDave]

Regarding insight - isn't this a problem for all similar companies and this problem would have solutions already available from the liner suppliers?

We aren't underestimating the heat required. Whoever is bidding these jobs for you is underestimating the heat required.

You are asking for a chemical to be added to the gas-phase of water to prevent condensation or some material that, added to condensed water, will eliminate the energy required to return it to the gas-phase. Neither chemical exists.

If you add water activated exothermic materials (used in MREs) they will react rapidly with the steam and produce heat right at the introduction point and be sludge in the pipe low spots.

If water is collecting in enough depth to affect curing this pipe isn't suitable as a sewer line. It needs to be re-trenched, graded to eliminate low spots, and replaced with new pipe.

 

[CraigH88]

So because no one has solved a problem before it's unsolvable?

I wouldn't inject it into steam. I would deliver it as a pellet and it would be easy to time delay with a coating.

Increasing waters thermal conductivity would also help.

I'm not looking for a magic bullet but 20F degrees in temp can save hours of time .

We manufacture our own liner. Other company's make their own

As far as what's suitable for a sewe pipe. That's up to the municipality not you or me.

 

[georgeverghese]

Since you have steam generation, another option is steam tracing. Desuperheat the steam to get saturated steam - 3/8 inch copper tubing is common. Temperature control is not as good as with electric tracing, but may be adequate for this purpose. And it is usually cheaper than electric tracing. Rig up temporary insulation over the tracer tubes to reduce heat loss to ambient during curing. Speak to Spirax Sarco and / or other similar companies to help out with this.

 

[Compositepro]

Water pooling interferes with heat transfer because natural convection causes heat to rise in the water, but you want it to go the other way. A steam tracing line that lies on the bottom of the sewer pipe will take care of that.