Boil Temp Control using Steam

[Patio29Dadio]

We just turned on our 1.2MM Btu steam boiler and have been very happy with our hot and fast stripping runs, but we are struggling to control still boiler temp for our finishing runs.  We have a very good Bray Flow-Tek v-port ball valve for steam to the jacket, but thinking we are going to need a thermostat-controlled servo on top of that valve.  I was hoping we could find a manual valve position that does the trick, but we are seeing too much variable boil as the boiler control keeps ramping up and down to deliver steam. 

Just interested in other distillers experience and solutions here.   I am going to talk to the boiler company too.

[vsaks]

1. You don't need a servo control. For precise steam control, you need to use a multi-turn globe valve, not a ball valve
2. Is your boiler control ramping up and down as you open and close the valve ? Or is it turning on and off with the valve in the same position ? What is the turndown ratio on your boiler burner ?
If you are not constantly opening and closing the valve and the boiler is cycling, then it might be an issue with the turndown with your boiler burner. If you are using too little steam, the boiler pressure will go to the max and it will turn off. Then you have to turn it back on.

18 minutes ago, Patio29Dadio said:

We just turned on our 1.2MM Btu steam boiler and have been very happy with our hot and fast stripping runs, but we are struggling to control still boiler temp for our finishing runs.  We have a very good Bray Flow-Tek v-port ball valve for steam to the jacket, but thinking we are going to need a thermostat-controlled servo on top of that valve.  I was hoping we could find a manual valve position that does the trick, but we are seeing too much variable boil as the boiler control keeps ramping up and down to deliver steam. 

Just interested in other distillers experience and solutions here.   I am going to talk to the boiler company too.

[Sudzie]

You may want to change differentials on your high limit and your low limit pressures.   Is your burner a high fire low fire one?  If so you may want to adjust that.   There are also pre & post  purge timing adjustments which is usually a chip replacement from the burner mfg. that can be done in the field.  It took us about a month in a half to dial our boiler in when first installed.  We high fire in the am when everything is coming up to temp and we stage start their times. When we throttle things back our boiler never shuts off (the greatest achievable efficiency) and remains on low fire and sips LPG the rest of the day.  We also own an oil and propane company and our service manager (my son) is quite savvy with steam. 

[Patio29Dadio]

Thanks.  I think both vsaks and Sudzie are on to something for me.  I have the boiler vendor coming out tomorrow to help with the differential settings.   It has a 5-1 turndown capability, but it is still cycling to 100% modulation and then will shut off.   That isn't helping our consistent heat.

Quote

You don't need a servo control. For precise steam control, you need to use a multi-turn globe valve, not a ball valve

That is what I thought and debated it with the boiler company, but in the end agreed that the Flow-tek v-port valve was a great choice.  At least that was the conclusion from research.  In operation maybe I am convinced otherwise. 

 

[captnKB]

I agree with the other posters. Sounds like you have a boiler set up issue. Your boiler should be able to maintain a near constant steam pressure if sized and set up proper. With that a steam rated globe valve is ideal for management of steam flow rate. 

If you need some help on any of this shoot me a PM.

[Roger]

My boiler runs less than 50% of the time. I have it set to come on at 6# and off at 14#. My stills running full on (morning heat up) at 3#. Once up to temp they run at aprox 2# all day long.

 

I believe you are way over thinking this. 

[Blackheart]

Ive used a thermostat controlled valve for steam control on my boiler and it was not the way to go.  A better tuned steam supply window from the boiler as Sudzie suggests is what worked for me.  

[Sudzie]

5 hours ago, Roger said:

My boiler runs less than 50% of the time. I have it set to come on at 6# and off at 14#. My stills running full on (morning heat up) at 3#. Once up to temp they run at aprox 2# all day long.

 

I believe you are way over thinking this. 

Your sending a whole lot of energy out of your system and taxing it more on heat up.  There’s a old time saying in Maine with energy company’s. “ On the coldest day of the year your system shouldn’t turn off”.  “It’s sized right”.  (Most techs will way over size systems to make up for their lack of expertise to make the sale).  Now most customers thought that they were wasting fuel and that was a tuff battle to over come.  So we would increase the nozzle size or orifice on the boiler and then it would not run as long (but cycle more) and this pleased them.  Albeit for just a month or two and then the calls would start. “Why is our bill so high”.  Did you raise our price?  We say no you wanted us to de-tune your system so it wouldn’t run so long.  And then so we go out and re-tune it to the way we do it and tell them if you don’t save money your service calls are on us for a year. Never have done a refund. Go figure?   Remember, long an slow is always better than short and fast!

Its not over thinking it, it’s dialing it in for the best efficiencies in energy (money) and system longevity (money).  I rather spend $$$ on grains and barrels than gas and boilers even having the luxury that we charge the distillery jobbers cost on everything.  Just comes out of the other pocket.

Ps if your system only runs 50% of the time you may want to change out the gun on your boiler.  The pay back should be less than 2 years for something that should last 8-10. 

BTW, We run a 500,000 BTU modulating steam boiler with a 4” header.  This supply’s a 275 gal stripping still a 109 gal spirit still and a 275 steam injected kettle. Every thing runs 7 Day’s a week.  We use 225 to 275 gal of LPG a week depending on season (2” globe valves on everything for adjustment).

First thing we get the spirit charged and running (1 hour heat up and 5.5 hour run). Meanwhile fill the kettle and bring up to temp while the spirit still is heating up.  Turn off the steam educator on the kettle and then turn on the stripping still. (1 hour heat up and 4.25 hour run).  The boiler stays between 7# & 12# (we might reduce to 11#) bouncing between low and high fire and doesn’t shut off throughout the day.  And our returning condensate pipe is typically warm not hot.

And believe it or not we are up grading to 750 gallon stripper and kettle and 275 spirit still starting next month and the same 500,000 BTU boiler will do it. Staging will change a bit and our still run times will increase 1.5 hours and our total cook time will go to 6 hours from 4.5 hours. It’s all in a day and if my math and heat loss calculations are off we’ll just install a Rinnai wall hung that we can re-chip to provide 180* water for the kettle with a fill time of 1 hour.  Worth every penny of $1500 vs 35k for for a bigger boiler. 

 Frugality marches on .

[Silk City Distillers]

Great thread!

We have two valves.  A full-port ball valve, and a globe valve.  On heat-up, we simply open the ball valve to allow full, unrestricted flow.  For fine control, we shut the ball valve and use the smaller globe valve.  It's common on the European stills to see two valves in parallel.  A large globe, and a small globe.  The reason for this is to maintain fine control, without significant flow restriction of a small globe valve.  

Using a single large globe is sometimes counterproductive, you use a globe for precise control, but a large globe valve typically has poor control at low flow rates.  So instead, use a less expensive ball valve on heat-up, and use a smaller globe valve for precise control during the run.  The technical term for what I'm talking about is turndown.  The higher the turndown, the more precise the control over the full valve range.  This applies to valves too.

Using a single small globe is always counterproductive - I've seen folks have really slow heat-up times, despite having properly sized boilers, because they were trying to force all the steam through a 3/4" globe valve.  Very very restrictive flow path.  We run a 1" globe and a 1" ball on a 1000 liter still.  Heatup easily takes twice as long if you try to heat through the globe valve alone.  Usually I stand around wondering what the hell is taking so long, and then I realize I didn't open the ball valve.

I would also agree to check the cut-in and cut-out on the pressuretrols.  If you are set really wide, and have really long pre and post-purge, you'll have a big swing.  But, looking at the boiler gauge - what's the full swing range you see - low to high?  It should be pretty obvious to know if this is an issue.  I'll say, most of us have 2-3psi swing on the boiler, this generally is not a problem.

[Silk City Distillers]

We have a very good local boiler shop, surprisingly, they are recommending we move to high pressure steam, regulated to 15psi for the stills, but full pressure for the steam injection on the mash tun.

They say even if we don't add horsepower, running a High pressure Fulton will dramatically outperform our Weil McLain cast iron, significantly faster mash-tun heat-up using the eductors at high pressure, where they can really shine.  They also say that running a regulated low-pressure line for the stills will provide rock-solid steam pressure control, especially trying to do multiple things at the same time (heat up on still 1, operating on still 2, heating mash tun).

They'll hang their engineering certs for 6 months, then we'd need to take the boiler operators licensing exams and put the seals in our name.  Most folks here seem to be vehemently anti-high-pressure, but those guys are telling me it's no big deal.  I'll quote -  "We've installed high pressure steam in thousands of dry cleaners in the state.  If an idiot dry cleaner can pass the licensing exam, pretty sure that you'll have no problem." 

[Blackheart]

Silk:  Forgive my ignorance, but is it possible to run a 100psi boiler at the low pressure range?  I've heard arguments to contrary on this and I'd like to get a different perspective.  

[Roger]

It makes sense to "right size" a process boiler for continuous operation if you always have the same demand, but that's not necessarily the case in many situation. We have 3 stills and a mash tun and very seldom run them all in the same sequence, and/or at the same time. 

[Silk City Distillers]

You can run a high pressure low, but you can’t run a low pressure high.

However, many boiler inspectors are going to hold you to the nameplate pressure.  Meaning you need a boiler operator seal/license.  You might even be required to install regulators before low pressure devices.

 

 

[captnKB]

High pressure boilers are fantastic pieces of equipment but the additional costs that come with them, make them unecessary in most distilling operations.

Add in the costs of pressure reducing stations, licensing, annual inspections on a high pressure system, and you now have a more complex piece of equipment that typically costs more than a low pressure boiler, that does the same job. 

Low pressure is the way to go. Sized properly a low pressure boiler should be able to maintain a full head of steam at all times.

[Silk City Distillers]

We live in a nanny state - we already have annual boiler and vessel inspections, for low pressure.  It's the same annual inspections already.

This past inspection, a few months ago, they required us to make changes to the condensate return, even though it had already been signed off and inspected by building and plumbing years ago.  Additional check valves, and additional ball valves to isolate.  Swap the pressuretrols for manual reset versions.  We just nodded our heads and did it, not worth the battle.  They wanted to x-ray the still jacket walls from the inside to verify that the thickness matched the engineering prints.  We drew the line there - they were going to charge us for the test.  Keep in mind, low pressure.

if you have your boiler covered by your insurance policy, they are going to want an annual inspection for coverage, whether the state comes out, or they send their own inspectors.  At least out here, that’s how it works.

 

[Patio29Dadio]

Had my visit and learned that the problem was bad controller settings and also learned that I needed a big lesson on steam boiler control settings.

This is a 1.2MBTU (30 HP) Aldrich boiler with a Riello burner.  The burner has a 1-5 turndown capability that works off a pressure sensor.  My problem was that the process value and the high mark were both set at 12 PSI... thus hitting and alarming the max setting at the same time, and stopping the system.   Then at the bottom it was set to zero which meant it fell all the way down before it reset and started back up again.   This controller has a self-learning mode, so we tried that while going through a run and it set a number of control parameters that we saved.  The last run was very smooth.  The steam boiler did stop at one point during the run, but kept in the 25%-50% modulation for most of it.   Went out to time the gas meter and the consumption was much, much less than I had seen the prior days.  So feeling good at this point that the steam boiler is dialed in. 

Next up... insulating all my steam and condensate return plumbing.  That will likely require some more tweaking of control parameters once done.

Related to high pressure, 15 PSI steam is 250 degrees.  100 PSI steam is 340 degrees.   Hi pressure steam is scary stuff IMO.    

[Sudzie]

3 hours ago, Patio29Dadio said:

Had my visit and learned that the problem was bad controller settings and also learned that I needed a big lesson on steam boiler control settings.

This is a 1.2MBTU (30 HP) Aldrich boiler with a Riello burner.  The burner has a 1-5 turndown capability that works off a pressure sensor.  My problem was that the process value and the high mark were both set at 12 PSI... thus hitting and alarming the max setting at the same time, and stopping the system.   Then at the bottom it was set to zero which meant it fell all the way down before it reset and started back up again.   This controller has a self-learning mode, so we tried that while going through a run and it set a number of control parameters that we saved.  The last run was very smooth.  The steam boiler did stop at one point during the run, but kept in the 25%-50% modulation for most of it.   Went out to time the gas meter and the consumption was much, much less than I had seen the prior days.  So feeling good at this point that the steam boiler is dialed in. 

Next up... insulating all my steam and condensate return plumbing.  That will likely require some more tweaking of control parameters once done.

Related to high pressure, 15 PSI steam is 250 degrees.  100 PSI steam is 340 degrees.   Hi pressure steam is scary stuff IMO.    

That’s Great!  Glad to here you got it sorted out.  Try to keep a weekly log of gas consumption  just to get some base lines. Then look for seasonal changes and after a while you’ll see a pattern.  Then look at it now and then and you will see when the efficiency falls off and when things need a good old tuneup.  The other thing don’t be surprised, you may need to replace the burner motor every year.  May has been our month to swap it out for the past 4 years. You’ll notice it going out on reset (the little read button) that’s a sign it’s almost spent. 

[Roger]

Just ran a complete yield analysis for the past 5 months. We are averaging $1.35 in propane usage per barrel put way.