A few questions on Boilers

[stevea]

On 11/26/2019 at 7:59 PM, Backset said:

As I have been trying to educate myself on boilers, a few questions have come to fruition that I can't seem to find an answer for. I was hoping some folks who have been down the road of purchasing a boiler would know the answers. 

#1: Is a blow down separator necessary? From my understanding it seems like an integral part for maintaining safety within the still house/boiler room. 

#2: What is the ball park installation cost of a boiler? We are looking at a 60 HP boiler.

#3: Opinions on Sellers or ? These are the two manufacturers we have narrowed it down to. I like that Sellers doesn't need any chemical treatment, but I like the footprint and the 5:1 turndown of the Aldrich better, vs. the 3:1 turndown on the Sellers.

Thanks.

 

#2 I got a quote for $47k for the 50bhp Sellers H-series installed from their local rep.  I expect their 60hp is ~10% more with similar installation costs.

#3.  Sellers H-series for direct steam injection.  You MUST soften the water well to prevent scaling, but you don't need to add chems to reduce O2 & raise pH as there is no ferrous metal in the H-series boiler.

I agree the limited turndown on the Sellers is a headache.  Aldrich got my consultant's "thumbs up" as well.   I must say the Miura's look very fine, but I would imagine corrosion could be a problem if you run them with RO-water and no chems.

 

There are broadly 3 classes of steam ...

http://stellarfoodforthought.net/plant-steam-vs-culinary-steam-vs-pure-steam-what-food-manufacturers-need-to-know/

and if you think you can put in a screen and convert plant steam to culinary steam, then you are on the wrong side of the FDA.

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=173.310

The FDA approved chems seem to cost  4x or more than typical boiler chems.   Given the high blow-down rates on DSI systems, the chem cost is significant over time.

[starcat]

The watchman unit noted is simplex and redundancy is needed as in 2 pumps. When a single pump system fails, you are DOWN.

This requires that you have a receiver AND a return station which is an extra expense and an extra point of failure when both can be done in one package as I have shown for small systems.

Receivers are not controlled in the same way return stations are. They are set up differently. You also need isolation capability on each pump [both electrical and mechanical] of a duplex unit so you can run on one if you have to. The best thing is to get the OEMs and return station-receiver builders into some kind of accord on dimensions that are practical in the field which would not really be that hard as I have also shown working with Silver State Stainless on recent projects. They were happy to build to a higher outlet dimension with no problems at all. It just has to be asked for. The simpler things can be kept, the more reliable they will be. Redundancy is just as it sounds and Mechanics like it six ways to Sunday. For sure it can be done as you are describing, but this would not be my choice or recommendation.

[Patio29Dadio]

14 hours ago, Skaalvenn said:

Not sure if I'm following this all correctly, but we just have our condensate plumbed into a receiving tank with a float switch that then pumps it back to the condensate tank next to the boiler?  Same unit that Silk posted an image of.

Our still is against a wall, and the tank is on the other side of the wall, so it's about as explosion proof as you can get.

 

You can see here what we are dealing with.  Note the messy floor around all that stuff. 

 

[Beach Time]

Sorry to be late responding, I don't log on that often these days...

Regarding the OP:

item 1) blow down separators, there are several "blow down" points on a boiler, so more info is needed to give a thorough answer. Having said that, the purpose of a separator is to separate the flash steam from the remaining liquid and give each of them a safe (not in your face) place to vent up (steam) or drain (liquid).  Most distillery boilers are really small capacity (relatively speaking) and low pressure so the amount of flash is less of a concern.

item 2) Install cost. Local codes vary widely and they will significantly impact cost.  Rough rule of thumb the same as the new boiler cost.

item 3) I'm not familiar with either brand but a quick look at their web pages and they both seem fine.  The 3-pass, wet-back fire-tube (scotch marine) design is rock solid.  properly matching the boiler to the process load and properly sizing the distribution piping is very important. If the boiler is over-sized for the load even the highest turn-down ratio burner will not correct the issue.  Don't walk but run away from anyone who touts that any boiler requires no water treatment.  This is simply untrue regardless of your source-water circumstance, including RO.  Even if your system & piping are properly cleaned & passivated prior to service and you get a very high % condensate return, (hint these are important) there will be make up water required.  There will also be periods that the boiler is turned off.  Both of these situations require scale & corrosion inhibitors (water treatment).  Modern H2O treatment can be food grade & kosher and will pay for itself in extending the life of your equipment.  If you ever see red rust in the condensate of a boiler system you have (or eventually will have) big problems.

Edited December 5, 2019 by Beach Time
typo

[starcat]

Again, the watchman receivers are fine units to use for their intended purpose. They are not meant to return directly to the boiler with the supplied controls, although you will see many boilers in the field set up this way, this is fully incorrect and will cause the " Normal Operating Water Level " of the boiler to swing too wide, and can cause some other failures which are beyond the scope of this discussion.

You can custom fit a receiver to become a return station and get rid of an extra piece of equipment for smaller systems. The Boiler is supposed to control the return water pumps in every case. if you have only a receiver and you are allowing it to control the return water pumps by action of the supplied float switch, your system is misconfigured. The sequence of operation goes like this:

The Boiler commands the action of the return pumps. Low water level in the " Return Station " commands introduction of fresh water + chemicals. Its that simple. For the systems that are set up backwards as I am describing, the float switch in the receiver is controlling the return water pumps and the low level contact on the boiler is controlling fresh water infeed. This is the wrong way around, and is a hack job way to roll. The contacts on those float switches and motors are not explosion proof unless you buy a rig that is EP rated and set up as such with rigid conduit.

The Modified Weinmann receiver I have shown has the stock inlet at about 10-1/4" off the floor which is reasonable. The condensate outlets being set so low on OEM devices is whats at issue and needs to be met by a response on both sides to optimize things.

[Angesteph]

Hello All,

I'm installing a Columbia MPH 15 low pressure steam boiler and installation is about evenly divided give or take 5,000 dollars.  

Is anybody using any temperature regulating valves on your stills?

Do you see any value as we have the option to install the below for an additional 10K

• Pnematic operated steam valve w/120V air solenoid. 2"NPT (Will need 120V and 60PSI compressed air at still location) 
• Self actuated mechcanical temp control for steam line 2" NPT union.

Thanks so much,
Angelo Tauro 
Elora Distilling Company 

[Beach Time]

would need more detail to make a better recommendation.

I would install an automated shutoff valve that kills the steam flow if the temperature exiting your condenser gets above 40 Deg C. This is a safety protocol that every still should have. This valve should be in a fail-safe configuration (normally closed, air to open) so if you loose air pressure (or the condenser gets too hot) it will shut down the steam.

I would skip the automatic valves and install 2 hand controlled valves in parallel, one large full pipe/port size (gate or ball ) for heat-up and a small globe with control markings so you can document the correct valve position for different spirit runs (search for "continuous blowdown valves").  Open the small valve to get the pipe & still jacket hot, only then open the big valve until you get the line arm warm then close the big valve.  With experience you will be able to dial in how many turns open on that globe valve gets you the sweet spot on your still.  The boiler burner cycling will effect the run, but there isn't much you can do about that other that oversizing the boiler to give the system more inertia or installing a 150 psi boiler and trim the pressure near the still.

The body size of a control valve is somewhat irrelevant; it is the valve coefficient Cv that determines capacity.

A boiler has to run 20% below the PRV setting which in this case is 12 psi max.  At that low pressure, steam volume per pound is relatively large so your pipe size might need to be 4" or more. Sizing steam pipe is all about the line velocity, I'd size for 5000 ft/min. So a 2" pipe at 5000 is going to pass 457 lb/hr of steam at 12 psi boiler gauge pressure.  That equals 13.2 BHP which isn't a very big boiler.  Will undersized pipe still work? maybe but it will be loud and could damage the steam jackets.

Automating steam flow in a meaningful way is going to require a flow meter & pressure transmitter so the automation can control based on energy flow into the still.  That's probably over $15,000 in equipment.

Likely the biggest overlooked issue on the steam side is air venting.  Be sure to have vents high on your steam jackets in order to vent out the non-condensables (air).  Air inside the jacket will act like a big blanket and shield your heating surfaces from the steam.  Then you'll get a slow heat-up and everyone will go over to see what's wrong with the boiler when the problem is air inside your steam jacket.  Don't get expensive automatic vents, just have a 1/4" ball valve piped 4' above the ground and extend the pipe to within a couple inches of the floor.  Once you get the jackets up to pressure open these valves and let them blow for 10-20 seconds.  If you have a slow heat up vent them again.

 

[Angesteph]

18 hours ago, Beach Time said:

would need more detail to make a better recommendation.

I would install an automated shutoff valve that kills the steam flow if the temperature exiting your condenser gets above 40 Deg C. This is a safety protocol that every still should have. This valve should be in a fail-safe configuration (normally closed, air to open) so if you loose air pressure (or the condenser gets too hot) it will shut down the steam.

I would skip the automatic valves and install 2 hand controlled valves in parallel, one large full pipe/port size (gate or ball ) for heat-up and a small globe with control markings so you can document the correct valve position for different spirit runs (search for "continuous blowdown valves").  Open the small valve to get the pipe & still jacket hot, only then open the big valve until you get the line arm warm then close the big valve.  With experience you will be able to dial in how many turns open on that globe valve gets you the sweet spot on your still.  The boiler burner cycling will effect the run, but there isn't much you can do about that other that oversizing the boiler to give the system more inertia or installing a 150 psi boiler and trim the pressure near the still.

The body size of a control valve is somewhat irrelevant; it is the valve coefficient Cv that determines capacity.

A boiler has to run 20% below the PRV setting which in this case is 12 psi max.  At that low pressure, steam volume per pound is relatively large so your pipe size might need to be 4" or more. Sizing steam pipe is all about the line velocity, I'd size for 5000 ft/min. So a 2" pipe at 5000 is going to pass 457 lb/hr of steam at 12 psi boiler gauge pressure.  That equals 13.2 BHP which isn't a very big boiler.  Will undersized pipe still work? maybe but it will be loud and could damage the steam jackets.

Automating steam flow in a meaningful way is going to require a flow meter & pressure transmitter so the automation can control based on energy flow into the still.  That's probably over $15,000 in equipment.

Likely the biggest overlooked issue on the steam side is air venting.  Be sure to have vents high on your steam jackets in order to vent out the non-condensables (air).  Air inside the jacket will act like a big blanket and shield your heating surfaces from the steam.  Then you'll get a slow heat-up and everyone will go over to see what's wrong with the boiler when the problem is air inside your steam jacket.  Don't get expensive automatic vents, just have a 1/4" ball valve piped 4' above the ground and extend the pipe to within a couple inches of the floor.  Once you get the jackets up to pressure open these valves and let them blow for 10-20 seconds.  If you have a slow heat up vent them again.

 

Hello Beachtime,

I believe the thought is to automate the temperature at our 300 gallon still as opposed to regulating the temperature with a valve. 
 

not sure if that helps but will have a face to face talk with the installer tomorrow. 
Angelo

[Beach Time]

Temperature is the wrong process variable to be controlling via automation.  The boiling temperature of the wash changes as the alcohol is depleted.  If you can’t afford the expense to control steam flow via a flow meter + pressure + temperature, then you are better off to control manually with a hand valve. Keep control simple.  Automating a safety interlock is more important than trying to automate steam flow.

[Angesteph]

Thanks so much for the advice @Beach Time

I think the manual process Is what we will do. 
 

Regards,

Angelo