Welcome to my first Barrel Brothers Brewing Blog post. The time to sit down, reflect and share some of the fun projects that have been going on at the brewery has finally arrived. The intent for this post is to be informative and a little entertaining.
To introduce myself, my name is Wes, I am the Brewmaster and a co-founder at BBBC, which is just a fancy title for wearing a lot of hats and doing a lot of jobs that aren’t necessarily all that fun. Today however, I would like to share a project that was fun. I am hoping to share some information on the internal calandria that I recently designed, built and installed on our brewhouse. The intent here isn’t to go too far into the thermodynamics and engineering involved, but to discuss some of the principles of calandrias and share my project more specifically. (Feel free to skip to the second half to see more pictures and the project build)
In brewing, we boil wort for 4 different reasons: the utilization of hops, sterilization, concentration of sugars by boiling off water, and most importantly for the sake of this article; the reduction of volatiles, namely dimethyl sulfide or DMS. It is for this reason that a vigorous boil is desired. A boil kettle calandria is useful tool for achieving this in steam-fired brewhouses.
A calandria in regards to brewing is a type of shell and tube heat exchanger that is used to boil wort. The reason why we care about these devices is because they are incredibly efficient at doing their jobs. Their efficiency is due to the large amount of surface area they present along with very little heat loss to the atmosphere. Calandrias serve to increase boil-off rates by not only heating, but by agitating wort. Imagine trying to boil off a pot of water on the stove. If you are constantly stirring, the water would boil off faster, this is because through agitation you are increasing the surface area of the water in contact with the atmosphere allowing for more energized water molecules to escape to their gas phase.
The ability to transfer heat is also improved with agitation. Engineers discuss this principle with a term called k-value. K-value is a unit that measures how much real heat is transferred. To give an example, if you were to go outside on a spring day when the temperature is in the mid 50F range you would likely be ok with a light jacket. But, if you were to jump into a lake of water at the same temperature you would find yourself to be very cold. The lake of water is much better at removing heat from your body, due to its higher k-value. The same is true with an agitated heating versus a stagnant one.
Specifically speaking, there are two type of calandrias used in brewing today. The first being an internal calandria, which is what I opted for in my build. The second being an external calandria. They both have their merits and drawbacks. A type of external calandria is pictured below:
As you can see, the heating takes place outside of the kettle. In this image EWB stands for “external wort boiler.” Wort is pumped from the kettle through a heat exchanger, super-heated then returned to the kettle onto a spreader plate/cone just above the surface of the wort in the kettle. This spreader plate can also be called a “Chinaman’s hat.”
External calandrias offer the brewer slightly more control over boiloff-rates, because the circulation pump can be operated at different speeds and the agitation they provide can be better controlled and replicated batch to batch. Steam flow to the EWB can also be adjusted.
The drawback of the external calandria is cost, and the unreliability of having more moving parts. Pumps are expensive and not without maintenance. Extra piping, valves and the EWB can break the bank as well.
The Internal Calandria pictured left and below, is a much simpler device. Suspended in the kettle and plumbed with a steam in and condensate out lines. It is operated without moving parts, and relies only on convection (heat rises). It is controlled with a steam throttling valve and is also fixed with a Chinaman’s hat to prevent boilovers and functions with similar principles.
The internal calandria is designed with a series of tubes inside of a larger cylinder that sits in the wort. Steam heats the outsides of the tubes while wort passes through the inside. As heat is transferred wort rises towards the surface and a convection current is produced. More info and photos on this to come below.
Not all boil kettles utilize a calandria. In many small to medium sized kettles only a bottom and side steam jacket is used. This can be enough to quickly heat and vigorously boil a kettle of wort. Some manufacturers have even gone as far as to unevenly place steam jackets on the exterior of a heating vessel to create a large singular convection current. There are many benefits to operating a kettle with only side and bottom jackets. They are easy to clean, cheaper to manufacture, and are often more than sufficient for heating and boiling wort. In modern small to medium systems, brewhouse processes are combined into fewer vessels. Hence, the mash/lauter and the boil/whirlpool kettle. If whirlpooling is to commence in a combination boil/whirlpool kettle then an internal calandria would disrupt the flow and the process would be less than effective.
Due to their simplicity, internal calandrias are often used in smaller brewhouses, while external calandrias are used in larger ones. While not every small brewhouse uses a calandria, pretty much every large brewhouse utilizes them. This is due mostly to the surface area/volume ratio of small kettles vs. larger ones. As a kettle gets larger the surface area of side and bottom kettle jackets increases by the square unit, whereas the volume of the kettle increases by the cubic unit. At a certain point there is simply not enough exterior jacket surface to heat the kettle, even with high pressure boilers with wide temperature deltas and massive steam output.
The drawbacks to operating a boil kettle without a calandria are due to losses in efficiency. Exterior jackets cannot transmit all of their thermal energy into the wort, there is always a certain amount of heat lost to the ambient surrounds, no matter how well they are insulated on the outside.
Enough, background information, lets get to the details of my project:
If you cannot tell already I am a little bit of a brew-tech nerd, so I had to have a 4 vessel brewhouse. The 4 vessels being separate: mash-tun, lauter-tun, boil kettle and whirlpool kettles. The benefit of having a fully expanded brewhouse is for improved efficiency and quicker throughput. One batch may yield me 10-12 barrels of wort, but I can produce nearly 3 batches in a 10 hour day. A larger condensed brewhouse may be able to only do 2 batches in that time and we both end up with the same quantity of wort at the end of the day. So what that gives me is flexibility, I can brew a small one-off batch or I can crank out multiple batches in a day.
Before I installed my calandria, I was having some heating issues and we were experiencing an unfortunate bottleneck in our system. At that time I was lucky to process 2 batches in 10-11 hours. Not good.
Earlier, while we were building-out our facility I was able to score an over-sized 15psi Rite steam boiler. The boiler was 40% over sized for our application, but I liked that I would be able to heat the kettle and the hot-liquor tank at the same time, which I would not have been able to do other-wise. It is a beast. Unfortunately since it is so over-sized it cycles on/off frequently. Boilers are simple creatures, they have a mini rocket engine-like burner under a chamber of water which it heats, turns to steam, then a pressure switch signals to kill the flame when the set pressure is reached. In between cycles a fan purges the combustion chamber with air to exhaust any residual gas so there isn’t an explosion when the burner turns back on. The cycle on my boiler was taking about 2 minutes per. Since my boiler was oversized it would heat-up to pressure, then turn off for a minute before going back through its start-up procedure. During that time the pressure (and heat) would drop significantly. If the boiler was smaller the steam supply would have equaled the demand and the cycling would not have occurred in the same way.
My solution was to build a calandria to increase the surface area of heating in my kettle. This would allow for longer boiler cycles due to the increased steam demand. Faster heat-ups and a shorter boil-time was the goal.
I began the design and construction of an internal calandria that would double surface area presently available in my kettle. It would have 30 1.5″ diameter tubes that were 2′ long. The entire calandria would be 14″ in diameter.
I luckily had some help from a friend with some water-jetting for the end plates and a slip roller for the cylinder exterior
Everything was constructed from 16 gauge 304 stainless steel except for the end plates which were 14 gauge to reduce warping when welding.
The tubes were 0.065″ seamless sanitary tubing. After a weekends worth of TIG welding I had the whole body fabricated, pressure tested and ready to go.
I installed a 2″ Tri-clover flange for the steam inlet and a 1″ TC flange for condensate out.
The trick with these internal calandrias is to design them so they can be cleaned in the easiest possible way. I designed the Chinaman’s hat so it could be removed. Spraying the tubes out after each batch reduces buildup. Significant build-up on the heating surfaces compromises the ability to transfer heat, so this is an important step.
After welding the bottom mounting tabs, fabrication was complete and it was time for the more daunting task of installing it in the boil kettle. In theory installation should be simple, but its hard to get past the idea of drilling a 1″ hole in the bottom of a perfectly good boil kettle. I first welded the calandria in place with some stainless flat-bar. Before I could get to installing the piping I had to modify the spray ball so the CIP system could still function. Otherwise I would have been left with a single spray ball directly above and blocked by the Chinaman’s hat.
Welding in such a confined space is not for the faint of heart and requires many breaks, but luckily I was finished with no leaks! Fortunately I had some help from another friend installing the steam line connection that goes through the top of the kettle. This enabled me to do a nice clean weld without any sugaring on the kettle interior. After adding the 2″ steam line on the kettle interior, I started running 1.5″ black pipe from the steam main.
The last thing to do was to add a steam trap and run the condensate line back to our brew-house condensate return pipe. Most boilers operate in a closed loop so that once the steam is used and condensed into water it can be sent back to the boiler for re-use. This saves significant energy because the condensate still contains a good amount of heat and will require less energy to turn back into steam. The steam trap acts as a gate-keeper so only condensate can pass through and not steam. It does this by requiring a certain level of water to lift a float that opens a valve to allow built up condensate to escape and flow back to a condensate return/feed-water tank.
Now that all the hard work was done, it was time to have some fun and boil some wort with the new hardware! I have attached some videos below that show the first test-run. I am quite happy with the results.
At calandria and steam jackets full throttle, heat-up from 180 to 212 takes about 10 minutes with a kettle volume around 400. This is an improvement from around 45 minutes. The boiler cycling that I described earlier has subsided and the boiler holds steady right at 11-12 PSI. This indicates that the boiler’s full capacity is being used (1,000,000 BTH/Hr and 1000lb of steam per hour) Very impressive!
Previously I was experiencing between 5-6% boil-off per hour. At the calandria throttle setting I was using during my first test batch I was seeing boil-off between 8-9% per hour. This is right where I want it. More testing and measuring will confirm these rates.
I have accomplished my goal of reducing the brewing time for each batch by just over one hour. I can now heat-up much faster and can reduce my boil times from 90 minutes to 60 minutes.
This will save me hundreds of hours each year. I estimate the cost of this project would have been in the ball-park of $10k had I payed someone else for the design, engineering, fabrication, and installation. My cost was under $2k so I see it as a worth-while investment, an incredible learning opportunity, and a fun project!
Images 1 and 4 Taken from: Bamforth, Charles W. Scientific Principles of Malting and Brewing. St. Paul, MN: American Society of Brewing Chemists, 2006. Print.