Monotube boiler for steam direct injection design (pic)
Posted: Thu Nov 19, 2015 5:17 pm
Wasn't quite sure where to put this.
Below is a crude drawing of a coil layout of a monotube boiler I want to use for steam direct injection at atmospheric pressure to heat a 55 gallon polypropylene fermenter up to boiling, in addition I want to use it in the still as the heat source.
I cribbed pretty heavily off of the Lynx monotube boiler, except he has the coils going continuously up for saturated steam and I've got the coils going up and then back down toward the flames for true counter-flow superheated dry steam generation. I'm shooting for 300F steam - a higher temp steam means less water added to the boiler, and it means I can bring it all the way up to boiling.
Temperature of the steam is regulated by water feed rate (mains water pressure) and gas burner flame intensity. Steam temp is fairly irrelevant though as it is just the transfer medium for the gas burner.
I want to use steam injection for a few reasons:
- According to what I've read steam injection is something like 40% more efficient than direct fire boilers and so will use less fuel for the same result.
- Its gentler on the contents of a fermenter
- Its about the only way to get gas powered heat into a plastic fermenter that doesn't involve filling a dozen buckets with boiling water and pouring it in.
- More precise temperature control
- I like the idea of having all the flames in a small contained unit AWAY from the still and just the heat is piped over.
- In a long term power out I can use wood heat by having the boiler and fire outside and the heat being piped in via steam.
And the biggest reason for using a atmospheric pressure monotube is:
- You can't make it go boom. Boom is bad. You could literally shoot the monotube boiler and all you're going to get is a steam cloud. Even if it's plugged up there's not enough water in it to go boom. You can burn the shit out of yourself if you stick a body part in a superheated steam stream but you can't blow the house off its foundation.
I know kegs are rated for something like 60PSI but I'm just not comfortable with having gallons of superheated water near me or the house.
With a keg all you need is 215 degree water and its already got enough thermal energy in it to flash into a house demolishing steam explosion if you have a "oh shit" like a seam split on the keg Call me overly paranoid but I'm VERY boom averse....
At any rate the design has a cylinder of coils going up the outside perimeter (basically a preheater) and then layers of "pancake" coils going back down towards the flames and then a very loose coil almost in the flames as a superheater to produce dry steam.
In the center is a wad of kaowool to keep unused hot gases from bypassing the coils.
At a rough guess I'll be using about 150 feet of 1/2" refrigeration tubing, which'll be expensive but then I'll have a heat source that I can use with any number of stills or fermenters.
I'll have the usual check valves in the inlet side to protect the house mains, and a 10PSI safety relief at the outlet. I'm also going to have a vacuum breaker in the steam line so if I forget to remove the injection wand when I turn off the heat I don't suck up wort or spent mash into the hoses and boiler.
The hose is going to be a PTFE lined hose attached to a stainless wand with a circle of SS hose mesh as a diffuser - about impossible to clog
Thoughts? Have I missed anything?
Thanks!
Below is a crude drawing of a coil layout of a monotube boiler I want to use for steam direct injection at atmospheric pressure to heat a 55 gallon polypropylene fermenter up to boiling, in addition I want to use it in the still as the heat source.
I cribbed pretty heavily off of the Lynx monotube boiler, except he has the coils going continuously up for saturated steam and I've got the coils going up and then back down toward the flames for true counter-flow superheated dry steam generation. I'm shooting for 300F steam - a higher temp steam means less water added to the boiler, and it means I can bring it all the way up to boiling.
Temperature of the steam is regulated by water feed rate (mains water pressure) and gas burner flame intensity. Steam temp is fairly irrelevant though as it is just the transfer medium for the gas burner.
I want to use steam injection for a few reasons:
- According to what I've read steam injection is something like 40% more efficient than direct fire boilers and so will use less fuel for the same result.
- Its gentler on the contents of a fermenter
- Its about the only way to get gas powered heat into a plastic fermenter that doesn't involve filling a dozen buckets with boiling water and pouring it in.
- More precise temperature control
- I like the idea of having all the flames in a small contained unit AWAY from the still and just the heat is piped over.
- In a long term power out I can use wood heat by having the boiler and fire outside and the heat being piped in via steam.
And the biggest reason for using a atmospheric pressure monotube is:
- You can't make it go boom. Boom is bad. You could literally shoot the monotube boiler and all you're going to get is a steam cloud. Even if it's plugged up there's not enough water in it to go boom. You can burn the shit out of yourself if you stick a body part in a superheated steam stream but you can't blow the house off its foundation.
I know kegs are rated for something like 60PSI but I'm just not comfortable with having gallons of superheated water near me or the house.
With a keg all you need is 215 degree water and its already got enough thermal energy in it to flash into a house demolishing steam explosion if you have a "oh shit" like a seam split on the keg Call me overly paranoid but I'm VERY boom averse....
At any rate the design has a cylinder of coils going up the outside perimeter (basically a preheater) and then layers of "pancake" coils going back down towards the flames and then a very loose coil almost in the flames as a superheater to produce dry steam.
In the center is a wad of kaowool to keep unused hot gases from bypassing the coils.
At a rough guess I'll be using about 150 feet of 1/2" refrigeration tubing, which'll be expensive but then I'll have a heat source that I can use with any number of stills or fermenters.
I'll have the usual check valves in the inlet side to protect the house mains, and a 10PSI safety relief at the outlet. I'm also going to have a vacuum breaker in the steam line so if I forget to remove the injection wand when I turn off the heat I don't suck up wort or spent mash into the hoses and boiler.
The hose is going to be a PTFE lined hose attached to a stainless wand with a circle of SS hose mesh as a diffuser - about impossible to clog
Thoughts? Have I missed anything?
Thanks!