In case someone is interested, I've done the preliminary analysis and investigation and I'm going to be building a steam boiler from a corny keg to supply steam for heating my mash.

Its not nearly as scary as it sounds.

Description

The corny keg will get a 4.5KW hot water heater element installed in the bottom. A temperature sensor will be installed in the top. A small $35 computer will monitor the temp (and other things about the brewing process) and turn the heater element on and off with a set point of 240F. A laptop computer will be used to control and monitor the process computer.

The pressure in the keg will be about 10 PSI. Corny kegs are rated for 130 PSI. A 15 PSI pressure relief valve will be installed to prevent any over pressure situations from occurring. Keep in mind that this is less pressure than a typical automotive cooling system. The keg will be pressure tested to 30 PSI with tap water before being fired up.

The keg will be equipped with a simple valve manual or computer controlled on-off valve for delivering the steam to the mash.

Parts List

The parts list is this thus far (McMasterCarr part numbers where applicable.)

1 good corny keg
1 4.5 KW hot water heater element, screw in (3555K32) $6.80
1 self sealing nut (5530K23) $4.90
1 pressure relief valve (4893K25) $7.70
1 bulk head fitting, nickel finish 5483K93 $9.80 for 2
5 feet high temp NFS hose 3184K1 $1.47 per foot
1 high temp electric solenoid valve 4807t21 $51.02

There are a few misc fittings missing from this list as well as the computer and relays or SCRs for turning the heater and control valve on and off. Temperature measurement will be done with a $3 thermistor.

Usage

The computer will be programmed from a PC to bring the strike water in the HLT and boiler up to their start temps (135F and 240F) respectively. It will take about 20 minutes to bring a nearly full keg up to 240F. The HLT will be electric heat as well, so that will take another 15 minutes or so.

Dough in will occur. There will be a temp sensor in the mash vessel, actually multiple of them on a floating thermometer setup.

When the computer senses a temperature differential in the bed, it will turn on the recirc pump to even things out.

When the computer senses the bed is too cool, it will modulate the steam valve a few times, injecting some steam, to heat it up.

As soon as the temp in the boiler drops, the heating element will be turned on to bring it back up.

At the first mash temp step the computer will change the temp setpoint from 130 to 155F and open the steam valve accordingly. The recirc pump will kick in. The operator will be encouraged to stir the bed.

The thermodynamics are such that the steam created from a corny nearly full of 240F water is enough to heat the mash from strike temp to mash out. The steam can be added as fast or slow as desired by throttling the flow. It will be possible to raise the temp of a bed containing 10 pounds of grain by over 20F per minute. Gone are the days of waiting around for the bed to get to the next temp. Multiple temp mash schedules should be a breeze.

The amount of water in the injected steam to heat the mash from strike to mash out will be small, less than a quart.

The boiler will contain 15 Litres of 210F water at the end of the mash out. It can be used for cleaning or sterilizing the counter flow chiller. It could also be used to top up the boiler if the sparge volume is less than the boil volume.