arrostosto rosso


Roasting coffee beans creates toxic gases including carbon monoxide.  Filters only remove solids such as tar and soot.  The toxic gases escape.  When coffee beans are roasted commercially, responsible roasters use an afterburner to break down the smoke toxins into harmless compounds.  When you roast coffee beans at home, why would you want to subject yourself and the world to harmful chemicals?

By employing an afterburner stage, my coffee machine needs no filter.  The exhaust can be vented into the room without concern.  The afterburner works by routing the exhaust fumes through a constricted chamber containing an open flame.  A flame is necessary because it serves as the oxidizing agent.  Electricity does not produce a flame,  so this flame is necessarily fueled by natural gas.

In fact the entire coffee machine is run off a household natural gas supply, or alternatively by a portable propane tank.  There is a battery to run electrical systems, but that is charged up each time by the heat turbine without having to ever plug in.  The turbine is powered by a rapid flow of ammonia.  Ammonia has a low boiling point below 20C, so heating it anywhere above room temperature will instantly energize the machine.  After leaving the turbine, gaseous ammonia is condensed back into liquid form, ready for another cycle.  The ammonia is contained in a closed system and never needs replacing.  The ammonia is heated and cooled using heat exchange devices, pumped with hot or cold water.  

The turbine fan brings ducted fresh air into the machine which keeps the coffee beans moving to prevent uneven roasting.  The powerful airflow also draws away the chaffs and smoke, which both exit to the afterburner.  They are heated under pressure, incinerating the chaffs, and breaking down all the hydrocarbons into base constituents.  The excess heat is recycled back into the system to passively idle the turbines to charge the battery without consuming any more fuel.  Clean warm air exits from the vented back of the unit.

Afterburners require extra energy, but the use of unseen ammonia in the main turbine keeps my whole system cost efficient.  What's more, it does not rely on household electrical current, which is more expensive to run than natural gas.  And most importantly, you won't be poisoning yourself and the environment with pollutants that inevitably get past the filter.

There are two water tanks on this system.  One is for drinking water, and the other is for distilled water.  Using distilled water in the cooling system minimizes hard water build up in the intricate plumbing.  Only the drinking water tank needs to be refilled often.

The user interface is similar to my other coffee machine entry, but I have added gauges which indicate water level and system pressure. It is still one button operation, with integrated twist and pull options.  Please read the details of operation there.

The coffee filter and spent grounds are accessed by pulling a disguised drawer located front and center.  Coffee beans are inserted at the top by first opening a pressure lock cap.

The machine runs cool to touch.  No water is ever heated beyond boiling point, which is the water in the final coffee.  That is proof of the system efficiency.  The only major energy consumption is in the afterburner, which is a sensible tradeoff in eliminating the need to ever empty a chaff tray or change air filters.

Other entries in this project