Furnace

A furnace is a appliance that generates heat, usually from combustible material.

The controlled environment allows for greater efficiency and control over the reaction.

Uses

Depending on the design, furnaces serve a multitude of functions and form the basis of a wide variety processes.

The most common and important furnaces are used for food preparation and curing.

History

The history of furnaces can be dated back to ancient civilizations. The Romans used their own version of it, called the "hypocausts". The Industrial Revolution sparked the development of many other variants of the furnace such as warm-air furnaces and the radiator.

Food

By cooking food, it can be more digestible for humans.

The resulting smoke from the fire can be used to cure food more effectively for long term storage.

Boiling can sterilize water.

Materials

Curing

Firing clay allows the vessel to become permanently set.

This process applies to all pottery, roof shingles, bricks, and earth ware.

Most drying processes can be accelerated with heat as the water evaporates faster.

Fuels

Great availability

Any dry plant matter will work to some degree.

Easily accessible sources of high yield fuels are wood and charcoal.

Both can be farmed on industrial scales or manufactured in small batches.

Good availability

Alcohol is a good source of liquid fuels that offer some advances over solid fuels but also carries additional risk.

Reliable combustion can be achieved with 50% to 60% alcohol content. To achieve this concentration, the alcohol needs to be distilled.

Situational availability

Turf and dried life stock dung can be burned. The smoke will be more irritating and harmful than other fuel sources.

Nonetheless it serves as a valuable alternative.

Natural Gas may be harvested in a bioreactor or sometimes found in nature.

Electricity

Heating elements made from resistant materials can be used to convert electricity into heat on demand in finely controlled quantities.

For steel production, plasma arcs are leveraged. Only the melting point of the electrodes limits the effective temperature of the furnace.

Alternatively, inductive heating can be used to effectively heat electrically conductive materials.

Construction

Pressure and airflow trough a chimney

The basis of any common furnace type forms the chimney effect.

Heat rises out of the chimney, any vaguely tubular structure will do, and pulls in fresh air from the bottom inlet.

The fresh, cold air provides more oxygen and stokes the fire. This effect can be enhanced with forced convection to reach the necessary temperatures for smelting and forging metal.

By constricting the air inlet, the rate of combustion can be adjusted.