Pyrolysis
Pyrolysis is basically heating in the absence of oxygen and can be executed as low or fast pyrolysis; whereas the first technology will be mainly used to produce oil, the second is the technology used for the production of a “biochar” as main product. Low means also really low in terms of it will take time to get to the desired result and the process needs a less high temperature, thus making it more efficient in terms of produced quantities. The temperature will depend on the wished end product: torrefied material requires a temperature of 280 to 350 °C, whereas carbonization will be using a temperature between 350 and 500 °C. The production time and operational parameters will depend on the specification of the wished end product.
Gasification
Gasification basically means sub stochiometric heating without combustion; the simplest way to add oxygen to the process is by blowing the desired amount oxygen into the gasifier, just sufficient to produce and maintain the heat in the gasifier system. The temperature needed for a proper gasification process will be well above 670 to 680 °C to assure complete conversion from the feedstock in combustible gases. The most common and affordable way of gasifying is to use air as gasification agent instead of steam or pure oxygen.
Combustion
Complete combustion means basically burning under stochiometric conditions; it seems easy: simply mixing some gas with the right amount of air and then activate the ignition source. The result should be a nice flame causing a rise of the temperature inside the combustion chamber, finally leaving the combustor as a relatively clean flue gas.
In praxis however many difficulties may be experienced, like unwanted gas concentrations due to bad adjustment of the control system or from poorly adjusted burners resulting in the formation of carbon monoxide and other unwanted hydrocarbons. This gets even more important when using more difficult feedstocks (biomass e.g.) which due to their natural origin contain also nitrogen compounds. See also the results of stubble burning after harvesting as is still done in many areas of the world.
Other thermal conversion technologies
Besides these almost classic technologies as mentioned here above, new technologies are being investigated and partly already developed, among which will be hydro thermal processes (HTP), which would open up some attractive application for SR2.0’s clients. HTP can efficiently convert biomass - and in particular highly-wet, biogenic residues and waste materials - under increased pressure and temperature into high-quality refined solid, liquid or gaseous carbonaceous products. A large variety of starting materials can be used to make a wide range of products available. Thus, HTP sustainably contribute to resource protection and are an essential component of a future bioeconomy.