Fluidyne Gasification Archive

Waste Reduction Carbons

Waste Reduction Carbons
 
An  opportunity to show, rather than talk about waste chars resulting from high temperature downdraft gasification, has resulted in this latest addition to the Fluidyne Archive. Considerable interest is shown to supply these waste chars as biochar, but their weight and quantity, are limiting factors from a process to make gas efficiently, rather than to make specific quality biochars.
 
In June 2012, four differing wood species were gasified for study of the upper bed changes to demonstrate the char evolution for a visitor from the University of Taiwan. Circumstances saw the waste chars left intact in the gasifier until December 30th 2012, when these interesting photos were taken.
 
It's important to understand that if a gasification process uses char extraction as a means to sustain the gas making process, this disturbs the natural char evolution and much of what you see, will not look like these photos.
 
While waste chars from gasifiers can have very valued properties as biochars, many factors affect the specific quality and how they may affect both the soils and the plant growth. It would seem that all carbon returned to the soil has benefits, but it is in everyone's interest for us who make it, to learn about these differing qualities, and find the best role for their application.
 
December 2012.

Four equal volume fuel block samples to provide a mix for the purpose of training in the examination of packed bed chars, and the points of change which determine their evolution in the transition from wood to gas.
Just raked out of the bottom end waste char, larger start-up char with sharp profile stand out against the smaller rounded chars resulting
 from reduction of CO2 into Co fuel gas. Finer chars and ash of higher density separate easily as the reduction char which lacks density
just floats on the top of the fines.
Seen under magnification, I have no explanation of why what you see as white ash on the surfaces, is actually a very black velvet surface. Ash is present, and you can see separate larger flakes in the dusty finer ash. This may be related to how light is reflected back from these activated carbon surfaces
Each wood type reacts differently in a gasifying environment from the moment the char enters the oxidation zone. Each has an order of segmentation and size reduction, and this is reflected by the variation of surfaces from smooth to porous, but all with soft rounded edges.
In the high temperature reduction phase, it is easier to see how chars give up their carbon to the incandescent CO2. Soft woods continue to segment and the carbon erodes from internal structures. Hardwoods shed carbon from their outer surfaces, and slowly shrink in size, like ice melting in water.

The final size of waste char is determined by how a gasifier is designed to make the gas. These are representative in size and appearance of those found in the waste of Fluidyne systems, where they are ejected at around 850-900C. Note that the dust is not dirty, and can be blown off the fingers, and can provide an indication of both the gas and char qualities