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Farmers Lab Advanced Theories and Techniques - Got a few grows under your belt and want to discuss more advanced theories and techniques? Discuss these matters here.

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Old 02-26-2006, 10:42 AM   #1 (permalink)
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Activated carbon

Some interesting info on what keeps outsiders from smelling our babies.

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There are two main methods of producing activated carbon: Chemical activation and Steam activation.

Chemical activation is generally used for the production of activated carbon from sawdust,
wood or peat and uses chemicals for activation.

Chemical activation involves mixing an inorganic chemical compound with the carbonaceous raw material
and the most widely used activating agents are phosphoric acid and zinc chloride.

Use of Zinc Chloride poses the danger of zinc traces in the end-product.
The fall in imports of Chinese activated carbon into the UK has been attributed to their continuous use of zinc chloride in the Chinese production process.

Steam activation is generally used for coal-based, coconut shell and grain
based activated carbons and uses gases, vapours, or a mixture of both.

Most activated carbon operations which have come on stream in the last twenty years have been based on coal,
mostly bituminous coal but also lignite and anthracite.

Coal is by far the most widely-used raw material in the industrialised countries,
as many companies are related to coal processing and steel industries.

In industrialised countries, capacity expansions are either underway or under consideration by American Norit,
Calgon Carbon, Chemviron and Atochem North America.

Examples where local suppliers and cost factors have led to the use of raw materials other than coal are
Norit's use of sawdust in the UK and Westvaco's use of wood in the USA.

Norit obtain wood raw materials as waste-products from the saw mill-milling industry located between Glasgow and Edinburgh.
Wood used by Westvaco is a waste-product from the company?s own paperboard operations.

In developing countries coconut shells are by far the most widely used raw material.

However, investment in activated carbon plants in developing countries have been slow,
due to high investment costs in plant and machinery and high licensing costs of proprietary production processes.
Individual manufacturers restrict the use of their proprietary production process,
stopping the transfer of technology of activated carbon manufacturing to developing countries to make good use
of valuable waste-product like refuse grain and coconut shells.

Coconut shells have a high volatile content and give a lower yield of activated carbon than grain and coal,
but their abundant supply as a waste-product from the coconut oil and desiccated coconut industry proves to be relative
competitive than grain and coal-based activated carbon producers who have to pay for their grain and coal feedstock.

The fixed carbon content of various raw materials used for the production of activated carbon is as follows:

Material Approximate carbon content (%)
Soft wood 35
Hard wood 40
Coconut shell 35
Grain and agro products 40
Lignite 60
Bituminous coal 75
Anthracite 90

The conceptual framework offered by the technology supplier is based on processing an existing feedstock,
which has resulted from an already operating processing line.

For example, the discarded shells from coconut, walnut or similar product operations are processed to produce a high quality activated carbon.
The technology for producing activated carbon is straightforward,
the refuse feedstock is processed with a thermal desorption process with a final product of activated carbon.
The thermal desorption process is a separation process that removes unwanted materials under varying heat applications.

This technique is low-cost and meets all environmental standards,
where others need expensive solutions to achieve the same results.
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Old 02-26-2006, 10:47 AM   #2 (permalink)
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A small blurb from Norit's web page

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Pound for pound NORIT Americas' activated carbons are the most cost effective in the world. Whatever your application, we can provide you with the pore size distribution to precisely match your needs?with no force fits. As the world's largest manufacturer of activated carbon we offer over 150 different grades in powdered, granular and extruded forms of activated carbon produced from several different raw materials. Choose from a range of pore sizes, particle sizes (4X6 mesh to <325 mesh), particle types (granular, extruded, powdered), virgin or reactivated, acid washed or unwashed, and various packaging from paper bag to bulk truck.
Wow, big business ain't it?
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Old 02-26-2006, 10:59 AM   #3 (permalink)
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Activated carbon is really just a pure amorphous (uncrystallized) form of carbon.
It's main value lie in it's ability to absorb chemicals within it's pore structure.

Activated carbon becomes "spent" when all the absorptive sites within the pores of the carbon get saturated with what it was absorbing.

Activated carbon has an indefinite shelf life when stored in sealed bags and kept away from liquids and chemical vapours in the air.

The absorbancy may be reduced during extended storage due to the absorption of trace quantities of
chemicals in the air that can migrate through the walls of packing material.
OK it will take 3 or 4 years under normal warehouse conditions where low concentrations of chems are present in the air...
but who knows how long the filters sit waitng for us to buy them right?

But realistically, even after storage in that fashion for four to six years the activated carbon would still have most of it's absorptive capaacity for use.
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Old 02-26-2006, 11:40 PM   #4 (permalink)
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carbon filters is the way to go

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Old 03-01-2006, 07:27 PM   #5 (permalink)
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Ahyuh, till ya gotta pay for them... or refill them

Really that's not true. A good filter should last a year.
Cheap security, or just to keep the place smelling good.
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Old 03-07-2006, 10:17 PM   #6 (permalink)
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Well you can make your own, then you know just how long its been on the shelf.
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Old 03-08-2006, 06:23 AM   #7 (permalink)
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Most home made filters can still not match the manufactured ones.

It's all in the math I guess. Optimum thickness of the carbon layer, size of the can, the way they are filled etc
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