[Gasification] Gasification Digest, steel making

Kelly Burnham kburnham at protonpowerbioenergy.com
Mon Aug 25 11:08:27 CDT 2014


We have been working with the Canadian Carbonization Research Association
(CCRA) http://www.cancarb.ca/ to explore the use of biocoal (biochar), in
steel making.

Preliminary tests show that with low ash and low sulfur content (feedstock
and process dependant), biochar can be a viable substitute for coal.

The challenge is the massive volume of material that's required in steel
making.  We are talking in the 1000's of tons per day.

The other issue is the characterization of the biochar.  Coal furnaces
require very durable and hopefully non dusty material.

Kelly
On Aug 16, 2014 2:31 AM, "Rex Zietsman" <rex at whitfieldfarm.co.za> wrote:

> Hi Geoff,
>
> South Africa exports some 65m tons of iron ore per year. All of this ore is
> >6.3mm as fines block gas flow in blast furnaces. We have millions of tons
> of fines on dumps as a result. We have developed a biogas from biomass
> process that can provide methane into the iron ore industry. Initially this
> gas will be compressed and used to replace diesel in the mine haul trucks.
> The second use for the gas is to supply a pellet plant that feeds an HBI
> (hot briquetted iron) plant. Milling and upgrading the fines (upgrading
> removes clay and other impurities) raises the iron content in the milled
> ore
> to about 67% Fe. These fines are made into 10 to 15mm diameter pellets.
> Carbon is added to the mix when making the pellet. The pellet is then fed
> to
> the HBI plant. Methane (CH4) is steam reformed to syngas - CO and H2 and
> fed
> to the HBI plant. The H2 and CO react with the iron oxide stripping away
> the
> oxygen. Typically pellets leaving the HBI have about 93% metallisation.
> While still hot, the reduced pellets are fed to compactors that produce a
> high density briquette. The briquettes are cooled and exported.
>
> When the briquettes are fed to a blast furnace, they have three major
> benefits:
>   - they require less carbon to strip out the balance of oxygen
>   - they bring their own carbon into the blast furnace
>   - the high strength of the briquettes reduces mechanical breakdown in the
> blast furnace providing low pressure drop gas flow paths
>
> All three benefits result in high blast furnace productivity that uses less
> coke. Coke is devolatalised coal as volatiles cause operational
> difficulties
> in blast furnaces. Coking coal is rare compared to thermal coal and its
> price is significantly higher. Hence a saving in coke and an increase in
> production results in a reduction in the cost of hot metal production.
>
> This addresses part of the story. The second part is that there is always a
> solid fraction coming out of anaerobic digestion. These solids will be
> filtered, dried and pyrolysed with pyrolysis gas used as a thermal energy
> source while the char is sent to pelletization for mixing in with the iron
> ore.
>
> The main problem with replacing coke in blast furnaces is the amount of
> char(coal) required. One industry we have smelts silicon. As silicon
> reports
> to the "slag" in the furnaces, the purity is affected by all elements that
> report to the slag fraction. This includes the ash fractions in coal. As a
> result, coal is not suitable as a reductant. Charcoal has the double
> benefit
> of high fixed carbon and low ash making it the only realistic carbon source
> that can be used. These guys have charcoal retorts spread across the entire
> country. The cost of charcoal delivered to the furnace consequently has a
> high transport element. As charcoal has low density, this simply
> exacerbates
> the transport problem. Needless to say, charcoal for the metallurgical
> industry is a major challenge. I simply cannot see how the world can grow
> enough biomass to be able to supply the requirements adequately as long as
> there is "cheap" coal available.
>
> There - my 2c worth.
>
> Rex Zietsman
>
>
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