Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Patent
1995-01-27
1997-06-17
Straub, Gary P.
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
588205, 588236, 423DIG12, A02N 300
Patent
active
056407084
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the treatment of inorganic solid waste.
In particular, the present invention relates to the treatment of inorganic solid waste which is commonly referred to as "dusts".
The term "dusts" as used herein is understood to mean any relatively finely divided particulate material and includes but is not limited to: by gas cleaning systems operated, for example, as a component of pyro-metallurgical production and processing; and/or toxic, hazardous and non-hazardous wastes, including fly ash, bottom ash and particulate material collected by gas cleaning systems.
In many instances, for a range of environmental and materials handling reasons it is difficult and expensive to dispose of dusts. For example, dusts often contain hazardous compounds and require particular processing before disposal. In addition, dusts often contain components which, whilst valuable, cannot be recovered economically.
It is an object of the present invention to provide a method of treating dusts which alleviates the disadvantages described in the preceding paragraphs.
According to the present invention there is provided a method of treating inorganic solid waste in a bath of molten metal contained in a vessel which has a space above the bath and a waste gas outlet, the method comprising: there are reactions between the waste and the bath or in which the waste undergoes a change of phase to convert the waste into more readily recoverable or disposable products; and a secondary reaction zone in a section of the space above the bath through which oxidisable products released from the primary reaction zone flow to reach the waste gas outlet in the vessel and in which the oxidisable products are oxidised and the heat released by such oxidation is transferred into the bath.
It is understood that references herein to "a bath of molten metal" cover a bath containing molten metal and slag as well as a bath containing molten metal only.
The present invention is based partly on the realisation that a molten metal bath provides a suitable environment, both in terms of temperature and composition, for converting inorganic solid waste, particularly dusts, into more readily disposable components. The present invention is also based partly on the realisation that the use of a secondary reaction zone for oxidising any oxidisable products released from the molten metal bath provides a means of minimising the energy input to maintain the temperature of the molten metal bath.
It is preferred that the method further comprises injecting a gas into the bath to cause splashes and/or droplets of molten metal to be ejected upwardly from the bath into the secondary reaction zone or into a section of the space above the bath which is between the secondary reaction zone and the waste gas outlet to facilitate efficient heat transfer to the bath and scrubbing of volatilised species and any particulate material in the products released from the primary reaction zone and/or produced in the secondary reaction zone.
It can readily be appreciated that the combination of the oxidation of any oxidisable products in the secondary reaction zone and the scrubbing effect provided by the splashes and/or droplets of molten metal in the secondary reaction zone or downstream thereof provides a high level of assurance against unreacted or partially reacted inorganic solid waste short-circuiting treatment altogether and reporting in the exit gas stream from the vessel. This is achieved by providing at least two separate reaction zones through which unreacted or partially reacted inorganic waste must pass before exiting the vessel.
It is particularly preferred that the method further comprises injecting carbonaceous material into the bath to form a carburising zone in which the carbon in the carbonaceous material dissolves into the bath and is available for reaction with waste in the primary reaction zone.
The term carbonaceous material is herein understood to include: solid carbonaceous fuels such as coke and coal; liquid fuels such as oil, light fuel oil
REFERENCES:
patent: 5191154 (1993-03-01), Nagel
patent: 5322547 (1994-06-01), Nagel
patent: 5354940 (1994-10-01), Nagel
patent: 5396850 (1995-03-01), Conochie et al.
International Search Report for International Application No. PCT/AU 93/00317.
Batterham Robin John
Conochie David Stewart
Matthews Terry Alan
Straub Gary P.
Technological Resources Pty. Limited
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