Management of Chemical Toxic Wastes

Conventional methods for dealing with such chemical toxic wastes as represented by the Love Canal crisis have been rejected as inadequate. Many similar disastrous discoveries have added to the immensity of the problem with the prospects of costs that are astronomical. The foundations of a practical solution were indeed discussed with the City of Niagra Falls in Aug. 1978, followed by a confidential disclosure more recently.

The Coal Reactor version of a vertical shaft furnace is envisioned as the best approach to the detoxification of hazardous chemical wastes, offering on site operation to minimize handling and transportation. In this fashion a clean, inexpensive energy source resulting from the burning of coal can give rise to an adequate thermal reservoir and slag volume for the treatment of such wastes, taking full advantage of a new type of utility station awaiting development. The symbiotic operation inherent in the innovative response to the health dangers posed by chemical toxic residues from industrial plants virtually insures successful resolution of an increasingly growing environmental menace for which there may be no other realistic solution.

Coal Reactor power stations of the future for the production of an abundance of clean energy can be adapted to remove toxic chemical wastes from the environment in offering a molten slag output that will encapsulate the pyrolyzed decomposition products from the high temperature exposure. The limestone, normally required to purge the impurities from even the poorest grades of coal and regulated additions of garbage, forms the basis of a slag (a mixture of oxides of calcium, magnesium, aluminium, silicon, etc.) that can react with the decomposed residues of the toxic wastes. Continuous operation is possible by feeding the dangerous wastes together with the lime and coal with possibly some municipal wastes allotments into the vertical shaft furnace to wind up with a slag that can be safely handled and disposed of keeping costs at a reasonable level. An alternative batch process entails pouring a suitably tailored slag over the contaminated mass placed inside a crucible whereupon, following a prolonged coating period, the decomposed residue is sealed into the solidified mass resulting.

The extent and chemical composition of the toxic waste matter to be treated provide vital information as to the scale of operation and the power level of the Coal Reactor needed to insure an adequate heat balance with an energy output to make the installation self-contained. Having decided on the throughput capacity, the amount of coal and limestone needed can be estimated and the size of the coal Reactor prescribed. Since tons of material may be generally expected on a daily basis, the power output of the station will fall well into the multi-megawatt range.

In the mode chosen for the treatment of the hazardous wastes involves the direct addition to the feedstock of limestone and coal at the top of the vertical shaft furnace, the danger of the toxic decomposition products escaping with the normal gaseous effluent of the Coal Reactor can be guarded against by invoking the reflux arrangement (described in U.S. Pat. No. 4,080,196). The so-called upcomer conduit for the escaping gases should be placed below the calcination zone of the reactor vessel.

The other manner of encapsulation by the slag addition to the toxic material resting at the bottom of the crucible may need to be accompanied by chemical additives to render the decomposition products from the high temperature exposure harmless. Thus, the use of a lime covering over the toxic charge may prove desirable. The effectiveness of whatever chemistry is selected to tie up toxic vapors produced by the pouring of the hot molten slag into the charged crucible will need evaluation by samplings of the resultant encapsulated products.

The latter mode of treatment requires a sufficiently long interval to permit mixing of the slag with the waste material and its decomposition products, a condition favored by employing large enough batches to slow down the cooling and the ensuing solidification. The crucible geometry also poses an important factor in this regard since the surface to volume ration plays an important role in the rate of cooling.

So for both modes of thermal destruction of toxic wastes a squat-cylindrically shaped crucible is to be preferred for closer control of the solidification in allowing ample time for degassing and the formation of sound castings that are relatively stress free. The porosity of the solidified mass represents another important consideration in minimizing leaching during the course of storage. The reduced surface to volume ratio will support the objective of curbing the overall weathering of the encapsulation product in reinforcing the effect of low porosity itself.

Indeed, ultrasonic diagnostics is advised to detect any flaws in the final product, a procedure that should help guide determination of the conditions necessary for satisfactory results. Other diagnostic tools may be invoked such as x-ray and chemical analysis to arrive at an understanding of the fate of the hazardous chemical wastes when subjected to the thermal destruction treatment. By such means the engineering specifications for a wholly new technology can be expected to evolve.