REVIEW OF SITE REMEDIATION AT TTL

This Review has been carried out by Mr. Robert (Bob) Rice, Metallurgist who has a working familiarity with the operations of the Temiskaming Testing Laboratory from previous operations with the Cobalt Refinery. As a probable partner in this revitalization project he will be responsible for all refining/smelting operations in the building as well as environmental controls and compliance. His company, Temrex, will retain an office in the complex and will conduct its R&D there.

SITE VISIT

The Trow and Beak Reports indicate an estimated 550 cubic metres of material of a toxic nature. This seems to be an excessive amount of material considering the shallow depth of the deposit and the small area of exposure that is evident. However, the materials themselves are normal assay reverts that any precious metal smelter or refinery would generate and would, in practice, be incorporated back into their reduction unit charges. The calcium/magnesium cupels and silica crucibles are ordinary flux components as are the assay slags. The entrained metals, except for the lead addition, are those normally found in base bullion which of course is the case, since the assay sample is, in fact, a profile of the feed stock with the precious metal removed, The lead addition is only a minor component given the difference in weight between the sample size and the quantities of material being smelted relative to samples taken. Two deposit areas are on surface and readily accessible for removal while one is overlain by pavement and the fourth was not evident on surface but was probably overlain with a shallow gravel fill. Removal does not appear to be a challenging task.

PROCESS

In the smelting of metal concentrate materials, fluxing agents are added to balance the insoluble portion of the concentrate. These insolubles may be alumina, silica, calcium, magnesium etc. (generally components of the rock or gangue material in the concentrate) and these materials are balanced to form both a low melting eutectic and to achieve a pH which is compatible with the lining of the furnace. The furnace lining in turn is designed to be compatible with the conditions (conditions can and do change as the melt proceeds) of the charge. Assay reverts are compatible in and a very minor addition to such a charge and are easily accommodated in furnace practice.

During the course of the smelt several chemical reactions take place and the conditions in the charge may change in a number of ways. Eventually after the gases are expelled along with substantial paniculate matter, the reactions go to completion and the soluble components, metals plus their solvents, will form either a matte, a speiss or both if both arsenic and sulphur are present, with or without a settled base bullion phase and the insolubles which are in the form of slag float free.

Furnace charges of precious metal concentrate may have a wide variance of constituents. Charges may or may not contain one or more solvent elements. Usually charges are mixtures of several different concentrates blended with secondary metal materials, assay and refinery reverts, particulates from fume recovery plus a reductant such as carbon to form a consistent feedstock. This minimizes the need to continually adjust flux additions and the charge would likely contain at least one solvent element (sulphur, arsenic, antimony etc). In base metal smelting these elements are sometimes eliminated by roasting before smelting and at times are used as a collector while smelting.

There are several products of furnacing:

Gases which are subject to scrubbing and which may carry compounds that require some control to stay within regulatory limits. These compounds cannot be controlled by dust collectors or dry scrubbing and require wet scrubbing where absorption and precipitation measures may be utilized. Scrubbed gases report to atmosphere and must fall within the regulatory parameters.

Particulates that are carried from the furnace by the expelled gases and can be effectively recovered by either dust collectors of the dry type or wet scrubbing and are returned to the furnace in subsequent charges. These particulates while very fine do not usually differ greatly from the composition of the feedstock other than some conversion to oxide may have occurred and this does not greatly change furnace process. These are all returned to the furnace.

Slag, which is the insoluble portion of the charge, is generally a fairly clean product but will carry traces of both metals and solubles usually in the form of tiny prills that have not enough weight to fall out into the matte or bullion phases. In base metal smelting these may be returned to a milling circuit provided the meta! content is sufficient to justify recovery. The same is true in precious metal smelting, however, the option of sending these slags to a base metal facility is often a preferred course. A base metal facility uses the slag as a fluxing agent for their metallurgical balance and can, due to the immense amount of base meta! present as a scavenger, gather all the precious metal available. The precious metals are recovered during the electrolytic refining of the base metal. Slags therefore need not be disposed of locally as they become part of a larger operation.

Matte, which is a solid solution of metals such as iron or copper and lead with sulphur, has the ability to hold large quantities of gold and silver in the liquid phase, iron additions to melts of matte will throw some of the gold and silver from the solution but never completely and sending matte as a form of concentrated metals to a base metal smelter is be a better prospect than conversion by blowing the sulphur to atmosphere as sulphur dioxide. Matte therefore does not remain as part of a local disposal problem.

Speiss is a similar solution of metals with arsenic however unlike matte, speiss with iron additions will release most of the precious metal to a base bullion phase. Low silver speiss that has significant quantities of copper, cobalt or nickel are a feedstock for recovery of these elements at a number of smelters interested in cobalt recovery and entrained precious metals, all as pay elements. Speiss can be either converted and all the products recovered for sate including the arsenic or sold to be recovered elsewhere. There are no residues to be disposed of locally.

Base bullion can be cleaned up by an oxidizing process to remove most of the solvent elements by conversion to oxides that report to the scrubber and the base elements that report to the slag. Both these products report back to the reduction unit as reverts. The bullion, now in a semi-refined state, can be cast to anode form for the final electrolytic refining phase or sold as a reduced bullion. There are no residues for disposal.

REMEDIATION OF SITE

The operation of the TTL site includes a minor smelting operation incorporated in the sampling and testing unit, which is intact, and with some revision can be brought up to exceed compliance.