Dapto Smelter Process Route

This is a brief description of what went on at the Kanahooka Road site of the Australian Smelting Company, better known as the Dapto Smelter in the late 1890sIearly 1900s. This is not a history of the company, but a guided tour through the site when it was operating.

The site was located on what were originally two hills, which were very close together and running south west to north east. The tops of the two hills were cut off then terraced down on the south eastern side into basically three benches. The terraces were formed with bluestone walls with the stones held together with what could be a limeIcement mortar, rather than a straight cement mortar, there are signs of shells in parts of the mortar. The bluestone used in the wall does not appear to be local to the site and probably came from the Berkeley area.

All the raw materials used in the process were imported into the plant, none was found on site. The exception being some raw materials used for the construction of the works. To bring the raw materials into the works site, and take products out, a branch railway line was taken off the Illawarra Harbour & Land Corporation standard gauge railway line running from Lake Illawarra to the escarpment to near West Dapto. The Corporation’s railway was connected to the Government’s South Coast railway, south of Dapto station and near where Clarke’s sawmill once stood. This gave the smelter direct rail access to the Government’s South Coast rail system.

Use is made of a 1988 aerial photograph and several photographs, which have been annotated, for guiding us through the works. The branch railway to the works crossed Kanahooka Road over a bridge (A) and rose up to the upper most terrace level. It was on this level that most of the ancillary activities were located. On the south western comer was the brick office building (B) and immediately to the north east of it was the brick laboratory and assay building (C). Some time after the smelting plant closed the office building was used as a residence for the Webb, and later, the Fackender families when they operated the area as a dairy farm. They used the laboratory and assay building as a storage shed. In much later years, when the Fackenders sold out, the office and laboratory assay buildings were joined together by an extension and it became the “Lake View” restaurant run by a Mr Bozic. The attached aerial photograph ( page 2) taken in 1988 shows the site when the restaurant was operating, the marked out car park is clearly visible. Beyond the laboratory and assay building was the sample preparation building (G) and beyond that were the store buildings (D). Still further to the north east are the various workshops (E). On the north eastern side of the uppermost terrace the incoming rail tracks run parallel with the top bluestone wall before entering a covered building (F). In this building (F) a sample of ore is taken from the rail trucks then taken to the sample house (G) for crushing and analysing to determine its gold and silver concentrations. This testing was necessary in order to determine the purchase price payable for the various ores.

 

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There were a number of bins set underneath the incoming rail lines. The south western most bins (H) are for the receival of high sulphur ores that require some form of pretreatment prior to smelting in the blast furnaces. The north western most bins (I) are for the receival of low sulphur ores that require no pretreatment prior to smelting. The north western bins also hold the coke used as fuel for the smelting process as well as the iron ore and limestone used as fluxes in the smelting process.

In the centre of the uppermost terrace level is the boiler house (J) which housed five large coal fired Lancashire type boilers for supplying steam for powering the various steam engines used to drive all of the machinery installed in the whole of the works. The brick stack (K) for these boilers features prominently in the landscape.

During construction of the works a steam driven saw mill and brickworks were located under cover on this uppermost terrace with logs for milling obtained from the property. The shale for brickmaking would have come from the excavations needed for the terracing. One other very prominent feature on this upper level was the very high brick stack (L) carrying away the fumes from the blast furnaces. This stack, and its associated flue system, will be discussed later.

To the north west of the above upper level the ground falls away naturally to a generally flat area. A small creek flowed through this area; the creek was excavated and dammed to form an 18,000,000 gallon fresh water reservoir (M) for the works. A pump house (N) and pipeline took water from this dam to a circular reservoir (0) located on the upper level. On this lower level, and just off Kanahooka Road, the manager’s residence (P) was built. At the manager’s request the house was clad with galvanised iron, it was completely surrounded by a picket fence with extensive plantings of exotic trees around the house. The house has long since gone. Between the manager’s house and the works were the horse stables and associated buildings (Q).

In mid 1993 all the remains on the upper terrace were bulldozed to make way for the Forest Grove village. The remains of the office and laboratory, and a beautiful old fig tree were mysteriously removed overnight, allegedly with the permission of a Wollongong City Council officer, but the officer claims that that he did not give permission.

The low sulphur ores, iron ore, limestone and coke were removed from the north western set of under track storage bins (I) and taken to the bedding and blending floor (R) by means of hand propelled side tipping skips (S), that ran on elevated tracks (T). The iron ore, limestone and coke skips dumped their loads into the specific areas for those materials. The low sulphur ore skips dumped their loads in a specific pattern to produce a correct blend of ore.

All ores from the south western end high sulphur ore bins (H) were sent into a crushing, screening and roasting plant that was covered by a series of buildings (U). Here a closed cycle system crushed and screened the ore to produce a product of fine gravel proportions. This crushed material was then stored in a bin for further treating. There were many machines such as crushers, grinding rolls, elevators, screens, conveyors, etc in these buildings that required powering. This power was provided by a single 250 hp steam engine (V). An intricate system of shafting, rope drives, belt drives and gearing was needed to transmit the power to the various devices. There were two streams for further treatment of the high sulphur ores, which stream was used was dependent on the type of ore being treated.

The lead bearing ores that needed slow roasting were treated in the ten hand-rabbled reverberatory furnaces. These reverberatory furnaces are like oversized bakers’ ovens; at one end of the furnace was a firebox where coal was burnt while the other end was connected to a flue leading to a stack (W) . In the middle of the furnace was a hearth where the fine ore to be treated was laid out and heated by the flames from the firebox passing over them. The ores were stirred over (rabbled) by hand to permit the sulphur in the ore to be burnt off. The treated product from the hand-rabbled furnaces was then transferred to the fusing plant.

Ores that could be quickly roasted were treated in two revolving furnaces. These steel furnaces were 25 ft long by 6 ft in diameter and were brick lined. The furnaces were built on a slight incline and slowly rotated at a speed that could be varied in steps. At the low end of the furnace was a coal fired firebox, the flames passed through furnace and entered the flue leading to the stack (W). The ore to be roasted was fed into the upper end of the rotary furnace and gradually made its way down the furnace to exit at the lower end. Lifter bars were built into the furnace to lift the ore to make them pass through the hot gasses from the firebox to burn off the sulphur. The treated ore then passed to the fusing plant.

The treated ores from the above two roasting plants were still quite fine and needed agglomerating into larger lumps to minimise dust losses in the smelting plant. This agglomeration was carried in the fusing or sinter plant. The fused material was then transferred to the bedding and blending floor (R) where it was blended with the low sulphur ores to achieve a consistent chemical mix.

There was a common flue carrying the sulphurous gases from the two roasting plants to a common stack (W). This was an on ground flue, one side of the flue utilised part of the upper bluestone retaining wall while the other wall of the flue was of brick construction. The roof of the flue was of arched brick construction; there are still distinct signs of the arched brickwork in the old bluestone wall. Baffles were built across the flue to induce eddies in the gases passing through it so as to deposit dust on the floor of the duct to help reduce stack emission. Those deposits could be periodically cleaned out. Adjacent to the stack (W) underground drains can now be seen that drained moisture from the flue. The bluestone that formed the south western wall of the above flue has been corroded by the acid fumes passing through the duct, that corrosion is still clearly visible today.

The various raw materials required for the blast furnace based smelting plant were held on the 15,000 ton bedding and blending floor (R). The coke, used as fuel in the blast furnace and the ironstone and limestone, which were used as fluxes in the smelting process, were stored in their individual areas or bins on the bedding floor. The ores were segregated into lead bearing or copper bearing sections of the floor. As the low sulphur ores come in they were dumped on to their appropriate areas, similarly as the roasted ores were fed to the bedding floor they were dumped on to their appropriate area. From the bedding floor the raw materials were wheeled to weighbridges adjacent to each furnace and then tipped into the top of the furnace through charging doors. Recipes were produced for each ore type to be smelted and the men charging the furnace were to rigidly strictly stick to that charging pattern to ensure that the blast furnace operated smoothly.

As in an iron producing blast furnace, coke was used as a fuel to achieve the required operating temperature and to produce a reducing atmosphere within the furnace. The ironstone and limestone acted as fluxes, to remove most of the silica and other impurities in the ore; these come away in the slag formed inside the furnace. The blast needed to burn the coke was produced by positive displacement blowers driven by a 250 hp steam engine identical to that used at the above crushing, screening and roasting plant.

Two 120 ton per day lead producing blast furnaces and one 60 ton per day copper producing blast furnace were housed in a common building (AD). A common overhead steel duct high up in the blast furnace building took the waste gases leaving the blast furnaces to just outside the building. The duct then dropped down into an on ground level brick flue (AE) that travelled in a horseshoe arc up to the base of the blast furnace brick stack (L) on the uppermost terrace level. Baffles were placed in the flue to create eddies in the waste gases, causing the dust to fall to the floor of the flue. This dust, which contained significant concentrations of silver and gold, was regularly cleared out for further processing of the dust to recover those valuable metals

Slag was tapped from the blast furnaces at regular intervals. Early reports describing the plant during its construction mention that the slag was to be run out into the launder taking cooling water away from blast furnace jackets. If this were the case granulated slag, which looks like sand would be formed; the launder was to run underground away from the furnace. The reports also mentioned that hand wheeled slag pots were also provided to allow liquid slag to be wheeled away, if needed, and dumped over the edge of the bank. Examination of the site would indicate that most of the slag was dumped in liquid form over the edge of the bank (AF). Any evidence of granulated slag having been dumped would have long since gone due to flooding or blown away by wind. At the south eastern comer of the slag dump (AN) some steel remains from the wrecking of the blast furnaces can still be seen.

Photographs show that lead was tapped from the blast furnace into moulds set on a rail-mounted trolley. The lead leaving the moulds was in a short bar form and was referred to as lead bullion. This lead bullion required further treatment before it could be sold. The copper blast furnace only produced matt copper that required further electrolytic refining to produce high-grade copper. This refining was carried out off site.

The salt water required for condenser and blast furnace jacket cooling was conveyed to near the blast furnace site along a man made channel (AG) from Mullet Creek (AH). At the western end of the channel was a pump house (AI) that housed the cooling water pumps and the condensing plant for the 250 hp engine that drove the blast furnace blowers and the cooling water pumps. This engine was identical to the engine used in the crushing, screening and roasting plant mentioned above. This 250 hp engine was housed in a building (AJ); the concrete foundations for that engine still stand today. The blowing engines were housed in a separate building (AK); the blowers and pumps were rope driven by the engine.

The lead bullion was taken from the blast furnace area to the lead refinery (AL) where the valuable metals of silver and gold were removed and the lead further purified. The pure lead produced was cast into moulds, when cooled, the lead is removed from the moulds and sold. The silver and gold were separated from the lead bullion in the refinery and underwent further complex treatment to separate them into pure silver, pure gold and a small amount of a silver/gold alloy called dore bullion. The dore bullion was sent overseas for final separation. The operations in the refinery were most complex and will not be discussed here.

The attached 1988 aerial photograph was of tremendous help when initially researching the site, it clearly showed things, such as the pyrites burners, which could not be seen when I walked over the ground in that same year. Remedial work was carried out on the site, south east of Forest Grove, in the late 1990s I early 2000s to remove any traces of heavy metals for environmental reason. This work has disfigured the site tremendously making further research very difficult.

D.K. Reynolds
RevO
3 April 2004