Manganese

Cato Ridge Works Furnace Building

Cato Ridge Works

In order to beneficiate the manganese ore from their mines in the Northern Cape, Assmang established Cato Ridge Works (formerly Feralloys Limited) in 1956 and construction was started on a ferromanganese smelter at Cato Ridge approximately 60km from Durban in KwaZulu-Natal. The first alloy from this plant was exported in 1959.

In 1997, Assmang formed a joint venture company, Cato Ridge Alloys, on its Cato Ridge site to produce medium and low carbon ferro-manganese alloys.

A metal from slag recovery plant with a capacity of 16000mt per annum of saleable product was commissioned in 2005 and improvements are ongoing.

Ferro-manganese production

The ferro-manganese smelter at Cato Ridge was commissioned in 1959 and originally consisted of two 9MVA submerged arc electric furnaces.

The smelter has been expanded over the years, culminating in the upgrade and re-engineering of each of furnaces 1 and 2 to state-of-the-art 22MVA units. These furnaces can produce either HCFeMn or SiMn but are currently operating on HCFeMn.

The furnace inventory is as follows:

	No. 1	No. 2	No. 3	No. 4	No. 5	No. 6
Manufacturer	Pyromet	Pyromet	Elkem	Elkem	Tagliaferri	Tanabe
Transformer rating	22 MVA	22 MVA	12 MVA	12 MVA	24 MVA	24 MVA
Shell diameter	9.72 m	9.72m	8.62m	8.62m	10.30m	11.50m
Shell depth	4.725m	4.725m	5.340m	5.340m	5.032m	6.341m
Hearth diameter	8.092m	8.092m	6.350m	6.350m	8.300m	9.000m
Hearth depth	3.285m	3.285m	3.083m	3.083m	3.532m	4.172m
Electrode diameter	1200mm	1200mm	1143mm	1143mm	1400mm	1400mm
Date commissioned	1997	1997	1964	1964	1977	1990
	Semi-	Semi-
Hood geometry			Closed	Closed	Open	Closed
	closed	closed

The furnace raw materials are delivered by rail and off-loaded using wagon tipplers and transported to the raw material bays by conveyor belts. Manganese ore is railed from the Nchwaning and Gloria mines in the Northern Cape. In addition, sintered manganese ore is obtained from the same area and used in the smelting process.

Reductants in the form of metallurgical coke and anthracite peas are procured locally and internationally and in conjunction with the Soderberg continuously baking electrodes form the source of carbon units required for the smelting reaction. The raw materials supplied are monitored closely for phosphorous, which allows the Cato Ridge Works to maintain its status as a low phosphorous alloy producer.

All furnaces are controlled by PLC based supervisory systems, which optimise the power input into the furnace and enhance the operation.

The manganese ore is reduced to an iron/manganese alloy inside the furnace on a continuous basis. The slag (which is fluxed with either limestone or quartzite) and metal are tapped from the furnace on a periodic basis.

The molten metal and slag separate as a result of density differences. The less dense slag is removed and the molten metal is cast into ingot trays. The metal is then cooled, crushed and sized to meet customer requirements. Slag is disposed of in such a way that it can later be recovered and re-used or rehabilitated.

Raw materials table

Ores
				Typica
	Mn%	Fe%	Ratio	of feed
Gloria	39.0	4.5	8.6	20
Nchwaning	48.5	7.9	6.1	55
Sinter	45.5	6.2	7.5	25

Reductants
		FC%	ASH%	VM%
		82.0	14.5	2.0
Coke
		85.0	13.0	2.0
Anthracite		79	13.4	7.6

HCFeMn specifications

Lumpy ferro-manganese metal is produced to two prime product specifications, typically:

Manganese	+78.0%	76.0-78.0%
Iron	14.0%	15.0%
Silicon	<1.0%	<1.0%
Phosphorous	<0.10%	<0.10%
Carbon	6.7-7.2%	6.7-7.2%

The fines generated (-6+3mm and -3mm products) are sold to different Manganese specifications due to the nature of the products. The metal is sized to the customer's specification in the crushing and screening plant.

Typical standard sizes for high carbon ferro-manganese are:

-100+25mm
-75+25mm
-50+20mm
-50+12mm
-35+12mm
-20+12mm
-12+6mm
-6+3mm
-3mm

Other sizes or chemical specifications of products can, however, be produced to order. Ferro-manganese metal is usually loaded onto trains in bulk and is then railed to the dedicated manganese alloy storage area at Richards Bay port whence it is loaded into the vessel’s hold. The facility also exists to containerize ferro-manganese, either in bulk or in one metric ton bags for export through Durban's container terminal.

Safety, health, environment and quality

Environment

HcFemn Stockpile with Works in the background

Cato Ridge sits at the head of one of the valleys leading into the picturesque Valley of 1000 Hills in KwaZulu-Natal. The plant lies midway between Pietermaritzburg and Durban. It is situated adjacent to the routes of the annual Comrades Marathon and Duzi Canoe race and as such has high public exposure.

All furnaces are fitted with off-gas scrubbing/filtration equipment, which minimises the exposure of airborne pollution to the environment. In addition, taphole extraction systems reduce the environmental impact of the metal/slag tapping operation.

The plant is situated at the top of an escarpment on a tillite and sandstone geological formation. Owing to the impervious nature of this structure all water leaving the site, as well as waterways outside the Works' boundaries, is monitored regularly for manganese and other contaminants.

The optimal use of all waste products is continually being investigated to further minimise the impact on the environment.

Cato Ridge Works is committed to environmental sustainability and minimum environmental impact and is ISO 14001 certified

In addition, Assmang has made significant capital investment in further improving its environmental performance, such as standby gas cleaning equipment, concreting of roads and grassing of areas around the plant. Further investments in dust extraction are planned.

Quality

Cato Ridge Works obtained its ISO 9002 Quality listing in 1992.

Quality and repeatability of the product received by the customer is guaranteed by the internal management system.

The concept of 'quality of service to the internal customer' is firmly entrenched within all areas of the operation. This ensures that the external customer receives the required product on time every time. Quality training for all personnel begins with their induction into the manganese division.

In order to ensure that our customers are satisfied, all incoming raw materials are ordered and checked against strict quality specification on arrival. Daily sampling and chemical analysis of all raw materials allows metallurgical control of the 'recipe' of the mix fed to the individual furnaces. All slag and metal tapped from each furnace is sampled and analysed and the internal tracking system allows metal of different manganese grades and sizes to be sorted and stored separately.

Before being dispatched, all orders are checked chemically and physically and certified analysis is provided.

Health

The Works is committed to all its stakeholders, including employees, the local community, suppliers, customers and financial shareholders.

The company's commitment to its employees is displayed in its active health and safety programme, which is based on the OHSAS 18001 series. The Works plans to be certified in terms of this system by December 2006. An on-site primary healthcare clinic caters for the health needs of all employees and contractors.

Social responsibility

Cato Ridge Works also sponsors community projects such as school building and tribal land development in the areas adjacent to the plant site, where many of its employees live. The company provides housing support to employees and administers the Cato Ridge Country Club. This facility is open to all local residents and membership is wide and varied.

The Works' commitment to its customers is demonstrated in its ISO 9002 Quality Control Programme. Direct interaction with customers or agents is carried out by the Ore and Metal Company Limited, a subsidiary of Assore Limited, the sole sales and shipping agents of all Assmang's products.