Roasting & calcination

Roasting & calcination services

Roasting and calcination essentially revolves around the available furnaces and gas delivery mechanisms to control the atmosphere at temperature. ALS's benchscale furnaces include the following:

• Muffle furnaces. These units are small brick lined electric furnaces, which can roast 5 kg charges at temperatures up to 1250 deg C. The sample is static and held in trays inside the furnace. Any rabbling of the furnace is by hand.
• Batch rotary (electric) kilns, including the Midrex. These units are capable of roasting up to 5 kg batches at temperatures of up to 1,100 °C at a variety of gas atmospheres.
• Continuous Across International dual zone rotary kiln, which can achieve temperatures up to 1400 deg C at a feed rate of 1 kg per hour, also within a variety of gas atmospheres to suit the required conditions.
• Batch fluid bed roaster. Housed in a ceramic brick electric furnace, the conical roaster tube can treat progressively fed charges up to 5 kg under fluidised gas conditions.
• Pilot scale fluid bed roasters. ALS Metallurgy’s pilot-scale Dorr Oliver fluid-bed roaster consists of a stainless-steel roaster tube housed in a brick lined chimney, together with a cyclone separator, particulate filter, and an off-gas scrubber assembly. Feed rate is a function of air flow, operating temperature and fluidising velocity (space rate). Air flow is dependent on reaction stoichiometry and any excess required to drive the desired result.

Common roasting and calcining applications are:

• Oxidation of sulphide minerals, such as pyrite and chalcopyrite prior to downstream cyanidation.
• Acid baking of REE and lithium concentrates to decompose the valuable minerals and convert the metals into water soluble salts. Typical conditions are 200°C to 400°C and 500-2000 kg sulphuric acid / t concentrate.
• Salt roasting of vanadium concentrates to convert the value metals into water soluble salts. Typical conditions are 1000°C to 1250°C and 20-200 kg soda ash / t concentrate.
• Calcining of purified salts to generate high purity products such as high purity alumina by converting the salts into metal oxides. Temperatures can vary from 600°C to 1200°C.

Note that ALS has strong alliances with local furnace manufacturers and can have bespoke furnaces fabricated to suit a specific roasting application.

Also, in cases where international kiln vendors have been engaged, ALS will happily organise the dispatch of testwork products (i.e. roast/calcination feed) to external vendors and receive calcine product back for further testing.

Don't see what you need or are unsure about some of the services and associated requirements?

Hydrometallurgical testwork is always complex, and so we are happy to help walk you through the process, or meet your requirements exactly.

Please contact us for further details.

Associated testwork services

Roasting and calcination never happens in isolation and typically many other processes are inter-related, such as leaching, CCD, filtration, recycles, impurity removal, purification etc.

Click on the above links or contact us for further information. We can integrate a full program for you if required.