Hi there, I'm new to this site. I know that the original post is very old but you may find the following information and products of interest.
Our company has been designing and manufacturing mineral sample preparation and sampling equipment in Perth, Australia for over 25 years.
You'll find our equipment in most of the major commercial laboratories around the world.
Sample preparation for gold samples, where the distribution and size of gold particles is often irregular, usually demands that a relatively large sample weight is taken to produce a representative sample for analysis.
Traditional sample preparation of gold samples incorporated multiple stages of coarse particle size reduction followed by subdivision of the sample prior to final fine pulverising. This technique developed because of the limited equipment options available to laboratories. As a result significant errors are introduced and the final sample size being pulverised is a small fraction of the original sample weight.
Three significant developments have occurred in the last 25 years to significantly improve sample preparation of gold samples:
- large capacity fine pulverising,
- fine jaw crushing, and
- whole sample coarse pulverising.
In the mid-1980s an Australian manufacturer developed large capacity pulverising bowls which had the ability to reduce samples with a mass of 1.5 – 3.5 kg to a nominal 0.075 mm product in approximately 3 to 5 minutes. Laboratories were able to produce a large homogeneous pulverised sample which significantly reduced the error in sampling. However exploration and mine samples are usually 7 to 10 kg and the sample requires a subdivision stage following crushing to produce the 3.5 kg for the pulverising step thus introducing potential for significant error.
The development of fine jaw crushing allowed particle size reduction to minus 2 mm which reduced the subdivision error of the bulk sample prior to fine pulverising. Subdivision of the crushed sample at minus 2 mm still results in potential sampling errors where the gold particles are not sufficiently liberated to be representatively sampled. Clearly the best option would be to reduce the particle size small enough to ensure a representative sample prior to final pulverising.
Continuous mills offer a partial solution but are relatively slow and subject the sample to differential pulverising prior to subdivision. Clearly this does not provide the best solution for routine laboratory applications where high volumes of samples are to be processed.
The recent development of a large capacity coarse pulverising system allows samples of up to 10 kg to be reduced to minus 0.25 mm prior to subdivision and fine pulverised to minus 0.075 mm.
Laboratories now have the necessary equipment to perform reliable large capacity sample preparation of gold samples. The exact choice of sample preparation scheme may still depend on particular ore types but the need for multiple crushing and subdivision stages is redundant.
Please feel free to download the paper at the following site to read more about these developments (it's titled
Large Capacity Sample Preparation)
http://www.essa.com.au/EssaProductsDefault.aspx?MenuID=104 If you are interested in our products that will enable you achieve these improved sample preparation techniques then please check out:
http://www.essa.com.au/EssaProductsCatalogue.aspx?PG=SP Here you will find pulverising mills that can fine pulverise up to 3.5kg of ore to 75 micron in 5-6 minutes...
http://www.essa.com.au/EssaProductsDetail.aspx?PG=SP&E=MI&M=MI05 ...or 1.5kg of ore to 75 micron in 2-3 minutes...
http://www.essa.com.au/EssaProductsDetail.aspx?PG=SP&E=MI&M=MI02 Our JC2500 fine jaw crusher will crush 110mm lump ore to 90% less than 2mm at a rate of 180kg per hour.
http://www.essa.com.au/EssaProductsDetail.aspx?PG=SP&E=CR&M=CR25 Our new Micron Mill, a coarse pulveriser with a patented ring and spigot milling arrangement, will pulverise up to 10kg of 15mm ore to 95% less than 250 micron in size.
http://www.essa.com.au/EssaProductsDetail.aspx?PG=SP&E=MI&M=MIMM There's a really good video of the Micron Mill located here...
http://www.essa.com.au/EssaProductsDefault.aspx?MenuID=110 If you want to check out some really interesting developments in the area of sample preparation automation and robotics then look at some of the other videos on this page.
Sample crushing and grinding and other unglamorous, repetitive and often hazardous tasks are now being done by industrial robots in most of Perth’s commercial mineral laboratories.
The Perth robot revolution started about 9 years ago and now the city is arguably the world centre of commercial laboratory automation. Today 30 industrial robots are performing jobs that were previously extremely manually demanding and often in hot, dusty and noisy environments.
In fact, by the end of this year all the major commercial assay labs in Perth will be using robots to meet the demand for more flexible and reliable testing systems in the face of increased labour and production costs. Robots allow them to maximise turnover with a relatively short payback period whilst achieving higher quality results.
Even in in the current downturn exciting times lie ahead in the field of crushing and pulverising.
I hope you find this post of interest.
Regards