GEOVIA Minex can store chemical or analytical data in a set of user-defined database tables. Typical datasets include coal seam proximate analysis, such as analysis of ash, moisture, FC, VM and UHV.
A unique feature of Minex is that the seam interpretation is separate to these data tables. Minex then composites or combines samples into a seam or working section.
Minex supports several types of compositing, one of them being Seam Compositing, which we will describe in today’s post. Our next post will focus on Bench Compositing.
The seam composite is based on accumulating samples within the seam. These samples are combined using:
1. Thickness weighting
2. Thickness and density weighting
3. Thickness and density and wash plant yield weighting
The following table and image show a set of sample data with a seam R2. The data is ash, moisture, UHV and density.
To deactivate (or activate) density weighting, set the database header as shown in the following image. Here the RD weighting has been inactivated and weighting is by sample length.
In situations where coal is washed, the product quality such as product ash must be weighted by the wash plant yield.
Consider an example where a product ash has been created as 70% of the insitu ash and yield is 100 – ASH/2. The Minex SQL is shown below:
WHERE ASH # NULL
IF SELECT X
YIELD = ASH/2
YIELD = 100 – YIELD
PROD_ASH = ASH * 0.7
YIELD = NULL
PROD_ASH = NULL
When initializing the product variable, the washery yield variable is specified.
The resultant data is as follows.
Seam composites are typically applied to a lithological correlatable seam. However, in thick coal seams it may be necessary to mine the seam in benches (for example benches of 10 metres height). In these cases the seam file is set up as a set of benches such as BEN1, BEN2 etc, and compositing occurs across the bench.
We will discuss this further in our next post on Bench Compositing.