Page 78 - Advances In Productive, Safe, and Responsible Coal Mining

64 Advances in Productive, Safe, and Responsible Coal Mining

continuous miner is likely to be lower. However, such mines do not have to move pro-
duction infrastructure as often since, once set up, production in a larger panel lasts
longer. Research has shown that the relationship between panel width and production
rate is not linear and engineers have to carefully consider the effect of panel width on
the production rate [2]. The number of entries (panel width) must, therefore, be opti-
mized to maximize production rates [1].
Consequently, while engineers may be motivated to use larger panel widths to
increase coal recovery, there is a possibility that larger panels may lead to lower pro-
duction rates. This leads to a dual-objective optimization problem where the objective
is to maximize recovery and production rate. However, to model this optimization
problem, the relationship between panel width and production rate must be established
for each particular mine.
There is a push to increase production rates in R&P mines with newer technology
and improved production practices. For example, the introduction of high-voltage
continuous miners and automated haulers has increased loading rates, tram speeds,
and payloads [3, 4]. Also, researchers have proposed approaches to improve produc-
tion practices like optimizing cut sequences, haulage routes, equipment utilization,
and equipment availability and minimizing roof bolt installation, change-out delays,
and the width of main and submain panels [5–7].
Although the geometry of R&P mines would suggest that it is possible to optimize
recovery by optimizing the layout of the series of panels and barrier pillars, the authors
have not found any work in the literature that has addressed this issue. Improving coal
recovery, even slightly, can have a significant effect on project economics. For instance,
given a thermal coal price of US$41.00/ton, a 1% increase in recovery for a 10 million
ton coal resource increases revenue by US$4.1 million over the mine life. These gains
could be even higher if the objective function can also maximize production rate so that
production rate is not unduly sacrificed in the quest for higher coal recovery.
In this chapter, an approach to optimizing coal recovery and production rate as a
function of panel dimensions is presented. First, discrete-event simulation (DES) is
used to model coal cutting and hauling operations in R&P mines in order to estimate
production rates. Experiments are conducted using the model to determine the rela-
tionship between production rate and panel width. Second, a dual-objective optimiza-
tion model is formulated that maximizes coal recovery and production rate. The model
uses the relationship between panel width and coal recovery, which can be established
for different mining conditions using the same model. The model is formulated as a
cutting stock problem [8] and the optimization problem is solved using the integer
programming solver in IBM’s CPLEX, which is based on the branch-and-cut algo-
rithm. A real-life case study is presented to illustrate how the relationship between
production rate and panel width can be established using the DES model. A simple
instance of the coal recovery optimization problem, which is formulated by incorpo-
rating the relationship established with the DES model, is then solved.
Section 5.2 of this chapter presents the DES model and the case study used to illus-
trate its usefulness. Section 5.3 presents the optimization model, the proposed solution
formulation, and the case study. The final section presents conclusions and recom-
mendations for future work.