Home Insights Blog Mining and metals blog Continuing process improvements by further optimization of the process advisor at kalgoorlie nickel smelter in kalgoorlie australia
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Apr 17, 2018

Continuing process improvements by further optimization of the process advisor at kalgoorlie nickel smelter in Kalgoorlie, Australia

A new integrated online process control model, Outotec® Process Advisor, started up in the Nickel smelter in Kalgoorlie, Australia back in 2014. Currently fully automated control (Laboratory – Process Advisor – PCS) is in use 98 % of the time for six main setpoints of the process (oxygen coefficient, oxygen enrichment, preheating temperature, fuel oil, silica flux and lime flux). In order to ensure a continuous support for the Customer a service agreement has been signed between Outotec and Kalgoorlie Nickel Smelter.
Process Advisor functional layout
Figure 1. Process Advisor functional layout

The software contains tables for feed mixture, matte/blister/metal and slag assays and melt temperatures. These can be directly linked to receive the values through an OPC link or they can also be manually entered in the Process Advisor. The Process Advisor can be installed as an operator advisor tool or as a fully closed loop system.

Process improvements

The Process Advisor is based on first principle models, meaning that thermodynamics and physics are modelled as accurately as possible. This means that even weak correlations found from further data analysis can in many cases be interpreted as physical model paramaters and thus it is easy to tune without the risk that the change causes any upsets in other part of the model. This is in contrast to pure statistical models, which are based on earlier correlations which do not necessarily describe the actual physical situation in an obvious way, i.e. the correlations are more difficult to interpret and incorporate. Additionally statistical models are very sensitive to changed conditions, which take the model outside of the initial data set. Part of the service agreement for the Process Advisor is to keep track of any correlation, which can be interpreted as physically relevant, and tune the Process Advisor model accordingly (case 1).

Case 1: Optimizing MgO mineralogy

A change in concentrate mineralogy was experienced in 2016 and a correlation was found showing that the MgO% in the feed material influenced the heat balance of the furnace more than the model accounted for. This was physically interpreted so that the mineralogy of MgO was more complex than assumed in the model. The new mineralogy was updated to the model and the correlation disappeared, which meant that the feedforward input to the online heat balance improved and the heat balance control works now stably regardless of the feed material’s MgO content. The following pictures show the correlations before and after the tuning.

Situation before and after tuning of feed mineralogy
Figure 2. Situation before and after tuning of feed mineralogy.

As a result of the change the matte temperature standard deviation compared to average improved from 3.5 % to 1.3 % and the matte temperature has not exceeded 1200° C after the mineralogy change. This assists in achieving the target furnace hearth lifetime as superheated matte tends to infiltrate the hearth brick layer.

Case 2: Changing fluxing principle to a slag based approach

Historically slag fluxing in Kalgoorlie has been based on concentrate analysis. In 2017 the decision was made to move to a slag based flux control with a flux target equation in the form:

Target Slag Fe:SiO2=f(Slag Fe:MgO)

The results after the change showed an improvement in the correlation R2 value for the realised function Slag Fe:SiO2=f(Slag Fe:MgO) from an earlier value of 0.24 to a value of 0.67. Additionally the slag Fe3O4% standard deviation vs. average Fe3O4% dropped from an earlier value of 29% to a value of 22%. This improves furnace buildup stability and in the longer run the furnace lifetime is extended.

Outotec would like to thank all the people involved in the Kalgoorlie Nickel smelter for great co-operation throughout the project and service phase.

Read more about Outotec Process Advisor and Support service for Process Advisor .

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