ACARP ACARP ACARP ACARP
Coal Preparation

Advanced Dynamic Control For Paste Thickeners - First Stage For Control Of Complete CHPP’s

Coal Preparation » Dewatering

Published: September 17Project Number: C21055

Get ReportAuthor: Götz Bickert, Jie Bao, Ridwan Setiawan and Chee Keong Tan | GBL Process, University of New South Wales

Paste thickeners produce significantly higher solids underflow concentrations than conventional thickeners through higher beds within the thickeners. They have been introduced into the coal preparation industry for coal tailings dewatering. Control of paste thickeners is critical because the underflow solids have to be within a required viscosity and density window to avoid problems in transportation of the coal tailings by pumps, conveyors or trucks and on the other hand to achieve the required high solids content.  Alone paste thickener underflow pumping is proved difficult with variations in thickener underflow density and viscosity resulting in the risks of pump bogging. In particular, due to the variability of paste thickener feed in terms of flow rates and coal types, existing control strategies are generally limited, resulting in large fluctuations in the underflow solids concentration.

The project was conducted to demonstrate the benefit of advanced dynamic control on paste thickeners through the development of dynamical models to describe the mechanism of paste thickening and to relate the underflow solids concentration to a number of key measurements (including bed level, feed solids concentration and feed flow) and operational variables (including underflow rate). Based on the developed dynamic process model, a control algorithm was designed for the paste thickeners.

Plant data from Xstrata's Bulga CHPP was then utilised to validate the process dynamic model. Based on the developed dynamic model, a Model Predictive Control (MPC) algorithm was proposed to control the underflow solids concentration of the paste thickener. The control algorithms were simulated based on the data from Bulga to provide predictions on the potential water saving improvements. The implementation of the MPC was based on a novel approach with three key components:

· A dynamic thickener process model validated by actual plant data;

· An extended Kalman Filter developed using the nonlinear process model to predict unknown model parameters;

· A Model Predictive Control algorithm.

The coal types used in this investigation were found to be difficult to dewater. In order to produce a good paste using these coal types, a high compressive force is required. A bed level of 9 - 10m (thickener height is 11m) is required to produce the paste with 50 wt% underflow solids concentration in all cases.

Analysis on the Bulga CHPP plant data has resulted in the following recommendations. All sensors require regular maintenance and calibration so that their measurements are usable in process monitoring and control, especially the flow meters, bed level and bed mass sensors and density gauge.

Different types of coal tailings require different flocculation dosage to achieve optimal dewatering. However, the effect of flocculation on the paste thickener operation is not measurable by any sensors. The flocculation dosage is controlled manually by the plant operators based on visual observation at the feed-well. Therefore, more investigation on the effect of flocculation dosage to the thickener operation is required if optimal flocculant usage is desired. Additionally, the underflow solids yield stress is also another important variable to control.  However, it is not the scope of this project. Additionally, yield stress measurements of the paste thickener product are unavailable. Without such measurement, it is impossible to model the effects of different operating variables to the yield stress and control the yield stress during plant operation.

This project has successfully developed an advanced control approach for the paste thickener underflow solids concentration. Based on the simulation results of the paste thickener using MPC algorithm, the potential improvements to the plant operation are as follows:

· The MPC was able to keep the underflow solids concentration close to 50 wt% more consistently in comparison to the existing plant operation (based on operational data from Bulga June, July, August and October 2012);

· Possible improvement of water savings by the MPC in the range of 6.7 - 30.3 %;

· The ability of MPC to handle physical limitations of the paste thickener (such as maximum sediment level) which translates to avoiding the operation of the paste thickener of solids overflowing.

In addition, the solids inventory inside the paste thickener is always maintained within a safe operating range, which reduces the risks of damaging the rake or stopping the paste thickener operation.

An e-newsletter has also been published for this project, highlighting its significance for the industry.

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C34019Longwall Bretby Cable Handling Monitoring With Fibre Optics

This project examined the potential of using fibre optic sensing tec...

C27049Mine Machine Radar Sensor Integration

The aim of this project was to develop an integrated radar sensor an...

C29007Innovative Coal Burst System To Investigate The Influence Of Confinement Loss And Pre-Conditioning On Coal Burst Mechanism

The challenges associated with designing and operating a safe and pr...

Underground

Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C28035Topsoil Deficits In Site Rehabilitation Accelerated Transformation Of Spoils To Functional Soils

The incorporation of commercial biological amendments (compost, worm...

C34036Tyre Handler Testing Rig Stage 2: Lifting Trials

Tyre handling is a major source of risk in surface mining operations...

C29052Autonomous Water Pressure Sensors For Spoil Dumps And Dams

The geotechnical integrity and stability of a mine spoil dump or tai...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C34060In-Situ Investigation Of Coke Structure Formation Under Stamp Charged Coking Conditions

Stamp charged cokemaking has emerged as an effective technique to im...

C34062Improving The Classification Of Microstructure Distribution In Coke CT Images Using Deep Learning And Lineal Path Calculations

This project builds on a number of earlier projects that have helped...

C29071Source Of Variability Of Reactivity Of Coke In The CSR Test

The Coke Strength after Reaction (CSR) test is used worldwide to det...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL)

This third and final stage of this project was the culmination of a ...

C29069Low-Cost Catalyst Materials For Effective VAM Catalytic Oxidation

Application of ventilation air methane (VAM) thermal oxidiser requir...

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community

NERDDC

National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook

NERDDC