ACARP ACARP ACARP ACARP
Technical Market Support

Effect of Coke Reactivity upon Coke Strength with Focus on Microstructure

Technical Market Support » Metallurgical Coal

Published: March 17Project Number: C24053

Get ReportAuthor: David Jenkins, Sherry Mayo, Merrick Mahoney, Alex Deev, Jason Donnelly, Rowan Davidson and Richard Sakurovs | CSIRO, University of Newcastle

The primary aim of this project was to examine changes in the microstructure of metallurgical coke during high-temperature reaction with CO2.  Additionally, the project aimed to relate the changes in microstructure to the quality of coke, in terms of its reactivity and strength.  In order for the work to be relevant to industry, the reaction process mimicked, as closely as possible, the standard CSR test.  CSR-sized samples of five cokes prepared from single coals coked in a pilot coke oven were obtained. The coals were selected to cover a range of measures: rank, vitrinite and CSR. CT scanning at the Australian Synchrotron was used to produce three dimensional images of microstructure of three unreacted lumps from each of the cokes at a pixel size of 8.9 micron. The same lumps were then imaged using CT after 30, 60, 90 and 120 min reaction with carbon dioxide under simulated CSR test conditions and the images were then compared. In this way the evolution of the coke structure during reaction with CO2 at 1100oC could be followed. After 120 min reaction a selection of samples was tumbled in an I-drum and the remaining core of each sample was imaged to identify where the structure failed.

 

After reaction, some cokes showed gradients in density near the particle surface, which is attributed to gas transport (pore diffusion) being significant in controlling the reaction rate. There were some cokes where gas transport did not appear to be the limiting process; these cokes appeared to react more uniformly. With the small number of cokes so far tested it was not possible to link this behaviour back to coal properties.

 

A method was developed for analysing the stress distribution in particles put under load, by comparing the density of high stress points (which we call the critical stress index, CSI) in the outer shell of the coke lumps compared with the bulk. Once again different cokes showed different developments of relative CSI between the shell and the interior, suggesting that that for some cokes the loss in strength was restricted to surface regions whereas for others it wasn't. Cokes that exhibit significant gradients in coke density near the surface (due to reaction) show increased CSI at the surface and hence are expected to be more susceptible to surface damage during the tumbling process, which would decrease the CSR value for that coke. Thus, our study seems to indicate that the cokes with the best CSR have a balance between reactivity and internal pore diffusion.  

 

It is clear from the images that inerts play an important role in the reactivity.  However, the response of the inert-derived material to CO2 attack varied quite markedly. Some inerts completely disappeared due to reaction, while others only partially reacted.  Some inerts reacted from the outside in (presumably due to low internal porosity), while others reacted throughout the inert.

 

A similar series of experiments were performed at 900oC to see if differences due to different rate limiting processes could be detected in the images. Unfortunately the weight loss was so low (1-8%) that it was difficult to detect changes in individual lumps within the time available.

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27052Site Trial And Demonstration Of Integrated Forward And Reverse Osmosis For Mine Water Reuse

The forward osmosis (FO) process, also known as direct osmosis, is a...

C28022Development Of A Simple Rotary Steerable System For Underground Inseam Drilling

The purpose of this project was to complete the design and testing o...

C21002Measurement And Reporting Of Fugitive Emissions From Underground Coal Mines

The National Greenhouse and Energy Reporting Act 2007 (Act), the ...

Underground

Open Cut

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

Recently Completed Projects

C28034Mining Equipment Human Factors Design For Workforce Diversity

The objectives of the project were to:

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27025Quantifying The Step-Change Benefit Of Reflux Flotation Cell Circuits

The objective of this project was to quantify the value proposition ...

C24047Characterisation Of Pressure (Hyperbaric) Filter Performance

Hyperbaric disc filter technology has been used to dewater fine coal...

C28058Phase Two Development Of A Low Cost Online Measurement Of Particle Size And Density For Diagnostics Across The Fine Coal Circuit (Particle Profiler)

This project is based around the development of a prototype system (...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26039Nanoporosity In Cokes: Their Origin, Control And Influence On CO2 Reactivity

This project using the outcomes of previous project C24060, examine...

C28063A Comprehensive Technical Review Of High-Efficiency Low-Emission (HELE) Pulverised Coal Combustion Technologies For Power Generation

Research and development has been undertaken worldwide to realise co...

C28064Carbon Structure Transformation During Coking Of Australian Coking Coals: Better Understanding The Coke Formation

Carbon structures of coke that are formed during the plastic layer a...

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) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

C26004CFD Modelling Of Reverse Thermal Oxidisers For VAM Abatement - CFD Modelling Of Fixed-Bed RTO Devices

The project is part of a larger multi‐phase program of study a...

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

Underground coal mining emits high volumes of methane, diluted in ve...

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