Technical Market Support » Metallurgical Coal
This project evaluated the combustion behaviour of the blends of Australian PCI coals under industry-scale blast furnaces (BFs) conditions using improved 3D computer modelling. The work was undertaken in two stages:
- Stage 1: Single Australian PCI coals were evaluated using a 3D PCI model.
- Stage 2: The model was further developed for evaluating the blends of Australian PCI coals by means of explicitly considering interactions between component coals in a blend, and then used to optimise blending parameters for improving overall burnout of the blends, from pilot-scale to industry-scale.
In both stages Australian PCI coals (blends) were evaluated under the industrial-scale conditions of a blast furnace.
Stage 1 Report
The stage 1 project outcomes, including a report and a customised PCI simulator, can be used as a cost-effective research tool and marketing tool for Australian coal industry to explore new markets.
PCI technology is widely operated in BFs worldwide, representing a significant amount of coal exports. Australian coals play an important role in PCI coal market. In the past, coal burnout in PCI operation in BFs was usually characterised along the tuyere centreline rather than the whole raceway due to technical difficulties. For example, drop tube furnaces (DTF) and pilot scale PCI rigs were successfully used for characterising coal combustion kinetics data, and were sometimes used for simulating coal combustion along the tuyere centreline only under lab and pilot-scale conditions. DTF tests were found to provide a generally similar ranking for coals on the basis of combustibility (burnout) against the proximate analysis volatile matter (VM) content to that from PCI pilot‐scale tests. It is important to understand the PCI coal combustion over the entire raceway, as the unburnt coal will exit from the entire raceway, rather than along the tuyere centreline only, and then enter the surrounding coke bed, reducing permeability of the coke bed and thus affecting the furnace stability. It is also significant to conduct PCI coal assessments under industry-scale conditions, as the industry-scale condition represents the real PCI operation.
A 3D integrated PCI model was improved and used to assess the in-furnace performance under industry-scale BF conditions for a range of Australian PCI coals. In particular, the effects of a range of key PCI operational variables on PCI operation were investigated under industry scale BF conditions for a range of Australian PCI coals.
The outcomes of stage 1 include:
- Detailed understanding of in-furnace phenomena of a range of Australian PCI coals at the lower part of BF under real BF conditions;
- Knowledge of effects of key operational parameters on PCI operation for Australian PCI coals under real BF conditions;
- A database of pulverised coals burnout for different Australian PCI coals under different coal and operational conditions.
Stage 2 Report
The combustion of pulverised coal blends is widely used in BFs worldwide, representing a significant amount of coal exports. Australian coals play an important role in the PCI coal market. At present, the majority of ironmaking operations inject coal blends, rather than single coals, to better control the coal quality and optimize the combustion level and overall cost of fuels. In the past, coal burnout in PCI operations in BFs was usually characterized along the tuyere centreline rather than the whole raceway due to technical difficulties. For example, drop tube furnaces (DTF), and pilot scale PCI rigs (particularly the one located at BHP Research Laboratory at Newcastle) were successfully used for characterising coal combustion kinetics data and were sometimes used for simulating coal combustion along the tuyere centreline only under lab and pilot-scale conditions. DTF tests were found to provide a generally similar ranking for coals on the basis of combustibility (burnout) against the proximate analysis volatile matter (VM) content to that from PCI pilot - scale tests. It is important to understand the PCI coal blends combustion over the entire raceway, as a coal blend is more complex than for a single coal. Each of the coal components devolatilizes and combusts at different temperatures and at different times, and their burnout could therefore vary considerably. Understanding the behaviours of individual components in a coal blend is significant for the design of coal blends to maximize the benefits for a BF operation. It is also significant to conduct PCI coal assessments under industry-scale conditions, as the industry-scale condition represents the real PCI operation. Recently, we developed a three-dimensional (3D) PCI coal blend model. It includes a 3D raceway and surrounding coke bed, and the combustion of three different fuels- pulverized coals and coke, allowing for calculating the overall performance of a blend, as well as the behaviours of its component coals over the whole raceway, in addition to along the tuyere axis. However, Australian PCI coal blends have not been examined over the entire raceway under real BF conditions.
A 3D integrated PCI model was further developed for evaluating the blends of Australian PCI coals by means of explicitly considering interactions between component coals in a blend, and then used to optimise blending parameters for improving overall burnout of the blends, from pilot- to industry-scale.