Online Elemental Analysis of Sinter

Sinter is the primary feed material for making iron and steel in a blast furnace. To ensure a high-quality product, iron and steel manufacturers must start with a high-quality sinter, based on a proper selection of raw materials. Online Elemental Analyzers are used for measuring and controlling sintering process fluctuations, inhomogeneous mixtures, and other parameters that affect productivity, physical and metallurgical quality, and raw material consumption and costs. Here are our most frequently asked questions and answers about Iron Ore Sintering Process in Steel Manufacturing.

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A:  Sinter is created by mixing iron ore concentrate with several additives such as limestone and silica to control the chemistry and then igniting it at 1200°C in a continuous belt-fed furnace.

A:  The production of high-quality sinter is crucial for assuring consistent, stable furnace productivity with a low consumption of reductants. Sinter quality begins with the proper selection and mixing of the raw materials. Inhomogeneous raw mix can affect permeability and cause an increase in fuel consumption. Sintering process fluctuations, inhomogeneous mixtures, and other parameters affect productivity, physical and metallurgical quality, and raw material consumption and costs.

A:  Basicity is a calculated chemical parameter composed of the ratio of two or more elements that are known to affect the alkalinity of the material. The basicity of sinter feed material is an important parameter in the efficient operation of the sintering and iron making process.

A:  Sinter feed composition control is important because the various sinter feed materials are not perfectly characterized and their chemical make-up varies within a batch and between batches. Therefore the raw feed material chemistry changes and the additives feed rates should be adjusted to smooth out these variations in the sinter strand feed chemistry.

In a typical sintering operation the control of the sinter feed chemistry is based on composite samples of the final sinter product. In addition to errors normally associated with sampling and analytical lab errors there is a lag of many hours between receipt of composite sample assays and current sinter feed chemistry. The sinter operation may also lack sampling equipment on the sinter feed conveyor. Sinter product composite samples are typically obtained by incremental sampling. If the sampling frequency is too long, short term variability in sinter composition will be missed. Composite samples tend to smooth out and hide true process variability so are not on a short enough time scale to achieve optimum sinter feed chemistry control. Consequently process upsets and missed chemistry targets in the Sinter product will unknowingly be passed along to the blast furnace.

Through the use of real-time chemical analysis data from an online analyzer the sinter feed basicity can be controlled to provide a more consistent feed to the sinter strand.

Control is made possible by using the analysis of CaO, SiO2, as well as other elements that affect basicity within a per-determined additives control strategy. 

A:  The physical properties of materials can present bulk handling challenges requiring precise moisture measurement and careful adjustment. The amount of moisture in sinter feed affects it thermal properties in the sinter furnace.

A: The blending strategy for sinter feed additives based on the mixed product chemistry measurements should take into account the plant objectives for control of costs and any process and material handling constraints that are unique to each industrial site. Control strategies are created by in-house or contracted process control engineers in consultation with process specialists and are implemented by process control specialists through the appropriate configuration of the plant control system.

A: An online elemental analyzer can help control the sinter feed basicity and provide a more consistent feed to the sinter strand. The benefits of real-time chemical analysis data include:

  • More consistent sinter product—improves sinter quality and stabilizes feed to the blast furnace
  • Increased sinter strand and blast furnace throughput due to reduced sinter product variability
  • Decreased return fines lowers material handling costs
  • Reduced load on laboratory, allowing capacity to be used elsewhere without incurring additional costs
  • Net reduction in cost per ton of sinter production
  • Increased operational flexibility by maintaining feed KPIs closer to operational limits and strategic use of the raw mix materials.

A:  Online sinter feed analysis systems utilize prompt gamma neutron activation analysis (PGNAA) and pulsed fast thermal neutron activation (PFTNA) to determine the elemental composition of bulk raw materials. Both of these techniques – which are non-contact, non-destructive analytical techniques -- are known collectively as neutron activation analysis and function by bombarding materials with neutrons.

The neutrons interact with elements in the materials, which then emit secondary, prompt high energy gamma rays that travel through the many centimeters of material and can be measured with a large area gamma ray detector without contacting the material. Because prompt gamma rays are measure the speed of the material passing through the analyzer does not affect the measurement. Similar to X-ray fluorescence (XRF), each element emits a characteristic energy signature as it returns to a stable state.

For more in-depth information, visit the PGNAA and PFTNA Technology page.

A: Online analyzers are situated directly on the conveyor belt and penetrate the entire raw material cross-section, providing minute-by-minute, uniform measurement of the entire material stream, not just a sub-sample. The location chosen for an online elemental analyzer should be after the agglomeration drum, taking into account safe access for installation and maintenance as well as environmental protection for service personnel.

Other critical factors to be considered in placement of sinter feed analysis equipment include:

  • Belt width and troughing angle
  • Maximum and minimum feed rates
  • Belt speed
  • Range of belt loading
  • Maximum burden height of material
  • Location of existing sampling infrastructure
  • Iron ore mineralogy
  • Intended process control strategy

 

Read more about products used in the sintering process and iron and steel manufacturing on our Iron Ore Sintering Process in Steel Manufacturing web page.

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