Introduction.
Stable preparation of iron ore raw materials is one of the key factors ensuring efficient operation of sintering and blast furnace production. Disruptions in the particle size distribution of the ore blend, reduced crushing equipment performance and increasing operating costs directly affect not only sinter quality, but also fuel consumption, the plant’s energy efficiency and stability of metallurgical processes.
As part of reconstruction of the crushing and sizing plant at Qarmet JSC, M HEAVY TECHNOLOGY in cooperation with Temir-Stroy LLP implemented a project for equipment replacement at Ore Crushing Units No. 1 and No. 2 receiving stations (Complexes No. 600 and No. 700) of the blending and crushing zone.
The project aim was increasing the complex’s productivity, stabilization of the granularity of the ore blend and reducing operating costs in sinter production.
Crushing and Sizing Plant (CSP): Purpose and Operating Principle.
The Crushing and Sizing Plant (CSP) is a critical element in the process chain of iron ore raw material preparation. The main objective of the complex is to ensure required material size for the subsequent sintering process.
The technological process flow for ore blend preparation includes:
- acceptance and unloading of iron ore raw materials into open stockpiles;
- transportation of material by belt conveyors;
- passage through transfer points;
- screening operations;
- primary and secondary crushing stages;
- classification of material by particle size.
At the existing complex ore crushing was carried out using the following cone crushers:
- KMDT -2200;
- KMD -2200;
- HP-400.
The production sector includes three buildings:
- primary crushing building;
- secondary crushing building;
- ore screening building.
Brief Process Description.
At the specified plant iron ore from the ore concentrate bunker is supplied by conveyor systems and accumulated in a receiving hopper with a capacity of V = 150 m³ of the primary crushing complex.
From the receiving hopper the ore is fed for screening at an 8 mm size classification. The coarse fraction (> 8 mm) is sent for crushing to a cone crusher. The fine fraction (< 8 mm) is combined with the crushed ore and then transferred to the secondary crushing building.
The process flow diagram provides for several screening stages using screens with mesh sizes of 10×10 mm at the primary crushing stage, 8×8 mm at the secondary crushing stage and 8×8 mm in the ore screening building, that makes it possible to obtain an ore blend with a particle size of up to 8 mm.
Explore engineering solutions for industrial equipment upgrading and process optimization.
Why the particle size distribution of sinter is critically important.
The quality of ore blend preparation directly determines the efficiency of the sintering process and the subsequent operation of blast furnaces.
An increased content of coarse fractions leads to:
- deterioration of the sinter mix gas permeability;
- increased consumption of solid fuel;
- increased FeO and sulfur content in the sinter;
- reduced strength and metallurgical properties of the finished product;
- instability of the sintering process
In the project under consideration exceeding the allowable content of coarse fractions increased solid fuel consumption by 3 kg per ton of sinter.
Main problems of the existing crushing complex.
▪️ Insufficient capacity.
The existing capacity of less than 350 t/h (8 400 t/day) did not provide the required volume of prepared ore blend for stable production of bunker sinter.
▪️ Unstable particle size distribution.
The increased content of particles larger than 8 mm reduced sinter quality and increased fuel consumption.
▪️ Equipment wear and shortage of spare parts.
The operation of obsolete KMD-2200 crushers was accompanied by spare parts supply problems. Manufacturing time for certain components exceeded 180 days, creating risks of prolonged production downtime.
▪️ Increased operating costs.
The existing equipment was characterized by:
- high power consumption;
- increased maintenance costs;
- higher repair expenses;
- reduced energy efficiency.
Technical solutions of the project.
As part of the project, M HEAVY TECHNOLOGY carried out detailed engineering and developed working documentation for replacement of equipment in the first and second stages of ore crushing.
Dismantling of the existing equipment.
The project provided for dismantling of the existing equipment, including concrete grouting under the KMD-2200 crusher and reconstruction of working platforms for:
- the KMD-2200 cone crusher;
- the crusher oil station;
- loading chutes;
- the screen enclosure;
- the vibrating screen;
- the belt feeder;
- supporting steel structures;
- loading units.
Installation of new equipment.
As part of the modernization, the following installations were provided:
- a new vibrating feeder under the ore hopper;
- a modern cone crusher;
- a new screen;
- a system of new ore chutes;
- steel structures and maintenance platforms.
The project also included installation of attachments for the new equipment to the existing steel structures, performing concrete works and installation of the main and auxiliary equipment.
Fig. Installation of a cone crusher.
Results and expected effects of the modernization.
Upgrading the process equipment improved reliability of the complex, enhanced stability of the technological process and reduced operational risks.
The project implementation ensures:
- the required volume of prepared ore blend;
- a stable particle size distribution of the sinter mix;
- reduced solid fuel consumption;
- lower energy consumption;
- reduced operating costs;
- improved equipment reliability;
- reduced failures and downtime.
In addition, modernization creates a foundation for further improvement of the efficiency of the sintering and blast furnace operations.
Conclusion.
Modern metallurgical enterprises are placing increasingly higher demands on the quality of iron ore raw material preparation. The crushing and screening complex efficiency directly affects sinter quality, energy consumption and stability of the entire production chain.
The ore crushing unit modernization project implemented by M HEAVY TECHNOLOGY specialists together with TEMIR-STROY LLP for Qarmet JSC is an example of a comprehensive engineering approach to improving productivity and energy efficiency of metallurgical production.
Replacement of process equipment, optimization of crushing processes and stabilization of the particle size distribution of the ore blend make it possible to improve sinter quality and significantly reduce the enterprise’s operating costs in the long term.
