Powering a sustainable mining future
Application of sustainability principles as a global trend also to mining is challenging for the nature and the type of business itself. However, a sustainable development defined as meeting present needs without compromising needs of future generations is increasingly incorporated into mine operation by environmental policy based on clear goals and roadmap supported by a forward-thinking management able to change paradigm and consider sustainability a key element of successful business.
The challenge for Optimisation Technology Performances (OTP) is one of the most complex: It is about developing technological solutions within an acceptable timeframe that make these achievable without negatively impacting the client's business.
OTP optimise technical performances: division
OTP optimise performance is a specialised division of CTP Team company set up to support mine companies and other industries in identifying the areas for improvement and optimisation of their industrial process regarding emissions and plant digitisation. The distinctive element is the method, custom and targeted with the goal of bringing systems to those desired performance goals.
Dedusting solutions are commonly focused on the filters/equipment only, but often problems start far away. High dust level, filter and ducting clogging have many causes, and fabric filters may be only marginally involved, that’s why it is necessary a full assessment of the system.
Full dust collector project
Recently OTP division has finalised the assessment and optimisation of 15 lines for a primary mine company's process plant. The client highlights the issues below:
Clogging and high slip of dust all along the process
Difficulty to stay below the limits imposed by local authorities
Risk for health and safety of personnel working on the process
The main complaint is the high quantity of dust in the working area and exposition of personnel to dust slipped and released in the air. Moreover, the environment impact, the dust slipped and released in the atmosphere has high impact on emissions level. In addition, no 2 processing lines present higher criticality compared to the others without a clear reason.
The targeted results are:
Eliminate the clogging of dust on the process
Improve the dedusting action and get an APC (Air Pollution Control) system efficient and adequate
Monitor all filter’s parameters and dust collector smooth operation in order to prevent future malfunctioning
First step is the site survey by OTP technical support, to deep assess the existing dedusting system and process. The site survey mapped the suctions points and highlighted that the dust could not be removed by the existing equipment. Based on the characteristics of the dust, the requirements of the served machines as well as the layouts aspects, OTP proposed a project consisting of the rerouting of ducts and full review of the engineering design of APC (Air Pollution Control) system.
The main problem for all the assessed lines was strictly related to the upstream equipment, only 8 lines showed the need to add additional dedusting unit. This means that in 50 % of the cases the dust problem is solved thanks to a deep engineering restudy: new geometry of the suction points and ducts rerouting. Feasible thanks to a gap analysis and Computational Fluid Dynamics (CFD) simulation.
New duct routing and geometry of hood improve suction capability. Fig. 2 shows the 3D drawing of existing ducts, as well as a picture and a CFD simulation of gases passing thought the ducts.
All the hoods changed geometry. Fig. 3 shows the 3d model of the new routing and new geometry of the suction hoods. Total air flow remain the same, but capturing speed is now reviewed. The larger design for hood and optimisation of all the devices and components of the system allows to relax the capturing speed keeping unchanged the total air flow. The CFD simulation of the optimized solution allows to verify the feasibility of the new geometry and technical calculations.
Focus points of the solution:
Optimised the capturing speed: monitoring the maximum capturing speed, to avoid draft product
Completely review the dust collector's inlet ducts geometry ensuring the right speed for the handled dust and avoid clogging inside the ducts
Review of Start/Stop control philosophy to avoid material build-up in ducts and dust collectors
Advisory and guidelines for required improvements of upstream equipment's dust handling (e.g. proper rubber skirts and enclosures at belt installation)
Manufacturing of the steelworks and inspections are carried out internally to guarantee the validity of the technical solutions and standards quality agreed with the mine company. Fig. 4 shows the welding and steelworks of ducts and support structures, Fig. 5 presents the quality control of the stack after the painting process.
Situation on-site
OTP provides full support during the maintenance procedures. All the machines are equipped with high quality spare parts. Each system is now controlled remotely thanks to the remote monitoring service. The challenge is to keep the balance of the suction points.
As explained above, the rerouting of ducts and the study of the new geometry, supported and validated by the CFD analysis, lead the optimisation of the dedusting system. The gap from design to reality is the balancing of the suction points: This was not possible before of the optmisation as every dust collector was connected to several intake points, in some case up to 20, making almost impossible to balance the system even with the installed slide gate dampers at every intake point. After OTP activity, restoring the correct intake points for each unit and improving the inlet duct design, the system balance activity resulted quick and effective.
The project in short:
Review of ducts engineering and size of APC system
CFD study of existing equipment
New equipment and optimization of existing hoods
Supply of high-quality spare parts
Maintenance and technical service
Assistance during commissioning and start-up
Full system fine tuning
Plan of preventive maintenance
The optimisation study on each equipment provides its own contribute to the whole project, reaching the targeted results and high level of performances and reliability of the dedusting system.Additional benefits are the reduction of the OPEX linked to sharpened maintenance procedures and spare parts quality, as well as a better management of the equipment after a fine tuning of all the components. Finally, the remote monitoring services allow a drastic reduction in unplanned shutdowns and consequently peak emissions.
This approach allows to select all the possible solution to maintain a satisfactory operation of the mining plant in terms of availability with a significative improvement of the quality of the environment for workers as well as the reduction of pollutant emissions. The optimised solution is designed to meet dust emissions below 10 mg/Nm3, during in performance test the equipment registered emissions below 2 mg/Nm3 (Fig. 6).
Often happen that a common technical solution cannot always cover all the requirements, this is the criticality of all the brown fields projects. In this perspective the choice of a partner with internal know how built in many years of activity, make the difference in finding a comprehensive solution, involving also aspects related to the control and management of the whole installation. Not to exclude in some cases to see also possible application of industry 4.0 technologies.
Author:
Matteo Colombo, Business Unit Manager OTP
CTP team, Bergamo/Italia
www.ctp.mi.it
