The development dynamic models for a dense medium separation circuit in coal in beneficiation

Dense medium separation (DMS) plants are typically used to beneficiate run-of-mine (ROM) coal in coal metallurgy. These plants normally make use of a dense medium cyclone as the primary processing unit. Because of the deviations in the ROM quality, the production yield and quality become difficult to maintain. A control system could benefit such operations to maintain and increase product throughput and quality. There are many different methods for developing a control system in a metallurgical operation; however, what is most fundamental is the use of a mathematical model to design a controller. For this reason, a first principle dynamic mathematical model has been developed for a DMS circuit. Each unit operation is modelled individually, then integrated together to form the complete system. The developed DMS circuit dynamic model is then used to simulate the process. It is also found that most models developed for DMS operations typically make use of steady-sate analysis and that very little literature is available on dynamic models of this kind. Difficulties that arise when validating a model in metallurgical processes are insufficient measurement points or the challenges in measuring certain variables, such as physical properties (e.g. particle size) or chemical components (e.g. ash percentage). This paper also explains how the Runge-Kutta approximation can be used in simulating DMS unit processes with intermediate online measurements that may be available. This can ultimately assist in verifying the accuracy of the simulation. One of the other problems that can occur when developing models from first principles is the estimation of model parameters. Specifically when non-linear state-space relationships are developed, one must ensure that there is a unique solution for the parameters in question. A method employing parameter identifiability is also presented in this dissertation to illustrate its use. In addition the process of estimating parameters is explained and illustrated. CopyrightDissertation (MEng)--University of Pretoria, 2010.Electrical, Electronic and Computer Engineeringunrestricte

Coal dense medium separation dynamic and steady-state modelling for process control

Coal dense medium separation is a popular beneficiation process used for the upgrading of coal ore into power station and metallurgical coal. The control systems used in coal beneficiation are often limited to localised regulatory control of feed rate and medium density. A coal dense medium separation process can benefit substantially from process control provided that a dynamic model for this process is available as was previously developed by the authors for a fine coal dense medium cyclone (DMC) circuit. In this paper, the previous model is adapted to a coarse coal DMC circuit and validated over a wider range of operating conditions using real plant data. The model is further validated by reducing it to steady-state to form a partition curve. This curve is then compared to one derived from actual production data. The derived model is able to provide an estimate of the DMC overflow coal product that should be sufficient for process control.http://www.elsevier.com/locate/minenghb201

Dynamic model for a dense medium drum separator in coal beneficiation

Dense medium drum (DMD) separators are unit processes that are typically used to beneficiate coal, iron ore and other minerals by making use of density separation. Some coal dense medium separation plants typically include a DMD separator. The operational management of this unit process is often limited to localised control of medium density and feed mass flow rate. Dynamic models for coal dense medium separation have been developed by the authors with the intention of using them for dynamic control. A suitable dynamic model for a DMD separator could not been found in the available literature. This paper shows how the dynamic model for a dense medium cyclone has been applied to a DMD separator. The model parameters were determined and the performance of the model is evaluated using actual plant data from a Wemco drum. Coal washability and drum partitioning behaviour are used to estimate the grade of the product for model grade simulation and validation.http://www.elsevier.com/locate/minenghb201

Modelling and control of coal processing plants

Models are developed and verified with industrial data. These models are then controlled using nonlinear model predictive control (NMPC). It was found that there are very few available dynamic models for coal processes, other than the separation unit models developed by the author and study leader. Additional dynamic models for a coal comminution circuit were also developed. The mathematical details of the models developed for a coal plant are presented in this thesis. Model system identification was used to solve for unknown model parameters, to fit the dynamic models to actual industrial production data. The specific coal unit process dynamic models developed and used in this thesis are: • Vibratory feeders; • Single- and double-deck screens; • Bin with three compartments; • A dense medium drum; and • A dense medium cyclone. Applying NMPC to the dynamic models allowed for simulated improvements to be made to the comminution and separation circuits used in this research. It was shown that the throughput on a comminution circuit could be increased by 3.6% resulting in a downstream separator yield improvement of 3.2%. By applying NMPC to the separation circuit, it was shown that separation yield can be improved by 6.9% with a decrease in product ash (improvement in grade) for a drum separator by 1.5% and cyclone separator by 0.4%. The unscented Kalman filter (UKF) was simulated on the dynamic models developed to illustrate how an actual controller could be implemented such that the dynamic model states could be updated over time. The UKF acts as an observer such that unmeasured states can be fed back to the controller. In summary, the thesis gives a realistic account for the application of NMPC for coal processing and with the potential yield improvements of 10% (based on the 3.2% yield improvement due to the comminution circuit control and the 6.9% improvement due to the separator circuit control), could increase a South African coal company’s annual revenue by approximately R175.5 million per annum. A proposal regarding the application of NMPC for coal mine-wide optimisation is also given.Afrikaans: Modelle is ontwikkel en geverifieer aan die hand van industriële data. Hierdie modelle is dan beheer met behulp van nie-lineêre model voorspellende kontrole (NMVK). Daar is gevind dat daar baie min dinamiese modelle vir steenkoolprosesse beskikbaar is buiten die skeiding-eenheid-modelle ontwikkel deur die outeur en studieleier. Addisionele dinamiese modelle vir ’n steenkool-komminusie-aanleg is ook ontwikkel. Die wiskundige besonderhede van die modelle wat ontwikkel is vir ’n steenkool-aanleg word aangebied in hierdie tesis. Modelstelsel-identifikasie is gebruik om oplossings te gee vir onbekende modelparameters en om die dinamiese modelle te pas by die werklike industriële produksiedata. Die spesifieke eenheidsproses steenkool dinamiese modelle wat geontwikkel en gebruik word in hierdie tesis is: • Vibrerende voerders; • Enkel- en dubbel-dek skerms; • Bin met drie kompartemente; • ’N digte medium drom; and • ’N digte medium sikloon. Die toepassing van NMVK op die dinamiese modelle het toegelaat dat gesimuleerde verbeterings aangebring kon word. Daar is getoon dat die deurset op ’n komminusie-aanleg 3.6% verhoog kan word wat kan lei tot ’n stroomaf skeiding-opbrengs verbetering van 3.2%. Deur die toepassing van NMVK op die skeiding-aanleg, is daar getoon dat skeiding-opbrengs met 6.9% verbeter kan word met ’n afname in die produk-as (verbetering in graad) vir ’n drom skeier met 1.5% en sikloon-skeier met 0.4%. Die unscented Kalman filter (UKF) is nageboots op die dinamiese modelle wat ontwikkel is om te illustreer hoe ’n werklike kontroleerder sodanig geïmplementeer kan word dat die toestand van die dinamiese modelle met verloop van tyd opgedateer kan word. Die UKF dien as ’n waarnemer sodat ongemete toestande teruggevoer kan word na die kontrolleerder. Om op te som: die tesis gee ’n realistiese scenario vir die toepassing van NMVK op steenkoolverwerking. Met die potensiële groter opbrengs van 10% (gebaseer op die 3.2% groter opbrengs as gevolg van die kontrole van die komminusie-aanleg en die 6.9% groter opbrengs weens die kontrole van die skeiding-eenheid) kan ’n Suid-Afrikaanse steenkoolmaatskappy se jaarlikse inkomste met 175.5 miljoen per jaar styg. Daar word ook ’n voorstel aan die hand gedoen oor die toepassing van NMVK vir die optimalisering van die steenkoolmyn in sy geheel.Thesis (PhD)--University of Pretoria, 2016.Electrical, Electronic and Computer EngineeringPhD (Electronic Engineering)Unrestricte

The development of dynamic models for a dense medium separation circuit in coal beneficiation

Often the most difficult step in establishing a control system is the development of a suitable dynamic process model. As such a model is not available elsewhere, a first principle dynamic mathematical model was developed for a coal dense medium separation circuit. Each unit operation was modelled individually and then integrated together to form a complete non-linear state–space model for the circuit. This model was used to simulate the process and it was validated using real process data derived from a plant experiment. When developing models from first principles, it is necessary to estimate the model parameters. These parameters, specifically for non-linear state–space relationships, require a unique solution. A parameter identifiability method was used to show that the non-linear dynamic models developed have unique parameters for a specific set of input–output data

The development of dynamic models for a dense medium separation circuit in coal beneficiation

Often the most difficult step in establishing a control system is the development of a suitable dynamic process model. As such a model is not available elsewhere, a first principle dynamic mathematical model was developed for a coal dense medium separation circuit. Each unit operation was modelled individually and then integrated together to form a complete non-linear state–space model for the circuit. This model was used to simulate the process and it was validated using real process data derived from a plant experiment. When developing models from first principles, it is necessary to estimate the model parameters. These parameters, specifically for non-linear state–space relationships, require a unique solution. A parameter identifiability method was used to show that the non-linear dynamic models developed have unique parameters for a specific set of input–output data

Model predictive control simulation, implementation and performance assessment of a coal comminution circuit

This paper describes the simulation, implementation and performance assessment of model predictive control (MPC) for a coal communition circuit, and describes, as far as can be ascertained, the first implementation of MPC in the coal processing industry. Dynamic models of an actual coal comminution circuit were derived in previous publications using the principle of mass conservation with unknown parameters that were identified with actual plant production data. The identified dynamic models are used in nonlinear MPC simulations to determine the process control objectives and to calculate a potential process improvement in throughput. This increase in potential throughput was estimated to be 5% and was used as motivation in a business case to obtain funding to implement MPC on the actual plant. After performing a tender process, General Electric was contracted to implement the MPC. The MPC was implemented successfully on the comminution system and compared to current manual plant operational performance. After evaluating the MPC through a statistical performance assessment, it was found that throughput was improved by a significant 8.22%. The methodology followed is presented in this paper and the improved production throughput motivates for further MPC technologies to be implemented at other plant operations.The National Research Foundation of South Africa (IRC Grant No. 111741).http://www.elsevier.com/locate/minenghj2020Electrical, Electronic and Computer Engineerin

Gênero, sexualidade e idade: tramas heteronormativas nas práticas pedagógicas da educação física escolar

Resumo O artigo analisa a produção da (hetero)normalização do gênero e da sexualidade em articulação com a idade na trama da educação física escolar. Apresenta parte dos resultados de uma pesquisa que buscou analisar as práticas pedagógicas desenvolvidas por docentes que ministram aulas de educação física em escolas estaduais distribuídas em sete cidades dos nove municípios que compõem a região do Vale do Jiquiriçá (BA). Para acessar esses sujeitos, foi realizado um seminário de formação de professores e utilizaram-se grupo focal e entrevistas como estratégias metodológicas. Tomando como referências teórico-metodológicas e políticas os estudos feministas pós-estruturalistas, a teoriaqueer e os estudos foucaultianos, discute-se como a dimensão cronológica é tratada de forma fixa e etapista e torna-se definidora do que se pode conhecer e de como se pode conhecer na escola. A pesquisa aponta para certa conexão, por vezes contínua e, em outros momentos, descontínua, entre gênero, sexualidade e idade nas aulas de educação física da região investigada. Por um lado, docentes indicam que a sexualidade se manifesta na escola desde cedo, ainda na infância, em função de fatores regionais, e de forma exacerbada nos meninos. Por outro lado, a idade cronológica dos corpos dos estudantes funciona como uma norma regulatória quando se trata dos temas da sexualidade, o que contribui para reforçar a promoção/assunção do pressuposto sexo-gênero-prática heterossexual como natural a partir da adolescência