Plant-Wide Control Framework for a Grinding Mill Circuit

Hybrid non-linear model predictive control of a run-of-mine ore grinding mill circuit

It is observed that the separated design of location for depots and routing for servicing customers often reach a suboptimal solution. So, solving location and routing problem simultaneously could achieve better results. In this paper, waste collection problem is considered with regard to economic and societal objective functions. A non-dominated sorting genetic algorithm (NSGA-II) is used to locate depots and treatment facilities and design the routes starting from depots to serve customers. A new mathematical model is proposed and two objective functions including economic objective (opening cost of depots and treatment facility and transportation cost) and societal objective; that is, negative impact of treatment facilities which are close to towns are addressed in this study. A straightforward order based solution representation is applied for coding solutions of the problem and clustering approach is used to generate appropriate initial solutions. Moreover, three multi-objective decomposition methods including weighted sum, goal programming, and goal attainment are applied to validate the performance of the proposed algorithm. Number of test problems are conducted and the results obtained by algorithms are compared with respect to some comparison metrics. Finally, the experimental results show that the proposed hybrid NSGA-II outperforms all decomposition methods, but the computational times for decomposition methods are less than NSGA-II.

A practical and rigorous approach for the integration of sustainability principles into the decision-making processes at minerals processing operations

Optimal allocation and sizing for profitability and voltage enhancement of PV systems on feeders

Catalytic naphtha reforming is a crucial process in producing gasoline or aromatic compounds. The characteristic of two production modes gives rise to different economic optimization and control objectives. In the present work, we design an economic model predictive control (EMPC) with a production mode switching strategy to cope with these problems. First, a rigorous dynamic process model is established to simulate the naphtha reforming process. Then, we formulate different economic objective functions and simplify the process model for each production mode, and also enable the EMPC controller to switch the production mode automatically according to empirical equations. Three case studies are presented to test the performance of our proposed control strategy. The results show that the designed EMPC controller with production mode switching can successfully overcome the economic disturbances and improve the production profits in different production modes. In addition, it also has a fast response time to drive the system to a new economic optimal operating point.

Nonlinear Model Predictive Control for Ecological Driver Assistance Systems in Electric Vehicles

Economic linear objective function approach for structure optimization of renewables-to-chemicals (R2Chem) networks

This paper analyzes costs of several biofuel production pathways in Australia from crop residues (stubble), a lignocellulosic feedstock. As well as land (and sea) transport suitable biofuels, we also consider electricity, and aviation biofuels. Some biofuel cost calculations assume a minimum processing plant scale, often based on contemporary fossil fuels production scales. The more theoretical approach here minimizes production cost by trading off processing and transport costs. Optimal scales and process component costs depend on feedstock spatial concentration; however total costs are less strongly dependent. Lower concentrations correspond to smaller processing plant and greater collection areas and costs. Processing costs are added to feedstock production and transport costs to derive biofuel supply cost ranges as a function of feedstock concentration in an Australian context. Sensitivity analysis then identifies significant parameters and confidence interval estimates. A companion paper generates Australian nationally aggregated supply cost curves. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd

1090. Properties of titanium-molybdenum alloy wire as a source of titanium for sublimation pumps: R W Lawson and J W Woodward, Vacuum, 17 (4), April, 1967 205–209

The working fluid flow and the machining debris movement in the machining gap exercise a great influence on the process performance in end electrical discharge milling and mechanical grinding compound machining. In this paper, the working fluid flow and the machining debris movement in the machining gap are modeled based on the liquid-solid two-phase flow theory. The gap flow field is calculated with the software of Fluent, and the velocity field and the pressure field are analyzed. The results show that in the gap flow field of the compound machining, the working fluid flow can be accelerated, and the machining debris can be ejected timely by the rapid rotation of the tool electrode, so the compound process performance can be enhanced.

The dynamics of Supply Chain Management (SCM) have changed over the years; new paradigms are added into the SCM as a response to changes related with increasing environmental concerns and pressures. Therefore, lean and green practices in a company belong to its most important factors to enhance the company’s performance. In this study a new model, inspired by an automotive supply chain, is proposed for lean and green closed-loop supply chain management. In this model, we deal with lean and green drivers to set the objectives of the decision makers (DMs) as follows; (1) Construction: The amount of emitted CO2 depends on the size of the potential facilities; (2) Production: Higher equipment or techniques in a production system means a higher environmental investment and leads to lower CO2 emissions; (3) Handling: The usage of a proper forklift is an important decision to increase the productivity and reduce CO2 emissions; (4) Transportation: Three different options in the transportation process which DMs can choose are considered: small-sized, medium-sized, and heavy-sized trucks. All of the truck types differ in transportation cost and CO2 emissions with respect to the engines. The benefits of the heavy-sized trucks are obvious: less transportation cost with bigger lot size deliveries but more environmental pollution as well; (v) On Time Deliveries: Lean manufacturing needs suppliers to comply with delivery times, which directly affect the buyer’s manufacturing lead times, operational performances and competitiveness. Thus, late deliveries of suppliers aimed to be minimized. Under these circumstances, there are few trade-offs which need to be optimized simultaneously. The developed model consists of six different objectives: minimization of transportation cost, purchasing and operational cost, fixed facility cost, environmental cost, handling cost and late deliveries. In order to validate the proposed model, a numerical example is implemented and analyzed by using fuzzy weighted additive method where the weights are determined via Fuzzy Analytic Hierarchy Process (Fuzzy AHP) method.

Aqaba Special Economic Zone Authority (ASEZA) City Bus Service is the only public enterprise that provides transport services in and around the city of Ababa. The city uses a fixed bus schedule system to serve passengers in 15 routes with buses (89) bus. However, this type of bus assignment system created a problem in the operational and financial performances. The objective of this paper is to develop an optimum bus assignment method using Linear Programming (LP). After thorough analysis of the existing bus scheduling system, the LP model is developed and used to determine the optimal number of buses for each route in four shifts. The output of the LP-model is then validated with the performances of the existing systems. The findings of the study show that There is a positive effect bus utilization on reduce cost in public transportation, there is a positive effect total number of trips made on reduce cost in public transportation, There is a positive effect total distance travelled on reduce cost in public transportation, There is a positive effect various operating costs on reduce cost in public transportation. The researcher recommended the (ASEZA) to adopt the new bus assignment system so that buses can be assigned based on the demand distribution of passengers for each route at a given shift.

Comminution is a frequently-required step in mineral processing and is responsible for almost 90% of all energy consumption in a mineral processing plant. Tumbling mill design has been studied since the middle of the XIX century. There are many comminution models in the literature, with preponderance, however, of Austin’s model (2002) for mineral impact breakage. In this paper, Austin’s model was applied to tubular tumbling mills. Once Austin’s model was proposed for batch processing of narrowly-distributed fraction sizes, an artifice has allowed it to be used in continuous grinding mill processes with widely-distributed fraction sizes. Interesting results were obtained with errors less than 0.005 for mills with sharp residence time distributions.

In this paper, an effective and reliable variant of particle swarm optimization with time-varying acceleration coefficients (PSO-TVAC) technique is proposed for the economic load dispatch problem considering valve-point loading effect. Main objective of the economic load dispatch (ELD) problem is to minimize the fuel cost by allocating the generation of the committed units subjected to the equality and inequality constraints. Equation of the economic dispatch objective function gets modified with the addition of a new parameter which represents the effect of valve-point loading. While exploring the use of PSO and its other variants to the economic dispatch problem, a number of research works have not considered the transmission losses properly. This paper represents the usefulness of the proposed PSO-TVAC algorithm to significantly reduce the fuel cost while taking into account the effect of transmission losses along with the non-convex characteristic due to valve loading. The results have been demonstrated for three-generator and ten-generator test systems.

The dramatic growth of online shopping worldwide in the last few years generated negative consequences for local small retailers who do not adopt information technologies. Furthermore, the e-commerce sector is considered a good opportunity to develop sustainable logistic processes. To reach this goal, the proposed paper presents a mathematical model and a metaheuristic algorithm to solve a multi-objective capacitated vehicle routing problem (CVRP) distinguished by economic, green, and ethical objective functions. The proposed algorithm is a multi-objective simulated annealing (MOSA) that is implemented in a software architecture and validated with real-world instances that differ for the product type delivered and the geographic distribution of customers. The main result of each test is a tri-dimensional Pareto front, i.e., a decision-support system for practitioners in selecting the best solution according to their needs. From these fronts, it can be observed that if the economic and environmental performances slightly deteriorate by 1.6% and 4.5%, respectively, the social one improves by 19.4%. Furthermore, the developed MOSA shows that the environmental and social objective functions depend on the product dimensions and the geographic distribution of customers. Regarding the former aspect, this paper reports that, counter-intuitively, the metabolic energy consumption per driver decreases with bigger products because the number of necessary vehicles (and drivers) increases, and, thus, the workload is divided among more employees. Regarding the geographic distribution, this manuscript illustrates that, despite similar traveled distances, highly variable altitudes cause more carbon emissions compared to flat distributions. Finally, this contribution shows that delivering small goods decreases the distance that vehicles travel empty by 59%, with a consequent cost reduction of 16%.