Power plant maintenance scheduling using ant colony optimization: an improved formulation

It is common practice in the hydropower industry to either shorten the maintenance duration or to postpone maintenance tasks in a hydropower system when there is expected unserved energy based on current water storage levels and forecast storage inflows. It is therefore essential that a maintenance scheduling optimizer can incorporate the options of shortening the maintenance duration and/or deferring maintenance tasks in the search for practical maintenance schedules. In this article, an improved ant colony optimization-power plant maintenance scheduling optimization (ACO-PPMSO) formulation that considers such options in the optimization process is introduced. As a result, both the optimum commencement time and the optimum outage duration are determined for each of the maintenance tasks that need to be scheduled. In addition, a local search strategy is presented in this article to boost the robustness of the algorithm. When tested on a five-station hydropower system problem, the improved formulation is shown to be capable of allowing shortening of maintenance duration in the event of expected demand shortfalls. In addition, the new local search strategy is also shown to have significantly improved the optimization ability of the ACO-PPMSO algorithm.     

Project,Design, and Use of a Pilot Plant for Nanocapsule Production

The aim of this study was to find the scale-up parameters necessary for the preparation of nanocapsules (NCs) for pharmaceutical purposes. Starting from the laboratory scale (0.06 L), we designed and assembled a pilot plant (2 L) to produce NCs with the so-called emulsification-diffusion technique. We wanted to check if classical tools adequate for the pharmaceutical industry and for industrial scale-up purposes according to well-known chemical engineering technique could be used to perform the NC preparation. Experiments were carried out by varying some operative parameters, such as the impeller speed, the agitation duration for the emulsion preparation, and the reagent concentrations. As expected, good accordance between the NC produced at the laboratory scale and at the pilot plant scale was obtained. We conclude that the pilot plant can be used to perform a scale-up study of the industrial production of NC.     

Applying a risk assessment approach for cost analysis and decision-making: a case study for a basic design engineering project

Abstract

Many uncertainties and cost variations occur in the work activities of a project, thereby causing many possibilities of under-estimating or over-estimating for a bid price. A comprehensive study for each process of risk management should be investigated to achieve project objectives. However, a limited number of studies have a comprehensive viewpoint to indicate the benefits of risk management and the effect on project performance for the engineering design stage of engineering–procurement–construction (EPC) projects, especially in the basic design stage. This research was conducted to identify and analyze the risks associated with a Basic Design Engineering (BDE) project for a high value-added petrochemical plant in Taiwan. First, a project risk management work flow was proposed as an effective tool to minimize the project risks and maximize the management capacity of practitioners. Second, the cost effect of project risks was described by conducting a case study for the design process of a high value-added petrochemical plant using a Monte Carlo simulation. A risk register was identified to support the data required for conducting simulation analysis. The results of this paper provide reference points for risk management planning of project execution and help project managers evaluate particular risks at the engineering design stage of EPC projects to avoid cost overruns.     

Test Facility for Low Potential Pumped Storage Power Plants and Hydrokinetic Turbines

The electric energy which is generated by wind power plants depends on the wind speed and exceeds with strong permissible wind speed the electric energy requirements of the country. In order not to reduce this electrical energy, it must be stored. The sensible energy storage is currently the pumped storage power plants. As the mountain ranges for conventional pumped storage power plants with drop heights of H 〉 600 m are strictly limited, the development of low potential pumped storage power plants has begun. Increasing the capacity of pumped storage power plants with regard to the wind power plants is urgently needed. In this paper, it is shown using the example of an unneeded port facility, how a port facility can be used after low conversion as a test facility for low potential pumped storage power plants and at the same time for the testing of hydro-kinetic turbines. This type of pump storage power plants does not save the energy due to large drop heights, but primarily due to the large volume flow of water.     

Creep behavior of seam-welded reheat steam pipes in thermal fossil power plant: feedback analysis and life assessment methodology

A methodology is developed to evaluate a residual life of the oldest seam-welded reheat pipes. The first step consists of a design concept based using a weld parameter depending on welding process, in order to classify pipes by their creep life fraction. This part is in progress. The second step consists of a metallurgical approach to optimize life assessment of the most damaged pipes, by estimating a residual life before crack initiation in the intercritical zone of a pipe tempered weld. Creep tests on a simulated intercritical microstructure were subjected to different creep life fractions. Creep damage was identified as the creep cavity density evaluated by image analysis. Tests results have shown that creep damage appears in the intercritical microstructure in the very end of life (last 16 ± 2 % of creep life). These results warrant a residual life of at least 24000 hours for a 150000 hours aged pipe under operating conditions, if no creep damage was found. Extra examinations have been performed on the oldest seam-welded (MMA process) reheat pipe of EDF thermal fossil power plants. Application of this metallographic approach have enabled one to estimate a residual life of at least 9000 hours before the creep crack initiation stage, in good agreement with creep tests performed on extracted welds. Applicability of this new approach seems to be very interesting for in service seam-welded reheat pipes, but it requires the previously identification of the most creep damaged section. In that way, NDT must be improved to be able to detect creep damage in the bulk.     

Development and application of a methodology for the measurement of corrosion and erosion damage in laboratory,burner rig and plant environments

Abstract

Fuel gases derived from solid fuels such as coal, biomass and waste and their mixes have the potential to cause both erosion and corrosion damage to components in gas turbines and diesel engines. To allow the statistically valid assessment of materials performance in short term plant runs, burner rig tests and laboratory simulated environments a methodology has been developed to collect compatible quantitative data on materials degradation. Accurate measurement techniques based on pre-exposure contact metrology and post-exposure optical microscopy/image analysis have been developed. These take into account both the low level of damage required for practical systems and the localised nature of hot corrosion damage. The data produced have been used to derive and test quantitative models for the prediction of the performance of candidate materials in such power systems. For these models to be used with confidence, similar damage morphologies must be produced in both the real and simulated conditions, as well as similar damage rates.     

选煤厂MES的建设

选煤厂MES的建设目标是完成管理与控制一体化,实现选煤厂生产的可视化、可追溯、可改进,降低生产成本,提高经济效益。介绍了选煤厂MES系统结构、平台建设、软件架构,叙述了选煤厂MES主要模块的功能,阐述了选煤厂MES的建设目标及其意义。     

Kinetic investigations of two processes for zinc recovery from zinc plant residue

Abstract

This paper presents a kinetic study of hydrometallurgical and pyrometallurgical processes employed for the recovery of zinc from a zinc plant residue (ZPR). The hydrometallurgical process investigated involved zinc leaching from the ZPR with sulphuric acid solution, while the pyrometallurgical process was based on zinc oxide reduction from the ZPR using activated carbon as the reducting agent. At the optimum leaching conditions, the zinc recovery was 89·5% at 95°C after 60?min. The data obtained for the leaching kinetics indicated that the dissolution of ZPR is a diffusion controlled process and the activation energy is equal to 21±2?kJ?mol^?1. The maximum zinc recovery, obtained during pyrometallurgical treatment was 72% at 1300°C after 60?min. Kinetic investigations revealed that the zinc oxide reduction is carried out in the transient kinetic area, where both diffusion and the chemical reaction control the overall process rate, with an activation energy of 38±5?kJ?mol^?1.

Cet article présente une étude cinétique d'un procédé hydrométallurgique et d'un procédé pyrométallurgique utilisés pour la récupération du zinc du résidu d'une usine de zinc (ZPR). Le procédé hydrométallurgique investigué impliquait la lixiviation du zinc du résidu de l'usine de zinc avec une solution d'acide sulfurique, alors que le procédé pyrométallurgique était basé sur la réduction de l'oxyde de zinc du résidu de l'usine de zinc en utilisant du charbon activé comme agent de réduction. Aux conditions optimales de lixiviation, la récupération du zinc était de 89·5% à 95°C après 60?min. Les données obtenues pour la cinétique de lixiviation ont indiqué que la dissolution du résidu de l'usine de zinc était un procédé contrôlé par la diffusion et l'énergie d'activation est égale à 21±2?kJ?mol^?1. La récupération maximale de zinc, obtenue lors du traitement pyrométallurgique, était de 72% à 1300°C après 60?min. Les investigations de la cinétique ont révélé que la réduction de l'oxyde de zinc était effectuée dans la zone de cinétique transitoire, où tant la diffusion que la réaction chimique contrôlent la vitesse globale du procédé, avec une activation d'énergie de 38±5?kJ?mol^?1.     

Scenario-Based Multi-Objective Genetic Algorithm Optimization of Closed Ball-Milling Circuit of Esfordi Phosphate Plant

The main goal of this article is to demonstrate an approach based on integration of process simulation and Multi-Objective Genetic Algorithm (MOGA) concepts to solve a real grinding circuit optimization problem by finding the best operating condition under which process objectives can be achieved. Esfordi phosphate plant is located near city of Bafgh at Yazd province of Iran and produces 5 Mt of phosphate annually. The fine particles (nearly ?20 µm) in hydrocyclone underflow which contain a high grade of iron are subjected to over grinding. In addition to electrical energy loss, this causes problems in the downstream process, i.e., flotation stage. The main goals of this study were to solve this problem by adjusting operating condition so that (a) hydrocyclone overflow particle size can be increased from 94.2 µm to 100 µm and (b) increase hydrocyclone underflow particle size from 205 to 500 µm. The second process objective will decrease fine particles in hydrocyclone underflow stream. First, plant sampling campaigns were carried out to calibrate ball mill and hydrocyclone models to be used for performing simulation trials. Then, full circuit simulations were done and optimized by MOGA search process to find the best operating condition that produces hydrocyclone overflow and underflow streams with predefined particle sizes simultaneously. The results indicate that there are various solutions that can be recommended for plant testing and performance improvements. The results of plant implementation of one solution for scenario No. 4 showed improved circuit performance and also validated simulator predictions.     

主换热器热端温差过大的故障分析及处理

针对在空分设备运行过程中主换热器热端温差过大的现象,从换热介质和热端温差变化阶段的系统运行情况入手,分析了热端温差过大的原因,用压缩空气从下塔对换热器至分子筛吸附器出口之间管道进行反吹,排除了故障,空分系统投入正常运行。