Recovery Strategies And Optimization Methods For Reverse Logistics System In Iron And Steel Industry

The iron and steel industry is a typical high comsumption, high discharge process industry. Recently, along with the rapid growth of steel output, development of the iron and steel industry is badly restricted because of the limitation of ore resource, energe resource and water resource, hence the recovery of waste gained more and more attention from people. How to effectively utilize different types of waste became very important to reducing production cost, improving resource utilization studio, energe saving and environment protection. Reverse logistics is the process of planning, implementing, and controlling the efficient, effective inbound flow and storage of secondary goods and related information opposite to the traditional supply chain direction for the purpose of recovering value or proper disposal. Based on the definition of reverse logistics, this thesis summarizes and analyzes the characteristics of return flows in the iron and steel industry, and investigates the actual situation of steel production process in several large iron and steel companies, and then focuses on the research on recovery strategies and optimization methods for reverse logistics system in the iron and steel industry. It is a constituent part of '985 project- Scientific and technological innovation of Integrated Automation of Process Industry platform research project', 'Liaoning provincial division of sicence and technology planning project' and 'National Natural Science Funds for Distinguished Young Scholar project'.In Chapter 2, basic theories about reverse logistics are firstly introduced, including definition and motives of reverse logistics, reasons of returing, manners of disposing returns, characteristics of returns, closed-loop and open-loop structures of reverse logistics system, and implementers of reverse logistics; and then the literatures about reverse logistics is overviewed from three main research orientations, namely network design, inventory management and production planning; furthermore, aiming to give some directions and references to the study of application of reverse logistics in the iron and steel industry, the application of reverse logistics in electronic industry, which is seemed as a typical discrete manufacturing industry, is special analyzed, including characteristics, motives, three collection modes of scrap electronic products, related literatures, etc.; finally, literatures about applications of reverse logistics in iron and steel industry are reviewed, and this work laies an important theoretical foundation for the study in this thesis. As a whole, this thesis focuses on following five key problems.As the Key Problem 1, Chapter 3 is the important foundation of the whole research, and supply directions and practical realities to the other four key problems. Some special reverse logistics systems are established considering characteristics of the iron and steel industy from two points of view. Firtly, focusing on the production procedure of the iron and steel industy, the three major production stages are illustrated, including constituent production procedures and characteristics; to be important and specialized, the return flows of each production stage are analyzed, and accordingly some reverse logistics systems for the whole production process of the iron and steel industry are established. Secondly, focusing on the major classes of solid and liquid wastes generated by the iron and steel industry, based on the illustration of their classification, characteristics and harmfulness, the return flows are further analyzed, and accordingly some special reverse logistics systems are established. Finally, in this chapter, some important investigation results in three large iron and steel companies are shown, which sufficiently approve the practical applications significance of this study.As the Key Problem 2, Chapter 4 focuses on recovery strategies optimization problem for acid waste recycling which is seemed as a typical class of liquid industrial waste recycling process. There are multiple strategies for waste recycling to generate multiple byproducts and then these byproducts are further transformed into multiple types of chemical products via different production patterns. A mixed integer programming model is developed to help determine which recycling strategy and which production pattern should be selected in a given quantity in order to maximize the marginal profits. A simulated annealing (SA) based heuristic algorithm is developed to solve the problem. Finally, an experiment is designed to test the effectiveness and feasibility of the proposed method, furthermore, the effects of model parameters on profit are discussed to help manufacturers organize their waste recycling network.As the Key Problem 3, Chapter 5 focuses on an EOQ inventory management problem with deterministic demands and returns for a three-stage steel roller producing process which is seemed as a typical class of closed-loop production process in the iron and steel industry. A three-stage manufacturing/remanufacturing system with three serviceable inventories and two recoverable inventories is introduced. By considering manufacturing and remanufacturing in the different stages, three modes of production are identified. The cycle times of each mode, demand rates for serviceable inventories, and their relationships in a planning horizon are further discussed through analyzing the characteristics of the production system. Then, the inventory profiles in the system are studied, and an EOQ model is proposed to decide on the timing for ordering serviceable inventories with the view to minimizing the average cost. Finally a numerical example is used to demonstrate the feasibility of the model, and to examine its effects on the orders response time and the average costs. As the Key Problem 4, Chapter 6 focuses on a network design problem for obsolete scrap steel recycling process which is seemed as a typical solid waste recycling process in the iron and steel industry, and proposes a location and allocation model basing on analysis of business flow from manufacturing of steel-made product, and collecting to recycling of scrap steel with multiple customer zones and multiple scrap steel collection centers. A Lagrange relaxation decomposition based heuristics combined with Depth First Search (DFS) approach is developed. Finally, an experiment is designed to test the effectiveness and feasibility of the proposed model and algorithm.As the Key Problem 5, Chapter 7 focuses on a dynamic economic lot sizing problem for the three types of scrap steel recycling. A specific closed-loop network for scrap steel recycling is established, and then the relationships between the forward chain and the reverse chain are investigated. A Dynamic Economic Lot Sizing model with time-varying demands is proposed to decide the optimal purchasing time and the optimal procurement quantity of obsolete scrap steel towards minimal total cost of the whole network. A dynamic programming based algorithm is discussed to solve the problem. Finally several numerical experiments are designed to validate the effectiveness of the model and the algorithm, as well as to examine the effects of parameters on the optimal results. From the results of experiments, one can observed that low unit holding cost in collection center and high return rates of home scrap steel and prompt scrap steel more contribute to reducing the total cost of the whole network and the optimal ordering times of obsolete scrap steel from society.