A two-stage approach for the synthesis of inter-plant water networks involving continuous and batch units

This paper presents a mathematical optimization model for inter-plant water network (IPWN) synthesis, where process units operate in mixed continuous and batch modes. The current developed model consists of a two-stage approach, and is dedicated to the special case where there are more continuous than batch units. In the first stage, all batch units are treated as continuous units by using auxiliary water storage tanks, and a continuously operated IPWN is synthesized to minimize the fresh water consumption. Subject to the determined IPWN flow rates, the water storage policy for the batch units is determined in the second stage to minimize the total storage capacity. Alternatively, the formulations of both stages can be combined and solved simultaneously to minimize the IPWN cost. Two modified literature examples are used to illustrate the proposed approach.     

Optimization-based method for calculating water networks with user specified characteristics

This paper addresses problem of designing water usage network that consists of fixed flow rate water using processes. A design method is founded on the solution of mixed-integer linear programming (MILP) model of network superstructure. The application of optimization to solve basic formulation of network synthesis has been reported in some works. However, this approach applies certain extensions of the standard formulation that allow accounting for several industrial scenarios. In particular, it is possible to apply various performance indices and imposing conditions on continuous variables as well as on network topology. Multiple contaminant case is easily accounted for. At least but not at last, the method is able to generate several solutions of identical values of major performance indices but of different structure and other features. All these possibilities are available within single optimization framework. Several examples are given to illustrate advantages of the approach.     

水解酸化—MSBR工艺处理工业园区污水

采用水解酸化—MSBR工艺处理工业园区污水,运行结果表明,该工艺对各种污染物的去除率较高,出水各项指标可稳定达到《城镇污水处理厂污染物排放标准》(GB18918--2002)的一级B标准.     

Combined mass and heat exchange network synthesis based on stage-wise superstructure model☆

Integrating multiple systems into one has become an important trend in Process Systems Engineering research field since there is strong demand from the modern industries. In this study, a stage-wise superstructure-based method is proposed to synthesize a combined mass and heat exchange network (CM&HEN) which has two parts as the mass exchange network (MEN) and heat exchange network (HEN) involved. To express the pos-sible heat exchange requirements resulted from mass exchange operations, a so cal ed“indistinct HEN super-structure (IHS)”, which can contain the all potential matches between streams, is constructed at first. Then, a non-linear programming (NLP) mathematical model is established for the simultaneous synthesis and optimiza-tion of networks. Therein, the interaction between mass exchange and heat exchange is modeling formulated. The NLP model has later been examined using an example from literature, and the effectiveness of the proposed method has been demonstrated with the results.     

Optimal design of reverse-osmosis networks for wastewater treatment

An optimization study of reverse-osmosis networks (RON) for wastewater treatment has been carried out by describing the system as a nonconvex mixed-integer nonlinear problem (MINLP). A mixed-integer linear problem (MILP) is derived from the original nonlinear problem by the convex relaxation of the nonconvex terms in the MINLP to provide bounds for the global optimum. The MILP model is solved iteratively to supply different initial guesses for the nonconvex MINLP model. It is found that such a procedure is effective in finding local optimum solutions in reasonable time and overcoming possible convergence difficulties associated with MINLP local search methods. Examples of water desalination and wastewater treatment from the pulp and paper industry are considered as case studies to illustrate the proposed solution strategy.     

Synthesis of non-isothermal heat integrated water networks in chemical processes

This paper presents a new approach for the simultaneous synthesis and optimization of heat integrated water networks. A new superstructure for heat exchanger network (HEN) synthesis is proposed. The procedure is based on mixed integer non-linear mathematical programming (MINLP). Four relevant examples are presented to illustrate various aspects of the proposed approach.     

A global optimal formulation for the water integration in eco-industrial parks considering multiple pollutants

A mathematical programming formulation for the water integration in eco-industrial parks considering streams with several pollutants is presented. The formulation is based on a superstructure that allows the wastewater reuse in the same plant, the water exchange with different plants, and a shared set of interceptors that must be selected to determine the network configuration that satisfies process equipments and environmental constraints. The model formulation considers wastewater with several pollutants, and optimizes the network according to the minimum total annual cost, which includes the costs of fresh water, piping and regeneration. A new discretization approach is also proposed to handle the large set of bilinear terms that appear in the model in order to yield a near global optimal solution. The results obtained in several examples show considerable savings with respect to the solutions of the individual plant integration policy commonly employed for these types of problems.     

基于全过程污染控制策略的钢铁工业园区水网络全局优化

作为典型的高耗水工业,节水减排是我国钢铁工业可持续发展亟须解决的关键问题之一。本研究基于全过程污染控制策略,提出了面向钢铁工业园区水网络特点的多尺度优化建模方法,充分考虑了钢铁园区涉水单元-工序水网络-园区水网络等不同尺度水系统的用排水特点及相互作用,有助于进一步发掘园区节水减排新空间。在此基础上建立了园区水网络全局优化模型,利用数学规划方法来探索综合用水成本最低的园区水网络优化方案。一年产能为500万吨钢材的钢铁工业园区水网络优化案例研究表明,采用全过程污染控制策略的钢铁园区水网络全局优化方案,综合用水成本、新水用量及新水成本占比等用水指标与其他采用局部水污染控制技术的方案相比有较大幅度的降低,与园区现用水指标相比,各指标均降低20%以上。案例研究表明所提出的园区水网络优化模型可行有效,优化结果对于钢铁园区水污染控制技术的集成和水网络全局优化方案的精准确定具有重要的参考价值。     

Synthesis of Rice Processing Plants. II. MINLP Optimization

A systematic design approach was applied to develop the optimal process flowsheet for a rice processing plant. The optimization problem was formulated as a Mixed-Integer NonLinear Programme, MINLP, consisting of vectors of binary and continuous variables. A superstructure flowsheet comprising all serial structures of drying, cooling, and tempering units in the process was postulated. The set of optimum decision variables including the number of drying, cooling, and tempering units, temperature and relative humidity of drying air, drying time, cooling time, and tempering time were determine as the solution of the corresponding MINLP. Six objective functions were investigated as possible performance criteria: production time, number of the operating units, energy consumption, total operating cost, head rice yield, and the profit. The choice of objective function was found to have a significant effect on the optimal solution. Comparison with typical design and operating conditions, the MINLP results showed that a 22% reduction in energy consumption was possible along with a 2.4% increase in head rice yield. These savings, if applied to the world-wide rice industry, translate into more than $3 billion dollars/year increase in profit.     

Synthesis of Rice Processing Plants. II. MINLP Optimization

Abstract

A systematic design approach was applied to develop the optimal process flowsheet for a rice processing plant. The optimization problem was formulated as a Mixed-Integer NonLinear Programme, MINLP, consisting of vectors of binary and continuous variables. A superstructure flowsheet comprising all serial structures of drying, cooling, and tempering units in the process was postulated. The set of optimum decision variables including the number of drying, cooling, and tempering units, temperature and relative humidity of drying air, drying time, cooling time, and tempering time were determine as the solution of the corresponding MINLP. Six objective functions were investigated as possible performance criteria: production time, number of the operating units, energy consumption, total operating cost, head rice yield, and the profit. The choice of objective function was found to have a significant effect on the optimal solution. Comparison with typical design and operating conditions, the MINLP results showed that a 22% reduction in energy consumption was possible along with a 2.4% increase in head rice yield. These savings, if applied to the world-wide rice industry, translate into more than $3 billion dollars/year increase in profit.     

实验室中工业锅炉水质检测注意问题探讨

当前,工业锅炉的应用已十分普遍。在实际的生产和生活中,锅炉水质监测工作尤为重要,定期、精细化的对工业锅炉水质的各项指标进行检测,有利于及时对水质情况进行掌握调整,为锅炉有效运行提供保障。作为实验室化验员,我们必须对每一项指标进行详细的分析,确保检验数据的真实性、科学性以及精确性。     

Polarized optical microscopy study on the superstructures of oxyethylene/oxybutylene block copolymers

The superstructures of oxyethylene/oxybutylene block copolymers with different compositions and architectures (E_mB_n, B_nE_mB_n and E_mB_nE_m) were studied using polarized optical microscopy (POM). Several novel superstructures, such as fibril crystals and different frontiers of spherulites and crystallized regions, have been observed. It is found that the ability of forming spherulites is reduced with the decrease in the volume fraction of the crystallizable block. The unfavorable interaction between the blocks, which can be indicated by order-disorder transition temperature (T_ODT), also affects the formation of superstructure. The B_nE_mB_n triblock copolymers exhibit the strongest ability of organization into spherulites, whereas the E_mB_nE_m triblock copolymers show the weakest ability of organization into spherulites.     

Industrial wastewaters treated by electrocoagulation

In this paper, we describe a novel design of electrocoagulation system for wastewater treatment using sacrificial aluminum electrodes. The wastewaters considered were contaminated by a fluorescent penetrant liquid used for non-destructive testing of parts in the aircraft industry and could not be treated satisfactorily by conventional physical, chemical or biological processes. The new electrochemical system clarified the contaminated rinse water and allowed it to be re-used 4 times. The system could reduce 95% of the chemical oxygen demand, 99% of color and 99% of turbidity in the discharged wastewater. Cost estimates for the process represent an investment-return time for the electrocoagulation system of about 17 weeks.     

Structure and the enhanced ferromagnetism in single phase Sr4Fe5CoO13-δ ceramic

Oxides with superstructure have attracted special attention for their great tolerance in structure and composition regulation, which enables them to have great potential in energy conversion devices, electromagnetic regulation devices, spintronic devices, and so on. Here, we successfully prepared a superstructure oxide Sr₄Fe₅CoO_13-δ via combustion method. X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectra (XAS) analysis suggest that Co dopant could improve the amount of oxygen vacancies in oxides. Unlike the thermal activated electrical conducting behavior of Sr₄Fe₆O_13-δ, Sr₄Fe₅CoO_13-δ demonstrates an electrical behavior in line with the Mott's variable range hopping (VRH) model at low temperatures, implying the localization of electrons. Sr₄Fe₅CoO_13-δ shows a ferromagnetic property with a high Curie temperature of 771 K, which should be attributed to the new formed Dzyaloshinskii-Moriya (D-M) interaction of Fe–O–Co, the increased lattice distortion and the increased amount of oxygen vacancies induced by Co dopant. These properties render it a broadened working temperature range and may contribute to explore high temperature spintronic devices.