Igor Bulatov

Cost estimation and energy price forecasts for economic evaluation of retrofit projects

Abstract A cost estimate can have a major impact both on project profitability and influences the technical solution. This leads to a commitment of substantial amounts of money and manpower over an extended time. Various methods often provide different results. These differences can be rather significant towards the real cost of a project and selection of the right arrangements. It is therefore important to use a proper estimate that generates enough confidence to choose the right alternative. Another source of uncertainty during the economic analysis of design and retrofit projects is the future energy price value as part of operating costs. This value can significantly affect the project viability and profitability. This paper gives a summary of the most common methods used for cost estimation of heat exchange equipment in the process industry and the sources of energy price projections. It shows the relevance of the choice of the right method and the most reliable source of energy price forecast used when choosing between alternative retrofit projects or when trying to determine the viability of a retrofit project. Ten methods for heat exchanger costing procedure are considered. Oil, natural gas and electricity price projection figures published in reports of nine established analytical centres are discussed. Web sites of institutions and companies are also included.

Novel MILP-based iterative method for the retrofit of heat exchanger networks with intensified heat transfer

Abstract Heat transfer intensification is an effective technique for improving energy recovery in heat exchanger networks (HEN) by enhancing heat transfer without any network topology modifications. In this paper, a novel optimization method has been developed for the synthesis of intensified heat exchanger networks with a simple mixed integer linear programming (MILP) model under retrofit scenario, and a robust solution strategy based on two iteration loops has been proposed. The new method has distinctive advantages over existing design methods, as the new MILP model can effectively and significantly reduce computational difficulties associated with nonlinear formulation in existing HEN retrofit formulations. Three cases have been tested to demonstrate the validity and efficiency of the proposed approach, which requires very short computational times to obtain optimal solutions when energy saving or profit is to be maximised through retrofit.

Novel energy saving technologies evaluation tool

The lead-time for the development of a new energy technology, from the initial idea to the commercial application, can take many years. The reduction of this time has been the main objective of the EC DGTREN, who have funded two related recent projects, EMINENT and EMINENT2 (Early Market Introduction of New Energy Technologies). These projects were implemented to identify and accelerate the introduction and implementation of leading edge European technology in the field of energy saving into the market place. The principal features included the production of a software tool and an integrated database of new technologies and sectoral energy supplies and demands. The software tool has the capability to analyse the potential impact of new and underdeveloped energy technologies in different sectors emerging from different countries. In addition, the software tool has been used to perform case studies which have been used to illustrate the new technologies.

Novel optimization method for retrofitting heat exchanger networks with intensified heat transfer

Abstract Enhancing heat transfer in an existing heat exchanger has received great attentions from process industries recently, as its implementation in heat exchanger networks is relatively simple, which only require very minor structural modifications in heat exchangers without modifying basic configuration of exchanger networks. In this study, a novel optimization approach is proposed for the retrofitting of heat exchanger networks with intensified heat transfer. The optimization framework has been developed to systematically identify the most appropriate location for the introduction of heat transfer enhancement and its optimal level in the retrofit scenarios. Iterative optimization of a simple MILP-based model has been proposed to deal with computational difficulties associated with non-linear terms in the optimization more effectively. A case study based on a literature example [1] has been carried out to demonstrate the validity and soundness of the proposed approach.

Improving energy recovery in heat exchanger network with intensified tube-side heat transfer

Implementing tube-inserts, namely tube-side enhancement, is an efficient way to increase the heat transfer coefficients of shell and tube heat exchangers, which can achieve substantial energy saving in heat exchanger network (HEN) if suitable retrofit strategies are used (Pan et al., 2011). In this paper, a new optimization method is proposed to consider more details of tube-side enhancement for HEN retrofitting, such as multiple tube passes, logarithmic mean temperature difference (LMTD), LMTD correction factor (FT). Even though LMTD and FT will lead to complex nonlinear terms in mathematical programming, the proposed approach can deal with the relevant computational difficulties efficiently. The validity of new optimization approach is illustrated with solving a literature example (Li and Chang, 2010). Copyright ? 2011, AIDIC Servizi S.r.l.

Site-wide process integration for low grade heat recovery

Abstract Large quantities of unrecovered low-grade heat are wasted across the process industry. Wide range of technologies and design options for recovering low grade heat are available, including heat pumps, organic Rankine cycle (ORC), energy recovery from gas turbine exhaust, absorption refrigeration, and boiler feed water heating. However, it is not straightforward to identify the most appropriate technology to be implemented, due to complex design interactions inside energy systems in process industry. Process integration of technologies using low-grade heat in the context of a process site has been considered. Simulation model for heat recovery processes has been developed to evaluate techno-economic performance of each technology and to assess the impact of quality and quantity of available low-grade heat sources on the site. Site-wide potential for the utilization of low grade heat has been evaluated with site analysis tool, and the integration of design options for using low-grade energy are systematically screened and compared in a holistic manner. A case study has been carried out to demonstrate the applicability of design methodology proposed in this work and significant benefits of using an integrated approach when implementing low-grade energy upgrading and/or recovery in the context of industrial application.

Exploitation of low-grade heat in site utility systems

Low-grade heat is available in large amounts across process industry from temperatures of 30 ?C to 250 ?C as gases (e.g. flue gas) and/or liquids (e.g. cooling water). Various technologies are available for generating, distributing, utilizing and disposing of low grade energy. The integration of these technologies with the site has not been fully studied, with regards to engineering and practical limitations for retrofit, the use of non-conventional sources of energy in energy generation, and consideration of variable energy demand loads. The identification of cogeneration potentials is one of the key performance indicators for screening various energy-saving technologies using low-grade heat and evaluating the integration-ability of these technologies to the overall site. The work in this study is therefore carried out to improve heat integration models which can systematically identify realistic cogeneration potentials, and provide the most appropriate strategies for exploiting low-grade energy technologies for the viewpoint of system analysis. An improved model has been proposed for the evaluation of power output by a combination of bottom-up and top-down procedure for the evaluation of steam header temperature and steam flow rates respectively. The applicability of the developed model is tested with other existing design methods and STAR? software through a case study. The proposed method is shown to give comparable results, and the targeting method is used for obtaining optimal steam levels. Identifying optimal conditions of steam levels is very important in the design of utility systems, as the selection of steam levels heavily influence the potential for cogeneration and energy recovery for the site. In this work, the optimization of steam levels of site utility systems has been carried out in the case study, in which the usefulness of the optimisation framework is clearly demonstrated for reducing the overall energy consumption for the site. Heat loads and steam levels can then be further used for subsequent evaluation of design options for low grade heat integration. Copyright ? 2010, AIDIC Servizi S.r.l.

Retrofit process heat transfer enhancement to upgrade performance, throughput and reduced energy use

AbstractThis paper summarises the views and experience of two companies specialising in providing technical solutions for increasing the performance of heat exchangers used in the process industries. It comments on the technical opportunities available to a processor to reduce overall energy use. Emphasis is made on the use of enhancement technologies retrofitted to existing heat exchangers, a scenario subsequently illustrated in associated case studies from either company. Enhancing heat transfer in existing and new heat exchangers constitutes a retrofit approach that can address some of the problems faced in a typical heat exchanger network (HEN). The paper thus demonstrates some of the driving forces leading companies to invest in saving energy, and sets out the benefits stemming from the use of process enhancement technologies. It concludes with the view that the most financially viable means of improving HEN efficiency frequently involves addressing the operation of existing heat exchangers first (by improving their performance via various retrofit/revamping options). Only when such options have been exhausted should end-users consider the usually much more costly and operationally difficult option of purchasing and maintaining more plant. Graphical Abstract

Novel MILP-based optimization method for retrofitting heat exchanger networks

Abstract This paper presents a novel optimization method for retrofitting heat exchanger networks (HENs). The optimization framework is developed based on the iterative optimization of a relatively simple mixed integer linear programming (MILP), which can effectively deal with the computational difficulties associated with nonlinearity, and facilitate the automated design of HEN retrofit with rigorous consideration of economic trade-off. A case study based on literature example has been carried out to demonstrate the validity and soundness of the proposed approach.

Estimation of enhanced heat transfer area targets in process industries

Abstract Heat transfer enhancement is one of the most promising methods to optimize heat transfer equipment and to increase heat recovery in industrial processes. Plate Heat Exchanger (PHE) is one of established types of enhanced HEs. To estimate possible benefits of that kind of heat transfer enhancement, a mathematical model of PHE, which accounts for different plate types and corresponding corrugations geometry, is used. Based on this model the optimization algorithm was developed using MINLP method with inequality constraints. The objective function is the heat transfer area of PHE unit. The plate spacing, plate length, the corrugations inclination angle to plates vertical axis and the ratio of corrugations’ pitch to its height are the optimized variables. The developed algorithm is implemented as DLL module, which can be used for multiple calculations when optimizing heat exchanger networks (HEN).