Retrofit Research Articles

Dividing Wall Columns in Operation

Dividing Wall Columns (DWC) provide a new approach to age-old distillation techniques (Dejanovic et al., 2010 and Kiss 2009). These columns have become popular lately owing to the energy and capital benefits that they provide. DWCs, with their versatility and flexible operation, are found in both retrofit and grassroots applications for reformate splitters, naphtha splitters, among others.DWCs work on the principle of removing thermodynamic design flaws in traditional distillation columns (Yildirim et al., 2011). These limitations are encountered in both two-column separation sequences as well as side-cut columns. This paper highlights these inherent design flaws in side-cut columns and illustrates how middle DWC technology helps to eliminate them.Two examples of revamping naphtha splitter columns with DWC technology are presented. In one case, a DWC column produces better product specifications than the original design. In the other case, a two-column sequence is replaced by a single DWC column for the same product quality. This results in freeing up the second column for use in another service. In both cases, a DWC helps to achieve a better side-cut product. The product specifications of the top and middle cuts are somewhat flexible. Both columns are operational in one of the largest refineries in South East Asia.

Limitations of Air/Water Testing in the Development of High Performance Trays

Retrofitting distillation columns with higher capacity mass transfer internals is an effective way of increasing productivity. In the last decades, tray research and development has focused on two areas – improvement of downcomer designs and development of high performance valves with the target to handle higher vapor loads. An example for the second approach is the development of the new Sulzer UFM™ valve. This paper discusses Sulzer’s experience with laboratory testing strategies for fractionation trays and limitation of hydraulic tests with water and air.Air/water testing is very popular due to the low cost and its simplicity. It is still considered as a reliable starting point for screening design options and to evaluate feasibility and capacity. The beginnings of the Sulzer UFM valve development followed this path, but soon weaknesses of the air/water test system were found. Prototype designs preceding the Sulzer UFM valve showed very promising results. Consequently, they were further optimized using air/water for maximum hydraulic capacity. But subsequent distillation tests using a standard binary test system at total reflux could not confirm previous findings. A reduction in liquid entrainment, as observed with water, does not necessarily lead to a capacity increase in distillation. The chosen testing strategy was obviously not efficient and disadvantageous regarding cost and timing.A more successful development path adds more weight to distillation testing, specifically in the early design evaluation phase, but air/water hydraulic tests are not entirely abandoned. Consequently, the later valve designs, currently known as the Sulzer UFM valve, were mainly performed in Sulzer’s 1000mm distillation column and external distillation columns of industrial size.

A New Graphical Approach for Heat Exchanger Network Retrofit Considering Capital and Utility Costs

Development of methodologies and tools for heat exchanger network (HEN) retrofit has focused on generating retrofit solutions to address issues of vital importance to industry including energy, economy and sustainability. This work extends the use of the individual stream temperature versus enthalpy plot (STEP) to enable users to select economically feasible retrofit alternative based on capital and utility costs estimation. A new graph known as the heat exchanger area versus enthalpy plot (A vs H plot) is proposed in this work to be used in combination with the STEP diagram to enable visualisation of the area of every heat exchanger in the HEN. Note that, both graphs share the same enthalpy axis. As a result, heat exchange between the stream pairs shown in the STEP diagram can be projected to the A vs H plot. The A vs H plot contains several useful information of the existing HEN which includes the total area and the number of heat exchanger in the HEN. Firstly, retrofit options are generated by using STEP diagram based on the procedure described in a prior work. Users can later use the A vs H plot to select retrofit option which requires the minimum total heat exchanger area or to minimise the total heat exchanger area needed for the retrofit design generated based on the retrofit methodology which is introduced in this work. Capital cost needed for the retrofit options can be estimated based on total area of new heat exchangers added. Application of the combination of A vs H plot with STEP diagram on a literature case study shows that the combined graphical tools are able to provide clear visual insights to assist users identify capital-energy trade off in generating cost-effective retrofit solutions. The retrofit design and area of the individual heat exchangers in the retrofitted HEN are clearly shown in the combined graphical tools to enable users to screen the most economically viable retrofit option prior to performing economic analysis. Application of the new method on a case study shows that the annualised total cost required by the retrofit design after area minimisation is lower than that of the retrofit design before area minimisation by 3.34 %.

Process Integration Accounting Fouling in Heat Exchanger Network: A Case Study of Crude Oil Distillation Retrofit

This paper presents the approach to predict the future performance of a heat exchanger network based on Pinch retrofit design and detailed historical performance of the unit to improve the operation efficiency, save an energy and increase a throughput. The main input is a finding of a profitable solution of heat exchanger network based on Pinch Analysis, fouling predictive management and a start-up and shut-down time. The approach demonstrates the importance of a dynamic assessment of the retrofit design and operation modes. The case study was developed for crude oil distillation unit with annual capacity of 6 Mt. Dynamic fouling models were built to assist with designing and revamping of heat exchanger network, to reduce the fouling and increase the throughput. Rigorous modelling of refinery heat exchangers network and Pinch Analysis were executed to achieve increased throughput, reduce operation cost and harmful emissions. A new heat exchangers network with improved operation conditions predicting efficient exchanger cleaning schedules under various economic and operational constraints was obtained. The calculations use an HTRI shell-and-tube heat exchanger models, operation data, properties of crude oil and cleaning schedule. Process Integration steps were done by HILECT software and new operation schedule of efficient heat exchangers network was created by HTRI software. The strategy and recommendations for the optimal operation of the retrofitted network were proposed taking into account the economic and process constraints such as exchanger by-passes, operation budget, furnace duty and pumping limit.

Retrofitting multi-period heat exchanger networks using the reduced superstructure synthesis approach

In this paper, the reduced superstructure synthesis method is applied to the retrofit of heat exchanger networks involving multi-period operations. The first step in the synthesis procedure entails solving the multi-period problem to obtain a grass-root solution using the existing multi-period stage-wise superstructure synthesis method. The second step entails the generation of the reduced multi-period superstructure using a combination of two sets of matches as the initialising binary variables. These matches include those selected in the grass-root solution of the first step and those that exist in the original network. The generated reduced superstructure of this second step is then solved as a mixed integer non-linear programming model to obtain a final retrofitted network. The solution obtained from the case study considered in this paper compares favourably with what was reported in the literature.

Optimal Planning for Regional Carbon Capture and Storage Systems under Uncertainty

Increasing emissions of greenhouse gases (GHGs) have been identified as the main contributor to global warming and climate change. Carbon dioxide (CO2) is the primary anthropogenic GHG. Carbon capture and storage (CCS) is widely recognized as a key mitigation technology that can significantly reduce CO2 emissions during combustion. It involves capturing CO2 from large stationary sources and subsequently storing it in various reservoirs such as depleted oil or gas reservoirs, saline aquifers and deep unmineable coal seams. In this work, a finite-scenario based two-stage stochastic mixed integer linear programming (MILP) model is developed for planning the retrofit of power plants with carbon capture (CC) technology and the subsequent CO2 source-sink matching in CCS supply chains under uncertainty. This model can be used to select appropriate sources, capture technologies and sinks and maximize the amount of captured and stored CO2 under the presence of uncertainty. Furthermore, to control risk at the optimal deployment of CCS systems, probabilistic financial risk metric is incorporated into the model. A case study is used to demonstrate the application of the proposed model. The computational results show that after risk management, risk of the expectation amount of captured and stored CO2 is reduced.

Semi-Empirical Computational Tool for Design of Air-Cooled Condensers

Many economic and environmental restrictions have resulted in the increase of use of dry cooling technology. An effort to minimize the consumption of water is one of main reasons why researchers and engineers are working on technologies for dry cooling which does not use water. Production of electricity in power plants is an important industrial activity where the wet cooling process is commonly utilized by means of cooling towers with a huge consumption of water which is evaporated into the atmosphere. An alternative technology for the withdrawal of the waste heat is the use of air-cooled condensers. Such condensers use the fan-forced air for water steam condensation and waste heat removal to the ambient environment. Apparently, the overall efficiency of the power plant is influenced by the design and performance characteristics of the air-cooled condenser. A proper setup and layout of the air-cooled condenser is therefore an important issue in the design and/or in the retrofits of power plants utilizing dry cooling systems and air-cooled condensers. A CFD analysis is a computational approach that is commonly utilized for the thermal analysis of the air-cooled condensers. However, CFD models and simulations are computationally demanding and often tricky. In the paper, the semi-empirical computational tool applicable for design and thermal investigations of air-cooled condensers is presented. The model is fast enough to complete simulations of operation of air-cooled condensers within dozens of minutes. The tool represents a unique combination of a simple numerical control-volume-based model of the air-cooled condenser which is coupled with empirical relationships gained from the literature. A good agreement between the semi-empirical model, data sheet parameters provided by producers of air-cooled condensers and experimentally gained data was achieved.

CFRP Application in Retrofitting of Masonry Wall

CFRP Application in Retrofitting of Masonry Wall

CFRP Application in Retrofitting of R.C.C Beam

CFRP Application in Retrofitting of R.C.C Beam

An Enhanced Tool for Heat Exchanger Network Retrofit Towards Cleaner Processes

The individual stream temperature versus enthalpy plot (STEP) is a graphical tool that can be used to simultaneously diagnose and retrofit existing heat exchanger networks (HEN). The Modified Energy Transfer Diagram (ETD) utilises the Grand Composite Curve (GCC) to provide insights on the scope for HEN retrofit and to pinpoint retrofit alternatives based on the Bridge Analysis method. Both the STEP and the Modified ETD methods are based on graphical representation of individual process streams that enable users to visually identify the potential scope for improvement in an existing HEN. It is found that, using the distance of the horizontal gap between the stream pairs of the STEP diagram can simplify the construction of the Modified ETD. The Modified ETD can help monitor the progress of HEN retrofit. This paper shows through a case study that, combining the use of STEP-ETD methods can simplify, facilitate and enhance the simultaneous targeting, diagnosis and retrofit of a HEN toward achieving cleaner processes, while yielding the same final retrofitted structure like those produced by using only the Modified ETD.

Energy retrofit of tower blocks in UK: making the case for an integrated approach

Tower blocks in UK are at a critical stage. They were built at a time when no energy efficiency requirements were considered. They are now approaching the end of their design service life and they are damp, and cold place to live. Starting from the analysis about the diffusion of multi-storey buildings in EU, and the findings of other research projects such as INSPIRE and Faro, this work debates the strategies applied for energy efficiency improvement of large panel concrete buildings. This work debates the structural retrofit that in many cases are required prior to any energy retrofit intervention and draw the attention on the necessity to develop more holistic retrofit approaches, aiming to the development of best practice for energy, safety and social benefits.

MedZEB: a new holistic approach for the deep energy retrofitting of residential buildings

The MedZEB (Mediterranean Zero Energy Building) approach aims at stimulating the market uptake of energy deep and beyond retrofitting of existing buildings of the Mediterranean. Its holistic nature implies the evaluation and integration of a range of relevant factors and the effective support to the retrofitting supply chain, also with the help of an ICT platform. Main concern of the approach are residential buildings within a framework dealing with High TRL levels and with already on the market technologies to be combined to create Med-specific cost-optimal Packages of technical Solutions, linked to a Voluntary Certification Scheme. The triggered creation of trust and information exchange will pave the way to new investments and strengthen the Med deep and beyond retrofitting network.

Direct displacement-based seismic assessment of concrete frames

Five previously-tested reinforced concrete frames were modelled using a nonlinear finite element analysis procedure to demonstrate the accurate response simulations for seismically-deficient frames through pushover analyses. The load capacities, story drifts, and failure modes were simulated. This procedure accounts for the effects of shear failures and the shearaxial force interaction, and thus is suitable for modeling seismically-deficient frames. It is demonstrated that a comprehensive analysis method with a capability of simulating material constitutive response and significant second-order mechanisms is essential in achieving a satisfactory response simulation. It is further shown that such analysis methods are invaluable in determining the expected seismic response, safety, and failure mode of the frame structures for a performance-based seismic evaluation. In addition, a new computer program was developed to aid researchers and engineers in the direct displacementbased seismic design process by assessing whether a frame structure meets the code-based performance requirements by analyzing the analysis results. As such, the proposed procedure facilitates the performance-based design of new buildings as well as the numerical assessment and retrofit design of existing buildings. A sample frame analysis was presented to demonstrate the application and verification of the approach.

Multi-scale and adaptive-mitigation design methods for climate resilient cities

Effectively addressing the issue of climate resilience in urban areas requires the development of innovative design methods that can handle the complexity of the information needed to guide sustainable urban regeneration and retrofitting strategies, as well as to manage the technological and environmental solutions in a multi-scale perspective. The paper presents the methodology developed by the ARC3-2 Urban Planning and Design working group of the Urban Climate Change Research Network (UCCRN) and the results of the experimental activities conducted within Studios and Workshops promoted in New York, Paris and Naples by the New York Institute of Technology, the Polytechnic of Milan and the University of Naples Federico II.

Climate vulnerability, impact scenarios and adaptation strategies for resilient cities

This paper deals with the results of the Research Project “METROPOLIS – Integrated and sustainable methods and technologies for resilience and safety in urban systems”, funded under PONREC 2007-2013. Among all the results of the work, the paper is focused on the development of a model to measure climate vulnerability in urban areas. The application of the model provides the assessment of impacts and the subsequent planning of corrective actions to increase building and urban resilience by means of technological retrofitting. The testing of the model for heat waves and pluvial flooding has been implemented in the urban system of Naples City which has been divided into the physical subsystem and the population subsystem.

Implementing a dual-touch 4-wire analog resistive touchscreen via regression analysis

As touch mania sweeps across many applications, a large number of venders seek to upgrade to dual-touch if not to multi-touch features, but cannot justify the price of capacitive touchscreens. To get around this, other methods - both legacy and cutting edge – are available. The idea is to create inexpensive alternatives to capacitive touchscreens or retrofit dual-touch/multi-touch gestures to existing resistive-touchscreen designs, for example. This paper introduces a new scheme to detect any dual-touch on an analog resistive touchscreen. A 4-wire version was chosen due to the simplicity of its structure. Both linear and polynomial regression, was used to support the ability of detecting any position. Four screen sizes, 4.3-inch, 5.7-inch, 7-inch, and 10.2-inch, were explored. The findings revealed that resistance changes during touch can be utilized for detecting the coordinates of finger(s), for a single-touch and any dual-touch. The maximum error across all screen sizes, evaluated by RMSE, is under 3mm from the exact position on both the X and Y-axes.

Influence of shear bolt connections on modular precast steel-concrete composites for track support structures

Through extensive research, there exist a new type of connection between railway bridge girders and steel-concrete composite panels. In addition to conventional shear connectors, newly developed blind bolts have been recently adopted for retrofitting. However, the body of knowledge on their influence and application to railway structures has not been thoroughly investigated. This study has thus placed a particular emphasis on the application of blind bolts on the Sydney Harbour Bridge as a feasible alternative constituent of railway track upgrading. Finite element modeling has been used to simulate the behaviours of the precast steel-concrete panels with common types of bolt connection using commercially available package, ABAQUS. The steel-concrete composite track slabs have been designed in accordance with Australian Standards AS5100. These precast steel-concrete panels are then numerically retrofitted by three types of most practical bold connections: head studded shear connector, Ajax blind bolt and Lindapter hollow bolt. The influences of bolt connections on load and stress transfers and structural behaviour of the composite track slabs are highlighted in this paper. The numerical results exhibit that all three bolts can distribute stresses effectively and can be installed on the bridge girder. However, it is also found that Lindapter hollow bolts are superior in minimising structural responses of the composite track slabs to train loading.

Experimental and numerical investigation of strengtheneddeficient steel SHS columns under axial compressive loads

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and over-loading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.

Seismic retrofit of a framed structure using damped cable systems

The purpose of this study is to investigate the effectiveness of damped cable systems (DCS) to mitigate the earthquake-induced responses of a building frame structure. The seismic performance of the DCS is investigated using the fragility analysis and life cycle cost evaluation of an existing building retrofitted with the DCS, and the results are compared with the structure retrofitted with conventional fluid viscous dampers. The comparison of the analysis results reveals that, due to the self-centering capability of the DCS, residual displacement approximately reaches to zero for the structure retrofitted with the DCS. The fragility analysis shows that the structure retrofitted with the DCS has the least probability of reaching the specific limit states compared to the bare structure and the structure with the conventional fluid viscous damper (VD), especially under the severe ground motions. It is also observed that both the initial and the life cycle costs of the DCS seismic retrofitting technique is lesser compare to the structure retrofitted with the VD.

Is PAD Worth It? Costs, Benefits, and Lessons Learned from the First PAD Retrofit in the US

Is PAD Worth It? Costs, Benefits, and Lessons Learned from the First PAD Retrofit in the US