Suraya Hanim Abu Bakar

Sensitivity analysis of industrial heat exchanger network design

The problem of interaction between economic design and controller design of heat exchanger network (HEN) is addressed in this work. The feasibility and sensitivity issues are incorporated in the classical design of HEN. HENs in industry seem to be very efficiently operated. The network that may have operated efficiently perhaps is the one that is not fully optimised in term of flexibility and sensitivity. It is important to do synthesis and sensitivity analyses of the designed network. The objective of this paper is to investigate and compare the sensitivity criteria of the originally designed HEN of the fatty acid fractionation process (FAFP) and the new HEN design. In this study, the HEN designs are already fixed at the value of ?Tmin = 40 °C. A new suggested HEN is redesigned from the original HEN of FAFP plant by obeying Pinch Analysis (PA) rules. The new HEN was redesigned by applying the PA stream splitting compared to the original HEN (that has been used in the industry), in which the design is not have stream splitting. The aim of this work is to determine the best optimised design whether the one that not followed Pinch Analysis rules or the other one. Using the new developed FNO HEN methodology framework, sensitivity analysis was applied which consists of two tests: 1) Flexibility Analysis and 2) Sensitivity Analysis. According to the results, the best candidate that satisfies the sensitivity and economy criteria is the new HEN design. It can be concluded that it is important to do stream splitting in order to obtain not only the best HEN in terms of design and economy criteria, but also in the matter of sensitivity criteria.

An industrial case study application in synthesizing a feasible heat exchanger network

Heat exchanger network synthesis (HENS) is an important part in the overall chemical process. HENS links the process flowsheet with the utility system and generally involves a large fraction of both the overall plant capital cost, operating costs in terms of energy requirements, which is a key factor for a profitable process. The aims of the synthesis consist of finding a network design that minimises the total annualised cost, i.e. the investment cost in units and the operating cost in terms of utility consumption. In HENS, the feasibility of the HEN design does not take into consideration. As a consequence, the HEN design may not be able to be implemented into industrial applications. It is essential to check the feasibility of a design before it is being implemented into the industry. The objective of this paper is to present the application of a new flexible and operable heat exchanger network (FNO HEN) methodology in synthesising a feasible heat exchanger network (F-HEN) using an industrial case study. The aim of this work is to verify the existing industrial HEN design in terms of the process design point of view as well as the process feasibility. The existing industrial HEN design is verified in terms of Tmin value that gives minimum external energy requirement (EER) and heat exchanger area (HEA) as well as simultaneously analyse the feasibility of the HEN design. Using the new developed FNO HEN methodology framework, HEN design target, which is the value of Tmin is determined in order to obtain the F-HEN design. From process design point of view, Tmin value determines the size of heat exchanger in the network as well as energy saving. A process simulator is used to check the process feasibility of the HEN designs. With the use of the F-HEN trade-off plot, which is a plot of EER and HEA at different value of Tmin. with additional of feasibility area, the optimal feasible HEN design which satisfies external energy requirement (operability), heat exchanger area (capital) and process feasibility has been successfully determined in an easy, systematic and efficient manner.

Initial analysis on heat exchanger networks of fatty acid fractionation plant to optimize energy recovery and controllability

The objective of this paper is to present the initial analysis on the energy recovery and controllability of the existing heat integrated fatty acid fractionation plant. From this initial analysis, the existing heat integrated fatty acid fractionation plant is analysed to know the either the existing heat exchanger networks (HENs) satisfied the design criteria, or controllability criteria by using trade-off plot. According to the trade-off plot, if the existing HENs is better in terms of design criteria, then more efforts need to be invested to control the network. On the other hand, if the existing HENs is better in terms of controllability criteria, then more efforts need to be invested to reduce the energy consumption. In this study, the initial analysis means the value of the ?Tmin used for the current HENs is investigated and the controllability of the network is predicted by using trade-off plot. In order to investigate the value of the ?Tmin used for the current HENs, only the first two stages of the model-based flexible and operable HENs is used. In the Stage 1, the value of the ?Tmin is investigated by selecting the value of the ?Tmin ranging from 10 °C to 40 °C with the increment of 10 °C. Then, HEN is synthesized for the selected value of the ?Tmin. Once the networks have been synthesized, all candidates are transferred into a process simulator to test their process feasibility in Stage 2 where the unfeasible candidates will be eliminated. Then all feasible candidates will be predicted in terms of their controllability performance by using trade-off plot. Energy integrated fatty acid fractionation plant is used as a case study for this initial analysis. This paper only considers steady state controllability test without considering process dynamics.

Feasibility, Flexibility, and Sensitivity Tests on Delta Temperature Minimum to Obtain Operable and Flexible Heat Exchanger Network

This paper explains about the controllability effect on delta temperature minimum (ΔTmin) in order to get flexible and operable heat exchanger network (HEN). There are many researches based on design and cost effect to ΔTmincontribution. However, there are lacks of study on how the ΔTmineffect to controllability of HENs. Therefore, this paper focuses on controllability analysis of different HENs design based on ΔTmincontribution. There are six HEN designs were obtained from different ΔTminvalues such as 20°C, 25°C, 30°C, 35°C, 40°C and 50°C and has been analyzed. The analysis consists of three different controllability tests which are feasibility, flexibility and sensitivity. Feasibility test is used to check either the HEN design is feasible or not. Next, the feasible HEN design is then analyzed in terms of flexibility. The flexibility test is used to calculate the design flexibility in terms of how much the percentage the design can handle under uncertainties. Lastly is to test the process sensitivity with respect to disturbance changes. Throughout the controllability tests, several options for control structure were built and analyzed. A simple HEN case study was used to analyze the controllability.