Simulation of hydrogen production for mobile fuel cell applications via autothermal reforming of methane

This paper presents a simulation of catalytic autothermal reforming (ATR) of methane (CH4) for hydrogen (H2) production. ATR is essentially an oxidative steam reforming, which combines the exothermic partial oxidation (PO) with the endothermic steam reforming (SR) under thermally neutral conditions. A model is developed using HYSYS 2004.1 to simulate the conversion behavior of the reformer. The model covers all aspects of major chemical kinetics and heat and mass transfer phenomena in the reformer. The ATR and preferential oxidation (PrOx) processes is modeled using conversion reactor, while the water gas shift (WGS) process is modeled using equilibrium reactor within HYSYS environment. The conditions used for high CH4 conversion and high H2 yield are at air to fuel ratio of 2.5 and water to fuel ratio of 1.5. Under this condition, CH4 conversion of 100% and H2 yield of 44% on wet basis can be achieved and the system efficiency is about 87.7%

Active statistical process control

PhD ThesisMost Statistical Process Control (SPC) research has focused on the development of charting techniques for process monitoring. Unfortunately, little attention has been paid to the importance of bringing the process in control automatically via these charting techniques. This thesis shows that by drawing upon concepts from Automatic Process Control (APC), it is possible to devise schemes whereby the process is monitored and automatically controlled via SPC procedures. It is shown that Partial Correlation Analysis (PCorrA) or Principal Component Analysis (PCA) can be used to determine the variables that have to be monitored and manipulated as well as the corresponding control laws. We call this proposed procedure Active SPC and the capabilities of various strategies that arise are demonstrated by application to a simulated reaction process. Reactor product concentration was controlled using different manipulated input configurations e.g. manipulating all input variables, manipulating only two input variables, and manipulating only a single input variable. The last two manipulating schemes consider the cases when all input variables can be measured on-line but not all can be manipulated on-line. Different types of control charts are also tested with the new Active SPC method e.g. Shewhart chart with action limits; Shewhart chart with action and warning limits for individual observations, and lastly the Exponentially Weighted Moving Average control chart. The effects of calculating control limits on-line to accommodate possible changes in process characteristics were also studied. The results indicate that the use of the Exponentially Weighted Moving Average control chart, with limits calculated using Partial Correlations, showed the best promise for further development. It is also shown that this particular combination could provide better performance than the common Proportional Integral (PI) controller when manipulations incur costs.Commonwealth Scholarship Commission: British Council: Universiti Telcnologi, Malaysia

Fault detection and diagnosis using Multivariate Statistical Process Control (MSPC)

Currently, chemical plants face numerous challenges like stringent requirements are needed on the desired final product quality, utilization of a lot of energy, must be environmentally friendly and fulfill safety requirements. High operation cost is needed in order for chemical plants to overcome the stated challenges. Any faults that are present in a chemical process will yield higher operation cost on the plant due to increase in production of waste, re-work, re-processing and consumption of utilities. Therefore, accurate process fault detection and diagnosis (FDD) on a chemical process at an early stage is important to reduce the cost of operation due to present of faults

Energy efficient distillation columns sequence for hydrocarbon mixtures fractionation process

The objective of this paper is to present the study and analysis of the energy saving improvement for the hydrocarbon mixtures (HM) fractionation process by using driving force method. To perform the study and analysis, the energy efficient HM fractionation plant methodology is developed. Accordingly, the methodology consists of four hierarchical steps; step 1: existing HM sequence energy analysis, step 2: optimal HM sequence determination, step 3: optimal HM sequence energy analysis, and step 4: energy comparison and economic analysis. In the first step, a simple and reliable short-cut method of process simulator (Aspen HYSYS) is used to simulate a base (existing) HM sequence. The energy used to recover individual fractions in the base sequence is analyzed and taken as a reference. In the second stage, an optimal HM sequence is determined by using driving force method. All individual driving force curves for all adjacent components are plotted and the optimal sequence is determined based on the plotted driving force curves. Once the optimal HM sequence has been determined, the new optimal sequence is then simulated in step three using a simple and reliable short-cut method (using Aspen HYSYS), where the energy used in the optimal HM sequence is analyzed. Finally, the energy used in the optimal HMs sequence is compared with the base sequence. The return of investment (ROI) and simple payback period are also calculated. Several case studies have been used to test the performance of the developed methodology. The results show that a maximum energy saving of 40% was achieved when compared the optimal (driving force) sequence with the existing direct sequence. The ROI of 3 was obtained with 4 month of payback period. It can be concluded that, the sequence determined by the driving force method is able to reduce energy used for HM fractionation process. Individual column energy has also been analyzed, and from that several columns that can be improved in terms of energy saving have been identified. All of this findings show that the methodology is able to design minimum energy distillation column sequence for HM fractionation process in an easy, practical and systematic manner

Energy efficient distillation columns analysis for aromatic separation process

Distillation operations became a major concern within energy savings challenge, which it becomes a primary target of energy saving efforts in industrially developed countries. However, there is still one problem, which is how do we improve the energy efficiency of the existing distillation columns systems by without having major modifications. Recently, a new energy efficient distillation columns methodology that will able to improve energy efficiency of the existing separation systems without having major modifications has been developed. Therefore, the objective of this paper is to present new improvement of existing methodology by designing an optimal sequence of energy efficient distillation columns using driving force method. Accordingly, the methodology is divided into four hierarchical sequential stages: i) existing sequence energy analysis, ii) optimal sequence determination, iii) optimal sequence energy analysis, and iv) energy comparison and economic analysis. In the first stage, a simple and reliable short-cut method is used to simulate a base (existing) sequence. The energy consumption of the base sequence is calculated and taken as a reference for the next stage. In the second stage, an optimal sequence is determined by using driving force method. All individual driving force curves is plotted and the optimal sequence is determined based on the plotted driving force curves. Then, by using a short-cut method, the new optimal sequence is simulated and the new energy consumption is calculated in the third stage. Lastly, in the fourth stage, the energy consumption for both sequences (base and optimal) is compared. The capability of this methodology is tested in designing an optimal synthesis of energy efficient distillation columns sequence of aromatics separation unit. The existing aromatics separation unit consists of six compounds (Methylcyclopentane (MCP), Benzene, Methylcyclohexane (MCH), Toluene, m-Xylene and o-Xylene) with five direct sequence distillation columns is simulated using a simple and reliable short-cut method and rigorous within Aspen HYSYS® simulation environment. The energy and economic analysis is performed and shows that the optimal sequence determined by the driving force method has better energy reduction with total of 6.78% energy savings and return of investment of 3.10 with payback period of 4 months. It can be concluded that, the sequence determined by the driving force method is not only capable in reducing energy consumption, but also has better economic cost for aromatic separation unit

Sustainable energy efficient distillation columns sequence design of aromatic separation unit

Distillation operations became a major concern within sustainability challenge, which it becomes a primary target of energy saving efforts in industrially developed countries. However, there is still one problem, which is how do we improve the energy efficiency of the existing distillation columns systems by considering the sustainability criteria without having major modifications. Recently, a new energy efficient distillation columns methodology that will able to improve energy efficiency of the existing separation systems without having major modifications has been developed. However, this developed methodology was only considered the energy savings without taking into consideration the sustainability criteria. Therefore, the objective of this paper is to present new improvement of existing methodology by including a sustainability analysis to design an optimal sequence of energy efficient distillation columns. Accordingly, the methodology is divided into four hierarchical sequential stages: i) existing sequence sustainability analysis, ii) optimal sequence determination, iii) optimal sequence sustainability analysis, and iv) sustainability comparison. In the first stage, a simple and reliable short-cut method is used to simulate a base (existing) sequence. The sustainability index of the base sequence is calculated and taken as a reference for the next stage. In the second stage, an optimal sequence is determined by using driving force method. All individual driving force curves is plotted and the optimal sequence is determined based on the plotted driving force curves. Then, by using a short-cut method, the new optimal sequence is simulated and the new sustainability index is calculated in the third stage. Lastly, in the fourth stage, the sustainability index for both sequences (base and optimal) is compared. The capability of this methodology is tested in designing an optimal sustainable energy efficient distillation columns sequence of aromatics separation unit. The existing aromatics separation unit consists of six compounds (Methylcyclopentane (MCP), Benzene, Methylcyclohexane (MCH), Toluene, m-Xylene and o-Xylene) with five direct sequence distillation columns is simulated using a simple and reliable short-cut method and rigorous within Aspen HYSYS simulation environment. The energy and sustainability analysis is performed and shows that the optimal sequence determined by the driving force method has better energy reduction with total of 6.78 % energy savings and 0.16 % sustainability reduction compared to existing sequence with. In addition, the economic analysis shows that the return of investment of 3.10 with payback period of 4 months. It can be concluded that, the sequence determined by the driving force method is not only capable in reducing energy consumption, but also has better sustainability index for aromatic separation unit

Sustainable design improvement for direct-indirect sequence of aromatic separation process

Distillation operations became a major concern within sustainability challenge, which it becomes a primary target of energy saving efforts in industrially developed countries. However, there is still one problem, which is how do we improve the energy efficiency of the existing distillation columns systems by considering the sustainability criteria without having major modifications. Recently, a new energy efficient distillation columns methodology that will able to improve energy efficiency of the existing separation systems without having major modifications has been developed. After all, this developed methodology was only considered the energy savings without taking into consideration the sustainability criteria

Temperature dependence of power generation of empty fruit bunch (EFB) based microbial fuel cell

Microbial fuel cell has been considered a new emerging technology for renewable and sustainable electricity production. The energy can be extracted from organic waste materials which time independently increase in mass. In the present study, it was demonstrated that lignocellulosic material such as empty fruit bunch (EFB) can be used to produce electricity. Clostridium cellulolyticum and Bacilli E1 were used to activate EFB degradation and electricity generation respectively. It was also demonstrated that the present EFB based MFC was affected in terms of power produced with much higher power was obtained at 37.5 ℃ with power value of 825 ± 3.08 mW/m2 compared to 25 and 50 ℃, which produced 756 ± 1.14 mW/m2 and 345 ± 1.78 mW/m2. At elevated temperature (50 ℃) showed decrease of power density value compared to lower temperature operated MFC, which is believed to be microbial metabolism dependent

Optimal synthesis of energy efficiency improvement for NGLS indirect sequence fractionation unit

Once natural gas liquids (NGLs) have been separated from natural gas stream, they are further separated into their component parts, or fractions, using a distillation process known as fractionation. Distillation is the primary separation process widely used in the natural gas processing. Although it has many advantages, the main drawback is its large energy requirement, which can significantly influence the overall plant profitability. Another question that needs to be answered here is there any systematic study and analysis to improve energy saving for the NGLs fractionation plant without having major modifications to the separation units, which is more practical to implement. The large energy requirement of these processes can be systematically reduced by determining the optimal sequence using driving force method. Therefore, the objective of this paper is to present the study and analysis of the energy saving improvement for the NGLs fractionation plant by using driving force method which will require only minor or less modifications to the separation units. Generally, the concept of driving force was applied in designing an energy efficient distillation column [Gani and Bek-Pedersen, 2004]. However, the concept has been extended its application in designing energy efficient distillation columns sequence [Mustafa et. al., 2014]. To perform the studies and analysis, the energy efficient NGLs fractionation plant methodology is developed. Basically, the methodology consists of four hierarchical steps. In the first step, the energy that is obtained from the base NGLs sequence will be used as guidance for the next step where the base NGLs sequence is developed from a simple and reliable short-cut method. In the second step, the energy efficiency in distillation column will be improved through driving force method where the optimum sequence will be determined in this step. In the third step, the optimum sequence was analyzed in term of energy analysis by using a simple and reliable shortcut method distillation column in Aspen HYSYS environment. In the final step, the comparison between the existing sequence and the optimum sequence by using driving force method will be done and at the same time the economic performance for the optimum sequence is also evaluated in this step. Then, the return of investment (ROI) will be calculated to make sure that the proposed modification to improve energy saving is practical. The capability of this methodology is tested in designing an optimal energy efficient distillation columns sequence of NGLs fractionation unit. The existing NGLs fractionation unit consists of nine compounds (methane, ethane, propane, i-butane, nbutane, i-pentane, n-pentane, n-hexane, n-heptane) with direct-splitter-direct sequence was simulated using a simple and reliable short-cut method within Aspen HYSYS environment. A total of 519.68 MW energy used to achieve 99.9% of product recovery. A new optimal sequence determined by driving force method was simulated using a short-cut method within Aspen HYSYS environment where a total of 376.60 MW of energy was used of the same product recovery. The results show that the maximum of 27.53 % energy reduction was able to achieve by changing the sequence suggested by the driving force method. It can be concluded that, the sequence determined by the driving force method is able to reduce energy used for NGLs fractionation. All of this findings show that the methodology is able to design energy efficient distillation columns for NGLs fractionation sequence in an easy, practical and systematic manner

Fault detection and diagnosis, FDD via improved univariate statistical process control charts, USPC

A new approach for detecting and diagnosing fault via correlation technique is introduced in this study. The correlation coefficient is determined using multivariate analysis technique, Partial Correlation Analysis (PCorrA). Individual charting technique such as Shewhart, Exponential Weight Moving Average (EWMA), and Moving Average and Moving Range (MAMR) charts are a used to facilitate the Fault Detection and Diagnosis (FDD). A precut multi component distillation is used as the case study in this work. Based on the result from this study Shewhart control chart gives the best performance with the highest FDD efficiency