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Alternatives for enhancing a cruise ship’s energy efficiency were investigated by introducing different waste heat recovery technologies and battery systems in the machinery. A ship designer’s in-house ship energy system simulator was applied in a cloud-based framework for simulation-based optimization. This multi-objective optimization with economic and environmental objectives used genetic algorithm for finding the best overall solution in a complex ship energy system design task. The results suggest that adding battery capacity alone contributes very moderately to reducing the case ship fuel consumption and, therefore, carbon emissions. Nevertheless, a combination of steam turbines and organic Rankine cycle units would offer the largest fuel saving potential with the lowest investment cost in the case setup. Also, the main engines’ running hours were of interest. The presented approach can bring significant added value for sustainable ship design with minimal additional effort.

A dynamic simulation of a modern ultra-supercritical circulating fluidized bed (USC-CFB) boiler system was performed using a physics-based model, where the boiler system was composed of an integrated system of heat exchanger (HEX) blocks. In each of the discretized elements of the HEX blocks, supercritical steam flow interacted with the solid–gas flow via heat transfer, and conservation laws, and physical phenomena of the CFB, and the supercritical steam flow was modeled to obtain the flow properties of each material side. By utilizing this model, the dynamic behavior of the main steam temperature, which was selected as the representative performance parameter for achieving safe and fast load changes, was simulated in response to changes applied to the main operating parameters such as the feedwater and fuel flow rates. The dynamic characteristics of the USC-CFB boiler were demonstrated by presenting the temperature responses of the steam and the circulating solid–gas after a step change in the feedwater and fuel flow rates. In the case of a load change, the dynamic response of the steam temperature was quantitatively presented by showing the transient overshoot and undershoot behavior, depending on the selection of the ramp speed when changing the feedwater and fuel flow rates. The steam temperature was also shown to be controlled by manipulating the inlet solid mass flow rate into the final superheater section of the external HEX. The comprehensive set of plant performance data that was generated from the model simulation can be utilized in setting up the operation strategies and/or in determining the control parameters for achieving stable steam temperature behavior during a load change.

In a circulating fluidized bed boiler, the large thermal mass and flow characteristics of the solids strongly affect the transient response of the circulating fluidized bed loop temperature, which determines the heat transfer rate to steam flow. Therefore, it is essential to interpret the dynamic response of the solid behavior in the circulating fluidized bed loop for the stable and efficient operation of the circulating fluidized bed boiler. In this study, the dynamic simulation of the solid behavior along with the flue gas flow in a circulating fluidized bed loop was performed by applying the core-annulus approach for the solid-gas flow inside the furnace and selected models for other physical phenomena of the fluidized bed. The circulating fluidized bed loop of a commercial boiler was selected as the target system. Especially, the model simulates the characteristics of the solid behavior, such as the local solid mass distribution, and the solid flow inside the furnace and the circulating solid according to the various operating conditions. These aspects are difficult to measure and quantify in a real power plant. In this paper, the simulated furnace temperature behavior as the representative performance parameter of the circulating fluidized bed loop was discussed along with the qualitative operation experiences reported in the literature. The operating conditions include the feed rate of fuel and air, the particle size, the solid inventory and the solid circulation rate. Furnace temperature behavior was reproduced through the simulation for each operating case in the literature and was analyzed with the solid behavior along with the combustion rate and heat transfer rate of the circulating fluidized bed loop. The simulation enables quantitative evaluation of the effect of the solid behavior on the temperatures of the furnace and return part in the various operating conditions.

Engineering efforts to handle contemporary energy supply challenges and mitigate pollutant emission lead towards more complicated systems. Power plants are supplementing with additional processing units, alternative production modes and higher level of automation. Wind and solar sources, biomass combustion, gasification, carbon capture and storage (CCS), and cogeneration have appeared as important players in the energy systems. The increasing complexity comprises a risk that the systems become less manageable and less stable than currently. Traditional steady-state engineering methods cannot fully address these challenges that are inherently dynamic in their nature. Dynamic process simulation appears as important tool to the systems design and optimisation tasks. A large variety of dynamic process modelling and simulation approaches has been presented recent years. This paper presents a brief review of methods and simulation packages that are generally applied for studying energy systems' transient behaviour. A CCS capable power plant is presented as an example of utilizing dynamic process simulation for virtual evaluation of a novel electricity production concept. The modelling was performed using two simulators Apros and Aspen Plus Dynamics, which were linked together for dynamic simulating the full chain of cryogenic oxygen distillation, oxy combustion, turbine islands and carbon dioxide purification and liquefaction operations.

Dynamic thermal-hydraulic simulation models have been extensively used by process industry for decision support in sectors such as power generation, mineral processing, pulp and paper, and oil and gas. Ever-growing competitiveness in the process industry forces experts to rely even more on dynamic simulation results to take decisions across the process plant lifecycle. However, time-consuming development of simulation models increases model generation costs, limiting their use in a wider number of applications. Detailed 3D plant models, developed during early plant engineering for process design, could potentially be used as a source of information to enable rapid development of high-fidelity simulation models. This paper presents a method for automatic generation of a thermal-hydraulic process simulation model from a 3D plant model. Process structure, dimensioning and component connection information included in the 3D plant model is extracted from the machine-readable export of the 3D design tool and used to automatically generate and configure a dynamic thermal-hydraulic simulation model. In particular, information about the piping dimensions and elevations is retrieved from the 3D plant model and used to calculate head loss coefficients of the pipelines and to configure the piping network model. This step, not considered in previous studies, is crucial for obtaining high-fidelity industrial process models. The proposed method is tested using a laboratory process and the results of the automatically generated model are compared with experimental data from the physical system as well as with a simulation model developed using design data utilized by existing methods on the state-of-the-art. Results show that the proposed method is able to generate high-fidelity models which are able to accurately predict the targeted system, even during operational transients.

Dynamic modelling and simulation offers a way to investigate the transient behavior of thermal energy storage (TES) systems. Most modelling work presented in literature focuses only to sub-processes of a TES facility, especially, if the comparison against experimental data is included. In this study, we combine experimental and computational work, and aim at modelling and investigating the whole TES system. We share experiences gained and discuss results, including the experiments planning, modelling scope, measurement uncertainty, heat exchange, heat losses, calibration and validation.Dynamic modelling and simulation offers a way to investigate the transient behavior of thermal energy storage (TES) systems. Most modelling work presented in literature focuses only to sub-processes of a TES facility, especially, if the comparison against experimental data is included. In this study, we combine experimental and computational work, and aim at modelling and investigating the whole TES system. We share experiences gained and discuss results, including the experiments planning, modelling scope, measurement uncertainty, heat exchange, heat losses, calibration and validation.

Energy efficiency has become increasingly important to ship owners and builders, due to fuel costs and tightening environmental regulations, but also due to public opinion and expectation for green technology. Improved energy efficiency and significant savings are achievable by increasing waste heat utilization. A probable side effect of commissioning new technology is increased system complexity. This makes it more difficult to make design decisions between alternative technologies; also, the operation of the system needs more attention. Dynamic system level simulation has been used for energy systems analysis already for decades in onshore energy industry; now it is increasingly applied in marine engineering. In this study a commercial simulator Apros was used to model and simulate energy systems of a cruise ferry Viking Grace, which features novel energy saving solutions, such as a waste heat accumulator system and cooling options by liquefied natural gas (LNG) vaporizing, and by seawater. Dynamic models of these systems were developed and validated against available measurement data. The study showed that modelling and dynamic system level simulation can provide substantial benefits in the design of energy efficient ship in new buildings, and in existing ships.

Supercritical carbon dioxide (sCO2) has recently gained a lot of interest as a working fluid in different power generation applications. For concentrated solar power (CSP) applications, sCO2 provides especially interesting option if it could be used both as the heat transfer fluid (HTF) in the solar field and as the working fluid in the power conversion unit. This work presents development of a dynamic model of CSP plant concept, in which sCO2 is used for extracting the solar heat in Linear Fresnel collector field, and directly applied as the working fluid in the recuperative Brayton cycle; these both in a single flow loop. We consider the dynamic model is capable to predict the system behavior in typical operational transients in a physically plausible way. The novel concept was tested through simulation cases under different weather conditions. The results suggest that the concept can be successfully controlled and operated in the supercritical region to generate electric power during the daytime, and perform start-up and shut down procedures in order to stay overnight in sub-critical conditions. Besides the normal daily operation, the control system was demonstrated to manage disturbances due to sudden irradiance changes.

In large and complex processes use of simulators will take place more and more in the future to avoid and learn about transients and unexpected situations. There are plenty of dynamic simulation tools in the markets but most of them have been developed and used for quite specific and limited application areas. At the moment there are just few simulation tools which are capable to handle dynamically in the same simulation case challenging process areas like combustion, distillation, chemistry and control of very large process areas. For this reason, in this study, there was a need to carry out co–simulation where two dynamic simulation tools Apros and Aspen Plus Dynamics were combined together by using Matlab Simulink as an interface. The co–simulation approach was a way to construct large dynamic process simulation environment, where typical operational transients and failure situations of an oxy fired power plant were possible to test and analyze. Under EU 7th Framework Programme (FP7) the FLEXI BURN CFB project an oxy firing concept based on circulated fluidized bed (CFB) combustion and supercritical once-through (OTU) water steam cycle was developed and successfully demonstrated [1] . This project also generated a dynamic simulation model of the 1st generation oxy firing concept, as we call it. In the EU 7th Framework Program's project O2GEN (Optimization of Oxygen-based CFBC Technology with CO2 capture), the 2nd generation concept of CFB based oxy firing was developed. The target of the project was, at first, to increase O2 content in recirculated flue gas to see what kind of effect it has to the heat exchange and corrosion in the boiler. Secondly, the target was to carry out exergy analysis to increase the whole concept efficiency by decreasing energy consumption in the boiler, Air Separation Unit (ASU) and CO2 -purification unit (CPU). Based on these steady state analysis means the refined concept was then modelled for dynamic simulations which were carried out by using Apros and Aspen Plus Dynamics dynamic modelling tools in a co–simulation mode. This paper deals with dynamic simulation of the 2nd generation 600 MW oxy fired CFB once trough boiler. In this paper we will present the dynamic model which includes oxy fired CFB boiler, turbine island, ASU and CPU with all needed equipment like heat exchangers, pipes, pumps, air and fuel feeding systems, distillation columns and sequestration vessels. Automation like measurements, controllers and actuators are included in the model. The simulation case selected for this paper presents an analysis what happens when one of the oxidant fans trips on boiler full load operation and how to handle this kind of failure by decreasing the boiler load to sufficient level of regarding the available oxidant feeding capacity. There were several items which were taken into account in the boiler, turbine island, ASU and CPU side when this kind of failure takes impact. The main findings in the failure analysis will be presented. Finally, discussion and future aspects of the simulation approach described will be given.

Dynamic process simulation provides a tool to evaluate operational issues of a new process concept before the plant construction. This paper studies a carbon capture and storage (CCS) capable power plant concept with a model including a supercritical once-through CFB boiler with gas and water steam sides, a turbine island, an interface from the air separation unit (ASU) and the control system to manage typical operational transients. Switching between the air and oxy firing modes is one of the key operations in oxy combustion processes. The selected mode switching strategy uses simultaneous linear ramps for the mass flows of the primary and secondary air, oxygen, and recirculated flue gas. The results show that the firing mode can be successfully switched within 25–37 min. The flue gas path difference between the air-firing and oxy-firing modes due to the flue gas recirculation causes significant differences in dynamic behaviour. The simulations emphasize importance of good control and coordination of the gas flows. Feedback control of the flue gas and/or oxidants O 2 content during the mode switching is suggested to improve robustness against disturbances, for example, in oxygen delivery, flow measurements, fuel feeding and combustion.

The purpose of this paper is to present a method for assessing whether optimized process design and operations, based on simplified simulation models, can be carried towards real life. The proposed method relies on a more realistic, or if available, a set of more and more realistic simulation models being compared with the original model utilized in the optimization problem. The models which are utilized are dynamic and stochastic in nature, necessitating statistical analyses of the results. The method is applied recursively to a generic papermaking process model with the addition of increasingly more realistic modifications. It is shown how the proposed comparison method detects the effects of such modifications and thus provides information on how well the optimization results are applicable to real life situations. The purpose of the presented method is to add one element to an overall framework of simulation-aided process design.

A dynamic simulation model of a 3-layer board machine was developed. The simulation model consists of stock preparation and proportioning, short circulations, wire and press sections, and drying section including the steam and condensate systems. Physical, first principles models were used whenever possible. The control system and automatic grade change program were modelled as well. The simulator was extensively validated against measurements. Two simulation cases concerning grade changes are discussed: re-tuning of the automatic grade change program, and studying the potential of a new dryer.

OBJECTIVE Transcription factor NF-E2-related factor 2 (Nrf2) regulates antioxidant and detoxifying enzymes affording cytoprotection in the cardiovascular system. We have previously reported that Nrf2 deficiency specific to bone marrow derived cells aggravates atherosclerosis in LDL receptor deficient (LDLR-/-) mice. Furthermore, Nrf2 deficiency in macrophages enhances foam cell formation and promotes the proinflammatory phenotype. In contrast, the total loss of Nrf2 has been shown to protect against atherogenesis in apoE-deficient mice. The mechanism by which Nrf2 deficiency affords atheroprotection in apoE-model is currently unknown, but combined systemic and local vascular effects have been proposed. Given these contrasting results, we aimed at assessing the effect of total loss of Nrf2 on atherogenesis in hypercholesterolemic LDLR-/- mice. METHODS AND RESULTS Nrf2-/- mice were cross-bred to LDLR-/- mice and fed a high fat diet (HFD) for 6 or 12 weeks. The degree of atherosclerosis was assessed from the cross-sections of proximal aorta. Nrf2 deficiency decreased atherosclerosis in females from 17.2±8.7 % (mean ±SD, n=11-25) to 12.3±4.6 % (p=0.1) and in males from 11.2±3.9 % to 7.6±4.6 % (p=0.025) after 6 weeks on HFD. After 12 weeks on HFD the effects were more pronounced, as Nrf2 deficiency decreased atherosclerosis from 36.5±5.5 % to 30.3±3.5 % in females (p=0.001) and from 30.6±5.7 % to 21.3±6.9 % in males (p=0.005). Nrf2 deficiency also increased the macrophage content relative to lesion area. Supporting systemic effects, Nrf2 deficiency reduced plasma total cholesterol from 24.0±8.4 mmol/l to 10.6±6,7 mmol/l (p=0.006) and triglyceride levels from 3.6±1.4 mmol/l to 1.7±1.2 mmol/l (p=0.008) in males after 6 weeks on HFD. CONCLUSIONS In contrast to bone marrow specific Nrf2 deficiency, total loss of Nrf2 aggravates atherosclerosis in LDLR-/- mice likely via systemic effects on lipid metabolism.

A dynamic simulation model of a 3-ply paperboard production process was developed. The simulation model consists of stock preparation and proportioning, short circulations, wire and press sections, and 75 drying cylinders including the steam and condensate system. Functionality of the automatic grade change program used on the machine was modeled as well. Physical, first principles models were used whenever possible. Simulator was extensively validated using historical data. The simulator has been used as a test bench in order to find better values for automatic grade change parameters. First set of the new simulator tested parameters has been carried out to the real machine with good results.

A simulation environment for the dynamic simulation of paper or board mills has been developed. APMS (advanced paper mill simulator) provides tools for fast and easy modelling of the plant comprising e.g. stock preparation, approach system, wet end and dry end of the machine. The models are based on the first principles of physics and chemistry whenever it is possible. This mechanistic modelling principle with efficient equation solution techniques ensures fast and accurate simulation for the purposes of process and automation design, analysis and operator training.

Automation awareness (AA) can be defined as user's conception of the utilized automation system's state in such a manner that enables the user to observe, control, and anticipate the process events mediated by automation. In this paper, we report a study where we utilized a customized simulation system to assess AA. The simulator included a process and automation model with emulated user interface displays for an emergency diesel generator system in a nuclear power plant. The results suggest that in addition to user-related factors, such as the users' automation-specific education, experience, and provided training, the quality of the automation system's user interface is a significant contributor to the development of AA; especially the digital presentation of the measurement values, graphical format of the values' status and their automation-related limits as well as illustrative trend displays seem to improve AA considerably.

It is often difficult for the operators and researchers to completely understand the complex behavior of the kiln. This is because of the many different phenomena inside the lime kiln and because of the slowness of the process. Dynamic simulation has been adapted as a powerful method for studying transient behavior of the process. When the most important chemical and physical phenomena are modelled using basic conformities of physical and chemical laws, the process can be studied in the computer environment and a better general understanding of the kiln can be gained. The model illustrated in this paper has been developed as a part of a larger simulation environment, APMS (Advanced Paper and Pulp Mill Simulator). The physical and chemical phenomena modeled in this work are water evaporation, calcining reaction, solid movement, gas flow, heat transfer inside the kiln, heat transfer through the wall and mass transfer between solid and gas phases. Also the burner, the draft fan and the automation related to these components have been modeled. The goal in the modeling process was to keep the models of the individual phenomena simple enough in order to achieve fast simulation, which is essential for training purposes. On the other hand, the used mechanistic models describe the process in a detailed way. Another aim was to make the model so general that it could be applied to different kilns. This means that the structure of the model is flexible enough for fast reparametrization. The validation of the model was done using process data from the Metsä-Sellu Äänekoski Mill. There are only a few measurements from the kiln so the comparison of the model with the real process had to be done with limited data. Temperatures in the hot and cold ends of the kiln as well as the outside temperature profiles measured with an infrared camera were the bench marks to compare with. These tests prove that the dynamic behavior of the model is logical and also the quantitative results are accurate in reasonable limits. Both steady state and dynamic results are shown in this paper. Also comparison to measured data is presented. When the simulator is used for operator training purposes a graphical user interface has a significant importance. In this work also a web user interface for the model has been developed. This enables flexible demonstration and training sessions.

The purpose of this work is to show that global sensitivity analysis combined with a process simulator can be used as a method of identifying process bottlenecks in the papermaking context. A variancedecomposition based Sobol' analysis is employed in three case studies with Aprosr Paper simulator. The results give evidence that the method is applicable in detecting process bottlenecks and can thus provide the process designer with useful information.