​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Process Dynamics Simulation

Process dynamics simulation involves creating a dynamic model of a chemical process to analyse and predict its behaviour over time. Unlike steady-state simulations, which assume the system is in equilibrium, dynamic simulations account for changes in process conditions, such as variations in feedstock, temperature, pressure, or other operating parameters. We are process simulation consultants, offering expert process modelling services backed by over 50 years of combined process engineering experience. Our team of engineers, holding advanced degrees in chemical engineering, brings unparalleled expertise to every project. We specialise in dynamic modelling to analyse and optimise processes, ensuring they operate efficiently and safely. Whether it is transient analysis, control system design, or safety evaluation, our comprehensive approach and deep industry knowledge guarantee superior solutions tailored to your specific needs.​​

Process Dynamics Simulation of Pressure Swing Adsorption

Pressure Swing Adsorption (PSA) is a widely used gas separation technology that plays a crucial role in hydrogen fuel production. It is a process that relies on the different adsorption capacities of various gases on a solid adsorbent material under different pressures. PSA is particularly valuable in applications where high-purity hydrogen gas is required, such as hydrogen fuel production for fuel cells.

Within the context of hydrogen fuel production, PSA is commonly used to purify hydrogen gas streams obtained from various sources (such as natural gas, water electrolysis, or biomass conversion) and upgrade them to high-purity levels suitable for use in fuel cells or other applications.

The process involves several steps:

Adsorption: The gas mixture (which usually contains hydrogen along with impurities like N2, CO2 and other trace gases) is introduced into a vessel containing a specialised adsorbent material. This material selectively adsorbs impurities with stronger affinity than hydrogen.

Pressurisation: The vessel is pressurised, which enhances the adsorption of the impurities onto the adsorbent material. This causes the hydrogen gas to be released and collected as a relatively pure stream.

Depressurisation (Desorption): The pressure in the vessel is reduced, causing the adsorbent material to release the adsorbed impurities. The released gases are then vented out of the H2 production system.

Purification: The process of pressurisation and depressurisation cycles (also known as "swing" cycles) is repeated multiple times to continually remove impurities from the hydrogen gas stream, thus purifying it to the desired level.

Hydrogen Recovery: The purified hydrogen gas is collected and stored for use in various applications, including as a clean fuel for fuel cells that produce electricity through a chemical reaction between hydrogen and oxygen.

The illustrations below show the process dynamics simulation of pressure swing adsorption (PSA).

advantages of using PSA for hydrogen production

Selectivity: Different adsorbents can be tailored to selectively adsorb specific impurities, resulting in high-purity hydrogen gas.
Reliability: PSA systems are robust and reliable, making them suitable for continuous operation.
Energy Efficiency: The process is based on pressure changes rather than extensive heating and cooling, making it relatively energy-efficient.
Scalability: PSA systems can be scaled up for various production capacities, making them suitable for a range of applications.

Plant Engineering Design - Jimmy Lea P/L

Benefits of Performing Process Dynamics Simulation

Employing process dynamics simulation offers numerous advantages across various aspects of process engineering and operations. Below are several key benefits:

Enhanced Process Understanding: By simulating the dynamic behaviour of processes, engineers gain a deeper understanding of how systems respond to changes over time. This knowledge is crucial for identifying potential issues and optimising operations.

Improved Control System Design: Dynamic simulations enable the design and testing of control strategies in a virtual environment. This helps in developing robust control systems that can maintain optimal operating conditions, improve product quality and enhance process stability.

Increased Safety: Simulating dynamic scenarios allows for the identification and mitigation of potential hazards before they occur in real operations. This proactive approach helps in designing safer processes and preparing effective emergency response plans.

Optimisation of Operations: Dynamic simulations provide insights into the transient behaviour of processes, allowing for the optimisation of start-up and shutdown procedures, reducing downtime and improving overall efficiency. This leads to cost savings and increased productivity.

Reduced Risk and Cost: By predicting the outcomes of changes in process conditions, dynamic simulations help in making informed decisions without the need for costly and potentially risky physical experiments. This reduces the likelihood of operational disruptions and associated costs.

Training and Development: Dynamic simulations offer a realistic training environment for operators and engineers, enabling them to experience and manage process changes and upsets in a safe and controlled manner. This enhances their skills and prepares them for real-world scenarios.

Regulatory Compliance: Many industries require rigorous testing and validation of processes to meet regulatory standards. Dynamic simulations provide the necessary documentation and proof of compliance, facilitating smoother regulatory approval processes.

Design and Scale-Up: For new processes or modifications to existing ones, dynamic simulations help in understanding the implications of scale-up and design changes. This ensures that processes perform as expected when implemented at full scale.

Resource Conservation: By optimising process operations, dynamic simulations contribute to more efficient use of resources such as energy, raw materials and utilities. This not only reduces operational costs but also supports sustainability initiatives.

Process Dynamic Simulation

The methodology employed in most of our engineering study projects includes using first principles calculations and process simulation software called Aspen HYSYS. HYSYS is an abbreviation for Hyprotech Systems, is a process-modelling software, capable of steady-state and dynamic simulations.

It was developed by AspenTech and usually used by chemical process engineers to mathematically model chemical processes, from unit operations to full chemical plants and refineries. HYSYS is able to perform many of the core calculations of chemical engineering, including those concerned with mass balance, energy balance, vapour-liquid equilibrium, heat transfer, mass transfer, chemical kinetics, fractionation and pressure drop. The diagram on the right shows a process, units operations and stream numbers.

The table shows the properties of each stream. 

ASPEN Simulation Hydrogen - Jimmy Lea P/L
Plant Engineering Design - Jimmy Lea P/L
ASPEN Simulation of PSA - Jimmy Lea P/L

What is process dynamics simulation?

Process dynamics simulation of a chemical plant refers to the use of computational models and software to simulate the behaviour and performance of a chemical plant over time. It is a crucial tool in the field of chemical engineering, helping engineers and operators understand the dynamic behaviour of complex chemical processes under various operating conditions. The simulation allows them to predict how the plant will respond to changes in inputs, disturbances and equipment performance. Here are some key aspects of process dynamics simulation of a chemical plant:

Modelling: The first step involves creating mathematical models that represent the physical and chemical processes occurring in the plant. These models include mass and energy balances, reaction kinetics, transport phenomena and thermodynamic properties of the materials involved.

Control Systems: Process dynamics simulation helps in the design, analysis and optimisation of control systems for the chemical plant. Engineers can develop and test different control strategies to maintain process variables within desired ranges and ensure stability and safety.

Equipment Performance: The simulation considers the behaviour of individual equipment such as reactors, distillation columns, pumps and heat exchangers. This information aids in identifying potential bottlenecks, inefficiencies and opportunities for improvement.

Transient Analysis: Unlike steady-state simulations, process dynamics simulations take into account time-dependent behaviour. It helps to analyse how the process variables change over time due to varying inputs, disturbances and system response. Such a simulation allows engineers to investigate the system's behaviour during start-up, shut-down, or when subjected to sudden changes or disturbances. Understanding transient behaviour is crucial for safety and process optimisation.

Scenario Analysis: Engineers can run various scenarios by altering parameters and inputs to assess the plant's response under different conditions. This helps in evaluating the plant's robustness and identifying critical operating points.

Troubleshooting and Optimisation: Process dynamics simulation assists in troubleshooting issues that may arise during plant operation. By analysing the dynamic behaviour, engineers can identify the root causes of problems and propose solutions for optimisation.

Training and Safety: Dynamic simulations can also be used for training operators, allowing them to learn how the plant behaves under different conditions without risking the actual plant. This contributes to improved safety and efficiency.


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