Challenges To Pilot Plant Scale Up

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Why does an effective lab scale process technology require an experienced engineering specialist to successfully scale-up a pilot or production plant? Why can’t you take a process technology that works in a beaker and drop it into a 500 gallon tank? Why doesn’t a lab scale system have a linear formula to increase production?  These are just a few challenges to pilot plant scale up.

The physical characteristics of a system inadvertently affect the chemical reaction, creating different results at each iterative size. Using your bench scale data, an experienced plant scale engineer can use Aspen / HYSYS modeling to successfully scale-up your technology. EPIC can achieve this in less time and cost through our proprietary industrial process scaleup design.

Non-Linear Pilot Plant Scale Up

As a system increases in pilot plant scale, many properties related to the system size change, such as the proportion of surface area to mass, which cause other things, such as laminar and turbulent flow regimes, to change, especially for non-Newtonian fluids.

In turn reaction kinetics, fluid mechanics and thermodynamics change in a non-linear fashion, affecting each other as they change. A productive process at lab scale may not produce the same results in larger scale.

Specific Challenges to Pilot Plant Scale-up

EPIC has experience navigating a wide range of issues during pilot plant scale up. Specific types of challenges we address include the following physical and chemical elements of a scale-up of process technology:

    • Reaction kinetics –In systems with good reaction kinetics, molecules from each element mix efficiently and quickly together, reaching a state of equilibrium for the solution. Various physical and chemical factors can prevent the molecules of the mixture from mixing and colliding correctly. This can create bad reaction kinetics without proper system design. .
    • Chemical Equilibrium – A reaction is not productive until chemical equilibrium is reached, which does not occur immediately. As increased quantities of chemicals are mixed, the time to reach equilibrium increases at a nonlinear rate.
    • Material properties – The properties of the materials in contact with process system chemicals are critical. Incorrectly selected materials can influence the reaction, erode over time, or make the system unnecessarily expensive.
    • Fluid dynamics – Keeping flow at the correct Reynolds number is important for thermal transfer and mixing efficiency. Fluid dynamics changes at a non-linear rate as systems increase in size, making changes between laminar and turbulent flow hard to predict.
    • Thermodynamics – Heat loss and gain can play a major role in chemical reactions. For example, some reactions discharge heat, increasing system temperature and further speeding up the reaction, letting off even more heat and causing temperatures to rise further. Controlling reaction temperature is important to a successful pilot plant scale up.
    • Equipment selection – The physical limitations of equipment can acutely impact the chemical reaction. Continuing the thermodynamics example, as some reactions create heat, it must escape the system in a timely matter so the reaction does not become unstable. The ratio of surface area to mixture volume determines how quickly heat can be discharged from the system. If the tank is the incorrect size, it will be difficult to control the chemical reaction, which will begin escalating quickly.
    • Agitation issues – Mixing techniques are crucial to achieving good reaction kinetics. As systems increase in volume, mixing presents several challenges. For example, as the volume of the reaction increases, so does the horsepower needed to stir the mixture. It is not always cost effective or feasible to add enough horsepower to stir the mixture as the system scales up. This problem is addressed by matching the tip speed of the larger agitator to the tip speed of the bench scale agitator. Creating the correct amount of turbulence within the tank to promote good reaction kinetics is an issue that is solved through angled agitators and baffles. Watch the video on the right for more information on how this works.

 

EPIC addresses these difficulties through Front-End Engineering and scale up design in Aspen HYSYS modeling. We established that the chemical technology can be scaled up for a reasonable cost and still produce the required output. We also look at specific system challenges based on whether your system is a sanitary process scaleup or an industrial process scale-up.

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Modeling Methods

The use of several semi-empirical modeling methods determines the limitations of your pilot plant scale up through modeling, reducing costs and eliminating the need to build successive test systems. EPIC’s professional engineers model this iterative process through computer simulations based on your lab scale data. The specific methods used to do this include:

    • Chemical similitude studies – This method is dimensional similitude applied to chemical reactions and is derived from the laws of conservation of mass, momentum and energy in a chemical reaction. If a reaction is fast enough, chemical similitude is not very important, but in slow reactions it is very important to study.
    • Mathematical modeling– This method involves using computer programs to set parameters based on physical properties of the system for chemical reaction equations and running the program iteratively until the desired reaction size is reached. Methods used by EPIC for this include:
        • Aspen/HYSYS modeling – computer simulation programs that develop kilo-scale processes from bench-scale recipes
        • Finite Elemental Analysis (FEA) – numerical method that finds solutions of partial differential equations (PDE)& integral equations
        • Computational Fluid Dynamics (CFD) – computer modeling technique used to produce flow simulations

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Equipment and Materials of Construction Selection

Non-linear pilot plant scale-up effects can be managed with the proper equipment, system sizing and materials of construction, but at what cost?

Materials of construction that are easily available and work in bench scale can be expensive and hard to find in large quantities. Finding feasible substitutes requires experienced scale-up design specialists with knowledge of material properties and available equipment.

Design Engineers must balance cost savings and equipment selection without compromising the end goal of proving viability of final pilot plant scale-up. Production level equipment may be required to prove production level ability, even though the size of the lab or pilot plant does not require the same equipment as the production sized plant in order to work. Special equipment and compliance is also designed and tested during sanitary process scale-up.

Selecting the proper amount of instrumentation and testing stations will keep costs under control and prove the process technology works.

EPIC can cut 3 months off of your project time and save you 24% of your costs through modular design of your scale up system. We maximize speed of delivery while minimizing downtime with offsite parallel fabrication of process systems and onsite facilities preparation. Visit our Advantages to Modular Design/Build page to learn more about how this approach can positively impact your project.

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Pilot Plant Scale Up: Modular Design