This Summer was fantastic. Our expanding team over the last year had an exciting time growing our capacity and navigating the needs of clients for new, larger scales of innovative extraction and distillation. We got to see many members of this incredible industry at events across the country, and meet new passionate allies as well as see great growth from old ones who are doing it right.
Ultimately, we are gladly progressing towards, and are in the midst of achieving, the fullfillment of the dream of having the partnerships, client-profiles, and room to engineer and create processing solutions that no one has seen before in our space, and that bring together disparate disciplines in new, fascinating ways to accomplish the challenges of the future.
In the Fall we are so excited to announce new products and projects, and will continually make a call for serious, research-focused clientele that want to push into the future with a single vendor that can work with them to create the most effective solutions to their problems. Clients that understand what it takes to bring new techniques onto market, and that are ready to shoot off into the skies of what’s next with us.
We are also ecstatic ro release this new website that goes deeper into our services and our ethos, as well as has a robust and growing content section for anyone interested in the science and engineering behind the scenes, at multiple levels of technical complexity so there is something for everyone.
To everyone out there on the grind of innovating in these spaces, good work and keep going! Its a collective objective we all share to get people the equipment and knowledge they need to create awesome products for the country and world.
If you’d like to begin your journey into the future of your processing business, contact us today.
]]>At an atomic level, the Internal Energy (U) of a thermodynamic system (system for short) is a measurement of the general movement of the molecules that make up the system, a measurement of how powerful the vibrations of the molecules are, of how fast the molecules are traveling, of how often chemical bonds are formed and broken.
On the other hand, Heat (Q), is a measurement of the transfer of energy between interacting systems. That is, as systems with different state variables (Volume, Pressure, Temperature, etc) interact with one another, there is a net transfer of heat from one system to another, which stops when the two systems reach thermal equilibrium. In other words, If two separate systems with a difference in temperature are brought together, the phenomenon of heat occurs, in which heat is transferred from the hotter system to the colder system until their temperatures are equal.
In the context of an extraction, the quantification of Internal Energy change is not helpful for making process decision—Heat, by contrast, is extremely important when making process decisions. The calculation of heat sets the foundation for sizing equipment, choosing equipment materials of construction, determining if the infrastructure of a facility has the capacity to meet the needs of heat-exchange equipment, the list goes on ad infinitum. So, diverging from the thermodynamics-driven discussion encountered in “EMB 101,” it is important to dive directly into the calculations and their rationale; the sooner one understands heat calculations, the sooner process decisions can be driven by the fundamental science.
Units and Unit Conversion (Note: It is of critical importance that the reader is familiar with all of this before proceeding further.)
Perhaps the most important practical skill to develop in terms of heat calculations is the ability to convert between units of measurement for relevant variables, like: temperature, energy, mass, density, volume, time, and so on. Below is a list of conversion skills that should be considered a pre-requisite to the understanding of the material to follow:
Converting Celsius (°C) to Kelvin (K)
Using Density (ρ) to convert between Mass and Volume
The Relationship between Energy in Joules (J) and Power in Watts (W)
Determining kWh from a Power measurement in Watts
A Brief Note Concerning Heat Capacity, Latent Heat and Density
Heat Capacity
Heat Capacity, is a measure of how much energy (in the form of heat) is required to raise the temperature of a system. Specific Heat Capacity, on the other hand, is a measurement of how much heat is required to raise a mass (or volume) of a pure component (i.e. a system made of one type of molecule) by a degree of temperature (in K or °C). Heat Capacities are exclusively used for determining heat required to change temperature—for instance, in a heat exchanger.
Latent Heat
Latent Heat has several forms, essentially it is a measure of how much energy is released or absorbed as a volume of molecules changes from one phase to another; i.e. during the process of freezing/melting (Latent Heat of Fusion) or condensing/vaporizing (Latent Heat of Vaporization). In the context of this conversation, only latent heat of vaporization will be utilized. Latent Heats are exclusively used for determining heat required to vaporize or condense fluids—for instance, in an evaporator or condenser.
A More Realistic Idea of Heat Capacity and Density
In the following discussion, Heat Capacity and Density will be regarded as unchanging numbers, but in a more realistic sense, these quantities vary depending on the temperature of a system—more formally stated: the heat capacity and/or density of a component is a function of temperature. For entry-level calculations, however, these considerations are over-kill.
Calculating Heat
There are two primary type of heat calculations, regarding the discussion at hand: the calculation of heat required to change the temperature of a fluid that does not change phases throughout the heating process and the calculation of heat required to change the phase of a fluid. The first type of heat calculation will be referred to as (Q_{Heat}) and the second type will be referred to as (Q_{PC}) (PC = Phase Change). Let’s get right to it.
These two equations are all that is needed to calculate the heat energy required to change a system from one temperature to another and/or to change the phase of a fluid. More importantly, since both types of heat are measured in Joules, they can be added together for a combined calculation when a situation involves both temperature change and phase change. Given that the reader has met the “pre-requisites” mentioned earlier in the article, one know has all the information needed to calculate the heat required for some common situations—so, let’s explore a relevant example.
The Example: Evaporating a Cold Solvent
An extraction technician uses Ethanol (EtOH) at -80 °C as a solvent for extraction. The crude EtOH-Extract mixture is fed into a batch evaporator that heats the crude mixture from -80 °C to the boiling point of ethanol (assume 80 °C, for simplification). After heating the crude mixture to 80 °C, heat continues to be added to the evaporator until all the EtOH has been vaporized. The extraction technician wants to know how much heat is required to heat and vaporize 10 L of a crude mixture, and how much it will cost.
Known Variables:
T_{2} = 80 °C = 353K T_{1} = -80 °C = 193K V = 10 L ρ_{Ethanol} = 789 g/L m = 7,890 g C_{P} = 2.44 J/g*K L_{V} = 918.2 J/g |
Unknown Variables:
Q_{Heat} Q_{PC} _{ } Note: Heat is technically in units of Joules, and power is in units of Joules/Time. So, these calculations are for POWER, but if we removed the “per hour” they would be Heat Calculations. This has been done for the sake of saving space. |
So, let’s plug in the variables and see what values we get:
Essentially, we have our answer, but that most-useful practical skill of unit conversion now becomes very important. Let’s assume the extraction tech wants to heat and vaporize this volume of Ethanol every hour:
Let’s further assume, that this process runs non-stop all year—24 hours a day, 365 days a year:
Now, finally, we are able to estimate the cost of the process of evaporating ethanol. If we determine the municipal cost for electricity, we can determine how this cost translate into an annual cost:
Unfortunately, this cost is not an accurate representation of the electric bill that an operation will receive. So, it’s about time we start discussing heat exchangers…
]]>Ah, heat exchangers, these little bundles of thermodynamic magic exist on a multi-level spectrum; they can drive the optimization of a process or create a major bottleneck, (when purchased correctly) they can be accompanied by a dedicated service team or remain inoperable indefinitely with not-so-much as an email reply, they can make extraction a joy or a nightmare, and they can be made to any specification of quality. Clearly, the primary concerns for an extraction operation are that a heat exchanger is appropriately sized for a process, that they are built to a standard of quality that is equivalent to the end-product, and that they are purchased from a company that ensures timely service and troubleshooting assistance.
Of course, heat exchangers are also extremely complex from a technical perspective—engineers spend countless hours determining operational parameters, flow characteristics, correction factors, fouling resistance, chemical compatibilities, pressure drops, efficiencies…the list goes on. As an individual focused on extractions, it is important to sift through this mound of data and focus on the kernels of relevant information that will empower them to make the appropriate purchasing decision.
Preparing for Purchase
Before contacting a company for a quote, it is imperative that an individual determines several operating parameters that they foresee for their heat exchangers:
Several of these questions have been answered in previous discussions, namely concerning temperatures and heat, but any further information that is indeterminable will be left to the engineers from the potential supplier. The more information provided to a manufacturer, the better the chance of procuring equipment that will benefit your process instead of hindering it. The purpose of the above discussion is simply a means of communicating that: the more one knows about the science of their process, the better one is equipped to interact with equipment manufacturers and suppliers. From this point on, the conversation will focus on the scientific understanding of this equipment and how this knowledge can translate to a net benefit for an extraction process.
Overall Heat Transfer Coefficient (U)
This quantity, which should not to be confused with a previously discussed “U” (Internal Energy), is a measure of the “overall heat transfer.” It is a function of the calculated heat requirement of the exchanger (Q), the surface area available for heat transfer (A) and the Log-Mean Temperature (T_{LM}) of the process fluid. As the value of U increases, so does the ability of the heat exchanger to deliver its intended function:
Calculation of U is no simple matter, it heavily relies on the materials, geometry, convection and fouling resistance of a heat exchanger, and is a bit beyond the scope of this discussion, see Figure 1 for an example. Instead, the value of U can be calculated periodically to assess the overall well-being of a heat exchanger being used.
Over time, U will decrease in value and therefore decrease the effectiveness of the heat-exchanger. When U dips below an acceptable value, it generally indicates that it needs to be cleaned—an extremely important consideration for extraction operations. On the other hand, if a unit is cleaned too frequently it creates a bottleneck in the operation and can decrease profitability. However, the value of U is also intimately connected with the quality of process-fluid entering the heat exchanger, for one batch of crude material U can be extremely high and for another it can be extremely low—its important to be flexible with process requirements for U so as to not create an unrealistic expectation from suppliers.
Fortunately, the calculation of this quantity is based on fairly simple variables—Q and A can be assumed to remain somewhat constant (see “Fouling” below)—the remaining variable T_{LM} is simply a measurement of the difference between the temperature of process fluid and cooling fluid entering and exiting the unit, and given its relative simplicity will be left to the reader to determine (which will save space for more important information).
In the context of making a purchasing decision, one should leverage historical information retained by the company, ask questions like: how quickly does the value of U decrease for this heat exchanger? At what value of U should a customer clean this equipment? Does the company provide instructions for efficiently cleaning this heat exchanger? If this heat exchanger cannot reach a certain value of U, will the company replace or service it?
These several questions alone will help buyers vet potential equipment suppliers to determine how well a company knows their product and to eliminate potentially troublesome suppliers.
Fouling
Fouling occurs when particulates in the heat-exchanging fluid or process fluid adhere to the surface of the heat exchanger. Over time, this particulate buildup reduces the flow of fluids through the equipment as well as the surface area (A) available for heat transfer and reduces the overall effectiveness of the unit. Unfortunately, and especially in the case of extraction, fouling is a major concern and should be considered before purchasing any heat exchanger.
In the opinion of the author, the first consideration in the context of fouling is controlling the input material to the heat exchanger. In the context of extraction, it becomes important to remove as many non-desirable constituents from the crude extract as possible; the removal of components such as lipids/waxes, filterable particulates and other easily seperable constituents can greatly increase the longevity of a heat exchanger. The second important factor for consideration is the material of construction of the heat exchanger. Heat-exchangers, no doubt come in many shapes and sizes and are made of any number of materials—it seems reasonable to model a process after analagous manufacturing processes to ensure that the appropriate decisions are made when selecting a heat exchanger.
Since the author is familiar with the pharmaceutical industry, it will be used as an example for the sake of discussion. Pharma processes often employ the use of stainless steel (SS) heat exchangers; SS is relatively resistant to chemical interactions, it is easily cleanable, it comes in a variety of material compositions and it can be polished to a finish that reduces the potential for fouling. SS, as mentioned, comes in a variety of material compositions (different percentages of elements are present in the final material) that increase in quality as follows: 304, 316, 316L. When selecting a material, an engineer will often prefer to choose 316L as it provides the largest protection against the above-mentioned issues. Moreover, manufacturers will often take the step of “electropolishing” the surface of the material to a certain roughness value (Ra). In the context of this discussion, SS is simply an example, what is more important is that the reader familiarize themselves with the various materials and material grades that can be selected from as it will allow them to make a more informed decision about purchasing.
Specifically, an individual could ask the following questions: what materials of construction are used for surfaces that directly contact the process fluid? Are several grades of the material avaialble for this heat exchanger? Does the manufacturer provide electropolish for this heat exchanger? Are material certificates and certificates of electropolish provided with this heat exchanger? Do these certificates match standardized requirements set forth by governing bodies (like ISO, ASME, etc)?
Conclusion
There are many concerns when purchasing heat exchangers, some are much more imperative to assess than others, but a rounded understanding of all factors is helpful in making the right process decisions. Make sure you ask as many questions as you can, and always remain vigilant when suppliers make outlandish promises—their motivation is to sell equipment, and sometimes they do so at the misfortune of a buyer. Ensure that you find an equipment supplier that takes the time to inform their customer, who provide accurate information when asked, and who aren’t afraid to tell you they aren’t sure.
As for an expansion of this conversation, there is much more to be discussed. Stay posted…
]]>The simple truth for anyone interested in extraction is this: scientific rabbit holes are unavoidable on the journey to perfecting any extraction process. A casual exploration of thermodynamics evolves into an endless pursuit of understanding; a continual clash between confusion and clarity, frustration and reward. At any rate, it becomes tempting to forfeit the pursuit of scientific understanding to the experts—engineers, chemists, and the like. But what is it exactly that these experts are doing? How can someone who is detached from the hours of countless, painstaking effort, make decisions that will positively benefit your extraction? The answer is, without a doubt: Energy and Mass Balance.
Energy and Mass Balance (EMB) is a concise, step-wise method by which a graphical representation of a process (and its equipment) can be transformed into a singular numeric outcome. For example, say you’ve got a known amount of a fluid flowing into a heat exchanger, how much energy is required for this heat exchanger to heat the fluid to the desired temperature? How much electricity will that require? How much does that cost? All of this begins with an EMB. Given that an EMB is a step-wise process, it makes sense to explain it a step-by-step manner.
A quick Wikipedia query provides the following definition for thermodynamic system: “the material and radiative content of a macroscopic volume in space, that can be adequately described by thermodynamic state variables such as temperature, entropy, internal energy and pressure.” In the context of basic understanding, this definition is already unsettling; radiative content, macroscopic volume, entropy—scientific rabbit holes aplenty. A thermodynamic system (or system for short) can be more simply characterized as a box (macroscopic volume) where the effects of temperature, pressure, etc. (thermodynamic state variables) can be interpreted in terms of how they affect the contents of the box. In extraction (or any chemical process for that matter) the thermodynamic system/box is equivalent to an individual piece process equipment: a heat exchanger, reactor, evaporator, etc. Moreover, the thermodynamic state variables are equivalent to the flow rates, temperatures and pressures of the various liquids interacting with the equipment at a given time.
Now, with the understanding that an individual piece of equipment is essentially a man-made thermodynamic system, one has a system to balance.
In order to balance a system, one must define the inputs and outputs of the system as well as the ‘thermodynamic state variables’ (see Step 1) of the inflowing and outflowing materials. For this discussion, let’s focus on the example of the heat exchanger where we can determine the following:
Note: The subscripts “in” and “out” represent components flowing into or out of the system, respectively.
The final step in creating a system boundary is graphically demarcating the system from its surroundings; in other words, draw a box around the piece of equipment. Now the hard part.
In academia, the mathematics of an EMB are generally presented (to the utter anguish of unsuspecting engineering students) as follows:
Note: This equation, in and of itself, evokes strong feelings of self-doubt, despair and anxiety in the author; a chemical engineer.
Now, this is about as terrible an equation as any; a total of ten variables, differentiable terms, double and triple integrals, subscripts and the rest, but the intent the author in providing this equation is to demonstrate the depth and robustness one can achieve with an energy balance after a great deal of practice. Clearly, this is beyond the scope of this article, but the following equation (which is directly related to the above equation) is well within the scope of the discussion:
Author Suggestion: Memorize the heck out of this equation.
Where:
This equation is essentially the mathematical equivalent of the First Law of Thermodynamics for a system. The First Law of Thermodynamics can be articulated as follows: the total energy of a thermodynamic system is constant; energy can be transformed from one form to another, but cannot be created nor destroyed.
As luck would have it, the symbol ∆ designates a change, and in the context of the entire preceding conversation, that change occurs between the inflow and the outflow across the system boundary. So, how does one determine the value of each of the variables listed above?
In this step, it is often prudent to begin with the simplest variable and gradually move to the most difficult variable…
W – Work
Using the example of the heat exchanger, one can reasonably assume that the system is doing no work. For now, that will suffice—and the work done by the system is equal to zero!
∆E_{P }– Potential Energy
The change in Potential Energy, in the context of this discussion, is dictated by the change in height (h) of the inflowing and outflowing fluid:
In the example of the heat exchanger, let’s make the assumption that the flow rates in and out are equal and the heights at which the fluid flows in and out are equal. g, the acceleration of gravity can be assumed to stay constant—which means that the change in potential energy is zero!
∆E_{K }– Kinetic Energy
The change in Kinetic Energy, in the context of this discussion, is dictated by the change in velocity (v) of the inflowing and outflowing fluid:
Again, let’s make the assumption that the flow rates in and out are equal and that the velocities are equal—the change in kinetic energy is zero!
Now, taking a brief pause to recollect, the original equation has reduced to the following:
At this point, it becomes necessary to define the intent of creating an EMB in the first place, perhaps the most realistic possibility (in the example of the heat exchanger) is how much will it cost to heat the fluid from one temperature to another? The answer can be derived by directly determining the value of Q (in units like kilowatts) and multiplying by the cost of electricity (in units of $ per kilowatt).
We’ll save that for next time.
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