Alcohol - part 2

Alcohol - part 2

So last week, I talked about the basic process of fermentation and how it has been/is utilized for the creation of alcoholic beverages around the world, but fermentation isn’t the end-all be-all of making alcohol. We can go one step further with distillation. Distillation is simply the process of using heat to separate components but it’s a bit more complicated than that in practice. Basically, most chemicals have very specific boiling points (the point where the liquid vaporizes) and distillation seeks to utilize the difference in boiling points of components in a mixture (like alcohol and water). So say we made our own wine (see my post on making wine if you want to try it yourself), and now you’ve got this mixture of ethanol (alcohol) and dihydrogen monoxide (water) along with a bunch of dissolved solids that give the drink distinct flavors and tasting notes. Now, we know alcohol boils 78.37 degrees Celsius and water boils at 100 degrees Celsius. So if we heat up a mixture of alcohol and water to the boiling point of ethanol, we will form a bubble (because we’re at the bubble point) and that bubble will contain more ethanol than water by concentration than the liquid it came from. Now if keep heating at that temperature until nothing else vaporizes and then we collect all of that vapor, we can cool it back down and now we have a much stronger alcoholic mixture than we started with. If you started with wine, you now have brandy. The difference now though is that we will have to use a slightly higher temperature to get a purer vapor this time.

Now what if we aren’t happy with brandy, rum, bourbon and other moderately strong drinks? What if for some reason we want our drinks to basically be jet fuel? Then we just distill it again! You may have seen bottles of vodka or other beverages that say something along the lines of “triple-distilled” or “double-distilled”. This just means they did the distillation process described above twice. Each time the temperature of distillation is just increased slightly but generally not above the temperature of the other component. So for alcohol, we don’t want to go above that 100 degrees Celsius point, in theory. We can keep distilling our drink with little stepwise increments until we get nearly 100% of one component, right? Unfortunately no. There are many mixtures out there made of two different things that can be nearly perfectly separated by distillation but water and ethanol are not one of them. Water and ethanol form what is known as an azeotrope (big word that means you can’t separate them with distillation alone). Basically water and ethanol have a very strong attraction to one another and so there is a certain point where you can no longer distill any further. For alcohol and water this is around 96.7% alcohol (200 proof, where 200 is the maximum achievable alcohol concentration by distillation). If we want to get even purer, we have to use something like a desiccant that would absorb the water or pass the mixture through a specialized filter made to only extract the water or ethanol. For most purposes, 96.7% ethanol is more than enough. You’ll generally only see 99.99% in very specialized lab situations.

Now on a side note, while it’s perfectly safe to try to make your own wine, you really should not try to do your own distillation. This is because ethanol has a tendency to break down into methanol during the heating process and methanol can easily make you go blind or kill you in very small amounts. Professional distillers harvest the beginning and end of each distillation (the heads and the tails) and dispose of them because these contain a large amount of methanol. Feel free to make your own wine and beer, but leave distillation to the professionals (and mountain men that have been doing it for a generations). So just stick to buying your own rums, vodkas, and tequilas. They’ll taste much better and you’ll be much less dead for it. 

Alcohol - part 1

So today, I'm going to be discussing something near and dear to many of our hearts (and livers): alcohol. Specifically today, I will be discussing the process by which alcohol is most commonly made and I will go into some of the history of it. Reaction is entirely dependent upon this little reaction here:

Now this just looks like a bunch of nonsense for many people, I realize. We've got some letters and numbers and somehow glucose (sugar) plus enzymes (yeast) gives us ethanol (alcohol) and carbon dioxide (the stuff you breathe out and plants use). So let's simplify this a bit. Basically yeast are little tiny, very robust lifeforms and they are incredibly ancient. They're classified as fungi (yep, like mushrooms) and are unicellular organisms and humans have been using them for thousands (if not tens of thousands) of years to make bread and alcohol. Yeast eat carbohydrates (so things like sugar) and they make alcohol and carbon dioxide from it. So yes, alcohol is basically yeast poop, but that doesn't mean it can't be delicious.

Now that we've discussed the basics of how fermentation occurs, let's get into the nitty-gritty about how people utilize this process to create drinks like beer and wine. In chemical engineering and process design, there are essentially two main kinds of reactors (with some exceptions). These are batch and flow reactors. A batch reactor is a reactor where you add all your components, seal the vessel and then wait for the reaction to occur. You may altar the heat over time, but essentially no mass is going in or out during that time period. A flow reactor is different because mass is moving in and out of the reactor at any interval in time. The first step in creating alcoholic beverages relies on batch reactors and if we wanted to make our drinks even stronger we would use a flow process to distill our drinks (see my next post on distillation and an instructional post on making wine). Now in any brewery or winery, they're going to start with some kind of plant matter or fruit. Beer uses hops, barley, and other grains. Wine uses grapes and occasionally some other flavors. This plant matter provides the starting material we need for making alcohol because it has the one thing yeast love to eat: sugar. So we take our carbohydrate-rich plant matter and we dump it into a big tank. Great, Now what? We can't just add yeast and have alcohol so generally, we add water to act as a house so the yeast can reproduce and move around to find the sugars and convert them into alcohol. So one we've added all our raw ingredients (fruit, grains, or any other flavorings we want, and yeast), we close up the vessel (often large stainless steel containers for beer and wooden casks for wine). We have to be safe though, yeast produce carbon dioxide when they eat sugar and carbon dioxide is a gas. This increase in pressure can cause an explosion if not properly vented. In the production of alcohol beverages, an air-lock is used. This is a device that lets out air produced inside, but prevents air from the outside from getting in and ruining the batch. Now we wait anywhere from a few months to a couple decades before we open up the vessel. Inside we'll find our alcoholic beverage if everything went as planned and we can enjoy our drinks.

So what happened to those yeasts? Well basically, they ate so much sugar and produced so much alcohol, that they basically died or went dormant because there either wasn't enough food left or their environment had too much alcohol in it (usually maxing out around 15% by volume). This alcohol is also what helps keep other bacteria and fungi from growing and ruining the drink and thus this is why alcohol was historically and still is a great way to preserve beverages. Take for example, Irish cream, a cream based alcohol drink. The presence of alcohol can prevent the dairy inside from spoiling near indefinitely where normally the cream would go bad in a week or two on it's own even with refrigeration. Some breweries and wineries choose to filter out the dead yeast from their drinks, but other ones choose to leave them in, but no worries, they're completely safe to consume and some wine and beer aficionados like the taste the yeast presence generates. Now what if we want to drink something stronger? You know, you're rums, vodkas, tequilas, and irish creams? Then we have to do something called distillation, so stop by next time and I'll explain how that happens! Until then, keep enjoying your drinks!

So what the heck is chemical engineering?

So I'm currently a junior studying chemical engineering at the University of Oklahoma and I often find that when I tell people what I studying, they usually act like it sounds impressive or they say they've heard that major is difficult, but I've found very few people actually know what chemical engineers do and thus the purpose of this first post is to create an overview of what chemical engineering is and what chemical engineers do. Chemical engineering isn't as simple to understand from just looking at the name. One might expect a civil engineer to work on bridges, an aeronautical engineer to work on airplanes or Petroleum engineer to work in oil and gas, so one might expect chemical engineers work with chemical and that's a pretty good guess but it's not a complete answer. Just like civil engineering can include working on roads, bridges, buildings, or focusing on maintaining existing structures, Chemical engineering can be pretty varied. Chemical engineering is often synonymous with process engineering and the word process is a better example of what it is chemical engineers often do - they focus on designing and maintaining processes. This could be designing a new distillation column for separating benzene and toluene, or it could be something more common like designing a batch reactor for fermentation in a brewery. 

Chemical engineers study many of the same topics as other engineering students - thermodynamics, fluid dynamics, numerical methods, lots and lots of math, but many of their classes have a heavier focus on process design and engineering. For example, thermodynamics for a mechanical engineer will focus much more on heat transfer and chemical engineering thermodynamics will focus heavily on the chemical reactions involved in that heat transfer. We also take many classes on process design -  these are classes where we learn how to design or optimize process systems and this can have some really practical applications. A solid understanding of heat transfer can be surprisingly useful in day to day life (one of my test had a problem that involved determining the costs of heating and cooling a house in winter and summer by determining the heat loss through the walls and ceiling and then finding the percent time the AC or the heater had to run to maintain a certain temperature in the house). A problem like this may not seem like something many people have to deal with on a daily basis, but understanding heat transfer well can help you determine exactly how much insulation you might need when you're working on remodeling your house. Now much of what we do is very technical (like the heat transfer coefficient of condensation for vertical and horizontal heat exchangers) but that doesn't mean the field should be hard to approach or understand for a new comer. There is value in being able to explain one's field to an outsider who may not have the same technical knowledge and thus the purpose of this blog is to discuss chemical engineering in a way that's accessible for lay people who may not know much about the field but still are interested in learning about it. I plan on creating weekly and occasionally bi-weekly posts that will explain specific examples of chemical engineering in the world today or perhaps discuss how chemical engineering applies to current issues like the water problems in Flint, Michigan. I hope to make the field of chemical engineering a little more approachable and clear to those that might not know much about it. If anyone has any suggestions on topics they'd be interested in, I'd love to hear it!