Traffic jams in the chemical plant

I have a blessedly short commute, but that means that when I decide to drive downtown to have a nice meal or visit the library, it makes me crazy to sit in a long, slow line of cars. It’s such a waste of time! But what the traffic jam represents is demand by many people (the drivers) for a limited resource (the road to a specific place).

It’s not too different for a custom chemical plant. The demand of your customers is dependent on their schedules – and they don’t really care about yours. They want their material when they want it, and they’re going to write a date on their purchase orders that is convenient to them. For the plant management, it’s all about smoothing out that demand over the year so that you don’t get traffic jams in the plant.

Any large production run where you run the process numerous times (often called a campaign) can already look like a freeway at rush hour, where it’s the workers or the actual chemicals literally moving. Once a customer places an order for a product, your team will purchase the needed raw materials, catalysts and solvents, carefully timing their arrival. Then when the raw material shows up in trucks outside the warehouse, you have the trouble of finding a place to put it.

Next, the samples of raw materials begin filtering into the quality control laboratory and the QC department begins grumbling about being buried in the work of making sure that the plant has good material to run. Solvents and reagents need to be tested as well, and piles of vials begin being fed into the autosamplers of gas chromatographs and HPLC instruments.

Once that’s complete, the approved drums move to the production plant and the chemical processing begins. The traffic hits the operators as well – when the plant is processing, you can see operators streaming in and out of the production plant, loading reactors with raw materials and solvents, and forklifts moving back and forth.

Parking lots

There are other places to see the pile-up. If it’s a liquid product and you’re working with an 8000 litre reactor, you’ll see 40 200 litre drums lined up to be filled. If it’s a dried product, that torrent of material will have to be crystallised in the reactor, isolated by centrifuge, placed in drums wet with solvent and then sent to the dryer room. Operators will load the material into the dryer and empty it, creating another large collection of drums ready to be tested and shipped.

The warehouse team will once again do its incredible work of reorganising everything. If you wander into the warehouse right before a big order ships, you’ll see piles of drums or mounds of supersacks stacked on top of one another. There might be drums in corners that you don’t expect, or a normally unused building suddenly full of odds and ends as your final product warehouse fills up. Your warehouse team will start to worry, calling the customer to ask if they are sending trucks to pick up all of this material.

That’s when you often get a great back-up and you can imagine all the drums figuratively beeping and honking. Sometimes the customer will say ‘actually, we can’t take this material right now’. After great hue and cry, your overworked warehouse staff will investigate if there are yet more potential warehouses to store material (often they can be rented) or if some empty shipping containers can be ordered to temporarily store the product. There is always an argument between you and the customer as to who exactly will pay the bill for this extra storage.

Queuing up

The worst kind of traffic jam in the plant is when you have one process (and one customer) backed up behind another. It’s often when you have a single specialised piece of equipment (say, a hydrogenator) and two projects that need it. At that point, you have to hope the first process runs smoothly so that the second product gets made on time. What happens when it doesn’t – say, your hydrogenation reaction proceeds to a certain level but stops before it will purge? Well, your team gets to pull out the toolbox. Is the hydrogen pressure correct? Can you add more catalyst? Maybe it’s a problem with agitation?

All the while, the second process is left waiting – and you can practically see the second customer sticking their head out the window, hoping to see the end of the traffic jam in front of them. Once that first process starts flowing smoothly again, a plant manager can breathe a little bit easier, awaiting the next inevitable traffic jam.