Chemicals, oil, and water are linked eternally in a faustian bargain. In order to produce most chemicals, and all petroleum products, it is necessary to have access to immense quantities of water. Thus, the infrastructure for these industries is found in the low-lying areas alongside of rivers, and within the inlets and bays along the coastline of the oceans. When the inevitable floods happen, the potential for releases of chemicals and oil, and even explosions as seen in Crosby Texas this week can and will occur.
Why is there this dependence on huge quantities of water? In order to make many chemical reactions occur, it is necessary to provide heat. That heat normally comes in the form of steam. Steam is also used to enable separations of chemicals through distillation. The tall columns seen in chemical plants and refineries are usually distillation towers, where products and wastes are drawn off at various levels in the towers. These products must then be condensed, and they are condensed in heat exchangers with water being used to cause the vapors to condense. The chemicals and the water don’t mix in these condensers, since they are found on opposite sides of the heat exchangers. But immense quantities of water are used in heat exchangers, and the water is thus warmed, reducing its effectiveness in condensing and cooling chemicals.
The water used in heat exchangers and condensers may only be used once. This is single-use water and it is necessary to have a large volume of water nearby in order to release the warmed water without adverse ecological impact. If the water is reused, then it is necessary to cool the water back down in order to use it again. This is done in cooling towers, and you normally will see the plumes of water vapor coming up from these large structures, where water is cooled through evaporation as it drips on down through the wooden framework of a cooling tower. Cooling towers increase the concentration of salts in the water, since a portion of the water is lost to evaporation and may have many cycles through the cooling tower before being discarded to a body of water.
Since it takes lots of energy to move large quantities of water, and lots of money to run long lengths of piping, most chemical plants are found just adjacent to the water. They are sited so that they are above the normal flooding levels, but when unprecedented flooding happens like with Harvey, they are supremely vulnerable to damage from water. In my career in the chemical industry, I worked at two plants (in Tennessee and in West Virginia) that were situated along rivers. The plant in Tennessee did have problems long after I left when flooding from the Mississippi caused backwater flooding that buried part of the plant, which was situated on a smaller feeder stream. Fortunately, it didn’t cause the release of chemicals, and was not a large problem, but it highlights how close proximity to water comes with its own set of risks.
I have been to plants in Texas that were totally inundated from the floods this week. One along the end of the Houston Ship channel, that immense concentration of oil and chemical plants along Texas 225. The other was in Beaumont, situated right next to the marshlands leading to the Gulf of Mexico. The facilities at these plants are designed to be safe and to be able to be shut down without causing chemical releases. But. There are limits to what you can do and still be safe. When you have feet of floodwaters covering a site, then the power of the water can do things that cannot be controlled. Water can erode pipe supports, and the dangling piping will bend and break, releasing the contents of the lines. Floodwaters can shove vehicles and boats into pumps and piping, causing them to break. Even in the normal process of shutting down facilities, excess venting and flaring of flammable and toxic compounds can happen, which can cause irritation and concern among the neighbors of these facilities.
Just as there is a faustian bargain between these facilities and water, there is another relationship that comes into play. That is the relationship between the workers and their families, and their proximity to the plant. Very often the workers for these facilities are found in the neighborhoods surrounding the plants. Entire generations of workers have grown up nearly in the shadow of the towers of refineries and chemical plants. This is especially true in the region around the Houston Ship Channel. The towns of La Porte, Pasadena, Deer Park, and Baytown have a symbiotic relationship with their industrial behemoths. Only a single road separates the residential areas from the properties of the oil and chemical companies. Quite literally, the companies and the towns are all in the same boat at times like now.
The plant that had the explosions this week was a different type of chemical plant. This plant was not adjacent to a large body of water. What it manufactured was a chemical that is essential in the manufacture of plastics, but by its own nature, it was extremely unstable. In my chemical plant in West Virginia, we also manufactured a similar material. These materials are known as polymerization initiators, and they make it possible for chemicals like ethylene (two carbons bound by double bonds) to react with each other, and form long chains that we know as plastics (polyethylene). The materials we produced in West Virginia also have to be kept refrigerated or they will grow unstable and catch fire. Part of the lore of the plant involved the time when the manufacturing line for this material had a problem, and the temperature rose to the point where the chemical decomposed and ignited. That fire was remembered long after everyone who worked during the fire had left the plant. What made the situation in Texas worse, was that the organic peroxides they made are not only flammable but are explosive when they decompose.
Part of the manufacturing process for chemical plants involves process hazards reviews. In these reviews, the participants go through a systematic review of the inherent hazards of the process and facilities, and determine if there were adequate safeguards to prevent incidents and injuries. Sometimes a significant hazard is discovered, one that had not been previously considered, and then the management of the plant faces the task of getting the fix done to remove the hazard. Since it takes time to implement new facilities (and get the authorization to spend the money to build facilities), normally there are administrative controls that are put in place to temporarily mitigate the risks. But even though I participated in many process hazards reviews in my career, I do not remember ever having considered the case of having my plant submerged in multiple feet of floodwater, and having no way to get anything working for days at a time. I imagine that the chemical and refining industries will have to go through substantial work trying to come up with new safeguards that will prevent releases and explosions such as are being seen in Texas now.