Merriam Webster’s defines irony as an ‘incongruity between the actual result of a sequence of events and the normal or expected result.’ In their excellent book, A Working Guide To Process Equipment, Norman and Liz Lieberman write about the end of run condition of a chemical reactor, giving an example of an ironic process.

The reaction in Lieberman’s example mixes diesel fuel and hydrogen together as reactants. This occurs at a relatively high temperature over a catalyst. The products yielded are low-sulfur diesel and hydrogen sulfide. The catalyst increases the rate of reaction, and the reaction rate increases with increasing temperature. The reaction takes place on the surface of the catalyst, so it is advantageous for the catalyst to have a large surface area.

After the reaction is run for some time, the catalyst begins to foul. That is, coke, a hard black substance that is mostly carbon, begins to deposit on the catalyst. This reduces the available surface area of the catalyst, and the reaction proceeds at a slower rate.

When the operator of the process becomes aware of the slower reaction rate, she increases the reaction temperature. When the temperature is increased, the reaction rate increases, and all is well. However, with this increase in temperature, the fouling of the catalyst by deposited coke also increases. When the catalyst is further fouled, the reaction rate slows. It becomes necessary to increase the temperature further to raise the reaction rate to set point. This fouls the catalyst…and on and on. Finally the catalyst becomes completely fouled, and the end of run is reached.

In the case of the fouled catalyst, the irony is that increasing the temperature of the reaction is needed to increase reaction rate, but it is in fact that higher temperature that fouls the catalyst, hastening the end of the process’s effectiveness. The cure to the disease hastens the disease itself.

There are certainly processes outside of chemical engineering that show a similar tendency toward irony:

Antibiotic use : Antibiotics admirably combat infection in individuals on short time scales, while creating resistant bacteria in the long time scales. Ironically, by curing individuals now, we risk being unable to cure many more later.

Struggling cities : As budgets in a struggling city are squeezed, taxes are raised to increase revenue. Rates of revenue collection show an initial increase. However higher taxes drive residents out, ultimately decreasing revenue on large time scales. Ironically, the steps taken to balance the budget in the short-term end up causing further shortfalls later.

Addiction : An addict takes an amount of drug that interacts with neuroreceptors, leading to a release of psychological and physical unease short-term. The body reacts by creating more receptors, creating more unease in the long-term. Ironically, the more drug the addict takes, the more he or she desires.

Arms races: One short-term, rational decision for any actor faced with an enemy with greater arms than itself is to become more armed in turn. The opposite actor then will become more armed in response. In the long-term, more destruction is often the result. Ironically, the rational choice for individual actors is often detrimental to the whole.

Each of these ironic processes rests on what is termed a positive-feedback loop. As the variable in question – be it temperature, antibiotics, revenues, drugs or arms – is increased, the process responds by demanding a further increase in turn. You can see why these types of processes are often called ‘death spirals,’ with death being, in each case respectively, a slow reaction, incurable infection, an insolvent city, an insatiable craving, and destruction of a population.

Crucially, ironic processes are ironic in that the increase of the process variable,while hastening the approach to ‘death’ in the long-term like any positive-feedback process, gives a temporary reprieve from the ‘death’ in the short-term. The short-term ‘cure’ accelerates the long-term ‘disease.’ From the definition of irony, the long term decay is contrary to the expectations of relief.