Industry chooses conditions that make the most product at the lowest cost, safely. The Haber process shows how. Nitrogen comes from the air, which is plentiful and costs very little. Hydrogen is made from natural gas, which is a limited resource whose price changes, so the cost of natural gas affects the cost of ammonia.
High pressure and high temperature need a lot of energy for pumping and heating, and this adds to the cost. Some energy is saved because the heat released by the reaction is used to warm the incoming gases. An iron catalyst makes the reaction fast enough at a moderate temperature, which also saves energy.
Only some of the nitrogen and hydrogen react each time the gases pass through the reactor. The mixture is cooled until the ammonia condenses to a liquid and is removed. Removing the product moves the position of equilibrium to the right, so more ammonia forms. The unreacted nitrogen and hydrogen are recycled back into the reactor, so the raw materials are not wasted. The company balances the rate of production, the position of equilibrium and the cost of raw materials and energy.
