Reducing the Cost of Steam Generation

Steam is one of the most important utilities in process industries. The cost of steam generation can affect OPEX costs and the cost of the product.

Graph showing cost of steam per ton generated

Energy use is growing exponentially, with a large percentage of demand being met by solid fuels like coal. While fuel price volatility and fuel price increases are a given, the recent doubling of solid fuel prices has led to a sharp escalation in the cost of steam generated with the help of solid fuels. The significant cost advantage of generating steam using solid fuel as against gas or oil is lost.

The current cost of steam generated by using coal is almost double the cost of steam generation using FO ten years ago. With the price escalation, cost of steam generation on coal itself has tripled to what it was ten years ago.

Actions to reduce the cost of steam generation can not only reduce the adverse effects of such price shocks but can also yield benefits in the long run, as fuel costs keep increasing year on year.

With the objective of understanding how to get the same amount of steam for less, a quick look at how the cost of steam is computed, throws light on the two key avenues for its reduction.

Cost of steam = (hg-hf) x cost of fuel / GCV x η

(hg-hf) – total heat supplied where hg is the enthalpy of steam and hf is the enthalpy of feed water. As the feed water temperature increases, it reduces the quantum of heat required, and consequently less fuel to generate steam. This results in a lower cost per unit of steam.

Similarly, as η, which denotes the direct efficiency of the boiler, increases the cost of steam decreases.

Actions to improve the feed water temperature include :

Recovering every drop of recoverable condensate ( >95% of indirect steam consumption)
Recovering flash steam
Recovering heat from other heat steams like blowdown flash recovery, blowdown water heat recovery, flue gas heat recovery