983688 - Helping Solve the Potable Water Problem: The WOFF Process

The world's total water supply is enormous compared with the presently conceivable needs of society, yet there is a growing water concern. Approximately 98% of the 320 million cubic miles of water in the earth's crust is salty and useful neither for irrigation by present techniques nor for the majority of other needs. The hydrologic cycle provides many times the world's annual water needs, but fresh water supplies vary widely not only over the earth's surface but also over time in a given region. This accounts for what has come to be referred to as the looming potable crisis.
An obvious way to increase potable water availability is to recover freshwater through desalination of seawater or from the large underground stores of brackish water which are available in many arid regions of the world. Desalination methods are well documented in the literature; key among them are evaporation, reverse osmosis (membrane separation), and crystallization, all of which are at various stages of commercial use or full-scale development and refinement in order to increase their efficiency and reduce their cost and energy requirements. Other alternatives to these conventional desalination processes are also being explored to broaden options available to address this potable shortage.
This paper introduces the reader to one such alternative: the Water Obtained from Fossil Fuels (WOFF) process. In the WOFF process, the technical feasibility of employing condensing heat exchangers following the combustion of a fossil fuel for capturing condensed water vapor from boiler flue gas is being explored. The WOFF process allows for the majority of any acid gases to be condensed early in the heat exchange condensation operation while “pure” water is condensed later in the heat exchanger. The result is the recovery of usable potable water from a source not generally considered, i.e., water contained in boiler flue gas. This paper reviews the status of potable water availability and the looming water crisis, natural gas combustion, an introduction to and calculational details of the WOFF process, along with a host of other operations that can improve the process to make it a feasible and cost-effective alternative for improving water availability in the future.