88-02: Staged Cooling at Signaal/Shasta a High Recycle Evaporative Cooling

Abstract: Signal/Shasta is a 55 MW waste wood burning power plant located in Northern California. Plant water comes from on-site wells and is high in silica. The plant is a zero wastewater discharge design. The cooling water system at the Signal/Shasta power plant is a state of the art, water conserving, cost effective, and energy efficient design. The system totally utilizes all process water entering the plant and there is no waste stream discharge at the plant boundary limits. Total plant water usage averages 700 GPM. The final affluent is 1.8 GPM that is consumed in the ash conditioning process. The system design uses conventional techniques in a patented process to achieve 350 concentration cycles of incoming water. Two separate and segregated cooling systems are used to evaporate 99.5% of the incoming water flow without the use of solar ponds or high-energy evaporation systems. This high water utilization is the result of leverage on concentration cycles obtained by staged cooling. This paper describes the system in detail.