Troubleshooting a Cooling Water System with a Rigorous Flow and Pressure Network Model

摘要

Cooling water is supplied to the entire NOVA Chemicals' Corunna Ethylene facility by a single 16 cells system, circulating 160,000 gallons/minute. Cooling water temperature is a production constraint during hot summer days. In June 2003, the cooling water supply pressure was observed to increase. Ultrasonic flow measurements and temperature surveys were used as a means of troubleshooting the problem. The results from these surveys suggested that the cause had originated in the olefins quench area. In order to validate the field survey, an existing rigorous flow and pressure network model of the cooling water system was modified to reflect the current quench area cooling water flows and other suspected conditions. The simulated cases indicated that the site was experiencing a widespread fouling problem. All simulated exchangers outside of the quench area had to have an 80% increase in pressure drop in order to match plant conditions. This evaluation of the entire cooling water network allowed the root cause of the pressure increase to be identified as system wide fouling. As a result, the final solution proved to be different than the action plan that had been developed based only on the results from the field surveys. This paper discusses the methodology that has been used to build the cooling water system model and how it has been used to diagnose the extent of fouling in the entire system. The model includes approximately 145 exchangers in a network that involves common supply and return headers, as well as 2 intermediate headers.