Client: Reaxis, Inc.
Date Completed: January 2016
Venture Engineering & Construction, Inc. (Venture) was contracted to present technical aspects and incurred costs for three (3) types of cooling system options for supporting equipment at a chemical manufacturing facility. The plant was operating on city water for once-through, non-contact cooling water (NCCW). The selected cooling system options evaluated were closed loop chiller, closed loop evaporative cooling, and geothermal heat rejection. The selected systems were compared on the basis of mechanical performance, initial capital investment cost, ongoing operating cost, and period of payback beyond installation.
The initial phase of the project included a site survey to identify and map all water uses in order to classify them as NCCW or as water being used for other purposes. A data collection plan was developed to obtain the necessary temperature and flow data required to perform heat duty calculations. Various operating scenarios were explored to establish the maximum cooling system requirements during peak production hours. Once the data collection plan was executed and engineering calculations performed, design criteria was established based on cooling loads and equipment operating schedules.
Venture prepared system descriptions and associated process flow diagrams for the three (3) cooling systems under consideration. Two thermal coolant outlet/inlet temperatures were considered for the closed loop chiller system and cost evaluation. Two cases were considered for evaporative cooling: an 8 degree approach to wet bulb temperature and a 12 degree approach. Additionally, an alternative approach to evaporative cooling, a wet surface air cooler (WSAC) was also considered. In total, six (6) cooling system options were evaluated based on thermal performance, initial investment, and operating cost.
The capital and operating cost estimates were prepared with a ± 30% margin. Further financial evaluation was performed based on the level of capital investment of a particular system and the related operating costs. This evaluation determined the rate of payback on the initial investment made; and the benchmark year defined as the breakeven point whereby the initial investment is paid off by discontinuing the use of city water for process cooling. After this point the savings to the plant was calculated on a steady annual rate.
Ultimately, Venture concluded that an evaporative cooling option, either evaporative tower with an 8 degree approach temperature or using a WSAC, was preferred. The WSAC was recommended as it had an edge over the other by producing 15 degree cooler water overall for the summertime period of operation.
Venture furnished the load calculations, conclusions, and recommendations along with all of the collected operating data in a comprehensive technical report.