Efficiency of the cooling system has a big impact on the productivity of chemical plants. Cooling systems are also significant consumers of energy which is needed to continuously circulate the cooling water and operate cooling tower fans.
Implementation of DHI’s Industrial Cooling Water Solution provided the client opportunities to:
ROI within maximum 6 months
Monitoring critical water side heat exchanger parameters
Estimated to be around EUR 200,000 on just one of eight systems
Cooling systems are significant consumers of energy
Cooling water is used extensively in a number of industries for the lowering of process temperatures. Cooling systems are significant consumers of energy. The energy is needed to pump water to heat exchangers and to operate fans in the cooling towers. Efficiency of the cooling system has a big impact on the productivity of some industrial plants. In many cases, there is a direct relation between the cold water temperature and process efficiency.
DHI examined the possibilities of improving the cooling system energy efficiency with our Industrial Cooling Water Solution, which applies new advanced algorithms based on online water distribution models. The study was executed based on historical data and operational measurements from a major petrochemical production site in a moderate climate.
Optimisation of pressures and flows
Our study revealed substantial energy-saving potential for the client, especially in cold and moderate climates. Applying just one of the identified options in the studied system would potentially provide 11% of energy savings annually.
To reach for further savings in the studied system, some significant challenges need to be handled with caution. The highest saving potential is directly linked to optimisation of cooling water flow and/or pressure. Such operations without the proper approach may however have a negative impact on the production processes. Thus, a deep understanding of the system’s hydraulics and thermal conditions is required.
An online water distribution model
To safely reduce cooling water flow and/or pressure, it is necessary to continuously monitor the conditions on the water aspects of all significant heat exchangers. Such monitoring is possible by application of an online water distribution model which can calculate the flows and pressures in the whole system.
The results of these calculations, in combination with basic process data, can be then used to monitor critical water-side heat exchange parameters like heat transfer coefficients, flow speeds and water temperatures. The control system would then compare the calculated values against predefined threshold values to trigger alarms when necessary, and ensure that any optimisation step will not adversely affect the production process.
Advanced monitoring and control
The described mechanism can also be by itself a valuable extension of existing process monitoring and control systems. Continuous monitoring of critical water-side heat exchanger parameters is a solution which can increase process safety and additionally enhance productivity in plants where cooling capacity is a limiting factor (for example, in warm climates) by providing answers to difficult questions like:
The study identified these promising optimisation measures for the client:
DHI’s Industrial Cooling Water Solution has been developed as a tool which enables users to access these identified gains. Depending on the local technical conditions and climate, the resulting improvements can be substantial: cooling capacity increase up to 20%; pumping energy savings up to 40%.
The client is an operator of several refining and petrochemical plants with high focus on innovation and process optimisation.
An integral part of the solution is a hydraulic cooling water distribution model developed in MIKE URBAN (now MIKE+) – DHI’s platform for water distribution and collection system modeling.
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