A major refining and petrochemical production plant needed ways to improve their cooling system capacity and energy efficiency. DHI examined the possibilities of efficiency improvement by implementing our Industrial Cooling Water Solution. The study we carried out as part of the solution revealed substantial energy-saving potential, 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.

Challenge

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.

Solution

Implementation of DHI’s Industrial Cooling Water Solution provided the client opportunities to:

  • improve cooling capacity by optimising water flows
  • reduce heat exchanger fouling by applying advanced model-based monitoring routines
  • save energy by optimising pressures, temperatures and water flows

Results

Return of Investment

ROI within maximum 6 months

Improved process safety

Monitoring critical water side heat exchanger parameters

Yearly savings

Estimated to be around EUR 200,000 on just one of eight systems


‘Results of the study revealed a potential which surpassed our initial expectations. As a result of our new approach to optimising cooling system efficiency, industrial operators can expect significant gains for their plant.’

Jan Kwiatkowski
Sales Executive
Industrial Water, DHI Group


The full story

Challenge

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.

Solution

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:

  • When and where is the risk of scaling significant?
  • When should I increase the water flow to improve process safety?
  • Which installations have the greatest ‘cooling comfort’?
  • What will be the impact of reduction of cooling water flow on various process nodes?
  • How to distribute the cooling water to particular process nodes in order to provide the highest productivity of the whole plant?
  • How to adjust the cooling system to diurnal and seasonal changes of air parameters?

Results

The study identified these promising optimisation measures for the client:

  • Improve hydraulics
    This will make it easier for the water to flow through the pipes, remove bottlenecks (replace old pipes, increase diameters where appropriate), open half-closed valves, and so on. A hydraulic model greatly facilitates finding and evaluating the required actions.
  • Improve system layout
    This is especially if you have heat exchangers on different levels. It might be worth fully or partially to separate pressure zones or add local pressure boosting pumps.
  • Optimise water distribution
    This optimisation measure ensures that the required amount of cooling water reaches the right heat exchangers in the right time. Advanced algorithms should be used to optimise water distribution in real time.
  • Optimise total flow and temperature
    Reducing air flow through the cooling tower on a cold day is often much less energy-effective than reducing water flow and achieving lower water temperatures.
  • Improve water distribution over the cooling towers
    Cooling tower performance may be strongly reduced when the water distribution is uneven.

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%.

About the client

The client is an operator of several refining and petrochemical plants with high focus on innovation and process optimisation.


Solution

Industrial Cooling Water Solution

Solution components

An integral part of the solution is a hydraulic cooling water distribution model developed in MIKE URBAN – DHI’s platform for water distribution and collection system modeling.

Case story - Highlights flyer

Increasing cooling system efficiency in a large petrochemical plant

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