Hot saving potentials in the cooling water supply of a chemical company
Many chemical processes require a constant operating temperature. This can be provided by complex cooling water systems with heat exchangers, for example, as is the case at a large international chemicals group. Experts from SES System Efficiency Service were commissioned to investigate one of these energy-intensive systems in detail, uncover potentials for optimisation and find ways of tapping into them.
Many chemical processes require a constant operating temperature. This can be provided by complex cooling water systems with heat exchangers, for example, as is the case at a large international chemicals group. Experts from SES System Efficiency Service were commissioned to investigate one of these energy-intensive systems in detail, uncover potentials for optimisation and find ways of tapping into them.
Optimisation
A system that has grown over the years, spanning several buildings and floors
- Determine the operating data of the seven pumps installed
- Create a pump characteristic curve incl. the current operating point/range
- Check the power input incl. efficiency
- Analyse the overall system and identify the overall efficiency
- Recommend actions for operation to be efficient and reliable in the future
- During normal operation (summer) the pumps are running at overload.
- Overload and wear have already decreased the pumps' efficiency to approx. 55 %.
- In winter, the pumps are operated outside the permissible operating range.
- During normal operation (summer), the pumps are operated outside their permissible operating range.
- The pressure booster pumps do not increase the pressure during normal operation.
- Overload and wear have reduced pump efficiency to a maximum of 25 %.
Data analysis revealed that the cooling water pumps to be investigated are operated at a markedly reduced efficiency.
The solution:
Replacing the pumps with new, more efficient models
- Replacing all five pumps with pumps of the type Etanorm E 350-300-375 driven by 160 kW motors in flameproof enclosure, for variable-speed operation
- Installing five frequency inverters and a higher-level, load-dependent control system
- Installing a bypass around the pressure booster pumps as these are currently not required in normal operation
KSB's pressure booster pump of the type Etanorm 125-250 without frequency inverter is also running at reduced efficiency.
The result:
An energy-efficient, reliable system with reduced CO₂ emissions
- Higher operating reliability with optimised materials
- Pump operation in permissible operating range at best possible efficiency
- Current flow rates will also be met in the future
- Flexible adjustment with variable speed pumps
- Similar pump characteristics enabled the upgrade to be implemented step by step
A comparison of life cycle costs shows: Despite the rather low energy price of 5 ct/kWh the investment costs are paid back within less than 3 years.
Figures I Data I Facts
Previous situation | Optimised situation | |
Drive rating [kW] | 5 x 190, fixed speed | 5 x 160, variable speed |
Energy savings [%] | - | 66.2 |
Energy input [kWh/a] | 3,970,000 | 1,343,000 |
| Emissions [t CO₂/a]1 | 1,453 | 492 |
| Electricity price [€/MWh] | 50 | 50 |
Payback period [years] | - | 2.8 |
