RWZI Deventer -> Big energy profits and improved process conditions.

What more could you possibly want?
This municipal plant was already equipped with blowers that had a high-speed permanent magnet motor and bearing.
These relatively old machines from Sulzer had lived through their finest hours and needed replacing or full-scale revision. An additional condition was that important parts were becoming scarce. ex: parts of the frequency controller was not available anymore. Taking this into account, combined with the fact that the new machines were significantly better in efficiency between 7-10%, it was then a matter of putting that into a TCO and decided by the municipality that it would be better to replace the old HST blowers with new ones.

Because the plant was equipped with a high-frequency intermittent aeration zone they were also doubting to split up their system in 2 separate headers.

OTB-Engineering helped in the first phase of the project by calculating precisely how much gain the municipal plant would have using 1Header vs 2Headers and which type of blowers best to use for the specific air profile based on one year worth of data.

Then based on our recommendations, calculations, and assurance that we would make an algorithm that would both reduce the energy and improve the process, the municipality decided to go ahead with our recommendations.

Below is a summation of all the core changes OTB-Engineering has implemented to achieve a huge energy saving in the aeration.

Machine control & blower energy efficiency
Before: The machines functioned under a cascade controller.

After: The machines are always chosen based on their most optimal control point in combination with eachother.

Pressure
Before: Fixed pressure of 570 mbar

After: Variabel pressure ranging between 490 – 540 mbar. Of which the current weighed average is around 510 mbar!

Valve position
Before: The valves all independendly worked to achieve a setpoint.

After: The valves now all work together in balancing the total request value in such a way there is always a minimum pressure loss.

Safety
Before: The system was inherently unsafe. As a consequence of the high pressure setpoint the aeration elements could be damaged when there was a lack of control.

After: Because of the balance control and communication between all components the system is now as safe as can be never exceeding a set maximum amount of air to protect the aeration elements. Both individually as the whole system.

Total energy efficiency & improved process control

All combined steps above and tweaked by our own hands we managed to save an estimated 40% energy consumption comparing the new consumption of the blowers vs the old machines.

All while increasing proces stability and reliability!