Climate-neutral heating for Herne: How KSB pumps enable district heating sourced from a chemical plant
The city of Herne is aiming to transition to providing climate-neutral heating by 2045. One of the sources it has opted for is district heating using industrial waste heat. A joint project with KSB illustrates how existing energy can be tapped into and used efficiently by means of networking and modern control technology. It also highlights the central role pump systems play in the transition towards sustainable heating solutions.
Part of Herne's characteristic skyline is formed by the INEOS Solvents plant's chimneys, gas tanks and distinctive cooling tower. The industrial plant not only produces solvents, such as ethanol, diethyl ether or isopropanol; it also supplies the city with climate-neutral heating.
The plant provides industrial waste heat for use in district heating. For its production processes the plant requires wet steam, also known as exhaust vapour. When steam is cooled and condensed, waste heat is generated. Heat exchangers make this heat available to a district heating network spanning about 5 km and supplying more than 1000 households in the plant's vicinity with heat. Up to 4 megawatts of thermal energy are provided by the INEOS network in this way. As this is heat for which no additional fossil fuels have to be burned, it is climate neutral.
The INEOS Solvents plant in Herne supplies 1000 households with district heating.
Image: ChemSim/Wikimedia CC BY-SA 4.0
For a long time, the operators of the district heating network had been facing two challenges. One of them was that the excess heat generated by the industrial plant exceeded the capacity of the existing network by far. Under optimal conditions, more than 8 megawatts of waste heat may be generated by the production process – clearly exceeding the 4 megawatts required by the households connected.
The other challenge was that in order to maintain the heat supply, expensive heat generation by steam had to be used whenever downtime in the INEOS production occurred, for instance during maintenance work.
By working with KSB the municipal utilities of Herne circumnavigated these obstacles and expanded the use of process waste heat for their district heating supply. The solution was to connect the existing network with another district heating network. The "centre" district heating network, which supplies the town centre of Herne with heat, only runs 500 metres from the INEOS plant. This network is provided with heat from fossil energy by the energy supplier Uniper.
Connecting the two networks enables excess heat from the INEOS network to be used for the "centre" district heating network. Consequently, less fossil-fuel-generated energy is needed. And the other way round, the "centre" network provides a back-up for the INEOS network when no waste heat is produced at the plant for a short time.
Practically speaking, connecting these networks was far from simple as they are designed based on very different technical principles.
The KSB-engineered pump control system flexibly and automatically adjusts operation to match the demand.
Some households are connected directly to the INEOS network, meaning that the heating water flows directly through their heaters. For this reason, the system has to be operated at relatively low temperatures and at a low pressure. The system temperatures are restricted to below 90 degrees Celsius. The static pressure of the system is about 3 bar and the maximum pressure in the supply line 4.5 bar.
By contrast, the "centre" district heating network is connected to the buildings via transfer stations equipped with heat exchangers. This means it can be operated at a higher pressure and at higher temperatures with system temperatures reaching up to 130 degrees Celsius in the supply line and 50 to 80 degrees Celsius in the return line. The static pressure of the system is about 12 bar.
This makes it impossible to connect the two networks directly. The solution: An intelligent heat transfer station fitted with two powerful plate heat exchangers with a rated capacity of 8 megawatts each. The station hydraulically separates the two systems from each other while enabling the exchange of heat. This transforms two previously separate systems into a flexible combined one.
The actual challenge was the control system as the demand in a district heating network fluctuates constantly. Fluctuations are not only caused by the seasons but also by the time of day and by the weather. The quantity of industrial waste heat also changes as it depends directly on the production process.
The task of adjusting the operation of the heat transfer station flexibly to the demand is taken on by the KSB-engineered pump control system, the system's centrepiece. On the side of the INEOS network, it controls four recirculation pumps of the type Etanorm 200-150-250 with grey cast iron casings and bronze impellers. They are driven by 4-pole asynchronous motors with a 45 kilowatt rating. The motors are operated over-synchronously up to 60 Hz on frequency inverters of the type KSB PumpDrive R via the KSB-engineered pump control system. The same control system is used for the two return pumps feeding water into the "centre" district heating network. The control system and frequency inverters adjust the pumps to the optimum return flow rate.
Four recirculation pumps of the type Etanorm 200-150-250 control the INEOS district heating network.
The pumps controlled in this way keep the water circuit in the INEOS network moving, stabilise the pressure and prevent any safety-relevant conditions such as excessive pressure or temperature, negative pressure or dry running. The control system especially monitors critical points, also called bad-value points, which are the first areas in which pressure may drop too much or the temperature may no longer be sufficient.
In line with the demand the system switches between several operating modes. Normally, process waste heat supplies the network surrounding the plant. If not enough heat is available, e.g. during maintenance work, the "centre" network takes over the heat supply for that network. If more waste heat is available than locally required, the excess energy is fed into the "centre" network. Switching between these two operating modes is quite a delicate procedure. If pumps are started up or stopped abruptly, pressure surges may occur. Such loads are problematic for the valves and piping. This is why the system was programmed with the pumps adjusting their speed using so-called dynamic start and stop ramps to be optimally matched to the system requirements.
The project was completed in March 2025. It demonstrates that climate-friendly heat not only depends on new energy sources. It also depends on smart technical solutions that make use of existing potentials and allow integration in existing systems. Herne illustrates what the transition towards sustainable heat solutions can look like: technically demanding, yet invisible in day-to-day life – and all the more important for meeting tomorrow’s climate targets.
