Hankinnan kuvaus
Heat pump for Pått-project: In this project the purpose is to use heat pumps to extract heat from purified sand filtered sewage water and produce part of the district heat in this way. The heat pump plant would have a total heat capacity of 9 – 12 MW divided on 2 or more individual, independently operating heat pumps or groups of interconnected heat pumps. The Vaasan Vesi Pått effluent treatment plant is positioned in Palosaari about 2 km north from the city center. The plant uses sand filtration as the final step prior to discharging the water to the sea.
The general process concept is to extract heat from purified sewage water directly or indirectly in the evaporator and condensing the heat in the condenser against district heating water with typical exit temperatures of 75 – 90 oC. The max. temperature shall be minimum 90 oC, but higher, if possible. The district heating water has an inlet temperature of 40 – 55 oC.
Sewage water at flows up to 1.200 m3/h and temporarily even more is available. The inlet temperature is typically 8 – 17 oC with minimum temperatures occasionally down to 6 oC. The preferred solution for using the sewage water is to use it directly in the evaporators. A tube cleaning system (e.g. ball cleaning) shall be included. The sewage exit temperature shall be as low as possible without a risk of freezing. The target is down to 2,5 oC, there will be a guarantee value.
In case the Bidder finds direct use of sewage water in the evaporators unacceptable, a closed loop system with indirect cooling will be implemented by the Puchaser. In order to achieve same heating capacity from the available heat source, the heat source temperatures need in this case to be about 2 oC less compared to direct use, the will be a guarantee value. In case there is a risk of freezing, the closed loop water includes an anti-freeze chemical.
The technical requirements are specified in more detail in the Technical Appendix, which will be sent out to the approved bidders.
Refrigerant:
The refrigerant type(s) shall be of a lower GWP type, which is not subject to the EU phase down programme (eg. R134a not accepted). Furthermore, ammonia (NH3) is not accepted due to problems in getting sufficient safety distances to the site border and nearby living areas.
The Request for Quotation outlines the requirements regarding the design, engineering, materials selection, manufacturing, delivery, erection, commissioning, personnel training, testing and maintenance issues of the heat pump for the project. Also, a proposal service agreement for the periodic annual maintenance of the Heat Pump should be included in the quotation.