3rd Method: Centralized exhaust air filtration with heat recovery system
On some winter days in Changchun the ambient median temperature goes down to -16°C, which also brings down the temperature inside the hall. Many foundries using a conventional exhaust ventilation system have to heat up the production halls, but due to the costs, this is quite an untenable solution.
In most production processes high amounts of heat and energy are created which can be used for follow-up processes. The centralized exhaust air filtration system, equipped with an integrated heat recovery system, enables an energy-efficient heating or cooling of the hall by performing in an exhaust air mode.
In this system, multiple machines are connected to one centralized large exhaust air filter system. The waste air from the machinery is extracted through exhaust ducts and led to the centralized filter system, which is equipped with electrostatic precipitators as well as integrated in-tube heat exchangers.
After filtering the aerosols out of the exhaust air, the heat pump, which is connected to the filter system, extracts the energy out of the purified air. The energy is transferred in the condenser of the heat pump to a heating water circuit. Afterwards, the heating water is led to a second heat exchanger, which is installed in the incoming air duct. With this method the incoming air is heated up in an energy-efficient and economical way before flowing into the production hall.
With a highly efficient heat pump, the foundry in Changchun increases the temperature inside the hall up to room temperature just by using the heat recovered out of the exhaust air. With an energy demand of 352 kW per hour, the heat pump creates almost 1,500 kW per hour for follow-up processes.
In this scenario the foundry in Changchun would have annual operation costs of RMB 4,235,717, going along with an annual carbon dioxide emission of almost 1000 tons. These energy savings are less than the foundry would achieve with the recirculating air mode, but the savings are still much higher than those of a conventional exhaust ventilation system.