Application Scopes

Implementing energy efficient solutions in compressed air productions

Compressed air is one of the most important utilities in common industrial activities, if not the most important. There hardly are production sites that work without the need of compressed air, which is a fundamental present and future asset for production.

Nonetheless, compressed air also plays a relevant role on the energy balance of a company. The electricity used in a compressed air system is about the 75% of the product cost in its entire lifetime. This is an unneglectable data since compressed air, in Italy, absorbs about 111% of all the energy used for industrial purpose. Therefore, an improvement of the energy efficiency in this area is critical in order to achieve significant savings in terms of energy, and therefore money.

RENOVIS proposes a great number of solutions to improve the energy efficiency in compressed air production:

INSTALLATION OF INVERTERS ON COMPRESSORS

Compressors are machines that consume electricity in order to perform their task (i.e. increasing the air pressure up to the desired value). In relation with the motor powering it, a compressor can have an ON/OFF or a proportional behavior. In the first case (nowadays the most widespread), this implies that, in situations of partial load, the energy waste related to the single machine is very high. It is then necessary to properly control the compressor. There are several ways to regulate these machines: a supply regulatory valve, an ON/OFF regulation, etc. The installation of an inverter regulating the speed (i.e. the operation) of the compressor in condition of a partial load represents the most efficient solution, being the output conditions (pressure, flow, etc.) equal, both energetically and economically (absorbed electric power and time to reward).

HEAT RECOVERY FROM COMPRESSORS

Part of the electrical energy consumed by a regular industrial compressor turns into heat during compression, due to the thermodynamic irreversibility of such process. A fraction of that heat can be recovered. There are two main methods of recovering heat, which can be used on screw compressors:

heat recovery through the cooling air coming from the compressors;
heat recovery from the oil lubrication circuit of the compressor.

In the first case, the heat generated by the electric motor, the oil radiator and the chiller comes out of the compressor through the cooling airflow. The latter can be reused directly to heat up environments or production facilities. In the second case, the heat generated by the compressor is recovered by the lubrication circuit through an oil/water heat exchanger. This way, it is possible to heat up a water flow (for heating or sanitary use) up to 70°C.

COMPRESSORS ACTIVATED BY STEAM TURBINES

There is the possibility to use process waste heat to produce steam, by recovering its thermal energy. Such steam can be transferred to compressed air production systems made by compressors activated by means of steam turbines instead of traditional electric motors. If properly designed and sized, these systems allow to use recovered heat (therefore, not expensive) in order to produce compressed air, with a significant benefit in terms of energy and money.