Energy-efficient filter system

A well-known manufacturer in the plastics industry has invested in a new disposal plant for production waste as part of a new construction project.

The chips and dust produced during the manufacture of parts made of GRP were to be collected and separated by an extraction and filter system that not only offered the highest possible 100% availability in compliance with all legal regulations, but also a high degree of energy efficiency and ease of operation with low maintenance requirements. Together with the specialists from SPÄNEX in Uslar, Germany, a concept was developed and realised after extensive market studies and competitive comparisons, which exactly fulfils these requirements.

The extraction and filter system for two special plastics processing machines was designed as a single-line system with a filter unit (see picture) operating under vacuum and an extraction fan on the clean air side. The chips and dust produced during the machining of the parts are extracted at the machine nozzles and conveyed to the filter system. The filter elements, which are stabilised by support cages and streamed in from the outside, remove the plastic particles from the raw air flow. When the filters are cleaned by compressed air pulses, the separated material enters an intermediate container underneath the filter unit. Due to the so-called jet pulse cleaning, filter regeneration is possible during the extraction operation, so that an uninterrupted availability of the system is achieved. The filter elements are made of special needle felt with an antistatic finish, which enables 100 % recirculation of the extraction air into the production halls.

The fan on the clean-air side conveys a maximum volume flow of 19,000 m³/h via a duct system with silencer, shut-off damper and fire damper either into the atmosphere or back into the production hall to prevent heat loss during the heating period. There, the return air is distributed draught-free through generously dimensioned discharge ducts. The arrangement of the extraction fan on the clean-air side reduces mechanical wear to a minimum and also enables the use of a special impeller for maximum efficiency. Thus, at a total pressure of 3450 Pa, the fan only requires a shaft power of 21.7 kW. A frequency converter for demand-dependent control of the fan during partial load operation also ensures considerable power and thus cost savings.

The separated chips and dust are collected in an intermediate silo located below the filter. The filling level is monitored. When full, the chip/dust mixture is conveyed through a discharging screw and a rotary valve into a container located below the intermediate silo during extraction operation. For better handling, this is equipped with a lifting and clamping device and castors.