Filtration system and method
Described are multi-stage drum filtration systems including a primary rotary drum filter stage, at least one passive filter stage, and a main fan configured to create a vacuum on an inlet side of the primary rotary drum filter stage. The multi-stage drum filtration system may also include a HEPA filter stage. A controller may be configured to control a speed of the main fan to maintain an inlet vacuum to the primary rotary drum filter stage that corresponds to an inlet vacuum set point input.
1. A multi-stage drum filtration system comprising:
(a) a primary rotary drum filter stage comprising a rotary drum and filtration media, wherein the filtration media is configured to achieve a pressure differential between 0.5-1.5 inches at 100 ft/min face velocity when the filtration media is clean and between 1.0-4.0 inches at 100 ft/min face velocity when the filtration media is loaded;
(b) at least two passive filter stages coupled to an outlet side of the primary rotary drum filter stage;
(c) a main fan coupled to the stages and configured to create a vacuum on an inlet side of the primary rotary drum filter stage;
(d) a pressure sensor configured to monitor inlet pressure to the primary rotary drum filter stage; and
(e) a controller connected to the pressure sensor and the main fan and configured to control a speed of the main fan to maintain the inlet pressure to the primary rotary drum filter stage at a pre-set level.
2. The multi-stage drum filtration system of claim 1 , further comprising a HEPA filter stage coupled to an outlet side of the at least two passive filter stages.
3. The multi-stage drum filtration system of claim 2 , wherein the HEPA filter stage comprises a plurality of individual filters, each individual filter comprising a rating of 2000 CFM at 1.4 inches w.g.
4. The multi-stage drum filtration system of claim 1 , further comprising a variable frequency drive connected to the main fan, wherein the variable frequency drive receives a speed signal from the controller, converts the speed signal into a new speed signal, and transmits the new speed signal to the main fan.
5. The multi-stage drum filtration system of claim 1 , further comprising a seal positioned between an open end of the rotary drum and an enclosure wall between the primary rotary drum filter stage and the at least two passive filter stages.