Gas filtration system and method

Abstract

The invention provides a filtration system for removing a target gas from a gas to be filtered in a space. The system has different modes of operation. Based on sensing of the current level of the target gas, the previous history of the sensing signals and the previous modes of operation, a degree of filter loading with the target gas can be determined. This information and the current sensed level of the target gas are together used to select a mode 5 of operation. In particular, the filter loading and the current pollutant level is used to determine whether absorption/adsorption or desorption will take place and which rates these processes will occur, which provides the basis for deciding what operation mode should be executed.

1 . A filtration system for removing a target gas from a gas to be filtered in a space, the filtration system comprising:
 a sensor arrangement, which comprises a gas sensor for sensing a concentration of the target gas in the space;   a filter for filtering the target gas from the air, wherein the filter comprises an absorption filter or an adsorption filter; and   a control system which comprises a ventilation system for controllably driving air through the filter, wherein the control system is adapted to implement different modes of operation of the filtration system, wherein   the control system is adapted, based on current sensor arrangement signals, previous sensor arrangement signals and previous modes of operation, to:
 determine a degree of filter loading with the target gas; and 
 select a mode of operation based on the degree of filter loading and the current sensor arrangement signals 
   wherein:   the control system is adapted to determine from the degree of filter loading with the target gas and the current sensor arrangement signals when filter absorption or adsorption is taking place and when filter desorption is taking place.   
     
     
         2 . (canceled) 
     
     
         3 . A filtration system as claimed in  claim 1 , wherein the control system is further adapted to determine from the degree of filter loading with the target gas and the current sensor arrangement signals the rate of absorption or adsorption, or desorption. 
     
     
         4 . A filtration system as claimed in  claim 1 , wherein the control system comprises a heater for heating the filter. 
     
     
         5 . A filtration system as claimed in  claim 1 , wherein the filter further comprises a catalyst filter. 
     
     
         6 . A filtration system as claimed in  claim 5 , wherein the catalyst filter comprises a photo-catalytic filter and the control system further comprises a light source for illuminating the photo-catalytic filter. 
     
     
         7 . A filtration system as claimed in  claim 1 , wherein the filter is part of an air purifier, and the control system is adapted to switch off the air purifier when it is determined that the concentration is above a threshold and the filter is operating in a desorption regime. 
     
     
         8 . A filtration system as claimed in  claim 1 , wherein the control system is further adapted to provide an output which indicates when additional ventilation of the space with outdoor air is desirable. 
     
     
         9 . A filtration system as claimed in  claim 1 , wherein the gas sensor comprises a formaldehyde sensor, and wherein the filter comprises an absorption formaldehyde filter. 
     
     
         10 . A method of controlling a filtration system for removing a target gas from a gas to be filtered in a space, the method comprising:
 sensing a concentration of the target gas in the space;   filtering the target gas from the air, wherein the filtering makes use of an absorption filter or an adsorption filter; and   implementing different modes of operation of the filtration system,   the method comprises, based on a current sensed concentration, a previously sensed concentration and previously adopted modes of operation:
 determining a degree of filter loading with the target gas; and 
 selecting a mode of operation based on the degree of filter loading and the current sensor arrangement signals 
   wherein:   the method further comprising determining from the degree of filter loading with the target gas and the current sensed concentration, when filter absorption or adsorption is taking place and when filter desorption is taking place.   
     
     
         11 . (canceled) 
     
     
         12 . A method as claimed in  claim 10 , comprising determining, from the degree of filter loading with the target gas and the current sensed concentration the rate of absorption or adsorption, or desorption. 
     
     
         13 . A method as claimed in  claim 10 , wherein one mode of operation comprises heating the filter and another mode of operation comprises illuminating a photo-catalytic filter. 
     
     
         14 . A method as claimed in  claim 10 , wherein the filtering step is carried out by an air purifier, the method further comprising switching off the air purifier when it is determined that the concentration is above a threshold and the filter is operating in a desorption regime. 
     
     
         15 . A computer program comprising code for implementing the method of  claim 10  when said program is run on a processor.