IL48153A - Cleaning of membrane surfaces - Google Patents

Description

Cleaning of membrane surfaces UOP C 45881 present relates to an improved for cleaning accu solids from a membrane surface used in an ration or reverse of More is directed to the relatively procedure of using water droplets in repeated ductions of a high speed air to effect a surface OF THE In connection all separation it is considered conventional to periodically the units and clean the surfaces with a cleaning flow The frequency and the type of cleaning operation vary the particular type of feed treated and generally the amount of fats and ls that can cause a fouling of the it is al so known and general ly conventional the separation field to periodically make use of certain addi tives or cleaning For exampl in connection the hand of certain food and in the processing of cheese whey to obtain protein and there can b the growth of fungus and bacteria on membranes and in headers or other parts of the particularly in the flow rate In order to assure an clean there can be the use of a tizing sol ution added to a fl ushing fluid during the periodic cleaning Such sol ution for comprise hypochlorous solution or an acid or various of the ing agents used in the dairy industry to remove wolds and various ological growths In any the typical cleaning operation has time consuming and cleaning fluid flow schemes In the present cleaning system rapidly carried out with pressuri zed air and util izes minimal amounts of water or cleaning l iquid SUMMARY OF THE INVENTION i t may be considered a principal object of the tion to util ize water droplets in a high speed air to effect the removal of the foul ing on a membrane In contrast to slower l iquid flows the present improved cleaning system is making use of high vel oci ty air fl ow and the or scouring effect from the accompanying high speed movements of l iquid droplets which wi ll carry along the surfaces with the air a related be considered an object of this invention to eliminate the of a liquid in conventional cleaning procedures and substitute a high speed water droplet cleaning In each the module is only partly filled and then purged high velocity air for a few so as force only small slugs of and subsequently only water along the membrane surfaces to effect the removal of accumulated a brief the Invention provides an rapid method for cleaning the surfaces of a separation unit after being 1n which comprises the steps o partially filling the fluid passageways with water and then purging with air at a her pressure to cause water droplets to move at speed over the surfaces and remove accumulated and repeating the operation of the preceding step to effect a substantial removal of all accumulated and substantially all water droplets from the surfaces without permitting any drying of the In connection with reverse osmosis which operate under higher pressure conditions than it may be to initially effect a removal of pressure through the system and permit an osmotic through the membranes in order to provide an initial lifting or loosening of accumulated material After permitting the sh then there say be the repeated ings of passageways membrane surfaces with high speed air and entrained water only a few minutes of operation will be needed for each purging stage and in many instances the entire cleaning procedure may be completed in an It of desirable to have pressurized high speed air with a pressure being 1n the psi The required sure will vary in accordance with the type of and resistance to pressure drop in a particular For in utilizing a plurality of diameter containing tubular particularly where the fluid is in a serpentine there be a higher pressure drop as compared to a unit ing the use of a small number of larger diameter or 1n with a with relatively large area flow It of intended to the present improved cleaning system to any one type of module or membrane separation unit i as the system my be applied to the various types of holding as well as to flat surface mefnbranes used in and is not intended to limit the present cleaning operation to any one type of membrane separation procedure although the length of time and the of purge liquid fil and high speed air stream flows can vary in accordance with the ease of removal of accumulated on the membrane For in cleaning cheese fat rane surfaces of an u unit handling cheese a relatively few purge stages of air and water droplets effect the desired cleaning of the membrane surfaces such that the entire operation may be carried out in a On the other in certain higher pressure operations carried out with reverse separation units there may be the need to have reverse ic pressure and multiplicity of purges embodying the of speed air and entrained Air alone may be utilized in cleaning it is not intended to the present cleaning system to the use of air only inasmuch as pressurized carbon nitrogen or other suitable gaseous my be used to In certain it may be of advantage to utilize mixtures of air and low pressure it is to be noted that the terra is used herein in a generic and the invention should not be limited to the use of air the partial fillings of in order to obtain the tray comprise water with additive cleaning a a such as the aforementioned hypochlorous for the purposes of the the tera is used in a generic manner and the scope of the invention is not limited to the use of water In still another care must be utilized to preclude the drying out of a surface inasmuch as cellulose acetate and other typical rana materials can be harmed when they are co pletely dried in any of the repeated purge or in a final care be exercised to preclude a continual flow of air after mos of the water and the water droplets have been purged the Reference to the accompanying drawing and the following thereof will serve to illustrate the present cleaning operation as well as point advantageous features connectio Figure 1 of the drawing is a partial sectional elevational view through a tubular forsi of separation module where surfaces are cast on the inside of a plurality of diameter tubular Figure 2 of drawing indicates a type of construction where membrane surfaces are cast onto flat porous supporting and a serpentine flow is provided carry a fluid stream over the plurality of surfaces in the Referring now to Figure 1 of there is rane separation module as defined by an outer housing a plurality of porous holding 2 and eader s 3 and The latter in clamped and held tight over the ends of the respective tubes 2 by end cap members and 6 which tightly engage the respective header 3 and 4 by virtue of a tensile clamping force supplied by threaded means 7 and threaded nuts 3 and In the present there is a path serpentine flow for the liquid to be treated by virtue of the plurality of means within each header means 3 and Inlet and outlet means are provided to the header such that the to be processed can be introduced into tne serpentine flow path to contact the rane surfaces within the rs In this the interior surfaces 11 are indicated as being cast on the interior of each of the r There is indicated an inlet at the side of header means 3 such that the feed will carry to the tubes 2 and then in the aforementioned serpentine path through the to an outlet port which can be in either header 3 or the header weans which will exude through the surfaces and through the porosity of the tube walls will collected within collecting zone confined by housing 1 and withdrawn by suitable port not shown in the present Various types of tube constructions may be in each the 5 of tubes 2 will be of a construction to have porosity such as those formed of fiber glass reinforced with porous resin so as to be permeable to pressurized fluid in the ma ner disclosed in Havens Patent To carry out the present improved cleaning in 10 dance with the present there will be a partial filling of the tubular with or with water and added cleaning or ing and then pressure is introduced through inlet means so as to cause a high speed air flow through the entire serpentine p3th of the ifi dule and simu taneously to carry a of snail water aroplets such as indicated the initial ube Z and the return passageways The high speed air stream carrying the ial slugs of water and the resulting entrained water rather than a slow of effect the desired scouring action and impingement against as well as against to rapidly dislodge accumulated solids materials the passageways and There can be the repeated partial fillings of fluid into the tubes 2 and the repeated pressurized ductions to effect a plurality of purges with the desired high speed air stream and entrained droplets until all accumulated seem be 25 from the As indicated in connection with ion types of it result that four purges quite efficiently clean the membrane surfaces and other of passageways so as to permit the return the module to an On the other with reverse systems which ra be operating at elevated pressures in the psi the solids and sufficiently embedded within reverse osmosis to the extent that pressured 1s desirable as a stage to effecting purges an air stream and entrained In certain the rapid dropping of pressure the reverse and the allowing of to effect from membrane surfaces suffice as a step to the repeated With reference to Figure 2 of the there is indicated a type of housing 14 which encompasses and around of porous members in have membrane surfaces each face thereof to provide for the desired separation of a feed stream being introduced by way of an port raeans Spacer raeans 18 are provided at the ends and side wall portions of supporting in order to turn provide the plurality of spaced fluid passageways between spaced members The latter are also suitable openings at alternate ends such that there my be a serpentine flow path for the feed entering the unit to pass over the of surfaces 17 along the plurality of passageways The arrangement cated of diagrammatic and not intended to be various types of flat porous members may be utilized to advantage 1n porting surfaces for a type Gf separation In any 1n accordance with the present when the a surfaces are fouled with an accumulation of solids materials a feed is shut down and there is the multiple air stream and water In this the entire would be partially filled water and then high pressure air introduced at an inlet such as and a high speed air caused to flow through the plurality of paths 19 so as to cause water droplets 21 to move at spaed along the air to effect the desired removal of accumulated from the the operation will be carried out three or four or a dozen depending on the of the tions on the membrane As heretofore a few cleanings over a minute period suffice in cleaning operations while other instances ten or more cleanings may be carried out advantageously to provide a desired clean state for the entire During the various as well as in a final the high speed flow of air will be carried out for only such period of time as be necessary to remove all or of the water droplets from the system at the care taken not to permit drying out of any of the surfaces the so as to preclude harming the separation efficiency for any one Reversing of purge direction has also proven to be effective in increasing the degree of cleaning and shortening the required to pli insufficientOCRQuality

Claims (5)

1. An improved rapid method for cleaning the membrane surfaces of a plurality of membrane separation units after being in use, said units having fluid passageways therebetween, which comprises the steps of: partially filling the fluid passageways with water and then purging with a continuous air stream at a superatmospheric pressure to cause a non-plug flow of water droplets to move at high speed over the membrane surfaces and remove accumulated materials; and intermittently repeating the operation of the preceding step to effect a substantial removal of all accumulated materials and all water droplets from the membrane surfaces without permitting any drying of a membrane during any stage.

2. The method of claim 1 characterized in that prior to partially filling the passageways with water there is permitted an osmotic back-flushing to occur through the membrane surfaces in order to effect an initial dislodging of materials from such surfaces.

3. The method of claim 1 or 2 characterized in that the fluid passageways are initially partially filled with water containing a cleaning component.

4. The method of claim 1 or 2 characterized in that the fluid passageways are initially partially filled with water containing a sanitizing fluid for the prevention of bacteriological growths.

5. The method of any of claims 1 to 4 characterized in that the air stream is at a pressure of at least 20 psi.(2.4 atmospheres). 48153/2 characterized in that during the repeating of the purging with an air stream there is a reversal of the direction of air flow for at least one of the purges. HE/AA