IVETHOD FOR INCREASED FILTRATION EFFICIENCY

Techni cal dorrai n

The present appl i cati on di scl oses a met hod for i ncreased fi l trati on effi ci ency, whi ch can be appl i ed as exanrpl e i n water treatment pl ants and food i ndustry and any i ndustri al activi ty that requi res i ncreased fi l trati on effi ci ency.

Pr i or art

The word "drai nage" i s currently used rel ated to the fl ow of i ntersti ti al aqueous fi l trate that can be taken fromthe mass of sl udge, ei ther by gravi ty or by mechani cal means dependi ng on the technol ogy enrpl oyed. To remove the fi l trate, equi pment such as bel t fi l ters, fi l ter presses, centri fugal decanters, among others, can be used. The ai m i s to extract the most of the water contai ni ng fi l trate from the sl udge. Thi s wi l l al l ow to reduce the quanti ty of excess sl udge transported and thus wi l l i nrpact i n the sl udge transport costs. The term sl udge i s conmrDnly enrpl oyed to descri be a process product of bi ol ogi cal , cherri cal or physi cal treatment of water and wastewater.

In an exanrpl e, the rel ease of the resi dual water can be obtai ned by gravi ty drai nage of sl udge on dryi ng beds or by mechani cal means. Dryi ng beds are fi l l ed wi th sand-gravel on whi ch the sl udge i s spread and l eft to drai n/evaporat e for a certai n ti me. By si mpl e drai nage a max of 20% sol i d- i n water-sl udge can be achi eved.

Ivechani cal dewateri ng can be achi eved by:

6 Fi l ter press: separati on process used to separate l i qui ds and sol i ds that uses the pri nci pl e of pressure drive, provi ded by a sl udge purrp. The sl udge i s fed i nto the machi ne, after whi ch a rrovi ng pl ate cl anrps a seri es of f i l ter pi at es t oget her ;

6 Centri f ugal decanter: sol i ds parti cl es are accel erated by fast rotati on thanks to the centri f ugal forces to the peri phery of a cyl i ndri cal or coni cal separator, f rom where i t i s removed by a screw conveyer or bl ades. Thi s i s a very compact system)

6 Bel t press: dewateri ng technol ogy that appl i es mechani cal pressure to a chemi cal l y condi ti oned sl udge, whi ch i s sandwi ched between two tensi oned bel ts. Typi cal l y, a bel t f i l ter press recei ves a sl urry rangi ng f rom 1-4% feed sol i ds and produces a f i nal product of 12-35% cake sol i ds; 6 Vacuum f i I t er : works on the pri nci pl e that i nsi de a drum rotati ng i n the sl udge i s created a vacuum) and consequentl y sl udge i s deposi ted on the drum surface and water i s sucked i nsi de. The sol i ds content i n the sl udge cake vari es wi th the type of sl udge, typi cal l y f rom 16-20% (for raw acti vated sl udge) to 32-40% (for wel l di gested pr i rrary si udge) .

The document DE3144314A1 di scl oses a process for the treatment of sewage sl udge where the sai d sewage sl udge i s contacted wi th CCk- cont ai ni ng gases at el evated pressure and then abruptl y l et down. However, thi s document does not di scl ose the use of a stati c or dynami c mi xer to i ntroduce pure CQ2 or mi xtures of CQ2 before the f i l trati on.

The document GB1088400A di scl oses a method of dewateri ng sl udge where the sewage sl udge i s dewatered i n a decanti ng centri f uge and l i me i s added to the centri f ugate i f not al ready present. Then, the mi xture i s treated wi th CQ2 unt i I pH i s be I ow 10. The resul t i ng I i qui d i s t hi ckened and the sol i ds fed back i nto the cycl e before or after the centri fuge. However, thi s document does not di scl ose the use of a stati c or dynarri c rrixer to i ntroduce pure CO2 or rrixtures of CQ2 before the fi l trati on.

Surrrrary

The present appl i cati on di scl oses a met hod for i ncreased fi l trati on effi ci ency conrpri si ng the fol l owi ng steps:

CQ2 or rrixtures of CQ2 are added to the fl ui d to be fi l tered, froma CQ2 regul ati on stati on;

- the fl ow of CO2 or rrixtures of CQ2 i s rri xed wi th the fl ui d to be fi l tered i n a rrixer;

- the pH of the rrixture i s measured after passi ng the rri xer ;

- the rrixture obtai ned proceeds to fi l trati on.

In an enrbodi ment, the rrixer used i n the method for i ncreased fi l trati on effi ci ency i s stati c.

In another enrbodi ment, the rrixer used i n the method for i ncreased fi l trati on effi ci ency i s dynanri c.

In even another enrbodi ment, the CQ2 or rrixtures of CQ2 used i n the method for i ncreased fi l trati on effi ci ency are i n sol i d forrn i n l i qui d forrn gaseous form or rri x gas wi th I i qui d.

In an enrbodi ment, the method for i ncreased fi l trati on effi ci ency conrpri ses the use of a CQ2 dosi ng stati on between the C02 regul ati on stati on and the rrixer. The present appl i cati on al so di scl oses the use of the met hod for i ncreased fi l trati on effi ci ency i n water treatment pl ants and food i ndustry.

General descr i pt i on

The present appl i cati on descri bes a method for i ncreased fi l trati on effi ci ency, whi ch can be appl i ed as exanrpl e i n water treatment pl ants and food i ndustry and any i ndustri al activi ty that requi res i ncreased fi l trati on effi ci ency.

In thi s method, pure CQ2 or rrixtures of CQ2 can be used before the dewateri ng step to i ncrease drai nage of i ntersti ti al water from the sl udge. The dewateri ng steps wi th the use of CO2 show a very i rrportant drai nage effect whi ch i ncreases the dewateri ng abi l i ty of the equi pment for mechani cal dewateri ng. Thi s CQ2 can come, for i nstance, froma tank or fromthe fl ue gases of a boi l er.

The pure CQ2 or rrixtures of CQ2, ei ther i n gas or l i qui d or sol i d forrn can be added usi ng a stati c rrixer, a dynarri c rrixer or any other devi ce to make react the CQ2 wi th the fl ui d to be fi l tered ^" i n thi s way wi th the same dose of fl occul ant, preferably a polymer fl occul ant, and even more preferably a modi fi ed pol yacryl arri de, the fl ui d wi l l drai n more effi ci ently i n the mechani cal dewateri ng system and a hi gher content of sol i ds wi l l be obtai ned i n the dewatered f I ui d.

If CQ2 i s used, for the same l evel of sol i ds i n the fl ui d pri or to dewateri ng, a reducti on of fl occul ant consumpti on i s al so possi bl e, namely a reducti on of up to 50% So the CQ2 can be vi ewed as a drai nage addi tive i n mechani cal s I udge dewat er i ng. The method conrpri ses the fol l owi ng stages:

- CQ2 or rrixtures of CQ2, i n sol i d forrn i n l i qui d forrn gaseous form or rri x gas with l i qui d, are added to the fl ui d to be fi l tered from a CQ2 regul ati on stati on, whi ch can have a CQ2 dosi ng stati on;

- The rrixture i s passed through a stati c or dynarri c rrixer i n order to i ncrease the transfer area between CO2 and fl ui d and thus promote the reacti on between the CQ2 and the f I ui d t 0 be fi l tered;

- the pH of the rrixture i s measured after passi ng the rri xer ;

- the rrixture obtai ned proceeds to fi l trati on.

The CQ2 regul ati on stati on regul ates the fl ow of CQ2 among the steps of rrixture to have a certai n quanti ty of CQ2. The usual dosage of CO2 i s conrpri sed between 30 to 350 Kg CO2 per t on of dry sol i ds.

In the step of passage of the rrixture i n the stati c or dynarri c rrixer, the resi dence t i me i s l ower than 2 seconds.

After passi ng the stati c or dynarri c rrixer, the pH of the rrixture i s analysed. Thi s i s an i nrportant step si nce the measured val ue of pH give us an i ndi cati on that the CQ2 has been properly di ssolved.

Bri ef Descri pti on of the Fi gures

The fol l owi ng fi gures provi de preferred errbodi ments for i l l ustrati ng the descri pti on and shoul d not be seen as I i rri t i ng the scope of i nventi on. Fi gure 1: Typi cal curve for drai nage i ncrease wi th addi ti on of COz.

Fi gure 2: Typi cal process l ayout for drai nage i ncrease wi th addi ti on of CQ2, where the reference nunrbers bel ong to:

1 ^" wat er ;

2 ^" polymer preparati on;

3 ^" pol ynrer ;

4 ^" si udge;

5 ^" f I ow met er ;

6 ^" t enrperat ur e;

7 ^" pr ess ur e;

8 ^" el ect r i cal cabi net ;

9 ^" pH;

10 rrixer;

11 ^" CC2;

13 CQ2 r egul at i on stati on;

14 fi l trate;

15 decanter;

16 si udge t ransport er;

17 si udge st orage.

Descri pti on of enrbodi ments

The fol l owi ng text provi des an expl anati on on the di fferent enrbodi ments of the technol ogy di scl osed i n the present appl i cati on. Thi s expl anati on i s not an extensive overvi ew and does not i ntend to del i neate the scope of the protecti on or any cri ti cal aspect or el ement of the same t echnol ogy.

The present appl i cati on di scl oses a method for i ncreased fi l trati on effi ci ency conrpri si ng the fol l owi ng steps: CQ2 or rrixtures of CQ2 are added to the fl ui d to be fi l tered, froma CQ2 regul ati on stati on;

- the fl ow of CO2 or rrixtures of CQ2 i s rri xed wi th the fl ui d to be fi l tered i n a rrixer;

- the pH of the rrixture i s measured after passi ng the stati c or dynarri c rrixer;

- the rrixture obtai ned proceeds to fi l trati on.

As can be seen i n Fi gure 1, the experi mental data tel l us that the curve for drai nage i ncrease wi th addi ti on of CO2, so wi th more quanti ty of CQ2, ei ther i n gas or l i qui d or sol i d forrn the drai nage wi l l al so i ncrease. W t h the method descri bed i n thi s appl i cati on, especi al ly wi th the use of a rrixer, there i s no need to i ncl ude so much CQ2 to obtai n a fl ui d that wi l l drai n more effi ci ently i n the mechani cal dewateri ng system and a hi gher content of sol i ds wi l l be obtai ned i n the dewatered fl ui d.

In Fi gure 2, we can see a typi cal process l ayout for drai nage i ncrease wi th addi ti on of CQ2, wherei n the sl udge (4) i s nixed wi th a polymer preparati on (2), whi ch work as a fl occul ant. Then the rrixture i s eval uated i n what concerns to fl ow, tenrperature (6) and pressure (7). After thi s steps, the rrixture i s passed i n the rrixer ( 10) wi th a resi dence ti me l ower than 2 seconds, whi ch i s enough to i ncrease the transfer area between CQ2 and fl ui d i n somewhat between 10.000 to 1.000.000 ti mes and thus promote t he r eact i on bet ween t he CQ2 and the fl ui d to be fi l tered. After these steps, the rrixture i s eval uated i n hi s pH (9) val ue to defi ne i f the CQ2 has been properly di ssolved. Afterwards, the rrixture i s i ntroduced i n the decanter ( 15) f or f i I t er i ng. The technol ogy i s of course not i n any way restri cted to the enrbodi nrent s descri bed herei n and a person of ordi nary ski l l i n the area can provi de many possi bi l i ti es to rrodi f i cat i ons thereof as defi ned i n the cl ai nrs.

The preferred enrbodi nrent s descri bed above are obvi ously conrbi nabl e. The fol l owi ng dependent cl ai nrs defi ne further preferred enrbodi nrent s of the di scl osed technol ogy.