Hydrodinamic Cavitation For Water and Oil Treatment

Leonardo TraversoniUniversidad Autònoma Metropolitana

IztapalapaMexico D.F.

Mexico

Cavitation as a Tool

Normally cavitation is to be avoided because it can damage turbo machinery.

However well directed it can destroy pollutants and do several useful things

It is important to note that in both cases the acting force cames from the implosion of the bubbles created by cavitation.

Implosion and not explosion, explosion is harmless

Main Design Condition

From the cloud of bubbles produced on cavitation, most of the bubbles coalesce and explode.

To avoid coalescence there are two ways, either the bubbles are separated enough or they have so short live they don’t have time to explode before the conditions of implosion are set.

This conditions can be achieved both restoring the pressure in the middle of the fluid or by impact against the walls of the device.

When fluid treatment is intended then it must be ensured all the portions of the fluid are covered by the shockwaves of the implosions so bubbles must be uniformly distributed

Existing Devices

Most of existing devices are for water cleaning on a residential basis (small amounts treated) and are based on converging cavitating jets.

Cavitating jets normally tend to form big bubbles in the middle coalescing most of the bubbles, colliding with one another increases its effect.

The consequence is that they need to recycle the water several times to ensure cavitation has reached the full body of the liquid

This makes this devices unpractical to compete with for example wastewater treatment plants.

The Ideal Device

It must be of only one pass, that is water must go trough it without cicles or delaying time.

It must be scalable, our first goal is to have a device of 5 lt/sec and after that reach 35 lt/sec in water higher amounts in oil

It must be efficient in energy consumption and cost.

The device

The idea is to obstruct the output of the impeller making the cavitation inside the centrifugal pump

With this device all water cavitates and bubbles implode on impact with the stator of the pump

There is no rejected water

The pump loses most of its power but its goal is not to move the water but to clean it

Results in water

We had very good results in:

1) Water desinfection killing most bacteria

2) Hardness reduction reducing 80%

3) Cleaning of big molecules mixed in the water (they are broken and degraded)

4) Burning of organic compounds dissolved in the water

We can affirm that municipal wastewater and even industrial wastewater may be treated safely and cheaply

Results hydrodinamic cavitation

0,00

10,00

20,00

30,00

40,00

50,00

60,00

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0 1 2 3 4 5 6

TIEMPO (horas)

REDUCCION DE AMONIACO Y MATERIA ORGANICA

% Red. NH3

%Red. DQO

Contaminant % Reduction

Dodecane 99

Toluene < 90

Amoniac < 63

Nitrato Amónico < 20

DQO < 60

Escherichia Coli

Results in oil

The main effect in crude oil is permanent viscosity reduction.

Other non negligible and very important effects are:

1) Cracking and formation of ligher compounds

2) Separation of associated products, particularly water

Hydrodinamic CavitationEnsayos en Cilindros

Essays at 3.000 and 11.000 rpm and 500-650W

IDCarga (gr)

Frec. (kHz)

Cámara

Tpo Trat. (min)

Red. (%)

F2-91-CH

100 ml

0,734x4 -

100 ml15

-18,707

F2-100-CH

150 ml

0,204x4 -

250 ml30

-10,399

F2-102-CH

150 ml

0,408x8 -

250 ml30

-16,050

F2-104-CH

150 ml

1,478x8 -

250 ml2 4,864

F2-105-CH

200 ml

1,478x8 -

250 ml5

-18,967

-25

-20

-15

-10

-5

0

5

0 0,25 0,5 0,75 1 1,25 1,5

Frecuencia (kHz)

Reducc

ión (

%)

650 W, 30 min500 W, 30 min

500 W, 5 min500 W, 2 min

-25

-20

-15

-10

-5

0

5

0 5 10 15 20 25 30

Tiempo (min)

Reducc

ión (

%)

0,73 kHz, 500 W 0,2 kHz, 650 W

0,4 kHz, 650 W1,47 kHz, 500 W

Viscosity reductionViscosity reduction

CONCLUSIONS

• The obtention of a working industrial device is in progress

• Several universities are collaborating completely or partially:

• UAM Mexico

• UNAM Mexico

• Shanghai University China

• Zaragoza University Spain

• Universidad de la Republica Montevideo Uruguay

• University of New Mexico USA