# US 7,744,786 B2 · Method and device for manufacturing extremely fine particles and porous materials by controlled low temperature drying

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- Number: US 7,744,786 B2
- Document ID: US7744786B2
- Status: Granted
- Kind: B2
- Application number: 12/416,681
- Filed: 2009-04-01
- Published: 2009-07-23
- Granted: 2010-06-29
- Earliest claimed: 2006-01-10
- Assignees: Nanomist Systems, LLC
- Inventors: Kayyani C. Adiga
- Web page: https://patentgrep.com/patent/US7744786B2

## CPC

- F26B 17/107: {pneumatically inducing within the drying enclosure a curved flow path, e.g. circular, spiral, helical; Cyclone or Vortex dryers (swirl or curved flow path induced mechanically, i.e. by rotating element F26B3/0923)}
- F26B 3/12: in the form of a spray {, i.e. sprayed or dispersed emulsions or suspensions (spray drying of solutions B01D1/18)}
- F26B: DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM (drying devices for combines A01D41/133; racks for drying fruit or vegetables A01F25/12; drying foodstuffs A23; drying hair A45D20/00; body-drying implements A47K10/00; drying household articles A47L; drying gases or vapours B01D; chemical or physical processes for dewatering or like separating liquids from solids B01D43/00; centrifugal apparatus B04; drying ceramics C04B33/30; drying yarns or fabrics in association with some other form of treatment D06C; drying frames for laundry without heating or positive air circulation, domestic laundry-or spin-driers, wringing or hot pressing laundry D06F; furnaces, kilns, ovens F27)

## Abstract

A method and device for manufacturing extremely fine particles and porous materials by controlled low temperature drying. An ambient-pressure and ambient-temperature atomizer atomizes a particle precursor solution to create a precursor mist. The precursor mist and dryer gas are fed into a dryer tube through a tangential inlet (swirl generating inlet). The mixed stream forms a helical flow structure within the dryer tube. The swirling mist undergoes drying and particle formation at a relatively low temperature. The flow continues to swirl and drying process continues with repeated passes until the required drying duration is reached. This dryer structure allows for a compact dryer with full control of residence time.

## Claims

### Claim 1

A method for manufacturing of fine particles or porous material comprising the steps of: (a) providing an atomized precursor mist from a precursor solution containing a dissolved solid; (b) mixing the precursor mist with a flow of a drying gas into a reactant stream; (c) generating a swirling flow of the reactant stream; (d) passing the swirling flow of the reactant stream through a reactor; (e) controlling residence time of the reactant stream in the reactor to control drying and morphology of particles in the reactant stream; and (f) removing dried particles from the reactor.

### Claim 2 (depends on 1)

A method for manufacturing of fine particles or porous material as in claim 1 in which the step of controlling residence time of the reactant stream in the reactor including the additional steps of: controlling velocity of the swirling flow of the reactant stream and controlling the path length of the swirling flow of the reactant stream.

### Claim 3 (depends on 2)

A method for manufacturing of fine particles or porous materials as in claim 2 in which the reactor includes a dryer tube, and the path length of the swirling flow of the reactant stream is controlled by a swirl number comprising the number of times the reactant stream swirls and circulates within the dryer tube, the dryer tube's length, and the dryer tube's diameter.

### Claim 4 (depends on 1)

A method for manufacturing of fine particles or porous materials as in claim 1 including the additional step of manipulating the diameter of fine particles or porous materials manufactured by controlling concentration of solid in the particle precursor solution.

### Claim 5 (depends on 1)

A method for manufacturing of fine particles or porous materials as in claim 1 in which the step of controlling residence time of the reactant stream in the reactor includes providing repeated passes of the swirling flow of the reactant stream through more than one of said reactor.

### Claim 6 (depends on 1)

A method for manufacturing of fine particles or porous materials as in claim 1 in which the swirling flow of reactant stream passing through the reactor is maintained at a temperature of less than 120 degrees Celsius.

### Claim 7 (depends on 1)

A method for manufacturing of fine particles or porous materials as in claim 1 in which the precursor solution containing a dissolved solid includes an additive dissolved in the precursor solution and including the additional step of post-processing the dried particles to remove the additive from the dried particles.

### Claim 8 (depends on 7)

A method for manufacturing of fine particles or porous materials as in claim 7 in which said dissolved solid is an inorganic compound and said additive is an organic compound and the step of post-processing the dried particles includes removal of the organic compound either by leaching or burning the dried particles.

### Claim 9 (depends on 7)

A method for manufacturing of fine particles or porous materials as in claim 7 in which said dissolved solid is an organic compound and said additive is an inorganic compound and the step of post-processing the dried particles includes removal of the inorganic compound by leaching.