Apparatus and method for producing dispersions and solids

Abstract

The invention relates to an apparatus and method for the production of dispersions and solids by way of controlled precipitation, co-precipitation and self-organization processes in a microjet reactor, a jet of solvent containing at least one target molecule and a jet of nonsolvent colliding with each other, at specified pressures and flow rates, at a collision point in the reactor chamber of the microjet reactor, and the microjet reactor having a gas inlet for introducing gas into the reactor chamber and an educt outlet for discharging the educts in a stream of gas. This results in very rapid precipitation, co-precipitation or a chemical reaction, during the course of which micro- or nanoparticles form. In order to create an apparatus with which solvent/nonsolvent precipitations may be carried out in such a way as to produce particles that are as small as possible and largely free of Ostwald ripening in the dispersion being formed, it is suggested according to the invention that the educt outlet be followed by a spray-drier unit and that a feedback control system be provided to optimize and maintain the operating parameters for the spray-drier unit.

Claims

1. An apparatus, comprising a microjet reactor and a spray-drier unit, for producing dispersions and solids by way of controlled precipitation, co-precipitation and self-organization processes, the microjet reactor being configured such that it has at least two mutually opposite nozzles, each with its own pump and feed line for injecting a liquid medium into a reactor chamber enclosed in a reactor housing and onto a common collision point (K), the microjet reactor having a gas inlet (5) for introducing gas into the reactor chamber (1) and an educt outlet (6) for discharging the educts in a stream of gas, wherein the educt outlet (6) is followed immediately by a spray-drier unit (7) configured as a length of piping connected to the educt outlet (6) of the microjet reactor and being supplied from the side with one or more streams of air or inert gas, and wherein a feedback control system (11) is provided to optimize and maintain the operating parameters for the spray-drier unit (7).

2. The apparatus according to claim 1, wherein the spray-dryer unit (7) includes means (9) for heating the stream of air or inert gas.

3. The apparatus according to claim 1, wherein the temperature of the stream of air or inert gas is controllable via the feedback control system (11).

4. The apparatus according to claim 1, wherein the volumetric flow rate of the stream of air or inert gas is controllable via the feedback control system (11).

5. The apparatus according to claim 1, wherein jets of solvent (2) and nonsolvent (3) collide with each other at an angle of 90 to 180.

6. A method of producing dispersions and solids by way of controlled precipitation, co-precipitation and self-organization processes in a microjet reactor, comprising the steps of: configuring the microjet reactor such that a jet of solvent (2) containing at least one target molecule and a jet of nonsolvent (3) are injected, through two mutually opposite nozzles, into the reactor chamber (1) of the microjet reactor at specified pressures and flow rates and collide at a collision point (K) in a reactor chamber enclosed in a reactor housing, introducing gas into said reactor chamber (1) via a gas inlet (5) and the educts being discharged through an educt outlet (6) in a stream of gas, having the educts exiting from the educt outlet (6) pass through a spray-drier unit (7) configured as a length of piping supplied from the side with one or more streams of air or inert gas, and controlling the operating parameters for the spray-drier unit (7) via a feedback control system (11).

7. The method according to claim 6, wherein the temperature of the stream(s) of air or inert gas is controlled by measuring the temperature, as controlled variable, at the end of the length of piping constituting the spray-drier unit (7).

8. The method according to claim 7, wherein the volumetric flow rate of the stream(s) of air or inert gas is controlled by measuring the temperature, as controlled variable, at the end of the length of piping constituting the spray-drier unit (7).

9. The method according to claim 6, wherein spray-drying is only continued long enough to concentrate the dispersion but not to dry it.

10. The method according to claim 6, wherein spray-drying is continued until the dispersion is, for the most part, completely dry.

11. The method according to claim 6, wherein the solvent (2) and nonsolvent (3) are selected such that the solvent (2) has the higher saturation pressure.

12. The method according to claim 6, wherein solvent-saturated gas is separated from the dispersion being formed.

Description

(1) The drawing in

(2) FIG. 1 is a schematic diagram of an apparatus according to the invention.

(3) In the reactor chamber 1 of a microjet reactor, a jet of a solvent 2 containing at least one target molecule and a jet of a nonsolvent 3, said solvents being delivered by high-pressure pumps 4a and 4b, respectively, exit nozzles and collide with each other at a collision point K. The jets of solvent 2 and nonsolvent 3 are injected into the reactor chamber at pressures in excess of 50 bar, preferably in excess of 500 bar and even more preferably at pressures of 1,000 to 4,000 bar. The reactor chamber 1 of the microjet reactor also features a gas inlet 5 for introducing gas into the reactor chamber 1 and an educt outlet 6 for discharging the educts in a stream of gas, said gas inlet 5 and educt outlet being disposed at right angles to the direction of the jets of solvent 2 and nonsolvent 3. The jets of solvent 2 and nonsolvent 3 collide at an angle of 180.

(4) The educt outlet 6 is followed immediately by a spray-drier unit 7 configured as a length of piping connected to the educt outlet 6 and supplied from the side, via infeed channels 8, with one or more streams of air or inert gas. These streams of air or inert gas are heated beforehand in means 9 for heating the stream(s) of air or inert gas.

(5) A feedback control system is also provided to optimise and maintain the operating parameters for the spray-drier unit 7. A thermocouple 10 is provided at the end of the length of piping constituting the spray-drier unit 7 and is used to measure the temperature of the educt/gas stream at the end of the length of piping constituting the spray-drier unit 7. This temperature serves as the controlled variable. The thermal output of the means 9 for heating the stream(s) of air or inert gas, and thus the temperature of the stream of air or inert gas, and/or the delivery rate of the means 9 for heating the stream(s) of air or inert gas, and thus the volumetric flow rate of the stream of air or inert gas, are regulated, via a feedback control system 11, as a function of the temperature at the end of the length of piping constituting the spray-drier unit in such a manner that optimal operating parameters prevail at any one time and particles are obtained that are as small as possible and largely free of Ostwald ripening in the dispersion being formed.

(6) If possible, the solvent and nonsolvent are selected such that the solvent has the higher vapour pressure and therefore vaporises with preference. The decrease in the solvent fraction of the solvent/nonsolvent mixture reduces the aerosol droplets' dissolving power for the precipitated particles to such an extent as to stop Ostwald ripening or at least considerably reduce it.

(7) The stream of aerosol cools down as the solvent and usually some of the nonsolvent vaporises and heat of vaporisation is removed from the aerosol. If the stream of aerosol cools down too much, solvent vaporisation decreases. If the stream of aerosol is heated too strongly, the particles are obtained as solids or are even destroyed thermally. The feedback control system ensures that the temperature of the aerosol stream is optimal.

(8) It is possible either to continue spray-drying long enough to concentrate the dispersion but not to dry it or to continue spray drying until the dispersion is, for the most part, completely dry.