PROCESS FOR MIXING A LIQUID OR MIXTURE OF A LIQUID AND A FINE SOLID PRESENT IN AN ESSENTIALLY SELF-CONTAINING VESSEL

Abstract

A process for mixing a liquid stored in a vessel, in which gas is sucked in from the gas phase present above the liquid interface with a suction apparatus present in the liquid, and released into it again for the gas-induced mixing of the liquid.

Description

WORKING EXAMPLE

In an outdoor tank (wall thickness: 5 mm, manufacturing material: DIN 1.4541) stainless steel) according to FIG. 13 (cylindrical footprint with a diameter of 8.5 m and a height of 10 m up to the start of the conical roof), glacial acrylic acid (GAA) stabilized with 200 ppm by weight of MEHQ was stored at a desired internal temperature of 20° C. under atmospheric pressure at maximum fill height. The maximum fill height in the storage tank was 9 m. The gas volume remaining at maximum fill height was 69 m³.

The withdrawal from the tank was effected by means of a CPK 50-200 centrifugal pump from KSB Aktiengesellschaft in D-67227 Frankenthal.

The barrier fluid present in the pump with double slip ring seal was a mixture of ethylene glycol and water. The glacial acrylic acid in the storage tank was covered by means of air. By means of an offgas system which was open to the atmosphere via a flare (orifice cross section in the conical roof=20 cm²), it was possible to release gas from the gas phase of the tank to a flare in the course of filling for pressure release.

In a corresponding manner, air was replenished via a pressure-retaining device for pressure equalization in the course of withdrawal of glacial acrylic acid from the tank. Close to the bottom, as can be seen in FIG. 13, the ejector jet nozzle (manufactured from DIN-1.4541 stainless steel) from FIG. 14 was mounted horizontally in such a way that the diffusor thereof projected into about the middle of the tank The dimensions in FIG. 14 are the accompanying dimensions (nominal widths) of the ejector jet nozzle in mm and angles in degrees (NW stands for nominal width). The wall thicknesses were from 1 to 6 mm. FIG. 15 additionally shows the swirl body disposed upstream of the motive nozzle of the ejector part from the side and from the front, and the swirl angle which was 300. FIG. 14 also shows the connection (12) of the riser tube projecting into the gas phase of the tank to the suction chamber of the ejector part of the ejector jet nozzle.

The centrifugal pump was used to withdraw 40 m³/h of glacial acrylic acid continuously from the tank over a period of 1 week, and to recycle it as the motive jet into the ejector jet nozzle via the heat exchanger in FIG. 13. Irrespective of the external temperature (which varied within the range of ±15° within the experimental period), the temperature was kept constant within the range of 20±1° C. at the withdrawal point of the storage tank.

Finally, 1 l of a 0.1% by weight solution of phenothiazine in glacial acrylic acid was introduced all at once into the tank from the top (at maximum fill height). After 5 minutes, the concentration of equal distribution of the added phenothiazine had arrived within the range of ±10% about its theoretical value at the withdrawal point.

Subsequently, the recycle rate was retained, but the withdrawal rate was increased by 20 m³/h, i.e. the tank was emptied by 20 m³/h. It was possible without any problem to withdraw 99% of its liquid contents from the tank without spray being formed in the tank (in principle, it was also possible to withdraw glacial acrylic acid from the tank via an outlet which did not lead through the circulation pump).

FIG. 16 additionally shows the three-dimensional diagram of the swirl body used.

FIG. 17 shows, for illustration, a three-dimensional diagram of the ejector jet nozzle (in section), and FIG. 18 shows the corresponding exploded diagram.

In addition, the abbreviations in FIG. 13 stand for:

• TIA⁺ for “temperature indicator alarm”;
• LIS for *level indicator switch”; as overfill protection (+) and as underfill protection (−);
• TIS⁺ for “temperature indicator security”;
• FIS for “flow indicator security”;
• F for “flow” (small safety flow as pump protection).

In addition, FIG. 13 shows, on the vessel roof, a two-way non-return valve and, beyond the pump but upstream of the withdrawal, a single-action (only opening outward) non-return valve.

U.S. Provisional Patent application No. 60/846,095, filed on Sep. 21, 2006, is incorporated into the present application by literature reference. With regard to the above-mentioned teachings, numerous changes and deviations from the present invention are possible. It can therefore be assumed that the invention, within the scope of the appended claims, can be performed differently from the way specifically described herein.

Claims

1. A process for mixing a liquid or mixture of a liquid and a fine solid present in an essentially self-contained vessel, with the proviso that the liquid or mixture fills only part of the internal volume of the vessel occupiable by a fluid phase, and the remaining occupiable internal volume of the vessel is filled by a gas phase, comprising supply of essentially the same liquid or essentially the same mixture into the vessel as a motive jet of a suction apparatus disposed in the liquid or in the mixture in the vessel, wherein the suction apparatus, with the aid of the motive jet, sucks in gas from the gas phase present in the vessel and releases the sucked-in gas together with the motive jet into the liquid or mixture present in the vessel.

2. The process according to claim 1, wherein the suction apparatus comprises at least one ejector which has a motive nozzle and a suction chamber which is connected to the gas phase, and through whose motive nozzle the motive jet is conducted.

3. The process according to claim 2, wherein a swirling motion is imparted to the motive jet before it passes through the motive nozzle.

4. The process according to claim 3, wherein the swirling motion is imparted with a swirl body installed upstream of the motive nozzle.

5. The process according to claim 3, wherein the swirling motion is imparted by supplying the motive liquid to the motive nozzle tangentially.

6. The process according to any of claims 1 to 5, wherein the motive jet is divided as it passes through the motive nozzle.

7. The process according to claim 6, wherein the motive nozzle is a screen nozzle or a slot nozzle.

8. The process according to claim 1, wherein the suction apparatus comprises at least one ejector jet nozzle which has a motive nozzle, a suction chamber which surrounds the motive nozzle and opens out into a mixing nozzle, and a momentum exchange chamber into which the outlet of the mixing nozzle points, the suction chamber being connected to the gas phase and the motive jet being conducted through its motive nozzle via the mixing nozzle into the momentum exchange chamber.

9. The process according to claim 8, wherein a swirling motion is imparted to the motive jet before it passes through the motive nozzle.

10. The process according to claim 9, wherein the swirling motion is imparted with a swirl body installed upstream of the motive nozzle.

11. The process according to claim 9, wherein the swirling motion is imparted by supplying the motive liquid to the motive nozzle tangentially.

12. The process according to any of claims 8 to 11, wherein the motive jet is divided as it passes through the motive nozzle.

13. The process according to claim 12, wherein the motive nozzle is a screen nozzle or a slot nozzle.

14. The process according to any of claims 1 to 7, wherein the ejector is installed horizontally into the vessel.

15. The process according to any of claims 8 to 13, wherein the ejector jet nozzle is installed horizontally into the vessel.

16. The process according to any of claims 8 to 13 and 15, wherein the transition from the mixing nozzle into the momentum exchange chamber is provided with a sheath having at least one orifice, with the proviso that the at least one orifice is below the central jet leading from the mixing nozzle into the momentum ex-change chamber.

17. The process according to any of claims 8 to 13 and 15, wherein the transition from the mixing nozzle into the momentum exchange chamber is provided with a sheath which has at least one orifice which opens out to an immersed tube leading in the direction of the vessel bottom.

18. The process according to any of claims 1 to 17, wherein the liquid comprises at least one of the organic compounds from the group comprising acrolein, methacrolein, acrylic acid, methacrylic acid, esters of acrylic acid and esters of methacrylic acid.

19. The process according to any of claims 1 to 17, wherein the liquid comprises N-vinylformamide.

20. The process according to claim 18 or 19, wherein the liquid comprises at least one dissolved polymerization inhibitor.

21. The process according to any of claims 1 to 20, wherein the gas phase comprises molecular oxygen.

22. The process according to any of claims 1 to 21, wherein the volume of the gas phase in the vessel is at least 5% by volume of the liquid or mixture volume stored in the vessel.

23. The process according to any of claims 1 to 22, wherein at least 10−5 standard liter of gas per minute per liter of liquid or mixture of liquid and fine solid present in the vessel is sucked out of the gas phase and released into the liquid or mixture present in the vessel.

24. The process according to any of claims 1 to 23, wherein the liquid or mixture fed into the vessel as a motive jet comprises a portion or the entirety of a portion of the liquid or mixture present in the vessel which has been withdrawn before-hand from the vessel.

25. The process according to any of claims 1 to 23, wherein the liquid or mixture fed into the vessel as a motive jet does not comprise a portion of the liquid or mixture present in the vessel which has been withdrawn beforehand from the vessel.

26. The process according to any of claims 1 to 25, wherein the liquid or mixture fed into the vessel as a motive jet has been conducted through a heat exchanger beforehand.

27. A vessel comprising, as well as a gas phase, a liquid or a mixture of a liquid and a fine solid, and also at least one ejector which comprises a motive jet and a suction chamber which has a connection to the gas phase.

28. A vessel comprising, as well as a gas phase, a liquid or a mixture of a liquid and a fine solid, and also at least one ejector jet nozzle which has a motive nozzle, a suction chamber which surrounds the motive nozzle and opens out into a mixing nozzle, and a momentum exchange chamber into which the outlet of the mixing nozzle points, and a connection of the suction chamber to the gas phase.

29. The use of an ejector for the gas-induced mixing of a liquid or mixture of a liquid and a fine solid present in an essentially self-contained vessel, with the proviso that the liquid or mixture fills only part of the internal volume of the vessel occupiable by a fluid phase, and the remaining occupiable internal volume of the vessel is filled by a gas phase.

30. The use of an ejector jet nozzle for the gas-induced mixing of a liquid or mixture of a liquid and a fine solid present in an essentially self-contained vessel, with the proviso that the liquid or mixture fills only part of the internal volume of the vessel occupiable by a fluid phase, and the remaining occupiable internal volume of the vessel is filled by a gas phase.

31. An ejector jet nozzle which has a motive nozzle, a suction chamber which surrounds the motive nozzle and opens out into a mixing nozzle, and a momentum exchange chamber into which the outlet of the mixing nozzle points, wherein the transition from the mixing nozzle into the momentum exchange chamber is pro-vided with a sheath, and the sheath has at least one connection for an immersed tube or at least one immersed tube leading into the sheath.

32. A process for mixing another liquid or another mixture into a liquid or mixture of a liquid and a fine solid present in an essentially self-contained vessel, with the proviso that the liquid or mixture fills only part of the internal volume of the vessel occupiable by a fluid phase and the remaining occupiable internal volume of the vessel is filled by a gas phase, comprising supply of the other liquid or the other mixture into the vessel as a motive jet of a suction apparatus present in the liquid or in the mixture in the vessel, wherein the suction apparatus, with the aid of the motive jet, sucks in gas from the gas phase present in the vessel, and releases the sucked-in gas, together with the motive jet, into the liquid or mixture present in the vessel.

33. The process according to claim 32, wherein the liquid present in the vessel comprises a compound having at least one ethylenically unsaturated moiety, and the other liquid supplied as a motive jet is an inhibitor solution which comprises at least 10% by weight of phenothiazine, from 5 to 10% by weight of p-methoxyphenol and at least 50% by weight of N-methylpyrrolidone.