Process for the preparation of a dried powder

Patent metadata

Field	Value
Publication number	US-10788262-B2
Application number	US-201716076198-A
Country	US
Kind code	B2
Filing date	Feb 14, 2017
Priority date	Feb 15, 2016
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A method for preparing a dried powder is provided. The facility includes a first drying chamber having a heating element and a second drying chamber. A mixture of powder and diluent is introduced into the first drying chamber. A pre-dried powder is transferred from the first drying chamber into the second drying chamber. A dried powder, including a recirculated amount of powder and a discharge amount of powder, is formed in the second drying chamber. The recirculated amount of the dried powder is transferred by a conveyor device from the second drying chamber into the first drying chamber. The discharge amount of the dried powder is discharged from the second drying chamber.

First claim

What is claimed is:

1. A method for the preparation of a dried powder in a facility comprising preparation steps:
wherein the facility comprises
i) a first drying chamber with a first upper end section, an opposing first lower end section and a first chamber side wall, the first drying chamber being a back-mixing drying chamber comprising a first heating element, a first powder inlet for receiving a mixture of powder and diluent, a first powder outlet for exiting a pre-dried powder, a first gas inlet and a first gas outlet,
ii) a second drying chamber with a second upper end section, an opposing second lower end section and a second chamber side wall, the second drying chamber comprising a second heating element, a second powder inlet for receiving the pre-dried powder, a second powder outlet for exiting a dried powder comprising a recirculated amount of dried powder and a discharge amount of dried powder, a second gas inlet and a second gas outlet,
iii) a first powder passage for transferring the pre-dried powder from the first drying chamber into the second drying chamber, having the first powder outlet connected to the second powder inlet or being identical with the second powder inlet,
iv) a conveyor device and optionally a second powder passage for transferring the recirculated amount of dried powder from the second drying chamber into the first drying chamber,
wherein in the facility, (A) the mixture of powder and diluent, having a first average concentration by weight of diluent based upon the total weight of the mixture, is introduced through the first powder inlet into the first drying chamber and (B) the pre-dried powder, having a second average concentration by weight of diluent based upon the total weight of the pre-dried powder, is transferred from the first drying chamber into the second drying chamber through the first powder passage,
wherein a first amount of the diluent is removed from the mixture after passage through the first drying chamber, yielding the pre-dried powder, and a second amount of the diluent is removed from the pre-dried powder after passage through the second drying chamber, yielding the dried powder, having a third average concentration by weight of diluent based upon the total weight of the dried powder,
wherein the first average concentration of diluent is higher than the second average concentration of diluent and the second average concentration of diluent is higher than the third average concentration of diluent,
wherein (C) the recirculated amount of the dried powder is transferred from the second drying chamber into the first drying chamber using the conveyor device and optionally the second powder passage, and
wherein (D) the discharge amount of the dried powder is discharged from the second drying chamber.

2. The method according to claim 1 comprising the following preparation steps:
a) introducing the mixture of powder and diluent through the first powder inlet into the first drying chamber,
b) heating the mixture by the first heating element to a first temperature in a first gas flow introduced through the first gas inlet and discharged through the first gas outlet, yielding the pre-dried powder,
c) transferring the pre-dried powder through the first powder passage into the second drying chamber,
d) heating the pre-dried powder by the second heating element to a second temperature in a second gas flow introduced through the second gas inlet and discharged through the second gas outlet, yielding the dried powder comprising the recirculated amount of dried powder and the discharge amount of dried powder,
e) transferring the recirculated amount of the dried powder through the conveyor device and optionally through the second powder passage from the second drying chamber into the first drying chamber, and discharging the discharge amount of the dried powder through the second powder outlet from the second drying chamber.

3. The method according to claim 2 , wherein the first and second gas flows are selected from a nitrogen gas flow or a hydrocarbon gas flow.

4. The method according to claim 2 , wherein an average combined residence time of powder in the first and second drying chamber is less than about 60 min.

5. The method according to claim 2 , wherein the first average concentration of diluent in the mixture of powder and diluent is in the range of from about 15 wt. % to about 50 wt. % based upon the total weight of the mixture, and the third average concentration of diluent in the dried powder is less than about 10 wt. %, based upon the total weight of the dried powder.

6. The method according to claim 2 , wherein the first gas flow, the second gas flow, and the diluents are recycled.

7. The method according to claim 2 , wherein the average recirculated amount of the dried powder is in the range of about 5 to about 60 weight % based upon the average total weight of the dried powder.

8. The method according to claim 1 , wherein the powder is a polymer powder.

9. The method according to claim 8 , wherein the powder is a polyolefin powder.

10. The method according to claim 9 , wherein the mixture of powder and diluent is a mixture of polyethylene and a hydrocarbon diluent.

11. The method according to claim 10 , wherein the polyolefin is a bimodal or multimodal polyolefin.

12. The method according to claim 1 , wherein the temperatures of the first and second heating elements are in the range from about 60 to about 125° C.

13. The method according to claim 1 , wherein the facility further comprises a first grid as a first intermediate floor comprising a heat resistant material, wherein the first powder outlet and the first gas outlet are arranged above the first grid and the first gas inlet is arranged below the first grid such that the first grid separates the first powder inlet and the first powder outlet from the first gas inlet, wherein the first grid is a first intermediate floor upon which powder is deposited in the first chamber, wherein a first gas is conducted from the first gas inlet through the first grid into the first gas outlet.

14. The method according to claim 1 , wherein the first chamber side wall (a) is a section of the second chamber side wall or is arranged next to the second chamber side wall and (b) comprises the first powder passage, which first powder passage is a first aperture in the first chamber side wall.

15. The method according to claim 1 , wherein the conveyor is selected from the group consisting of a spiral conveyor, a tube chain conveyor and a pneumatic conveying device.

16. The method according to claim 1 , wherein the first and second heating elements are of the tube bundle type or of the plate type and are arranged inside the chamber at a distance from the first and second chamber walls.

17. The method according to claim 1 , wherein the first and second heating elements are heated using water or steam.

18. The method according to claim 1 , wherein the facility further comprises a second grid as a second intermediate floor comprising a heat resistant material, wherein the second powder outlet and the second gas outlet are arranged above the second grid and the second gas inlet is arranged below the second grid such that the second grid separates the second powder inlet and the second powder outlet from the second gas inlet, wherein the second grid is a second intermediate floor upon which powder is deposited in the second chamber and a second gas is conducted from the second gas inlet through the second grid into the second gas outlet.

Assignees

• Basell Polyolefine Gmbh

Inventors

• Prang Harald
• Chatterjee Michael
• Kuehl Reinhard
• Seifert Alexander

Classifications

• F26B21/40

  using gases other than air · CPC title

• C08F10/02

  Ethene · CPC title

• B01J8/36

  with fluidised bed through which there is an essentially horizontal flow of particles · CPC title

• B01J8/26

  with two or more fluidised beds, e.g. reactor and regeneration installations · CPC title

• B01J8/1845

  with particles moving upwards while fluidised · CPC title