Hydrothermal dehalogenation of chemicals

Patent metadata

Field	Value
Publication number	US-11674088-B1
Application number	US-202217939573-A
Country	US
Kind code	B1
Filing date	Sep 7, 2022
Priority date	Sep 7, 2022
Publication date	Jun 13, 2023
Grant date	Jun 13, 2023

Abstract

A process for treating a plastic waste and a spent caustic, the process comprising the steps of mixing a feed plastic and a spent caustic stream in a feed mixer to produce a mixed feed, wherein the feed plastic comprises the plastic waste in the form of plastic waste chips; introducing the mixed feed to a hydrothermal reactor; reacting the mixed feed in the hydrothermal reactor to produce an effluent, wherein chlorine is removed from the plastic waste in the presence of the sodium hydroxide, wherein the chlorine reacts with sodium hydroxide to produce sodium chloride and water; introducing the effluent to a washing and dewatering unit, wherein the effluent comprises liquid phase materials and solid materials, wherein the solid materials comprise dechlorinated plastics; and separating the liquid phase materials and solid materials in the washing and dewatering unit to produce a dechlorinated plastic waste and a neutralized wastewater.

First claim

That which is claimed is:

1. A process for treating a plastic waste and a spent caustic, the process comprising the steps of:
mixing a feed plastic and a spent caustic stream in a feed mixer to produce a mixed feed, wherein the feed plastic comprises the plastic waste in the form of plastic waste chips, wherein the plastic waste is selected from polyvinyl chloride (PVC), halogenated plastics, and combinations of the same, wherein the spent caustic stream comprises sodium hydroxide;
introducing the mixed feed to a hydrothermal reactor;
reacting the mixed feed in the hydrothermal reactor to produce an effluent, wherein a residence time in the hydrothermal reactor is in the range between 0.2 hours and 5 hours, wherein a pressure in the hydrothermal reactor is greater than the saturation pressure of water at the temperature in the hydrothermal reactor such that water in the hydrothermal reactor in liquid phase, wherein a temperature in the hydrothermal reactor is in the range between 150° C. and 350° C., wherein chlorine is removed from the plastic waste in the presence of the sodium hydroxide, wherein the chlorine reacts with sodium hydroxide to produce sodium chloride and water;
introducing the effluent to a washing and dewatering unit, wherein the effluent comprises liquid phase materials and solid materials, wherein the solid materials comprise dechlorinated plastics; and
separating the liquid phase materials and solid materials in the washing and dewatering unit to produce a dechlorinated plastic waste and a neutralized wastewater.

2. The process of claim 1 , wherein the plastic waste chips are less than 1 mm.

3. The process of claim 1 , wherein the halogenated plastics are selected from the group consisting of chlorinated polyvinyl chloride (CPVC), polyvinylidene dichloride (PVDC), and combinations of the same.

4. The process of claim 1 , wherein the plastic waste further comprises thermoplastic polymers selected from the group consisting of polyethylene, polystyrene, polypropylene, and combinations of the same.

5. The process of claim 1 , wherein a flow rate of the feed plastic and the spent caustic are adjusted to achieve a target pH between 5 and 6 in the hydrothermal reactor.

6. The process of claim 1 , further comprising the step of processing the neutralized wastewater into a demineralization unit to produce a demineralized water.

7. The process of claim 1 , further comprising the step of introducing a demineralized water to hydrothermal reactor, wherein the demineralized water can adjust a target pH in the hydrothermal reactor.

8. The process of claim 1 , wherein a chlorine content of the feed plastic is at least 5 wt %.

9. The process of claim 1 , wherein the spent caustic in the spent caustic stream has a chemical oxygen demand between 1,000 mg/L and 100,000 mg/L, a total organic carbon between 500 mg/L and 10,000 mg/L, sulfide content between 1,000 mg/L and 40,000 mg/L, an alkaline metals content between 1.5 wt % and 8.5 wt %, and a pH between 11.5 and 13.9.

10. A system for treating a plastic waste and a spent caustic, the system comprises:
a plastic waste storage bin configured to store the plastic waste in the form of plastic waste chips, wherein the plastic waste is selected from polyvinyl chloride (PVC), halogenated plastics, and combinations of the same;
a spent caustic storage tank configured to store the spent caustic, wherein the spent caustic comprises sodium hydroxide;
a feed mixer fluidly connected to the plastic waste storage bin and the spent caustic storage tank, the feed mixer configured to mix a feed plastic and a spent caustic stream to produce a mixed feed, wherein the feed plastic comprises the plastic waste and the spent caustic stream comprises the spent caustic;
a hydrothermal reactor, the hydrothermal reactor fluidly connected to the feed mixer, the hydrothermal reactor configured to react the mixed feed to produce an effluent, wherein a residence time in the hydrothermal reactor is in the range between 0.2 hours and 5 hours, wherein a pressure in the hydrothermal reactor is greater than the saturation pressure of water at the temperature in the hydrothermal reactor such that water in the hydrothermal reactor in liquid phase, wherein a temperature in the hydrothermal reactor is in the range between 150° C. and 350° C., wherein chlorine is removed from the plastic waste in the presence of the sodium hydroxide, wherein the chlorine reacts with sodium hydroxide to produce sodium chloride and water; and
a washing and dewatering unit fluidly connected to the hydrothermal reactor, the washing and dewatering unit configured to separate solid materials and liquid phase materials in the effluent to produce a dechlorinated plastic waste and a neutralized wastewater, wherein the solid materials comprise dechlorinated plastics.

11. The system of claim 10 , wherein the plastic waste chips are less than 1 mm.

12. The system of claim 10 , wherein the halogenated plastics are selected from the group consisting of chlorinated polyvinyl chloride (CPVC), polyvinylidene dichloride (PVDC), and combinations of the same.

13. The system of claim 10 , wherein the plastic waste further comprises thermoplastic polymers selected from the group consisting of polyethylene, polystyrene, polypropylene, and combinations of the same.

14. The system of claim 10 , wherein a flow rate of the feed plastic and the spent caustic are adjusted to achieve a target pH between 5 and 6 in the hydrothermal reactor.

15. The system of claim 10 , further comprising a demineralization unit fluidly connected to the washing and dewatering unit, the demineralization unit configured to treat the neutralized wastewater to produce a demineralized water.

16. The system of claim 10 , wherein a chlorine content of the feed plastic is at least 5 wt %.

17. The system of claim 10 , wherein the spent caustic in the spent caustic stream has a chemical oxygen demand between 1,000 mg/L and 100,000 mg/L, a total organic carbon between 500 mg/L and 10,000 mg/L, sulfide content between 1,000 mg/L and 40,000 mg/L, an alkaline metals content between 1.5 wt % and 8.5 wt %, and a pH between 11.5 and 13.9.

18. The system of claim 10 , wherein the feed mixer is selected from an inline mixer, T-fitting, Y-fitting, and combinations of the same.

19. The system of claim 10 , wherein the hydrothermal reactor is selected from a batch reactor having an internal mixing device and a CSTR.

Assignees

• Saudi Arabian Oil Co

Inventors

• Choi Ki-Hyouk

Classifications

• C10G2300/4012

  Pressure · CPC title

• C10G2300/1003

  Waste materials · CPC title

• C10G1/002 Primary

  in combination with oil conversion- or refining processes · CPC title

• C10G1/10 Primary

  from rubber or rubber waste · CPC title

• C10G2300/4081

  Recycling aspects · CPC title