Process and system for the separation and drying of carboxylic acid crystals
View Patent ↗In a process for the separation and drying of crude carboxylic acid crystals from a slurry in a solvent, the slurry is supplied to a filter operating at pressure and at a temperature above the atmospheric boiling point of the solvent. A cake of separated crystals is removed from the filter and passed to a thermal dryer. In a system for the separation and drying of crude carboxylic acid from a slurry in a solvent, a pressure filter device has a slurry inlet and an outlet for a cake of carboxylic acid crystals. The system also has a thermal dryer and means for transporting the cake of carboxylic acid crystals from the pressure filter device to the dryer. The pressure filter device is configured to operate at a pressure and temperature above the atmospheric boiling point of the solvent.
1. A process for the separation and drying of crude carboxylic acid crystals from a slurry in a solvent, the process comprising the steps of:
supplying the slurry comprising crystals of carboxylic acid to a filter operating at pressure and at a temperature above the atmospheric boiling point of the solvent;
removing a cake of separated crystals from said filter; and
passing said cake to a thermal dryer, wherein a once pass sweep gas is provided to the dryer.
2. The process of claim 1 wherein the carboxylic acid is an aromatic carboxylic acid.
3. The process of claim 2 wherein the aromatic carboxylic acid is terephthalic acid or isophthalic acid and the solvent is acetic acid.
4. The process of claim 1 wherein the temperature of the filter is from 110° C. to about 160° C.
5. The process of claim 1 wherein the pressure of the filter is from 2 to 5 bara.
6. The process of claim 1 wherein the temperature at which the dryer operates is from about 110° C. to about 160° C.
7. The process of claim 1 wherein the pressure at which the dryer operates is from about 0 bara to about 5 bara.
8. The process of claim 1 wherein the flow of sweep gas in the dryer is less than about 45 m 3 /tonne of crude terephthalic acid powder.
9. The process of claim 1 wherein the flow of sweep gas in the dryer is less than about 25 m 3 /tonne of crude terephthalic acid powder.
10. The process of claim 1 wherein the flow of sweep gas in the dryer is less than about 5 m 3 /tonne of crude terephthalic acid powder.
11. The process of claim 1 wherein sweep gas is not provided to the dryer.
12. The process of claim 1 wherein the moisture content of the carboxylic acid from the thermal dryer is about 2% or less.
13. The process of claim 1 wherein the moisture content of the carboxylic acid from the thermal dryer is about 1% less.
14. The process of claim 1 wherein the moisture content of the carboxylic acid from the thermal dryer is about 0.5% or less.
15. A system for the separation and drying of crude carboxylic acid from a slurry in a solvent, the system comprising:
a pressure filter device comprising a slurry inlet and an outlet for a cake of carboxylic acid crystals;
a thermal dryer configured to provide a once pass sweep gas; and
means for transporting the cake of carboxylic acid crystals from the pressure filter device to the thermal dryer;
wherein said pressure filter device is configured to operate at a pressure and temperature above the atmospheric boiling point of the solvent.
16. The system of claim 15 wherein the pressure filter device is a rotary pressure filter.
17. The system of claim 15 wherein the dryer is a rotary steam tube dryer.