Using pressurized wet gas lines to avoid fouling in purified terephthalic acid (PTA) filters and lines
Processes for recovering a purified aromatic carboxylic acid include contacting a crude aromatic carboxylic acid with hydrogen in the presence of a catalyst in a hydrogenation reactor to form a purified aromatic carboxylic acid; crystallizing the purified aromatic carboxylic acid to form a solid/liquid mixture comprising purified aromatic carboxylic acid solids; filtering the solid/liquid mixture in a rotary pressure filter apparatus to remove a liquid filtrate, washing the solid/liquid mixture in the rotary pressure apparatus with a wash fluid to form a washed solid/liquid mixture, and drying the washed solid/liquid mixture in the rotary pressure apparatus with an inert gas to form a filter cake comprising purified aromatic carboxylic acid solids and a wet gas stream; withdrawing the wet gas stream from the rotary pressure filter apparatus while maintaining the wet gas stream at a pressure above ambient; and recovering the purified aromatic carboxylic acid solids from the filter cake.
1. A process for recovering a purified aromatic carboxylic acid comprising:
contacting a crude aromatic carboxylic acid with hydrogen in the presence of a catalyst in a hydrogenation reactor to form a purified aromatic carboxylic acid;
crystallizing the purified aromatic carboxylic acid to form a solid/liquid mixture comprising purified aromatic carboxylic acid solids;
filtering the solid/liquid mixture in a filtering zone of a rotary pressure filter apparatus to form a filtered solid-liquid mixture and a liquid filtrate stream;
withdrawing the liquid filtrate stream from the filtering zone of the rotary pressure filter apparatus;
washing the filtered solid/liquid mixture in a washing zone of the rotary pressure filter apparatus with a wash fluid to form a washed solid/liquid mixture;
drying the washed solid/liquid mixture in a drying zone of the rotary pressure filter apparatus with an inert gas to form a filter cake comprising purified aromatic carboxylic acid solids and a wet gas stream;
withdrawing the wet gas stream from the drying zone of the rotary pressure filter apparatus while maintaining the wet gas stream at a pressure above ambient; and
recovering the purified aromatic carboxylic acid solids from the filter cake.
2. The process of claim 1 , further comprising flashing the wet gas stream to form a gas stream and a solid/liquid stream.
3. The process of claim 2 , further comprising recycling the solid/liquid stream to the hydrogenation reactor.
4. The process of claim 1 , wherein the wet gas stream is at a pressure above 1.5 bar.
5. The process of claim 1 , wherein the wet gas stream is at a pressure of between 2 bar and 3 bar.
6. The process of claim 1 , wherein the wet gas stream is at a pressure between 1.5 bar and 4 bar.
7. The process of claim 1 , wherein the pressure in the wet gas line is controlled with a pressure control mechanism located at an entry of a separation zone.
8. The process of claim 2 , wherein the flashing step is performed in a separation zone at atmospheric pressure.
9. The process of claim 1 , wherein the wash fluid removes impurities from the filter cake.
10. The process of claim 1 , further comprising oxidizing a substituted aromatic compound in a reaction zone to form the crude aromatic carboxylic acid.
11. The process of claim 1 , further comprising drying the filter cake in a dryer to form a purified aromatic carboxylic acid product.
12. The process of claim 1 , wherein the aromatic carboxylic acid comprises terephthalic acid.
13. The process of claim 1 , further comprising, after washing the filtered solid/liquid mixture, withdrawing at least a portion of the wash fluid from the washing zone of the rotary pressure filter apparatus.
14. The process of claim 1 , further comprising separating the wet gas stream to form a gas stream and a solid/liquid stream.