1. Process for co-production of paraxylene and metaxylene andor orthoxylene from a feedstock that contains xylenes, ethylbenzene and C9-C10 hydrocarbons, whereby the process successively comprises:
A passage of feedstock (1) in a column (2) for distillation of xylenes from where a mixture (3) that comprises the majority of metaxylene, paraxylene, ethylbenzene and at least a portion of orthoxylene is drawn off at the top, and from where a flow (4) of C9-C10 hydrocarbons and the remaining portion of orthoxylene is drawn off at the bottom;
A separation of top mixture (3) in a simulated moving bed in at least one chromatographic column (9) containing a number of beds of an adsorbent that are interconnected in a closed loop and having a different selectivity for paraxylene, ethylbenzene, metaxylene and orthoxylene, whereby said column comprises at least five zones that are delimited by injections of mixture (3) (adsorption feedstock) and a desorbent (8) and draw-offs of an extract (10) that contains paraxylene, an intermediate fraction (11) that contains ethylbenzene, a raffinate (R2) (12) that contains orthoxylene and metaxylene, whereby a paraxylene desorption zone 1 is included between the injection of the desorbent and the sampling of the extract, whereby a zone 2 for desorption of ethylbenzene, orthoxylene and metaxylene is included between the sampling of the extract and the injection of the adsorption feedstock, whereby a zone 3A for paraxylene adsorption is included between the injection of the feedstock and the draw-off of the intermediate fraction, whereby a zone 3B for ethylbenzene adsorption is included between the draw-off of the intermediate fraction and the draw-off of raffinate (R2), and whereby a zone 4 is included between the draw-off of raffinate (R2) and the injection of desorbent, whereby the process is characterized in that
Raffinate (2) is distilled to eliminate essentially all of the desorbent, and a distilled raffinate (18) is drawn off,
The extract is distilled to recover a paraxylene-enriched fraction (16).
The process is also characterized in that:
Either distilled raffinate (18) is sent at least in part to at least one crystallization zone (27), and metaxylene with a purity of at least 99% is recovered,
Or distilled raffinate (18) is sent at least in part into a second distillation zone (23), a top flow (24) that contains metaxylene and a bottom fraction (25) that contains orthoxylene (24) are recovered, the top flow is crystallized at least in part, metaxylene with a purity of at least 99% is recovered, andor said bottom fraction is crystallized at least in part, and orthoxylene with a purity of at least 98.5% is recovered.
2. A process according to claim 1, in which flow (4) is distilled in a distillation column (5) to produce a high-purity orthoxylene flow (6) at the top and a flow (7) that contains C9-C10 hydrocarbons at the bottom.
3. A process according to one of claim 1, in which the crystallization of metaxylene and the crystallization of orthoxylene are carried out in a single crystallization zone, in runs, to produce metaxylene or orthoxylene separately.
4. A process according to one of claim 1, in which the crystallization of metaxylene and the crystallization of orthoxylene are carried out in separate crystallization zones.
5. A process according to one of claim 1, in which a portion of orthoxylene-enriched bottom fraction (25) is isomerized in at least one isomerization zone, and the isomerate that is obtained is recycled in distillation column (2).
6. A process according to one of claims 1, in which the adsorbent that is used in the separation stage is a barium-exchanged X zeolite or a potassium-exchanged Y zeolite or a barium- and potassium-exchanged Y zeolite.
7. A process according to one of claims 1, in which the desorbent is selected from among paradiethylbenzene, toluene, paradifluorobenzene or mixed with diethylbenzenes.
8. A process according to one of claims 1, in which the volumetric ratio of desorbent to adsorption feedstock is between 0.5 and 2.5.
9. A process according to claim 1, in which the separation stage is conducted at a temperature that is generally between 20\xb0 C. and 250\xb0 C., and under a pressure that is between the bubble pressure of xylenes at the operating temperature and 20 bar.
10. A process according to claim 1, in which to produce high-purity metaxylene, the flow rates of zones 3A and 3B as well as the distillation of orthoxylene in column (2) andor second column (23) are regulated to obtain as a crystallization feedstock an effluent that is essentially free of ethylbenzene and desorbent, with a molar composition that is delimited by the four points: pure metaxylene, eutectic binary metaxylene-paraxylene (metaxylene 87.0%, paraxylene 13.0%), eutectic ternary meta-ortho-paraxylene (metaxylene 61.4%, orthoxylene 30.5%, paraxylene 8.1%), and eutectic binary meta-orthoxylene (metaxylene 66.6%, orthoxylene 33.4%).
11. A process according to claim 1, in which at least a portion of paraxylene-enriched fraction (16) feeds a crystallization batch vat to obtain, in runs, after passage into crystallization zone (27), a paraxylene flow (28) at at least 99.90%.
12. A process according to claim 1, in which to produce orthoxylene, the flow rates of zones 3A and 3B as well as the distillation of orthoxylene in column (2) andor second column (23) are regulated to obtain as a crystallization feedstock an effluent that is essentially free of ethylbenzene and desorbent, with a molar composition that is delimited by the four pure orthoxylene points: eutectic binary orthoxylene-paraxylene (orthoxylene 75.7%, paraxylene 24.3%), eutectic ternary meta-ortho-paraxylene (metaxylene 61.4%, orthoxylene 30.5%, paraxylene 8.1%), and eutectic binary meta-orthoxylene (metaxylene 66.6%, orthoxylene 33.4%).
13. A process according to claim 1, in which the crystallization zone or zones comprise at least one crystallizer and in which a refrigeration unit is used to operate at a temperature of between \u221245\xb0 C. and \u221260\xb0 C. in the case where it is sought to produce metaxylene, between \u221220\xb0 C. and \u221260\xb0 C. in the case where it is sought to produce orthoxylene and between 20\xb0 C. and \u221250\xb0 C. in the case where it is sought to produce paraxylene and in which the mother liquor that is separated from the crystals is entrained to a storage vat after the crystallization stage to be recycled in the isomerization unit.
14. A process according to claim 1, in which the chromatographic column contains at least 24 beds, including at least 3 beds in zone 3B.
15. A process according to claim 1, in which fraction (16) is enriched with paraxylene at at least 50% purity and is sent into at least one crystallization zone to deliver paraxylene crystals and a mother liquor, the crystals are separated from the mother liquor, optionally resuspended, washed and recovered, and the mother liquor is recycled in the chromatographic column.
16. A process according to claim 8, wherein said volumetric ratio is between 1.4 and 1.7.
17. A process according to claim 9, wherein said temperature is between 90\xb0 C. and 210\xb0 C.
18. A process according to claim 9, wherein said temperature is between 160\xb0 C. and 200\xb0 C.
19. A process according to claim 1, wherein distilled raffinate (18) is sent at least in part to at least one crystallization zone (27), and metaxylene with a purity of at least 99% is recovered.
20. A process according to claim 1, wherein distilled raffinate (18) is sent at least in part into a second distillation zone (23), a top flow (24) that contains metaxylene and a bottom fraction (25) that contains orthoxylene (24) that contains metaxylene and a bottom fraction (25) that contains orthoxylene (24) are recovered, the top flow is crystallized at least in part, metaxylene with a purity of at least 99% is recovered, andor said bottom fraction is crystallized at least in part, and orthoxylene with a purity of at least 98.5% is recovered.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of power control for a wireless terminal comprising the steps of:
receiving at least one input parameter indicative of a transmission power level;
generating a control parameter based on the at least one input parameter; and
regulating an output transmission power level of the wireless terminal based on the control parameter.
2. The method of claim 1, wherein the at least one input parameter is associated with transmission power level characteristics of a received signal.
3. The method of claim 1, wherein the at least one input parameter is associated with power fading characteristics of a received signal.
4. The method of claim 1, wherein the output transmission power level is regulated based on a predetermined minimum power level.
5. The method of claim 1, wherein the output transmission power level is regulated relative to the transmission power level indicated by the received input parameter.
6. The method of claim 1, further comprising regulating at least one power level controller based on the control parameter.
7. The method of claim 6, wherein the at least one power level controller is associated with at least one digital polar modulator for regulating the output transmission power level of the wireless terminal.
8. The method of claim 1, wherein the wireless terminal is a radiotelephone handset.
9. The method of claim 1, wherein the wireless terminal is a base station.
10. An apparatus for power control in a wireless terminal comprising:
a receiver for receiving at least one input parameter indicative of a transmission power level;
a processor for generating a control parameter based on the at least one input parameter; and
a controller for regulating an output transmission power level of the wireless terminal based on the control parameter.
11. The apparatus of claim 10, wherein the at least one input parameter is associated with transmission power level characteristics of a received signal.
12. The apparatus of claim 10, wherein the at least one input parameter is associated with power fading characteristics of a received signal.
13. The apparatus of claim 10, wherein the output transmission power level is regulated by the controller based on a predetermined minimum power level.
14. The apparatus of claim 10, wherein the output transmission power level is regulated relative to the transmission power level indicated by the received input parameter.
15. The apparatus of claim 10, further comprising the processor sending a control parameter to each of a plurality of controllers.
16. The method of claim 15, wherein each of the plurality of controllers is associated with at least one digital polar modulator for regulating the output transmission power level of the mobile terminal.
17. The method of claim 10, wherein the wireless terminal is a radiotelephone handset.
18. The method of claim 10, wherein the wireless terminal is a base station.
19. A computer-readable medium having computer executable instructions for performing steps comprising:
determining at least one parameter indicative of a power level of a transmitting wireless terminal;
generating a control parameter based on the at least one parameter; and
regulating an output transmission power level of a receiving wireless terminal based on the control parameter.
20. The computer-readable medium of claim 19, wherein the at least one input parameter is associated with power fading characteristics of the transmitting wireless terminal.