Process for recovering paraxylene utilizing ammonia absorption refrigeration
AssigneeBP Corporation North America Inc.
InventorJeffrey A. Amelse
Life of this patent
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Abstract
A process for recovering paraxylene from a substantially hydrocarbon feedstock. The recovery comprises cooling the hydrocarbon feedstock in at least one refrigerated crystallization stage that is indirectly refrigerated by evaporating at least a portion of a substantially liquid stream comprising ammonia. The crystallization stage may also be cooled by an ethylene refrigerant, which has been cooled by heat exchange with a substantially liquid stream comprising ammonia. The process further comprises a series of cooling substeps. This invention is also directed to an ammonia absorption refrigeration process powered by an enthalpy source from or near a paraxylene recovery unit.
Claims13
A crystallization process for recovering paraxylene from a substantially hydrocarbon feedstock comprising cooling said hydrocarbon feedstock in at least one refrigerated crystallization stage that is indirectly refrigerated by evaporating at least a portion of a substantially liquid stream comprising ammonia wherein said at least one crystallization stage is refrigerated by:
- a) evaporating at least a portion of said substantially liquid stream comprising ammonia from enthalpy supplied by a heat source from said crystallization process, and
- b) absorbing said evaporated ammonia from step (a) into a stream comprising a mixture enriched in water relative to ammonia.
A crystallization process for recovering paraxylene from a substantially hydrocarbon feedstock comprising cooling said hydrocarbon feedstock in at least one refrigerated crystallization stage that is indirectly refrigerated by cooling substeps comprising:
- a) contacting a stream comprising ammonia vapor with a stream comprising water and forming a liquid mixture comprising water and ammonia,
- b) recovering from said liquid mixture comprising water and ammonia a substantially liquid stream comprising ammonia, and
- c) vaporizing at least a portion of said substantially liquid stream comprising ammonia by transferring at least a portion of the enthalpy of vaporization to said substantially liquid stream comprising ammonia from said hydrocarbon feedstock.
An ammonia absorption refrigeration process comprising:
- a. conveying a liquid ammonia stream to an ammonia evaporator to chill and remove process heat from a crystallization process to recover paraxylene;
- b. sending ammonia vapor to an absorber to generate a strong ammonia aqua solution;
- c. pumping said strong ammonia aqua solution to an ammonia fractionator;
- d. reboiling said ammonia fractionator with an enthalpy source to create very pure ammonia vapor and then condensing said very pure ammonia vapor, and e. vaporizing at least a portion of said condensed ammonia by indirect heat transfer of heat from a hydrocarbon feedstock to said condensed ammonia, wherein said enthalpy source is selected from the group consisting of:
- condensing overhead vapors of distillation towers used to separate products, byproducts, and/or recycle streams of a crystallization process to recover paraxylene;
- reactor effluent streams of a crystallization process to recover paraxylene;
- furnace flue gas of a crystallization process to recover paraxylene;
- steam generated during a crystallization process to recover paraxylene;
- and warm streams on other chemical or refinery process units located near a paraxylene crystallization process unit.
Dependencies are inferred from the claim text.