Fresh plant inventory hydrofluoric acid eduction process
AssigneeMarathon Ashland Petroleum LLC
InventorDan R. Schlaeppi
Life of this patent
Estimating the term…
Abstract
A slipstream of high pressure, cooled isobutane recycle from within an alkylation process unit is used to withdraw hydrofluoric acid from a storage vessel by means of an eductor and discharges the same into a reactor section of the unit. The eductor is preferably constructed of HASTELLOY “C” which provides both corrosion resistance to HF acid and has excellent surface hardness to withstand the highly erosive eductor application. This eductor eliminates potential release of HF acid due to failure of conventional rotating equipment seals or sealing systems, is low cost, has no moving parts, and is fireproof (will not lose containment during a fire).
Claims13
A HF alkylation process comprising:
- (a) mixing liquid HF acid, a fresh isobutane feed stream, a recycle isobutane stream and a fresh olefin feed stream to form a liquid mixture;
- (b) alkylating said olefins in said mixture with isobutane in an HF alkylation reactor operating at HF alkylation conditions including a pressure sufficiently high to maintain said isobutane in the liquid phase in at least a portion of said reactor, to form a liquid mixture comprising isoparafinnic alkylate produced in the course of said alkylation reaction, alkyl fluorides, and HF contaminated with a minor amount of acid soluble oil (ASO) produced during said alkylation reaction;
- (c) separating said mixture into an alkylate product rich phase, a recycle liquid HF acid phase contaminated with ASO, and an isobutane recycle phase,
- (d) regenerating, at least periodically, a portion of said recycle liquid HF acid in an acid regenerator to remove ASO therefrom and produce an ASO-rich stream containing a minor portion of acid or alkyl fluorides and a regenerated HF acid stream which is recycled to said alkylation reactor;
- (e) consuming, at least a portion of said liquid HF acid by at least one of mechanical loss, formation of alkyl fluorides which remain in a liquid alkylate product phase, or losses associated with a regeneration step;
- (f) storing fresh liquid HF acid in an HF acid storage vessel at liquid HF storage conditions sufficient to maintain said acid in a liquid phase and at a superatmospheric pressure which is below the pressure of said alkylation reactor;
- and
- (g) educting, at least periodically, liquid HF acid from said storage vessel to said HF alkylation process by educting liquid HF acid from said storage vessel using an eductor and as a motive fluid a liquid phase hydrocarbon feed or product stream associated with said alkylation process.
A method of periodically adding fresh or makeup HF acid to an HF alkylation process operating at a pressure above 200 psig from a liquid HF acid storage tank operating at a pressure below 200 psig and wherein said pressure differential between said process and said storage tank is sufficient to preclude use of a recycle isobutane stream produced in said alkylation process to educt liquid HF from said storage tank into said alkylation process comprising:
- (a) temporarily increasing the pressure in said liquid HF storage tank above said normal storage tank operating pressure;
- (b) diverting a portion of a recycle isobutane stream from said plant to use as a motive fluid in an eductor fluidly connected with said liquid HF storage tank;
- and said alkylation reaction;
- and
- (c) discharging from said eductor a stream comprising isobutane motive fluid and educted liquid HF acid into a portion of said HF alkylation process.
A method of restoring an inventory of HF acid to an HF alkylation process after a shutdown of the HF alkylation plant to permit using said inventory of HF acid to alkylate a fresh olefin stream with a stream comprising recycle isobutane produced in one or more fractionators to produce alkylate comprising:
- (a) restoring isobutane recycle by adding isobutane and a startup alkylate stream to said alkylation unit and-fractionating same in said one or more fractionators to produce an isobutane recycle stream and a startup alkylate stream with a reduced isobutane content to establish temperatures and operating conditions in said one or more fractionators and startup pressures in said process;
- (b) educting a stored HF inventory from an HF inventory storage tank operating at HF storage conditions including a pressure less than said startup pressure in said process into said HF alkylation plant using a recycle isobutane stream produced by said one or more fractionators to produce an HF alkylation plant with isobutane recycle established and an inventory of HF acid in the plant.
Dependencies are inferred from the claim text.