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US-12623990-B2 - Methods for improved control of glacial acetic acid processes

US12623990B2US 12623990 B2US12623990 B2US 12623990B2US-12623990-B2

Abstract

Methods and systems for measuring component concentrations. The methods may include providing a system configured for contacting a first component, a second component, and a third component; determining a concentration of the second component in a reactor; determining a concentration of the third component in the reactor; determining a temperature and a pressure of a first apparatus downstream of the reactor; and calculating a first concentration of the first component in the reactor based on (i) the concentration of the second component in the reactor, (ii) the concentration of the third component in the reactor, and (iii) the temperature and the pressure of the first apparatus.

Inventors

  • Austin R. Straussner
  • Shane J. Weber
  • Noel C. Hallinan
  • David A. HEAPS

Assignees

  • LYONDELLBASELL ACETYLS, LLC

Dates

Publication Date
20260512
Application Date
20230517

Claims (15)

  1. 1 . A method for measuring component concentration, the method comprising: providing a system configured for contacting a first component, a second component, and a third component, the system comprising a reactor, and a first apparatus downstream of the reactor; determining a concentration of the second component in the reactor; determining a concentration of the third component in the reactor; determining a temperature and a pressure of the first apparatus; and calculating a first concentration of the first component in the reactor based on (i) the concentration of the second component in the reactor, (ii) the concentration of the third component in the reactor, and (iii) the temperature and the pressure of the first apparatus, wherein the first component is methyl acetate, the second component is methyl iodide, the third component is water, the first apparatus is a flash tank, and the calculating of the first concentration of the first component in the reactor comprises solving Equation 1: [ M ⁢ e ⁢ A ⁢ c ] R ⁢ eactor = T F ⁢ l ⁢ a ⁢ s ⁢ h ⁢ Tank - C w [ H 2 ⁢ O ] Reactor + C m ⁢ ( [ MeI ] Reactor ) + C p ⁢ P FlashTank C a ( Eq . 1 ) wherein: [MeAc] Reactor is the reactor MeAc concentration; T FlashTank is the flash tank temperature; C w is the reactor water coefficient; [H 2 O] Reactor is the reactor H 2 O concentration; C m is the reactor MeI coefficient; [MeI] Reactor is the reactor MeI concentration; C p is the flash tank operating pressure coefficient; P FlashTank is the flash tank pressure; and C a is the flash tank temperature coefficient.
  2. 2 . The method of claim 1 , wherein the system further comprises an analyzer configured to measure directly a second concentration of the first component in the reactor.
  3. 3 . The method of claim 2 , further comprising directly measuring the second concentration of the first component with the analyzer via Fourier transform infrared spectroscopy and/or Raman spectroscopy.
  4. 4 . The method of claim 3 , further comprising generating an alarm if a difference between the first concentration and the second concentration of the first component exceeds a predetermined threshold.
  5. 5 . The method of claim 4 , further comprising replacing or repairing the analyzer if a difference between the first concentration and the second concentration of the first component exceeds a predetermined threshold.
  6. 6 . The method of claim 1 , wherein the determining of the concentration of the second component in the reactor comprises determining the concentration of the second component in the reactor directly via Fourier transform infrared spectroscopy and/or Raman spectroscopy.
  7. 7 . The method of claim 1 , wherein the determining of the concentration of the second component in the reactor and the concentration of the third component in the reactor comprises determining the concentration of the second component and the concentration of the third component in the reactor directly via Fourier transform infrared spectroscopy and/or Raman spectroscopy.
  8. 8 . The method of claim 1 , wherein the first component is methyl acetate, the second component is methyl iodide, and the third component is water.
  9. 9 . The method of claim 1 , wherein the first apparatus is a flash tank.
  10. 10 . The method of claim 1 , wherein the system further comprises a second apparatus downstream of the reactor.
  11. 11 . The method of claim 10 , wherein the determining of the concentration of the third component in the reactor comprises determining a concentration of the third component in the second apparatus or in a feed provided to the second apparatus; and calculating the concentration of the third component in the reactor based on the concentration of the third component in (i) the second apparatus or (ii) the feed provided to the second apparatus.
  12. 12 . The method of claim 11 , wherein the second apparatus is a drying column, and the third component is water.
  13. 13 . The method of claim 12 , wherein the determining of the concentration of water in the drying column or the feed provided to the drying column comprises determining the concentration of water via Fourier transform infrared spectroscopy and/or Raman spectroscopy.
  14. 14 . The method of claim 12 , wherein the determining of the concentration of water in the drying column or the feed provided to the drying column comprises— determining a light ends column (LEC) reflux ratio; and correlating the concentration of water according to Equations 2a and 2b: [ H 2 ⁢ O ] DCf = C 1 + C 2 ⁢ T D ⁢ C ⁢ T ⁢ y + C 3 ( P DCovr + d ⁢ P D ⁢ C ( x - y x ) C 4 + C 5 ( R D ⁢ C D D ⁢ C ) + C 6 ( D D ⁢ C F D ⁢ C ) , ( Eq . 2 ⁢ a ) and [ H 2 ⁢ O ] LECT s = [ H 2 ⁢ O ] D ⁢ C ⁢ f ⁢ ( F D ⁢ C + D H ⁢ E ⁢ C + F r ⁢ e ⁢ r ⁢ u ⁢ n ) - [ H 2 ⁢ O ] H ⁢ E ⁢ C ⁢ d ⁢ D H ⁢ E ⁢ C - [ H 2 ⁢ O ] r ⁢ e ⁢ r ⁢ u ⁢ n ⁢ F r ⁢ e ⁢ r ⁢ u ⁢ n F D ⁢ C ( Eq . 2 ⁢ b ) wherein: [H 2 O] DCf is the mass fraction of water in the drying column or feed provided to the drying column; C 1 , C 2 and C 3 are drying column temperature profile coefficients; T DCTy is the drying column reactor water concentration correlation temperature at tray y; P DCovr is the drying column operating pressure; dP DC is the drying column total pressure drop from all trays; C 4 , C 5 and C 6 are drying column mass transfer operating line coefficients; R DC is the drying column reflux rate; D DC is the drying column distillate rate; F DC is the drying column feed rate; [H 2 O] LECTs is the light ends column sidedraw water concentration; D HEC is the heavy ends distillate rate; F rerun is the drying column feed rate from rerun tank; [H 2 O] HECd is the heavy ends distillate water concentration; D HEC is the heavy ends distillate rate; and [H 2 O] rerun is the rerun tank water concentration.
  15. 15 . The method of claim 14 , wherein the calculating of the concentration of water in the reactor based on the concentration of the water in the second apparatus or the feed provided to the second apparatus comprises solving Equation 3: [ H 2 ⁢ O ] Reactor ≅ f ⁢ { [ H 2 ⁢ O ] L ⁢ E ⁢ C ⁢ T s ′ ⁢ R L ⁢ E ⁢ C D L ⁢ E ⁢ C } ( Eq . 3 ) wherein: [H 2 O] Reactor is the mass fraction of water in the reactor based on the concentration of water in the second apparatus of the feed thereto; [H 2 O] LECTs is the light ends column sidedraw water concentration; R LEC is the light ends column reflux rate; and D LEC is the light ends column total distillate rate where the total refers to combined decanter light and heavy phase.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The application claims the benefit of priority to U.S. Provisional Patent Application No. 63/343,690, filed on May 19, 2022, which is incorporated herein by reference in its entirety. FIELD OF THE INVENTION This disclosure relates to the production of acetic acid. More particularly, the disclosure relates to methods for controlling the production of acetic acid. BACKGROUND In some glacial acetic acid processes, maintaining a steady state reactor methyl acetate concentration can depend on one or more variables, such as methanol feed, carbon monoxide feed, and/or active catalyst, e.g., rhodium, concentration. For processes operating at a methyl acetate reactor concentration of greater than 3 wt. %, a mis-match of any of methyl acetate's dependent variables, in some instances, can cause methyl acetate concentration to increase rapidly, thereby increasing the likelihood of significant disturbances in downstream equipment and plant trips. Several different methods have been devised to perform direct or indirect methyl acetate measurement. As reactor methyl acetate generally correlates inversely with decanter heavy phase density, one method relies on an on-line heavy phase density measurement to calculate reactor methyl acetate concentration. This method, however, has several disadvantages. For example, due to the fact that the decanter is downstream of the reactor, there is a time lag. The method is a reactive, not a proactive, technique. Other reactive methods for controlling methyl acetate concentration include controlling carbon monoxide flow rate in response to temperature. Some methods directly measure reactor methyl acetate and other reactor components in real time via Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy (see, e.g., U.S. Pat. Nos. 6,103,934; 6,362,366; 8,519,182; and 10,227,283). These methods typically use either flow through cells or in-situ probes. Although these methods can contribute to improved process control, they can face one or more difficulties. For example, in both the near infrared (NIR FTIR) and Raman spectra of reactor solutions, the methyl acetate peak at least partially overlaps with other peaks, which can adversely impact the accuracy of a measurement. As an additional example, random signal fluctuation in Raman spectra can result in a need for normalization in order to prevent over- or under-prediction of component concentrations (see, e.g., U.S. Pat. Nos. 9,656,939; and 10,118,884). There remains a need for methods for directly or indirectly measuring one or more reactor components, such as methyl acetate, including reliable methods that measure methyl acetate in real time so that upward and/or downward trends in methyl acetate concentration can be identified quickly. SUMMARY OF THE INVENTION An aspect of the disclosure relates to methods for measuring one or more reactor components, including methods in which pseudo-analyzers or surrogate analyzers are used as (i) a cross-check of FTIR and/or Raman analyzer data, or (ii) an independent method of real time calculation of various reactor component concentrations. An aspect of the present disclosure relates to methods for calculating a concentration of a first component in a reactor based on (i) a concentration of a second component in the reactor, (ii) a concentration of a third component in the reactor, and (iii) the temperature and the pressure of a first apparatus downstream of the reactor. Yet another aspect of the present disclosure relates to methods that include providing a system configured for contacting a first component, a second component, and a third component, wherein the system includes a reactor, and a first apparatus downstream of the reactor; determining a concentration of the second component in the reactor; determining a concentration of the third component in the reactor; determining a temperature and a pressure of the first apparatus; and calculating a first concentration of the first component in the reactor based on (i) the concentration of the second component in the reactor, (ii) the concentration of the third component in the reactor, and (iii) the temperature and the pressure of the first apparatus. Additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the aspects described herein. The advantages described herein will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive. BRIEF DESCRIPTION OF THE DRAWINGS The claimed subject matter may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: F