Method for in-line quantitative analysis of a stream in a production plant for the synthesis of urea

Patent metadata

Field	Value
Publication number	US-10209191-B2
Application number	US-201515316960-A
Country	US
Kind code	B2
Filing date	Jun 2, 2015
Priority date	Jun 11, 2014
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

The invention discloses the use of Raman spectroscopy to analyze one or more process streams ( 5 ) of a urea synthesis production plant, where urea is synthesised from ammonia and carbon dioxide at high pressure (100-300 bar) and high temperature (50-250° C.). The radiation generated by the Raman scattering is analyzed to determine the concentration of components such as urea, ammonia and carbon dioxide in the process streams ( 5 ). A logic system implemented in a plant control unit ( 1 ) generates signals to target plant actuators to optimize the operation.

First claim

The invention claimed is:

1. A method of in-line quantitative analysis of at least one process stream of a urea synthesis process where urea is synthesized from ammonia and carbon dioxide, at a pressure in the range of 100 to 300 bar and temperature in the range of 50 to 250° C., said method comprising the use of Raman spectroscopy for said in-line quantitative analysis, wherein:
the concentration of urea in said process stream is determined by Raman spectroscopy and through the detection of a spectroscopy band corresponding to excitation of the carbonyl di-amide bond;
the concentration in said process stream of carbon-containing molecules other than urea and having a carboxyl group is determined by Raman spectroscopy as an equivalent concentration of carbon dioxide corresponding to the excitation of the atomic bonds in the carboxyl form.

2. The method according to claim 1 , wherein the Raman spectroscopy is carried out with a laser beam focused in said at least one process stream.

3. The method according to claim 2 , wherein said laser beam has a wavelength in the visible or near-visible range between 300 and 1400 nm.

4. The method according to claim 1 , wherein:
excitation of the carbonyl di-amide bond of molecules of urea is detected by means of Raman shift of an incident laser beam having a suitable wavelength, in a frequency range of 900 to 1050 cm−1, and
said molecules other than urea are detected by means of Raman shift of said incident laser beam, in a frequency range of 1000 to 1150 cm−1.

5. The method according to claim 4 , wherein the concentration of ammonia is determined by means of Raman shift of said incident laser beam, in a frequency range of 1350 to 1750 cm−1.

6. The method according to claim 4 , said incident laser beam having a wavelength of 785 nm.

7. The method according to claim 1 , wherein the Raman spectroscopy is carried out directly on a process pipe carrying a process stream.

8. The method according to claim 1 , wherein the Raman spectroscopy is carried out on a side stream taken from said process stream.

9. The method for controlling a plant for synthesis of urea, characterized by including a quantitative analysis of at least one process stream of said plant with the application of Raman spectroscopy according to claim 1 .

10. The method for controlling a plant according to claim 9 , wherein the Raman spectroscopy include the steps of:
sending an incident radiation, preferably a laser beam, to a focus point in at least one process stream;
receiving a scattered radiation;
analyzing the scattered radiation with a Raman spectroscope; and
using the detected composition of said process streams as input to a logic control system of the plant.

11. The method according to claim 2 , wherein said laser beam has a wavelength in the visible or near-visible range between 400 and 1000 nm.

Assignees

• Casale Sa

Inventors

• Rugnone Luca

Classifications

• G01N21/65 Primary

  Raman scattering · CPC title

• C07C273/04 Primary

  from carbon dioxide and ammonia · CPC title

• G01N2021/8578

  Gaseous flow · CPC title

• G01N2021/8416

  and process controlling, not otherwise provided for · CPC title

• G01N2021/8411

  Application to online plant, process monitoring · CPC title