System and a method for analysis of vent gas of a urea plant

Patent metadata

Field	Value
Publication number	US-11243168-B2
Application number	US-201716330986-A
Country	US
Kind code	B2
Filing date	Sep 19, 2017
Priority date	Sep 19, 2016
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

A system for analysis of vent gas of a urea plant, comprising: a Raman spectroscope; a sampling conduit that connects the spectroscope to a main pipe of the urea plant configured to convey a sample stream to be analysed to the spectroscope; and a temperature-adjusting device, operated by a temperature controller and acting on at least one thermal treatment portion of the conduit configured to adjust the temperature of the sample stream circulating in the conduit.

First claim

The invention claimed is:

1. A urea plant vent gas analysis system comprising:
a Raman spectroscope;
a sampling conduit having a connector connectable to a main pipe of a urea plant and configured to convey a sample stream of gas from the main pipe to the Raman spectroscope;
a temperature-adjusting device, operated by a temperature controller and configured to act on a thermal treatment portion of the sampling conduit to adjust a temperature of the sample stream circulating in the sampling conduit, wherein the temperature controller is set to a temperature lower than a threshold temperature that can damage components of the Raman spectroscope and the temperature-adjusting device comprises:
a cooling circuit arranged around the thermal treatment portion of the sampling conduit and in which a cooling fluid circulates,
a circulation member controllable by the temperature controller and configured to circulate the cooling fluid in the cooling circuit, and
a heating element positioned in the sampling conduit downstream, in a circulation direction of the sample stream in the sampling conduit, of the thermal treatment portion and of the cooling circuit, the temperature controller configured to cause the heating element to raise the temperature of the sample stream after the cooling of the sample stream caused by the cooling circuit to ward off saturation conditions of the sample stream entering the Raman spectroscope; and

a reflux device configured to collect and return to the main pipe a condensate fraction of the sample stream that is condensed following a cooling of the sample stream in the thermal treatment portion of the sampling conduit.

2. The urea plant vent gas analysis system of claim 1 , further comprising a processing and control unit configured to calculate an amount of condensable species returned to the main pipe.

3. The urea plant vent gas analysis system of claim 1 , wherein the reflux device comprises a collecting portion of the sampling conduit, the collecting portion being positioned above the main pipe and beneath the thermal treatment portion of the sampling conduit, the collecting portion being positioned such that the condensate fraction falls, based on gravity, through the collecting portion and into the main pipe.

4. The urea plant vent gas analysis system of claim 3 , wherein the collecting portion is one of: vertically positioned and slantedly positioned toward the connector.

5. The urea plant vent gas analysis system of claim 1 , wherein the Raman spectroscope is positioned above the main pipe of the urea plant and the sampling conduit is in a position selected from the group consisting of: vertically departing from the main pipe, vertically extending from the connector, and slantedly upwards extending from the connector.

6. The urea plant vent gas analysis system of claim 1 , wherein the temperature controller comprises a dual-loop type controller and is connected to a first temperature sensor positioned upstream in a circulation direction of the sample stream in the sampling conduit, and a second temperature sensor positioned downstream in the circulation direction of the sample stream in the sampling conduit.

7. The urea plant vent gas analysis system of claim 1 , further comprising an automatic emergency shut-off valve configured to interrupt a supply of the sample stream to the Raman spectroscope if the temperature of the sample stream rises above a preset danger threshold temperature, the automatic emergency shut-off valve positioned at one of: an inlet of the Raman spectroscope and along the sampling conduit.

8. The urea plant vent gas analysis system of claim 1 , wherein the Raman spectroscope has an outlet connected to a return conduit that is connectable to the main pipe, the outlet being configured to return the sample stream conveyed through the Raman spectroscope back to the main pipe downstream, in a vent gas circulation direction through the main pipe, of the connector.

9. The urea plant vent gas analysis system of claim 1 , wherein the sampling conduit conveys a continuous sample stream of gas from the main pipe to the Raman spectroscope.

10. A urea plant comprising:
a main pipe; and
a urea plant vent gas analysis system comprising:
a Raman spectroscope;
a sampling conduit having a connector connectable to the main pipe and configured to convey a sample stream of gas from the main pipe to the Raman spectroscope;
a temperature-adjusting device, operated by a temperature controller and configured to act on a thermal treatment portion of the sampling conduit to adjust a temperature of the sample stream circulating in the sampling conduit, wherein the temperature controller is set to a temperature lower than a threshold temperature that can damage components of the Raman spectroscope and the temperature-adjusting device comprises:
a cooling circuit arranged around the thermal treatment portion of the sampling conduit and in which a cooling fluid circulates,
a circulation member controllable by the temperature controller and configured to circulate the cooling fluid in the cooling circuit, and
a heating element positioned in the sampling conduit downstream, in a circulation direction of the sample stream in the sampling conduit, of the thermal treatment portion and of the cooling circuit, the temperature controller configured to cause the heating element to raise the temperature of the sample stream after the cooling of the sample stream caused by the cooling circuit to ward off saturation conditions of the sample stream entering the Raman spectroscope; and

a reflux device configured to collect and return to the main pipe a condensate fraction of the sample stream that is condensed following a cooling of the sample stream in the thermal treatment portion of the sampling conduit.

11. A method for analyzing vent gas of a urea plant, the method comprising:
taking a sample stream of gas from a main pipe of the urea plant for analysis by Raman spectroscopy performed in a Raman spectroscope; and
controlling a temperature of the sample stream to maintain the temperature below a preset threshold temperature that can damage components of the Raman spectroscope, the controlling of the temperature of the sample stream including:
detecting the temperature of the sample stream in a sampling conduit that conveys the sample stream to the Raman spectroscope,
responsive to the detected temperature being higher than the preset threshold temperature:
cooling, via a cooling circuit in which a cooling fluid circulates, the sample stream,
thereafter, heating, via a heating element, the sample stream to raise the temperature of the sample stream to ward off saturation conditions of the sample stream entering the Raman spectroscope,
collecting a condensate fraction of the sample stream condensed in the cooling of the sample stream, and
returning said condensate fraction back to the main pipe.

12. The method of claim 11 , wherein detecting the temperature of the sample stream comprises detecting the temperature upstream and downstream, in a circulation direction of the sample stream in the sampling conduit, of a thermal treatment portion of the sampling conduit in which the sample stream is cooled.

13. The method of claim 11 , further comprising calculating an amount of condensable species brought back into the main pipe.

14. The method of claim 11 , wherein the Raman spectroscope is positioned above the main pipe and connected to the main pipe via a sampling conduit which is in a position selected from the group consisting of: vertically departing from the main pipe, vertically extending from a connector

Assignees

• Saipem Spa

Inventors

• Cerrone Cristina
• Carlessi Lino
• Serrafero Alberto
• Viola Francesco

Classifications

• Y02P20/141

  Feedstock · CPC title

• G01N2021/0193

  the sample being taken from a stream or flow to the measurement cell · CPC title

• G01N2021/158

  Eliminating condensation · CPC title

• G01N2021/8578

  Gaseous flow · CPC title

• G01N21/65 Primary

  Raman scattering · CPC title