US20140295356A1

US20140295356A1 - In situ flue gas analyzer with improved process communication

Info

Publication number: US20140295356A1
Application number: US14/227,476
Authority: US
Inventors: Joseph C. Nemer; Behzad Rezvani; Anni S. Wey; James D. Kramer
Original assignee: Rosemount Analytical Inc
Current assignee: Rosemount Inc
Priority date: 2013-03-29
Filing date: 2014-03-27
Publication date: 2014-10-02
Also published as: EP2984477A1; ES2738318T3; EP2984477B1; AU2014240954A1; CN105074445B; AU2014240954B2; CA2905211A1; WO2014160944A1; EP2984477A4; CN105074445A

Abstract

An in situ flue gas analyzer includes a probe extendable into a flue. The probe has a measurement cell providing a signal responsive to a concentration of a gas within the flue. A controller is coupled to the probe and configured to provide an output based on the signal from the measurement cell. A first media access unit is coupled to the controller and is operably coupleable to a first process communication link. The first media access unit is configured to communicate in accordance with an all-digital process communication protocol. A second media access unit is coupled to the controller and is operably coupleable to a second process communication link. The second media access unit is configured to communicate in accordance with a second process communication protocol that is different than the all-digital process communication protocol. The first and second media access units are enabled simultaneously.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of U.S. Provisional Patent Application Ser. No. 61/806,621, filed Mar. 29, 2013, the content of which is hereby incorporated in its entirety.

BACKGROUND

Industrial process industries often rely on energy sources that include one or more combustion processes. Such combustion processes include operation of a furnace or boiler to generate energy from combustion, which is then used for the process. While combustion provides relatively low-cost energy, its use is typically regulated and combustion efficiency is sought to be maximized. Accordingly, one goal of the process management industry is to reduce the production of greenhouse gases by maintaining combustion efficiency of existing furnaces and boilers.
In situ or in-process flue gas analyzers are commonly used for monitoring, optimizing and/or controlling combustion processes. Typically, these analyzers employ an oxygen sensor that is similar in both technology and application to oxygen sensors found in automobiles. Such sensors are heated to an elevated temperature and provide a sensor output that is indicative of a parameter of interest (oxygen) relative to the exhaust/flue gas stream. In situ or in-process analyzers are particularly advantageous because they have no moving parts or sampling apparatus resulting in an extremely reliable probe that requires very little maintenance. While in situ flue gas analyzers may be considered to be field devices in the sense that they are often located out in the field and subjected to climatological extremes of temperature, humidity, mechanical vibration, and electrical interference, they are substantially different from most field devices. While many field devices measure a single physical quantity, such as temperature, pressure or flow, of a process fluid, process analyzers actually measure the composition of flue gas process streams. Accordingly, the processing performed within a flue gas analyzer is relatively complex and high-speed. Thus, the flue gas analyzer must often perform significant calculations and analyses in order to effectively control a combustion process. Additionally, it must do so quickly since the flue gas concentration sensor signal can also vary quickly.
Traditionally, some in situ flue gas analyzers were provided that communicated in accordance with a hybrid digital-analog process communication protocol. An example of this process communication protocol is the digital Highway Addressable Remote Transducer (HART®) protocol. The HART® communication protocol specifies the manner in which digital information is arranged in digital packets (i.e., HART® packets) and the manner in which the digital packets are physically conveyed through the wired transmission media. Typically, an in situ flue gas oxygen transmitter, such as that sold under the trade designation Model 6888 Oxygen Transmitter from the Rosemount Analytical, Inc. business unit of Emerson Process Management, transmits its flue gas concentration information in accordance with an analog signaling technique, such as the well-known 4-20 milliamp signaling technique. Optionally, the transmitter can be configured or otherwise specified to provide an analog signal representing flue gas oxygen in the form of a raw millivolt signal in order to interoperate with a variety of systems. Additionally, since the HART® protocol superimposes digital information upon the analog process variable signal, it is also known for an in situ flue gas oxygen transmitter to transmit digital information to an optional user interface, such as the known Xi Electronics module available from Rosemount Analytical.
While existing products provide significant benefits for users thereof in the monitoring and/or controlling of combustion processes, the sheer volume of data generated by the analysis of the flue gas stream and the speed with which the constituents of the flue gas stream may change, can be a challenge for the communications of the flue gas analyzer. Providing an in situ flue analyzer with improved process communication abilities would benefit the art of process combustion monitoring and control.

SUMMARY

An in situ flue gas analyzer includes a probe extendable into a flue. The probe has a measurement cell providing a signal responsive to a concentration of a gas within the flue. A controller is coupled to the probe and is configured to provide an output based on the signal from the measurement cell. A first media access unit is coupled to the controller and is operably coupleable to a first process communication link. The first media access unit is configured to communicate in accordance with an all-digital process communication protocol. A second media access unit is coupled to the controller and is operably coupleable to a second process communication link. The second media access unit is configured to communicate in accordance with a second process communication protocol that is different than the all-digital process communication protocol. The first and second media access units are enabled simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an in situ flue gas analyzer with which embodiments of the present invention are particularly useful.

FIG. 2 is a diagrammatic perspective view of an in situ flue gas analyzer in accordance with an embodiment of the present invention.

FIG. 3 is a block diagram of an in situ flue gas analyzer in accordance with an embodiment of the present invention.

FIG. 4 is a diagrammatic view of an in situ flue gas analyzer operating within a combustion process in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 is a diagrammatic view of an in situ flue gas analyzer operating in a combustion process. One example of such an analyzer 10 is that sold under the trade designation Model 6888 In Situ Flue Gas Oxygen Transmitter available from Rosemount Analytical Inc. Analyzer 10 includes a probe assembly 12 that is disposed within a stack or flue 14 and measures at least one parameter related to combustion occurring at burner 16. Typically, analyzer 10 is an oxygen analyzer, but can be any device that measures any suitable parameter related to constituents within the flue gas stream.
Burner 16 is operably coupled to a source of air or oxygen 18 and a source 20 of combustible fuel. Each of sources 18 and 20 is preferably coupled to burner 16 through a respective valve to deliver a controlled amount of oxygen and/or fuel to burner 16 in order to control the combustion process. Analyzer 10 measures the amount of oxygen in the combustion exhaust flow and provides an indication of the oxygen level to combustion controller 22. In the past, this signal was an analog signal either in the form of a 4-20 milliamp current loop or a raw millivolt signal. Controller 22 controls one or both of valves 24, 26 to provide closed loop combustion control. Analyzer 10 includes an oxygen sensor that typically employs a zirconia oxide sensor substrate to provide an electrical signal indicative of oxygen concentration, content or percentage in the exhaust. Zirconia oxide sensors operate at a temperature of about 700° Celsius and thus analyzer 10 includes, within probe assembly 12, an electrical heater that is operably coupled to AC power source 29. The oxygen sensor within probe 12 is similar in technology to oxygen sensors found in automobiles. Such sensors are highly effective in permitting control systems to maintain optimum fuel to ratios in order to achieve high efficiency, low NO_xproduction, and also the least amount of greenhouse gas emissions possible.
FIG. 2 is a diagrammatic perspective view of an in situ flue gas analyzer in accordance with an embodiment of the present invention. Probe assembly 12 is generally configured to house a sensor core assembly which includes diffuser disposed proximate end 32. The measurement cell within probe 12 is operable at an elevated temperature and the elevated temperature. The measurement cell and heater within probe 12 are electrically coupled to analyzer electronics (shown in FIG. 3) within electronics housing 36. Analyzer electronics 42 is configured to obtain a measurement from the measurement cell and provides suitable signal conditioning in order to provide a signal representing flue gas oxygen. Additionally, analyzer electronics 42 includes a controller or other suitable circuitry to control energization of the heater within probe 12 in order to maintain suitable thermal control of the measurement cell.
In accordance with an embodiment of the present invention, analyzer electronics 42 also includes a plurality of media access units to communicate in accordance with a plurality of distinct process communication protocols, such as the HART® process communication protocol described above and the FOUNDATION™ Fieldbus (FF). In accordance with an embodiment of the present invention, analyzer electronics 42 communicates using a plurality of distinct process communication protocols simultaneously or at substantially the same time. Thus, communication in accordance with a first process communication protocol may be performed for a first purpose, such as combustion burner control, and communication in accordance with the second distinct process communication protocol may be done in order to provide a second purpose, such as interacting with an optional user interface, such as the Model Xi operator interface (shown in FIG. 4) available from Rosemount Analytical Inc.
FIG. 3 is a block diagram of an electronics board of an in situ flue gas analyzer in accordance with an embodiment of the present invention. Electronics 42 includes power module 50 that is configured to receive AC electrical power, such as 110 or 220 VAC and condition the power for provision to various components of the analyzer. Additionally, since the heater within probe 12 will typically receive the full AC voltage, power module 50 will also generally include at least one line that passes to switch 53 such that full AC voltage to the heater can be controlled by controller 52. Controller 52 is coupled to first and second media access units (MAU) 54 and 56, respectively. Each media access unit 54, 56 is operably coupleable to communication media appropriate for that respective media access unit. While terminals 58, 60, 62, and 64 are shown, it is noted that if either of media access units 54, 56 is a wireless media access unit, the terminals for that respective media access unit may simply be replaced with a coupling to an antenna. Additionally, while four distinct terminals 58, 60, 62 and 64 are shown, it is also contemplated that the common or ground of the circuit may be shared, such that only three terminals need be actually provided. In one embodiment, media access unit 54 is configured to communicate in accordance with the known HART® process communication protocol. In such embodiment, terminals 58 and 60 may be operably coupled to a user interface, such as the Xi Operator Interface available from Rosemount Analytical Inc., or any other suitable device that can receive and provide a useful function relative to the HART® communication. Media access unit 56 is configured to communicate in accordance with an all-digital process communication protocol. All-digital process communication protocols are generally considered to be somewhat faster than hybrid-based process communication protocols. An example of an all-digital process communication protocol includes the FF process communication protocol as well as the known PROFIBUS-PA process communication protocol. The FF protocol is an all-digital, serial, two-way communication protocol that provides a standardized physical interface to a 2 or 4-wire loop or bus interconnecting field devices, such as sensors, actuators, controllers, valves, et cetera, that may, for example, be located in an instrumentation or process control environment of factory or plant. The FF protocol provides a local area network for field devices within a process to enable these devices to interoperate and perform control functions at locations distributed throughout the process and to communicate with one another before and after performance of these control functions to implement an overall control strategy. The FF protocol generally provides relatively high speed digital communication, which speed is particularly advantageous for the communication of flue gas stream constituent information in accordance with embodiments of the present invention. This is because such analyzers must generally measure the composition of the flue gas process streams and provide information indicative of such composition to a controller of the combustion process or Distributed Control System (DCS). Additionally, since the combustion process occurs quite rapidly, the flue gas stream constituents can vary quickly. Thus, it is quite advantageous for media access unit 56, which communicates in accordance with an all-digital process communication protocol, to be coupled to a distributed control system and/or to combustion controller 22 illustrated with respect to FIG. 1.
FIG. 3 also illustrates measurement circuitry 66 being operably coupled to controller 52 as well as terminals 68 and 70. Terminals 68 and 70 couple to the measurement cell within probe 12 and thus measurement circuitry 66 is able to provide a digital indication of the analog measurement cell output. Measurement circuitry 66 may include one or more suitable analog-to-digital converters as well as linearization circuitry and/or suitable filters, as appropriate.
FIG. 4 is a diagrammatic view of a process combustion monitoring and control system in accordance with an embodiment of the present invention. Many components of the system shown in FIG. 4 are similar to that shown in FIG. 1 and like components are numbered similarly. FIG. 4 shows in situ flue gas analyzer 110 communicating with combustion controller 22 via link 100. This communication link 100 between in situ flue gas analyzer 110 and combustion controller 22 is all-digital process communication, such as that in accordance with the FF protocol. Additionally, in situ flue gas analyzer 110 is operably coupled to user interface 28 via a second communication link 102. Link 102 may be in accordance with a known hybrid process communication protocol, such as the HART® process communication protocol. This allows embodiments of the present invention to function with legacy Xi User Interfaces available from Rosemount Analytical Inc., which are configured to receive HART® data and provide useful user interface functions relative to the gas analyzer. However, the communication link 100 between in situ flue gas analyzer 110 and process combustion controller 22 is a high speed, all-digital link. Thus, embodiments of the present invention generally include a first link or channel from in situ flue gas analyzer 110 to a combustion control system having a first data communication rate, and a second link or channel from the in situ flue gas analyzer 110 to a second device, such as a user interface thereof, having process communication in accordance with a second protocol having a second communication rate, where the first communication rate is higher than the second communication rate. Communication on the first and second links occurs simultaneously, or substantially simultaneously. As used herein, “substantially simultaneously” is intended to mean that although physical layer signaling on both links may not be occurring during the same instant, such signaling occurs within a short period, such as one minute. Additionally, the communication on each link occurs with such frequency that analyzer 110 is considered to be online with respect to each link. Accordingly, even when analyzer 110 is not actively transmitting data on the first and second links, analyzer 110 is monitoring such links for communication. Thus, it can be said that both links and the corresponding media access units within analyzer 110 are enabled simultaneously. Accordingly, changes in the flue gas constituent concentrations occurring rapidly within flue 14 can be analyzed and communicated very rapidly to combustion analyzer 22 for more effective control, while information relative to a user interface can be exchanged with optional user interface 28 at a slower rate. Additionally, the utilization of multiple process communication protocols insures that user interface communication does not consume bandwidth on the distributed control system link 100 or otherwise interfere with DCS communication. This further increases the effectiveness of the all-digital communication link between process combustion flue gas analyzer 110 and combustion controller 22.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. An in situ flue gas analyzer comprising:

a probe extendable into a flue, the probe having a measurement cell providing a signal responsive to a concentration of a gas within the flue;

a controller coupled to the probe and configured to provide an output based on the signal from the measurement cell;

a first media access unit coupled to the controller and operably coupleable to a first process communication link, the first media access unit being configured to communicate in accordance with an all-digital process communication protocol;

a second media access unit coupled to the controller and operably coupleable to a second process communication link, the second media access unit being configured to communicate in accordance with a second process communication protocol that is different than the all-digital process communication protocol; and

wherein the first and second media access units are enabled simultaneously

2. The in situ flue gas analyzer of claim 1, wherein the measurement cell includes an oxygen sensor.

3. The in situ flue gas analyzer of claim 1, wherein the all-digital process communication protocol is in accordance with the FOUNDATION Fieldbus protocol.

4. The in situ flue gas analyzer of claim 1, wherein a communication rate of the all-digital process communication protocol is faster than a communication rate of the second process communication protocol.

5. The in situ flue gas analyzer of claim 1, wherein the second process communication protocol is a hybrid process communication protocol.

6. The in situ flue gas analyzer of claim 5, wherein the hybrid process communication protocol superimposes a digital signal on an analog signal.

7. A process combustion control system comprising:

a combustion source operably coupled to a source of fuel and a source of air, the combustion source being configured to provide combustion gasses through a flue;

a combustion controller coupled to at least one of the source of fuel and source of air;

an in situ flue gas analyzer coupled to the combustion controller and disposed to sense a concentration of a gas of interest within the flue and convey process information related to the concentration to the combustion controller in accordance with an all-digital process communication protocol; and

wherein the in situ flue gas analyzer is communicatively coupled to a second device and communicates with the second device, in accordance with a second process communication protocol different than the all-digital process communication protocol, wherein communication with the combustion controller and the second device occurs substantially simultaneously.

8. The process combustion control system of claim 7, wherein the gas of interest is oxygen.

9. The process combustion control system of claim 7, wherein the in situ flue gas analyzer communicates with the combustion controller at a first communication rate, and communicates with the second device at a second rate that is less than the first rate.

10. The process combustion control system of claim 7, wherein the second device is a user interface.

11. The process combustion control system of claim 10, wherein the second process communication protocol is in accordance with the Highway Addressable Remote Transducer (HART) protocol.

12. A method of operating an in situ flue gas analyzer, the method comprising:

disposing a probe of the in situ flue gas analyzer within a flue;

measuring a concentration of a gas on interest using the probe;

communicating information regarding the measured concentration to a combustion controller in accordance with an all-digital process communication protocol; and

communicating with a second device in accordance with a second process communication protocol different than the all-digital process communication protocol.

13. The method of claim 12, wherein the all-digital process communication protocol is the FOUNDATION Fieldbus protocol.

14. The method of claim 13, wherein the second process communication protocol is the Highway Addressable Remote Transducer (HART) protocol.

15. The method of claim 12, wherein communication with the combustion controller and the second device occurs substantially simultaneously.

16. The method of claim 15, wherein communication with the combustion controller occurs at a first communication rate, and communication with the second device occurs at a second rate that is less than the first rate.