Thermal power plant carbon dioxide monitoring device with bidirectional automatic cleaning function and method

Abstract

The invention discloses a thermal power plant carbon dioxide monitoring device with a bidirectional automatic cleaning function and a method. The device comprises a flue gas sampling port, a sampling pipeline, a gas treatment device, a gas flow switching valve, an automatic cleaning pump, a clean gas source and a flue gas analyzer, the flue gas sampling port is in direct contact with flue gas and is responsible for collecting a flue gas sample and conveying the collected flue gas to the gas treatment device through the sampling pipeline, the airflow switching valve switches the gas flowing direction and realizes switching between a flue gas sampling mode and a cleaning mode, and in the sampling mode, the airflow switching valve allows the flue gas to enter from the flue gas sampling port; in the cleaning mode, clean gas flows back from the clean gas source and is cleaned through the sampling pipeline; the automatic cleaning pump pumps clean gas into the sampling pipeline for reverse cleaning; and the flue gas analyzer is responsible for analyzing the concentration of carbon dioxide in the treated flue gas sample. According to the invention, the defects of the prior art in the aspects of sampling cleaning and monitoring precision are effectively overcome, and the method has high practicability and economical efficiency.

Description

Technical Field

[0001] This invention relates to a carbon dioxide monitoring device for thermal power plants, specifically to a carbon dioxide monitoring device and method for thermal power plants with bidirectional automatic cleaning function. Background Technology

[0002] With increasingly stringent environmental protection regulations, carbon dioxide emission monitoring technology in thermal power plants faces serious challenges. Currently, most flue gas monitoring devices in thermal power plants use traditional unidirectional sampling pipelines, allowing flue gas to flow into the analyzer only from the flue side. This lack of reverse cleaning or automatic pipeline cleaning means that dust, particles, and moisture in the flue gas can easily accumulate in the sampling pipeline after prolonged use, leading to blockages or contamination and affecting sampling accuracy. Traditional systems lack effective pipeline cleaning mechanisms, typically requiring periodic shutdowns for manual cleaning, which not only increases maintenance costs but also results in downtime and data loss. Furthermore, the pretreatment modules of traditional sampling devices often lack targeted optimization designs. Especially in high-humidity, high-temperature, or complex flue gas environments, existing pretreatment technologies often fail to effectively remove moisture, particles, and other interfering substances, resulting in poor gas quality entering the analyzer and affecting the accuracy of the final measurement.

[0003] While some monitoring systems on the market attempt to improve their adaptability through more complex gas pretreatment and sampling techniques, these efforts have significantly increased system maintenance costs and typically only extend the lifespan of sampling pipelines, failing to fundamentally address the challenges of sampling pipeline contamination, cleanliness, and monitoring accuracy. Therefore, existing carbon dioxide monitoring devices in thermal power plants urgently need an innovative sampling technology with automatic cleaning and bidirectional flow capabilities to reduce maintenance costs and improve the long-term stability and reliability of the system while maintaining efficient sampling and high-precision monitoring.

[0004] Current carbon dioxide monitoring devices in thermal power plants mostly use unidirectional sampling pipelines, allowing flue gas to flow into the analyzer in only one direction. Over time, particulate matter, moisture, and dust in the flue gas easily accumulate in the pipeline, leading to blockages or contamination and affecting the accuracy of the monitoring data. Traditional systems lack effective automatic cleaning mechanisms, typically requiring manual cleaning of the sampling pipeline after shutdown. This not only increases maintenance costs but also leads to increased downtime and data loss. Furthermore, the pretreatment module design of existing sampling devices is not optimized enough, especially in high-temperature, high-humidity, or complex flue gas environments, failing to efficiently remove moisture, impurities, and other interfering substances, affecting the measurement accuracy of the analyzer. Even with the introduction of anti-interference designs in some devices, the measurement error problems caused by unstable flue gas flow and complex gas composition remain unresolved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to design a carbon dioxide monitoring device and method for thermal power plants with bidirectional automatic cleaning capabilities. This device enables automatic reverse cleaning of sampling pipelines, preventing the accumulation of contaminants during long-term use, thereby reducing equipment maintenance frequency and costs, and ensuring the continuity and accuracy of data monitoring. The invention also aims to optimize the gas pretreatment module to efficiently remove moisture and impurities from flue gas, improving the purity of gas samples and further enhancing the measurement performance of analytical instruments. Through bidirectional automatic cleaning design and optimized gas pretreatment, the present invention effectively solves the deficiencies of existing technologies in sampling cleaning and monitoring accuracy, possessing high practicality and economic efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function includes a flue gas sampling port, a sampling pipeline, a gas processing device, an airflow switching valve, an automatic cleaning pump, a clean gas source, and a flue gas analyzer. The flue gas sampling port is installed on the sampling flue, and the flue gas sampling port delivers the collected flue gas to the gas processing device through the sampling pipeline. The flue gas analyzer is connected downstream of the gas processing device to analyze the carbon dioxide concentration in the processed flue gas sample. The clean gas source is connected to the sampling pipeline through the airflow switching valve, and the automatic cleaning pump is connected to the clean gas source to pump clean gas into the sampling pipeline for reverse cleaning.

[0007] A further improvement of the present invention is that a pressure sensor is installed at the inlet of the sampling pipeline to detect the pressure of the flue gas in the sampling pipeline.

[0008] A further improvement of the present invention is that a flow sensor is provided at the outlet of the gas treatment device to detect the flow rate of the treated flue gas.

[0009] A further improvement of the present invention is that it also includes a cleaning valve electronic control device for controlling the opening, closing and switching of the airflow switching valve.

[0010] A further improvement of the present invention is that the airflow switching valve is installed in the middle and end section of the sampling pipeline, which can control the flow direction of gas from the flue to the flue gas analyzer.

[0011] A further improvement of the present invention is that the core part of the airflow switching valve is provided with a switching ball valve to control the direction of gas flow.

[0012] A further improvement of the present invention is that the cleaning gas is N2 gas.

[0013] A further improvement of the present invention is that it also includes a clean channel check valve, which is installed between the clean gas source and the sampling pipeline.

[0014] A method for monitoring carbon dioxide in thermal power plants with bidirectional automatic cleaning function, the method being based on the aforementioned carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function, comprising: The flue gas sampling port directly contacts the flue gas and is responsible for collecting flue gas samples. The collected flue gas is then transported to the gas processing device through the sampling pipeline. The airflow switching valve switches the gas flow direction to switch between flue gas sampling mode and cleaning mode. In sampling mode, the airflow switching valve allows flue gas to enter from the flue gas sampling port; in cleaning mode, the cleaning gas flows back from the cleaning gas source and is used for cleaning through the sampling pipeline. An automatic cleaning pump pumps the cleaning gas into the sampling pipeline for reverse cleaning. The flue gas analyzer is responsible for analyzing the carbon dioxide concentration in the processed flue gas sample.

[0015] A further improvement of this invention is that the core part of the airflow switching valve is equipped with a switching ball valve. In sampling mode, the switching ball valve is in the 0° position, and the channel inside the valve body is connected to the sampling pipeline, allowing flue gas to flow in from the flue and enter the flue gas analyzer through the pipeline, while the cleaning channel is completely closed. When entering the cleaning mode, the driving device rotates the switching ball valve to 90°, the cleaning airflow channel opens, and the gas from the cleaning gas source enters the pipeline and flows in the opposite direction to clean the inside of the sampling pipeline.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: This invention proposes a carbon dioxide monitoring device and method for thermal power plants with bidirectional automatic cleaning function, possessing significant technical advantages. Through a bidirectional airflow switching design, it flexibly switches between conventional sampling mode and cleaning mode, ensuring that the sampling pipeline is not blocked or contaminated by dust, particles, and moisture in the flue gas during long-term use. Compared to traditional unidirectional sampling pipelines, this invention reduces the frequency and cost of manual maintenance through automatic cleaning, avoiding downtime and data loss due to pipeline blockage, thereby improving the stability and long-term reliability of the device. Furthermore, the cleaning mode of this invention allows clean gas to periodically clean impurities in the sampling pipeline through reverse flow, ensuring the purity of the sampled gas and improving the accuracy of carbon dioxide monitoring data. The airflow switching valve design ensures that the airflow in cleaning mode only passes through the cleaning channel, without affecting the conventional flue gas sampling process, enabling the equipment to perform automatic cleaning without shutdown, greatly reducing maintenance costs and equipment downtime. Simultaneously, this invention optimizes the gas pretreatment module, employing innovative materials to enhance its corrosion resistance and high-temperature resistance, ensuring stable operation under complex conditions and improving the efficiency and accuracy of flue gas treatment. With real-time monitoring by flow and pressure sensors, the device can automatically adjust the cleaning cycle, further ensuring the stability of airflow and the reliability of data.

[0017] In summary, this invention not only solves the pipeline contamination problem of traditional carbon dioxide monitoring devices during long-term use, but also significantly improves monitoring accuracy and system reliability through a two-way automatic cleaning function, while reducing maintenance costs. The innovative design of this device can be widely applied to flue gas emission monitoring in thermal power plants, meets modern environmental protection standards, and has significant market application prospects and promotional value. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a structural diagram of the carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to the present invention.

[0020] Figure 2 This is a structural diagram of the self-cleaning device of the carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Flue gas sampling port, 2. Sampling pipeline, 3. Pressure sensor, 4. Gas processing device, 5. Flow sensor, 6. Airflow switching valve, 7. Automatic cleaning pump, 8. Clean gas source, 9. Flue gas analyzer, 10. Cleaning valve control device, 11. Sampling flue, 12. Switching ball valve, 13. Cleaning channel check valve. Detailed Implementation

[0022] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0029] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0030] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0031] Example 1 Please see Figure 1 The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function provided by the present invention includes a flue gas sampling port 1, a sampling pipeline 2, a gas processing device 4, an airflow switching valve 6, an automatic cleaning pump 7, a clean gas source 8, and a flue gas analyzer 9. The flue gas sampling port 1 is installed on the sampling flue duct 11. The flue gas sampling port 1 transports the collected flue gas to the gas processing device 4 through the sampling pipeline 2. The flue gas analyzer 9 is connected downstream of the gas processing device 4 and is used to analyze the carbon dioxide concentration in the processed flue gas sample. The clean gas source 8 is connected to the sampling pipeline 2 through the airflow switching valve 6. The automatic cleaning pump 7 is connected to the clean gas source 8 and is used to pump clean gas into the sampling pipeline 2 for reverse cleaning.

[0032] In this embodiment, a pressure sensor 3 is installed at the inlet of the sampling pipeline 2 to detect the pressure of the flue gas in the sampling pipeline 2.

[0033] In this embodiment, a flow sensor 5 is installed at the outlet of the gas processing device 4 to detect the flow rate of the processed flue gas.

[0034] In this embodiment, a cleaning valve electronic control device 10 is also included, which is used to control the opening, closing and switching of the airflow switching valve 6.

[0035] In this embodiment, the core part of the airflow switching valve 6 is provided with a switching ball valve 12, which is used to control the flow direction of the gas.

[0036] In this embodiment, the cleaning gas is N2 gas.

[0037] In this embodiment, a clean passage check valve 13 is also included, which is installed between the clean air source 8 and the sampling pipeline 2.

[0038] Example 2 Please see Figure 1The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function provided by the present invention mainly consists of a flue gas sampling port 1, a sampling pipeline 2, a pressure sensor 3, a gas processing device 4, a flow sensor 5, an airflow switching valve 6, an automatic cleaning pump 7, a clean gas source 8, a flue gas analyzer 9, a cleaning valve electrical control device 10, and a sampling flue duct 11.

[0039] A flue gas sampling port 1 is installed on the sampling flue duct 11, directly contacting the flue gas to collect samples. The collected flue gas is then transported to the gas processing device 4 via sampling line 2. Sampling line 2 connects the flue gas sampling port 1 and the gas processing device 4. This line is part of a bidirectional automatic cleaning system, using a switching valve to perform sampling or cleaning in different modes. A pressure sensor 3 is installed at the inlet of sampling line 2, near the front end of the gas processing device 4, to detect the pressure of the flue gas in sampling line 2, ensuring sampling stability. The inlet of the gas processing device 4 is connected to the sampling line 2, and the outlet is connected to the flow sensor 5. A ceramic matrix composite material (alumina ceramic and silicon carbide ceramic composite) is used as the filter layer. This material is resistant to high temperatures and acid / alkali corrosion, making it suitable for use in the complex high-temperature flue gas environment of thermal power plants. After flue gas pretreatment, moisture, particulate matter, and other impurities are removed, ensuring sample purity and the accuracy of subsequent monitoring results. The flow sensor 5 is installed at the outlet of the gas processing device 4 to detect the flow rate of the treated flue gas, ensuring a stable flow as it enters the analytical equipment. A gas flow switching valve 6 is located between sampling line 2 and clean gas source 8. This valve can switch the gas flow direction, enabling the conversion between flue gas sampling mode and cleaning mode. In sampling mode, the valve allows flue gas to enter from flue gas sampling port 1; in cleaning mode, the valve switches, allowing clean gas to flow back from clean gas source 8 and be used for cleaning through sampling line 2. An automatic cleaning pump 7 is connected to clean gas source 8 and is responsible for pumping clean gas N2 into sampling line 2 at a certain pressure for reverse cleaning. A flue gas analyzer 9 is connected downstream of gas processing device 4 and is responsible for analyzing the carbon dioxide concentration in the processed flue gas sample. Gas pretreatment module 4 ensures the quality of the gas entering the analyzer. A cleaning valve electronic control device 10 controls the opening, closing, and switching of gas flow switching valve 6, achieving automated operation through an electronic control system. It switches cleaning modes at set times or under set conditions without manual intervention. The sampling port of sampling flue duct 11 is connected to it, directly receiving flue gas from the flue.

[0040] Example 3 The present invention provides a method for monitoring carbon dioxide in thermal power plants with bidirectional automatic cleaning function, comprising: The flue gas sampling port 1 is in direct contact with the flue gas and is responsible for collecting flue gas samples. The collected flue gas is transported to the gas processing device 4 through the sampling pipeline 2. The airflow switching valve 6 switches the gas flow direction to realize the conversion between flue gas sampling mode and cleaning mode. In sampling mode, the airflow switching valve 6 allows flue gas to enter from the flue gas sampling port 1; in cleaning mode, the cleaning gas flows back from the cleaning gas source 8 and is cleaned through the sampling pipeline 2. The automatic cleaning pump 7 pumps the cleaning gas into the sampling pipeline 2 for reverse cleaning. The flue gas analyzer 9 is responsible for analyzing the carbon dioxide concentration in the processed flue gas sample.

[0041] In this implementation, please refer to Figure 2 The airflow switching valve 6 is installed in the middle and end section of the sampling pipeline 2, controlling the flow direction of gas from the flue to the flue gas analyzer. A clean gas source 8 is connected to the other side to introduce clean gas. The switching ball valve 12 is located in the core part of the airflow switching valve 6, between the sampling pipeline 2 and the clean gas channel, controlling the flow direction of the gas. In sampling mode, the switching ball valve 12 is at a 0° angle, with the channel inside the valve body connected to the sampling pipeline 2, allowing flue gas to flow in from the flue and through the pipeline into the flue gas analyzer 9. The clean channel is completely closed, and gas can only flow unidirectionally to the analyzer, without entering the clean pipeline. The ball valve closes the clean gas channel, preventing clean gas from entering the sampling pipeline and ensuring that flue gas only flows unidirectionally into the analyzer. When entering clean mode, the drive device rotates the switching ball valve 12 to 90°, opening the clean airflow channel. Gas from the clean gas source 8 enters the pipeline and flows in the opposite direction to clean the interior of the sampling pipeline. The channel for the forward airflow is completely closed to prevent flue gas from flowing back into the clean gas source. The clean passage check valve 13 is installed between the clean gas source 8 and the sampling line 2. In the cleaning mode, the check valve opens, allowing clean gas to enter the sampling line and flow in the opposite direction to remove dust, particulate matter and moisture from the pipeline. In the normal sampling mode, the check valve closes to prevent external clean gas from entering the sampling line and ensure that the gas flows only from the flue to the flue gas analyzer.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0043] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function, characterized in that, It includes a flue gas sampling port, sampling pipeline, gas processing device, airflow switching valve, automatic cleaning pump, clean gas source and flue gas analyzer; The flue gas sampling port is installed on the sampling flue. The flue gas sampling port transports the collected flue gas to the gas processing device through the sampling pipeline. The flue gas analyzer is connected downstream of the gas processing device to analyze the carbon dioxide concentration in the processed flue gas sample. The clean gas source is connected to the sampling pipeline through the airflow switching valve. The automatic cleaning pump is connected to the clean gas source to pump the clean gas into the sampling pipeline for reverse cleaning.

2. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 1, characterized in that, A pressure sensor is installed at the inlet of the sampling pipeline to detect the pressure of the flue gas in the sampling pipeline.

3. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 1, characterized in that, A flow sensor is installed at the outlet of the gas treatment device to detect the flow rate of the treated flue gas.

4. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 1, characterized in that, It also includes a cleaning valve control device for controlling the opening, closing, and switching of the airflow switching valve.

5. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 1, characterized in that, The gas flow switching valve is installed in the middle and end section of the sampling pipeline and can control the flow direction of gas from the flue to the flue gas analyzer.

6. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 5, characterized in that, The core component of the airflow switching valve is a switching ball valve, which is used to control the direction of gas flow.

7. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 1, characterized in that, The cleaning gas is N2 gas.

8. The carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function according to claim 1, characterized in that, It also includes a clean passage check valve, which is installed between the clean gas source and the sampling line.

9. A method for monitoring carbon dioxide in thermal power plants with bidirectional automatic cleaning function, characterized in that, This method is based on the carbon dioxide monitoring device for thermal power plants with bidirectional automatic cleaning function as described in any one of claims 1 to 8, comprising: The flue gas sampling port directly contacts the flue gas and is responsible for collecting flue gas samples. The collected flue gas is then transported to the gas processing device through the sampling pipeline. The airflow switching valve switches the gas flow direction to switch between flue gas sampling mode and cleaning mode. In sampling mode, the airflow switching valve allows flue gas to enter from the flue gas sampling port; in cleaning mode, the cleaning gas flows back from the cleaning gas source and is used for cleaning through the sampling pipeline. An automatic cleaning pump pumps the cleaning gas into the sampling pipeline for reverse cleaning. The flue gas analyzer is responsible for analyzing the carbon dioxide concentration in the processed flue gas sample.

10. The carbon dioxide monitoring method for thermal power plants with bidirectional automatic cleaning function according to claim 9, characterized in that, The core component of the airflow switching valve is a switching ball valve. In sampling mode, the switching ball valve is in the 0° position, and the channel inside the valve body is connected to the sampling pipeline, allowing flue gas to flow in from the flue and enter the flue gas analyzer through the pipeline, while the cleaning channel is completely closed. When entering the cleaning mode, the drive device rotates the switching ball valve to 90°, the cleaning airflow channel opens, and the gas from the cleaning gas source enters the pipeline and flows in the opposite direction to clean the inside of the sampling pipeline.

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