Inlet flue gas multi-point sampling device and sampling method suitable for gas waste heat boiler

Abstract

The invention relates to the technical field of flue gas denitration, in particular to an inlet flue gas multi-point sampling device suitable for a gas waste heat boiler and a sampling method.The inlet flue gas multi-point sampling device comprises a sampling mechanism and a flue gas pipeline, the sampling mechanism is fixedly installed at the top end of the outer wall of the flue gas pipeline, and a sampling probe device is fixedly installed at the top end of the sampling mechanism; the sampling probe rod penetrates into the flue gas pipeline to complete flue gas sampling, a flue heat preservation layer is arranged on the inner wall of the flue gas pipeline, and the sampling mechanism penetrates into the flue gas pipeline to be connected with a gas collection mechanism and is fixed to the inner wall of the flue gas pipeline in a sleeving mode. Through mutual cooperation of internal parts of the sampling mechanism and internal parts of the gas collection mechanism, installation and fixation of the sampling probe device on the outer wall of the flue gas pipeline can be completed, and installation and fixation of the sampling gas collection pipe and the gas collection main pipe on the inner wall of the flue gas pipeline can be completed, so that sampling and collection of flue gas in the flue gas pipeline are completed.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitrification, and in particular to a multi-point sampling device and a sampling method for inlet flue gas of a gas-fired waste heat boiler. Background Art

[0002] With the increasing requirements for atmospheric emissions, the requirements for nitrogen oxide emissions from waste heat boiler flue gas in gas-steam combined cycle units have continued to increase in recent years. Some regions (including Guangdong, Beijing, Hebei and other places) have raised the nitrogen oxide emission standards for gas-fired waste heat boilers to 12-15 mg / Nm3. Therefore, in recent years, waste heat boilers of gas-steam combined cycle units in many places have been equipped with SCR denitrification systems as required. In order to save the equipment cost of the SCR denitrification system and waste heat boiler, a urea solution direct injection system has been introduced. The system requires a urea solution spray gun to be set at the inlet of the waste heat boiler for denitrification reducing agent injection. Based on this design, as well as the SCR denitrification operating specifications, the denitrification inlet flue gas components upstream of the reducing agent injection need to be sampled at multiple points in accordance with relevant specifications to ensure the accuracy and comprehensiveness of the sampled flue gas.

[0003] In gas-steam combined cycle units, the inlet flue of the waste heat boiler is relatively large, typically with a circular cross-section. The flue gas temperature can reach 600°C or above. Using traditional multi-point sampling methods, multiple sampling probes are typically evenly distributed across the flue cross-section. This not only results in high equipment costs, but also makes it impossible to arrange the probes on the lower circumference, as the height does not meet the required slope for the probe sampling tube. Furthermore, when the flue cross-section is too large, the flue gas in the center of the flue cannot be sampled properly due to the limited size of the sampling probe's probe rod. Alternatively, the probe rods of some sampling probes are too slender, making the probes inside the large-cross-section flue too long and unsupported. These rods are easily broken, damaged, deformed, or bent under the impact of high-temperature, strong airflow, thus defeating the purpose of multi-point sampling.

[0004] Therefore, it is necessary to develop a multi-point sampling device for the inlet flue gas of a gas-fired waste heat boiler to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-point sampling device for the inlet flue gas of a gas-fired waste heat boiler. Through the mutual cooperation between the internal parts of the sampling mechanism and the internal parts of the gas collecting mechanism, the sampling probe device can be installed and fixed on the outer wall of the flue gas duct, and the sampling gas collecting pipe and the gas collecting main pipe can be installed and fixed on the inner wall of the flue gas duct, thereby completing the sampling and collection of the flue gas in the flue gas duct, so as to solve the problem in the prior art that the flue gas in the center of the flue cannot be sampled normally due to the limitation of the probe rod size of the sampling probe, or the probe rods of some sampling probes are too slender, so that the probe rods inside the large-section flue are too long and unsupported, and are easily broken, damaged or deformed and bent under the impact of high temperature and strong airflow, thereby failing to achieve the multi-point sampling effect.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler, comprising a sampling mechanism and a flue gas duct, wherein the sampling mechanism is mounted and fixed on the top of the outer wall of the flue gas duct, a sampling probe device is mounted and fixed on the top of the sampling mechanism, and the sampling probe rod penetrates into the interior of the flue gas duct to complete flue gas sampling, the inner wall of the flue gas duct is provided with a flue insulation layer, the sampling mechanism penetrates into the interior of the flue gas duct and is connected to a gas collecting mechanism, the interior of the gas collecting mechanism includes a sampling tube mounting socket and a gas collecting main pipe mounting socket, and is fixed to the inner wall of the flue gas duct in a sleeve manner;

[0007] The sampling mechanism includes a probe mounting pipe seat, which is welded and fixed to the top of the flue gas duct, and the lower end is inserted into the inside of the flue gas duct, the top and bottom ends of the probe mounting pipe seat are respectively installed and connected with a No. 1 flange and a No. 2 flange, and the bottom end of the No. 2 flange is installed and connected to a No. 1 gas collecting main pipe, and a No. 2 gas collecting main pipe is connected below the No. 1 gas collecting main pipe, and a sampling four-way pipe is placed on the top and bottom ends of the No. 2 gas collecting main pipe, and is welded to the bottom end of the No. 1 gas collecting main pipe, and the bottom end of the sampling four-way pipe is welded to the No. 3 gas collecting main pipe, and is located at the bottom end of the No. 2 gas collecting main pipe away from the No. 1 gas collecting main pipe, the outer wall of the No. 3 gas collecting main pipe is inserted into the center of the gas collecting main pipe mounting pipe seat, and a plurality of No. 1 limit blocks are welded and fixed to the outer wall of the No. 3 gas collecting main pipe;

[0008] The gas collecting mechanism includes a sampling gas collecting pipe, which has four sampling gas collecting pipes and has the same diameter. The four sampling gas collecting pipes are respectively welded and fixed on both sides of the sampling four-way pipe. The sampling pipe mounting seat is welded and fixed on the inner wall of the flue gas pipe and is sleeved with the outer wall of the sampling gas collecting pipe. The gas collecting mother pipe mounting seat is welded and fixed on the inner wall of the flue gas pipe and is sleeved with the outer wall of the bottom end of the No. 3 gas collecting mother pipe. The outer wall of the sampling gas collecting pipe and the sampling pipe mounting seat is welded and fixed with a No. 2 limit block, and fits with the inner wall of the sampling pipe mounting seat.

[0009] Preferably, the interior of the sampling tube mounting socket and the gas collecting main pipe mounting socket is filled with thermal insulation cotton, and the filling thickness is consistent with the thermal insulation thickness of the flue insulation layer.

[0010] Preferably, a 2MM assembly gap is left between the No. 1 limit block, the No. 2 limit block and the inner walls of the sampling tube mounting socket and the gas collecting main pipe mounting socket, and the sampling tube mounting socket, the gas collecting main pipe mounting socket and the sampling gas collecting pipe are all standard parts.

[0011] Preferably, a plurality of air intake holes are provided on the windward side of the sampling gas collecting pipe, and the number of the air intake holes is determined according to the sampling quantity requirement, and an exhaust hole is provided on the leeward side of the No. 1 gas collecting main pipe.

[0012] Preferably, air intake holes are provided on the windward side and side surfaces of the sampling gas collecting pipe (301).

[0013] Preferably, the sampling gas collecting pipe is connected to the interior of the No. 1 gas collecting main pipe and the No. 2 gas collecting main pipe, and the length of the probe rod of the sampling probe device is greater than the length between the exhaust hole and the No. 1 flange.

[0014] The present invention also provides a multi-point sampling method for inlet flue gas of a gas-fired waste heat boiler, based on the aforementioned multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler, comprising the following steps:

[0015] S10, the sampling mechanism (1) is welded and fixed to the top of the outer wall of the flue gas duct (2) through the probe mounting pipe seat (101), the lower end of the probe mounting pipe seat (101) is inserted into the interior of the flue gas duct (2), and the sampling probe device is connected and fixed to the No. 1 gas collecting main pipe (104) through the No. 1 flange (102) and the No. 2 flange (103);

[0016] S20, welding the four sampling gas collecting pipes (301) in the gas collecting mechanism (3) to the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106) through the sampling four-way pipe (105), so that the sampling gas collecting pipes (301) are symmetrically distributed on both sides of the sampling four-way pipe (105), and the sampling gas collecting pipes (301) are fixed to the inner wall of the flue gas pipe (2) through the sampling pipe mounting socket (302);

[0017] S30, the flue gas in the flue gas pipe (2) enters the sampling gas collecting pipe (301) through the air intake hole on the windward side of the sampling gas collecting pipe (301), and is collected to the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106) through the sampling four-way pipe (105);

[0018] S40, the probe rod of the sampling probe device penetrates into the gas collecting main pipe to collect multi-point data of the collected flue gas;

[0019] S50. The sampled flue gas is discharged through the exhaust holes on the leeward side of the No. 1 gas collecting main pipe (104).

[0020] The present invention also provides a method for achieving multi-point uniform sampling of a flue gas duct cross section, using the aforementioned multi-point sampling device for inlet flue gas based on the aforementioned device applicable to a gas-fired waste heat boiler, and the steps are as follows:

[0021] Δ, four sampling gas collecting pipes (301) of the same diameter are welded to both sides of the sampling four-way pipe (105) respectively, so that the sampling gas collecting pipes (301) are symmetrically distributed in the flue gas duct (2);

[0022] B. According to the sampling quantity requirement, multiple air holes are opened on the windward side of the sampling gas collecting pipe (301) to ensure that different areas in the flue gas duct (2) are covered;

[0023] C. The flue gas enters the sampling gas collecting pipe (301) through each gas extraction hole and is collected to the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106) through the sampling four-way pipe (105) to form a mixed flue gas sample;

[0024] D. The sampling probe device samples and analyzes the mixed flue gas sample, thereby achieving uniform collection of flue gas at multiple points within the cross section of the flue gas duct (2).

[0025] The present invention finally provides a waste heat boiler, comprising a boiler body and a multi-point sampling device for inlet flue gas suitable for a gas-fired waste heat boiler as described above, wherein the flue gas pipe (2) of the sampling device is connected to the inlet flue of the boiler body and is used for multi-point sampling of the flue gas entering the boiler body.

[0026] Preferably, the sampling mechanism (1) of the sampling device is mounted and fixed on the top of the outer wall of the inlet flue of the boiler body, the sampling probe of the sampling mechanism (1) penetrates into the interior of the inlet flue, the gas collecting mechanism (3) is located inside the inlet flue and connected to the sampling mechanism (1), and the gas collecting mechanism (3) is fixed to the inner wall of the inlet flue through the sampling tube mounting socket (302).

[0027] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0028] 1. Fix the sampling probe device on the probe mounting pipe seat, so that the probe rod of the sampling probe device passes through the No. 1 gas collecting main pipe, the No. 2 gas collecting main pipe to the No. 3 gas collecting main pipe, and a plurality of air intake holes are opened on the windward side of the surface of the sampling gas collecting pipe, and an exhaust hole is opened on the leeward side of the No. 1 gas collecting main pipe. The sampling gas collecting pipe is connected with the interiors of the No. 1 gas collecting main pipe and the No. 2 gas collecting main pipe, so that the flue gas in the flue gas pipeline flows into the sampling gas collecting pipe through the air intake holes, and circulates inside the sampling gas collecting pipe to the No. 1 gas collecting main pipe and the No. 2 gas collecting main pipe, so that the probe rod of the sampling probe device samples the flue gas, and the sampled flue gas can be discharged through the exhaust hole on the back of the No. 1 gas collecting main pipe;

[0029] 2. A 2MM assembly gap is left between the No. 1 limit block, the No. 2 limit block and the inner walls of the sampling tube mounting socket and the gas collecting main pipe mounting socket, and the sampling tube mounting socket, the gas collecting main pipe mounting socket and the sampling gas collecting pipe are all standard parts. This is convenient for the sampling gas collecting pipe and the No. 3 gas collecting main pipe to expand due to heat in the flue gas duct. The sampling tube mounting socket and the gas collecting main pipe mounting socket have a certain expansion space, which can avoid the sampling gas collecting pipe and the No. 3 gas collecting main pipe from bending due to heat expansion inside the flue gas duct, thereby improving the service life of the No. 1 gas collecting main pipe, the No. 2 gas collecting main pipe, the No. 3 gas collecting main pipe and the sampling gas collecting pipe.

[0030] 3. The interior of the sampling tube mounting socket and the gas collecting main pipe mounting socket is filled with thermal insulation cotton, and the filling thickness is consistent with the thermal insulation thickness of the flue gas insulation layer. This design can effectively reduce the heat exchange inside and outside the flue gas duct (2), ensure the temperature inside the flue gas duct is stable, avoid the influence of temperature fluctuation on the sampling results, and at the same time reduce the temperature of the outer wall of the flue gas duct, thereby improving the safety of the device.

[0031] 4. Four sampling gas collecting pipes with the same diameter are welded and fixed on both sides of the sampling four-way pipe. This symmetrical arrangement can achieve uniform sampling of flue gas at different positions in the flue gas duct, improve the comprehensiveness and accuracy of sampling, and solve the problem of sampling result deviation caused by uneven distribution of sampling points in traditional sampling methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0034] Figure 2 Schematic diagram of the cross-sectional structure of the flue gas duct of the present invention;

[0035] Figure 3 It is a schematic cross-sectional structural diagram of the sampling tube mounting socket and the gas collecting main pipe mounting socket of the present invention;

[0036] Figure 4 This is a cross-sectional schematic diagram of the connection structure between the No. 3 gas collecting main pipe and the gas collecting main pipe mounting socket of the present invention;

[0037] Figure 5 It is a cross-sectional schematic diagram of the connection structure between the sampling gas collecting pipe and the sampling pipe mounting pipe seat of the present invention.

[0038] Description of reference numerals:

[0039] 1. Sampling mechanism; 101. Probe mounting socket; 102. Flange No. 1; 103. Flange No. 2; 104. Gas collecting main pipe No. 1; 105. Sampling cross-piece; 106. Gas collecting main pipe No. 2; 107. Gas collecting main pipe No. 3; 108. Limit block No. 1; 2. Flue gas duct; 201. Flue duct insulation layer; 3. Gas collecting mechanism; 301. Sampling gas collecting pipe; 302. Sampling tube mounting socket; 303. Gas collecting main pipe mounting socket; 304. Limit block No. 2. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] Example 1

[0042] The present invention provides Figure 1-5 The multi-point sampling device for the inlet flue gas of a gas-fired waste heat boiler shown in the figure includes a sampling mechanism 1 and a flue gas duct 2. The sampling mechanism 1 is mounted and fixed to the top of the outer wall of the flue gas duct 2. A sampling probe device is mounted and fixed to the top of the sampling mechanism 1, and the sampling probe rod penetrates the interior of the flue gas duct 2 to complete flue gas sampling. The inner wall of the flue gas duct 2 is provided with a flue insulation layer 201. The sampling mechanism 1 penetrates the interior of the flue gas duct 2 and is connected to a gas collecting mechanism 3. The gas collecting mechanism 3 includes a sampling tube mounting socket 302 and a gas collecting main pipe mounting socket 303, and is fixed to the inner wall of the flue gas duct 2 by a sleeve connection.

[0043] The sampling mechanism 1 includes a probe mounting pipe seat 101, which is welded and fixed to the top of the flue gas pipe 2, and the lower end is inserted into the flue gas pipe 2. The top and bottom ends of the probe mounting pipe seat 101 are respectively connected to the No. 1 flange 102 and the No. 2 flange 103. The bottom end of the No. 2 flange 103 is connected to the No. 1 gas collecting main pipe 104. The lower part of the No. 1 gas collecting main pipe 104 is connected to the No. 2 gas collecting main pipe 106. The No. 2 gas collecting main pipe 106 is connected to the No. 1 gas collecting main pipe 104. Sampling four-way pipes 105 are placed at the top and bottom of 06 respectively, and are welded to the bottom end of the No. 1 gas collecting mother pipe 104. The bottom end of the sampling four-way pipe 105 is welded to the No. 3 gas collecting mother pipe 107, and is located at the bottom end of the No. 2 gas collecting mother pipe 106 away from the No. 1 gas collecting mother pipe 104. The outer wall of the No. 3 gas collecting mother pipe 107 is inserted into the center of the gas collecting mother pipe mounting socket 303, and a plurality of No. 1 limit blocks 108 are welded and fixed to the outer wall of the No. 3 gas collecting mother pipe 107;

[0044] The gas collecting mechanism 3 includes a sampling gas collecting pipe 301. There are four sampling gas collecting pipes 301, and the four sampling gas collecting pipes 301 have the same diameter. The four sampling gas collecting pipes 301 are respectively welded and fixed on both sides of the sampling four-way pipe 105. The sampling tube mounting pipe seat 302 is welded and fixed on the inner wall of the flue gas pipe 2, and is sleeved with the outer wall of the sampling gas collecting pipe 301. The gas collecting mother pipe mounting pipe seat 303 is welded and fixed on the inner wall of the flue gas pipe 2, and is sleeved with the outer wall of the bottom end of the No. 3 gas collecting mother pipe 107. The outer wall of the sampling gas collecting pipe 301 and the sampling tube mounting pipe seat 302 is welded and fixed with a No. 2 limit block 304, and fits with the inner wall of the sampling tube mounting pipe seat 302.

[0045] Through the mutual cooperation between the internal parts of the sampling mechanism 1 and the internal parts of the gas collecting mechanism 3, the sampling probe device can be installed and fixed on the outer wall of the flue gas duct 2, and the sampling gas collecting pipe 301 and the gas collecting main pipe can be installed and fixed on the inner wall of the flue gas duct 2, thereby completing the sampling and collection of the flue gas in the flue gas duct 2.

[0046] Refer to the instruction manual Figure 1-5 The sampling tube mounting seat 302 and the gas collecting main tube mounting seat 303 are filled with thermal insulation cotton, and the filling thickness is consistent with the thermal insulation thickness of the flue thermal insulation layer 201. By filling the sampling tube mounting seat 302 and the gas collecting main tube mounting seat 303 with thermal insulation cotton, the filling thickness is consistent with the thermal insulation thickness of the flue thermal insulation layer 201, which is convenient for improving the thermal insulation performance of the flue gas duct 2 and the sampling tube mounting seat 302 and the gas collecting main tube mounting seat 303, and reducing the temperature of the outer wall of the flue gas duct 2.

[0047] Refer to the instruction manual Figure 1-5 , a 2MM assembly gap is left between the No. 1 limit block 108, the No. 2 limit block 304 and the inner wall of the sampling tube mounting seat 302 and the gas collecting main pipe mounting seat 303, and the sampling tube mounting seat 302, the gas collecting main pipe mounting seat 303 and the sampling gas collecting pipe 301 are all standard parts, and a 2MM assembly gap is left between the No. 1 limit block 108, the No. 2 limit block 304 and the inner wall of the sampling tube mounting seat 302 and the gas collecting main pipe mounting seat 303, Moreover, the sampling tube mounting socket 302, the gas collecting main pipe mounting socket 303, and the sampling gas collecting pipe 301 all use standard parts, which facilitates the expansion and contraction of the sampling gas collecting pipe 301 and the No. 3 gas collecting main pipe 107 due to heat in the flue gas duct 2. The sampling tube mounting socket 302 and the gas collecting main pipe mounting socket 303 leave a certain expansion space, thereby avoiding the sampling gas collecting pipe 301 and the No. 3 gas collecting main pipe 107 from bending due to heat expansion inside the flue gas duct 2.

[0048] Refer to the instruction manual Figure 1-5The windward side of the surface of the gas collecting mother pipe installation socket 303 is provided with multiple air intake holes, and the number of the air intake holes is determined according to the sampling quantity requirements. The leeward side of the No. 1 gas collecting mother pipe 104 is provided with an exhaust hole, which facilitates the smoke inside the smoke pipe 2 to flow into the gas collecting mother pipe installation socket 303 through the air intake hole, and be discharged from the exhaust hole on the No. 1 gas collecting mother pipe 104 after data sampling is completed.

[0049] Refer to the instruction manual Figure 1-5 The sampling gas collecting pipe 301 is connected to the interior of the No. 1 gas collecting main pipe 104 and the No. 2 gas collecting main pipe 106, and the length of the probe rod of the sampling probe device is greater than the length distance between the exhaust hole and the No. 1 flange 102. The sampling gas collecting pipe 301 is connected to the interior of the No. 1 gas collecting main pipe 104 and the No. 2 gas collecting main pipe 106, and the length of the probe rod of the sampling probe device is greater than the length distance between the exhaust hole and the No. 1 flange 102, which facilitates the high-temperature flue gas inside the flue gas pipe 2 to flow inside the sampling gas collecting pipe 301 and the No. 1 gas collecting main pipe 104 and the No. 2 gas collecting main pipe 106, thereby facilitating the probe rod of the sampling probe device to collect data on the flue gas.

[0050] This utility works as follows:

[0051] Refer to the instruction manual Figure 1-5 , by fixing the sampling probe device on the probe mounting pipe seat 101, the probe rod of the sampling probe device passes through the No. 1 gas collecting main pipe 104, the No. 2 gas collecting main pipe 106 to the No. 3 gas collecting main pipe 107, and a plurality of air intake holes are opened on the windward side of the surface of the sampling gas collecting pipe 301, and an exhaust hole is opened on the leeward side of the No. 1 gas collecting main pipe 104, and the sampling gas collecting pipe 301 is communicated with the interior of the No. 1 gas collecting main pipe 104 and the No. 2 gas collecting main pipe 106, so that the flue gas in the flue gas duct 2 flows into the sampling gas collecting pipe 301 through the air intake holes, and circulates inside the sampling gas collecting pipe 301 to the No. 1 gas collecting main pipe 104 and the No. 2 gas collecting main pipe 106, so that the probe rod of the sampling probe device samples the flue gas, and the sampled flue gas can be discharged through the exhaust hole on the back of the No. 1 gas collecting main pipe 104;

[0052] Refer to the instruction manual Figure 1-5A 2MM assembly gap is left between the No. 1 limit block 108, the No. 2 limit block 304 and the inner walls of the sampling tube mounting socket 302 and the gas collecting main pipe mounting socket 303, and the sampling tube mounting socket 302, the gas collecting main pipe mounting socket 303 and the sampling gas collecting pipe 301 are all standard parts, so that after the sampling gas collecting pipe 301 and the No. 3 gas collecting main pipe 107 are heated and expanded in the flue gas duct 2, the sampling tube mounting socket 302 and the gas collecting main pipe mounting socket 303 have a certain expansion space, which can avoid the sampling gas collecting pipe 301 and the No. 3 gas collecting main pipe 107 from bending due to thermal expansion inside the flue gas duct 2, thereby improving the service life of the No. 1 gas collecting main pipe 104, the No. 2 gas collecting main pipe 106, the No. 3 gas collecting main pipe 107 and the sampling gas collecting pipe 301.

[0053] Other functions of this embodiment are:

[0054] (1) This device can indirectly reflect the flow state of flue gas in the pipeline (such as flow velocity distribution, turbulence intensity, whether there is vortex, etc.) by sampling the gas distribution and air flow pressure changes of the gas collecting pipe, providing key data for the flow field optimization design of the boiler inlet flue.

[0055] The device's gas collection mechanism consists of four sampling gas collection pipes of the same diameter, symmetrically welded to either side of the sampling four-way pipe. Each sampling gas collection pipe has multiple air holes on its windward side, with the number of holes determined based on sampling requirements. This design allows the sampling gas collection pipes to cover different radial locations within the flue gas duct (such as the edge and middle of the duct). The differences in flue gas flow and pressure at the air holes at different locations directly reflect the flue gas flow rate and flow stability in that area.

[0056] For example, if the air intake holes on a sampling manifold are located at the edge of the pipe and the air intake is significantly lower than the air intake holes in the middle, this may indicate the presence of a "stagnant flow zone" with low flow velocity at the edge of the pipe. If the flow rate at the air intake holes at different locations on the same sampling manifold fluctuates significantly, it may indicate the presence of turbulence or eddies in that area. This data can provide a direct basis for optimizing the flue gas structure (such as installing guide plates or adjusting the flue gas cross-section shape).

[0057] (2) The air flow mixing state of the gas collecting main pipe reflects the uniformity of the overall flow field. The sampling gas collecting pipe is connected to the interior of the No. 1 gas collecting main pipe and the No. 2 gas collecting main pipe. The flue gas collected by each sampling gas collecting pipe will be mixed in the gas collecting main pipe. By monitoring the flue gas composition (such as temperature, flow rate, and pressure) at different positions in the gas collecting main pipe, it can be determined whether the flue gas entering the main pipe is uniform. If the flue gas parameters fluctuate slightly after mixing, it means that the original flue gas flows evenly in the pipe; if the fluctuation is large, it indicates that the original flue gas has problems such as stratification and deviation. This characteristic is particularly important for gas-fired waste heat boilers, because the flow uniformity of the inlet flue gas directly affects the efficiency of the subsequent denitrification reaction (such as the mixing uniformity of the reducing agent and the flue gas). This device can provide long-term data support for evaluating the rationality of the flue flow field design by continuously monitoring the mixed flue gas in the gas collecting main pipe.

[0058] (3) The pressure change of the exhaust hole can indirectly infer the main flue gas velocity. There is an exhaust hole on the leeward side of the No. 1 gas collecting main pipe, and the sampled flue gas flows back to the main flue gas duct through this hole. There is a correlation between the pressure of the exhaust hole and the flue gas flow velocity in the main duct: the higher the flow velocity, the lower the static pressure in the main duct, the smaller the exhaust resistance of the exhaust hole, and the faster the exhaust speed. By monitoring the pressure and exhaust volume of the exhaust hole, the main flue gas velocity in the main duct can be inferred by combining the fluid mechanics formula, without the need to install an additional flow velocity sensor, which reduces equipment cost and installation complexity.

[0059] (4) Changes in the gap between the stopper and the assembly can monitor the degree of thermal deformation of the components. A 2mm assembly gap is left between the device's stopper No. 108, stopper No. 2 34, and the inner walls of the sampling tube mounting base 302 and the gas collecting main pipe mounting base 303. This gap is designed to allow space for thermal expansion of the sampling collecting pipe 301 and the gas collecting main pipe No. 3 107 at high temperatures. By regularly measuring the actual size of this gap, the degree of thermal deformation of the components can be directly assessed:

[0060] If the gap is reduced to zero, it means that the expansion of the component has exceeded the design expectation, and there may be problems such as material overheating or excessive installation stress. Long-term operation may cause pipe bending and cracking of welds.

[0061] If the gap is uneven (for example, the gap on one side is significantly smaller than the other side), it indicates that the component may be skewed or heated unevenly. It is necessary to check whether there is a local high-temperature area in the flue (such as biased flame or flue gas short circuit).

[0062] These data can provide a quantitative basis for formulating equipment maintenance cycles (such as regular straightening of pipelines and replacement of high-temperature vulnerable parts) to avoid equipment failures caused by thermal deformation.

[0063] (5) Multi-point sampling data provides a basis for allocating the amount of reducing agent injection. To save costs, gas-fired waste heat boilers use a urea solution direct injection system, which requires a spray gun to be installed at the inlet to spray the reducing agent. The amount of reducing agent injection needs to be adjusted according to the nitrogen oxide concentration distribution of the inlet flue gas. The four sampling gas collection pipes of this device cover different positions in the pipeline and can accurately obtain the nitrogen oxide concentration in each area. If the nitrogen oxide concentration of the flue gas on the left side of the pipeline is higher than that on the right side, the injection amount of the spray gun on the left side can be increased accordingly to achieve "on-demand injection" and avoid local excess (causing ammonia escape) or deficiency (denitrification failure) caused by uniform injection.

[0064] For example, in Guangdong and Beijing, the nitrogen oxide emission standards are strict (12-15 mg / Nm 3 ) in areas with low emissions, this precise adjustment can ensure that emissions meet standards while reducing urea consumption (it is estimated that on-demand injection can reduce the amount of reducing agent by 5% to 10%).

[0065] (6) Analysis of airflow characteristics guides the layout and angle design of the spray guns. If monitoring reveals that the flow velocity in the middle of the pipeline is fast and the flow velocity at the edge is slow, the spray guns can be tilted toward the middle to allow the reducing agent to diffuse rapidly with the high-speed airflow. If there is eddy current in a certain area, the number of spray guns can be increased at the corresponding position to avoid local excess of reducing agent due to eddy current aggregation.

[0066] Furthermore, the difference in gas pressure from the sampling collection pipe can reflect the direction of flue gas flow. If the pressure at the top of the pipe is higher than that at the bottom, it indicates an upward bias in the flue gas flow. In this case, the spray gun can be adjusted to tilt upward to ensure adequate contact between the reducing agent and the flue gas. This optimization based on the actual flow field can increase denitrification efficiency by 3% to 5%, significantly reducing emission concentrations.

[0067] (7) Verification of injection uniformity of mixed flue gas parameters of gas collecting main pipe

[0068] The uniformity of the reductant-flue gas mixture is a key factor influencing denitrification efficiency. Uneven injection can cause fluctuating NOx concentrations in the flue gas within the main gas collection pipe (e.g., sudden increases and decreases in concentration over time). This device continuously monitors the main gas collection pipe flue gas, enabling real-time assessment of mixing effectiveness. If the fluctuation exceeds 5%, the injection system may have issues such as nozzle blockage or uneven flow, requiring prompt repair. Long-term stability indicates that the injection parameters are appropriately configured.

[0069] This dynamic verification mechanism can avoid excessive emissions due to spray gun failure, while providing feedback signals for the automated control of the injection system (such as PID adjustment) to achieve precise control of the denitrification process.

[0070] Example 2

[0071] The difference between this embodiment and the first embodiment lies in the material of the thermal insulation cotton and the length of the probe rod of the sampling probe device. Other structures and parameters are the same.

[0072] In this embodiment, the insulation cotton filled inside the sampling tube mounting socket 302 and the gas collecting main pipe mounting socket 303 is aluminum silicate insulation cotton, with a filling thickness of 120 mm, which is consistent with the insulation thickness of the flue insulation layer 201. The probe rod of the sampling probe device is 2 m long, which is greater than the distance of 1.6 m between the exhaust hole and the first flange (102).

[0073] Aluminum silicate insulation offers excellent high-temperature resistance and thermal insulation, enabling long-term stable operation in high-temperature environments. This further enhances the device's thermal insulation performance and ensures accurate sampling results. The longer probe rod is suitable for larger flue gas ducts, ensuring it reaches key sampling locations within the duct, meeting the sampling needs of flue gas ducts of varying sizes.

[0074] Example 3

[0075] The difference between this embodiment and the first embodiment lies in the distribution of the air intake holes; other structures and parameters are the same.

[0076] In this embodiment, air intake holes are provided on the windward side and the side surfaces of the sampling gas collecting pipe 301. There are 6 air intake holes on the windward side and 4 air intake holes on the side surfaces. The diameter of each air intake hole is 5 mm.

[0077] This distribution of air holes can collect smoke samples from different directions, avoiding sampling deviations caused by the direction of smoke flow. It is suitable for scenarios where the direction of smoke flow is unstable, and improves the accuracy and reliability of sampling.

[0078] Example 4

[0079] This embodiment provides a multi-point sampling method for the inlet flue gas of a gas-fired waste heat boiler. Based on the multi-point device for the inlet flue gas of a gas-fired waste heat boiler of Example 1, it is applied to the waste heat boiler of a certain type of gas-steam combined cycle unit. The specific steps are as follows:

[0080] Device installation and fixation: Fix the probe mounting socket 101 of the sampling mechanism 1 to the top of the outer wall of the flue gas duct 2 by welding, ensuring that the lower end of the probe mounting socket 101 is vertically inserted 500 mm into the flue gas duct 2; fix the sampling probe device to the top of the probe mounting socket 101 through the No. 1 flange 102, connect it to the No. 1 gas collecting main pipe 104 through the No. 2 flange 103, and tighten the flange bolts to a torque value of 35 N·m.

[0081] Gas collection mechanism assembly: Four 50mm diameter sampling gas collection pipes 301 are symmetrically welded to both sides of the sampling four-way pipe 105, two on each side, and the ends of the sampling gas collection pipes 301 are connected to the sampling pipe mounting pipe seat 302 and limited by the No. 2 limit block (304); the top of the sampling four-way pipe 105 is welded to the No. 1 gas collection mother pipe 104, and the bottom end is connected to the No. 2 gas collection mother pipe 106 and the No. 3 gas collection mother pipe 107 in sequence. The No. 3 gas collection mother pipe 107 is inserted into the gas collection mother pipe mounting pipe seat 303 and fixed by the No. 1 limit block 108.

[0082] Flue gas collection process: Flue gas with a temperature of 620°C in the flue gas duct 2 enters the duct through 12 8mm diameter air holes opened on the windward side of the sampling collecting pipe 301, and is collected to the No. 1 collecting main pipe 104 and the No. 2 collecting main pipe 106 through the sampling four-way pipe 105 to form a mixed flow.

[0083] Data sampling: The probe rod of the sampling probe device penetrates the middle section of the No. 1 gas collecting main pipe 104 to continuously sample the mixed flue gas. The sampling frequency is set to 1 time / second, and the single sampling volume is 50mL.

[0084] Exhaust treatment: The sampled flue gas is discharged through the exhaust hole with a diameter of 15 mm on the leeward side of the No. 1 gas collecting main pipe 104 and flows back into the main air flow of the flue gas duct 2.

[0085] In this embodiment, the above method can achieve multi-point sampling at different radial positions in the flue gas duct 2, and the sampling error is controlled within ±3%, meeting the accuracy requirements of the SCR denitrification system for inlet flue gas analysis.

[0086] Example 5

[0087] This embodiment provides a method for achieving uniform multi-point sampling of a flue gas duct cross section. The sampling device described in Example 1 is used for a circular flue gas inlet with a diameter of 3 m. The steps are as follows:

[0088] Sampling point distribution design: Four sampling gas collecting pipes 301 with a diameter of 60 mm are distributed symmetrically at 90° along both sides of the sampling four-way pipe 105, with two on each side pointing to the flue in the directions of 0°, 90°, 180°, and 270° respectively. The length of the sampling gas collecting pipe 301 covers 80% of the flue radius.

[0089] Air sampling hole configuration: According to the flow velocity distribution of the flue cross section, air sampling holes are opened at different positions on the windward side of the sampling collecting pipe 301: 3 air sampling holes with a diameter of 6mm are opened at a distance of 500mm from the sampling four-way pipe 105, 4 air sampling holes with a diameter of 6mm are opened at a distance of 1000mm, and 5 air sampling holes with a diameter of 6mm are opened at a distance of 1500mm to ensure that the flue gas at different radial positions can be collected.

[0090] Mixed sampling is achieved by: after the flue gas enters the sampling gas collecting pipe 301 through each gas extraction hole, it is gathered to the No. 1 gas collecting main pipe 104 through the sampling four-way pipe 105 to form a mixed flue gas representing the average state of the flue cross section, with a mixing uniformity of ≥95%.

[0091] Data verification: By arranging 8 independent detection points in the same cross-section of the flue for comparative testing, the deviation between the mixed flue gas data collected by this method and the average value of each detection point is ≤4%, which is significantly better than the traditional single-point sampling method (deviation 15-20%).

[0092] This embodiment achieves uniform sampling of flue gas in a large-section flue by optimizing the layout of the sampling gas collection pipe and the distribution of the gas intake holes, providing reliable data support for the precise control of the reductant injection amount of the denitrification system.

[0093] Example 6

[0094] This embodiment provides a waste heat boiler including the aforementioned sampling device, the specific structure of which is as follows:

[0095] Boiler body: rated evaporation capacity 200t / h, inlet flue diameter 2.8m, designed flue gas temperature 600℃, suitable for gas-steam combined cycle unit, meeting nitrogen oxide emission ≤15mg / Nm 3 local standard requirements.

[0096] Integration of sampling device: The flue gas pipe 2 of the sampling device is connected to the boiler inlet flue with a flange, and a high-temperature resistant sealing gasket is provided at the connection; the probe mounting pipe seat 101 of the sampling mechanism 1 is welded to the center position of the top of the inlet flue, and the sampling probe rod is 2200mm long and penetrates the center area of ​​the flue; the four sampling gas collecting pipes 301 of the gas collecting mechanism 3 extend radially along the flue, and the ends are fixed to the inner wall of the flue through the sampling tube mounting pipe seat 302. The sampling tube mounting pipe seat 302 is integrated with the flue insulation layer 201 and filled with 120mm thick aluminum silicate insulation cotton.

[0097] Operation effect: When the boiler is running at full load, the sampling device can complete 3600 multi-point samplings per hour. The sampling data is transmitted to the denitrification control system in real time through the transmitter. The urea solution injection volume is dynamically adjusted according to the sampling results, saving 8-12% of the reducing agent consumption compared with the traditional fixed injection volume mode, and the outlet nitrogen oxide concentration is stably controlled at 12-14mg / Nm 3 .

[0098] The waste heat boiler of this embodiment realizes precise control of the denitrification process by integrating a multi-point sampling device, taking into account both environmental protection standards and operational economy.

[0099] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler, characterized by: The invention comprises a sampling mechanism (1) and a flue gas duct (2), wherein the sampling mechanism (1) is fixedly mounted on the top of the outer wall of the flue gas duct (2), a sampling probe device is fixedly mounted on the top of the sampling mechanism (1), and the sampling probe rod penetrates into the interior of the flue gas duct (2) to complete flue gas sampling, the inner wall of the flue gas duct (2) is provided with a flue heat-insulating layer (201), the sampling mechanism (1) penetrates into the interior of the flue gas duct (2) and is connected to a gas collecting mechanism (3), the interior of the gas collecting mechanism (3) comprises a sampling tube mounting seat (302) and a gas collecting main pipe mounting seat (303), and the sampling tube mounting seat (302) is fixed to the inner wall of the flue gas duct (2) in a sleeve connection manner; The sampling mechanism (1) includes a probe mounting pipe seat (101), the probe mounting pipe seat (101) is welded and fixed to the top of the flue gas pipe (2), and the lower end is inserted into the flue gas pipe (2), the top and bottom ends of the probe mounting pipe seat (101) are respectively connected to a No. 1 flange (102) and a No. 2 flange (103), the bottom end of the No. 2 flange (103) is connected to a No. 1 gas collecting main pipe (104), the lower end of the No. 1 gas collecting main pipe (104) is connected to a No. 2 gas collecting main pipe (106), and the No. 2 flange (103) is connected to the No. 1 gas collecting main pipe (106). A sampling four-way pipe (105) is placed at the top and bottom of the gas collecting mother pipe (106), and is welded to the bottom end of the No. 1 gas collecting mother pipe (104). The bottom end of the sampling four-way pipe (105) is welded to the No. 3 gas collecting mother pipe (107), and is located at the bottom end of the No. 2 gas collecting mother pipe (106) away from the No. 1 gas collecting mother pipe (104). The outer wall of the No. 3 gas collecting mother pipe (107) is inserted into the center of the gas collecting mother pipe mounting socket (303), and a plurality of No. 1 limit blocks (108) are welded and fixed to the outer wall of the No. 3 gas collecting mother pipe (107); The gas collecting mechanism (3) includes a sampling gas collecting pipe (301), and there are four sampling gas collecting pipes (301), and the four sampling gas collecting pipes (301) have the same diameter. The four sampling gas collecting pipes (301) are respectively welded and fixed on both sides of the sampling four-way pipe (105). The sampling pipe mounting seat (302) is welded and fixed on the inner wall of the flue gas pipe (2), and is sleeved with the outer wall of the sampling gas collecting pipe (301). The gas collecting mother pipe mounting seat (303) is welded and fixed on the inner wall of the flue gas pipe (2), and is sleeved with the outer wall of the bottom end of the third gas collecting mother pipe (107). The sampling gas collecting pipe (301) and the sampling pipe mounting seat (302) are sleeved with a second limit block (304) welded and fixed on the outer wall, and are in contact with the inner wall of the sampling pipe mounting seat (302).

2. The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to claim 1, characterized in that: The interiors of the sampling tube mounting base (302) and the gas collecting main tube mounting base (303) are filled with thermal insulation cotton, and the filling thickness is consistent with the thermal insulation thickness of the flue thermal insulation layer (201).

3. The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to claim 1, characterized in that: A 2MM assembly gap is left between the No. 1 limit block (108), the No. 2 limit block (304) and the inner walls of the sampling tube mounting base (302) and the gas collecting main pipe mounting base (303), and the sampling tube mounting base (302), the gas collecting main pipe mounting base (303) and the sampling gas collecting pipe (301) are all standard parts.

4. The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to claim 1, characterized in that: The windward side of the sampling gas collecting pipe (301) is provided with a plurality of air intake holes, and the number of the air intake holes is determined according to the sampling quantity requirement. The leeward side of the No. 1 gas collecting main pipe (104) is provided with an exhaust hole.

5. The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to claim 4, characterized in that: The windward side and side surfaces of the sampling gas collecting pipe (301) are both provided with air intake holes.

6. The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to claim 1, characterized in that: The sampling gas collecting pipe (301) is connected to the interior of the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106), and the length of the probe rod of the sampling probe device is greater than the distance between the exhaust hole and the No. 1 flange (102).

7. A multi-point sampling method for inlet flue gas of a gas-fired waste heat boiler, characterized in that: The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to any one of claims 1 to 6 comprises the following steps: S10, the sampling mechanism (1) is welded and fixed to the top of the outer wall of the flue gas duct (2) through the probe mounting pipe seat (101), the lower end of the probe mounting pipe seat (101) is inserted into the interior of the flue gas duct (2), and the sampling probe device is connected and fixed to the No. 1 gas collecting main pipe (104) through the No. 1 flange (102) and the No. 2 flange (103); S20, welding the four sampling gas collecting pipes (301) in the gas collecting mechanism (3) to the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106) through the sampling four-way pipe (105), so that the sampling gas collecting pipes (301) are symmetrically distributed on both sides of the sampling four-way pipe (105), and the sampling gas collecting pipes (301) are fixed to the inner wall of the flue gas pipe (2) through the sampling pipe mounting socket (302); S30, the flue gas in the flue gas pipe (2) enters the sampling gas collecting pipe (301) through the air intake hole on the windward side of the sampling gas collecting pipe (301), and is collected to the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106) through the sampling four-way pipe (105); S40, the probe rod of the sampling probe device penetrates into the gas collecting main pipe to collect multi-point data of the collected flue gas; S50. The sampled flue gas is discharged through the exhaust holes on the leeward side of the No. 1 gas collecting main pipe (104).

8. A method for achieving multi-point uniform sampling of a flue gas duct cross section, characterized in that: The multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler according to any one of claims 1 to 6 is used, and the steps are as follows: Δ, four sampling gas collecting pipes (301) of the same diameter are welded to both sides of the sampling four-way pipe (105) respectively, so that the sampling gas collecting pipes (301) are symmetrically distributed in the flue gas duct (2); B. According to the sampling quantity requirement, multiple air holes are opened on the windward side of the sampling gas collecting pipe (301) to ensure that different areas in the flue gas duct (2) are covered; C. The flue gas enters the sampling gas collecting pipe (301) through each gas extraction hole and is collected to the No. 1 gas collecting main pipe (104) and the No. 2 gas collecting main pipe (106) through the sampling four-way pipe (105) to form a mixed flue gas sample; D. The sampling probe device samples and analyzes the mixed flue gas sample, thereby achieving uniform collection of flue gas at multiple points within the cross section of the flue gas duct (2).

9. A waste heat boiler, characterized in that: The invention comprises a boiler body and a multi-point sampling device for inlet flue gas of a gas-fired waste heat boiler as claimed in any one of claims 1 to 6, wherein the flue gas pipe (2) of the sampling device is connected to the inlet flue of the boiler body and is used for multi-point sampling of the flue gas entering the boiler body.

10. The waste heat boiler according to claim 9, characterized in that: The sampling mechanism (1) of the sampling device is mounted and fixed on the top of the outer wall of the boiler body inlet flue, the sampling probe of the sampling mechanism (1) penetrates into the interior of the inlet flue, the gas collecting mechanism (3) is located inside the inlet flue and connected to the sampling mechanism (1), and the gas collecting mechanism (3) is fixedly sleeved with the inner wall of the inlet flue through the sampling tube mounting socket (302).

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