Sample pretreatment and its role:
1 Sample processing systems need to be configured when the sensing elements of the online analytical instrument are not directly installed in process lines and equipment.
2 The role of pretreatment of the sample is to ensure that the analytical instrument obtains a representative sample of the process in the shortest lag time, and the state of the sample is suitable for the operating conditions required by the analytical instrument.
3 Whether the online analytical instrument can be used well is not always the analyzer itself, but depends on the perfection and reliability of the sample system. Therefore, analytical instruments are in any case complex and precise, and the analytical precision is also limited by the representativeness, real-time and physical state of the sample. In fact, the problem encountered in the use of the sample system is often more than the analyzer, and the maintenance of the sample system often exceeds the analyzer itself. Therefore, we must pay attention to the role of the sample system, at least put it in the same position and analysis of the instrument to consider.
General requirements for sample systems:
1 Make the sample obtained by the analyzer consistent with the hungry component and content of the material in the process line or equipment.
2 The consumption of the process sample is very small.
3 Easy to operate and maintain.
4 can work reliably for a long time.
5 The system is as simple as possible.
6 Use a fast loop to reduce the sample transfer latency.
Requirements for sampling methods:
1 Drilling cannot be done on the pipe wall If sampling is performed directly on the pipe arm, the representativeness of the sample cannot be guaranteed. This is not only true when the fluid is in a laminar or turbulent state, but it is also difficult to ensure that the sample is taken out during turbulence. Secondly, due to absorption or adsorption of the inner wall of the pipeline, it will cause a memory effect, reduce the actual concentration of the fluid, and cause desorption, which will change the composition of the sample. Especially when analyzing trace components, the effect is particularly significant. . Therefore, the samples were all taken out using the plug-in sampling probe.
2 Sampling probe insertion orientation should be considered For horizontal piping, gas sampling, the probe should be inserted from the top of the pipe to avoid the possible presence of condensate or liquid droplets; the liquid sampling, the probe should be inserted from the side wall of the pipe to avoid the possible existence of the upper pipe Vapors and bubbles, as well as residues and deposits that may be present at the bottom of the pipe.
For the vertical pipe to be inserted from the side wall of the pipe, the liquid should be taken from the pipe section flowing from the bottom to the top to prevent the gas from entering when the liquid flow is not normal.
About fast loop:
1 Fast loop is a pipeline that is used to speed up the sample flow to shorten the sample transmission lag time.
There are two types of fast loops, namely a fast loop return to the device and a fast bypass loop to waste.
When the distance between the sample removal point and the return point is long, special care must be taken not to bypass the flow meter and the emergency shut-off valve.
When the differential pressure across the bridge is small, a pump can be added to the fast circuit. The selection of the pump should avoid contamination or degradation of the sample by the lubricating oil system.
The sample loop of the analyzer is usually led through a self-cleaning bypass filter. The road should provide flow indication and regulation instruments.
2 Fast Bypass Loop Pass Applicable Environment When the sample discharge will not cause environmental hazards and pollution, a quick bypass circuit can be used;
When the process of returning the sample is unrealistic, such as depressurized gas and liquid vaporized vapor, a rapid bypass circuit can be used;
When the sample recovery cost is higher than its own value, it is not economical to return it to the process and a rapid bypass loop can be used;
When the sample is returned to the process which may result in contamination or degradation, as in mixed samples of multiple flow path measurements, a fast bypass loop can be used.
About heat tracing and heat insulation:
1 Heat tracing Steam heating tubes and electric heat exchangers are used to heat the sample line to supplement the heat lost during sample transfer to maintain the sample temperature within a certain range.
2 Insulation In order to reduce heat transfer from the sample to the surrounding environment during transport, or to absorb heat from the surrounding environment, coating measures are taken on the outer surface of the sample line. Or, insulation measures taken to ensure that the sample is not affected by the ambient temperature during transmission.
Basic tasks and functions of sample processing:
Analytical instruments usually require clean, non-corrosive samples that contain no interfering components. Under normal conditions, the sample must be within a defined range of temperature, pressure, and flow. The pretreatment unit performs further processing and adjustment of the sample, such as temperature, pressure, flow regulation, filtration, dehumidification, removal of harmful substances, etc. Safety relief pressure, current limiting, and flow path switching are also generally included in the unit.
The basic tasks and functions of sample processing are summarized as follows:
1 Flow regulation, including fast loops and analysis loops.
2 pressure regulation, including buck, suction and regulation.
3 temperature regulation, including cooling and insulation;
4 Dedusting, dewatering and gas-liquid separation;
4 Remove harmful substances, including components that are harmful to the analyzer and interference components that affect the analysis.
About sample preparation unit:
The sample processing unit should be installed in the instrument protection box, insulation box or metal plate. The box or plate can be installed on the site or on the external wall of the analysis hut. If it needs to be installed in the house, it should be approved by the user. Sample handling units for non-hazardous media can be placed in the analysis cabin.
Sample flow processing system commonly used flow regulating components:
Ball valve, plug valve, check valve, needle valve, steady flow valve, flow restriction valve, flow restriction orifice, float flow meter.
Sample processing system commonly used pressure regulating components:
1 Pressure regulator valve is a widely used decompression and pressure regulation unit in sampling and sample processing systems.
2 Safety Pressure Relief Valves Protect analyzers and some sample processing components with limited pressure capabilities from high-pressure samples.
3 pressure gauges.
Dust removal methods used in dust removal in sample processing systems and their respective characteristics:
1 Filter dust removal mainly removes solid particles and sometimes also removes liquid particles.
2 Cyclone Separation Dust removal is widely used in liquid samples, and it is also effective for gas samples with large dust particle size.
3 Electrostatic dedusting removes solid and liquid particles with a particle size of less than 1 μM.
4 Washing dust is used for high temperature and high dust gas samples.
Common filter types in sample processors:
Type 1Y coarse filter; 2 mesh filter; 3 sintered filter; 4 fiber or paper filter; 5 membrane filter.
Selection of corrosive samples with a float meter:
The measuring tube of the glass tube float meter can be made of high-aluminum glass, boron glass or organic glass, and the float can be made of glass, fluorine plastic or corrosion-resistant metal. If the glass tube does not meet the requirements of temperature resistance, pressure resistance and corrosion resistance, a metal tube float flow meter with corrosion-resistant material may be selected.
About the analysis system:
1 Single-stream analysis system - refers to a sample analyzer that analyzes only one flow path.
Compared with multi-stream systems, the single-stream system has a short analysis cycle, there is no problem of mixture contamination between samples, and the system reliability is high, but its price is also much higher, and the price of the two is evaluated. At this time, the obvious advantages of speed and reliability of the single-stream analysis system must be taken into consideration. For on-line analysis, a single-stream analysis system is preferred for important measurement points, and a single-stream analysis system must be used for automatic control of closed-loop applications.
2 multi-stream analysis system - refers to an analyzer to analyze more than two streams of the sample, it through the flow switching system for each sample flow channel switching.
Compared with several single-stream analysis systems, the price of a multi-stream analysis system is significantly lower. However, the shortcomings are also obvious. When the analyzer fails, the analysis of all flow paths is interrupted and the information is lost; contamination contamination may occur between the samples; the time delay between one flow path in the cyclic analysis; and the flow path switching Complexity increases the probability of failure and maintenance.
When the process change is relatively slow, the speed of on-line analysis is not high, and the analysis results do not involve in the closed-loop control. As a guide to process operation, a multi-stream analysis system can be used.
Basic requirements for sample discharge:
The basic requirement is not to bring danger to the environment and cause pollution.
About the analyzer's masking shields - On-line analyzers are installed in the field and thus require varying degrees of climate and environmental protection to ensure instrument performance and use for maintenance. Parts or facilities that provide climate and environmental protection for the analyzer are called shelters.
On-line analyzer screens include analyzer housings, analyzer cabinets, analyzer shelters, and analytics cabanas.
Climate and environmental protection advantages and disadvantages provided by the analyzer housing:
The analyzer housing is one of the components of the analyzer. Instruments such as PH meter and conductivity meter can be directly installed in the open air, and their weather and environmental protection are entirely borne by the housing.
The advantage of this type of installation is natural ventilation around the enclosure, there is no danger of explosive gas accumulation, and the installation cost is the lowest. The disadvantage is that the instrument and maintenance personnel have no climate protection, the instrument is vulnerable to the corrosive atmosphere, and its service life may be longer than the installation. Short in bins, shelters and huts, this method is more suitable when the instrument needs to be heated or turned on for maintenance.
To analyze the lighting of the cabin:
1 Analyze the lighting in the cabin should have enough illumination to facilitate operation and maintenance. When accident lighting is provided when necessary, lighting fixtures with inverters and batteries can be used. The standby time for power outage should be no less than 30 minutes. The lighting equipment should be suitable for use in hazardous areas in Zone 1. The lighting switch shall be installed next to the main door outside the analysis cabin and shall be fitted with an explosion-proof power switch.
2 In order to facilitate night maintenance operations, the sample handling tank and gas tank barriers outside the analysis shed should also be provided with lighting and equipped with lighting switches.
Analyze the electrical supply of the huts and meters:
1 Analyze the hut's lighting, ventilators, air conditioners, service outlets and other public equipment from the utility power supply;
2 The analyzer and its accessories, such as the motorized parts in the sample system, should be powered by the instrument's power supply.
3 Safety detection The alarm and interlock system is generally powered by the UPS. Analytical instruments that participate in closed-loop control can also be powered by the UPS.
The 4HVAC (Heating Ventilating and Air Conditioning System) unit and the electric heat tracing system have high power consumption and should be individually distributed. They should not be mixed with other equipment for distribution so as to avoid mutual interference.
1 Sample processing systems need to be configured when the sensing elements of the online analytical instrument are not directly installed in process lines and equipment.
2 The role of pretreatment of the sample is to ensure that the analytical instrument obtains a representative sample of the process in the shortest lag time, and the state of the sample is suitable for the operating conditions required by the analytical instrument.
3 Whether the online analytical instrument can be used well is not always the analyzer itself, but depends on the perfection and reliability of the sample system. Therefore, analytical instruments are in any case complex and precise, and the analytical precision is also limited by the representativeness, real-time and physical state of the sample. In fact, the problem encountered in the use of the sample system is often more than the analyzer, and the maintenance of the sample system often exceeds the analyzer itself. Therefore, we must pay attention to the role of the sample system, at least put it in the same position and analysis of the instrument to consider.
General requirements for sample systems:
1 Make the sample obtained by the analyzer consistent with the hungry component and content of the material in the process line or equipment.
2 The consumption of the process sample is very small.
3 Easy to operate and maintain.
4 can work reliably for a long time.
5 The system is as simple as possible.
6 Use a fast loop to reduce the sample transfer latency.
Requirements for sampling methods:
1 Drilling cannot be done on the pipe wall If sampling is performed directly on the pipe arm, the representativeness of the sample cannot be guaranteed. This is not only true when the fluid is in a laminar or turbulent state, but it is also difficult to ensure that the sample is taken out during turbulence. Secondly, due to absorption or adsorption of the inner wall of the pipeline, it will cause a memory effect, reduce the actual concentration of the fluid, and cause desorption, which will change the composition of the sample. Especially when analyzing trace components, the effect is particularly significant. . Therefore, the samples were all taken out using the plug-in sampling probe.
2 Sampling probe insertion orientation should be considered For horizontal piping, gas sampling, the probe should be inserted from the top of the pipe to avoid the possible presence of condensate or liquid droplets; the liquid sampling, the probe should be inserted from the side wall of the pipe to avoid the possible existence of the upper pipe Vapors and bubbles, as well as residues and deposits that may be present at the bottom of the pipe.
For the vertical pipe to be inserted from the side wall of the pipe, the liquid should be taken from the pipe section flowing from the bottom to the top to prevent the gas from entering when the liquid flow is not normal.
About fast loop:
1 Fast loop is a pipeline that is used to speed up the sample flow to shorten the sample transmission lag time.
There are two types of fast loops, namely a fast loop return to the device and a fast bypass loop to waste.
When the distance between the sample removal point and the return point is long, special care must be taken not to bypass the flow meter and the emergency shut-off valve.
When the differential pressure across the bridge is small, a pump can be added to the fast circuit. The selection of the pump should avoid contamination or degradation of the sample by the lubricating oil system.
The sample loop of the analyzer is usually led through a self-cleaning bypass filter. The road should provide flow indication and regulation instruments.
2 Fast Bypass Loop Pass Applicable Environment When the sample discharge will not cause environmental hazards and pollution, a quick bypass circuit can be used;
When the process of returning the sample is unrealistic, such as depressurized gas and liquid vaporized vapor, a rapid bypass circuit can be used;
When the sample recovery cost is higher than its own value, it is not economical to return it to the process and a rapid bypass loop can be used;
When the sample is returned to the process which may result in contamination or degradation, as in mixed samples of multiple flow path measurements, a fast bypass loop can be used.
About heat tracing and heat insulation:
1 Heat tracing Steam heating tubes and electric heat exchangers are used to heat the sample line to supplement the heat lost during sample transfer to maintain the sample temperature within a certain range.
2 Insulation In order to reduce heat transfer from the sample to the surrounding environment during transport, or to absorb heat from the surrounding environment, coating measures are taken on the outer surface of the sample line. Or, insulation measures taken to ensure that the sample is not affected by the ambient temperature during transmission.
Basic tasks and functions of sample processing:
Analytical instruments usually require clean, non-corrosive samples that contain no interfering components. Under normal conditions, the sample must be within a defined range of temperature, pressure, and flow. The pretreatment unit performs further processing and adjustment of the sample, such as temperature, pressure, flow regulation, filtration, dehumidification, removal of harmful substances, etc. Safety relief pressure, current limiting, and flow path switching are also generally included in the unit.
The basic tasks and functions of sample processing are summarized as follows:
1 Flow regulation, including fast loops and analysis loops.
2 pressure regulation, including buck, suction and regulation.
3 temperature regulation, including cooling and insulation;
4 Dedusting, dewatering and gas-liquid separation;
4 Remove harmful substances, including components that are harmful to the analyzer and interference components that affect the analysis.
About sample preparation unit:
The sample processing unit should be installed in the instrument protection box, insulation box or metal plate. The box or plate can be installed on the site or on the external wall of the analysis hut. If it needs to be installed in the house, it should be approved by the user. Sample handling units for non-hazardous media can be placed in the analysis cabin.
Sample flow processing system commonly used flow regulating components:
Ball valve, plug valve, check valve, needle valve, steady flow valve, flow restriction valve, flow restriction orifice, float flow meter.
Sample processing system commonly used pressure regulating components:
1 Pressure regulator valve is a widely used decompression and pressure regulation unit in sampling and sample processing systems.
2 Safety Pressure Relief Valves Protect analyzers and some sample processing components with limited pressure capabilities from high-pressure samples.
3 pressure gauges.
Dust removal methods used in dust removal in sample processing systems and their respective characteristics:
1 Filter dust removal mainly removes solid particles and sometimes also removes liquid particles.
2 Cyclone Separation Dust removal is widely used in liquid samples, and it is also effective for gas samples with large dust particle size.
3 Electrostatic dedusting removes solid and liquid particles with a particle size of less than 1 μM.
4 Washing dust is used for high temperature and high dust gas samples.
Common filter types in sample processors:
Type 1Y coarse filter; 2 mesh filter; 3 sintered filter; 4 fiber or paper filter; 5 membrane filter.
Selection of corrosive samples with a float meter:
The measuring tube of the glass tube float meter can be made of high-aluminum glass, boron glass or organic glass, and the float can be made of glass, fluorine plastic or corrosion-resistant metal. If the glass tube does not meet the requirements of temperature resistance, pressure resistance and corrosion resistance, a metal tube float flow meter with corrosion-resistant material may be selected.
About the analysis system:
1 Single-stream analysis system - refers to a sample analyzer that analyzes only one flow path.
Compared with multi-stream systems, the single-stream system has a short analysis cycle, there is no problem of mixture contamination between samples, and the system reliability is high, but its price is also much higher, and the price of the two is evaluated. At this time, the obvious advantages of speed and reliability of the single-stream analysis system must be taken into consideration. For on-line analysis, a single-stream analysis system is preferred for important measurement points, and a single-stream analysis system must be used for automatic control of closed-loop applications.
2 multi-stream analysis system - refers to an analyzer to analyze more than two streams of the sample, it through the flow switching system for each sample flow channel switching.
Compared with several single-stream analysis systems, the price of a multi-stream analysis system is significantly lower. However, the shortcomings are also obvious. When the analyzer fails, the analysis of all flow paths is interrupted and the information is lost; contamination contamination may occur between the samples; the time delay between one flow path in the cyclic analysis; and the flow path switching Complexity increases the probability of failure and maintenance.
When the process change is relatively slow, the speed of on-line analysis is not high, and the analysis results do not involve in the closed-loop control. As a guide to process operation, a multi-stream analysis system can be used.
Basic requirements for sample discharge:
The basic requirement is not to bring danger to the environment and cause pollution.
About the analyzer's masking shields - On-line analyzers are installed in the field and thus require varying degrees of climate and environmental protection to ensure instrument performance and use for maintenance. Parts or facilities that provide climate and environmental protection for the analyzer are called shelters.
On-line analyzer screens include analyzer housings, analyzer cabinets, analyzer shelters, and analytics cabanas.
Climate and environmental protection advantages and disadvantages provided by the analyzer housing:
The analyzer housing is one of the components of the analyzer. Instruments such as PH meter and conductivity meter can be directly installed in the open air, and their weather and environmental protection are entirely borne by the housing.
The advantage of this type of installation is natural ventilation around the enclosure, there is no danger of explosive gas accumulation, and the installation cost is the lowest. The disadvantage is that the instrument and maintenance personnel have no climate protection, the instrument is vulnerable to the corrosive atmosphere, and its service life may be longer than the installation. Short in bins, shelters and huts, this method is more suitable when the instrument needs to be heated or turned on for maintenance.
To analyze the lighting of the cabin:
1 Analyze the lighting in the cabin should have enough illumination to facilitate operation and maintenance. When accident lighting is provided when necessary, lighting fixtures with inverters and batteries can be used. The standby time for power outage should be no less than 30 minutes. The lighting equipment should be suitable for use in hazardous areas in Zone 1. The lighting switch shall be installed next to the main door outside the analysis cabin and shall be fitted with an explosion-proof power switch.
2 In order to facilitate night maintenance operations, the sample handling tank and gas tank barriers outside the analysis shed should also be provided with lighting and equipped with lighting switches.
Analyze the electrical supply of the huts and meters:
1 Analyze the hut's lighting, ventilators, air conditioners, service outlets and other public equipment from the utility power supply;
2 The analyzer and its accessories, such as the motorized parts in the sample system, should be powered by the instrument's power supply.
3 Safety detection The alarm and interlock system is generally powered by the UPS. Analytical instruments that participate in closed-loop control can also be powered by the UPS.
The 4HVAC (Heating Ventilating and Air Conditioning System) unit and the electric heat tracing system have high power consumption and should be individually distributed. They should not be mixed with other equipment for distribution so as to avoid mutual interference.
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