Gas Monitoring System

1.Gas Monitoring System Project Introduction

Gas Monitoring System is designed to detect a range of gases associated with flue gases, from toxic and flammable gases to oxygen and combustible gases.According to the measurement needs proposed by you, the Gas Monitoring System launched by Fengtu Technology can continuously monitor SO2, NOX, O2 (standard, wet basis, dry basis and conversion), particulate matter concentration, flue gas temperature, pressure, flow rate and other related parameters, and count emission rates, total emissions, etc.Therefore, the measured data is effectively managed.

Gas Monitoring System consists of four necessary subsystems: gaseous pollutants (SO2, NOX, 02, etc.), particulate matter monitoring, flue gas parameters (temperature, pressure, flow rate, etc.), and data acquisition and processing.

The gaseous pollutant monitoring uses the extraction condensation method.The principle is to measure the SO2 and NOX content in the flue gas by using ultraviolet differential method, measure the wet oxygen content through electrochemical method, and then calculate the dry flue gas concentration of SO2, NOX and 02 through dry and wet conversion.

Particulate matter monitoring is done by laser-scattering method, the temperature of the flue gas is measured by a temperature sensor, the pressure of the flue gas is measured by a pressure sensor, and the flue gas flow rate is measured by a pitot tube; all measurement signals are sent to the data acquisition and processing system.

The output processing system has functions such as real-time on-site data transmission, remote fault diagnosis, report statistics and graphical data analysis, which realizes unattended work site.The entire system has a simple structure, wide dynamic range, strong real-time performance, flexible networking and low operating costs.At the same time, the system adopts a modular structure, which is convenient for combination, and can fully meet the requirements of communication with the internal DCS system and the data system of the environmental protection department.

000011 Project Implementation Standard

The design, manufacturing and acceptance specifications of this system are mainly carried out in accordance with the following standards and technical specifications:

u GB3095-1996 "Atmospheric Environmental Quality Standards"

u GB13223-2003 "Standards for Atmospheric Pollutants in Thermal Power Plants"

u GB18485-2007 "Standards for Control of Pollutants for Incineration of Domestic Waste"

u HJ/T75-2007 "Technical Specifications for Continuous Monitoring of Flue Gas Emissions in Thermal Power Plants"

u CJJ90—2002 "Technical Specifications for Urban Domestic Waste Incineration Engineering"

u CJ/T118—2002 "Technical Specifications for Urban Domestic Waste Incinerators"

u HJ/T76-2007 "Technical requirements and detection methods for continuous monitoring system for flue gas emissions from fixed pollution sources"

u GB16297-1996 "Comprehensive Emission Standard for Air Pollutants"

u GB/T16157-1996 "Determination of Particulate matter in Exhaust Gas of Solid Pollutants and Sampling Methods of Gas Pollutants"

u GB9078-1996 "Comprehensive Emission Standard for Air Pollutants in Industrial Furnace Kilns"

u GB 3095-1996 "Ambient Air Quality Standards"

u GB12519-1990 "General Technical Conditions of Analytical Instruments"

000012 Project Plan

000012.1 Measurement item

ØSO2, NOX, O2, smoke, temperature, pressure, flow rate

000012.2 Measurement method

ØFlue gas sampling method: extraction condensation method

ØSO2 and NOX monitoring method: differential optical absorption spectroscopy

ØO2 monitoring method: electrochemical method

ØSmoke measurement method: laser post-scattering method

ØTemperature measurement method: temperature sensor

ØHumidity measurement method: humidity sensor

ØPressure measurement method: pressure sensor

ØFlow velocity flow measurement method: differential pressure method (pito tube)

2.General rules of Gas Monitoring System

The technical requirements for functional design, structure, performance, installation and testing of this system equipment all meet the relevant national environmental protection standards and meet the standards requirements of the Environmental Protection Industry of the People's Republic of China (HJ/T75-2007, HJ/T76-2007).

Our company's CEMS system consists of a gaseous pollutant monitoring subsystem, a particulate matter monitoring subsystem, a flue gas parameter monitoring subsystem and a data acquisition and processing subsystem.The gaseous pollutant monitoring subsystem and a data acquisition and processing subsystem are installed in a standard 19-inch cabinet.The system composition is as follows:

Figure 1, CEMS system composition diagram

ØGasy pollutant monitoring subsystem: consists of sampling unit, pretreatment unit and analysis unit.

Ø Particle monitoring subsystem: Use laser post-scattering smoke monitor.

ØFlue gas parameter monitoring subsystem: Pito tube is used to measure flow velocity, pressure sensor is used to measure pressure, temperature sensor is used to measure temperature, and flue gas humidity is measured by high-temperature capacitance humidity sensor.

ØData acquisition and processing subsystem: consists of data collector, industrial control machine, display and system software.

The above subsystems are cropped according to customer needs.

Figure 2.CEMS system installation diagram

3.Gas Monitoring System System Component

3.1 Monitoring of gaseous pollutants

3.1.1 Sampling and Preprocessing Unit

The sample gas is taken out by the sampling probe under the suction force of the sampling pump.Most of the particulate matter in the sample gas is filtered off by the filter in the sampling probe.After filtering, it is transported to the refrigeration system by the heating pipeline to condense and remove water, and sent to the analysis unit for analysis.The condensed water is discharged through the drainage system.The control unit realizes functions such as backblowing, calibration, and refrigeration temperature alarm prompts, and displays various working statuses of the system.

The first-stage rapid condensation is used in the pretreatment system to ensure that the gas components remain unchanged.Secondary fine filtration is adopted to ensure that the gas measuring chamber is not contaminated, thereby improving the service life of the analyzer.The following figure is the flow chart of the gaseous pollutant monitoring system.

3.1.2 Gas analyzer

Instrument: UV spectrum gas analyzer

Model: FT-UVA-100

Measurement principle: Differential optical absorption spectroscopy (DOAS)

Measurement principle

UV spectroscopy gas analyzer is a gas analysis instrument based on multi-channel spectroscopy analysis technology (OMA) and differential optical absorption spectroscopy technology (DOAS).The beam emitted by the light source converges into the optical fiber and is transmitted to the gas chamber through the optical fiber.When passing through the gas chamber, it is absorbed by the gas to be measured and transmitted to the spectrometer.After being spectroscopic through gratings inside the spectrometer, the spectroscopic signal is converted into an electrical signal by the array sensor to obtain the continuous absorption spectral information of the gas.Based on this spectral information, the instrument uses differential absorption spectroscopy algorithm (DOAS) and partial least squares algorithm (PLS) to obtain the concentration of the measured gas.

ØMulti-band spectroscopy analysis technology (OMA)

Since various gas molecules have different absorption of light waves in different bands, the simultaneous measurement of multiple gases is achieved through the analysis of the continuous spectrum after gas absorption.

The UV spectroscopy gas analyzer uses ultraviolet band light sources and sensors to measure the concentration of gases absorbed by light waves in the ultraviolet band, such as SO2, NO, NO2 and other gases.

ØDifferent optical absorption spectroscopy (DOAS)

The core idea of DOAS is to decompose the absorption spectrum of the gas into two parts: fast change and slow change.The fast-changing part is related to the structure of the gas molecules and the elements it consists of, and is a characteristic part of the absorption spectrum of the gas molecules; the slow-changing part is related to the interference of smoke, water vapor, background gas, and changes in the measurement system, and is an interference part.DOAS uses the fast-changing part to calculate the concentration of the measured gas, and the measurement results are not disturbed and have high accuracy.

The UV spectroscopy gas analyzer adopts a unique DOAS algorithm and PLS algorithm to eliminate interference from smoke, water vapor and background gas, and also eliminate the impact of measurement system fluctuations on measurement results, ensuring the accuracy and stability of measurement.

Technical Indicators

SO2: 0~100~1000ppm (can be customized according to the buyer's needs)

NO: 0～100～1000ppm (can be customized according to the buyer's needs)

Accuracy: ≤±2%

Linear error: ≤±2%FS

Zero point drift: ≤±2%FS/7D

Range drift: ≤±2%FS/7D

Response time: ≤30s

other

O2 measurement electrochemistry, 0～25%, ≤±2%FS

Power supply: 220VAC, 50Hz

Ambient temperature limit: -10~40℃

Communication interface: 1 channel RS232; 1 channel RS485/RS232

Digital interface: 4 relay output, 2 binary input

Analog interface: 5 channels 4~20mA output, 2 channels 4~20mA input

Instrument features

ØHigh reliability

It uses pulse xenon lamp with a lifespan of up to 10 years as the light source, and uses a curing spectrometer, with no moving parts and high reliability.

ØCombined gas chamber design

The combined gas chamber design makes spectral adjustment simple and improves spectral intensity.

ØHigh measurement accuracy and good stability

The DOAS (differential optical absorption spectrum) algorithm is used, and the measurement results are not disturbed by factors such as smoke and moisture, and have high measurement accuracy; at the same time, the DOAS algorithm also eliminates errors caused by instrument aging and has good measurement stability.

ØHighly intelligent and digital

It has built-in multiple high-performance processors, and the processors use high-speed data bus communication technology.Each module has powerful digital configuration and detection functions; it is simple to operate and easy to use.

Ø Rich user interface

Provides rich interfaces that can be easily integrated into various control and monitoring systems.Wireless or wired networks can be formed through communication methods such as RS485 and RS232 to facilitate the daily operation, maintenance and management of the instrument.

ØComparison with common analyzers

3.1.3 Analysis system

The analysis system is composed of:

ØSampling unit (probe, filter, thermostat);

The sampling unit of the FT-CEMS-A system is mainly composed of a sampling probe and a heat tracing pipeline.Install the sampling probe in the appropriate position of the flue (or chimney) in accordance with national specifications, collect gas in the flue, and transport the gas to the heating box located inside the cabinet through a heat tracing pipe.To ensure the accuracy of the measurement results, the sampling probe and the heating pipeline are both electrically heat-tracing, which can keep the gas at a set temperature to prevent moisture from condensing in the gas.The length of the heating pipeline can be customized according to the actual needs of the buyer.

Ø Pretreatment unit (sampling pump, dehumidification, fine filtration, drainage, etc.);

The flue gas reaches the pretreatment system through the high-temperature sampling probe and heat tracing pipe.The pretreatment system enters the condenser through the sampling ball valve for steam separation.The condensed water is discharged in time through the peristaltic pump.The condensed water is dehydrated through the condenser, and dust filtered through the third-level fine filter.The treated clean dust-free sample gas enters the flue gas analyzer for analysis and measurement.

ØAnalysis unit (SO2, NO, NO2, O2);

ØSignal output (SO2, NO, NO2, O2 concentration, range conversion, calibration state, fault state, etc.);

ØOthers (gas circuits, circuits, etc.);

ØAnalytical instrument cabinet: 2000×700×800MM (height*deep*width).

3.2 Particle monitoring

Instrument: smoke (powder) dust measuring instrument

Model: LSS2004

Measurement principle: laser post-scattering method

Technical parameter table:

Implementation standard: HJ/T 76-2007 Technical requirements and detection methods for continuous monitoring system for flue gas emissions from fixed pollution sources.

Product performance features:

It adopts a homogeneous probe for speed measurement and sampling to support accurate isometric sampling.

Supports four parameters to output simultaneously: flue temperature, flue pressure, flue flow rate, and flue concentration.

The instrument adopts a variety of advanced technologies.Including: related noise cancellation technology, laser emission power stability technology, extremely low noise TIA, interference control and signal integrity design, and anti-hard environment design technology, providing fast, reliable and accurate quantitative smoke emission data.

3.3 Flue gas parameter monitoring

3.3.1 Temperature and pressure flow integrated probe (temperature, pressure, flow rate)

The structure of the temperature-pressure-flow integrated probe measuring device mainly includes micro-differential pressure transmitter, static pressure sensor, thermal resistance (or thermocouple), pitot tube, back-blowing solenoid valve, temperature and pressure compensation, etc.The measurement principle is: the primary pressure-taking element adopts the traditional pitot tube measurement method.After correct installation, the full pressure and back pressure pressure picking tube of the pitot tube transmit the detected dynamic pressure and static pressure to the differential pressure transmitter respectively.The differential pressure transmitter converts the difference between the dynamic pressure and static pressure into 4~20mA square proportional current to transmit to the distribution box data acquisition module, and the computer in the CEMS cabinet performs data processing.

The inner and outer surfaces of the pitot tube have been specially treated to effectively avoid flue gas corrosion and reduce dust adhesion.The back-blowing solenoid valve is mainly used for system back-blowing when measuring dirty gases (such as flue gas discharged from the boiler): When the probe detection hole adheres to and accumulates dust and dirt, the solenoid valve is opened regularly or according to the predetermined procedure, and the compressed air is connected to two pressure-taking pipes at the same time for blow-off operation.During normal measurement, the solenoid valve is in a closed state.

Technical Features

l Can measure the temperature, pressure and flow rate of the flue gas in real time, and output 4~20mA through 3 analog signals two-wire system.

l Automatically and regularly blow back the dynamic and static pressure ends of the Pito tube.

lHigh measurement accuracy, good reliability, and can work continuously for a long time.

lEasy installation and wiring, and low maintenance.

Technical Indicators

ØSpan: Linear output 0-40m/s, effective measurement range: 5~30m/s;

ØOutput signal: 4~20mA two-wire system;

ØMeasurement accuracy: ±2%FS;

ØCheck frequency: 12 months;

ØResponse time: <1s;

Ø Differential pressure (temperature, pressure) transmitter power supply: 24VDC, two-wire system;

ØDifferential pressure transmitter overvoltage limit: 4.0MPa;

ØPitto tube material: 304, 316L stainless steel;

ØNormal closed back-blowing solenoid valve power supply: 220VAC, 50Hz;

ØPitto tube insertion length: 500~2000mm optional;

ØPressure transmitter range: -10~10kPa;

ØTemperature transmitter range: 0~300℃;

ØMedia temperature range: -40~500℃;

ØAmbient temperature: -40~85℃;

ØStorage temperature: 0~50℃;

ØStorage humidity: 0~85%RH.

ØInstallation flange: DN50;

ØMaterial: SUS316L

Select the installation location

The installation position of the temperature-pressure flow integrated probe should be selected as the straight pipe section with stable and uniform flue gas flow rate as much as possible.For details, please refer to the relevant requirements in HJ/T 75-2001 "Technical Specifications for Continuous Monitoring of Flue Gas Emissions in Thermal Power Plants" or HJ/T 76-2001 "Technical Requirements and Detection Methods for Continuous Monitoring Systems for Fixed Pollution Sources".

Butt flange welding and pre-burial

Before installing the temperature-pressure flow integrated probe, the DN50 docking flange pipe must be pre-buried or welded at the selected flue opening position.When installing the flange, you must pay attention to the installation direction (as shown in the figure below).The flange and flue must ensure a 100mm wrench space.The flange size is shown in the figure below.Pay attention to the direction of the flange when welding the flange, as shown in the figure below.

Instrument installation

On-site installation is based on the aspect of the flue gas air flow, so that the direction of the Pito tube dynamic pressure port (H port) is facing the direction of the air flow, and the static pressure port (L port) is facing the direction of the air flow, and then butt the instrument with the installed flange and tighten it with screws and nuts.

The pitot ports are defined as: the forward air flow direction is the positive pressure port, and the back air flow direction is the static pressure port, which are inserted into the quick plug connectors of the dynamic pressure port (H) and the static pressure port (L) respectively.

Gas circuit connection

There is an 8mm quick plug connector at the bottom of the temperature pressure flow, which is used to connect to external purge gas sources.The backblowing must be oil-free and dust-free, with a pressure of 0.4~0.7MPa.

The connected 220VAC power cord and signal cable are both crimped terminals, and the three 4~20mA signal cords are connected to the distribution box using shielded wires.

Maintenance cycle

It is recommended that users check the instrument for the first time 3 days after the system is installed, and then check again 15 days later.If there is no problem, they can check at intervals of 3 months.

The back-blowing pressure of the pitot tube is 0.2-0.7MPa.The back-blowing time is adjusted according to the smoke concentration, temperature, moisture, etc.of the working condition.It is generally back-blowing once every 12 hours, and the back-blowing time is 1-3 minutes.

Maintenance content

Check whether the power supply of the instrument and the gas source of the instrument are normal, observe whether the flue gas temperature, pressure, flow rate, etc.displayed by the upper computer are within a reasonable range, and make a simple judgment based on the on-site environment and unit operation.

3.3.2 Humidity measurement (optional)

Instrument: Flue gas moisture meter

Instrument model: HF-SD-100

Measurement principle: high temperature capacitance humidity sensor

Measurement range: 0~100% (can be customized according to the buyer's needs)

Measurement accuracy: ±2%

Input voltage: 220VAC

Output current: 4~20mA

3.4 Data acquisition and processing

Ø Data collector (optional)

Analog input: 8 input channels

Output: Analog output 8 channels or GPRS

ØIntegrated chemical control machine

Windows XP operating system, 6 232 truncated ports, providing 232 interface for data upload of digital instruments

ØSplitter (optional)

Reserve 4-20mA all the way, and upload data to enterprise DCS

Ø System software: Online monitoring and management system for pollution sources HFMonitor1.0

The system is developed based on national and local air pollutant emission standards, implements government decisions on controlling air pollution and improving air quality, implements online continuous monitoring of fixed air pollution sources, and provides timely and effective data for pollution emission declaration, total control, and pollution discharge charges.It can be used in a continuous monitoring system for individual pollution source emissions, and can also be widely used in environmental monitoring stations and large and medium-sized enterprises to conduct air quality monitoring and evaluation and air quality daily reports.

Ø Features:

² Has complete data acquisition, processing and transmission functions.Supports local area network distribution operations.

² The system works in real time.Real-time data collection is fast and stable, and the transmission speed is fast.The real-time situation of air pollution can be quickly and timely grasped through remote communication; it has a high time resolution.

² The system has regular automatic calibration, automatic diagnosis and automatic alarm functions; it runs under strict quality control procedures, and the obtained data is relatively comparable and traceable.

² The long-term continuous operation of the system not only allows a large amount of data to be obtained, and can calmly adapt to the monitoring requirements of various pollution sources, comprehensively reflect the real situation of pollution source emissions and control facilities, but also obtain pollution changes laws, providing detailed and reliable technical basis for pollution forecasting and environmental evaluation.

² The system provides good parameter modification function according to different situations, which can help system administrators and maintenance personnel to diagnose the working status of various measuring instruments and sensors.

² The system provides real-time data display and real-time curves, and can automatically generate various reports.

4.Features of Gas Monitoring System

ØThe core instrument uses ultraviolet spectroscopy to measure flue gas, with high measurement accuracy, good reliability, less affected by dust and moisture, and low maintenance cost.

ØHigh temperature sampling and high temperature heat tracing (120℃~180℃) transmission, dust removal and dew prevention.

ØFast condensation is used in the pretreatment system to ensure that the gas components remain unchanged.Directly measure the dry basis value of the flue gas, which meets the national standard requirements.

Ø The system cabinet can be fully opened, greatly improving the convenience of system maintenance.

Ø System Control

²PLC is used to perform calibration and system purge.The sampler temperature, heat tracing tube temperature, and condenser temperature are all involved in the system control to ensure that the system is in the best operating state.

² The system can also use various shortcuts for calibration and system purge, etc., to provide convenience for operators.Quick methods reduce operator requirements.

² System control also displays various statuses in the system online to ensure real-time grasp of the system's operating status.

5.Gas Monitoring System project installation

5.1 Public conditions to be provided by the demander

ØPower supply: 220VAC, 50Hz, 2kW, excluding heating pipelines and air conditioners.Heating line 60W/m, air conditioning (if required) 1000W.

ØInstrument air: 0.4~0.7MPa, clean and oil-free compressed air, dew point -30℃.

ØMain tools used during installation:

²Open drilling and matching tools, water pipes, etc.; drill bit diameter: 60mm, 75mm, 100mm.(For brick flue)

² Impact drill; drill bit diameter 10mm.

² Commonly used tools;

ØInstallation materials:

²Ordinary expansion bolts (metal): M8mm;

²Tube clamp expansion bolt (metal): 8mm; fixed pipe size: 20mm, 50mm.

²Ordinary expansion bolts (plastic): 6mm, 8mm;

²Cable wire guard tube and other common materials.

5.2 Basic operating costs

5.3 Design division

The demander provides the environmental parameters of the sampling point, including design data such as sampling point temperature, dust content, flue gas content, as well as flue diameter, wall thickness, height from the ground, flue structure materials, annual average environmental temperature, maximum and minimum temperature, atmospheric pressure, etc.According to the on-site data, the supplier selects the model and designs the best solution to meet the usage requirements.The supplier proposes the construction plan as a design reference.

5.4 System installation and implementation

5.4.1 Opening position

The location of the sampling point is generally selected on the horizontal flue center line of the brick or steel structure before the flue gas enters the chimney; it can also be installed on the chimney, and it is best to specify the installation location by a professional in accordance with the project requirements to meet the needs.

See Appendix 1 for a schematic diagram of the opening position

5.4.2 Installation platform

The height of the guardrail for the installation platform is 1.2m, and the bottom of the platform should be made of anti-slip steel plates; at the bottom of the platform, weld a 150mm wide steel plate along the perimeter of the guardrail to prevent the mounting parts from falling off the platform.

The distance between the bottom surface of the platform and the center of the flue is 1.4m, and the height of the guardrail is 1.2m; the platform is supported by a steel frame structure and is fixed with the flue; a ladder for up and down platforms is built on one side of the platform.

See Appendix II for the platform diagram

5.4.3 Instrument room requirements

Ø Position: Try to be close to the measurement position on the flue (consider it can be considered below the flue).

ØBuilding size: The usable area between the instruments should not be less than 6m2 (single system).The indoor net height shall not be less than 2.6m.

ØIndoor environment requirements: temperature between 10-35℃, relative humidity below 80%, ventilation, no vibration, no strong magnetic field interference.

ØPower power: The power cord enters under the instrument cabinet through the cable trench.The distance between the instrument and the wall shall not be less than 500mm.

See Appendix III for analyzing the hut

5.5 Opening and flange welding

ØSampling probe opening size: Ø60mm;

See Appendix IV for embedded flange of sampling probe

ØPitot tube flowmeter measurement hole: Ø60 mm;

See Appendix IV for embedded flange of sampling probe

Ø Dust instrument sampling hole: Ø75mm;

See Appendix V for dust meter pre-embedded flange

ØReference hole: (Reference hole is reserved for environmental protection data comparison, and the company needs to provide it by itself, generally between DN80 and DN120)

See Appendix VI for reference hole embedded flange

Note: The spacing between the openings on the flue should be greater than 500mm; if it is a brick flue, it is recommended to embed the steel pipe and then weld it to the flange.

Just above the instrument position in the instrument room, 2.5m from the ground height, are the sample gas pipeline and exhaust pipe openings.The opening size is φ60-80mm and the number of openings is 2.

5.5 Layout of power cord and signal cord:

The demander provides: There should be a 220VAC, 50Hz power supply on the working platform, with a power of about 2000W; the power cord is arranged 0.5 meters below the gas sampling hole (entered into the power box provided by the supplier); in addition, signal cables are laid from the analysis cabinet of the instrument cottage to the power box.

See Appendix 7 for system routing and layout diagrams

5.6 Arrangement and fixation of gas sampling tubes

Ø The sampling pipeline above the instrument chamber can be directly fixed to the wall and platform support columns, and finally enter the instrument chamber.Starting from the sampling probe, the sampling tube should be tilted downward to the instrument chamber at a slope of no less than 1%;

ØOr fix the sampling tube to the steel cable, and fix the steel cable to the flue and the chimney wall (also need to be tilted).However, it must be ensured that there will be no scratches between the sampling tube and the wall at any time.

5.7 On-site installation guidance, debugging and acceptance

Under the guidance of on-site technical service personnel, the equipment of this project will be installed and debugged based on the technical information, inspection standards, drawings and instructions provided by us.The installation and debugging process is arranged as follows:

After the contract equipment is installed, we will send someone to guide the debugging and resolve the equipment problems that arise during the debugging as soon as possible.Performance acceptance is carried out after the installation and commissioning of all equipment is completed.The acceptance inspection and buyer and seller participate.After the acceptance of all performances meet the indicators, the buyer signs the equipment acceptance certificate for this project.

Training Program

The specific contents of the training time, number of people, location, etc.shall be agreed with both the supply and demand parties.

6.Quality assurance and after-sales service

(1) Our company provides a twelve-month quality assurance period for the entire system.During the warranty period, the company regularly maintains the system for free and replaces spare parts for free.If the system fails, we will respond within 24 hours.If necessary, the technical engineer will arrive at the site within 48 hours.

(2) After the warranty period expires, our company will provide lifelong paid maintenance services and provide the best prices for spare parts.

(3) Free upgrade of system software.

(4) Provide free training for factory personnel.