Tools/raw materials

TVOC gas sensor, XL90 intelligent gateway

40. VIEW configuration upper computer monitoring software

1、 Basic characteristics of VOCs

Method/Step 1:

Definition of VOCs

Academic definition of VOCs: refers to organic chemical substances with vapor pressure above 0.1mmHg (13.3Pa) and boiling point below 260 ℃ (500 ℉) under normal conditions (20 ℃, 101.3kPa).

Method/Step 2:

Characteristics of VOCs

● They all contain carbon elements, as well as H, O, N, P, S, halogen and other non-metallic elements.

● It has low melting point, is easy to decompose and volatilize, and can participate in atmospheric photochemical reaction. The ultra-low emission dust meter generates photochemical smoke under the sun.

● At room temperature, most of them are colorless liquids with irritating or special smell.

● Most of them are insoluble in water or insoluble in water and soluble in organic solvents.

● There are millions of species, most of which are flammable and explosive, some of which are toxic or even highly toxic.

● Relative vapor density is heavier than air.

Method/Step 3:

Classification of VOCs

VOCs can be divided into hydrocarbons (alkanes, olefins and aromatics), ketones, esters, alcohols, phenols, aldehydes, amines, nitriles (cyanides), etc. according to their chemical structures.

2、 Source and harm of VOCs

Method/Step 1:

Source of VOCs

The study of VOCs emission sources and their pollutant emissions is the basis for controlling VOCs in the atmosphere, and the sources of VOCs are very wide. Typical VOCs emission sources can be divided into two categories: anthropogenic emission sources (including fixed sources and mobile sources) and natural emission sources (including biological sources and non biological sources). Among them, anthropogenic emission sources are mainly caused by the production process, product consumption behavior and motor vehicle exhaust of petrochemical related industries. Through analysis and summary, VOCs mainly come from the following aspects:

(1) Process tail gas discharged from petrochemical plants, such as petroleum refining process, petrochemical oxidation process, and petrochemical tank production process;

(2) A large amount of VOCs can be produced during the exploitation, storage and transportation of oil, coal, natural gas, etc;

(3) Incomplete combustion products of coal, petroleum, petroleum products, natural gas, wood and tobacco during combustion, flue gas generated during waste incineration, and incompletely burned hydrocarbon substances contained in exhaust gas from motor vehicles;

(4) Indoor decoration and decoration materials such as paint, spray paint and its solvents, wood preservatives, coatings, plywood, etc. can release benzene, toluene, formaldehyde, phenols, xylene, formaldehyde and other volatile organic substances at room temperature;

(5) Volatile organic substances such as phenols, ethers and polycyclic aromatic hydrocarbons can be produced during the processing and use of cosmetics, organic pesticides, deodorants, disinfectants, preservatives and various detergents used in daily life;

(6) Various synthetic materials, organic adhesives and other organic products are oxidized and cracked at high temperatures, which can produce some low molecular organic pollutants;

(7) Some organic pollutants are generated during oxidation and decomposition of starch, fat, protein, cellulose, sugar, etc

Dye.

In addition, according to the survey results, the industrial distribution of industrial VOCs emission sources in China is shown in Figure 1-1.

Method/Step 2:

2.2 Hazards of VOCs

There are many kinds of VOCs, and their harm to human health and living environment is mainly reflected in the following aspects:

(1) Most VOCs have a pungent smell or odor, which can cause people's unpleasant senses. The ultra-low CEMS system seriously reduces people's quality of life. Odorous gas refers to all gas substances that stimulate the olfactory organs and cause people to be unhappy.

(2) VOCs have complex components, special smell, permeability, volatilization, fat solubility and other characteristics, which can lead to many discomfort symptoms in the human body. It also has toxic, irritating, teratogenic and carcinogenic effects, especially benzene, toluene, xylene and formaldehyde, which are harmful to human health. Long term exposure will cause anemia and leukemia. In addition, VOCs can also cause pathological changes in respiratory tract, kidney, lung, liver, nervous system, digestive system and hematopoietic system. With the increase of VOCs concentration, the human body will have nausea, headache, convulsions, coma and other symptoms.

(3) Most VOCs have photochemical reactivity. Under sunlight, VOCs will react with NOx in the atmosphere to form secondary pollutants (such as ozone) or intermediates with strong chemical activity (such as free radicals), thus increasing the surface concentration of smoke and ozone, which will endanger people's lives, and also endanger the growth of crops, even lead to the death of crops. In addition to reducing visibility, the smog caused by photochemical reaction can also produce ozone, peroxyacetonitrate (PAN), peroxybenzoyl nitrate (PBN), aldehydes and other substances that can stimulate people's eyes and respiratory system and endanger people's health. Photochemical smog pollution incidents have occurred in London, Tokyo and other cities.

(4) Some VOCs are flammable, such as benzene, toluene, acetone, dimethylamine and thiohydrocarbons. If static sparks or other ignition sources are encountered when the emission concentration of these substances is high, they are likely to cause fire. In recent years, fire and explosion accidents caused by VOCs occur frequently, especially in petrochemical enterprises.

(5) Some VOCs can destroy the ozone layer, such as chlorofluorocarbons. When it is exposed to ultraviolet radiation from the sun, it can generate photochemical reactions to generate chlorine atoms, thus catalyzing the destruction of ozone in the ozone layer. The reduction of ozone and the destruction of the ozone layer increase the amount of ultraviolet radiation reaching the ground. Ultraviolet radiation is harmful to human skin, eyes and immune system.

VOCS is ubiquitous in daily life, work, operation and other environments, so the detection and governance of VOCS should be strengthened and popularized.

3、 Legal basis for VOCs detection

Method/Step 1:

Safety production regulations

(1) Article 18 of the Regulations on the Safety Administration of Hazardous Chemicals (Decree No. 344 of the State Council of the People's Republic of China): The units that produce, store and use hazardous chemicals shall install alarm devices at the places where they are produced, stored and used.

(2) 5.3.1. c in General Principles for Safety and Health Requirements in Production Process (GB/T 12801 - 2008): Monitoring and testing instruments shall be configured for processes that generate hazards and harmful factors.

(3) Article 6 of the Regulations on Production License (Decree No. 397 of the State Council, 2004): An enterprise shall meet the following safety production conditions when obtaining a safety production license: (XI) There shall be detection, evaluation, monitoring measures and emergency plans for major hazard installations. (4) Code for Setting of On site Safety Monitoring Equipment in Tank Farm of Major Hazard Installations for Hazardous Chemicals (AQ 3036-2010)

Method/Step 2:

Occupational health regulations

(1) Article 23 of the Law of the People's Republic of China on the Prevention and Control of Occupational Diseases: The Employer shall set up alarm devices in toxic and harmful workplaces where occupational injuries may occur.

(2) According to Article 6.1.6 of the National Occupational Health Standards - Hygienic Standards for the Design of Industrial Enterprises (GBZ 1-2010), automatic alarm or detection devices should be designed according to the technical development level of automatic alarm devices in workplaces where acute occupational poisoning is likely to occur in combination with the production process and toxic characteristics.

(3) Occupational Exposure Limits for Hazardous Agents in the Workplace - Chemical Hazardous Agents (GBZ2.1-2007)

(4) Article 11 of the Regulations on Labor Protection in the Workplace Using Toxic Substances (Article 352 of the State Council in 2002): Automatic alarm devices shall be installed in workplaces where a large amount of toxic substances may suddenly leak or acute poisoning is likely to occur.

Method/Step 3:

Environmental protection regulations

(1) The 12th Five Year Plan for Scientific and Technological Development of National Environmental Protection (2011, Ministry of Environmental Protection) lists the "Automatic Monitoring System for Organic Pollutants" as a project to "support the research and development of key technologies, equipment and products".

(2) The Twelfth Five Year Plan for the Prevention and Control of Air Pollution in Key Areas (2012, Ministry of Environmental Protection) stipulates that "industrial VOCs emissions shall be gradually installed with online continuous monitoring systems, and VOCs environmental monitoring facilities shall be installed at the plant boundary".

(3) Guidance on Promoting the Joint Prevention and Control of Air Pollution to Improve Regional Air Quality (GBF [2010] No. 33) (XXIII) Local environmental protection departments should strengthen the supervisory monitoring of key enterprises and promote the installation of online monitoring devices for pollution sources.

Method/Step 4:

Production and use regulations

(1) Code for Design of Combustible Gas and Toxic Gas Detection and Alarm in Petrochemical Industry (GB50493-2009)

(2) Article 4.6.11 of Code for Fire Protection Design of Petrochemical Enterprises (GB50160-2008): The VOCs online monitoring system should be equipped with combustible gas alarm probe in the device that uses or produces Class A gas or Class A, B A liquid according to the principle of combining regional control with key control.

4、 Detection range of toxic VOCs

Method/Step 1:

Basis of determination

(1) 5.3.1 (4) in Code for Design of Combustible Gas and Toxic Gas Detection and Alarm in Petrochemical Industry (GB50493-2009), "The measurement range of toxic gas should be 0-300% of the higher allowable concentration or 0-300% of the allowable concentration for short-term exposure".

(2) National Occupational Health Standard Occupational Exposure Limits for Hazardous Factors in the Workplace (GBZ2.1-2007) 4.1 Allowable concentration of chemical substances in the air of workplace: PC-STEL of benzene is 10mg/m3 (2.87ppm)

(3) National Occupational Health Standard - Code for Setting Toxic Gas Detection and Alarm Devices in the Workplace (GBZ/T223-2009) 5.3 The detection range of gas detector is 0~10 times PC-STEL, and the smaller detection is ≤ 0.5 times PC-STEL

Method/Step 2:

Detection range of benzene

(1) According to the above provisions, the detection range of benzene is 2.87ppm × 3 = 8.61 ppm≈ 9 ppm

(2) At present, the actual measurement range of benzene detectors at home and abroad:

① Fixed: 0-10/20 ppm

② Portable: 0-1000/2000 ppm (mainly for leak detection)

5、 Setting of toxic VOCs detector alarm point (benzene as an example)

Method/Step 1:

Setting basis

(1) National Occupational Health Standard - Hygienic Standard for the Design of Industrial Enterprises (GBZ 1-2010) 6.1.6.3 The alarm value of toxic substances shall be set at least according to the toxicity of toxic gases and the actual situation on site. The prediction value is 1/2 of MAC or PC-STEL. For chemical substances without PC-STEL, the prediction value can be set at 1/2 of the corresponding overrun times; The alarm value is PC-STEL value. If there is no PC-STEL chemical substance, the alarm value can be set to the corresponding exceeding limit multiple value; The high alarm value shall be set after comprehensive consideration of toxic gas toxicity, operators, accident consequences, process equipment and other factors.

(2) 5.3.3 (3) In Code for Design of Combustible Gas and Toxic Gas Detection and Alarm in Petrochemical Industry (GB50493-2009), the alarm setting value of toxic gas should be less than or equal to 100 percent of the higher allowable concentration or the allowable concentration for short-term exposure.

(3) 4.3.6 Toxic gas alarm is divided into at least two levels in 4.3.6 of the Code for the Setting of On site Safety Monitoring Equipment in Tank Farm of Major Hazard Installations of Dangerous Chemicals (AQ3036-2010), and the threshold value of the first level alarm is 75% of the higher allowable concentration; The second level alarm value is 2 to 3 times of the higher allowable concentration.

Method/Step 2:

Alarm setpoint of benzene detector

(1) According to the above requirements, the alarm set value of benzene detector shall be:

① Low level alarm setting value: 1/2 of PC-STEL 3.08ppm (10mg/m3), about 1.5ppm (actually 3-5 ppm);

② High level alarm setting value: PC-STEL 3.08ppm (10mg/m3), about 3ppm (actually 5-7ppm).

(2) The recommended alarm setting value of benzene detector in practical application is:

① Low level alarm setting value: generally 1.5-3ppm (range 0-10ppm);

② High range alarm setting value: generally 3-7ppm (range 0-10ppm).

6、 Solutions

Method/Step 1:

Scheme introduction

The TVOC, VOC, VOCS gas wireless detection system solution of Shenzhen Xinli Technology Co., Ltd. based on wireless sensor network technology has the advantages of low power consumption, high accuracy, stable performance, and support for multiple communication methods and protocols. Based on the actual situation of the clean room environment in Huawei's southern factory, a set of practical solutions has been developed.

(1) There are two floors in total. Each floor is equipped with 15 wireless TVOC wireless gas sensors, which are powered by batteries and evenly distributed in every corner of the room. The TVOC gas concentration is uploaded to the XL90 management device in real time through wireless transmission upload;

(2) A total XL90 wireless management device receives the data of the following 15 TVOC wireless gas sensors on each floor. The receiving antenna of the XL90 wireless management device is located indoors and the transmitting antenna is located outdoors. The wireless management device on the second floor collects data in this way;

(3) Later, an XL91 intelligent gateway is installed in the central control room to receive the data uploaded by the two total XL90 wireless management devices, and provide real-time data to the upper computer software on the PC in the form of 485 or Ethernet after processing;

(4) The upper computer monitoring software provided can collect and display data in real time, provide curves and alarm records or output, and can consult historical data at any time to fully grasp the change of TVOC gas concentration in the clean room. 2. Structure Diagram

Method/Step 2:

Programme structure

Method/Step 3:

Scheme equipment list

(1) 30 wireless TVOC gas sensors, battery powered, 490MHZ sucker antenna

(2) 2 wireless management devices, XL90, 2 490MHZ sucker antennas

(3) 1 intelligent gateway, XL90, 1 490MHZ sucker antenna

(4) 1 set of data monitoring software, iView128 points

Method/Step 4:

Similar Performance Chart

Method/Step 5:

Scope of application

TVOC, VOC, VOCS gas detection system solutions are applicable to school scientific research, building construction, fire alarm, sewage treatment, industrial gas process control, boiler room, garbage treatment plant, tunnel construction, oil pipeline, gas station, underground gas pipeline maintenance, indoor air quality detection, safety protection in dangerous places, aerospace, military equipment monitoring, etc.