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Portable Room Temperature Sulfur Dioxide Sensor
  • Overview
  • Quick View Leaflet
  • Detail Technical Brochure
  • Application Procedure
Portable Room Temperature Sulfur Dioxide Sensor
Overview

SO2 is one of the highly toxic gases, which poisons humans by inhalation. Sulfur dioxide is released when compounds containing sulfur, such as fossil fuels like coal are burned. Nanocrystalline SnO2 thin film based portable sensor detects SO2 from 2 ppm onwards at room temperature with fast response and recovery. The sensor works on the principle of decrease in electrical resistance upon a chemical interaction with SO2.

Commercially available SO2 sensors are usually operated at high temperature to achieve reversibility and fast response. Shortcomings of high temperature operation of these sensors are: shorter life time, does not have portability and is not favorable in explosive environment.

Portable Room Temperature Sulfur Dioxide Sensor

   Sensor for on-site monitoring

 

Quick View Leaflet

Gas sensors are usually operated at high temperature to achieve fast response and reversibility and this leads to shorter lifetime of the sensor. Nanocrystalline SnO2 thin films fabricated from the thermal decomposition of Langmuir Blodgett (LB) film precursor, exhibit room temperature gas sensitivity comparable to that required for air quality monitoring. LB technique offers control over SnO2 film thickness and crystallite size. By controlling the crystallite size and film thickness room temperature operation is achieved. The sensor is specific to SO2 gas at room temperature and shows fast response and recovery without any carrier gas flow. The stability studies indicated that these sensors are stable at least for a year with no significant change in sensitivity.

ADVANTAGES

  • Room temperature operation, low power requirement and portable.

  • Reliable over a period of 1 year.

SPECIFICATIONS

  • SO2 detection range
: 1-30 ppm
  • Operating temperature
: Room temperature
  • Safe operating temperature
: 25-50°C
  • Response time (time to reach 90% of the resistance change)
: 50 sec
  • Recovery time (time to reach 10% of the resistance change)
: 30 min
  • Response at 2 ppm SO2 [(Rair - Rgas)x100]/Rair
: 80-100%
  • Selectivity for SO2 (in comparison to CH4, CO, NH3, NO2, H2 etc.)
: Detectable increase in current only for SO2 among these gases
  • Life time under operating conditions
: ~ 1 year


APPLICATIONS

  • Sulfur- Iodine cycle for Hydrogen production

  • Coal based power plants

  • Industries where sulfuric acid at high temperature is used

  • Pollution monitoring agencies
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Detail Technical Brochure


SO2 is one of the highly toxic gases, which poisons humans by inhalation. SO2 combines with water to form sulfuric acid and can irritate the throat by inhalation. Sulfur dioxide is released when compounds containing sulfur, such as fossil fuels like coal are burned. Its long-term (8 h) and short-term (10 minutes) exposure limits are 2 and 5 ppm respectively. The nanocrystalline SnO2 thin film based sensor detects SO2 with high sensitivity, selectivity, and is stable for more than 1 year. Commercially available SnO2 gas sensors are usually operated at high temperature to achieve reversibility and fast response. High temperature operation causes shorter life time and not favorable in explosive environment.

WORKING PRINCIPLE

The sensor works on the principle of decrease in electrical resistance upon a chemical interaction with SO2. This change is calibrated and displayed directly on a digital monitor as SO2 concentration in ppm.

Preparation of SnO2 thin film and sensing mechanism :

The sensor element is nanocrystalline SnO2 thin film which is prepared by using Langmuir- Blodgett (LB) film precursors. Multilayer LB films (100 ± 20 layers) of ODA–stannate complex deposited on quartz are decomposed at 600 °C in the presence of ambient oxygen.

Nanocrystalline SnO2 surface has net negative charge due to the large number of surface species O2-,O- present on the SnO2 surface. SO2 is a strong reducing gas. When SO2 gas is injected into the gas testing chamber containing SnO2 thin film, it reacts with surface oxygen species ( O2-,O-) forming SO3 while releasing electrons to the SnO2 conduction band, thereby decreasing the resistance. Ambient oxygen subsequently chemisorbs on the oxygen vacant SnO2 surface attracting electrons from SnO2 conduction band during the recovery phase. This makes the sensor specific to sulfur dioxide at room temperature.

SPECIFICATIONS

Property Value
  • Drift in base current

: 2-3 %

  • Sensitivity (towards SO2)
    S=((Rair-RSO2)x 100)/Rair
: 80-100 % at 2 ppm of SO2
  • Response time
: 50 sec
  • Recovery time (after opening of stopcocks, without any carrier gas flow) 
: 30 min for 90 % recovery
  • Range of the sensor 
: 1-30 ppm
  • Repeatability 
: 90%
  • Percentage error in sensitivity
: 10-15%
  • Sensor Housing
: Water and light proof

Selectivity in presence of other gases

Selectivity and Sensitivity (as change in current )
Gas Change in current Gas concentration
  • NH3

decrease

1 ppm

  • H2

no change

6 ppm
  • H2O

no change

< 97% RH
  • CO

no change

6 ppm
  • H2S

increase

> 1 ppm (interfering gas)
  • SO2

increase

> 1 ppm
  • NO2

decrease (with recovery only after heating at 70°C for 2 hours)

> 85 ppb
  • Conclusion
Sensor is highly selective for SO2 in presence of other gases (except for H2S gas) as mentioned above in the table.

APPLICATIONS

  • Sulfur- Iodine cycle for Hydrogen production
  • Coal based power plants
  • Industries where sulfuric acid at high temperature is used
  • Pollution monitoring agencies

REQUIREMENTS FOR SENSOR PREPARATION

A. Raw materials

  1. Chemicals: Octadecyl amine, Choloroform and Sodium stannate
  2. Distilled water for making sodium stannate solution
  3. Quartz substrate (1cm x 2 cm) for SnO2 film deposition
  4. Gold (24 ct)

B. Equipments

  1. LB trough or stepper motor controlled deposition unit
  2. Furnace for heating at 600°C
  3. Thermal evaporation system for gold contact electrode deposition
  4. Enclosure for the SnO2 film, connector cable
  5. Calibration chamber
  6. Gas canisters and syringes (Electronics for the sensor is not included)

C. Space

  • The space requirement is approximately 12ft by 15ft to comfortably accommodate the process equipments such as LB trough, CVD system, Furnace, space for assembling and packaging, testing and calibration setup etc.

MANPOWER REQUIREMENT

2 Numbers :

  • 1 person with B.Sc. degree in Physics/Chemistry
  • 1 person with diploma in Electrical/Electronics

Who Should apply


Interested parties with Engineering & Scientific knowledge, good financial background and adequate experience of products manufacturing & fabrication with technical capability in the area of interested technology and having or interested in setting –up facilities for production would be preferred.


How to apply

Send your Technology Transfer Application form duly filled and signed alongwith a Demand Draft/Bankers cheque of Rs. 500/- (for Indian entities) or US $50/- (for foreign entities) drawn in favour of “Accounts Officer, BARC” as application processing fee on following address: 

Head, Technology Transfer and Collaboration Division 
Bhabha Atomic Research Centre,
Trombay, Mumbai – 400 085, India.

Fax : +91-22-25505151


Note:Applications without processing fee as applicable above of Rs. 500/- or US $50/- for each technology will not be considered.


Click here for Technology Transfer Application Form

Contact Us

Head, 
Technology Transfer and Collaboration Division
Bhabha Atomic Research Centre,
Trombay, Mumbai 400 085.

Tel  : 091-022-25595137
Fax : 091-022- 25505151
Email : technology@barc.gov.in

How to apply

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