4 Gas Detection CARBON MONOXIDE TOXIC AND FLAMMABLE GAS DETECTION
Gas detection is designed to protect people and plant. The risk to people comes from both toxicity and any potential fi re or explosion. For the plant, the physical damage of a fi re or explosion is the main hazard.
is not common to focus on the toxic gas detection requirements. Flue gas testing on a boiler
Some gases such as carbon monoxide and ammonia are both fl ammable and toxic. The toxic limit is generally much less than the fl ammable limit. Portable devices designed to protect people must be confi gured with an appropriate alarm setting at the toxic level. Fixed gas detection equipment installed to protect plant items may be confi gured with a higher alarm setting at 50% of the LEL.
Carbon monoxide (CO) is present in syngas, which is produced when waste, biomass or coal is gasifi ed. Syngas is also formed when natural gas is reformed to produce hydrogen for ammonia or other applications. CO can also be present in boiler fl ue gases, if the combustion of natural gas is incomplete.
Maintenance and gas testing on an industrial boiler
Pellistor sensors are low-cost, but suffer from drift, are infl uenced by poisons, and they are not considered to be fail safe devices. To overcome these issues, IR sensor technology has been introduced for fl ammable gas detection. IR sensors have been implemented in industrial applications.
An attraction of the IR sensor is that optical systems are regarded as being fail safe. However, there is still a requirement for regular calibration and cleaning of the optical surfaces. And the price tag of the sensor can be two to three times more than a pellistor.
Hong Kong Towngas production with reforming of hydrocarbons to syngas Syngas calls for carbon monoxide
gas detection Syngas is produced from hydrocarbons when they are heated. The main constituents of syngas are CO, hydrogen, and carbon dioxide. Syngas can be upgraded to convert the CO to yield additional hydrogen. More than 95% of the hydrogen produced today worldwide is made in this way. Syngas and the toxic CO gas molecule are unavailable hazards of the hydrogen production.
Town gas was commonly used in the USA and Europe in the early to mid-20th century. It was a type of syngas derived from coal gasifi cation. Syngas from liquid and gaseous hydrocarbon reforming is still extensively used in Hong Kong and Singapore as one of the main piped gases for heating and cooking in domestic and commercial buildings. In these grids, fl ammable gas detectors are the most common way to monitor for leaks. It
Safe operations rely on protecting plant and people with gas detection Carbon monoxide –
hidden in boiler fl ue gas Gas detection of carbon monoxide (CO) has been undertaken in industrial premises and commercial buildings for decades. It is
The most widely used LEL, or fl ammable gas sensor is a pellistor bead that works on a catalytic oxidation principle. The sensor is integrated into a Wheatstone bridge circuit. As fl ammable gases fl ow over the sensor, it becomes hot and its resistance increases. This is identifi ed by the electronic circuit.
Testing fl ue gases from a domestic boiler
common in boiler rooms for heating and steam generation where incomplete combustion of gas can result in CO poisoning due if the fl ue gas leaks. Portable devices can be used to detect CO in the atmosphere and protect personnel.
The toxic risk posed to personnel for the limited time that they are present in the boiler house. However, the fl ammable hazard of the CO and other boiler room gases such as methane, or hydrogen in the future poses a 24 / 7 risk of explosion with the potential for collateral damage. Many heating system boilers are in the basement of high-rise buildings. An explosion in this location could result in collapse of the tower block with multiple fatalities. Therefore, the fl ammability risk must continuously be monitored with suitable gas detection equipment.
Incomplete combustion results in toxic CO in the fl ue gas
If the gas detection system is focused on identifying the toxic hazards of CO, an electrochemical sensor would be appropriate. This is a mature, low cost and reliable sensor technology. The generally accepted alarm levels for CO are 100ppm for a 15-minute exposure and 20 ppm over an 8-hour shift. These are commonly implemented as alarm levels in CO gas detection systems.
Author Contact Details Stephen B. Harrison • sbh4 GmbH • Address: Kranzlstraße 21, 82538 Geretsried, Germany • Tel: +49 (0)8171 24 64 954 • Email:
sbh@sbh4.de • Web:
www.sbh4.de
AET ANNUAL BUYERS’ GUIDE 2024
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
