Typical processes and associated gas detection issues

The production of electricity begins with the loading of fuel into a power plant. The fuel is burned in a giant furnace, and heat energy is released. In the boiler, heat from the furnace flows around pipes that are full of cold water. The heat boils the water and turns it into high-pressure steam. The heated steam flows at high pressure around a turbine wheel, the blades of which start turning as the steam flows past.

The turbine is linked by an axle to a generator, so the generator spins around with the turbine blades. As it spins, the generator uses the kinetic energy from the turbine to make electricity. Boiling hot water from the steam turbine is cooled in a condenser (which is a form of heat exchanger) then sprayed into giant cooling towers and pumped back for reuse.

The transport and pulverisation of coal poses a high risk of combustion. Fine coal dust becomes suspended in air and highly explosive. The smallest spark, for example from plant equipment, can ignite the dust cloud and cause an explosion that sweeps up more dust, which explodes in turn, and so on in a chain reaction. Coal power plants now require combustible dust certification, in addition to hazardous gas certification.

Coal power plants generate large volumes of carbon monoxide (CO) which is both highly toxic and flammable and must be accurately monitored. A toxic component of incomplete combustion, CO comes from boiler casing leaks and smouldering coal. It is vital to monitor CO in coal tunnels, bunkers, hoppers and tipper rooms, along with infrared-type flammable gas detection to detect pre-fire conditions.

Hydrogen must be monitored, to prevent seal-oil system fires, unscheduled shutdowns and to protect personnel from fire. Hydrogen burns with a pale blue, almost invisible, flame that can cause serious injuries and severe equipment damage.

In addition, power plants must have back-up batteries, to ensure the continued functioning of critical control systems in cases of power outage. Battery rooms generate considerable hydrogen, and monitoring is often carried out in conjunction with ventilation.

The addition of disinfectant chemicals to the cooling tower reservoir is to prevent the build-up of micro-organisms. Ammonia is also dosed to maintain optimal pH in the system. Chlorine, ozone and ammonia are strong toxic gases and should be monitored in case of leaks. Leak monitoring is required in the chemical storage and dosing areas.

Although non-toxic, SF6 is considered the worst greenhouse gas, having an atmospheric lifetime above 1,000 years. The use and storage of SF6 (and other fluorinated greenhouse gases, often called F-gases) are regulated in the US and EU. SF6 is also costly, so any leakage generates operational inefficiencies and higher operating costs.