Australia, China, CO2 emissions, coal seam fire, cumbria, Cumbria GDF, England, environment, environmental impact, fire, flammable geology, hubris, kerogen, methane, Mississippi, Mississippi nuclear waste, New Zealand, nuclear energy, nuclear waste, oil shale, Pennsylvania, petroleum, UK, US
Coal seam fires, like nuclear energy and waste, point to the hubris of humankind:
“Hubris /ˈhjuːbrɪs/, also hybris, from ancient Greek ὕβρις, means extreme pride or arrogance. Hubris often indicates a loss of contact with reality and an overestimation of one’s own competence, accomplishments or capabilities, especially when the person exhibiting it is in a position of power.” http://en.wikipedia.org/wiki/Hubris
Nuclear waste and these old mine fires must be mastered. This mastery will only come with time, innovation and appropriate investment. In the interim humans must learn from their mistakes and stop nuclear energy and new
wastes. Also, humans should stop coal mining.
The flammable potential of the geology should be taken into consideration in the placement of nuclear waste dumps (and also non-nuclear dumps). Imagine flammable gases from a nuclear waste dump meeting an old coal seam or natural gas reserve? Or oil shale (kerogen)? Or petroleum? We think particularly of proposed nuclear waste sites in Cumbria (UK) and Mississippi (USA) in this context. It is something which will require careful evaluation in Australia, Germany, or any other country in the process of siting a nuclear waste facility.
“Coal Seam – Mine Fire
From Wikipedia, the free encyclopedia
View of a coal fire (China). By Rueter, Horst via Wikimedia.
A coal seam fire or mine fire is the underground smouldering of a coal deposit, often in a coal mine. Such fires have economic, social and ecological impacts. They are often started by lightning, grass, or forest fires, and are particularly insidious because they continue to smoulder underground after surface fires have been extinguished, sometimes for many years, before flaring up and restarting forest and brush fires nearby. They propagate in a creeping fashion along mine shafts and cracks in geologic structures.
Coal fires are a serious health and safety hazard as well as affecting the environment by releasing toxic fumes, reigniting grass, brush, or forest fires, and causing subsidence of surface infrastructure such as roads, pipelines, electric lines, bridge supports, buildings and homes. Whether started by humans or by natural causes, coal seam fires continue to burn for decades or even centuries until either the fuel source is exhausted, a permanent groundwater table is encountered, the depth of the burn becomes greater than the ground’s capacity to subside and vent, or humans intervene. Because they burn underground, coal seam fires are extremely difficult and costly to extinguish, and are unlikely to be suppressed by rainfall. There are strong similarities between coal fires and peat fires.
Across the world, thousands of underground coal fires are burning at any given moment. The problem is most acute in industrializing, coal-rich nations such as China. Global coal fire emission are estimated to include 40 tons of mercury going into the atmosphere annually, and three percent of the world’s annual CO2 emissions.
Coal seam fires can be divided into near-surface fires, in which seams extend to the surface and the oxygen required for their ignition comes from the atmosphere, and fires in deep underground mines, where the oxygen comes from the ventilation.
Mine fires may begin as a result of an industrial accident, generally involving a gas explosion. Historically, some mine fires were started when bootleg mining was stopped by authorities, usually by blowing the mine up. Many recent mine fires have started from people burning trash in a landfill that was in proximity to abandoned coal mines, including the much publicized Centralia, Pennsylvania, fire, which has been burning since 1962. Of the hundreds of mine fires in the United States burning today, most are found in the state of Pennsylvania.
Some fires along coal seams are natural occurrences. Some coals may self-ignite at temperatures as low as 40 °C (104 °F) for brown coal in the right conditions of moisture and grain size. The fire usually begins a few decimeters inside the coal at a depth in which the permeability of the coal allows the inflow of air but in which the ventilation does not remove the heat which is generated.
Two basic factors determine whether spontaneous combustion occurs or not, the ambient temperature and the grain size:
The higher the ambient temperature, the more quickly the oxidation reactions proceed.
The grain size and structure determine its surface area. Kinetics will be limited by availability of reactant, which in this case is carbon exposed to oxygen.
Wildfires (lightning-caused or others) can ignite the coal closer to the surface or entrance, and the smouldering fire can spread through the seam, creating subsidence that may open further seams to oxygen and spawn future wildfires when the fire breaks to the surface. Prehistoric clinker outcrops in the American West are the result of prehistoric coal fires that left a residue that resists erosion better than the matrix, leaving buttes and mesa. It is estimated that Australia’s Burning Mountain, the oldest known coal fire, has burned for 6,000 years.
Globally, thousands of inextinguishable mine fires are burning, especially in China where poverty, lack of government regulations and runaway development combine to create an environmental disaster. Modern strip mining exposes smoldering coal seams to the air, revitalizing the flames.
Rural Chinese in coal-bearing regions often dig coal for household use, abandoning the pits when they become unworkably deep, leaving highly combustible coal dust exposed to the air. Using satellite imagery to map China’s coal fires resulted in the discovery of many previously unknown fires. The oldest coal fire in China is in Baijigou and is said to have been burning since the Qing Dynasty (before 1812).
Besides destruction of the affected areas, coal fires often emit toxic gases, including carbon monoxide, sulfur dioxide and methane. China’s coal fires, which consume an estimated 20–200 million tons of coal a year, make up as much as 1 percent of the global carbon dioxide emissions from fossil fuels. One of the most visible changes will be the effect of subsidence upon the landscape. Another local environmental effect, can include the presence of plants or animals that are aided by the coal fire. The prevalence of otherwise non-native plants can depend upon the fire’s duration and the size of the affected area. For example, near a coal fire in Germany, many Mediterranean insects and spiders were identified in a region with cold winters, and it is believed that elevated ground temperatures above the fires permitted their survival.
Extinguishing coal fires
In order to thrive, a fire requires fuel, oxygen, and heat. As underground fires are very difficult to reach directly, firefighting involves finding an appropriate methodology which addresses the interaction of fuel and oxygen for the specific fire in question. A fire can be isolated from its fuel source, for example through firebreaks or fireproof barriers. Many fires, particularly those on steep slopes, can be completely excavated. In the case of near-surface coal seam fires, the influx of oxygen in the air can be interrupted by covering the area or installing gas-tight barriers. Another possibility is to hinder the outflow of combustion gases so that the fire is quenched by its own exhaust fumes. Energy can be removed by cooling, usually by injecting large amounts of water. However, if any remaining dry coal absorbs water, the resulting heat of absorption can lead to re-ignition of a once-quenched fire as the area dries. Accordingly, more energy must be removed than the fire generates. In practice these methods are combined, and each case depends on the resources available. This is especially true for water, for example in arid regions, and for covering material, such as loess or clay, to prevent contact with the atmosphere.
Extinguishing underground coal fires, which sometimes exceed temperatures of 540°C (1,000°F), is both highly dangerous and very expensive.
Near-surface coal seam fires are routinely extinguished in China following a standard method basically consisting of the following phases:
Smoothing the surface above the fire with heavy equipment to make it fit for traffic.
Drilling holes in the fire zone about 20 m apart down to the source of the fire, following a regular grid.
Injecting water or mud in the boreholes long term, usually 1 to 2 years.
Covering the entire area with an impermeable layer about 1 m thick, e.g., of loess.
Planting vegetation to the extent the climate allows.
Efforts are underway to refine this method, for example with additives to the quenching water or with alternative extinguishing agents.
Underground coal seam fires are customarily quenched by inertization through mine rescue personnel. Toward this end the affected area is isolated by dam constructions in the galleries. Then an inert gas, usually nitrogen, is introduced for a period of time, usually making use of available pipelines.
In 2004, the Chinese government claimed success in extinguishing a mine fire at a colliery near Urumqi in China’s Xinjiang province that had been burning since 1874. However, a March 2008 Time magazine article quotes researcher Steven Q. Andrews as saying, ‘I decided to go to see how it was extinguished, and flames were visible and the entire thing was still burning…. They said it was put out, and who is to say otherwise?'
A jet engine unit, known as Gorniczy Agregat Gasniczy (GAG), was developed in Poland and successfully utilised for fighting coal fires and displacing firedamp in mines.
Current research and new developments in extinguishing fires
Time magazine reported in July 2010 that less expensive alternatives for extinguishing coal seam fires were beginning to reach the market, including special heat-resistant grouts and a fire-smothering nitrogen foam, with other innovative solutions on the way. Bold added for emphasis.
The original wikipedia article explains fire detection and has links to mine fires in the following countries along with the references. http://en.wikipedia.org/wiki/Coal_seam_fire :
6.7 New Zealand
6.9 South Africa
6.10 United States