Fuel check (11): what is the fossil fuel hard coal??

The fossil fuel hard coal has been providing us with heat since the Middle Ages. The first evidence of this comes from the late 12th century. Century from Liège in Belgium and Aachen in Germany. In the Ruhr area, people began digging for coal around 1370. In 2017, 2.7 million metric tons of the fossil fuel hard coal were produced in the Ruhr area. In the same year, Germany also imported 3.4 million tons of hard coal from the EU. Here we explain why the fossil fuel hard coal once had what it takes to keep us warm, but now urgently needs to be phased out as an energy source for generating electricity and heat.

What is hard coal?

Black. Hard. Solid. This is hard coal. The sedimentary rock, which also often has a greasy sheen, consists of

  • to more than 50 percent of its weight
  • and to more than 70 percent of its volume

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How hard coal was created?

Hard coal was created when, almost 300 million years ago, plants died as a result of climate change and sank into the swamp of primeval forest that covered what is now Germany. Due to the lack of oxygen, the sunken plant parts were not decomposed by aerobic bacteria, for which oxygen is existential, and thus did not rot. Instead, they became peat under exclusion of air. The is considered the first stage of the so-called incarbonation (carbonization of plants), in which plants turn into hard coal. The longer the carbonization process takes, the less oxygen and hydrogen the coal contains. Depending on the duration of the coalification process, first peat, then lignite, hard coal and finally graphite are produced.

It took a lot of pressure to turn peat into hard coal. This came with the oceans, which later flooded the swamps and brought with them lots of heavy sand and debris, which were deposited and – in addition to the pressure caused by the ocean water itself – in turn exerted pressure on the underlying strata. This process was repeated over thousands of years. The growing masses of earth pressed the water out of the peat. This process was accompanied by high temperatures and complex biochemical processes. This is how peat first became lignite. We will deal with this in detail in a separate part of our fuel check, we promise.

With the growing layers on top, the lignite layer "sank" deeper and deeper, pressure and temperature increased and finally the lignite became hard coal.

How did the coal seams in North Rhine-Westphalia come to the surface again?

The Planet Wissen portal explains this process by the fact that Europe separated from North America in the Tertiary period, about 50 million years ago. The Rhine rift had sunk in the process, connecting the North Sea with the Mediterranean Sea. Continental plates had crashed into each other and the Alps had unfolded. Besides, fire struck from volcanoes. In what is now North Rhine-Westphalia, the Rhenish-Westphalian shale mountains were growing at the time. The hard coal layers, which were formed ages ago, were lifted up between the Rhine, Ruhr and Lippe rivers as a result of earth faults. According to the Tagesschau online, the hard coal layers (also called coal seams) extend over many square kilometers. In the Ruhr area, coal deposits down to a depth of 1.500 meters more than such 100 seams between them. According to this, however, only the thickest.

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How and when was hard coal discovered as a fuel??

There are legends about the discovery of hard coal, but nobody really knows what is true about them. Presumably coal was already used like other mineral resources in the Neolithic Age. However, historical evidence shows that it was actively mined by the Celts in ancient times. There is written evidence that as early as the late 12th century, coal was being burned. In the nineteenth century, a coal mine near Liège (now Belgium) extracted coal. At about the same time, hard coal was also mined near Aachen, Germany.

What hard coal is used for?

Hard coal was primarily used to generate heat and electricity, i.e. thermal and electrical energy. According to Tagesschau online, every tenth kilowatt-hour of electricity in Germany is generated with domestic hard coal. And Germany’s heat mix, which we recently presented here on the blog, put coal’s share of heat generation in 2016 at 9.1 percent (131 billion kilowatt hours (kWh), although it did not break down coal types into hard coal, lignite& Co. was broken down).

According to Tagesschau online, there are other purposes for which hard coal is used: Coke, which is obtained in the so-called dry distillation in coke ovens, is used as fuel for blast furnaces and foundries in which iron and iron steel are produced and processed. Hard coal is also used as a raw material in the chemical industry, where it is used to produce sulfur, tar, town gas and ammonia, among other things. In addition, gasoline can be produced in a process called coal hydrogenation.

What makes hard coal fuel?

In addition to carbon contents of between 75 and 95 percent, hard coal also contains substances such as metals, water, nitrogen and sulfur. Because of its high carbon content, hard coal burns for a very long time and very hot. The calorific value of hard coal is between 32 and 36 megajoules per kilogram (MJ/kg).

Are there qualitative differences in hard coal?

Hard coal types are differentiated according to their "age" and thus according to the carbon contents and calorific values resulting from the varying duration of coalification (from young to old) in:

  • Flame coal (with about 76 percent carbon content),
  • Gas-fired coal (82 percent),
  • Gas coal (85 percent),
  • Bituminous coal (88 percent)
  • Lean coal (90 percent)
  • And anthracite coal (about 92 percent).

How to make heat from hard coal?

Hard coal is mainly burned as a solid fuel to generate heat by combustion.

How to make electricity from coal?

Coal-fired power plants burn coal and use the heat released to generate steam, which in turn drives steam turbines that generate electricity.

What happens when hard coal is burned??

When hard coal is burned, air pollutants are formed, including sulfur dioxide (SO2), nitrogen oxide (Nox), dust and traces of heavy metals. According to Wikipedia, power plant coal contains up to 12 percent non-combustible solid components (so-called ash content). Modern coal-fired power plants would cut emissions

  • in flue gas desulfurization plants of sulfur dioxide,
  • with catalytic or non-catalytic denitrification of nitrogen oxides
  • and clean it from dust (fly ash) by means of electrostatic precipitators,

writes the Wiki further. After that, the greenhouse gas carbon dioxide, which is released into the atmosphere, would remain the most important.

Who still heats with hard coal at all??

According to the Federal Environment Agency, 13 million gas boilers, 5.6 million oil boilers and 0.7 million solid fuel boilers were in operation in Germany in 2016. In addition, there were almost 12 million so-called single-room furnaces such as wood-burning stoves or tiled stoves that can be fired with wood or coal.

Hard coal is often burned in the private sector in so-called continuous combustion stoves. They are designed for very high temperatures and keep the embers stable for a long time – without the need to add coal frequently. In contrast to traditional fireplaces, the hard coal burns slowly in a furnace trough like in a funnel in endurance furnaces. The air supply is regulated from below.

In addition, large coal-fired heating systems with automatic charging are also in operation in private buildings, which ensure fully automatic heating operation over several weeks. They work similarly to wood pellet boilers. At the boiler there’s a fuel tank for the coal. It arrives there via a conveying system with a screw conveyor.

Why is there no future for hard coal as a fuel??

Hard coal as a fuel has had its day: its disadvantages, including

  • Pollution from the exhaust gases
  • of controlled coal combustion
  • and the uncontrolled eruption of coal fires in seams near the surface (in China alone, 25 million tons of hard coal are burned annually, according to Wikipedia)

now make them unsustainable as a fuel. Especially since there are renewable alternatives to generate heat and electricity in an environmentally friendly way.

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But the phase-out of this fuel is being approached too hesitantly in this country – at least on the part of politicians and industry:

The so-called Coal Commission has just set the end date for the phase-out of coal-fired power generation in Germany: 2038. No reason to celebrate, says Volker Quaschning, professor of regenerative energies at HTW Berlin, because that is "far too late to keep the climate impact within reasonable bounds. Actually, the coal phase-out should have been fixed more than ten years ago. Instead, new coal-fired power plants were blithely built. Even in the year 2020 a new coal-fired power station is to be connected to the grid, although experts could not see any sense in it already at the planning stage. Now we taxpayers are supposed to pay for this and other corporate blunders. That is absurd. 50 billion of taxpayers’ money is now to be wasted to softly cushion the mistakes made by politicians and energy companies without solving the open questions of climate protection. I cannot see any success in this."Environmental protection organizations such as BUND are also calling for an earlier coal phase-out.

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