When the ITLUS tour was in North Dakota, we visited one of the main areas where fracking is taking place in the state. There is said to be a lot of oil deep in the ground in the state, but there are also significant reserves of lower quality lignite coal elsewhere in the state and close to the surface.

Lignite is generally regarded as a low-quality coal and high in moisture content and so is not highly regarded as a source of heat or energy. However, if you wish to gasify coal, this requires the addition of water which is already present in lignite and so this is regarded as a useful methodology to harness energy from this fuel source.

Gasifying coal was conceived as a process back in the 1970s during the global energy crisis. This is one of two plants in the world and the only one in the US which converts lignite coal to synthetic natural gas to be used as an energy source.

The plant and lignite mine were located near Beulah in North Dakota. The gasification process effectively uses coal, water and oxygen in huge quantities. So, the fact that lignite contains water is a potential advantage.

The daily requirement in the plant is 18,000t of lignite, plus 31,000t oxygen and 25m litres of water. This requires a lot of movement of products in different directions. The water comes in by pipe from a reservoir and the synthetic gas goes out by pipeline. The facility gasifies close to 6m tonnes (t) of lignite coal annually to produce the range of products listed later.

Many lives

The plant began processing lignite into synthetic natural gas (SNG) in 1984. However, because the political and energy environments had changed considerably, the owners went bankrupt within a year. The US Department of Energy acquired the plant in 1985 and operated it for a few years. It was acquired by Dakota Gas in 1988 who subsequently invested substantial capital to help broaden the product base produced from the plant.

It is now known as the Great Pains Synfuels Plant and it is now manufacturing a range of products, as well as natural gas. In addition to SNG, the plant produces a range of other products, including nitrogen fertilisers, to help spread the commercial risk in a range of markets.

A square-mile facility

The scale of the facility is impressive. As well as the quantities of inputs stated previously, it produces an average of 153m ft3 (4.332m3) of SNG per day, the bulk of which is piped east to Iowa for network distribution. The synfuels plant also generates between 2.5m and 3mt of carbon dioxide per year, which goes mainly to Saskatchewan in Canada.

This was the first gasification plant to be constructed and so it is reasonable to ask how it was designed and constructed. Well, the answer may surprise you somewhat. It was actually designed and constructed as a 1:32 scale model, which showed every single pipe and process and this was then taken to the site to aid construction. It was all the engineers had to go by.

The 1:32 scale model of the plant cost a whopping $8m in 1980, so it is hardly surprising that it is still there today and remains a very impressive structure. The initial plant cost $2.1bn and began operating in 1984. The major raw material was lignite and this was available locally in copious amounts. It is mined from opencast mines and hauled to the plant. This is all big-gear activity, which includes giant drag lines in the mines with scoops that are at least five motor cars wide with proportionately huge dumpers for transport.

Coal haulers

We occasionally hear about the massive equipment used in working mines. In the case of lignite, this usually means big drag-lines, which dig out the rock, huge loaders for loading and then big haulage gear.

All of these were to be seen at the facility, as were coal haulers. These are huge bottom-opening dumpers used to transport over 300t loads from the mine.

These Kress machines, made in Illinois, are monstrous bits of gear with two wheels at each corner and over 2,000ph under the bonnet at the rear of the machine. With a purchase cost in excess of $4m, they need to be worked hard and continuously.

These machines use a lot of CAT components and come with a high degree of manoeuvrability, despite their huge size. They appear to run on suspension to provide fast transport and a smooth ride. The machine can turn almost within its own length.

Gasification process

Gasifying coal involves the dismantling of its molecular structure using combustion and reassembling the resulting hydrogen and carbon atoms as methane gas. The process is called methanation. This is happening simultaneously in 14 different gasifiers.

Steam and oxygen are injected into the bottom of the lignite beds, causing intense combustion and temperatures of around 1,204oC. The hot gases break down the molecular bonds of the coal and the steam, releasing compounds of carbon, hydrogen, sulphur, nitrogen and other substances to form a raw gas that exits the gasifiers. This is then cooled and different compounds are purified out and the gas is cleaned.

Methanation occurs when the cleaned gas is passed over a nickel catalyst causing carbon monoxide and any remaining carbon dioxide to react with free hydrogen to form methane. The bulk of the carbon dioxide is removed for sale during the process and the methane is cooled, dried and compressed to enter the pipeline.

Range of products

The Dakota Gasification Company has invested over half of the initial construction cost again in the Great Plains Synfuels Plant. This has enabled it to produce many different end products for sale in different markets. These range from chemicals to gasses to nitrogen fertiliser products.

  • Synthetic natural gas (SNG): about 41.6m dekatherms are produced annually.
  • Ammonium sulphate fertiliser: approximately 95,200t are produced yearly and marketed under the name Dak Sul 45.
  • Anhydrous ammonia: used as a source of gaseous nitrogen for agriculture and as a feedstock for producing various chemicals. The annual production is about 362,000t per year.
  • Carbon dioxide: mainly used in the oil recovery business and up to 3mt are shipped to Canada annually.
  • Crude cresylic acid: used in the manufacture of pesticides, enamel solvent, resins, and antioxidants. About 13.6mt are produced annually.
  • Krypton and xenon gases: used for speciality lighting and for thermopane window insulation. About 3.5m litres are produced annually.
  • Liquid nitrogen: used for food processing refrigeration, as an oil well additive, and in chemical processes. About 44,300 litres are produced annually.
  • Naphtha: this can be used as a gasoline blend, for solvent manufacture and in benzene production. About 31.8m litres are produced annually.
  • Phenol: used to produce resins for plywood manufacture and also in the casting industry. About 12,700t are produced annually.
  • Tar oil: this is effectively a fuel and about 20.4m litres are anticipated to be produced for sale annually.

    • When we visited in late June, the construction of a new urea manufacturing plant was well under way in the facility. This was to further expand the output capability of the plant and add another product to the market where urea is becoming an increasingly important nitrogen source globally.

    The development included investment in both manufacture and storage on site. It was estimated that this plant would produce about 1,000t of urea per day, or close to 350,000t per annum.

    When we visited, we could see the different construction projects at the site, including the shell for a giant urea store. However, a few weeks later, a huge storm hit and left over 700t of mangled steel entangled over the various bits of construction equipment that were in the store area at the time. Photos looked a bit like gossamer sitting on the obstacles that lay beneath.

    Watch a news report on the disaster below: