Coal liquefaction, CTL ( English Coal to Liquids ), coal liquefaction - technology for producing liquid fuel from coal raw materials. It allows the use of traditional gasoline consumers (for example, motor vehicles) in conditions of oil shortage.
At the beginning of the XXI century. The following main processes of coal processing with the final production of liquid products are known: gasification followed by the production of synthetic fuels based on synthesis gas , hydrogenation , pyrolysis , etc. " Thermal dissolution ." The optimal dissolution rate for most solid fossil fuels is in the range of 380-450 ° C, pressure 2-15 MPa, the duration of the process is 20-60 minutes. Depending on the type of coal and the liquefaction process, the yield of liquid products at the level of 75-85% is achieved.
It is predicted that by 2030 the share of liquefied coal in the overall structure of fuel resources will reach approx. 20%.
Content
Historical background
Coal liquefaction was originally developed at the beginning of the 20th century. The most famous CTL ( Coal into Liquid Fuel ) process is the Fischer-Tropsch (FT) synthesis , named after the inventors Franz Fischer and Hans Tropsch of the Kaiser Wilhelm Institute in the 1920s. FT synthesis is the foundation of Indirect Coal Liquefaction (ICL) technology. Friedrich Bergius , also a German chemist, invented direct coal liquefaction (DCL) as a way to convert lignite into synthetic oil ( the Bergius process ) in 1913.
Coal liquefaction became an integral part of German industry during World War II. Coal liquefaction was an important part of Adolf Hitler's four-year plan for 1936. In the mid-30s, companies such as I.G. Farben and Roorkhemi began the industrial production of synthetic fuels derived from coal. This led to the construction of twelve DCL units using hydrogenation and nine ICL units using Fischer-Tropsch synthesis by the end of World War II. In total, CTL provided 92% of German aviation fuel and more than 50% of oil supplies in the 1940s. The DCL and ICL plants effectively complemented each other, rather than competing. The reason for this is that coal hydrogenation provides high-quality gasoline for aircraft and engines, while FT synthesis mainly produces high-quality diesel, lubricating oil and waxes, along with some smaller quantities of low-quality motor gasoline. DCL plants were also more developed, as lignite - the only coal available in many parts of Germany - worked better in hydrogenation than in FT synthesis. After the war, Germany was forced to abandon the production of synthetic fuel, as it was prohibited by the Potsdam Conference in 1945.
South Africa developed its own CTL technology in the 1950s. The South African Coal, Oil and Gas Corporation ( Sasol ) was founded in 1950 as part of the industrialization process that the South African government considered necessary for further economic development and autonomy. However, South Africa did not have domestic oil reserves, and this made the country very vulnerable to interruptions from external supplies. Sasol was a successful way to protect the country from growing dependence on foreign oil. For many years, its main product was synthetic fuel, and this business enjoyed significant state protection during the apartheid years for its contribution to the country's energy security. Although the extraction of oil from coal, as a rule, was much more expensive than from natural oil, the political and economic importance of achieving the greatest possible independence in this area was sufficient to overcome any objections. Early attempts to attract private capital, foreign or domestic, were unsuccessful, and only with government support could liquefaction of coal begin. CTL continued to play a vital role in the South African national economy, providing about 30% of domestic fuel demand. Democratization in the 1990s led Sasol to seek products that could become more competitive in the global market, and since the new millennium, Sasol has focused primarily on its petrochemical business, as well as efforts to convert natural gas to crude oil ( GTL ) and uses his experience in the Fischer-Tropsch synthesis.
CTL technology has been continuously improved since World War II. Technical development has led to the creation of many systems capable of processing a wide range of types of coal. However, only a few coal-fired liquid fuel enterprises have been undertaken, most of which are based on ICL technology. The most successful is the South African company Sasol. CTL also gained new interest in the early 2000s as a possible option to reduce oil dependence, as rising oil prices and concerns about peak oil levels forced planners to rethink existing liquid fuel supply chains.
Traditional ways of processing
- Coal → synthesis gas → hydrocarbon production by the Fischer-Tropsch method .
- Coal → synthesis gas → methanol production by the Fischer-Tropsch method → production of motor fuels through the Mobile process (methanol → DME → degrades to alkenes → polymerizes and cyclizes to alkanes , cycloalkanes and aromatics [1] ).
- Destructive hydrogenation of coal ( Bergius process ).
There is also information about a promising method of processing:
- Transformations in a mixture of ethers [2] .
Hydrogenation
A large number of catalytic reactions are associated with the activation of a hydrogen atom and some other molecule, leading to their chemical interaction. This process is called hydrogenation and is the basis of many stages of oil refining and liquid fuel production from coal ( Bergius process ). The production of aviation gasoline and motor fuel from coal was developed in Germany during the Second World War, since there are no oil fields in this country. The first commercial hydrocracking process was implemented by IG Farben Industrie in 1927 to produce lignite gasoline. The Bergius process is the direct addition of hydrogen to coal. Coal is heated under pressure in the presence of hydrogen to obtain a liquid product, which is then processed into aviation gasoline and motor fuel. As a catalyst, iron oxide is used, as well as tin and molybdenum-based catalysts. During the war, about 1400 tons of liquid fuel per day were obtained at 12 German plants using the Bergius process. Another process, Fischer - Tropsch, consists of two stages. Initially, coal is gasified, that is, it is reacted with water vapor and oxygen and a mixture of hydrogen and carbon oxides is obtained. This mixture is converted to liquid fuel using catalysts containing iron or cobalt. With the end of the war, the production of synthetic fuel from coal in Germany was discontinued. As a result of the increase in oil prices that followed the oil embargo in 1973-1974, vigorous efforts were made to develop a cost-effective way to produce gasoline from coal. Thus, direct liquefaction of coal can be carried out more efficiently using a two-stage process in which coal is first contacted with an alumina-cobalt molybdenum catalyst at a relatively low temperature and then at a higher temperature.
Methanol to Gasoline
Methanol to Gasoline, ( Methanol-to-Gasoline for short, MTG) is a chemical process for producing gasoline from methanol.
The process is useful for producing gasoline from natural gas or coal instead of oil. The process was developed in the 70s by Mobil (now ExxonMobil ). Coal or natural gas is first converted to synthesis gas , and then to methanol. Then methanol is dehydrated to dimethyl ether (DME). Then dimethyl ether is additionally dehydrated on the catalyst. The chemical reaction proceeds as follows:
: The degree of conversion of methanol to hydrocarbons with five or more carbon atoms 80%. The catalyst is typically a zeolite , for example ZSM-5 . ZSM-5 loses its activity due to carbon accumulation. Then the catalyst must be regenerated by burning carbon in air at 500 ° C. The number of possible regenerations is limited, and ultimately the catalyst must be replaced.
Economics
On August 17, 2006, the Wall Street Journal indicated that oil must remain above $ 30-35 per barrel to ensure profitability. Sasol in South Africa is the world's largest producer of liquefied coal. There is no oil in South Africa, but coal reserves are abundant. Since the 1950s, Sasol began operating a coal liquefaction plant, producing 150,000 barrels of liquefied coal per day, replacing one-third of South Africa's oil needs. (Given that Russia produces 10.3 million barrels per day, and Saudi Arabia produces 99.5 million barrels of crude oil as of May 2017, this is very small) Sasol Limited currently accounts for 20% of the South African automotive fuel market . “Our coal liquefaction plant is economically viable if global crude oil prices exceed $ 16-17 a barrel,” said Sasol CTO John Bocca. In April 2017, the average price of Dubai's oil in the Middle East is $ 52.3 per barrel.
Sasol is currently building 27 coal liquefaction plants in Ningbo, China. To build a refinery capable of producing 80,000 barrels of oil per day (about 4 million tons per year), six billion dollars are needed.
Synthetic gasoline during World War II
Research on liquefying coal was carried out in the 1920s in Germany, mainly because the country was cut off from oil sources after the First World War. The first liquefaction process was invented by Franz Fischer and Hans Tropsch of the Institute of Emperor Wilhelm. During World War II, it was used to produce gasoline for the needs of the armaments of Germany and Japan. At the peak of production in Germany, 124,000 barrels of gas were produced per day, a total of 6.5 million tons in 1944.
Obtaining liquid fuels from coal by distillation
The production of liquid hydrocarbon fuels from brown coal by dry distillation is spreading with great speed [3] [4] . After distillation, the residue is suitable for the production of soot . Combustible gas is extracted from it, carbon-alkaline reagents and montan wax (mountain wax) are obtained.
Liptobiolites are characterized by an increased yield of volatile substances (45-57%), primary tar during dry distillation, high hydrogen content, high heat of combustion (34.3-36.4 MJ / kg) and low ash content (8-9%).
Sapropelites are massive viscous rocks of brown, brown-gray and black color , contain 55–70% of volatile substances (60–90% [5] ).
- Table - The yield of semi-coking products (% dry weight)
| Type of THC | semi-coke | primary resin | Pyrogenetic water | Primary gas |
| Peat | 33.6-50.9 | 7.7-23.1 | 14.2-26.8 | 15.9-31.8 |
| Brown coal near Moscow | 71.0-76.0 | 5.5-14.3 | 2.5-12.6 | 5.8-21.0 |
| Oleksandrіyske storm vugіllya | 55.4-61.8 | 10.6-15.8 | 7.4-9.2 | 18.3-21.1 |
| Kizelovské Kam'yan Vugіllya | 73.0 | 16.7 | 2.5 | 7.8 |
| Donetsk vug_lya: | ||||
| brand D | 70.1-74.3 | 10.3-18.1 | 3.1-8.7 | 10.7-16.5 |
| brand G | 75.8 | 10.3 | 3.6 | 10.3 |
| brand K | 84.8 | 5.8 | 1.7 | 7.7 |
| PS brands | 91.1 | 2,4 | 0.5 | 6.0 |
| Sapropelite ( balhashit ) | 10.3 | 65.9 | 8.4 | 15.4 |
| Liptobiolite ( pyropysit ) | 13,2 | 68.3 | 3.8 | 14.7 |
| Baltic oil shale | 52.6-86.4 | 8.2-34.1 | 1.8-9.9 | 2.7-6.1 |
| Oil shale Volga | 75.6-79.1 | 9.6-11.6 | 6.4-7.2 | 4.9-5.7 |
| Baltic oil shale | 14.2 * | 59.0 * | 8.1 * | 18.7 * |
- fuel mass
See also
- Coal tar
- Gas-to-liquids
- Gas generator
- Synthetic fuel
- Synthesis gas
Notes
- ↑ Mobile process (inaccessible link) . Date of treatment May 25, 2019. Archived November 1, 2014.
- ↑ Commercial evaluation of new coal liquefaction technology
- ↑ Energy Investment Company
- ↑ Alternative perspectives: VUT (coal-water fuel), CCGT and synthetic fuel
- ↑ Error in footnotes ? : Invalid
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Literature
- Coal - To - Liquids (CTL) & Fischer - Tropsch Processing (FT) // Indiana Center for Coal Technology Research, Purdue, 2007
- Liquid Fuels from US Coal // National mining association, USA
- Why Liquid Coal Is Not a Viable Option to Move America Beyond Oil // Natural Resources Defense Council , December 2011
- REVIEW OF WORLDWIDE COAL TO LIQUIDS. R, D&D ACTIVITIES AND THE NEED FOR FURTHER INITIATIVES WITHIN EUROPE // IEA Clean Coal Center, June 2009