What is Coal Liquefaction?

Coal liquefaction is a hot spot in the current coal chemical industry. Many coal mines are eager to try it. It is not known that coal liquefaction has certain requirements on coal quality. Not all coals can be liquefied. Coal liquefaction is divided into direct liquefaction and indirect liquefaction. These two liquefaction methods have different requirements for coal quality.

Direct coal liquefaction technology was discovered by the Germans in 1913 and industrialized in Germany during World War II. In Germany, 12 sets of direct coal liquefaction plants have been completed and put into operation. By 1944, the oil production capacity of German direct coal liquefaction plants had reached 4.23 million tons per year. After World War II, the development of a large amount of cheap oil in the Middle East caused direct coal liquefaction plants to lose competitiveness and shut down.

In the early 1970s, due to the worldwide oil crisis,

Coal

Coal liquefaction methods are mainly divided into two categories: direct coal liquefaction and indirect coal liquefaction.

(1)

According to a large amount of research work at home and abroad, it can be summarized as follows: Coal is not a homogeneous reactant. Coal has components that are easy to liquefy and components that are difficult to liquefy. Coal liquefaction includes a series of sequential reactions and parallel reactions. However, the sequence reaction is the main one, that is, the relative molecular mass of the reaction product is from high to low, the structure is from complex to simple, and the appearance time is roughly in an order; pre-asphaltene and asphaltene are intermediate products, and their composition is Uncertainly, at different reaction stages, the generated asphaltenes and pre-asphaltenenes must be different. The rate of conversion from them to oil is slower and requires a more active catalyst; Coking reverse reactions may also occur. ^[1]

There are two types of catalysts for direct coal liquefaction. One type is iron system catalysts, such as iron oxide-containing minerals, iron salts, and pyrite in coal. When used, sulfur must be present in the system. Otherwise, the activity is not high. Iron-based catalysts are used. The paste phase of coal is hydrogenated and is not recovered after the reaction. The other is an industrial hydrogenation catalyst commonly used in the petroleum industry. Its active ingredients are NiO, MoO ₃ , CoO, WO3, etc., with Al ₂ 0 ₃ as a carrier. Pre-vulcanization is required before use, and sufficient H2S is also required in the gas phase. These catalysts have significantly higher activity than iron catalysts, but they are more expensive and need to be used repeatedly. They are not suitable for paste-phase hydrogenation.

Typical conditions for direct liquefaction of coal are: pressure: 15-30 MPa, temperature: 450-460 ° C, actual residence time: 2 h, coal slurry concentration: 40% -50%, catalyst addition amount: 0.5% -4 %, Gas / liquid ratio: 700 1000, circulating hydrogen concentration:> 75%, different coal types have different optimal liquefaction reaction process conditions. ^[1]

Requirements for direct liquefaction

(1) in coal

Coal liquefaction distribution

China's coal resources are abundant and are distributed in all provinces except Shanghai, but the distribution is extremely uneven. In the region between the Greater Xing'an Mountains-Taihang Mountain and Helan Mountain in northern China, the geographic scope includes all or most of the six provinces and autonomous regions of Inner Mongolia, Shanxi, Shaanxi, Ningxia, Gansu, and Henan, which are coal resources of more than 100 billion tons, which are China's coal resources Centrally distributed areas account for about 50% of the country's coal resources and more than 55% of the coal resources in northern China. In southern China, coal resources are mainly concentrated in the three provinces of Guizhou, Yunnan, and Sichuan. The sum of coal resources in these three provinces is 352.574 billion tons, accounting for 91.47% of coal resources in southern China; proven reserves also account for southern China. More than 90% of resources are kept.

11th Five-year Plan for Coal Liquefaction

The "Eleventh Five-Year Plan" period is the best period for structural adjustment and industrial transformation of the coal industry. Coal is China's basic energy source, accounting for about 70% of the primary energy mix. The "Eleventh Five-Year Plan" proposal further established the basic strategy of "coal-based and diversified development", which laid the foundation for the prosperity and development of China's coal industry. During the "Eleventh Five-Year Plan" period, the size of new coal mines will need to be about 300 million tons, of which 200 million tons will be put into production and 100 million tons will be transferred to the "Twelfth Five-Year Plan". China's coal industry will continue to maintain a strong development trend. For a long period of time in the future, the development prospects of China's coal industry will be very broad.