Lurgi pressure carburetor

The Lurgi pressure gasifier is used to gasify coal or lignite at increased pressure in counterflow . The gasifier is operated either continuously or in cyclic mode, with air and water alternating with the coal. In this type of gasifier, large quantities of coal degassing products such as naphtha , ammonia , tar and phenols are produced as by-products.

Procedure

Scheme of the Lurgi pressure gasifier

The gasifier is designed as a cylindrical vertical reactor with an outer water jacket. The coal is fed into the generator from above through a double sluice. This travels downwards at a speed of 0.1 to 0.4 meters per hour. A distributor and a rotating grate prevent the coal from caking. Oxygen and steam are blown in from below. By the rising hot gases of the gasifier find at the top of drying the coal used and a desorption of physisorbed instead gases. Following the drying zone is the reaction zone, in the upper part of which the coal is degassed. The resulting gas is therefore rich in typical degassing products and has to be condensed after leaving the reactor in order to separate off the easily liquefied components and to wash out acidic components such as carbon dioxide , hydrogen sulfide and organic sulfur compounds. The gasification of the coal follows the degassing zone. According to the Boudouard equilibrium , the hot coal in this zone reacts with rising carbon dioxide according to equation (1) to form carbon monoxide:

${\displaystyle \mathrm {(1)\ C\ +\ CO_{2}\ \longrightarrow \ 2\ CO} }$

In the next zone, the coal is burned and the water-gas and water-gas shift reactions take place according to equations (2) to (5):

${\displaystyle \mathrm {(2)\ C\ +\ O_{2}\ \longrightarrow \ CO_{2}} }$

${\displaystyle \mathrm {(3)\ C\ +\ H_{2}O\ \longrightarrow \ CO\ +\ H_{2}} }$

${\displaystyle \mathrm {(4)\ CO\ +\ H_{2}O\ \longrightarrow \ CO_{2}\ +\ H_{2}} }$

${\displaystyle \mathrm {(5)\ 2\ C\ +\ O_{2}\ \longrightarrow \ 2\ CO} }$

In the lowest zone of the generator, the ash is discharged either as ash in the conventional Lurgi process or as liquid slag in the BGL (British Gas Lurgi) process, depending on the process modification.

The diameter of larger systems is around 3.8 m with a raw gas throughput of up to 32,000 Nm ³ / h. The gas composition depends on the selected feed coal and the specific process conditions. In a typical composition, the carbon dioxide content is about 28 to 33%; Carbon monoxide and hydrogen make up about 60% of the gas mixture. An increase in the reaction temperature shifts the equilibrium strongly to the side of carbon monoxide and hydrogen, whereas the formation of carbon dioxide and methane is suppressed.

The steam generated in the jacket pipe can be used to supply energy to secondary processes such as the regeneration of washing solutions to separate acidic components.

literature

• Coal, Oil, Natural Gas: Chemistry and Technology ; by Karl-Heinz Schmidt, Ingo Romey, Fritz Mensch, 256 pages, Vogel Verlag (1981), ISBN 3-8023-0684-8 , ISBN 978-3-8023-0684-6 .

Web links

• The pressurized gasification of solid fuels with oxygen (PDF; 614 kB), by F. Danulat at Archive.org, accessed on August 1, 2018
• Process engineering basics (PDF; 524 kB)

Individual evidence

1. ↑ F. Bošnjaković, KF Knoche: Technical Thermodynamics, Part 1. Verlag Steinkopff, Darmstadt, 1998, p. 457. ( Excerpt from Google book search)