Functioning in Angren since 1961 station «Podzemgas» (now JSC «Yerostigaz») is the most powerful industrial object of such kind, which doesn’t have analogues in the world.
The main purpose of the enterprise is transforming brown coal into power generating gas with the it’s following use in Angren thermal power station. The enterprise develops part of Angren brown coal deposit, which is not suitable for underground and open cut mining on account of technical and economical causes and mining and geological conditions.
More than 40 year experience of enterprise operation showed that method of Underground coal gasification allows to obtain power generating gas in large industrial scales and provide it’s uninterrupted delivery to the consumer.
Prospecting projects on reconstruction of Angren and Novo-Angren thermal power stations, forming demand for such kind of production, can stimulate development of UCG.
One of main sources of thermal and electric energy in many countries is coal whose share in the world reserves of hydrocarbon fuel exceeds 80 %.
The conventional methods of coal extraction require the presence of man at the stope. In addition, the non-combustible mass (about 50 %) extracted together with coal and consisting of ash and moisture causes pollution of the earth’s surface and atmosphere in the same way as the coal dust does.
The most advanced and safe method of extraction is the mineless method of underground gasification. The idea of the possibility of such a process was expressed in 1888 by great Russian scientist D.I. Mendeleyev. In 1911 Ramsay, an Englishman, was the first to obtain gas from a generator hole.
Hard and dangerous underground labour becomes unnecessary, working conditions are much better, and the extraction process can be completely mechanized and automatically controlled.
Unlike coal combustion, the –underground gasification requires no fuel preparation, and consequently, no ash and slag disposal. No environmental pollution occurs because the gas combustion products are free of solid particles, carbon oxide, sulphur and nitrogen oxides.
The power-generating gas is produced by the station "Podzemgaz" in underground air-blow gas generators. An underground gas generator is a system of air blow and gas outlet holes bored from the surface to a coal seam following a certain scheme.
Subsequent gasification of the coal seam by air blow.
Air is forced into the coal seam through the air blow holes arranged in parallel rows along the gas generator gasification front. The gas at a temperature of 150 to 350 °C (at the heads) produced in the underground gas generators is passed through a system of gas conduits to the station area where it is cooled and dedusted in cooler scrubbers. The cooler scrubbers are provided with an independent water circulation system including cold and hot water pumps, settlers, and cooling towers. The scrubber cycle sewage is cleaned in a dephenolizing plant and then discharged into the sewerage system. The cooled and dedusted gas is fed to the Angren thermal power station through a gas conduit of 2 m in diameter.
The gas is forced to the power station under the excessive pressure at the gas outlet hole mouth.
The initial duct in coal between the holes is produced by hydraulic blasting, and then air is fed into the duct. After the coal duct is dried by the air flow, the hole is lighted up.
The coal seam is lighted up by throwing burning-hot coke into the hole through a sluice without any interruption of the air blow intended to maintain the coal seam burning.
After the gas generator is lighted up, air is forced for connection of the adjacent holes. Thus, the fire initiation site gradually moving from one hole to another interconnects all the holes and forms gasification ducts. A sharp drop in pressure and increase in air flow rate are indicative of the complete connection of holes.
(h) pumping plant intended to feed fresh water to the station area.