Adsorptive cleaning of the gas
ADSORPTIVE CLEANING OF THE GAS (EN: adsorption gas cleaning; DE: adsorptive Gasreiningung, adsorptive Gasaufbereitung; FR: epuration de gaz par adsorption; ES: depuracion de gas por adsorcion; RU: адсорбционная очистка газа) is the selective extraction of the acidic components (H2S, CO2), organosulfur compounds, and other admixtures, by their intake by the adsorbent.
It is performed at the oil and gas processing plants, and at the extraction facilities. The adsorptive cleaning of the gas by the (rust) hydrate of the ferric oxide as the adsorbent has been performed for the first time in the Great Britain in the middle of the 19th century. It is widely used in the USSR since the early 70's. The process of the adsorptive cleaning of the gas is cyclical. In the adsorption cycle, the target component moves from the stream of the raw material into the bed (layer) of the adsorbent; in the regeneration cycle the target component moves from the adsorbent into the stream of the regeneration of the gas at the temperature of less than 400 degrees Celsius. The oldest method of the adsorptive cleaning of the gas is the so-called method of the sponge iron; the adsorbent is the wooden shavings, which are imbued with the (rust) ferric oxide in the hydrated form. It is used in the modern production at the installations of the low productive capacity (10.3 million cubic metres per year), and high degree of the cleaning (less than 2 milligrams per cubic metre). It distinguishes itself with the good selectivity in relation for H2S.
The adsorptive cleaning of the gas with the usage of the molecular sieves (zeolites) has got the greatest distribution in the USSR and abroad. The process has been used for the first time in the USA in the middle of 50s. The adsorptive zeolitic installations, in the dependence on the concentration of the sulfurous components in the raw material, the volume and the speed of the delivery of the cleaned gas, have from two to four columns. The regeneration of the adsorbent is usually performed by the dry cleaned gas at the temperature of 250-400 degrees Celsius. The consumption of the gas for the regeneration is 5-20% of the processed gas. The decrease of the consumption of the gas for the regeneration at the installations with the low productive capacity (up to 500 million cubic metres per year) is achieved by the usage of the so-called effect of the peak desorption, while there is burned at the torch only the part of the gas, which has escaped at the moment of the greatest desorption of the sulfurous components, and the remaining part is returned to the main stream. For the high productive capacity of the equipment of the adsorptive cleaning of the gas (more than 500 million cubic metres per year), they pass the regeneration gas through the installations of the amine cleaning (see Absorptive gas cleaning).
They also use as the adsorbent in the installations of the adsorptive cleaning of the gas the activated carbon; they extract thiophene, carbon disulfide, partially carbonyl sulfide and disulfides. In order to clean the gas of the organosulfur compounds, the chemical adsorption method is used, which is based on the direct binding of the admixtures, which are removed (at 300-400 degrees Celsius) by the solid adsorbers, which are based on the oxides of zinc, iron and copper.
The advantages of the adsorption processes are: the fine cleaning of the gas up to 0.1-0.5 milligrams per cubic metre, selectivity, the non-complexity of the work, and the simplicity of the construction of the apparatuses. The disadvantages are: the possibility of the usage only for the low content of the admixtures in the source gas, the difficulty of the processing of the gases of the regeneration, the mechanical destruction of the adsorbent, the decreasing of its activity in the process of the exploitation, the large losses of the pressure in the apparatuses.
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