Patent EA-000764-B1 (EA)
Title: Method for eliminating h2s, so2, cos and/or cs2 sulphur compounds, contained in a sulphur factory waste gas with recuperation of said compounds in the form of sulphur
Inventor: NOUGAYREDE JEAN
IPC: C01B17/04
Filed: 1998-04-23
Abstract: 1. A method for eliminating H2S, SO2, COS and/or CS2 sulfur compounds contained in a sulfur factory waste gas with recuperation of said compounds in the form of sulfur comprising the following steps: (i) interaction of waste gas fed from a sulfur factory with hydrolysis catalyst of COS and CS2 in H2S disposed in a hydrolysis unit (1) at a temperature sufficient to produce hydrolyzed (15) containing H2S and SO2 and substantially free from COS and CS2, (ii) after cooling (17) to the temperature below sulfur dew point the hydrolyzed gas is introduced into a purification unit (2) comprising a plurality of catalytic zones (2a, 2b) each of which comprises catalyzer-promoter of Claus reaction passing sequentially reaction regeneration  and finally cooling phases so that at each moment at least one catalytic zone is in the reaction phase (2a) and the other is in regeneration (2b) or cooling phases, (iii) passing the hydrolyzed gas fed into the purification unit through one or a plurality catalytic zones in the reaction phase (2a) at a temperature below the sulfur dew point so that H2S and SO2 contained in said gas react to form sulfur deposed on a catalyzer (23a) in said zones and at outlet of the purification unit (33) substantially pure gas is obtained, (iv) passing though the catalytic zone in the regeneration phase (2b), containing Claus catalyst (23b) charged with sulfur a stream of hot non-oxidizing gas, temperature of which between 200 to 500 degree C, particularly between 250 and 400 degree C for regenerating said catalyst and forming gaseous effluent containing sulfur vapors, and (v) passing the gas stream with a temperature below 160 degree C through the catalytic zone (2b) comprising newly-regenerated catalyst for cooling said catalyst after its regeneration to a temperature at which it can again contact with waste hydrolyzed gas, characterized in that at least one fraction of the hydrolyzed gas outgoing from the hydrolysis unit is used (19) to form a hot gas stream, circulating in the catalyst zone (2b) in the regeneration phase, and gaseous effluent outgoing from said zone is introduced (24b, 29, 20) into hydrolyzed outgoing gas fed into the purification unit at a point below the intake of said fraction and above the point where the cooling phase is carried out with condensing sulfur vapors which pass the hydrolyzed outgoing gas before being introduced into the purification unit wherein at least one fraction of waste gas is taken and fed into the hydrolysis unit to form a cooling gas stream, contacting the newly-regenerated catalyst in the catalyst zone (2b) in the cooling phase, and gaseous effluent, outgoing from this zone is introduced (24b,29, 13) at a point below intake point of said fraction and above the heating phase performance prior to feeding said gas into the hydrolysis unit. 2. A method according to claim 1, characterized in that gas fraction taken from hydrolyzed gas for forming gas stream circulating in the catalytic zone in the regeneration phase represents from 30 to 100% of said hydrolyzed gas consumption, preferably from 30 to 80% and specially from 40 to 60%. 3. A method according to claim 1 or 2, characterized in that gas fraction taken from hydrolyzed gas for forming gas stream contacting with newly-regenerated catalyst in the catalytic zone in the cooling phase represents from 30 to 100%, preferably from 30 to 80% and specially from 40 to 60%. 4. A method according to any one claim 1-3, characterized in that a gas stream containing free oxygen is introduced into the hydrolysis unit with gas discharge being controlled. 5. A method according to claim 4, characterized in that gas stream containing free oxygen is introduced into the outgoing gas fed into the hydrolysis unit at a point below the gaseous effluent feed into said outgoing gas drawing from the catalytic zone in the cooling phase, and, preferably prior to feed said gas into the hydrolysis unit. 6. A method according to any one claim 1-5, characterized in that the purification unit operates so that at each moment at least one catalytic zone is in the reaction phase and one catalytic zone in the regeneration/cooling phase. 7. A method according to any one claim 1-5, characterized in that at each moment at least one catalytic zone is in the reaction phase, one catalytic zone in the regeneration phase and one catalytic phase in the cooling phase. 8. A method according to claim 6 or 7, characterized in that the purification unit has a plurality of catalytic zones which function in parallel. 9. A method according to any one claim 1-8, characterized in that gaseous effluent outgoing from the purification unit is subjected to thermal or catalytic incineration prior rejected to the atmosphere. 10. A method according to any one claim 1-8, characterized in that the hydrolyzed waste gas treated in the purification unit contains H2S and SO2in molar ratio H2S:SO2 more 2:1 and, for example such, that concentration H2S and SO2 in said gas, expressed in volumetric percentages (H2S) and (SO2) such that amount (H2S)-2(SO2) is from 0.1 to 0.5%, and the gas outgoing from the purification unit contains mainly H2S as a sulfur compound, wherein said outgoing gas is introduced into a unit of catalytic oxydation, in which happens selective oxidation  of residual H2S to sulfur using gas containing free oxygen and contacting corresponding catalyst and at a temperature below sulfur dew point and being, for example, between 60 and 150 degree C, in particular between 90 to 130 degree C for final purification of gas. 11. A method according to claim 10, characterized in that each Claus catalytic zone of the purification unit corresponds associated with it in series a zone of catalytic oxydation of the catalytic oxydation unit, wherein each pair of formed from the Claus catalytic zone and the catalytic oxydation zone are in turn in the reaction phase, then in the regeneration phase and finally in the cooling phase. 12. A method according to claim 11, characterized in that at each moment at least one pair of zones is in the reaction phase and one pair of zones is in the regeneration/cooling phase. 13. A method according to claim 11, characterized in that at each moment at least one pair of zones is in the reaction phase, one pair of zones is in the regeneration phase and one pair of zones in the cooling phase. 14. A method according to claim 11, characterized in that hot gas stream circulating in Claus catalytic zone of the purification unit in the regeneration phase feeds into a corresponding zone of the catalytic oxydation which is also in the regeneration phase associated with the catalytic oxydation unit, and gaseous effluent, outgoing from said catalytic oxydation unit in the regeneration phase, forms gaseous effluent which is introduced unto the hydrolyzed gas feeding into the purification unit, wherein the cooling gas stream contacting with newly-regenerated catalyst of Claus catalytic zone of the purification unit in the cooling phase is then introduced into corresponding zone of the catalytic oxydation which is also in the cooling phase, connected to the catalytic oxydation unit, and gaseous effluent, outgoing from said zone of the catalytic oxydation  in the cooling phase, forms gaseous effluent, which is introduced into waste gas feeding into the hydrolysis unit. 15. A method according to any one claim 10-14, characterized in that purified gaseous effluent outgoing from the catalytic oxydation unit is subjected to thermal or catalytic incineration prior rejected to the atmosphere. 16. A method according to claim 9 or 15, characterized in that waste gas after introducing into it gaseous effluent, outgoing from Claus catalytic zone of the purification unit in the cooling phase or from corresponding zone of the catalytic oxydation is heated prior to feeding into the hydrolysis unit by indirect heat exchange between said waste gas and hot gaseous products of purified gas incineration.