Partial oxidation of hydrogen sulphide

Details Partial oxidation of hydrogen sulphide Partial oxidation of hydrogen sulphide

2002-11-04

2003-10-28

Basichas, Alfred (Department: 3743)

Combustion

Fuel disperser installed in furnace

Spaced fuel dispersing orifices within furnace

C431S178000, C431S186000, C431S187000

Reexamination Certificate

active

06638057

ABSTRACT:

This invention relates to a method of and apparatus for the partial oxidation of hydrogen sulphide and to burners for use in the method and apparatus.
So-called acid gas streams containing hydrogen sulphide and carbon dioxide are formed as waste streams in, for example, oil and gas refineries. It is necessary to treat an acid gas stream so as to remove substantially all its content of hydrogen sulphide before it is discharged to the atmosphere. This removal of hydrogen sulphide is conventially performed by the Claus process, in which a part of the hydrogen sulphide content is burned in a furnace to form sulphur dioxide and water vapour; some of the resultant sulphur dioxide reacts in the furnace with residual hydrogen sulphide to form sulphur vapour and water vapour (with the result therefore that some of the hydrogen sulphide is partially oxidised). An effluent gas stream comprising hydrogen sulphide, sulphur dioxide, carbon dioxide, water vapour, and sulphur vapour therefore flows out of the furnace. The sulphur vapour is extracted from the gas mixture by condensation, and the resulting gas mixture substantially free of sulphur vapour is subjected to a plurality of catalytic stages of further reaction between sulphur dioxide and hydrogen sulphide so as to form sulphur vapour. The further sulphur vapour is extracted from the gas mixture downstream of each stage of catalytic reaction. A tail gas containing typically from 2 to 6% of the original sulphur content of the acid gases thereby formed. The tail gas is typically sent for further treatment to remove substantially all the remaining sulphur compounds.
Traditionally, air is employed to support the combustion of the hydrogen sulphide. Typically the air is supplied at a rate sufficient to provide enough oxygen molecules to oxidise completely any ammonia present to nitrogen and water vapour and to oxidise completely any hydrocarbons present to carbon dioxide and water vapour and to effect oxidation to sulphur dioxide and water vapour of about one third of the hydrogen sulphide content of the acid gas. It has more recently been recognised that improvements in the Claus process can be achieved by substituting commercially pure oxygen for some of the air. As a result, the size of the furnace and downstream units can be reduced for a given throughput of hydrogen sulphide.
EP-A-0 486 285 relates to an oxygen-air-hydrogen sulphide burner, for use in the Claus process. The burner comprises a hollow body member having an open distal end and defining a passage through which extends a plurality of first elongate, open-ended, tubular members able to conduct fluid and a plurality of second, elongate, open-ended tubular members also able to conduct fluid, each second tubular member being located within a respective first tubular member. The first tubular members communicate with a source of hydrogen sulphide and the second tubular members with a source of oxygen. The purpose of providing each oxygen tube within a respective hydrogen sulphide tube is to make possible the achievement of particularly good mixing of the oxygen and the fuel and to obtain uniform conditions within the flame. In addition, stable operating conditions can be obtained at relatively low fuel and oxygen velocities.
Although the burner according to EP-A-0 486 285 performs well in practice, we believe that in the Claus process a higher percentage conversion of hydrogen sulphide to sulphur in the gas mixture leaving the sulphur condenser associated with the furnace can be achieved if, in fact, a suitable non-uniform flame is provided. Accordingly it is an aim of the present invention to provide a method of and apparatus for the partial oxidation of hydrogen sulphide in which the burner has a construction which facilitates the attainment of relatively high percentage conversions of hydrogen sulphide to sulphur in the furnace.
According to the present invention there is provided apparatus for the partial oxidation of hydrogen sulphide comprising a furnace and an air-oxygen-hydrogen sulphide burner that fires into the furnace, wherein the burner comprises a main passage for combustion-supporting gas containing air, a multiplicity of spaced apart outer elongate fluid-conducting open-ended tubes extending in parallel with each other along the main passage, each of the outer tubes surrounding at least at the distal end of the burner a respective inner elongate fluid-conducting open-ended tube, the inner tubes extending in parallel with one another, a first inlet to the burner for oxygen or oxygen-enriched air, and at least one second inlet to the burner for feed gas containing hydrogen sulphide, the first inlet communicating with the inner tubes, and the second inlet communicating with the outer tubes, wherein the outlets of the inner and outer tubes are so disposed that, in operation, essentially all mixing of hydrogen sulphide with oxygen and air takes place downstream of the distal end of the burner, and wherein the outlets of the inner and outer tubes are so juxtaposed and dimensioned as to enable there to be maintained in the furnace, in operation, a stable flame with at least one high temperature first stage, and at least one second lower temperature stage, the first stage being more remote than the second stage from a chosen area of the inner wall or walls of the furnace, the chosen area thereby being shielded from the first stage by the second stage, and the said tubes are arranged in two groups, there being a first group of inner and outer tubes which in operation feed the first stage of the flame, and a second group of inner and outer tubes which in operation feed the second stage of the flame, the inner tubes in the internal first group being of greater internal diameter than the inner tubes in the second group.
As a result of its being relatively oxygen-rich, an average flame temperature in the range of 1700 to 2300° C. can be achieved in the inner stage of the flame. Such high temperatures are believed to favour cracking, i.e. thermal dissociation, of the hydrogen sulphide into hydrogen and sulphur. As a result, it is believed that a higher proportion of the hydrogen sulphide is converted to sulphur than at lower temperatures. In addition, having a high temperature oxygen-rich first stage also facilitates the complete destruction of any ammonia in the feed gas not only because of the high temperature of the first stage but also because the second stage although relatively oxygen poor can still be operated at temperatures in excess of 1400° C. It is highly desirable to effect such complete removal of ammonia since if any of this gas passes from the furnace to any catalytic stages of a Claus process it can form ammonia salts which poison the catalyst or block other units operating at lower temperatures.
Preferably the outlets of the outer tubes in the first group are spaced wider apart than the outlets of the outer tubes in the second group. As a result, proportionately more air tends to be made available to the first group of tubes than to the second group of tubes, thereby facilitating the achievement of the desired oxygen-rich conditions in the first stage of the burner. This result is particularly facilitated if there are more tubes in the second group than the first group; typically there are at least twice as many tubes in the second group than in the first.
Preferably the tubes in the first group may have an internal diameter typically from 1.3 to 3 times the internal diameter of such tubes in the second group. Such an arrangement facilitates in operation the sending of proportionately more oxygen or oxygen-enriched air to the first stage of the flame than to the second stage, thereby particularly helping to achieve a high temperature in the first stage. In such an arrangement, it is convenient that the internal diameter of the tubes in the first group that communicate with the second inlet are of the same internal diameter as the tubes in the second group that communicate with the second inlet.
There are generally two different ways in which the burner can

Affiliated with

Also associated with

Rating

Partial oxidation of hydrogen sulphide does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Partial oxidation of hydrogen sulphide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Partial oxidation of hydrogen sulphide will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3156256