DE2845622A1 - Continuous multistage degasification of liq. sulphur - by contact with hydrogen sulphide-lean carrier gas in a series of contact chambers - Google Patents

Abstract

H2S-rich liq. S is degasified by (a) continuously supplying the S to the first stage of a contacting zone contg. >1 discrete contacting stage, the S occupying the lower part of the zone (b) continuously feeding an H2S-lean carrier gas into the upper part of the first stage such that gas and liq. S are sepd. by an interface, (c) continuously withdrawing H2S-lean liq. S from the lower part of a subsequent stage and (d) continuously withdrawing H2S-rich carrier gas from the upper part of a subsequent stage. The liq. S is maintained at 120-160 degrees C and is recirculated within >=1 stage at a rate of 1-100X the S feed rate. In a pref. process the liq. S feed contains 70-300wt. ppm H2S and the liq. S withdrawn contains 15 wt ppm H2S. Used esp. in a Claus process; in a pref. operation the S pit for storing the liq. S prod. comprises the contacting zone. Method is continuous and does not require a separate degasification vessel.

Description

Process for the continuous multi-stage degassing of sulfur the The invention relates to a method for degassing sulfur. In particular concerns the invention a multi-step process for the continuous removal of H2S h2S-rich liquid sulfur.

In some petroleum refining processes, sulfur is derived from different ones Hydrocarbon compounds through reaction with hydrogen and formation of H2S removed. H2S also occurs in acidic natural gas. In both cases it will H2S is usually removed therefrom by absorption in a solution of an alkanolamine and subsequently released in concentrated form when the solution is heated.

The H2S can then be converted to elemental sulfur by the well-known Claus process implemented (see Kirk Othmer, The Encyclopedia of Chemical Technology, 2. Output

Vol. 4, pp. 376-377, 1964, and Vol. 19, pp. 353-354, 1969).

In short, this procedure uses a portion (approximately 1/3) of the concentrated H2 s burned with air and then forms 5021 that with the remaining H2S reacts at about 3000C in the presence of a catalyst and becomes gaseous Forms sulfur. Usually 3 combustion stages, i.e. H2S conversions are used, each stage operating at progressively lower temperature and progressively Contains reduced amounts of H2S, so that the conversion to sulfur strives towards the state of equilibrium. When using 3 levels, approx 95% of the H2S in the gas supplied to the Claus plant is converted into sulfur. To At each stage the sulfur is cooled and the 3 streams of liquid sulfur are added Formed in this way, liquid sulfur becomes liquid sulfur in an H2S-rich stream summarized, which is then fed to a sulfur container for storage of the sulfur is used until further use.

Usually the H2S-rich liquid sulfur contains about 70 to about 300 parts per million by weight of H2S, including the hydrogen polysulfides of the formula H2SX, where x is in the range from 1 to 6. For the sake of simplicity, will that of the H2S, that in the H2S-poor liquid sulfur as H2S and H2Sx is, equivalent H2S hereinafter referred to as "equivalent H2S".

Besides being H2S in relatively dilute concentrations is harmful gas, H2S becomes more and more dangerous when its concentration in a gas exceeds about 70 parts per million by weight, the fatal Concentration for humans is about 700 parts by weight per million. if the H2S content of a gas down to at least 3.6 vol.% (which is an equilibrium value of 15 parts by weight per million H2S in liquid sulfur) in the present of an oxygen-containing gas such as air grows the Flammability threshold of the gas exceeded. Furthermore, liquid sulfur should be used be enclosed in a vessel with iron as a building material, this can affect the inner Walls of the vessel formed iron sulfide to be spontaneously flammable and in the presence an oxygen-containing gas lead to a spontaneous ignition of the H2S 5, without a flame or a spark having appeared. Therefore it is desirable the concentration of equivalent H2S in liquid sulfur less than 15 parts by weight keep per million.

A method for removing H2 S from H2S-rich liquid sulfur was suggested in U.S. Patent 3,364,655. According to the method shown there, a batch of sulfur is transferred to a separate degassing vessel and carried out Spray nozzles circulated so that the sulfur spray formed in this way with a Gas in the vapor space above the liquid sulfur comes into contact. This method However, it is expensive because of the separate degassing vessel required and has the economic and procedural disadvantages, usually with most Processes which are carried out batchwise, e.g. that the product is not continuous is generated that a larger storage space is required during the process that more and more attentive operators and / or instruments are needed, increased maintenance expenses and the like., Are connected.

Another method of removing H2S from H2S-rich liquid Sulfur is described in U.S. Patent 3,920,424. According to the procedure described there a batch of H2S-rich liquid sulfur is continuously drawn from a storage tank recirculated through a vertical gas scrubber until the desired H2S content is reached of liquid sulfur has been reached. The washing device contains plates, or Lamellae that increase the surface area of the liquid sulfur flowing down help and thereby facilitate the escape of H2S from the sulfur. This method however, again has the disadvantages of most processes using batch-wise are performed, are connected.

Another method of degassing liquid sulfur is in the UK U.S. Patent 1,402,274 where a continuous one-step process is used However, the present multi-step process is not in the prior art suggested.

According to the invention, H2S can continuously from B2S-rich Sinmg £ n Sulfur, such as can be obtained from a Claus plant, for example, can be removed, placing the sulfur with a lean carrier gas in a zone of contact that is more than contains a separate contact stage, is brought into contact In A preferred embodiment of the invention, the sulfur is within at least circulates a touch zone; e.g. by spray nozzles around the touch of the sulfur to promote with the carrier gas within the contact stage and thereby the degassing of sulfur. The E2S 5 excreted during the degassing is over the carrier gas is continuously removed and in the form of an H S-rich carrier gas 2 eliminated. The carrier gas can either flow with or counter-flow to the Flow of sulfur to be supplied. If desired, ammonia can be added to the circulating system Sulfur can be added during degassing to prevent the decomposition of hydrogen polysulphides, which are contained in it to accelerate to H2S. A sulfur container that usually is used to digest a process that forms liquid sulfur Storage (e.g. a Claus process) is a particularly suitable contact zone for carrying out the invention.

The invention is explained in more detail below with reference to the drawings The figures show: FIG. 1 a schematic isometric view of an embodiment of the invention and Figure 2 is a schematic side view one individual contact level.

Having now generally described the invention, reference is now made to the figures Referenced. The figures explain the present invention. There are such Include details as necessary for a clear understanding of how the invention is made applied to the system. The invention is not intended to thereby a particular arrangement shown can be set, as other arrangements are included in the consideration. Various details such as steam pipes, instruments and other process equipment and control devices associated with the invention only marginally related have been left out for simplicity. Modifications, which are apparent to those skilled in the art for degassing liquid sulfur included in the scope of the invention In Figure 1, a sulfur container 1 is shown, which involves the effluent of a process for the formation of liquid sulfur from H2S, e.g.

of the Claus process. -The sulfur container shown is into separate sections or discrete stages of contact through an internal system-of Divided partitions that have sections 2, 3 and 4. Section 2 extends extends in the longitudinal direction from approximately the middle of a transverse wall of the sulfur container 1 to the opposite wall until it intersects section 4. Section 4 is vertical to section 2 and extends from said cutting line to to a longitudinal wall as shown. Section 3 is parallel to Section 4 and divides Section 2 near its center into two areas. All sections are tight with the Walls of the sulfur container connected except at the openings 2a, 2b, 3a and 3b. In this way, the partition system forms a first contact level 5, a second contact level 6, a 3rd contact level 7 and a 4th contact level 8. A Sanel area 9 is through Section 4 and a transverse wall formed in the manner shown. H2S-rich liquid Sulfur @ l is continuously fed into the first contact stage 5 via the supply line 10 and passes successively through stages 5, 6, 7 and 8 in countercurrent to a low-H2S carrier gas, which is continuously fed into the sulfur container via the Feed line 11 is introduced. A carrier gas rich in H2S and a liquid poor in H2S Sulfur are then continuously from the sulfur container 1 via pipes 12 or; 13 deducted.

The H2S-rich liquid sulfur can be obtained from any suitable source, such as from a Claus plant. The amount of sulfur in the liquid -H2S contained therein is not critical and can fluctuate within a wide range. However the liquid sulfur will generally be at least 70 parts per million by weight equivalent H2S and normally it will be from about 100 to about 300 parts by weight per million contain equivalent H2 S. the however, hydrogen polysulfides contained therein are quite unstable and become decompose during degassing with formation of H2S. The temperature of the sulfuric mine Entering the sulfur canister is not critical provided it is in is kept in a range that prevents undesirable viscosity effects (see F.J. Touro and T.K. Wiewiorowski, J. Physical Chemistry, Vol. 70, no. 1 pp. 239-241, 1966).

The H2S-poor carrier gas can be any gas that is not detrimental reacts with the sulfur. Examples of suitable gases are an inert gas such as oxygen, Air, steam, exhaust gases from the Claus plant and the like. As a result, the H2S-poor gas H2 S included or not. However, the H2S gas should only be contained in it in quantities that does not have the equilibrium amount of the desired level of H2 S in the sulfur exceed (information about the equilibrium conditions in the sulfur-H2S system can in T.K. Wiewiorowski and F.J. Touro, J. of Physical Chemistry, Vol. 70, no. 1, pp. 234-238, 1966). If desired, the carrier gas, which is low in H2S, can be used be fed to the sulfur flowing in instead of counter-flowing. However, the countercurrent will be preferably to keep the required amount of cleaning gas as small as possible. That Ratio in which the H2S-poor carrier gas in line 11 in the sulfur container is introduced changes with the amount of those in the H2S-rich Carrier gas is contained in line 12. The higher the concentration of the E2S-rich Carrier gas in line 12, the lower the ratio or the amount of H2S-poor gas.

In the first step 5, liquid sulfur becomes rich in H2S partially degassed when it comes into contact with the carrier gas low in H2S, as follows is described in more detail. The H2S-rich liquid sulfur d'ssnH25 content partially decreased, is then successive through the touch levels 5, 6, 7 and 8 passed through openings 2a and 3a and depleted more in each stage and more H2S until the desired H25 content in the sulfur is reached.

The flow of liquid sulfur under rather than over the bulkhead assembly has the advantage that it leads to a progressive reduction in the H2S content of sulfur allowed, while the backmixing is kept as low as possible and the storage purpose of the sulfur container is obtained. Although the H2S-rich liquid sulfur Can be degassed to any desired degree, the B25 should be poor liquid Sulfur have an H2S content of less than 15 parts per million by weight to avoid the generation of a flammable gas mixture when containing an oxygen Gas is in contact with the sulfur. If desired, however, the H2S content can be of H2S-poor liquid sulfur down to 10 parts by weight per million or less, up to 5 parts by weight per million or less, or up to 1 part by weight per Million or less can be decreased by using the invention. The H2S poor liquid sulfur is then fed into a collection area 9, from which it is via a Line 13 is removed.

Similarly, the carrier gas lean of 112S goes through line 11 sequentially through steps 8, 7, 6 and 5 through openings 2a and 3b and comes with the in it located liquid sulfur in contact so that it more and more with the out The H2S released into the liquid sulfur is enriched1 and finally occurs through the line 12 as an H2 S-rich carrier gas from the sulfur container 1 the end. In addition, that there are essentially the same constituents as they are in the H2S-poor Contains carrier gas, the H2S-rich carrier gas also contains H2S and 502i that have been removed from the liquid sulfur, as well as sulfur in one Amount of its vapor pressure at the temperature and then the pressure of the sulfur container 1 corresponds.

As noted above, the H2S concentration in the H2S-rich carrier gas can not exceed the one determined by the equilibrium. The upper limit of the H2S concentration in the H2S-rich sulfur.

should be 3.6% by volume in the presence of an oxygen-containing gas do not exceed, according to the inflammation threshold mentioned above. The lower limit will be determined by economic considerations, since lower H2S levels are higher Require amounts of low H2S carrier gas. In general, it is preferable to have the Limit the amount of H2S in the H2S-rich carrier gas to no more than 1 to 2% by volume, preferably between 0.5 and 1.5% by volume, during normal operation. The in the present The amount of carrier gas used in continuous degassing processes is less than that required in conventional batch processes because it is at the end of the batch cycle the gas above the liquid sulfur is so enriched with H2S that it is with large amounts of said gas must be diluted in order to obtain the necessary force to remove sufficient H2S from the liquid sulfur to reduce the content to achieve, i.e. less than 15 parts by weight per million of H2S in it. There the H2S-rich carrier gas in the sulfur container 1 to the temperature of the sulfur is heated, it is desirable that the velocity of the H2S-rich carrier gas so is that the entrainment of liquid sulfur is kept as low as possible will. It is also desirable to heat the conduit 12 to cause it to solidify to prevent any sulfur entrained in it. When leaving the sulfur container 1 can be the H2S-rich carrier gas can be eliminated, e.g. by flaring.

Figure 2 shows a single level of touch, e.g., the first level of touch 5, which H2S-rich liquid sulfur enters as described above and a liquid sulfur phase 14 forms in the lower portion of stage 5. The carrier gas is located in the upper section 15 of stage 5 above the liquid sulfur phase 14 and is separated from it by the separating surface 16. A pump 17 with a shaft 18, which is connected to a motor 19, rolls the liquid sulfur over the Line 20 and preferably through at least one spray nozzle 21 from which the sulfur in the form of a spray. The spray delivers one large surface area for contact between the carrier gas and the H2S-rich liquid Sulfur to cause degassing of the latter. The pump, the nozzle and the Motor are commercially available items and as such at any time of the corresponding To obtain suppliers.

The circulation ratio of the sulfur is not critical and can be used in vary widely, i.e. from about 1 to about 100 times the amount of sulfur added at each stage, depending on the desired H 2S content of the H2S-poor liquid Sulfur, the H2S content of the H2S-rich sulfur and the number of used Contact levels. Preferably, the circulation ratio of the sulfur is between about 4 and 50, more preferably between about 4 and 10 times the amount of sulfur added at every level.

The sulfur is preferably circulated in at least one contact stage and particularly preferably within each contact stage. The number of used Contact levels can range from 2 to 10 or more, preferably from 2 up to 5 levels.

The liquid sulfur in the sulfur container should be in a temperature range of about 120 ° C and 160 ° C to avoid the above-mentioned undesirable Avoid flow properties. However, if the H2S-rich liquid sulfur is a If the temperature is higher than 1600C, it can be allowed to enter the sulfur container 1 can be cooled to a suitable temperature. A heat exchanger in the line 20 of the first contact stage 5 are arranged in order to effect the cooling. Normally the sulfur container is at essentially atmospheric pressure operated.

The residence time of the liquid sulfur can vary over a wide range depending on the amount of H2 S to be removed and also on the amount of low H2S Carrier gas, the amount of H2S in the H2S-rich carrier gas and the like vary. in the Normally, however, the residence time will be in the range of approximately 10 Minutes to about 2 hours per step.

The dwell time can be modified according to the level of the liquid Sulfur is allowed to vary. Such adaptability cannot come with conventional processes which are carried out in batches can be achieved. If the liquid sulfur is obtained from a Claus plant, it may be desirable be at least some of the sulfur from the first stage condenser in the contact stage 5, at least part of the sulfur from the condenser of the 2nd stage in the 2nd contact stage 6 and at least some of the sulfur from the Introduce the 3rd stage capacitor into the 3rd contact stage. That way has the sulfur from the first stage condenser, which is high temperature and accordingly has a higher content of equivalent H2S than that from others Condensers the longest dwell time. Similarly, at least a part can of the carrier gas other than the first or last stage supplied and / or from are discharged there, i.e.

at an intermediate level. If desired, the liquid sulfur can Ammonia can be added. The ammonia works during the degassing of the sulfur as a catalyst and in particular contributes to the bonds between the molecules of sulfur and H2 S to break. Because the liquid sulfur has a temperature between about 120 ° and about 160 ° C., and ammonium sulfide at temperatures above Dissociated at 1180C, there are only slight chemical reactions between the ammonia and the H2S instead, if at all. Normally this will be Ammonia added in amounts less than 100 parts per million by weight.

Although the above description was based on a sulfur container, that contained the liquid sulfur from a Claus plant can of course be any suitable contact zone can be used. Suitable materials for the construction of the contact zones include concrete, acid-proof concrete, carbon steel and the like alloy materials can be used when there is an excessively corrosive atmosphere in the system is present.

Claims (10)

Claims: 1. Process for degassing H2S-rich liquids Sulfur, characterized by (1) continuous introduction of the sulfur into the 1st stage of a contact zone that contains more than one separate contact stage, such that the sulfur occupies the lower region of the contact zone; (2) continuous Introduction of a low-H2S carrier gas into the upper area of the 1st stage of the contact zone such that the carrier gas is separated from the liquid sulfur by an interface is; (3) continuous withdrawal of H2S-poor liquid sulfur at which the H2S content was reduced from the lower range at least one subsequent stage of the Contact zone; and (4) continuously withdrawing at least a portion of an H2S-rich Carrier gas from the top of a subsequent stage of Contact zone, the liquid sulfur within the contact zone in a temperature range from about 1200 to about 1600 C and also within at least a separate contact step in an amount of about 1 to 100 times the amount of sulfur supplied is circulated to this contact level. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h Not that the H2S-rich liquid sulfur is from about 70 to about 300 weight percent contains per million H2S. 3. The method according to claim 1 or 2, d a d u r c h g e -k e n n z e i c h n e t that the contact zone has three separate contact stages. 4. The method according to any one of claims 1 to 3, d a d u r c h g e k It is noted that ammonia is added to the liquid sulfur. 5. The method according to any one of claims 1 to 4, d a d u r c h g e k It is noted that the carrier gas that is low in H2S is free of H2S. 6. The method according to any one of claims 1 to 5, d a d u r c h G It is not noted that the H2S-poor liquid sulfur from the contact zone is withdrawn, contains less than 15 parts by weight per million H2S. 7. The method according to any one of claims 1 to 6, d a -d u r c h g e it is not stated that the contact zone is a sulfur container, that the Process product of a process in which liquid sulfur is obtained from H2S formed wftd 8. The method according to any one of claims 1 to 7, d a -d u r c h g e does not indicate that the poor carrier gas is an inert gas or air. 9. The method according to any one of claims 1 to 8, d a -d u r c h g e it is not stated that the H2S content of the H2S-rich carrier gas is between 0.5 and 1.5 vol-8. 10. The method according to any one of claims 1 to 9, d a -d u r c h g e it is not indicated that the carrier gas low in H2S from (2) enters the last stage the contact zone is introduced and the H2S-poor liquid sulfur from (3) from the last step of the contact zone is withdrawn