JPS6037041B2 - Production of elemental sulfur - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing elemental sulfur.

It is known to produce elemental sulfur by contacting oxides of sulfur such as S02 and S03 (hereinafter referred to as "SO") with a reducing agent, e.g. carbon, at high temperatures; is oxidized to carbon oxide. However, by increasing the contact temperature between S○k and carbon appropriately, S○×
Difficulties arise in ensuring an effective and economical conversion of sulfur to sulfur. To maintain a suitably high temperature, an oxygen-containing gas, such as air, is injected into the conversion vessel to generate heat from the oxidation of the carbon. This clearly has a detrimental effect on the overall economics of the process, since carbon is consumed simply to maintain the reaction temperature. Methods are known for producing substantially oxygen-free Sok-containing gas streams.

In one such method, when SO skin-containing flue gas is contacted with oxidized steel, the oxidized steel solidifies S○× as CuS04 in the presence of oxygen normally present in Katsudo gas, and The CuS04 is treated with a reducing gas to recover the Cu○ for subsequent use, liberating S02 and some S03. In other methods, a sulfur-containing fuel, such as fuel oil or coal, is partially or completely combusted in a fluidized bed of calcium oxide-containing particles to produce a combustible fuel containing almost no sulfur. A gas or nearly sulfur-free flue gas is produced, and the sulfur is fixed in the particles as either CaS or CaS04. The particles are then exposed to an oxygen-containing gas (in the case of CaS) or a reducing atmosphere (CaS).
S04) to regenerate Ca○, liberate S02 and some S03, and reuse the regenerated Ca○ to fix the next amount of sulfur from the sulfur-containing fuel. . This latter type of method is described in British Patent Nos. 1,183,937 and 1,336,563. S○x-containing gas streams from the above and other methods can be prepared to be relatively rich and largely oxygen-free, so that they can be
It has been proposed to send the coal into a single vessel containing a non-fluidized bed of crushed coal with a particle size of 5 to -27 skins.

In order to make the contact temperature of S○k and coal suitably high so that the reduction of elemental sulfur from the SO gas proceeds at an operational rate, an oxygen-containing gas, e.g. air, can be injected into the vessel. The coal must be oxidized and the necessary heat supplied. It is clear that the consumption of coal to maintain the temperature has an economic disadvantage in the implementation of this method of converting S0k to elemental sulfur. In addition to the above-mentioned shortcomings which increase operating costs, the vessel, the land area and volume occupied by it, and the conduit transport of the S○k-containing gas and the supply of oxygen-containing gas into the interior of the vessel There is also additional capital expenditure for the installation of blowers. It has now been discovered that elemental sulfur can be recovered effectively, inexpensively, and directly from sulfur-containing solid materials, such as those mentioned above, by simple means that avoid the drawbacks of conventional processes.

According to one aspect of the invention, particles containing at least one solid compound of sulfur are treated and preferably fluidized in a subbed under conditions in which sulfur is liberated as SO, and the resulting SO
The skin is passed upwardly at high temperature into an upper bed containing a char as defined below, preferably fluidized by a Sok-containing gas from the underbed, thereby converting at least some S○× into the element. of sulfur, the char has a density lower than that of the particles in the subbed, such that the bottom of the top bed is level with and in contact with the top of the bottom bed. Because the densities of the char and particles are different, the char in the top bed floats onto the particles in the bottom bed, and the char effectively begins to layer at the top of the bottom bed.

There is a region between the upper bed and the lower bed where some mixing of char and particles occurs. The term "char" is used herein to include coal, lignite, shale and their solid pyrolysis products (e.g. coke, coal char), charcoal, petroleum coke (substances having petroleum coke on their surface or in their pores). )
and mixtures of the foregoing.

Although the invention can be carried out batchwise, it can also be operated continuously by sending particles containing solid compounds of sulfur to a lower bed and sending char or materials that produce char under operating conditions to an upper bed. is suitable. In such continuous operations, it is preferred to remove the particles from the subbed after a certain time in the subbed, so as to avoid accumulation of particles with reduced sulfur content. Removal of particles is preferably carried out from a part remote from the part into which the particles enter. Depending on the material of the char, it may or may not be necessary to remove the "spent" char.

This is because if the char is powdered coal or coke, the reaction with S○k leaves an ash residue that leaves the upper bed and is entrained in the exiting gas or steam stream. It is. However, the pyrolysis of a char on an "inert" low-density solid support, such as a fluid petroleum material (e.g. heavy oil, residual oil or cycle oil from catalytic cracking) in contact with lightweight brick fragments or pumice, In the case of petroleum coke on light-weight porous refractory brick fragments or pumice made by . The support solid effluent may contain recoverable metals, such as vanadium originally present in the petroleum material. The amount of char present in the upper bed is preferably kept approximately constant by sending char or char-forming material to the upper bed to replace that lost by reaction with SO. The conversion of sulfur-containing solid components to S○k and the conversion of elemental S○× to sulfur are all carried out in a single process operated at some conversion temperature which is critical for either conversion to occur. It should be appreciated from the foregoing that this can occur in a reaction vessel and preferentially in an oxygen-free atmosphere where chert reactions can occur.

Compared to previous methods, capital expenditures are therefore reduced and operating efficiency and conversion are increased. The invention will now be described by way of example and without limitation with reference to the accompanying drawings, in which: FIG. In FIG. 1, the container 16 has a gas distributor 18 on its base, and the solid particles of sulfur-containing material are transferred to the transfer tube 1.
9 into a container 16 to form a bed 20 which is supported on a distributor 18 . If the process is carried out continuously, as is usually the case, the treated solid material is removed from the bed 20 via a pipe 21 located remote from pipe 19 to form a substantially constant sulfur-containing material. Maintain the amount held. As shown, tube 19 delivers material into the top region of bed 20 and tube 21 discharges material from the bottom region of the bed, but their relative positions are not critical. What is generally important is that the incoming material should have an adequate residence time to be treated in bed 20 before being removed, and this should be done by some means such as tubes 19 and This can be ensured by the installation of a regulating device for directing the particles into the elongated passage between the tubes 21. The process gas is routed from line 24 into vessel 16 under distributor 18 to cause it to pass through bed 20 in a relatively uniform manner.

Preferably, the process gas fluidizes the particles in bed 20. The nature of the process gas depends on the chemical composition of the sulfur-containing particles.

The particles are metal sulfides, such as zinc blende (ZnS), chalcopyrite (
CuS) or calcium sulfide (CaS), the process gas is preferably heated in a subheater (not shown).
It is the air that is heated inside.

The reaction between metal sulfides (MS) and oxygen is usually exothermic and, provided the temperature and amount of oxygen are within certain ranges that can be determined by one skilled in the art, the main reaction product is sulfur oxide. (S○x) and metal oxides (MO), other products possibly being eg metal sulfates. If the particles contain metal sulfates, such as CuS04, CaS04, etc., the process gas can be at least partially reducing. That is, it can be reducing in some areas of the bed 20 and neutral or even oxidizing in other parts of the bed. This type of non-uniform process gas is preferably produced by burning fuel from line 25 in an oxygen-containing gas from line 24 in bed 20. Mixing of the gases in the fluidized bed tends to be relatively poor, and if combustion near the fuel injection region is carried out with substoichiometric oxygen, the portion of the atmosphere in bed 20 is reducing. .
If the total amount of oxygen admitted to the bed 20 is clearly in excess of the stoichiometrically required amount, no reduction of the metal sulfates will take place as the fuel will be completely combusted inside the bed. Non-uniform reducing process gases tend to avoid metal sulfide formation. Good particle circulation in the fluidized bed means that sulfide is converted back to sulfate and then reduced in the reducing region, or liberates S○k and oxidizes to metal oxide. This is because it moves sulfide through the oxidizing regions of the bed where it can be removed. Alternatively, a mild thermal reducing gas can be introduced via line 24 to liberate S0k and convert the sulfate to oxide. The sulfur oxide is primarily S02 with some S03, but in the presence of excess oxygen the proportion of S03 is increased by catalysis from the bed material. To maintain a suitably high temperature in bed 20, fuel (which can be a flammable gas or hydrocarbon liquid or solid fuel) can be injected into bed 20 through line 25.

The gas reaching the top of the bed 20 contains little oxygen;
Preferably it contains a small amount of sulfur oxide and an inert gas such as nitrogen, and if the fuel is supplied from line 25, it preferably contains fuel combustion products such as CO2 and CO2.

As previously defined, at the upper end of bed 20 there is a bottom of bed 26 of char, and bed 26 is preferably fluidized by upwardly passing gas. The reaction conditions in bed 20 are such that the gas passing upwardly is at a temperature at which the sulfur oxide and char react to give elemental sulfur and carbon oxides such as CO2 and CO, preferably CO2. must be adjusted. The minimum reaction temperature depends on the nature of the char.
For example, if the char is a reactive carbonaceous material, such as petroleum coke on or mixed with a suitable reaction promoter, such as bauxite, the reaction will proceed at temperatures as low as 310 qo. The highest reaction temperature was in vessel 16.
limited by its constituent materials and economic factors. floor 26
The concentration of free oxygen should be as low as possible, since the presence of free oxygen in the gas passing through consumes the char by oxidation while generating significant amounts of heat, without contributing to the yield of elemental sulfur. It is. The maximum temperature in floor 26 is 13
It can be as high as 50pm. But 600
It is preferred to use a temperature in the range of ~1250 oo, the temperature in the bed 26 being dependent, at least to some extent, on the temperature of the gas being routed from the top of the bed 20 into the bottom of the bed 20; The temperature of will depend on the process conditions in bed 20. The gas and vapor products of the reaction in bed 26 are collected in line 28 and passed through a solids removal device 29, such as a cyclone, precipitator or furnace, and the solids thus removed are passed through line 30. The product that is recovered or disposed of and contains almost no solids is sent via line 31 to a sulfur recovery cooler 32, the sulfur is recovered via line 33, and the gases and vapors containing almost no elemental sulfur are It exits the cooler 32 via line 34.

Any unconverted residue of sulfur oxides or other sulfur fractions, when the sulfur concentration is unacceptably high, may be removed from the gas or vapor stream by any known method before discharging the stream to the atmosphere. can do. To maintain the amount of char in bed 26, additional char or char-generating material can be passed into bed 26 via line 27.

The activity of bed 26 can be maintained by removing material from bed 26 via line 35. The material removed is ash or a substrate or carrier on which reactive char has been deposited. As indicated above, char is coke, or coal, preferably coal that pyrolyzes into highly porous coke, or char is carbonized liquid, preferably having a high carbon to hydrogen atomic ratio. Hydrogen materials, such as heavy cycle oils or residual oils from thermal and catalytic cracking operations, asphalt or pitch, can be produced in situ by injecting them onto a porous, low density substrate or carrier.

For low carbon-to-hydrogen atomic ratio hydrocarbon materials, it is preferred, but not necessary, to make the coked substrate or carrier in a separate coking apparatus outside vessel 16. This is because the hydrogen-rich vapors and gases produced by the coking or pyrolysis of such materials in bed 26 reduce at least some of the oxidized sulfur sent in contact with them to hydrogen sulfide, which further This is because it requires treatment to recover elemental sulfur. FIG. 2 shows the apparatus of FIG. 1, generally designated 10, incorporating the combustion system as part of a fluidized bed. The system 10 includes a combustion vessel 11
containing 12 beds of lime or dolomite powder.
is supported on an air distributor 13 spaced from the base of the container 11.

The particles in bed 12 are fluidized by air supplied from line 14, which is directed from distributor 13 into the base of bed 12. A sulfur-containing fuel, such as fuel oil or coal or a slurry of coal and oil, is conveyed into the bed 12 from one or more injectors 15 (only one shown), the fuel having a molecular weight of 750 to 125,000, preferably 800 to 1000q
The heat is combusted in the bed at a temperature in the range of 850-95 and 0, more preferably about 870 qo and removed by heat exchange coils (not shown) immersed in the bed and a nearly sulfur-free flue gas, with the fuel sulfur fixed in the particles as CaS04. The leech gas escapes upwardly via line 36 to a dedusting unit 37 and via line 38 to a conventional heat recovery unit (not shown). Particles containing CaS04 are passed through line 19 to bed 2.
In a river feed, fuel, e.g.
4, a non-homogeneous atmosphere is created in the bed 20 which is generally suitably mildly reducing.

At least some CaS04 was converted to Ca0 and S02 was liberated.

The Ca0-containing particles thus regenerated are returned to the bed 12 via line 21 and are used to fix sulfur from a further fresh quantity of sulfur-containing fuel. To maintain the sulfur fixation activity of bed 12, fresh Ca○ or CaC
Add 03 (limestone) or dolomite via line 39, line 2
When particles are removed via 1a, the amount of particles retained in system 10 remains approximately constant.

The temperature in bed 20 depends on the type of fuel sent therein from line 25 and the relative amounts of fuel and oxygen in the bed, but Ca
Good conversion of S04 to CaO and S○k is 1000
~1350 qo, for example about 1070 qo. S
The O-containing gas passes upwardly through bed 20 and into bed 26 where it is reduced to elemental sulfur at a temperature approximately the same as, or slightly above, the operating temperature of SO subsurface bed 20. .

Referring now to FIG. 3, containers 11 and 16 are constructed from a refractory material, such as shaped refractory cement or blocks of refractory cement.

System 10 is constructed as a single unit, as shown in FIG. 2, rather than as two separate vessels, although in very large plants it may be preferable to use two separate vessels. There is something that happens. Next to the combustion vessel 11 is a vessel 16 constituting a regenerator, and between the vessel 11 and the regenerator 16 is a separation wall 17.

This regenerator 16 has an air distributor 18 on its base;
Particle bed 20 is supported on distributor 18 . The transport duct 19 extends from the upper region of the floor 12 downwardly through the separating wall 17 and through the elbow portion to the distributor 18 some distance [e.g. 0.3048 or 0.6096 (1 or 2 feet)] above the floor. 20 lower regions. Similarly,
The transport duct 21 extends downwardly from the upper area of the floor 20 to the separating wall 1
7 and connects via an elbow section to the lower region of the floor 12, somewhat directly above the distributor 13. A gas pipe 22 is connected to the adjacent bottom ends of the two elbow parts, and an inert gas supply line 23 is connected to the pipe 22. Pulsations of inert gas (e.g. cooled flue gas) supplied in line 23 transport particles in transport ducts 19, 21 from the ducts to beds 20 and 1, respectively.
2 intermittently by the action of gas. In this way, particles containing CaS04 are transferred from bed 12 to bed 2.
0 and the particles are transported from bed 20 to bed 12.
Particles in bed 20 are fluidized by air from line 24 and fuel (e.g. natural gas, fuel oil or coal) is injected into bed 20 from one or more injectors 25 (only one shown). The amount of oxygen sent is preferably no more than sufficient to combust the fuel, and is also sufficient to provide mild, overall reducing conditions in the bed 20.

If the amount of air to provide a suitable amount of oxygen is inadequate to fluidize bed 20, flue gas or water vapor may be included in the air to increase the apparent gas velocity in bed 20. Under these conditions CaS04 is mainly converted to CaO, which is transferred via duct 21 to bed 1 for reuse.
2, thereby liberating sulfur mainly as S02. The temperature in bed 20 can be between 900 and 1350 qo, preferably between 1050 and 1090 qo. floor 20
Floating above the top of the char is a fluidized bed 26 of char as defined above.

This means, for example, that the coal particles are passed through the injection hole 27 to the regenerator 16.
It can be made by feeding it just above the top of the floor 20. - The coal particles are pyrolyzed at the temperature of the bed 20 and expand into a porous low density coke, which is S○
reducing the latter exothermically reacting with k to elemental sulfur,
Coke is converted to carbon monoxide and carbon dioxide. The gas stream containing elemental sulfur is passed through a device (not shown) for recovering the sulfur. Such devices include coolers of the type described in GB 1,331,238. In the method in which the fuel injected at 15 is converted to a substantially sulfur-free combustible gas by combustion in bed 12 with insufficient air for complete combustion, the sulfur of the fuel is fixed as CaS in the particles of bed 12.

The CaS-containing particles are transported via duct 19 to bed 2 and air (with the addition of flue gas if the apparent velocity in bed 20 is otherwise too low for adequate fluidization). The oxygen fluidized in the bed 20 by
00002CaS+202→CaS04 3CaS040CaS→4Ca014 Less than sufficient, preferably slightly less than sufficient, to convert CaS to Ca0 by S02.

Preferably, the above reaction, which is entirely exothermic, is 900 to 1
It is carried out at a temperature of 350 oo, more preferably within the range of 950 to 1200 oo. The regenerated Ca○-containing particles are returned via duct 21 to bed 12 for reuse.

The S02 produced during the above reaction is passed through a "floating" bed 26 of char and is converted, at least in part, to elemental sulfur.

Particularly if the sulfur is initially fixed as CaS04, it is possible to inject char or char-forming material into the regenerator bed 20, since this advantageously promotes the conversion of CaS04 to Ca○. It is.

However, it is nevertheless desirable that the char or char-forming material in this manner be less dense than the other particles that make up the bed 20, creating a "floating" bed 26 above the surface of the bed 20. Since the char has a lower density than the density of the particles forming the regenerator bed 20, creating a regenerator bed with a wider cross-section than the bed 201 at the level of the bed 26 allows the char to have a relatively high apparent velocity. low floor 2
6 to virtually eliminate the tendency to sink into the relatively high bed 20 of gas velocity. This is illustrated in the regenerator bed 20, which has an upwardly flared cross section.
It can be conveniently adjusted by creating a wall of
For simplicity and conciseness of explanation, herein the density of the char is lower than that of the fluidized particles, floating above the top of the fluidized particle bed from which sulfur oxide is made;
Although a fluidized bed of contacting "char" has been described, it is clear to those skilled in the art that factors other than or in addition to density are practical for retaining char in a separate fluidized bed. It should be understood and known that it plays a role.

Among these factors are the size of the char particles and the gas dynamic resistance in the upward passage of the gas, and the upward velocity of the gas. If the resistance is too low, the char particles will tend to sink into the flow particles and mix with them; if the gas velocity is too high or relatively large gas bubbles form in either fluidized bed, Beds of fluidized particles can tend to start mixing with the char. In the practice of this invention, the density, size, and gas dynamic resistance of the char particles are such that the char particles float above and form another fluidized bed in contact with the top of the fluidized bed forming the sulfur oxide. chosen, the upward velocity of the gas through the beds should be lower than the velocity at which mixing of the two beds becomes significant. The embodiments of the method of the present invention are as follows.

2. The method of claim 1, wherein the m char is fluidized by SOk-containing gas from the subbed.

(2) Particles containing a solid compound of sulfur are continuously sent to the lower bed, and particles in which the sulfur content of the solid sulfur compound has been reduced are removed from the lower bed. The method described in.

{3} The method according to item (1) above, wherein at least some of the particles removed from the subbed are used to remove sulfur or fix sulfur as a solid compound of sulfur from the fuel or fuel gas.
{4) The method according to item (3) above, wherein the particles containing the solid compound of sulfur are returned to the subbed.

(5) The method according to paragraph 1 or {4}, wherein the solid compound is produced under generally oxidizing conditions, and the conditions in the subbed are oxidizing on a global basis.

'6) The method according to paragraph (3' or '4) above, wherein the group of compounds is produced under overall oxidizing conditions and the conditions in the subbed are at least partially reducing. . {7-
partially burning the fuel in the underbed in the presence of oxidizing gases;
The method of item (1) above, thereby creating an atmosphere of a non-homogeneous composition that is at least partially reducing.

(2) The method according to any one of claims m to '7'', wherein the solid compound is a compound of sulfur and zinc, calcium or copper. t9) A method according to any one of claims 1 to 8, wherein the char is produced by contacting a hydrocarbon or hydrocarbon monster with a thermal substrate or support material. (1
A method according to the first aspect, wherein the heated substrate or thermal support material is contacted with the hydrocarbon or hydrocarbon material in an overbed.

(11) The method according to item (1) above, wherein a thermal substrate or a thermal support material is brought into contact with a hydrocarbon or a hydrocarbonaceous material outside the upper bed, and the resulting char and substrate or char and support material are sent into the upper bed.

(12) The method according to any one of items [9' to (11)], wherein the substrate or support material is selected from bauxite, brick fragments, and pumice.

(13) The method according to any one of claims m to (12) above, wherein the char is coke or semi-coke produced in situ from coal in the upper bed.

(14) Remove some char from the upper bed and use fresh char.
The scope of claims and the above-mentioned {1} to (13)
).

(15) Claims and the above {1} to (14)
Elemental sulfur made by Kotoki Hagi's method in any one of the above.

[Brief explanation of drawings]

FIG. 1 is a process route diagram of the main parts of one embodiment of an apparatus for carrying out the present invention. FIG. 2 is a process flow diagram of the main parts of another embodiment of the apparatus for carrying out the present invention. FIG. 3 is an enlarged and detailed cross-sectional view of the principal parts of a preferred apparatus of the type shown in FIG. 2; F no G. 7. F'○. 2 F'G. 3.

Claims (1)

[Claims] 1. A process for producing elemental sulfur from a solid compound of sulfur, in which particles containing the solid compound are treated in a lower fluidized bed under conditions in which sulfur is liberated as SOx;
x upwardly at elevated temperatures into an upper fluidized bed containing char, thereby reducing at least some of the SOx to elemental sulfur, the char in the upper bed having a lower density than the density of the particles in the lower bed. , whereby the bottom of the upper bed is at the same level as and in contact with the top of the lower bed.