FR2672819A1 - PROCESS AND APPARATUS FOR DESULFURIZING PROCESSING GAS. - Google Patents

Abstract

A method and apparatus for process gas desulfurization is disclosed. It relates to a process in which the sulfur-containing gases are contacted with a particulate sorption material forming a fluidized bed, and are transported to a reaction zone for fixing the sulfur to the sorption material. This is separated from the gases. According to the invention, the sorption material which has been separated from the gases is cooled in a return duct (17) before undergoing regeneration, so that the temperatures of the recycled mass and of the reactor (3) are regulated. Application to the desulfurization of process gases.

Description

The present invention relates to a desul-

  treatment gas treatment using a recycled mass

  key which is regenerated, in which the sulfur-containing gases are brought into contact with a particulate sorption material forming a fluidized bed and are transported with the sorption material in a reaction zone ensuring the fixing of the sulfur to the sorption material, and the

  sorption material containing sulfur is separated from the gases.

  which are transported for further processing, then the sulfur containing sorption material is transported to a regeneration operation for separating the sulfur from the sorption material, the sulfur separated from the sorption material is transported for treatment additional, and the sulfur-free sorption material is brought back into contact with the gas

treatment.

  The invention further relates to an apparatus comprising a desulfurization reactor having a fluidized bed chamber which contains a fluidized bed formed by a material.

  sorption particulate and in which a process gas

  transported, a reactor chamber placed above

  above the fluidized bed chamber, a separate device

  tor placed in the upper part of the reactor chamber and intended to separate the sorption material containing sulfur from the treatment gases, an exhaust duct intended to evacuate the treatment gases, a

  regeneration reactor, and at least one trans-

  port of sorption material containing sulfur to the regeneration reactor, a gas transport pipe

  and sulfur separated from the regeneration reactor

  ration, and a sorption material return pipe from the bottom of the regeneration reactor to the

fluidized bed.

  A central problem posed by desul-

  furation based on the direct fixation of sulfur, for example on calcium, concerns the high quantity of

  waste produced In addition, when the hydroso-

  Since the waste products produced pose a danger to the groundwater of the waste discharge regions, it is evident that, in the long term, processes must be developed which minimize the amount of waste produced. At the present time, a large number of processes for fixing sulfur oxides are known, in which the final fixing is carried out in the form of elementary sulfur in the solid phase. In principle, in an intermediate stage of all these processes, the sulfur oxide content must first be increased by concentration so that it reaches a value high enough for the elementary sulfur production operation to be profitable In the concentration operation, the sulfur oxides are

  first attached to a sorption material having pro-

  suitable properties and which is regenerated, and in this case the sulfur is released and a sorption material again capable of fixing sulfur is formed.

  sulfur and the regeneration of sorption material

  of sulfur are then produced in reactors

  between which the sorption material is trans-

  carried so that the sulfur-containing sorption material is transported to a regeneration reactor and, correspondingly, the regenerated sorption material is transported to a sulfur fixation reactor at the same time as a purified gas is removed from the

  reactor and sulfur is removed separately from the apparatus

  reil of regeneration The transport of the material of sorp-

  tion must be carried out in a stable manner and so that the mixture of gaseous compounds between the reactors is reduced. Currently, a device which implements the fixed bed and fluidized bed technique for the sulfur fixing operations with regeneration is being developed. As the temperature control is very important for the desulfurization with regeneration, the forecasts concerning the fixed bed technique do not seem promising, since the adjustment of the

  temperature and reaction control are difficult.

  From the point of view of efficient mass transport, it would also be important that a finely divided sorption material could be used, and this is difficult in the case of a fixed bed reactor Correspondingly, obtaining a quantity sufficient recycled mass and, with a sufficient separation capacity requires sufficient space, so that the diameters of the reactors putting

  implement the fluidized bed technique are important.

  However, as the amount of gas from the regeneration reactor

  ration is for example only from 1 to 3% of the gas stream of the sulfur fixing reactor, the problem posed by the large diameter essentially concerns the reactor

fixing sulfur.

  The object of the present invention is to provide

  sition of a process and an apparatus allowing the elimination-

  tion of the aforementioned drawbacks The process according to the invention

  is characterized in that the sulfur-containing sorption material, which has been separated from the process gas, is cooled before being transported to be regenerated so that the temperature of the recycled mass and that of

of the reactor are regulated.

  The apparatus according to the invention is characterized in that the reactor chamber has a cross-section, in the direction of gas flow, which is less than that of the

  fluidized bed chamber, and in that the trans-

  port of sorption material containing sulfur to the regeneration reactor has a heat exchanger

  intended to regulate the temperatures of the material of sorp-

  tion and so the whole reactor.

  Thus, in the process according to the invention, the fixing

  tion of sulfur occurs in a mass-recycled reactor

  key, and in this case, a finely sorption material

  divided, for example metal oxides or preferably

  An alloyed metal oxide, for example a zinc ferrite oxide (diameter between 0.05 and 0.3 mm) and a high gas velocity (3 to 6 m / s) can be used, and the diameter of the sulfur fixing reactor is not excessively large If a bubbling fluidized bed technique is used, the speed of the gas must be limited below 0.5 m / s depending on the size of the sorption material. gas stream from the reactor

  regeneration is for example between 1 and 3% alone.

  of the gas stream from the sulfur fixation reactor, and the diameter of the regeneration reactor is not important, although the gas speed is limited to the

  speed range of a bubbling fluidized bed, i.e.

  say at a speed of about 1 m / s.

  The stabilization of the temperature of the sulfur fixing reactor is carried out, by implementing the essential characteristic of the invention, so that the cooling surfaces are essentially placed in the return or recycling conduit of the recycled mass, and in this case the stream of solids circulating in the cooler, and thus the efficiency of the cooler, are automatically adjusted in

  function of the gas stream to be treated In addition, the temperature

  ture can be regulated, if necessary, by using a separate stream of recycled gases intended for regulation

the efficiency of the cooler.

  The process for adjusting the streams of solid materials between the reactors is also essential according to the invention. It is implemented using organs

  pulse power supply, the operating principle of which

  nement is as follows A plug-like layer, that is to say an area forming a layer of solid matter, is placed at the beginning of the pulse feed member, and the solid matter is transported from the part lower of this member using gas charges similar to pulses, by the most suitable pneumatic technique. The regulated recycling of solid materials between the sulfur fixing reactor and the regeneration reactor is carried out by connection of the

  desulphurization reactor using a feed member

  pulsation to the regeneration reactor, and vice versa. Other features and advantages of the invention

  tion will be better understood on reading the description

  which will follow of embodiments, made with reference to the appended drawings in which: FIGS. 1 and schematically represent it, in side elevation in partial section and in section through a horizontal plane AA, a reactor with recycled mass according to the invention ; and FIG. 2 represents another embodiment of a recycled mass reactor according to the invention, with

parts torn off.

  The recycled mass reactor represented in FIG. 1 comprises a sulfur fixing reactor having a projection base 1 by which the gas to be treated and any recycled gas are transported to a chamber 2 with a fluidized bed placed at the bottom of the reactor at

  recycled mass The lower part of the reactor, i.e.

  say the fluidized bed chamber 2, preferably has a section, in the direction of gas flow, which is greater than that of the actual reactor chamber 3 placed above Then, a high density of particles can be maintained in the lower part, without excessive increase in the density of the particles in the entire reactor space In the annular chamber 3 of the reactor shown in the figure, the gases and the sorption material are transported upwards to the inside the reactor in the form of a suspension and arrive at a grid 4 with cyclone fins placed at the top of the reactor with recycled mass, the fins being used as a separation device and as a guide for circulation The suspension is then transported tangentially in a cyclone chamber 5 in which the particles of sorption material are

  separated from the gas The gas separated from the particles is trans-

  carried to a subsequent treatment stage by a discharge conduit, that is to say the tube 6 placed in the center of the cyclone, and the mass of particles separated on the walls of the cyclone falls into a distribution chamber 7 placed under a deflector plate The role of the distribution chamber 7 is to distribute the recycled particulate mass

  evenly over the entire surface of the gold section

  cooling duct, i.e. heat exchanger 9, which is placed symmetrically in the direction

  axial This result is obtained with a projection plate 8

  tion of suitable configuration Figure la shows schematically the section of the reactor along line A-A

  and it shows how the reactor is built The sample

  heat exchanger located in the center of the reactor has a regenerative operating mode The heat exchanger 9 has several return conduits or heat exchange conduits 9 through which the recycled mass is

  returned to cooler 9 to the bottom.

  There is an intermediate space from which circulates a cooling fluid, for example a gas, air, water, another liquid or a mixture of steam and steam, from the lower end of the cooler through the conduit 11 and directed towards the upper end against the current of the recycled mass, so that the external surface of the conduits 9a is cooled and the

  recycled mass circulating inside is also.

  A lower cone 10 is placed at the lower end

  of the cooler 9, the free end of the cone being not more than 10% of the section of the annular space 3 so that the gas stream from the mass-recycled reactor is guided The inlet and

  outflow of gas or other coolant

  transmitted to the cooler have been designated by the

references 11 and 12.

  In FIG. 1, the regeneration reactor 13 has been placed annularly around the sulfur fixing reactor 3. The inlet tubes for the regeneration gas, for example steam or another suitable gas, have been designated by the reference 14, the reference 13 indicates the annular regeneration chamber, and the reference 20 designates the tube intended for the gas containing the sulfur, coming from the regeneration A transport conduit, for example, a conduit 16, starting from a lower part of the heat exchanger, leads to the upper part of the. reactor 13, the end of the tube close to the cooler 910 comprising a front vertical part 15 in which the sulfur-containing sorption material forms a layer

  analogous to a plug The transport gas, which is preferably transmitted in a pulsed manner, transports the sorption material containing the sulfur in the tube 1615 to the regeneration reactor 13, via the horizontal part.

  adjacent plate 16 of tube and a gas conduit 19 placed at the corner of the horizontal tube 16 and forming an extension thereof The reference 17 designates a return conduit of the regenerated sorption material, connected to the lower part of the regeneration reactor , the regenerated sorption material forming another layer similar to a

  plug in the vertical part which is at the end

  mite before the return pipe, and the gas, which is still preferably transmitted in a pulsed manner by the tube 18, then transports the sorption material to the sulfur fixing reactor The layer of solid material in the form of a plug ensuring the sealing is formed by circulation of solid materials in the substantially vertical tube 15 or 17 of the conveyor passage and, in this tube, the level of solid materials is maintained sufficiently

  high above the horizontal part of the transport tube

  If no gas is transmitted to the transport tube by tube 19 or 18, the circulation of solid materials is interrupted, since the solid materials cannot

  flow by themselves in the sensitive transport tube-

  horizontal If the gas is transmitted to the transport tube

  sorption, the layer of sorption material in the vertical tube begins to flow down like a plug while its lower part is removed with the gas and the gas tightness remains intact A a solid material transport tube is connected to the lower end of the vertical tube part in which the solid material is pneumatically transported with a suitable gas vehicle by means of a continuous gas stream or gas pulses. In the sulfur fixing reactor, the gas speed calculated for the entire section 3 varies for example between 3 and 6 m / s In the sulfur fixing reactor, the density of the suspension which is at the part lower is most advantageously between 50 and 300 kg / m 3 and, in the upper part, between 5 and 30 kg / m The temperature range is determined according to the chemical kinetics of the fixing reaction and it usually varies between 450 and 1050 OC It is essential that, by using a technology using the recycled mass, the temperature can be adjusted to the desired value throughout the reactor volume

of fixation.

  In the regeneration reactor in which the gas stream is very reduced compared to the stream

  gaseous from the sulfur fixation reactor, one can obviously

  use a very low gas speed, without increasing

  important dimension of the external dimensions of the device.

  An advantageous solution from the technical point of view as regards the apparatus is the arrangement of the regeneration reactor, in the embodiment of FIG. 1,

  with rotational symmetry around the fixing reactor

  tion of sulfur A suitable gas velocity in the regeneration reactor is between 0.2 and 1.0 m / s, with a finely divided sorption material The average density of the suspension zone of a fluidized bed reactor working in a bubbling state is preferably between 100 and 500 kg / m 3 The temperature is determined according to the kinetics of the regeneration reaction and it varies between 700 and 1300 OC The temperature range of the regeneration reactor is relati - narrow clothing for most sorption materials, so that it must also be possible to regulate the temperature of the regeneration reactor with precision As the thermal energy released is relatively reduced, the fine adjustment of the temperature can be done by a

  direct process, using steam.

  water In most cases, water is the

most advantageous cooling.

  FIG. 2 schematically represents another embodiment of a reactor according to the invention, with parts cut away. In FIG. 2, the actual desulphurization reactor, in which the sulfur gases are transmitted to the

  reactor by line 1, is shown on the right.

  Then, they are transported to the chamber 2 with a fluidized bed in which they circulate through the material of the fluidized bed and flow in the annular duct 3 towards the upper part of the reactor, before returning while being guided by the guide 4, that is to say the finned grid, towards the separation chamber 5 in which the recycled material, that is to say the sorption material containing the sulfur, is separated from the gases The gases are evacuated in the manner represented in FIG. 1, by the

  conduit 6, from the center of the separation chamber 5

  tion, and the sorption material falls from the separation chamber into the recycling conduit 5a and into the chamber 2 again. Part of the sorption material falls into the vertical evacuation conduit 15 and into the horizontal part 16 of the discharge pipe, and it is transported in the regeneration reactor by the transport gas transmitted in the pipe 19 The regeneration reactor works in principle in the same way as the desulfurization reactor, a regeneration gas and / or the water vapor being transmitted to the lower part of the regeneration reactor via line 14, and in this case, the regeneration gas and / or water vapor enters the chamber 13 ′ which is preferably a bed chamber

  fluidized, and flow in its annular part, that is to say

  say chamber 13 a of regeneration, towards the upper part

  of the reactor and again arrive in the separation chamber 5 ′, being guided by the fin grid 4 ′. In the separation chamber, the regenerated sorption material is separated from the regeneration gas and the

  water vapor which carries sulfur through line 20.

  placed in the center of the chamber, during evacuation In chamber 5 ', the sorption material which has been separated falls into another duct Sa' for recycling to the

  chamber 13 'and again comes into contact with the regeneration gas

  However, part of the regenerated material falls back into the

  return, i.e. the 15 'tube, and in the hori-

  zontale 17, at the bottom, by which the regenerated sorption material is transported to the chamber of the desulphurization reactor by transmission of the gaseous vehicle which transports the sorption material in the conduit 18 In the solution of FIG. 2, heat exchangers heat have been placed around the horizontal transport duct, that is to say of the tube 16, leading from the desulfurization reactor to the regeneration reactor, as well as around the return pipe of the sorption material, that is ie the tube 17 A cooling fluid is transported to the heat exchanger 21 placed around the transport duct 16, by a tube 22, and it is evacuated by a tube 23, that is to say that the 'heat exchanger works against the current Correspondingly, the coolant is transported to the heat exchanger placed around the return duct 17 by the tube 22', and it is withdrawn by the tube 23 ', followed nt the principle of the counter current In addition, in Figure 2 heat exchangers or coolers 24 and 24 'are placed around

  of the desulfurization reactor and the regeneration reactor

  tion, and a heat exchange fluid is transported by it from the tubes 11, 11 'and 12, 12' in the heat exchangers or coolers. The invention has only been described by way of example and can be the subject of numerous variants. Apart from the arrangement of the reactor constructed as a whole and as a fixed assembly, separate assemblies can be used.

  as shown in Figure 2 and, in this case, the desulfurization reactor can be constructed so that it. has the highest possible desulfurization efficiency10, and the regeneration reactor can be built

  trout with another type so that it is as profitable as possible. In addition and preferably, the fluidized bed uses a particulate material having at least two sizes in order to

  that it gives a suitable density to the suspension

  sion, and in this case, the particulate material has a diameter between 0.5 and 2 mm, and the recycled mass stream is produced using a material having a markedly smaller diameter, preferably between 0 , 05 and

0.3 mm.

  Of course, various modifications can be made by those skilled in the art to the methods and apparatuses which have just been described only by way of examples.

  non-limiting without departing from the scope of the invention.

Claims (13)

  1 Process for the desulfurization of process gases, with regeneration, by using a recycled mass, in which the gases containing sulfur are brought into contact with a particulate sorption material forming a fluidized bed and are transported with the material of   sorption in a reaction zone intended to fix the sulfur to the sorption material, and the sorption material. containing the sulfur is separated from the process gases which are transported for further treatment, and the sorption material containing the sulfur is then passed   worn to undergo the regeneration which separates the sulfur from the sorption material, the sulfur separated from the sorption material is transported for further treatment15 and the sulfur-free sorption material is returned in contact with the treatment gases, characterized in that the sulfur-containing sorption material, which has been separated   process gases, is cooled before being trans-   scope for regeneration so that the temperatures of the   recycled mass and the reactor are regulated.   2 Method according to claim 1, characterized in   what cooling is achieved using a swap   heat sink (9, 21) placed in the duct which trans-   carries the recycled mass towards regeneration, in that a layer of recycled mass similar to a plug is formed in the transport duct (15, 16) so that the gas flow is regulated, in that the sorption material is transported from the layer formed by the plug to the regeneration reactor (13) by means of gas pulses transmitted to the transport conduit (16), and in that another layer of regenerated sorption material, similar to a plug, is formed at the lower end of the reactor   regeneration (13), the sorption material being trans-   reach of the second layer similar to a plug in the fluidized bed using gas pulses transmitted to the conduit back (17).   3 Method according to one of claims 1 and 2,   characterized in that the current of the recycled mass flowing in the heat exchanger (9) is regulated by transmission of a suitable recycled gas or an equivalent gas towards the fluidized bed.   4 Method according to one of claims 2 and 3,   characterized in that the fluidized bed uses a particulate material having at least two sizes so that it gives a suitable density for the suspension, and in this case, the particulate material has a diameter of between 0.5 and 2 mm, and the recycled mass stream is produced using a material having a markedly diameter   smaller, preferably between 0.05 and 0.3 mm.   Method according to any of the claims   previous, characterized in that the sorption material   containing sulfur is formed from at least one metal oxide   lique or a metal alloy oxide.   6 Apparatus for carrying out the process   according to claim 1, comprising a desul-   furation which comprises a fluidized bed chamber (2) which contains a fluidized bed formed by the particulate material   sorption and in which the process gas is transported   A reactor chamber (3) placed above the fluidized bed chamber (2), a separator device placed at the top of the reactor chamber (3) and intended to separate the sorption material containing the sulfur. process gas, exhaust pipe (6)   intended to evacuate the treated gases, a regeneration reactor   tion (13), at least one transport conduit (15, 16) intended to transport the sorption material containing sulfur towards the regeneration reactor (13), a conduit (20) intended to transport the regeneration gas and the sulfur separated from the regeneration reactor (13), and a return conduit (17) intended to return the material of   sorption of the lower part of the regeneration reactor   ration (13) to the fluidized bed, characterized in that the reactor chamber (3) has, in the direction of gas flow, a smaller cross-section than that of the fluidized bed chamber (2), and in that the duct for transporting the sulfur-containing sorption material to the regeneration reactor (13) has a heat exchanger (9, 21) intended to regulate the temperatures of the sorption material and thus of the whole reactor.   7 Apparatus according to claim 6, characterized in   what the fluidized bed chamber (2), the reaction chamber.   tor (3) and the part of the transport duct (15, 16) which transport the sorption material to the regeneration reactor are constructed in substantially cylindrical and coaxial form, so that the part (15) of the transport duct which transports the sorption material towards the regeneration reactor is located above and is substantially coaxial with the fluidized bed chamber (2) and in that the reactor chamber (3) is constructed around the transport duct in the form of an annular duct, in that a cyclone chamber (5) is placed in the upper part of the reactor chamber   (3) and has circulation guides (4) at its upper part   so that the suspension formed by the gas   treatment and the sorption material is directed tangent   tially towards the center of the cyclone chamber (5), and in that the exhaust duct (6) is located in the center of the cyclone chamber (5) and coaxially with it, and in this case, the treatment gas is discharged through the exhaust duct (6) and the sorption material falls into a distribution chamber (7) placed below the cyclone chamber (5) then at least partially in the part of the exhaust duct transport (15) which is located below the distribution chamber (7).   8 Apparatus according to claim 7, characterized in that the heat exchanger (9) is constructed in the transport conduit placed above the chamber (2) with a fluidized bed, in a direction substantially coaxial with the   fluidized bed chamber (2), in that the trans-   port includes several heat transfer conduits passing through the heat exchanger and through which the sulfur-containing sorption material circulates and the   external surface is cooled by the coolant   which circulates in the heat exchanger (9).   9 Apparatus according to claim 8, characterized in   that the regeneration reactor (13) is arranged annu-   around the reactor chamber (3).   Apparatus according to claim 7, characterized.   in that the regeneration reactor (13) is a separate reactor in which the sorption material which has reacted with sulfur is transported and from which the regenerated sorption material is returned to the fluidized bed chamber (2) of the reactor and in that a recycling conduit (5 a) is arranged in the desulfurization reactor around the conduit (15) for transporting the sorption material, in a substantially coaxial direction, so that part of the material of sorption comes back   directly in the fluidized bed chamber (2).   11 Apparatus according to claim 10, characterized in that the regeneration reactor (13) has another fluidized bed chamber (13 ') which has a fluidized bed of a particulate sorption material and in which the regeneration gas is transported , a regeneration chamber (13 a) placed above the second fluidized bed chamber (13 '), the regeneration chamber having a section, in the direction of flow of the regeneration gas, which is smaller than that of the second fluidized bed chamber (13 ′), a separating device placed at the top of the regeneration chamber (13 a) and intended to separate the material to be regenerated from sorption from the regeneration gas, and a discharge duct ( 20) of regeneration gas and a conduit (15 ′, 17) for returning the regenerated sorption material from the lower part of the regeneration reactor (13) to the fluidized bed of the reactor desulfurization (13).   12 Apparatus according to claim 11, characterized in that the second fluidized bed chamber (13 '), the regeneration chamber (13a) and a part of the return duct (15') which transports the regenerated sorption material to the fluidized bed chamber (2) of the desulfurization reactor are made so that they are cylindrical5 and substantially coaxial, so that the part (15 ') of the return duct which transports the sorption material to the desulfurization reactor is located above the second fluidized chamber (13 ') so that another, cyclone chamber (5') is placed in the upper part of the regeneration chamber (13a), this chamber having circulation guides (4 ') at its upper end so that the suspension formed by the regeneration gas and the sorption material is directed tangentially towards the center of the other cyclone chamber (5'), and in this that the idiot evacuation hose (20) is in the center of the second cyclone chamber (5 ')   coaxially with it, and in this case the regeneration gas   tion and the separated sulfur is extracted through the exhaust pipe (20) and at least part of the regenerated sorption material falls into the return pipe (15 ')   placed under the second cyclone chamber (5 ').   13 Apparatus according to claim 12, characterized in that a second recycling conduit (5 a ') is placed   around the return duct (15 ') of the sorp material   tion, in a substantially coaxial position, so that part of the sorption material is returned in the second fluidized bed chamber (13 ').   14 Apparatus according to any one of the claims   tions 10 to 13, characterized in that a heat exchanger   at least (21) is placed in the tube (16) running from the reaction   desulfurization reactor and regeneration reactor the role of a transport conduit.   Apparatus according to any of the claims   tions 10 to 14, characterized in that at least one heat exchanger (21 ') is placed in the tube (17) going from the regeneration reactor to the desulphurization reactor and   used as a transport conduit.   16 Apparatus according to any one of claims 6 to 15, characterized in that an essential part-   The horizontal line (16) of the transport duct joining the regeneration reactor (13) is connected to the lower end of the vertical part (15) of the sorption material transport passage in which the sorption material containing the sulfur forms a plug-like layer, a gas conduit (19) being connected to this. part (16) so that it transports sorption material10 coming from the plug-like layer using gas pulses transmitted by the horizontal part of conduit (16) to the regeneration reactor (13), that a substantially horizontal portion of duct (17) joining the fluidized bed chamber (2) is connected to the lower end of the portion (15 ') of the vertical sorption material return duct placed in the center of the reactor. regeneration (13), the sorption material   which fixed the sulfur forming, in this lower end   upper (15 '), another layer similar to a plug, a second gas supply duct (18) being connected to the duct part (17) so that the sorption material advances under the action of pulses gas, from the second layer similar to a plug to the chamber (2) with fluidity bed.