LV11188B

LV11188B - A process for the refining of a raw gas

Info

Publication number: LV11188B
Application number: LVP-93-1170A
Authority: LV
Inventors: Ekstroem Clas; Bengt-Goeran Espenaes; Kowalic Waclaw; Rensfelt Erik; Waldheim Lars
Original assignee: Tps Termiska Processer Aktiebo
Priority date: 1987-10-02
Filing date: 1993-10-25
Publication date: 1996-10-20
Also published as: ATE88210T1; JPH03500420A; LTIP1598A; EP0310584B1; CA1335694C; EP0310584A3; FI95924B; EP0310584A2; ES2039698T3; SE459584B; SE8703816L; WO1989002909A1; DK81090A; DK175009B1; FI901613A0; FI95924C; JP2573681B2; LV11188A; AU612199B2; SE8703816D0

Abstract

The invention relates to a process for the refining of a raw gas produced from a carbonaceous material by means of a gasification process, refining taking place in a secondary stage separated from the gasifier. In order to reduce the gas contents of tar in the form of organic compounds condensible at lower temperatures, such as ambient temperatures, and of ammonia, the refining is carried out in a secondary stage being a fast circulating fluidized bed, the bed material of which at least mainly being an active material in the form of a material that is catalytic for tar and ammonia conversion, whereby a catalytic conversion of tar and ammonia contained in the raw gas is obtained. In order to decrease the content of hydrogen chloride in the gas, an active material that also can absorb chloride is used. Fresh catalytic and absorbing material is supplied in an amount sufficient to have the hydrogen chloride present in the raw gas absorbed on the material, a corresponding amount of the material containing absorbed chloride being discharged from the secondary stage.

Description

LV 11188 1 Refinlng

Descrtptlon

This mvention relates to a process for the refm-ing of a ravv gas produced from a carbonaceous material by means of a gasification process in which the refmmg takes place m a secondary stage separated from the gasīfier of the gasification process. A raw gas produced from different kinds of biofueis and used as a fuei gas is a valuable oil substitute for demanding applications in which the process demands make direct solīd fuel firmg im-possible, e.g. fireing of lime kilns or conversion of existing oil fired boilers.

For other types of applications. e.g. so-called cogeneration (of electrical power and heat) by use of diesel engmes. very high demands on the gas purity concernmg pnmanly tars and dust are set Moreover. environmental aspects often lead to demands on low concentrations of compounds which when combusted form harmful emissions, such as NO». SO» and various chlorinated compounds. The last mentioned is valid especially for a gas pro-duced from refuse derived fuel. RDF. These demands on the gas punty can be satisfied by the raw gas being refined by an appropnate method.

Gasification of RDF with subsequent refinmg of the raw gas means an environmentally favourable method for energy recovery from wastes by utiliza-tion of refined gas in existmg boilers or for cogeneration in diesel engmes and/or boilers.

Besides, utilization of raw gas often is con-nected with other techmcal probiems.

At temperatures beiow 1200 * C tar is always present in a raw gas produced by gasification of a carbonaceous material, e.g. coal. peat, bark, wood or RDF. which limits the utilization to combustion of hot gas m direct or close connection to the gasīfier. Operational disturbances caused by tarcoatmg on apparatuses and armatūras are a great problem which limits the availability. Durmg combustion of hot gas. mtrogen and in cērtam cases also sulphur (e.g. from peat) bound in tars. as well as ammoma, HjS (peat) or HCI (from RDF), furthermore give rise to emissions which are harmful to the environment (NO», SO» and HCI, respectively, and chlorinated hydrocarbons, i.a. dioxmes).

Despite extensive research concerning tar and ammonia conversion, so far no process which in an industrial scale can achieve sufficiently far-reachmg raw gas refinmg has been developed. The tradi-tional way of reducmg tar contents m a raw gas is by means of wet scrubbing. but aerosol formation in the scrubber makes the tar removal ineflicient. Furthermore. a process vvater with high contents of orgamc compounds and ammonia is obtained. Con-sequently, this vvater in its turn must be cleaned before bemg discharged to a sevverage. When ravv gas. 2 gasifying RDF the process water also contams high concentrations of dissolved hydrochloric acid and/or ammonium chloride When gasifymg more sulphur rīch luels. eg. peat or coal. the raw gas also has to be punfied to remove hydrogen sui-phide

The object of the presented mvention is to provide a raw gas refinmg process. by means of which the above mentioned probiems wili be solved to a great extent

This object is achieved by the process accord-mg to the invention havmg the features delmed m the enclosed claims.

The invention thus concerns a process for the refining of a raw gas to be used as a fuel gas, the raw gas contammg tar and ammonia. m speciai cases also contammg consideraoie quantities of hydrogen chloride. the raw gas bemg produced by means of an arbitrary gasification process Irom a carbonaceous material. e.g. bark, wooa. peat or Refuse Derived Fuel. RDF, vvherem m a secondary stage conversion takes place m contact with an appropriate active (catalytic and possibly absorb-ing) material.

Accordmg to the mvention. the process is char-actenzed in that in order to reduce the gas contents of orgamc compounds m form of tar condens-ible at lower temperatures sucn as ambient temperatures, and of ammoma the refinmg is carned out in a secondary stage m the form of a last circulatmg fluidized bed (CFB) havmg an upnght reactor shaft, the bed material of which at ieast to a major part includes an active material m the form of a material that is catalytic for tar and ammonia conversion, consistmg of a magnesium-calcium carbonate contammg material. preferably doiormte. and/or the correspondmg caicmed (burnt) product, the particle size of the material bemg smaller than 2 mm, preferably smaller than 1 mm, vvhile mam-tainrng the operatmg temperature of the secondary stage withm the mterval of 600-1000'0, preferably vvithm the mterval of 700-900’C. the average sus-pension density m the reactor shaft withm the mterval of 80-250 kg m3. the gas velocity m the reactor shaft calculated on an empty reactor shaft beiow 10 m/s, preferably below 6 m.s. and the residence time of the gas calculated on an empty reactor shaft. withm the mterval of 0 2-20 s. prelerabiy withm the mterval of 0.5-7 s. so as to provide a contact betvveen the passing gas and the active material for a catalytic conversion of tar and ammonia present in the gas to concentrations m the refined gas below 500 and 300 mg Nm3 respec-tive!y.

We have found that sufficient conversion of tars and ammon.a and in special cases simulta-neous absorption of hydrogen chloride can be achieved. by first separatmg the lar contammg gas 2 3 4 trom pyrolysing larger fuel pārticies in the gasifying stage and then in a separate secondary stage in tre i(vm of a circulating fast fluidi2ed bed contact-ing the gas with a suitable active material, such as doiomite. at suitable process parameters. lf the carbonaceous material also contains sul-phur m considerable amounts, which eg is the case for peat. absorption of hydrogen sulphide on the catalytic and absorbmg matenal will of course aiso take piace. ιn speciai cases to almost thermo-dynamic equilibrium

The amount of actīve matenal which is required m relation to the raw gas amount is determined by the required space-velocity for catalytic conversion of tars and ammoma and depends on several parameters such as the temperature, the residence time of the gas, the particle size of the active material, the partial pressure of reactants and the degree of deactivation of the actīve material, Too lo* temperature and/or CO? partial pressure can resuil m the tar conversion causmg carbon deposi-tion on the active surtace, vvhich results in deactivation ll this occurs the material can be activated by treatment with an oxidizing gas, e.g. air and/or steam. Absorption of HCl (and/or H2S) takes piace so rapidiy at the temperatūras of interest that these reactions Oecome almost determined by the equi-librium and result in a consumption of active matenal corresponding to the formed solid chloride (and sulphide resp).

We have thus found that absorption of chloride (and in cērtam cases also of hydrogen sulphide) on an active material such as dolomite is a rapid reaction and requires presence of a considerably less amount of active material in relation to the gas ticw than catalytic conversion of tars and ammonia.

Uiiiization of a secondary stage m the form of a fast circuiatmg lluidized bed (CFB) means consid-erable advantages.

Such a bed is able to handle dust entrained from the gasifier. gives very uniform temperatūras m the reaction zone and also gives a homogeneous contact betvveen gas and bed material. that is to say littie nsk for variations in conversion/absorption degree Funher. the particle size can be varied do<vnwards to a great extent, for those cases in wmch this is needed to give increased conversion at a given temperature and space-velocity Consid-erabie erosion of the bed material also results in increased accessible active surtace Also, a secon-dary stage designed as a CFB with advantage can be mtegrated with an arbitrary CFB gasifier, which merely has a primary particle separator, or another type of gasifier. One also achieves relatively small diameters when scaling up. since the gas velocities can be ķept relativeiy high, up to about 10 m/s, preferabiy up to 6 m/s.

In case the gasifier consists of a CFB gasifier, a connection directly afler primary dust separation can thus be made. If an active material is used as a bed material in the CFB gasifier, the secondary stage can in an advantageous manner be inte-grated with the gasifier, e.g. so that dust from a secondary particle separator after the secondary stage is totally or partly recycled to the gasifier. In this way, the total losses of bed material also become lower, and one also obtams the advantage of using only one type of bed material.

The necessary amount of active material in the reactor shatt of the secondary stage for sufficient catalytic conversion of tar and ammonia can be controlled by the totally added amount and by controlled recirculation of bed matenal. Required conversion determinēs suitable combmation of temperature, particle size and amount of active material. Because of abrasion, deactivation and/or absorption of HCl (and possibly H2S) consumed active matenal is replaced by adding corresponding amounts of fresh active material and/or activated such material. The residence time of the gas can be controlled by the combination diameter/height above the gas inlet.

In those special cases, when HCl is present in the raw gas in considerable amounts, the active material entrained by the outlet gas from the sec-ondary stage means that the HCl absorption is improved, since thermodynamically it becomes more far-reaching at lower temperatures, under the condition that the refined gas is cooled down to an essentially lower temperature before final dust re-moval.

In the followmg the invention will be described by way of a non-limitmg embodiment while refer-rmg to the enclosed drawmg. vvhich schematically shows a gasification and gas refinmg system which embodies the present invention.

In the system shown in the dravving carbonaceous material 1 is conveyed to a gasifier 3. which consists of a circulating fast fluidized bed (CFB). This comprises a reactor 51. a primary separator 52 and recirculation means 53 for bed material separated in the primary separator. The bed material consists of an active catalytic and absorbing material, preferably in the form of dolomite, mixed with ungasified carbonaceous material, char. The pnmary separator 52 is a mechanical separator of non-centnfugal type, suitably a U-beam separator, m accordance with what is described in our Eu-ropean Patent EP 0 103 613. relating to a CFB boiler and hereby referred to.

The hot raw gas 2 produced in the gasifier 3 is withdrawn directly from the primary separator 52 and is fed directly to a gas cleaning secondary stage 25 vvithout any additional dust removal. The secondary stage 25 is designed as a circulating 3 LV 11188 5 (ast fluidized bed (CF8) 26 and has the sama kind o( active bed material as the gasifier 3.

The raw gas 2 is supplied to the secondary stage 25 so that it constitutes a fluidizmg gas.

The secondary stage 25 is designed with a long and narrow reactor shaft with arbitrary cross section (e.g. circular or square). Bed material which follows with the gas stream out from the top of the reactor shaft is separated to a maior part in a pnmary particle separator 27, preferably a U-beam separator of the same kind as the U-beam separator of the gasifier, followed by a secondary separator 28, preferably a cyclone. The material 30 separated in the primary particle separator Is recycled to the lower part of the circulating bed 26 through a recirculation facility. The material 29 separated in the secondary particle separator 28 is added mam-ly to the lower part of the gasifier 3. stream 31. When needed. a part of the material stream 29 also can be supplied to the lower part of the circulating bed 26, stream 34, and/or be discharged out of the system, stream 43.

For feedmg fresh catalytic and absorbing material 14 to the secondary stage 25 a side feeding device 15 located on a suitable height is used. Consumed and/or deactivated bed material 35 is discharged by means of a dischargmg device 36 located in connection with the bottom of the secon-dary stage 25.

The active material used in the secondary stage in this example consists of a calcium-magne-sium carbonate contaimng material, preferably do-lomite, with a particle size smaller than 2 mm, preferably smaller than 1 mm, which in combina-tion with the passing gas forms the fast circulating fluidized bed 26.

The gas velocity in the upper section of the reactor shaft, calculated on the free cross section, is adjusted so that it is below 10 m/s, preferably not above 6 m/s.

The fluidizing gas of the fast circulating bed 26 consists of the raw gas 2 and added oxidizing gas 13, e.g. air. When needed additional oxidizing gas 33 can be added to the secondary stage 25 on one or on several other suitable, higher located Ievels.

Conversion of tar and ammonia contained m the raw gas 2 and absorption of chlonde contained m the raw gas take place by means of contact with the catalytic and absorbing material m the circulating bed 26 vvithin a temperatūra interval of 600-1000*C, preferably 700-900*C or most preferably 850-950' C. The required temperatūra Ievel is mamtained by burmng combustibie gas compo-nents inside the secondary stage 25. which is controiled by adjustment of the amount of added oxidizing gas. streams 13 and 33.

The average suspension density in the reactor shaft of the secondary stage 25 is mamtained with- 6 in an interval of 20-300 kg/m3, preferably vvithin an interval of 80-250 kg/m3, so that a necessary contact between the passing gas and the active material is obtamed. This is achieved by adjustmg the total amount of circulating material m combmation with controlling the flow rāte of recycled material 30 and 34,

The residence time of the gas m the reactor shaft, calculated on an empty reactor shaft. is maintained vvithin an interval of 0.2-20 s. preferably within an interval of 0 5-7 s.

When needed, activation of deactivateo cata-lytic and absorbing material can be performed by adding oxidizing gas 32, e.g. air, to the material which is recycled to the lower part of the circulating bed. streams 30 and 34 The amount of added oxidizing gas 32 is controiled so that the activation takes place within a temperature interval of 600-1000’C, preferably vvithin an interval of 750-900 * C.

Before starting operation of the process heatmg of the secondary stage 25 mcludmg its bed material takes place by means of comoustion of LP gas 24 therem.

The refmed gas stream 4 leaving the secon-dary separator 28 of the secondary stage 25 is relieved from entramed finely divided bed material and steam m the subsequent gas treatment stages

The gas passes through two heat exchangers. In the first heat exchanger 37 heat exchange takes place with oxidizing gas. stream 10. intended for both the gasifier 3 and the secondary stage 25. so that preheated oxidizmg gas 11 at the outlet from the heat exchanger 37 has a suitable temperature. preferably about 400 * C. The preheated oxidizmg gas 11 is used both in the gasifier 3 (among others as fluidizing gas), stream 12, and in the secondary stage 25, streams 13, 32 and 33.

In the subsequent second heat exchanger 38 the temperature of the gas 5 is lovvered to a ievel which permits the outlet gas 6 to be further cleaned by using eg Standard textile filters or a cyclone for further dust removal, at 39. i e prefer-ably down to 150-300 * C. The removed dust 18 is withdrawn from the dust removal stage 39

As mentioned before. the gas stream 4 con-tams entramed fmely divided active material which follovvs with the gas stream out of the secondary separator 28. In special cases, e g. m connection with gasification of RDF, the raw gas 2 from the gasifier contams considerable amounts of HCl Since absorption of HCl on calcareous matenals. such as dolomite, is favoured by smkmg temperature. the gas cooling in the heat exchangers 37 and 38 contnbutes to increase the degree of absorption of residual HCl on the entramed matenai

The almost dust-free gas 7, vvhich leaves the dust removal stage 39, is fed to a scrubber 40. m 4 7 θ which it is relieved from moisture and other water soiuble components In the scrubber 40 bolh moist-enmg of the gas stream 7 and condensation of steam take place. At the current conditions also precipitation of almost ali of the residual fines and absorption of water soiuble gas components, eg. NH], HCI and/or NH.CI, take place,

The water stream 20 leaving the scrubber 40 is recirculated by a pump 4i. whereby it is cooled in a heat exchanger 42, so that the temperature of the water 19 recycled to the scrubber 40 is ķept vvithin the interval 15*20' C. Excess water 21 is drained from the water Circuit,

The gas 8 leaving the scrubber can for indus-trial applications be regarded as pure, i.e. it is almost free from tars, ammonia, dust, HCI and H2S. However, at the present outlet temperatūras (about 30'C) it is saturated with steam. Oepending on the apphcation, in order to decrease the relative humid-ity, the gas stream 8 can be preheated or passed through an additional drymg stage in order to reducē its moīsture content. The pure gas satisfies the requirements for engine operation, e.g. by means of turbocharged diesel engines, and can be burned vvithout any subsequent exhaust gas clean-ing.

For more simple applications. e g. heat genera-tion m boilers, the scrubber 40 can be omitted, so that the refined gas can be utilized either directly after the heat exchanger 37, stream 22, or after the dust separator 39, stream 23.

In the described example the secondary stage 25 has been integrated with a gasifier 3 based on CFB technology The gasifier 3 can producē the raw gas 2 trom several different kmds of fuels, e g. coarse bark, peat or refuse derived fuels RDF, As bed material in the circulating bed of the gasifier 3 it is, as mentioned, convenient to use a catalytic and absorbing material of the same type as in the secondary stage 25.

The total pressure drop of the oxidizing gas supphed. eg air, at the passage through the pro-duction loop, is stightty above 1 bar. This sets requirements on using a compressor 16. which increases the oxidizing gas pressure in stream 9 to the pressure Ievel in stream 10 necessary in view of the purpose involved.

Clalms 1. A process for the refining of a raw gas to be used as a fuel gas and produced from a car-bonaceous material by means of a gasification process, vvherem the refining takes place in a secondary stage separated from the gasifying process, charactertzed in that in order to re-duce the gas contents of organic compounds m form of tar condensible at lower temperatūras such as ambient temperatūras, and of ammonia the refining is carried out in a secon-dary stage m the form of a fast circulating fluidized bed having an upright reactor shaft, the bed material of which at least to a major part includes an active material in the form of a material that is catalytic for tar and ammonia conversion, consisting of a magnesium-calcium carbonate containing material, preferably dolo-mite. and/or the corresponding calcined (burnt) product, the particle size of the material being smaller than 2 mm, preferably smaller than 1 mm, vvhile maintaining the operating temperature of the secondary stage within the interval of 600-1000‘C, preferably within the interval of 700-900 *C, the average suspension density in the reactor shaft vvithin the interval of 80-250 kg/m3, the gas velocity in the reactor shaft of the secondary stage calculated on an empty reactor shaft. belovv 10 m/s, preferably belovv 6 m/s, and the residence time of the gas calculated on an empty reactor shaft, vvithin the interval of 0.2-20 s, preferably vvithin the interval of 0.5-7 s. so as to provide a contact betvveen the passing gas and the active material for a catalytic conversion of tar and ammonia present in the gas to concentrations in the refined gas below 500 and 300 mg/Nm3 respectively 2. A process according to claim 1, vvherein the raw gas includes hydrogen chloride. charac* terlzed by discharging intermittently or con-tmuously active material containing absorbed chloride from the secondary stage and feeding mtermittently or continuously a corresponding amount of fresh active material to the secon-dary stage. 3. A process accordmg to claim 1 or 2. char-acterlzed by a contemporaneous addition of oxidizmg gas. preferably an oxygen containing gas and/or steam to the reactor of the secon-dary stage. 4. A process according to any one of claims 1. 2 or 3, charactertzed in that the operating temperature of the secondary stage is controlled by added amounts of oxygen containing gas. 5. A process according to any one of the preced-ing claims, characterlzed in that active material deactivated as a result of carbon deposi-tion or by any other reason intermittently or contmuously is discharged from the secondary stage and is replaced by equivalent amounts of fresh and/or activated material 5 LV 11188 9 6. A process according to ciaim 5. characterlzed in that deactivated active material dis-charged from the secondary stage is activated by treatment vvith an oxidizing gas, preferably an oxygen contaming gas and/or steam, in a separate activatmg stage, thus activated material being returned to the secondary stage. 7. A process according to any one o( the preced-ing claims, characterlzed in that active material deactivated as a result ol carbon deposi-tion or by any other reason is activated by treatment with an oxidizing gas, preferably an oxygen contaming gas and.'or steam, in the system recirculatmg separated bed material of the secondary stage. 8. A process according to claim 6 or claim 7, characterlzed in that the activation takes place at an operating temperature withm the interval of 600-1000‘C, preferably withm the interval of 750-900' C. 9. A process according to any one of claims 6, 7 or 8, characterlzed in that the operating temperature of the activation is controlled by means of added amounts of gas containing oxygen. 10. A process according to any one of the preced-ing claims, characterlzed in that the raw gas is supplied to the secondary stage directly from the gasifier without any intermediate dust removal. 11. A process according to claim 10. wherein the gasifier comprises a fast circulating fluidized bed. characterlzed in that the raw gas is supplied to the secondary stage directly from the primary separator of the gasifier. 12. A process according to any one of the preced* ing claims, characterlzed in that the fluidizing gas of the secondary stage comprises the raw gas and possibly an oxidizing gas. 13. A process according to claim 12, character* izēd in that oxidizing gas which does not con-stitute a fluidizing gas, is added to the reactor of the secondary stage at one or several Ievels above the fluidizing gas supply. 14. A process according to any one of the preced* mg claims, characterized in that the hydrogen chlonde content in the refined gas. whīch leaves the secondary stage. is lowered further by means of absorption on the catalytic and absorbmg material remaming in the gas after 10 the particle separation of the secondary stage. wherein the gas after the secondary stage first is cooled to a consideraoly lov<er temperature. preferably to a temperature between 150 and 300‘C, and then is subiect to additional dust separation. 15. A process according to any one of the preced-ing claims, characterized in that the raw gas feeding of the secondary stage is connected directly to the primary particle separator of a gasifier having a fast circulating fluidised bed, in which the circulating bed material consists of an active material of the same type as m the secondary stage, in that dust separated m the secondary stage, preterably m a seconoary particle separator, at least partly is recyded to the lower part of the gasitymg reactor. and m that bed material entramed with the raw gas from the gasifier and material possioly dis-charged from the botlom of the gasifier are replaced by the material recycled to the gasilying reactor from the secondary stage m combination with fresh cataiytic and absorbmg material which is added to the gasfier mtermit-tently or contmuously. 6

Claims

1. A method for purifying uncleaned gas which is usable as a fuel gas and obtained from a carbonaceous material by means of a gasification process, wherein the purification is carried out in the separated secondary phase of the gasification process, in order to reduce gas at the treatment at a temperature below 10 for the ambient temperature, tar-condensing organic compounds and ammonia content, is carried out in a secondary phase in the form of a rapidly circulating boiling layer in an upright reactor shaft, the material of which at least in most of it contains active material in the form of material catalyzed by tar and \ t the conversion of ammonia and 15 consists of magnesium-calcium carbonate-containing material, preferably dolomite, and / or the corresponding calcined (burnt) product with a particle size of less than 2 mm, preferably less than 1 mm, and the parameters are maintained underate phase operating temperature in the range of 600-1000 ° C, preferably in the range of 700-900 ° C, average 20 suspension density in the reactor shaft - in the range 80-250 kg / m3, gas velocity in the secondary phase reactor shaft, calculated on the empty reactor shaft below 10 m / s, preferably below 6 m / s, and gas residence time on an empty reactor shaft, in the range of 0.2-20 s, preferably in the range 0.5-7 s, to ensure contact between the flowing 25 gas and the active material , during which catalytic conversion of tar and ammonia in the gas occurs and the concentration of gas in the purified gas is reduced to 500 or 300 mg / Nm3.

A method according to claim 1, wherein the unpurified gas contains hydrogen chloride 30, characterized in that, with or without interruption from the secondary phase, the active material absorbed by the chloride is removed and a corresponding amount of fresh active material is administered intermittently or continuously in the secondary phase.

3. A method according to claim 1 or 2, characterized in that simultaneous oxidizing gas, preferably oxygen-containing gas, and / or water vapor is introduced into the secondary phase reactor. 2

The method of any one of claims 1-3. characterized in that the secondary phase operating temperature is controlled by the amount of oxygen-containing gas to be added.

Method according to one of the preceding claims, characterized in that the carbon deposition or otherwise the deactivated active material is removed from the secondary phase intermittently or continuously and replaced by an equivalent amount of fresh and / or activated material.

Method according to claim 5, characterized in that the deactivated active material removed from the secondary phase is activated in a separate activation phase by treatment with an oxidizing gas, preferably with an oxygen-containing gas and / or water vapor, wherein the activated material is returned in this way back in the secondary phase.

Method according to one of the preceding claims, characterized in that the carbon deposition or otherwise the deactivated active material is activated by treatment with an oxidizing gas, preferably with oxygen-containing gas or water vapor, in a system that recirculates the secondary-phase separated layer material .

Method according to claim 6 or 7, characterized in that the activation is carried out at a working temperature in the range of 600 to 1200 ° C, preferably in the range of 750 to 900 ° C.

The method according to any one of claims 6 to 8, characterized in that the activation temperature is controlled by the amount of oxygen-containing gas to be added.

Method according to one of the preceding claims, characterized in that the untreated gas is introduced into the secondary phase directly from the trench without prior removal of the dust from it.

A method according to claim 10, wherein the transducer comprises a rapidly circulating boiling layer, characterized in that the uncleaned gas is introduced into the secondary phase directly from the primary distributor of the trap.

12. A method according to any one of the preceding claims, characterized in that the secondary-phase boiling gas contains unpurified gas and possibly oxidizing gas.

Method according to claim 12, characterized in that the oxidizing gas, which does not form boiling gas, is introduced into the secondary phase reactor at one or more levels above the gas injection site I.

A method according to any one of the preceding claims, characterized in that the hydrochloric acid content of the secondary gas leaving the purified gas is further reduced by absorption on a catalytic and absorbent material left in the gas after the removal of the secondary phase particles, the gas of which after the secondary phase first is cooled to a significantly lower temperature, preferably between 150 and 300 ° C, and then dust removal is performed additionally.

15. A method according to any one of the preceding claims, characterized in that the secondary-phase uncleaned gas supply is directly connected to the primary particle separator of the fast-circulating fluidised bed including the circulating layer material of the same active material type as the secondary phase. that the dust separated in the secondary phase, especially in the secondary particle separator, is at least partially fed back to the lower part of the overflow reactor, and that the material removed from the trench by the uncleaned gas and possibly the material removed from the base of the trap is replaced by a secondary phase to the return material of the overthrow reactor in combination with fresh catalytic and absorbent material which is fed continuously or continuously to the transporter.