FI87148C - Method and apparatus for treating hot gases in a circulating fluidized bed reactor - Google Patents

Description

87148

METHOD AND APPARATUS FOR TREATING HOT GASES IN A CIRCULAR REACTOR

FARRING REQUIREMENTS FOR BEHAVIOR WITH A GASER AND A REACTOR WITH CIRCULAR FLUIDISERAD BÄDD

The present invention relates to a method and apparatus for treating hot gases generated in high temperature processes in a circulating fluidized bed reactor. The circulating mass reactor according to the invention typically comprises means for supplying hot gases to the fluidized bed reactor, a mixing chamber into which the hot gases are introduced as fluidizing gas through an inlet duct at the bottom of the mixing chamber. or concave heating surfaces arranged in the slot, to separate the solids forming the circulating mass of the particle separator from the solid gas suspension, to remove the gases from the degassing duct from the particle separator, to return the separated solids from the solids return pipe to the particle separator

The gases are introduced as a fluidizing gas to the lower part 20 of the mixing chamber to fluidize and transport the solid as a gas suspension from the mixing chamber through the rising part to the particle separator. The solid separated in the particle separator is returned to the mixing chamber.

The circulating fluidized bed reactor is particularly suitable for cooling gases containing hot, molten and / or vaporized components and / or tarry particles.

30 The FLUXFLOW ™ gas cooler 2 87148, which operates on the circulating principle and has cooling surfaces as described above, is suitable, for example, for the dry cleaning of dusts, tars and gases containing other condensable components from the partial oxidation of biomass, peat or coal. With a large stream of solids entering the mixing chamber from the particle separator, the gas fed to the mixing chamber is cooled in a very short time to a temperature level where the harmful gaseous or liquid components in the gases condense and the tarry substances become dry solids. From the cooled gas 10, the solids are then easily separated.

If necessary, the FLUXFL0W ™ gas cooler can also be used for chemical processing, e.g. preheating and pre-reduction of iron concentrate 15, where the concentrate is preheated and pre-reduced with hot process gas from the iron smelting process. However, when the preferred reduction temperature range is 800 to 950 ° C, 20 cooling surfaces have to be built in the circulating mass reactor to maintain this temperature, because preheating and reduction of the iron does not provide sufficient cooling. The required heating surfaces are generally located as convection heating surfaces in a gas duct or slot arranged above the mixing chamber.

25

The mixing chamber in the FLUXFL0W ™ gas coolers described above is formed by a so-called spouted bed type, i.e. as a jet flow type fluidizing chamber. For example, the fluidizing chamber is formed of an upwardly expanding conical lower portion 30, a cylindrical central portion connected thereto, and an upwardly tapering conical upper portion connected to the central portion. A simple inlet opening is provided in the lower part of the spouted bed-type fluidizing chamber for conducting gases into the chamber.

35

The spouted bed type chamber structure solution is particularly suitable for use in cooling hot gases containing at least partially molten solids that would easily block other types of gas supply solutions, such as a conventional fluidized bed grate with nozzles.

5 As the incoming gas flow in the spouted bed type fluidization chamber increases, the particles at the inlet will protrude into the chamber, out of the path of the gas jet, and an area will form above the inlet where the solids density of the suspension is low. As the velocity of the incoming gas stream 10 increases, this area of sparse suspension also protrudes deeper into the mixing chamber, i.e. a jet flow of gas suspension is formed in the mixing chamber even through the entire fluidized bed.

As a result of the gas jet, part of the fluidized bed particles 15 flows upwards in the mixing chamber and part towards the edge areas of the chamber. However, the velocity of the solid particles slows as you go to the edge areas and even becomes downward. A fountain-shaped solid flow is thus formed in the mixing chamber. The solid flows 20 downwards along the walls of the mixing chamber. Some gas also travels downward under the action of the solid. However, the gas flow is mainly upwards.

25 In the vicinity of the walls of the mixing chamber, the downward flowing solid flows towards the inlet opening in the conical bottom of the mixing chamber and encounters the gas suspension entering from the opening, which again fluidizes the solid upwards. This creates an internal mass circulation of solids 30 in the chamber. Some of the solids also continuously flows out from the top of the fluidization chamber to the riser and from there on to the particle separator.

In a circulating mass reactor with a spouted bed type fluidization chamber 35, the circulating mass suspension is smaller in the riser, due to the large internal circulation, than in a reactor in which no significant gas jet flow occurs. Consequently, the heat transfer to the convection heating surfaces of the riser is also weaker in such a reactor.

In circulating mass reactors with a strong gas suspension jet flow, wear has also been observed in the convection surfaces located at the beginning of the riser 5. Wear is assumed to be due to the hot gas jet flow, because some of the hot gases may reach the convection surfaces without cooling due to the jet flow if the gas jet flow is very strong. The wear is partly due to the heat of the gases 10, partly due to the high flow rate of the gases.

As the jet flow reaches the convection surfaces, soiling and clogging of the surfaces can also become a problem. If the hot gases only cool on the thermal surfaces, then the impurities also only condense on the surfaces and not on the circulating mass particles as is usually intended.

It is therefore an object of the present invention to provide a method and apparatus for minimizing the above-mentioned disadvantages. The purpose is to act on the gas jet flowing inside the mixing chamber so as to enhance the transverse mixing of the gas suspension with the fluidized bed.

25 It is also intended to slow down the velocity of the central part of the incoming gas flow so as to avoid its detrimental effects in the convection part.

It is also intended to provide better heat recovery from the 30 gases.

In order to achieve the objects of the invention, the method according to the invention is characterized in that the entry of hot gases from the inlet directly through the mixing chamber without cooling into the convection temperatures in the mixing chamber.

The device according to the invention is characterized in that the above-mentioned member is arranged in the gas inlet opening or in the mixing cannon above the opening 5.

It has been found that the flow pattern prevailing in a spouted bed type fluidization chamber depends on the amount of bed, the bed material list and the gas flow. However, it has now been found that the shape of the flow can be influenced in a desired manner by fitting to the inlet of the mixing chamber or at a suitable distance therefrom to the actual mixing chamber a member which directs or distributes the gas flow to the mixing chamber as desired. The member prevents gas from flowing directly from the inlet 15 through the mixing chamber without mixing with the circulating mass in the mixing chamber. With the shape and location of the member, the gas flow can be adjusted as desired.

The member can advantageously direct the gas flow radially outwards towards the walls of the mixing chamber and / or divide the gas flow into a plurality of gas streams evenly directed to the edge areas of the mixing chamber.

By fitting a member which constitutes a barrier to the flow of gas to the center of the inlet opening or to the mixing chamber on its central axis, a part of the gas flow is directed outwards towards the edges of the chamber. After the obstacle, the gas flow returns mainly to the upward direction.

The member is able to slow down the flow of gas at its center so that the gas does not meet the heating surfaces of the convection part when hot. This also leaves more time for the gas flow in the mixing chamber, whereby the heat transfer or other reactions between the gas and the circulating mass are intensified.

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The shape of the member can be chosen to achieve an appropriate gas flow, also taking into account the shape of the cross-section of the inlet and / or the mixing chamber and its size 87148 6. The member may be, for example, a plate-shaped body or a spherical, pyramidal or conical body at the bottom. With the horizontal plate, it is possible, for example, to prevent an upward flow in the desired size range and, if desired, at the same time a strong vortex is produced in the mixing chamber. A spherical or conical member also prevents flow, but with this shape, excessive swirling can be avoided if desired.

The shape of the member is also preferably chosen so that the components condensable from the gas do not easily adhere to it. For example, the upper part of the member is preferably shaped in such a way that no solid can accumulate on it.

According to a preferred embodiment, the member according to the invention is a transverse flow guide which, viewed from the direction of the inlet opening, has substantially the same shape as the cross-sectional area of the inlet opening. In this case, the gas flow on the different sides of the body can be adjusted equally. The flow guide 20 distributes the flow of gas to the sides and promotes a steady upward flow of solids by "pulling" along a larger area of solids.

Thus, in various applications and structures, a body shaped to suit the particular process conditions can be used to extinguish the gas jet formed in the spouted bed reactor.

The dimensioning of the member shall take into account the cross-sectional area of the gas inlet so that the total flow or suspension density in the riser is not adversely affected.

The member can be fixed in place by hanging from above or by fastening it to the walls of the mixing chamber or inlet with fasteners. Depending on the method of attachment, the member can be easily removed, e.g. for cleaning, or its position can be adjusted if necessary.

7 87148

The attachment and also the body itself can also be arranged to be cooled. The fastening can, for example, be connected to the heating surfaces of the riser so that the cooling pipe is led down to the mixing chamber and a suitably shaped body is fastened to the lowest point of the pipe in order to switch off the spray flow. Both this piece and the cooling pipe can be protected by masonry or massaging. Also when the fastening members come from the sides of the mixing chamber, they can be cooling pipes or the like.

10

The member according to the invention can be made of a material resistant to hot conditions, such as a special metal alloy or a special ceramic. A suitably shaped body can, for example, be made of alumina. If the member is manufactured as a cooled tubular structure, it must be protected by massaging.

The method and apparatus according to the invention are able to prevent, in a very simple manner, the hot nuclear flow of gas from penetrating too deep into the mixing chamber 20 without mixing with the solid in a spouted bed type fluidization chamber. This makes it possible to prevent or considerably reduce the detrimental effect of hot dirty gases on the convection surfaces in the rising section.

At the same time, especially when the member is fitted to the lower part of the mixing chamber, the turbulence in the mixing chamber is improved and a better distribution of gas throughout the mixing chamber is achieved and thus also better contact between the solid and the gas in the mixing chamber. A more even distribution of the gas in the mixing chamber 30 reduces the internal circulation of the solids in the mixing chamber, but increases the circulation of the main mass through the riser and the particle separator. The ability of the gas to lift solids from the mixing chamber to the riser is greater with a more even solids distribution. The increasing suspension density 35 in the riser has a heat transfer promoting effect on the heating surfaces placed in the riser.

The method and apparatus according to the invention, which 87148 8 improves the transverse agitation of the reactor, have a particularly advantageous effect, especially in units of a larger size class, in which the transverse agitation distance is greater.

The invention will now be described in more detail with reference to the accompanying drawings, in which

Figure 1 shows a schematic view of an apparatus according to the invention in a circulating mass reactor, 10

Figures 2-3 show in schematic views other embodiments of a device according to the invention fitted to a rotary mass reactor.

Figure 1 shows a circulating mass reactor 10 comprising a circular diameter mixing chamber 12, a riser 14 and a particle separator 16. The mixing chamber is fitted with a hot process gas supply passage 18 and a solids feed passage 20. The mixing chamber is formed of an upwardly extending conical bottom from the top 26. The mixing chamber acts as a fluidizing chamber into which the fluidizing gas is introduced from the supply duct 18 through the supply opening 28. There is no actual grate in the fluidizing chamber from which 25 fluidizing gases would be fed through the nozzles to the fluidizing chamber. Therefore, hot dirty gases and hot gases containing easily condensable volatile or molten components that would clog conventional nozzles or inlets can also be used as fluidizing gas in this circulating mass reactor.

The cross-sectional area of the riser is smaller than the cross-sectional area of the mixing chamber to increase the flow rate in the riser. Convection heating surfaces 30 are arranged in the riser. In particular, the lower parts of the heating surfaces are susceptible to fouling and wear if hot dirty gases are allowed to flow freely at high speed from the inlet through the mixing chamber. The riser is connected at its top by a channel 32 to the vortex chamber 16 of the cyclone 16. The gas solids suspension, which has cooled as it rises, flows tangentially into the vortex chamber, whereby the solid separates into the walls of the vortex chamber and flows downwards. The gases from which the solids have been separated exit 5 through an exhaust duct 34 arranged in the center of the upper part of the vortex chamber. The solids separated in the vortex chamber flow downward to a return pipe 36 connected to the mixing chamber 12 to return the separated solids as a circulating mass thereto. A solids outlet passage 38 is further connected to the return pipe 36.

According to the invention, a member 40 is arranged in the mixing chamber to slow down the flow of gas from the inlet opening 28. In the embodiment according to Figure 1, the member is round, spherical and suspended from the walls of the mixing chamber downwards into cooling pipes 42 in the middle of the mixing chamber. The cooling pipes may e.g. be connected to the heat transfer system of the reactor convection section 14. This connection is not shown in the figure. The surfaces of the tubes 42 of the body 40 and 20 are protected from heat and wear by masonry 44.

The gas jet from the inlet 28 is directed to the sides along the lower surface of the ball and is evenly distributed in the mixing chamber. The ball 40 "shuts off" the central part of the gas jet so that it cannot directly face the heating surfaces of the rising part at high speed.

Figure 2 shows another embodiment of the device according to the invention. The same reference numerals are used in the figure as in Figure 1. A conical member 46 is arranged at the top and bottom of the mixing chamber. The lower part of the member is a downwardly tapering body and the upper part is an upwardly tapering body. The inclination of the walls 35 of the cone can, for example, be chosen to be the same as the inclination of the conical lower part of the mixing chamber.

The conical body can be arranged close to the inlet opening, where it on the one hand "switches off" the gas jet and on the other hand directs the gas in the direction of the walls of the mixing chamber. The walls of the mixing chamber can be protected by a mass 48 which protects the walls from erosion by dirty hot gases.

In the embodiment of Figure 3, the member 50 according to the invention is arranged relatively high in the mixing chamber, the effect of which is mainly limited to "extinguishing" the gas jet 10 and has less effect on the internal circulation in the mixing chamber and thus on the suspension density in the riser. The member is in the shape of a horizontal plate and has a diameter of about half the diameter of the gas inlet duct. The member is attached to the heating surfaces of the 15 risers by fastening members 52.

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Claims (15)

A process for treating hot process gases generated in high temperature processes in fluidized bed reactors, wherein the fluidized bed reactor comprises - means for supplying hot gases to the fluidized bed reactor; - a mixing chamber into which the hot gases are conducted as fluidizing gas through an inlet channel in the lower part of the mixing chamber and in which the gases are mixed into the circulating mass; - a ladder portion or channel arranged in conjunction with the mixing chamber above this conduit for conducting the gas suspension containing solid material from the mixing chamber to the particle separator; - convection heating surfaces arranged in the riser or rabbit; a particle separator for separating the solid material forming the circulating mass from the gas suspension containing solid material; - a gas outlet duct for removing the gases from the particle separator; - a solid material return pipe for returning the separated solid from the particulate separator to the mixing chamber; and - solid and feed supply and outlet connections, characterized in that the hot gases coming from the inlet opening are at least partially prevented from penetrating unmixed mixes. the contact chamber for contact with the convection heat surfaces by arranging in the inlet opening for the gas or in the mixing chamber above the opening on the inlet opening shaft an element which promotes the transverse distribution of the gas flow in the mixing chamber. -35 2. A process according to claim 1, characterized in that solid material, for example, is treated with hot process gases in the fluidized bed reactor. li 87148 3. A process according to claim 1, characterized in that hot gases are cooled in the fluidized bed reactor for condensing melt and / or diluted components. 5 4. A method according to claim 1, characterized in that hot gases are treated to separate particles containing the gases from the gases. 10 5. A method according to claim 1, characterized in that the flow rate in the middle portion of the gas stream entering the mixing chamber is retarded. 6. A method according to claim 1, characterized in that the hot gas stream is distributed by means such that a radially leaking directional flow from a central portion disturbs. Apparatus for treating hot gases generated in high temperature processes in a fluidized bed reactor (10) comprising circulating bed material, comprising: lower portion and in which the gases are mixed into the circulating mass; . .25 - a ladder portion (14) or duct for conducting the gas suspension containing solid material in conjunction with the mixing chamber from the mixing chamber to the particle separator (16); - convection heating surfaces (30) arranged in the riser or channel for lowering the temperature of the gas suspension; a particle separator (16) for separating the solid material forming the circulating mass from the gas suspension containing solid material; a gas outlet duct (34) for removing the gases from the particulate separator; - a solid feed tube (36) for returning the separated solid material from the particulate separator to the mixing chamber and 87148 - solids supply and outlet connections (20,38), characterized in that in the gas inlet port (28) or in the mixing chamber A member (40, 46, 50) has been arranged above the opening of the mixing chamber on the axis of the inlet opening, which promotes cross-distribution of the gas flow in the mixing chamber, and thus at least partially prevents the hot gases coming from the inlet opening from the contact surface of the mixing chamber through the noncooling chamber through the cold chamber. Device according to claim 7, characterized in that the lower part of the member (40) is spherical. 9. Device according to claim 7, characterized in that the member (46) is in the form of a pyramid. 10. Device according to claim 7, characterized in that the lower part of the member (46) is tapered. 20 Device according to claim 7, characterized in that the means (50) is flat and arranged perpendicular to the direction of flow of the gas. Device according to claim 7, characterized in that the means (40, 50) is arranged on the center axis of the mixing chamber or inlet opening suspended from above. Device according to Claim 7, characterized in that the means is arranged in a vertical direction. Device according to claim 7, characterized in that the means (40,46,50) is arranged on the center axis of the cylindrical central portion of the mixing chamber. 35 Device according to claim 7, characterized in that the means (40) is arranged in the mixing chamber by means of fasteners supported in its walls. IN;