FI85185C - Method and apparatus in a circulating fluidized bed reactor - Google Patents

Description

85185

METHOD AND APPARATUS IN A ROTARY STATION IN THE LAYER REACTOR

FRAMEWORK FOR THE ENTRY IN CIRCULATION VIRVELBÄDDSREAK-TOR 5

The invention relates to a process for treating substances in a circulating fluidized bed reactor, in which - the substances are treated in a first reactor chamber in a fluidized bed with a bottom-up gas flow, 10 - and returned to the reactor chamber.

The invention also relates to a fluidized bed type fluidized bed reactor comprising - a first reactor chamber having a feed point 20 for feeding solids to the reactor chamber and a base plate for supplying fluidizing gas to the reactor chamber and a process gas outlet process gas and to return the circulating mass of the return channel to the reactor chamber.

Fluidized bed reactors are used in many different processes, both heat-releasing and heat-demanding. 30 Fluidized bed reactors are used, for example, in combustion and gasification processes, heat treatment such as drying, pelletizing, and metallurgical and chemical processes. Different processes impose different requirements on the fluidized bed in terms of temperature, flow rate 35 and the particle size of the fluidized bed.

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High-speed fluidized bed reactors of the circulating type have achieved several advantages over conventional slow bubbling fluidized bed reactors. In particular, due to the good mixing of the solid particles, a uniform temperature is achieved in the 5 fast fluidized beds over the entire area covered by the circulating mass. Due to the rapid mixing, the material fed to the fluidized bed reaches the temperature of the circulating mass in a very short time. In addition, processes in which heat is transferred from the circulating mass 10 to the heat exchange surfaces arranged in the reactor provide faster heat conduction than in the slow fluidized bed.

The reactions that take place in a fluidized bed type fluidized bed reactor are also generally faster than in the slow fluidized bed. In particular, better and longer contact time is achieved between the gas and the solid particles in the circulating fluidized bed than in the bubbling bed. In addition to the denser fluidized bed zone at the bottom of the reactor, the gases and solids particles are in contact with each other throughout the reactor chamber up to the particle separator. Due to the good contact between the particles and the gas, the circulating mass reactors can be built considerably smaller and thus cheaper than conventional bubbling fluidized bed reactors.

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However, problems may be encountered in the construction of large fluidized bed reactors, including those of the circulating mass type. Some processes, despite good mixing, require a very high reactor chamber to complete the desired reactions in the reactor chamber. On the other hand, high reaction chambers are also needed to provide a sufficiently large heat transfer surface area, e.g. for combustion plants. Adapting a reactor high enough to, for example, old premises can be difficult. Also, in some cases, it may be easier to accommodate a lower-level reactor than a high one in new plants 35.

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On the other hand, increasing the reactor by increasing the cross-sectional area can also in some cases be detrimental to the optimal operation of the reactor. For example, a uniform supply of secondary air to the entire cross-sectional area of the reactor chamber as a supply from the walls of the chamber is difficult in reactors with a large cross-sectional area. The fluidized bed prevents air from penetrating deep into the reactor chamber.

10 In fluidized bed reactors, both fast and slow, the bed material also circulates in the reactor chamber itself. In the vicinity of the walls of the chamber, the bed material flows downwards and in the middle stages of the chamber mainly upwards. In addition, the bed material easily forms random dense upward particle flows, in which the flow of particles gradually slows down until the entire accumulated particle mass falls back to the lower part of the chamber. Since, on the other hand, the gases tend to flow upwards as vanes where there are the fewest particles, i.e. avoiding the above-mentioned particle flows, there is a tendency to form particle and gas deposits in the chamber. The larger and higher the reactor chamber, the greater the formation of scraps and the need for more efficient mixing.

In very high reactor chambers, it can also be a problem to obtain a circulating mass. The particles do not travel with the gases up to the degassing opening of the reactor chamber but remain in the internal circulation in the chamber.

In addition, in a fluidized bed reactor, it is difficult to influence the process in the reactor chamber in one individual zone without affecting the course of the process in the other zones. However, from the point of view of process control, in some processes, e.g. in combustion processes 35, when the load varies, it would be advantageous to be able to better control the course of the process also in zones.

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It is known, for example, from Finnish patent application FI 850708 to improve the possibility of partial load control of a steam boiler equipped with a slow fluidized bed furnace by dividing the lower part of the boiler into different compartments which can be switched off according to need. Each compartment of a fluidised bed furnace is equipped with all the parts that allow that compartment to be used independently. However, the flue gases coalesce and mix with each other above the fluidized beds. In such separately controlled fluidized bed compartments, it would be difficult to arrange a functioning circulating system so that the circulating mass could be returned to each compartment.

It is also known from Swedish patent publication SE 15 457 905 to burn solid fuel in two adjacent fluid communication layers communicating with each other, in which incompletely burned fuel in the first fluidized bed flows overflow to the second fluidized bed. Also in this embodiment, the flue gases and the entrained fine solids from the different fluidized beds can be mixed above the fluidized beds, whereby the process gases leaving the reactor are easily mixed with incompletely reacted substances flowing from the first fluidized bed stage.

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The fluidized bed reactor and process according to the invention are intended to reduce the above-mentioned disadvantages. It is an object of the invention to enable better controllability of the processes in the different reaction zones. It is therefore an object of the invention to provide a fluidized bed reactor of the circulating mass type in which a gradual combustion or other process requiring a secondary gas or other material can be better controlled. It is a further object of the invention to provide a process by which additives required by the process, such as absorbents required for gas purification, can be better mixed into the process, even after the first reaction zone.

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It is an object of the invention to provide a lower type fluidized bed reactor which is also suitable for construction in existing, space-limited spaces.

The fluidized bed reactor according to the invention is characterized in that it comprises, in addition to the first reactor chamber, an extension of a two-chamber reactor chamber with a base plate for a two-chamber extension to two chambers so that the chambers communicate with each other at their lower portions through a flow port, 15 - a second process gas outlet arranged at the top of the second chamber of the two-chamber extension to discharge process gases out of the two-chamber extension;

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The process according to the invention is characterized in that the process gases leaving the upper part of the first reactor chamber are passed through at least one two-chamber fluidized bed reactor, in which the process gases are first a bottom plate fitted to the bottom.

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By directing the flow in the fluidized bed reactor through the different chambers alternately upwards and downwards, a long flow distance is achieved without a high reaction chamber. Thus, a long residence time can be achieved without the disadvantages of a high reaction chamber 35. The upward and downward alternating flow divides the reactor into zones between which there is essentially no backflow as in high reactors.

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A two-chamber fluidized bed extension arranged downstream of the actual reactor chamber of the fluidized bed reactor provides good opportunities for supplying secondary air to the gas / particle stream from the first reactor. In this way, for example, good stepwise combustion, substoichiometric combustion in the actual reactor chamber and final combustion of the formed gas in two or more partial extensions can be achieved.

Other gas, liquid or even solids used in the processes can thus also be uniformly fed to the process gas stream at a later stage. In combustion processes, for example, it is advantageous to add sulfur-absorbing substances to the process gas, ammonia to reduce NOX or water to increase the reactivity of the lime. These additions can preferably be made in the second zone in a two-part extension, so that the added substances do not travel back to the first zone to the bottom of the actual reactor.

Thus, one important advantage of the invention is that as process-20 gas flows in a two-chamber extension through a flow port from the first chamber to the second chamber, either gas, liquid or solid can be efficiently fed to the gas over a wide area through the base plate. In the lower part of the two-chamber extension, when the process gas changes direction 25 from downstream to upstream, good mixing is also achieved in the actual flow.

The fluidized bed reactor according to the invention also allows the bed material to be discharged from the gas stream other than at the bottom of the first reactor or from the particle separator. At the bottom of the fluidized bed of the second zone, it is easy to provide a solids outlet pipe with which solids of different sizes and reacted to a different stage can be removed from the process than from the 35 outlets previously mentioned.

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

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7 85185 Fig. 1 schematically shows an embodiment of the invention in vertical section, Fig. 2 schematically shows another embodiment of the invention, Fig. 3 shows a cross-section of the reactor shown in Fig. 2 and Fig. 4 schematically shows a third embodiment of the invention.

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Figure 1 shows a circulating mass type fluidized bed reactor 1 comprising an actual reactor chamber 2, a two-chamber reactor chamber extension 3 and a particle separator 4. In the embodiment according to the figure, the particle separator is preferably a horizontal cyclone, but in other applications other types of particles can be used. Connected to the particle separator is a purified gas outlet 5 and a separated solids return channel 6. The return channel 20 is connected at one end 20 to the lower part of the actual reactor chamber to return the circulating mass to the process. A base plate 7 is arranged in the lower part of the actual reactor chamber for supplying fluidizing gas from the air cabinet 8 to the reactor chamber. The base plate may be a simple grate plate with air inlets only, a grate plate with air nozzles or some other means for distributing the fluidizing gas suitably to the reactor chamber. An ash outlet pipe 15 is arranged in the reactor chamber for discharging the ash and the bed material. The reactor chamber is further provided with means known per se, not shown in the figure, for feeding the substance to be treated, the bed material and any other additives into the reactor chamber. A gas outlet 9 is arranged in the upper part of the reactor chamber 2 for discharging upwardly flowing process gas therefrom.

Adjacent to the actual reactor chamber 2 is a two-chamber reactor chamber extension 3, which is divided by a partition wall 11 into two chambers 12 and 13. The chambers of the extension are connected to each other via a flow opening 14 to the lower part 35 β 85185. The degassing opening 9 of the actual reactor chamber is connected to the upper part of the first chamber 12 of the extension. Also arranged in the lower part of the reactor chamber extension is a base plate 17 and below it an air cabinet 18 for supplying fluidizing gas to the chambers 12 and 13. A channel 19 above the reactors is connected to the upper part 13. also in some other way, e.g. on the side of the reactor chambers.

The circulating mass reactor according to Figure 1 is suitable for use, for example, for burning solid fuel in plants producing steam or heat. The fuel is fed to the actual reactor chamber, where it burns at least in part in the fluidized bed. The upward flow of fluidizing gas and generated process gases in the reactor chamber carries finely divided solids 20 such as ash, non-combustible carbonaceous material and any other inert bed material to the top of the reactor chamber from where it flows through the opening into the first chamber of the extension. In the first part of the extension, the gas flow changes downwards. In the lower part 25 of the extension, on the other hand, the flow changes direction by first flowing through the flow opening into the second chamber and further as an upward flow therein. Changes in the direction of the flow cause turbulence in the flow and promote mixing.

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In the lower part of the extension, the solid particles pass close to the additional air grate, whereby good mixing of the secondary air with the solid is achieved and combustion is accelerated.

35 Absorbents, catalysts or other reagents or other reagents or additional fuels promoting gas cleaning may be added to the gas stream through the additional air grate or otherwise.

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In addition, ash or bed material outlet pipes 15 can be fitted to both the bottom plate of the actual reactor chamber and the additional air grate 15.

The walls of the fluidized bed reactor can be formed from tubular panels to allow heat recovery from the combustion process. Particularly susceptible areas should be massaged. Of course, separate heat exchanger surfaces can also be arranged in the reactor chambers, although they are not shown in the figure.

Fig. 2 shows another fluidized bed type fluidized bed reactor 101 according to the invention, in which a two-chamber extension 103 is arranged after the actual reactor chamber 102, as in the embodiment shown in Fig. 1. In the embodiment shown in Fig. 2, a second two-chamber extension 123 is further arranged after the extension 103, which is divided by a partition wall 131 into two chambers 132 20 and 133, which communicate with each other at the lower part of the extension through the flow opening 134. The first chamber 132 of the second extension 123 is connected at the top to the degassing opening 119 of the second chamber of the first extension and the second chamber 133 of the extension is connected at the top by a channel 139 to a particle separator 104. A bottom plate 137 is provided at the bottom of the second extension. The figure shows the fuel supply point 110 to the first reactor chamber 102.

The actual reactor chamber 102 and the chambers 112, 113, 132 and 133 of both extensions 103 and 123 are arranged as shown in Figure 3 curved one after the other so that the last chamber 133 of the last extension 123 meets the first reactor chamber 102. Thus, the particle separator 35 can advantageously be above said reactor chamber, wherein the process gases or circulating particles do not have to be transported separately in a horizontal direction between the first and last reactor chambers.

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In the fluidized bed reactor shown in Figures 2 and 3, a horizontal cyclone separator is arranged in the reactor above the last chamber. In some cases, it is preferable to use a conventional vertical cyclone instead of a horizontal cyclone, which can be arranged in the empty space between the curved chambers. In addition to the actual reactor chamber, circulating dust can be returned from the return pipe of the vertical cyclone to one or more two-chamber extensions. 10 Thus, the return can be arranged at the most suitable place for the process.

In the embodiments according to Figures 1 and 2, the base plates 7, 17 and 107 arranged in the reactor chambers are shown in 15 planar planes. To promote ash extraction and flow, the base plates 117 and 137 may be arranged obliquely downwardly from the first chamber to the second chamber. The base plates can also be shaped, e.g. funnel-shaped, to facilitate the extraction of ash and bedding material. By fitting 20 air nozzles of different sizes to the bottom plates of the two-part chambers, the supply of fluidizing air can be adjusted so that optimal fluidization is achieved in both the downstream and upstream parts. The process can also be controlled by the distance between the nozzles.

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If desired, the base plates in the actual reactor chamber and extensions can be arranged on different levels, e.g. as shown in Fig. 4, so that the base plate of the extension is considerably lower than the base plate 30 of the actual reactor chamber. In this case, in addition to the fluidizing air coming from below, secondary air can be supplied to the extension of the reactor chamber from a higher level, e.g. by utilizing the air cabinet of the first reactor.

The invention is not intended to be limited to the embodiments shown by way of example, but may be modified and applied within the scope of the inventive idea defined by the claims.

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Claims (17)

A method for treating material in a circulating fluidized bed reactor, according to which the material is treated in a first reactor chamber in a fluidized bed, where the gas flows downwards from upstairs, - process gas is removed through an outlet opening arranged in the upper part of the reactor chamber, the process gas comprises fluidizing gas, formed gases and solids accompanying the gases, and - solids are separated from the process gas and fed to the reactor chamber, characterized in that process gases discharging from the upper portion of the first reactor chamber are passed through at least one double chambered reactor with fluidized bed, in which the process gases are first conducted as a downstream gas stream through the first chamber and then as an upstream gas stream through the second chamber and into which the fluidized bed double chambered reactor is provided through a lower portion thereof base. 2. A process according to claim 1, characterized in that oxygen-containing gas is fed into the fluidized bed reactor for combustion and / or gasification of the material to be treated. 3. A process according to claim 1, characterized in that fuel and / or other reagents are fed into the double-chambered fluidized bed reactor mainly above the bottom plate of the first chamber. 4. Process according to claim 1, characterized in that fuel and / or other reagents are fed into the double-chambered fluidized bed reactor mainly above the bottom plate of the second chamber. A circulating fluidized bed reactor (1,101), comprising: i. 85185 - a first reactor chamber (2,102) having an inflow site (110) for inflowing solids into the reactor chamber and a bottom plate ( 7,107) for introducing fluidizing gas into the reactor chamber 5 and in the upper part of which an outlet (9,109) is provided for discharging process gases from the reactor chamber, - a particle separator (4,104) for separating the circulating bed material from the process gas, and - an re-introduction of the circulating bed material into the reactor chamber, characterized in that the fluidized bed reactor further comprises - a double chamber extension (3,103) of the reactor chamber, in which the lower part of the reactor is provided with a bottom plate (17,117) which in the direction of flow of the process gas first chamber (12,112) in its Upper one end in contact with the outlet (9,109) for process gases in the first reactor chamber, 20. devices (11,111) which share the double-chamber extension in two chambers (12,13,112,113) so that the chambers interconnect by means of a flow opening (14,114) with one another, - a second process gas outlet (19,119) arranged in the upper part of the second chamber of the double-chamber extension to discharge the process gas from the double-chamber extension, - means (14,114) for passing process gas from the double-chamber extension to a particle separator 30 (4,104). A fluidized bed reactor according to claim 5, characterized in that the bottom plate (17,117) arranged in the lower part of the double chamber extension has been arranged substantially at the same level or at a lower level than the bottom plate (7,107). in the first reactor chamber. i: i7 8 5 1 85 A fluidized bed reactor according to claim 5, characterized in that the bottom plate (117) 1 of the lower chamber of the double chamber extension is sealed downwardly from the first chamber to the second chamber. 5 8. A fluidized bed reactor according to claim 5, characterized in that the double chambered reactor is arranged at substantially the same level as the first reactor chamber. 10 9. A fluidized bed reactor according to claim 5, characterized in that the particle separator (4,104) is a horizontal cyclone. 10. A fluidized bed reactor according to claim 9, characterized in that the horizontal cyclone is provided at least partially above the first reactor chamber. 11. A fluidized bed reactor according to claim 5, characterized in that a second double chamber extension (123) is provided for the double chamber extension, in the lower part of which is provided a bottom plate (137) for supply of fluidizing gas and which is divided by a partition wall. (131) in two chambers (132,133) which, in their lower part, interfere with each other, and of which the first chamber (132) additionally in their upper part is in communication with the upper part of the first extension (113), for supplying process gases to the chamber (132) and of which the upper part of the second chamber (133) interferes with the process gas outlet duct 30 (139) in connection with devices for introducing the process gas into a particle separator. A fluidized bed reactor according to claim 11, characterized in that the second double chamber extension is arranged substantially at the same level as the first reactor chamber and the second double chamber extension. 18 851 85 A fluidized bed reactor according to claim 11, characterized in that the second double chamber extension is arranged at a higher level at least partially than the first reactor gun and / or the first double chamber extension. A fluidized bed reactor according to claim 11, characterized in that the first reactor gun, the first double chamber extension and the second double chamber extension are arranged side by side so that the reactor chambers form a bore. A fluidized bed reactor according to claim 14, characterized in that the second chamber of the second double chamber extension is arranged next to the first reactor chamber. 16. A fluidized bed reactor according to claim 5, characterized in that an outlet for bed material or ash collection tubes (15,115) is arranged in the lower part of the first reactor chamber 20 and / or in the lower chamber of the double chamber extension. 17. A fluidized bed reactor according to claim 5, characterized in that the fluidizing gas fed into the double chamber extension is secondary air. ii