JP2854417B2 - Fluidized bed reactor using capped double side wall contactor unit and method of use - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a fluidized bed gas-solid contact reactor module utilizing a double side wall contactor unit having integral concentric walls for heat exchange with a liquid. It relates in particular to a reactor module containing a liquid and using a capped double side wall concentric riser-downcomer unit located in the casing. The reactor module is useful for burning a fluidized particulate fuel such as coal to heat a liquid and generate a saturated liquid or steam.

The use of a fluidized bed generates heat, for example, by using it with a heat exchange tube in a boiler to generate high pressure steam from a feed water that exchanges heat with hot combustion gases from a fluidized bed of fuel. Therefore, it has been recognized as an effective method for reacting gas and solid. The fluidized bed uses a granular carbonaceous fuel such as coal, and is fluidized by flowing air through the bed to cause a combustion reaction. The advantages of fluidized bed combustion systems are high heat transfer rates, increased combustion efficiency, and reduced boiler size.

One known form of gas-solid contactor is disclosed in U.S. Pat. No. 3,826,738 to Zenz, which discloses a fold for circulating particulates for a fluid catalytic cracking (FFC) unit. Overlapping transfer line reactors. However, the folded riser downcomer configuration has clearly not been used previously in fluidized bed combustors for particulate fuels such as coal to generate saturated steam such as steam. Another type of fluidized bed combustor is U.S. Pat. No. 3,910,235 to Hiray, which discloses a fluidized bed combustor using each internal circulating bed surrounded by a heat exchange jacket. Also U.S. Pat.
No. 0,377 discloses a fluidized bed boiler utilizing circulation of solids, and U.S. Pat.No. 4,539,939 to Johnson discloses a fluidized bed combustion tubular boiler apparatus for burning coal with limestone to produce steam. Has been disclosed.

These known large fluidized bed combustion boiler units are very complex and difficult to control the granular solids flow,
It is also expensive. Disadvantages of conventional reactors and combustion systems are:
The present invention has been effectively overcome. The present invention uses at least one downcomer unit having a double side wall heat exchange configuration and located at the top of a fluidized bed and concentric with a central riser to exchange heat with liquid in a reactor module. An excellent flow reactor and method are provided.

SUMMARY OF THE INVENTION The present invention provides a gas-solid catalytic reactor module having a central capped riser positioned over a dense phase fluidized bed and at least one circulating dilute phase solid loop provided by a concentric downcomer unit. And how to use it. The riser downcomer unit has concentric inner and outer walls, each providing a cavity for containing a liquid to utilize an exothermic or endothermic reaction between the gas flowing through the apparatus and the particulate solid. In an exothermic reaction, a reaction such as a combustion reaction between a gas and a solid heats a liquid. In an endothermic reaction, a heated gas is used to treat a particulate solid, or alternatively, a heated solid is used to create a reaction in a gas. The present invention includes a gas-solid catalytic reactor module for use in an improved fluidized bed system, a method of burning particulate fuel solids to produce a heated liquid or vapor, and relatively low combustion. Moves at temperature, giving liquids or gases high heat transfer efficiency.

The present invention utilizes a circulation loop of dilute phase particulate solids entrained upward from a dense phase fluidized bed. The circulating solids loop is provided by at least one double side wall concentric riser downcomer unit for handling dilute phase flowing gas-solids, the unit comprising an outer downcomer passage concentric with a central capped inner riser passage. To provide a continuous folding path for continuous flow and reaction of particulate solids and gases flowing through the unit. In the fold path, the cross-sectional area is dimensioned so that the gas and particles react almost completely while flowing through the downcomer passage of the riser downcomer unit above the fluidized bed, and the flow rate is determined by the particle temperature And the residence time is controlled.

The capped central riser and the concentric outer downcomer passage of each unit are formed by two concentric tubes sealed at each end together to create two inner and two outer walls, Thus, each wall defines a cavity or compartment interposed therebetween, forming a double heat exchange panel and being filled with liquid. The particles are continuously entrained upwardly through the central riser passage by the upwardly flowing secondary gas stream injected therein. Heat exchange occurs primarily by convection and radiation between the flowing gas-solid, the exposed walls of the riser downcomer unit and the liquid contained in the dual compartment. The downcomer passage outlet provides for effective separation of entrained gas from downward flowing particulate solids near the fluidized bed upper level, so that the solids effectively return to the bed for circulation through the riser downcomer unit . Circulation of the particulate solids back to the fluidized bed is effectively assisted by a cylindrical skirt located radially outward from the downcomer passage outlet. The skirt has its lower part immersed in the fluidized bed.

The gas-solid contactor unit and the fluidized bed are enclosed in a casing to form the module, which is below the fluidized bed to evenly distribute the main gas flow flowing upward through the shallow fluidized bed. An integrated plenum and flow distribution grid are incorporated. The capped riser downcomer unit embodies the concept of gas particle separation by collision and utilizes the increased velocity in the riser passage compared to the downcomer passage. The cross-sectional area of the annular downcomer passage is greater than the cross-sectional area of the central riser passage by an area ratio ranging from 1.5: 1 to 5: 1, thereby slowing down in the downcomer passage for effective complete reaction of gas and particles. Provide increased velocity and increased particle residence time.
The apparent gas velocity in the central riser passage must be sufficient to entrain particles flowing upwards from the fluidized bed, typically 4.5 to 7.62 m / sec (15 to 25 ft / sec), while the outer downcomer of large area The apparent gas velocity in the passage is typically 1.52
It is reduced to 4.57m / sec (5-15ft / sec).

The apparent upward gas velocity in the central riser passage should exceed the maximum particle end or free fall velocity required for the largest particles to be carried vertically upwards. On the other hand, the apparent gas velocity flowing down the outer downcomer passage is only a function of the terminal or free fall velocity of the circulating smallest sized particles.

The total cross-sectional area of the fluidized bed is greater than the total cross-sectional area of the downcomer outermost tube wall with an area ratio ranging from 1.5: 1 to 3: 1. The shape of each capped riser downcomer unit depends on the desired performance. The unit height and diameter are determined by the desired contact or residence time and throughput with the particulate solid, and the ratio of height to outer diameter is:
At least about 8: 1 and usually not more than about 20: 1. For example,
The riser height of the riser or the total length of the downcomer and downcomer aisle is based on the complete combustion of coal particles averaging 500 microns in size. Downcomer passage exit
A vertical distance equal to 0.75 to 5 times the radial width of the annular downcomer passage is maintained above the fluidized bed upper level, or the downcomer outlet is at a similar vertical distance, preferably below the bed. Can be dipped. The ratio of recycle solids flowing through the riser downcomer passage exceeds the weight recycle ratio of at least 2: 1 for the feed rate of fresh solids from line 27 to the fluidized bed, but is typically about 10: 1. Do not exceed the ratio. The folded down riser downcomer circulation loop reduces the height of the fluidized bed and reactor module, significantly improves heat transfer due to double side wall exposure to high speed solids, and reduces the return to shallow fluidized bed. Reduce particle entrainment by reducing particle velocity. The fluidized bed reactor module is designed to be easy to manufacture, install, clean and maintain. A preferred design for a large-scale reaction system consists of a plurality of modules, each module containing, in the assembly apparatus, a riser downcomer unit with caps arranged in a parallel configuration.

The invention further provides a method for contacting gas-solids of a reactor module having a dense phase fluidized bed provided below a riser downcomer unit with a diluted phase cap. The present invention relates to a process for measuring the distance between 0.001 micron and 1.27 cm (0.5
It is useful for reacting gases with particulate solids having a wide dimensional range (0 inches). The present invention relates to the combustion of coke deposited from catalyst particles, as in the regeneration of petroleum cracking catalysts, and the roasting of metal ores, the chlorination of titanium dioxide ores, or the production of acrylonitrile, or the oxychlorination of hydrocarbons. To cool or heat the gas that undergoes the reaction in the presence of the conveyed solids or catalyst particles, or to burn a particulate solid such as coal to produce a heated liquid such as saturated steam. Can be used for Depending on the process used, the temperature rise across the folded flow passage of the contactor unit may be 5.6 ° C (1 ° C).
It is as small as 0 ° F or as large as 1000 ° C (1800 ° F). The present invention relates to a particulate fuel such as coal, coke, and oil shale with a particulate adsorbent such as limestone in a fluidized bed below a double side wall riser downcomer unit having a central riser passage and a concentric outer downcomer passage of the module. It is particularly useful for burning.

The present invention provides a compact and efficient gas-solid reaction for contacting a gas with a particulate solid to heat the circulating liquid exothermically or to endothermically heat the gas-solid with the circulating liquid. Module or system and method are provided. The present invention provides, inter alia, an improved method for heating a liquid, for example, pressurized water, to generate saturated steam by burning particulate solids such as coal to generate saturated steam. . To obtain the desired high percentage turndown for the reactor or system,
One or more capped riser downcomer units are used, and the turndown percentage is adjusted by varying the feed rate for each riser downcomer unit.

Description of the Invention A fluidized bed gas-solid reactor module having a single capped double side wall circulating gas-solid contactor unit comprises:
As shown in FIG. The reactor module 9 has a central dilution phase cap having a shallow dense phase fluidized bed 11 and a central riser passage 12 and a concentric outer downcomer passage 14 centrally located at the top of the fluidized bed 11 in an enclosed casing 20. Riser
It consists of a downcomer unit 10. An inner compartment 13 containing liquid is provided between the passages 12 and 14, and an outer compartment 15 containing liquid is provided surrounding the downcomer passage 14. The enclosure 20 can be cylindrical or rectangular parallelepiped.

The downcomer passage outlet area 14a is configured to effectively separate solids from entrained gases and return downward flowing solids to the fluidized bed 11 for return to the mouth of the central riser passage 12 and the riser downcomer. Promote solid recycling of unit 10. To help ensure the recycling of particulate solids to the fluidized bed, a cylindrical baffle 16 is provided radially outward from the downcomer outlet 14a at a location intermediate the downcomer outlet 14a and the inner wall of the enclosed casing 20. ing. The lower baffle 16a is immersed in the fluidized bed 11.
The radial distance or spacing between the downcomer outlet 14a and the baffle 16 should be 1-2 times the maximum radial width of the downcomer passage 14 so that the gas flow in the baffle 16 is lower than the gas velocity of the downcomer passage 14. Give gas velocity. If desired, a plurality of vertical gaps or slots 14b may be provided circumferentially spaced around the lower end of the outer wall of the passage 14 to radially outward and upward from solids flowing downward in the downcomer passage 14. Facilitates gas dissipation.

FIG. 2 shows two alternative shapes of the downcomer passage outlet area 14a to the upper level 11a of the fluidized bed 11. In FIG. 2 (a), the fluidized bed upper level 11a is located above the lower end of the down cover outlet 14a. The lower portion of the outer wall 15a can be extended outwardly at a vertical plane at an angle A of 0-45 °, thereby reducing the downward velocity and facilitating the separation of the downward flowing gas from the particulate solid. If desired, the entire outer wall 15a can be tapered outwardly, as shown in FIG.
As shown in FIG. 5, the baffle 16 can be used in combination with a cylindrical baffle 16.

The riser / downcomer unit 10 has double concentric compartments 13 each formed by two concentric cylindrical tubular walls.
And 15 are provided. Thus, passages 12 and 14 are completely covered with liquid on all sides for heat absorption or heating by the liquid. Limited heat removal into the liquid or limited introduction into the liquid is made through a shallow fluidized bed 11. The inner compartment 13 is provided between the two inner walls, and the outer compartment 15
Is provided between the two outer walls, and both compartments 13 and 15 are connected to a source 17 of heating or cooling liquid. The saturated liquid generated in the compartments 13 and 15 from the exothermic reaction in the riser and the downcomer passage is discharged in the upper outlet line 18. Riser downcomer unit 10 in enclosed casing 20
Structural support is provided by a central conduit 18 in combination with three lateral stabilizing struts 19 provided near the lower end of the unit 10 and extending between the unit and the wall of the casing 20.

Each module 9 has a primary reaction feed gas or air 21 entering a plenum 22 and a flow distributor 23 for fluidizing the bed 11.
And flows upwardly into riser 12 to cause continuous circulation of solids through the loop. The secondary reaction gas or air supplied at 24 is supplied. Such dual gas introduction does not allow premixing of air, ammonia or ethylene, etc., due to explosive or uncontrollable side reactions in reactions where the feed gas forms acrylonitrile and similar processes in pyridine chemical industry, the production of nicotinic acid. Useful for reactions. Floor drain 26
Performs removal of spent catalyst or high-temperature ash and limestone from the fluidized bed 11. The main cyclone separator 28 performs gas-solid separation from the outlet gas. Gas is released from the cyclone at outlet 30 and particulate solids are passed through a line for further combustion.
It is recycled to the fluidized bed 11 via 27.

During operation of the reactor as a fuel combustion unit, particulate fuel such as pulverized coal and adsorbent such as limestone are supplied via cyclone diplegs 27 and are supplied to each module 9 at inlet 31. These fuels and adsorbent materials are preferably supplied at another supply location 32 adjacent to the main cyclone gas separator outlet 30. The arrangement in which the cooler solid feed is contacted with the hot 538 ° C. + (1000 ° F.) flue gas from the fluidized bed before the solids enter the shallow fluidized bed of the reactor via the cyclone dipleg tube 27 At 482 ° C
Heat to + (900 ° F). Primary air entering the reactor plenum 22 enters the fluidized bed 11 upwardly by the porous flow distribution grid 23 and is uniformly dispersed. The grid 23 is substantially flat or conical and comprises a number of inverted angle metal plates 33 having a plurality of holes 33a oriented substantially horizontally as shown in FIG. Lateral introduction of the primary gas into the fluidized bed prevents high upward velocity of the particles and erosion of the lower part of the compartment 13.
The secondary air introduced into the bottom of the riser passage 12 is used to continuously flow fluidized bed particulate solids upward in the riser 12 and to react or combust fuel or other solids that occur in the riser and downcomer continuous passages. Used to provide the necessary gas such as oxygen.

A single inlet for coal and limestone feed to the fluidized bed via the main cyclone dipleg 27 is oriented to circumferentially supply fluid bed solids with new solids. Further, the reactor floor drain 28 is provided with a cyclone dipleg 27
Located as far from the inlet as possible,
To minimize the bypass loss of new granular coal and limestone from coal. The proportion of the apparent gas velocity flowing upward through the bed 11, as required to fluidize the bed, depends on the size and density of the particles making up the bed and is usually between 0.91 and 6.1 m / sec (3
~ 20 ft / sec). The apparent gas velocity of the secondary air flowing upward from conduit 24 toward riser passage 12 should be sufficient to entrain dilute phase particulate solids therefrom from the dense phase fluidized bed, typically between 4.57 and 9.14 m / sec (15-30ft / se
c) Should be. Due to coal combustion, fluidized bed temperature is usually 649-871 ° C (1200-1600 ° F)
The temperature rise due to the burning of coal granules in the downcomer passage is
2.8 to 55.6
° C (5-10 ° F). At the downcomer outlet 14a, the downward flowing gas changes direction and rises upward toward the gas outlet 25 to the main coal separator 28. On the other hand, the remaining unburned particles are returned downward to the fluidized bed 11 by the movement and the bed collision, further burn, and recycled to the riser 12.
The primary and secondary air are preheated with a hotter discharge stream, such as a reactor hot flue gas, preferably at 25 ° C.

Each reaction module 9 is successfully sized for a combustion system that burns the desired throughput, for example, coal, to produce about 10,000 lb / hr of saturated steam. Each module is preferably square shaped and is individually factory-fabricated and can be combined with other adjacent modules for special installation.
As shown in FIG. 4, multiple modules 9 can be used as needed for larger throughput systems. Each module 9 can be separated from adjacent modules by a plenum separation wall 34, and the spacing between riser downcomer units in each adjacent module is
It should be 1.5 to 2.5 times the outside diameter of the unit.

EXAMPLES A typical fluidized bed combustion reactor module comprises a dense phase fluidized bed located below a riser downcomer unit in a casing. The pulverized coal and limestone granular solids are separated into one to preheat the feedstock before they enter the shallow fluidized bed via the cyclone dipleg line.
The gas is then introduced into the fluidized bed through a line in the gas-solid cyclone separation unit. The riser and downcomer aisle
Formed by four concentric tubes, which are provided with inner and outer cavities filled with boiler feed water to heat the water and generate saturated steam. Primary air is
The porous grid uniformly distributes upward from the plenum into the fluidized bed. The secondary air is injected upwards at a sufficient velocity into the central riser passage to provide a controlled particle velocity and residence time, and through the recycle of solids to the fluidized bed,
Provides almost complete combustion of coal.

Important properties of a typical reactor module having a fluidized bed below a capped riser downcomer unit for burning coal with limestone are shown in Table 1 below.

Table 1 Fluidized bed depth, m (ft) 1.22 (4) Apparent gas velocity of fluidized bed, m / sec (ft / sec) 3.05 (10) Riser passage height, m (ft) 6.1 (20) Downcomer passage Height, m (ft) 5.5 (18) Cross sectional area ratio of downcomer passage to riser passage 2: 1 Apparent gas velocity at riser, m / sec (ft / sec) 6.1 to 9.14 (20 to 30) Downcomer Apparent gas velocity, m / sec (ft / sec)
3.05 to 4.57 (10 to 15) m (ft) above or below the fluidized bed upper level +0.46 to -0.46 Height of downcomer outlet (+1.5 to -1.5) Fluidized bed coal and limestone particle size, Flue gas from micron 200-700 fuel combustion flows through a cyclone separator for solids removal, and the removed solids are recycled to a fluidized bed, while ash and limestone are removed from the bottom of the bed .

BRIEF DESCRIPTION OF THE DRAWINGS Hereinafter, the present invention will be described in more detail based on embodiments with reference to the accompanying drawings.

FIG. 1 shows a gas-solid catalytic reactor module having a capped central riser passage surrounded by a concentric downcomer passage provided above a fluidized bed in a casing.

2a and 2b are schematic illustrations of two alternative shapes for the lower part of the reactor module downcomer passage with respect to the fluidized bed.

FIG. 3 is a partial perspective view of a grate device for flow distribution of gas flowing upwardly into a fluidized bed of a reactor module.

FIG. 4 is a plan view of a plurality of adjacent reactor modules each having a gas-solid contactor unit according to the present invention.

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Claims (16)

(57) [Claims] 1. A casing having a dense-phase fluidized bed of granular solid material (11) in the lower part; and (b) means for supplying fresh granular solid matter to the fluidized bed (11) of said casing. (C) a riser downcomer unit (10) having a central riser passage (12) connected to the concentric outer downcomer passage (14), said unit comprising:
Extending substantially vertically within the casing, the downcomer passage outlet is located near an upper level of the fluidized bed (11) and directs downward flowing particulate solids into the downcomer passage (14).
The riser downcomer unit (10), which is adapted to be diverted back to the fluidized bed (11).
Has a double concentric compartment, each of which is formed by two concentric cylindrical tubes whose ends are sealed together to provide heat exchange panel means for containing a liquid. Forming; (d) dispersing means (23) for introducing the primary gas upward into the fluidized bed (11) and means (24) for introducing the secondary gas upward into the central riser passage (12).
And (e) a cyclone separator (28) connected to the upper end of the casing (20) for flowing gas and entrained solids outward, whereby the particulate solids are supplied to the fluidized bed and further to the panel wall and its The particulate solid which can exchange heat with the liquid in it and flow through the riser downcomer unit (10) passage to the dilution phase and is collected by the gas-solid cyclone separator (28) A fluidized bed gas-solid reactor module characterized in that it can be recycled back to 11). 2. The method according to claim 1, wherein a cylindrical baffle (16) is provided outwardly from the downcomer passage outlet to return downward flowing particulate solids to the fluidized bed (11). A gas-solid reactor module as described. 3. The dispersing means (23) has a number of flow lines (33) oriented substantially horizontally and having a plurality of openings (33a) for supplying primary gas to the fluidized bed (11). The gas-solid reactor module according to claim 1, wherein: 4. Means for introducing a liquid below the heat exchange panel means (17), and means (18) provided at the upper end of the panel for removing heated or cooled liquid from the panel means. The gas-solid reactor module according to claim 1, comprising: 5. The cross-sectional area of the outer downcomer passage (14) is:
2. The gas-solid reactor module according to claim 1, wherein the cross-sectional area of the central riser passage (12) is greater than the cross-sectional area of the central riser passage (12) by a ratio in the range of 1.5: 1 to 3: 1. 6. The gas-solid reaction according to claim 1, wherein the ratio of the height to the outer diameter of the riser downcomer unit (10) is between 8: 1 and 20: 1. Vessel module. 7. The downcomer passage outlet end is maintained below the fluidized bed upper level (11a) at a distance equal to 0.75 to 5 times the radial width of the downcomer passage (14). The gas-solid reactor module according to claim 1. 8. A particulate solid supply means (32) is arranged to exchange heat with the gas flowing outward in said cyclone separator (28), and feed particles are supplied from the cyclone separator to the fluidized bed (11). 2. The gas-solid reactor module according to claim 1, wherein the gas-solid reactor module can be mixed with solid particles which are recycled back to). 9. A riser downcomer unit (10) is held by each module, and a number of adjacent modules (9) are combined to constitute a large-scale reactor system. The gas-solid reactor module according to claim 1. 10. The gas-solid reactor module according to claim 9, wherein the interval between adjacent riser downcomer units (10) is 1.5 to 2.5 times the outer diameter of the unit. 11. A method comprising the steps of: (a) disposing a particulate reactive or catalytic solid in an outer downcomer passage (1) concentric with a central riser passage (12);
A dense phase fluidized bed (11) located below the casing (20) under at least one riser downcomer contactor unit having a central riser passage (12) flow connected to 4). (B) supplying the primary gas stream upwards to the fluidized bed to fluidize the bed, and supplying the secondary gas upwards to the central riser passage (12) to entrain particles from the fluidized bed (11) into the riser passage. (C) the evaporative lower portion of the double heat exchange panel carried by the riser downcomer unit (10) and in contact with the downcomer passage (14) concentric with the central riser passage (12). Supply liquid;
(D) continuously converting a portion of the particulate solids in the dilution phase from the fluidized bed (11) to the riser downcomer contactor unit at a temperature and flow rate selected to substantially completely react the feed gas with the solids. Passing upward through the central riser passage (12) and then downward through the fluidized bed through the concentric outer passage (14); (e) heating the liquid in the heat exchange panel to generate a saturated liquid. Removing a saturated liquid from the top of the panel and reacting the gas with the particulate solid in a fluidized bed reactor system. 12. The apparent upward gas velocity of the central riser passage (12) is 4.57 to 9.14 m / sec (15 to 30 ft / sec), and the apparent gas velocity of the downcomer passage (14) is 1.52 to 4.57 m / sec.
12. The method according to claim 11, wherein the speed is sec (5 to 15 ft / sec).
The gas-solid reaction method described in 1. 13. The recycle ratio of solids circulating through the riser and downcomer passages (12, 14) of the riser downcomer unit is at least 2: 1 by weight relative to the feed rate of fresh solids to the fluidized bed. 12. The gas-solid reaction method according to claim 11, wherein the ratio exceeds the ratio. 14. The solids exiting the downcomer passage (14) substantially return to the fluidized bed (11) and the gas exiting the downcomer passage passes to a cyclone gas-solid separator (28) from which particulate solids are removed. 12. Return to the fluidized bed
The gas-solid reaction method described in 1. 15. The gas-solid according to claim 11, wherein the particulate solid is a fuel solid and an adsorbent for removing sulfur, the primary gas is air, and the evaporable liquid is water. Reaction method. 16. The fuel solid according to claim 15, wherein the fuel solid is coal, the adsorbent is limestone, and a step of removing unburned coal ash and limestone from the lower part of the fluidized bed (11). The gas-solid reaction method as described.