JPS6237608A - Method of operating fluidized bed type reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a method for operating a fluidized bed reactor, and particularly to a method for operating a fluidized bed reactor in which heat is generated by combustion of fuel within the fluidized bed. Concerning operating methods.

1. Fluidized bed reactors, combustors or gasifiers are already well known. In such devices.

A bed of particulate matter containing a fossil fuel such as coal and an absorbent for sulfur produced by the combustion of the coal is fluidized and air is passed through the bed of particulate matter to promote combustion of the fuel at relatively low temperatures.

When water is converted to steam using the heat created by a fluidized bed, as in a steam generator, fluidized bed systems offer high heat release, high sulfur absorption, low nitrogen oxide production, and low fuel consumption. Offering benefits such as flexibility.

The most typical fluidized bed combustion device is commonly referred to as an effervescent fluidized bed. In such a fluidized bed, a bed of particulate material is supported by a perforated air distribution plate, and combustion sustaining air is introduced into the particulate material bed through a number of holes in the distribution plate;
The particulate material is expanded and made to float and fluidize. If the reactor is a steam generator, the walls of the reactor are formed by a number of heat exchanger tubes. Heat generated by combustion within the fluidized bed is transferred to a heat transfer medium, such as water, circulating through heat transfer tubes. The heat exchanger tubes are usually connected to a natural circulation circuit that includes a steam drum for separating water from the created steam. The steam is delivered to turbines or other uses for power generation.

Fluidized bed reactors using rapid fluidized bed processes have been developed in an attempt to improve combustion efficiency, pollutant production control, and throttle control of fluidized bed combustion rates. According to this process, the solid particle content of a normal boiling fluidized bed is 30% by volume, but it is much lower than that of 5-20% by volume.
The fluidized bed density in volume % solid particles is obtained. The formation of such a low-density, rapidly fluidized bed is possible because of the small particle size of the particulate material and the high particle throughput rate, and therefore the particle circulation rate must be high. The speed range of the rapidly fluidized bed is between the falling speed of the white particles and the upper limit speed (a function of the particle passing speed) above which the fluidized bed becomes a pneumatic transport tube. Therefore, for any particle circulation speed, there is an upper limit speed above which the fluidized bed enters a state of pneumatic transport.

The rapid circulation of particles required by rapidly fluidized beds reduces requirements on the heat release pattern of the fuel, thus minimizing temperature changes within the combustor and gasifier, thus reducing nitrogen oxide production. . Also, high particle loading increases the efficiency of the mechanical separator for separating gas from particles for particle recirculation. As a result, the sulfur sorbent and fuel residence time is extended, thus saving sorbent and fuel consumption. Additionally, rapidly fluidized beds have, as an inherent property, a higher combustion rate throttling range than conventional boiling fluidized beds.

However, rapid fluidized bed systems are not without problems. For example, granular fuels and absorbents used in rapid fluidized bed systems must be relatively fine and therefore
Processing costs are higher because the particulate material must be crushed into finer particles and dried. Additionally, the bed height required for sufficient sulfur absorption is higher than in conventional boiling fluidized beds, which also increases capital and operating costs.

It is also an object of the present invention to provide a method of operating a fluidized bed reactor in which fuel and absorbent particles of a wide range of particle sizes can be used.

Another object of the invention is to provide a fluidized bed operating method that allows sufficient sulfur absorption to be achieved with a relatively low fluidized bed.

Still another object of the present invention is to provide a method for operating a fluidized bed reactor in which a gas column is formed in a fluidized bed boiler (reactor) saturated with particulate matter. It is to be.

Yet another object of the present invention is to operate a fluidized bed reactor to collect particulate material in a gas column and return substantially the same amount of particulate material to the fluidized bed to maintain the gas column in a saturated state. The purpose is to provide a method.

Another object of the present invention is to provide a method of operating a fluidized bed reactor that allows the amount of particles contained within the boiler furnace (reactor) to be increased compared to conventional boiling fluidized beds. be.

Yet another object of the present invention is to provide a method of operating a fluidized bed reactor in which the temperature of the fluidized bed is varied by varying the amount of air introduced into the fluidized bed.

Another object of the present invention is to provide a method of operating a fluidized bed reactor that brings a cooling surface into contact with the fluidized bed and gas column.

Yet another object of the present invention is to provide a method of operating a fluidized bed reactor that incorporates the operating principles and advantages of both boiling fluidized beds and rapid fluidized beds.

The method of operating a fluidized bed reactor of the present invention to achieve the above objects comprises air and combustion gas products from the fluidized bed entrained by the air and combustion gas products above the fluidized bed. It is characterized by forming a gas column containing a mixture with particulate matter. The gas column is saturated with particulate material which is separated from the mixture and returned into the fluidized bed to maintain saturation.

The method of the present invention uses natural water circulation type steam generator 10 (first
This will be explained in relation to the fluidized bed boiler (reactor) that constitutes a part of the reactor (Fig.). The steam generator 10 includes a water supply pipe 14
A steam drum 12 is provided which receives water from the steam tank and delivers steam through a plurality of steam pipes.

The fluidized bed boiler (reactor) 18 is arranged close to the steam drum 12, and includes a front wall 2OA that constitutes a rectangular boiler furnace 24, a rear wall 2OB arranged in equilibrium with the front wall,
and two side walls extending perpendicularly to the front and rear walls.
2 (only one side wall is shown in the figure).

The walls 20A, 20B, 22 of the boiler 18 are all formed in the form of panels of a number of vertical tubes (heat exchanger tubes) connected to each other by vertical elongated bars, forming a continuous airtight structure. This type of structure is not shown in the drawings, as it is well known, and there is no need to explain it in detail here. Wall 20A.

The ends of the winter clothing 20B, 22 are arranged horizontally in a lower header 26 and an upper header 2 for purposes to be explained later.
8 is connected. The upper part of the furnace 24 is connected to the boiler 18
In order to communicate with the water/steam portion m 32 disposed adjacent to the rear wall 20p, some of the pipes (not shown) constituting the rear wall 20p are bent rearward to connect the upper portion of the rear wall The lower part of the three-separator section 32, in which the opening 30 is formed, is constituted by a cyclone separator 34. The cyclone separator 34 has a coaxial cylindrical portion 35 that cooperates with the peripheral wall of the separator to define an annular flow path for gas entering the separator from the boiler 18. The gas flows spirally in this annular flow path or annular chamber, separating the entrained particles by centrifugal force, and the gas component rises to the upper part of the separating section 32. Meanwhile, the separated particles fall into a portion of the lower hopper of the separator 34, and the recirculation conduit 3, as will be described in detail below.
6 and returned into the boiler 18.

A heat recovery compartment 38 is formed adjacent to the separator 32 and has an opening 39 formed in the upper wall portion of the compartment for receiving clean gas from the separator 32 .

A pair of superheaters 40A in the gas flow path in the heat recovery compartment 38,
40B is placed. Each superheater consists of a plurality of tubes connected to form a fluid circuit through which steam passes in a conventional manner to recover heat from the clean gas passing therearound.

The boiler bank in the heat recovery compartment 38 includes a steam drum 12
It is constituted by a series of parallel tubes 42 connecting the water drum 44 to a water drum 44. Parallel tube 42 serves to transfer water to water drum 44 under conditions as described below. tube 42
A gas passage is provided adjacent to and a gas outlet 45 is provided.

The walls constituting the upper part of the separation section 32 and the heat recovery compartment 38 are also, like the walls of the boiler 18, a continuous panel structure formed by a number of vertical tubes connected to each other by vertical elongated bars or fins. It is. The upper ends of these walls are connected to a plurality of horizontally arranged upper headers 46, and the lower ends of these walls are connected to a plurality of horizontally arranged lower headers 48 (only one shown). ing.

Although not shown in the figures, a water flow circuit including downcomers or the like is provided to connect the steam drum 12 and/or the water drum 44 to the header 26.28.46.48, including downcomers or the like. water drum 44, wall of boiler 18,
A fluid circuit is established through the walls of the separation section 32 and the walls of the heat recovery compartment 38 . Since this is a conventional configuration,
No further explanation is necessary.

A suitable air supply source (
An air chamber 5o is provided in the lower part of the boiler for introducing pressurized air into the boiler 18 (not shown).

A perforated air distribution plate 52 is supported above the plenum chamber 50 in the lower part of the combustion chamber of the boiler 18 .

The air introduced through the plenum chamber 50 passes through the air distribution plate 52
rises through the numerous pores of the If necessary.

This air can be preheated by an air preheater (not shown), and the flow rate can be adjusted appropriately by an air flow control damper.

The air distribution plate 52 is adapted to support a layer 54 of particulate material, generally consisting of pulverized coal and limestone or dolomite to absorb the sulfur produced by the combustion of the coal.

The inner surfaces of the lower portions of the walls 20A, 20B, 24 of the boiler 18 are lined with refractory material 56 or other suitable insulating material for a height range above the air distribution plate 52.

A fuel distributor 58 extends through the front wall 20A for introducing granular fuel (crushed coal) onto the top surface of the bed 54. Distributors for distributing particulate sulfur absorbent (such as limestone) and/or additional particulate fuel onto bed 54 may be provided in walls 20A, 20B, 22 as desired.

A discharge pipe 60 for discharging spent fuel and absorbent from bed 54 to external equipment aligns with the opening in air distribution plate 52 and extends through plenum chamber 50 .

A number of air ports 62 are drilled in the side wall 22 at a predetermined height from the layer 54 for introducing secondary air into the boiler for purposes described below. If necessary, add additional air ports to wall 20A.

20B can also be drilled at various different heights.

When operating the steam generator 10, air is pumped into the aeration chamber 50.
A portion of the particulate material within layer 54 is ignited by introduction into the layer 54 . A quantity of starting coal is introduced through distributor 58 and dispersed on top of the granular material in bed 54 . layer 5
The coal in 4 and starting coal are ignited by a burner (not shown) disposed in bed 54 . As coal combustion progresses, additional air is introduced into the plenum chamber 50 at a relatively high pressure and velocity. Alternatively, one layer 54 can be added to the air chamber 50.
It can also be heated by a burner placed inside. The amount of primary air introduced through the plenum chamber 50 is less than the total amount of air required for complete combustion so that combustion within the lower portion of the furnace 24 is incomplete. Thus, the lower portion of the furnace 24 operates under reducing conditions and the remaining air (secondary air) required for complete combustion is supplied through the air port 62. The amount of air supplied through the plenum chamber 50 may range from 40% to 90% of the amount required for complete combustion, with the remaining air (60% to 10%) supplied through the boat 62.

The high-pressure, high-velocity combustion sustaining air introduced into the plenum chamber 50 through the air distribution plate 52 entrains relatively fine particulate matter, including coal ash and spent limestone particles, into the combustion product gas, causing the gas to Transport energy. This mixture of entrained particles and gas rises within the furnace 24 to form a gas column containing the entrained particles, and flows from the boiler 18 through the opening 30 into the separation section 32 .

According to one feature of the invention, the gas column formed in furnace 24 above layer 54 is saturated with particles or solids. That is, the gas column is entrained with the maximum amount of particles that it can entrain. This maximum particle (solids) loading is shown in the graph of Figure 2 as a function of fluidizing air velocity.6 When applying the graph of Figure 2, the particle size that can be carried by the gas is The proportion of fluidized bed material and the partial separation of relatively coarse particles must be taken into account. As shown in Fig. 2, 12ft/sec, (
The same amount of solids (i.e. particles) at a fluidizing air velocity of 3,66 m/5ee) is gas I Qb (0,45 kg)
As a result of the gas column being saturated with particles, a significant amount of fine particles is retained within layer 54. Boiler 1
8, the volume of particles deposited in the reaction vessel is relatively high, 20% of the total volume of the vessel when operating at maximum capacity.
It is about 30%.

The coarse particulate material is deposited in the lower part of layer 54 along with a portion of the fine particles, and the remaining portion of the fine particles rise through the gas column. The fine particles traveling along the length of the gas column and exiting the boiler 18 through the opening 30 are
A stream M is separated from the combustion product gases (also referred to simply as "combustion gases") in a separator 34 and passed through a recirculation conduit 36.
54. With this recycled fines and additional particulate fuel introduced through distributor 58,
A saturated gas column (ie, a gas column saturated with fine particles) is maintained above layer 54. In other words, the gas column above layer 54 is kept saturated with fine particles.

Water is introduced into the steam drum 12 through the water supply pipe 14, where it mixes with the water in the drum. Water is directed from drum 12 downwardly through pipe 42 to water drum 44, as described above, through downcomers, etc., to lower header 2.
6 and into the tubes of the boiler walls 20A, 20B, 22. Heat from the fluidized bed, the gas column and the particles entrained by the gas column converts a portion of the water flowing in the tubes of the boiler wall to steam and a mixture of steam and water rises in those tubes and into the upper header 46. were gathered in
It is transferred to the steam drum 12. Steam and water are separated in the steam drum 12 in a conventional manner, and the separated steam is conducted from the steam drum 12 through a steam pipe 16 to a steam turbine or the like. Meanwhile, the separated water mixes with fresh water supply from the water supply pipe 14 and is recirculated through the fluid circuit in the manner described above. Additional cooling surfaces, preferably in the form of partitions consisting of a number of vertical tubes, can also be provided in the furnace interior 24 in contact with the fluidized bed and the gas column. It is also possible to provide a steam-cooled (cooled by steam) cooling surface that contacts only the gas column.

The clean hot gas from the separation section 32 is sent to the superheaters 40A and 40.
B and flows over tube 42, superheating the steam in the superheater and imparting heat to the water flowing in tube 42 before exiting the steam generator through outlet 45. If the air introduced into the plenum chamber 50 is at a relatively high pressure, on the order of 10 atmospheres, the gas from the outlet 39 can be directed to a gas turbine or the like (not shown).

The temperature of the fluidized bed 54 changes the amount of air supplied to the boiler through the plenum chamber 50 and the air boat 62, as shown in the graph of FIG. 3, in response to changes in the steam turbine load. maintained at a predetermined tolerance by The graph of FIG. 3 shows the variation of the load, temperature and amount of air supplied to the charge chamber 50 as a percentage of the theoretical amount of air required for complete combustion.

Curve A shown in FIG. 3 represents the temperature versus load of a mixture of gas and entrained particles exiting the gas column in boiler 18 through opening 30. The temperature increases with increasing load.

Curve B shows that fluidized bed temperature and load are substantially proportional. Curve C shows the relationship between the change in load and the change in the percentage of the amount of air supplied to the fluidized bed relative to the theoretical air requirement for complete combustion.

As can be seen from the above description, the method of the present invention incorporates the operating principles of both boiling fluidized bed and rapid fluidized bed systems, thereby providing many advantages. For example, the relatively high amount of lateral mixing of particulate material within a fluidized bed is approximately the same as that achieved by a boiling fluidized bed. Moreover, as in the case of rapid fluidized beds,
Fine particulate material is maintained within the reaction zone and fuels and sulfur absorbers having a wide range of particle sizes can be utilized.

Moreover, compared to the case of a rapidly fluidized bed, the height of the bed when at rest can be lowered, and the height of the bed when fluidized and expanded can be much lower. This, combined with the release of overfire (meaning "above the flame") air through air ports 62 above the fluidized bed, reduces the power requirements of the air delivery fan.
Reduces mechanical stress caused by pressure fluctuations in the fluidized bed. Additionally, most of the reactions between particles and gases, including particularly combustion reactions, occur only below the overfire air port 62 - minimizing carbon oxide and hydrocarbon emissions. Supplying air in two stages, primary air through the plenum chamber 50 and secondary air (overfire air) through the air boat 62, reduces nitrogen oxide emissions in addition to the above advantages. Bringing benefits to the market.

Furthermore, the wall surface is exposed to the reducing gas. Preferably, highly conductive refractory materials can be used below the overfire air and other corrosion-prone locations. Further, since the circulation of solid particles is restricted by maintaining a saturated gas column at all times, active control of the particle circulation flow rate by a particle recirculation system is not required. Furthermore, by being able to extract relatively small amounts of solid particles from the recirculation system and fluidized bed tap, the residence time of coarse and fine particles in the system can be adjusted to suit their reaction characteristics. can do.

Although not specifically shown in the accompanying drawings, it will be apparent to those skilled in the art that other additional necessary equipment and structural elements are provided and that they and each of the above-described components form a complete operating system. are combined to form a

Furthermore, various modifications can be made to the method of the invention without departing from the scope of the invention. For example, the fuel supplied to the boiler is not ``double particulate matter'' but
It may be liquid or gaseous.

[Brief explanation of the drawing]

The core diagram is a schematic cross-sectional view of the atmospheric pressure fluidized bed combustion section that constitutes a part of the natural circulation steam generator, Figure 2 is a graph showing the relationship between the velocity of fluidized air and the amount of particle band, and Figure 3 is a graph showing the relationship between load, air ratio (%), bed temperature, and furnace outlet temperature. 18... Fluidized bed boiler, 30... Opening, 32... Separation section, 34... Cyclone separator, 36... Recirculation conduit,
50...Air chamber, 62...Air port. Patent applicant Foster Wheeler Energy
Corporation Representative Patent Attorney Naoma Saka
Sakai - Kanesaka
Shuttle 1B...Sink tube boiler, 30...Closed

Claims (1)

[Claims] forming a layer of solid particulate material within the container, introducing air into the layer at a rate sufficient to fluidize the layer and sustain a combustion or gasification reaction of the fuel within the layer; forming a gas column containing a mixture of the air, the gas products of combustion, and particulate matter entrained by the air and the gas products of combustion; separating the particulate matter from the mixture; returning the entrained particulate matter to the bed and maintaining an amount of entrainable particulate matter in the bed and in the gas column sufficient to saturate the gas column with gas-entrainable particulate matter. How to operate a fluidized bed reactor.