FI119179B - Reactor with circulating bed - Google Patents

Description

1,119,179

Circulating fluidized bed reactor

The present invention relates to a circulating mass reactor according to the preamble of claim 1.

Such a reactor generally comprises an elongated riser channel having at least a substantially vertical central axis. The riser has a lower portion which is connected to gas and solid inlet and outlet ports through which the solid and fluidizing gas can be introduced into and removed from the riser. At the top of the riser passage there is a separating unit 10 for separating the solid from the fluidizing gas. The separation unit then consists of a multi-aperture cyclone comprising a separation chamber and a guide impeller for conducting solids-containing gas against the separation chamber wall and for rotating motion. At least substantially solids-free gas from the separation chamber is removed from the cyclone via an outlet, and the separated solids 15 are, in turn, removed through a return conduit.

The reactor type described above, the so-called circulating mass reactor (hereinafter also referred to as the "CFB reactor"), can be used both as a steam boiler, as a fuel gasifier, as a solid catalyst circulating reactor and as a drying device. An example of a commercial 20 implementation is Tampella's so-called CYMIC boiler. This structure is characterized by ··· 1 • · * ··; * characterized in that the cooled multi-aperture cyclone and the return channel are coaxially aligned with the ascending channel ··· ** ”. Problems with this structure include that the cyclone • · * • · «''" * I becomes flow-tight and additionally interferes with the upstream flow and mixing.

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In addition, the structure is relatively expensive when cooled. Especially the cone connecting the cyclone chamber and the return foot, ···, 25 is technically difficult if it has to be done in a cooled t ·· structure.

·· * 4 * · **: Finnish Patent No. 106242 discloses an improved CFB reactor structure wherein, ···. the multi-aperture cyclone and the return channel are annularly arranged around the riser ··· 30. One of the key advantages of this known solution over all prior art * · CFB reactor types is that it removes the previous limitation that in practice the height to diameter ratio of · · · must be substantially greater than that of 1. Patent · ··· · 106242 said ratio may be 1 or less, up to 0.5-0.95.

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The structure disclosed in patent 106242 is particularly suitable for use at low temperatures.

However, there are still some disadvantages in said structure, particularly with regard to its use in applications requiring high temperatures and high resolution. These disadvantages are mainly due to the fact that the cyclone outlet is arranged annularly around the riser channel. Implementing an outlet duct built around the riser when cooled will inevitably lead to a complicated and expensive structure. The cooled central tube should be shielded due to wear, making the structure heavy, bulky and expensive. Especially in small units, the cooled cyclone outlet becomes very clumsy due to the thick wall. It is difficult and costly to damage such a structure in the event of damage. Clogging of complex ductwork can also be a problem. Gas removal from the annular central tube requires multiple outlet connections in large devices, after which gas streams must be recombined into a single stream. These joints also need to be cooled to avoid problems with thermal expansion, which also makes them expensive, cumbersome and difficult to cook. In addition, the diameter of the outlet pipe arranged around the riser becomes problematically large, which significantly limits the separator's resolution.

It is an object of the present invention to overcome the above problems and to provide a · ··· • · * ··· 1 completely novel circulating mass reactor which is more suitable than existing structures. also in the form of a cooled structure which is simpler in structure and functionally superior to 1 · • · · '2 I.

The invention is based on the improvement of the structure disclosed in patent 106242 by replacing the annular cyclone arranged around the riser channel with a cylindrical: V. cyclone located above the inflow impeller. Thus, in the structure α · · '1' · of the invention, the vertical axis of the cyclone is inverted with respect to that shown in patent 106242 *. reversed.

• · · ♦ · 30 • ·. More specifically, the reactor according to the invention is essentially characterized in what is stated in the characterizing part of claim 1.

• ·· 2 • · 3 119179

The use according to the invention, in turn, is characterized by what is claimed in claim 9.

The invention provides considerable structural and functional advantages. The structure of invention 5 is an essential improvement of the invention in terms of thermal expansions, since the ascending passage can expand completely freely in the vertical direction. This is of great importance, for example, in combustion or gasification reactors, because in this case the riser and the jacket generally expand in different ways. In addition, the impellers can be made easily replaceable, since they do not need to join the riser in a gas-tight manner. Since the 10 impellers are the most consumable part of the device, its easy replacement is a major advantage. In the structure of patent 106242, even in relatively small units, it is generally necessary to remove gas from the central tube at multiple points and to recombine gas streams into one. In the structure according to the invention, the degassing of the cyclone takes place in the simplest possible way.

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In addition to the aforementioned structural advantages, the structure of the invention provides substantial enhancement of the cyclone resolution over the invention of patent 106242, since the outlet pipe diameter can be made small and flow disturbances characteristic of viscous suspension flows cannot enter the outlet pipe. In a vortex flow, the peripheral velocity increases as the 20 rotation radii decrease, resulting in an increase in centrifugal acceleration at low friction flow, inversely proportional to the rotation radius cube. In the construction of the invention ·· * ••• | The flow phenomenon mentioned in the invention can be fully utilized, but only to a minor extent in the solution of patent 106242 • * · \.

Another significant functional advantage over the solution of patent 106242 is that the disturbance of the flow characteristic of high particle-containing streams does not allow the particles to be transported to the exhaust pipe and to reduce the separation efficiency. For the above reasons • *. * · *. the cyclone resolution of the structure according to the invention is significantly increased compared to the cyclone resolution of M · 10,642. Also, the pressure drop in the gas in the cyclone of the invention is smaller than in the cyclone of patent 106242 due, among other things, to the simpler gas exhaust duct.

• · • * • * * • · * • · 4 119179

Compared to, for example, the Tampella CYMIC reactor, the structure of the present invention provides better gas / solid separation when the structure of the invention flows radially, with up to 98% solids already colliding with gas and particulates . After effective pre-separation, the gas to be cleaned in the actual cyclone is low, which enhances cyclone performance and reduces wear. In the CYMIC solution, gas and circulating inflow occurs from the center of the cyclone wall to no pre-separation. A further disadvantage of the CYMIC solution is that the cyclone fitted within the 10 rise chambers becomes narrow, subject to erosion and corrosion, and impedes the gas mixing important for combustion. The ratio of the inflow impeller diameter to the diameter of the central tube in CYMIC remains small, which results in inadequate cyclone resolution for many purposes. With respect to CYMIC, the structure of the present invention also has the advantage of reducing the upstream flow of the return channel, which interferes with the separation power, and of preventing the return channel riser flows from transporting particles to the gas exhaust pipe.

For these reasons, the structure disclosed herein provides substantial functional and structural improvements over the structure disclosed in Fl patent 106242, as well as with the CYMIC solution patented by Tampella. The operational benefits are significant,. both refrigerated and non-refrigerated. Structural improvements are • · • · ·.:. especially important in applications requiring refrigeration, but also non-refrigeration • ΜΦ:. *. in which structures the structure of this invention results in a simpler, less expensive, less maintenance-intensive and easier-to-repair structure: ·: 25 • · · · · · · · · · axially above the control impeller, the outlet connection diameter can be optimally dimensioned for the separation ratio • · ·: *. * and no return channel interference flows reach the outlet connection. in addition, the pressure loss of the cyclone * * · * ... * will minimize the return channel loading.

• · ·:: 30 * * a * "" The circulating mass reactor according to the invention can be used e.g. in a manner known per se ·; * ·: as a steam boiler, as a fuel gasifier, as a reactor in which solid catalyst is circulated, or as a drying device.Especially it is used as a cooled structure.

5,119,179

The invention will now be further explored by means of a detailed description with reference to the accompanying drawing.

Figure 1 is a sectional side elevational view of the CFB reactor of the present invention and Figure 2 is a horizontal sectional view of the reactor of Figure 1 from A-A.

The CFB reactor according to the invention consists essentially of three parts I - ΙΠ, namely I. an elongated riser channel or tube 4, the central axis of which is substantially vertically tracked, Π. gas and solid supply means at the lower end of the riser, 1,2,3 and 11, and H1, solid and gas separator means at the upper end of the riser, respectively.

The device can still be equipped with IV. with cooling fluid supply and outlet means 12, 13 for cooling the riser.

20th · 1 ·, The basic structure of the device is shown in Figure 1, with reference numeral 1 denoting a fluidization • · 1 gas inlet connected to a manifold 2 for uniformly distributing flow ···· •: 1: upstream flow of riser channel 4 to achieve.

In this case, solids can be fed into the fluidizing gas stream via the feed line 11.

! The solid inlet connection is preferably located on the wall of the riser duct • ♦ ♦ :: so that it opens inside the riser duct just above the manifold 2.

·· · • · · · 1 The riser channel 4 may have the desired cross section perpendicular to the longitudinal axis. It may be of circular or polygonal cross-section. Of the polygons, • ... · 30 especially 4, 5, 6, 7 and 8 angles can be mentioned. The advantage of polygonal cross-sections * 1 1 1; the circular shape is that they can be made of flat panels. The ascending channel may also be *: 1 1: composed of a plurality of adjacent tubes of circular cross-section or • ♦: .1 ·> polygonal tubes. The riser passage is preferably coaxially disposed within the reactor casing 6 119179, whereby a solid return passage 9 is formed between the riser passageway and the reactor casing casing.

Figure 2 shows a cross-section of the riser at position A-A. In this case, the riser channel has a hexagonal cross-section. As shown in Figs. 1 and 2, a multi-aperture cyclone 5-10 is structurally symmetrical in the direction of the center axis of the riser, along the upper end of the riser.

The cyclone has inlet connections 5 arranged completely symmetrically to the wall 10 of the ascending channel. Section A-A illustrates an embodiment of cyclone inlet connections in which a single cyclone inlet is fitted to each planar surface of a 6-angle ascent channel. Such a structure is advantageous when it is desired to cool the riser channel as well. Uncooled structures are preferably implemented as circular sheet structures.

The wall of the cyclone chamber 6 is formed by the upper portion 14 of the reactor shell, which is connected to the return conduit 9 via the collar portion 8. The cyclone chamber 6 extends from the level of the inlet connections 5 parallel to the longitudinal axis of the riser upwards past the upper end of the riser. The cross-section of the cyclone chamber 6 is preferably shaped as a circle even when the return channel 9 is a polygon for manufacturing reasons. The ratio of the distance between the lower edge of the cyclone central tube 7 and the upper end of the riser channel to the central tube diameter is: ***: at least 0.2, preferably greater than 1.0 (e.g., about 1.1 to 10). At the upper end of the cyclone chamber • «·, at least substantially coaxial with the center axis of the riser chamber, is m · LI1 2 3 4 5 a gas outlet 7 which is connected to an outlet pipe (not shown). The collar 8 at the bottom of the cyclone chamber *: "extends the bottom of the wall of the return conduit 9. The outlet end of the return conduit 9 has a solid return connection 10 through which the separated solids can be returned to the riser. higher than the feed line 11 in the direction of the longitudinal axis of the riser.

According to the invention, the cyclone inlet connections 5 are preferably disposed in a fully symmetrical manner 3 with respect to the gas outlet connection 30, and this is arranged at the riser axis 4, respectively. This results in the smoothest possible circulation of gas and solid 5 in the cyclone chamber.

• · • »· • ·· • ♦ 7 119179

To cool the riser channel 4, it may be provided with a cooling stream inlet 12 and a cooling stream outlet 13 as shown in Figure 1. In a preferred embodiment, the cooling medium may be introduced symmetrically into the riser walls and led out of the cyclone chamber walls symmetrically.

5

According to the invention, a fluidizing gas, such as air, is fed through an inlet 1 to a manifold 2. From the manifold, the fluidizing gas is led to the lower part of the riser 4, where the gas and the fluidized particles are mixed. A significant part of the fluid particles with the gas is carried into the riser channel 4 and further to the inlet ports 5 arranged around the upper part of the riser channel.

The inlet connections 3 direct the flow so that gas and particles are transported in a circular motion towards the wall of cyclone chamber 6, where upon collision most of the particles are separated. After the collision, the centrifugal acceleration due to the vortex drives the particles of gas to the wall of the cyclone chamber 6, from which they drop by gravity to the collar 8 as the gas continues 4 at the bottom. The part of the solid that does not rise with the gas is removed together via 3.

When the control wing (5) guides towards the wall of the gas separation chamber, a pre-separation of 20 solids occurs and a vortex flow is obtained. The separation chamber (6) takes place. * * *. in turn, the separation of the particles left after the pre-separation of the gas by the centrifugal force • »· ···.

The present invention achieves e.g. The following functional benefits.

··: 7 25 ··· 1. The cyclone resolution can be maximized because the centrifugal acceleration of the particles increases approximately inversely to the third power of the center tube • · · • · ·.

• · * · * · * 2. Adequate resolution is obtained at a lower inlet flow rate than FI- · · ·: ... · 30 in patent 106242, thereby reducing wear on the structures.

* * 3. The upstream currents of the return channel 9 cannot proceed to the cyclone outlet 7, * i * "because the return channel and the cyclone outlet are located across the cyclone inlets 5.

4. 119 The diameter ratio of the inlet impeller to the exhaust can be made large without increasing the pressure difference across the return duct that increases the return duct flow.

These functional benefits have been proven by both computational analysis and model tests. In comparative tests with similar performance and main dimensions, the wastewater solids loss of the new structure was only 7 g / h, whereas it was otherwise 350 g / h in a completely similar test run with equipment according to FI patent 106242. The effect of the central tube diameter on the permeability was verified by a larger test apparatus, where, when changing the central tube diameter from 168 mm to 100 mm, the sand loss was reduced from 1670 to 10 g / h to 3.9 g / h. In both experiments, sand with a particle size of 0.1-0.5 mm was used as a solid. The greater enrichment of the fine fraction into the reactor has several significant advantages, of which the following may be mentioned as examples: 1. A finer fluidized material can be used, whereby the wear of the structures is reduced.

2. The plant power control ratio increases because the fluidity and solids circulation can be maintained at lower gas velocities.

3. In many cases, the cyclone of the recycle gas line can be avoided.

4. Self-propelled power is reduced in applications where the fluidized gas flow is determined by 20 minimum fluidity.

. * * *; 5. In solid matter combustion, the combustion efficiency increases because the unburned carbon ··· ··· more efficiently returns to the ascent channel.

· »· *! A: 6. The use of powdered sorbents and catalysts is enhanced.

·: **: 7. Dust from the reactor is reduced, thus reducing the need for lifting the boiler's after-treatment surfaces and reducing the dust load on the V 25 particulate separator.

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In summary, the present invention, with its slight modification, significant functional and structural advantages are achieved with respect to the solution which is known from the H-patent 106242.

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Claims (10)

119179 A circulating mass reactor comprising: - an elongate riser channel (4) having at least a substantially vertical central axis 5 having a lower portion and an upper portion, wherein the solid and fluidizing gas can be fed into the riser channel through the lower portion, and - a separating unit (5 - 9) fluidizing gas consisting of a multi-aperture cyclone comprising: - a control impeller (5), a separation chamber (6) connected to the control impeller, and - a return channel (9) connected to the separation chamber for collecting solids and exhaust gas (7) from the separation chamber, the control vane (5), the return passage (9) and the gas exhaust pipe (7) 15 are symmetrically arranged around the riser channel (4), and - the cyclone chamber (6) and the gas exhaust pipe (7) are located above the control vane (5). The circulating mass reactor according to claim 1, characterized in that the outlet assembly (7) is coaxially aligned with the riser chamber. • * * Φ The circulating mass reactor according to claim 1 or 2, characterized in that a cooling medium feed line (12) and an outlet line (13) are provided in the riser channel. ♦ · ·· · • · «S · * 25 The circulating mass reactor according to claim 3, characterized in that the walls of the riser channel (4) and the return channel (9) and the cyclone chamber (6) consist of planar, cooled tube panels. The circulating mass reactor according to any one of the preceding claims, characterized in that the multi-aperture cyclone return channel (9) is at the lower end of the solid return port. (10) connected via a riser channel (4) to recycle the solid. ♦ • • • · 10 10 10 119179 The circulating mass reactor according to claim S, characterized in that the solid return channel (9) consists of a plurality of parallel channels. The circulating mass reactor according to claim 6, characterized in that some of the parallel channels of the return channel (9) include heat transfer surfaces. The circulating mass reactor according to any one of the preceding claims, characterized by a cylindrical cyclone (6) located at least mainly above the control impeller (S). Use of a circulating pulp reactor according to any one of the preceding claims, as a steam boiler, as a fuel gasifier, as a solid catalyst circulating reactor, or as a drying device. Use according to claim 9, characterized in that the reactor is used as a cooled structure. • · · · · 1 • M ··· • f · 1 • 1 »· 1 • · · · · 1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · »• · 1« · · • • • • • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Ro1: Patent Application No. 119179