FI92955B - Floor Swirl Enterprise - Google Patents

Description

92955

The present invention relates to a vortex bed reactor, a solid fuel separator and a return vortex plant 5 for carrying out exothermic processes in a circulating vortex bed having % of the reactor height, and a fuel line opening from the outer wall to the vortex bed reactor between the primary and secondary gas feed, whereby one or more displacements with a maximum height 15 equal to 75% of the vortex bed reactor half of the vortex bed reactor are covered.

Methods and devices operating on rotating vortex layers have proven to be very advantageous, especially for burning carbonaceous materials. They are superior for many reasons compared to those used with so-called classical or conventional vortex layers.

In particular for combustion processes, the basic method is described in DE-AS 25 39 546 (corresponding to U.S. Pat. No. 4,165,717). It proceeds in such a way that the combustion takes place in two stages and the heat of combustion is dissipated by means of cooling surfaces arranged above the secondary gas supply to the vortex bed reactor. A particular advantage of the method is that the combustion process can be adapted to the power requirement in a technically simple manner, while in the upper reactor space the suspension density and thus the heat transfer to the cooling surfaces are controlled.

35 DE-OS 26 24 302 (corresponding to the U.S. patent publication • comprising a rotating vortex layer).

2 92955 4 111 158), the heat of combustion is partially or completely removed in a vortex cooler connected downstream of the fuel vortex reactor and the cooled solid fuel is returned to the vortex reactor to keep the temperature constant. The adjustment to the power demand then takes place by increasing or decreasing the vortex bed through the condenser and then again the solid fuel stream fed to the vortex bed reactor.

10 Although the method outlined above has proved to be largely useful, the current trend towards plant units with increasing thermal power presents certain difficulties in controlling the method. They consist essentially of higher thermal efficiencies requiring larger reactor dimensions, in particular larger reactor cross-sections, in which proper cross-mixing of the fuel and the corresponding or oxygen-containing secondary gas required for the chemical exchange reaction is no longer fed over the entire surface of the vortex reactor. As a result, a substantial chemical exchange reaction takes place in the upper reactor space, possibly afterburning after separation of the solid fuel and gas in the solid fuel separator.

The situation described above occurs in plants with a combustion capacity of more than about 300 MW (thermal) and with a bottom vortex reactor of about 50 m2.

According to a previous proposal, the problem is eliminated by covering 40-75% of the bottom surface of the vortex reactor with one or more displacement bodies with a maximum height equal to half the height of the vortex bed reactor. In this case, the geometric shape of the displacement body can be largely arbitrary. For example, in the case of a circular cross-section of a vortex bed reactor, it may have the shape of a cylinder 3 92955 or a truncated cone, the center of the lower circular surface being approximately at the center of the bottom surface. In the case of a rectangular reactor cross-section, the displacement body may have the shape of a dam, possibly connected at its 5 ends to parallel reactor walls and thus dividing the reactor space into two separate chambers. Also, two dams running practically at right angles to each other are possible, which - insofar as they are connected to the reactor walls - divide the lower reactor space into four separate chambers.

As it has been shown, in connection with the above-mentioned formation of the vortex bed plant, adverse effects can occur when the displacement body divides the lower reactor space into separate chambers. Namely, it can happen that the primary air flow pulls out the substrate material, and as a result of the internal circulation of the solid fuel always present in the vortex bed reactor, the material enters the second chamber or chambers. The backward or equalizing material flow does not occur in practice without considerable adjustment work, because the passage of fluidizing air through the "emptied" chamber is promoted and impeded through the "filled" chamber (different hydrostatic pressure above the respective chamber bottoms).

The object of the invention is to provide a vortex bed plant consisting of a vortex bed reactor, a solid fuel separator and a return line for carrying out exothermic processes in a circulating vortex bed, which plant ensures even and high combustion power 30 proper and safe operation without considerable adjustment work.

This object is achieved by a vortex bed plant according to the invention, characterized in that the displacement body or bodies cover the bottom surface of the vortex bed 35 reactor so that the remaining bottom surface forms a uniform surface, and that the displacement bodies or bodies comprise fuel injection devices. the devices are preferably arranged on several levels.

A single unitary surface is formed such that the displacement body or bodies are formed in such a way that the individual segments of the reactor bottom are connected to each other. This is achieved, for example, by maintaining a gas-permeable bottom surface between the displacement bodies and the reactor wall, or by maintaining only a 10 - if the displacement body passes from wall to wall - opening, which may be open or tunnel-like, between the individual bottom segments. The formation of the displacement bodies in such a way as to form separate bottom segments and thus separate vortex chambers must be preserved. The mating surfaces formed by the displacement body or bodies may be fluidized at a potentially lower rate than the main surfaces of the grate. According to the invention, the displacement body or bodies are provided with devices for supplying fuel. They can possibly be located on several levels. This guarantees a good distribution of the fuel.

The geometric shape of the displacement body can be largely arbitrary. For example, in the case of a circular cross-section of a vortex bed reactor, it may have the shape of a cylinder or a truncated cone, the center of the lower circular surface being approximately above the center of the bottom surface. In the case of a rectangular reactor cross-section, the displacement bodies may have the shape of a dam. Two dams practically at right angles to each other are also possible.

However, it is particularly advantageous to form a square or rectangular cross-section for the displacement bodies. In this case, certain deviations from the exact geometric shape are possible, for example by rounding the corners.

5,92995

The displacement body can be made of a conventional refractory material during furnace construction. It can also be made of membrane or fin walls which, for protection, are coated on the side facing the reactor space 5 with a sealing compound. The displacement body or bodies are integrally connected to the reactor and form a structural unit with it.

The material useful for the exothermic chemical exchange reaction is fed via a plurality of feeders, so that the material is fed separately to the individual segments formed in the reactor space.

According to another preferred embodiment of the invention, the vortex bed plant has a displacement body, possibly with devices arranged in several levels for supplying oxygen-containing secondary gas. This creates the possibility of supplying secondary gas both in the wall and through the feed means inside the vortex bed reactor. Thus, optimal thorough mixing with the secondary gas 20 is guaranteed.

If the secondary gas is fed through lines in the vortex bed reactor wall, the nozzle of the displacement body should be above these lines. When supplying the secondary gas in several overlapping planes, the displacement body must extend at least above the height of the lowest supply line.

In another preferred embodiment of the invention, the displacement body or bodies are made so that its or their cross-sectional area decreases upwards. As a result of this and in connection with the above-mentioned embodiment, it is possible that the flow rate in the reactor region comprising the displacement body, despite the supply of secondary gas, varies only within certain limits.

The principle of the vortex layer 35 in the vortex bed plant used in the vortex bed plant is characterized in that - in contrast to the "classical" vortex bed, in which the dense phase 6 92955 is separated by a clear density jump from the gas space above it, the distribution conditions are without a defined boundary layer. There is no density hyp-5 end between the dense phase and the dust space above it; however, inside the reactor, the solid fuel concentration continuously decreases from the bottom up.

Areas occurring in connection with the definition of the conditions of use by means of the Froude and Archimedean indicators: 10 0,1 <3/4 · Fr2 · __ <10,

Pk - Pg or 0.01 <Ar <100, 15 where dk3 · 9 <Pk - Pg)

Ar = ---- and 20 u2

Fr2 = - g · dk In these means: 25 '· u relative gas velocity m / s

Ar Archimedes chapter

Fr Froude number pg gas density kg / m3 30 Pk solid fuel density kg / m3 dk spherical particle diameter m '! *. t kinematic toughness m2 / s g gravity constant m / s2 35 The exothermic reaction is carried out in two stages with oxygen-containing gases fed to different heights 7 92955 la. They have the advantage of a "soft" chemical exchange reaction in which local overheating phenomena are avoided and NOx formation is largely displaced. In this case, the upper supply point for the oxygen-containing gas should be so far above the lower one that the oxygen content of the gas introduced at the lower point is already well spent.

If steam is desired as the process heat, a preferred embodiment of the invention consists in creating an average suspension density of 15 to 100 kg / m 3 above the secondary gas feed by adjusting the fluidization and secondary gases and removing and / or with heating surfaces arranged in the wall of the vortex bed reactor. Such a working method 15 is described in more detail in DE-AS 25 39 546 or in the corresponding U.S. patent publication 4,165,717.

The gas velocities prevailing in the vortex reactor above the secondary gas supply are normally more than 5 m / s at normal pressure and may be up to 15 m / s 20, and the ratio of the diameter of the vortex reactor to the altitude should be chosen so that gas residence times are 0.5 to 8.9 seconds, preferably 1-4 seconds.

Inside each supply level, there are preferably 25 several supply openings for the secondary gas.

In particular, this method has the advantage that, in the simplest way, a change in the process heat input is possible by changing the suspension density in the furnace space of the vortex bed reactor 30 above the secondary gas supply.

The prevailing operating state in connection with the previously given volumes of fluidizing gas and secondary gas and the resulting average suspension density is associated with a certain heat transfer, so that by increasing the amount of fluidizing gas and possibly also the amount of secondary gas, the suspension density is increased to 8,99595. In connection with the transfer of the added heat, in connection with the practically constant combustion temperature, it has been possible to remove the amounts of heat generated in connection with the increased combustion power. The increased oxygen demand required due to the higher combustion power is then seemingly automatically at hand through the higher amounts of fluidizing gas and possibly secondary gas used to increase the suspension density.

Analogously, to accommodate the reduced process heat demand, the combustion power can be adjusted by reducing the suspension density in the furnace space of the vortex bed reactor above the secondary gas line. By lowering the suspension density, the heat transfer is also reduced so that less heat is dissipated from the vortex bed reactor. Thus, substantially without changing the temperature, the combustion power can be restored to the previous value.

Another suitable universally available embodiment of the invention consists in arranging the vortex layer 20 so as to have at least one vortex layer cooler connected via the solid fuel supply and solid fuel return lines. The rotary bed reactor is adjusted above the secondary gas supply with an average suspension density of 10 to 40 kg / m3 by suitable control of the amounts of flux-25 dislocation and secondary gases, the hot solid fuel in the 30 moving vortex layer.

This embodiment is described in more detail in DE-OS 26 24 302 or in the corresponding U.S. patent publication 4,111,158.

In this case, the temperature constant can be achieved in practice without changing the operating conditions prevailing in the vortex bed reactor, i.e. possibly without changing e.g. sus- 9 92955 pension density, by means of controlled removal of hot solid fuel alone and by controlled recovery of cooled solid fuel. In each case, depending on the power and the set reaction temperature, the degree of recirculation is greater or less. The temperatures can be adjusted arbitrarily from very low temperatures close to the ignition limit to very high temperatures which may be limited by the softening of the reaction residues. They can be between about 450 and 950 ° C.

Since the removal of heat generated in the exothermic chemical exchange reaction takes place mainly in a vortex cooler connected downstream of the solid fuel side and by transferring the heat to a cooling control device in the vortex reactor, a sufficiently high that the suspension density in the region of the vortex bed reactor above the secondary gas feed 20 can be kept low and thus the pressure drop in the whole region of the vortex bed reactor is relatively small. Instead, heat is removed in a vortex cooler under conditions that cause very high heat transfer, approximately in the range of 25 to 500 W / m2 · ° C.

The temperature in the vortex bed reactor is controlled so that at least one sub-stream of cooled solid fuel is returned from the vortex bed cooler. For example, the required partial flow of cooled solid fuel can be taken directly into the vortex bed reactor. In addition, the exhaust gas can also be cooled by supplying a cooled solid fuel, which is charged, for example, to a pneumatic conveying journey or a suspension exchange step, in which case the solid fuel later separated from the exhaust gas is then returned to the vortex cooler. As a result, the heat of the exhaust gas 10 92955 also finally enters the vortex bed cooler. It is very advantageous to feed the cooled solid fuel as one partial stream directly and as another partial stream indirectly after cooling the exhaust gas to the vortex bed reactor.

Also in this embodiment of the invention, the residence times of the gas, the gas velocities above the secondary gas line at the normal pressure and manner of fluidization or secondary gas supply are consistent with the same parameters of the previously discussed embodiment.

The reflux cooling of the hot solid fuel in the vortex bed reactor should take place in a vortex bed cooler with a plurality of flow-through cooling chambers, into which the interconnected cooling control devices go, countercurrent to the coolant. Thus, it is possible to bind the heat of combustion to a relatively small amount of refrigerant.

Another application of a vortex bed plant with a vortex bed cooler consists in combining the cooler with the vortex bed reactor into one structural unit. In this case, the vortex bed reactor and the vortex bed cooler have a common, suitably cooled wall with a flow opening to the vortex bed reactor for the cooled solid fuel. In this case, the vortex cooler 25 - as previously explained - has several cooling chambers, however, it can also consist of several units with cooling surfaces, each having a common wall with the vortex reactor and one separate solid fuel supply line. Such a device is described in EP-A-206 066.

The versatility of the formation with the vortex bed cooler is obtained in particular by allowing approximately arbitrary heat carriers to be heated in the vortex bed cooler. From a technical point of view, the production of steam in various forms and the heating of the heat can salt are of particular importance.

11 92955

In the invention, air or oxygen-enriched air or technically pure oxygen can be used as the oxygen-containing gas. Finally, an increase in power can be achieved if the chemical exchange reaction is carried out under pressure, up to approximately 20 bar.

In principle, all spontaneously combustible materials can be used in the vortex bed device according to the invention. Examples are all types of coal, especially those of lower quality, such as landfills of carbon-wet enrichment, washed coal, high-salinity coal but also lignite and oil shale. They can also act for roasting sulphide ores or ore concentrates.

Preferred embodiments of the vortex bed plant according to the invention appear from the appended dependent claims 2-6.

The invention will be described by way of example and in more detail with the aid of the accompanying figures and example.

They illustrate: Fig. 1 various examples of forming a displacement body in vortex bed reactors having a circular or rectangular cross-section in the form of a top view, Fig. 2 the lower area of the vortex bed reactor with the displacement-25 in perspective view, Fig. 3

Fig. 2 schematically shows a vortex bed reactor, denoted by reference numeral 1. Its bottom surface is partially covered by faceted displacement bodies 7 so as to form a plurality of fluidization segments 6. The displacement bodies 7 have secondary gas openings 11 in the upper region and fuel inlets 3.

The vortex bed reactor according to Figure 3 has six feed surfaces marked as membrane walls. The feed to the lower reactor chamber 8, which is divided by a dam-like displacement body 7 into four segments (two segments parallel to the dam, one segment each in front and behind the dam), takes place via line 5 and fluidization grate 6 with oxygen-containing fluidizing gas, lines 3 with fuel and lines 9 through an oxygen-containing secondary gas. Additional fuel is supplied through line 10 and secondary gas ports 11. The gas / solid fuel suspension is discharged via line 4.

Example 10 Coal was burned with air to produce saturated steam.

The vortex bed reactor 1 of the vortex bed plant had a bottom surface of 12.5 x 10.1 m and a height of 30.5 m. Its bottom surface was covered with a bottom surface of 8.5 x 8.1 m 15 in such a way as to result in four segments with fluidization gratings 6. Two of the 2 m plates were parallel to the longer reactor wall, two of the 1 m plates were between the displacement body 7 and the reactor wall. The displacement body 7 had a triangular shape with a height of 6.8 m.

The wall surface of the vortex bed reactor 1 was completely covered with water-cooled membrane walls. The walls of the displacement body 7 were also formed as water-cooled membrane walls, which were protected on the reactor side with a refractory material.

A total of 110.4 t / h of coal with a calorific value Hu = 15.9 MJ / kg and an average grain size of 0.2 mm and 10.4 t / h of limestone with a grain size of approximately the same size, about 100 °, were fed to the vortex bed reactor 1. C il-30 man 11 040 Nm3 / h through a total of six lines 3. The fluidizing gas was 260 ° C air, which was fed in an amount of 280,000 Nm 3 / h through the fluidization gratings 6. A total of 206,000 Nm3 / h of additional air was supplied via secondary lines 9 and 11 without a total supply of 206,000 Nm3 / h. The feed took place in three levels, at 2 m (51,500 Nm3 / h), at 4.6 m II: 92955 at 13 (51,500 Nm3 / h) and at 7.3 m (103,000 Nm3 / h). above.

Based on the selected operating conditions, a temperature of 850 eC prevailed in the vortex bed reactor 1. 140 bar of saturated steam and 102 MW of thermal power were produced through the membrane walls of the heating-5 surfaces 2 and the displacement body 7, respectively.

Claims (6)

92955 14 A vortex bed plant comprising a vortex bed reactor (1), a solid fuel separator and a return line for performing exothermic processes in a circulating vortex bed having lines for feeding oxygen-containing primary gases (5) through the bottom (6) of the vortex bed reactor (1) and lines (9) for feeding at a height of at least 1 m 10 above the reactor bottom (6), but not more than 30% of the reactor height, and between the primary and secondary gas feed to the vortex bed reactor a fuel line (3) opening from the outer wall, with one or more displacements (7) having a maximum height 15 equal to half the height of the vortex bed reactor (1) is covered by 40 ... 75% of the bottom surface (6) of the vortex bed reactor (1), characterized in that the displacement body (s) (s) cover the bottom surface (6) of the vortex bed reactor that the remaining 20 on the bottom surface (6) forms a single surface, and in that syrjäytyskappale- or pieces comprise devices (3) the fuel sisäänsyöttämiseksi, which equipment is preferably arranged in a plurality of planes. Vortex layer plant according to Claim 1, characterized by one or more displacement bodies (7) having a square or rectangular cross-section. Vortex bed plant according to Claim 1 or 2, characterized by one or more displacement bodies (7), which have or means (11) for introducing oxygen-containing secondary gases, which devices are optionally arranged in several levels. Vortex layer plant according to Claim 1 or 3, characterized by one or more displacement bodies (7) whose cross-sectional area decreases upwards. Il 15 92955 Vortex plant according to one of Claims 1 to 4, characterized by heating surfaces (2) arranged in the free space of the vortex bed reactor (1) above the uppermost secondary gas supply (9) and / or in the wall of the vortex bed reactor (1). Vortex plant according to one of Claims 1 to 5, characterized by at least one vortex condenser connected above the solid fuel supply and solid fuel return lines. 16 92955