EA027447B1 - Cooled annular gas collector - Google Patents

Abstract

In the gasification of solids with oxygen and/or steam in a fixed bed, the reactor (10) operated under pressure must continuously be charged with the solids. These solids are supplied to the fixed bed (12) from a lock via a ring-shaped apron (30) open at the top and at the bottom. The apron (30) includes an inner (31) and an outer (32) jackets, so that a cooling gap is formed with at least one inlet and/or outlet for the supply and discharge of a cooling medium.

Description

This invention relates to a device for loading carbon-containing solids of a pressurized reactor, in which the solids are gasified with oxygen and / or steam in a fixed bed, the device including an annular apron open to the top and bottom, to which the solids are fed through gateway, and, in addition, to the reactor for gasification in a fixed bed with this device and to the method of operation of such a reactor.

Gasification is understood to mean the conversion of a solid or liquid substance containing carbon (for example, coal, biomass or oil) with a gasifying agent (oxygen / air, steam) to the so-called synthesis gas. The synthesis gas contains hydrogen (H ₂ ), water (H ₂ O), carbon monoxide (CO), carbon dioxide (CO ₂ ) and methane (CH ₄ ) as the main components. CO and H ₂ are the starting materials for many chemical synthesis processes by which long-chain products such as gasoline and diesel fuel can be produced in the form of so-called synthetic liquid fuels (obtained by converting coal into liquid fuels) or other valuable materials (LNG = synthetic natural gas substitute, H2 for the production of ammonia, fertilizers, urea, methanol and so on).

However, synthesis gas also contains hydrogen sulfide (H ₂ 8), carbon sulfide (CO8), hydrochloric acid (HC1), ammonia (ΝΉ ₃ ), hydrocyanic acid (NSO), partially hydrogen fluoride (HP) and, possibly, higher hydrocarbons and coal oil. The gas composition depends on the composition of the raw material, the type and amount of gasifying agents used, the reaction conditions and the boundary kinetic conditions of the reactions occurring due to the selected gasification process.

In principle, there are three different methods for the gasification of solids: gasification in a fluidized bed, gasification in a fixed bed formed by solids, and finally gasification in a reactor with gasification in a stream. Different gasification technologies present different fuel requirements, which must be taken into account, respectively, when choosing a fuel or fuel processing concept.

If the real reactor is in the form of a fixed-bed reactor, it contains a substantially cylindrical vertical reactor with an external water jacket. Solid carbon-containing fuels, usually coal or biomass, are loaded from above through a lock into a coal distributor located inside the reactor, in which a fixed layer is formed lying on the rotatable grate located at the bottom of the reactor. Oxygen and steam are blown from the bottom of the reactor into the fixed bed.

These hot gases pass through the fixed bed from the bottom up, while solids are fed from above through the lock system. Therefore, they also speak of gasification in a fixed bed in countercurrent mode. Since the newly arrived solids have a temperature of about 40 ° C, the entire fixed layer has a temperature profile, on which the hottest part is located near the grate, which is rotatable, and the temperature drops up the layer, in the direction of supply of solids. In accordance with this temperature profile, different reactions occur inside the fixed layer. Therefore, they also often speak of reaction zones, where there is no clear division into separate sections, but separate zones pass into each other. In the upper part of the gasifier, near newly loaded solids, physically sorbed gases are dried. Below the drying zone is the so-called reaction zone, in the upper part of which degassing of solids is carried out. Degassing is accompanied by the actual gasification of solids by the Boudoir reaction, as well as direct and reverse water gas reactions. The next zone is the burning of solids.

The ash obtained primarily during incineration falls through a rotary grate and is then removed from there. Unconverted gas fractions of the reagents, mainly steam, nitrogen and argon, are discharged together with the generated synthesis gas through a gas outlet provided above the fixed bed.

A lock system for supplying fuel to the reactor is necessary since the reactor operates at a pressure of up to 100 bar gauge pressure, preferably up to 60 bar gauge pressure, particularly preferably at a working pressure of at least 50 bar gauge pressure, therefore, solids must be supplied under pressure. The loading through the lock system is carried out intermittently, at first the fuel under atmospheric conditions is loaded into the lock, ending with the reactor, then the pressure in it is increased in the lock system and under this pressure it is fed into the reactor. Then the reactor is again closed with a lock system. In order to, despite this, the process can be carried out in a stationary mode under constant conditions, an additional container for solids must be provided inside the reactor, ensuring that the fixed bed always has the same height. For use for this purpose, various internal devices are known, developed, for example, by Bigsche® or UEV RKM Apladepai Schr / sch. such as the so-called coal distributors. Using various designs of these devices, attempts have been made to selectively affect the natural separation of the grain spectrum of coal. The results obtained allowed only a limited degree to improve gasification. The range of granularity and grinding characteristics are largely dependent on the type and characteristics of the coals.

- 1 027447

A similar device is described, for example, in document No. 112005002983 T5. It is a cylindrical or tapering inward, that is, a hollow, truncated cone-shaped apron hanging down from the reactor lid in such a way that the coal discharged from the coal lock moves along the inside of the apron and is distributed into the solid layer. The lower end of the apron is usually located inside the fixed layer. An annular gas collection zone is formed between the apron and the gas generator wall, from which the raw gas collected there is diverted laterally through the gas outlet.

In the largest plants currently in operation, coal is usually converted to synthesis gas in a fixed-bed gasification method, at which the outlet temperature and final reaction temperature are so low that the resulting synthesis gas is removed from the reactor with temperature from 200 to 300 ° C (for moist brown coals) or from 400 to 450 ° C (for young fossil fuels). It is necessary to distinguish between the average temperature and temperature maxima due to the inhomogeneities of the fixed layer. Average temperature is critical in terms of corrosion and therefore component life. Temperature maxima determine the thermal and mechanical load and, therefore, should not exceed the limit values.

The limiting values for the installation of coal gasification in a fixed bed have so far been set so that at temperature maximums of 650 or 670 ° C it has become necessary to reduce the power or even shut down the reactor to limit the heat load of the raw gas outlet pipe. The low quality or characteristics of coal and heavy loads increase the amplitude and frequency of such temperature maximums.

In view of the ever-growing shortage of fossil raw materials in the future, solidifier gasifiers need to be designed in such a way that not only moist brown coals or young coals, but other coals with higher final reaction temperatures and lower quality can be gasified. In addition, the gasification of renewable raw materials or secondary raw materials, which in most cases has the worst characteristics in terms of gasification in a fixed bed, is becoming increasingly important. The temperatures resulting from this can determine the outlet temperatures of at least 700 ° C, mainly up to 800 ° C, and in some cases even up to 1000 ° C. At these temperatures, the apron used will experience significantly greater material stress.

In addition, coal with a high content of sulfur or halogens is increasingly being gasified. As already noted, this leads to the fact that the resulting crude synthesis gas contains compounds such as H ₂ 8, CO8. HC1 and NOT. In combination with temperatures in excess of the temperatures commonly used so far (for example, about 250 ° C of moist brown coal, 450 ° C of coal compared to 450-550 ° C of older coal and 550-600 ° C of anthracite), this leads to more severe apron corrosion. To normal operating temperatures, it is also necessary to add temperature peaks, depending on the quality and spectrum of the grain size of the coal. For example, highly decomposed brown coals cause channel formation due to the high content of fines, which leads to the formation of CO2 and the appearance of temperature peaks. To replace the apron, it is necessary to stop the installation, which will lead to production losses. On the other hand, the apron is so large that the use of heat-resistant materials will cause a significant increase in capital costs and, therefore, is economically disadvantageous, especially since the use of heat-resistant materials would only prevent corrosion under the influence of, for example, hydrogen halides.

In this regard, the purpose of this invention is the creation of such an apron, also called an annular gas collector, that even at gasification temperatures above 450 ° C and / or when using fuels containing sulfur and / or halogens, long service life of the installation becomes possible. Along with this, frequent temperature maxima should be maintained without the need to reduce the load or short-term or long-term shutdown of the reactor.

According to the invention, this goal is achieved using the boot device according to claim 1. The apron is made cooled and for this purpose contains an inner shell and an outer shell, between which a cooling gap is formed with at least one inlet and one outlet for supplying and discharging a cooling medium.

According to a further embodiment of the invention, the apron is axisymmetric, in particular cylindrical, conical or partially conical. The cylindrical shape has the advantage that the fuel loaded through the lock system is distributed over the entire cross section of the fuel layer. In addition, in this way, the volume of the chute of the coal feeder can be maximized so that, with an equal volume of filling, the latter has a relatively short length and the useful height of the reactor is not significantly reduced. Nevertheless, it is possible to take as much coal as is necessary to overlap the time between two coal sluice operations and possible irregularities in gasification and loading methods.

When the apron shell is tapered, the loading device should taper towards the fixed layer. This has the advantage that the free surface for the raw gas to exit from the fixed bed is as large as possible. By creating the largest possible exit surface, the corresponding gas velocity and therefore the amount of entrained dust can be minimized. In addition, the resulting gas collection space has the largest possible volume, as a result of which the flow rate of raw gas in the gas collection space is also reduced and dust retention is improved. Finally, the exit surface should be made as large as possible so that the raw gas can flow more evenly over the entire cross section of the fuel layer and the entrainment of coal particles is minimized.

To ensure uniform reaction conditions throughout the fixed bed, cross flows must be reduced.

A partially conical design mounted on a cylindrical part combines the advantages of both designs.

During operation, coolant, preferably boiler feed water, is supplied to the cooling gap. If water is used, the water must meet the requirements for steam generators to prevent the formation of carbonate deposits or scale. In principle, the cooling gap should be designed in such a way that the coolant is inlet at one edge and the coolant is discharged at the opposite edge. However, it is preferable if the cooling gap is made not to allow liquid to pass on one edge, in the sense that the inner and outer shells are connected in a liquid-tight manner. Preferably, this edge faces the fixed bed, i.e. is located at the bottom of the reactor. The coolant can be supplied to the cooling gap by means of a common inlet and outlet pipe, or at least one inlet and one outlet must be provided.

On the edge of the apron facing the opposite fixed layer, that is, on the upper edge, the cooling gap is preferably closed by an annular cover in which there are numerous openings for supplying and discharging the cooling medium. Then the cooling medium can be supplied to the cooling gap around the entire circumference of the apron. When a cooling medium, such as water, is heated by hot synthesis gas rising from the outside of the apron, it evaporates and rises, so as to escape from the cooling gap in the form of steam through the openings of the lid.

Preferably, the inner and outer shells run in parallel, since in this way the device can be easily manufactured and the resulting cooling gap has the same width at each point. In the same way, it is also possible here to create a cooling gap so that at those points where the volumetric gas flow along the apron and, consequently, the amount of heat dissipated is especially large, it has a larger width than at points where the amount of gas passed through is small. For example, the area facing the gas outlet is subjected to a large load. Therefore, it can be guaranteed that virtually the entire apron is sufficiently cooled.

In a particularly preferred embodiment of the invention, to provide an even supply of coolant, a partition is provided between the inner and outer shell of the apron, preferably extending parallel to the inner and outer partition. The partition forms internal and external cooling gaps, communicating with each other at least in one place, preferably around the entire circumference of the apron.

Communication between the internal and external cooling gap is achieved especially easily due to the fact that there is free space between the partition and the part of the shell connecting the inner shell to the outer shell, that is, the partition does not reach the bottom of the apron. Thanks to this design, it can be ensured that the coolant flows through the apron without the need for a pump. The external cooling gap is adjacent to the outer shell of the apron, which is in direct contact with the gas collection space, and is exposed to the temperature of the rising hot crude synthesis gas and, accordingly, is heated. Through the inner shell, the coolant in the inner cooling gap is in contact with newly charged solids having a temperature of only about 40 ° C. Therefore, the coolant in the external cooling gap is subject to significantly greater heat transfer than the coolant in the internal cooling gap, as a result of which convection leads to directed flow through the cooling gap.

If water is now used as a coolant, then the boiling point of water lies below the temperature of the raw synthesis gas. This is also true for a pressure cooling system (30 bar absolute pressure: boiling point 234 ° C; 51 bar absolute pressure: 265 ° C). The generated steam in all cases will pass up to the exit. In a particularly preferred embodiment of the invention, coolant is supplied to the internal cooling gap and removed from the external cooling gap. Thus, the supplied cooling water passes through the internal cooling gap, heats up slightly upon contact with the partition and transfers this heat to the newly loaded solids inside the apron, which, albeit to a small extent, leads to a decrease in the temperature of the cooling water, and then falls into the external cooling gap . Due to contact with the hot outer shell of the apron, the water evaporates there and, thus

- 3 027447 thus removes heat from the system. The generated steam exits through the steam outlet provided in the external cooling gap. Thanks to the steam outlet, fresh cooling water continuously flows from the internal cooling gap to the external cooling gap. Thus, in this system, passage through the internal and external cooling gap occurs due to natural convection. Natural convection is determined by the difference in the density of the column of water at the inlet and the column of the steam-water mixture at the outlet. As a result, this gives the so-called multiplicity of circulation, as the ratio of the generated steam and the passing water, limited by pressure losses for a given configuration. The device works especially efficiently when the inlet and outlet of cooling water are produced on the upper edge of the apron with a vertical reactor structure.

Preferably, the baffle should be designed such that the internal cooling gap has a smaller width than the external cooling gap. This has the advantage that when using water as a coolant, the generated vapor provides sufficient volume in the external cooling gap. Thus, it becomes possible to provide the optimum water / steam circulation ratio and minimize pressure loss.

The subject of the invention is also a reactor for the gasification of carbon-containing solids with oxygen and steam with the hallmarks of claim 7. Such a reactor comprises a rotatable grate near the bottom and a solids lock on the reactor lid, followed by the apron described above.

Preferably, the reactor is configured such that the inlet and / or outlet of the cooling gap of the apron communicates with the cooling system of the reactor itself.

This has the advantage that it is not necessary to install a separate cooling circuit for cooling the apron, therefore, capital costs can be reduced and, in addition, the reliability and operational safety of the cooling system can be increased. Preferably, the reactor itself also comprises a cooling jacket, in which an apron cooling jacket is included.

In addition, the apron and the reactor are preferably welded to each other. This allows you to significantly reduce the temperature of the inner and outer shell when cooling the device compared to an uncooled apron. When water is used as a coolant at an absolute pressure below 51 bar, its boiling point is about 265 ° C and, thus, lies well below the critical temperature of 300 ° C, starting from which gas corrosion gradually occurs in carbon steel. Due to the fact that, thanks to cooling, the apron to be cooled is protected not only from corrosion, but also from erosion resulting from the coal moving downward, it no longer has to be replaced regularly, so there is no need for expensive detachable joints.

Finally, the idea of this invention also extends to a method for gasifying carbon-containing solids with oxygen and steam with the hallmarks of claim 10. Gasification is carried out in a fixed bed, and solids are introduced into the fixed bed of the reactor in portions through a gateway, and then continuously, through a loading device according to the invention. The cooling medium is introduced into the jacket in liquid form and withdrawn, at least partially, in vapor form. By such cooling, the device can be effectively protected from corrosion and at the same time, a small initial cooling of the hot crude synthesis gas can be performed, as a result of which subsequent parts also experience less load.

Such cooling is particularly preferred when the vented steam can be re-used energetically in the process as a reagent / gasification agent. Inside the gasifier in a fixed bed, steam acts as a moderator to limit the combustion temperature so that the coal ash does not melt. Steam should be added in excess.

The use of steam is particularly preferred when water is used as the cooling liquid, and the cooling water withdrawn in vapor form can itself be used as a reagent, i.e. the steam flow necessary for the gasification of solids in a fixed bed is partially fed by steam, formed by cooling. Thus, the steam consumption of the method can be reduced, which reduces operating costs. When the reactor itself also contains a water cooling jacket and steam is also generated in it, about 20 volume percent of the required total amount of steam can be saved by collecting and recycling steam from all components to be cooled.

Additional features, advantages, and applications of the invention may also be taken from the following description of an exemplary embodiment of the invention and the drawings. All described or illustrated features of the invention form the subject of the invention on their own or in any combination, regardless of whether they are included in the claims or their backlinks.

The drawings show:

in FIG. 1 schematically shows a fixed bed reactor operating in countercurrent mode, FIG. 2 - annular gas collector according to the invention,

- 4,027447 in FIG. 3 - cover of the annular gas collector according to the invention.

In FIG. 1 schematically shows the reactor 10. This is a vertical reactor with a fixed bed, operating in countercurrent mode, containing rotatable grate 11 near the bottom.

On this rotatable grate 11, a layer 12 of solids is formed during operation. Steam and / or an oxygen-containing medium, such as air, oxygen-enriched air or pure oxygen, are supplied and blown into the layer 12 from below through a feed device 13, providing uniform distribution. The ash resulting from the reactions in the fixed bed 12 is discharged through the grate 11 and removed through the ash pan 14 followed by the ash gate. The reactor 10 has water cooling and comprises a cooling gap 17 between the outer shell 18 and the inner shell 19 (Fig. 2).

A lock 20 is provided above the reactor 10 through which coal or other carbon-containing solids are fed. The gateway 20 is followed by the apron 30 shown in FIG. 2, serving as a container for solids, so that the fixed bed 12 in the reactor has a uniform and sufficient level of filling, despite the fact that coal is charged through the gateway 20 intermittently. Above the fixed layer 12 around the apron 30 there is a free space in which reaction gases are collected, as well as unused steam. The gases collected in this gas collection space 15 are discharged through the gas outlet 16.

In FIG. 2 schematically and in section shows the right half of the boot device 1 according to the invention. Typically, a gas outlet 16 is provided on only one side of the reactor.

The loading device 1 comprises a two-wall apron 30 with an inner shell 31 and an outer shell 32, between which a cooling gap 33 is formed. At the lower end of the apron 30 facing the fixed layer 12, the inner shell 31 and the inner shell 32 are connected in a liquid-tight manner by the shell part 35 . Inside the apron 30, a partition 34 is provided between the inner shell 31 and the outer shell 32. This shell 34 divides the cooling gap 33 formed between the inner shell 31 and the outer shell 32 into the inner cooling gap 33ΐ and the outer cooling gap 33a. During operation, the internal cooling gap 33Ϊ is adjacent to the solids held in the apron 30 by the inner shell 31, while the external cooling gap 33a is adjacent to the gas collection space 15 and the stationary layer 12 by the outer shell 32.

Between the partition 34 and the shell portion 35 connecting the inner shell 31 and the outer shell 32, a free space 36 is provided by which the inner cooling gap 33ΐ and the outer cooling gap 33a communicate with each other at the lower end of the apron 30.

Coolant, preferably water, is supplied between the baffle 34 and the inner shell, under the influence of gravity, it flows down and is in heat exchange with cold coal (about 40 ° C) stored inside the apron. Since the partition 34 does not end close to part 35 of the shell, water can enter the external cooling gap 33a at the lower edge of the apron 30. On the outer shell 32, the cooling liquid is in direct heat exchange with hot gas in the gas collection space 15. Due to the gas temperature of up to 700 ° C, preferably up to 800 ° C, the water is heated to the corresponding boiling point (approximately 265 ° C at a working pressure of 51 bar absolute pressure) and evaporates. Due to the significantly lower density, the steam rises (convection) in the external cooling gap 33a and can be diverted to the upper end of the cooling gap 33a. The surface temperature of the outer shell 32 will be higher than the temperature of the cooling water by up to 30 ° (depending on the gas temperature and load) due to the large heat transfer on the gas side. On the outer shell 32, the temperature will still be slightly below 300 ° C, which is significantly lower than the temperature obtained in the uncooled annular gas collector, which essentially corresponds to the temperature of the gas. Gas corrosion of carbon steel can be avoided or at least significantly reduced.

When the reactor 10 itself also comprises a water cooling jacket, the cooling gap 33 of the apron 30 is preferably in communication with the cooling system of the reactor 10 so that cooling water from the cooling gap 17 between the outer shell 18 and the inner shell 19 of the reactor 10 can also be used to fill the cooling gap 33 apron 30.

In FIG. 3 shows an annular cover 40 mounted on a loading device, preferably welded to it, and along with this, the inlet and outlet of the coolant, as well as the connection with the reactor 10 are presented.

A circular opening 41 is provided in the center of the lid 40 through which solids can enter from the airlock system 20 into the loading device 1. Two rows of outwardly spaced and concentric circles openings 42, 43 are connected to the jacket of the apron 30, through which coolant, respectively is supplied to the internal cooling gap 33ΐ and is withdrawn from the external cooling gap 33a. By means of the circular protrusion 44, the cover 40 can be attached, for example, welded, to the inner shell 19 of the reactor 10 (see FIG. 2).

In a cooled annular gas collector according to the invention, abrasive wear on the inside

- 5 027447 shell, due to the constant passage of coal, is significantly reduced by the reduced wall temperature, thereby increasing the possible service life. Due to the reduced temperature, corrosion of the outer shell is prevented or reduced to a large extent, regardless of the concentration of corrosive substances in the raw gas. The presence of corrosive substances in the raw gas is determined by the composition of the coal.

In addition, the gas is slightly cooled on the outer shell of the annular gas collector, which leads to a decrease in the heat load of the subsequent parts of the installation. When gas is cooled in an annular gas collector, heat is removed from the process at one point, and the coolant evaporates.

When using water as a coolant, the subsequently formed steam can be supplied to the system as steam for gasification, thereby reducing the cost of consumable reagents.

List of reference signs.

I - boot device

- reactor

II - made with the possibility of rotation of the grate,

- fixed bed

- the supply of oxygen-containing gas and / or steam,

- ashman

- gas gathering space,

- gas outlet pipe,

- cooling gap

- the outer shell of the reactor,

- the inner shell of the reactor,

- Gateway,

- an apron

- inner shell

- outer shell,

- cooling gap

33a - external cooling clearance

33ΐ - internal cooling gap,

- partition,

- part of the shell

- free space,

- cover

- hole

- holes

- holes

- ledge.

Claims (9)

CLAIM 1. Device (1) for loading carbon-containing solids of a pressure-operated reactor (10), in which solids are gasified with oxygen and / or steam in a fixed bed (12), the device comprising an annular apron open from above and below (30), to which solids are fed through a lock (20), and which contains an inner shell (31) and an outer shell (32), between which a cooling gap (33) is formed with at least one inlet and / or outlet for supply and the removal of the cooling medium, I distinguish This is due to the fact that a partition (34) is provided between the inner shell (31) and the outer shell (32) of the apron (30), so that internal and external cooling gaps (33Ϊ, 33a) are formed, and the internal and external cooling gaps (33ί, 33a) ) communicate with each other at least at one point. 2. The device according to claim 1, characterized in that the apron (30) is made axisymmetric, especially cylindrical, conical or partially conical. 3. The device according to claim 1 or 2, characterized in that the inner shell (31) and the outer shell (32) of the apron (30) are connected to each other on the lower side facing the fixed layer (12) in the reactor (10). 4. The device according to one of the preceding paragraphs, characterized in that on the upper edge of the apron (30), facing the fixed layer (12), the cooling gap (33) is closed by a lid (40) containing several holes (42, 43) for feeding and removal of the cooling medium. 5. The device according to claim 1, characterized in that the internal and external cooling gaps (33ί, 33 a) communicate with each other around the entire circumference of the apron (30). 6. The device according to claim 1 or 5, characterized in that a free space (36) is provided between the partition (34) and the part (35) of the shell connecting the inner shell (31) and the outer shell (32). 7. A reactor (10) for the gasification of carbon-containing solids with oxygen and / or steam in a fixed bed, containing a loading device (1) according to one of the preceding paragraphs. 8. The reactor according to claim 7, characterized in that the input and / or output of the cooling gap (33) of the loading device (1) is connected / connected to the cooling gap (17) between the inner shell (19) and the outer shell (18) of the reactor ( 10). 9. The method of gasification of carbon-containing solids using oxygen and steam, and gasification is carried out in a fixed-bed reactor operated under pressure, and the solids are introduced through a gateway through the charging device according to any one of claims 1 to 6 into a fixed bed, characterized in that the cooling medium is introduced in liquid form into the cooling gap of the loading device; and that the cooling medium is withdrawn from the cooling gap at least partially in vapor form.