KR20150014909A - Cooled annular gas collector - Google Patents

Abstract

When gasifying the carbonaceous solids with oxygen and / or steam in the fixed bed, the reactor (10) operated under pressure must be continuously charged with solids. These solids are supplied from the lock portion to the fixation layer 12 through the ring-shaped apron 1 which is open at the top and bottom. The apron 1 includes an inner jacket and an outer jacket 32, thus forming a cooling gap with at least one inlet and / or outlet for the cooling medium.

Description

[0001] COOLED ANNULAR GAS COLLECTOR [0002]

The present invention relates to a charging apparatus for charging a reactor operated under pressure with carbonaceous solids, wherein the solids are gasified into oxygen and / or steam in a fixed bed, the charging apparatus comprising a ring-shaped apron apron, the solids being supplied to the apron through a lock, and also to a reactor for fixed bed gasification by the filling device and to a method of operating such a reactor.

Gasification is understood to convert carbonaceous solid or liquid material (e.g. coal, biomass or petroleum) into so-called syngas by means of a gasification medium (oxygen / air, steam). As a main component, the synthesis gas comprises hydrogen (H _2), water (H ₂ O), carbon monoxide (CO), carbon dioxide (CO _2), and methane (CH _4). CO and H ₂ are starting materials for a number of chemical compounds and then based thereon diesel and gasoline or other valuable materials (SNGs), such as long chain products, for example so-called Coal to Liquids (CtL) Substitute Natural Gas, H ₂ for ammonia / fertilizer / urea, methanol, etc.).

However, syngas can also contain hydrogen sulfide (H ₂ S), carbon oxide sulfide (COS), hydrochloric acid (HCl), ammonia (NH ₃ ), hydrocyanic acid (HCN), partially hydrogen fluoride And tar oils. The composition of the gas depends on the composition of the feed, the type and amount of the gasification medium used, the reaction conditions and kinematic boundary conditions of the reactions occurring as specified by the selected gasification process.

Mainly, three different types of processes for gasifying solids are known: gasification in fluidized beds, gasification in a fixed bed formed with solids, and finally gasification in an entrained-bed reactor. Different gasification techniques impose different requirements on the fuel, and these requirements must therefore be taken into consideration in the selection of the fuel or the concept of fuel treatment accordingly.

When an actual reactor is constructed as a fixed bed reactor, this actual reactor comprises a substantially cylindrical vertical reactor with an outer water jacket. The solid carbonaceous fuel, generally coal or biomass, is introduced from above into the coal distributor existing in the interior of the reactor through the lock, and a fixed bed is formed, which is placed in a rotating grate arranged in the lower region of the reactor. From the lower region, oxygen and steam are blown into the fixed bed.

These hot gases flow upward from the bottom through the fixed bed, while solids are recharged from above through the lock system. Thus, reference is also made to counterflow fixed bed gasification. Because the recharged solids have a temperature of about 40 캜, the entire fixation layer has a temperature profile in which the hottest portion is located around the rotating grate and the temperature is reduced upward toward the solids feed. Corresponding to this temperature profile, different reactions occur within the fixation layer. Thus, it is often necessary to refer to reaction zones that do not have a clear separation into individual zones, but merge individual zones together. At the top of the gasifier around the recharged solids, drying and desorption of the physically adsorbed gases is carried out. A so-called reaction zone is located below the drying zone, and degassing of the solids is carried out at the top of the reaction zone. Following deaeration is followed by actual gasification of the solids as a function of Boudouard reactions as well as water gas and water-gas shift reactions. In the subsequent zone, the combustion of solids is carried out.

In particular, the ash obtained during combustion falls through the rotating grate and is further discharged therefrom. Unreacted gas fractions of reactants, mainly steam, nitrogen and argon, are discharged through the gas draw provided on the fixed bed, along with the syngas formed.

The reactor is particularly preferably operated at a pressure of at most 100 barg, preferably at most 60 barg at an operating pressure of at least 50 barg, so that solids are introduced under pressure, so that a locking system is required to supply fuel to the reactor. Introduction through the lock system is carried out discontinuously, after the fuel is first supplied to the lock terminated by the reactor under atmospheric conditions, then it is pressurized in the lock system and charged to the reactor under this pressure. Thereafter, the reactor is again closed against the locking system. Thus, nonetheless, a solids reservoir must be provided inside the reactor to ensure that the process can be operated in a static state under certain conditions, ensuring that the fixed bed always has the same height. For this purpose, various constructions, for example so-called coal distributors, for example from Lurgi® or VEB PKM Anlagenbau Leipzig are known. Attempts have been made to selectively influence the natural separation of the coal particle spectra by the various configurations of these devices. Resulting in only a limited range of achieving improved gasification. Particle spectra and disintegration behavior are highly dependent on the types and properties of coal.

Such a device is disclosed, for example, in DE 11 2005 002 983 T5. This is a hollow, inverted truncated conical apron tapered or internally tapered, with the apron hanging down from the head of the reactor, so that the coal discharged from the coal lock is distributed to the inner side of the apron . The lower end of the apron is typically located inside the fixed bed. A ring-shaped gas concentration zone is formed between the wall and the apron of the gas-gasifier, and the raw material gas converged from the gas concentration zone is discharged laterally through the gas outlet.

In the largest currently operated plants, coal is mostly converted to syngas in a fixed bed gasification process where the temperatures at the outlet and reaction ends are on average low, and the resulting syngas is heated to 200 to 300 ° C ) Or 400 to 500 ° C (for young hard coal). Here, distinctions must be made between the temperature peaks induced by the heterogeneity of the fixed bed and the average temperature. The average temperature is crucial to the corrosion and hence the service life of the components. The temperature peaks shall determine the thermal and mechanical load and shall not exceed the limits.

The limits of the coal gasification plant in the fixed bed should still be specified so as to limit the thermal load of the feed gas outlet at temperature peaks of 650 or 670 ° C so that a power reduction or even a shutdown of the reactor is required. Poor coal quality or characteristics and high loads increase the amplitude and frequency of these temperature peaks.

Due to the increasing lack of fossil feedstocks, solids gasifiers must be configured in the future to be able to gasify, for example, moisture coal or new hard coal as well as other coal with higher reaction end temperatures and poorer characteristics. In addition, fixed-bed gasification of renewable raw materials or secondary raw materials is becoming important, and it has poorer characteristics than most fixed bed gasification. As a result, the temperatures can reach a gas outlet temperature of at least 700 캜, preferably at most 800 캜, and even partly at most 1000 캜. At these temperatures, the apron used is exposed to significantly higher material stresses.

Also, coal with a high content of sulfur or halogens is gasified to an increased extent. As already mentioned, this leads to compounds such as H ₂ S, COS, HCl and HF in the resulting feed syngas. (For example, about 450 deg. C for old hard coal, about 250 deg. C for moisture brown coal, and about 450 deg. C for new hard coal) compared to temperatures used up to now Together, it induces stronger corrosion on the apron. Temperature peaks also have to be added to these typical operating temperatures, and these temperature peaks depend on the quality and particle spectra of the coals. Highly dissociated lignites, for example, lead to channeling due to high content of fine particles, which leads to CO ₂ and temperature peaks. To change the apron, the plant must be shut down, thus causing production losses. On the other hand, the aprons are too large to cause a significant increase in investment costs through the use of high temperature resistant materials, which is uneconomical and furthermore prevents the corrosion by, for example, hydrogen halides to a limited extent with the use of high temperature resistant materials.

It is therefore an object of the present invention to provide an apron which is called an annular gas collector to enable the long life of the plant, even when using fuels containing sulfur and / or halogens at gasification temperatures exceeding 450 DEG C will be. At the same time, frequent temperature peaks must be allowed without load reduction or short or long term shutdown of the reactor.

According to the present application, this object is solved by a charging device according to claim 1. The apron is cooled and includes an inner jacket and an outer jacket for this purpose and a cooling gap is formed between the inner jacket and the outer jacket with at least one inlet and outlet for supply and discharge of the cooling medium .

According to an improvement of the present application, the apron is formed in rotational symmetry, especially cylindrical, conical or part conical. The cylindrical shape has the advantage that the fuel introduced through the locking system diffuses over the entire cross section of the fuel layer. In addition, the volume of the fuel feeder chute can thus be maximized, so that the fuel feeder chute has a relatively short length and the effective reactor height is not reduced significantly with the same filling volume. Nevertheless, the amount of coal required to fill the time between two coal lock operations and the possible irregularities of gasification and supply can be taken.

When the apron jacket is conical, the filling device must be tapered toward the fixed bed. This has the advantage that the free exit surface for the raw material gas from the fixed bed is as wide as possible. By providing as wide a outlet face as possible, the respective gas velocities and hence the amount of entrained dust can be minimized. In addition, the resulting gas focussing space has as large a volume as possible, so that the flow rate of the source gas is also reduced in the gas focussing space and the dust retention is improved. Finally, the outlet surface should be constructed as wide as possible, so that the feed gas can flow more uniformly over the entire cross section of the fuel layer and the incorporation of coal particles is minimized. Crossflows must be reduced to ensure homogeneous reaction conditions across the entire fixed bed.

The partial conical shape mounted on the cylindrical portion combines the advantages of the two configurations.

In an ongoing operation, the cooling gap is filled with refrigerant, particularly a boiler feed. If water is used, water must meet the guidelines for steam generators to prevent deposits of carbonate or boiler scale. In principle, the cooling gap should be configured such that the inlet of the refrigerant is provided at one edge and the outlet of the refrigerant is provided at the opposite edge. Preferably, however, the cooling gap is made liquid impermeable at one edge so that the inner jacket and the outer jacket are here connected in a liquid-tight manner. Preferably, the edges are opposite the fixed bed, i.e., arranged at the bottom of the reactor. The filling of the cooling gaps with the refrigerant can be effected through a common supply and discharge conduit, or at least one inlet and one outlet are provided.

At the edge of the apron facing away from the fixed bed, i. E. At the top edge, the cooling gap is preferably closed by a ring-shaped cover, which is provided with a plurality of openings for introducing and discharging the cooling medium. The cooling medium may then be introduced into the cooling gap over the entire circumference of the apron. When a cooling medium, such as water, is heated by the hot syngas rising through the outside of the apron, the cooling medium evaporates and rises upwardly to escape in vapor form through the opening of the cover from the cooling gap.

Preferably, the inner jacket and the outer jacket extend parallel, since the device can be easily manufactured accordingly and the resulting cooling gaps have the same width at each point. In the same way, it may be assumed that the volumetric flow of the gas along the apron and thus the calories to be dissipated, at these points particularly high, form a cooling gap with a width greater than at some transversal points. For example, a large load is applied to the region facing the gas outlet. Thus, in practice, it can be ensured that the entire apron is sufficiently cooled.

In a particularly preferred embodiment of the present application, a bulkhead is provided between the inner jacket and the outer jacket of the apron, which preferably extends parallel to the inner jacket and the outer jacket so as to provide for uniform charging by the cooling liquid do. By the bulkhead, an inner cooling gap and an outer cooling gap are formed, which are preferably connected to each other at least at one point over the entire circumference of the apron.

The connection between the inner cooling gap and the outer cooling gap is particularly advantageous in that the free space is provided between the jacket connecting the inner jacket and the outer jacket and the bulkhead, i.e. the bulkhead does not extend downwardly to the bottom of the apron . With this arrangement, it is possible to achieve a refrigerant flow through the apron without the need for a pump. The outer cooling gap is heated adjacent to an outer jacket of the apron that is in direct contact with the gas fog space and exposed to the temperature of the rising hot raw syngas. Through the inner jacket, the refrigerant in the inner cooling gap is connected to the recharged solids with a temperature of only about 40 ° C. Thus, the refrigerant in the outer cooling gap is exposed to significantly higher heat transfer than the refrigerant in the inner cooling gap, so that the directional flow through the cooling gap occurs due to convection.

When water is now used as the refrigerant liquid, the boiling point of water lies below the temperature of the high temperature raw material synthesis gas. This is also the case when the cooling system is operated under pressure (30 bara: boiling point 234 DEG C; 51 bara: 265 DEG C). The resulting steam will always flow upward into the outlet. In a particularly preferred embodiment, the refrigerant is fed to the inner cooling gap and out of the outer cooling gap. Thus, the introduced cooling water passes through the inner cooling gap, is slightly heated by contact with the bulkhead, passes the heat through the solidified material inside the apron, which even leads to a slight reduction in the temperature of the cooling water , And goes to the external cooling gap. Due to the contact of the apron with the hot outer jacket, the water is here evaporated and discharges heat from the system. The resulting steam flows out of the steam outlet provided in the external cooling gap. Due to the discharge of steam, the new cooling water continues to be conveyed from the internal cooling gap to the external cooling gap. Thus, in such a system, the internal cooling gap and the external cooling gap are traversed by natural convection. Natural convection is defined by the difference in density between the water column at the inlet and the steam-water column at the outlet. This causes a so-called circulation number as a quotient of steam generation and water circulation, which is limited by the pressure loss due to the predetermined shape. The apparatus is particularly efficient when the inflow and outflow of cooling water is carried out at the top edge of the apron with the vertical structure of the reactor.

Preferably, the bulkhead should be configured such that the inner cooling gap has a smaller width than the outer cooling gap. This has the advantage that, when water is used as the refrigerant, the resulting steam provides a sufficient volume for the external cooling gap. Thus, an optimal circulation rate of water / steam can be made possible, and the pressure loss can be minimized.

The subject matter of the present application is a reactor for gasifying carbonaceous solids with oxygen and steam, having the features of claim 7. These reactors include a rotating grate at the periphery of the bottom and a solids lock at the head of the reactor, followed by the apron described above.

Advantageously, the reactor is formed such that the inlet and / or outlet of the cooling gaps of the apron are connected to the cooling system of the reactor itself. This has the advantage that no separate cooling circuit should be installed to cool the apron, thus lowering the investment cost and further increasing the reliability and operational safety of the cooling system. Preferably, the reactor itself also has a cooling jacket in which the cooling jacket of the apron is integrated.

Moreover, the aprons and the reactor are preferably welded together. This is possible in that the temperature of the inner jacket and the outer jacket can be significantly lowered compared to the uncooled apron by cooling the device. If less than 51 bara of water is used as the cooling liquid, the boiling point is about 265 ° C, so that it is distinctively below the critical temperature of 300 ° C, from which the hot gas corrosion progressively occurs to carbon steel. The cooling prevents the aprons from being replaced regularly in that the aprons are protected against corrosion and are protected against corrosion due to the downward movement of the coal so that costly and reliable connections are unnecessary.

Finally, the idea according to the present application also extends to a method of gasifying carbonaceous solids into oxygen and steam, with the features of claim 10. Gasification is carried out in the fixed bed and the solids are introduced into the fixed bed of the reactor through the locking part and then in a continuous manner via the filling device according to the invention. The cooling medium is introduced into the jacket in liquid form and is at least partially exhausted in vapor form. By such cooling, the device can be effectively protected against corrosion, and at the same time, a slight first cooling of the high-temperature raw material synthesis gas can be carried out, so that the load on the subsequent components is also less.

This cooling is particularly advantageous when the exhausted steam can be effectively reused as a reactant / gasification medium inside the process. Inside the fixed bed gasification, steam acts as a "moderator" to limit the combustion temperature so that the coal ash is not melted. Steam should be added in excess.

When water is used as the cooling liquid and the cooling water itself discharged in the form of vapor can be used as a reactant, i. E. When the steam stream required to gasify the solids in the fixed bed is supplied in part with steam generated during cooling, It proved to be very particularly advantageous. Thus, the steam requirement of the process can be lowered, which lowers operating costs. If the reactor itself also includes a water-cooled jacket, where steam is also formed, about 20 vol% of the total amount of steam needed by the recirculation of the steam from all the cooled components can be saved.

Other features, advantages and possible applications of the present invention are also apparent from the following description and drawings of the exemplary embodiments. All the features disclosed or shown, whether themselves or in combination, constitute the subject matter of the present invention, apart from their inclusion in the claims or their recitals.

Figure 1 schematically shows a fixed bed reactor operated in countercurrent flow.
Figure 2 shows an annular gas concentrator according to the present invention.
3 shows a cover of an annular gas collector according to the present invention.

Figure 1 schematically shows a reactor 10. This reactor is a vertical fixed bed reactor operated in countercurrent, including rotating grate 11 at the periphery of the bottom. In this rotary grate 11 a layer of solids 12 is formed in operation. Through the feeder 13, steam and / or an oxygen-containing medium, such as air, oxygen-enriched air or pure oxygen, is also introduced and injected into the layer 12 from a uniformly distributed lower portion. The ash formed by the reactants in the fixed bed 12 is discharged through the rotating grate 11 and removed through the ash draw-out 14 by the subsequent ash lock. The reactor 10 is water cooled and includes a cooling gap 17 between the outer jacket 18 and the inner jacket 19 (FIG. 2).

Above the reactor 10, a lock 20 is provided through which coal or other carbonaceous solids are fed. The apron 30 shown in FIG. 2 is followed by the lock portion 20 which is used as a solids reservoir so that even if the coal is charged discontinuously through the lock portion 20, Lt; / RTI > has a uniform and sufficient fill level. A free space is provided around the apron 30 on the fixed layer 12, and the unused steam as well as the reaction gases are concentrated in this free space. The gases collected in the gas concentration space 15 are discharged through the gas outlet 16.

Fig. 2 schematically shows a cross section of the right half of the filling device 1 according to the invention. The gas outlet portion 16 is mainly provided on only one side of the reactor.

The charging apparatus 1 includes a double wall apron 30 having an inner jacket 31 and an outer jacket 32 and a cooling gap 33 is formed between the inner jacket and the outer jacket. The inner jacket 31 and the outer jacket 32 are connected in a liquid-tight manner by the jacket portion 35 at the lower end portion of the apron 30 opposed to the fixed layer 12. [ Between the inner jacket 31 and the outer jacket 32, a bulkhead 34 is provided inside the apron 30. The bulkhead 34 divides the cooling gap 33 formed between the inner jacket 31 and the outer jacket 32 into an inner cooling gap 33i and an outer cooling gap 33a. In subsequent operation, the inner cooling gap 33i is adjacent to the solids held in the apron 30 through the inner jacket 31, while the outer cooling gap 33a is connected to the gas focusing space 15 ) And the fixed layer (12).

A free space 36 is provided between the jacket 35 connecting the inner jacket 31 and the outer jacket 32 and the bulkhead 34 and the inner cooling gap 33i and the outer cooling The gaps 33a are connected to each other at the lower end of the apron 30.

A cooling liquid, preferably water, is introduced between the bulkhead 34 and the inner jacket 31, flows downward by gravity and heat exchanges with cold coal (about 40 ° C) provided inside the apron. Because the bulkhead 34 is not terminated at the same height as the jacket 35, water can flow into the external cooling gap 33a at the lower edge of the apron 30. In the outer jacket 32, the cooling liquid directly exchanges heat with the hot gas in the gas focussing space 15. Due to the gas temperature of up to 700 ° C, preferably up to 800 ° C, the water is heated to a temperature of the respective boiling point (about 265 ° C at the operating pressure of 51 bara) and evaporated. Due to the remarkably low density of water, steam can be raised upward (convection) from the outer cooling gap 33a and exhausted from the upper end of the cooling gap 33a. Because of the high heat transfer at the gas side, the surface temperature of the outer jacket 32 will be higher than the cooling water temperature by a maximum of 30 degrees (depending on the gas temperature and load). At the outer jacket 32, a temperature of slightly below 300 [deg.] C can still be obtained, which is clearly below the temperature obtained in the uncooled annular gas collector which substantially corresponds to the gas temperature. Hot gas corrosion of the carbon steel can be prevented or at least greatly reduced.

The cooling water from the cooling gap 17 between the outer jacket 18 and the inner jacket 19 of the reactor 10 is supplied to the cooling gap 33 of the apron 30 when the reactor 10 itself also includes a water- The cooling gap 33 of the apron 30 is preferably connected to the cooling system of the reactor 10 so that it can also be used to charge the reactor 10.

Fig. 3 shows a ring-shaped cover 40, which is mounted on the charging device 1, preferably welded to a charging device, and also shows the connection to the reactor 10 as well as the inflow and outflow of refrigerant.

A circular opening 41 is provided in the center of the cover 40 through which solids can go from the locking system 20 to the filling device 1. Two rows of openings 42 and 43 associated with the jacket of the apron 30 and offset to the outside are provided in concentric circles through which coolant is introduced into the inner cooling gap 33i and the outer cooling gap 33a. The cover 40 can be connected through the circumferential projection 44 and welded to the inner jacket 19 of the reactor 10, for example (see FIG. 2).

In the cooled annular gas collector according to the present application, the wear in the inner jacket due to the successively passing coal is greatly reduced by the low wall temperature, thus extending the possible service life. Due to the low temperature, high temperature gas corrosion in the outer jacket can be prevented or significantly reduced, independent of the concentration of corrosive components in the source gas. Corrosion components in the feed gas are determined by the coal composition.

In addition, the gas is slightly cooled in the outer jacket of the annular gas collector, thereby causing a low temperature load in subsequent plant sections. By cooling the gas in the annular gas collector, heat is released from the process at one point, and the refrigerant is evaporated.

If water is used as the refrigerant, the steam formed thereafter can be supplied to the system as steam for gasification, thereby reducing the cost for the reactants to be produced.

1: Charging device
10: Reactor
11: Rotating grate
12: fixed layer
13: supply of oxygen-containing gas and / or steam
14:
15: Gas collecting space
16:
17: cooling gap
18: outer jacket of the reactor
19: inner jacket of the reactor
20:
30: Apron
31: inner jacket
32: Outer jacket
33: cooling gap
33a: external cooling gap
33i: Internal cooling gap
34: Bulkhead
35: Jacket portion
36: free space
40: cover
41: opening
42:
43:
44:

Claims (10)

A charging device (1) for charging a reactor (10) operated under pressure with carbonaceous solids, the solids being gasified by oxygen and / or steam in a fixed bed (12)
The charging device includes a ring-shaped apron (30) open at the top and bottom, the solids are supplied to the apron through a lock (20)
The apron 30 includes an inner jacket 31 and an outer jacket 32,
Characterized in that a cooling gap (33) is formed between the inner jacket and the outer jacket, the cooling gap (33) having at least one inlet and / or outlet for supplying and discharging a cooling medium. The method according to claim 1,
Characterized in that the apron (30) is formed to be rotationally symmetrical, in particular cylindrical, conical or part conical. 3. The method according to claim 1 or 2,
Characterized in that the inner jacket (31) and the outer jacket (32) of the apron (30) are connected to each other at the lower side of the reactor (10) opposite the fixed layer (12). 4. The method according to any one of claims 1 to 3,
At the top edge of the apron 30 facing the fixation layer 12 the cooling gap 33 includes a cover 40 comprising a plurality of openings 42 and 43 for feeding and discharging the cooling medium, Is closed. 5. The method according to any one of claims 1 to 4,
A bulkhead 34 is provided between the inner jacket 31 and the outer jacket 32 of the apron 30 to form an inner cooling gap 33i and an outer cooling gap 33a, Characterized in that the gap (33i) and said external cooling gap (33a) are connected to each other at least at one point. 6. The method of claim 5,
Characterized in that the inner cooling gap (33i) and the outer cooling gap (33a) are connected to each other over the entire circumference of the apron (30). The method according to claim 5 or 6,
Characterized in that a free space (36) is provided between the bulkhead (34) and the jacket (35) connecting the inner jacket (31) and the outer jacket (32). A reactor (10) for gasifying carbonaceous solids into oxygen and / or steam in a fixed bed, comprising a charging device (1) according to any one of claims 1 to 7. 9. The method of claim 8,
Characterized in that the inlet and / or the outlet of the cooling gap (33) of the charging device (1) is connected to a cooling gap (17) between the outer jacket (18) and the inner jacket (19) of the reactor , A reactor. A method for gasifying carbonaceous solids into oxygen and steam,
Said gasification being carried out in a fixed-bed reactor operated under pressure, said solids being introduced into the fixed bed through a filling device according to any one of claims 1 to 7 via a locking part,
Characterized in that a cooling medium in the form of a liquid is introduced into the cooling gap of the charging device and the cooling medium is discharged at least partially from the cooling gap in the form of vapor.

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