GB1598169A

GB1598169A - Supply of solid particles to a pressurised vessel

Info

Publication number: GB1598169A
Application number: GB22228/78A
Authority: GB
Original assignee: Dr C Otto and Co GmbH; Saarbergwerke AG; Eisenbau Wyhlen AG
Current assignee: Dr C Otto and Co GmbH; Saarbergwerke AG; Eisenbau Wyhlen AG
Priority date: 1977-05-25
Filing date: 1978-05-25
Publication date: 1981-09-16
Also published as: AU521598B2; DE2723542A1; ZA783006B; FR2392319A1; IN150302B; CA1094609A; AU3649578A; BR7803310A; JPS549881A; FR2392319B1

Description

(54) IMPROVEMENTS IN OR RELATING TO THE SUPPLY OF SOLID PARTICLES TO A PRESSURISED VESSEL (71) We, SAARBERGWERKE AKTIEN GESELLSCHAFT, a German Company, of Triererstrasse 1, D-6600 Saarbrticken, Federal Republic of Germany; EISENBAU WYHLEN GmbH (formerly Eisenbau Wyhlen Aktiengesellschaft), a German Company, of D-7889 Grenzach-Wylen, Federal Republic of Germany; and DR. C. OTTO & COMP. GmbH, a German Company, of Christstrasse 9, D4630 Bochum; Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method of supplying solid particles to a pressurised vessel and also to apparatus herefor. More particularly, although not exclusively, the invention relates to a method and apparatus for charging controllable quantities of fine solid particles from a pressurised storage container to a highly pressurised apparatus in a smooth and uniform fashion.

Such apparatus may be, for example, autoclaves, gas-purification chambers, furnaces containing molten material, jet mills and like mills, coal-dust firing apparatus and, in particular, apparatus intended for liquid gas catalytic or gasification reactions.

It is known in the art of effecting continuous reactions between solid particles and vapours or gaseous substances, that in certain temperature and pressure ranges the manner in which the solid particles are conveyed between the gas-filled chamber and the reaction vessel can influence the conversion rate at the surface of the solid particles or in the interior thereof and, in certain circumstances, can even be the sole determining factor. In order to obtain a good yield it is therefore desirable, and advantageous, to ensure that the reactants are dispersed as uniformly as possible. To this it may be added that reaction speeds and equilibrium yields are often varied one in relation to the other by suitable selection of temperature and pressure and can be favourably influ- enced when different reaction directions can arise. Examples are the known gas catalytic and pressure gasification processes, among others.

If the reactions have to take place at fairly high pressures, a considerable technical problem is encountered in feeding the solid particles evenly. In an attempt to overcome these difficulties, it has been suggested that the particularly finely ground particles are mixed with a carrier liquid, to provide a pumpable slurry that can be pumped into the reaction vessel under pressure. Another possibility consists in pumping the solid particles mixed with water into a heating coil and there evaporating the water, whereupon the steam-dust mixture is allowed to flow into the reaction vessel.

Another method of conveying finely ground coal into high-pressure reaction vessel is one in which the coal is first fed into an intermediate storage container at normal pressure. The pressure in the intermediate storage container is then increased until it is higher than the prevailing pressure of the reaction vessel and the coal is transferred into the reaction vessel through a line. The volume vacated in the intermediate storage container by the coal removed thereform is then filled with a non-compressible medium, without increasing the pressure of the coal particles (see in this respect German Offenlegungsschrift No. 1787453).

Apart from the very high cost in terms of equipment, this known method also has the considerable disadvantage that the amount of coal conveyed to the reaction vessel over a given unit of time cannot be metered exactly.

If the reactions are to take place smoothly in the reaction vessel, however, it is essential that the amount of coal can be metered exactly per unit of time. In addition there is the danger of the reaction gases blowing brock into the material feed system, should this suddenly lose pressure. This can lead to crepitation or even dangerous dust explosions.

An object of the invention is to provide a method and apparatus with which the ex actly metered amount of solid material can be Eed d continuously to a highly-pressurised vessel in a simple and safe manner.

According to one aspect this invention consists in a method of continuously and uniformly feeding solid particles from a closed, solid particle storage vessel to a pressurised reaction vessel, comprising adjusting the pressure of the storage container to the prevailing pressure of the reaction vessel; feeding a quantity of solid particles in the storage vessel through at least one first feed zone to at least one second feed zone by at least one adjustable conveying device; feeding said particles through at least one second feed zone to at least one third feed zone by means of a relatively slow-flowing gas; and feeding said particles through said at least one third feed zone to said reaction vessel by means of a relatively fast-flowing propellant gas, said at least one first, second and third feed zones being incorporated in a single feed line.

According to another aspect this invention consists in an apparatus for carrying out the method described in the preceding paragraph, said apparatus comprising a solid particle storage vessel and a reaction vessel; at least one feed line connecting said storage vessel with said vessel for the supply of solid particles thereto; and means for adjusting the pressure within the storage vessel to the prevailing pressure in the reaction vessel, said at least one feed line comprising a first feed zone having an adjustable device for feeding said particles therethrough, a second feed zone having means for introducing thereinto and passing therethrough a relatively slowly-flowing carrier gas, and a third zone having means for introducing thereinto and passing therethrough a relatively fastflowing propellant gas.

Thus the quantity of material conveyed can be changed in dependence upon the quantity of particles measured in the conveying zone through which passage of the particles is rapid.

When practicing the method of the present invention, a finely-ground solid material, such as coal, can be continuously fed in metered quantities to a highly-pressurised reaction vessel in a simple manner in that the coal is gasified in the presence of oxygen and water vapour at high temperatures. By using in the first conveying zone such adjustable conveying device as bucket wheels, dust pumps and, in particularly, screw conveyors, it is possible to prevent uncontrolled discharge of solid particles from the intermediate container. When using screw conveyors exact metering of the quantity of solid material to be conveyed can be obtained by adjusting the speed at which the screw conveyors rotate. The higher the rotational speed of the screw conveyors, the greater the amount of solid material moved from the first to the second conveying zone. In the second conveying zone, which consititues the largest part of the feed line as a whole, the solid maerial is conveyed with the aid of a slow-flowing carrier gas. The carrier gas, which primarily serves the purpose of a friction-reducing agent and is added in tiny quantities, has the effect that the coal advances through this conveying zone in a slow-moving dense column. In this way, wear in piping, which is primarily caused by friction between solid particles and the interior of the piping, is reduced to a minimum. It may be added that because of the relatively high density of the stream of particles, propellant gas is prevented from flowing out of the third conveying zone in the reverse direction, back through the first two conveying zones and entering the intermediate container, which is not desired. The solid material is conveyed in the third conveying zone by means of a fast-flowing propellant gas, which is blown into the feed line. The propellant gas draws the stream out of the second conveying zone powerfully and evenly, so that the solid material passes into the reactor in an extremely finely dispersed state with the result that right from the start the reacting agents in the reactor are in a state of great turbulence, thereby making a large surface area of solid material freely available for the reactions in progress.

In a manner known per se gases or vapours which either participate in the subsequent reactions in the pressurised reaction vessel or behave inertly, or again part of the gas obtained as reaction product which is fed back in a circuit, can be used as means for pressurising the intermediate container with gas, for the gas-assisted slow conveyance of the particles in the second conveying zone and as the propellant gas in the third conveying zone.

Here it has been bound expendient to use different types of gas for the carrier and the propellant gas, advantageously using as a carrier gas the same gas as that serving to build up the pressure in the intermediate storage container, whereas as propellant gas, which passes into the reactor in a largish quantity together with the solid material, one should first consider a gas which takes part in the reactions in the reaction vessel as a reagent-in the gasification of coal this might be, for example, oxygen or water vapour.

For measuring the solid particles flowing in the rapidly passed third conveying zone, one can utilise the physical properties of the material being conveyed in a manner known per se, for example density per unit volume and time, through radiation, change in capacitance and measurable properties.

Since the material passes through the third conveying zone at high speed at high pressure, the amount of solid material is preferably measured in the simplest way, with the aid of the drop in pressure registered by the stream of solid material against a reference value obtained with the aid of a stream of pure gas. The value to which the conveying device discharging the intermediate container should preferably be adjusted, and which can also be used when re-adjusting the quantities of gas, can then be derived from the value measured.

However the same measurement in the second conveying zone would be less advantageous as plugs or agglomerations can detach themselves from the dense stream in a known manner and then the measurement would be too imprecise and variable.

So that the invention will be more readily understood and optional features thereof made apparent, an exemplary embodiment will now be described with reference to the accompanying drawing, the single Figure of which illustrates schematically an apparatus for feeding solid particles into a pressurised reaction vessel.

By way of example, the following description will be made with reference to the gasification of ground solid-material, for instance coal under pressure, in a pressure reactor 2 which is not shown in detail and from which the reaction gases developed are continuously extracted in a manner to maintain the pressure in the reactor 2 constant.

An important feature of the reactor 2 with regard to the method of this invention is the inlet pipes 3 of the reaction vessel, through which pipes fuel to be gasified is introduced with a mixture of gasification agents, such as oxygen, air or water vapour. The reaction vessel is pressurised to approximately 25 bar and the solid particles are gasified in said vessel in the presence of oxygen and water vapour at temperatures of between 1200 and 2400do. The synthetic gas occurring as a biproduct is extracted at the top of the reaction vessel through a line 5, and slag located at the bottom of the vessel is removed therefrom through a line 4. The reaction vessel 2 is preferably a so-called slag-bath reaction vessel in which a liquid pool of slag is maintained in a lower part of vessel and the gasification reactions are essentially carried out in the highly turbulent multi-phase zone above the slag bath. The solid material which is to be gasified and which has a residual moisture content of, for example, 2% is fed together with an inert gas pneumatically from a pulverising and drying apparatus (not shown) into a bunker 7, which is located on top of an intermediate vessel 6 and a storage container 1 designed as the source unit, stopvalves 8' and 8" being disposed between the bunker 7 and the vessel 6, and the vessel 6 and the container 1, respectively. In order to be able to monitor the content of the storage container 1 at any time, the container is arranged to co-operate with pressure measuring devices 29 and the lines are connected by flexible couplings. The maximum level in the intermediate vessel is monitored by a level gauge 9', while the minimum level in the container 1 is monitored by a level gauge 9", these gauges being arranged to control the feeding programme.

Inside the intermediate vessel 6 and the storage container 1, the coal is placed under a positive pressure of approximately 28 to 32 bar by introducing a carrier gas, for example a synthetic gas, into the top part of the container 1, through a line 21, whereafter the coal is conveyed from the container along a feed line 10, into the reaction vessel 2. In the illustrated embodiment, the material is conveyed along four similar feed lines, although for the sake of clarity only one is shown fully.

Each feed line 10 consists of three conveying zones 11, 12 and 14.

In conveying zone 11 the solid particles are conveyed by means of adjustable screw conveyors 16, which are driven through drive shafts 17 by motors 18. The drive shafts suitably extend vertically through the storage container 1 and are each provided with agitating arms 19. Those sections of the shafts which need be sealed will thus be located at the top of the container 1, which is free of solid particles. The agitating arms 19, which assist to break up any agglomerates which might form, ensure that the material runs into the screw conveyors satisfactorily.

The material is prevented from rushing through the screw conveyors by using a pressure equalising device with a non-return valve (not shown) between the conveying lines and the storage container 1. The pitch of the screw conveyors 16 is selected in a manner to prevent solid particles shooting through and simultaneously effectively separate the gas in the storage container 1 when the minimum level indicated by the gauge 9" is reached from the conveying zones 12 and 14 charged with carrier and propellant gas.

The storage container 1 is fed cyclically by extracting gas from the intermediate vessel 6 through a filter unit 20 and passing the extracted gas to a further gas collector 30, the valves 8' and 8" being closed during the extraction process. By using an additional gas collector 30, not all the expanded gas is lost. Subsequent to completing this extraction, the valve 8', which is a slide valve, is opened and material is fed to the intermedi ate vessel 6 from the bunker 7 up to the level of the gauge 9', said valve being arranged to send a signal to the valve 8' when the maximum level is reached, to close said valve 8'. The charge in the intermediate vessel 6 is then pressurised by introducing gas thereinto through the line 21. When the level gauge 9" in the storage vessel I detects that the minimum level has been reached, the gauge will send a signal to the valve 8", causing the valve to open slowly, to cause the charge to flow out of the intermediate vessel 6 into the storage container 1. Discharge from the storage container I is effected with the four screw conveyors 16 which make continuous coal-dust transfer possible and moreover, through suitable adjustment of the speed of rotation, also permit exact metering of the amount being transferred according to the coal-dust requirement determined by the progress of the reaction in the reaction vessel.

The quantities of carrier-gas and propellant gas are each measured by a gas-quantity metering device. The screw conveyors meter the solid material into conveying zones 12 without any pressure difference.

In the second conveying zone 12 adjoining the first conveying zone 11 the coal is conveyed through the introduction of a carrier gas, which is fed into the corresponding feed lines along lines 22. Here the material is conveyed through the second conveying zone 12 in the form of a slowmoving, very compact solid stream. The flow rate is only approximately 0.5 to 4.0 m/sec while the quantitative ratio of coal dust being conveyed and carrier gas used is about 100, giving a dense stream.

In the example chosen here, the carrier gas used is the same gas as that which serves to increase the pressure in the intermediate storage vessel 1. In this way, should carrier gas for some reason seep through the first conveying zone 11 into the storage container 1, undesired mixing of two different gases is prevented. In the third conveying zone 14 adjoining the second conveying zone 12, the coal-dust is now conveyed by means of a fast-flowing propellant gas which is introduced through lines 23 and mixing nozzles 24. The flow speed of the fast-moving stream set up in the third conveying zone is approximately from 12 to 20 m/sec, while the quantitative ratio between coal-dust and propellant gas is only about 20. The introduction of the propellant gas brings an even and strong break-up and dissipation of the stream of solid material from the second conveying zone, with the result that the coaldust is blown into the reactor 2 through the inlets 3 in a finely dispersed state and that the total surface area of the coal particles is immediately available as an exposed area for the gasification reactions proceeding in the reaction vessel. In addition, the fuel-propellant gas mixture streaming into the reacting vessel at high speed stirs up the phase interface of the liquid and very hot slag bath in the vessel in a manner such that the fuel particles are heated up very quickly and the corresponding reactions rapidly commence.

The amount of coal-dust conveyed in each feed line is measured by means of a measuring device 25 disposed in the third conveying zone, whereby any deviation from a preset, theoretical value is established and a signal is produced and signal converted in an amplifier 26; the output signal of the amplifier is then used for the continuous fine adjustment of the material discharge, by varying the speed of rotation of corresponding screw conveyors, in such a manner as to reduce the feed when the signal indicates a magnitude in excess of the preset value, and to increase the feed when the variation represents a magnitude lower than the preset value.

Because of the high flow rate in the third conveying zone, the quantity is advantageously measured by determining the pressure drop produced by the dispersed stream of solid material against a reference provided by a stream of pure gas.

With the aid of the gas-quantity measuring devices, the speeds in both the conveying zones 12 and 14 and the inlet pipes 3 can be established at any moment. The sum of the gas quantities introduced through lines 22 and 23 is kept constant.

Apart from good controllability and flexibility, there is another advantage in the fact that a substantial part of the gases escaping rapidly from the reaction zone can be returned through conveying zone 14 so as to take part in the reactions again. It should also be particularly emphasised that an advantageous automatic safeguard against blow-back is provided by the arrangement in accordance with the method. This is constituted by the plug of material conveyed in a dense stream through conveying zones 11 and 12, which plug is held braced by the pitch of the screw conveyor so as to be practically incompressible in the opposite direction to that of conveying. Consequently, in the event of breakdowns and sudden pressure drop in the storage container or with the valve in the intermediate vessel open, the very hot gas from the reactor cannot blow back through the screw conveyor into the storage container.

The flow rate of the material in the second conveying zone 12 may fall within the range between 0.5 m/sec and to 10 m/sec but the preferred range is as stated above, namely, between 0.5 m/sec and 4.0 m/sec. Similarly, the flow rate of the material in the third conveying zone 14 may fall within the range between 12 m/sec and 25 m/sec but the preferred range is as stated above, namely, between 12 m/sec and 20 m/sec.

The drawing illustrates various reversible and other regulating valves 27 installed in the lines 5, 21, 22 and 23; their function will have become apparent from the preceding description of the single Figure of drawing.

WHAT WE CLAIM IS: 1. A method of continuously and uniformly feeding solid particles from a closed, solid particle storage vessel to a pressurized reaction vessel, comprising adjusting the pressure of the storage vessel to the prevailing pressure of the reaction vessel, feeding a quantity of solid particles in the storage vessel through at least one first feed zone to at least one second feed zone, by at least one adjustable conveying device; feeding said particles through said at least one second feed zone to at least one third feed zone by means of a relatively slow-flowing gas; and feeding said particles through said at least one third feed zone to said reaction vessel by means of a relatively fast-flowing propellant gas, said at least one first, second and third feed zones being incorporated in a single feed line.

2. A method as claimed in Claim 1, wherein said at least one adjustable conveying device is a screw conveyor.

3. A method as claimed in Claim 1 or Claim 2, wherein the propellant gas is fed into the feed line via mixing nozzles.

4. A method as claimed in any one of Claims 1 to 3, comprising measuring the amount of solid material flowing in the third conveying zone and adjusting the amount of material fed by said adjustable feed device on the basis of the value obtained.

5. A method as claimed in Claim 4, wherein the amount of solid material conveyed in said third zone is measured by the pressure drop caused by the stream of solid material.

6. A method as claimed in any one of Claims 1 to 5, wherein different types of gases are used for the carrier gas and the propellant gas.

7. A method as claimed in Claim 5, wherein the gas used to increase the pressure of the intermediate storage container is the same gas as the carrier gas, and wherein part of the gas produced in the pressurised vessel is used as the propellant gas.

8. A method as claimed in any one of Claims 1 to 7, wherein the fuel is conveyed in four feed lines.

9. A method as in any one of Claims 1 to 8, characterised in that the flow speed of the solid particles lies between 0.5 and 10 m/sec.

in the second conveying zone.

10. A method as in Claim 9, characterised in that said flow speed lies between 0.5 and 4 m/sec.

II. A method as in any one of Claims 1 to 10, characterised in that the flow speed of the solid particles lies between 12 and 25 m/sec. in the third conveying zone.

12. A method as in Claim 11, characterised in that said flow speed lies between 12 and 20 m/sec.

13. A method as in any one of Claims 1 to 12, characterised in that said reaction vessel is pressurised to approximately 25 bar and said storage vessel is pressurised to approximately 28 to 32 bar.

14. A method as in any one of Claims 1 to 13, characterised in that the feeding of said quantity of solid particles through said at least one feed zone by said at least one adjustable conveying device leads to the formation of a plug of practically incompressible material which prevents gas blowback through the conveying device into the storage vessel.

15. A method substantially as hereinbefore described with reference to, and as illustrated in, the drawing accompanying this Specification.

15. An apparatus for carrying out the method as claimed in Claim 1 or Claim 2, comprising a solid particle storage vessel and a reaction vessel; at least one feed line connecting said storage vessel with said reaction vessel for the supply of solid particles thereto; and means for adjusting the pressure within the storage vessel to the prevailing pressure in the reaction vessel, said at least one feed line comprising a first feed zone having an adjustable device for feeding said particles therethrough, a second feed zone having means for introducing thereinto and passing therethrough a relatively slowly-flowing carrier gas, and a third feed zone having means for introducing thereinto and passing therethrough a relatively fast-flowing propellant gas.

16. An apparatus as claimed in Claim 15, wherein the respective lines for the pressurising gas and carrier gas are connected by means of reversible regulating valves to an intermediate vessel, to the storage vessel and to said second feed zone, the propellant gas being passed, by way of another line connected in parallel with the storage vessel, through a mixing device to the third feed zone; said intermediate vessel having an outlet which is connected to the inlet of the storage vessel.

17. An apparatus as claimed in Claim 16, wherein, downstream of said mixing device, a measuring device is incorporated in the or each feed line and is linked to said adjustable device for changing the amount of particles discharged from the storage vessel.

18. An apparatus as claimed in Claim 17, wherein the adjustable device is operated by an adjustable motor which is controlled by the measuring device through an amplifier.

19. An apparatus as claimed in any one of Claims 16 to 18, wherein a bunker has its

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The drawing illustrates various reversible and other regulating valves 27 installed in the lines 5, 21, 22 and 23; their function will have become apparent from the preceding description of the single Figure of drawing. WHAT WE CLAIM IS:

1. A method of continuously and uniformly feeding solid particles from a closed, solid particle storage vessel to a pressurized reaction vessel, comprising adjusting the pressure of the storage vessel to the prevailing pressure of the reaction vessel, feeding a quantity of solid particles in the storage vessel through at least one first feed zone to at least one second feed zone, by at least one adjustable conveying device; feeding said particles through said at least one second feed zone to at least one third feed zone by means of a relatively slow-flowing gas; and feeding said particles through said at least one third feed zone to said reaction vessel by means of a relatively fast-flowing propellant gas, said at least one first, second and third feed zones being incorporated in a single feed line.

in the second conveying zone.

outlet connected to the inlet of said intermediate vessel and is adapted to deliver solid materials to said intermediate vessel under the influence of gravity and under the control of a stop valve which is located between the bunker and the intermediate vessel, another stop valve being disposed between the intermediate vessel and the storage vessel to control the delivery of a charge to the storage vessel.

20. An apparatus as claimed in any one of Claims 16 to 19, wherein the intermediate vessel and the storage vessel are each equipped with a gauge which is adapted to detect the level of the contents of the respective vessel.

21. An apparatus as claimed in any one of Claims 16 to 20, wherein the intermediate vessel is provided with a filter unit which is connected by way of some of said reversible regulating valves either to the inlet line or to a gas collector vessel for reducing the pressure.

22. An apparatus as claimed in any one of Claims 12 to 21, wherein the or each adjustable feeding device has a drive shaft which is disposed vertically in the storage vessel and which is provided with agitating arms and which is supported near one end thereof by pressure-tight seals in a cover of the storage vessel and which extends at the other end thereof out of the storage vessel container into said first feed zone.

23. An apparatus as claimed in any one of Claims 12 to 22, wherein the storage vessel, together with the intermediate vessel, is placed on pressure pick-ups, the lines to the two units being connected flexibly.

24. An apparatus for continuously and uniformly feeding solid particles from a closed storage vessel to a pressurised reaction vessel, substantially as hereinbefore described with reference to, and as illustrated in, the drawing accompanying this Specification.