GB1588553A - Feed apparatus for particulate solids - Google Patents

Description

(54) FEED APPARATUS FOR PARTICULATE SOLIDS (71) We, ROCKWELL INTERNATIONAL CORPORATION, a corporation organised and existing under the laws of the State of Delaware, United States of America, of 2230 East Imperial Highway, El Segundo, California, 90245, United States of America, 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 feed apparatus for particulate solids, The apparatus may be used in coal processing plant, wherein fluidized coal is equally divided between multiple injection passages in an injector from a single coal feed line and fed to a coal reaction chamber for hydrogenation of the coal particles by hot hydrogen injected through the injector.

U.S. Patent Specification 2,684,870 describes a selective adsorption process in which a granular adsorbent is conveyed upwardly through a lift line and downwardly through an adsorption column with substantially the same bulk density as in the static state. It has been found that a vertically rising mass of solid granular adsorbent can be maintained in a conduit at this high bulk density and the flow under these conditions may be referred to as dense-phase flow.

Such flow is accomplished by forcing a flow of lift gas upwardly through the interstices of the granules to establish frictional forces (indicated by the pressure differential) which are sufficient to overcome the gravitational forces on the adsorbent granules as well as the frictional forces of the conduit walls on the moving bed of adsorbent and cause the mass to move upward. The actual velocity of the lift gas necessary to accomplish this result is dependent upon the size and density of the granules, and the viscosity of the lift gas which is directly determined by the pressure and temperature. The velocities are generally sufficient to cause fluidization of the adsorbent granules if the adsorbent granules were free to fluidize or become suspended in the lift gas.

The said U.S. Specification relates primarily to vertical movement or solids in a continuous flow loop and describes a vertical column that has a narrow opening at the bottom of the column and a wide opening at the top, the column having a somewhat conical shape. The reason for this is to prevent clogging of the column as the granules are moved upwardly through the pipe.

The present invention enables dense-phase flow of particulates solids to take place through horizontal and/or vertical feed pipes.

According to the present invention, there is provided feed apparatus for particulate solids, comprising a feeder vessel having a sealable charging inlet for particulate solids, a gas inlet line connected to the vessel for introducing a gas into the vessel to estlish an initial pressure in excess of that in an outlet feeder line, the outlet feeder line being connected at one end to a lower portion of the feeder vessel and at its other end to a conduit extending to a flow splitting device, and a valve connected between the outlet feeder line and the conduit, the arrangement being such that the valve can be opened when the initial pressure inside the vessel is sufficient to discharge the solids through the conduit and the flow splitting device at their bulk density.

The valve may be a ball valve immediately adjacent to the feeder exit to allow flow of solid particles to be established. The U.S. Specification heretofore described initiates the flow by simply providing a pressure differential in the vertical feeder line. In the present invention, if the valve positioned at the exit of the feeder vessel were not used and flow were initiated by simply pressurising the feeder vessel, the feed line would consistently plug. In addition, the U.S. Specification employs a "thrust plate" or choke at the exit of the diverging vertical tube.

The present invention does not require such a choke to control flow of densephase material through feeder lines.

A coal feeder system embodying the invention is disclosed, wherein a coal feeder bin is pressurised by introducing gas to the top of the feeder vessel containing pulverised coal, the vessel being adapted to allow the pulverised coal to flow out of the bottom of the vessel. A ball valve or other full opening valve is positioned at the bottom of the coal feeder bin which allows the feeder vessel to be pressurised prior to the initiation of the flow. In order to establish and maintain an adequate flow, an adequate pressure drop must be created between the feeder bin and the feeder line downstream. Without the valve or an adequate pressure drop between the feeder bin and the feeder line, the feed line would frequently plug.An even flow of dense-phase coal particles is essential when those are directed into a coal feed splitter to assure ai even distribution between a multiplicity of separate coal feed lines divering from the feed splitter.

Pulverized coal with a mass-median size of 50 to 170 microns, for example, is placed in the coal feeder bin. It has been determined that the coal with these average particle sizes will flow readily as long as the coal is sufficiently dispersed in a carrier gas to prevent intimate particle-to-particle contact. Successful flow tests were made utilising this system to obtain coal flow rates of 0-1 to about 10 lbs/sec with a pressure drop in the feeder tube of 5 to about 100 psi over line lengths from a few feet to about 80 feet. The gas flow rate necessary to transport the finely divided coal was found to be very small.

This flow rate was inferred from the volumetric flow rate into the column by subtracting the volume of the coal dispersed from the column. The results indicate that on the average only the gas in the interstices of the coal at its compressed bulk density is carried with the coal.

The feed system has been successfully used with the pulverised coal and several transport gases. Tests were run with a feeder coal particulate carrier gas of nitrogen, helium and carbon dioxide as well as hydrogen.

Where it is desirable to transport particulate materials such as coal particles from a feeder at maximum solid density and with a minimum amount of gas for transport of the solid, the foregoing system is ideal.

The feed system, without the flow splitter, is currently being utilised to feed pulverised coal into a single injector element liquefaction or gasification reactor, and has been additionally successfully demonstrated in combination with a coal splitter assembly whereby an even distribution of coal was fed to six individual injector elements. The feeder system comprises a vessel which is pressurized, a gas source for pressurization, and an outlet line with a relatively full opening ball valve located immediately adjacent to the feeder. A line downstream of the valve feeds into the coal splitter assembly.The feeder is operated by loading the vessel with particulate material such as pulverized coal and pressurizing to a level determined by the pressure drop in the outlet line and the downstream pressure, and opening the ball valve to allow the material to flow out towards the splitter assembly. The valve, close-coupled to the feeder, and a relatively empty downstream line when flow is initiated are important for successful operation of the system. If the line between the feeder and the valve is too long, the particulate material will pack in the line and prevent flow of the material. However, if the full-opening valve is close-coupled to the feeder vessel and the downstream line is initially free of solids, the pulverized coal material will flow readily from the feeder at its bulk density towards the coal splitter apparatus.A consistent flow of dense-phase coal is essential for an even distribution of coal particles in each of the separated coal distribution lines downstream of the splitter apparatus. For example, if the coal splitter divides the incoming coal particles from the single feed line from the feeder vessel into six equal distribution feed lines, each of these feed lines terminates at an injector face. Each of the six feed lines may have separate impinging streams of hot hydrogen downstream of the injector face; the hydrogenation process taking place in a downstream reaction chamber.

The reaction of hot hydrogen and densephase coal particles is controlled to a specific residence time by quenching the reacting products as they leave the reaction chamber.

This process is described in detail in the specification of our co-pending U.K. patent application 18085/77 (Serial No. 1582547).

Although this invention has been applied to pulverized coal, it will also operate successfully with a variety of other pulverized or granular materials.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a schematic diagram of a densephase particulate solids feeder and flow splitter as used in a coal hydrogenation plant; Fig. 2 is a section taken along lines 2-2 of Fig.l of the coal splitter apparatus; Fig. 3 is a section taken along lines 3-3 of Fig. 2 illustrating the coal splitter appar atus; and Fig. 4 is a cross-section of a typical coal hydrogenation injector assembly that is attached to the separate coal feed lines from the splitter apparatus.

Turning to the schematic diagram of Fig. 1, a dense-phase particulate solids feeder and flow splitter 10 consists of a coal feed hopper 12 comprising a vessel 14 with a conical bottom section 18 and a sealable Iid 16 at the uppermost portion of the vessel. The conical bottom section 18 directs fine particles of coal towards an outlet at the bottom of the feeder vessel. A ball valve 26 is placed immediately adjacent to the end of the conical section 18 of the vessel 14. A gas pressurizing line 20 through which N2, H2 or other gases may be directed into the interior of the coal feed hopper 12 after it is filled, is used to provide a pressure differential between the interior of the coal feed hopper 12 and the downstream line 28 in communication with the valve 26. The valve 26 is normally closed during filling of the feed hopper 12.

When the hopper is filled, the lid 16 is secured at the top of the hopper, sealing the feeder vessel, and the pressurizing gas is fed through line 20 to the interior of the vessel. A series of gauges 22, 23, 24 and 32 may be used to monitor the pressures in the various parts of the apparatus.

The feed line 28 is connected between the downstream side of the ball valve 26 and the top of a feed splitter device 34. The splitter device divides the coal dust equally into feed lines 52 extending from the bottom of the splitter 34. The diverging feed lines 52 lead into an injector device 54 to provide equal amounts of dense-phase coal to the base of the injector (Fig. 4). Heated hydrogen is fed through a line 56 to the interior of the injector 54, and the hot hydrogen and injected coal particles react within a reaction chamber 58 beneath the injector device 54 and are quenched by a quench source 60 to arrest the hydrogenation process after a predetermined short residence time period, and the resultant produce is deposited within a collection tank 62.A line 64 from the collection tank 62 taps off the reacted products to, for example, cyclone separators, condensers, gas samplers etc., none of which is shown.

In operation, the coal feed hopper 12 is filled with finely divided coal particles such as, for example, 70% 200 mesh. After the hopper is filled (ball valve 26 being in the closed position), the top of the hopper 16 is sealed and a gas such as N2 is admitted through line 20 to the interior of the coal hopper to a predetermined pressure. Tests have been performed with a hopper pressure as low as 7 psi, but typically 20 to 100 psi, and a downstream pressure of atmospheric pressure in line 28 below valve 26. The pressure differential between the interior of the hopper 12 and the interior of the line 28 emanating from the downstream end of valve 26 provides the driving force for the particulate coal particles when the ball valve 26 is open.After the pressure differential is established, as shown by monitoring gauge 23, the valve 26 is opened to admit coal to the downstream line 28. The coal flows rapidly (for example, at 2000 Ib/hr through a 3/8 inch line) towards the coal splitter 34; the splitter 34 then divides the constantly flowing coal particles evenly between the respective channels 40 in the coal splitter housing 36 (Figs. 2 and 3) towards the injector 54 via feed tubes 52 emanating from the base 41 of the splitter body 36. At the same time, heated hydrogen is admitted to the interior of the injector 54 through line 56; the hot hydrogen then passes through orifices 84 to impinge on the coal particles injected below the injector face 80 (fig. 4) to react within the reaction chamber 58.

Upon shutdown of the ball valve 26, a purge line 30 is activated, N2 being admitted below the valve 26 to clear line 28 from any residual coal particles that might be remaining. The inert gas simply cleans the passages in the line 28, coal splitter 34, injector 54, and into the interior of the reaction chamber 58 in preparation for subsequent operation of the hydrogenation process. An on-off valve 31 is provided within the line 30 to controI this line purge process.

Turning now to Figs. 2 and 3, the feed splitter device 34 consists of a body 36 which is welded or otherwise joined to the end of the coal feed line 28. Within the end of the coal feed line 28 is defined a chamber 38.

The body 36 has a generally conical shape.

Six divergent channels 40 are drilled through the body 36 from the base side 41 in such a manner that the axis of each of the channels intersects the centre line of the feed line 28.

The mouths of the channels 40 flare into machined, conical counter sinks whose axes B intersect the axes A of the channels 40. The counter sinks have a cone angle of about 30 and are all tangential at a central apex 42 and intersect along radial ridge lines 44. The entire upper surface of the body 36 is thus formed by the intersecting counter sinks and there are no blunt edges of ledges on which coal dust could accumulate and cause clogging. The apex 42 and ridge lines 44 divide the flow equally between the channels 40 and hence the feed tubes 52.

Turning now to Fig. 4, each of the coal feed lines 52 emanating from the base 41 of the body 36 leads towards the injector housing 54. The tops of the tubes 52 are welded into sockets 48 in the base 41 of the body 36. The feed tubes 52 lead into short vertical tubes 76 which pass through a top wall 72 of the injector housing and across a hydrogen plenum 74 to and through an injector plate 78. The hydrogen feed line 56 communicates with the chamber 74 to provide a source of hot hydrogen for the solid particulate coal. A series of inclined bores 84 is provided through the injector plate 78 around each coal feed tube 76, whereby jets of hydrogen are directed into the flow of coal dust. These bores may be two, or four per tube 76 depending upon the mixture ratio desired within the reaction chamber as 58.

An example of the value of dividing solids flow to multiple injectors has been demonstrated in a coal combustion experiment. In this application a six-element injection pattern was required to provide a very uniform mixing distribution in the combustion chamber.

A six-element splitter was used to provide equal fiowrate to each of the injection elements and the gaseous reactant in this case was pressurized air. Another related application planned for this feeding and dividing technique is for injection of "seed" materials (potassium or calcium compounds in powder form) into combustion chambers for magneto hydrodynamic generators. Again, the reason is to provide uniform distribution of the materials by injecting equal amounts at numerous locations.

During operation, as the coal is directed through the tubes 52 into the short tubes 76, the heated hydrogen is simultaneously fed in, thus directing hot hydrogen through the bores 84 into the reaction space 90 within the reaction chamber 58. The angle 86 determines the point of impingement 88 of the hot hydrogen on the coal particles ejected from the end 77 of the coal feed tube 76. Impingement, for example, may occur approximately one-half inch below the face 80 of the injector-plate 78.

Obviously, other types of injectors may be shown. For example, each of the coal feed tubes 76 could be surrounded by concentric opening in the injector-plate 78, whereby the hot hydrogen simply passes by the outer walls of the tubes 76 and intermingles with the coal particles downstream of the injector face 80 as explained in the specification of the aforementioned application 18085/77 (Serial No. 1582547).

WHAT WE CLAIM IS:- 1. Feed apparatus for particulate solids, comprising a feeder vessel having a sealable charging inlet for particulate solids, a gas inlet line connected to the vessel for introducing a gas into the vessel to establish an initial pressure in excess of that in an outlet feeder line, the outlet feeder line being connected at one end to a lower portion of the feeder vessel and at its other end to a conduit extending to a flow splitting device, and a valve connected between the outlet feeder line and the conduit, the arrangement being such that the valve can be opened when the initial pressure inside the vessel is sufficient to discharge the solids through the conduit and the flow splitting device at their bulk density.

2. Feed apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. bores 84 is provided through the injector plate 78 around each coal feed tube 76, whereby jets of hydrogen are directed into the flow of coal dust. These bores may be two, or four per tube 76 depending upon the mixture ratio desired within the reaction chamber as 58. An example of the value of dividing solids flow to multiple injectors has been demonstrated in a coal combustion experiment. In this application a six-element injection pattern was required to provide a very uniform mixing distribution in the combustion chamber. A six-element splitter was used to provide equal fiowrate to each of the injection elements and the gaseous reactant in this case was pressurized air. Another related application planned for this feeding and dividing technique is for injection of "seed" materials (potassium or calcium compounds in powder form) into combustion chambers for magneto hydrodynamic generators. Again, the reason is to provide uniform distribution of the materials by injecting equal amounts at numerous locations. During operation, as the coal is directed through the tubes 52 into the short tubes 76, the heated hydrogen is simultaneously fed in, thus directing hot hydrogen through the bores 84 into the reaction space 90 within the reaction chamber 58. The angle 86 determines the point of impingement 88 of the hot hydrogen on the coal particles ejected from the end 77 of the coal feed tube 76. Impingement, for example, may occur approximately one-half inch below the face 80 of the injector-plate 78. Obviously, other types of injectors may be shown. For example, each of the coal feed tubes 76 could be surrounded by concentric opening in the injector-plate 78, whereby the hot hydrogen simply passes by the outer walls of the tubes 76 and intermingles with the coal particles downstream of the injector face 80 as explained in the specification of the aforementioned application 18085/77 (Serial No. 1582547). WHAT WE CLAIM IS:-

1. Feed apparatus for particulate solids, comprising a feeder vessel having a sealable charging inlet for particulate solids, a gas inlet line connected to the vessel for introducing a gas into the vessel to establish an initial pressure in excess of that in an outlet feeder line, the outlet feeder line being connected at one end to a lower portion of the feeder vessel and at its other end to a conduit extending to a flow splitting device, and a valve connected between the outlet feeder line and the conduit, the arrangement being such that the valve can be opened when the initial pressure inside the vessel is sufficient to discharge the solids through the conduit and the flow splitting device at their bulk density.

2. Feed apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.