CA1094609A

CA1094609A - Apparatus and method for injecting particulate solid material into a pressurized process apparatus

Info

Publication number: CA1094609A
Application number: CA304,075A
Authority: CA
Inventors: Manfrd Rossbach; Adelbert Meyer; Harro Taubmann; Jurgen Stelter; Wilhelm Danguillier; Wolfgang Grams
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: 1981-01-27
Also published as: JPS549881A; ZA783006B; DE2723542A1; BR7803310A; IN150302B; AU521598B2; FR2392319A1; FR2392319B1; AU3649578A; GB1598169A

Abstract

SPECIFICATION
ABSTRACT OF THE DISCLOSURE

An apparatus for continuously feeding particulate solid material into a pressurized process apparatus such as a reactor, includes a pressurized storage vessel and a conduit connecting the storage vessel with the process apparatus.
controlled extracting mechanism, such as a helical screw conveyor, moves the material out of the storage vessel and through a first portion of the conduit. The material is moved through a second portion of the conduit utilizing a slowly flowing carrier gas. A rapidly flowing propellant gas is provided to move the material through a third portion of the conduit and blow the particulate material into the process apparatus.

Description

BACICG~OI~D C)F THE: INVENTl:ON

The presen~; i.nventioIl relates ~o an apparatus ~nd 15 met:~lod or continuously eedin~ particu];ate solid material in~o a pressu.~ized process apparai:~ls. In particular, tlle invention relates to SUCIl appaxatus ~herein the solid .
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material is contained in a prPssuxized sto~age vessel, having an internal pressure approximately ~he same as the process apparatus, and wherein the material is pneumatically con-` veyed from the storage vessel through a conduit into the S pressurized process app~ratus.
Equipment and methods of the type to which the present invention relate are useful for autoclaves, gas cleaning chambers, closed ladels wit~ melts, jet mills and other dust burners, and particularly to catal~tir apparatus 1~ operating with gases or liquids for coal gasification.
In contlnuous reactions between particles and vapors, ~he transfer rate between the gas filled space ana the surface and interstices of the particles has an incr~ased - in~luence on the xeaction rate ~or certain ranges of tempera~ure and pressure, and may even be the single dominan~ factor~
Cons~quently, to obtain goo~ process ~ield, it is desirable to have the best possi~le uniformity o~ distribution of the rea~en~s. In some cases, it is possible to select ~emperatures and pressures to control the trans~er rate and yield, for xeversable reactions. This type of control is applicable to gaseous catalysts and pressure gasification.
- High pressure process reactions present technical di~ficulties in uniformly feeding solid par-ticulate material.
In prior equipment, the particulatematerial has been sluxried with a liquid carrier and pumped into the reactor under pressure. I~ another arrangement, the matexial is wetted with ~ater and p~mped through a heating coil so that the water ~460~
vaporizes, and -the steam and particle mixture is driven into -the reactor by -the force of vapori~ation.
In German Pa~nt Application No. P 17 67 453.2 in the name Petrocarb, Inc, and published September 16, 1971 as Ofenlegungsschrit 1,767,453, there is disclosed an arran~ement for feeding finely ground coal into a high pressure reactor. According to that arrangement, the coal is initially introduced into an intermediate storage vessel under normal pressure. Thereafter, the vessel is closed and raised to a pressure which is higher than the reactor pressure and the coal is transferred through a feed line into the reactor.
A non-compressable means is provided in the storage vessel for compensating for the pressure loss caused by the transfer of the coal.
The prior devices, while having significan~
complexity, does not provide for precise control o~ the quantity of coal particles being provid~d to the rea~tor.
Such control i5 important to proper reactor operation without disturbances. A further problem with the prior device is that there exists the possibility of a blowbac~ oE reacto~
gases into the feed conduit in -the event of a pressure loss in the storage vessel~ Such a blowback can result in a dangerous ignition of ~he coal, or possibly a coal dust explosion~ ^
It is an object o~ the present invention to provide an inherently safe method and apparatus or the continuous ~eeding of particulate material in controlled quantity into a pressurized process apparatus.

235~5 SUM~R~ OF THE :[NVENTION
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In accordance with the invention, there is provided a method for continuously feeding particulate solid matexial ~rom a pressurized stora~e vessel into a pressuxized process apparatus over at least one conduit. The method comprises the steps of moving the matexial out of the ve~sel and through a first portion of the conduit utilizin~ a controllable extracting mechanism, ~o~in~ the materi~l through a second portion of the conduit utilizin~ a slo~ly flo~ing carrier ~as, and moving the material through a third portion ~ the conduit and ~lowing the particulate materi~l into the process apparatus by means of a rapi~ly f~owing propeIlan~ ~as~
The method may also include mea.suri.ng the quantity of the material flo~ing thxough the third conduit por.tion and contxolling the speed of the extracting mech~nism in accordance ~ith the measured quantity~ The material quantity may be measured by determi~ing the pxessure diffe.rence of the propellant gas arising out of the solid material flow.
The carrier gas used in the second conduit portion may be different than the propellant gas used in the third conduit portion. In such cases, the carrier gas may be the same ~as ~hich is used to pressuxize the storage vessel, and the propellant gas may ~e a gaseous product of the pxo~ess apparatus. The solid material may ~low through the secolld conduit portion at a velocity of ~.5 to 1~ m~sec J preferably 0.5 to 4 m/sec. The solid ma~erial may f~.ow through the third conduit portion at a velocity of 12 tQ 25 m~sec, preferably 12 to 20 m/sec~. .

235~5 In accordance wi~h the invention, there is also provided an apparatus fo~ carrying out the method of the invention and continuously supplying particulate solid ma-terial into a pressurized process appaxatus. ~he apparatus of the invention includes a conduit having a first portion con nected to the storage vessel, a third portion connected to ~he process apparatus and a second portion interconnectiny the first and third conduit portions. Ext~acting means a~e provided in the irst por~ion for movin~ the $olid material from ~he vessel and through the first conduit portion. T~e second portion is provided with means for supplyin~ carrier gas to mo~e the material therethrough~ and the thixd conduit portion is provided ~ith means for supplying a propellant gas to propel the material through the third portion and into the lS process apparatus.
The controllahle extracting means may include a helical screw conveyor~ The means for providing propellant gas prPferably consists of mixing nozzlPs fox mixing the soli~ particulate material with the propellant ~as.
Typ~cally~ there may be provided more than one conduit connecting the storage vessel with the pressurized pxocess apparatus.
The apparatus of the invention may be provided with - a plurality of switchable controllable valves to control the flow of pressurized gas to the storage vessel, and the s~cond and third condui~ portions, and there may also be pro-vided an interm~diate vessel for supplying material to the pressurized storage vessel~ The intermediate vessel may ~e .-5 ~

235~5 j0~ -periodically pressurized.using the controlled valves to permit the flow of matexial into the stora~e vessel~
The third conduit portion may be provided with an apparatus for measuxing the quantity of material ~low into the process apparatus. The quantity may be used.for regulating the operation of the controlled extracting mechanism. The extracting mechanism may include a va~iable speed motor, the speed of which is regulated by use of an amplifier which is responsive to a signal representative of the measured material quantity.
In one arrangemen~, a storage bin for solid material is arranged over an intermediate vessel, ~hich is axranged over the pressurized storage vessel. Slide valves are arrange~ be-tween the bin, the in~ermediate vessel ~nd the storage vessel for controlling the flo~ of ~aterial from th.e storage bin into the storage vessel. Th.e p~essurized storage vessel and intermediate vessel may ~e provided ~ith gauges ~or detecting the level of material in each of the essels. The intermediate vessel.may be provided with a ~ ~ilter for permitting the release of internal gas pressuxe so ~hat materi~l can be permitted to flow from the bin lnto - the intexmediate vessel~
In one arxan~ement, the extracting mechanism may comprise a helic~l screw conveyor mounted on a vertical ~S ~ha~t, which passes through the pressurized stora~e vessel ~nd is provided with stirring elem~nts fox mixing the material in the vessel.

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?~35~5 The arran~ment of the storage vessel, the intermediate vessel and ~he storage bin may be mounted on a pressure sensor and provided with flexi~lP condui~s so that the total weight of the vessel, bin and material can be determined, and material supplied to the bin as required.
In accordance with the invention, it is possible to blow a finely ground solid, ~or example~ coal dust, continuously and at a control rate into a reactor operating under high pressure and wherein the coal is gasi~ied in the presence of oxygen and w~ter vap~r at high temperature~ The extracting mechanism in the first portion of the conduit between the pressuri~ed storage vessel and the pressurized process apparatus prevents the irxegular discharge of particles from the storage vessel and ~lso permits c~ntrol of the rate at which the material is delivexed to the process apparatus b~ control of the operating speed of the extracting mechanism. In the second portion of the conduit, ~hich consists of the ma~or lenyth of the conduit/ the m~terial is ccnveyed as a densely packed mass mixed with a small quantity of carrier gas which moves the particulate m~terial and serVes as a lubricant. The carrier gas reduces the ab~asion of ~he particulate material on the inside ~all o~ the conduit.
The high density of the material in the second portion of the conduit prevents khe xeverse fl~w of propellant gases from the third portion of the condult back in th~ direction of the pressuxi~ed storage vessel. In the third conduit portion, the propellant gas largely dilutes the ~low of particulate material and provides a relatively uniform ~35~5 flow o~ propellant gas and ma~erial which enters the process apparatus or re~ctor at high velocity and with even distributi.on, resulting in turbulen~ flow into the - reactor to promote a con~inuous runniny ~eaction~
The gases used for pressurizing the storage vessel, as a carrier in ~he second conduit portion, and as a pro-pellant in the third conduit portion ~ay be a ~ariety of well known gases or vapors, provided the ~ases can either -take part in the proGess apparatus reaction or xemain inert to it. Gases which result as a product o~ ~h.e appaxatus reaction may be ~ecirculated as carrier or propellant gases.
It is appropriate in some cases to use different ~ases as carrier gas and propellant gas. . The carrier gas - is suitably the same ~as which is used to pressurize the intermediate storage ~essel~ The propellant gas is p~ovided in.much larger ~uantities and ~lows continuously into the process apparatus and is therefore advankageousl.y a gas which ~ould ordinarily be supplied to the process apparatus, for example, oxygen or water vapor in a coal gasification process.
In ordex to measure the quantity of material flow in the third conduit portion, it is possible to measure the ~ensi.ty of the propellant gas and parti.culate material 10w ~y the use of radiation, by measurement of capacitance chan~e, or by similar devices. Since the flow throug~l the third conduit.portion is at high velocity and high pressure, ik is preferable to measure the quant.ity of material 10w by ~.he diference in pr~ssure between the particle laden propellant gas flow as compared to a pure propellant gas flow, This 235~5 ~easurement can provide an electric~l signal which can be used to control the rate of material flow from the pressuri~ed storage vessel, and can also be used to xegulate the flow of carrier and propellant gas, Measurement of the rate of material flow in the second conduit por~ion is less reliable because the dense packing of the material can result in intermitten~ material movement and conse~uently errati~
measurement of material flow.
For ~ better understanding of the invention, toge~her with other and further objects, reference is made to the follow~ ng description, taken in conjunction with the accompanying dra~ing and its scope will be~pointed out in the appended claims.

B~IEF DRSCRIPTIO~ C7 Tll~ Dl~lilO

15 The drawing illustrates a material feed apparatus in accordance with the present invention.

DESCRIPTION OF THE INVENTION

As an example o an embodiment o~ the invention, the drawing shows a reactor 2 ~or coal gasification under pressure. The reastor is supplied with ~i~ely ground coal, oxygen or air, and water vapor and operates at a pressure of appxoximately 25 bar, and at temp~ratuxes between 1~00 and 2400~ C. Synthesis gas produced in reactor 2 is wi.th-~rawn through outlet line 5. Residual ~Jaste matexial in the form of slag flows from the reactor through lower outlet .4.
Pre~erably the reactox 2 is of the molten slag type in ~.~hich ~he high turbulent xeaction ;.s conducted in multiple phases above a molten slag surface.

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Finely ground coal havin~ 2g~ residual humidity, which is to be gasifled is pneumatically introduced using an inert gas from a drying and grinding unit into storage - bin 7. Storage bin 7 is mounted on top of an intermediate vessel 6, which in turn is mounted on top of a pressurized storage vessel 1. The entire assembly of the vessels 1l 6, and 7 are mounted on pressure detec~crs 29 and flexibly connected to the remaining components of the system so that by a reading o~ pressure detectors ~ it is possible to determine the ~uantity of material contained in the stoxage bin and vessels 1 and 6. Le~el detectoxs 9' and 9" are provided in vessels 1 and 6 for monitoring the ~uantity of material contained in these vessels and there~y controlling ; the steps fox recharging o~ these vessels as ~ill be described, 15- Flexible bellows are provided connecting bin 7 ~ith ~essel 6 and vessel 6 ~ith vessel 1.
Storage vessel 1 is continuously pressuxlzed at to 32 bar~ Pxessuri~ation may be by the use of ~s ~ithdrawn from the rQactor 2 or by another appropriatel~
selected gas. There are provided four conduits lQ leading from the base of vessel 1 to re~ctor 2 of which three are partially illustrated and only one is completel~ ustrated for simplicity of the dra~ing. Each conduit 10 is divided intro three conduit portions. In the first portion 11 o~

~5 ea~h ~onduit lQ, there is provided a helical conveying screw 16 which is driven by shaft 17 and motor lB~ Screws 16 axe pxeferably ~ounted in a vertical orien~ation as illustrated so that stirrers 19 may be mounted on the upper poxtion of ~10- .

23~5 the extended shaft to stir the rnaterial and ensure the continuous flow of particulate ma~erial from storage vessel l into the first por~ion ll of conduit 10~ There may be provided a pressure equalizer line with a back pressure valve between COl~Uit 10 and storage vessel l to prevent the.reverse flow of the particulate material over conveying screws 16. The pitch and clearance of th~
screws 16 can be selected to prevent the ree flow of particles from vessel 1 into conduit lO and will thereby effectively separate vessel l from the second portion 12 of '~ ~he conduit which re~ei~7es additional carxier ~as, Discharge of material from vessel l into the condui.t is continuously effected by screws 16~ By variation of the speed of driving motors 18l there is lS provided a variable control o~er the amount of particulate .material which is 10wing lnto the conduit and thereby the amount flowing into reactor 2. Since vessel l is continuously pressurized there is no di~ferential pressure to be o~7erc~me by screws 16 in moving particulate material into the conduit~
~0 In the second conduit portion 12, the InoYerQent of particulate material is aided ~y the addition of a carrier gas through lines 22 into ~ach of the conduits~ In the second conduit portion 12, the 10w of material is in the form of a densely packed particle flow moving at a velocity of 0~5 to lO m/sec, preferably in the range of 0~5 to 4 mJsec. The ratio between the transferred coal dust and the carrier gas is approximately lO0 to l, corresponding to a ~7ery densPly packed flow. In the illustrated embodiment of the invention, `9~ 9 .

the carrieL gas supplied over line 22 to the second conduit p4rtion is the same gas as is provided for pressurizing storage vessel 1 by pressure line 21"~ The use o the ident.ical gas prevents the reverse flow vf gas through first conduit portion 11 into vessel 1 and also prevents the undesired mixture of different gases.
In the third conduit portion 14~ the flow o~

particulate ma~erial is under the influence of a propellant L~
gas which is injected into mixing ~e ~ ~ 2~ from line 23 ... ..
The propellant gas is introduced with suf~icient speed and sufficient quantity to bring about a loosenin~ and thinning of the densely packed particulate flow so that the coal dust is blown in finely divided particles into reactor 2 and all c~al particle surfaces are available to take part in the reaction. The quantity of propellant gas provided lowers the ratio o~ coal dust to gas to approximately 20 to l and causes an increase in the flow v`elocity of the material to 1~ to ~5 m~sec, preferably 12 tc 20 m/sec. The high injection ~elocity of the flow into the reactor will create a turbulence 2Q in the molten slag bath and.'cause rapid heating of the ~reshl~ introduced particles~
Sensor 25 monitors the flow o material ~.:hrough the third condui~ portion into the reactor~ ~ de~iation from the p~escribed rate of material 10w will provide an error signal, which is amplified by amplifier ~ and us~d to control the rate of operation o~ motor 18 to bring the rate o~ material flow within prescribed limits. As previously mentioned, the high veloc~ty of the stream ;n the thixd conduit portion 235~5 makes it advantageous to measure material flo~ by differential pressure. Gas volu~es and velocities may also be measured at various po~tions of the system by gas measuring devices.
The total amount of gas in~roduced by lines 22 and 23 should be kept constant by the use of control valves 27~
While the flow of material from pressurized storage vessel l over conduit lO is continuous, recharging o~ vessel l occurs stepwise. Prior to rechar~ing the gas in pressuri~ed intermediate vessel 6 i5 exhausted through 10 ~ filter -~ with valves 8' and 8" closed~ Gas receiving ~ ,=., vessel 30 may be used for storing the gas which is exhausted from vessel 6 in the recharging process~ When intermediate vessel is depressurized, slide valve 8 t can be opened and - ~essel 6 is charyed with material frGm bin 7 to the level regulated by d~ector 9'. Slide valve 8 is then closed and intermediate vessel 6 can be pressurized by gas from line 212 o When gauge 911 detects that more material is required in pressurized vessel l, slide valve ~" is opened and the charge of material will flow from vessel 6 into vessel lc The material feeding arrangement according to the invention, in addition ~o providin~ control of feedin~
rate, can also provide the recirculatio~ of a portlo~ of the reaction gases, Further, the arrangement provides sa~ety against the reverse ~low of reaction gases into the storage vessel. This is prevented by the densely packed ma-terial in conduit portions ll and 12, which is held against reverse flow b~ screw conveyor 16, In the event of a disturbance in the pressurization of storage vessel l, for example by the .

23rj~

iladvertent o-ening ~f slide va~ve R", the blowback oi reaction gases into the storage vessel is prevented.
While there has been described what is helieved . to be the preferred embodiment of the invention~ those S skilled in the art will recognize that other and fur~her - modifications may be made thereto without departing from the spirit of the invention, and it is intended -to claim all such embodimer~s as fall within the true scope of the invention~

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for continuously feeding particulate solid material from a pressurized storage vessel into a pressurized process apparatus through at least one conduit comprising the steps of moving said material out of said vessel and through a first portion of said conduit in a dense current preventing reverse flow of said material utilizing a controllable extracting mechanism, moving said material through a second portion of said conduit utilizing a slowly flowing carrier gas and moving said material through a third portion of said conduit and blowing said particulate material into said process apparatus by means of a rapidly flowing propellant gas.

2. A method as specified in claim 1 further comprising the steps of monitoring the quantity of said material flowing through said third portion and controlling the speed of said controllable extracting mechanism in accordance with said quantity.

3. A method as specified in claim 2 wherein said step of monitoring said quantity comprises the step of measuring the pressure drop arising out of the flow of said solids.

4. A method as specified in claim 1, wherein said carrier gas is different from said propellant gas.

5. A method as specified in claim 4 wherein said carrier gas is used to pressurize said vessel and wherein said propellant gas comprises a gaseous product produced in said process apparatus.

6. A method as specified in claim 1 wherein said solid material flows through said second portion at a velocity of 0.5 to 10 m/sec.

7. A method as specified in claim 6 wherein said solid material flows through said second portion at a velocity of 0.5 to 4 m/sec.

8. A method as specified in claim 1 wherein said solid material flows through said third portion at a velocity of 12 to 25 m/sec.

9. A method as specified in claim 8 wherein said solid material flows through said third portion at a velocity of 12 to 20 m/sec.

10. Apparatus for continuously supplying particulate solid material into a pressurized process apparatus from a pressurized storage vessel comprising a conduit having a first conduit portion connected to said storage vessel, a third conduit portion connected to said process apparatus and a second conduit portion interconnecting said first and third portions, extracting means including means for preventing reverse flow of said material, having a controllable rate, for moving said material from said vessel and through said first conduit portion, means for supplying a carrier gas to said second conduit portion to move said material there-through and means for supplying a propellant gas to said third conduit portion to propel said material through said portion and into said apparatus.

11. Apparatus as specified in claim 10 wherein the said extracting means comprises a helical screw conveyor.

12. Apparatus as specified in claim 10 wherein said means for supplying a propellant gas comprises a mixing nozzle for mixing said gas and said particulate material.

13. Apparatus as specified in claim 10 wherein there are provided a plurality of said conduits.

14. Apparatus as specified in claim 10 wherein there are provided means for supplying said carrier gas and said propellant gas, said supplying means including valves for controlling the quantity of supplied gas.

15. Apparatus as specified in claim 10 wherein said third conduit portion further includes means for measuring the rate of material flow through said portion, and wherein there are provided control means responsive to said rate of material flow for controlling the rate of said extracting means.

16. Apparatus as specified in claim 15 wherein said control means includes an amplifier and wherein said extracting means includes a variable speed motor responsive to the output of said amplifier.

17. Apparatus as specified in claim 10 wherein there is further provided an intermediate storage vessel connected to said pressurized storage vessel by a slide valve and a storage bin connected to said intermediate storage vessel by a slide valve.

18. Apparatus as specified in claim 17 wherein said storage vessel and said intermediate storage vessel are provided with level gauges.

19. Apparatus as specified in claim 17 wherein said intermediate storage vessel is provided with means for controlling the gas pressure within said vessel, including control valves for connecting the interior of said vessel to a gas reservoir and a gas supply line.

20. Apparatus as specified in claim 17 wherein said storage vessel, said intermediate storage vessel and said bin are moveably mounted together on pressure detectors.

21. Apparatus as specified in claim 10 wherein said extracting means includes a screw conveyor in said first conduit portion, said conveyor having a shaft extending into said pressurized storage vessel, and wherein said shaft includes stirring arms for stirring the material in said vessel.

22. A method as specified in claim 1 wherein said storage vessel is at a greater pressure than said reactor.

23. A method as specified in claim 22 wherein said storage vessel is at a pressure of approximately 28 to 32 bar and wherein said reactor is at a pressure of approximately 25 bar.