AU603162B2 - Process for injecting, by pneumatic means, metered quantities of pulverulent material into a chamber which is under variable pressure - Google Patents

Description

1 2 5 1 1 ZAXMA IdON IH Id a1 1 .11 I I I II I I I I I I I I T i f T i i i i I i -i 162 Australia Form PATENTS ACT 1952 COMPLETE SPECIFICATION (FOR iilNAL) FOR OFFICE USE Short Title: Int. CI: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: lit Priority: iv; 3 ii

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~unr3PR' elated Art: Related Art: TO BE COMPLETED BY APPLICANT PAUL WURTH S.A. Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: 32 rue d'Alsace, L-1122 Luxembourg, Grand Duchy of Luxembourg.

LOUIS SCHMIT, RADOMIR ANDONOV and HANS-KLAUS SCHOTT.

CALLINANS Patent Attorneys, of 48-50 Bridge Road, Richmond, State of Victoria, Australia.

Complete Specification MEANS, METERED UNDER VARIABLE for the invention entitled: "PROCESS FOR INJECTING, BY PNEUMATIC QUANTITIES OF PULVERULENT MATERIAL INTO A CHAMBER WHICa IS

PRESSURE".

The following statement is a full description of this invention, including the best method of performing it known to me:-' SNote: The description is to be typed in double spacing, pica type face, in an area not exceeding 250 mm in depth and 160 mm in width, on tough white paper of good quality and it is to be inserted inside this form.

i_ i i 1A- Process for injecting, by pneumatic means, metered quantities of puLveruLent material into a chamber which is under variable pressure The present invention relates to a process for injecting, by pneumatic means, metered quantities of pulveruLent material at different points -~na chamber which is under variable pressure, according to which a pneumatic mixture comprising a relatively high content of pulverulent material in a propellent gas is formed in a single metering device and this mixture is propelled through a common primary conduit as far as a distribution head in which the mixture is divided into secondary currents which are each sent through secondary conduits 15 to one of the injection points.

The invention will be described more particularly with reference to its preferred application, while not being limited to it, this preferred application being the injection of solid combustible materials, especially 20 oowdered coal, into an industrial furnace such as a blast furnace.

94 9e B 9 *o 999.

0e 99 9 94 9 t *1 .o The known processes and installations for injecting solid combustible materials into a shaft-furnace are classified essentially into two different types. The first 25 functions with relatively "dilute" pneumatic currents, whereas in the second the pneumatic currents have a relatively high concentration of powdered coal.

In installations of the first type, with a dilute current, the powdered coal is released under pressure from a distribution hopper into a series of metering apparatus@e-, in which the mixture of powdered coal and proPLIc'nt propelle.ti. gases is formed, and from which the mixture thus formed is conveyed towards the injection points in the shaft-furnace. In these installations, one metering apparatus is generally used for each pipe or for each pair of pipes, with the result that the quantities injected through the pipes can be metered individually.

A The metering apparatuses used are of a type known per se, i n

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M 1< I .I U I V 2 for example metering apparatuse- with aLveoLar rotors or slotted metering apparatuses such as those proposed in European Patent Application No. 0,126,917. These instaLLations have the disadvantage that they require a Large number of reLativeLy long conduits between the distribution hopper and the shaft-furnace. In addition, metering can be made difficuLt by the different variabLe parameters, especiaLLy the fLuctuations in pressure inside the furnace.

In the second type of instaLL.ation, which empLoys pneumatic currents of high concentration, only a singLe metering device is used, at or downstream of the distribu- ,0 tion hopper. In this metering apparatus, the totaL fLow t of the powdered coaL is reguLated so that a predetermined 15 quantity of powdered coaL is injected per unit time.

These instaLLations empLoy the process described in the introduction, i.e. the metered current containing the necessary quantity of coaL is divided, in a distribution head, into secondary currents which are identicaL to one 20 another. These instaLLations have the advantage that the I H. distribution head is placed in the immediate proximity of the furnace, so that the Length of the secondary conduits, Sand consequentLy the congestion around the furnace, are I reduced. In these instaLLations, there is furthermore pro- 0 25 vided either in the secondary conduits or in the distribution head a throttle section where a drop in pressure necessary for the pneumatic current to accelerate up to the speed of sound is brought about. The acceleration of the pneumatic current up to the speed of sound has the advantage that the flow conditions upstream of the Location where the supercritical speed is produced are no longer influenced by the flow conditions downstream of this location. Of course, this gives the great advantage that fluctuations in pressure and other variable parameters within the chamber into which the pulverulent material is injected no longer need to be taken into account. Compared with the first type of installation, the installations working with concentrated current of the type described above i r i _II_ -3- 4

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have the disadvantage that it is no longer possible to r, ,ulate the flow in each pipe individually.

The present invention seeks to provide a process of the type described in the introduction, which combines the advantages of the two known processes.

To achieve this aim, the invention provides an injection process, of the type described in the introduction, wherein the flowrate of the pneumatic means is regulated in each of the secondary conduits, said regulation being carried out at a variable throttle section in which the acceleration of the current up to supercritical speed is also brought about.

G The regulation can be carried out manually, or automatically under the control of flowrate detectors provided in each of the secondary conduits.

A preferred embodiment will be described below by way of example, with reference to the single figure which shows, very schematically, a circuit for the pneumatic injection of combustible materials into a shaft-furnace. The pneumatic mixture, consisting of powdered coal and propellant gas, and whose flowrate corresponds to the quantity of coal needed per unit time by the shafta t furnace, is formed in a primary conduit 10 with the aid of a metering device 12, which may be a metering apparatus of the type having mobile slots, or a hopper with pneumatic metering or another type. In this metering apparatus 12 there is formed a pneumatic mixture with a high concentration of coal, which may if necessary be diluted by the addition of a variable quantity of inert gas injected through a conduit 14 upstream of the distributor. This pneumatic mixture is sent to a distribution head 16 of the type recommended in Australian Patent No. 587046. In this distribution head 16, the primary pneumatic current is divided into secondary currents which are each sent through secondary conduits to one of the tuyeres 22 of a blast furnace (not shown).

C EA 4 The number of secondary conduits 18 may, for example, correspond to the number of pipes or to haLf the number of pipes.

In accordance with the present invention, there is provided in each of the secondary conduits 18 a throttle 20 of variable section. This throttle is preferabLy constructed with a valve of the type recommended by L haxembourglPatent Application No. 3 1, i.e. a valve of which the passage is defined by the rotation of a mobile socket inside a fixed socket, the two sockets being provided with openings and slots which can more or Less overlap to give a larger or smaller passage. The acceleration of the secondary pneumatic currents is preferably carried out at the throttles 15 The process according to the present invention thus has all the advantages of the system of injection *0 at the speed of sound, i.e. the secondary conduits can be as short as possible in order to reduce congestion around the furnace. Moreover, the metering conditions 20 at the metering apparatus "2 are not affected by fluctuao* tions in pressure downstream of the throttles 0o. especially fluctuations in pressure in the shaft-furnace.

t The valves 20 can be regulated manually in order to take into account conditions in the furnace. The o 25 flowrates through the different secondary conduits 18 are thus established as a function of the openings at the throttles 20, whereas the total quantity of coal injected per unit time is determined by the metering apparatus 12.

The function of the distributor 16 is thus different to that of the distributor proposed in if ir-fO'ai on 5'8-704 L.u c b-e. m bou--Patent cpptc i Whereas, in the latter, the distributor did indeed have a f.unction of distribution, this was also of uniform distribution, i.e.

a division such that the same flowrate of coal circulates in each of the secondary conduits. In contrast, in the process according to the present invention the distributor 16 simply serves to divide the primary current into secondary f currents, the flowrates of which are variable as a iOx 5 function of the variable sections of the throttles It is also possible to measure the flowrate of coal in each of the secondary conduits 18 and to regulate the section of passage of the valves 20 automatically, so that there is an injection flowrate determined at each JtuyPare.

of the p-i-p-es 2. This automatic regulation allows disturbing factors such as, for example, partial obstruction of the secondary conduits 18 or of the passages in the distributor 16 to be compensated or eliminated.

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Claims (4)

1. The process for injecting, by pneumatic means, metered quantities of pulverulent material at different points into a chamber which is under variable pressure, according to which a pneumatic mixture comprising a relatively high content of pulverulent material in a propellent gas is formed in a single metering device and this mixture is propelled through a common primary conduit as far as a distribution head in which the mixture is divided into secondary currents which are each sent through secondary conduits to one of the injection points, wherein the flow rate of said pneumatic means is regulated in each of said secondary conduits, said regulation being carried out at a variable throttle section in each of said secondary conduits. 00 0

2. The process according to claim 1, wherein the pressure at said vaibethrottle sections is decreased to the extent required to accelerate the current up to the speed of sound.

3. The process according to claim 1 or claim 2, wherein said regulation is carried out manually.

4. The process according to claim 1 or claim 2, wherein said regulation is carried out automatically under the control of flowrate detectors provided in each of the secondary conduits. A process as claimed in claim 1, substantially as described herein with reference to the accompanying drawings. DATED the 15th day of August, 1990 PAUL WURTH S.A. by their Patent Attorneys CALLINAN LAWRIE k 0-