WO1991008991A1

WO1991008991A1 - Process and apparatus for burning blanks in continuous passage

Info

Publication number: WO1991008991A1
Application number: PCT/US1990/007207
Authority: WO
Inventors: Horst J. Feist
Original assignee: Ucar Carbon Technology Corporation
Priority date: 1989-12-15
Filing date: 1990-12-13
Publication date: 1991-06-27
Also published as: CA2049061A1; BR9007121A; EP0463131A1; CN1053289A; JPH04505443A; AU7036891A; KR920701075A; PL288302A1

Abstract

For burning electrode blanks, the latter pass in coaxial succeeding manner through a burning section and hot gas flows round them. This hot gas flow is segmentally regulated along the burning section. From the actual and desired values of this flow regulation is derived a control quantity for the fuel supply, which is used for heating with fresh hot gas the hot gas conveyed in the circuit, accompanied by the simultaneous burning of its charge of combustible constituents, this taking place stoichiometrically in such a way that no harmful oxygen is present in the fresh hot gas.

Description

PROCESS AND APPARATUS FOR BURNING BLANKS IN CONTINUOUS PASSAGE

The invention relates to a process for burning blanks in th continuous passage of a burning section by having a substan tially oxygen-free hot gas flow around the same and which i supplied as a function of the combustion temperature in do¬ sed manner along the burning or combustion section and is returned to the heating means as spent or waste hot gas and accompanied by the combustion of the combustible charge ta¬ ken up on the burning section and accompanied by air and fu el supply heating occurs and it is worked up to form a sub¬ stantially oxygen-free, fresh hot gas, in that the air sup¬ ply for the combustion is regulated as a function of the oxygen content of the fresh hot gas to a stoichiometric, mi nimum desired value and then the fresh hot gas is again sup plied to the combustion section and the flow of hot gas through said section is segmentally regulated as a function of the hot gas temperature in the particular segment in ac¬ cordance with predetermined desired values and an apparatus using said process.

The term blanks is here understood to mean in particular electrode blanks intended for graphitization, which contain carbon in the form of petroleum coke, metallurgical coke, graphite, etc., with a binder which, as e.g. in the case of pitch, becomes volatile in the presence of heat and whose volatile constituents are combustible.

A process of this kind is described within the elder but no yet published European patent application No. 89111262.5.

On flowing round the blanks during such a process the hot gas takes up volatile constituents, as e.g. pitch, as the charge and the latter is then con-comitantly burnt during reheating, which saves fuel. Charging of the environment will be reduced due to the fact that spent or waste hot gas will not be blown untreated into the open air.

The fuel supply can be controlled as a function of the fresh hot gas temperature. However, this requires the supply of energy in excess to ensure that the needs are met at all times.

With a view to an optimum uniform combustion or burning ope¬ ration and the sparing use of fuel, the problem of the in¬ vention is to better adapt the fuel supply to needs.

This problem is solved in that the actual and desired values of the process quantities for the segmental flow regulation are linked with one another to form a control quantity for the fuel supply.

Therefore the fuel supply is controlled in accordance with the needs established in the individual combustion segments and which is expressed by the temperature there and this oc¬ curs in an optimum updated manner, without a significant ad¬ ditional expenditure being required.

It is merely necessary to supply the actual and desired values, which are in any case present for local control purposes, to a central computer and correspondingly link them together and the resulting control quantity is then supplied to a control component or the control unit for the fuel supply. This link or combination is appropriately brought about in such a way that for the individual combu¬ stion segments an energy deficiency or excess is calculated from the measured temperature and hot gas throughput and the fuel supply is readjusted in accordance with the overall energy excess or deficiency determined by addition for the different combustion segments, in such a way that there is a decrease for an energy excess and an increase for an energy deficiency.

The computer provided can be used to facilitate operation and control in other ways, in that the actual and desired values of process quantities and/or other measured values are centrally stored and prepared to provide an updated, historical, trend-caused or malfunction-caused indication and/or control quantity.

Individual selected actual, desired or measured values or all these values can be centrally stored and processed. The indication or display can take place in tabular form, but preferably within a stylized displayed picture of a plant for performing the process, the values in question being di¬ splayed at the spatially associated point of the plant pic¬ ture or image.

Such a central computer can also be used for centrally con¬ trolling in the preset details of the desired values for the process quantities. Such a central controlling in can be provided alongside a local controlling in possibility posi¬ tioned at the location of the particular control unit.

In order to protect the blanks, it is important in many use cases that the fresh hot gas is substantially oxygen-free. Account can be taken of this during combustion, in that the air supply during combustion is correspondignly stoichiome- trically adjusted. If the consumed hot gases are charged with combustzible fractions, e.g. binder fractions, the com bustion not only takes place in the original flame supplied by fuel from the outside, but following on to the same, so that a volume combustion occurs, where the remaining hot ga charge is burnt. In order to maintain this volume combustion, it is necessary to have oxygen and maintain a specific minimum temperature, which can be produced by an external enclosure or insulation.

If a complete combustion is required on one side and on the other oxygen-free, fresh hot gas, then the setting of the conditions under which burning or combustion takes place is critical.

An optimum solution of this problem is characterized in that a complete stoichiometric combustion of the supplied fuel, including the charge which has taken up the old hot gas, and an oxygen-free, fresh hot gas is controlled, in that a first supply takes place in a stoichiometrically predetermined dependence on the fuel supply in the new flame area for hea¬ ting purposes and in that a second air supply takes place as a function of the hot gas content of oxygen and/or incomple¬ tely burnt carbon compounds in a volume combustion area for¬ med immediately following on to the new flame area.

If the second air supply is controlled as a function of the oxygen measurement, then it is advantageous that on excee¬ ding a predetermined tolerance quantity for the oxygen con¬ tent in the fresh hot gas and preferably in the case of a predetermined tolerance quantity of 0.3%, the second air supply is reduced.

Instead of this or in addition thereto for the same purpose oxygen can be supplied to the hot gas following on to the flame area in order to burn the excess oxygen.

If the second air supply is regulated as afunction of the unburnt carbon compounds, then it is advantageous that on dropping below a predetermined tolerance quantity for the CO-content in the fesh hot gas and preferably at a predeter- mined tolerance quantity of 0.1%, for the second air supply to be reduced.

It is possible to combine these two dependences of the oxy¬ gen content and the CO-content. What is of an optimum natur and should be sought is for the fresh hot gas to obtain no carbon and no oxygen. The oxygen is appropriately supplied in the form of fresh air.

The necessary constant supply of oxygen or fresh air leads to a hot gas excess, which must be compensated by blowing off into the open. This should take place with maximum pro¬ tection to the environment and account of this is taken in further development of the invention, which is characterize in that the hot gas circuit is sealed to the outside in pressure-tigth manner and is constantly driven and that par of the fresh hot gas is blown off into the open, regulated as a function of the pressure of the fresh hot gas, measure at a measuring point, which provides valid information for an extreme pressure value in the hot gas circuit outside th combustion means.

The hot gas let off into the open can be filtered in a filter, or purified in a combustion chamber or catalyst, so as to avoid unnecessary contamination of the atmosphere.

This brings about the necessary compensation or balance by blowing off fresh hot gas which, due to the preceding combustion, no longer contains any charge prejudicial to th environment.

Air with its oxygen is only harmful if said oxygen reaches the blanks. However, this is not possible with this oxygen if it penetrates the returned spent or waste hot gas, becau se said oxygen is then burnt during the subsequent combusti on process before it can harmfully reach the blanks.

For this purpose it is possible to determine at which point in the critical area the lowest pressure forms during opera¬ tion and how high the pressure measured in the fresh hot gas flow must be in order not to drop below this critical mini¬ mum pressure. In place of this, it is also possible to pro¬ vide additional pressure measurements at critical points and to control these in correspondingly when determining the control quantity for the blowing off of hot gas.

If it is wished to protect the blanks agains undesired oxy¬ gen contact, it is advantageous to block off external air access to the fresh hot gas and into the .hot gas flowing round the blanks, in that by pressure regulation in that part of the hot gas circuit in which the fresh hot gas flows or flows round the fuel elements, an overpressure of min. 0.5 to 20 mm w.g. (millimeters water gauge), preferably 5 mm w.g. is maintained.

In such a case it is advantageous for the fresh hot gas pro¬ portion which is blown off into the open is regulated as afunction of the pressure of the fresh hot gas upstream of the flow round the blanks. Experience has shown that this pressure provides valid information for the lowest pressure occuring in the critical area. If the pressure upstream of the flow round the blanks is kept at a predetermined value, it should be certain that throughput the critical area there is no drop below the desired minimum overpressure at any point.

If it is wished to avoid waste hot gas reaching the environment, it is advantageous to avoid any discharge of charged hot gas, in that a vacuum of -0.5 to -20 mm w.g., preferably -5 mm w.g. is maintained in that part of the hot gas circuit, in which the gas flows round the blanks and/or in that part of the hot gas circuit in which the waste hot gas is returned from the combustion pipe to the heating means.

The two set problems of not allowing oxygen to reach the blanks and of not allowing any charge to pass into the atmosphere, are in competition with one another and in cer¬ tain circumstances cannot both be fulfilled in optimum man¬ ner side by side. In this case with critical blanks prece¬ dence is given to keeping the oxygen away from the blanks.

Based on the combustion section length, it is desirable to maintain a predetermined temperature path or gradient in the hot gas flowing round the blanks. This is brought about by the segmental flow-through on the basis of predetermined, temperature-dependent desired values. However, preferably the individual segments communicate with one another.

The problem of a further development is in simple manner to maintain in precise form a predetermined temperature gra¬ dient along the combustion section.

This problem is solved in that distributed over the length of the combustion section there are several fresh hot gas flows to the blanks which can be individually regulated with regards to the throughput volume, that, based on the length of the combustion section, between in each case two inflow points there is an outflow line for the spent hot gas which is adjustable with regards to the throughput volume and that the regulation of the hot gas throughput of the fresh hot gas flows takes place as a function of the temperature mea¬ sured in the hot gas flow on the blank side facing the hot gas supply line opening. The arrangement of the temperature measuring point on the opposite side of the blank ensures that the latter is not exposed to the direct temperature influence of the new in¬ flowing hot gas and instead of this an average temperature is measured wuch as occurs in the particular segment.

Such a segment need not necessarily extend to the two next adjacent discharge lines. It can in fact extent further, in that one or other discharge line is shut off or in that one or other supply line is supplied with particularly lager fresh hot gas quantities, which then have an influence on the flow direction in the adjacent segments.

The desired values for the control units essential for the fresh hot gas inflow can be set to empirical values for maintaining the sought temperature gradient, or can be con¬ stantly readjusted by the central computer. It is advanta¬ geous to provide for the outflow or discharge lines valves which, from the outset, are adjusted to empirical values and then require no furhter adjustment. In place of this the outflow side can be regulated with fixed settings on the in¬ flow side and finally the outflow and inflow sides can be regulated in combined manner. However, a linked control is then required, because otherwise overshooting errors could easily occur.

The invention also relates to an apparatus for burning blanks in continuous passage with an elongated, thermically insulated burning pipe, with an intake sluice at one end of the burning pipe and with a discharging sluice at the other end of the burning pipe for intake respectively discharge of blanks, with hot gas supply lines distributed over the length of the burning pipe and leading into said burning pipe, which lines are equipped with adjustable valves emana¬ ting from a hot gas collection supply line, with hot gas discharge lines distributed over the length of the burning pipe, which issue into a hot gas collective discharge line, with a burner equipped with a volume combustion chamber into which issues the hot gas collective discharge line and with a fuel supply line for the burner equipped with a valve.

For using the process according to this invention the appa¬ ratus is characterized in that control means is provided controlling connected with the valve of the fuel supply line, that temperature sensors are provided, each of them controlling connected to one of said valves of the hot gas supply lines and located within the burning pipe near the issue of the belonging hot gas supply line, and that said temperature sensors also control said control means.

During burning, particularly in the initial phase, the addi tive becoming fluid, such as a binder or the like, passes out of the blanks, drips downwards and contaminates the com bustion chamber or is evaporated by the hot gases and conse quently contaminates teh latter.

The problem of a further development of the invention is to avoid or at least reduce contaimations and losses by additi ves passing out during burning, such as binders or the like

According to the invention this problem is solved in that upstream of the combustion chamber is placed a gastight sea lable preheating chamber, that the latter can be connected to lines for the supply and removal of hot gas, that in the preheating chamber is provided a grate for carrying the blanks and that below the grate in the preheating chamber i provided at least one collecting container for dripping or draining additives or similar deposits.

The first phase of the heating process takes place in the preheating chamber, int hat most of the additives which have become liquid pass out. The temperature and residence time of the blanks in the preheating chamber can be easily adju¬ sted in such a way that deposits exclusively or at least mainly only pass out in the preheating chamber. In general, the preheating temperature can be kept so low from the outset, that the additive passing out substantially drips and does not evaporate. As a result of collecting containers, in conjunction with the grate, it is possible to collect the liquid deposits and therefore also avoid losses.

Outwardly leading outflows for the collected additive can be provided for the collecting container or containers, said outflows appropriately being heated in accordance with the flow temperature of the additive. However, it is simpler to construct the collecting container or containers as a drawer or drawers replaceable from the outside.

For cases in which significant additive quantities from the blanks in the combustion chamber pass out in liquid form and collect on the bottom, it is advantageous to provide on the combustion chamber for liquid deposits an outflow emanating from the base thereof, which leads to the outside and which can be shut off. Therefore these deposits can be lead to the outside, do not contaminate the combustion chamber and in particualr do not give off volatile constituents to the hot gas, which would additionally contaminate the latter.

In those cases where the combustion chamber is an elongated burning pipe through which the blanks are forced in coaxial- ly succeeding, lined up manner, such liquid deposits mainly occur in the passage-upstream portion of the burning pipe. Thus, the outflow or outflows for the deposits collecting on the bottom are appropriately provided in said portion. Preferably means for heating the grate are provided. Heating the grate ensures the no deposits adhere to it. The heated grate also leads to a heating of the blanks resting thereon starting from the bottom and aiding dripping or draining.

Advantageously with the grate are associated means for turn¬ ing over the blanks, so that the different circumferential areas of the blanks are directed downwards, where the liquid deposits can be more easily drip downwards.

In many cases circular cylindrical blanks can be processed ans for this case it is advantageous for the purpose of turning over said blanks to have a construction of a parti- cualrly simple nature and which requires no drive for turn¬ ing over purposes. It is characterized in that the grate is so longitudinally inclined that axially parallel, successi¬ vely arranged blanks resting transversely thereon roll for¬ wards and that the resulting rolling section at least corre¬ sponds to one circumference of a blank.

Charging can then be carried out easily in such a way that the blanks are individually and successively lined up in axially parallel manner on the grate, so that if a blank is removed at the front, the rear blanks must move forwards and thereby roll. As the path is correspondingly long, each blank performs at least one complete rotation and can there¬ fore drip over its entire circumference.

A preferred, simple construction of a grate of this type, which is inclined and heatable, is characterized in that the grate has elongated, parallel, spaced juxtaposed pipes which, when the grate is inclined extend in the inclination direction and said pipes can be connected to hot gas lines.

Generally, the blanks must be indivicually and successively introduces into the combustiori chamber. The necessary sepa¬ ration can be performed in operationally reliable manner using simple means, in that at one end of the grate, with the grate inclined at the lower end, a separator for the blanks is provided, that the separator comprises two identi¬ cally dimensioned bucket wheels, which are congruently di¬ rected with respect to their buckets and whose axis is par¬ allel to the axis of the blanks and in each of whose buckets fits a blank, that a drive is provided for said bucket wheels, which advances by one bucket for each separating stroke or cycle of the bucket wheels and that as a result the furthest forward blank is advanced and freed, whilst the next following blank is stopped in the next bucket and sup¬ ports all following blanks. The construction according to the invention can be used with particular advantage for cir¬ cular cylindrical blanks.

In many cases and in particual in a preferred case, where the combustion chamber is an elongated burning or combustion pipe, through which the blanks are moved coaxially in a suc¬ ceeding lined up manner, it is desirable to orient the blanks made ready for insertion in the preheating chamber oriented with the axis of the combustion chamber preferably constructed as a combustion- pipe and to insert same from said oriented position into the combusiton chamber. This can be very simply brought about in that at the advance-remote end of the grate is provided a substrate for the blank i nthe readiness position, which for said blanks is oriented with the combustion chamber, that said substrate continues a sliding surface extending into the combustion chamber, that with said substrate is associated a linearly driveable punch, with the aid of which the blank located in the readi¬ ness position can be inserted on the sliding surface into the combustion chamber, accompanied by the simultaneous ad¬ vance by in each case one blank length of any blanks or al- ready coaxially lined up there.

For the case that the combustion chamber is an elongated combustion pipe, through which the blanks are moved in a coaxially succeeding, lined up manner, it is advantageous for the punch to be operated stepwise, so as to avoid adhe¬ sive friction. On the other side a uniform passage of the blanks through the burning pipe is desirable for uniform processing purposes and it is therefore advantageous to car¬ ry out the advance stepwise in uniform small steps, whereby with each step is associated a length portion of the comple te blank length, so taht for 1 metre blank length there are 1 to 200 and preferably 10 steps. This also has the advanta ge that the punch, which is preferably operated by a hydrau lic linear motor, only requires a small power stroke.

The preheating chamber, like the combustion chamber, is ap¬ propriately sealed in gastight manner, so that on the one hand there is no undesired air access from the outside, which could have the consequence of a harmful oxygen enrich ment of the hot gas and on the other hand no hot gas passes to the outside, because this would involve an energy loss and also because the environment would be contaminated by the fact that the hot gas would be charged with evaporated additive. It ist therefore advantageous that the preheating chamber is equipped with an intake sluice or lock for the gastight filling of individual blanks.

Appropriately there is a hot gas discharge line issuing int the atmosphere to let off excess hot gas for the joint hot gas supply of the combustion chamber and the preheating chamber. The combustible constituents of the charge of this hot gas are burnt off beforehand, so as not to unnecessaril contaimate the environment. It is advantageous in such case for the heating pipes or ducts and preferably those forming the grate to be connected in a dosable shunt separated from these blanks with respect to said hot gas discharge line.

Thus, use is made of the heating capacity of the lost hot gas and there can be no contamination of the outflowing hot gas, because the latter, which only flows in the pipes or ducts, has no contact with the blanks and cannot therefore absorb any contaminants evaporating out of the blanks.

The problem of a further embodiment of the invention is to so construct a burning pipe of the aforementioned type that, using a single flow of fresh hot gas at a unitry temperature, in economic manner and in predetermined seg¬ ments different predetermined temperatures can act on the blanks located in said segments.

This embodiment is characterized in that one segment of the burning pipe with which higher burning temperatures are as¬ sociated has a larger inside cross-section than a segment with which lower burning temperatures are associated.

In the segments having the larger inside cross-section a greater clearance through which the hot gas can circulate is available. This facilitates the sought, more intensive hea¬ ting in such a segment and in economic manner the heating of the segments can be branched from a common flow of fresh hot gas with a unitary temperature.

Correspondingly several segments associated with different areas can have different inside cross-sections and the lar¬ ger the same the higher the associated burning or combustion temperature, so that for higher burning temperatures there is a larger free cross-section for the hot gas flow-round.

For stability reasons the construction is advantageously such that the burning pipe has a steel jacket wall over who¬ se external circumference are distributed vertical braces, preferably formed by channes sections, which extend in the longitudinal direction of the burning pipe and are welded on, that connection bands extending tangentially to the bur¬ ning pipe are welded between adjacent vertical braces and that several connection bands located at the same level of the burning pipe form a closed ring surrounding said pipe and that several such rings are distributed over the burning pipe length.

In a segment associated with lower temperatures it is gene¬ rally sufficient to have an external coating of an insula- tint material to avoid unnecessary heat losses. A preferably steel jacket wall forming the burning pipe then forms with its inside the sliding surface.

However, in a segment associated with higher temperatures it is advantageous for thermal insulation purposes to provide an inner lining of a thermal insulating material, optionall in addition to an outer coating. The inner surface of the inner lining in the lower circumferential or support sector then forms the sliding surface.

Such an inner lining must fulfill different functions. It must form a sliding surface for the blanks sliding through the burning pipe and this sliding surface must be hard and abrasion-resistant. In addition, the inner lining must form a thermal insulation, must be sufficiently dimensionally stable and must be manufacturable from inexpensive materials.

This problem is solved by a further development of the invention, which is characterized in that an innermost laye forming the sliding surface is made from insulating material, which is harder than the remaining parts of the inner lining.

According to a further development thereof, which is charac¬ terized by the use of less costly materials and a favourable effect with respect to insulation and stability is characte¬ rized in that the circumferential or support sector forming the sliding surface of the inner lining is much thicker, na¬ mely at least 10% thicker than the inner lining in an upper circumferential sector.

It is advantageous in the case that in a lower circumferent¬ ial sector, which preferably extends over roughly, half the total circumference, the inner free cross-section is bounded by the shape of a spread U and that the remaining inside cross-section is bounded by the shape of an arc.

If the radius of the sliding surface is only a few % larger than that of the blanks, then the latter pass almost positi¬ vely into the sliding surface, which leads to a desired di¬ stribution of the sliding load. As a function of the materi- als used, this is not in all cases advantageous. In many ca¬ ses it is better for the sliding surface radius to be much larger that that of the blanks, so that between the sliding surface and the blanks and on either side there is a narrow, crescent-shaped gap. Hot gas can then also flow into this gap, which heats the blank from below. It is also desirable in some cases to vibrate or shake the blanks through the ac¬ tion of external vibrating means, so that dirt particles can drop off. This is also favoured by a relatively large radius of the sliding surface.

Due to the necessary support of the blanks, less hot air flows round the same in the lower region, i.e. where they are supported than in the remaining circumferential sector. Normally this is not disadvantageous because the blanks are thoroughly heated. However, in those cases where this is not desired, it can be compensated by providing an additional heating means for the lower circumferential sector of the burning pipe.

Such an additional heating means can be an electric heater. However, it is also possible to provide pipes or ducts through which flows a heating medium, e.g. hot gas. Such ducts can e.g. be provided in the inner lining and the lat¬ ter can be connected to the gap, so that the hot gas flowing there also flows through it or hot gas can flow through it via a separate supply and removal connection.

In certain circumstances condensate or liquid passing out of the blanks, such as e.g. binder collects at the bottom of the burning pipe. It is harmful there, because it can be ta¬ ken up by the hot gas flow and therefore unnecessarily char¬ ges the latter. This can be avoided by providing at least one downwardly leading outflow, which can be preferably shut off, for the fluid deposits collecting in the bottom of the burning pipe and hwich passes out from the lower part of the latter and preferably is located in the burning pipe segment positioned upstream in the passage direction. This liquid can be allowed to flow off every so often or permanently. It is advantageous for this purpose to if necessary heat the components participating in the outflow, such as shut-off valves and lines.

The invention is described in greater detail hereinafter re lative to the drawings, wherein show: Fig. 1 Diagrammatically an apparatus for burning blanks .

Fig. 2 The circuit for the apparatus according to fig. l.

Fig. 3 A horizontal partial section through the apparatus according to fig. 1, under A the left- hand part, under B the middle part and under C the right-hand part. Fig. 4 In plan view the apparatus according to fig . 1, under A the left-hand part, under B the middle part and under C the right-hand part .

Section V from fig. 4B.

Section VI from fig. 4B.

Section VII from fig. 4C.

Section VIII from fig. 4A.

Section IX from fig. 4A.

In vertical section the burning or combustion pipe of fig. 1, broken away and interrupted.

The partial view along arrow XI in fig. 4C.

Section XII from fig. 11.

The view along arrow XIII in fig. 12.

A grate with a few further details in view along arrow XIV in fig. 12. Fig. 15 The view along arrow XV of fig. 14, but in which to facilitate understanding of the drawing the collecting containers and draining plates have been omitted.

The drawings show an elongated, horizontally positioned bur¬ ning or combustion pipe 1, which is connected at the intake side to a preheating chamber 2. The burning pipe and prehea¬ ting chamber are sealed in gastight manner to the outside and through them flow hot gas through the lines indicated in fig. 1 and as shown by the arrows in the latter. The lines contain valves enabling these flows to be controlled, so that within the combustion or burning pipe there can be dif¬ ferent flow conditions to those indicated by the arrows. The heating device 3 is equipped with a burner 77 and is supplied by a fuel supply line 4 with fuel and by means of an air supply line 5 with air. The through-flow can be adju¬ sted at valves Vi in said lines. There is a blower 116, which drives the hot gas circuit. Ther is a hot gas dischar¬ ge line issuing into the atmosphere and is used for drawing off excess hot gas.

According to arrow 8 individually successive, axially paral¬ lel blanks are fed into the preheating chamber 2 and advance in arrow direction 9 and are the individually inserted in the burning pipe 1, so as to advance the blanks already lo¬ cated therein and the in each case last blank passes out of the pipe end in accordance with arrow 9. The blans are of similar size and circular cylindrical and are electrode blanks intended for subsequent graphitization, which contain carbon in the form of petroleum coke, metallurgical coke, graphite, etc., as well as a binder, e.g. pitch.

Hot air flows round the blanks during their passage. For this purpose fresh hot gas passes out of the heating device 3 into the burning pipe 1 and into the preheating chamber 2, flows round the blanks located there and then as spent or waste hot gas, which has taken up as the charge the carbon- containing substances evaporated off from the blanks, passe out of the burning pipe 1 and the preheating chamber 2 and flows to the heating device 3, where said waste hot gas is heated by the flame of the burner 77 and burns the charge. The air supply necessary for combustion purposes takes plac in the stoichiometric minimum, so that the fresh hot gas es sentially contains no oxygen, because if the latter reaches the blanks it can damage them.

The hot gas flow and its temperature, particularly within the burning pipe 1 and the preheating chamber 2, is regula¬ ted by temperature-dependent regulators or control units Ri for the fresh hot gas, controlled by a central control means 10 equipped with a computer and a memory. This control means 10 also controls the fuel and air supply for the heating device, as a function of the actual and desired values of the process quantities in the hot gas flow of the burning pipe 1.

At the preheating chamber 2 an intake sluice or lock 11 is provided for the entry of the blanks. The blanks lined up in axially parallel form in the preheating chamber are given reference numerals 12 to 20 and there is also a blank 21 in a readiness position axially oriented with respect to the burning pipe 1. Further blans 22 to 45 are located in coaxi¬ al densely lined up form within the pipe 1.

As will be explained in greater detail hereinafter, the blanks do not fill up completely the interior of the burning pipe. Into the remaining free gap 132, 133 issue hot gas supply lines 46 to 53 distributed over the length and which emanate from the hot gas collective supply line 74. From said gap and distributed over the length of the burning pipe 1 and displaced with respect to the hot gas supply lines 46 to 53 there are hot gas discharge lines 54 to 61, which is¬ sue into a hot gas collective discharge line 62 for the spent or waste hot gas, which in turn issues into the hea¬ ting device via the blower 116 and two branches 63, 64.

In the hot gas collective supply line 74 fresh hot gas flows via the hot gas supply line 65 into the interior of the pre¬ heating chamber 2. The spent hot gas flows out of the pre¬ heating chamber 2 via the hot gas discharge line 91 into the hot gas collective line 62. A hot gas supply line 66 leads via a blower 67 to the hot gas discharge line 7, which issu- es into the open. On the pressure side a hot gas supply lin 81 branches off from the blower 67 and leads into the entry sluice 11. From the hot gas supply line 66 passes a shunt 68, 69, which flows through the pipes 183 to 186 of a grate 191 located within the preheating chamber 2 and as will be explained hereinafter.

From the hot gas collective supply line 74 passes a further hot gas supply line 70, which is connected via a blower 71 to an additional heating means 72, which is located at the bottom on the burning pipe 1. The hot gas flows through the additional heating means 72 and from there flows back via the hot gas discharge line 73 and the hot gas collective di scharge line 62. The additional heating means preferably he ats the lower circumferential sector of the burning pipe 1 and is correspondingly arranged there. However, it can also be disposed of and is not shown in the other drawings.

The fuel supply line 4, via which the gaseous fuel is supplied, issues via two branches 75, 76 into the burner 77 of the heating device 3. The air supply line 5 issues via a blower 78 and two branches 79, 80 into the heating device 3

There are adjustable valves Vi making it possible to modify the flow cross-section of the associated line. There are re gulators or control units Ri, which are followed by the sam index as the associated valves Vi, which are adjusted by th regulators Ri as control elements. There are temperature sensors Ti, which are measuring elements to the regulators Ri given the same index. There are pressure sensors Pi and an oxygen content sensor S, which are corresponding sensors to the regulators designated by the same index. Valves Vi with which no regulators are associated, can be adjusted in unregulated form from the location of the valve and/or the control means 10. The measured values of all the temperature sensors Ti, pres¬ sure sensorsPi and the oxxygen content sensor S are passed via not shown electric cables to the controle means 10. A desired value is associated with each regulator Ri and is set by the control means. The control means can also set the valves not equipped with regulators. The control means sets the desired values in accordance with a predetermined pro¬ gram or in accordance with inputs made.

The control means 10 centrally stores the values supplied and prepares the updated, historical, trend-caused or malfunction-caused indications and/or control quantities. An updated indication relates to the updated state. A histori¬ cal indication relates to the updated state to a time which can be determined by. the operator. A trend-caused indication relates to changes in the operating conditions occuring over a period of time, whilst a malfunction-caused indication mainly relates to alarms, which optically or acoustically draw the operator's attention to malfunctions and which may require immediate intervention. The indications or displays can be in tabular form, but preferably take place within a displayed stylized picture, roughly as shown in fig. 2, the values in question being displayed at the spatially associa¬ ted points, i.e. for example the desired and actual values associated with the regulator R6 are displayed alongside the image of the latter.

The hot gas circuit functions as follows. The fuel is blown in via branches 75 and 76 into the flame source of the bur¬ ner 77 and into a flame area positioned further forwards. The stoichiometric quantity of fresh air is supplied as a first air supply to the flame area of the burner 77 via the branch 79, so that complete combustion takes place. Into the flame area of the burner of the heating device 3 and speci- fically following the opening^' of the branch 75, 76 in the flame direction, issues the branch 63, which blows in waste hot gas, so that part of the charge of said waste hot gas is also burnt in the flame area. Following the same the branch 80 for a second air supply issues into a volume combustion chamber 90 into which is directed the flame of the burner 77. The opening of the branch 80 is followed by the issuing of the branch 64 for spent ht gas into the volume combustion chamber 90.

Volume combustion takes place in the volume combustion cham ber 90^', which is optionally thermally insulated to the out¬ side and the remainder of the spent hot gas charge and op¬ tionally fuel residues are burnt there, so that at the end of the volume combustion chamber fresh hot gas flows into the hot gas collective line 74, which should contain no 0₂ and preferably no incompletely burnt carbon and heating ta¬ kes place. For the necessary stoichiometric combustion the second air supply is dosed via branch 80 as a function of the oxygen content. The associated regulator R4 is control¬ led by the oxygen content sensor S as a primary element. Th oxygen content sensor S is positioned at the downstream end of the volume combustion chamber 90 close to the point from which the hot gas collective supply line 74 emanates.

The regulator R4 is set in such a way that, as soon as the oxygen content sensor S indicates the exceeding of a prede¬ termined tolerance quantity of the oxygen content, the se¬ cond air supply is reduced. The predetermined tolerance quantity is preferably 0.3% oxygen content. The correspon¬ ding control can also take place as a function of the CO- content. Then, in place of the oxygen content sensor S or i addition thereto, it is necessary to install a CO-content sensor. In this case the second air supply is reduced on ex ceeding a predetermined CO-content tolerance quantity and preferably 0.1%.

The oxygen content sensor S or a CO-content sensor can also be positioned downstream of the point in the hot gas collec¬ tive supply line 74 or a hot gas line designated for the sensor S, but must be positioned upstream of the entry of the hot gas into the burning pipe 1. However, the further the measurement point from the measurement point of the in¬ dicated oxygen content sensor S, the greater the undesired control or regulation delay.

The fuel supply is doesed or proportioned by the regulator RI at valves Via and Vlb, as a function of the hot gas tem¬ perature at the downstream end of the volume combustion chamber 9 measured by the temperature sensor TI. Regulation takes place accompanied by a constant readjustment of the desired value for the regulator RI by the control device 10. The control device 10 calculates the control quantity neces¬ sary for this constantly as a function of the measured actu¬ al and desired values of the process quantities for the seg- mental flow regulation within the burning pipe 1 and the preheating chamber 2 and mathematically links the values with the desired control quantity. For this purpose the ac¬ tual values of the temperature sensors T5 to TlO and T13, as well as the actual values of the throughput quantities ob¬ tained from the settings of the valves V5 to V10 and V13, are calculated to give an overall energy balance. Correspon¬ dingly calculation takes place of the energy balance which would occur if the actual temperatur values corresponded to the desired temperature values. These two energy values are subtracted from one another and the difference constitutes the operand for the desired value of the regulator RI.

The intensity and also the direction of the hot gas flow within the burning pipe is influenced by the hot gas throug- hput in the hot gas supply lines 46 to 53. As a result of a more or less intense charging of the burning pipe segment with hot gas, it is possible to influence the temperature there, i.e. it can be increased or decreased compared with neighbouring segments, although fresh gas is only supplied at a unitary temperature. The hot gas flow and therefore the influencing ist also dependent on the selected setting of the valves Vi in the hot gas discharge lines 54 to 61, which can be fixed from the outset on the basis of empirical values.

For compensating the volume increase through the fuel and air supplied from the outside, fesh hot gas is let off into the atmospherevia the hot gas discharge line 7. This is con¬ trolled by the valve Vll as a function of the pressure mea¬ surement of the pressure gauge Pll at the downstream end of the hot gas collective supply line 74. The associated regu¬ lator Rll operates under a predetermined desired value, which ensures that in all the lines into which fresh hot gas flows and in the preheating chamber 2, together with in the burning chamber 1 there is a slight overpressure of 0.5 to 20 mm w.g., preferably 5 mm w.g., compared with the externa atmosphere. Therefore no undesired oxygen-containing air ca be sucked through the outside through leaks and reach the blanks. This ensures that only oxygen-free hot gas flows round the blanks and the latter cannot come into contact with oxygen in the hot state.

The lowest pressure is set close to the suction side of the blower 116. The pressure sensor Pll can also be positioned close to the suction side of the blower 116 or at some othe point able to provide valid information on the lowest over¬ pressure in the burning pipe or in the preheating chamber.

In many cases it is desirably to ensure that no charged hot gas passes through leaks or the like in uncontrolled manner into the atmosphere. It is advantageous in this case to maintain a slight vacuum in that part of the hot gas circuit to which same is returned as waste hot gas, i.e. essentially the hot gas discharge lines 54, 61, the hot gas collective discharge line 62 and the branches 63, 64. The blower 116 is the ngiven a corresponding downstream displaced position, roughly at the downstream end of the hot gas collective di¬ scharge line 62. It is sufficient to have a vacuum of -0.5 to -20 mm w.g. and preferably -5 mm w.g. Such a vacuum can also be maintained or set for the same purpose in the bur¬ ning pipe 1 and in the preheating chamber 2 if there is to be no uncontrolled outflow through leaks of charged hot gas.

The hot gas flowing into the open through the hot gas di¬ scharge line 7 is fresh, i.e. clean hot gas, which contains no charges, so that there is no unnecessary contamination of the environment.

The shunt 68, 69 passes through the pipes 183 to 186 located within the preheating chamber 2, as will be described hereinafter. The fresh hot gases flowing through said shunt remain in the pipe system and cannot come into contact with blanks and consequently absorb no charges. Therefore they can bel et off into the atmosphere without causing problems.

The fresh hot gas flowing via the line 81 to the entry slui¬ ce 11, partly flows from there into the open and partly into the preheating chamber 2. It cannot take up contamination at the sluice 11, because the blank there is cold.

If the addicional heating means 72 or some other heating me¬ ans is a pipe or system sealed against the blanks, said hea¬ ting means can be switched in accordance with the shunt 68, 69 and fresh hot gas which is to be let off into the atmo- sphere can flow through the same, so as to utilize the heat capacity thereof.

The apparatus can be operated in accordance with the follo¬ wing process examples.

PROCESS EXAMPLE 1

A pulpy mass is formed fram Al = 20% by weight Ml = pitch and A2 = 80% by weight M2 = coke powder, which is shaped in¬ to circular cylindrical, green electrode blanks with a dia¬ meter Dl = 65 cm and a length LI = 240 cm. These electrode blanks undergo afirst burning and for this purpose the blanks are heated for a time Zl = 300 hours to Tl = 850°C and are kept for Z2 = 30 hours at said temperature T2 = 850°C and are subsequently cooled for Z3 = 24 hours to T3 = 350°C. The electrode blanks can then be cooled in the open to T4 = 20°C. As a result the electrode blanks harden and the thus treated blanks are dimensionally stable and porous.

These electrode blanks are impregnated with pitch. For this purpose they are heated to T5 = 300°C and evacuated in a closed container. Then pitch at T6 = 250°C is introduced in¬ to the container and the container content is kept for Z4 = 2 hours at Pl = 15 bar pressure. Subsequently the pressure and the pitch are drained off and the now impregnated elec¬ trode blanks are removed from the container, drained and cooled.

The thus impregnated electrode blanks are individually and successively introduced into the preheating chamber 2 and slowly heated there to T7 = 250°C. The residence time of the individual electrodes in the preheating chamber is Z5 = 10 hours. Following onto this residence time the electrodes are individually and successively introduced into the burning or combustion pipe 1 and pass through the latter stepwise. An advance step is SI = 10 cm and the advance speed is VI = 0.96 m/h, so that for a total burning pipe length L2 = 50 m, the electrode blanks spend Z6 = 30 hours in said pipe. They are initially heated for Z7 = 30 hours in uniform manner to T8 = 740°C and then kept at this temperature for Z8 = 14 hours, before finally being uniformly cooled for Z9 = 8 hours to T9 = 350°C. The electrodes then pass into the open and can be cooled there to TlO = 20°C. However, they can al¬ so be supplied in the still hot state to graphitization.

Hot gas flows round the electrodes in the preheating chamber and in the burning pipe and its oxygen content Gl = 0.5%, its inlet temperature is min. Til = 800°C and max. T12 = 950°C, as a function of the desired value on the regulator RI, i.e. the total energy requirement. The hot gas throug¬ hput quantity flowing through the free gap of the burning pipe in its individual segments is dependent on the energy requirement in the particular segments and is individually controlled for each segment. The individual segments can ex¬ tend from an opening of a hot gas discharge line, e.g. 56, to the opening of the next, adjacent hot gas discharge line, e.g. 55 and 57, or to the one from next hot gas discharge line, e.g. 54 or 58 and so on. This is individually adjusted according to the local requirements on the particular valves Vi.

Combustion in the heating device 3 is controlled in such a way that the fresh hot gas has an oxygen content of G2 = 0.5%. By blowing off fresh hot gas at the hot gas stack a pressure of min. P2 = 23 mm w.g. is maintained during opera¬ tion at the measuring point of the pressure gauge Pll. This ensures that there is no drop below an overpressure pf P3 = 5 mm w.g. even at the lowest pressure point in the prehea¬ ting chamber and burning pipe.

Further process examples differ from process example 1 by the details given in the following table. TABLE 1

The construction of the apparatus according to fig. 1 will now be explained relative to figs. 3 to 15, where the same parts are given the same references as in figs. 1 and 2.

The burning or combustion pipe 1 comprises three segments

101, 102 and 103. In the first segment 101 the free internal cross-section is circular and of diameter 104 and is defined by a steel, circular, tubular jacket wall 105. In the second segment 102 the inside diameter 106, measured vertically, is much larger than the diameter 104. In the third segment 103 the inside cross-section is circular and the internal diame¬ ter 108 determined by the jacket wall 117 and is the same as the diameter 104. The inside cross-section in the second segment 102 ist 25% larger than the inside cross-section in the first and third segments 101, 103.

As can in particular be gathered from fig. 7, there is a cross-sectionally crescent-shaped gap 133 alongside the blank 22 in the first segment 101. As can in particular be gathered from fig. 6, there is a cross-sectionally crescent- shaped gap 132 alongside the blank 24 in the second segment

102. As can in particular be gathered from fig. 8, there is a cross-sectionally crescent-shaped gap 134 alongside the blank 43 in the third segment 103.

For blanks of the same size, the gaps 133, 134 have the same cross-section. However, the cross-section of gap 132 is muc larger and is roughly 3.5 times larger in the represented embodiment and the blank dimensions used therein. Thus, for the hot gas flowing alon the gap 132 there is in the second segment 102 a much wider path than in the gap 133 in the first segment 101.

The necessary temperature is still low in the first segment 101. It is much higher in the second segment 102. More hot gas can flow through the larger gap 132 in the second segment, so that it is easy to maintain the higher tempera¬ ture desired there. In the third segment 103 the temperature is lower than in the second segment and consequently the gap 134 can be smaller than the gap 132.

The jacket wall 118 is also circular in the second segment 102, but is much wider than the jacket wall 105 in the first segment 101 and is much wider than the jacket wall 117 in the third segment 103. The jacket walls are lined up against one another by steel annular disks 219, 220. As can be gat¬ hered from fig. 8, the jacket wall in the first segment 101 is externally surrounded by a thermolight material insulati¬ on 107.

Extending from the bottom of the first segment 101 and di¬ stributed over the length from the interior of the burning pipe 1 are provided outwardly leading outflows 110, 111, which can be shut off, enabling flowable deposits collecting at the bottom in the pipe to be drained or sucked downwards out of the said pipe. The outflow 110 comprises a hopper 112 fixed to the jacket wall 105 and an outflow line 113, which can be shut off with a valve 114. The hopper 112 is incorpo¬ rated into the insulation 107. The outflows can be heated, e.g. by a not shown additional heating means corresponding to additional heating means 72.

According to fig. 6, in the second segment 102, the steel jacket wall 117 and having a much larger diameter than the jacket wall 105, is lined with a thermal internal lining 125. The inner face of this internal lining forms in a lower circumferential sector or support sector 126 a sliding sur¬ face 123. An innermost layer 127, indicated by hatching and forming the sliding surface 123 is made from an insulating material, which is harder than the remaining parts of the internal lining 125.

The internal lining support sector forming the sliding sur¬ face 123 is, according to double arrow 128, much thicker than the internal lining according to double arrow 131 in an upper circumferential sector and in the bottom area in the embodiment it is approximately 30% thicker.

The lower half of the free internal cross-section is bounded by an upwardly open, spread U 129. The remaining internal cross-section is bounded by an arc 130. An additional hea¬ ting means corresponding to additional heating means 72 can also be provided in segment 102.

The segment 103 comprises the jacket wall 117, which is sur¬ rounded by a cooling jacket 135, which forms a closed space surrounding in annular manner the jacket wall 117 and through which flows cooling air. This cooling air is intro¬ duced through the cooling air supply line 140 and flows out through the cooling air discharge line 141, cf. also fig. 4.

In the segments 101 and 103 the bottom sector of the jacket wall 105 forms a sliding surfache 142 or 143. The sliding surfaces 142, 143 are circular cylindrical jacket surfaces with a radius somewhat larger than that of the blanks. In tis central circumferential portion the sliding surface 123 of the segment 102 has the same radius as the sliding surfa ces 142, 143. Along the bottom sector of the jacket wall th sliding surfaces 143, 123 and 142 are linearly aligned. At the transitions from and to the segment 102 not shown expan sion bevels are provided in the lateral portions of the sli ding surface, in order to permit a smooth, stepless sliding of the blanks in the longitudinal direction through the bur ning pipe 1. In the first segment 101 with the relatively small gap 133 the blanks are heated to a relatively low temperature of e.g. 530°C. In teh second segment 102 with the larger gap 132 they are heated to a higher burning temperature, e.g. 830°C. In the third segment 103 with the relatively small gap there is only a cooling and no heating.

Over its entire length the jacket wall 105 is externally reinforced. For this purpose distributed externally over the surface of the jacket wall are provided vertical braces, e.g. the vertical braces 150, 151 constituted by channel sections are welded on and in each case extend over a seg¬ ment 101, 102, 103 in the longitudinal direction of the bur¬ ning pipe. In addition, there are connection bands, e.g. connection bands 152, which extend tangentially to the bur¬ ning pipe and are welded between two adjacent vertical braces, e.g. 150 and 151. There are several connection bands at the same level of the burning pipe and in each case form a closed ring, e.g. ring 153. Several such rings are distri¬ buted over the burning pipe length and in each case adapted to the circumference of the jacket wall 105.

At the passage-remote end of the third segment 103 is provi¬ ded a lock or discharge sluice 160 (cf. fig. 10) for a sand- filled, upwardly open connecting piece 162, which issues from above into the crescent-shaped gap 134 left free bet¬ ween the blanks and the jacket wall 105. The sand trickles out of the connecting piece 132 into the gap and continuous¬ ly fills the latter, which leads to a gastight labyrinth packing there. The sand trickles out at the free end of the burning pipe, where the blanks pass out, is collected, clea¬ ned and returned to the connecting piece 162 by a not shown screw conveyor.

The hot gas supply line 49 is connected to the burning pipe 1 via the valve V7 and said line issues in upwardly inclined manner into the burning pipe. Diametrically facing said ope¬ ning is provided the associated temperature sensor T8, which is protected by the interposed blanks 30 from the direct ac¬ tion of the inflowing, fresh hot gas. The other hot gas sup¬ ply lines 46 to 53 and the associated temperature sensors and valves are correspondingly constructed and arranged.

The hot gas collective discharge line 62 is a pipe laid par¬ allel to and above the burning pipe 1 and from which the hot gas discharge lines, e.g. line 57 pass ve4rtically downwards. The hot gas discharge line 59 issues from above into the burning pipe 1. The other hot gas discharge lines 54 to 61 and the associated valves are correspondingly con¬ structed and arranged.

Fig. 5 also shows a frame 182, which is partly also visible in fig. 9 and extends over the entire length of the burning pipe and carries the latter. The frame is not shown in all the drawings so as not to overburden them. At the passage- upstream end of the burning pipe is connected the already mentioned preheating chamber 2, which will now be explained relative to figs. 11 to 15.

The preheating chamber 2 has a gastight-sealable casing 190 within which there is a grate 191 inclined with respect to the horizontal in the manner of an oblique plane. On the preheating chamber 2 is provided at least one outflow 218 for liquid deposits, which can be shut off, which leads to the outside and which emanates from the bottom thereof. The grate has elongated, parallel spaced, juxtaposed pipes 183 to 186, which extend in the direction of the slope. These pipes are linked with one another by transverse lines 196, 197 and are jointly connected to the shunt 68, 69. The pi¬ pes carry the blanks 12 to 20, which rest thereon axially : parallel to the axis 223 and at right angles to the longitu¬ dinal axis of the pipes 183 to 186 and are supported by the separator 193.

As a result of the slope of the grate 191 the bearing surfa¬ ce 227 formed by the latter is inclined at an acute angle 124, so that the axially parallel, successively arranged blanks 12 to 21 resting thereon at right angles to the in¬ clination direction, as a result of gravity, roll off the bearing surface 227 towards the separator 193.

The separator has a bucket wheel 194, whose axis 192 extends parallel to the axis 223 of the blanks and a blank fits into each of it buckets. A drive 224 for the bucket wheel rotates the same forwards by one bucket for each separation stroke or cycle. In each case the furthest forward blank 20 is ad¬ vanced and freed, whilst the next-following blank 90 is stopped in the next bucket and all the gravity after-rolling blanks 12 to 18 are supported. At the advance-remote end of the grate is provided a substrate 198 for a blank 21 in the readiness position and which is oriented with the burning pipe for said blank, so that the blank 21 extends coaxially to the blanks 45 to 22 located in the burning pipe.

The substrate 198 is an extension of the sliding surface 142, which is directed at a hole 226 i nthe wall 228 of the casing 190. The burning pipe 1, i.e. the jacket wall 105 is connected in gastight manner to the wall 228 aligned with the hole 226. With the substrate 198 is associated a punch 200, which can be reciprocated in linear manner by a hydrau¬ lic drive 225, namely in the axial direction of the blank 21. The punch is located in a gastight-sealed guide 199, which is connected by its front, open side so as to communi¬ cate with the interior of the preheating chamber 2. By means of said punch the blank 21 is advanced stepwise or in a stroke or cycle in arrow direction 201 and advances before it the entire row of blanks located in the burning pipe. As soon as the blank 21 has completely entered the burning pipe, the next blank 20 rolls onto the substrate 198 as a result of the next separating stroke of the separator 193. The punch 200 is operated stepwise with uniform steps and with each step is associated a longitudinal portion of the total blank length, so that there are 1 to 200 and prefera¬ bly 10 steps for one metre of blank length.

The intake sluice 11 is dimensioned appropriately for the reception of a blank and is axially oriented to the last free blank position on the grate, which is assumed by blank 12 in fig. 14, Sealed in gastight manner with respect to th outside and the preheating chamber, the sluice contains a new blank 82, which can be introduced by a punch 203 driva- ble by a hydraulic drive 2202 into the position previously occupied by the blank 12. A sluice gate 204 between the en¬ try sluice 11 and the preheating chamber 2 automatically opens.

As stated, hot gas flows round the blanks within the prehea ting chamber, which flows in via the hot gas supply line 65 ' and is consequently heated. During this heating pitch or si milar deposits pass out of the blanks and drips downwards a grate 191. For collecting said pitch below the grate are di stributed four upwardly open collecting containers 210, 211 212, 213 constructed in the manner of drawers and which, as shown in fig. 15, jointly extend over the entire width of the grate. The gaps between the collecting containers are covered by roof-shaped drain plates 214, 215, 216, so that deposits dripping onto the same pass into the collecting containers. The collecting conatiners can be drawn outwards in the manner of drawers and can be replaced by empty col¬ lecting containers or can be pumped out. 3; 8

The rolling section formed by the bearing surface 227 and along which each individual blank must roll from the positi¬ on of the blank 12 to the position of the blank 20 on the grate, is almost three times as long as the circumference of a blank, so that each blank rotates almost three times and consequently all the circumferential sides pass several ti¬ mes into a position favourable for dripping or draining.

Claims

*"

1. Process for burning blanks in the continuous passage of a burning section by having a substantially oxygen-free hot gas flow around the same and which is supplied as a function of the combustion temperature in dosed manner along the bur¬ ning or combustion section and is returned to the heating means as spent or waste hot gas and, accompanied by the com¬ bustion of the combustible charge taken up on the burning section and accompanied by air and fuel supply heating oc¬ curs and it is worked up to form a substantially oxygen- free, fresh hot gas, in that the air supply for the combu¬ stion is regulated as a function of the oxygen content of the fresh hot gas to a stoichiometric, minimum desired value and then the fresh hot gas is again supplied to the combu¬ stion section and the flow of hot gas through said section is segmentally regulated as a function of the hot gas tempe¬ rature in the particular segment in accordance with prede¬ termined desired values, characterized in that actual and desired values of the process quantity for the segmental flow regulation are combined with one another to form a con¬ trol quantity for the fuel supply.

2. Process according to claim 1, characterized in that the actual and desired values of process quantities and/or othe measured values are centrally stored and prepared to form an updated, historical, trend-caused or malfunction-caused in¬ dication and/or control quantity..

3. Process according to claims 1 or 2, characterized in that the preset items of the desired values are centrally controlled in.

4. Process according to one of the preceding claims, cha¬ racterized in that a complete stoichiometric combustion of _

the supplied fuel, including the charge which has been taken up by the old hot gas and an oxygen-free, fresh hot gas is controlled, in that a first air supply takes place in a stoichiometrically determined dependence on the fuel supply into the new flame area for heating purposes and in that a second air supply takes place as a function of the hot gas content of oxygen and/or incompletely burnt carbon compounds in the fresh hot gas, preferably measured in a volume combu¬ stion area formed directly following on to the new flame area.

5. Process according to claim 4, characterized in that on exceeding a predetermined tolerance quantity of the oxygen content of the fresh hot gas, preferably at a predetermined tolerance quantity of 0.3%, the second air supply is reduced.

6. Process according to claims 4 or 5, characterised in that on dropping below a predetermined tolerance quantity of the CO-content of the fresh hot gas, preferably a predeter¬ mined tolerance quantity of 0.1%, the second air supply is ' reduced.

7. Process according to one of the preceding claims, cha¬ racterized in that the hot gas circuit is sealed in pressure tight manner from the outside and is constantly driven and that a fraction of the fresh hot gas is drawn off into the atmoshpere, regulated as a function of the pressure of the fresh hot gas, measured at a measuring point, which provides valid information on an extreme pressure value in the hot gac circuit outside the combustion means.

8. Process according to claim 7, characterized in that the external air supply into the fresh hot gas flowing round the blanks is cut off, in that by pressure regulation in that part of the hot gas circuit in which flows the fresh hot ga or where said gas flows round the blanks, an overpressure o 0.5 to 20 mm w.g. (millimetres water gauge), preferably 5 m w.g. is maintained.

9. Process according to claim 8, characterized in that the fraction of the fresh hot gas, which is blown off into the atmosphere is regulated as a function of the pressure of th fresh hot gas upstream of the flow round the blanks.

10. Process according to claim 7, characterized in that the discharge of any charged hot gas is avoided, in that by pressure regulation in that part of the hot gas circuit in which the hot gas flows round the blanks and/or in that par of the hot gas circuit in which the spent hot gas is retur¬ ned by the burning pipe to the heating device, a vacuum of -0.5 to -20 mm w.g., preferably -5 mm w.g. is maintained.

11. Process according to one of the preceding claims, cha¬ racterized in that distributed over the length of the bur¬ ning section several fresh hot gas flows regulatable indivi dually with respect to the throughput volume are supplied the blanks, that, based on the burning section length, bet¬ ween in each case two inflow points is provided an outflow line for the old hot gas adjustable with respect to the throughput volume and that the regulation of the hot gas throughput of the flows of fresh hot gas takes place as a function of the temperature measured in the hot gas flow o the blank side facing the hot gas supply line opening.

12. Apparatus to perform the process according to claim 1 for burning blanks in continuous passage with an elongated, thermically insulated burning pipe (1), with an intake slu ce (11) at one end of the burning pipe and with a dischar¬ ging sluice (160) at the other end of the burning pipe for intake respectively discharge^' of blanks, with hot gas supply lines (46-53) distributed over the length of the burning pi¬ pe and leading into said burning pipe, which lines are equipped with adjustable valves (V10-V13) and emanate from a hot gas collective supply line (74), with hot gas discharge lines (54-61) distributed over the length of the burning pipe, which issue into a hot gas collective discharge line (62), with a burner (77) equipped with a volume combustion chamber (90) into which issues the hot gas collective discharge line and with a fuel supply line (4) for the bur¬ ner (77) equipped with a valve (Via), characterized in that control means (10) is provided controlling connected to said valve (Via) of the fuel supply line (4), that temperature sensors (T10-T13) ) are provided, each of them controlling connected to one of said valves (V10-V13) of the hot gas supply lines (46-53) and located within the burning pipe (1) near the issue of the belonging hot gas supply line, and that said temperature sensors (T10-T13) also control said control means (10).

13. Apparatus for burning blanks according to claim 12, cha¬ racterized in that upstream of the combustion chamber (1) is provided a gas tight sealable preheating chamber (2), that the preheating chamber can be connected to lines (65,66,62,68,69) for the hot gas supply and removal, that in the preheating chamber is provided a grate (191) for carry¬ ing the blanks (12-21) and that below the grate in the pre¬ heating chamber is provided at least one collecting contai¬ ner (210) for dripping additives or similar deposits.

14. Apparatus according to claim 13, characterized in that a collecting container (210) is a drawer which can be repla¬ ced from the outside.

15. Apparatus according to claims 13 or 14, characterized in that on the preheating chamber (2) is provided at least one outflow (218) for liquid deposits, which emanates from the bottom thereof, leads to the outside and can be shut off.

16. Apparatus according to one of the precieding claims con¬ cerning an apparatus, characterized in that means (68,69) for heating the grate (191) are provided.

17. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that with the grate

(191) are associated means (227) for turning over the blanks (12-21).

18. Apparatus for burning circular cylindrical blanks accor¬ ding to claim 17, characterized in that the grate (191) is inclined in the longitudinal direction that axially parallel, succeeding blanks (12-21) positioned transversely thereon roll forwards and that the resulting rolling section (227) corresponds to at least on blank circumference.

19. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that the grate (191) has elongated, parallel, spaced, juxtaposed pipes (183-186), which, in the case of the inclined grate, extend in the di¬ rection of the inclination and that the pipes can be connec¬ ted to the hot gas lines (68,69).

20. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that at the end of the grate (191), with the grate inclined at the bottom end, is provided a separator (193) for the blanks (12-21), that the separator (193) has a bucket wheel (194), whose axis

(192) is extends parallel to the axis (223) of the blanks and a blank fits into each bucket thereof, that a drive (224) is provided for the bucket wheel and which during eac separation stroke advances the bucket wheel by one bucket and that as a result during each separating cycle the in each case furthest forwards blank is advanced and freed, whilst the next following blank is stopped in the next bucket and all possible following blanks are supported.

21. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that at the advance- remote end of the grate (191) is provided a substrate (198) for a blank (21) in the readiness position and hwich, for said blank, is aligned with the combustion chamber (90) that said substrate continues in a sliding surface (123,142,143) extending into the combustion chamber and that with said substrate is associated a linearly drivable punch (200) with the aid of which the blank located in the readiness position can be inserted on the sliding surface into the combustion chamber and accompanied by the simultaneous advance by one blank length of any blanks or already coaxially lined up there.

22. Apparatus according to claim 21, characterized in that the punch (200) is operated stepwise with uniform steps, a length portion of the total blank length being associated with each step, so that for 1 metre blank length there are 1-200 and preferably 10 steps.

23. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that the preheating chamber (2) for the gastight filling of individual blanks (82) is equipped with an intake sluice (11).

24. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that there is a hot gas discharge line (7) issuing into the atmosphere and is used for drawing off excess hot gas and that heating pipes or ducts, preferably the pipes (183-186) forming the grate (191) are connected in a dosable shunt (68,69) separated from the blanks with respect to said hot gas discharge line.

25. Apparatus according to one of the preceding claims con¬ cerning an apparatus, characterized in that one segment (102) of the burning pipe (1) which is associated with the higher burning temperatures has a larger inside cross- section (132) than a segment (101,103) associated with the lower burning temperatures.

26. Apparatus according to claim 25, characterized in that the burning pipe (1) has a steel jacket wall (105), that a segment (101) of the burning pipe (1) associated with the lower temperatures is thermally insulated by an external, insulating material coating (107) and that a lower portion of the jacket wall forms the sliding surfache (142).

27. Apparatus according to claim 25 or 26, characterized in hat the burning pipe (1) has a steel jacket wall (105), tha a segment (102) of the burning pipe (1) associated with the higher temperatures has a thermal insulating material insid lining (125) and that the inner face of the said lining forms in al lower circumferential or support sector (126) the sliding surface (123).

28. Apparatus according to claim 27, characterized in that an innermost layer (127) forming the sliding surface (123) is made from insulating material, which is harder than the remaining part of the inside lining.

29. Apparatus according to claims 27 or 28, characterized i that the circumferential or support sector (126) of the in¬ ner lining (125) forming the sliding surface is much, namel at least 10% thicker than the inside lining in an upper cir cumferential sector.

30. Apparatus according to claim 29, characterized in that in a lower circumferential sector extending preferably over roughly half the total circumference, the inner free cross- section is bounded by the shape of a spread U (129 and that the remaining inside cross-section is bounded by the shape of an arc (130) .

31. Apparatus according to the claims 25 to 30, characteri¬ zed in that an additional heating means (72) is provided for the lower circumferential sector of the burning pipe (1).

32. Apparatus according to the claims 25 to 31, characteri¬ zed in that there is at least one downwardly directed out¬ flow (110), which can preferably be shut off, for fluid de¬ posits collecting at the bottom of the burning pipe (1) and which emanates from the lower part of the burning pipe and is preferably located in the burning pipe segment (101) lo¬ cated upwards in the passage direction.

33. Apparatus for burning blanks, which contain additives, such as binders or the like, which become fluid on heating and in particular electrode blanks intended for graphitization and formed from carbon- containing filler material and binders constituted by pitch or the like, by having hot gas flow round the same in a gas tight sealable combustion chamber, characterized in that upstream of the combustion chamber (1) is provided a gas tight sealable preheating chamber (2), that the preheating chamber can be connected to lines (65,66,62,68,69) for the hot gas supply and removal, that in the preheating chamber is provided a grate (19D or carrying the blanks (12-21) and that below the grate in the preheating chamber is provided at least one collecting container (210) for dripping additives or similar deposits.

^. Apparatus according to claim 33 characterized in that a collecting container (210) is a drawer which can be replaced from the outside.

35. Apparatus according to clairπ33 or 3.4 characterized in that on the preheating chamber (2) is provided at least one outflow (218) for liquid deposits, which emanates from the bottom thereof, leads to the outside and can be shut off.

36. Apparatus according to one of the preceding claims, characterized in that means (68,69) for heating the grate (19D are provided.

37. Apparatus according to one of the preceding claims, characterized in that with the grate (191) are associated means (227) for turning over the blanks (12-21).

38. Apparatus for burning circular cylindrical blanks according to claim 37 characterized in that the grate ( 191) is inclined in the longitudinal direction that axially parallel, succeeding blanks (12- 21) positioned transversely thereon roll forwards and that the resulting rolling section (227) corresponds to at least one blank circumference. 39. Apparatus according to one of the preceding claims, characterized in that the grate (191) has elongated, parallel, spaced, juxtaposed pipes (183-186), which , in the case of the inclined grate, extend in the direction of the inclination and that the pipes can be connected to the hot gas lines (68,69).

.40. Apparatus according to one of the preceding claims, characterized in that at the end of the grate (19D, with the grate inclined at the bottom end, is provided a separator (193) _r the blanks (12-21), that the separator (193) has a bucket wheel (194), whose axis (192) is extends parallel to the axis (223) of the blanks and a blank fits into each bucket thereof, that a drive (224) is provided for the bucket wheel and which during each separation stroke advances the bucket wheel by one bucket and that as a result during each separating cycle the in each case furthest forwards blank is advanced and freed, whilst the next following blank is stopped in the next bucket and all possible following blanks are supported.

_.41. Apparatus according to one of the preceding claims, characterized in that at the advance-remote end of the grate (19 ) is provided a substrate (198) for a blank (21) in the readiness position and which, for said blank, is aligned with the combustion chamber (90) that said substrate continues in a sliding surface (123,142,143) extending into the combustion chamber and that with said substrate is associated a linearly drivable punch (200) with the aid of which the blank located in the readiness position can be inserted on the sliding surface into the combustion chamber and accompanied by the simultaneous advance by one blank length of any blanks or already coaxially lined up there.

4.2. Apparatus according to claim 4J characterized in that the punch (200) is operated stepwise with uniform steps, a length portion of the total blank length being associated with each step, so that for 1 metre blank length there are 1-200 and preferably 10 steps.

43. Apparatus according to one of the preceding claims, characterized in that the preheating chamber (2) for the gas tight filling of individual blanks (82) is equipped with an intake sluice (11). 44. Apparatus according to one of the preceding claims, characterized in that there is a hot gas discharge line (7) issuing into the atmosphere and is used for drawing off excess hot gas and that heating pipes or ducts, preferably the pipes (183-186) forming the grate (19D are connected in a dosable shunt (68,69) separated from the blanks with respect to said hot gas discharge line.

45. Apparatus for burning blanks, particularly electrode blanks intended for graphitization, which contain a carbon-containing filler and a binder and which are preferably supported on one another in lined up manner, with an elongated, gas tight sealable burning pipe (1) into which, based on the cross-section, the blanks (22-45) pass with a clearance, with a following, straight, smooth sliding surface (142,123,143) for the blanks at the bottom within the burning pipe, with an intake sluice (2,11,200) at the first end of the burning pipe and a discharge sluice (160) at the second end of the burning pipe for the gas tight introduction or removal of individual blanks (22- 45), with an advance unit (200) at the first end of the burning pipe for inserting the in each case next blank (21) accompanied by the simultaneous advance of the entire blank row (22-45) located in the burning pipe, with hot gas supply lines (46-53) which, distributed over the length, issue into the interior of the burning pipe^and with hot gas discharge lines (54-61), which distributed over the length, emanate from the interior of the burning pipe, characterized in that one segment (102) of the burning pipe (1) which is associated with the higher burning temperatures has a larger inside cross-section (132) than a segment (101,103) associated with the lower burning temperatures.

46. Apparatus according to claim 45 characterized in that the burning pipe (1) has a steel jacket wall (105), that a segment (101) of the burning pipe (1) associated with the lower temperatures is thermally insulated by an external, insulating material coating (107) and that a lower portion of the jacket wall forms the sliding surface (142).

47. Apparatus according to one of the preceding claims, characterized in that the burning pipe (1) has a steel jacket wall (105), that a segment (102) of the burning pipe (1) associated with the higher temp¬ eratures has a thermal insulating material inside lining (125) and that the inner face of the said lining forms in a lower circumferential or support sector (126) the sliding surface (123). 48. Apparatus according to claim 4/ characterized in that an innermost layer (127) forming the sliding surface (123) is made from insulating material, which is harder than the remaining part of the inside lining.

49. Apparatus according to claims47 or 4ξi characterized in that the circumferential or support sector (126) of the inner lining (125) forming the sliding surface is much, namely at least 10% thicker than the inside lining in an upper circumferential sector.

50. Apparatus according to claim 4.9 characterized in that in a lower circumferential sector extending preferably over roughly half the total circumference, the inner free cross-section is bounded by the shape of a spread U (129) and that the remaining inside cross-section is bounded by the shape of an arc (130).

5,1. Apparatus according to one of the preceding claims, characterized in that an additional heating means (72) is provided for the lower circumferential sector of the burning pipe (1).

ξ>2 . Apparatus according to one of the preceding claims, characterized in that there is at least one downwardly directed outflow (110), which can preferably be shut off, for fluid deposits collecting at the bottom of the burning pipe (1) and which emanates from the lower part of the burning pipe and is preferably located in the burning pipe segment (101) located upwards in the passage direction.