[go: up one dir, main page]

US3601377A - Shaft furnaces - Google Patents

Shaft furnaces Download PDF

Info

Publication number
US3601377A
US3601377A US809876A US3601377DA US3601377A US 3601377 A US3601377 A US 3601377A US 809876 A US809876 A US 809876A US 3601377D A US3601377D A US 3601377DA US 3601377 A US3601377 A US 3601377A
Authority
US
United States
Prior art keywords
gas
shaft
mineral
furnace
shafts
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US809876A
Other languages
English (en)
Inventor
Edward Charles Jope
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Application granted granted Critical
Publication of US3601377A publication Critical patent/US3601377A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B1/00—Shaft or like vertical or substantially vertical furnaces
    • F27B1/005—Shaft or like vertical or substantially vertical furnaces wherein no smelting of the charge occurs, e.g. calcining or sintering furnaces

Definitions

  • Camby Attorney Maisroth, Lind & Ponack ABSTRACT An apparatus for the calcination of a mineral, for example lime, magnesite or dolomite which consists of a fuel oil-fired furnace provided with two parallel shafts. Each of the shafts communicate with one or more gas bypass passages one of which is common to both shafts, which enables the downwardly moving charge to be isolated from the upwardly flowing furnace gases at a point in the furnace where a high degree of temperature uniformity is necessary in the charge.
  • SHEET 5 [IF 5 EDWARD CHARLES JOPE, Inventor Attorneys SHAFI FURNACES 1. Field of the Invention The field of the invention is believed to be encompasses in class C04 of the International Classification of Patents. 2. Description of the Prior Art Shaft kilns have been in use for many years for calcining limestone of a relatively large stone size, i.e. 3-7 inches in diameter. However, the known apparatus are not satisfactory for calcining stone of smaller dimensions than this. In addition the product is not uniformly calcined, since heating gases cannot readily flow through the fine material, and channelling occurs. This reduces the accuracy to which the calcining process can be controlled and some of the lime emerges dead burned.
  • the present invention provides a process for calcining a mineral, which process comprises charging the mineral to a furnace, heating the mineral in a preheating zone of the furnace, passing the preheatedmineral into a preheat soaking zone as hereinafter defined, in whichthe temperature of the mineral becomes substantially uniform, passing the resulting mineral to a burning zone in which the mineral is contacted with hot combustion gases from a fuel gasifier or burner and in which the mineral undergoes a chemical change with evolution of gas, withdrawing the evolved gas-and combustion gas from the furnace via a gas passage, whichmay be in the form of a chamber, and which, for example, is adjacent to the forms part of the preheat soaking zone, passing said gas through the preheating zone, cooling the calcined products in a cooling zone by the injection of air, and withdrawing the calcined product.
  • the present invention also provides apparatus for calcining a mineral which apparatuscomprises a furnace provided with at least one substantially vertical shaft lined with refractory material, with at least one inlet means for the mineral and with at least one discharge means for calcined mineral, which shaft is provided with at least one fuel supply means, with atleast one gas exit means and with at least one gas passage bypassing a preheat soaking zone as hereinbefore defined.
  • preheat soaking zone as used herein is meant the zone in the shaft below the preheat zone where the charge is heated initially and above the burning zone where the hot charge is calcined.
  • a further aspect of the present invention provides a method of operating an apparatus of the invention having at least two shafts wherein gases from the combustion and calcination processes in the furnace are passed into a gas passage common to at least two shafts and are subsequently removed via the gas exit means of one shaft or via both shafts,either alternately or simultaneously.
  • the 4s to be calcined is usually limestone, but may also be dolomite, magnesite, gypsum or any other calcinable material. Limestone with an average stone size of 20 mm. to 45 mm. is preferred.
  • the apparatus of the invention comprises a shaft, whose preferred cross section is rectangular, or rectangular with round corners, or elliptical.
  • the most preferred cross section is rectangular with two sides longer than the other two.
  • the width of the shaft may be as narrow as is consistent with an even and steady flow of material, since the temperature differences ina horizontal direction will then be minimized.
  • the shaft may be lined with any suitable refractory material, for example the lower temperature portions of the shaft may be lined with alumina, and the higher temperature portions with rammed, tarred dolomite.
  • the width of the shaft may be gradually increased to allow for expansion of the stone as it becomes heated, and also to avoid physical blockage. It should be noted that when small stone calcinable material is processed, heating up of the charge, and hence its expansion, may be more rapid than that of a normal sized charge.
  • the calcinable material may be fed to the shaft by means of a hopper, and since the apparatus will be operating at a pressure different from atmospheric pressure, it is preferred that the hopper is sealed.
  • the discharge means forthe calcined material preferably operates continuously, so that a uniform flow of material down the shaft occurs.
  • the fuel supply means of the apparatus may comprise any number of gas ports or oil gasifying/burning units. However it is preferred that the fuel supply means should be Catagas" heavy fuel oil gasifiers as described in the applicants British Pat. No. 904,435. In the apparatus of the present invention most of the combustion air is introduced to the central core of the shaft very close to the discharge units, so that it is warmed by the outflowing material before reaching the fuel supply means. Air may also be introduced elsewhere, according to necessity.
  • Gas exit means are provided at the top of the apparatus and it has been found useful, as hereinafter described, to provide valve means in the exit means, so that strict control over the exit gases can be maintained.
  • the gas exit means is connected to a powerful fan, capable of producing a substantial reduction in the pressure at the top of the shaft.
  • the gas may also be extracted through an outlet provided at the level of the preheat soaking zone, in a crossflow manner.
  • a feature of the apparatus of the present invention is the provision of a gas passage in the shaft at a level between that of the fuel supply means and the gas exit means. Solid material cannot pass into the gas passage.
  • the walls of the passage are preferably constructed of a refractory or other suitable material capable of conducting sensible heat, provided by the gas, to the solid material in the preheat soaking zone.
  • the apparatus of the invention may comprise a plurality of shafts wherein at least one gas passage is common to at least two of the shafts.
  • the gas passage is formed in the dividing wall between the shafts.
  • the invention provides an apparatus comprising two shafts as described above, constructed with their longer sides adjacent and a gas passage common to both shafts.
  • the apparatus consists of two tapered shafts l and 11 formed by a structure of refractory brick.
  • the structure is partially supported on two foundation blocks 12 and 13 and partially by a steel framework of Double I or box section girders 14 which framework is covered with sheet steel.
  • Two delivery cones 15 and 16 extend from the shafts between the foundation blocks 12 and 13 so that they are easily accessible.
  • Each shaft is fed by a hopper 17 (shown in part) supported on top on the framework 14 directly above the shaft.
  • the shape of the refractory structure is complex but symmetrical about a line bisecting the section shown in FIG. 1 and so it will be described with reference to half of the section only. It should be understood that there are corresponding services to the right shaft of the furnace shown in the drawing.
  • FIGS. 2 and 3 at a level slightly above the top of foundation block 12 there is located an air main 18 which surrounds a steel jacket 19 of the furnace. Connected to the main and passing through the central partition of the furnace is an air pipe 20. As can be seen from FIGS. 1 and 2 the pipe 20 is connected to the shaft by eleven supply pipes 21 and as can be seen from FIGS. 1 and 3 there is a similar connection between the main l8 and the shaft via supply pipes 22.
  • a channel 23 of rectangular cross section pierces the central partition and is connected to the shaft by fifteen subchannels 24, again of rectangular cross section, as shown in FIGS. 2.
  • a joint 35 is provided in the external refractory structure of the furnace at a level slightly above that of the air and gas pipe 33, to allow for expansion and contraction.
  • a set of eleven gas passages 36 set in the central partition communicates with each shaft by three sets 37, 38 and 39 of eleven channels of rectangular cross section.
  • the passage 36 is provided with an inspection door 40.
  • a combined air and gas pipe 41 is set into the central partition at the bottom of the gas passage and is connected to each of the channels 37 by l I T-shaped parts 42.
  • the external walls of the shafts are each provided with a set of 10 gas bypass ducts 43 connected at one end to the shaft by entry channels 44 and at the other end by 10 exit channels 45, both ofwhich are clearly shown in FIG. 3.
  • the exit channels 45 are controlled by baffles 46 and at this level the refractory structure is provided with supports 51 and 57.
  • the former whichis rectangular in cross section may be used for heating incoming air and/or gas.
  • a preheat channel 48 Disposed in the central partition slightly above the level of the gas exit channels 45 is a preheat channel 48 which is connected externally of the furnace to the various air and gas pipes used lower down the furnace through the conduit 51. From this level the shape of the refractory structure is such that the shafts broaden out until they meet two orifices 49 from the hopper 17. At the sides of the furnace the refractory structure is pierced by vents 53 communicating with the exhaust pipes 50 which lead to a powerful fan (not shown) and to the atmosphere.
  • FIG. 4 it can be seen that the central portion of the refractory structure is pierced by the l 1 gas passages 36 communicating with the shafts by the channels 39 and that the outer walls of the structure are pierced by the IQ gas bypass tubes 43.
  • the shafts 10 and 11 are also shown, as is the steelwork 51 and part of the double I section framework 14.
  • FIG. 5 of the accompanying drawing the hoppers 17 are shown in section and the framework 14 and hopper supports 52 in plan.
  • FIG. 6 of the accompanying drawings the exhaust pipes 50 are shown in section and the dust hopper 54 in plan.
  • lime of small stone size 20-45 mm. in diameter is cleaned for instance by flotation, washing with water or by passage over an efficient vibratory screen to remove dirt and fines and is fed to the hopper 17 which may feed material to the shaft continuously.
  • the material is then dried and preheated by warm gases which filter through from lower down the shaft to the gas exit means that is, to the exhaust pipes 50. It is preferred that the material reaches a temperature of at least 830 C. in this preheating zone 56 which extends down the shafts about as far as the baffle 55, from where it passes to a preheat soaking zone 57 which extends approximately from the baffie 55 to the joint 35.
  • the preheat soaking zone includes the narrowest part of the shaft, since it is at this level that the gas passages 35 are constructed. Gases from lower down the shaft do not pass through the material, but pass either through the gas passage, or through the gas bypass tubes 43 and so onto the preheating zone. This allows the preheated material in the preheat soaking zone to come to equilibrium with the surroundings and to attain a good degree of temperature uniformity. The absence of gas in this zone also eliminates the bad effects of channelling," i.e. the nonuniform passage of gas through the material, which is one of the most difficult problems in conventional small stone-burning processes, and which leads to uneven calcining in the burning region of the furnace.
  • the temperature of the gases passing through the gas passage and/or the bypass tubes should be at least 950 C., since at this temperature any free carbon remaining in the gases will be oxidized when it comes into contact with the preheated air which may be introduced into the passage as required.
  • 950 C. is also the minimum temperature of the gas which will both raise the incoming stone to 830 C, and keep the stone in the preheat soaking zone at a temperature of at least 830 C.
  • the material may be heated by the hot refractories of the gas passage.
  • the calcinable material emerges from the preheat soaking zone at a uniform rate, at a uniform temperature, and unaffected by channelling, passes to the burning zone.
  • the calcinable material is burnt, for example, limestone is burnt to lime, with the evolution of gas. Burning is achieved by the oxidation of a fuel, for example heavy fuel oil, with air or oxygen, and the hot exhaust gases pass with the evolved gas to the preheat soaking zone and preheating zone described above.
  • the temperature in the burning zone may be from about 1,100 C., to about l,240 C, and is preferably about l,l50 C.
  • the calcined material then passes out of the shaft via the discharge-cones, exchanging its heat with the cool air for combustion in a heat exchanger, not shown.
  • the temperature of the calcinable material in the various zones of the furnace may be controlled by the addition of air or waste furnace gases through some or all of the ducts 18, 20, 24, 26, 27, 33, 42 as well as by regulation of the amount of gas
  • the introduction of combustion air at various levels in the furnace ensures complete combustion of fuel within the charge.
  • the possibility of adding combustion air to the central gas passages 36 means that any carbon particles which may pass up from the burning zones may be oxidized without interfering with the ratio of air to fuel in the burning zones. The result of this is that only an absolute minimum of excess air need be employed in the burning zones, which is very desirable in calcination processes. Another result is that smoke emission will be reduced.
  • the furnace gases are withdrawn from the gas passages through first the preheating zone of the one shaft of apparatus, and then through that of the other.
  • the direction of flow may be switched about every 30 minutes, or there may be a gradual change from total flow of the gas through one preheating zone to total flow through the other.
  • the gases may also, of course, be withdrawn through both zones equally and simultaneously.
  • a charge of small stone limestone is first cleaned of quarry dirt and fine chippings by washing or by passing it over efficient vibratory screens. It is then passed to the hopper of the kiln from where it is fed into one or other of the shafts at a rate of 130 tons per day and moves towards the discharge cones at a rate of 34 per hour. Heavy fuel oil is fed tothe Catagas units at the rate of pounds per minute and air is fed to the apparatus at a rate of 2,170 cubic feet perminute at normal temperature and pressure.
  • the temperature in the burning zones is 1,200 C., and the stone remains in the zone for about 1 hour. Sixty-four tons per day of calcined lime is produced.
  • the combustion gas, excess air and evolved CO pass at therate of 2,470 cubic feet per minute at normal temperature pressure from the burning zones to the gas passages, which they reach at a temperature of950 C. minimum.
  • the gas exit means is provided with movable shutters and with valves. By means of the latter, the gas entering the gas passages may be withdrawn through first one preheating zone, and then the other, alternately, the direction offlow may be switched at desired intervals.
  • the Catagas Units may be pressurized in relation to the combustion air pressure, and these pressures may be varied without creating any major problems in draught balance.
  • primary and secondary combustion air may be pushed"'through the burning zone at any required volume and pressure.
  • This hasthe advantage that the power of the main exhaust fan may be reduced, and that the process is flexible enough to accommodate any changes brought about by a fluctuation in stone size.
  • one shaft of the apparatus may be'shut down while the other continues to operate with no loss of efficiency.
  • the wide gas ports at the top of the burning zone reduce the amount oflime dust deposited and may even be self-cleaning.
  • the invention also includes calcined minerals whenever prepared in the apparatus or by the process described above.
  • a shaft furnace for converting a mineral to a calcined mineral with the production of gas comprising two substantially parallel and vertical shafts of substantially rectangular cross section lined with refractory material said refractory material forming a single dividing wall between said shafts and three external walls of each shaft, each shaft being provided close to its upper end with an inlet means for said mineral and with an exit means for said gas and close to its lower end with an exit means for said calcined mineral, a heavy fuel oil gasifyer protruding into each shaft between said inlet means and said calcined mineral exit means, each shaft being provided with means for the introduction of recirculated furnace gas and air at various levels in the furnace wherein a gas passage common to both shafts is constructed in said dividing wall, said gas passage bypassing a preheat soaking zone in each of said shafts and being provided with means for the introduction of a free oxygen containing gas and wherein the two refractory external walls opposite said dividing wall are each provided with a gas passage which bypasses
  • a shaft furnace for converting a mineral to a calcined mineral with the production of gas said furnace comprises a substantially vertical shaft lined with refractory material, said shaft being provided close to its upper end with an inlet means for said mineral and with an exit means for said gas and close to its lower end with .an exit means for said calcined mineral,
  • a shaft furnace according to claim 2 comprising at least two gas passages, the gas entry and exit points of at least one of said gas passages being respectively at a level in the kiln above the gas entry and exit points of at least one of the remaining gas passages.
  • a shaft furnace according to claim 2 wherein there are two of said shafts and at least one of said gas passages is constructed in a dividing wall between said shafts to communicate with both shafts and bypasses a soaking zone in each of said shafts.
  • a shaft furnace for converting a mineral to a calcined mineral with the production of gas comprising two substantially parallel and vertical shafts of substantially rectangular cross section lined with refractory material, said refractory material forming a single dividing wall between said shafts and three external walls of each shaft, each shaft being provided close to its upper end with an inlet means for said mineral and with an exit means for said gas and close to' its lower end with an exit means for said calcined mineral, a heavy fuel oil gasifyer opening into each shaft between said inlet means and said calcined mineral exit means, each shaft being provided with means for the introduction of recirculated furnace gas and air at various levels in the furnace, a soaking zone in each of said shafts, a gas passage common to both shafts in said dividing wall bypassing said soaking zone, means for the introduction of a free oxygen containing gas into said gas passage and two refractory external walls opposite said dividing wall each provided with a gas passage bypassing a preheat soaking zone in each ofsaid
  • a continuous process for calcining a mineral comprising the steps of a. charging said mineral to a shaft furnace.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Furnace Details (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
US809876A 1968-03-29 1969-03-24 Shaft furnaces Expired - Lifetime US3601377A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1527168 1968-03-29

Publications (1)

Publication Number Publication Date
US3601377A true US3601377A (en) 1971-08-24

Family

ID=10056087

Family Applications (1)

Application Number Title Priority Date Filing Date
US809876A Expired - Lifetime US3601377A (en) 1968-03-29 1969-03-24 Shaft furnaces

Country Status (5)

Country Link
US (1) US3601377A (es)
CA (1) CA940706A (es)
DE (1) DE1915781B2 (es)
FR (1) FR2005064A1 (es)
GB (1) GB1259603A (es)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4147504A (en) * 1974-06-12 1979-04-03 Unitika Limited Apparatus for regenerating activated carbon
US10455224B2 (en) 2013-03-13 2019-10-22 Sony Interactive Entertainment Inc. Digital inter-pupillary distance adjustment
CN111233351A (zh) * 2020-03-10 2020-06-05 中冶京诚工程技术有限公司 双膛窑及煅烧方法
CN114700349A (zh) * 2022-04-07 2022-07-05 广西大学 生物燃料竖窑、赤泥磁化装置和赤泥磁化方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5816934B2 (ja) * 1976-03-31 1983-04-04 日揮株式会社 活性炭の再生装置
AT377248B (de) * 1982-07-12 1985-02-25 Maerz Ofenbau Verfahren und schachtofen zum brennen von kalkstein
CN214223157U (zh) * 2020-10-28 2021-09-17 杭州正隆环保科技有限公司 一种烟气处理设备

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2650814A (en) * 1949-11-23 1953-09-01 Ernest Newell & Company Ltd Kiln
DE1124863B (de) * 1954-05-22 1962-03-01 Polysius Gmbh Mittels Brenner beheizbarer Schachtofen zum Brennen von Zement und aehnlichem Gut
US3175302A (en) * 1961-01-04 1965-03-30 Fives Lille Cail Gravity-type heat exchanger for treating particulate solid material

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2650814A (en) * 1949-11-23 1953-09-01 Ernest Newell & Company Ltd Kiln
DE1124863B (de) * 1954-05-22 1962-03-01 Polysius Gmbh Mittels Brenner beheizbarer Schachtofen zum Brennen von Zement und aehnlichem Gut
US3175302A (en) * 1961-01-04 1965-03-30 Fives Lille Cail Gravity-type heat exchanger for treating particulate solid material

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4147504A (en) * 1974-06-12 1979-04-03 Unitika Limited Apparatus for regenerating activated carbon
US10455224B2 (en) 2013-03-13 2019-10-22 Sony Interactive Entertainment Inc. Digital inter-pupillary distance adjustment
US11082683B2 (en) 2013-03-13 2021-08-03 Sony Interactive Entertainment Inc. Digital inter-pupillary distance adjustment
US11729369B2 (en) 2013-03-13 2023-08-15 Sony Interactive Entertainment Inc. Digital inter-pupillary distance adjustment
CN111233351A (zh) * 2020-03-10 2020-06-05 中冶京诚工程技术有限公司 双膛窑及煅烧方法
CN111233351B (zh) * 2020-03-10 2023-12-01 中冶京诚工程技术有限公司 双膛窑及煅烧方法
CN114700349A (zh) * 2022-04-07 2022-07-05 广西大学 生物燃料竖窑、赤泥磁化装置和赤泥磁化方法
CN114700349B (zh) * 2022-04-07 2023-06-09 广西产研院智慧农业研究院有限公司 生物燃料竖窑、赤泥磁化装置和赤泥磁化方法

Also Published As

Publication number Publication date
CA940706A (en) 1974-01-29
GB1259603A (es) 1972-01-05
FR2005064A1 (es) 1969-12-05
DE1915781B2 (de) 1971-06-16
DE1915781A1 (de) 1971-01-28

Similar Documents

Publication Publication Date Title
US4259081A (en) Process of calcining limestone in a rotary kiln
US3601377A (en) Shaft furnaces
US3404199A (en) Heating process in a rotary kiln
CS223966B2 (en) Method of baking the lime and device for executing the said method
US3722867A (en) Method of calcining limestone
US2603476A (en) Circular open hearth melting furnace
US3356351A (en) Vertical lime kiln
CA1159647A (en) Calcining furnace with gas-permeable wall structure
US3954391A (en) Process for endothermic heat treatment of materials
US3202405A (en) Vertical shaft kiln and method of operation thereof
US3743697A (en) Process of calcination
US3544096A (en) Cross-current blast furnace
US3241823A (en) Air-heater cupola constructions
US3695595A (en) Method and means for sintering materials, particularly dolomite and magnesite, in a shaft furnace
US3427367A (en) Prefiring of refractory materials
US2489211A (en) Apparatus for producing cement clinker and the like
CN115516264A (zh) 用于对自由浮动原材料进行热处理的设备和用于运行这种设备的方法
US3690636A (en) Recuperative furnaces
US1011804A (en) Process of burning lime.
SU1025977A1 (ru) Вращающа с печь
SU1315478A1 (ru) Способ обжига сидеритовых руд и шахтна печь дл его осуществлени
SU549663A1 (ru) Шахтна печь дл обжига кускового материала
US3321559A (en) Kiln operation
US2776825A (en) Pebble furnaces and method of heating pebbles
US829957A (en) Apparatus for making cement clinker.