Patent Application
20060108721
This invention relates to the control of continuous and direct iron-making or gasification using pulverized or finely ground coal, iron ore (where applicable) and other materials and unique sensors and computer control techniques and methods in a continuous smelting process such that through the judicious application of these specialized sensors and techniques that this present invention does not require people to interface with the process directly except by keeping the lock hoppers full of previously pre-heated (not shown) feed ingredients, and two lock hoppers are used for each ingredient to insure continuous and interrupted feeding of materials.
Much of present steel making is manually controlled with manual sampling of steel quality, manual control of molten levels within the furnace, long time lags, high expense of apparatus since coke, recuperator, peepholes, excessive labor and reduced productivity result. Current gasification apparatuses are not well suited to recovery of materials, including metal recovery from the coal or carbon gasified.
A related invention, while nowhere as descriptive and fully controlled as the present invention, is the Hlsmelt process. There are no specific means or ways specified to control the Hlsmelt steel making process as outlined in U.S. Pat. No. 6,626,977. And it is not necessarily advantageous to feed mix materials with multiple lances immersed in the molten steel such as Hlsmelt teaches, which is therefore more cumbersome and expensive to build and maintain since material feed and blast can be more simply done as outlined in U.S. Pat. No. 4,639,269, which the present invention greatly improves upon, and adapts to steel making. What is lacking in U.S. Pat. No. 6,626,977 to achieve inexpensive and highly productive continuous direct steel making technology that is cost effective are means to measure and control the process, which presently is left up to the design and construction engineers and not specified in U.S. Pat. No. 6,626,977. These are complex matters not practiced in the art, and this invention shows how to do this with a very high degree of specificity for process control and optimization so necessary to produce low grade steel quality directly from a single smelting/steel-making crucible within the furnace process while minimizing labor, capital and maximizing productivity income opportunities simultaneously. Similarly, gasifiers do not practice the art of a molten slag pools or control thereof of sufficient depth to recover metals that sink to the base for recovery or that more easily makes a saleable aggregate that such practice can make possible. The control over the gasification and steel making process is also greatly enhanced as described herein.
A direct and continuous controlled smelting and low-grade steel making process or coal or carbon gasification which involves blasting a mixture of pulverized ore (but not if just a gasifier), coal, and a flux mixture(s) through a concentric water cooled downward lance close into a molten slag, with ore mix flowing between the outer cooled shell and inner core air blast tube which expels air/oxygen mixture at high velocity onto the top of the molten slag and steel layers, and to make steel with air/oxygen blast under the molten layer from the base of the crucible distributed evenly through a fine bubbling diffuser mounted within the crucible floor so as to reduce carbon in the molten iron, means to separately meter ore mix ingredients from lock hoppers with bubble-tight valves to prevent gas from flowing back though the hoppers, and with in-line mixer before entering the concentric lance, and with CO2 /CO and temperature exit gas measurement instrument with exit gas concentric pipes allowing heating of inlet air/oxygen blast, including circulating such air/oxygen within the top metal plenum of the furnace with inner shell made of high temperature steel alloys enabling achievement of 1200 F air/oxygen blast, and it has slag and low-grade steel outlet trough with above laser spectrometer measurements to determine chemical composition of both flows, and crucible vertical scanning nuclear gage of molten steel, slag and fresh mix layers to determine their vertical profile density and relative depths and placements, all this instrumentation so as to combine and with suitable computer control and optimizing algorithms and software to properly control preheated ore mix feed rate and composition, levels of molten iron, air/oxygen blast rates, and to manipulate molten levels using either an actuated tap hole plug controller or refrigerant to freeze a portion of the tap hole exit area or eddy current inducing forces to slow down steel exit flow so as to provide reliable backup methods of slag and steel flows so as to accurately maintain molten steel and slag level set points within the crucible, all to produce a quality low-grade steel output with proper carbon, sulfur and potassium contents to the maximum practical extent so as to optimize steel making within one vessel in terms of quality and production requirements and to maximize the overall cost effectiveness of process of smelting and steel-making or gasification.
Specifically, one process of the present invention includes the following:
At least 2 lock hoppers for each ingredient of combination of similar ingredients such as pulverized coal, ore, and fluxes (mix) are used to guarantee their continuous feed. These lock hoppers have specially designed variable speed flotation helical undercutting rotors to undercut and simultaneously unload and regulate feeds, after calibration with rotary rpm, as necessary to maximize production consistent with steel desired quality, generally carbon content, and more than one flux material lock hoppers (one set is shown) may be added to control sulfur and phosphorous content of the final low-grade output. The invention is not intended to make a high grade steel which would take place in further downstream operations not described here. These lock hopers would use bubble tight high-temperature valves on their inlet and outlet that are capable of hundreds of thousands of operations, such a valve made by Macawber Engineering Incorporated, which are especially suited to this application since it's necessary that no air blast can pass up into the air or nitrogen purged lock hoppers (to avoid possible dust explosions in the pulverized coal lock hoppers when filling, it may be desirable to nitrogen purge these hoppers and all other hoppers as well).
An in-line mixer at the start of the chute or pipe that feeds into the concentric lane entering through the center top of the furnace. All ingredients converge by gravity flow or other means at this point for gravity flow into the slag and molten slag mass for smelting into iron and eventual conversion into low grade steel as the ingredients work their way into the discharge tap hole on the center floor of the crucible.
From the in-line mixer, a vertical pipe with an enlarged section where the water cooled lance section begins and where the hot air/oxygen enters through the outer cooled enlarged shell into the center air blast tube, whereby such cooled lance enlargement is sufficient for all feed materials to flow at maximum rates easily passing by the narrow vertical rectangular tube penetrating into the lance outer core on one side to feed the center circular round tube of the lance with hot blast air/oxygen.
A concentric lance section with cooled outer upper furnace ceiling close to the molten ash level, such gap between end of lance and top of molten slag made adjustable by the control set point level of the molten ash, with ore mix flowing between the other cooled shell and inner tube with the tube shorter than the cooled outer shell, or in the case of gasification, radial water or steam spraying to create gasification reactions, at the end where ore mix and air/oxygen impinge into the molten mass inside the furnace, whereby such hot air tube is shorter and inside the outer shell sufficiently to create a venturi or suction effect to pull the ore mix down the lance, and whereby the high velocity of the air/oxygen achieves thorough mixing and combustion of coal to smelt the ore and relying on then remaining molten slag and steel to finish smelting and conversion into iron at the upper region of the molten iron layer while impinging at sufficient velocity to push aside molten slag. In the case of gasification, preheating ingredients and last oxygen is not as critical as with steal making where smelting operations are involved whereby the whole of the gasification vessel can be refractory lined and cyclone cleaner made contiguous with the gasifying vessel.
The upper shell of the furnace with insulated outer layer and high temperature steel alloy inner layer allow the inner layer to finish heating the pre-heated air/oxygen blast to 1200 F, designed with sufficient inner surface area of the exposed upper furnace to achieve these final blast temperatures at full load steel flow given that such allow inner steel alloy surfaces may be coated with ceramic or other high temperature material to additionally protect the inner steel shell from corrosion and provide sufficient insulating layer to prevent excessive temperature from melting or excessively lowering the strength of this steel alloy. However, in any event, this upper furnace steel section would be supported above by a frame (not shown) surrounding the furnace on its sides as necessary.
Concentric exhaust high temperature allows pipes for exit gases to be ceramic coated as necessary for corrosion protection and excessive temperatures, such that the air/oxygen mixture flowing in the outer concentric space pre-heats the incoming air/oxygen blast before it circulates around the top shroud of the furnace for final temperature increase and entrance into the center air tube of the lance, whereby the inner exhaust gas tube section at the exits into a co-generating boiler (not shown) or other energy recovery system with comprehensive emission abatement additions, generally a high efficiency power boiler, has a combination CO2, CO and temperature measurement instrument mounted there to measure the character of the exhaust gas for computer control optimization purposes of the process.
A refractory lined and insulated (insulation not shown) crucible below the upper air cooled metal portion of the furnace has a center bottom tap hole for finished low grade steel and a tap hole some distance above the floor on the side wall of the refractory crucible to accommodate slag removal, the height of this slag hole would be determined by design. For example, if for basic steel making 600 tons were to be maintained in the crucible, the slag tap hole may be as high as 6-7 feet. It has a ceramic fine air/oxygen bubbler diffuser of sufficient diameter and flow to cause adequate carbon reduction in the iron in the lower section of the molten iron layer to convert smelted iron to low-grade quality steel, whereby such steel (or recovered metals as in gasification) flows down through an open center hole of this diffuser and tap hole passage is a ceramic pipe which turns at right angles to let out steel from a side wall tap hole below the crucible floor but above the lower steel shell of the furnace and imbedded within the refractory, and such ceramic passage hole pipe is a magnetic inducing coil or plates to produce counter forces to steel flow to assist in the control of steel outflow for crucible molten level control purposes.
Also to further assist in steel or molten flow control, the outer steel tap hole ceramic pipe can be wrapped with refrigeration coils through which refrigerant at various temperatures and flow rates can be used to solidify steel to form smaller or larger openings tap hole openings to control the flow of molten steel out. Or, further molten steel and slag flow control reliability is achieved with an outer tap hole tapered plug usually used to control such molten steel flows with suitable actuator, and readily available in the art. Or, the bottom hole can be arranged to use a tapered plug valve for flow control.
These flows of slag and steel into a trough of sufficient volume and weir dam sufficiently higher than the tap hole to cover the tap hole such that the velocity of the flow does not overly agitate flow over the weir for weir vertical level measurement purposes. A radar or sound type level measurement instrument locate above the weir can accurately determine the flow height in the weir notch to measure the volume of slag or steel flowing over the weirs.
A laser spectrometer above the troughs to measure steel and slag chemical properties to judge steel quality and slag carbon losses, such information manipulated by the degree of air/oxygen blasts, mass flow rates through the crucible, feed rates of all individual ingredients, including combustion of coal as measured by a combined CO2, CO, and temperature sensor mounted on the final exhaust gas pipe or other known means necessary to control these parameters. Or laser spectrometry rays shooting across the combustion area also be used, both for steel and gasification.
A vertical scanning nuclear level gage means to send the usual high energy beam through a uniform vertical section of the crucible, in effect a chord of the crucible measuring only a segments chord length to minimize the nuclear penetrating emission required, and such crucible may be so arranged in shape as to be elliptical to make the amount of thickness of the chord further minimized, and the full vertical height of the refractory lined crucible designed to be vertically uniform, with suitable detector on the other side to continuously scan into the total design depth of the molten slag, steel, and fresh ingredients depth within the crucible so as to determine density profile to control molten steel and ash and fresh ingredient levels or thickness by control of outflow molten steel rate, slag flow rate, ore mix inflow rate to insure fresh material are not accumulating above the slag (is being smelted at an adequate rate) which might require more blast or a higher ratio of coal in the final mix admitted into the furnace, or that the slag and molten steel levels are being properly maintained. The computer algorithms to control these variables can be created by those skilled in the art of steel making and are discussed further below. Thus with this level measurement and other measurements noted, the direct and continuous steel making processes is fully automated and optimized.
Such a crucible arrangement can also be advantageously used to create and control a molten ash system under the hoppers of municipal solid waste burning or low temperature coal gasification systems, coal boilers, or any system where it's desirable to create molten ash so as to minimize its carbon content, except in this instance the vertical scanning nuclear gage and outflow tap hole level control plug/actuator combination etc. are used to control, the molten level of ash, and that a level of fresh ash material is maintained atop this molten ash layer, and that water cooled lance is inserted at an angle from the side of the crucible to inject pulverized coal or other inexpensive polarized fuel plus air or oxygen with excess air needed to combust the fuel, preferably an enhanced air/oxygen mixture is used as an oxidant to assure supply adequately high temperatures as necessary to maintain the molten ash state and control the thickness of the insulating ash layer. In this case, the computer gives out two primary control signals, one for molten ash level control by controlling the tap hole flow, and one to regulate the amount of pulverized coal energy entering the lance to maintain a suitable insulating ash level above the molten ash, whereby both these level conditions inside the crucible are measured by the scanning nuclear gage.
In the case of making steel, control valve means to adjust air/oxygen blast rates into the top lance and bottom fine bubble diffuser and optimizing algorithms to computer control the whole furnace process as follows in items A-H below:
A. If more production is needed, the computer looks to increase steel and slag levels and if it can, does so to increase mass in the system and then adjusts to a higher steel and slag flows out with the scanning nuclear gage input enabling precise levels and thickness of iron and slag to be maintained within the furnace, and if final steel carbon is increasing per spectrometer measurements, it increases bubbling air/oxygen flows. If CO is excessive, it increases the hot air/oxygen blast from the lance.
B. If steel carbon content too high, the computer increases bubbling air/oxygen, and if that does not correct it, increases the lance air/oxygen blast as well. If it is still too high or reducing atmosphere in the furnace is getting too low (as evidenced by decreasing CO measurement), the ore mix feed is reduced to bring the carbon reducing capability of the diffuser into it's acceptable range of capability.
C. For furnace molten iron level for any given ore feed rate (production set point), the nuclear scanning gage enables furnace iron level to be adjusted by the steel outlet tap hole plug position or refrigerant temperature or flow rate, eddy inducing restricting forces whichever means of flow control are used or necessary to be used. All three can be designed to operate in staggered way; eddy current first, refrigerant flow second, and use of the tapered plug force or position third.
D. Or for any given production level, the nuclear scanning gage enables slag level to be adjusted by the slag outlet tap hole plug position or force level. If exit gas CO level is too low (thus CO2 level too high) this indicates the air/oxygen lance blast is too high for the production level set, therefore blast is reduced and if, however, fresh feed level or slag thickness continues to accumulate beyond a safe or acceptable level, then either blast has to increase, or ore feed has to decrease, and iron level control follows from these changes.
E. If the steel carbon level is acceptable, but other steel chemical parameters are too high or too low the only remedy is a change of the ore mixture by adjusting lock hopper discharge rates. It will take a long time constant for these changes to show up in the final steel since there can be up to 6 hours of steel capacity contained within the crucible for basic steel manufacturing operations (calcium carbonate used as flux).
F. The laser spectrometer on slag monitors it for iron and carbon content indicating an ore mix change may be needed or that more lance blast is needed. It may be desirable to let out-of-limit carbon conditions prevail in the slag if it is the most cost effective operation. The computer can be capable of calculating the cost consequences of various operation modes.
G. Since it's almost always desired to evolve to maximum possible production capability of the furnace, the computer can always be set to a evolutionary operations standard of maximum production, say as determined by an upper level carbon content of the final steel or iron or slag. In this instance, the computer will slowly ramp up input or mix feed rate and adjust crucible molten slag and iron levels to maximize production. Maximum possible levels of slag and iron will be determined over time. Increasing top air/oxygen lance blast and bubbling O2 rates should maximize steel production until a limiting condition is reached (say excessive carbon in the final output steel, then the computer will back down production to within a safe production level such that there is a measure of control over the process using the parameters of CO2 /CO, final spectrometer measurements of steel and slag, furnace iron and slag level or thickness, air blast, air/oxygen bubbling rate, or ore mix composition, all automatically adjusted by the computer control system algorithm determinations.
H. Steel and slag weir flows (weir levels) are measured since they indicate production levels of actual steel and slag and they can also indicate an upper limit has been reached or that there are flow molten steel or slag flow control problems. For example, if the plug opens the tap hole more but no increased flow is noted in either slag or steel, then ether the flow control actuating methods are failing and computer historical data can immediately enable the computer algorithm to alarm, and determine what the operator should check first.
Thus, it can be seen that this invention teaches a very advanced method of continuous steel making and/or gasification and uses the most modern combination of instruments and sensors to accomplish this, and it teaches a unique arrangement of equipment and process to avoid the need for coke and expensive recuperator to preheat air/oxygen blast to proper temperatures, and finally, optimization algorithms are suggested such that those skilled in the computer programming arts in combination with steel process engineer experts in acid or basic steel making processes could enable such software to take advantage of with the instrument signals provide to gain precise and accurate control over the process including ingredient mix ratios and all material flows to optimize steel outflow rates with quality for maximum economic advantage with a minimum of labor input and capital cost.
The present invention and its advantages over the prior art will be more readily understood upon reading the following detailed description and the appended claims with reference to the accompanying drawings.
The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
Three lock hoppers 1, 2, and 3 are shown and there would be an identical hopper behind each one so as to allow continuous flow of materials from the one in front or behind. That is, while one of the lock hoppers of each pair is operating, the other lock hopper is being filled. Each lock hopper is fed pulverized materials to the extent practical for coal 4, ore 5, and fluxes 6 through conveyors (not shown) to re-fill the hoppers as determined by level sensors 7′. In such a fill cycle, the hopper being filled is not operating, its outlet valve 8 is closed, its fill valve 7 is open, and the appropriate material is entering the hopper.
Each hopper has an unloader/feeder unit 10 such as one comprised of a loose spline drive inward floating helical plate (not shown) with rotating cap 11 preventing free fall of material 12 in the center outlet hole, not shown, whereby material is made to flow at a rate determined by the speed of drive motor 13. Such an unloader feeder is described more fully in U.S. Pat. No. 4,659,340, issued Apr. 21, 1987 to Lloyd E. Weaver and incorporated herein by reference in its entirety. Alternatively, there are other commercial versions of such technology that can be used to advantage in this invention.
As a gasifier, because it's desirable to keep nitrogen out of the gasification reactions to avoid noxious nitrogen based compounds, once filled, it's desirable to close valves 7 and 8 and evacuate the chamber by vacuum pumps (not shown) and purge with an non-reactive or inert gas to repressurizing (apparatus not shown) so as to prevent undesirable gasification reactions when oxidizing reactions take pace from pure oxygen addition 20 through inner lance 19 tube 30.
Also, in feeding coal and flux or any materials to gasifiers, it should be a dry and finely ground material, but it does not have to be a fine powder, as pure oxygen is highly reactive with carbon under such circumstances of process as depicted in the invention. Therefore, just as in times past coal was prepared and stored in large bins prior to feeding to boiler burners, a better practice for this invention would be to adequately dry and prepare the granular material to be gasified or utilized when such surge bins (not shown) are used before feeding coal to the lock hoppers 1, 2, or 3 or however many are required to get the chemical reactions desired, prior to applying vacuum and re-pressurization of the hopers and subsequent feeding the mixed materials 18 to the gasification or reactive chamber respectively.
Materials 4′, 5′, 6′ (coal, ore, and fluxes respectively) flow by gravity through chutes all to combine into mixed flow 18 by mixer 15 outputting into pipe 16, whereby the flow 18 splits to flow around inner lance air/oxygen tube 30. Pipe 16 which can be as large as twenty-four inches in diameter or more for furnaces with 800,000 tons per year of steel producing ability. Also, as shown, pipe 16 is shown to enlarge to pipe diameter 17 to allow mix 18 to freely bypass into concentric lance 19. At this point, the shell 17 and lance 19, now larger than pipe diameter 16 as appropriate, have cooled outer shells.
In describing the upper furnace area, starting with air/oxygen blast 20, passing through flow control valve 21, air enters concentric pipe assembly 22 and 23 where 22 is the other shell and 23 is the hot inner alloy pipe for furnace exit gases 24. It should be noted here that the terms “air” and “oxygen” can be used interchangeably here and the either term, whether used alone or together, refers to air, pure oxygen or any other oxygen-containing substance. The pipe assembly is close coupled to a heat recovery or boiler apparatus, not shown but the inner pipe 22 has a combination CO2, CO, and temperature sensing unit 25 mounted at the end for purposes of assisting in computer (not shown) control the blast furnace of
The lower furnace area is comprised of refractory lined crucible with base 35 and outer shell 35′ and straight vertical inner refractory walls 36 and tapered in with section 37 to the inner upper furnace shell 27. The inner diameter of this crucible could be as large as 20 feet inside diameter to accommodate say 600 tons of steel maintained in the furnace for basic steel operations for an 800,000 tons per year furnace. To control upper molten ash level 38 and molten steel level 39, a scanning nuclear gage is used which is a well known measurement technology and is generally comprised of a scanning source 40 and corresponding scanning detector 41. These would not generally scan through the center of the diameter but rather off to one side scanning a chord of minimum suitable length for suitable nuclear ray penetration through the furnace and furnace mass to detect the full range of slag 38 and steel 39 and upper fresh feed mass thickness 42 to the extent that it exists. This signal is feed into a computer programmed to show a complete vertical density profile of the vertical height measured which can be used to make decisions of inflows and outflows to the furnace to be discussed below.
The upper layer of the molten steel molten mass 43 is expected to be what would be considered as smelted iron and the lower level of 43 to be low-grade steel created by the carbon reducing action of air/oxygen blast 44 controlled by valve 45 which passes into the base of the crucible 35 through fine bubbling diffuser 46 and up though the mass of molten steel and slag depicted as bubble streams 47.
The low grade steel 48 exits the base 35 through ceramic pipe passage way 49 which through most of its length is surrounded by eddy current inducing forces coil or plate(s) 50 which can be activated by electricity so as to act as a countervailing force to slow the exit flow of steel 48 through passage way 49. The outer tap hole area 51 of pipe 49 is surrounded by refrigerated coil 52 which can have cooled fluids at various flow rates and temperatures, adjusted by computer control based on nuclear sensor 40, 41, to cause the exit tap hole 51 to shrink in size at coil 52 so as to assist in control of steel 48 flow out to maintain molten steel level 39. Or, the computer can activate the actuator 53, well known in the art, which actuates submerged tapered plug 54 away from or towards tap hole 51 to increase or decrease out flow as required, thereby acting as a further backup molten steel level 39 control method.
Having described this level control process of molten steel and slag, and referring to the nuclear vertical scanning gage 40, 41 above, this same process can be used to advantageously create and control a molten ash making process which is advantageous to reduce the volume of ash from ash hoppers of waste to energy boilers, coal boilers, low-temperature gasifiers, one known as PCPG, and to make this ash suitable for recycling in road aggregate and the like, and this would work as follows: in this instance, there would be a source of excess air/oxygen mixture and pulverized coal or any low-cost energy fuel injected through cooled inclined lance 55 shown as a dotted lines in
To complete the description of the outflow control of the molten steel and slag process, steel passes out though tap hole 51 into trough 56 which has sufficient volume and height to allow steel level 57 to extend sufficiently in level above tap hole 51 such that the steel flow 58 over notched weir 58′ is not unduly agitated such that non-contacting sonic or radar level sensor 59′ can accurately measure level 57 for accurate steel volume flow measurement. In addition, above the trough steel level 57 is mounted laser spectrometer measurement unit 59 which is used to feed the control computer a chemical analysis of the steel such as iron, carbon, sulfur, and potassium and other elements to insure adequate steel quality is being maintained.
Similar methods are used to control the molten slag flow and characteristics such as carbon content including such previously described elements as eddy current coil 60, refrigerant coil 60′, tap hole 61, plug controller 62, tapered plug 63, trough 64, weir 65, trough level 66, weir notch level sensor 67 and laser spectrometer 68 to maintain slag flow 69 to control slag levels 32, 38.
To begin operations of the furnace, molten steel would be added to the crucible though an upper furnace opening (not shown), and then the hot blast 31 would commence in conjunction with the feed 18 driven by blast 31 into the slag as 31′. The computer would be determining the amount of CO2, CO, and temperature of the final exit gas 24 and begin to adjust feed rate 18, steel and slag flows 58 and 69 respectively and starting the adjustments of mix 18 consentient ratios or rates depending on spectroscopic measurements 59 and 68. But because there is such a long time constant for turnover of steel 43 within the crucible, about 6 hours, previous data and experience in steel operations contained within the computer data base, plus known experience and nuances about steel making programmed into the computer, enables quite accurate initial conditions for all the control variables to be set such as pulverized coal, flux, and ore ratios to the total mix flow 18 and what blast 31 is appropriate for what total feed mix flow 18 selected. The final measurements of the spectrometers and outlet gas 24, of CO2, CO, and temperature and other gases will enable to computer to bring the whole process under control and then fine tune the process for best steel quality consistent with carbon losses in the molten ash and needed production level.
Some examples follow of how the computer (not shown) control algorithms would be set up:
1. If more production is needed the computer looks to see if it can increase steel and slag levels 32 and 39 and if it can, does so to increase the steel 43 and slag masses in the crucible, and then it adjusts to a higher steel and slag flows 58 and 69 out with the vertical scanning nuclear gage 40, 41 that determines the crucible vertical mass density profile enabling precise levels and thickness of iron and slag to be maintained within the furnaces. And if final carbon is increasing per spectrometer measurements 59, it increases bubbling air/oxygen flow 44 and if CO is increasing too much, it increases the hot air/oxygen blast 20, 31 blast from above which is increased as ore mix feed 18 increases.
2. If the final steel 58 carbon content too high the computer increases bubbling air/oxygen 44, and if that does not correct it, increases above air/oxygen blast 20, 31 as well, if it is still too high or reducing atmosphere in the furnace is getting too low (as evidenced by decreasing CO measurement 25), ore mix feed 18 is reduced to bring the carbon reducing capability of the diffuser into it's acceptable range of capability.
3. For furnace molten iron level, for any given ore mix 18 feed rate (production set point), the vertical nuclear scanning gage 40, 41 enables furnace iron level 39 to be adjusted by the steel outlet tap hole plug position 54 or refrigerant 52 temperature or flow rate (not shown), or increased eddy currents to slow steel flow through 50, whichever means of flow control can be used to best advantage.
4. If CO level as measured by 25 is too low (thus CO2 level too high) this indicates the air/oxygen lance blast 20, 31 is too high for the production level set, therefore blast 20, 31 is reduced and if, however, fresh feed level or slag level 32,38 continues to accumulate beyond a safe or acceptable level like become too close to the lance 19, then either blast 20, 31 has to increase, or ore feed mix rate 18 by decreasing the unloader motor 13 speeds have to decrease, and iron level 39 control follows from these changes by action of the nuclear gage combination 40, 41 and flow control measures mentioned previously. More coal feed 4′ percentage may also be needed.
5. If the steel carbon level is acceptable as measure by steel laser spectrometer 59, but other steel chemical parameters are too high or too low, a remedy may be a change of the flux 6 mixture and or it's rate of addition. Because there may be up to 6 hours of steel production 43 retained in the crucible for basic processes, it will take a long time for these changes to show up in the final steel 58, but it is still capable of automatic control and optimization by the computer since the computer clock can wait these intervals to check final results from the spectrometers.
6. The laser spectrometer 68 use on slag monitors slag for iron and carbon content indicating an ore mix 18 ratio change may be needed or that production can be increased or must be reduced or top blast 20, 31 changed to reduce this carbon content. Or it may be desirable to let out of limit conditions for slag carbon content prevail to achieve the production level desired. Those skilled in the art of steel making will enable the computer programmer to fine tune the logic to optimally control the process.
7. Since it's almost always desired to evolve to maximum possible steel 58 production capability of the furnace, the computer can always be set to a evolutionary operations standard of maximum production say as determined by an upper level steel 58 carbon content. In this instance, the computer will slowly ramp up input feed 18 and adjust levels to higher slag 38 and steel mass level 39 in the furnace (maximum possible levels will be determined over time or as observed through high temperature peep holes in the furnace walls) while increasing top 20, 31 blast and bubbling blast 44 until an upper limit of any one of these parameters is reached such it's then known steel 58 carbon content will start to rise, then the computer will back down production to within a safe production level such that there is a measure of control over the process using the parameters of CO2/CO, final spectrometer measurements of steel 58 and slag 69, furnace iron and slag level or thickness 39 and 32, 38 respectively, air/oxygen blast 20, 31, air/oxygen bubbling rate 44, or ore mix 18 composition and flow rate.
8. Steel and slag weir notch flow levels 57 and 66 respectively are measured since they indicate production levels of actual steel 58 and slag 69 which can indicate an upper limit has been reached or that flow controls are malfunctioning. For example, if the plug opens the tap hole more but no increased flow is noted in either slag 69 or steel 58, then either the tap hole is too small, the plug is malfunctioning, or a limit has been reached, and computer historical data can immediately enable the computer algorithm to manage a determination and alarm output which the operator then evaluates. All of the various sensor measurements such as CO2/CO/temrpature 25, nuclear gage 40, 41, spectrometers 59 and 68, weir level sensors 59′ and 67 can be programmed to alarm if extremes in their condition are reached.
Slag flow 69 would flow to a water quenching recycling operation to make aggregate from the slag, and steel flow 58 would go on to finishing operations or to other vessels to enhance steel quality for more specialized applications.
Referring now to
The apparatus of the second embodiment differs from that of the first embodiment in that gas 26, whether from steel making or gasification, passes into a ceramic cyclone 33 to remove particulate matter of slag and carbon that melts and runs down into a cyclone leg 33′ before hot exhaust gases 26 leave the furnace through top furnace plenum opening 34 to enter inner exhaust high temperature alloy pipe 23, which may be ceramic lined to withstand corrosion and high temperature effects. Also, cyclone 33 doesn't necessarily have to be inside the gasifier since refractory lined cyclones are routinely placed outside enclosed in a refractory lined and insulated steel vessel. With this outside contiguous approach to the hot cyclone operation, the cyclone should be very well insulated refractory, and the leg 33′ contiguous outside equivalent is brought back into the vessel and immersed in the molten slag to seal off the cone base. Preferably, the cyclone 33 would be built inside the vessel from ceramic parts, but that may not be practical with present ceramics parts technology for large systems, whereby for large systems, the ceramic lined steel shell contiguous outside cyclone noted above would be used. As noted, molten rejects (not specifically identified) of cyclone 33 run down eject leg 33′ inserted deep enough into molten slag layer 38 which seals off the base of the cyclone so that it will operate. The pressure drop inside the cyclone will use slag layer 32 to rise up into leg 33′ (not shown). At high pressure drops, this cyclone will capture nearly all the larger particles in the excite gas stream and the pressure drop to do this can be made as large as necessary by enlarging the inside depth of the incandescent chamber 33″ as much as necessary to achieve the desired result of practically eliminating all entrained flow particulates, including liquid particulate which drains down leg 33′ to become part of the molten slag 38 and 32. And to complete gasification reactions if no iron ore is being added but just coal and flux as in gasification, the water cooled outer steel of the lance would emit the water as 31′ or as steam air both at various elevations around the lance as required and around the perimeter of the lance so as to thoroughly penetrate the inner depth of the entrained flow space to complete the gasification reactions to hydrogen and carbon monoxide. The amount of steam or water 31′ emitted from periphery nozzles on lance 19 (details not shown) will depend of the temperature of the reaction desired, whether blast 31 is mostly air or mostly pure oxygen. Regardless of the characteristic of the blast 31, better control of either steel or gasification burn reactions can be achieved by actual gas and internal temperature measurements by using steam gas purged (because steam or water vapor is easily removed from gasification gases) laser spectrometry 28′ and receiver areas 28″ and shooting laser rays 28′″ across the furnace in sector space where there are no obstructions. Gas constituent sensors 25 would also be installed as a back-up and calibration check on spectrometer 28′ and 28″. Alternatively, multiple units of laser spectrometer 28′ and 28″ could be used or, they could become correlated scanning units as depicted by 70 and 70′, scanning apparatus drives are not shown but they would be outside magnetic devices moving the laser emitter 28′ and sensor 28″ up and down in a correlated manner within steam purged casement 70 and 70′ respectively, with such rectangular steam purged casements made stiff and rugged enough to withstand the hoop stress on outer casement 28, providing and even more accurate picture of combustion or gasification within the entrained flow space depicted by 33″.
Other variations of the present invention are possible, but the previous descriptions are low cost ways to make the invention for an integrated steel making operation whereby the apparatus of
While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention as defined in the appended claims.
This application claims the benefit of U.S. Provisional Application No. 60/629,486, filed Nov. 19, 2004 and U.S. Provisional Application No. 60/635,117, filed Dec. 10, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60629486 | Nov 2004 | US | |
| 60635117 | Dec 2004 | US |
