METHOD FOR COOLING HOUSING OF MELTING UNIT AND MELTING UNIT

Abstract

 The invention relates to a method and device for cooling the housing of a melting unit melting chamber. In the method, a liquid metal heat carrier is used to cool the upper portion of an airtight cavity, formed by a double-walled metal shell of the melting chamber housing, by means of inputting the liquid metal heat carrier into the cavity which encompasses a free space, a slag bath and the upper portion of a lined metal bath, while the lower portion of the airtight cavity, formed by the double-walled metal shell of the housing and separated from the upper portion thereof and encompassing the lower portion of the lined metal bath, is cooled only by means of a gaseous heat carrier which is inputted through pipe fittings situated on the lateral surface of an external wall of a heat-exchanger, heated gaseous heat carrier is removed from the heat-exchanger by means of pipe fittings situated on the lateral surface of the external wall of the heat-exchanger, and the temperature of the liquid metal heat carrier is maintained within certain limits by means of adjusting the flow rate of the cold gaseous heat carrier which passes through the heat-exchanger in accordance with readings of a device which sets the temperature of the liquid metal heat carrier. A device is disclosed for carrying out the method. Higher output and lower costs are achieved.

Description

[0001] The inventions relate to metallurgy and processing of industrial and domestic solid wastes. They can also be used in the power industry for burning or gasifying high-ash coal on a layer of molten slag.

[0002] High temperature in the working zone of melting chambers necessitates using fire-resistant lagging to protect the walls of the metal body. In the course of operation of the melting chamber, the fire-resistant lagging gradually breaks up (wears out) due to high temperatures, chemical corrosion and mechanic erosion of fire-resistant material. Therefore, its operation has to be interrupted at certain intervals for cold maintenance of the lagging, which slackens overall productivity and performance of the melting chamber.

[0003] The intervals of uninterrupted operation can be increased dramatically through maintaining conditions for building a slag lining (high melting aggregate which consists of furnace charge mixture, fire-resistant lagging, slag, dust, etc. caked together) on the inner surface of melting chamber walls.

[0004] Cases of using water for cooling of melting chamber body walls have also been reported. This method is successfully used for cooling of cavity walls and roofs of arc steelmaking furnaces [1] and furnaces for non-ferrous metal processing [2]. But as a coolant, water has substantial drawbacks described below:

• heating water up to 55°C and above causes an intensive buildup of scaling on the surface of the cooled unit. As a result, the heat exchange slows down, and the unit gradually goes out of operation; therefore, the maximum temperature has to be maintained below 45°C which leads to high water consumption;
• certain amounts of water overheated locally inside the cooled unit may cause vapor locks due to the low boiling point of water, which slows down the cooling process and results in deterioration of chamber walls;
• water leaking through deteriorated walls of the water-cooled unit into the molten slag and metal may cause an explosion which can destroy the melting unit.

[0005] Melting units designers have recently demonstrated rising interest in creating a system for cooling the melting unit body by using liquid metals as a primary coolant, rather than water. These new coolants have a number of advantages compared to water [3]: higher boiling points, better thermal properties (conductivity for heat, thermal capacity, etc.).

[0006] In actual practice, melting chambers with cooling systems using liquid metal coolants are not available yet because of their complicated design and also maintenance and repair difficulties [4-7].

[0007] A simpler method for a melting unit body cooling and the type of a melting unit to practice such cooling are described in [8].

[0008] The applicant has chosen the prior "Method for a Melting Unit Body Cooling and Type of Melting Unit for Such Cooling" (patent RU2383837) [8] as the closest analog for technical solutions claimed.

[0009] As described in the prior method for a melting unit body cooling, sodium is supplied as a coolant into the melting chamber body designed as a double-walled metal shell with a hermetically sealed cavity inside. The liquid metal coolant is cooled by a cold gaseous coolant which travels through a heat exchanger. The cold gaseous coolant is supplied to the cavity made by outer wall of the melting chamber body and outer shell of the heat exchanger positioned directly on the melting chamber body, having pipe sleeves on its ends for inletting cold and recovering heated gaseous coolant. After being swirled in the heat exchanger, the cold gaseous coolant is first supplied to those parts of the heat exchanger that adjoin sections of the melting chamber with maximum heat loads, and then to the parts of the heat exchanger that adjoin sections of the melting chamber with lesser heat loads.

[0010] The prior melting unit consists of a melting chamber set in metal body made as a double-walled metal shell with a hermetically sealed cavity filled with sodium as a liquid metal coolant, a heat exchanger for cooling the liquid metal coolant by a gaseous coolant, fire-resistant lagging of a molten metal bath, units for loading, heating and melting the furnace charge mixture, separate outlets for draining metal and slag, discharging and cleaning furnace gases and recovering produced heat.

[0011] The heat exchanger for cooling the liquid metal coolant by the gaseous coolant is positioned directly on the melting chamber body, its outer shell 50-300 mm diametrically away from the outer wall of the chamber body. The shell is shaped as a hermetically sealed metal cylinder or its part, and it encircles the melting chamber and includes pipe sleeves for inletting cold and recovering heated gaseous coolant. The outer wall of the chamber makes an inner shell of the heat exchanger, and curved copper strips are fixed to the outer wall of the melting chamber in the cavity between the outer wall of the chamber and the outer shell of the heat exchanger at 3-300 mm intervals from one another. The prior method for a melting chamber body cooling and the melting unit to practice such cooling have the following disadvantages:

• overcooled lower section of the molten bath, a buildup of solidified metal on the fire-resistant bath lagging, contraction of the metal bath capacity, problems with metal taphole opening when draining metal from the melting chamber, caused by rapid cooling of the entire inner wall of the chamber body by the liquid metal coolant;
• difficulties in transportation, storage and maintenance of the liquid metal coolant (sodium);
• no provisions made for changing or controlling the flow of the gaseous coolant in the heat exchanger so as to reduce power consumption, improve melting chamber performance and increase its inter-maintenance periods;
• pipe sleeves located at the ends of the melting unit for inletting cold and recovering heated gaseous coolant leave no room for placing combined oxy-fuel burners-tuyeres for faster melting of furnace charge mixture or attaching molten metal and slag outlets;
• the copper strips in the heat exchanger cavity are expensive and dramatically increase the weight of the melting chamber.

[0012] The aim of proposed inventions is to improve
efficiency of both the cooling method and the melting unit for practicing such cooling.

[0013] The technical result of this cooling method and the type of the melting unit has been enhanced performance and savings through:

• better heat absorption from the inner functional body wall and rapid cooling of only those sections of the body that require such cooling;
• elimination of problem with overcooled lower part of the molten bath, or buildup of solidified metal on the fire-resistant lagging of the metal bath;
• preservation of proper metal bath capacity;
• better means of transportation of coolant and maintenance of the melting unit cooling system;
• savings of electric power and gaseous coolant through lowering the temperature of liquid metal coolant; preservation of the slag lining and its proper thickness;
• fast and even melting of the furnace charge mixture and a well-minded disposition of the combined oxy-fuel burners-tuyeres along with molten metal and slag outlets.
• reduction of overall melting chamber weight and its manufacturing expenses.

[0014] The technical result has been achieved by following solutions combined in a single inventive concept.

[0015] The method for a melting unit body cooling includes supplying liquid metal coolant into the melting chamber body made as a double-walled shell with hermetically sealed cavity, cooling the liquid metal coolant by a gaseous coolant traveling through the heat exchanger positioned directly on the melting chamber body, in accordance with the first invention, the liquid metal coolant is used to cool the upper part of the hermetically sealed cavity formed by double-walled metal shell of the melting chamber body by supplying liquid metal coolant into the cavity which encircles the free space, the slag bath and the upper part of the lagged metal bath. The lower part of the hermetically sealed cavity formed by the double-walled metal body shell and separated from its upper part, which encircles the lower part of the lagged metal bath, is cooled only by the gaseous coolant supplied through pipe sleeves on side of the heat exchanger outer wall. Heated gaseous coolant is recovered from the heat exchanger through pipe sleeves on side of the heat exchanger outer walls. The temperature of liquid metal coolant is maintained within specified limits by automatically or manually changing the flow of the gaseous coolant through the heat exchanger depending on information provided by a device that senses the temperature of liquid metal coolant.

[0016] The gaseous coolant is supplied to the cavity made by the outer wall of melting chamber body and heat exchanger outer wall.

[0017] The temperature of liquid metal coolant is maintained at 450-500°C.

[0018] Sodium may be used as liquid metal coolant.

[0019] Lead may be used as liquid metal coolant.

[0020] Lead and bismuth alloy may be used as liquid metal coolant. Air may be used as gaseous coolant.

[0021] Nitrogen may be used as gaseous coolant.

[0022] Heated gaseous coolant from the heat exchanger is used for injecting fine parts of furnace charge mixture and dust caught by gas treatment into molten metal in the melting chamber.

[0023] Heated gaseous coolant from the heat exchanger is mixed with 1600-1800°C stack gases from the melting chamber or charge mixture preheater.

[0024] Heated gaseous coolant from the heat exchanger may be used to re-burn CO and H2 in stack gases from the melting chamber or charge mixture preheater.

[0025] The melting unit which consists of a melting chamber and its metal body made as a the double-walled metal shell with a hermetically sealed cavity filled with liquid metal coolant, a heat exchanger for cooling the liquid metal coolant with a gaseous coolant, fire-resistant lagging of the molten bath, devices for loading, heating and melting the furnace charge mixture, separate outlets for draining metal and slag, discharging and cleaning furnace gases and recovering produced heat, in accordance with the second invention, has the upper part of the hermetically sealed cavity made by double-walled metal shell of the melting chamber body and filled with liquid metal coolant encircling the free space, the slag bath and the upper part of the metal bath, separated with a partition wall from the lower part of the same cavity which is filled with gaseous coolant and encircles the lower part of the lagged metal bath. The lower outer wall of the melting chamber double-walled shell has holes for inletting and recovering the gaseous coolant from the liquid metal coolant secondary cooling system, pipe sleeves on the heat exchanger outer sidewalls for supplying the cold gaseous coolant into the heat exchanger positioned on the melting chamber body to cool the liquid metal coolant and recover the heated gaseous coolant. A temperature sensing device for measuring temperature of liquid metal coolant is placed in the upper part of the chamber body and the cavity filled with liquid metal coolant, and is connected to the process control system or the melting chamber operator who can adjust the gaseous coolant flow in the heat exchanger.

[0026] The holes in the lower outer wall of the metal body shell are 30-50 mm in diameter.

[0027] The holes in the lower outer wall of the metal body shell can be placed at 150-200 mm intervals from each other.

[0028] The cavity in the melting chamber body for the liquid metal coolant may be filled with sodium.

[0029] The cavity for liquid metal coolant in the chamber body can be filled with lead.

[0030] The cavity for liquid metal coolant in the chamber body can be filled with lead and bismuth alloy.

[0031] The combined oxy-fuel burners-tuyeres are located in the side and end walls of the melting chamber body.

[0032] Molten metal and slag outlets are located in the end walls of the melting chamber body.

[0033] Curved aluminum or aluminum alloy strips are fixed at intervals to the outer wall of the melting chamber in the cavity between the chamber outer wall and the heat exchanger outer shell.

[0034] According to the cooling method, the upper part of the hermetically sealed cavity made by double-walled metal shell of the melting chamber is cooled by supplying liquid metal coolant into the cavity
that encircles the free space, the slag bath and the upper part of the lagged metal bath which ensures rapid heat absorption only in those parts of the inner functional walls of the chamber body that experience maximum heat loads, and secures the buildup of slag lining on these walls. The slag lining protects the inner functional chamber walls, reduces heat losses from the chamber ensuring efficient performance of the unit when using this method.

[0035] The lower part of the hermetically sealed cavity made by double-walled metal body shell and separated from its upper part, which encircles the lower part of the lagged metal bath, is cooled only by gaseous coolant. Heat in the lower part of the metal bath is absorbed more slowly to keep the metal in the bath from getting overcooled, eliminating problems with opening
the metal taphole and draining metal from the melting chamber. It prolongs the lagging life cycle and ensures that continuous melting and furnace mixture processing operations can be done without interruptions, thus improving performance and cost-effectiveness of this method.

[0036] By supplying gaseous coolant into the cavity made by the outer chamber body wall and the outer heat exchanger wall, and by recovering heated gaseous coolant from the cavity through pipe sleeves on the outer heat exchanger sidewalls, the end walls of the melting chamber are free to be used for supporting the combined oxy-fuel burners-tuyeres to provide
a faster and more even melting of furnace charge mixture, and tapholes for discharging metal and slag which increases performance and cost-effectiveness of this method.

[0037] By adjusting the gaseous coolant flow through the heat exchanger based on the information of the heat sensing device which measures the temperature of liquid metal coolant in the upper part of the melting chamber body, it is possible to save power by lowering consumption of gaseous coolant when the liquid metal coolant temperature goes down to 450° C or below, to preserve slag lining and its proper thickness, and to increase the gaseous coolant flow when the liquid metal coolant temperature increases to 500° C. Using sodium as a liquid metal coolant helps to absorb heat rapidly from the cooled inner surfaces of the melting chamber. Sodium has high heat conducting and thermal capacity properties, low melting point and high boiling point

[0038] (900°C). But using sodium calls for high production standards, discipline and careful maintenance of the cooling system.

[0039] Using lead as a liquid metal coolant considerably simplifies its transportation and maintenance of the melting unit cooling system. It does not call for high production standards and discipline. However, lead has lower heat conducting and thermal capacity properties and a higher melting point than sodium.

[0040] Using lead and bismuth alloy as liquid metal coolant leads to the same advantages as with lead; however, it has the same kind of drawbacks as lead. But lead and bismuth alloy has a lower melting point which is an advantage compared with lead.

[0041] Using air as gaseous coolant is the simplest and cheapest option for secondary cooling of liquid metal coolant. Using nitrogen as gaseous coolant helps diminish fire hazards in the operation of the melting chamber cooling system during primary cooling of the chamber body by sodium because sodium, if leaking from the cooling cavity, will not oxidize in the nitrogen environment.

[0042] Usage of heated gaseous coolant from the heat exchanger instead of a cold carrier gas for injecting fine parts of the furnace charge mixture and dust caught by the gas treatment into the molten metal in the melting chamber helps to reduce heat losses in the molten metal, to cut down fuel consumption and to increase overall performance of the melting chamber.

[0043] By mixing heated gaseous coolant from the heat exchanger with 1600-1800°C stack gases from the melting chamber or the charge mixture preheater helps to lower stack gas temperature, yo use the heat produced in the melting chamber in a more efficient way by using the heat produced by the heated gaseous coolant and to reduce dust buildup on the functional surface of the waste heat boiler.

[0044] Using heated gaseous coolant from the heat exchanger to re-burn CO and H2 in the stack gases from the melting chamber or the charge mixture preheater helps to use the heat produced in the melting chamber in a more efficient way by using the heat produced by heated air, to reduce power consumption and an overall amount of gases going through gas treatment.

[0045] Separation with a partition wall of the upper part of the hermetically sealed cavity made by the double-walled metal body shell of the melting chamber and filled with liquid metal coolant encircling the free space, the slag bath and the upper part of the metal bath, from the lower part of the same cavity filled with gaseous coolant around the lower part of the lagged metal bath, increases
performance and cost-effectiveness of the unit. Heat is absorbed rapidly from those parts of the melting chamber body only, that experience maximum heat loads because the liquid metal coolant fills only that part of the hermetically sealed cavity which goes around the free space, the slag bath and the upper part of the lagged metal bath. Slag lining builds up on the melting chamber walls protecting the outer walls of the body
and reducing heat losses through the walls. Heat in the lower part of the metal bath is not absorbed as rapidly, so it keeps the metal in the bath from getting overcooled. There are no problems with opening metal tapholes (to outlet metal), and discharging metal from the melting chamber becomes easier.

[0046] Holes, 30-50 mm in diameter, made at 150-200 mm intervals from one another in the lower outer wall of the double-walled shell of the melting chamber body and separated from the upper part are used to inlet and recover the gaseous coolant from the chamber secondary cooling system. Supplying gaseous coolant into the lower part of the double-walled melting chamber body shell allows for a less aggressive cooling of fire-resistant lagging of the metal bath which increases lagging service life and keeps the metal in the bath from getting overcooled.

[0047] By placing pipe sleeves for supplying the cold gaseous coolant into the heat exchanger which sits on the melting chamber body and is used for cooling liquid metal coolant and recovering from it heated gaseous coolant, on the heat exchanger outer sidewall, room is made on the end walls of the melting chamber to place the combined oxy-fuel burners-tuyeres and tapholes for discharging molten metal and slag. Placing the combined oxy-fuel burners-tuyeres on the end walls of the melting chamber ensures faster and more even melting of the furnace charge mixture.

[0048] Placing the tapholes for discharging metal and slag on the end walls of the melting chamber allows for simpler layout of the melting department at the facility, by separating the flows of slag and metal after they have been discharged from the melting chamber.

[0049] By placing the liquid metal coolant temperature sensing device in the upper part of the melting chamber body and in the cavity filled with the liquid metal coolant, it is possible to sense the highest temperature of liquid metal coolant (450-500 C) in the melting chamber. This temperature determines the flow of the cold gaseous coolant in the heat exchanger required to cool the liquid metal coolant. The communication between the temperature sensing device and the process control system or the melting chamber operator helps to quickly adjust the gaseous coolant flow in the heat exchanger. By adjusting the gaseous coolant flow depending on the maximum temperature of liquid metal coolant, power can be saved and slag lining on the chamber walls increased and sustained.

[0050] When the cavity for liquid metal coolant in the melting chamber body is filled with sodium, heat can rapidly be absorbed from the inner functional wall of the melting chamber ensuring buildup and sustaining of slag lining on the chamber walls.

[0051] Filling the cavity for liquid metal coolant in the melting chamber body with lead or lead and bismuth alloy also ensures rapid heat absorption from the inner functional wall of the melting chamber while building up and sustaining the slag lining on the chamber walls.

[0052] Lead or lead and bismuth alloy should be used if provision of the high production standards and highly skilled maintenance personnel for the work in a facility with the melting chamber can pose a problem.

[0053] Setting the combined oxy-fuel burners-tuyeres on the side and end walls of the melting chamber body ensures quicker and more even melting of the furnace charge mixture compare do the burners-tuyeres set only in the side chamber walls. Placing the holes (tapholes) for discharging metal and slag on the end walls of the melting chamber helps to separate the slag and metal flows and to improve facility management and performance of the melting unit.

[0054] Fixing the curved aluminum or aluminum alloy strips at intervals from one another on the chamber outer wall in the cavity between the chamber outer wall and the heat exchanger outer shell helps to swirl the gaseous coolant flows, reduces the overall weight of the melting chamber and its manufacturing expenses, compared to an option of using the copper strips.

[0055] Below is a description of the method for a melting unit body cooling and the melting unit itself including references to the attached drawings.

Fig.1 is a longitudinal section drawing of an assembly of the melting unit and the heat exchanger.

Fig.2 is a cross section drawing of an assembly of the melting unit and the heat exchanger.

Fig.3 is a top view drawing of an assembly of the melting unit and the heat exchanger.

[0056] The method of ca melting unit body cooling includes supplying a transitory liquid metal coolant into the upper hermetically sealed cavity 10 made by the double-walled metal body shell of the melting chamber 20 having outer wall 8 and inner wall 9. Liquid metal coolant is supplied into the cavity 10 which goes around the free space 3, the slag bath 2 and the upper part of the lagged metal bath 1 of the melting chamber 20. Transitory liquid metal coolant is cooled in the heat exchanger 21 positioned directly on the body of the melting chamber 20, with a gaseous coolant. The lower part of the hermetically sealed cavity separated from the upper part 10 and made by the double-walled metal body shell of the melting chamber 20, which goes around the lower part 7 of the metal bath 1, is only cooled by the cold gaseous coolant. Cold gaseous coolant is supplied to the cavity 7 made by the outer wall 8 of the body of the melting chamber 20 and the outer wall 4 of the heat exchanger 21 through the pipe sleeve 17 on the side of the outer wall 4 of the heat exchanger 21. Heated gaseous coolant is recovered from the heat exchanger 21 through the pipe sleeve 18 on the side of the outer wall 4 of the heat exchanger 21. The temperature of liquid metal coolant is maintained at 450-500°C by automatically or manually changing the flow of gaseous coolant through the heat exchanger 21 depending on the information provided by the device 12 which senses the temperature of liquid metal coolant in the upper part 10 of the cavity in the melting chamber 20. Sodium, lead or lead and bismuth alloy may be used as liquid metal coolant.

[0057] Air or nitrogen may be used as gaseous coolant.

[0058] Hated gaseous coolant from the heat exchanger 21 is used for injecting (not shown on the figures) fine parts of the furnace charge mixture and dust caught by the gas treatment (not shown on the figures), into the molten metal in the melting chamber 20.

[0059] Heated gaseous coolant from the heat exchanger 21 is mixed with 1600-1800°C stack gases from the melting chamber 20 or the charge mixture preheater which helps to lower the stack gas temperature and to reduce dust buildup on the functional surface of the waste heat boiler (not shown on the figures) where the gases are used for producing steam. Heated gaseous coolant from the heat exchanger is used to re-burn CO and H2 in the stack gases from the melting chamber or the charge mixture preheater which helps to use the heat produced in the melting chamber 20 in a more efficient way.

[0060] The melting unit for practicing this method has a melting chamber 20 with a metal body, made as a double-walled metal shell in the cooling zone, a heat exchanger 21 for cooling a primary liquid metal coolant, which encircles the body of the melting chamber 20, devices for loading, heating, and melting the furnace charge mixture (not shown on the figures), removing and cleaning stack gases from the melting chamber and utilizing their heat (not shown on the figures).

[0061] The body of the melting chamber 20 is made as a double-walled (walls 8 and 9) metal shell. The upper part of the hermetically sealed cavity made by the double-walled metal shell 10 is filled with liquid metal coolant and encircles only the free space 3, the slag bath 2, and the upper part of the metal bath 1 of the melting chamber 20. The lower part of the cavity 7 made by the double-walled metal shell of the melting chamber 20 is separated from the upper part 10 of the cavity by a partition wall 19. The outer wall of the lower part of the double-walled metal shell of the melting chamber has holes 30-50 mm in diameter (not shown schematically on the figure) placed at 150-200 mm intervals from each other for inletting and recovering gaseous coolant from the secondary cooling system of liquid metal coolant. On the side of the outer wall 4 of the heat exchanger 21 positioned on the body of the melting chamber 20, there are pipe sleeves 17 for supplying cold gaseous coolant and pipe sleeves 18 for recovering heated gaseous coolant. A device 12 for sensing liquid metal coolant temperature which is connected to the process control system or the melting chamber operator who can adjust the flow of the gaseous coolant in the heat exchanger, is located in the upper part of the melting chamber 20 and in the upper part of the body cavity filled with liquid metal coolant.

[0062] The cavity in the chamber body for liquid metal coolant is filled with sodium or lead, or lead and bismuth alloy. Combined oxy-fuel burners-tuyeres 11 are located on the side and end walls of the melting chamber 20.

[0063] Outlet 5 for discharging metal and outlet 14 for discharging slag, gutters 6 for discharging metal and gutters 15 for discharging slag are located on the end walls of the metal chamber 20.

[0064] Curved aluminum or aluminum alloy strips (not shown schematically on the figures) are fixed at intervals from one another on the outer wall 8 of the melting chamber in the cavity between the outer wall 8 of the melting chamber 20 and the outer shell 4 of the heat exchanger 21.

[0065] The molten metal bath 1 is lagged with firebricks 16 (for example, fused magnesite bricks).

[0066] The method of melting chamber body cooling and the melting unit to practice such cooling work as follows:

The body of the melting chamber 20 is heated by switching on the combined oxy-fuel burners-tuyeres 11 at a lower power mode. The body walls 8 and 9 are heated to 200-250°C, liquid metal coolant being heated in the reserve tank by a special heating system and then pumped into the upper part of the cavity 10 between the body walls 8 and 9 of the melting chamber 20. After that the power input into the melting chamber 20 produced by the combined burners-tuyeres 11 is increased, and cold gaseous coolant is supplied to the heat exchanger 21 to cool the liquid metal coolant.

Low-melting metal charge mixture, for instance, iron chips, is loaded into the melting chamber 20 through the hole 13.
It is melted and used to fill the metal bath 1 to protect the fire-resistant lagging 16 from aggressive impact of the melted slag. After that, standard charge mixture is loaded at required speed through the furnace charge pre-heater heated by stack gas (not shown schematically), and the melting chamber 20 then works on a continuous basis without interruptions. After the slag bath 2 is filled up, the slag taphole14 is opened, and excessive slag drains down the gutter 15 into a slag pot or a slag granulation facility.
The slag should be drained at maintained speed ensuring that when the charge mixture is loaded on a continuous or periodic basis, the level of the melted slag in the melting chamber changes only slightly or remains the same. Melted metal piling up in the metal bath 1 is regularly drained from the melting chamber 20 through the metal tap-hole 5 down the lagged gutter 6 into a casting ladle, making sure that the level of the melted metal never drops by more than 150-250 mm.
Due to rapid heat absorption by the liquid metal coolant from the inner body wall 9 of the melting chamber, a layer of slag lining made of slag, dust and unmolten charge mixture, builds up on the wall surface in the free space 3 and in the melted slag zone (the slag bath 2). It protects the wall from destruction and reduces heat losses from the chamber. By cooling the upper and the most vulnerable part of the fire-resistant lagging of the metal bath by liquid metal coolant, and the rest of the metal bath lagging by cold gaseous coolant, the lagging 16 service life increases dramatically. With that, there are no problems with draining metal from the melting chamber.

[0067] Therefore, the proposed inventions provide opportunity for running a continuous uninterrupted melting process or processing different furnace charge materials without having to stop the melting chamber for lagging maintenance. It helps to lower operational costs associated with operating the melting chamber.

Reference list

[0068] 

1. Y.A. Gudim Steel production in arc furnaces. Designs, technologies, materials. Y.A. Gudim, I.Y. Zinurov, A.D. Kiselyov - Novosibirsk: NSTU Publishing house, 2012, p. 547

2. N.I. Utkin Non-ferrous metal production. Moscow: In-termet Engineering, 2004, p. 442

3. Liquid metal coolants. V.M. Borishansky, S.S. Kutateladze, I.I. Novikov, et al. Moscow: Atomizdat, 1976, p. 328

4. UK patent No. 1566980, class F27D 1/12, 1980.

5. US patent No. 4913734, class F27B 11/08, 1990.

6. US patent No. 3735010, class F27D 1/12, 1973.

7. Patent RU 2067273 "Method of a melting furnace cooling and type of melting furnace for practicing the method". Authors: V.S. Belinsky, V.V. Borisov, V.I. Oleychik, V.M. Poplavsky, V.V. Denisov, O.I. Reshetov, A.S. Reshetin, K.V. Oleychik, I.N. Kravchenko. Patentee: Technoliga, Stock company (AO)

8. Patent RU2383837 "Method of cooling the melting unit body and a type of melting unit to practice such cooling" Authors: A.A. Golubev, Y.A. Gudim, I.O. Treguboye, V.V.Sergeev, Y.N. Nadinsky. Patentee: Technologia metallov, Industrial company, Limited Liability Company.

Claims

1. A method for a melting chamber body cooling including supplying a liquid metal coolant into the melting chamber body made as a double-walled metal shell with a hermetically sealed cavity, cooling the liquid metal coolant by a gaseous coolant which travels through a heat exchanger positioned directly on the body of the melting chamber, wherein the liquid metal coolant cools the upper part
of the hermetically sealed cavity made by the double-walled metal shell of the melting chamber body, by supplying liquid metal coolant into the cavity that encircles free space, a slag bath and an upper part of a lagged metal bath, however, the lower part of the hermetically sealed cavity made by the double-walled metal shell of the melting chamber body and separated from its upper part, which encircles a lower part of the lagged metal bath, is only cooled by the gaseous coolant supplied via pipe sleeves on the side of the heat exchanger outer wall. The heated gaseous coolant is recovered from the heat exchanger through pipe sleeves on the side of the heat exchanger outer wall. The temperature of liquid metal coolant is maintained within the specified limits by automatically or manually changing the flow of the cold gaseous coolant through the heat exchanger based on the information provided by a device which senses temperature of the liquid metal coolant.

2. A method as defined in claim 1 wherein the gaseous coolant is supplied to the cavity made by the outer wall of the melting chamber body and the outer wall of the heat exchanger.

3. A method as defined in claim 1 wherein the temperature of liquid metal coolant is maintained at 450-500°C.

4. A method as defined in claim 1 wherein sodium is used as liquid metal coolant.

5. A method as defined in claim 1 wherein lead is used as liquid metal coolant.

6. A method as defined in claim 1 wherein lead and bismuth alloy is used as liquid metal coolant.

7. A method as defined in claim 1 wherein air is used as gaseous coolant.

8. A method as defined in claim 1 wherein nitrogen is used as gaseous coolant.

9. A method as defined in claim 1 wherein the heated gaseous coolant from the heat exchanger is used for injecting fine parts of the charge mixture and dust caught by the gas treatment, into the molten metal in the melting chamber.

10. A method as defined in claim 1 wherein the heated gaseous coolant from the heat exchanger is mixed with 1600-1800°C stack gases from the melting chamber or the charge mixture preheater.

11. A method as defined in claim 1 wherein the heated gaseous coolant from the heat exchanger can be used to re-burn CO and H2 in the stack gases from the melting chamber or the charge mixture preheater.

12. A melting unit with a melting chamber having a metal body made as a double-walled metal shell with a hermetically sealed cavity filled with liquid metal coolant, a heat exchanger for cooling the liquid metal coolant by a gaseous coolant, fire-resistant lagging of a molten metal bath, devices for loading, heating and melting furnace charge mixture, separate outlets for metal and slag discharge, for removing, cleaning furnace gases and utilizing heat produced by them, wherein the upper part of the hermetically sealed cavity made by the double-walled metal shell of the melting chamber body and filled with liquid metal coolant encircling the free space, the slag bath and the upper part of the metal bath, is separated by a partition wall from the lower part of the same cavity filled with gaseous coolant in the area around the lower part of the lagged metal bath. The outer wall of the lower part of the double-walled metal shell of the chamber body has holes for supplying and recovering the gaseous coolant from the secondary cooling system of the liquid metal coolant, pipe sleeves for supplying cold gaseous coolant into the heat exchanger positioned on the melting chamber body for cooling the liquid metal coolant and recovering the heated gaseous coolant, are placed on the side of the heat exchanger outer wall. A device sensing liquid metal coolant temperature is located in the upper part of the melting chamber and in the cavity filled with the liquid metal coolant.
The device is connected to the process control system or the melting chamber operator for adjusting the flow of gaseous coolant in the heat exchanger.

13. A melting unit as defined in claim 12 wherein the diameter of holes in the lower part of the outer metal body shell wall is 30-50 mm.

14. A melting unit as defined in claim 12 wherein the holes in the lower part of the metal body shell are place at 150-200 mm intervals from one another.

15. A melting unit as defined in claim 12 wherein the cavity for liquid metal coolant in the melting chamber body is filled with sodium.

16. A melting unit as defined in claim 12 wherein the cavity for liquid metal coolant in the melting chamber body is filled with lead.

17. A melting unit as defined in claim 12 wherein the cavity for liquid metal coolant in the melting chamber body is filled with lead and bismuth alloy.

18. A melting unit as defined in claim 12 wherein the combined oxy-fuel burners-tuyeres are placed in the side and end walls of the melting chamber body.

19. A melting unit as defined in claim 12 wherein the outlet holes for metal and slag are placed on the end walls of the melting chamber body.

20. A melting unit as defined in claim 12 wherein aluminum or aluminum alloy curved strips are fixed at intervals on the outer wall of the melting chamber in the cavity between the outer wall of the melting chamber and the outer shell of the heat exchanger.

Drawing