Glendon substitution in cast-iron production blast furnaces which use vegetable charcoal as a reducing thermor

Description

1 / 9 “REPLACEMENT OF GLENDON IN BLAST FURNACES FOR PIG IRON PRODUCTION THAT USE CHARCOAL AS A REDUCING AGENT. OBJECTIVE

[001] The present utility model aims to present an alternative to heat exchangers that heat the injection air in the tuyeres (blowing air) in blast furnaces for pig iron production that use charcoal as a reducing agent, known as "glendon". The present innovation results in an alternative with lower implementation investment ("CapEx") and lower operating cost ("OpEx"), in addition to increased furnace productivity.

[002] The alternative proposed here achieves these results by replacing glendons with more modern and efficient equipment, called shell and tube heat exchangers, with updated technology and proven in industrial use.

[003] Brazil is the world's largest producer of pig iron from charcoal, the so-called "Green Pig Iron". This production is distributed between the so-called "integrated" mills, those whose product is steel where pig iron is a stage in their process, and the "independent" mills, which produce and market their own pig iron.

[004] Designed to heat the atmospheric air injected into the bottom of blast furnaces, glendons use as a heat source the fuel gases emitted from the process itself, emanating from the top of the furnace, cycloned and treated. The lower heating value (LHV) of these gases is in the range of 750 to 900 Kcal / Nm3. These gases are known as “Blast Furnace Gases, or simply BFG.” CURRENT STATE OF THE ART

[005] The flowchart presented in Figure 1, attached hereto, refers to the current state of the art, with emphasis on the blast furnace gas circuit and the glendon, as shown in Figure 1. Its parts are numbered as follows: Petition 870250089436, dated 10 / 01 / 2025, page 4 / 15 2 / 9 Table 1 — List of Parts of the State of the Art Flowchart (Figure 1) ITEM PARTS 1 BLAST FURNACE 2 RAW MATERIAL FEEDER 3 BLAST FURNACE EFFLUENT GAS DUCT 4 SAFETY VALVE (BLEEDER VALVE) 5 CYCLONE 6 VALVE 7 TRAY FOR FINES REMOVED FROM EFFLUENT GASES 8 CYCLONE OUTLET DUCT 9 GAS TREATMENT (SCRUBBER) 10 TREATED BLAST FURNACE GAS (GAF) DUCT FOR RECYCLING 11 THERMOELECTRIC COGENERATOR (GAF RECYCLING OPTION) 12 GAF DUCT FOR COGENERATION 13 GAF FLOW CONTROL VALVE FOR COGENERATION 14 GAF FLOW CONTROL VALVE FOR COMBUSTOR 15 BLOWER 16 Combustion Air to Combustor Regulator Valve 17 Combustion Air to Combustor Duct 18 Combustion Air to Combustor Duct 19 Glendon 20 Combustion Gas Outlet Duct 21 Pressurized Air Generator Machine Room for Blast Furnace Tuyeres 22 Atmospheric Air Ducts at Machine Room Inlet 23 Atmospheric Air Regulator Valve at Machine Room Inlet 24 Pressurized Atmospheric Air Duct 25 Air DuctPRESSURIZED AND HEATED ATMOSPHERIC 26 GAS DISCHARGE DUCT Petition 870250089436, dated 10 / 01 / 2025, page 5 / 15 3 / 9 27 Gas-fired regulating valve for discharge 28 Gas-fired combustor for releasing combustible gases into the atmosphere 29 Glendon coils (artificial air) 30 Glendon combustion chamber

[006] The number of glendons in each blast furnace varies according to the size and capacity of each plant. Normally two or three glendons are used in parallel for each blast furnace. In the flowchart presented in Figure 1, to simplify the description there is only one glendon (19).

[007] The blast furnace (1), shown in cross-section, receives at the top a metered mixture of raw material which is iron ore, in addition to the reducing agent (charcoal) and various fluxes with lower mass content. This feed is generally made by conveyor belt from the base of the furnace (1) to its top and tilted in a double seal device. In figure 1 this solids feed, also for simplification, was indicated by a feed line (2). The effluent gases from the process are collected by the effluent duct (3) in which a safety valve (4) is located, activated only in cases of operational failure, such as the collapse of the internal charge of the furnace (1).

[008] The gases collected in the duct (3) are discharged into a cyclone (5) (or multicyclones) where some of the solids are separated from the gases and, through the valve (6), are removed and stored for disposal in a tray (7). The effluent gases from the cyclone (5) are discharged into the duct (8) to feed the gas scrubber (9) for the removal of more solid impurities, mostly using hydrocyclones. Recently, dry multicycloning is also used for the same function. Furthermore, as a simplification, the scrubber (9) is represented Petition 870250089436, dated 10 / 01 / 2025, p. 6 / 15 4 / 9 seated by a rectangle where waste composed of particulates is generated.

[009] The effluent gases from the Scrubber (9), the aforementioned Blast Furnace Gases (BFG), are discharged into the BFG duct (10). These combustible gases are generated in a much greater quantity than the thermal demand required to heat the blast furnace injection air. Therefore, some steel mills use this surplus in the cogeneration of electrical energy, thermoelectric cogenerator (11), supplied with BFG through the duct (12), regulated by the valve (13), with valve 14 being responsible for supplying BFG to the glendons (19).

[010] To meet the thermal demand of the glendons (19), combustion air is pressurized by a blower (15), with flow regulated by the valve (16), and through a duct (17) is fed into a combustor (18) which, in turn, receives fuel gas regulated by a valve (14), generating a flame and, consequently, combustion gases in the glendons (19), the energy source of the assembly. These combustion gases, after heat exchange, are released into the atmosphere through a chimney represented by the duct (20).

[011] With the function of capturing and pressurizing the air to be released into the blast furnace tuyeres (blowing air), the so-called Machine Room (21) is a set of blowers connected in series, and through the duct (22) fed by a line of atmospheric air at ambient temperature, with flow regulated by a valve (23). This atmospheric air is released into the glendons (19) through the duct (24).

[012] These gases are heated in the glendons (19) and released into the blast furnace tuyeres through a duct (25).

[013] All plants that do not have cogeneration of electrical energy, and even those, depending on their sizing or even in case of shutdown for maintenance, need to dispose of the excess GAF generated, for this purpose a duct (26) is installed at the outlet of the scrubber (9) Petition 870250089436, dated 10 / 01 / 2025, page 7 / 15 5 / 9 for disposal of GAF, with flow regulated by valve (27) to feed the combustor (28) where excess GAF is burned and the combustion gases resulting from this combustion are released into the atmosphere.

[014] The product removed from the blast furnace is liquid pig iron which can be transported directly to customers by specially designed and adapted trucks or converted into solid ingots after the casting process. Glendon deficiencies

[015] Glendons (19) were developed, in short, as a solution of the time, to apply thermodynamic technology to available refractory materials. Thus, the coils (29) of the first glendons were constructed of cast iron and molded with the pig iron itself from the blast furnaces, some industries still maintain this procedure today.

[016] With the availability of new refractory materials, notably refractory stainless steel, such materials have become commonly used in glendons, especially in the hottest zone, on the combustor side (18), increasing their service life to approximately five years.

[017] As shown in Figure 1, in the glendons (19) the atmospheric air to be heated passes through the coil (29) in countercurrent flow to the combustion gases generated in the combustion chamber (30). This configuration sharply reduces the overall heat transfer coefficient, which limits the maximum temperature in the injection air, a factor directly linked to the consumption of charcoal per ton of pig iron produced, affecting the operating cost (OpEx).

[018] Glendons (19), to compensate for this conceptual thermal deficiency, require large coils (29) and combustion chambers (30) in addition to the need to install more Petition 870250089436, dated 10 / 01 / 2025, page 8 / 15 6 / 9 of one of them operating in parallel, resulting in high implementation costs (CapEx).

[019] Due to its dimensions and construction material, its thermal insulation loses efficiency.

[020] Even after treatment, GAF carries particulates that cause incrustations throughout the environment where it is burned. Constantly, the accumulation of these impurities directly affects the efficiency of heat exchange by attaching to the outside of the coil (29) and inside the chamber (30) of the glendon (19). As a consequence, there is a need for periodic cleaning of the incrustations on the coil (29). For this cleaning, a complete shutdown of the glendon (19) is necessary, waiting for it to cool down, so that a team can enter the chamber (30) and proceed with the descaling. This procedure, depending on the efficiency of the GAF treatment system and the operational parameters of each plant, is carried out approximately every 7 days.

[021] Due to the novelty of replacing the glendon (19) with the heat exchanger (31), the following list of parts relating to it has lost the numbers (19), (29) and (30), which have been replaced by the numbers (31) to (37) relating to the heat exchanger (31).

[022] Figure 2 shows the proposed alternative for the present “utility model”, its parts are numbered as follows: Table 2 — List of Parts of the Flowchart of the Present Utility Model (Figure 2) ITEM PARTS 1 BLAST FURNACE 2 RAW MATERIAL FEEDER 3 BLAST FURNACE EFFLUENT GAS DUCT 4 SAFETY VALVE (BLEEDER VALVE) 5 CYCLONE 6 VALVE 7 TRAY FOR FINES REMOVED FROM EFFLUENT GASES Petition 870250089436, dated 10 / 01 / 2025, page 9 / 15 7 / 9 8 Cyclone Outlet Duct 9 Gas Treater (Scrubber) 10 Treated Blast Furnace Gas (TBG) Duct for Recovery 11 Thermoelectric Cogenerator (TBG Recovery Option) 12 TBG Duct for Cogeneration 13 TBG Flow Control Valve for Cogeneration 14 TBG Flow Control Valve for Combustor 15 Combustion Air Blower for Combustor 16 Combustion Air Regulator Valve for Combustor 17 Combustion Air Duct for Combustor 18 Combustor 20 Combustion Gas Outlet Duct 21 Air Generating Machine Room Pressurized air for blast furnace tuyeres 22 Atmospheric air ducts at the entrance of the machine room 23 Atmospheric air regulating valve at the entrance of the machine room 24 Pressurized atmospheric air duct 25 Pressurized and heated atmospheric air duct 26 Gas discharge duct 27 Gas discharge regulating valve 28 Gas discharge combustor for releasing combustible gases into the atmosphere 31 Shell and tube heat exchanger 32 Chamber ofShell and Tube Heat Exchanger Combustion 33 Shell and Tube Heat Exchanger Tube Bundle (Combustion Gases) 34 Shell and Tube Heat Exchanger Atmospheric Air Chamber 35 Baffles for Cross-Flow of Atmospheric Air in the Shell and Tube Heat Exchanger Petition 870250089436, dated 10 / 01 / 2025, p. 10 / 15 8 / 9 36 Shell and Tube Heat Exchanger Cleaning Cover 37 Shell and Tube Heat Exchanger Cleaning Cover

[023] In the flowchart shown in figure 2, the glendon with its coil and chamber was removed, resulting in the corresponding numbers (19), (29) and (30) not appearing in the table above, and a shell and tube type heat exchanger (31) fitted with a combustion chamber (32), tube bundle (33), chamber (34), atmospheric air baffles (35) and opposite caps (36) and (37) was adapted in its place.

[024] To meet the thermal demand of this exchanger (31), a combustion air blower (15), with flow regulated by valve (16), and fed by duct (17), supplies the combustor (18), which in turn receives the GAF, flow regulated by valve (14) promoting combustion in the chamber (32) of the heat exchanger (31). The combustion gases from the combustion chamber (32) enter half of the tube bundle (33), return through the other half, and are released to the atmosphere through the chimney, represented by the duct (20).

[025] Shell and tube heat exchangers can have different flow configurations, such as parallel, countercurrent and / or cross flow. Figure 2 shows the heat exchanger (31) with “countercurrent and cross flow”, a high heat transfer coefficient configuration.

[026] The exchanger (31) receives pressurized atmospheric air in a chamber (34), through a duct (24), coming from the machine room (21), fed by a duct (22) with flow regulated by a valve (23).

[027] Atmospheric air passes through the duct (22), through the valve (23), enters the machine room (21) and, after being pressurized, enters the chamber (34), makes contact with the external part of the tube bundle (33) in a sinuous (zigzag) trajectory due to the baffles (35) and, through its outlet Petition 870250089436, dated 10 / 01 / 2025, p. 11 / 15 9 / 9 opposite as well as the duct (25), feeds the blast furnace tuyeres (1). ADVANTAGES OF THIS UTILITY MODEL •

[028] Smaller equipment and lower implementation cost, lower CapEx. •

[029] Equipment with high thermodynamic efficiency technology and a design that provides excellent thermal insulation, generating high-temperature, homogeneous, and controllable injection air, resulting in lower consumption of reducing agent and lower OpEx. •

[030] Simpler, more effective and faster encrustation removal. This is because the fouling in the shell and tube heat exchanger introduced here is removed from the outside of the equipment. This operation consists of opening the covers (36) and (37) and “swiping the inside of the tube bundle, without the need for the operator to enter the equipment, in a more comfortable way and in a shorter time, resulting in reduced labor costs. Petition 870250089436, dated 10 / 01 / 2025, page 12 / 15

Claims

1 / 1 CLAIM 1- “REPLACEMENT OF GLENDON IN BLAST FURNACES FOR THE PRODUCTION OF PIG IRON THAT USE VEGETABLE COAL AS A REDUCING AGENT characterized by being carried out by interdependent devices whose blast furnace (1) has a feeder (2), duct (3) for effluent gases and safety valve (4), duct (3) this in communication with cyclone (5) equipped with rotary valve (6) arranged on tray (7), said cyclone having an outlet duct (8) in communication with scrubber (9) which, through duct (26) and valve (27), has communication with burner (28);scrubber (9) also communicates with electric cogenerator (11), through ducts (10) and (12) in addition to valve (13), the extension of this duct (10), through valve (14), communicates with the combustor (18) which communicates with duct (17), blower (15) and regulating valve (16), combustor (18) characterized by being coupled to the combustion chamber (32) of a shell and tube type heat exchanger (31), this chamber connected to the chimney represented by duct (20), the aforementioned exchanger (31) having an atmospheric air chamber (34), a tube bundle enclosure (33) complemented by opposite covers (36) and (37) in addition to opposite inlet and outlet, the inlet, through duct (24), communicating with the outlet of the machine room (21) whose inlet adapts duct (22) and regulating valve (23), considering that the outlet from the exchanger (31) through the duct (25), it communicates with the blast furnace tuyeres (1).; Petition 870250017743, dated 06 / 03 / 2025, page 14 / 19

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