A special type of semi-coke for smelting silicon-manganese, its preparation method and application

Abstract

This invention discloses a special semi-coke for ferrosilicon smelting, its preparation method, and its application. The preparation method includes coal crushing, acid washing and ash removal, low-temperature dry distillation, briquetting, and medium-temperature dry distillation. This invention utilizes acid washing to dissolve and heat the coal, causing some of the pyrite sulfur to react and generate colloidal sulfur. Combined with medium-temperature dry distillation in a reducing atmosphere, the colloidal sulfur and residual FeS2 are converted into H2S and volatilized. Volatile organic sulfur is removed at low temperatures, achieving deep desulfurization of the coal. Simultaneously, the acid washing process effectively reduces the ash content of the semi-coke. Low-temperature dry distillation is used for pre-separation of the gas, solid, and three phases, and the sulfur enrichment effect of the gas and liquid phases further improves the desulfurization effect. Through a synergistic process of acid washing and ash removal, two-stage temperature-controlled dry distillation, enhanced desulfurization in a reducing atmosphere, and tar bonding and molding, this invention solves the industry problems of high sulfur content, high ash content, and low strength, providing a highly efficient and low-cost special reducing agent for ferrosilicon smelting.

Description

Technical Field

[0001] This invention relates to the field of semi-coke preparation and desulfurization technology, and in particular to a special semi-coke for smelting silicon-manganese, its preparation method and application. Background Technology

[0002] Manganese-silicon alloys are important composite deoxidizers in steelmaking, while high-carbon ferrochrome is mainly used as an alloying agent for high-carbon ball bearing steel, tool steel, and high-speed steel. Carbon reducing agents and electricity account for approximately 30% to 60% of the production cost of ferroalloys. In recent years, with the gradual increase in metallurgical coke prices, the cost of coke used in manganese-silicon alloy production has continued to rise. The domestic ferroalloy industry has widely adopted semi-coke as a substitute for metallurgical coke and gas coke as a carbonaceous reducing agent in ferroalloy production. Due to its high fixed carbon, low ash content, low sulfur content, low alumina content, and high resistivity, semi-coke is used as a primary reducing agent in the production of ferrosilicon alloys, achieving the effects of reducing smelting power consumption and reducing agent usage, improving silicon utilization, and thus reducing production costs. However, there are few successful cases in manganese-silicon alloy production where semi-coke has been used to replace coke, achieving improved technical and economic indicators and significantly reduced production costs.

[0003] Both manganese-silicon alloy smelting and furnace smelting are high-temperature, endothermic physicochemical processes. Higher furnace temperatures result in more efficient heating and faster chemical reactions. However, semi-coke is highly reactive, and in the preheating zone, some semi-coke is relatively easily oxidized, leading to insufficient reducing agent in the high-temperature zone of the furnace. This results in carbon deficiency at the furnace bottom and the formation of an unstable residual carbon layer, reducing the permeability of the furnace charge and causing sparking and collapse. Secondly, with the increasing size of electric furnaces for manganese-silicon alloy smelting, the relatively poor mechanical strength of semi-coke leads to an increased breakage rate after entering the furnace due to chemical reactions and thermal stress, affecting the permeability of the furnace charge and the overall furnace condition. The stability of semi-coke makes it unsuitable for high-proportion replacement of metallurgical coke in the smelting of ferromanganese alloys. In addition, the resistivity of carbonaceous reducing agents plays a decisive role in the resistivity of the furnace charge. The resistivity of semi-coke at lower temperatures is much higher than that of metallurgical coke. This is the root cause of the gradual replacement of metallurgical coke with gas coke, semi-coke and other new carbonaceous reducing agents for ferrosilicon. The smelting of ferromanganese alloys and high-carbon ferrochrome is mainly carried out in a high-temperature environment. Although the high-temperature resistivity of semi-coke is still higher than that of metallurgical coke, it is significantly reduced. The current passing through the furnace charge will increase, causing the electrodes to rise, which is not conducive to reducing power consumption. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a special type of semi-coke for silicon-manganese smelting, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a special semi-coke for smelting ferrosilicon manganese includes the following steps:

[0007] S1. Coal crushing:

[0008] The coal used in industrial boilers / kilns should have the following characteristics: Moisture content: 6-8% by weight (too high moisture content reduces calorific value and increases flue gas volume, too low moisture content increases susceptibility to spontaneous combustion); Ash content: 18-24% by weight (high ash content leads to a decrease in calorific value (1% increase in ash content → 200-300 kJ / kg decrease in calorific value) and increases the risk of slagging); Volatile matter content: 27-30% by volume (too high volatile matter makes it flammable but results in poor flame stability, too low volatile matter makes ignition difficult (requires >25%)); Fixed carbon (FC) content: 52-60% by weight. When the residual carbon content is fixed, FC > 45% is suitable for producing semi-coke. The typical calorific value of the furnace coal is 18-25 MJ / kg. The sulfur weight content is 2.5-3%, and the sulfur forms include pyrite sulfur (FeS2, 40-70%), organic sulfur (thiophene, etc., 30-50%), and sulfate sulfur (<10%). When the sulfur content is >1%, forced desulfurization is required. The coal is crushed to 20-50 mesh to obtain furnace coal particles. The smaller the particle size, the higher the desulfurization rate and ash removal rate, but the weaker the mechanical strength of the formed semi-coke. Therefore, it is necessary to select a suitable filter screen for processing.

[0009] S2, pickling and descaling:

[0010] The coal particles were soaked in hydrochloric acid solution for 15 minutes to dissolve minerals such as Ca / Mg carbonate and FeS2 in the coal and reduce ash content (CO2 and soluble chlorides were generated and removed by filtration).

[0011] The mixture was stirred and sealed at 85-90℃ for 30-45 minutes, during which some of the FeS2 was reacted into colloidal sulfur, and the iron content was reduced.

[0012] FeS2 + 4HCl + O2 → FeCl2 + 2S + 2H2O

[0013] The filter residue and filtrate are then obtained by filtration. The coal slag is washed with water until it is neutral. The washing liquid and filtrate are combined to obtain acid waste liquid. The filter residue is dried and dehydrated at 110°C until the moisture content is <3% to obtain coal slag.

[0014] S3, Low-temperature dry distillation:

[0015] The coal slag is placed in a carbonization furnace under a nitrogen protective atmosphere, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to remove organic sulfur.

[0016] The temperature was then increased to 500-600℃ at a rate of 10℃ / min, and held at 500-600℃ for 1.5-2 hours to obtain gaseous, liquid, and solid products. If the temperature was too low, the yields of the gas, liquid, and solid phases would be low (i.e., incomplete dry distillation). If the temperature was too high, the tar would volatilize excessively, reducing the effect of the liquid phase on sulfur enrichment and reducing the yield of the tar, the binder for later briquetting.

[0017] The gaseous products are desulfurized to obtain desulfurized gas, and the liquid products are desulfurized to obtain desulfurized tar.

[0018] S4. Ball pressing and forming:

[0019] Semi-coke, desulfurized tar, and deionized water are mixed and placed in the mold cavity of a briquetting machine (particle size 5-15mm). The mold cavity temperature is 110-130℃ (to prevent tar condensation and blockage of the mold holes). The mixture is pre-pressed at 10-15MPa for 2-3 minutes, then degassed and compacted. It is then pressed at 45-50MPa for 15-30 minutes and held at 25-30MPa for 45-60 minutes to obtain semi-coke precursor.

[0020] S5, Medium-temperature dry distillation:

[0021] The semi-coke precursor is placed in a carbonization furnace, a reducing atmosphere is introduced, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to further remove organic sulfur.

[0022] The temperature is then increased to 650-720℃ at a rate of 10℃ / min, and held at 650-720℃ for 1.5-2 hours to obtain low-sulfur semi-coke, which is a special semi-coke product for ferrosilicon smelting.

[0023] Preferably, in S2, the ratio of the coal particles and the 5wt% hydrochloric acid aqueous solution is 1:2-3.

[0024] Preferably, the gaseous products obtained from S3 are sequentially discharged into a 30wt% diethanolamine (DEA) aqueous solution (excluding organic sulfur) and a 20wt% sodium hydroxide aqueous solution (excluding H2S, SO2, and CO2) to obtain desulfurized gas. The desulfurized gas mainly contains H2, CH4, CO, N2, water, and other hydrocarbons. It can be used as fuel to provide fuel for the carbonization furnace and can also provide a reducing atmosphere for the carbonization furnace. At 650-700℃, it can reduce colloidal sulfur and residual FeS2 to H2S for volatilization. At temperatures above 700℃, it can also promote sulfate reduction, converting difficult-to-decompose sulfates into S, sulfites (decomposition temperature < 650℃), and H2S, further reducing the sulfur content, ultimately reducing the sulfur content to < 0.3% and improving the reduction efficiency of smelting semi-coke.

[0025] Preferably, after the carbonization furnace in S3 is cooled, the non-gas phase substances in the carbonization furnace are filtered to obtain liquid phase products and solid phase products. The solid phase products are dried at 120°C for 30 minutes to obtain semi-coke.

[0026] Preferably, the liquid product obtained in S3 and a 10% calcium hydroxide aqueous solution are mixed at a volume ratio of 1:1. After mixing, the mixture is aged for 30-60 minutes and separates into three layers: a white paste in the lower layer, a light gray aqueous solution in the middle layer, and a transparent clear liquid in the upper layer. The upper clear liquid is taken out and dehydrated at 120°C to obtain desulfurized tar with a sulfur content ≤0.5%.

[0027] Preferably, the weight ratio of semi-coke, desulfurized tar, and deionized water in S4 is 100:10-15:5-8.

[0028] Preferably, the reducing atmosphere is formed by mixing desulfurization gas and nitrogen in a volume ratio of 1.5-2:10. After circulation treatment, the tail gas is successively discharged into a 30wt% diethanolamine (DEA) aqueous solution (to remove organic sulfur) and a 20wt% sodium hydroxide aqueous solution (to remove H2S, SO2 and CO2) to obtain desulfurized tail gas. The desulfurized tail gas provides heat to the carbonization furnace after combustion.

[0029] The present invention also proposes a special semi-coke for smelting silicon-manganese by the aforementioned preparation method, wherein the ash content is <10%, the sulfur content is <0.5%, and the compressive strength is ≥500N / ball.

[0030] Furthermore, this invention also proposes the application of the aforementioned specially prepared semi-coke in the ferrosilicon manganese smelting process, according to the following weight percentage ratio: 60%-65% manganese ore, 18-20% low-sulfur semi-coke, 10%-12% silica, 11-15% medium iron ore, 5%-8% limestone, and a small amount of manganese-rich slag (manganese content of 34%-48%). After mixing, the mixture is smelted and shaped under the following process temperature parameters:

[0031] Preheating phase:

[0032] 1) Manganese ore preheating temperature: 600℃-800℃, which can increase the initial temperature of the charge entering the smelting furnace, reduce energy consumption during smelting, shorten smelting time, and also help remove moisture and impurities from the ore surface. Coke preheating temperature is generally 300℃-500℃, which helps increase the initial temperature of the coke, enhance its reducibility, and reduce volatilization losses during smelting.

[0033] Smelting stage:

[0034] 2) Low-temperature reduction zone temperature: 1100℃-1200℃; In this temperature range, the high-valence oxides of manganese and iron in the furnace charge are reduced to low-valence oxides, and FeO is further reduced to Fe;

[0035] 3) Temperature in the intermediate temperature reaction zone: 1250℃-1300℃; at this temperature, the composite silicate formed by the combination of MnO and SiO2 melts and the following reaction begins to occur: MnO·SiO2 + 4 / 3 C → 1 / 3 Mn3C + SiO2 + CO increases;

[0036] 4) High-temperature reduction zone temperature: 1200℃-1400℃; a large amount of manganese is reduced, and as the temperature increases, silicon is also reduced (its initial reduction temperature is 1665℃). The main reactions in this zone are: SiO2 + 2C = Si + 2CO increases. At the same time, when the reduced Si encounters Mn3C, the following reaction occurs: 1 / 3 Mn3C + Si = MnSi + 1 / 3 C, which reduces the carbon content in the alloy.

[0037] 5) Temperature of the high-temperature zone of the molten pool: 1600℃-1650℃; This is the core high-temperature zone of ferrosilicon smelting, which can ensure that the materials in the furnace are in a molten state, so that various reactions can proceed efficiently. At the same time, it helps to quickly reduce MnO in the slag, and silicon is also reduced to generate MnSi.

[0038] Iron tapping and casting cooling stages:

[0039] 6) Tap temperature: Generally higher than the melting temperature of silicon-manganese alloy (1200℃-1400℃) to ensure that the molten iron can flow out smoothly; after the molten iron flows out, it is cooled for 20 minutes before casting. The molten iron poured into the ingot mold will gradually cool down and solidify completely before being crushed, refined and bagged and stored.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] The low-sulfur semi-coke preparation method and its application in ferrosilicon manganese smelting provided by this invention have the following significant advantages:

[0042] 1. This invention utilizes acid washing (hydrochloric acid) to preferentially dissolve and heat the pyrite to react with sulfur to form colloidal sulfur. Subsequently, combined with medium-temperature dry distillation in a reducing atmosphere, the colloidal sulfur and residual FeS2 are converted into H2S and volatilized. Volatile organic sulfur is removed at a low temperature of 300℃, thereby achieving deep desulfurization of the coal. At the same time, the acid washing process can also effectively dissolve minerals such as Ca / Mg carbonates. Combined with dry distillation to remove impurities, the ash content of semi-coke can be reduced to 7.2-8.5%.

[0043] 2. This invention utilizes low-temperature dry distillation for pre-separation of the gas, solid, and three phases. The sulfur enrichment effect of the gas and liquid phases further enhances the desulfurization efficiency. Furthermore, the gas and liquid products, after desulfurization treatment, yield desulfurized gas and desulfurized tar. The desulfurized gas can be used as a reducing atmosphere and heat source in medium-temperature dry distillation, while the desulfurized tar can be used as a binder in the briquetting process. The resulting low-sulfur semi-coke has an ash content <10%, a sulfur content <0.5%, a compressive strength ≥500 N / ball, a calorific value of 27.9 MJ / kg, and a resistivity of 1185-1235 Ω·mm. 2 / m, thereby reducing the current passing through the furnace charge, which helps to reduce the power consumption of silicon-manganese smelting.

[0044] 3. This invention solves the industry problems of high sulfur, high ash content and low strength by using a synergistic process of acid washing and ash removal, two-stage temperature-controlled dry distillation, desulfurization enhanced by reducing atmosphere and tar bonding and molding, and provides a high-efficiency and low-cost special reducing agent for ferrosilicon manganese smelting. Attached Figure Description

[0045] Figure 1 This is a process flow diagram of a method for preparing special semi-coke for silicon-manganese smelting proposed in this invention. Detailed Implementation

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0047] I. Preparation of Low-Sulfur Semi-Coke

[0048] Example 1

[0049] A method for preparing a special semi-coke for smelting ferrosilicon manganese includes the following steps:

[0050] S1. Coal crushing:

[0051] The coal used in industrial boilers / kilns has the following characteristics: Moisture content: 7.2% by weight (too high moisture content reduces calorific value and increases flue gas volume, too low moisture content increases susceptibility to spontaneous combustion); Ash content: 19.3% by weight (high ash content leads to a decrease in calorific value (a 1% increase in ash content results in a 200-300 kJ / kg decrease in calorific value) and increases the risk of slagging); Volatile matter content: 26.3% by volume (too high volatile matter makes it flammable but results in poor flame stability, too low volatile matter makes ignition difficult (requires >25%)); Fixed carbon (FC) content: 54.3% by weight. The residual char content determines the yield. When FC > 45%, it is suitable for producing semi-coke. The typical calorific value of furnace coal is 18-25 MJ / kg. The sulfur content by weight is 2.76%, and the sulfur forms include pyrite sulfur (FeS2, 65.3%), organic sulfur (thiophene, etc., 32.1%), and sulfate sulfur (<10%). When the sulfur content is >1%, forced desulfurization is required. The coal is crushed to 20 mesh to obtain furnace coal particles. The smaller the particle size, the higher the desulfurization rate and ash removal rate, but the weaker the mechanical strength of the formed semi-coke. Therefore, it is necessary to select a suitable filter screen for processing.

[0052] S2, pickling and descaling:

[0053] The coal particles were soaked in hydrochloric acid solution for 15 minutes to dissolve minerals such as Ca / Mg carbonate and FeS2 in the coal and reduce ash content (CO2 and soluble chlorides were generated and removed by filtration).

[0054] The mixture was stirred and sealed at 85°C for 45 minutes, during which some of the FeS2 was reacted into colloidal sulfur, and the iron content was reduced.

[0055] FeS2 + 4HCl + O2 → FeCl2 + 2S + 2H2O

[0056] The filter residue and filtrate are then obtained by filtration. The coal slag is washed with water until it is neutral. The washing liquid and filtrate are combined to obtain acid waste liquid. The filter residue is dried and dehydrated at 110°C until the moisture content is <3% to obtain coal slag.

[0057] S3, Low-temperature dry distillation:

[0058] The coal slag is placed in a carbonization furnace under a nitrogen protective atmosphere, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to remove organic sulfur.

[0059] The temperature was then increased to 500℃ at a rate of 10℃ / min and held at 500℃ for 2 hours to obtain gaseous, liquid, and solid products. If the temperature was too low, the yields of the gas, liquid, and solid phases would be low (i.e., incomplete dry distillation). If the temperature was too high, the tar would volatilize excessively, reducing the effect of the liquid phase on sulfur enrichment and reducing the yield of the tar, the binder for later briquetting.

[0060] The gaseous products are desulfurized to obtain desulfurized gas, and the liquid products are desulfurized to obtain desulfurized tar.

[0061] S4. Ball pressing and forming:

[0062] Semi-coke, desulfurized tar, and deionized water are mixed and placed in the mold cavity of a briquetting machine (particle size 5-15mm). The mold cavity temperature is 110-130℃ (to prevent tar condensation and blockage of the mold holes). The mixture is pre-pressed at 10-15MPa for 2-3 minutes, then degassed and compacted. It is then pressed at 45-50MPa for 15-30 minutes and held at 25-30MPa for 45-60 minutes to obtain semi-coke precursor.

[0063] S5, Medium-temperature dry distillation:

[0064] The semi-coke precursor is placed in a carbonization furnace, a reducing atmosphere is introduced, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to further remove organic sulfur.

[0065] The temperature was then increased to 650℃ at a rate of 10℃ / min and held at 650℃ for 2 hours to obtain low-sulfur semi-coke, which is a special semi-coke product for silicon-manganese smelting.

[0066] In S2, the ratio of pulverized coal particles to a 5 wt% hydrochloric acid aqueous solution is 1:3.

[0067] The gaseous products obtained from S3 are sequentially discharged into a 30 wt% diethanolamine (DEA) aqueous solution (excluding organic sulfur) and a 20 wt% sodium hydroxide aqueous solution (excluding H2S, SO2, and CO2) to obtain desulfurized gas. The desulfurized gas mainly contains H2, CH4, CO, N2, water, and other hydrocarbons. It can be used as fuel to provide fuel for the carbonization furnace and can also provide a reducing atmosphere for the carbonization furnace. At 650-700℃, it can reduce colloidal sulfur and residual FeS2 to H2S volatilization. At temperatures above 700℃, it can also promote sulfate reduction, converting difficult-to-decompose sulfates into S, sulfites (decomposition temperature < 650℃), and H2S, further reducing the sulfur content, ultimately reducing the sulfur content to < 0.3% and improving the reduction efficiency of smelting semi-coke.

[0068] After the carbonization furnace in S3 is cooled, the non-gas phase substances in the carbonization furnace are filtered to obtain liquid phase products and solid phase products. The solid phase products are dried at 120°C for 30 minutes to obtain semi-coke.

[0069] The liquid product obtained in S3 and a 10% calcium hydroxide aqueous solution were mixed at a volume ratio of 1:1. After mixing, the mixture was aged for 30-60 minutes and separated into three layers: a white paste at the bottom, a light gray aqueous solution in the middle, and a clear liquid at the top. The clear liquid at the top was removed and dehydrated at 120°C to obtain desulfurized tar with a sulfur content of ≤0.5%.

[0070] The weight ratio of semi-coke, desulfurized tar, and deionized water in S4 is 100:10:8.

[0071] The reducing atmosphere is composed of desulfurization gas and nitrogen mixed at a volume ratio of 1.5:10. Through circulation treatment, the tail gas is successively discharged into a 30wt% diethanolamine (DEA) aqueous solution (to remove organic sulfur) and a 20wt% sodium hydroxide aqueous solution (to remove H2S, SO2 and CO2) to obtain desulfurized tail gas. The desulfurized tail gas provides heat to the carbonization furnace after combustion.

[0072] Example 2

[0073] A method for preparing a special semi-coke for smelting ferrosilicon manganese includes the following steps:

[0074] S1. Coal crushing:

[0075] The furnace coal is crushed to 30 mesh to obtain furnace coal particles. The smaller the particle size, the higher the desulfurization rate and ash removal rate, but the weaker the mechanical strength of the formed semi-coke. Therefore, it is necessary to select a suitable filter screen for processing.

[0076] S2, pickling and descaling:

[0077] The coal particles were soaked in hydrochloric acid solution for 15 minutes to dissolve minerals such as Ca / Mg carbonate and FeS2 in the coal and reduce ash content (CO2 and soluble chlorides were generated and removed by filtration).

[0078] The mixture was stirred and sealed at 87°C for 40 minutes, during which some of the FeS2 was reacted into colloidal sulfur, and the iron content was reduced.

[0079] FeS2 + 4HCl + O2 → FeCl2 + 2S + 2H2O

[0080] The filter residue and filtrate are then obtained by filtration. The coal slag is washed with water until it is neutral. The washing liquid and filtrate are combined to obtain acid waste liquid. The filter residue is dried and dehydrated at 110°C until the moisture content is <3% to obtain coal slag.

[0081] S3, Low-temperature dry distillation:

[0082] The coal slag is placed in a carbonization furnace under a nitrogen protective atmosphere, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to remove organic sulfur.

[0083] The temperature was then increased to 550℃ at a rate of 10℃ / min and held at 550℃ for 1.8h to obtain gaseous, liquid, and solid products. If the temperature was too low, the yields of the gas, liquid, and solid phases would be low (i.e., incomplete dry distillation). If the temperature was too high, the tar would volatilize excessively, reducing the effect of the liquid phase on sulfur enrichment and reducing the yield of the tar, the binder for later briquetting.

[0084] The gaseous products are desulfurized to obtain desulfurized gas, and the liquid products are desulfurized to obtain desulfurized tar.

[0085] S4. Ball pressing and forming:

[0086] Semi-coke, desulfurized tar, and deionized water are mixed and placed in the mold cavity of a briquetting machine (particle size 5-15mm). The mold cavity temperature is 110-130℃ (to prevent tar condensation and blockage of the mold holes). The mixture is pre-pressed at 10-15MPa for 2-3 minutes, then degassed and compacted. It is then pressed at 45-50MPa for 15-30 minutes and held at 25-30MPa for 45-60 minutes to obtain semi-coke precursor.

[0087] S5, Medium-temperature dry distillation:

[0088] The semi-coke precursor is placed in a carbonization furnace, a reducing atmosphere is introduced, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to further remove organic sulfur.

[0089] The temperature was then increased to 700℃ at a rate of 10℃ / min and held at 700℃ for 1.8 hours to obtain low-sulfur semi-coke, a special semi-coke product for silicon-manganese smelting.

[0090] In S2, the ratio of pulverized coal particles to a 5 wt% hydrochloric acid aqueous solution is 1:2.5.

[0091] The gaseous products obtained from S3 are sequentially discharged into a 30 wt% diethanolamine (DEA) aqueous solution (excluding organic sulfur) and a 20 wt% sodium hydroxide aqueous solution (excluding H2S, SO2, and CO2) to obtain desulfurized gas. The desulfurized gas mainly contains H2, CH4, CO, N2, water, and other hydrocarbons. It can be used as fuel to provide fuel for the carbonization furnace and can also provide a reducing atmosphere for the carbonization furnace. At 650-700℃, it can reduce colloidal sulfur and residual FeS2 to H2S volatilization. At temperatures above 700℃, it can also promote sulfate reduction, converting difficult-to-decompose sulfates into S, sulfites (decomposition temperature < 650℃), and H2S, further reducing the sulfur content, ultimately reducing the sulfur content to < 0.3% and improving the reduction efficiency of smelting semi-coke.

[0092] After the carbonization furnace in S3 is cooled, the non-gas phase substances in the carbonization furnace are filtered to obtain liquid phase products and solid phase products. The solid phase products are dried at 120°C for 30 minutes to obtain semi-coke.

[0093] The liquid product obtained in S3 and a 10% calcium hydroxide aqueous solution were mixed at a volume ratio of 1:1. After mixing, the mixture was aged for 30-60 minutes and separated into three layers: a white paste at the bottom, a light gray aqueous solution in the middle, and a clear liquid at the top. The clear liquid at the top was removed and dehydrated at 120°C to obtain desulfurized tar with a sulfur content of ≤0.5%.

[0094] The weight ratio of semi-coke, desulfurized tar, and deionized water in S4 is 100:12:7.

[0095] The reducing atmosphere is composed of desulfurization gas and nitrogen mixed at a volume ratio of 1.8:10. Through circulation treatment, the tail gas is successively discharged into a 30wt% diethanolamine (DEA) aqueous solution (to remove organic sulfur) and a 20wt% sodium hydroxide aqueous solution (to remove H2S, SO2 and CO2) to obtain desulfurized tail gas. The desulfurized tail gas provides heat to the carbonization furnace after combustion.

[0096] Example 3

[0097] A method for preparing a special semi-coke for smelting ferrosilicon manganese includes the following steps:

[0098] S1. Coal crushing:

[0099] The furnace coal is crushed to 50 mesh to obtain furnace coal particles. The smaller the particle size, the higher the desulfurization rate and ash removal rate, but the weaker the mechanical strength of the formed semi-coke. Therefore, it is necessary to select a suitable filter screen for processing.

[0100] S2, pickling and descaling:

[0101] The coal particles were soaked in hydrochloric acid solution for 15 minutes to dissolve minerals such as Ca / Mg carbonate and FeS2 in the coal and reduce ash content (CO2 and soluble chlorides were generated and removed by filtration).

[0102] The mixture was stirred and sealed at 90°C for 30 minutes, during which some of the FeS2 was reacted into colloidal sulfur, and the iron content was reduced.

[0103] FeS2 + 4HCl + O2 → FeCl2 + 2S + 2H2O

[0104] The filter residue and filtrate are then obtained by filtration. The coal slag is washed with water until it is neutral. The washing liquid and filtrate are combined to obtain acid waste liquid. The filter residue is dried and dehydrated at 110°C until the moisture content is <3% to obtain coal slag.

[0105] S3, Low-temperature dry distillation:

[0106] The coal slag is placed in a carbonization furnace under a nitrogen protective atmosphere, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to remove organic sulfur.

[0107] The temperature was then increased to 600℃ at a rate of 10℃ / min and held at 600℃ for 1.5h to obtain gaseous, liquid, and solid products. If the temperature was too low, the yields of the gas, liquid, and solid phases would be low (i.e., incomplete dry distillation). If the temperature was too high, the tar would volatilize excessively, reducing the effect of the liquid phase on sulfur enrichment and reducing the yield of the tar, the binder for later briquetting.

[0108] The gaseous products are desulfurized to obtain desulfurized gas, and the liquid products are desulfurized to obtain desulfurized tar.

[0109] S4. Ball pressing and forming:

[0110] Semi-coke, desulfurized tar, and deionized water are mixed and placed in the mold cavity of a briquetting machine (particle size 5-15mm). The mold cavity temperature is 110-130℃ (to prevent tar condensation and blockage of the mold holes). The mixture is pre-pressed at 10-15MPa for 2-3 minutes, then degassed and compacted. It is then pressed at 45-50MPa for 15-30 minutes and held at 25-30MPa for 45-60 minutes to obtain semi-coke precursor.

[0111] S5, Medium-temperature dry distillation:

[0112] The semi-coke precursor is placed in a carbonization furnace, a reducing atmosphere is introduced, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to further remove organic sulfur.

[0113] The temperature was then increased to 720℃ at a rate of 10℃ / min and held at 720℃ for 1.5 hours to obtain low-sulfur semi-coke, a special semi-coke product for silicon-manganese smelting.

[0114] In S2, the ratio of pulverized coal particles to a 5 wt% hydrochloric acid aqueous solution is 1:3.

[0115] The gaseous products obtained from S3 are sequentially discharged into a 30 wt% diethanolamine (DEA) aqueous solution (excluding organic sulfur) and a 20 wt% sodium hydroxide aqueous solution (excluding H2S, SO2, and CO2) to obtain desulfurized gas. The desulfurized gas mainly contains H2, CH4, CO, N2, water, and other hydrocarbons. It can be used as fuel to provide fuel for the carbonization furnace and can also provide a reducing atmosphere for the carbonization furnace. At 650-700℃, it can reduce colloidal sulfur and residual FeS2 to H2S volatilization. At temperatures above 700℃, it can also promote sulfate reduction, converting difficult-to-decompose sulfates into S, sulfites (decomposition temperature < 650℃), and H2S, further reducing the sulfur content, ultimately reducing the sulfur content to < 0.3% and improving the reduction efficiency of smelting semi-coke.

[0116] After the carbonization furnace in S3 is cooled, the non-gas phase substances in the carbonization furnace are filtered to obtain liquid phase products and solid phase products. The solid phase products are dried at 120°C for 30 minutes to obtain semi-coke.

[0117] The liquid product obtained in S3 and a 10% calcium hydroxide aqueous solution were mixed at a volume ratio of 1:1. After mixing, the mixture was aged for 30-60 minutes and separated into three layers: a white paste at the bottom, a light gray aqueous solution in the middle, and a clear liquid at the top. The clear liquid at the top was removed and dehydrated at 120°C to obtain desulfurized tar with a sulfur content of ≤0.5%.

[0118] The weight ratio of semi-coke, desulfurized tar, and deionized water in S4 is 100:15:5.

[0119] The reducing atmosphere is composed of desulfurization gas and nitrogen mixed in a volume ratio of 2:10. After circulation treatment, the tail gas is successively discharged into a 30wt% diethanolamine (DEA) aqueous solution (to remove organic sulfur) and a 20wt% sodium hydroxide aqueous solution (to remove H2S, SO2 and CO2) to obtain desulfurized tail gas. The desulfurized tail gas provides heat to the carbonization furnace after combustion.

[0120] The following comparative examples were designed based on Example 2:

[0121] Comparative Example 1:

[0122] The S2 step and acid washing and ash removal step in Example 2 are omitted.

[0123] Comparative Example 2:

[0124] S5. In medium-temperature dry distillation, pure nitrogen is used instead of a reducing atmosphere.

[0125] Comparative Example 3:

[0126] The temperature of S5 is 620℃.

[0127] Comparative Example 4:

[0128] The temperature of S5 is 750℃.

[0129] Comparative Example 5:

[0130] No deionized water is added to S4.

[0131] Comparative Example 6:

[0132] The ratio of semi-coke / desulfurized tar / deionized water in S4 is 100:5:7.

[0133] II. Product Performance Testing

[0134] Table 1. Performance of Semi-coke Products

[0135]

[0136] As shown in Table 1, comparing Comparative Example 1 and Example 2, it is evident that acid washing and ash removal can significantly reduce ash content.

[0137] Compared with Example 2, the reducing atmosphere can significantly improve the desulfurization efficiency.

[0138] The comparison of Examples 1-3 and Comparative Examples 3-4 demonstrates that a temperature of 650-720℃ is optimal, and in particular, temperatures above 700℃ promote sulfate decomposition, thereby reducing sulfur content.

[0139] Factors affecting mechanical strength (compared with Example 2):

[0140] Tar dosage: Comparative Example 6 (5% tar) showed a 25% decrease in strength;

[0141] Molding moisture content: Comparative Example 5 (anhydrous) had a powdering rate exceeding 15%;

[0142] High-temperature overheating: Comparative Example 4 (750℃) showed a 17% decrease in strength.

[0143] III. Product and Process Analysis

[0144] 1. Composition and characteristics of products from low-temperature carbonization (taking Example 2 as an example)

[0145] Table 2. Solid products: Compositional analysis of semi-coke

[0146]

[0147] Table 3. Composition analysis of liquid phase products: tar (Tar) + pyrolysis water

[0148]

[0149] Table 4. Compositional analysis of gaseous products: Pyrolysis Gas

[0150]

[0151] 2. The role of reducing atmosphere

[0152] Table 5. The role of reducing atmosphere in intermediate-temperature dry distillation

[0153]

[0154] Table 6. Comparison of process parameters for reducing atmosphere and non-reducing atmosphere

[0155]

[0156] Conclusion: High-activity, low-sulfur semi-coke can be produced by using the reducing gas after desulfurization (H2≥5%) and completing deep desulfurization and pore control at temperatures above 650℃.

[0157] 3. Production of low-sulfur semi-coke

[0158] Composition of reducing atmosphere: H2 ≥ 5% (vol), space velocity 500-800 h⁻¹ -1 ;

[0159] Temperature control: 650-720℃;

[0160] Desulfurization effect:

[0161] Inorganic sulfur removal rate: 80-90%;

[0162] Organic sulfur (thiophene) removal rate: 40-60%.

[0163] The resulting low-sulfur semi-coke has the following characteristics: low ash (ash content <10%), low sulfur (sulfur content <0.5%), and high strength (compression strength ≥500N / ball).

[0164] III. Application

[0165] Example 2: Application of specially prepared semi-coke in the ferrosilicon manganese smelting process. The mixture is prepared according to the following weight percentages: 60%-65% manganese ore, 18-20% low-sulfur semi-coke, 10%-12% silica, 11-15% medium iron ore, 5%-8% limestone, and a small amount of manganese-rich slag (manganese content 34%-48%). The mixture is then smelted and shaped under the following process temperature parameters:

[0166] Preheating phase:

[0167] 1) Manganese ore preheating temperature: 600℃-800℃, which can increase the initial temperature of the charge entering the smelting furnace, reduce energy consumption during smelting, shorten smelting time, and also help remove moisture and impurities from the ore surface. Coke preheating temperature is generally 300℃-500℃, which helps increase the initial temperature of the coke, enhance its reducibility, and reduce volatilization losses during smelting.

[0168] Smelting stage:

[0169] 2) Low-temperature reduction zone temperature: 1100℃-1200℃; In this temperature range, the high-valence oxides of manganese and iron in the furnace charge are reduced to low-valence oxides, and FeO is further reduced to Fe;

[0170] 3) Temperature in the intermediate temperature reaction zone: 1250℃-1300℃; at this temperature, the composite silicate formed by the combination of MnO and SiO2 melts and the following reaction begins to occur: MnO·SiO2 + 4 / 3 C → 1 / 3 Mn3C + SiO2 + CO increases;

[0171] 4) High-temperature reduction zone temperature: 1200℃-1400℃; a large amount of manganese is reduced, and as the temperature increases, silicon is also reduced (its initial reduction temperature is 1665℃). The main reactions in this zone are: SiO2 + 2C = Si + 2CO increases. At the same time, when the reduced Si encounters Mn3C, the following reaction occurs: 1 / 3 Mn3C + Si = MnSi + 1 / 3 C, which reduces the carbon content in the alloy.

[0172] 5) Temperature of the high-temperature zone of the molten pool: 1600℃-1650℃; This is the core high-temperature zone of ferrosilicon smelting, which can ensure that the materials in the furnace are in a molten state, so that various reactions can proceed efficiently. At the same time, it helps to quickly reduce MnO in the slag, and silicon is also reduced to generate MnSi.

[0173] Iron tapping and casting cooling stages:

[0174] 6) Tap temperature: Generally higher than the melting temperature of silicon-manganese alloy (1200℃-1400℃) to ensure that the molten iron can flow out smoothly; after the molten iron flows out, it is cooled for 20 minutes before casting. The molten iron poured into the ingot mold will gradually cool down and solidify completely before being crushed, refined and bagged and stored.

[0175] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing specially formulated semi-coke for smelting silicon-manganese, characterized in that, Includes the following steps: S1. Coal crushing: The furnace coal is crushed to 20-50 mesh to obtain furnace coal particles; S2, pickling and descaling: The coal particles were soaked in hydrochloric acid aqueous solution for 15 minutes. The mixture is stirred and sealed at 85-90℃ for 30-45 minutes, then filtered to obtain filter residue and filtrate. The coal slag is washed with water until neutral. The washing liquid and filtrate are combined to obtain acid waste liquid. The filter residue is dried and dehydrated at 110℃ until the moisture content is <3% to obtain coal slag. S3, Low-temperature dry distillation: The coal slag is placed in a carbonization furnace under a nitrogen protective atmosphere, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to remove organic sulfur. The temperature was then increased to 500-600℃ at a rate of 10℃ / min, and held at 500-600℃ for 1.5-2 hours to obtain gaseous products and non-gaseous substances. The gaseous products are desulfurized to obtain desulfurized gas. After cooling in the carbonization furnace, the non-gaseous substances in the carbonization furnace are filtered to obtain liquid and solid products. The liquid products are desulfurized to obtain desulfurized tar, and the solid products are dried at 120°C for 30 minutes to obtain semi-coke. S4. Ball pressing and molding: Semi-coke, desulfurized tar and deionized water are mixed and placed in the mold cavity of a briquetting machine. The mold cavity temperature is 110-130℃. The mixture is pre-pressed at 10-15MPa for 2-3 minutes, then degassed and compacted. The mixture is then pressed at 45-50MPa for 15-30 minutes and held at 25-30MPa for 45-60 minutes to obtain semi-coke precursor. S5, Medium-temperature dry distillation: The semi-coke precursor is placed in a carbonization furnace, a reducing atmosphere is introduced, and the negative pressure inside the furnace is maintained at 0.5-1 kPa. The temperature is increased to 300℃ at a heating rate of 5℃ / min, and held at 300℃ for 30-60 min to further remove organic sulfur. The temperature is then increased to 650-720℃ at a rate of 10℃ / min, and held at 650-720℃ for 1.5-2 hours to obtain low-sulfur semi-coke, which is a special semi-coke product for ferrosilicon smelting.

2. The method for preparing special semi-coke for silicon-manganese smelting according to claim 1, characterized in that, In S2, the ratio of pulverized coal particles to a 5 wt% hydrochloric acid aqueous solution is 1:2-3 by weight.

3. The method for preparing special semi-coke for silicon-manganese smelting according to claim 1, characterized in that, The gaseous product obtained in S3 is sequentially discharged into a 30 wt% aqueous solution of diethanolamine and a 20 wt% aqueous solution of sodium hydroxide to obtain desulfurized gas.

4. The method for preparing special semi-coke for silicon-manganese smelting according to claim 1, characterized in that, The liquid product obtained in S3 and a 10% calcium hydroxide aqueous solution were mixed at a volume ratio of 1:

1. After mixing, the mixture was aged for 30-60 minutes and separated into three layers: a white paste at the bottom, a light gray aqueous solution in the middle, and a clear liquid at the top. The clear liquid at the top was removed and dehydrated at 120°C to obtain desulfurized tar with a sulfur content of ≤0.5%.

5. The method for preparing special semi-coke for silicon-manganese smelting according to claim 1, characterized in that, The weight ratio of semi-coke, desulfurized tar, and deionized water in S4 is 100:10-15:5-8.

6. The method for preparing special semi-coke for silicon-manganese smelting according to claim 1, characterized in that, The reducing atmosphere is composed of desulfurization gas and nitrogen mixed at a volume ratio of 1.5-2:

10. After circulation treatment, the tail gas is successively discharged into a 30wt% diethanolamine aqueous solution and a 20wt% sodium hydroxide aqueous solution to obtain desulfurized tail gas. The desulfurized tail gas provides heat to the carbonization furnace after combustion.

7. The special semi-coke for smelting silicon-manganese prepared by any one of the preparation methods described in claims 1-6, characterized in that, The ash content is <10%, the sulfur content is <0.5%, and the compressive strength is ≥500N / ball.

8. The application of the specially prepared semi-coke as described in claim 7 in the smelting process of ferrosilicon manganese, characterized in that, The following components are mixed according to the following weight percentages: 60%-65% manganese ore, 18-20% low-sulfur semi-coke, 10%-12% silica, 11-15% medium iron ore, 5%-8% limestone, and a small amount of manganese-rich slag. The mixture is then smelted and shaped under the following process temperature parameters: Preheating phase: 1) Manganese ore preheating temperature: 600℃-800℃; Smelting stage: 2) Low-temperature reduction zone temperature: 1100℃-1200℃; 3) Temperature of the intermediate temperature reaction zone: 1250℃-1300℃; 4) Temperature of the high-temperature reduction zone: 1200℃-1400℃; 5) Temperature of the high-temperature zone of the molten pool: 1600℃-1650℃; Iron tapping and casting cooling stages: 6) Tap temperature: 1200℃-1400℃ to ensure smooth flow of molten iron; after the molten iron flows out, it is cooled for 20 minutes before casting. The molten iron poured into the ingot mold will gradually cool and solidify completely before being crushed, refined, bagged and stored.

Images