A method for producing yellow phosphorus by-product calcium carbide and ferrosilicon

Abstract

This invention relates to a method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus production, belonging to the field of thermal phosphorus processing technology. The invention involves adding iron-containing slag and a carbonaceous reducing agent to phosphate rock, and conducting a reduction reaction at 1800℃-2200℃ in the absence of air. This converts silicon dioxide into ferrosilicon and calcium oxide into calcium carbide. The resulting slag is primarily composed of high-value-added ferrosilicon and calcium carbide, which not only reduces slag production but also significantly increases the utilization value of the slag and reduces the amount of phosphorus lost in the slag. Furthermore, it shortens the phosphate rock reduction time from 3-4 hours to within 0.5 hours, greatly improving yellow phosphorus production efficiency. Simultaneously, due to the shortened phosphate rock reduction time, the byproducts of ferrosilicon and calcium carbide can be continuously discharged, avoiding the heat loss problem caused by the long intermittent slag discharge time in traditional electric furnace methods, and achieving effective recovery of high-temperature heat. This invention effectively solves the problems of high energy consumption, low phosphate rock reduction efficiency, and low slag added value in yellow phosphorus production, obtaining high-value-added calcium carbide and ferrosilicon products.

Description

Technical Field

[0001] This invention belongs to the field of thermal phosphorus processing technology, specifically, it relates to a method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus. Background Technology

[0002] Yellow phosphorus is a fundamental raw material for the production of thermal phosphoric acid and high-end phosphates, organophosphorus pesticides, phosphorus-based flame retardants, feed-grade calcium phosphate, organophosphonic acids for water treatment, electronic-grade high-purity phosphoric acid, phosphine and other electronic specialty gases, as well as precursor materials for new energy batteries. Currently, the electric furnace method is the only industrial method for producing yellow phosphorus. This method involves mixing phosphate rock, silica, and coke in a certain proportion and heating them to approximately 1450 °C in an electric furnace via electrodes, resulting in a carbothermic reduction reaction that produces gaseous elemental phosphorus (P4) and carbon monoxide (CO). The generated phosphorus vapor is discharged from the top of the furnace, captured and separated by a water spray condensation system, yielding liquid yellow phosphorus. This process produces a large amount of yellow phosphorus slag as a byproduct. The main phase of the yellow phosphorus slag is calcium silicate (CaSiO3) glass, containing small amounts of fluorides, residual phosphorus, and trace metal impurities. Due to the low activity, large compositional fluctuations, and limited economic value of yellow phosphorus slag, it is currently mainly used for stockpiling or low-value building materials, resulting in low comprehensive utilization rate, which is a key challenge restricting the green and low-carbon transformation of the yellow phosphorus industry. Furthermore, the iron oxides (mainly in the form of Fe2O3) associated with phosphate rock are reduced to metallic iron by coke under high-temperature, strong reducing atmosphere. This metallic iron reacts with gaseous phosphorus (P4) to form ferrophosphorus (FeP, Fe2P, etc.), which deposits at the bottom of the furnace, causing irreversible phosphorus loss and resulting in a yellow phosphorus yield typically only 85%–90%. Simultaneously, limited by the volume of the molten pool and the fluidity of the high-viscosity calcium silicate slag, yellow phosphorus electric furnaces are currently mainly operated intermittently, typically with slag removal every 3-4 hours, resulting in low continuity and limited single-furnace production efficiency. Currently, the largest industrial-scale yellow phosphorus plant has a capacity of approximately 15,000 tons / year, which is small in scale. In the existing electric furnace method for producing yellow phosphorus, the phosphate rock is in a solid state, requiring the addition of silica as a flux to generate calcium silicate melt to promote the reduction reaction of the phosphate rock. However, the calcium silicate byproduct produced after adding silica encapsulates some impurities such as metal phosphides and fluorides, making it difficult to utilize. In addition, phosphate rock usually contains more than 8% carbonate, which decomposes to produce calcium oxide (CaO), consuming a lot of electrical energy. At the same time, calcium oxide reacts with silicon dioxide to produce calcium silicate solid waste, consuming a lot of silica. This is also one of the key factors leading to the high energy consumption of yellow phosphorus production.

[0003] my country's annual demand for calcium carbide (CaC2) is about 40 million tons, making it the world's largest producer and consumer of calcium carbide. The production of calcium carbide requires the calcination of limestone to produce calcium oxide, which is also a high-energy-consuming and high-polluting industry. Summary of the Invention

[0004] In view of the problems existing in the background technology, the present invention provides a method for producing calcium carbide and ferrosilicon as by-products of yellow phosphorus, which can effectively solve the problems of high energy consumption in yellow phosphorus production, low reduction efficiency of phosphate rock, and low added value of yellow phosphorus slag utilization, while producing calcium carbide and ferrosilicon products with high added value as by-products.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] The method for producing yellow phosphorus byproducts calcium carbide and ferrosilicon involves taking phosphate rock, iron-containing slag, and carbonaceous reducing agent, and mixing them according to a carbon excess coefficient of 1.0-1.2. The mixture is then reacted at a temperature of 1800 ℃-2200 ℃ in the absence of air. The furnace gas generated during the reaction enters a water washing tower from the upper outlet of the reactor, and is washed and cooled to obtain yellow phosphorus and tail gas rich in carbon monoxide. The byproducts calcium carbide and ferrosilicon are discharged from the bottom of the reactor.

[0007] Furthermore, the iron-containing slag is industrial mining waste or byproduct containing iron.

[0008] Furthermore, the iron-containing industrial mining waste or byproducts are one or more of coal gangue, coal ash, iron slag, or iron filings.

[0009] Furthermore, the water content of the phosphate rock, iron-containing slag, and carbonaceous reducing agent after batching is less than 0.2%.

[0010] Furthermore, the carbonaceous reducing agent contains more than 75% carbon.

[0011] Furthermore, the carbonaceous reducing agent is one or more of coke, white coal, or semi-coke.

[0012] Furthermore, the phosphate rock has a phosphorus content of 5%-30% based on P2O5 and a silicon content of more than 5% based on SiO2.

[0013] The beneficial effects of this invention are:

[0014] This invention introduces iron-containing slag, which reacts with silicon dioxide to form ferrosilicon, thereby avoiding or reducing phosphorus loss caused by the formation of ferrosilicon and effectively improving phosphorus yield.

[0015] This invention involves reacting iron-containing slag and carbonaceous reducing agents under air-isolated conditions, while simultaneously increasing the phosphate rock reduction temperature from 1450℃ to over 1800℃ (1800℃-2200℃). This process converts silicon dioxide into ferrosilicon and calcium oxide into calcium carbide, resulting in slag primarily composed of high-value-added ferrosilicon and calcium carbide. This not only reduces slag production but also significantly increases the utilization value of the slag and reduces phosphorus loss in the slag. Furthermore, it shortens the phosphate rock reduction time from 3-4 hours to within 0.5 hours, greatly improving yellow phosphorus production efficiency. Simultaneously, due to the shortened phosphate rock reduction time, the byproducts of ferrosilicon and calcium carbide can be continuously discharged, avoiding the heat loss problem caused by the long intermittent slag discharge time in traditional electric furnace methods, and achieving effective recovery of high-temperature heat.

[0016] This invention improves the reduction efficiency of phosphate rock, increases the scale of the unit equipment, reduces production energy consumption, and achieves energy conservation and carbon reduction.

[0017] This invention can fully utilize the calcium element in low-grade phosphate rock to produce calcium carbide, solving the problem of high energy consumption caused by the high calcium carbonate content in low-grade phosphate rock during the traditional electric furnace method for producing yellow phosphorus.

[0018] This invention raises the reaction temperature to over 1800℃, directly converting phosphate rock from solid to liquid state. This not only greatly improves the phosphate rock reduction efficiency, but also eliminates the need to add additional silica as a flux, saving a significant amount of energy and reducing the amount of byproducts.

[0019] The method of this invention increases the phosphate rock reduction rate from 85%–93% to over 99%, greatly improving the phosphate yield. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0022] The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus, wherein the yellow phosphorus undergoes a reduction reaction in a reactor, includes the following steps:

[0023] (1) Dry the phosphate rock, iron-containing slag, and carbonaceous reducing agent until the moisture content is below 0.2%;

[0024] Phosphate rock contains 5%-30% phosphorus as P2O5 and more than 5% silicon as SiO2.

[0025] Iron-containing waste residue refers to industrial mining waste or byproducts containing iron, such as coal gangue, coal ash, iron slag, or iron filings.

[0026] Carbonaceous reducing agents include coke, white coal, semi-coke, etc., with a carbon content greater than 75%.

[0027] (2) Weigh out phosphate rock, iron-containing waste residue and carbonaceous reducing agent, mix them according to a carbon excess coefficient of 1.0-1.2, and mix them thoroughly to obtain a mixture.

[0028] (3) The mixture is placed in the reactor and reacted at a high temperature of 1800 ℃-2200 ℃ in the reactor in the absence of air. The furnace gas from the upper outlet of the reactor enters the water washing tower and is cooled by washing to obtain yellow phosphorus and tail gas rich in carbon monoxide. The slag is discharged from the bottom of the reactor. The main components of the slag are calcium carbide and ferrosilicon.

[0029] To illustrate the present invention more clearly, the following embodiments will be described in detail.

[0030] Example 1

[0031] Take 100g of phosphate rock, 6.3g of coal gangue, and 52.7g of coke for batching. The moisture content of the mixture is less than 0.2%. Among them, the phosphate rock has a P2O5 content of 20%, a CaO content of 38%, a SiO2 content of 24%, and a Fe2O3 content of 1%; the coal gangue has a Fe2O3 content of 14%, a CaO content of 3%, a SiO2 content of 43%, and a C content of 10%; the coke has a fixed carbon content of 75%; and the carbon excess coefficient is 1.1.

[0032] The mixed materials were reacted at 1450℃, 1800℃, 1900℃, 2000℃, 2100℃, and 2200℃ for 10 minutes each. After the reaction was completed and cooled to room temperature, the phosphate rock reduction rate, the mass of calcium carbide in the by-product furnace charge, and the mass of ferrosilicon were calculated by analyzing the residue (Table 1). Table 1 shows that at 1450℃, almost no calcium carbide or ferrosilicon was produced. After 1800℃, calcium carbide was formed, accounting for 38.8%, and remained basically stable after 1900℃. Ferrosilicon remained basically stable after 1800℃.

[0033] Table 1. Product Results Analysis of Example 1

[0034]

[0035] Comparative Example 1

[0036] Using the same ingredients as in Example 1, a reduction reaction was carried out at 1450°C for different durations. After the reaction, the phosphate rock reduction rate, the mass of calcium carbide in the by-product charge, and the mass of ferrosilicon were calculated by analyzing the residue. As shown in Table 2, at 1450°C, the phosphate rock reduction rate gradually increased with increasing reduction reaction time. However, because some phosphorus was carried away by the formation of ferrophosphorus during the reaction, the highest phosphate rock reduction rate was only 92.7%, far lower than the reduction rate of 99.8% in Example 1. In addition, at this temperature, the slag was mainly composed of calcium silicate, with no calcium carbide or ferrosilicon formed.

[0037] Table 2. Analysis of product results for Comparative Example 1

[0038]

[0039] Example 2

[0040] Take 100g of phosphate rock, 2.2g of iron slag, and 54g of coke for batching. The moisture content of the mixture should be less than 0.2%. Specifically, the phosphate rock contains 20% P2O5, 38% CaO, 24% SiO2, and 1% Fe2O3; the iron slag contains 40% Fe2O3, 30% CaO, and 20% SiO2; the coke has a fixed carbon content of 75% and a carbon excess coefficient of 1.1.

[0041] The mixed materials were reacted at 1800℃, 1900℃, 2000℃, 2100℃, and 2200℃ for 10 minutes each. After the reaction was completed, the mixture was cooled to room temperature. The phosphate rock reduction rate, the mass of calcium carbide in the by-product furnace charge, and the mass of ferrosilicon were calculated by analyzing the residue. As shown in Table 3, the phosphate rock reduction rate was as high as 99.5%, the product calcium carbide accounted for more than 45.4%, and the ferrosilicon accounted for more than 2.37%.

[0042] Table 3. Product Results Analysis of Example 2

[0043]

[0044] Example 3

[0045] Compared to Example 2, the amounts of added iron slag and coke were changed so that all the calcium in the slag after the reaction was converted into calcium carbide, and all the iron and silicon were converted into ferrosilicon. 216g of iron slag and 180g of coke were added. Everything else was the same as in Example 2.

[0046] The mixed materials were reacted at 1800℃, 1900℃, 2000℃, 2100℃, and 2200℃ for 10 minutes each. After the reaction was completed, the mixture was cooled to room temperature. The phosphate rock reduction rate, the mass of calcium carbide in the by-product furnace charge, and the mass of ferrosilicon were calculated by analyzing the residue. As shown in Table 4, compared with Example 2, when the iron slag and coke are used to completely produce calcium carbide and ferrosilicon according to the designed proportions, the reduction of phosphate rock to produce yellow phosphorus becomes a secondary objective. The by-product slag contains calcium carbide and ferrosilicon, accounting for more than 96%. In this case, if the market value of calcium carbide and ferrosilicon is high, this method can be used for production.

[0047] Table 4. Product Results Analysis of Example 3

[0048]

[0049] Example 4

[0050] Take 100g of phosphate rock, 4.4g of coal ash, and 59g of coke for batching. The moisture content of the mixture is less than 0.2%. The phosphate rock contains 20% P2O5, 38% CaO, 24% SiO2, and 1% Fe2O3; the coal ash contains 20% Fe2O3, 4% CaO, and 53% SiO2; the coke has a fixed carbon content of 85% and a carbon excess coefficient of 1.2.

[0051] The mixed materials were reacted at 1800℃, 1900℃, 2000℃, 2100℃, and 2200℃ for 10 minutes each. After the reaction was completed, the mixture was cooled to room temperature. The residue was analyzed to calculate the phosphate rock reduction rate, the mass of calcium carbide in the by-product furnace charge, and the mass of ferrosilicon. Table 6 shows that the phosphate rock reduction rate was as high as 99.7%. The by-product calcium carbide accounted for more than 45.4%, and the ferrosilicon accounted for more than 2.32%.

[0052] Table 6. Product Results Analysis of Example 4

[0053]

[0054] Example 5

[0055] Take 100g of phosphate rock, 22.2g of iron filings, and 57.8g of coke for batching. The moisture content of the mixture is less than 0.2%. The phosphate rock contains 20% P2O5, 38% CaO, 24% SiO2, and 1% Fe2O3; the iron filings contain 92% Fe; the coke contains 85% fixed carbon; and the carbon excess coefficient is 1.2.

[0056] The mixed materials were reacted at 1800℃, 1900℃, 2000℃, 2100℃, and 2200℃ for 10 minutes each. After the reaction was completed, the mixture was cooled to room temperature. The residue was analyzed to calculate the phosphate rock reduction rate, the mass of calcium carbide in the by-product furnace charge, and the mass of ferrosilicon. Table 6 shows that the phosphate rock reduction rate was as high as 99.6%. The by-product calcium carbide accounted for more than 34.6%, and the ferrosilicon accounted for more than 28.1%.

[0057] Table 6. Product Results Analysis of Example 5

[0058]

[0059] Note: Unless otherwise specified, all percentage contents mentioned in this invention are mass percentage contents.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus, characterized in that, Take phosphate rock, iron-containing slag and carbonaceous reducing agent, mix them according to a carbon excess coefficient of 1.0-1.2, and react them in the absence of air at a temperature of 1800 ℃-2200 ℃. The furnace gas generated during the reaction process enters the water washing tower from the upper outlet of the reactor, and is washed and cooled to obtain yellow phosphorus and tail gas rich in carbon monoxide; The byproducts, calcium carbide and ferrosilicon, are discharged from the bottom of the reactor.

2. The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus according to claim 1, characterized in that, The iron-containing slag is industrial mining waste or byproduct containing iron.

3. The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus according to claim 2, characterized in that, The iron-containing industrial mining waste or byproducts mentioned are one or more of coal gangue, coal ash, iron slag, or iron filings.

4. The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus according to claim 1, characterized in that, The water content of the phosphate rock, iron-containing slag, and carbonaceous reducing agent after batching is less than 0.2%.

5. The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus according to claim 1, characterized in that, The carbonaceous reducing agent contains more than 75% carbon.

6. The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus according to claim 5, characterized in that, The carbonaceous reducing agent is one or more of coke, white coal, or semi-coke.

7. The method for producing calcium carbide and ferrosilicon as byproducts of yellow phosphorus according to any one of claims 1 to 6, characterized in that, The phosphate rock has a phosphorus content of 5%-30% based on P2O5 and a silicon content of more than 5% based on SiO2.

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