A cast iron machine demolding agent using hot blast furnace desulfurization by-product and a preparation method thereof

Abstract

The application discloses a cast iron machine demolding agent using hot blast furnace desulfurization by-products and a preparation method thereof, and belongs to the technical field of steel smelting auxiliary materials and solid waste resource utilization. The cast iron machine demolding agent comprises the following raw materials: pretreated desulfurization powder 55-70 parts, quartz powder 6-12 parts, bentonite 8-12 parts, attapulgite 4-8 parts, graphite powder 5-10 parts, silicon powder 3-6 parts and water 100-150 parts; the pretreated desulfurization powder is obtained by drying, crushing and sieving the filter cake discharged from a calcium-based wet desulfurization system of a blast furnace hot blast furnace, and the content of CaSO3*0.5H2O in the dry base component of the pretreated desulfurization powder is 50-70%. The application realizes resource utilization of the desulfurization by-products, and has remarkable economic benefits and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of blast furnace smelting and comprehensive resource utilization technology, specifically to a cast iron machine release agent using desulfurization byproducts from a hot blast stove and its preparation method. Background Technology

[0002] In the steel production process, molten iron from blast furnaces is typically cast into iron blocks using a casting machine. To prevent the molten iron from sticking to the cast iron mold, a release agent needs to be sprayed onto the inner wall of the mold cavity. Traditional release agents are mostly graphite-based, water glass-based, or composite powder materials, which have problems such as high raw material costs, corrosion of the cast iron mold by alkali metals (such as sodium ions), and generation of organic waste gas at high temperatures.

[0003] On the other hand, when calcium-based wet desulfurization technology is used in blast furnace hot blast stoves, a large amount of desulfurization by-product filter cake is generated. Its main component is calcium sulfite, with small amounts of calcium sulfate, calcium hydroxide, and fly ash. This by-product has a high water content, and calcium sulfite is difficult to oxidize naturally. Long-term storage not only occupies land but also causes secondary pollution. Currently, there is a lack of economically effective ways to utilize it.

[0004] Therefore, developing a technical solution that can solve the demolding problem at low cost and can also consume large quantities of desulfurization byproducts has significant economic and environmental benefits. Summary of the Invention

[0005] The present invention aims to provide an economical, environmentally friendly, and efficient release agent for cast iron machines. It makes full use of the desulfurization by-products of hot blast stoves to realize the resource utilization of solid waste, while reducing the release cost, reducing the corrosion of cast iron molds, and avoiding the high-temperature pollution problem of traditional release agents.

[0006] The specific technical solution of the present invention is as follows: In a first aspect, the present invention provides a cast iron machine release agent using desulfurization byproducts from a hot blast furnace, comprising the following raw materials in parts by weight: 55-70 parts of pretreated desulfurization powder, 6-12 parts of quartz powder, 8-12 parts of bentonite, 4-8 parts of attapulgite, 5-10 parts of graphite powder, 3-6 parts of silica powder, and 100-150 parts of water. The pretreated desulfurization powder is obtained by drying, crushing and sieving the filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove. The content of CaSO3·0.5H2O in its dry basis composition is 50~70%.

[0007] Furthermore, the quartz powder has a particle size ≤75μm and a SiO2 content ≥95%; the graphite powder is flake graphite with a particle size ≤45μm; and the silicon micro powder has a particle size ≤75μm and a SiO2 content ≥98%.

[0008] The present invention also provides a method for preparing the cast iron machine release agent as described above, comprising the following steps: The filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove is collected, dried with industrial waste heat to a moisture content of ≤3%, and then crushed and sieved to obtain pretreated desulfurization powder. Weigh out the pretreated desulfurization powder, quartz powder, bentonite, attapulgite, graphite powder, and silica powder according to the formula ratio, and mix them to obtain a mixed dry powder. Add the mixed dry powder to the water and stir to form a uniform suspension slurry; The slurry is sieved to obtain the finished release agent.

[0009] Furthermore, the industrial waste heat is the waste heat from blast furnace slag flushing water or the waste heat from hot blast stove flue gas, and the drying temperature is 80~200℃.

[0010] Furthermore, the process of stirring to form a uniform suspension slurry involves two stages: first, stirring at 400-600 rpm and slowly adding the mixed dry powder over a period of 5-10 minutes; then increasing the speed to 800-1000 rpm and stirring for 30-40 minutes.

[0011] Furthermore, the solid content of the suspension slurry is 45-55%, and the pH value is 7.5-9.0.

[0012] Furthermore, the slurry is passed through a 60-mesh sieve.

[0013] The present invention also provides a method for using the cast iron machine release agent as described above, comprising the following steps: S1. Clean the inner wall and bottom of the cast iron mold; S2. Spray the release agent slurry evenly onto the inner wall and bottom of the cast iron mold, controlling the wet film thickness to be 0.4~0.6mm; S3. Dry the coating surface until the water film disappears; S4. Cast molten iron, and demold after the molten iron solidifies.

[0014] Furthermore, in S2, the spraying is carried out using a compressed air spray gun or an automatic spraying device, with a compressed air pressure of 0.4~0.6MPa, a spray gun nozzle diameter of 1.5~2.5mm, and a spraying distance of 150~250mm.

[0015] Furthermore, the drying process in S3 specifically involves naturally drying the cast iron mold for 30 to 60 seconds using its own residual heat at 80 to 120°C, or supplementing it with hot air drying at 80 to 100°C for 10 to 15 seconds.

[0016] Compared with the prior art, the advantages of the present invention are as follows: 1. The present invention provides a method for preparing a casting iron release agent using desulfurization byproducts of hot blast stove flue gas, which realizes resource utilization; it can consume a large amount of calcium-based wet desulfurization byproducts of blast furnace hot blast stove, solve the problems of their storage and pollution, turn waste into treasure, and conform to the concept of circular economy.

[0017] In addition, the cost is low; the raw materials for desulfurization by-products are almost zero cost, and the auxiliary materials (quartz powder, bentonite, attapulgite, graphite powder, and silica powder) are all commercially available inexpensive mineral materials. The overall raw material cost is reduced by more than 80% compared with traditional release agents.

[0018] It has a good demolding effect; through the high-temperature decomposition of CaSO3 to produce gas in conjunction with graphite lubrication, the demolding rate can reach more than 95%, and the iron block can be automatically peeled off or only requires slight tapping, which improves production efficiency.

[0019] It is non-corrosive to cast iron molds; the all-inorganic formula does not contain alkali metal ions such as sodium and potassium, thus avoiding the high-temperature corrosion of cast iron molds by traditional water glass-based mold release agents and extending the service life of the molds.

[0020] Environmentally friendly and safe; the preparation process does not require high-temperature roasting, and uses industrial waste heat for drying, resulting in low energy consumption; the amount of trace SO2 generated during use is extremely low, and can be effectively treated with conventional dust removal and desulfurization facilities, meeting environmental protection requirements.

[0021] The process is simple; it uses conventional mixing and stirring equipment, requires no complex processing, and is easy to industrialize. Specific Implementation In an embodiment of the present invention, in a first aspect, the present invention provides a cast iron machine release agent using desulfurization byproducts from a hot blast furnace, comprising the following raw materials in parts by weight: 55-70 parts of pretreated desulfurization powder, 6-12 parts of quartz powder, 8-12 parts of bentonite, 4-8 parts of attapulgite, 5-10 parts of graphite powder, 3-6 parts of silica powder, and 100-150 parts of water. The pretreated desulfurization powder is obtained by drying, crushing and sieving the filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove. The content of CaSO3·0.5H2O in its dry basis composition is 50~70%.

[0023] It is understandable that the main component of the pretreated desulfurization powder, CaSO3·0.5H2O, undergoes a decomposition reaction at high temperatures (1250~1350℃) in molten iron: CaSO3→CaO+SO2↑. The generated SO2 microbubbles form a gas isolation layer between the iron block and the mold, assisting in the peeling and demolding of the iron block.

[0024] Simultaneously, the CaO generated from the decomposition reacts with the quartz powder (SiO2) added to the formula at high temperature to form high-melting-point wollastonite (CaSiO3, melting point approximately 1540℃): CaO + SiO2 → CaSiO3. This reaction effectively prevents free CaO from reacting with Fe and SiO2 in the cast iron mold or molten iron to form low-melting-point sticking products (such as fir olivine, melting point approximately 1200℃), thus preventing the sticking phenomenon.

[0025] Graphite powder, acting as a high-temperature solid lubricant, forms a lubricating layer between the iron block and the mold, further reducing demolding resistance. Bentonite and attapulgite act as binders and suspending agents, ensuring the coating's strength at room temperature and the slurry's suspension stability during storage and spraying. Attapulgite, in particular, possesses a unique needle-like crystal structure that forms a three-dimensional network in water, exhibiting excellent suspension and thixotropic properties. Silica powder promotes coating sintering at high temperatures, forming a dense ceramic protective layer and enhancing the coating's high-temperature strength.

[0026] Furthermore, the formulation design of this invention also exhibits good tolerance to fluctuations in the content of common impurities (such as Ca(OH)2, CaSO4, fly ash, etc.) in the desulfurization byproducts of hot blast stoves, ensuring stable demolding within a CaSO3•0.5H2O content range of 50-70%. Through extensive experiments, the inventors have discovered that the formulation design of this invention has good tolerance to fluctuations in the content of common impurities (such as Ca(OH)2, CaSO4, fly ash, etc.) in the desulfurization byproducts of hot blast stoves. As long as the CaSO3•0.5H2O content in the pretreated desulfurization powder is within the range of 50-70%, even if the Ca(OH)2 content in the filter cake varies within the ranges of 5-15%, CaSO4 content within 10-25%, and fly ash content within 10-25%, the demolding agent obtained according to the formulation and method of this invention can achieve a demolding rate of over 95%.

[0027] In summary, this invention achieves excellent demolding effect through the synergistic effect of high-temperature decomposition of CaSO3·0.5H2O to produce gas, solidification of CaO by quartz powder, solid lubrication by graphite powder, and sintering enhancement by silicon micropowder.

[0028] In some embodiments of the present invention, the quartz powder has a particle size ≤75μm and a SiO2 content ≥95%; the graphite powder is flake graphite with a particle size ≤45μm; and the silicon micro powder has a particle size ≤75μm and a SiO2 content ≥98%.

[0029] The present invention also provides a method for preparing the cast iron machine release agent as described above, comprising the following steps: The filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove is collected, dried with industrial waste heat to a moisture content of ≤3%, and then crushed and sieved to obtain pretreated desulfurization powder. Weigh out the pretreated desulfurization powder, quartz powder, bentonite, attapulgite, graphite powder, and silica powder according to the formula ratio, and mix them to obtain a mixed dry powder. Add the mixed dry powder to the water and stir to form a uniform suspension slurry; The slurry is sieved to obtain the finished release agent.

[0030] In some embodiments of the present invention, the industrial waste heat is the waste heat of blast furnace slag flushing water or the waste heat of hot blast stove flue gas, and the drying temperature is 80~200℃.

[0031] In some embodiments of the present invention, the process of stirring to form a uniform suspension slurry includes two stages: first, stirring at 400-600 rpm and slowly adding the mixed dry powder for 5-10 minutes; then increasing the speed to 800-1000 rpm and stirring for 30-40 minutes.

[0032] In some embodiments of the present invention, the solid content of the suspension slurry is 45-55%, and the pH value is 7.5-9.0.

[0033] In some embodiments of the present invention, the slurry is passed through a 60-mesh sieve.

[0034] The present invention also provides a method for using the cast iron machine release agent as described above, comprising the following steps: S1. Clean the inner wall and bottom of the cast iron mold; S2. Spray the release agent slurry evenly onto the inner wall and bottom of the cast iron mold, controlling the wet film thickness to be 0.4~0.6mm; S3. Dry the coating surface until the water film disappears; S4. Cast molten iron, and demold after the molten iron solidifies.

[0035] In some embodiments of the present invention, the spraying in S2 is performed using a compressed air spray gun or an automatic spraying device, with a compressed air pressure of 0.4~0.6MPa, a spray gun nozzle diameter of 1.5~2.5mm, and a spraying distance of 150~250mm.

[0036] In some embodiments of the present invention, the drying in S3 specifically involves naturally drying the cast iron mold for 30 to 60 seconds using the residual heat of the cast iron mold itself at 80 to 120°C, or supplementing it with hot air drying at 80 to 100°C for 10 to 15 seconds.

[0037] The pretreated desulfurization powder used in the following examples was prepared according to the following method: Filter cakes discharged from the calcium-based wet desulfurization system of a blast furnace hot blast stove in a steel plant were collected. Different batches of filter cakes were selected according to experimental needs (the CaSO3·0.5H2O content in their dry basis composition could vary within the range of 50-70%). The cakes were dried using industrial waste heat (blast furnace slag flushing water waste heat or hot blast stove flue gas waste heat, temperature 80-200℃) until the moisture content was ≤3%. The dried material was then pulverized using a Raymond mill and passed through a 200-mesh standard sieve (pore size 75μm) to obtain pretreated desulfurization powder, which was then sealed and stored for later use. Specific parameters of the desulfurization powder used in the following examples are detailed in the descriptions of each example.

[0038] Example 1 Raw material formula (parts by weight): The pretreated desulfurization powder consists of 65 parts, quartz powder (200 mesh, particle size ≤75μm, SiO2 content 96%), 10 parts, bentonite (sodium bentonite, 200 mesh), 5 parts, attapulgite (200 mesh), 8 parts, graphite powder (flake-like, 325 mesh, particle size ≤45μm), 4 parts, silica powder (200 mesh, particle size ≤75μm, SiO2 content 99%), and 120 parts, water.

[0039] The pretreated desulfurization powder is obtained by drying, crushing and sieving the filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove. Its dry basis composition contains 62% CaSO3·0.5H2O, about 7% Ca(OH)2, about 15% CaSO4 and about 16% fly ash.

[0040] Preparation method: Weigh out the dry powder raw materials according to the above-mentioned mass proportions and put them into a V-type mixer. Mix for 18 minutes to obtain a mixed dry powder. Add 120 parts of water to the mixing tank and turn on the mixer at 500 rpm. Slowly add the mixed dry powder, controlling the feeding time to be within 8 minutes. After the feeding is complete, increase the speed to 900 rpm and continue mixing for 35 minutes to form a uniform suspension slurry. Pass the above slurry through a 60-mesh vibrating screen to remove undispersed particles and impurities to obtain the finished release agent. The slurry was tested and found to have a solid content of 48% and a pH value of 8.2.

[0041] How to use: Clean the inner wall and bottom of the cast iron mold to remove residual slag and old release agent. Apply the release agent slurry evenly to the inner wall and bottom of the cast iron mold using a compressed air spray gun at a pressure of 0.5 MPa, a nozzle diameter of 2.0 mm, and a spraying distance of 200 mm. Control the wet film thickness to 0.5 mm. Allow the mold to dry naturally for 40 seconds using its residual heat (approximately 100°C). Then pour molten iron into the blast furnace at a temperature of 1320°C.

[0042] Effect evaluation: After the molten iron solidifies, the iron block automatically demolds smoothly without the need for hammering. Upon inspection of the cast iron mold surface, a uniform grayish-white coating remains, and no iron adhesion is observed. After 50 consecutive uses, the demolding rate remains 100%, and the cast iron mold surface shows no obvious corrosion or wear.

[0043] Example 2 (adjusting the formula ratio and increasing the amount of graphite powder and quartz powder) Raw material formula (parts by weight): The pretreated desulfurization powder consisted of 60 parts (same batch as in Example 1), 12 parts quartz powder, 9 parts bentonite, 6 parts attapulgite, 10 parts graphite powder, 5 parts silica powder, and 140 parts water.

[0044] Preparation method and usage method: Same as in Example 1.

[0045] Effect evaluation: Compared to Example 1, this example increased the amount of graphite powder and quartz powder, and also increased the amount of water. After the molten iron solidified, the iron block automatically detached, and there was no slag adhering to the mold surface, with a demolding rate of over 98%. Due to the slightly thinner slurry, the atomization effect during spraying was better, but the coating drying time was slightly prolonged. Overall, the demolding effect was good.

[0046] Example 3 (Adjusting the formula ratio, increasing the amount of desulfurization powder, and reducing the amount of graphite powder and silicon micro powder) Raw material formula (parts by weight): 70 parts of pretreated desulfurization powder (same batch as in Example 1), 8 parts of quartz powder, 11 parts of bentonite, 4 parts of attapulgite, 6 parts of graphite powder, 3 parts of silica powder, and 110 parts of water.

[0047] Preparation method and usage method: Same as in Example 1.

[0048] Effect evaluation: Compared to Example 1, this example increases the amount of desulfurization powder and bentonite, while reducing the amount of graphite powder, silica powder, and water. After the molten iron solidifies, the iron block occasionally requires slight tapping to demold, with no sticking to the mold, and a demolding rate of over 95%. This still meets production requirements.

[0049] Example 4 (using desulfurization powder with low CaSO3·0.5H2O content) Preparation of pretreated desulfurization powder: Filter cake discharged from the calcium-based wet desulfurization system of a blast furnace hot blast stove in a steel plant was collected. Testing revealed that its dry basis composition included 50% CaSO3·0.5H2O, 18% CaSO4·2H2O, 10% Ca(OH)2, 22% fly ash and impurities, and a moisture content of 39%. The material was dried using industrial waste heat (blast furnace slag flushing water waste heat, approximately 85℃) until the moisture content reached 2.8%. The dried material was then pulverized using a Raymond mill and passed through a 200-mesh standard sieve to obtain pretreated desulfurization powder, which was then sealed and stored for later use.

[0050] Raw material formula (parts by weight): The pretreatment desulfurization powder consists of 65 parts, quartz powder, 10 parts, bentonite, 5 parts, attapulgite, 8 parts, graphite powder, 4 parts, and water.

[0051] Preparation method and usage method: Same as in Example 1.

[0052] Effect evaluation: Compared to Example 1 (CaSO3·0.5H2O content 62%), this example used desulfurization powder with a CaSO3 content at the lower limit (50%), while having higher Ca(OH)2 content (10%) and fly ash content (22%). After the molten iron solidified, the iron block automatically demolded smoothly without the need for hammering. After 50 consecutive uses, the demolding rate was 99%, and there was no corrosion on the surface of the cast iron mold. The results show that even when the CaSO3 content is reduced to 50% and the impurity content is at a high level, sufficient SO2 gas can still be generated to achieve effective demolding, verifying the adaptability of this invention to low-content raw materials.

[0053] Example 5 (using desulfurization powder with high CaSO3·0.5H2O content) Preparation of pretreated desulfurization powder: Filter cake discharged from the calcium-based wet desulfurization system of a blast furnace hot blast stove in a steel plant was collected. Testing revealed that its dry basis composition included 69% CaSO3·0.5H2O, 12% CaSO4·2H2O, 8% Ca(OH)2, 11% fly ash and impurities, and a moisture content of 37%. The material was dried using the waste heat of the blast furnace slag flushing water (approximately 85°C) until the moisture content reached 2.7%. The dried material was then pulverized using a Raymond mill and passed through a 200-mesh standard sieve to obtain pretreated desulfurization powder, which was then sealed and stored for later use.

[0054] Raw material formula (parts by weight): The pretreatment desulfurization powder consists of 65 parts, quartz powder, 10 parts, bentonite, 5 parts, attapulgite, 8 parts, graphite powder, 4 parts, and water.

[0055] Preparation method and usage method: Same as in Example 1.

[0056] Effect evaluation: Compared to Example 1 (CaSO3 content 62%), this example used desulfurization powder with a CaSO3 content of 69%, resulting in lower impurity content. After the molten iron solidified, the iron block automatically demolded smoothly. Observation revealed a trace amount of SO2 gas escaping at the moment of demolding (which could be normally collected by the gas collection hood), and slight porosity on the coating surface, but this did not affect the integrity of the coating. After 50 consecutive uses, the demolding rate was 100%, and there was no corrosion on the surface of the cast iron mold. This indicates that a higher content of calcium sulfite can also achieve excellent demolding results, and the increased gas production did not adversely affect the coating.

[0057] Example 6 (using different drying temperatures, 150°C) Preparation of pretreated desulfurization powder: Collect the same batch of desulfurization filter cake as in Example 1. Dry it using waste heat from the flue gas in the hot air furnace (temperature controlled at 150°C) until the moisture content is 2.5%. The dried material is then pulverized by a Raymond mill and passed through a 200-mesh standard sieve to obtain pretreated desulfurization powder, which is then sealed and stored for later use.

[0058] Raw material formula (parts by weight): Same as Example 1 (65 parts of pretreated desulfurization powder, the rest are the same).

[0059] Preparation method and usage method: Same as in Example 1.

[0060] Effect evaluation: Compared to Example 1 (drying temperature approximately 85°C), this example uses drying at 150°C. After the molten iron solidifies, the iron block automatically demolds, with a demolding effect comparable to Example 1. Testing showed that at a drying temperature of 150°C, the CaSO3·0.5H2O content in the pretreated desulfurization powder was 61% (only a 1% decrease compared to before drying), indicating that calcium sulfite did not undergo significant decomposition at this temperature. After 50 consecutive uses, the demolding rate was 100%. This demonstrates that effective desulfurization powder can still be obtained at a drying temperature of 150°C (within the range of 80–200°C), indicating that industrial waste heat drying has good process adaptability.

[0061] Example 7 Preparation of pretreated desulfurization powder: The filter cake from the same batch as in Example 1 was dried, pulverized, and then used for later use.

[0062] Raw material formula (parts by weight): The pretreatment desulfurization powder consists of 55 parts, 6 parts, bentonite 8 parts, attapulgite 8 parts, graphite powder 5 parts, silica powder 3 parts, and water 150 parts.

[0063] Preparation method and usage method: Same as in Example 1.

[0064] Effect evaluation: In this embodiment, after the molten iron solidifies, the iron block automatically demolds smoothly without the need for hammering. Testing revealed that the slurry had a solid content of 44% and a pH of 7.9. After 50 consecutive uses, the demolding rate was 97%, and there was no significant corrosion or wear on the cast iron mold surface. Because the amount of desulfurization powder was reduced to the lower limit and the amount of water increased to the upper limit, the slurry was slightly thinner. Slight care was needed during spraying to avoid dripping, but overall, the workability was good, and a stable and reliable demolding effect was still achieved.

[0065] Example 8 Preparation of pretreated desulfurization powder: The filter cake from the same batch as in Example 1 was dried, pulverized, and then used for later use.

[0066] Raw material formula (parts by weight): The pretreatment desulfurization powder consists of 70 parts, quartz powder, 12 parts, bentonite, 4 parts, attapulgite, 10 parts, graphite powder, 6 parts, and water.

[0067] Preparation method: basically the same as in Example 1. Note: Due to the small amount of water used, the solid content of the slurry is relatively high (about 55%) after the dry powder is added. In the initial stage of stirring, the feeding time needs to be appropriately extended (controlled within 10 minutes), and high speed (1000 rpm) should be ensured to fully stir for 40 minutes to obtain a uniform slurry.

[0068] Usage method: Same as Example 1.

[0069] Effect evaluation: After the molten iron solidifies, the iron block automatically demolds smoothly without the need for hammering. After 50 consecutive uses, the demolding rate is 100%, the coating exhibits good wear resistance, and there is no significant peeling. The slurry has a solid content of 54%, a pH of 8.5, and a slightly viscous consistency, but it can still be sprayed normally.

[0070] The results show that a stable and reliable demolding effect can still be obtained within the upper and lower limits of each component as defined in this invention.

[0071] It should be noted that the impurity content of the calcium-based wet desulfurization filter cake used in this invention fluctuates depending on the desulfurization process operating conditions of the steel plant (such as the calcium-to-sulfur ratio and the dust content in the flue gas). To verify the tolerance of the formulation of this invention to impurity fluctuations, the applicant conducted repeated experiments based on multiple batches of desulfurization filter cakes with different impurity contents. Extensive experiments revealed that the formulation design of this invention has good tolerance to fluctuations in the content of common impurities (such as Ca(OH)2, CaSO4, and fly ash) in hot blast stove desulfurization byproducts. As long as the CaSO3•0.5H2O content in the pretreated desulfurization powder is within the range of 50-70%, even if the Ca(OH)2 content in the filter cake varies within the ranges of 5-15%, CaSO4 content within 10-25%, and fly ash content within 10-25%, the release agent obtained according to the formulation and method of this invention can achieve a release rate of over 95%. Furthermore, no significant equipment corrosion or coating failure occurred. This further confirms the good adaptability of the technical solution of this invention to fluctuations in industrial raw materials.

[0072] Comparative Example 1 (quartz powder omitted) Raw material formula: Same as in Example 1, but quartz powder is omitted.

[0073] Preparation method and usage method: Same as in Example 1.

[0074] Effect evaluation: Compared to Example 1, this comparative example omitted quartz powder. After casting, it was found that some iron blocks slightly adhered to the cast iron mold, and localized iron slag residue remained on the mold surface after demolding. Analysis suggests that omitting quartz powder prevented the effective solidification of CaO produced by the decomposition of the desulfurization powder, which reacted with the cast iron mold or molten iron to form low-melting-point sticking products, leading to a decrease in demolding effectiveness. This indicates that the addition of quartz powder is crucial for preventing CaO-induced sticking.

[0075] Comparative Example 2 (attapulgite soil omitted) Raw material formula: Same as in Example 1, but attapulgite clay is omitted.

[0076] Preparation method and usage method: Same as in Example 1.

[0077] Effect evaluation: Compared to Example 1, this comparative example omitted attapulgite. After the slurry was prepared and allowed to stand for 30 minutes, obvious stratification and sedimentation occurred, with solid particles settling at the bottom of the container. Uneven slurry concentration during spraying resulted in inconsistent coating thickness and poor demolding in some areas. This indicates that attapulgite plays an important role in maintaining the suspension stability of the slurry, and without its addition, it is difficult to achieve the same suspension effect as in Example 1.

[0078] Comparative Example 3 (graphite powder omitted) Raw material formula: Same as in Example 1, but graphite powder is omitted.

[0079] Preparation method and usage method: Same as in Example 1.

[0080] Effect evaluation: Compared to Example 1, graphite powder was omitted in this comparative example. After the molten iron solidified, the iron block adhered significantly to the cast iron mold, requiring considerable external force to remove it during demolding. A large amount of iron slag remained on the surface of the cast iron mold after demolding, resulting in a demolding rate of only about 65%. Analysis suggests that omitting graphite powder resulted in a lack of a high-temperature solid lubricating layer between the iron block and the mold, increasing frictional resistance and making demolding difficult. This indicates that graphite powder, as a high-temperature lubricant, is a key component for ensuring effective demolding; smooth demolding cannot be achieved solely with SO2 gas.

[0081] Comparative Example 4 (silicon micropowder omitted) Raw material formulation: Same as in Example 1, but with silicon micro powder omitted.

[0082] Preparation method and usage method: Same as in Example 1.

[0083] Effect evaluation: Compared to Example 1, this comparative example omitted the silica powder. The demolding effect was acceptable; the iron block could be automatically demolded. However, after 30 consecutive uses, the coating on the surface of the cast iron mold showed significant peeling and wear, exposing the mold substrate in some areas, leading to localized iron adhesion during subsequent casting. Analysis suggests that omitting the silica powder resulted in insufficient high-temperature sintering strength of the coating, preventing the formation of a dense ceramic protective layer, and causing the coating to gradually deteriorate during repeated use. This indicates that silica powder plays a crucial role in improving the durability and reusability of the coating.

[0084] Comparative Example 5 (using ordinary graphite powder instead of flake graphite) Raw material formulation: Same as in Example 1, but ordinary earthy graphite powder (particle size ≤75μm) is used instead of flake graphite.

[0085] Preparation method and usage method: Same as in Example 1.

[0086] Effect evaluation: Compared to Example 1, this comparative example used ordinary earthy graphite powder. The demolding effect was lower than in Example 1; the iron block occasionally required slight tapping to demold after solidification, with a demolding rate of approximately 90%. Observations revealed that the earthy graphite powder had poor dispersibility in the slurry, resulting in uneven graphite distribution on the coating surface after spraying, leading to insufficient local lubrication. This indicates that using flake graphite is more beneficial for obtaining a uniform lubricated layer and stable demolding effect.

[0087] Comparative Example 6 (using other industrial waste residues to replace desulfurization byproducts) Raw material formulation: Replace the pretreated desulfurization powder in Example 1 with an equal amount of blast furnace slag powder (main components are CaO, SiO2, Al2O3, particle size ≤75μm), and the remaining components and proportions are the same as in Example 1.

[0088] Preparation method and usage method: Same as in Example 1.

[0089] Effect evaluation: Compared to Example 1, this comparative example uses blast furnace slag instead of desulfurization byproducts. After the molten iron solidified, the iron block adhered severely to the cast iron mold and could not be automatically demolded, requiring strong hammering or even breaking the iron block to remove it. Analysis suggests that the blast furnace slag does not contain calcium sulfite, and therefore cannot decompose at high temperatures to produce an SO2 gas isolation layer. Furthermore, the CaO in the slag failed to react effectively with the quartz powder to form high-melting-point wollastonite, instead leading to mold adhesion. This indicates that the calcium-based wet desulfurization byproduct of the hot blast stove used in this invention has irreplaceable technical advantages due to its unique CaSO3·0.5H2O composition.

[0090] Comparative Example 7 (quartz powder usage exceeds the scope of this invention) Raw material formula: 65 parts of pretreated desulfurization powder, 15 parts of quartz powder (12 parts exceeding the upper limit of this invention), 10 parts of bentonite, 5 parts of attapulgite, 8 parts of graphite powder, 4 parts of silica powder, and 120 parts of water.

[0091] Preparation method and usage method: Same as in Example 1.

[0092] Effect evaluation: Compared to Example 1, this comparative example increased the amount of quartz powder to 15 parts. The demolding effect was acceptable, but the slurry viscosity increased significantly, easily causing spray gun clogging during spraying. Furthermore, the coating surface was rough after drying, with localized cracks. The iron block automatically demolded after casting, but a large amount of white powder (unreacted excess quartz powder) remained on the surface of the cast iron mold, making cleaning difficult. This indicates that more quartz powder is not necessarily better; exceeding the scope of this invention will affect the slurry's workability and coating quality.

[0093] Comparative Example 8 (Bentonite dosage exceeds the scope of this invention) Raw material formula: 65 parts of pretreated desulfurization powder, 10 parts of quartz powder, 14 parts of bentonite (12 parts exceeding the upper limit of this invention), 5 parts of attapulgite, 8 parts of graphite powder, 4 parts of silica powder, and 120 parts of water.

[0094] Preparation method and usage method: Same as in Example 1.

[0095] Effect evaluation: Compared to Example 1, this comparative example increased the amount of bentonite to 14 parts. The slurry viscosity was too high, resulting in poor fluidity, poor atomization during spraying, and uneven coating thickness, with some areas being too thick and others too thin. After casting, cracks appeared in the areas with excessively thick coatings, and hard lumps remained on the mold surface after the iron block was demolded; in the areas with excessively thin coatings, localized iron adhesion occurred. This indicates that the amount of bentonite needs to be controlled within a reasonable range; excessive bentonite content will impair workability and coating uniformity.

[0096] The above provides a detailed description of a method for preparing a cast iron machine release agent using desulfurization byproducts of hot blast stove flue gas. Specific examples have been used to illustrate the principle and implementation of the invention. The above description of the embodiments is only intended to help understand the method and core idea of ​​the invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principle of the invention, and these improvements and modifications also fall within the protection scope of the claims of the invention.

Claims

1. A mold release agent for cast iron machines utilizing desulfurization byproducts from a hot blast stove, characterized in that, The raw materials contain the following parts by weight: 55-70 parts of pretreated desulfurization powder, 6-12 parts of quartz powder, 8-12 parts of bentonite, 4-8 parts of attapulgite, 5-10 parts of graphite powder, 3-6 parts of silica powder, and 100-150 parts of water. The pretreated desulfurization powder is obtained by drying, crushing and sieving the filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove. The content of CaSO3·0.5H2O in its dry basis composition is 50~70%.

2. The casting iron machine release agent according to claim 1, characterized in that, The quartz powder has a particle size ≤75μm and a SiO2 content ≥95%; the graphite powder is flake graphite with a particle size ≤45μm; and the silicon micro powder has a particle size ≤75μm and a SiO2 content ≥98%.

3. A method for preparing a release agent for cast iron machines according to claim 1 or 2, characterized in that, Includes the following steps: The filter cake discharged from the calcium-based wet desulfurization system of the blast furnace hot blast stove is collected, dried with industrial waste heat to a moisture content of ≤3%, and then crushed and sieved to obtain pretreated desulfurization powder. Weigh out the pretreated desulfurization powder, quartz powder, bentonite, attapulgite, graphite powder, and silica powder according to the formula ratio, and mix them to obtain a mixed dry powder. Add the mixed dry powder to the water and stir to form a uniform suspension slurry; The slurry is sieved to obtain the finished release agent.

4. The preparation method according to claim 3, characterized in that, The industrial waste heat is the waste heat from blast furnace slag flushing water or the waste heat from hot blast stove flue gas, and the drying temperature is 80~200℃.

5. The preparation method according to claim 3, characterized in that, The process of mixing to form a uniform suspension slurry involves two stages: first, mixing at 400-600 rpm and slowly adding the mixed dry powder over a period of 5-10 minutes; then increasing the speed to 800-1000 rpm and mixing for 30-40 minutes.

6. The preparation method according to claim 3, characterized in that, The solid content of the suspension slurry is 45-55%, and the pH value is 7.5-9.

0.

7. The preparation method according to claim 3, characterized in that, The slurry is passed through a 60-mesh sieve.

8. A method of using the cast iron machine release agent according to claim 1 or 2, characterized in that, Includes the following steps: S1. Clean the inner wall and bottom of the cast iron mold; S2. Spray the release agent slurry evenly onto the inner wall and bottom of the cast iron mold, controlling the wet film thickness to be 0.4~0.6mm; S3. Dry the coating surface until the water film disappears; S4. Cast molten iron, and demold after the molten iron solidifies.

9. The method of use according to claim 8, characterized in that, In S2, spraying is performed using a compressed air spray gun or an automatic spraying device. The compressed air pressure is 0.4~0.6MPa, the spray gun nozzle diameter is 1.5~2.5mm, and the spraying distance is 150~250mm.

10. The method of use according to claim 8, characterized in that, The drying process in S3 specifically involves using the residual heat of the cast iron mold itself (80-120°C) to naturally dry for 30-60 seconds, or supplementing with hot air drying at 80-100°C for 10-15 seconds.