A process for producing road de-icing agent using magnesium chloride concentrate.

Abstract

This invention discloses a process for producing road de-icing agent using magnesium chloride concentrate, comprising the following steps: S1, crushing agricultural and forestry waste to a certain size, mixing it with recycled mother liquor at a certain mass ratio to obtain a mixture; S2, subjecting the mixture to hydrothermal treatment, followed by filtration and solid-phase processing to obtain a porous framework mixture; S3, placing 80°C biochar in a vacuum impregnation tank, preheating the tank to 115-120°C, pouring the porous framework mixture into the tank for impregnation for a period of time, opening the bottom valve to complete negative pressure siphoning within 30 seconds, then rapidly cooling with liquid nitrogen, performing surface modification after cooling, and obtaining the de-icing agent after sieving. This invention utilizes "silicon-rich biochar" derived from magnesium oxychloride board solid waste as a framework, loading it with 25-30% eutectic nitrate, and then coating it with a 5-7% hemihydrate gypsum-starch biodegradable shell to form dual-functional particles of "phase change heat storage + chloride slow release".

Description

Technical Field

[0001] This invention relates to the field of snow melting technology, and in particular to a process for producing road snow melting agents using magnesium chloride concentrate. Background Technology

[0002] Road surface condition is a crucial factor affecting road safety. In cold winters, when roads are covered in snow or ice, the adhesion is significantly reduced, posing a serious risk to pedestrians and vehicles. Therefore, the issue of snow and ice removal in winter cannot be ignored. Currently, there are five main methods for snow and ice removal: manual and mechanical snow removal, snow removal with de-icing agents, external heating snow removal, and self-stressing snow removal. Due to the high investment, energy consumption, and maintenance costs of external heating and self-stressing snow removal, they have not been widely adopted. Manual and mechanical snow removal, due to their low efficiency, play a limited role in winter snow and ice removal. Therefore, snow removal with de-icing agents has become the simplest, fastest, and lowest-cost method for winter snow and ice removal.

[0003] Over 90% of highways and urban roads in China still use traditional chloride salt granules (1–6 mm in diameter, freezing point -10 °C) with a ratio of NaCl:CaCl2 = 7:3. According to statistics from the Ministry of Transport in 2023, the annual consumption of chloride salt de-icing agents nationwide... ≈ 6.8 million tons, but it brings three major problems: ① The rate of steel corrosion increases by 4–7 times, and bridges develop cracks after 8–10 years; ②The mortality rate from greening is ≥35% (taking the data from Beijing's Fourth Ring Road in 2022 as an example); ③After 1 t of chloride salt melts, 3–4 m are produced. 3 High-salinity runoff, instantaneous conductivity of drainage outlet >15 mS / cm -1 It far exceeds the Class IV limit (1.5 mS / cm) of the "Surface Water Environmental Quality Standard". -1 ).

[0004] Among environmentally friendly alternatives, calcium magnesium acetate (CMA) has low corrosivity, but its raw material cost is high (> 3200 yuan / ton). -1 Furthermore, their activity drops sharply below 0°C; bio-based polyols (such as molasses and glycerol) have a freezing point of only -8°C and require large quantities (80 gm). -2 (Above), secondary icing after rain; slow-release encapsulated chloride salts - with asphalt, sulfur, and urea-formaldehyde resin as shells, with a slow-release period of 3–6 hours, but the shells are non-degradable, resulting in blackening of the road surface and a decrease in SKID resistance of 8–12%. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the present invention proposes a process for producing road de-icing agent using magnesium chloride concentrate.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a process for producing road de-icing agent using magnesium chloride concentrate, comprising the following steps: S1. After crushing agricultural and forestry waste to a certain size, mix it with recycled mother liquor in a certain mass ratio to obtain a mixture; S2. The above mixture is subjected to hydrothermal treatment. After treatment, it is filtered and subjected to solid-phase process to obtain a porous skeleton mixture. Hydrothermal pretreatment (HTP) is not simply "soaking rice husks in hot water". Instead, it utilizes the self-generated pressure system of MgCl2·6H2O from the previous step to complete the three-in-one deep activation of "silicon-cellulose interface bursting + micropore carving + active silicon dissolution" under the coexistence of liquid-solid-vapor three phases.

[0007] S3. Place biochar in the vacuum impregnation tank, preheat the vacuum impregnation tank to 115-120℃, pour the above porous skeleton mixture into the tank after heating, impregnate for a period of time, open the bottom valve, complete the negative pressure siphon within 30s, then use liquid nitrogen to cool quickly, perform surface modification after cooling, and obtain the de-icing agent after sieving.

[0008] To avoid high-temperature hydrolysis of MgCl2 (>120℃ to generate MgOHCl), six molecules of water of crystallization are retained to maintain the eutectic point at -33℃.

[0009] Preferably, in step S1, agricultural and forestry waste is crushed to ≤2mm and mixed with recycled mother liquor in a reactor at a ratio of 1:2-3, with the total solid-liquid volume accounting for 70% of the reactor cavity. Preferably, in step S2, the hydrothermal treatment includes: The initial temperature is 25-30℃. The temperature is then increased to 110-130℃ at a rate of 5-7℃ / min and held for 10 minutes. Next, the temperature is increased to 180℃ at a rate of 3-4℃ / min and held for 20-30 minutes. Then, the temperature is increased to 200℃ at a rate of 23-25℃ / min and held for 30 minutes. The temperature is then cooled to 90℃ within 5 minutes using a 5℃ cold water jacket. The mixture is filtered through a plate and frame filter to obtain wet carbon (55% water content) and a silica-rich mother liquor. The silica-rich mother liquor, containing all the Mg required for the next HTP treatment, is directly reused in the next heat treatment. 2+ It contains SiO2 colloids and some organic acids, so it can be directly recycled to close the loop without the need for additional reagents.

[0010] Preferably, in step S2, the hydrothermal treatment includes: The initial temperature is 25-30℃. The temperature is increased to 120℃ at a rate of 5℃ / min and held for 10 minutes. Then, the temperature is increased to 180℃ at a rate of 3℃ / min and held for 20 minutes. Next, the temperature is increased to 200℃ at a rate of 23℃ / min and held for 30 minutes. Then, the temperature is cooled to 90℃ within 5 minutes using a 5℃ cold water jacket. The mixture is then filtered through a plate and frame filter to obtain wet carbon with a water content of 55%, and a silica-rich mother liquor. The silica-rich mother liquor is directly reused in the next HTP process. The wet carbon is dried to reduce the moisture content to ≤3%, resulting in 400m³. 2 / g porous carbon-silicon framework.

[0011] In this process, the self-generated pressure (0.15–1.55 MPa) generated by the dehydration of MgCl2·6H2O within the system itself is utilized to perform acidic hydrothermal activation of rice husks / corn residue at ≤200℃. During the heating process from 25℃ to 120℃, the autogenous pressure was 0.15MPa, magnesium hexahydrate lost water → a eutectic solution appeared, the local pH dropped to 3.8, and 60% of hemicellulose dissolved. During the heating process from 120℃ to 180℃, the self-generated pressure was 0.75MPa, and a "micro-explosion" occurred at the silicon-cellulose interface. SiO2 The hydrogen bonds between the particles and cellulose break, generating cracks ≤50 nm. During the process of heating from 180℃ to 200℃, the autogenous pressure was 1.55MPa, and 15% of the amorphous SiO2 on the surface of the rice husk dissolved into the liquid phase to form 20–40 nm colloids; the micropore volume increased by 2.3 times.

[0012] A three-in-one process combining MgCl2 self-pressure acid etching, silicon-cellulose micro-explosion, and activated silicon pre-dissolution transforms rice husks into 400m³ particles within 60 minutes. 2 A high liquid absorption framework, primarily composed of 4 nm micropores, provides a prerequisite for subsequent vacuum siphon melting of MgCl2, achieving a 92% pore filling rate and a -33℃ eutectic point; Preferably, the recycled mother liquor comprises 49% MgCl2, 40% bound water, 6% oligosaccharide-potassium acetate complex, and 5% active SiO colloid.

[0013] Preferably, rapid cooling includes: After the vacuum was removed, liquid nitrogen was immediately sprayed, and the cooling rate was 50℃ / min. The eutectic solution recrystallized into nanoscale MgCl26H2O glass, which was "anchored" within the carbon framework, forming 1–3 mm sustained-release microcapsules. Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Slow-release properties: A **“biochar-magnesium chloride microcapsule” structure is introduced. Through in-situ melting-vacuum impregnation-rapid cooling technology, MgCl26H2O is encapsulated within a porous biochar framework to form slow-release microspheres** (particle size 1-3 mm), achieving continuous snow melting for 6-12 hours. 2. Corrosion resistance: During the biochar pyrolysis process, 0.5-1.0 wt% of agricultural waste-derived silicon (rice husk ash) is incorporated in situ to form a silicon-carbon-magnesium ternary composite structure. Silicates preferentially react with Cl during snow melting. - Friedel's salt (3CaO·Al2O3CaCl2·10H2O) reduces free Cl - Over 60%. Combined with generation... 3. Utilizing the crystallization water of magnesium chloride concentrate (MgCl₂·6H₂O) as a "hydrothermal reaction medium," agricultural and forestry waste (such as corn cobs and rice husks) is pretreated under self-pressure conditions at 200℃, without the need for an external water source. 4. Introduce 5 wt% beet molasses byproduct (containing potassium) during the melt impregnation stage. + Ca 2+ At -45℃, the organic acid salts (such as potassium acetate) in molasses can further inhibit metal corrosion. This, along with other factors, lowers the eutectic point through the eutectic effect. Detailed Implementation

[0014] The invention will now be described in detail with reference to the embodiments.

[0015] Example 1 A process for producing road de-icing agent using magnesium chloride concentrate includes the following steps: S1. Crush the rice husks to ≤2mm, and mix them with the recycled mother liquor in a reactor at a ratio of 1:2-3, with the total solid-liquid volume accounting for 70% of the reactor cavity, to obtain a mixture; 其中，回用母液包括MgCl249 %，结合水40 %，低聚糖-乙酸钾络合物6%，活性SiO2胶体5%； S2. The above mixture is subjected to hydrothermal treatment. After treatment, it is filtered and subjected to solid-phase process to obtain a porous skeleton mixture. The initial temperature is 25-30℃. The temperature is increased to 110-130℃ at a rate of 5-7℃ / min and held for 10 minutes. Then, the temperature is increased to 180℃ at a rate of 3-4℃ / min and held for 20-30 minutes. The temperature is then increased to 200℃ at a rate of 23-25℃ / min and held for 30 minutes. The temperature is then cooled to 90℃ within 5 minutes by a 5℃ cold water jacket. The mixture is then filtered through a plate and frame filter to obtain wet carbon (containing 55% water) and a silicon-rich mother liquor. The silicon-rich mother liquor is directly reused in the next HTP process. After filtration and solid-phase processing, a porous framework mixture is obtained. S3. Place biochar in the vacuum impregnation tank, and preheat the vacuum impregnation tank to 115-120℃. After heating, pour the above porous skeleton mixture into the tank and impregnate for a period of time. Then, open the bottom valve to complete the negative pressure siphon within 30 seconds. After de-vacuuming, immediately spray liquid nitrogen at a cooling rate of 50℃ / min to form 1-3mm sustained-release microcapsules. After cooling, perform surface modification and sieve to obtain the de-icing agent.

[0016] Example 2 A process for producing road de-icing agent using magnesium chloride concentrate includes the following steps: S1. Crush the rice husks to ≤2mm, and mix them with the recycled mother liquor in a reactor at a ratio of 1:2-3, with the total solid-liquid volume accounting for 70% of the reactor cavity, to obtain a mixture; 其中，回用母液包括MgCl2 49 %，结合水 40 %，低聚糖-乙酸钾络合物6%，活性SiO2胶体5%； S2. The above mixture is subjected to hydrothermal treatment. After treatment, it is filtered and subjected to solid-phase process to obtain a porous skeleton mixture. The initial temperature is 25-30℃. The temperature is increased to 120℃ at a rate of 5℃ / min and held for 10 minutes. Then, the temperature is increased to 180℃ at a rate of 3℃ / min and held for 20 minutes. Then, the temperature is increased to 200℃ at a rate of 23℃ / min and held for 30 minutes. Then, the temperature is cooled to 90℃ within 5 minutes by a 5℃ cold water jacket. The mixture is then filtered through a plate and frame filter to obtain wet carbon (containing 55% water) and a silicon-rich mother liquor. The silicon-rich mother liquor is directly reused in the next HTP. After filtration and solid-phase processing, a porous framework mixture is obtained. S3. Place biochar in the vacuum impregnation tank, and preheat the vacuum impregnation tank to 115-120℃. After heating, pour the above porous skeleton mixture into the tank and impregnate for a period of time. Then, open the bottom valve to complete the negative pressure siphon within 30 seconds. After de-vacuuming, immediately spray liquid nitrogen at a cooling rate of 50℃ / min to form 1-3mm sustained-release microcapsules. After cooling, perform surface modification and sieve to obtain the de-icing agent.

[0017] Example 3 A process for producing road de-icing agent using magnesium chloride concentrate includes the following steps: S1. Crush the rice husks to ≤2mm, and mix them with the recycled mother liquor in a reactor at a ratio of 1:2-3, with the total solid-liquid volume accounting for 70% of the reactor cavity, to obtain a mixture; 其中，回用母液包括MgCl2 49 %，结合水 40 %，低聚糖-乙酸钾络合物6%，活性SiO2胶体5%； S2. The above mixture is subjected to hydrothermal treatment. After treatment, it is filtered and subjected to solid-phase process to obtain a porous skeleton mixture. The initial temperature is 25-30℃. The temperature is increased to 110-130℃ at a rate of 5-7℃ / min and held for 10 minutes. Then, the temperature is increased to 180℃ at a rate of 3-4℃ / min and held for 20-30 minutes. The temperature is then increased to 200℃ at a rate of 23-25℃ / min and held for 30 minutes. The temperature is then cooled to 90℃ within 5 minutes by a 5℃ cold water jacket. The mixture is then filtered through a plate and frame filter to obtain wet carbon (containing 55% water) and a silicon-rich mother liquor. The silicon-rich mother liquor is directly reused in the next HTP process. After filtration and solid-phase processing, a porous framework mixture is obtained. S3. Place biochar in the vacuum impregnation tank, and preheat the vacuum impregnation tank to 115-120℃. After heating, pour the above porous skeleton mixture into the tank and impregnate for a period of time. Then, open the bottom valve to complete the negative pressure siphon within 30 seconds. After de-vacuuming, immediately spray liquid nitrogen at a cooling rate of 50℃ / min to form 1-3mm sustained-release microcapsules. After cooling, perform surface modification and sieve to obtain the de-icing agent.

[0018] The experimental data of the de-icing agents prepared in Examples 1-3 and the traditional magnesium chloride de-icing agent were compared. The specific data are shown in Table 1. Traditional magnesium chloride de-icing agents are products of direct granulation of magnesium chloride hexahydrate, with a particle size of 2–6 mm, white to slightly yellow in color, easily deliquescent, and containing no porous carriers or phase change composite structures. Table 1

[0019] As shown in Table 1, the snow melting agents prepared in Examples 1-3 have a higher snow melting rate and a lower corrosion rate than traditional snow melting agents.

[0020] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the patent and its protection scope should be determined by the appended claims.

Claims

1. A process for producing road de-icing agent using magnesium chloride concentrate, characterized in that, Includes the following steps: S1. After crushing agricultural and forestry waste to a certain size, mix it with recycled mother liquor in a certain mass ratio to obtain a mixture; S2. The above mixture is subjected to hydrothermal treatment. After treatment, it is filtered and subjected to solid-phase process to obtain a porous skeleton mixture. S3. Place biochar in the vacuum impregnation tank, preheat the vacuum impregnation tank to 115-120℃, pour the above porous skeleton mixture into the tank after heating, impregnate for a period of time, open the bottom valve, complete the negative pressure siphon within 30s, then use liquid nitrogen to cool quickly, perform surface modification after cooling, and obtain the de-icing agent after sieving.

2. The process for producing road de-icing agent using magnesium chloride concentrate as described in claim 1, characterized in that, In step S1, agricultural and forestry waste is crushed to ≤2mm and mixed with recycled mother liquor in a reactor at a ratio of 1:2-3, with the total solid-liquid volume accounting for 70% of the reactor cavity.

3. The process for producing road de-icing agent using magnesium chloride concentrate as described in claim 2, characterized in that, In step S2, the hydrothermal treatment includes: The initial temperature is 25-30℃. The temperature is increased to 110-130℃ at a rate of 5-7℃ / min and held for 10 minutes. Then, the temperature is increased to 180℃ at a rate of 3-4℃ / min and held for 20-30 minutes. The temperature is then increased to 200℃ at a rate of 23-25℃ / min and held for 30 minutes. The temperature is then cooled to 90℃ within 5 minutes by a 5℃ cold water jacket. The mixture is then filtered through a plate and frame filter to obtain wet carbon (containing 55% water) and a silica-rich mother liquor. The silica-rich mother liquor is directly reused in the next HTP cycle.

4. The process for producing road de-icing agent using magnesium chloride concentrate as described in claim 2, characterized in that, In step S2, the hydrothermal treatment includes: The initial temperature is 25-30℃. The temperature is increased to 120℃ at a rate of 5℃ / min and held for 10 minutes. Then, the temperature is increased to 180℃ at a rate of 3℃ / min and held for 20 minutes. Next, the temperature is increased to 200℃ at a rate of 23℃ / min and held for 30 minutes. Then, the temperature is cooled to 90℃ within 5 minutes by a 5℃ cold water jacket. The mixture is then filtered through a plate and frame filter to obtain wet carbon (containing 55% water) and a silica-rich mother liquor. The silica-rich mother liquor is directly reused in the next HTP cycle.

5. The process for producing road de-icing agent using magnesium chloride concentrate as described in claim 3, characterized in that, The recycled mother liquor consists of 49% MgCl2, 40% bound water, 6% oligosaccharide-potassium acetate complex, and 5% active SiO2 colloid.

6. The process for producing road de-icing agent using magnesium chloride concentrate as described in claim 1, characterized in that, The rapid cooling includes: Immediately after the vacuum is released, liquid nitrogen is sprayed, with a cooling rate of [missing information]. At 50 °C / min, sustained-release microcapsules of 1–3 mm are formed.

7. The process for producing road de-icing agent using magnesium chloride concentrate as described in claim 1, characterized in that, The agricultural and forestry waste is one or more of rice husks or corn residue.

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