Method for efficiently extracting sodium silicate from rice hull ash

Abstract

The invention discloses a method for efficiently extracting sodium silicate from rice hull ash, and relates to the technical field of extraction of sodium silicate from rice hulls, and the method comprises the following steps: (1) placing pretreated rice hulls in a carbonization furnace at 400-800 DEG C, and carrying out constant-temperature combustion for 3-4 hours to obtain incompletely combusted rice hull ash; (2) removing impurities from the rice hull ash, crushing, sieving, uniformly mixing with a 1.5-2.0 mol / L sodium hydroxide solution, and carrying out pressurized reaction for 20-40 minutes to obtain a first liquid; (3) adding a 1.0-1.5 mol / L sodium hydroxide solution into the first liquid according to the addition amount accounting for 300-500% of the mass of the rice hull ash in the step (2), and carrying out pressurized reaction for 30-50 minutes to obtain a second liquid; (4) adding a 0.5-1.0 mol / L sodium hydroxide solution into the second liquid according to the addition amount accounting for 200-400% of the mass of the rice hull ash in the step (2), and carrying out pressurized reaction for 40-60 minutes to obtain a third liquid; and (5) carrying out plate-frame pressure filtration on the third liquid to obtain the sodium silicate solution. The sodium silicate prepared by the method is stable in modulus, high in dissolution efficiency and good in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of extracting sodium silicate from rice husk, and in particular relates to a method for efficiently extracting sodium silicate from rice husk ash. Background Art

[0002] Rice husk is the main by-product of rice processing, accounting for 20-30% of the weight of rice. For a long time, the utilization of rice husk resources, except for a small part used as primary fuel, feed, building materials or combustion for power generation, most of them are used as agricultural waste and waste gas, which not only seriously pollutes the environment, but also causes potential safety risks of spontaneous combustion when piled up. With people's attention to various biomass renewable resources, rice husk is a member of the biomass family, which has been favored by researchers because of its large quantity, wide range, cheap and easy to obtain, clean and renewable. Extensive research has been carried out on the comprehensive utilization of rice husk resources at home and abroad, and many rice husk-based high value-added products have been developed, achieving significant economic benefits.

[0003] Among the many uses, the development of rice husk silicon is the most active. The content of amorphous hydrated silicon dioxide in rice husk is 15-20%, and the content of silicon dioxide in completely burned rice husk ash is as high as 93%. After purification, high-purity SiO2 products can be obtained. Mineral siliceous materials in nature mostly exist in crystalline form with stable structure, while the amorphous SiO2 in rice husk has high reaction activity and large specific surface area, which can be used as an ideal silicon source for siliceous materials. Alkali fusion method is a traditional method for preparing SiO2 using rice husk as raw material. It is also a relatively mature and widely studied method. Its key steps are the reaction of rice husk ash with alkali solution to prepare silicate and the precipitation reaction of silicate with acidifier. At present, the preparation of silicate by alkali fusion method has problems such as unstable modulus (molar ratio of SiO2 and Na2O), low dissolution efficiency, low yield, and high cost. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and provide a method for efficiently extracting sodium silicate from rice husk ash. The method is simple and easy to operate, has a high yield, and the obtained sodium silicate has a stable modulus and high dissolution efficiency, which can reduce production costs.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] As a first aspect of the present invention, the present invention provides a method for efficiently extracting sodium silicate from rice husk ash, comprising the following steps:

[0007] (1) placing the pretreated rice husk in a carbonization furnace at 400-800° C. and burning at a constant temperature for 3-4 hours to obtain incompletely burned rice husk ash, wherein the pretreatment step includes washing, filtering, drying and removing impurities from the rice husk;

[0008] (2) removing impurities, crushing and screening the rice husk ash obtained in step (1), and then mixing it evenly with a sodium hydroxide solution having a concentration of 1.5 to 2.0 mol / L in a mass ratio of 1:(4 to 6), and reacting it under pressure for 20 to 40 minutes to obtain a first liquid;

[0009] (3) adding a sodium hydroxide solution having a concentration of 1.0 to 1.5 mol / L to the first liquid in an amount accounting for 300 to 500% of the mass of the rice husk ash in step (2), and reacting under pressure for 30 to 50 minutes to obtain a second liquid;

[0010] (4) adding a sodium hydroxide solution having a concentration of 0.5 to 1.0 mol / L to the second liquid in an amount accounting for 200 to 400% of the mass of the rice husk ash in step (2), and reacting under pressure for 40 to 60 minutes to obtain a third liquid;

[0011] In the reaction system of step (2) to step (4), the pressure value of the pressurized reaction is set in an increasing manner;

[0012] (5) The third liquid is filtered through a plate and frame filter press to obtain a sodium silicate solution.

[0013] As a further optimization scheme of the present invention, in step (1), the pretreatment further includes subjecting the rice husk to a puffing composite acid treatment, and the specific steps are as follows:

[0014] (a) firstly crushing and sieving the rice husk after washing, filtering, drying and impurity removal to obtain rice husk powder, then mixing the rice husk powder and a swelling agent evenly and then performing a puffing treatment, and finally sieving the puffed rice husk powder to obtain puffed rice husk powder;

[0015] (b) adding citric acid aqueous solution to the puffed rice husk powder for ultrasonic soaking treatment, and after the soaking is completed, centrifugally filtering, washing and drying.

[0016] As a further optimization scheme of the present invention, in step (a), the mass ratio of the rice husk powder to the swelling agent is 50:1, and the swelling agent is prepared by uniformly mixing 200g of sodium bicarbonate, 100g of ammonium bicarbonate and 200g of water.

[0017] As a further optimization scheme of the present invention, in step (b), the weight percentage of the citric acid aqueous solution is 8-10wt%, and the mass volume ratio of the puffed rice husk powder to the citric acid solution is 50-60g:1500-1600mL.

[0018] As a further optimization scheme of the present invention, in step (b), the process conditions of the ultrasonic immersion treatment are as follows: ultrasonic power of 20-25kHz, ultrasonic power of 300-350W, immersion temperature of 50-70°C and immersion time of 2-4h.

[0019] As a further optimization scheme of the present invention, the pressurizing pressure in step (2) is 0.4-0.6 MPa; the pressurizing pressure in step (3) is 0.6-0.8 MPa; and the pressurizing pressure in step (4) is 0.8-1.0 MPa.

[0020] As a further optimization scheme of the present invention, in steps (2) to (4), the reaction temperature is 120 to 140°C.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention adopts step-by-step reaction and step-by-step discharge to quickly obtain sodium silicate liquid, shorten the sodium silicate dissolution time, and improve the efficiency of extracting sodium silicate from rice husk ash. In addition, as the reaction proceeds, the amount of SiO2 in the rice husk ash gradually decreases. The concentration of the sodium hydroxide solution is gradually reduced to maintain the ratio of Na2O to SiO2 in the reaction system within a certain range, thereby avoiding a reduction in the modulus of the dissolved sodium silicate solution due to an increase in Na2O in the reaction system.

[0023] (2) The present invention further improves the efficiency of extracting sodium silicate by gradually increasing the pressure of the reaction system, increasing the sodium silicate dissolution rate and shortening the sodium silicate dissolution time.

[0024] (3) In addition to the conventional cleaning, filtering, drying and impurity removal pretreatment of the rice husk, the present invention also adds a puffing compound acid treatment process. It has been verified through experiments that the addition of puffing compound acid treatment to the rice husk can increase the SiO2 dissolution rate to a certain extent. At the same time, the modulus of the extracted sodium silicate is also improved to a certain extent, which is conducive to obtaining a sodium silicate product with higher quality. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technicians in this field can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0026] Example 1

[0027] This embodiment provides a method for efficiently extracting sodium silicate from rice husk ash, comprising the following steps:

[0028] (1) The pretreated rice husks were placed in a carbonization furnace at 700°C and burned at a constant temperature for 3.5 hours to obtain incompletely burned rice husk ash. The SiO2 content in the rice husk ash was analyzed. The pretreatment steps included washing, filtering, drying and removing impurities from the rice husks.

[0029] (2) After removing impurities from the rice husk ash, crush it and pass it through a 100-mesh screen. In the static autoclave A, add 200 kg of rice husk ash and 1000 kg of a sodium hydroxide solution with a concentration of 1.8 mol / L, pressurize to 0.5 MPa, and the reaction temperature is 120-140° C., preferably 140° C., and react at constant pressure for 30 minutes. After the reaction is completed, a first liquid is obtained, and the first liquid is transported to the static autoclave B.

[0030] (3) Add 800 kg of 1.3 mol / L sodium hydroxide solution to the autoclave B, pressurize to 0.7 MPa, set the reaction temperature to 120-140° C., preferably 140° C., and react at constant pressure for 40 min. After the reaction is completed, obtain a second liquid, which is transported to the autoclave C.

[0031] (4) Add 600 kg of 0.8 mol / L sodium hydroxide solution to the autoclave C, pressurize to 0.9 MPa, set the reaction temperature to 120-140° C., preferably 140° C., and react at constant pressure for 50 min.

[0032] (5) The turbid liquid from the autoclave C is filtered through a plate and frame filter press to obtain a sodium silicate solution, and the residual solid (a mixture of carbon and unextracted SiO2) is collected and analyzed for the residual SiO2 content.

[0033] Example 2

[0034] This embodiment provides a method for efficiently extracting sodium silicate from rice husk ash, comprising the following steps:

[0035] (1) The pretreated rice husks were placed in a carbonization furnace at 700°C and burned at a constant temperature for 3.5 hours to obtain incompletely burned rice husk ash. The SiO2 content in the rice husk ash was analyzed. The pretreatment steps included washing, filtering, drying and removing impurities from the rice husks.

[0036] (2) After removing impurities from the rice husk ash, crush it and pass it through a 100-mesh sieve. In the autoclave A, add 200 kg of rice husk ash and 1100 kg of a 1.9 mol / L sodium hydroxide solution, pressurize to 0.55 MPa, set the reaction temperature to 140°C, and react at constant pressure for 35 minutes. After the reaction is completed, a first liquid is obtained, which is transported to the autoclave B.

[0037] (3) Add 900 kg of 1.4 mol / L sodium hydroxide solution to the autoclave B, pressurize to 0.8 MPa, set the reaction temperature to 140°C, and react at constant pressure for 45 minutes. After the reaction is completed, obtain the second liquid, and transport the second liquid to the autoclave C.

[0038] (4) Add 700 kg of 0.9 mol / L sodium hydroxide solution to the autoclave C, pressurize to 1.0 MPa, set the reaction temperature to 140°C, and react at constant pressure for 55 min.

[0039] (5) The turbid liquid from the autoclave C was filtered through a plate and frame filter press to obtain a sodium silicate solution, and the residual solid (a mixture of carbon and unextracted SiO2) was collected and analyzed for the residual SiO2 content.

[0040] Example 3

[0041] This embodiment provides a method for efficiently extracting sodium silicate from rice husk ash, comprising the following steps:

[0042] (1) The pretreated rice husks were placed in a carbonization furnace at 700°C and burned at a constant temperature for 3.5 hours to obtain incompletely burned rice husk ash. The SiO2 content in the rice husk ash was analyzed. The pretreatment steps included washing, filtering, drying and removing impurities from the rice husks.

[0043] (2) After removing impurities from the rice husk ash, crush it and pass it through a 100-mesh sieve. In the autoclave A, add 200 kg of rice husk ash and 1100 kg of a 1.9 mol / L sodium hydroxide solution, pressurize to 0.55 MPa, set the reaction temperature to 140°C, and react at constant pressure for 35 minutes. After the reaction is completed, a first liquid is obtained, which is transported to the autoclave B.

[0044] (3) Add 900 kg of 1.4 mol / L sodium hydroxide solution to the autoclave B, pressurize to 0.8 MPa, set the reaction temperature to 140°C, and react at constant pressure for 45 minutes. After the reaction is completed, obtain the second liquid, and transport the second liquid to the autoclave C.

[0045] (4) Add 700 kg of 0.9 mol / L sodium hydroxide solution to the autoclave C, pressurize to 1.0 MPa, set the reaction temperature to 140°C, and react at constant pressure for 55 min.

[0046] (5) The turbid liquid from the autoclave C was filtered through a plate and frame filter press to obtain a sodium silicate solution, and the residual solid (a mixture of carbon and unextracted SiO2) was collected and analyzed for the residual SiO2 content.

[0047] Example 4

[0048] This embodiment provides a method for efficiently extracting sodium silicate from rice husk ash. Except for step (1), the other steps are the same as those in Example 1.

[0049] In this embodiment, step (1) is specifically as follows:

[0050] The rice husk is washed, filtered, dried and impurity-removed, and then crushed through a 20-mesh sieve to obtain rice husk powder;

[0051] Then, the rice husk powder and the swelling agent are uniformly mixed in a mass ratio of 50:1, the extrusion puffing machine is preheated, the feed temperature is controlled to be 80° C., and the discharge temperature is controlled to be 110° C., the mixed raw materials are put into a twin-screw puffing machine for puffing treatment, and the puffed product is crushed through a 60-mesh sieve to obtain puffed rice husk powder, and the swelling agent is prepared by uniformly mixing 200 g of sodium bicarbonate, 100 g of ammonium bicarbonate and 200 g of water;

[0052] Finally, add 8-10wt% citric acid aqueous solution to the puffed rice husk powder for ultrasonic soaking treatment. The mass volume ratio of puffed rice husk powder to citric acid solution is 50-60g:1500-1600mL. The process conditions of ultrasonic soaking treatment are ultrasonic power of 20-25kHz, ultrasonic power of 300-350W, soaking temperature of 50-70℃ and soaking time of 2-4h. After soaking, centrifuge, filter, wash and dry.

[0053] In this embodiment, the citric acid aqueous solution is preferably 8wt%, the mass volume ratio of puffed rice husk powder to citric acid solution is 50g:1500mL, and the process conditions for ultrasonic immersion treatment are preferably ultrasonic power of 20kHz, ultrasonic power of 300W, immersion temperature of 60°C and immersion time of 2h.

[0054] Verification test

[0055] 1. In order to explore the effect of reaction method on the performance of extracted sodium silicate products, the following comparative examples were set up:

[0056] Comparative Example 1

[0057] This comparative example provides a method for extracting sodium silicate from rice husk ash, comprising the following steps:

[0058] (1) The pretreated rice husks were placed in a carbonization furnace at 700°C and burned at a constant temperature for 3.5 hours to obtain incompletely burned rice husk ash. The SiO2 content in the rice husk ash was analyzed. The pretreatment steps included washing, filtering, drying and removing impurities from the rice husks.

[0059] (2) After removing impurities from the rice husk ash, crush it and pass it through a 100-mesh screen. In a static autoclave, add 200 kg of rice husk ash and 3000 kg of 2 mol / L sodium hydroxide solution, pressurize to 1.0 MPa, set the reaction temperature to 140°C, and react at constant pressure for 240 minutes.

[0060] (3) After the reaction is completed, the turbid liquid in the autoclave is filtered through a plate and frame filter press to obtain a sodium silicate solution, and the residual solid (a mixture of carbon and unextracted SiO2) is collected and analyzed for the residual SiO2 content.

[0061] Comparative Example 2

[0062] This comparative example provides a method for extracting sodium silicate from rice husk ash, comprising the following steps:

[0063] (1) The pretreated rice husks were placed in a carbonization furnace at 700°C and burned at a constant temperature for 3.5 hours to obtain incompletely burned rice husk ash. The SiO2 content in the rice husk ash was analyzed. The pretreatment steps included washing, filtering, drying and removing impurities from the rice husks.

[0064] (2) After removing impurities from the rice husk ash, crush it and pass it through a 100-mesh screen. In a static autoclave, add 200 kg of rice husk ash and 3000 kg of 2 mol / L sodium hydroxide solution, pressurize to 1.2 MPa, set the reaction temperature to 140°C, and react at constant pressure for 300 minutes.

[0065] (3) After the reaction is completed, the turbid liquid in the autoclave is filtered through a plate and frame filter press to obtain a sodium silicate solution, and the residual solid (a mixture of C and unextracted SiO2) is collected to analyze the residual SiO2 content.

[0066] The following product tests were performed on Examples 1-3 and Comparative Examples 1-2:

[0067] (1) Determination of SiO2 content in rice husk ash and residual solids: according to HG / T3061-2020 (precipitated hydrated silica for rubber compounding agents).

[0068] (2) Determination of the modulus of sodium silicate. The modulus of sodium silicate, that is, the molar ratio of SiO2 and alkali metal oxides in sodium silicate, is an important indicator for evaluating the quality of sodium silicate products. The modulus of sodium silicate not only affects the viscosity, density, boiling point and characteristics when boiling, freezing point and characteristics when freezing, but also has a certain influence on its chemical properties. The modulus of sodium silicate is determined in accordance with GB4209-1996.

[0069] (3) The SiO2 dissolution rate is calculated according to the following formula:

[0070]

[0071] The results are shown in Table 1.

[0072] Table 1 Technical indicators of sodium silicate product testing

[0073]

[0074] It can be seen from the table that compared with the comparative example, the total reaction time of the embodiment is short, the dissolution rate is high, and the modulus of sodium silicate is high. In the embodiment, compared with embodiment 1, the total reaction time of embodiment 2 is prolonged, but the dissolution rate is not much improved; the total reaction time of embodiment 3 is reduced, but the dissolution rate is reduced too much. And the modulus of sodium silicate in embodiment 1 is also within the ideal range. In summary, the comprehensive technical indicators of embodiment 1 are the best, and it is the best embodiment.

[0075] 2. In order to explore the effect of rice husk pretreatment on the performance of extracted sodium silicate products, the following comparative examples were set up:

[0076] Comparative Example 3

[0077] This comparative example provides a method for efficiently extracting sodium silicate from rice husk ash. Except for step (1), the other steps are the same as those in Example 1.

[0078] In this comparative example, step (1) specifically comprises: washing, filtering, drying and removing impurities from the rice husk, and then crushing and passing through a 20-mesh sieve to obtain rice husk powder; then, uniformly mixing the rice husk powder and the swelling agent in a mass ratio of 50:1, preheating the extrusion puffing machine, controlling its feed temperature to 80° C. and its discharge temperature to 110° C., placing the above-mentioned mixed raw materials into a twin-screw puffing machine for puffing treatment, and crushing the puffed product through a 60-mesh sieve to obtain puffed rice husk powder, wherein the swelling agent is prepared by uniformly mixing 200 g of sodium bicarbonate, 100 g of ammonium bicarbonate and 200 g of water.

[0079] The obtained expanded rice husk powder is subjected to the same steps (2) to (5) as described in Example 1 to obtain a sodium silicate solution.

[0080] Comparative Example 4

[0081] This comparative example provides a method for efficiently extracting sodium silicate from rice husk ash. Except for step (1), the other steps are the same as those in Example 1.

[0082] In this comparative example, step (1) is specifically as follows: after washing, filtering, drying and removing impurities from the rice husk, the rice husk is crushed through a 60-mesh sieve to obtain rice husk powder, and an 8wt% citric acid aqueous solution is added to the rice husk powder for ultrasonic immersion treatment. The mass volume ratio of the rice husk powder to the citric acid solution is 50g:1500mL. The process conditions for the ultrasonic immersion treatment are an ultrasonic power of 20kHz, an ultrasonic power of 300W, an immersion temperature of 60°C and an immersion time of 2h.

[0083] The obtained rice husk powder is subjected to steps (2) to (5) as described in Example 1 to obtain a sodium silicate solution.

[0084] Comparative Example 5

[0085] This comparative example provides a method for efficiently extracting sodium silicate from rice husk ash. Except for step (1), the other steps are the same as those in Example 1.

[0086] In this comparative example, the rice husks were cleaned, filtered, dried and decontaminated, heated to 450°C at a rate of 12°C / min, roasted at 450°C for 30 min, then heated to 700°C at a rate of 10°C / min, roasted at 700°C for 3 h, and the rice husk ash was taken out after the roasting was completed.

[0087] The same product test was performed on the sodium silicate obtained in Example 4 and Comparative Examples 3-5. The results are shown in Table 2.

[0088] Table 2 Technical indicators of sodium silicate product testing

[0089]

[0090] As can be seen from the table, compared with Example 1, Example 4 adds puffing composite acid treatment to the rice husk, so that the rice husk has the advantages of porosity, low density, large specific surface area and rich active groups, which can improve the contact effect with the reaction raw materials in the subsequent synthesis reaction, promote the synthesis reaction to be more complete, improve the SiO2 dissolution rate to a certain extent, and the modulus of sodium silicate can also be improved to a certain extent. Compared with Example 4, Comparative Examples 3-4 omit the acid treatment and puffing treatment respectively. From the results in the table, the combination of puffing treatment and acid treatment has a positive significance for simultaneously improving the SiO2 dissolution rate and the modulus of sodium silicate.

[0091] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for efficiently extracting sodium silicate from rice husk ash, characterized in that: The following steps are involved: (1) placing the pretreated rice husk in a carbonization furnace at 400-800° C. and burning at a constant temperature for 3-4 hours to obtain incompletely burned rice husk ash, wherein the pretreatment step includes washing, filtering, drying and removing impurities from the rice husk; (2) removing impurities, crushing and screening the rice husk ash obtained in step (1), and then mixing it evenly with a sodium hydroxide solution having a concentration of 1.5 to 2.0 mol / L in a mass ratio of 1:(4 to 6), and reacting it under pressure for 20 to 40 minutes to obtain a first liquid; (3) adding a sodium hydroxide solution having a concentration of 1.0 to 1.5 mol / L to the first liquid in an amount accounting for 300 to 500% of the mass of the rice husk ash in step (2), and reacting under pressure for 30 to 50 minutes to obtain a second liquid; (4) adding a sodium hydroxide solution having a concentration of 0.5 to 1.0 mol / L to the second liquid in an amount accounting for 200 to 400% of the mass of the rice husk ash in step (2), and reacting under pressure for 40 to 60 minutes to obtain a third liquid; In the reaction system of step (2) to step (4), the pressure value of the pressurized reaction is set in an increasing manner; (5) The third liquid is filtered through a plate and frame filter press to obtain a sodium silicate solution.

2. The method for efficiently extracting sodium silicate from rice husk ash according to claim 1, characterized in that: In step (1), the pretreatment further comprises subjecting the rice husk to a puffing composite acid treatment, and the specific steps are as follows: (a) firstly crushing the washed, filtered, dried and impurity-free rice husks and sieving them to obtain rice husk powder, then uniformly mixing the rice husk powder with a swelling agent and performing a puffing treatment, and finally sieving the puffed rice husk powder to obtain puffed rice husk powder; (b) adding citric acid aqueous solution to the puffed rice husk powder for ultrasonic soaking treatment, and after the soaking is completed, centrifugally filtering, washing and drying.

3. The method for efficiently extracting sodium silicate from rice husk ash according to claim 2, characterized in that: In step (a), the mass ratio of the rice husk powder to the swelling agent is 50:1, and the swelling agent is prepared by uniformly mixing 200g of sodium bicarbonate, 100g of ammonium bicarbonate and 200g of water.

4. The method for efficiently extracting sodium silicate from rice husk ash according to claim 2, characterized in that: In step (b), the weight percentage of the citric acid aqueous solution is 8-10wt%, and the mass volume ratio of the puffed rice husk powder to the citric acid solution is 50-60g:1500-1600mL.

5. The method for efficiently extracting sodium silicate from rice husk ash according to claim 2, characterized in that: In step (b), the process conditions of the ultrasonic immersion treatment are as follows: ultrasonic power of 20-25 kHz, ultrasonic power of 300-350 W, immersion temperature of 50-70° C. and immersion time of 2-4 h.

6. The method for efficiently extracting sodium silicate from rice husk ash according to claim 1, characterized in that: The pressurizing pressure in step (2) is 0.4 to 0.6 MPa; the pressurizing pressure in step (3) is 0.6 to 0.8 MPa; and the pressurizing pressure in step (4) is 0.8 to 1.0 MPa.

7. The method for efficiently extracting sodium silicate from rice husk ash according to claim 1, characterized in that: In steps (2) to (4), the reaction temperature is 120 to 140°C.

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