Method for remelting and utilizing titanium slag smelting dedusting ash

Abstract

The invention discloses a method for remelting and utilizing titanium slag smelting fly ash, which comprises the following steps: mixing the fly ash and wet titanium concentrate, drying to obtain a mixture, and smelting and deslagging by controlling the feeding and power supply of the mixture, the titanium concentrate and a reducing agent. The method provided by the invention can effectively improve the TiO2 recovery rate and reduce the production cost.

Description

Technical Field

[0001] The invention relates to the technical field of titanium slag smelting, and in particular to a method for recycling dust removed from titanium slag smelting. Background Art

[0002] In the titanium slag electric furnace production process, due to the fine particle size of titanium concentrate, some fine particles are carried away by the flue gas when directly put into the furnace for smelting, and enter the dust removal system to form dust ash, resulting in a decrease in the yield of TiO2. Some domestic manufacturers have tried to return the dust ash directly to the furnace for smelting, but due to the high impurity content in the dust ash, uneven material mixing, improper feeding and power supply system, etc., serious foam slag and material difficulties are prone to occur, affecting normal production. Therefore, the dust ash is often discarded as solid waste, resulting in a waste of TiO2 resources.

[0003] CN 109385533 A discloses a method for recycling titanium slag dust, comprising the following steps: a. mixing titanium slag dust, titanium-containing material and / or carbonaceous reducing agent to prepare pellets, and drying the pellets; b. solid-phase reducing the pellets dried in step a to reduce pellets containing metallic iron, and separating the metallic iron and titanium-containing slag; c. alkali leaching and washing the titanium-containing slag obtained in step b to obtain titanium-rich material; the titanium-containing material in step a is at least one of titanium concentrate, ilmenite or titanium-containing iron concentrate, and the carbonaceous reducing agent in step a is at least one of coal, coke, petroleum coke or graphite. The prior art realizes the separation and comprehensive utilization of valuable elements such as iron and titanium in dust. However, the prior art does not disclose the recycling of titanium slag dust in titanium concentrate electric furnace smelting.

[0004] The titanium slag electric furnace dust removal powder recycling method disclosed in CN 107119198 A includes the following steps: A, adding water to the titanium slag electric furnace dust removal powder to form a slurry; B, magnetic separation of the slurry to form titanium concentrate; C, filtering the titanium concentrate slurry after magnetic separation to make its water content less than 15%; D, balling the titanium concentrate obtained by magnetic separation; E, drying the prepared pellets and adding them to the electric furnace smelting titanium slag, in step D, adding the filtered titanium concentrate to the fine-grained titanium concentrate raw material for initial mixing, adding a binder and water in turn, and controlling the moisture content of the mixed material to be 5% to 8%. The prior art humidifies the titanium slag electric furnace dust removal powder, sorts it, obtains titanium concentrate, presses and dries it, and then adds it to the electric furnace smelting titanium slag, shortens the process links, and reduces dust generation. However, the prior art includes magnetic separation and ball pressing processes, and requires subsequent slurry recovery and other treatments.

[0005] CN 109279606 A discloses a method for promoting the growth of TiC in slag. In the process of preparing titanium carbide slag by carbon thermal reduction of titanium-containing raw materials, dust ash produced in the smelting process is added into an electric furnace, smelted together with the titanium-containing raw materials and a reducing agent, and the slag is cooled after smelting to obtain titanium carbide slag. The dust ash contains 10-45% fixed carbon, 5-18% K2O, and 5-15% Na2O. The reducing agent is a carbonaceous reducing agent, and at least one of coke powder, lean coal, and anthracite is selected. The prior art discloses adding dust ash produced in the smelting process to the titanium slag smelting process, and effectively recycling the dust ash produced in the smelting process. However, the prior art is used to promote the growth of TiC in slag.

[0006] Based on this, there is room for improvement in the recovery of titanium slag smelting electric furnace dust as raw material. Summary of the invention

[0007] In view of this, the present invention provides a method for recycling dust from titanium slag smelting to solve the problem of foamy slag in the smelting process using dust.

[0008] The present invention provides a method for recycling dust ash from titanium slag smelting, comprising: mixing dust ash with wet titanium concentrate ore and drying to obtain a mixture, and smelting and slag removal by controlling the addition of the mixture, titanium concentrate and reducing agent and power supply.

[0009] In some embodiments, the dust ash is mixed with wet titanium concentrate and dried to obtain a mixture, including: mixing the dust ash and wet titanium concentrate in a first mass ratio to obtain a first mixture, and using a drying device to dry the first mixture to obtain a mixture.

[0010] In some embodiments, the moisture content in the mixture is 2% to 5%, and the first mass ratio of dust ash to wet titanium concentrate is 0.03 to 0.06:1.

[0011] In some embodiments, smelting and slag production is performed by controlling the addition of a mixture, titanium concentrate, and a reducing agent, as well as power supply, including: smelting the mixture, titanium concentrate, and reducing agent in two stages, wherein the first stage smelting includes mixing the titanium concentrate and a first amount of reducing agent into an electric furnace and supplying power with a first power supply, and the second stage smelting includes mixing the mixture and a second amount of reducing agent into an electric furnace and supplying power with a second power supply, and smelting and slag production.

[0012] In some embodiments, the ratio of the mass of the reducing agent to the total mass of the titanium concentrate and the mixed material is 0.08-0.2:1, wherein the total mass of the first amount of reducing agent and the second amount of reducing agent is the mass of the reducing agent.

[0013] In some embodiments, in the titanium concentrate and the mixed material, the ratio of the mass of the mixed material to the total mass of the titanium concentrate and the mixed material is 0.7-0.9:1.

[0014] In some embodiments, titanium concentrate and a first amount of reducing agent are mixed into an electric furnace and powered by a first power supply amount, including: after uniformly mixing the titanium concentrate and the first amount of reducing agent, adding the mixture to the electric furnace within the first time, and powering the electric furnace, and when the power supply amount to the electric furnace reaches the first power supply amount, the first stage of smelting is completed.

[0015] In some embodiments, the first time is 0.5 hours, the ratio of the mass of the first amount of reducing agent to the mass of the reducing agent is 0.08-0.24:1, and the first power transmission amount is controlled according to the ratio of the value of the first power transmission amount to the mass value of the titanium concentrate of 1.0-1.2:1.

[0016] In some embodiments, the mixture and the second amount of reducing agent are mixed into an electric furnace and powered by a second power supply, and smelting and slag are produced, including: the mixture and the second amount of reducing agent are evenly mixed and then added to the electric furnace, and the electric furnace is powered, after the power supply to the electric furnace reaches the second power supply, and the mixture and the second amount of reducing agent are all put into the electric furnace, the power supply is maintained, and slag is produced after overheating for a second time, thereby completing the second smelting stage.

[0017] In some embodiments, the ratio of the mass of the second amount of reducing agent to the mass of the reducing agent is 0.76-0.92:1, the second power transmission amount is controlled according to the ratio of the value of the second power transmission amount to the value of the total mass of the mixture and the second amount of reducing agent of 1.1-1.4:1, and the second time is 10-30 minutes: Beneficial effects of the present invention: The method for recycling dust ash from titanium slag smelting of the present invention improves the uniformity of materials by mixing dust ash with wet titanium concentrate and drying, and greatly reduces the foam slag in the smelting process using dust ash by controlling the addition of materials containing dust ash and controlling the power supply, and effectively improves the material smelting situation, so that dust ash can be put into the furnace to smelt titanium slag. The method of the present invention can effectively improve the recovery rate of TiO2 and reduce production costs. For an annual production scale of 180,000 tons of titanium slag, it is estimated that an annual economic benefit of about 3 million yuan can be created. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.

[0019] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0020] The method for recycling dust ash from titanium slag smelting of the present invention comprises: mixing dust ash with wet titanium concentrate to obtain a mixture after drying, and smelting and slag removal by controlling the addition of the mixture, titanium concentrate and reducing agent and power supply.

[0021] In some embodiments, the dust ash is mixed with wet titanium concentrate and dried to obtain a mixture, including: mixing the dust ash and wet titanium concentrate in a first mass ratio to obtain a first mixture, and using a drying device to dry the first mixture to obtain a mixture.

[0022] In some embodiments, dust ash and wet titanium concentrate are mixed according to a first mass ratio to obtain a first mixture, including: respectively loading the dust ash and wet titanium concentrate into corresponding raw material bins, controlling the dust ash and wet titanium concentrate to be simultaneously fed onto a feeding belt according to the first mass ratio through a metering system, and uniformly mixing the dust ash and wet titanium concentrate on the feeding belt to obtain the first mixture.

[0023] In some embodiments, the moisture content in the mixture is 2% to 5%. Here, the moisture content refers to the mass percentage of moisture, that is, the mass percentage of moisture in the mixture is 2% to 5%.

[0024] In some embodiments, the drying equipment is a rotary kiln.

[0025] In some embodiments, the first mass ratio of dust removal ash to wet titanium concentrate is 0.03-0.06:1. Therefore, the mass ratio of dust removal ash to wet titanium concentrate in the first mixture is 0.03-0.06:1.

[0026] In some embodiments, the dust removal ash includes the following components in mass percentage: TiO2, 20%~35%; FeO, 10%~30%; Fe2O3, 10%~30%; water, <1%.

[0027] In some embodiments, the wet ore of titanium concentrate includes the following components in percentage by mass: TiO2, 45% to 53%; FeO, 30% to 40%; Fe2O3, 5% to 20%; and moisture, 8% to 15%.

[0028] In some embodiments, the reductant is a carbonaceous reductant, and the mass percentage of fixed carbon in the reductant is greater than 80%.

[0029] In some embodiments, smelting and slag production is performed by controlling the addition of a mixture, titanium concentrate, and a reducing agent, as well as power supply, including: smelting the mixture, titanium concentrate, and reducing agent in two stages, wherein the first stage smelting includes mixing the titanium concentrate and a first amount of reducing agent into an electric furnace and supplying power with a first power supply, and the second stage smelting includes mixing the mixture and a second amount of reducing agent into an electric furnace and supplying power with a second power supply, and smelting and slag production.

[0030] In some embodiments, smelting and slag production are performed by controlling the addition of a mixture, titanium concentrate and a reducing agent, as well as power supply, including: loading the mixture, titanium concentrate and reducing agent into corresponding silos as electric furnace smelting raw materials, and calculating the total mass of titanium concentrate and mixture required for smelting the entire furnace of titanium slag according to the installed power of the electric furnace and the target titanium slag composition.

[0031] In some embodiments, the ratio of the mass of the reducing agent to the total mass of the titanium concentrate and the mixed material is 0.08 to 0.2: 1. The total mass of the first amount of reducing agent and the second amount of reducing agent is the mass of the reducing agent.

[0032] In some embodiments, in the titanium concentrate and the mixture, the ratio of the mass of the mixture to the total mass of the titanium concentrate and the mixture is 0.5 to 1: 1. The ratio of the mass of the mixture to the total mass of the titanium concentrate and the mixture is related to the ratio of dust removal ash in the first mixture. For example, when the mass ratio of dust removal ash to wet titanium concentrate in the first mixture is 0.03 to 0.06: 1, the ratio of the mass of the mixture to the total mass of the titanium concentrate and the mixture is 0.5 to 1: 1.

[0033] In some embodiments, in the titanium concentrate and the mixture, the ratio of the mass of the mixture to the total mass of the titanium concentrate and the mixture is 0.7-0.9:1, and the ratio of the mass of the titanium concentrate to the total mass of the titanium concentrate and the mixture is 0.1-0.3:1.

[0034] In some embodiments, titanium concentrate and a first amount of reducing agent are mixed into an electric furnace and powered by a first power supply amount, including: after uniformly mixing the titanium concentrate and the first amount of reducing agent, adding the mixture to the electric furnace within the first time, and powering the electric furnace, and when the power supply amount to the electric furnace reaches the first power supply amount, the first stage of smelting is completed.

[0035] In some embodiments, uniformly mixing the titanium concentrate and the first amount of the reducing agent comprises: uniformly feeding the titanium concentrate and the first amount of the reducing agent in a continuous feeding mode and then uniformly mixing them.

[0036] In some embodiments, the first time is 0.5 hours.

[0037] In some embodiments, mixing the titanium concentrate and the first amount of reducing agent into the electric furnace and supplying power with a first power supply includes: supplying power to the electric furnace with a first input power. For example, the first input power is 16 MW.

[0038] In some embodiments, the ratio of the mass of the first amount of reducing agent to the mass of the reducing agent is 0.08-0.24:1.

[0039] In some embodiments, the first power transmission amount is controlled according to a ratio of the value of the first power transmission amount to the value of the mass of the titanium concentrate of 1.0 to 1.2: 1. That is, the value of the first power transmission amount is 1.0 to 1.2 times the value of the mass of the titanium concentrate, wherein the unit of the first power transmission amount is MWh, and the unit of the mass of the titanium concentrate is ton.

[0040] In some embodiments, the mixture and the second amount of reducing agent are mixed into an electric furnace and powered by a second power supply, and smelting and slag are produced, including: the mixture and the second amount of reducing agent are evenly mixed and then added to the electric furnace, and the electric furnace is powered, after the power supply to the electric furnace reaches the second power supply, and the mixture and the second amount of reducing agent are all put into the electric furnace, the power supply is maintained, and slag is produced after overheating for a second time, thereby completing the second smelting stage.

[0041] In some embodiments, uniformly mixing the mixed material and the second amount of the reducing agent comprises: uniformly feeding the mixed material and the second amount of the reducing agent in a continuous feeding mode and then uniformly mixing them.

[0042] In some embodiments, the mixed material and the second amount of reducing agent are mixed into the electric furnace and powered by the second power supply to smelt and slag, including: powering the electric furnace with the second input power. For example, the second input power is 20MW.

[0043] In some embodiments, the mixed material and the second amount of reducing agent are mixed into the electric furnace and powered by the second power supply, and smelting and slag production includes: maintaining power supply with the second input power.

[0044] In some embodiments, the ratio of the mass of the second amount of reducing agent to the mass of the reducing agent is 0.76-0.92:1.

[0045] In some embodiments, the second power transmission amount is controlled according to a ratio of the value of the second power transmission amount to the value of the total mass of the mixture and the second amount of the reducing agent of 1.1 to 1.4: 1. That is, the value of the second power transmission amount is 1.1 to 1.4 times the value of the total mass of the mixture and the second amount of the reducing agent, wherein the unit of the second power transmission amount is MWh, and the units of the mass of the mixture and the second amount of the reducing agent are both tons.

[0046] In some embodiments, the second time period is 10 to 30 minutes.

[0047] The method for recycling dust from titanium slag smelting according to the present invention comprises the following steps: Step 1, mixing dust removal ash and wet titanium concentrate in a mass ratio of 0.03 to 0.06:1 through a metering system to obtain a first mixed material; Step 2, drying the first mixed material using a drying device to obtain a mixed material; Step 3, calculating the total mass of titanium concentrate and mixed material and the mass of reducing agent required for smelting the whole furnace of titanium slag, the ratio of the mass of reducing agent to the total mass of titanium concentrate and mixed material is 0.08-0.2:1; Step 4, after uniformly mixing the titanium concentrate and the first amount of reducing agent, adding them to the electric furnace within 0.5 hours, and supplying power to the electric furnace, when the power supply to the electric furnace reaches the first power supply, the first stage of smelting is completed, the ratio of the mass of the titanium concentrate to the total mass of the titanium concentrate and the mixture is 0.1-0.3:1, the ratio of the mass of the first amount of reducing agent to the mass of the reducing agent is 0.08-0.24:1, and the first power supply is controlled according to the ratio of the value of the first power supply to the value of the mass of the titanium concentrate of 1.0-1.2:1; Step 5, after uniformly mixing the mixture and the second amount of reducing agent, add them into the electric furnace and supply power to the electric furnace. After the power supply to the electric furnace reaches the second power supply and the mixture and the second amount of reducing agent are all put into the electric furnace, maintain power supply, start slag discharge after overheating for 10 to 30 minutes, and complete the second smelting stage. The ratio of the mass of the mixture to the total mass of the titanium concentrate and the mixture is 0.7 to 0.9:1, the ratio of the mass of the second amount of reducing agent to the mass of the reducing agent is 0.76 to 0.92:1, and the second power supply is controlled according to the ratio of the value of the second power supply to the total mass of the mixture and the second amount of reducing agent, which is 1.1 to 1.4:1.

[0048] In some embodiments, the titanium concentrate wet ore is titanium concentrate wet ore obtained by beneficiation.

[0049] In some embodiments, the main components of the titanium concentrate wet ore and the titanium concentrate are the same, the difference is that the moisture content they contain is different, and the moisture content in the titanium concentrate is less than 1%.

[0050] In the method of recycling dust ash from titanium slag smelting of the present invention, the material uniformity is improved by mixing and drying the dust ash with wet titanium concentrate, and the foamed slag in the smelting process using the dust ash is greatly reduced by controlling the addition of materials containing the dust ash and the amount of power supplied, and the material smelting condition is effectively improved, so that the dust ash can be used in the furnace to smelt titanium slag.

[0051] A titanium slag plant produces acid-soluble titanium slag with a TiO2 content of 74%. The wet titanium concentrate used includes the following components in mass percentage: TiO2, 47%; FeO, 36%; Fe2O3, 7%; moisture, 12%, where the mass percentages of TiO2, FeO, and Fe2O3 are their respective mass percentages in the dry basis of the wet titanium concentrate, and the mass percentage of fixed carbon in the reducing agent used is 84%. The generated dust ash includes the following components in mass percentage: TiO2, 25%; FeO, 21%; Fe2O3, 12%; moisture, 0.5%. A furnace adopts the method of recycling the dust ash from titanium slag smelting, using the dust ash from the previous furnace. The implementation process is as follows: The dust removal ash and wet titanium concentrate ore are loaded into two silos respectively, and the dust removal ash and wet titanium concentrate ore are quantitatively discharged to the feeding belt using their respective weighing belts. The discharge speed of the dust removal ash is controlled to be 2 tons / hour and the discharge speed of the wet titanium concentrate ore is controlled to be 40 tons / hour. The two silos start discharging at the same time to achieve uniform mixing of the dust removal ash and the wet titanium concentrate ore at a mass ratio of 0.05:1 on the feeding belt to obtain the first mixture.

[0052] The first mixed material is transported to the feeding port of the rotary kiln by a feeding belt. The mixed material is obtained and discharged by controlling parameters such as the temperature and rotation speed of the rotary kiln. The moisture content in the mixed material is maintained at 3.5%.

[0053] The mixed material, titanium concentrate and reducing agent are transported by belts into three silos respectively. The total amount of the furnace is controlled at 122 tons, including 110 tons of titanium concentrate and mixed material and 12 tons of reducing agent. The dynamic metering system under the silo is used to feed materials at a specific feeding speed.

[0054] In the first stage of smelting, a total of 20 tons of titanium concentrate and 2 tons of reducing agent were added. By adjusting the dynamic metering system, 50 tons / hour of titanium concentrate and 5 tons / hour of reducing agent were evenly fed and mixed into the electric furnace, and the feeding was completed in 0.4 hours. At the same time, the power supply was 16MW. When the power supply reached 20MWh, the first stage of smelting was completed.

[0055] In the second stage of smelting, a total of 90 tons of mixed materials and 10 tons of reducing agents were added. By adjusting the dynamic metering system, 15 tons / hour of mixed materials and 1.67 tons / hour of reducing agents were fed evenly and mixed evenly before entering the electric furnace. At the same time, the power supply was supplied with an input power of 20MW, and the ratio of the power supply (unit MWh) to the value of the added amount (total mass of mixed materials and reducing agents, tons) was controlled to be 1.2. After all the mixed materials and reducing agents were put into the electric furnace, the input power of 20MW was maintained for power supply. Slag was discharged after 15 minutes of overheating, completing the second stage of smelting.

[0056] The titanium slag smelted according to the method of the present invention has a stable smelting process, no foam slag is generated, and there is basically no raw material accumulation in the electric furnace. The stable application of dust removal ash is achieved, and the power consumption per ton of slag is only 50kWh / ton higher than that without dust removal ash, which has good economic efficiency.

[0057] The method for recycling the dust-removed ash from titanium slag smelting of the present invention has a simple process, eliminates the cost of traditional granulation treatment, effectively improves the TiO2 recovery rate, reduces production costs, and has a certain prospect for promotion and application.

[0058] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for recycling dust from titanium slag smelting, characterized in that: include: The dust removal ash is mixed with wet titanium concentrate and dried to obtain a mixture, and slag is smelted and discharged by controlling the addition of the mixture, titanium concentrate and reducing agent as well as power supply.

2. The method for recycling dust from titanium slag smelting according to claim 1 is characterized in that: The dust removal ash is mixed with the wet titanium concentrate and dried to obtain a mixture, including: mixing the dust removal ash and the wet titanium concentrate in a first mass ratio to obtain a first mixture, and drying the first mixture using a drying device to obtain the mixture.

3. The method for recycling dust from titanium slag smelting according to claim 2 is characterized in that: The moisture content in the mixture is 2% to 5%, and the first mass ratio of the dust removal ash to the wet titanium concentrate is 0.03 to 0.06:

1.

4. The method for recycling dust from titanium slag smelting according to claim 1 is characterized in that: The smelting and slag production is carried out by controlling the feeding of the mixture, titanium concentrate and reducing agent and the power supply, including: smelting the mixture, titanium concentrate and reducing agent in two stages, wherein the first stage smelting includes mixing the titanium concentrate and a first amount of the reducing agent into an electric furnace and supplying power with a first power supply, and the second stage smelting includes mixing the mixture and a second amount of the reducing agent into the electric furnace and supplying power with a second power supply, and smelting and slag production.

5. The method for recycling dust from titanium slag smelting according to claim 4 is characterized in that: The ratio of the mass of the reducing agent to the total mass of the titanium concentrate and the mixture is 0.08-0.2:1, wherein the total mass of the first amount of the reducing agent and the second amount of the reducing agent is the mass of the reducing agent.

6. The method for recycling dust from titanium slag smelting according to claim 4 is characterized in that: In the titanium concentrate and the mixed material, the ratio of the mass of the mixed material to the total mass of the titanium concentrate and the mixed material is 0.7-0.9:

1.

7. The method for recycling dust from titanium slag smelting according to claim 4 is characterized in that: The titanium concentrate and the first amount of the reducing agent are mixed into an electric furnace and powered by a first power supply, including: after the titanium concentrate and the first amount of the reducing agent are evenly mixed, they are added into the electric furnace within the first time, and the electric furnace is powered, and when the power supply to the electric furnace reaches the first power supply, the first stage of smelting is completed.

8. The method for recycling dust from titanium slag smelting according to claim 7 is characterized in that: The first time is 0.5 hours, the ratio of the mass of the first amount of the reducing agent to the mass of the reducing agent is 0.08-0.24:1, and the first power transmission amount is controlled according to the ratio of the value of the first power transmission amount to the mass of the titanium concentrate of 1.0-1.2:

1.

9. The method for recycling dust from titanium slag smelting according to claim 4, characterized in that: The mixture and the second amount of the reducing agent are mixed into the electric furnace and powered by a second power supply, and smelting and slag is produced, including: the mixture and the second amount of the reducing agent are uniformly mixed and then added to the electric furnace, and the electric furnace is powered, and after the power supply to the electric furnace reaches the second power supply and the mixture and the second amount of the reducing agent are all put into the electric furnace, the power supply is maintained, and slag is produced after the second overheating time, thereby completing the second smelting stage.

10. The method for recycling dust from titanium slag smelting according to claim 9, characterized in that: The ratio of the mass of the second amount of the reducing agent to the mass of the reducing agent is 0.76 to 0.92:1, the second power transmission amount is controlled according to the ratio of the value of the second power transmission amount to the value of the total mass of the mixture and the second amount of the reducing agent of 1.1 to 1.4:1, and the second time is 10 to 30 minutes.