Device and method for purifying high-temperature oil-containing and dust-containing coal gas

Abstract

The invention discloses a device and a method for purifying high-temperature oil-containing and dust-containing coal gas. The device comprises a first-stage cooling and dust removal unit, a second-stage oil product separation unit and a third-stage purification unit, the first-stage cooling and dust removing unit is used for rapidly cooling high-temperature oil-containing and dust-containing coal gas and removing large-particle dust; the second-stage oil product separation unit is used for cooling and separating the oil product from which the large-particle dust is removed by the first-stage cooling and dust removal unit; and the third-stage purification unit is used for removing fine particles in coal gas in the oil product separated by the second-stage oil product separation unit, so that coal gas purification is realized. The method has the characteristics of being easy to operate, good in purification effect and capable of realizing cyclic utilization of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of coal chemical processing, and in particular to a purification device and method for high-temperature oily and dusty coal gas. Background Art

[0002] Low-rank coal pyrolysis is a technology that utilizes coal in a graded manner according to its own characteristics, extracts high value-added products such as coal gas, tar, and semi-coke, and truly realizes the comprehensive resource utilization of coal. The raw coal gas produced by pyrolysis of pulverized coal has the characteristics of high temperature, oil content, and dust content. If it is not purified and separated, the tar after condensation contains unreacted fine powder, resulting in low tar purity, which affects the next step of processing and utilization; at the same time, a small amount of fly ash or semi-coke is entrained in the gas, resulting in a low overall process added value.

[0003] Purifying and separating high-temperature, oily and dusty coal gas to obtain clean coal tar and synthesis gas is a common technical problem in the coal chemical industry. Conventional dust removal technology cannot meet the production process requirements, resulting in excessively high ash content in coal tar products, which cannot be efficiently utilized, and to a certain extent restricts the development of low-grade coal graded utilization technology.

[0004] In the prior art, the separation effect of high-temperature dusty coal gas is low, which can easily cause blockage of system equipment and inability of the transport pump to function normally.

[0005] Therefore, it is urgent to design a method to achieve high-quality separation of high-temperature oily and dusty coal gas, obtain high-quality synthesis gas with low fine powder content, reduce system blockage, and increase the service life of dynamic equipment such as transport pumps. Summary of the invention

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a purification device and method for high-temperature oily and dusty coal gas, which has the characteristics of easy operation, good purification effect and resource recycling.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A purification device for high-temperature oily and dusty coal gas, comprising a primary cooling and dust removal unit, a secondary oil separation unit and a tertiary purification unit;

[0009] The first-stage cooling and dust removal unit is used to quickly cool down the high-temperature oily and dusty coal gas to remove large dust particles;

[0010] The secondary oil separation unit is used to cool and separate the oil from which the large dust particles are removed by the primary cooling and dust removal unit;

[0011] The three-stage purification unit is used to remove fine particles in the coal gas from the oil separated by the two-stage oil separation unit, thereby achieving coal gas purification.

[0012] The first-stage cooling and dust removal unit includes a high-temperature oily and dusty coal gas 1, which is connected to the lower part of the cooling dust collector 2, and the bottom of the cooling dust collector 2 is connected to the heavy oil tank I3, and the side of the heavy oil tank I3 is connected to the upper part of the cooling dust collector 2 through the heavy oil pump I4 to form a cycle;

[0013] The bottom of the heavy oil tank I3 is connected to the heavy oil tank II6 through a regulating valve 5, the side line of the bottom of the heavy oil tank I3 is connected to the upper part of the flash tower 8 through a regulating valve 7, the bottom of the heavy oil tank II6 is connected to the lower part of the flash tower 8 through a regulating valve 9, a grinder 10 is provided at the bottom of the flash tower 8, the outlet of the grinder 10 is connected to the horizontal screw centrifuge 12 through a heavy oil pump 11, the top of the flash tower 8 is connected to the top of the buffer tank 13, the bottom of the buffer tank 13 is connected to the upper part of the cooling dust collector 2 through a delivery pump 29, the side of the buffer tank 13 is connected to the heavy oil product system 24, and the horizontal screw centrifuge 12 is connected to the sludge system 25.

[0014] The secondary oil separation unit includes an oil separator 14 connected to the top of the cooling dust collector 2, a regulating valve 15 is provided at the bottom of the oil separator 14, the regulating valve 15 is connected to the delivery pump 16, the delivery pump 16 is connected to the upper part of the oil separator 14, and the delivery pump 16 is connected to the coal tar product system 22, and the middle part of the oil separator 14 is connected to the flushing oil system 23.

[0015] The three-stage purification unit includes a purification purifier 17 connected to the top of the oil separator 14, and the purification purifier 17 is provided with a regulating valve 18 at the bottom, and the regulating valve 18 is connected to a delivery pump 19, and the delivery pump 19 is connected to the water replenishment system 20 and connected to the upper part of the purification purifier 17, and is connected to the wastewater / light oil system 21 on one side, and the top of the purification purifier 17 is connected to the synthesis gas system 22;

[0016] The top cylinder of the cooling dust collector 2 is provided with a herringbone plate 26, and the herringbone plate 26 has 2 to 8 layers; the specific shape and structure of the herringbone plate 26 is that the herringbone angle is 60 to 150 degrees.

[0017] The upper cylinder of the oil separator 14 is provided with an overflow cross-flow tray 27, and the overflow cross-flow tray 27 is provided with 2 to 10 layers;

[0018] The specific structure of the overflow cross-flow tray 27 is that the overflow height is 10 to 30 cm.

[0019] The upper cylinder of the purifier 17 is provided with an overflow cross-flow tray 28, and the overflow cross-flow tray 28 is provided with 2 to 5 layers.

[0020] The herringbone tray 26 or the overflow cross-flow tray 28 can be one or a combination of a cross-flow plate, a ceramic filter membrane, or a stainless steel packing layer;

[0021] A method for purifying high-temperature oily and dusty coal gas comprises the following steps:

[0022] Step 1: The high-temperature oily and dusty coal gas 1 enters the cooling dust collector 2 and is reversely mixed with the liquid delivered by the heavy oil pump 4 under the action of the herringbone tray 26 to achieve primary cooling and dust removal;

[0023] Step 2: The cooled and dust-removed synthesis gas output from the high-temperature oily and dusty coal gas 1 enters the oil separator 14, and is reversely fractionated with the liquid output from the delivery pump 16 under the action of the overflow extended cross-flow tray 27 to obtain the coal tar product 22 and the flushing oil 23. At the same time, the heavy oil separated at the bottom of the oil separator 14 is self-circulated through the delivery pump 16;

[0024] Step 3: The separated coal gas enters the purifier 17 from the top of the oil separator 14 for further oil removal and water separation. The liquid at the bottom of the purifier 17 is self-circulated. The top gas enters the synthesis gas system 22, and part of the bottom liquid enters the wastewater / light oil system 21. At the same time, the water replenishment system 20 replenishes fresh water to the purifier 17.

[0025] Step 4: The dusty heavy oil at the bottom of the cooling dust collector 2 continuously enters the heavy oil tank I3 and the heavy oil tank II6, and the heavy oil enters the flash tower 8. By increasing the reduced pressure flash process, the dust in the oil is further separated and the amount of circulating oil is reduced. The solid particles in the high-viscosity circulating oil at the bottom of the flash tower 8 enter the horizontal screw centrifuge 12 to realize liquid-solid separation; the separated oil at the top of the flash tower 8 enters the buffer tank 13 to realize the self-circulation of the oil.

[0026] The high temperature oily and dusty coal gas 1 in step 1 has a temperature of 500-700°C, a pressure of 1.0-4.0 MPa, and a dust content of 50-200 g / Nm 3 ;

[0027] The dust content in the material transported by the heavy oil pump I4 in step 1 is less than 5%.

[0028] The solid content of the gas entering the synthesis gas system 22 at the outlet of the purification and purifying device 17 in step 3 is 0.01-0.1 g / Nm 3 ;

[0029] The temperature of the heavy oil tank II6 in step 4 is 250-350°C; the temperature of the heavy oil tank I3 is 300-500°C;

[0030] The oil content in the oil sludge at the outlet of the horizontal screw centrifuge 12 in the step 4 is less than 10%.

[0031] Beneficial effects of the present invention:

[0032] 1. To recover fine particles in raw coal gas and coal tar in the gas phase, a circulating oil washing process is used. While recovering oil, gas, dust and steam, no liquid water is introduced into the system, which greatly reduces the water consumption of coal chemical industry;

[0033] 2 In order to solve the problem of low tar content and dust in crude synthesis gas, a three-tower process of "cooling and dust removal unit + secondary oil separation unit + tertiary purification and refining unit" was designed. The quenching tower realizes dust removal and washing of crude synthesis gas; the fractionation tower realizes cooling, preliminary oil removal and oil fractionation of crude synthesis gas; the water washing tower realizes the final oil removal and partial water removal of synthesis gas;

[0034] 3 In order to solve the problem of solid particle accumulation in high-viscosity circulating oil, a horizontal screw centrifuge is designed to achieve liquid-solid separation; in order to reduce the number of solid-liquid separation equipment, the distillation range of the circulating oil is increased to reduce the oil volume of the circulating oil, and at the same time, the vacuum flash evaporation process is added to reduce the oil volume of the circulating oil; this method has obvious advantages such as high tar recovery rate, no generation of difficult-to-degrade toxic organic wastewater, and a high degree of device integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the present invention. Description of the drawings:

[0037] 1. High-temperature oily and dusty coal gas, 2. Cooling dust collector, 3. Heavy oil tank I, 4. Heavy oil pump I, 5. Regulating valve, 6. Heavy oil tank II, 7. Regulating valve, 8. Flash tower, 9. Regulating valve, 10. Grinding machine, 11. Heavy oil pump, 12. Horizontal screw centrifuge, 13. Buffer tank, 14. Oil separator, 15 Regulating valve, 16. Transfer pump, 17. Purifier, 18. Regulating valve, 19. Transfer pump, 20. Water make-up system, 21. Wastewater / light oil system, 22. Syngas system, 23. Flushing oil system, 24. Heavy oil product system, 25. Sludge system, 26. Herringbone tower plate, 27. Overflow extended cross-flow tower plate, 28. Cross-flow tower plate 29. Transfer pump. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0039] See also Figure 1 , the present invention comprises a primary cooling and dust removal unit, a secondary oil separation unit and a tertiary purification unit;

[0040] The first-stage cooling and dust removal unit is used to quickly cool down the high-temperature oily and dusty coal gas to remove large dust particles;

[0041] The secondary oil separation unit is used to cool and separate the oil from which the large dust particles are removed by the primary cooling and dust removal unit;

[0042] The three-stage purification unit is used to remove fine particles in the coal gas from the oil separated by the two-stage oil separation unit, thereby achieving coal gas purification.

[0043] The first-stage cooling and dust removal unit includes a high-temperature oily and dusty coal gas 1, which is connected to the lower part of the cooling dust collector 2, and the bottom of the cooling dust collector 2 is connected to the heavy oil tank I3, and the side of the heavy oil tank I3 is connected to the upper part of the cooling dust collector 2 through the heavy oil pump I4 to form a cycle;

[0044] The bottom of the heavy oil tank I3 is connected to the heavy oil tank II6 through a regulating valve 5, the side line of the bottom of the heavy oil tank I3 is connected to the upper part of the flash tower 8 through a regulating valve 7, the bottom of the heavy oil tank II6 is connected to the lower part of the flash tower 8 through a regulating valve 9, a grinder 10 is provided at the bottom of the flash tower 8, the outlet of the grinder 10 is connected to the horizontal screw centrifuge 12 through a heavy oil pump 11, the top of the flash tower 8 is connected to the top of the buffer tank 13, the bottom of the buffer tank 13 is connected to the upper part of the cooling dust collector 2 through a delivery pump 29, the side of the buffer tank 13 is connected to the heavy oil product system 24, and the horizontal screw centrifuge 12 is connected to the sludge system 25.

[0045] The secondary oil separation unit includes an oil separator 14 connected to the top of the cooling dust collector 2, a regulating valve 15 is provided at the bottom of the oil separator 14, the regulating valve 15 is connected to the delivery pump 16, the delivery pump 16 is connected to the upper part of the oil separator 14, and the delivery pump 16 is connected to the coal tar product system 22, and the middle part of the oil separator 14 is connected to the flushing oil system 23.

[0046] The three-stage purification unit includes a purification purifier 17 connected to the top of the oil separator 14, and the purification purifier 17 is provided with a regulating valve 18 at the bottom, and the regulating valve 18 is connected to a delivery pump 19, and the delivery pump 19 is connected to the water replenishment system 20 and connected to the upper part of the purification purifier 17, and is connected to the wastewater / light oil system 21 on one side, and the top of the purification purifier 17 is connected to the synthesis gas system 22;

[0047] The top cylinder of the cooling dust collector 2 is provided with a herringbone plate 26, and the herringbone plate 26 has 2 to 8 layers; the specific shape and structure of the herringbone plate 26 is that the herringbone angle is 60 to 150 degrees.

[0048] The upper cylinder of the oil separator 14 is provided with an overflow cross-flow tray 27, and the overflow cross-flow tray 27 is provided with 2 to 10 layers;

[0049] The specific structure of the overflow cross-flow tray 27 is that the overflow height is 10 to 30 cm.

[0050] The upper cylinder of the purifier 17 is provided with an overflow cross-flow tray 28, and the overflow cross-flow tray 28 is provided with 2 to 5 layers.

[0051] The herringbone tray 26 or the overflow cross-flow tray 28 can be one or a combination of a cross-flow plate, a ceramic filter membrane, or a stainless steel packing layer;

[0052] A method for purifying high-temperature oily and dusty coal gas comprises the following steps:

[0053] Step 1: The high-temperature oily and dusty coal gas 1 enters the cooling dust collector 2 and is reversely mixed with the liquid delivered by the heavy oil pump 4 under the action of the herringbone tray 26 to achieve primary cooling and dust removal;

[0054] Step 2: The cooled and dust-removed synthesis gas output from the high-temperature oily and dusty coal gas 1 enters the oil separator 14, and is reversely fractionated with the liquid output from the delivery pump 16 under the action of the overflow extended cross-flow tray 27 to obtain the coal tar product 22 and the flushing oil 23. At the same time, the heavy oil separated at the bottom of the oil separator 14 is self-circulated through the delivery pump 16;

[0055] Step 3: The separated coal gas enters the purifier 17 from the top of the oil separator 14 for further oil removal and water separation. The liquid at the bottom of the purifier 17 is self-circulated. The top gas enters the synthesis gas system 22, and part of the bottom liquid enters the wastewater / light oil system 21. At the same time, the water replenishment system 20 replenishes fresh water to the purifier 17.

[0056] Step 4: The dusty heavy oil at the bottom of the cooling dust collector 2 continuously enters the heavy oil tank I3 and the heavy oil tank II6, and the heavy oil enters the flash tower 8. By increasing the reduced pressure flash process, the dust in the oil is further separated and the amount of circulating oil is reduced. The solid particles in the high-viscosity circulating oil at the bottom of the flash tower 8 enter the horizontal screw centrifuge 12 to realize liquid-solid separation; the separated oil at the top of the flash tower 8 enters the buffer tank 13 to realize the self-circulation of the oil.

[0057] The high temperature oily and dusty coal gas 1 in step 1 has a temperature of 500-700°C, a pressure of 1.0-4.0 MPa, and a dust content of 50-200 g / Nm 3 ;

[0058] The dust content in the material transported by the heavy oil pump I4 in step 1 is less than 5%.

[0059] The solid content of the gas entering the synthesis gas system 22 at the outlet of the purification and purifying device 17 in step 3 is 0.01-0.1 g / Nm 3 ;

[0060] The temperature of the heavy oil tank II6 in step 4 is 250-350°C; the temperature of the heavy oil tank I3 is 300-500°C;

[0061] The oil content in the oil sludge at the outlet of the horizontal screw centrifuge 12 in the step 4 is less than 10%.

[0062] The first-stage cooling and dust removal unit, the second-stage oil separation unit and the third-stage purification and refining unit can be designed by coupling one or more methods according to different crude synthesis gas indicators and actual needs to achieve a solid content reduction rate of >95% in the gas.

[0063] Example:

[0064] Temperature is 600℃, dust content is 6g / Nm 3 The high-temperature oily and dusty coal gas 1 enters the cooling dust collector 2. The raw coal gas is reversely mixed with the cooling medium in the cooling dust collector 2 under the action of the herringbone plate 26 at an angle of 120°, so as to achieve primary cooling and dust removal. The dust content of the coal gas at the top outlet of the cooling dust collector 2 is reduced by 80%, and the temperature is reduced to 300°C. The cooling medium delivered by the heavy oil pump 4 is sent to the cooling dust collector 2.

[0065] The coal gas discharged from the top of the cooling dust collector 2 enters the oil separator 14, and is reversely fractionated with the cooling medium output by the delivery pump 16 under the action of the overflow extended cross-flow tray 27 to obtain the coal tar product 22 and the flushing oil 23. At the same time, the heavy oil separated from the bottom of the oil separator 14 is self-circulated through the delivery pump 16. The dust content of the coal gas washed by the oil separator 14 is further reduced by 90%, and the temperature is about 100°C, and enters the purification and purifying device 17;

[0066] In the purifier 17, the gas is washed with water and the dust content at the top is less than 0.1 g / Nm 3 The synthesis gas enters the synthesis gas system 22; part of the liquid washed out from the bottom enters the purification purifier 17 for circulation, and part enters the wastewater / light oil system 21, and the water replenishment system 20 replenishes fresh water to the purification purifier 17;

[0067] The dusty heavy oil at the bottom of the cooling dust collector 2 continuously enters the heavy oil tank I3 and the heavy oil tank II6, and the heavy oil enters the flash tower 8. By adding the reduced pressure flash evaporation process, the dust in the oil is further separated and the amount of circulating oil is reduced. The solid particles in the high-viscosity circulating oil at the bottom of the flash tower 8 enter the horizontal screw centrifuge 12 to realize liquid-solid separation; the separated oil at the top of the flash tower 8 enters the buffer tank 13 to realize the self-circulation of the oil.

Claims

1. A purification device for high-temperature oily and dusty coal gas, characterized in that: It includes a first-stage cooling and dust removal unit, a second-stage oil separation unit and a third-stage purification and refining unit; The first-stage cooling and dust removal unit is used to quickly cool down the high-temperature oily and dusty coal gas to remove large dust particles; The secondary oil separation unit is used to cool and separate the oil from which the large dust particles are removed by the primary cooling and dust removal unit; The three-stage purification unit is used to remove fine particles in the coal gas from the oil separated by the two-stage oil separation unit, thereby achieving coal gas purification.

2. A purification device for high-temperature oily and dusty coal gas according to claim 1, characterized in that: The first-stage cooling and dust removal unit comprises a high-temperature oily and dusty coal gas (1), the high-temperature oily and dusty coal gas (1) is connected to the lower part of the cooling and dust removal device (2), the bottom of the cooling and dust removal device (2) is connected to the heavy oil tank I (3), and the side of the heavy oil tank I (3) is connected to the upper part of the cooling and dust removal device (2) through a heavy oil pump I (4), so as to form a circulation; The bottom of the heavy oil tank I (3) is connected to the heavy oil tank II (6) through a regulating valve (5); the side line of the bottom of the heavy oil tank I (3) is connected to the upper part of the flash tower (8) through a regulating valve (7); the bottom of the heavy oil tank II (6) is connected to the lower part of the flash tower (8) through a regulating valve (9); a grinder (10) is provided at the bottom of the flash tower (8); the outlet of the grinder (10) is connected to the horizontal screw centrifuge (12) through a heavy oil pump (11); the top of the flash tower (8) is connected to the top of the buffer tank (13); the bottom of the buffer tank (13) is connected to the upper part of the cooling dust collector (2) through a delivery pump (29); the side of the buffer tank (13) is connected to the heavy oil product system (24); and the horizontal screw centrifuge (12) is connected to the sludge system (25).

3. The purification device for high-temperature oily and dusty coal gas according to claim 1, characterized in that: The secondary oil separation unit comprises an oil separator (14) connected to the top of the cooling dust collector (2); a regulating valve (15) is provided at the bottom of the oil separator (14); the regulating valve (15) is connected to a delivery pump (16); the delivery pump (16) is connected to the upper part of the oil separator (14); the delivery pump (16) is connected to a coal tar product system (22); and the middle part of the oil separator (14) is connected to a flushing oil system (23).

4. The purification device for high-temperature oily and dusty coal gas according to claim 1 is characterized in that: The three-stage purification and refining unit comprises a purifier (17) connected to the top of the oil separator (14); the purifier (17) is provided with a regulating valve (18) at the bottom; the regulating valve (18) is connected to a delivery pump (19); the delivery pump (19) is connected to a water replenishment system (20) and connected to the upper part of the purifier (17); and is connected to a wastewater / light oil system (21) at the other end; and the top of the purifier (17) is connected to a synthesis gas system (22).

5. The purification device for high-temperature oily and dusty coal gas according to claim 1, characterized in that: The cooling dust collector (2) is provided with a herringbone tower plate (26) in the top cylinder, and the herringbone tower plate (26) is provided with 2 to 8 layers; the specific shape and structure of the herringbone tower plate (26) is that the herringbone angle is 60 to 150 degrees; The upper cylinder of the oil product separator (14) is provided with an overflow cross-flow tray (27), and the overflow cross-flow tray (27) is provided with 2 to 10 layers; The specific structure of the overflow extension cross-flow tray (27) is that the overflow extension height is 10 to 30 cm; The upper cylinder of the purifier (17) is provided with an overflow cross-flow tray (28), and the overflow cross-flow tray (28) is provided with 2 to 5 layers; The herringbone tray (26) or overflow cross-flow tray (28) can be one or a combination of two of a cross-flow plate, a ceramic filter membrane, and a stainless steel packing layer.

6. A purification method for a high-temperature oily and dusty coal gas purification device according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: The high-temperature oil-containing and dust-containing coal gas (1) enters the cooling dust collector (2) and is reversely mixed with the liquid delivered by the heavy oil pump (4) under the action of the herringbone tower plate (26), thereby achieving primary cooling and dust removal; Step 2: The cooled and dust-removed synthesis gas output from the high-temperature oily and dusty coal gas (1) enters the oil separator (14), and is reversely fractionated with the liquid output from the delivery pump (16) under the action of the overflow extended cross-flow tray (27) to obtain coal tar product (22) and flushing oil (23). At the same time, the heavy oil separated at the bottom of the oil separator (14) is self-circulated through the delivery pump (16); Step 3: After separation, the coal gas enters the purifier (17) from the top of the oil separator (14) for further oil removal and water separation. The liquid at the bottom of the purifier (17) is self-circulated. The gas at the top enters the synthesis gas system (22), and part of the liquid at the bottom enters the wastewater / light oil system (21). At the same time, the water replenishment system (20) replenishes fresh water to the purifier (17); Step 4: The dusty heavy oil at the bottom of the cooling dust collector (2) continuously enters the heavy oil tank I (3) and the heavy oil tank II (6), and the heavy oil enters the flash tower (8). By adding a reduced pressure flash evaporation process, the dust in the oil is further separated and the amount of circulating oil is reduced. The solid particles in the high-viscosity circulating oil at the bottom of the flash tower (8) enter the horizontal screw centrifuge (12) to achieve liquid-solid separation; the separated oil at the top of the flash tower (8) enters the buffer tank (13) to achieve self-circulation of the oil.

7. A method for purifying high-temperature oily and dusty coal gas according to claim 6, characterized in that: The high-temperature oily and dusty coal gas (1) in step 1 has a temperature of 500-700°C, a pressure of 1.0-4.0 MPa, and a dust content of 50-200 g / Nm 3 ; The dust content of the material transported by the heavy oil pump I (4) in step 1 is less than 5%.

8. A method for purifying high-temperature oily and dusty coal gas according to claim 6, characterized in that: The solid content of the gas entering the synthesis gas system (22) from the outlet of the purification and purifying device (17) in step 3 is 0.01-0.1 g / Nm 3 .

9. A method for purifying high-temperature oily and dusty coal gas according to claim 6, characterized in that: The temperature of the heavy oil tank II (6) in step 4 is 250-350°C; the temperature of the heavy oil tank I (3) is 300-500°C; The oil content in the oil sludge at the outlet of the horizontal screw centrifuge (12) in step 4 is less than 10%.

Images