Multi-point coupling energy-saving design method for electrolytic aluminum exhaust purification system

Abstract

The present invention discloses a multi-point coupling energy-saving design method for an electrolytic aluminum smoke exhaust purification system, which is specifically as follows: by adjusting the valves of each branch pipe, the suction flow rate in different branch pipes is balanced, thereby reducing the total smoke volume of the purification system without changing the working environment of the plant; for a smoke purification system with a heat exchanger, a bypass pipe is welded, and the angle between the bypass pipe and the original pipe at the intersection is less than or equal to 45°, which is used to reduce the system resistance when the heat exchanger is partially loaded or shut down; for a smoke purification system with a smoke exhaust fan standby machine, a sealing valve is added at the outlet or inlet of the fan to block the smoke backflow, thereby reducing the smoke volume passing through the smoke exhaust fan; the above smoke volume reduction and system resistance reduction are coupled with the fan design, and the fan is selected and designed under the new operating point to improve the actual operating efficiency of the fan, thereby reducing the fan energy consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy conservation and emission reduction of electrolytic aluminum, and specifically relates to a multi-point coupling energy-saving design method for an electrolytic aluminum fume purification system. Background Art

[0002] During the electrolytic aluminum production process, a large amount of flue gas will be emitted from the electrolytic cell. The flue gas is composed of gaseous and solid substances. The flue gas enters the main network from the electrolytic cell gas hood, enters the exhaust purification fan after the dust collector, and finally enters the atmosphere through the chimney. The exhaust fan consumes a lot of electricity. Taking an electrolytic aluminum enterprise in Xining as an example, for every 100,000 tons of aluminum, the annual power consumption of the exhaust fan is about 15 million kW·h.

[0003] Flue gas flow, system resistance and fan efficiency are the main factors affecting the energy consumption of the smoke exhaust system. The flue gas flow depends on the gas collection efficiency of the hood itself and the pressure balance between the hoods of each electrolytic cell. Due to the gap between the electrolytic cell covers, air is inevitably sucked into the pipe network while capturing flue gas. In actual design, multiple electrolytic cell hoods are connected to the same main pipe through branch pipes. The negative pressure in the hood close to the main pipe source is low, and the air in the plant is sucked into the hood through the gap between the electrolytic cell covers, resulting in a large amount of extracted flue gas; while the hoods farther away are the opposite, and the amount of extracted flue gas is small. This causes the flue gas capture capacity of different electrolytic cells to differ too much, which overall makes the flue gas flow large, the environment in the plant poor, and the flue gas concentration high. The sources of system resistance include pipe networks, dust bags, and heat exchangers for waste heat recovery. Heat exchangers generally work in winter to provide hot water for the factory, but in summer they generally operate at partial load or stop operating. However, the system resistance caused by the heat exchanger has not been reduced, resulting in a waste of system pressure. The exhaust fan is the power component of the entire purification system. There are generally multiple exhaust fans for electrolytic aluminum, one of which is used as a standby fan. However, after the flue gas enters the outlet pipe through the running fan, part of the flue gas flows back to the main network through the standby fan under the action of the pressure difference, and then enters the chimney through the fan again, forming a flue gas reflux cycle, causing the fan to do useless work. In addition, due to the above reasons, the fan design operating point and the actual working parameters are often seriously deviated, and the fan working efficiency is low.

[0004] The above factors lead to excessive flue gas flow in the electrolytic aluminum exhaust purification system, high system resistance, and low operating efficiency due to the fan's off-duty operation, which in turn leads to high energy consumption in the exhaust purification system. The current common method for this system is to use a fan with variable frequency or permanent magnet for speed regulation, but this method saves energy at the expense of reducing the system's air volume, which leads to increased flue gas concentration in the electrolytic plant and a poor working environment for workers. It is urgent to explore new energy-saving technologies to reduce the overall energy consumption of the purification system without changing the flue gas concentration in the plant or slightly reducing the flue gas concentration. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-point coupling energy-saving design method for an electrolytic aluminum smoke exhaust purification system, which can significantly reduce the total amount of smoke and system resistance of the system without changing the working environment of the factory, block the smoke backflow and improve the fan operation efficiency.

[0006] The technical solution adopted by the present invention is a multi-point coupling energy-saving design method for an electrolytic aluminum fume purification system, which is specifically implemented according to the following steps:

[0007] Step 1: Balance the suction flow in different branches by adjusting the valves of each branch pipe, thereby reducing the total flue gas volume of the purification system without changing the working environment of the plant;

[0008] Step 2: For a flue gas purification system with a heat exchanger, holes are opened upstream and downstream of the heat exchanger, and bypass pipes are welded. The angle between the bypass pipe and the original pipe is less than or equal to 45°, which is used to reduce system resistance when the heat exchanger is operated at partial load or shut down;

[0009] Step 3: For a flue gas purification system with a smoke exhaust fan standby, add a sealing valve at the fan outlet or inlet to block the smoke backflow, thereby reducing the amount of smoke passing through the smoke exhaust fan;

[0010] Step 4: Couple the above reduction in flue gas volume and system resistance with the fan design, select and design the fan under the new operating point, improve the actual operating efficiency of the fan, and thus reduce the fan energy consumption.

[0011] The present invention is also characterized in that:

[0012] In step 1, the adjustment process of each branch valve is as follows:

[0013] Step 1.1: Measure the negative pressure P0 of the main pipe and the local atmospheric pressure P0 through the pressure sensor. a , measure the negative pressure P at any gas hood i , i = 1, 2, 3 ... N, N is the number of gas hoods, measure the branch pipe diameter d; and measure the flow rate U at the branch pipe of the gas hood through a flow meter i , measure the flue gas temperature T0 through the temperature sensor, and measure the distance L from the gas hood to the main pipe i ;

[0014] Step 1.2, calculate the smoke density and the pipe friction coefficient, as shown in formula (1) and formula (2) respectively;

[0015] ρ=(P a -P0) / RT0 (1);

[0016]

[0017] In formula (1), ρ is the smoke density, R is the smoke gas constant,

[0018] Step 1.3, measure the valve resistance P on the i-th branch pipe through the pressure sensor f,i , and calculate the smoke flow rate of the i-th hood, as shown in formula (3);

[0019]

[0020] Step 1.4, if the design flue gas flow rate of the hood is known to be V0, the excess exhaust gas volume ΔV is as shown in formula (4);

[0021]

[0022] Step 1.5, the resistance of the dust collector and the pipe network is known to be P c , then the system resistance ΔP caused by the excess exhaust gas c As shown in formula (5);

[0023]

[0024] Step 1.6, adjust the valve opening on the i-th branch pipe electrically or manually until V i The relative error with V0 is within 5%, achieving flue gas collection balance.

[0025] In step 2, a differential pressure sensor is used to measure the heat exchanger resistance P without a bypass pipe. h , after adding the bypass pipe, measure the heat exchanger resistance at this time The resistance ΔP reduced here h As shown in formula (6);

[0026]

[0027] In step 3, a flow meter is used to measure the return flue gas volume V of the exhaust fan standby unit. re , after adding the sealing valve, measure the return flow of the exhaust fan standby machine at this time The reduced reflux flow ΔV re As shown in formula (7);

[0028]

[0029] In step 4, specifically:

[0030] Step 4.1: According to the requirements of GB / T1236-2017 Standardized Air Duct Performance Test for Industrial Fans, use a flow meter to measure the total flow rate V of the exhaust fan before the transformation. s After the transformation is completed, calculate the total flow of the system As shown in formula (8);

[0031]

[0032] Step 4.2: Use a pressure sensor to measure the static pressure p at the fan inlet. s ' ,ιn and outlet static pressure p s, ' out , use the temperature sensor to measure the fan inlet temperature T s , and according to GB / T1236-2017 Standardized Duct Performance Test for Industrial Ventilators, calculate the total pressure rise P of the exhaust fan before transformation s After the transformation is completed, the total pressure rise of the exhaust fan is calculated to be As shown in formula (9);

[0033]

[0034] Smoke density at fan inlet ρ s As shown in formula (10);

[0035] ρ s =(P a -p′ s,ιn ) / RT s (10);

[0036] Step 4.3, read the input power W of the motor through the electric meter. The motor efficiency is known to be η e , the transmission efficiency is η m , calculate the operating efficiency η of the original fan s As shown in formula (11);

[0037] η s =V s P s / (1000Wη e η m ) (11);

[0038] Step 4.4, based on the total system flow and the total pressure rise of the exhaust fan Calculate the specific speed n of the fresh air fan s As shown in formula (12);

[0039]

[0040] Step 4.5, use the "Blower Handbook" (ISBN: 9787111317760) to select and design the fan. First, according to the specific speed n s The relationship curve with the pressure coefficient is given by the pressure coefficient ψ s Perform trial calculations and calculate the impeller diameter as shown in formula (13);

[0041]

[0042] Select with n s and ψ s The fan model that is close to the one that is used as the new exhaust fan has a density of ρ s , diameter D s The new exhaust fan flow V gb , full pressure rise P gb and efficiency η gb , and guarantee and If the requirements are not met, the pressure coefficient is reset and calculated again until the requirements are met.

[0043] The beneficial effect of the present invention is that after adopting this method to design the energy-saving of the smoke exhaust purification system, the total amount of smoke and system resistance of the system can be greatly reduced without changing the working environment of the factory, and the smoke backflow can be blocked while improving the fan operation efficiency. The energy consumption of the smoke exhaust fan can be reduced by 20%-45% under the coupling effect. After the transformation, the production cost of the enterprise can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of the electrolytic aluminum fume purification system after transformation;

[0045] Figure 2 This is the flue gas flow rate of each branch pipe before and after the transformation of the electrolytic aluminum plant and the valve resistance diagram after the transformation;

[0046] Figure 3 This is the flue gas flow rate of each branch pipe before and after the transformation of the second aluminum smelter and the valve resistance diagram after the transformation;

[0047] Figure 4 This is the flue gas flow rate of each branch pipe before and after the third transformation of the electrolytic aluminum plant and the valve resistance diagram after the transformation. DETAILED DESCRIPTION

[0048] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] The multi-point coupling energy-saving design method for the electrolytic aluminum fume purification system of the present invention is specifically implemented according to the following steps:

[0050] Step 1: In view of the inconsistent amount of flue gas collected by each gas collecting hood of the electrolytic cell, that is, the problem of unbalanced gas collection, the balance of the suction flow in different branch pipes is achieved by adjusting the valves of each branch pipe, thereby reducing the total flue gas volume of the purification system without changing the working environment of the plant;

[0051] The specific process of adjustment is:

[0052] Step 1.1: Measure the negative pressure P0 of the main pipe and the local atmospheric pressure P0 through the pressure sensor. a , measure the negative pressure P at any gas hood i (i=1,2,3…N, N is the number of gas collecting hoods), measure the branch pipe diameter d (the diameter of each branch pipe is equal);

[0053] The flow rate U at the gas collecting hood branch pipe is measured by a flow meter i , measure the flue gas temperature T0 through the temperature sensor, and measure the distance L from the gas hood to the main pipe i ;

[0054] Step 1.2, calculate the smoke density and the pipe friction coefficient, as shown in formula (1) and formula (2) respectively;

[0055] ρ=(P a -P0) / RT0 (1);

[0056]

[0057] In formula (1), ρ is the smoke density, R is the smoke gas constant,

[0058] In formula (2), g is the local acceleration;

[0059] Step 1.3, measure the valve resistance P on the i-th branch pipe through the pressure sensor f,i , and calculate the smoke flow rate of the i-th hood, as shown in formula (3);

[0060]

[0061] Step 1.4, if the design flue gas flow rate of the hood is known to be v0, then the excess exhaust gas volume Δv is as shown in formula (4);

[0062]

[0063] Step 1.5, the resistance of the dust collector and the pipe network is known to be P c , then the system resistance ΔP caused by the excess exhaust gas c As shown in formula (5);

[0064]

[0065] Step 1.6, adjust the valve opening on the i-th branch pipe electrically or manually to make v i As close to v0 as possible, due to the mutual influence between the branches, it is necessary to repeat steps 1.3 to 1.5 until V i The relative error with V0 is within 5%, achieving flue gas collection balance;

[0066] Step 2: For flue gas purification systems with heat exchangers, holes are opened at locations larger than 3D (D is the pipe diameter) upstream and downstream of the heat exchanger, and bypass pipes are welded. The bypass pipe material is consistent with the original pipe. The bypass pipe diameter can be 0.8 to 1D, and the angle between the bypass pipe and the original pipe is less than or equal to 45°, which is used to reduce system resistance when the heat exchanger is partially loaded or shut down. An electric butterfly valve needs to be installed on the bypass pipe to close the bypass pipe when the heat exchanger is fully loaded.

[0067] Using a differential pressure sensor to measure the heat exchanger resistance P without bypass pipe h , after adding the bypass pipe, measure the heat exchanger resistance at this time The resistance ΔP reduced here h As shown in formula (6);

[0068]

[0069] Step 3: For a flue gas purification system with a smoke exhaust fan standby, add a sealing valve at the fan outlet or inlet to block the smoke backflow, thereby reducing the amount of smoke passing through the smoke exhaust fan;

[0070] For round pipe sealing valves, butterfly valves with better sealing performance can be selected; for square pipe sealing valves, gate valves with better sealing performance can be selected. There is no special requirement for the valve material, which can be consistent with the pipe.

[0071] Since the fans need to run in reverse, sealing valves need to be added at the inlet or outlet of each fan, and the number of valves should be the same as the number of fans. The sealing valves can block the backflow of smoke, thereby reducing the amount of smoke passing through the exhaust fan; a flow meter is used to measure the backflow of smoke V from the standby exhaust fan. re , after adding the sealing valve, measure the return flow of the exhaust fan standby machine at this time The reduced reflux flow ΔV re As shown in formula (7);

[0072]

[0073] Step 4: Coupling the above reduction in flue gas flow and system resistance with the fan design, select and design the fan under the new operating point to improve the actual operating efficiency of the fan, thereby reducing the fan energy consumption;

[0074] The specific implementation steps are:

[0075] Step 4.1: According to the requirements of GB / T1236-2017 Standardized Air Duct Performance Test for Industrial Fans, use a flow meter to measure the total flow rate V of the exhaust fan before the transformation. s After the above transformation is completed, the total flow of the calculation system As shown in formula (8);

[0076]

[0077] Step 4.2: Use a pressure sensor to measure the static pressure p at the fan inlet. s ' ,ιn and outlet static pressure p s, ' out , use the temperature sensor to measure the fan inlet temperature T s , and according to GB / T1236-2017 Standardized Duct Performance Test for Industrial Ventilators, calculate the total pressure rise P of the exhaust fan before transformation s After the above transformation is completed, the total pressure rise of the smoke exhaust fan is calculated to be As shown in formula (9);

[0078]

[0079] Smoke density at fan inlet ρ s As shown in formula (10);

[0080] ρ s =(p a -p′ s,ln ) / RT s (10);

[0081] Step 4.3, read the input power W of the motor through the electric meter. The motor efficiency is known to be η e , the transmission efficiency is η m , calculate the operating efficiency η of the original fan s As shown in formula (11);

[0082] η s =V s P s / (1000Wη e η m ) (11);

[0083] Step 4.4, based on the total system flow and the total pressure rise of the exhaust fan Calculate the specific speed n of the fresh air fan s As shown in formula (12);

[0084]

[0085] Among them, N s is the motor speed;

[0086] Step 4.5, use the "Blower Handbook" (ISBN: 9787111317760) to select and design the fan. First, according to the specific speed n sThe relationship curve with the pressure coefficient is given by the pressure coefficient ψ s Perform trial calculations and calculate the impeller diameter as shown in formula (13);

[0087]

[0088] Among them, ζ is the margin coefficient, which ranges from 1 to 1.05 depending on the system;

[0089] Select with n s and ψ s The fan model that is close to the one that is used as the new exhaust fan has a density of ρ s , diameter D s The new exhaust fan flow V gb , full pressure rise P gb and efficiency η gb , and guarantee and If the requirements are not met, the pressure coefficient is given again and calculated again until the requirements are met;

[0090] Step 4.6, after the transformation, the system energy saving rate ε is calculated as shown in formula (14);

[0091]

[0092] It is known that the annual power consumption of the current system is W s , the system saves W of electricity per year n =εW s ;

[0093] Example 1

[0094] The parameters of an electrolytic aluminum plant are given in Table 1. The exhaust system has 4 main pipes, each with 24 electrolytic cells, and a total of 96 electrolytic cells. The smoke collection volume of 84 gas hoods exceeds the design value, and the smoke collection volume of other gas hoods is lower than the design value. The multi-point coupling energy-saving design method is used for transformation. The smoke collection volume of the gas hood is adjusted to the design value by adjusting the branch pipe valve. The smoke collection volume before and after the transformation is compared, and the resistance P after the valve adjustment is compared. f,i Depend on Figure 2 In addition, by adding a bypass to the heat exchanger, the system resistance was reduced by 120Pa, and a sealing valve was added to the exhaust fan standby to reduce the smoke backflow by 25134m 3 / h. Combining the above measures, and redesigning the fan, the fan was selected because its specific speed was 94, slightly exceeding the selection range of conventional centrifugal fans. Therefore, the Y4-75 No19 fan, which was closest to it, was selected. The system energy saving rate reached 43.64%, and the annual energy saving was 3.59 million kW·h.

[0095] Example 2

[0096] The parameters of the second electrolytic aluminum plant are given in Table 1. The exhaust system has 4 main pipes, each with 36 electrolytic cells, a total of 144 electrolytic cells, and each gas hood has been adjusted by a valve. The flue gas collection volume of 128 gas hoods exceeds the design value, and the flue gas collection volume of other gas hoods is lower than the design value. The multi-point coupling energy-saving design method is used for transformation. The flue gas collection volume of 128 gas hoods is adjusted to the design value by adjusting the branch pipe valve. However, due to the negative pressure limit of the main pipe, the flue gas collection volume of other gas hoods cannot be effectively changed. The flue gas collection volume before and after the transformation and the resistance P after the valve adjustment f,i Depend on Figure 3 In addition, the aluminum electrolytic plant has no heat exchanger, so it is impossible to reduce the resistance of this part. The exhaust fan has a spare machine, and adding a sealing valve can reduce the flue gas reflux 42814m 3 / h. Combining the above measures and redesigning the fan, the specific speed of the single-suction design is as high as 128, and there is no national standard centrifugal fan that matches it. Therefore, the double-suction design is adopted, the specific speed of the fan on one side is 91, and the fan model is selected as Y4-2×75No18.4. The system energy saving rate is 36.58%, and the annual energy saving is 4.17 million kW·h.

[0097] Example 3

[0098] The parameters of Case 3 of an aluminum smelter are basically the same as those of Case 2, but the valve of the gas hood has been deeply adjusted, and the flue gas collection volume has been reduced from Figure 4 Given. The multi-point coupling energy-saving design method is used for transformation. The valves of some gas hoods are further closed by adjusting the branch valves, and the valves of some gas hoods are slightly opened (the valve resistance is negative) to make the flue gas collection volume as close to the design value as possible. In addition, the flue gas system of the electrolytic aluminum plant has no heat exchanger, so it is impossible to reduce the resistance of this part, and the backup machine of the exhaust fan has added a sealing valve. Therefore, the transformation of the system mainly focuses on reducing the total flue gas flow and improving the efficiency of the fan. The fan is re-selected and designed. When the single-suction design is adopted, the specific speed is as high as 123, and there is no national standard centrifugal fan that matches it. Therefore, a double-suction design is adopted, and the specific speed of the fan on one side is 87. The fan model is selected as Y4-2×75No19. After the transformation, the energy saving rate of the system reaches 21.27%, and the annual energy saving is 2.16 million kW·h.

[0099] Table 1 Parameters and energy-saving transformation effects of exhaust gas purification systems in three electrolytic aluminum plants

[0100]

[0101]

[0102] The multi-point coupling energy-saving design method is applicable to all electrolytic aluminum exhaust purification systems. Before the design using this method, the system had a large amount of flue gas emissions, high pipe network resistance, flue gas reflux, and low fan efficiency, and the overall energy consumption remained high. After adopting this method to design the exhaust purification system for energy saving, the total amount of flue gas and system resistance of the system can be greatly reduced without changing the working environment of the plant, while blocking the flue gas reflux and improving the fan operation efficiency. The coupling effect can reduce the exhaust fan energy consumption by 20%-45%.

Claims

1. A multi-point coupling energy-saving design method for an electrolytic aluminum fume purification system, characterized in that: Follow the steps below to implement it: Step 1: Balance the suction flow in different branches by adjusting the valves of each branch pipe, thereby reducing the total flue gas volume of the purification system without changing the working environment of the plant; The adjustment process of each branch valve is as follows: Step 1.1: Measure the negative pressure P0 of the main pipe and the local atmospheric pressure P0 through the pressure sensor. a , measure the negative pressure P at any gas hood i , i = 1, 2, 3 ... N, N is the number of gas hoods, measure the branch pipe diameter d; and measure the flow rate U at the branch pipe of the gas hood through a flow meter i , measure the flue gas temperature T0 through the temperature sensor, and measure the distance L from the gas hood to the main pipe i ; Step 1.2, calculate the smoke density and the pipe friction coefficient, as shown in formula (1) and formula (2) respectively; ρ=(P a -P0) / RT0 (1); In formula (1), ρ is the smoke density, R is the smoke gas constant, In formula (2), g is the local acceleration; Step 1.3, measure the valve resistance P on the i-th branch pipe through the pressure sensor f,i , and calculate the smoke flow rate of the i-th hood, as shown in formula (3); Step 1.4, the design flue gas flow rate of the hood is known to be V O , then the extra exhaust gas volume ΔV is as shown in formula (4); Step 1.5, the resistance of the dust collector and the pipe network is known to be P c , then the system resistance ΔP caused by the excess exhaust gas c As shown in formula (5); Step 1.6, adjust the valve opening on the i-th branch until V i and V O The relative error is within 5%, achieving flue gas collection balance; Step 2: For a flue gas purification system with a heat exchanger, holes are opened upstream and downstream of the heat exchanger, and bypass pipes are welded. The angle between the bypass pipe and the original pipe is less than or equal to 45°, which is used to reduce system resistance when the heat exchanger is operated at partial load or shut down; Step 3: For a flue gas purification system with a smoke exhaust fan standby, add sealing valves at the fan outlet and inlet to block the smoke backflow, thereby reducing the amount of smoke passing through the smoke exhaust fan; Step 4: Couple the above reduction in flue gas volume and system resistance with the fan design, select and design the fan under the new operating point, improve the actual operating efficiency of the fan, and thus reduce the fan energy consumption.

2. The multi-point coupling energy-saving design method for electrolytic aluminum fume purification system according to claim 1 is characterized in that: In step 2, a pressure differential sensor is used to measure the heat exchanger resistance P when there is no bypass pipeline. h , after adding the bypass pipe, measure the heat exchanger resistance at this time The resistance ΔP reduced here h As shown in formula (6); 3. The multi-point coupling energy-saving design method for electrolytic aluminum fume purification system according to claim 2 is characterized in that: In step 3, a flow meter is used to measure the return flue gas volume V of the exhaust fan standby unit. re , after adding the sealing valve, measure the return flow of the exhaust fan standby machine at this time The reduced reflux flow ΔV re As shown in formula (7); 4. The multi-point coupling energy-saving design method for electrolytic aluminum fume purification system according to claim 3 is characterized in that: In the step 4, specifically: Step 4.1: According to the requirements of GB / T1236-2017 Standardized Air Duct Performance Test for Industrial Fans, use a flow meter to measure the total flow rate V of the exhaust fan before the transformation. s After the transformation is completed, calculate the total flow of the system As shown in formula (8); Step 4.2: Use a pressure sensor to measure the static pressure at the fan inlet and outlet static pressure Use temperature sensor to measure fan inlet temperature T s , and according to GB / T1236-2017 Standardized Duct Performance Test for Industrial Ventilators, calculate the total pressure rise P of the exhaust fan before transformation s After the transformation is completed, the total pressure rise of the exhaust fan is calculated to be As shown in formula (9); Smoke density at fan inlet ρ s As shown in formula (10); Step 4.3, read the input power W of the motor through the electric meter. The motor efficiency is known to be η e , the transmission efficiency is η m , calculate the operating efficiency η of the original fan s As shown in formula (11); or s =V s P s / (1000Wh e or m ) (11); Step 4.4, based on the total system flow and the total pressure rise of the exhaust fan Calculate the specific speed n of the fresh air fan s As shown in formula (12); Among them, N s is the motor speed; Step 4.5, use the "Fan Manual" to select and design the fan. First, according to the specific speed n s The relationship curve with the pressure coefficient is given by the pressure coefficient ψ s Perform trial calculations and calculate the impeller diameter as shown in formula (13); Among them, ζ is the margin coefficient; Select with n s and ψ s The same fan model is used as the new exhaust fan, and the density is ρ s , diameter D s The new exhaust fan flow V gb , full pressure rise P gb and efficiency η gb , and guarantee and If the requirements are not met, the pressure coefficient is reset and calculated again until the requirements are met.

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