CA1214686A - Method for regulating the function of a centrifugal pump - Google Patents
Method for regulating the function of a centrifugal pumpInfo
- Publication number
- CA1214686A CA1214686A CA000414618A CA414618A CA1214686A CA 1214686 A CA1214686 A CA 1214686A CA 000414618 A CA000414618 A CA 000414618A CA 414618 A CA414618 A CA 414618A CA 1214686 A CA1214686 A CA 1214686A
- Authority
- CA
- Canada
- Prior art keywords
- pump
- gas
- air
- bubble
- pulp
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
- D21D5/26—De-aeration of paper stock
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D7/00—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts
- F04D7/02—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type
- F04D7/04—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type the fluids being viscous or non-homogenous
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Non-Positive-Displacement Pumps (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Paper (AREA)
Abstract
SUMMARY
Method for controlling the function of a centrifugal pump when pumping liquids or suspensions containing gas by separating the gas into a bubble in the pump central part and discharging gas at a rate depending on the differential pressure between the entering liquid or suspension and the discharged gas so that a suitable part of the pump impeller wings are engaged in pumping in order to reach a desired pump flow capacity and/or head.
Method for controlling the function of a centrifugal pump when pumping liquids or suspensions containing gas by separating the gas into a bubble in the pump central part and discharging gas at a rate depending on the differential pressure between the entering liquid or suspension and the discharged gas so that a suitable part of the pump impeller wings are engaged in pumping in order to reach a desired pump flow capacity and/or head.
Description
~ o p This invention relates to a method for controlling the function of a centrifugal pump when pumping a liquid or suspension which contains gas. In the pump gas will be separated frorn the liquid or suspension by bringing it to rotation so that a gas bubble is created in the center of the pump impeller from which bubble gas will be removed.
The method has been meant especially to be applled in the pulp and paper industry for pumping of medium consistency pulp suspensions for instance 8 - 12 % pulps.
It has been stated that especially air in the pulp troubles the pumping of high consistency pulp with centrifugal pumps. Air tends to separate in the centrifugal pumps in the center of the impeller suction opening to form an air bubble which slowly grows and fills the vanes of the impeller, until the function of the pump is interrupted.
To remove this problem it has been developed centrifugal pumps, in which pulp containing gas will be made to rotate in the suction channel of the pump by means of rotor wings made to fit into that channel and in which separated air will be exhausted from the bubble formed in the suction channel.
Such solutions have been shown in US-patents 3,323,465 and 3,597,904 and in a Finnish patent application 81-0795 (corresponding to US Patent 4,410,337).
In the control system according to US-patent 3,323,465 the pressure difference between the liquid near the wall in the inlet channel and the liquid near the centerline will be 4 ~ ~
controlled by a valve situated in the discharge line. The pressure difference will be kept within given limits in order to guarantee enough suc-tion head, so that the impeller remains filled with liquid In the control system represented in the U.S. patent 4,410,337 the proper pressure difference is maintained between the inlet and outlet pressures of the fiber suspension ky controlliny gas exhaust from the gas cavity of the pump.
It has surprisingly appeared, when pumping pulp containing gas with centrifugal pumps worklng on the previous principle, that it is possible to control the function of the pumps by controlling the pressure difference between the pulp flowing into the pump and the gas leaving the pump. The size of the air bubble in the center of the rotor is dependent on the pressure difference between the suction pressure and the pressure in the gas space. The smaller the dP, the bigger is the air bubble. By changing the size of the air bubble it is possible to affect the Quantity/Head curve (QH-curve) of the pump in the same way as speed control affects a conventional centrifugal pump. When pumping pulp at high consistency the speed control is limited, because at low speeds it is not possible to get tangential speed high enough for fluidization in the air separator.
The present invention is represented in the drawings where Fig. 1 is a section of the pump which is possible to control according to the invention. Fig. 2 is a control system for application of the method according to the invention. Fig. 3 is a graphic plot of the application of the invention. Fig. 4 is another application.
The apparatus described in Fig. 1 contains a housing which contains an inlet channel 2, connected to a pulp container 3, and an outlet channel 4, through which pulp is discharged. In the housing there is a rotor 5 which is provided with axial wings 6 rotating in the inlet channel and reaching into the container 3, the rotor also being provided with radial wings 8 which rotate in the spiral housing 7. To the housing there belongs also a gas space 10 with an exhaust opening 11. The gas space 10 is separated from the spiral housing by a partition wall 9.
When the rotor 5 rotates in the pulp it becomes fluidized and flows into the inlet channel 2. The rotor causes the pulp containing gas to rotate so that pulp and air separate from each other forming an air bubble surrounded by pulp at the center of the rotor.
The air can be removed via an opening 12 in the partition wall 9 to the gas space 10, from where it can be led away via the gas exhaust opening 11. PUlp, from which air has been removed, will be discharged via outlet channel 4.
In the control system represented in Fig. 2 there is an air separator pump 20 according to Fig. 1 fitted to the bottom of a pulp container 3. By means of a control valve 22, a flow meter 21 and a flow controller 21 A which are fitted to the discharge line of the pump it is possible to keep a desired flow rate of the pump. Pressure difference between the inle-t opening and the outlet opening (pressure head of the pump) is measured with a dP-instrument 23 which will change the set point for the controller 28 below.
An air chamber or expansion vessel 25, vacuum pump 26 and control valve 27 are connected in the outlet pipe 24 fitted to the gas exhaust opening of the pump 20. Pressure difference in the air removal system is measured and controlled by a dP-controller 28 connected to the inlet of the pump and to the expansion vessel 25 as well as to the control valve 27. The dP-control of the air removal controls the size of the air bubble in the inlet channel by means of the control valve 27 so that a set point of the pressure head of the pump is reached.
To the system there also belongs a water pipe 29 connected to the air chamber for flushing purpose and to the expansion vessel 25 there is connected a pressure air pipe 30 which can feed pressure and flow controlled air at start-up and when a rapid dP change is required. A valve 31 serves as shut-off valve in the degassing line.
-3a-~`2~8~
The pressure difference in the air removal system also controls how much of the impeller wings which are used in the pumping from which follows that the QH-curve of the pump moves vertically so that higher dP lifts the curve and lower dP lowers the curve.
In pumps where the control is based on throttle valves, such as valve 22, part of the pressure head is lost because of the pressure drop in the valve. This pressure drop is large in case the back pressure of the system is considerably lower than the highest pressure head of the pump. When the pressure difference in the gas removal system is small, it is possible to lower the pressure head and therefore minimize also energy demand and pressure loss in the control valve.
Continued on page 5 EXample 1 A pump according to Fig. 1 which has a control system according to Fig. 2 pumps pulp at consistency 10 - 12 ~ from a storage tower to a chlorination tower. The pump makes nominal pressure head 7.5 bar and the back pressure in -this case is only 3.5 bar. Thus the pressure loss at the control valve 22 is about 4 bar and the valve is open only 30. The pressure difference in the air removing system is under these circumstances about 4 mWc (meter water column) and the ~power consumption is 90 kW. By lowering the pressure difference in the air system to about 2.5 mWc the following values were reached:
A B
Pump speed, rpm 3000 3000 Flow 10 ~ pulp, Q l/s 46 46 Pressure difference in air removal system, mWc 4 2.5 Pressure head, bar 7.54.5 Power consumption, kW 90 65 Control valve ~osition, degrees 30 70 QH-curves according to Example 1 are shown in Fig. 3.
It is also possible to run the system without the control valve 22 so that the flow ~ controlled directly by means of the pressure difference in the air removing system as in the following example and as represented in Fig. 4.
6 ~ ~
Example 2 C D
Flow Q, l/s 35 46 Back pressure in the system, H bar 3.2 3.5 Pressure difference, dP mWc 2,0 2,5 Power consumption, kW 58 65 When it is known how the QH-curve depends on the dP
and on the back pressure it is thus possible to control the flow with the dP-controller without throttle valve and flow meter.
-- oOo --
The method has been meant especially to be applled in the pulp and paper industry for pumping of medium consistency pulp suspensions for instance 8 - 12 % pulps.
It has been stated that especially air in the pulp troubles the pumping of high consistency pulp with centrifugal pumps. Air tends to separate in the centrifugal pumps in the center of the impeller suction opening to form an air bubble which slowly grows and fills the vanes of the impeller, until the function of the pump is interrupted.
To remove this problem it has been developed centrifugal pumps, in which pulp containing gas will be made to rotate in the suction channel of the pump by means of rotor wings made to fit into that channel and in which separated air will be exhausted from the bubble formed in the suction channel.
Such solutions have been shown in US-patents 3,323,465 and 3,597,904 and in a Finnish patent application 81-0795 (corresponding to US Patent 4,410,337).
In the control system according to US-patent 3,323,465 the pressure difference between the liquid near the wall in the inlet channel and the liquid near the centerline will be 4 ~ ~
controlled by a valve situated in the discharge line. The pressure difference will be kept within given limits in order to guarantee enough suc-tion head, so that the impeller remains filled with liquid In the control system represented in the U.S. patent 4,410,337 the proper pressure difference is maintained between the inlet and outlet pressures of the fiber suspension ky controlliny gas exhaust from the gas cavity of the pump.
It has surprisingly appeared, when pumping pulp containing gas with centrifugal pumps worklng on the previous principle, that it is possible to control the function of the pumps by controlling the pressure difference between the pulp flowing into the pump and the gas leaving the pump. The size of the air bubble in the center of the rotor is dependent on the pressure difference between the suction pressure and the pressure in the gas space. The smaller the dP, the bigger is the air bubble. By changing the size of the air bubble it is possible to affect the Quantity/Head curve (QH-curve) of the pump in the same way as speed control affects a conventional centrifugal pump. When pumping pulp at high consistency the speed control is limited, because at low speeds it is not possible to get tangential speed high enough for fluidization in the air separator.
The present invention is represented in the drawings where Fig. 1 is a section of the pump which is possible to control according to the invention. Fig. 2 is a control system for application of the method according to the invention. Fig. 3 is a graphic plot of the application of the invention. Fig. 4 is another application.
The apparatus described in Fig. 1 contains a housing which contains an inlet channel 2, connected to a pulp container 3, and an outlet channel 4, through which pulp is discharged. In the housing there is a rotor 5 which is provided with axial wings 6 rotating in the inlet channel and reaching into the container 3, the rotor also being provided with radial wings 8 which rotate in the spiral housing 7. To the housing there belongs also a gas space 10 with an exhaust opening 11. The gas space 10 is separated from the spiral housing by a partition wall 9.
When the rotor 5 rotates in the pulp it becomes fluidized and flows into the inlet channel 2. The rotor causes the pulp containing gas to rotate so that pulp and air separate from each other forming an air bubble surrounded by pulp at the center of the rotor.
The air can be removed via an opening 12 in the partition wall 9 to the gas space 10, from where it can be led away via the gas exhaust opening 11. PUlp, from which air has been removed, will be discharged via outlet channel 4.
In the control system represented in Fig. 2 there is an air separator pump 20 according to Fig. 1 fitted to the bottom of a pulp container 3. By means of a control valve 22, a flow meter 21 and a flow controller 21 A which are fitted to the discharge line of the pump it is possible to keep a desired flow rate of the pump. Pressure difference between the inle-t opening and the outlet opening (pressure head of the pump) is measured with a dP-instrument 23 which will change the set point for the controller 28 below.
An air chamber or expansion vessel 25, vacuum pump 26 and control valve 27 are connected in the outlet pipe 24 fitted to the gas exhaust opening of the pump 20. Pressure difference in the air removal system is measured and controlled by a dP-controller 28 connected to the inlet of the pump and to the expansion vessel 25 as well as to the control valve 27. The dP-control of the air removal controls the size of the air bubble in the inlet channel by means of the control valve 27 so that a set point of the pressure head of the pump is reached.
To the system there also belongs a water pipe 29 connected to the air chamber for flushing purpose and to the expansion vessel 25 there is connected a pressure air pipe 30 which can feed pressure and flow controlled air at start-up and when a rapid dP change is required. A valve 31 serves as shut-off valve in the degassing line.
-3a-~`2~8~
The pressure difference in the air removal system also controls how much of the impeller wings which are used in the pumping from which follows that the QH-curve of the pump moves vertically so that higher dP lifts the curve and lower dP lowers the curve.
In pumps where the control is based on throttle valves, such as valve 22, part of the pressure head is lost because of the pressure drop in the valve. This pressure drop is large in case the back pressure of the system is considerably lower than the highest pressure head of the pump. When the pressure difference in the gas removal system is small, it is possible to lower the pressure head and therefore minimize also energy demand and pressure loss in the control valve.
Continued on page 5 EXample 1 A pump according to Fig. 1 which has a control system according to Fig. 2 pumps pulp at consistency 10 - 12 ~ from a storage tower to a chlorination tower. The pump makes nominal pressure head 7.5 bar and the back pressure in -this case is only 3.5 bar. Thus the pressure loss at the control valve 22 is about 4 bar and the valve is open only 30. The pressure difference in the air removing system is under these circumstances about 4 mWc (meter water column) and the ~power consumption is 90 kW. By lowering the pressure difference in the air system to about 2.5 mWc the following values were reached:
A B
Pump speed, rpm 3000 3000 Flow 10 ~ pulp, Q l/s 46 46 Pressure difference in air removal system, mWc 4 2.5 Pressure head, bar 7.54.5 Power consumption, kW 90 65 Control valve ~osition, degrees 30 70 QH-curves according to Example 1 are shown in Fig. 3.
It is also possible to run the system without the control valve 22 so that the flow ~ controlled directly by means of the pressure difference in the air removing system as in the following example and as represented in Fig. 4.
6 ~ ~
Example 2 C D
Flow Q, l/s 35 46 Back pressure in the system, H bar 3.2 3.5 Pressure difference, dP mWc 2,0 2,5 Power consumption, kW 58 65 When it is known how the QH-curve depends on the dP
and on the back pressure it is thus possible to control the flow with the dP-controller without throttle valve and flow meter.
-- oOo --
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for controlling the function of a centrifugal pump when pumping liquids or suspensions containing gas, by separating the gas by rotating the liquid or suspension so that a gas bubble is created in the pump central part from which gas is discharged, characterized in that the pump head and/or volume capacity is controlled by varying the bubble size through removal of more or less air as indicated by the differential pressure between the entering liquid or suspension and the discharged gas.
2. A method according to claim 1, characterized in that the volume capacity of the pump is kept constant at a desired rate by means of a control valve in the pump discharge line so that the pump head only is controlled by the bubble size.
3. A method according to claim 2, characterized in that the range of pressure loss required through the valve is controlled so that the power consumption of the pump is kept at a minimum.
4. A method according to any of claims 1-3 characterized in that the pumping medium consists of cellulosic fiber pulp of about 8 - 12% consistency.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI81.3428 | 1981-11-02 | ||
| FI813428A FI813428L (en) | 1981-11-02 | 1981-11-02 | FOERFARANDE FOER REGLERING AV EN CENTRIFUGALPUMPS FUNKTION |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1214686A true CA1214686A (en) | 1986-12-02 |
Family
ID=8514819
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000414618A Expired CA1214686A (en) | 1981-11-02 | 1982-11-01 | Method for regulating the function of a centrifugal pump |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5885392A (en) |
| BR (1) | BR8206336A (en) |
| CA (1) | CA1214686A (en) |
| FI (1) | FI813428L (en) |
| SE (1) | SE457212B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5413460A (en) * | 1993-06-17 | 1995-05-09 | Goulds Pumps, Incorporated | Centrifugal pump for pumping fiber suspensions |
| WO2020109667A1 (en) * | 2018-11-30 | 2020-06-04 | Andritz Oy | Arrangement and method for degassing a pump |
| RU2795774C2 (en) * | 2018-11-30 | 2023-05-11 | Андритц Ой | Device and method for pump degassing |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2488025C1 (en) * | 2011-12-15 | 2013-07-20 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Юго-Западный государственный университет" (ЮЗ ГУ) | Beet lifting pump |
-
1981
- 1981-11-02 FI FI813428A patent/FI813428L/en not_active Application Discontinuation
-
1982
- 1982-10-29 BR BR8206336A patent/BR8206336A/en not_active IP Right Cessation
- 1982-11-01 JP JP57190896A patent/JPS5885392A/en active Pending
- 1982-11-01 CA CA000414618A patent/CA1214686A/en not_active Expired
- 1982-11-01 SE SE8206203A patent/SE457212B/en not_active IP Right Cessation
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5413460A (en) * | 1993-06-17 | 1995-05-09 | Goulds Pumps, Incorporated | Centrifugal pump for pumping fiber suspensions |
| WO2020109667A1 (en) * | 2018-11-30 | 2020-06-04 | Andritz Oy | Arrangement and method for degassing a pump |
| CN113164835A (en) * | 2018-11-30 | 2021-07-23 | 安德里兹公司 | Apparatus and method for degassing a pump |
| RU2795774C2 (en) * | 2018-11-30 | 2023-05-11 | Андритц Ой | Device and method for pump degassing |
Also Published As
| Publication number | Publication date |
|---|---|
| SE8206203L (en) | 1983-05-03 |
| JPS5885392A (en) | 1983-05-21 |
| SE457212B (en) | 1988-12-05 |
| SE8206203D0 (en) | 1982-11-01 |
| FI813428L (en) | 1983-05-03 |
| BR8206336A (en) | 1983-09-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |