GB1587853A

GB1587853A - Separator control method and device

Info

Publication number: GB1587853A
Application number: GB913778A
Authority: GB
Original assignee: Mulyar V B; Zoblin P V
Current assignee: Mulyar V B; Zoblin P V
Priority date: 1978-03-08
Filing date: 1978-03-08
Publication date: 1981-04-08

Description

(54) SEPARATOR CONTROL METHOD AND DEVICE (71) We, RUSLAN IVANOVICH BATYREV of 3 kvartira, 23, Vadkovsky pereulok, Moscow; MIKHAIL MAX OVICH ELENBOGEN, of 466 kvartira, korpus 1, 2, Sumskoi proezd, Moscow; VLADIMIR BORISOVICH MULYAR, of 210 kvartira, korpus 2, 2 Veshnyakovskaya ulitsa, Moscow; and PAVEL VASI LIEVICH ZOBNIN, of 27 kvartira, korpus 1, 26 ulitsa Yablochkova, Moscow, all of the Union of Soviet Socialist Republics (USSR) and all citizens of the USSR, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to methods for controlling centrifuges, for example, continuous and cyclic action centrifuges, and is applicable to the food, chemical and other industries.

The invention further relates to devices intended to control the sequence of working cycles of commercial liquid centrifuges of periodic action.

Operation of a centrifuge is always accompanied by variations in the parameters of a mixture to be separated, such as the ratio between the solids and liquids, temperature and feed rate. If the separation time is constant, the separation process ends earlier or later than required due to fluctuations of the above-mentioned parameters, which affects the quality of separation and reduces the mean throughput.

The conventional centrifugal technique has a number of disadvantages. These are as follows: As the separation chamber of the centrifuge is completely filled with solids, increasing amounts of solid matter are drawn away with the centrifuge effluent; this increases the density of the centrifuge effluent and discontinues the feeding of the initial solid/ liquid mixture to the centrifuge; as a result, it is impossible to effectively separate the initial mixture and control the separation process.

The moment the separating chamber is filled with solids is determined from the solids in the centrifuge effluent; it is impossible to determine the amount of the sepa rated solids as well as the ratio between the solids and liquid in the effluent.

The mean throughput cannot reach the maximum value for the predetermined concentration of solids in the centrifuge effluent.

It is an object of the present invention to obviate or mitigate the foregoing disadvantages, improve the quality of separation and increase the throughput of centrifuges by providing an improved method and device for controlling centrifuges of the above..

mentioned types.

It is another object of the invention to select a set of controlled separation process parameters so as to ensure a maximum throughput, while keeping the quality of separation at a desired level, and cut down the cleaning and maintenance time.

According to the present invention, we provide a method for controlling the periodic discharge of separated solids from the separating chamber of a centrifuge intended to separate non-uniform solids: liquid mixtures which method includes the steps of simultaneously measuring the flow rates of the non-uniform solids/liquid mix ture at the inlet and of the effluent at the outlet of the centrifuge and the concentration of solids in the mixture and effluent and using the paramters thus measured to deter mine the amount of separated solids accu.- mulated in the centrifuge separating cham ber and periodically unload the centrifuge as a predetermined amount of separated solids is accumulated in the separating chamber.

The proposed method makes it possible to continuously follow variations in the flow rate of the initial solid/liquid mixture and the concentration of the solids in that mixture, so that the contents are not removed from the centrifuge before the separation chamber is completely filled with solids, or before the separated solids are compacted to a maximum degree.

The flow rate of the initial mixture is preferably continuously compared with a predetermined minimum value; as soon as that value is reached, the contents are removed from the centrifuge, and the centrifuge is washed. This makes it possible to keep track of the gradual accumulation of solids in the centrifuge so that the centrifuge can be emptied and washed whenever the throughput reaches a minimum predetermined level.

Also according to the present invention, we provide a centrifugal control device for carrying out the method according to the invention, said device comprising a flow meter for measuring the flow rate of the centrifuge effluent and a concentration meter for measuring the concentration of solids in the centrifuge effluent, said flow meter and concentration meter being placed in series, their outputs being connected to a computer unit intended to determine the amount of solids accumulated in the separation chamber of the centrifuge, the computer unit further being connected to a flow meter for measuring the flow rate of the initial solids/liquid mixture and a concentration meter for measuring the concentration of solids in the initial mixture, which flow meter and concentration meter are also placed in series; the device further including two OR gates intended to instruct unloading and washing of the centrifuge, outputs of the OR gates being connected to a unit for controlling valves installed in pipelines connected to the centrifuge via a circuit containing in series a clock pulse generator, a pulse counter and a decoder, which are connected to the first of the two OR gates; the device further including threshold elements actuated whenever the amount of solids reaches a maximum permissible level, their inputs being connected to the computer unit, whereas their outputs are connected to the first of the two OR gates and the clock pulse generator; the device further including threshold elements actuated whenever the flow rate of the initial mixture reaches a minimum level, and whenever the concentration of solids in the centrifuge effluent reaches a certain level, respectively, their inputs being connected to the flow meter for measuring the flow rate of the initial mixture and the concentration meter for measuring the concentration of solids in the centrifuge effluent, whereas their outputs are connected to the second of the two OR gates.

With the use of the above-mentioned functional elements, the proposed centrifuge al control device provides for the most effective realization of the proposed method for controlling a centrifuge.

Preferably, the computer unit comprises two multipliers, an adder and an integrator, which are interconnected, inputs of the first of the two multipliers being connected to outputs of the flow meter for measuring the flow rate of the initial solids/liquid mixture and the concentration meter for measuring the concentration of solids in the initial mixture, inputs of the second of the two multipliers being connected to outputs of the flow meter for measuring the flow rate of the centrifuge effluent and the concentration meter for measuring the concentration of solids in the centrifuge effluent an input of the adder being connected to outputs of the multipliers, whereas the adder's output is connected to the integrator.

Irrespective of the physical properties of solids/liquid mixtures subjected to separation, the proposed computer unit makes it possible to determine the amount of solids accumulating in the centrifuge and flow rates of the initial solids/liquid mixture and centrifuge effluent.

Other objects and advantages of the present invention will become more apparent from the following detailed description of a preferred embodiment thereof to be read in conjunction with the accompanying drawings, wherein: Figure I is a schematic illustration of the proposed method; Figure 2 is a block diagram of a centrifuge control device provided with meters for measuring the flow rate of the initial solids/ liquid mixture and the centrifuge effluent, as well as the concentration of solids in the initial mixture and the centrifuge effluent, which meters are connected to a computer unit; Figure 3 is a block diagram of the proposed centrifuge control device, showing its connections to the meters, as well as interconnections between individual elements of the computer unit.

Referring to the accompanying drawings, the arrangement intended to realize the proposed method for controlling a centrifuge comprises a centrifuge 1 (Figure 1), a concentration meter 2 for measuring the concentration of solids in the initial solids/ liquid mixture, an initial mixture flow meter 3, and a valve unit 4 intended for controlling use of the pipelines of the centrifuge 1. The arrangement further includes a concentration meter 5 for measuring the concentration of the solids in the centrifuge effluent; a centrifuge effluent flow meter 6; a computer unit 7; a feed regulator 8; an actuator 9; a control valve 10; comparison units 11, 13, 15, 16 and 17; a counter 12; adders 14 and 18; and a unit 19, for controlling the valve unit 4.

The proposed method of separator control is carried out as follows.

An initial solids/liquid mixture is fed to the centrifuge 1, and the centrifuge effluent is removed therefrom, while the concentrated solids collect in the separation chamber of the centrifuge 1. The meters 2, 3, 5 and 6 measure the feed rate Q of the initial mixture, the concentration CO of solids in the initial mixture, the flow rate Qf of the centrifuge effluent, and the concentration Cf of solids in the centrifuge effluent, respectively. The measurements thus taken make it possible for the computer unit 7 to determine the amount Vt of the accumulated separated solids.The concentration Cf of solids in the centrifuge effluent is compared with a predetermined concentration value Cp, and the result of the comparison is used to control the feed of the initial mixture, for which purpose the feed regulator 8 acts upon the actuator 9 of the control valve 10 which changes the feed rate. The comparison unit 11 compares the amount Vt of the separated solids with the value Vn which corresponds to an optimum amount of separated solids for a given mixture. If the amount is in excess of Vn, the solids may become overcompacted if they remain in the separation chamber for a period of time greater than tmaX. When the amount of solids is equal to Vn, the counter 12 starts counting the separation cycle time t.The comparison unit 13 compares t with tmax.

The comparison unit 15 compares Vt with Vs, Vs being equal to a maximum permissible amount of separated solids. The adder 14 adds up the results, whereby the time for the removal of solids is determined. The comparison unit 16 then compares Q0 with min whereas the comparison unit 17 compares Cf with Coax. The adder 18 adds up the results of the comparison, thus indicating if it is necessary to wash the centrifuge after the removal of the solids. The sequence of working cycles is controlled by the control unit 19 which controls the valve unit 4.

Unlike the conventional methods, the proposed method for controlling a separator of continuous-cyclic action makes it possible to control the qualitative parameters of the separation process.

Consider Figure 2 which shows an automatic centrifuge control device for carrying out the proposed centrifuge control method.

The device comprises flow meters 20 and 21 (Figure 2) for measuring the flow rate of the initial solids/liquid mixture and centrifuge effluent, respectively; concentration meters 22 and 23 for measuring the concentration of the solids in the initial mixture and centrifuge effluent; threshold elements 24, 25, 26 and 27 actuated as soon as a maximum concentration of solids in the centrifuge effluent, a minimum flow rate of the initial mixture, a maximum amount of separated solids, and an optimum amount of separated solids for a given mixture are reached; the device further includes valves installed in pipelines connected to a centrifuge 28; a computer unit 29; a pulse generator 30; a pulse counter 31; a decoder 32; two OR gates 33 and 34 intended to instruct unloading and washing of the centrifuge; a valve control unit 35; an initial mixture feed regulator 36; and a feed control valve 37.

The computer unit serves to calculate the volume of solids accumulated in the separation chamber, which it does by signals arriving from the flow meters 20 and 21 and the concentration meters 22 and 23 which measure the concentration of solids in the initial mixture and the centrifuge effluent.

The volume of the separated solids is calculated from this formula: Vt = I (Co-Qo - Cf Qf) dt, where CO and Cf are the solids concentrations in the initial mixture and centrifuge effluent, respectively; Q and Qf are flow rates of the initial mixture and centrifuge effluent, respectively.

The computer unit 29 is connected to a first input of the OR gate 33 intended to produce an unload instruction; this connection is effected through the following seriesly placed units: the threshold element 27, the generator 30, the pulse counter 31 and the decoder 32. A second input of the OR gate 33 is connected to the computer unit via the threshold element 26 which is actuated whenever the amount of solids in the separation chamber reaches a maximum; an output of the OR gate 33 is connected to the valve control unit 35.

An output of the initial mixture flow meter 20 is connected to an input of the threshold element 25 actuated when the flow rate of the initial mixture reaches a minimum; an output of the threshold element 25 is connected to a first input of the OR gate 34 intended to produce a wash instruction.

A second input of the OR gate 34 is connected to the threshold element 24 which is actuated when the concentration of solids in the centrifuge effluent reaches a maximum (when a maximum amount of solids is washed away with the centrifuge effluent); an output of the OR gate 34 is connected to the valve control unit 35.

The device operates as follows.

By signals arriving from the flow meters 20 and 21 for measuring the flow rates of the initial mixture and centrifuge effluent, respectively, and the concentration meters 22 and 23 for measuring the concentrations of solids in the initial mixture and centrifuge effluent, respectively, the computer unit 29 produces a signal whose value is proportional to the amount of solids accumulated in the separation chamber of the centrifuge 28.

This signal is applied to the inputs of the threshold elements 26 and 27. When the amount of solids reaches level Vn above which the solids are bound to become overcompacted, if they remain in the separation chamber for more than tmax (Vn and tmaX vary with different mixtures), the threshold element 27 is brought into play and actuates the pulse generator 30 which sends its signals to the pulse counter 31. The decoder 32 stores a number equal to tmax.

The OR gate 33 is actuated by the decoder 32 or the threshold element 26 which is brought into play when the amount of solids accumulated in the separation chamber reaches a maximum; thus the OR gate determines the time the centrifuge is to be unloaded.

The concentration meter 23 for measuring the concentration of solids in the centrifuge effluent sends a signal to the threshold element 24 which is actuated when a maximum amount of solids is washed away with the centrifuge effluent. The initial mixture flow meter 20 sends a signal to the threshold element 25 which is actuated whenever the flow rate of the initial mixture reaches a minimum. The OR gate 34 is actuated by any of these threshold elements and sends a signal to the valve control unit 35, whereby the centrifuge is washed. If the valve control unit 35 receives a signal from the OR gate 33 alone, the unloading cycle follows; if the OR gate 34 also sends a signal to the unit 35, the unloading cycle is followed by a washing cycle.

The proposed centrifuge control device makes it possible to automatically control a separation process irrespective of variations in process parameters, such as the feed rate, the concentration of solids in the initial mixture, the centrifuge effluent flow rate, and the amount of solids in the separation chamber of the centrifuge.

The function of the flow meters 20 and 21 can be performed by rotameters and induction flow meters.

The solids concentration meter may be a vibration density meter or some other type of density meter having a satisfactory sensitivity within a required range of variations in the concentration; the function of the solids concentration meter can also be performed by a turbidimeter and a radioisotope or laser concentration meter.

An extremely important unit of the proposed device, when employed in industrial conditions, is the unit for controlling the quality of separation of two-phase systems.

Such units may be installed in centrifugal separators or centrifuges, and periodic- and continuous-action filters. Units for controlling the quality of separation of two-phase systems in separators or centrifuges operate on the time basis and use the degree to which the separation chamber is filled with solids as the basic parameter. This parameter is measured with the aid of different types of sensors (cf. USSR Inventor's Certificate No. 301,174, UK Patent Specification No. 1,099,916, and FRG - Patents Nos.

1,176,573 and 1,148,945).

The known types of sensors are not reliable enough; in addition, they often make serious errors in determining the amount of solids accumulated in the separation chamber, which may lead to an unnecessarily great amount of solids being washed away with the centrifuge effluent (this takes place when the time limit for the basic operation is exceeded), or to a decrease in the throughput (when the unloading is carried out earlier than required).

Federal German Patent No. 1,186,414 discloses a device for controlling the quantity of separation of two-phase systems, comprising a concentration meter installed in the effluent line. The concentration meter is a radioactive density meter.

The radioactive density meter is a complicated, hard-to-operate and expensive device.

Apart from these disadvantages, the radioactive density meter can determine the filling of the separation chamber only by registering a sharp change in the concentration of the effluent; it cannot control the quality of separation.

Finally, the device under review cannot be used to control the separation process oil continuous-operation apparatus.

Effective continuous control of the quality of concentrated separated solids can be done by calculating quantitative characteristics of the separation process and objectively evaluating that process; the computer unit, which is discussed below, is intended to serve these purposes.

Figure 3 is a diagram of a computer unit which serves to control the quality of separation of two-phase liquid systems.

The unit comprises flow meters 38 and 39 for measuring the flow rates of the initial mixture and the effluent, respectively, concentration meters 40 and 41 for measuring the concentrations of the initial mixture and outgoing effluent, respectively, and a subunit for determining quantitative characteristics of the separation process; the latter subunit contains a first multiplier 42, a second multiplier 43, an integrator 44, and an adder 45.

In order to produce a signal whose value is proportional to the amount of solids in the separation chamber, inputs of the multiplier 42 are connected to the initial mixture flow meter 38 and the concentration meter 40 intended to measure the concentration of the solids in the initial mixture. The output of the multiplier.42 is connected via the adder 45 to the integrator 44. Inputs of the second multiplier 43 are connected to the flow meter 39 and the concentration meter 41 intended to measure the solids concentration in the effluent. The output of the multiplier 43 is connected via the adder 45 to the integrator 44.

The computer unit operates as follows.

The separation process is carried out in a centrifuge 46; the initial mixture is directed to the centrifuge 46 through a pipeline 47.

The flow meters 38 and 39 measure the flow rate Q0 of the initial mixture and the flow rate Qf of the effluent leaving the apparatus through a pipeline 48, respectively. The concentration meters 40 and 41 measure the solids concentrations CO and Cf in the initial mixture and the effluent, respectively.

The flow meter 38 and the concentration meter 40 send their signals to the multiplier 42; the value of the output signal of the multiplier 42 is equal to an amount Qt of the solids in the initial mixture, measured on the per second basis.

The flow meter 39 and the concentration meter 41 send their signals to the multiplier 43; the value of the output signal of the multiplier 43 is equal to an amount Qt of solids in the effluent, also measured on the per second basis.

The signals of the multipliers 42 and 43 are of opposite signs and added together by the adder 45 which forms a signal whose value is equal to the amount Qt of solids separated in the centrifuge 46 during one second. The signal is integrated by the integrator 44 at whose output there is produced a signal of value equal to the amount Vt of solids separated since the beginning of the separation process.

The proposed device enables one to effectively control the separation process so that the process is adapted to such varying process parameters as the feed rate, concentration of solids in the initial mixture.

and temperature and dispersion of the solids.

The device may serve as the basis for an effective automatic control system intended to control two-phase system centrifuges.

WHAT WE CLAIM IS: 1. A method for controlling the periodic discharge of separated solids from the separating chamber of a centrifuge intended to separate non-uniform solids/liquid mixtures, which method includes the steps of simultaneously measuring the flow rates of the non-uniform solids/liquid mixture at the inlet and of the effluent at the outlet of the centrifuge and the concentration of solids in the mixture and effluent and using the parameters thus measured to determine the amount of separated solids accumulated in the centrifuge separating chamber and periodically unload the centrifuge as a predetermined amount of separated solids is accumulated in the separating chamber.

2. A method as claimed in claim 1, wherein the flow rate of the mixture is continuously compared with a predetermined minimum value and the centrifuge is emptied and washed immediately after this value is reached.

3. A centrifuge control device for carrying out the method claimed in claim 1 or 2, comprising a flow meter for measuring the flow rate of the centrifuge effluent and a concentration meter for measuring the concentration of solids in the centrifuge effluent, said flow meter and concentration meter being placed in series, their outputs being connected to a computer unit intended to determine the amount of solids accumulated in the separation chamber of the centrifuge, the computer unit further being connected to a flow meter for measuring the flow rate of the initial solids/liquid mixture and a concentration meter for measuring the concentration of solids in the initial mixture, which flow meter and concentration meter are also placed in series; the device further including two OR gates intended to instruct unloading and washing of the centrifuge, outputs of the OR gates being connected to the unit for controlling valves installed in pipelines connected to the centrifuge via a circuit containing in series a clock pulse generator, a pulse counter and a decoder, which are connected to the first of the two OR gates; the device further including threshold elements actuated whenever the amount of solids reaches a maximum permissible level, their inputs being connected to the computer unit, whereas their outputs are connected to the first of the two OR gates and the clock pulse generator; the device further including threshold elements actuated whenever the flow rate of the initial mixture reaches a minimum level, and whenever the concentration of solids in the centrifuge effluent reaches a certain level, respectively, their inputs being connected to the flow meter for measuring the flow rate of the initial mixture and the concentration meter for measuring the concentration of solids in the centrifuge effluent, whereas their outputs are connected to the second of the two OR gates.

4. A device as claimed in claim 3, wherein the computer unit comprises two multipliers, an adder and an integrator

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. In order to produce a signal whose value is proportional to the amount of solids in the separation chamber, inputs of the multiplier 42 are connected to the initial mixture flow meter 38 and the concentration meter 40 intended to measure the concentration of the solids in the initial mixture. The output of the multiplier.42 is connected via the adder 45 to the integrator 44. Inputs of the second multiplier 43 are connected to the flow meter 39 and the concentration meter 41 intended to measure the solids concentration in the effluent. The output of the multiplier 43 is connected via the adder 45 to the integrator 44. The computer unit operates as follows. The separation process is carried out in a centrifuge 46; the initial mixture is directed to the centrifuge 46 through a pipeline 47. The flow meters 38 and 39 measure the flow rate Q0 of the initial mixture and the flow rate Qf of the effluent leaving the apparatus through a pipeline 48, respectively. The concentration meters 40 and 41 measure the solids concentrations CO and Cf in the initial mixture and the effluent, respectively. The flow meter 38 and the concentration meter 40 send their signals to the multiplier 42; the value of the output signal of the multiplier 42 is equal to an amount Qt of the solids in the initial mixture, measured on the per second basis. The flow meter 39 and the concentration meter 41 send their signals to the multiplier 43; the value of the output signal of the multiplier 43 is equal to an amount Qt of solids in the effluent, also measured on the per second basis. The signals of the multipliers 42 and 43 are of opposite signs and added together by the adder 45 which forms a signal whose value is equal to the amount Qt of solids separated in the centrifuge 46 during one second. The signal is integrated by the integrator 44 at whose output there is produced a signal of value equal to the amount Vt of solids separated since the beginning of the separation process. The proposed device enables one to effectively control the separation process so that the process is adapted to such varying process parameters as the feed rate, concentration of solids in the initial mixture. and temperature and dispersion of the solids. The device may serve as the basis for an effective automatic control system intended to control two-phase system centrifuges. WHAT WE CLAIM IS:

1. A method for controlling the periodic discharge of separated solids from the separating chamber of a centrifuge intended to separate non-uniform solids/liquid mixtures, which method includes the steps of simultaneously measuring the flow rates of the non-uniform solids/liquid mixture at the inlet and of the effluent at the outlet of the centrifuge and the concentration of solids in the mixture and effluent and using the parameters thus measured to determine the amount of separated solids accumulated in the centrifuge separating chamber and periodically unload the centrifuge as a predetermined amount of separated solids is accumulated in the separating chamber.

which are interconnected, inputs of the first of the two multipliers being connected to outputs of the flow meter for measuring the flow rate of the initial solids/liquid mixture and the concentration meter for measuring the concentration of solids in the initial mixture, inputs of the second of the two multipliers being connected to outputs of the-flow meter for measuring the flow rate of the centrifuge effluent and the concentration meter for measuring the concentration of solids in the centrifuge effluent an input of the adder being connected to outputs of the multipliers, whereas the adder's output is connected to the integrator.

5. A method as claimed in claim 1 or 2 for controlling a centrifuge, substantially as hereinbefore described with reference to the accompanying drawings.

6. A device as claimed in claim 3 or 4 for controlling a centrifuge, substantially as hereinbefore described with reference to the accompanying drawings.