JP2019077914A - Control system and control method of autoclave - Google Patents

Abstract

To provide a control system for keeping the temperature and pressure of an autoclave constant.SOLUTION: There are provided a steam discharge valve (10) for controlling pressure in an autoclave (90), and a valve opening control part (60). The valve opening control part (60) has a control index of first to third valve openings (α-γ) with respect to each opening, set in a magnitude relation of full closed<first valve opening (α)<second valve opening (β)<third valve opening (γ)<full opening, and controls correspondingly to a valve opening in accordance with a control characteristic curve which comprises: a quick opening characteristic (S10) of rapidly increasing/decreasing an interval between a full closed state and the first valve opening (α) just after valve opening; a slow linear characteristic (S20) of slowly increasing/decreasing an interval between the first and second valve openings (α-β) by a linear characteristic; an equal percentage characteristic (S30) of changing an interval between the second and third valve openings (β-γ) by an equal percentage characteristic; and a rapid linear characteristic (S40) of rapidly increasing/decreasing an interval between the third valve opening (γ) and a full opening state by a linear characteristic.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an autoclave control system and control method, and more specifically, in a high pressure acid leaching process, in a process of pressurizing a slurry supplied to the autoclave with high pressure air and heating with high pressure steam, Control system and control method that make it possible to keep the temperature and pressure of

  As a technology for recovering nickel from low grade nickel oxide ore which has been considered difficult to recover, a high pressure acid leach (HPAL) method has been established. As a result, nickel is efficiently recovered from the low grade nickel oxide ore through the high temperature pressurized sulfuric acid leaching step. In addition, about HPAL, "high temperature pressurization sulfuric acid leaching", "high pressure sulfuric acid leaching", or only "pressure leaching" may be called.

  For example, Patent Document 1 discloses a high pressure acid leaching process including a flash vessel (also referred to as a flash tank) for leaching the raw material slurry under high temperature and high pressure with an autoclave and then lowering and lowering the leached slurry to normal temperature and pressure. A method of operating a flash vessel is disclosed that makes it possible to reduce troubles in the steam discharge pipe, the slurry discharge pipe, and the slurry discharge valve by performing certain valve opening / closing control.

  The method disclosed in Patent Document 1 defines predetermined upper and lower limits of the slurry liquid level in the flash vessel in relation to the height of the slurry outlet and the values of the height and the diameter of the flash vessel body. It is a thing.

Patent No. 5482970

  Temperature and pressure control are important in the HPAL process to achieve high nickel leach rates. In addition, the slurry after high pressure acid leaching is sent to a flash tank installed at the latter stage of the autoclave and decompressed to normal pressure in the flash tank. Here, fluctuations in temperature and pressure in the autoclave are The discharge piping to the flash tank and damage to the level control valve installed in the flash tank were caused. In addition, fluctuations in pressure may cause vibration of the flash tank body, resulting in failure of the flash tank level meter. In addition, since the influence of pressure fluctuation also affects temperature fluctuation, the leaching rate of nickel sometimes decreased. Although the method of reducing the trouble of the steam discharge pipe of a flash tank, a slurry discharge pipe, and a slurry discharge valve is disclosed by patent document 1, in order not to damage discharge piping, a level control valve, or the level of a flash tank There is no disclosure of a method of precisely controlling the temperature and pressure in the autoclave so as not to break the meter.

  The present invention has been made in view of such problems, and the object of the present invention is the temperature and pressure of an autoclave in a hydrometallurgical process for nickel oxide ore using a high temperature pressurized sulfuric acid leaching (HPAL) method. It is an object of the present invention to provide a control system and control method of an autoclave which make it possible to keep constant.

  In order to achieve the above object, the inventor conducted researches on the method of temperature and pressure control of the autoclave, and as a result, defined the flow characteristic curve of the steam discharge valve and controlled according to the flow characteristic curve. Pressure control was realized. As a result, it has been found that the temperature and pressure of the autoclave can be stabilized and the above problems can be solved, and the present invention has been completed.

[1] One embodiment of the present invention is a control system (100) for controlling operation of an autoclave (90) in high pressure acid leaching process of nickel oxide ore,
A steam discharge valve (10) for controlling the pressure in the autoclave (90);
A valve opening control unit (60) for controlling the valve opening of the steam discharge valve (10);
Equipped with
The valve opening control unit (60)
The control indexes of the first valve opening (α), the second valve opening (β) and the third valve opening (γ) are set according to the opening from the fully closed state to the fully open state,
The control index has a magnitude relation of fully closed <first valve opening (α) <second valve opening (β) <third valve opening (γ) <full opening,
Quick open characteristics (S10) for rapidly increasing or decreasing between the fully closed state and the first valve opening (α) slightly opened from the fully closed state;
A slow linear characteristic (S20) in which the interval between the first valve opening degree (α) and the second valve opening degree (β) is slowly increased / decreased in a linear characteristic.
The equal percent characteristic (S30) which changes between the second valve opening degree (β) and the third valve opening degree (γ) according to equal percentage characteristics.
An abrupt linear characteristic (S40) which causes the linear characteristic to rapidly increase / decrease between the third valve opening degree (γ) and the fully open state;
According to the control characteristic curve
The control is performed while being adapted to any one of the valve opening characteristics (S10 to S40) previously associated with the valve opening distinguished by the different control indexes (α, β, γ).

[2] Further, according to one aspect of the present invention, the valve opening degree in the above [1],
The first valve opening (α) is less than 2% over the fully closed state,
The second valve opening degree (β) is in the range of 50% to 69%,
The third valve opening degree (γ) is preferably a value of 1 in the range of 71% to 90%.

[3] Further, in one aspect of the present invention, a Cv value corresponding to the valve opening degree in the above [1] or [2] is
In the quick open characteristic (S10), the sudden change is made between 0% and the first point (1) of 5% or more,
In the slow linear characteristic (S20), increase / decrease slowly between the first point (1) and the second point (2) of 12% or more,
In the equal percent characteristic (S30), it is preferable to change the equal point characteristic between the second point (2) and the third point (3) of 30% or more.

[4] Further, an aspect of the present invention is a steam discharge valve (10) used in the control system (100) according to any one of the above [1] to [3],
A trim (11) connected to the axial displacement mechanism (8) via the stem (9) and operable to adjust the distance (X) facing the seat (13);
A plug (12) projecting with the center (Q) of the conical shape coinciding with the axial center (O) of the surface (15) of the face (15) of the trim (11) facing the sheet (13);
The sheet (13) having a flow passage hole (14) of an inner diameter (M) capable of receiving the maximum outer diameter (K) of the plug (12) and fixed in the valve box (19);
Equipped with
The maximum outer diameter (K) of the plug (12) is set to 80% or more and 95% or less of the inner diameter (M) of the flow path hole (14).
It is a steam discharge valve (10).

[5] Further, one aspect of the present invention is a control method of controlling operation of an autoclave used for high pressure acid leaching process of nickel oxide ore by a valve opening control unit (60),
A steam discharge valve (10) for controlling the pressure in the autoclave (90);
A valve opening control unit (60) for controlling the valve opening of the steam discharge valve (10);
Equipped with
The valve opening control unit (60)
The control indexes of the first valve opening (α), the second valve opening (β) and the third valve opening (γ) are set according to the opening from the fully closed state to the fully open state,
The control index has a magnitude relation of fully closed <first valve opening (α) <second valve opening (β) <third valve opening (γ) <full opening,
Quick open characteristics (S10) for rapidly increasing or decreasing between the fully closed state and the first valve opening (α) slightly opened from the fully closed state;
A slow linear characteristic (S20) in which the interval between the first valve opening degree (α) and the second valve opening degree (β) is slowly increased / decreased in a linear characteristic.
The equal percent characteristic (S30) which changes between the second valve opening degree (β) and the third valve opening degree (γ) according to equal percentage characteristics.
An abrupt linear characteristic (S40) which causes the linear characteristic to rapidly increase / decrease between the third valve opening degree (γ) and the fully open state;
According to the control characteristic curve
The control is performed while being adapted to any one of the valve opening characteristics (S10 to S40) previously associated with the valve opening distinguished by the different control index.

[6] Moreover, in one aspect of the present invention, the valve opening degree in the above-mentioned [5],
The first valve opening (α) is less than 2% over the fully closed state,
The second valve opening degree (β) is in the range of 50% to 69%,
The third valve opening degree (γ) is preferably a value of 1 in the range of 71% to 90%.
[7] In one aspect of the present invention, the characteristic of the Cv value corresponding to the valve opening degree in the above [5] or [6] is
In the quick open characteristic (S10), it is suddenly changed between 0% and 5% or more,
In the slow linear characteristic (S20), increase / decrease slowly between 5% or more and 12% or more,
In the equal percent characteristic (S30), it is preferable to change the equal percent characteristic between 12% and 30%.

  According to the present invention, it is possible to provide a control system which makes it possible to keep constant the temperature and pressure of the autoclave in the high pressure acid leaching process of nickel oxide ore.

BRIEF DESCRIPTION OF THE DRAWINGS It is a model apparatus figure for demonstrating the leaching process by the autoclave in the high pressure acid leaching process of the nickel oxide ore which becomes a premise technology of this invention. It is a schematic apparatus figure for demonstrating the temperature control in the leaching process of FIG. 1, and a liquid level control method. It is a schematic apparatus figure for demonstrating the pressure control of the autoclave by the control system (henceforth "this system") of the autoclave concerning one embodiment of the present invention. The control method of the autoclave according to one embodiment of the present invention (hereinafter, also referred to as "the present method") and a cross-sectional view of the main part for explaining the modification applied to the existing steam discharge valve as an example. 4A shows the state before plug modification, and FIG. 4B shows the state after plug modification. It is a control characteristic curve which shows the flow characteristic before and behind remodeling to a steam discharge valve, and a dashed line shows before a plug remodeling, and a solid line shows after a plug remodeling, respectively. It is a block diagram for demonstrating that this system controls a flow volume characteristic according to a valve-opening degree. It is an appearance perspective view for explaining the structure of an example of the steam discharge valve used for this method and this system. In order to demonstrate the structure of the steam discharge valve of FIG. 7, it is the front view which visually recognized the whole from the front direction of the inflow port. It is principal part sectional drawing which cut off the principal part by the AA line centering on the rotating shaft of a stem about the steam discharge valve of FIG. It is the principal part expanded sectional view which expanded the principal part enclosed with the dashed-dotted line B of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all of the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily. In addition, throughout the drawings, the same effect members and places are denoted by the same reference numerals even if there is a slight difference in the outer shape, and the description will not be repeated.

  The nickel smelting process by the high pressure acid leaching process is carried out, for example, in the following procedure. First, in the ore slurry preparation step, the nickel oxide ore is slurried to prepare an ore slurry. In the next leaching step, sulfuric acid is added to the prepared ore slurry, and leached under high pressure and high temperature of 220 to 280 ° C. using a pressure leaching reactor (autoclave) to leach nickel and cobalt and leach it. Get a slurry.

  In the next solid-liquid separation step, the leaching residue in the leaching slurry and the leaching solution containing nickel and cobalt are solid-liquid separated. In the neutralization step, the pH of the leachate containing the impurity element together with nickel and cobalt obtained in the solid-liquid separation step is adjusted to 3 to 4, the impurity element such as iron is neutralized, and the leachate after the neutralization step It separates into water and neutralization deposit. In the final sulfurization step, hydrogen sulfide gas is supplied to the leachate after the neutralization step to recover the nickel-cobalt mixed sulfide.

In this high pressure acid leaching method, in the leaching step, iron, which is the main impurity, is converted to the leaching residue in the form of hematite (Fe ₂ O ₃ ) by controlling the oxygen partial pressure in the autoclave and the redox potential and temperature of the leachate. Fix it. This has the great advantage of being able to leach nickel and cobalt selectively to iron. Although the temperature and pressure of the autoclave vary depending on the conditions of the ore slurry, the autoclave is often operated at a temperature of about 220 to 280 ° C. and a pressure of about 3 to 6 MPa.

  FIG. 1 is a schematic device diagram for explaining a leaching step in an autoclave in a high pressure acid leaching process of nickel oxide ore, which is a premise technology of the present invention. In the above-described leaching step, sulfuric acid is supplied to the compartment 91 of the autoclave 90 together with the ore slurry through the sulfuric acid addition line and the ore slurry addition line as shown in FIG. While the ore slurry to which sulfuric acid is added overflows sequentially from the compartment 91 having the stirrer 99 to the compartment 97, nickel and cobalt, impurities, etc. are leached from the ore. In actual operation, the temperature T, the liquid level H and the pressure P of the autoclave 90 are appropriately controlled in order to efficiently leach nickel and cobalt.

  The control system and control method of an autoclave according to one embodiment of the present invention comprises: an ore slurry preparation step of slurrying low grade nickel oxide ore; transferring the ore slurry to a high pressure acid leaching facility; Adopted for hydrometallurgical process of nickel oxide ore using high pressure acid leaching (HPAL) method including leaching process of leaching cobalt and obtaining leached slurry and solid-liquid separation process of the leached slurry It is a thing. The present invention is aimed at improving the process control of a pressure leaching reactor, in particular autoclave 90, in a high pressure acid leaching (HPAL) process.

  The present invention, as an embodiment, slurries nickel oxide ore and adds sulfuric acid to the ore slurry transferred to autoclave 90, and high pressure air from high pressure air supply line and high pressure steam from high pressure steam supply line Treatment that raises the temperature with high-temperature steam and raises the pressure with high-pressure air while maintaining the balance of the slurry while discharging the leached slurry appropriately from the leached slurry discharge line (discharge pipe 80) while leaching while blowing In the above, a control system and control method that make it possible to keep the temperature and pressure of the autoclave 90 constant are disclosed.

  FIG. 2 is a schematic device diagram for explaining a temperature control and liquid level control method in the high pressure acid leaching step of FIG. As shown in FIG. 2, the control system of the autoclave includes an autoclave 90, a flash tank 40, a high pressure steam supply line, a steam control valve 20, valve opening control units 61 and 62 (60), and a thermometer T. And a liquid level (level) meter L, and a level (liquid level) control valve 30. The autoclave 90 is connected to a high pressure steam supply line through a steam control valve 20, and is piping-configured so that high pressure steam can be charged appropriately. The steam control valve 20 has a high pressure as high as 50 atm during operation of the autoclave 90, and handles high temperature steam, so a special specification of the steam control valve 20 is used that is suitable for the conditions of use.

  The valve opening control unit 62 (60) controls the level control valve 30 based on the result of comparing the detection value H of the liquid level meter L with the control value so that the optimum liquid level H can be maintained in the autoclave 90. Adjust the degree of valve opening. The flash tank 40 is a container for reducing the pressure of the slurry discharged from the autoclave 90 to atmospheric pressure and reducing the temperature to 100 ° C. or less. The valve opening control unit 61 (60) is a steam valve based on the result of comparing the detected value of the thermometer T (the same reference numeral with the temperature T) with the control value so that the optimum liquid temperature can be maintained in the autoclave 90. Adjust the valve opening of 20.

  In the system for controlling the temperature of the autoclave 90 shown in FIG. 2 (hereinafter, also referred to as “temperature control system”), if the liquid temperature changes by 1 ° C., the leaching rate of nickel is affected. Therefore, the temperature control system is important for achieving efficient nickel leaching, so it is necessary to keep the liquid temperature less fluctuating from the set temperature. In order to heat and keep the autoclave 90, the temperature control system heats and keeps the autoclave 90 while adjusting the amount of steam Y blown from the high pressure steam supply line.

  The steam control valve 20 increases or decreases the steam flow rate Y which is pressured into the autoclave 90 from the high pressure steam line. The valve opening degree control unit 60 controls the valve opening degree of the steam control valve 20.

  Further, in the system for controlling the liquid level of the autoclave 90 shown in FIG. 2 (hereinafter also referred to as “liquid level control system”), the flow rates of the slurry and sulfuric acid charged into the autoclave 90 and The balance of the flow rate with the leaching slurry sent to the flash tank 40 is performed. The liquid level control system detects the liquid level (level) H of the leachate with a liquid level meter (level meter) L installed in the compartment 97 of the autoclave 90, and the level control valve 30 installed above the flash tank 40. Adjusting the opening degree of On the other hand, with regard to the discharge of the leached slurry from the autoclave 90 to the flash tank 40, the leached slurry is pressure fed to the flash tank 40 by appropriately controlling the pressure of the autoclave.

  FIG. 3 is a schematic device diagram for explaining pressure control of the autoclave by the control system (the present system) of the autoclave according to one embodiment of the present invention. As shown in FIG. 3, the autoclave 90 is connected to the blast spool 70 via a steam discharge valve (hereinafter, also simply referred to as "steam valve") 10, and piping is configured so that the steam inside the autoclave can be discharged appropriately. ing. The pressure PD for pumping the leached slurry from the autoclave 90 to the flash tank 40 is obtained from the temperature T of the leached slurry in the autoclave 90 using the saturated vapor pressure table to determine the saturated vapor pressure P1 of the leachate in the leached slurry. The pressure difference P between the pressure P in the gas phase portion of and the saturated vapor pressure P1 of the leachate. In order to ensure that this differential pressure PD exceeds the head pressure from the liquid surface of the autoclave 90 to the level control valve (30) of the flash tank 40 and maintain it constant, the amount of discharged steam Z is reduced by the steam discharge valve 10 I'm adjusting.

  If this differential pressure PD is lower than the head pressure required to the flush tank 40, the leachate evaporates in the discharge pipe 80 of the autoclave 90, causing a serious problem such as damage to the discharge pipe 80 or the level control valve 30. I will. Also, even when the head pressure is maintained, if the differential pressure PD fluctuates, the vapor flow rate Y to the autoclave 90 fluctuates, and as a result, the temperature T fluctuates, and the nickel leaching rate decreases. was there. In addition, the inlet pressure of the liquid level control valve, that is, the pressure of the flash tank 40 will fluctuate due to the fluctuation of the differential pressure PD.

  This may cause the flash tank 40 to vibrate and cause the level meter of the flash tank 40 to break down. As described above, the control of the temperature T and the pressure P of the autoclave 90 used in the high pressure acid leaching step causes serious troubles, and thus has a large effect on the operation efficiency of the entire process. In addition, since the leaching rate of nickel may be lowered, it is very important to stabilize the control.

  The present invention has solved the problem of further stabilizing the temperature control and pressure control of the autoclave 90. As a solution, in order to stabilize these controls, the flow characteristic of the steam discharge valve 10 was changed in order to realize particularly precise pressure control. The plug shape of the steam discharge valve 10 was modified as a means to change the flow rate characteristics. As a result, significant effects were confirmed.

  FIG. 4 is a cross-sectional view of a main part for describing a modification of a built-in steam valve for use in an autoclave control method (the present method) and a control system (the present system) according to an embodiment of the present invention. 4 (A) shows the plug before remodeling, and FIG. 4 (B) shows the plug after remodeling. The difference between FIG. 4A and FIG. 4B is that the outer diameters J and E of the plug 22 are made thinner at the outer diameters K and N of the plug 12. The outer diameter J is the maximum outer diameter of the plug 22, the outer diameter E is the outer diameter near the tip of the plug 22, the outer diameter K is the maximum outer diameter of the plug 21, and the outer diameter N is the outer diameter near the tip of the plug 12, respectively. It shows.

  As shown in FIG. 4 (A), the steam discharge valve (hereinafter, also simply referred to as a "steam valve") 21 before remodeling which is already used other than the present system 100 includes at least a trim 11 and a plug 22; And a seat 13. The trim 11 is operable to increase or decrease the distance X facing the seat 13 connected to the axial movement mechanism 8 via the stem 9. The valve opening degree (valve opening degree) is proportional to the distance X.

  The plug 22 is coaxially protruded so that the conical center Q of the trim 11 coincides with the axial center O of the facing surface 15 to the seat 13. The sheet 13 is provided with a flow passage hole 14 having an inner diameter M capable of receiving the maximum outer diameter J of the plug 22. The seat 13 is fixed to the lower side in the valve box 19 (see FIG. 10).

  In the steam valve 21 provided with the plug 22 before remodeling shown in FIG. 4A, when the trim 11 is lowered and the opposing surface 15 is brought into close contact with the distance X to the sheet 13 as 0, the fully closed state is established. In the steam valve 21 in the fully closed state, the flow passage hole 14 of the inner diameter M drilled in the sheet 13 is configured to be receivable with respect to the maximum outer diameter J of the plug 22. That is, it is a relation of J <M.

  Further, in the steam valve 21, when the trim 11 is raised and the facing surface 15 is separated from the seat 13 to a predetermined distance, it is fully opened. In the steam valve 21 in the fully open state, the outer diameter E near the tip end of the plug 22 is reduced so as to create a gap F with respect to the inner diameter M pierced in the sheet 13. That is, there is a relationship of E + 2 × F = M. The flow rate characteristic of the discharged steam changes with the size of the gap F.

  As shown in FIG. 4 (B), the steam valve 10 used in the present system 100 is also configured to include a trim 11, a plug 12, and a sheet 13, as in the conventional steam valve 21. As described above, the plug 12 is the one in which the outer diameter of the plug 22 is reduced. Here, K <J <M, N <E. Further, in the fully open steam valve 10, the outer diameter N near the tip end of the plug 12 is reduced so as to create a gap G with respect to the inner diameter M drilled in the sheet 13. That is, there is a relationship of N + 2 × G = M. The flow rate characteristic of the discharged steam changes with the size of the gap G.

  As described above, the steam valve 21 in FIG. 4A has a relationship of E + 2 × F = M. Here, N <E. Therefore, the magnitude relationship between the gaps F and G is F <G. That is, in the comparison of the gaps F and G at the time of valve opening, the gap G of the steam valve 10 used in the system 100 as shown in FIG. 4B is the conventional steam shown in FIG. It is larger than the clearance F of the valve 21.

  The maximum outer diameter K of the plug 12 is set to 80% or more and 95% or less of the inner diameter M of the flow path hole 14. In addition, although the principal part cross-sectional view of FIG. 4 depicts an embodiment of the present invention in an enlarged scale, the entire volume of the steam valves 10 and 21 will be briefly described later with reference to FIGS. In addition, one of the indicators indicating the performance and specifications of the valve is the volume of the valve (hereinafter also referred to as "valve volume"). The valve volume refers to the volume or weight of fluid passing through the valve per unit time when the valve is fully opened. This valve capacity generally depends on the type of valve and the port diameter.

  However, even if valves of the same type and diameter have different manufacturers, their capacities will be different. Furthermore, depending on the type of valve, there are various types of valves with the same bore but with large or small pressure loss, which makes it difficult to select the valve to be procured.

  Therefore, the numerical value represented by keeping the fluid specification at a certain standard value is called the capacity coefficient. By using this capacity factor, it is relatively easy to select the type and diameter of the valve.

There are Cv value, Kv value, and Av value as a capacity factor, and among them, Cv value is generally used frequently. This Cv value is the US gal / min fluid at a temperature of 60 ° F. flowing through the valve when the pressure differential is 1 (lbf / in ² ) at a particular travel. For the same differential pressure, the larger the Cv value, the larger the flow rate that passes through, and for the same Cv value, the larger the differential pressure, the larger the flow rate that passes through. The Cv value can be determined by the following equation [1].

Cv = Q√ (G / Δp) ··· Formula [1]
Cv: Cv value, Q: flow rate (US gal / min),
G: Specific gravity (1 for water), Δp: Differential pressure 1 (lbf / in ² )

  FIG. 5 is a graph showing the flow rate characteristics before and after remodeling for the steam discharge valve, and the broken line indicates the plug before remodeling and the solid line indicates the plug after remodeling. Although the “Cv value” is indicated on the vertical axis in FIG. 5, the “Cv value” referred to here is a ratio when the valve opening is 100%, that is, the Cv value at full opening is 100%. Represents The flow rate characteristic shown in FIG. 5 can be realized by converting the steam valve 21 in FIG. 4 into the steam valve 10 as described above, but is not limited thereto. That is, as long as the valve opening degree control unit 60 has a function of freely controlling the flow rate characteristic so as to obtain the optimum Cv value according to the valve opening degree, it is still possible. For example, the flow rate characteristic may be controlled by a combination of a plurality of steam valves.

  In the valve opening degree control unit 60, control indexes of the first valve opening degree α, the second valve opening degree β, and the third valve opening degree γ are set according to the opening degree from the fully closed state to the fully open state. The first valve opening degree α is a valve opening degree less than 2% beyond the fully closed state. The second valve opening degree β is one valve opening degree within the range of 50% to 69%. The third valve opening degree γ is one valve opening degree within the range of 71% to 90%.

  The present system 100 performs control while adapting to any one of the four types of valve opening characteristics S10 to S40 previously associated with the valve openings distinguished by different control indices α, β, γ. Each of the four types of valve opening characteristics S10 to S40 is referred to as follows.

  The quick open characteristic S10 rapidly increases and decreases between the fully closed state and the first valve opening degree α slightly opened from the fully closed state. The slow linear characteristic S20 causes the linear characteristic to slowly increase and decrease between the first valve opening degree α and the second valve opening degree β. The equal percent characteristic S30 changes between the second valve opening degree β and the third valve opening degree γ with the equal percent characteristic. The abrupt linear characteristic S40 causes the linear characteristic to rapidly increase or decrease between the third valve opening degree γ and the fully open state.

  The equal percent characteristic is a characteristic in which the rate of Cv change is the same as Cv before change, regardless of where the valve opening (0 to 100%) changes. Therefore, if the equal percent characteristic is plotted on a semilog graph paper, it can be displayed linearly. In other words, it is a characteristic that equalizes the flow sensitivity to the valve opening at any position of the valve opening (0 to 100%). As described above, in the present invention, the equal percentage characteristic is changed only between the second valve opening degree β and the third valve opening degree γ.

  Cv values corresponding to the valve opening degree are set as follows for the four types of valve opening degree characteristics S10 to S40 described above. In the quick open characteristic S10, a sudden change is made between 0% (the origin at the lower left of the graph) and the first point 1 of 5% or more. In the slow linear characteristic S20, the first point 1 of 5% or more and the second point 2 of 12% or more are slowly increased and decreased. In the equal percent characteristic S30, sudden change occurs between the second point 2 of 12% or more and the third point 3 of 30% or more. The abrupt linear characteristic S40 causes the linear characteristic to rapidly increase and decrease between the third point 3 of 30% or more and the fully open state.

  The present system 100 includes the four types of valve opening characteristics S10 to S40 described above in the valve opening control unit 60, and enables precise pressure control. As a result, the temperature and pressure of the autoclave can be stabilized. With regard to the flow rate characteristics before and after the remodeling of the plug, as shown in FIG. 5, the flow control characteristics of the discharged steam were improved as illustrated after the remodeling of the solid line before the remodeling of the broken line.

  The difference between the broken line and the solid line in FIG. 5 will be described in more detail. In order to reach the Cv value of 10% in the conventional valve opening characteristic shown by the broken line, it is necessary to move the steam valve discharge opening to a large extent to 70%, and the follow-up performance was poor at low speed. On the other hand, in the quick open characteristic S10 indicated by the solid line, it is possible to secure a Cv value of about 10% at the first point 1 which is reached instantaneously by opening the steam valve discharge opening by only about 1%. That is, the control response in this section has been accelerated to improve the tracking performance. Note that the speed can be increased in the reverse direction as well.

  In the slow linear characteristic S20, for example, the second point 2 is set to a Cv value of 10%, and the third point 3 is set to a Cv value of 15%. In this section, fine control is possible while greatly moving the steam valve discharge opening to approximately 1% to 58%. The speed can be increased similarly in the reverse direction, that is, in the valve closing direction.

  Further, in the equal percent characteristic S30, for example, the third point 3 is set to a Cv value of 15%, and the fourth point 4 is set to a Cv value of 40%. In addition, if it is a semi-logarithmic graph, this section can be plotted linearly. In this section, it is possible to control with the characteristic close to human sensitivity while moving the steam valve discharge opening to about 58% to 78%.

  The control of characteristics close to human sensitivity includes, for example, the change in sound volume with respect to the rotation angle of the sound volume knob in the audio device, the acceleration angle with respect to the accelerator depression angle in an automobile, or the twist angle of an accelerator in a two-wheeled vehicle. It is preferable that these can be controlled in the reverse direction with similar characteristics.

  Further, in the abrupt linear characteristic S40, for example, the fourth point 4 is set to a Cv value of 40%, and the Cv value of 100% in the fully open state and the interval between them are rapidly increased or decreased by the linear characteristic. In this section, it is possible to quickly control the Cv value of 60% with moderate operation up to about 78% to 100% of the steam valve discharge opening.

  Thus, the valve opening degree control unit 60 of the present system 100 realizes optimum control unique to each section so as to satisfy the control purpose over the entire section, and also performs bidirectional control, that is, any one of valve opening and valve closing. The direction can be controlled with similar characteristics. The control purpose is to reduce the fluctuation range of each of the temperature and the pressure of the autoclave 90 and to perform more stable operation control.

  FIG. 6 is a block diagram for explaining that the present system controls the flow rate characteristic according to the valve opening degree. As shown in FIG. 6, the present system 100 is configured to include at least an autoclave 90, a steam valve 10, a valve opening degree detecting unit 50, and a valve opening degree control unit 60. The present system 100 is a control system for reducing the fluctuation range of the temperature and pressure of the autoclave 90 in the HPAL process of nickel oxide ore and for more stable operation control.

  The autoclave 90 is connected to the high pressure steam line via the steam control valve 20, and is piping-configured so that the high pressure steam can be appropriately injected. In addition, the autoclave 90 is connected to the blast spool 70 via the steam valve 10, and has a piping configuration so that the internal vapor can be discharged appropriately.

  The system 100 functions to detect the valve opening degree of the steam valve 10 by the valve opening degree detecting unit 50, and to perform feedback control of the detection results while referring to the valve opening degree control unit 60. As described with reference to FIG. 5, the present system 100 has any one of the four types of valve opening characteristics S10 to S40 previously associated with the transition of the valve opening distinguished by different control indexes α, β, and γ. Control while adapting to heels.

  In addition, in FIG. 5, although the flow characteristic with respect to the steam discharge valve was shown, it is not limited to it. That is, the valve opening degree control unit 60 may freely control the flow rate characteristic so as to obtain an optimal Cv value according to the valve opening degree. That is, as one of the means for realizing the flow rate characteristic shown in the graph of FIG. 5, the steam discharge valve is connected to the plug 22 of the steam valve 20 shown in FIG. The plug 12 has been modified to change its shape, but this is merely an example.

  As shown in FIG. 6, if the present system 100 has a control function for causing the steam valve 10 to realize the four types of valve opening degree characteristics S10 to S40 described above, another shape different from the steam valve 10 is used. A steam valve may be used. The four types of valve opening characteristics S10 to S40 described above are as described above.

  The entire steam valve will be briefly described using FIGS. 7 to 10. FIG. 7 is an external perspective view for explaining the structure of an example of the steam discharge valve used in the present method and the present system. As shown in FIG. 7, the steam valve 10 has an axial moving mechanism 8 above the valve box 19, an inflow port 5 in the horizontal direction of the valve box 19, and a discharge port 6 bent downward at a right angle to the valve box 19. And at least. The steam valve 10 is provided with a valve opening degree detection unit 50 and a valve opening degree control unit 60, and a control system (this system) 100 for operation control of the autoclave 90 piping connected to the HPAL process of nickel oxide ore. Configured.

  FIG. 8 is a front view of the whole of the inlet viewed from the front direction in order to explain the structure of the steam discharge valve of FIG. 7. FIG. 9 is a cross-sectional view of the main part of the steam discharge valve of FIG. 8 cut along the line A-A at the center of rotation axis of the stem. FIG. 10 is an enlarged sectional view of an essential part in which an essential part surrounded by an alternate long and short dash line B in FIG. 9 is enlarged.

  As shown in FIGS. 7 to 10, the steam valve 10 used in the present system 100 is a ball-shaped valve, which is inserted into a bending point of steam piping through which high-pressure steam flows and is basically configured in a ball shape (glove type) There is. The steam valve 10 includes a trim 11, a plug 12, and a seat 13 inside a valve box 19. Above the valve box 19, the steam valve 10 is connected to an axial movement mechanism 8 and is maintained in a sealed state to slide. It is configured to have a free stem 9.

  The trim 11 is operable to increase or decrease the distance X (FIG. 4) connected to the axial displacement mechanism 8 via the stem 9 and facing the seat 13. The plug 12 is provided so as to project from the trim 11 with the central axis Q of the conical shape coinciding with the central axis O of the trim 11.

  As the gap G is shown in FIGS. 4 and 10, the steam valve 10 used in the present system 100 has outer diameters K and N of the plug 12 with respect to the inner diameter M of the flow passage hole 14 drilled in the sheet 13. It has been somewhat remodeled. Therefore, since the gap G of the steam valve 10 is set wider than the gap F of the conventional steam valve 21, the flow rate characteristic shown in FIG. 5 is obtained. By changing the plug shape of the steam discharge valve in this way, the followability of pressure control is improved by changing the flow characteristics of the discharged steam. As a result, an autoclave control system and control method have been realized which make it possible to keep the temperature and pressure of the autoclave constant.

  In the control system 100 according to the embodiment of the present invention, as a means for solving the problem, a desired effect is obtained by modifying the plug shape. That is, as shown in FIG. 4 (B), the shape of the plug 12 of the steam discharge valve 10 is finely remodeled to increase the Cv value at each valve opening degree of the flow characteristics S10 to S40 of FIG. Shifted to In particular, the system 100 is configured to reach a Cv value of 20% or more at a stage where the steam valve opening is 70%. Hereinafter, the effects that can be objectively recognized by Example 1 and Example 2 will be shown.

Example 1
In Example 1, standard deviations were calculated and compared as fluctuation ranges of the temperature and pressure of the autoclave during steady operation with respect to the presence or absence of the effect before and after practicing the present invention, and the results are shown in Table 1. That is, Table 1 shows, as one embodiment of the present invention, the standard deviation during steady operation for one month of November of the same year after remodeling the plug shape of the steam discharge valve in April 2014, and 2013 before the remodeling. It is the result of pairwise comparison with the standard deviation during steady operation for one month in December.

  As apparent from Table 1, according to the present invention, the fluctuation range of each of the temperature and pressure of the autoclave can be reduced and made more stable.

Example 2
In Example 2, in particular, recovery times from the abnormal stop state were compared before and after the implementation of the present invention. The abnormal stop state as referred to herein means a state in which a trouble occurs in the previous step of the leaching step and the charging of the ore slurry to the autoclave and the addition of the sulfuric acid are stopped. In this second embodiment, in addition to comparison of the fluctuations of the temperature and pressure of the autoclave for one month before and after the implementation of the present invention in amplitude values, the recovery time from abnormal shutdown to steady operation is also compared. The results are shown in Table 2.

  That is, Table 2 shows the results of pairwise comparison of the operation data of December 2014 when the abnormal shutdown occurred and March 2014. As apparent from Table 2, according to the present invention, the recovery time from the abnormal shutdown state can be shortened as an effect of suppressing the fluctuation of each of the temperature and the pressure of the autoclave.

[Example 3]
In the third embodiment, in particular, the number of troubles of the flash tank level meter generated in a predetermined period is compared. That is, Table 3 shows the six months from May 2014 to October of the same year after the steam discharge valve plug remodeling, and the six months from October 2013 to the next March, before the steam discharge valve plug remodeling. It is the result of comparing the number of trouble occurrences of the flash tank level meter with a pair.

  From Table 3 of Example 3, referring to Table 1 of Example 1 and Table 2 of Example 2, the following can be estimated. That is, according to the present invention, control of each of the temperature and pressure of the autoclave is stabilized. As a result, it is considered that the trouble occurrence of the flash tank level meter is suppressed.

  As specifically shown by Examples 1 to 3 and Tables 1 to 3, according to the control system and control method of an autoclave according to one embodiment of the present invention, stabilization of control and trouble Elimination can contribute to the improvement of productivity. In more detail, as shown by <1> and <2> below, the industrially remarkable effect is produced.

<1> By following the shape of the plug of the steam discharge valve, etc., the flow characteristic is shifted in the direction of increasing the Cv value at each valve opening, so that the control follow-up property against the temperature and pressure fluctuation of the autoclave is obtained. It can be improved. This makes it possible to suppress and stabilize fluctuations in temperature and pressure of the autoclave during steady operation.

<2> Even if problems occur in the previous step of the leaching step and charging of the ore slurry to the autoclave and addition of sulfuric acid are stopped, accurate pressure control with high compliance is used immediately after operation resumes. It can be restored to operation. Furthermore, by stabilization of temperature and pressure control, vibration of the flash tank can be suppressed, and trouble occurrence of the flash tank level meter can be eliminated.

  As described above, according to the present invention, it is possible to provide an autoclave control system and control method which make it possible to keep the temperature and pressure of the autoclave constant. Specifically, as shown in FIG. 4 as one embodiment, the clearance between the plug of the steam discharge valve and the sheet is increased. As a result, as shown in FIG. 5, the flow rate characteristics were improved, and the followability of pressure control could be enhanced. This has the effect of improving the controllability of pressure and temperature in the high pressure acid leaching step of low grade nickel oxide ore.

  Although the embodiments of the present invention have been described in detail as described above, it is easily understood by those skilled in the art that many modifications can be made without substantially departing from the novel items and effects of the present invention. Will. Accordingly, all such modifications are intended to be included within the scope of the present invention.

  For example, in the specification or the drawings, the terms described together with the broader or synonymous different terms at least once can be replaced with the different terms anywhere in the specification or the drawings. Further, the configuration and operation of the autoclave in the HPAL process, and the specific method for the treatment for raising and pressurizing the temperature of the slurry are not limited to those described in the embodiment of the present invention, and various modifications can be made. is there.

  The present invention is employed in a hydrometallurgical process for low grade nickel oxide ores, in particular for process control of pressure leaching reactors (autoclaves) in high pressure acid leaching (HPAL) processes.

1 to 3 1st to 3rd points, 5 inlets, 6 discharge ports, 8 axial movement mechanisms, 9 stems, 10 steam discharge valves (steam valves), 11 trims, 12 plugs, 13 sheets, 14 (sheet 13 Flow hole, drilled in 15) Opposite surface of sheet (with trim 11), 19 valve box, 20 steam control valve, 21 steam discharge valve (steam valve), 30 level control valve, 40 flush tank, 50 valve opening detection unit, 60 (61 to 63) opening control unit, 70 blast spool, 80 (for autoclave 90) discharge piping, 90 autoclave, 91 to 97 compartments, 99 stirrer, 100 control system (this system ), E (for plug 22) outer diameter near tip, F, G gap, H liquid level (level), K (for plug 12) maximum outer diameter, L level gauge, N (for plug 12) tip Neighborhood Outer diameter, M (for flow channel hole 14) inner diameter, T thermometer, X (the trim 11 faces the facing surface 15 of the sheet 13) distance, O (at the facing surface) axial center, P pressure gauge, Q ( Conical) Center, Y (extracting) steam flow, Z (discharging) steam flow

Claims (7)

A control system for controlling operation of an autoclave in a high pressure acid leaching process of nickel oxide ore, comprising:
A steam discharge valve for controlling the pressure in the autoclave;
A valve opening control unit for controlling the valve opening of the steam discharge valve;
Equipped with
The valve opening control unit
The control indexes of the first valve opening degree, the second valve opening degree and the third valve opening degree are set according to the opening degree from the fully closed state to the fully open state,
The control index has a magnitude relationship of fully closed <first valve opening degree <second valve opening degree <third valve opening degree <full opening.
Quick open characteristics for rapidly increasing and decreasing between the fully closed state and the first valve opening slightly opened from the fully closed state;
A slow linear characteristic that slowly increases and decreases between the first valve opening degree and the second valve opening degree with linear characteristics;
Equal percent characteristics that are changed in equal percent characteristics between the second valve opening degree and the third valve opening degree;
An abrupt linear characteristic that causes the linear characteristic to rapidly increase and decrease between the third valve opening degree and the fully open state;
According to the control characteristic curve
Control is performed while adapting to any one of the valve opening degree characteristics previously associated with the valve opening degree distinguished by the different control index,
Control system. About the valve opening degree,
The first valve opening is less than 2% beyond the fully closed state,
The second valve opening degree is in the range of 50% to 69%,
The third valve opening degree is in the range of 71% to 90%,
The control system according to claim 1, wherein the control system has a value of one of The Cv value corresponding to the valve opening degree is
In the quick open characteristic, the sudden change is made between 0% and the first point of 5% or more,
In the slow linear characteristic, it is slowly increased and decreased between the first point and the second point of 12% or more,
In the equal percent characteristic, the equal percent characteristic is changed between the second point and the third point of 30% or more.
A control system according to claim 1 or 2. A steam discharge valve used in the control system according to any one of claims 1 to 3,
A trim connected to the axial transfer mechanism through the stem and operable to adjust the distance facing the seat;
A plug projecting with a conical center at the center of the axis of the face of the trim facing the seat;
The sheet having an inner diameter passage hole capable of receiving the maximum outer diameter of the plug and fixed in the valve box;
Equipped with
The maximum outer diameter of the plug is set to 80% or more and 95% or less of the inner diameter of the flow passage hole.
Steam exhaust valve. A control method for controlling the operation of an autoclave used in a high pressure acid leaching process of nickel oxide ore with a valve opening control unit,
A steam discharge valve for controlling the pressure in the autoclave;
The valve opening control unit that controls the valve opening of the steam discharge valve;
Equipped with
The valve opening control unit
The control indexes of the first valve opening degree, the second valve opening degree and the third valve opening degree are set according to the opening degree from the fully closed state to the fully open state,
The control index has a magnitude relationship of fully closed <first valve opening degree <second valve opening degree <third valve opening degree <full opening.
Quick open characteristics for rapidly increasing and decreasing between the fully closed state and the first valve opening slightly opened from the fully closed state;
A slow linear characteristic that slowly increases and decreases between the first valve opening degree and the second valve opening degree with linear characteristics;
Equal percent characteristics that are changed in equal percent characteristics between the second valve opening degree and the third valve opening degree;
An abrupt linear characteristic that causes the linear characteristic to rapidly increase and decrease between the third valve opening degree and the fully open state;
According to the control characteristic curve
Control is performed while adapting to any one of the valve opening degree characteristics previously associated with the valve opening degree distinguished by the different control index,
Control method. About the valve opening degree,
The first valve opening is less than 2% beyond the fully closed state,
The second valve opening degree is in the range of 50% to 69%,
The third valve opening degree is in the range of 71% to 90%,
The control method according to claim 5, wherein each of the values is one. The characteristic of the Cv value corresponding to the said valve opening degree,
In the quick open characteristic, it is suddenly changed between 0% and 5%,
In the slow linear characteristic, increase / decrease slowly between 5% or more and 12% or more,
In the equal percent characteristic, the equal percent characteristic is changed between 12% and 30%.
A control method according to claim 5 or 6.

Images