1 dosage design principle

1.1 Dosing process and requirements

The main production process of the enterprise is: the iron red plant fine grinding of iron red slurry with the transfer pump into the reactor; in the reaction tank for dehydration treatment and then reserve down; and then use automated detection and control technology will be highly concentrated solution (concentration value higher than 60%) through the transfer pump into the mixing modulation mixing tank; in the mixing tank with water stirring and mixing, slurry adjustment processing (slurry concentration of 50%, the accuracy requirements), slurry adjustment 5%), the total amount of solution after slurry to reach a predetermined value; finally control the feed pump will be slurry solution in accordance with the predetermined amount of output to the calibration pool, and then the subsequent processing. Batching control requirements are: according to process requirements, automatic regulation of controlled parameters, start and stop various types of equipment; automatic storage of historical data and print reports; real-time display of the main operating parameters and curves; mixing tank slurry concentration of 50%, the accuracy of 5%; daily output of T tons of ore, the accuracy of 0.3%.

1.2 Batching design program

Difficulty of batching control requirements mainly lies in the precision control of slurry mixing process and slurry process, the concentration precision of slurry mixing process is 5%, because the precision of the concentration meter, densitometer and other instruments is basically between 1%-5%, so it can be realized through these instruments to control the precision requirements. And out of the pulp process accuracy requirements for 0.3%, so out of the pulp process control should be realized through the higher precision instruments, such as manometer (accuracy of the lowest up to 0.05%).

According to the control requirements of the production, analyze the difficulties of the dosage control, the dosage control process is divided into three major parts: slurry concentration control process, mixing and adjusting slurry control process, and discharging control process.

1) The slurry concentration control process is responsible for starting and stopping the reaction tank, concentrating the finely ground iron red slurry from the iron red plant; and controlling the slurry switch of the reaction tank according to the sampling value of the concentration meter, so as to ensure that the solution going out from the reaction tank is a high-concentration solution. There are only two control points in this control process: the start-stop motor of the reaction tank and the slurry valve, the control process is relatively simple.

2) Stirring and adjusting slurry control process mainly controls the addition of water. Since the enterprise does not require high precision of slurry mixing concentration, the amount of water is calculated on the basis of the average concentration of the solution within 10min from the start of slurry feeding into the mixing tank.

After the completion of mixing slurry control, the concentration of slurry solution in the mixing tank is about 50%, and the height of the solution in the barrel reaches the predetermined height of the liquid level meter.

3) Discharge control process is the most critical step, the principle of control is as follows:

First of all, through the gasoline dispenser to the mixing tank in the glue tank into the tap water, each time the glue tank into the 2000L, through the pressure gauge sampling calibration corresponding to the water pressure P2, respectively, 2000L, 4000L, 6000L, ..., 100000L and so on, 50 water pressure values, and deposited into the alcoholic solution dosage. 100,000 liters of water solution height corresponds to the position is the position of the liquid level gauge. The height of 100,000 liters of water solution corresponds to the position of liquid level meter.

Secondly, the solution is fully stirred after the slurry mixing is completed and before the slurry is discharged, and the stirring time is a predetermined value. After stirring, the pressure value of the solution at the height of the level meter is taken from the manometer.

Finally, the alcohol solution dosage system starts the slurry switch, and continuously circulates the sampling test manometer, the sampling interval is 1 s. When the sampling value reaches the calculated pressure value of the remaining slurry, stop the slurry, and at the same time shut down all kinds of equipment, the dosage control process is over.

The above program has the following advantages: make full use of the high-precision performance of the manometer to ensure the control accuracy of the dosing system; each module is independent and does not interfere with each other, which is convenient for operation and maintenance; avoid the use of expensive densitometers and other instruments, and reduce the cost of the ammonia solution dosage system through the use of manometers and other instruments.

2 dosage design realization

2.1 Hardware structure of dosage

The measurement of each physical parameter in the dosage is chosen to be detected by the corresponding stainless steel weighing module, the concentration meter is chosen to be HT-2310 of Lanzhou Isotope Instrumentation Factory, with 1% accuracy; the flow meter is chosen to be W3000-0401211-100 of Xi'an Instrumentation Factory, with 2% accuracy; the pressure meter is chosen to be 315/AGS5S22M of Xi'an Instrumentation Factory, with 0.2% accuracy; the mixing speed and the control of slurry delivery speed are chosen to be TD1000 series frequency converter of Emerson; the data acquisition card is chosen to be PCL-812PG of Advantech. As well as the control of slurry speed, slurry speed of Emerson's TD1000 series of inverters; data acquisition card used Advantech's PCL-812PG, through the realization of the control data of the A/D, DI conversion; taking into account the PCL-812PG's input and output signals required for the 0-5V voltage or 4-20ma current, and these signals do not meet the output of the module to drive switchgear requirements, it is necessary to use the PCL-812PG through the PCL-812PG, which is the first time in the history of the module to control the output of the module. Requirements, it is necessary to PCLD-880 and PCLD-885 to do transit, rectification of signals. The upper computer of dosage selects IPC-810/PV industrial control computer produced by Advantech.

2.2 dosage software structure and each part of the function

The software framework of the dosage software is to develop vivid and convenient operation interface, and the domestic configuration software Controx2000 is used in the upper computer for the design of the control interface. ControX2000 is a software package based on the operation of the dosage of Windows98/2000/NT, and it adopts the Client/Sever system structure internally, which can provide real-time control of many field controllers and other field intelligent components. ControX2000 is a Windows98/2000/NT based software package for dosage operation. It adopts the Client/Sever architecture, which can control and monitor numerous field controllers and other on-site intelligent components in real time, with high performance and reliability, and can react to various emergencies at any time without losing any data and alarm information.

In addition, the communication between Controx2000 and the data acquisition card does not require the preparation of a communication program, Controx2000 will be collected by the hardware devices in the field through the device driver of the configuration software to transfer the data to the configuration software. In ControX2000, you only need to configure the drivers for the hardware, for example, for the data acquisition card PCL-812PG, Controx2000 has to configure the corresponding driver for this hardware. And in the dosage can be set up through the different addresses of the label amount to correspond to the data acquisition card channel, through the label value of the change reaction, control the data acquisition card channel input and output.

The dosage function modules are independent of each other, ensuring the stability of the system, good human-computer interaction performance, to facilitate the user real-time effective control and management of the production site.

2.3 Main program of dosage

According to the control structure of dosage, it is divided into three control stages: thickening and feeding process, adding water and adjusting slurry process and discharging control process.

Concentration feeding control process: manually start the reaction tank feeding switch, start the reaction tank mixing motor switch, the dosage system starts the reaction tank feeding process. When the reaction tank is full, stop the feed switch and stirring motor switch; according to the production needs, start the reaction tank slurry switch, slurry hose pump, in the process of slurry, the data acquisition card real-time detection of the sampling value of the concentration meter, the dosage according to the sampling value of the slurry solution to determine whether the concentration is greater than 60% of the high-concentration solution. If the judgment is no, turn off the slurry switch and hose pump.

Adding water and adjusting slurry control process: at the same time of starting the reaction tank slurry switch, the dosage carries out sampling on the concentration meter through the data acquisition card for about 10mins, with the sampling interval of 1S; the dosage calculates the amount of added water according to the sampling data, then automatically starts the water adding switch, and calculates the amount of added water through the sampling on the flowmeter by the data acquisition card. When the amount of water is satisfied, the dosage automatically stops the water adding switch. When adding water, the slurry feeding process continues until the height of slurry solution reaches the height of liquid level meter, the dosage stops feeding slurry according to the signal of dynamic weighing module.

Discharging control process: after the slurry feeding process, start the stirring motor according to the production needs, stir the slurry for 30min (can be set), after the stirring is completed, the slurry concentration and other parameters are calculated; when the user inputs the shift volume H and daily output I, the residual slurry pressure is calculated, and at the same time, start the discharging switch and the hose pump, and start discharging process; in the process of discharging, the real-time detection of the pressure gauge sampling value, and when the sampling value reaches the calculated value, it stops the discharge switch and the hose pump, and the discharging process is finished. When the sampling value reaches the calculated value and the predetermined accuracy range, the discharge switch and hose pump are stopped and the discharge process is finished.

3 Running results and its analysis

The interfaces of various functional modules can be converted to each other during the dosing operation, and the interface of the dosing control slurry process. Good response to the state of the field equipment, real-time display of the dosage control parameters and their curves, the set parameter value of the alarm, well completed the production design requirements. The overall operation result of the dosage is good, which meets the control requirements well and achieves the original design purpose. In order to ensure the good operation of the dosage, in addition to the automatic control of each control quantity in the dosage, but also set up manual control. In the manual control process, the software system is only responsible for monitoring.