Dosing composition and function

1 Gypsum powder production process Gypsum powder production main process flow

(1) Gypsum block coarse crushing, homogenization, fine crushing: mainly complete the crushing of raw materials, gypsum block is crushed by coarse jaw crusher for the first time, homogenization arrangement in the unloading yard, and then crushed by fine jaw crusher for the second time, and then enter into the silo. In this process, the coarse jaw crusher is forbidden to start with load, and there should be alarm signal when stopping; the unloading yard is divided into two unloading zones, and the unloading trucks should be switched freely in two zones, and the fabric should be uniform.

(2) Pre-grinding link: the gypsum powder out of the silo enters the column mill for further grinding through screw weigher and belt scale, and then is separated by the powder selector for selecting grades, and the qualified materials are transported to the raw powder silo through the corner screw conveyor, vertical bucket elevator, and silo top screw conveyor. In this process, the spiral scale should be measured at a constant value and required to calculate the cumulative output; the column mill can not be started with a load as well, and the current needs to be detected; the bin filling is selected by the material level signal.

(3)a powder reaction workshop to the dihydrate gypsum for vaporization, drainage of a series of physical and chemical treatment, through the fine grinding system and powder selection, semi-finished products into the mixing bin. This process is very complex, complex batching system, circuit control parameters, drainage process and equipment is α half-water high-strength gypsum powder quality of the key, get it wrong and transformed into β-type ordinary gypsum. Domestic equipment is difficult to meet the process requirements, the introduction of foreign equipment, batching system provided by the manufacturer.

(4) in b powder workshop gypsum powder after frying into semi-water gypsum, after the fine grinding system and powder selection, semi-finished products also into the mixing bin. In order to achieve precise control of gypsum dehydration process, in addition to the frying temperature, discharge temperature and calcination time must be strictly controlled, but also must strictly control the material into the frying pan feeding amount or feeding continuous stability, especially for intermittent equipment, must be strictly controlled every time the amount of feed (fluctuations can not be more than ± 100kg), and as far as possible to shorten the feeding time and discharge time. Each step in the frying process may affect the quality of the product, in order to ensure the quality of the product and the stability of the quality, must be strict and precise control of the process of each process parameter. b powder frying link control requirements are complex, frying pan feeding weighing to be fixed value given, need to detect the pot, furnace, inlet, exhaust gas temperature, wind pressure, wind flow, are 4 ~ 20mA standard signals. (5) Mixing bin is the deep processing of gypsum products, not in this batching system. 2.2, the design of the system hardware This system adopts the ABBIndustrialFreelance2000 batching system, the batching system is a new generation of open DCS system for factory automation.

DCS system batching structure

According to the production process characteristics of the feeding system and the distribution of field equipment, the DCS system batching structure is set.

DCS system batching structure is divided into field level I/O station, process control level and operation monitoring level. The weighing control system connects the layers together through computer network to complete data acquisition and control information transmission.

System hardware configuration

(1) Process control station

The process control station is divided into field controller and input/output station, the field controller adopts ABB weighing, embedded with 32-bit RISCCPU. 3 I/O stations, among which I/O station No. I: raw material crushing; I/O station No. II: a powder workshop; I/O station No. III: b powder workshop, complete the functions of on-site signal acquisition and A/D, D/A conversion.

(2) DCS system batching structure (2) Operator station (OS)

This weighing system is installed with 3 operator stations. The operator station is equipped with DELL industrial computer suitable for industrial site, with hardware configuration of RAM256MB, hard disk 40GB, 19″ color CRT; the operator can conduct man-machine dialogue with the system through keyboard and CRT to complete the starting, stopping, valve adjustment, speed adjustment of the equipment, process parameter setting, monitoring of on-site equipment operation and displaying the process parameters, printing reports and so on.

(3) Engineer Station (ES)

The system is set up with 1 engineer station and 1 operator station. The engineer station can realize hardware editing, on-site process station programming, fieldbus intelligent weighing instrument configuration, operator station configuration integrated programming and debugging.

The engineer station, operator station, field controller and I/O station are installed in the central control room.

(4) Communication network

The communication structure of the weighing and batching system is two layers: the first layer is the field control layer, which realizes the communication between the controller, I/O module and intelligent weighing instrument, and adopts ProfiBus field bus communication protocol, and the transmission medium adopts standard twisted pair wire, the state information of the field equipments and the analog signals are transmitted to the controller in real time through the network of the layer; the second layer is the central monitoring layer, which realizes the communication between the controller and the operator station and engineer station, and the system communication adopts TCP protocol, and the system communication adopts TCP protocol, and the system communication adopts TCP protocol. The second layer is the central monitoring layer, which realizes the communication between the controller and operator station and engineer station. The system communication adopts TCP/IP protocol Ethernet, the transmission medium is coaxial cable, the communication rate is 10MB/S, the transmission distance can reach more than 1km, and the anti-interference ability is strong.

Communication between different systems: In gypsum powder production line, in addition to DCS, there are other dosage systems, such as fine mill dosage system with Mitsubishi's PLC (FXON-16EX), the reaction workshop of the German dosage with Siemens S5-400 PLC, DCS system and these systems to transfer and exchange information between the DCS system and the interconnection of the PLC approach with the Hardwire connection, following the Modbus protocol RS-485 serial communication.

The system's software ABBIndustrialFreelance2000 provides a wealth of system software, capable of accomplishing a variety of functions. This system engineer station installed DigiTool6.1 version of the software, running on WindowsNT4.0 system. The programming language adopts the international standard IEC1131-3 graphical programming language, using tools such as Function Block Diagram FBD, Ladder Diagram LD, Instruction List IL, and Shun Control Chart SFC, etc., which can not only complete the configuration of the control process, but also carry out the engineering debugging and diagnostic functions; the completed configuration result is downloaded from the Engineer Station through the system network to the corresponding PS, FC, and the OS of the Operator Station. The operator station is installed with DigiVis 6.1 version software, the operation interface and menu are in Chinese, running on WindowsNT4.0 Workstation operating system. The main functions include graphic display, data monitoring, system status display, trend archiving, recording, process and system alarms, control operation, system diagnosis and so on. The whole production line of gypsum powder plant can be divided into three areas: raw material crushing, a powder production workshop and b powder production workshop, and each area is divided into several groups to be controlled separately. The whole dosage system is divided into coarse crushing group, fine crushing group and pre-milling group, which is the grouping of raw material crushing system; in the a-powder production workshop, it is divided into a-powder reaction workshop feeding group, a-powder storage, a-powder fine grinding feeding group and a-powder fine grinding group; in the b-powder production workshop, it is divided into frying pan feeding group, b-powder storage, mixing workshop, b-powder fine grinding feeding and b-powder fine grinding group. Each group of batching system keep relatively independent, when a part of the failure, will not affect the other part of the work, which reflects the advantages of DCS system danger decentralization.

(1) Logic control gypsum powder production in the various parts of the equipment needs to be in a certain order of action. Motor start and stop and valve opening and closing have a certain order and chain relationship. In order to ensure the normal operation of the process and equipment safety, must strictly follow these relationships. Weighing controllers provide this sequential start of the "automatic control" idea. In the central control room, the operator, through the keyboard, can start and stop a group of equipment in sequence, without human intervention. During the production process, when a device fails, the controller's chain protection, so that the relevant equipment to stop working. industrialIT programming using IEC61131-3 standard, support for the logic ladder diagram (LD), with LD language programming can be very good to achieve the above control functions. Take the fine broken group as an example to illustrate this control idea. There are four devices in the fine crushing group, namely, 1 - electric shock feeder, 2 - fine jaw crusher, 3 - bucket elevator, 4 - bin top distributor. The normal starting and stopping sequence is shown in Figure 3:

When programming in LD language, the normally open contact of the return signal from the operation of the dosage system is used as the starting condition of the equipment, the normally open contact of the return signal from the operation of the dosage equipment is used as the starting condition of the weighing equipment, and the same relationship between the dosage equipment and the dosage system is used, so that the four devices have a chain relationship and a starting sequence. In the configuration, the fine broken group has 4 writing variables, which are STA1, STA2, STA3, STA4, respectively, as the starting conditions of equipment 4, 3, 2, 1. The normally open contacts of STA1, STA2, STA3, STA4 are delayed for 5s in turn, which also ensures the sequential startup of the equipment, and also meets the requirements of the equipment motor startup. STP1, STP2, STP3, STP4, respectively, as equipment 1, 2, 3, 4 stop conditions, STP1, STP2, STP3, STP4 normally closed contacts sequentially delayed 5s action, when stopping, stopping the equipment 1, can automatically delay the stopping of the equipment 2, 3, 4. (2) metering control system control for the totalization, metering and calculation of the problem, the system provides the Function block, through the configuration can complete the complex mathematical operations. The use of multiplication, logarithmic, signal selection, logic operations, analog totalization input module and other function blocks, to complete the following arithmetic formula: W = ∑ KLN (UI / U0) VT where: W - material totalization; K - material calibration coefficients; T - machine running time; Ui Ui - output signal when there is material; U0 - output signal when there is no material; V - conveyor speed; N - calculation times.

The arithmetic completed by the above function blocks can realize quantitative control, proportioning, and class output calculation, and realize quantitative management.