In recent years, with the development of modern production, batching system has been widely used, and the combination of on-site weighing instrument, actuator, etc., forms an automatic feeding system, which improves the process control level of the factory, reduces the energy consumption of the products, and reduces the labor intensity of the workers.

Main technical indexes:

1. four-effect with heat pump, DC falling film low-temperature continuous crystallization evaporation process is adopted, and each evaporated ton of water consumes less than 0.23 tons of raw steam;

2. Ammonium chloride evaporation, the secondary steam is equipped with purification device, so that the distilled water meets the emission requirements;

3. DCS dosing system is adopted.

Process characteristics

Ammonium chloride (NH4Cl), also known as electric salt, salt alarm, electric medicine powder, salt essence, halogen salt, etc., is a kind of white crystal or granule, stable in air, hygroscopic, easily soluble in water with the rise of temperature in water solubility increases. Mainly used in the production of dry batteries, dyeing, electroplating, precision casting, etc., also used in agricultural fertilizer. NH4Cl production in the industry is mainly by evaporation: dilute NH4Cl solution after preheating and then successively through the four falling-film evaporator, steam-liquid separator, evaporate the excessive water in the solution to get the concentrated NH4Cl solution, evaporate the water with the steam was vacuum pumped away, the thick NH4Cl solution and then through the continuous crystallizer, the water is extracted by the steam pump. The concentrated NH4Cl solution is then cooled and crystallized out of NH4Cl crystals through a continuous crystallizer. Raw material, main product, by-product.

Ammonium chloride continuous evaporation crystallization process mainly has the following control requirements:

1. high vacuum requirements, automatic dosage system normal operation, the vacuum is -0.95Mpa, its requirements need to be atmospheric condenser in the water level is strictly controlled at about 20mm, the height of its tank is 2.5 meters, only in this way to ensure that the equipment for continuous crystallization, LCA-403 for the condenser level control, H101, H102, H103 for the evaporator.

2. Ammonium chloride is easy to crystallize, requires strict control of the liquid level of the continuous crystallizer (H104), and four steam cleaner differential pressure (H106, H107, H108, H109), to ensure that the material level in the crystallizer, so that the quality of the crystals to meet the requirements, and in addition to preventing the double-flange transmitter due to the flotation of the material in the membrane box on the crystal because of the ammonium chloride is easy to crystalize, so it is easy to cause the steam cleaner Because ammonium chloride is easy to crystallize, so it is easy to cause the blockage of the partition plate of the steam cleaner, so it is required to prevent the crystallization by automatic spraying when the differential pressure before and after the steam cleaner reaches +25mmH2O to ensure the vacuum degree of the automatic dosage system.

3. Ammonium chloride is easy to corrode, so when selecting the type, use corrosion-resistant components. In direct contact with the material parts, the use of differential with Hastelloy, pressure change, electromagnetic flowmeter, and casing for the titanium RTD, the heart of the valve actuator for PTFE.

Process control program

The automatic feeding system realizes ammonium chloride process control, logic control, sequence control and other functions; it has modular and flexible design; it provides open data interface, field bus and internet access; it conforms to the trend of the times and absorbs the latest electronic technology of weighing module, network technology and control technology, and it is featured with high reliability, open dosage, flexible composition, user-friendly interface, powerful function and easy maintenance.

I/O points statistics of ammonium chloride evaporation device:

Each I/O points are mainly pressure, temperature, flow, liquid level, control requirements are more stringent, automatic batching system configuration is as follows:

This automatic batching system consists of one field control station and one operation station (also used as engineer station). The control station is installed in 1800mm standard cabinet, which is equipped with high-performance redundant control template and intelligent I/O conditioning template as well as redundant power supply components, heat dissipation components, 24V power supply components, etc., and it can be installed in the control room or on-site control machine room. The control station is responsible for collecting on-site signals, monitoring important parameters, adjusting and calculating, and giving control signals to guide the valve action. The control station is embedded with various advanced control algorithm modules for automatic dosage program to call, which greatly improves the quality of control. At the same time, the control station is also responsible for communicating with the upper operating station, transmitting the real-time information of each parameter, and reproducing the process situation in the form of man-machine interface.

The operation station/engineer station adopts the configuration of highly reliable mainstream industrial computer (American ICSC-4000 series), running the Tech industrial control application software platform based on the weighing and batching system Windows2000, which provides users with flexible, convenient and powerful configuration software IEC algorithm editor, and users can realize the programming of various control strategies. The operation station and control station are connected through industrial Ethernet, which is used for monitoring and managing the process, setting or modifying the process parameters, printing production reports and so on. At the same time, any parameter exceeding the limit will be reflected on the HMI, such as different sound and light alarm signals to remind the operator. Different operators are assigned different accounts and passwords and have different operating privileges, which greatly improves the safety factor of automatic dosage. Engineer station is used for function configuration of automatic dosage and loading of configuration data, and it can also play the role of monitoring and management instead of operator station. The engineer station can be connected to higher enterprise management network to provide decision-making support for enterprise production scheduling and information sharing, and realize comprehensive scheduling and coordination of the whole plant.

The weighing and batching system is also equipped with a laser printer (hp6L) for real-time printing of production reports (morning, midday and evening reports) and alarm information of automatic batching system, historical information of important parameters, etc., which provide reliable references for production operation.