In the project construction, according to the actual needs of the process, in line with the advanced nature, reliability, practicality of the principle, the completion of the natural drug pilot production process of the unit computer process control system design and development, successfully achieved the natural medicine The automatic extraction and control of the various technological parameters in the pilot production process is realized. The extraction unit realizes the whole process computer control of the various extraction methods, thus providing the reliable and effective research for the natural medicine extraction technology and the extraction equipment in the future. s method.
2 extraction process of traditional Chinese medicine extraction equipment, the main process and automatic control requirements
2.1 Extraction process control
(1) feeding control
Extraction of herbs into the tank, adding herbs 5-l0 times the solvent. Liquid level control method to control the amount of solvent added.
(2) dynamic extraction
Dynamic extraction is the core of the extraction process of traditional Chinese medicine. It is required to control the temperature of the liquid in the tank, keep the pressure in the tank normal and manage the opening and closing of the electromagnetic valve and the manual valve in the circulation channel. Start and stop.
Chinese medicine extraction process commonly used solvent (solvent) with water or ethanol. Extraction solvent is different from the control requirements are not the same. When water is used as solvent, the vent valve should always be on during the extraction process, ie the pressure inside the tank is constant, only alarm when the accident happens (such as the exhaust channel is blocked). Alcohol as a solvent, the vent valve should always be in a closed state, to maintain the tank pressure is constant, the adjustment of water and solvent for different.
2.2 Chinese medicine extraction equipment monitoring and control parameters
Detection parameters: extraction tank temperature, extract the pressure inside the tank, extract the tank level, cooler inlet cooling water temperature and outlet temperature, heat pump outlet temperature and oil inlet temperature. Control parameters: extraction tank temperature, extraction tank pressure, feed control, discharge control, circulating pump, heat pump, pump and pump start and stop control.
2.3 automatic control requirements
According to the characteristics of the pilot process uncertainty of this project, the automatic control design requirement of the extraction part is to realize the whole process automatic control of different extraction modes conveniently and flexibly under the condition of limited and fixed equipment and pipelines. It can be either "single-tank extraction" or "double-tank extraction"; it can be "cyclic extraction" or "non-cyclic extraction." Extraction of the tank liquid rehydration, extraction tank temperature and constant temperature, drug leaching, recycling, extraction of the material until the end of the extraction or re-extraction of the entire process are reliable and automatic completion.
The automatic control circuit of the extraction part mainly includes the automatic control of the extraction tank temperature; the automatic control of the extraction tank quantification and addition liquid; the automatic control of the extraction tank extraction; the automatic detection of the temperature of the extraction tank and the extraction liquid storage tank; Level automatic detection. The extraction times, extraction temperatures and cycle times of a batch of herbs are determined by the process. This program uses hot oil on the jacket with the extraction tank heating, boiling pot of herbs, while circulating liquid circulation.
3 system features
In the overall system design, selection and synchronization with the domestic and foreign systems to ensure that the computer used by the measurement and control system in the advanced nature of technology and with international practice. After considering the relevant systems at home and abroad such as: Honeywell control system, Yokogawa μXLDCS and SIEMES control system, decided to choose SIEMENS control system. Thus ensuring the maturity of the system. Another reason for choosing the Siemens system is that it is easy to maintain and easy to expand. The production process of traditional Chinese medicine, often "bubble-induced escape of liquid" phenomenon. Using CTN-XM series of two-level automatic elimination of foam control device, which based on the principle of resistance of the foam detection electrode has a strong anti-pollution ability, due to serious pollution and scaling circumstances, can still detect the liquid level Position, so as to achieve reliable and effective elimination of foam, to control the "escape liquid" purposes.
4 system structure and configuration
PROFIBUS-DP was used to construct the underlying network of the monitoring system of TCM extraction process. The new fieldbus control system broke through the DCS system communication by the private network closed system to achieve the defects caused by the closed, dedicated solutions based on open, standardized solutions, fieldbus standard Dozens of. Each bus standard has its own characteristics, and in the specific application areas show their advantages. Process Fieldbus PROFIBUS, as an international, open, fieldbus standard independent of equipment manufacturers, is a fieldbus solution for fully integrated processes and factory automation, and is widely used in the process control and process industries. PROFIBUS uses the OSI model of the physical layer, data link layer. When the transmission rate of 9.6Kbps - 12Mbps, its transmission distance can reach 100m. When the transmission rate is 1.5Mbps, its transmission distance can reach 400m. PROFIBUS transmission medium can be twisted pair, can also be fiber optic cable. It can mount up to 127 sub-sites. PROFIBUS uses a functional modular design, different application systems using different modules for design.