A kilo-plant is built and implemented in authors' lab for integrated research on process development and operation optimization. It is designed specifically for development of fine chemicals in kilogram scale. It could be easily manipulated into different configurations, and its kilogram-scale makes itself less expensive than usual pilot plants to build, to facilitate product development, process design and production operation, to response to rapid changing marketplaces.
The kilo-plant consists of main features of a complete process system, including reactors, separation units, heating and cooling utilities, instrumentation, control system and recycles. There are two glass jacketed stirred reactors with maximum capacities of 2 and 10 liters, respectively. The processing capacity is 30-300g/h. The temperature range is from -40°C up to +200°C, and the pressure ranges from 10 mbar to 1.45 bar absolute. The heater/chillers offer temperature control of reaction and crystallization processes, thereby high quality products are obtained. The kilo-plant allows for changes in the process flowsheet (feed point location, recycle, etc.) for the investigation of process alternatives.
Besides the kilo-plant, a number of process simulators, like ASPEN Plus, gPROMS, Simulink, SuperPro, and real-time platform G2, have been applied to facilitate the integration of chemical process operations. A data acquisition/rectification interface and a database are utilized together to realize the data exchange among the basic control system of the kilo-plant and advanced applications. Opening Data Base Connection (ODBC) and Common Object Request Broker Agent (CORBA) are followed to realize communication among these softwares in the platform. The standard for exchange of product data (STEP) is used for information integration.
Advanced applications include process monitoring, dynamic simulation of the process, Abnormal situation management, production scheduling, advanced control, online optimization, and product quality control. Integration of process conditions, operation and control strategies are studied.
One of the case studies carried out in the kilo-plant is the synthesis of Nipagin ester, which is a new anti-mildew and antiseptic agent with the best inhibiting effect on aflatoxin in food, drink, cosmetics and medicine. The esterifications of Nipagin acid (p-hydroxyl benzoate acid) and series alcohol (methanol, ethanol, propyl alcohol, and butyl alcohol) are controlled under different temperature. Based on the performance analysis of small volume experiment, reaction dynamics and conversion ratio are studied. Factors of process conditions, operation and control strategies are analysed.
Operation of the kilo-plant is monitored with 15 sensors of a variety of process variables, including temperature, pressure, flow rate, pH value, and the rotation speed of the stirrer. The instruments ensure high frequency data collection and high accuracy parameter measurement and control. In the kilo-plant, the accuracy of temperature measurement is of ±0.1°C. To facilitate a reliable real time monitoring and dynamic analysis, the remote data transmission interval from the installation to the database is 0.2 s.
Many uncertainties of process models and phenomena of a full-scale unit are learned and validated with experiments on the kilo-plant. The development of new products and processes benefit from the integration of rigorous mathematical modeling and the results obtained from the mini-plant. The characteristics of product synthesis, process operation, and product quality control are investigated in coupled with computer-aided monitoring, online modeling, simulation, and operation optimization. With the integration of process design and operation, product property could be tailored to accelerate development progress. In this case, morphology of the crystal product may be greatly influenced by operation variables, including temperature, pH, and stirrer rotating rate etc.
Experimental screening of feasible operation schemes on the kilo-plant will hopefully accelerate process design of new products, make it more convenient to adjust the processing route, to discover and to solve the problems occurred in actual industrial production in advance, to more quickly respond to the technical difficulty of the chemical product manufacture and to satisfy market demands for a variety of chemical products.