At present, in chemical production, the materials used in the reactor, stirring device, heating method, shaft seal structure, volume size, temperature, pressure, etc. are various and there are many types, but they basically have the following common characteristics.
(1) The structure is basically the same. In addition to the reactor body, there are also transmission devices, stirrers and heating (or cooling) devices to improve the heat transfer conditions to control the reaction temperature more uniformly and to enhance the mass transfer process.
(2) The operating pressure is higher. The pressure in the reactor is caused by chemical reactions or by the rise of temperature. The pressure fluctuates greatly, and sometimes the operation is unstable. The sudden increase in pressure exceeds several times the normal pressure, so most of the reactors are Pressurized container.
(3) Higher operating temperature, chemical reactions need to be carried out under certain temperature conditions
OK, so the reactor can withstand both pressure and temperature. There are several ways to obtain high temperature.
①Water heating: It can be used when the temperature is not high. The heating system is divided into open type and closed type. The open type is the simplest. It consists of a circulating pump, a water tank, a pipeline and a control gate number regulator. When high-pressure water is used, the equipment requires high mechanical strength. The outer surface of the reaction sign is welded with a coiled tube, and there is a gap between the coiled tube and the wall of the kettle. As a result, the thermal resistance increases and the heat transfer effect decreases.
②Hot steam heating: when the heating temperature is below 100℃, steam under one atmospheric pressure can be used for heating; saturated steam is used in the range of 100～180℃, and high pressure superheated steam can be used when the temperature is higher.
③ Heating with other media: If the process requires operation at high temperatures, or if you want to avoid the use of high-pressure heating systems, other media can be used to replace water and steam, such as mineral oil (275～300℃), biphenyl secondary mixture ( Boiling point: 258℃), molten salt (140~540℃), liquid lead (melting point: 327℃), etc.
④Electric heating: Wrap the resistance wire on the insulating layer of the reactor cylinder, or install it on a special insulator some distance away from the reactor, so a small space gap is formed between the resistance wire and the reactor body .
The use of the first three methods to obtain high temperature requires an additional jacket on the kettle body. Due to the large range of temperature changes, the jacket and shell of the kettle are subjected to temperature changes, resulting in temperature difference stress. Electric heating is used, the equipment is light and simple, and the temperature is easy to adjust. At the same time, pumps, stoves, chimneys and other facilities are not required. The start-up is very simple, the risk is small, and the cost is not high, but the operating cost is higher than other heating methods, and the thermal efficiency is below 85%. This method is suitable for places where the heating temperature is below 400 ℃ and the price of electricity is low.
(4) Chemical reactions are usually carried out in order to ensure that the reaction can proceed evenly and quickly, and to improve efficiency, so the reactor is equipped with a corresponding stirring device, which brings about problems such as dynamic sealing of the drive shaft and prevention of leakage.
(5) It is mostly intermittent operation. Sometimes in order to ensure product quality, cleaning is required after each batch is discharged. The top of the kettle is equipped with quick-opening manholes and hand holes for easy sampling, volume measurement, reaction observation and access to the internal maintenance of the equipment.