The open-type flat-lid structure reactor has two types: flat end flange type and flat cover reverse flange type. The design concepts of these two structures are basically the same, but the flat cover reverse flange type is more expensive than flat cover. The flange type of the cover end is cheaper. The design concept is based on certain chemical products that require higher pressure (4.0-35Mpa) during the production process, without too much restriction on temperature, and small volume (below 3000L). Because the open structure is more convenient for equipment maintenance and disassembly, especially for highly toxic and flammable chemical products, this structure can improve the working environment of workers and reduce their labor intensity. Because this structure is suitable for higher pressure and the barrel is thicker, the processing cycle is longer.