Introduction to Johnson Filter (Reforming Reactor Internal Components)

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Introduction to Johnson Screen Q: What is Johnson Screen? Answer: Johnson Screen, also known as slit screen, is an industrial screen developed by Johnson Company. It consists of special-shaped metal wires and support rods of different shapes, which are continuously welded by a specially designed resistance welding machine. Its structural form is detailed in Figure 1. The slit screen can be made into a flat plate shape, or into a cylindrical, semicircular, fan-shaped and other shapes, and its special-shaped metal wires can be arranged in vertical strips or rings. Figure 1 Structural diagram of slit screen (flat plate and cylindrical) Q: What are the characteristics of slit screen? Answer: In the past, metal wire screens were mostly used in industry. Due to the large contact area between solid particles (catalysts, molecular sieves and various filter materials) and the wire mesh, the particles are easy to block and get stuck in the square holes of the wire mesh, causing an increase in pressure drop and making the device inoperable and maintenance difficult. However, the slit screen has only two points of contact with the solid particles, so it is not easy to block and get stuck. The comparison between slit screen, wire mesh and porous plate is shown in Figure 2. Figure 2 Comparison of the advantages and disadvantages of the slit screen and the metal wire mesh structure The slit screen has the following characteristics: 　　(1) The opening range is larger and the opening rate is higher. 　　(2) Every intersection point of the special-shaped metal wire and the support rod is welded, so the accuracy is high and the gap is accurate. 　　(3) There are only two points of contact between the continuous gaps and solid particles, which is not easy to block. 　　(4) The surface is smooth, the catalyst wears less, the particles are not easily crushed, and the surface roughness of the screen bars can be as low as 6.3 μm. 　　(5) Continuous gaps and smooth surfaces make the catalyst flow smooth. 　　(6) The screen mesh combined with different gap sizes and special-shaped metal wires and connecting rods has good strength. If the operating conditions are harsh and the load is large, reinforced materials and large-section connecting rods can be used, and the tensile force of each welding point can reach 2000~3000 N. 　　(7) According to the process requirements, there is a large range of choices. 　　(8) Long service life, easy to install, light weight and more economical. 　　ask: What are the uses of slit screens in the petrochemical industry? Answer: In refineries and petrochemical plants, it is mainly used in the fan-shaped barrel, central tube, inner basket and outer basket of the radial reactor in the catalytic reforming unit. ； Inlet distributor, fouling basket, catalyst bed support grid, outlet collector, etc. in general reactors ； Also used in filter tubes, centrifuge filter baskets and vibrating screens. It is versatile and can be specially designed according to process requirements. 　　 　　ask: What are the specifications of the special-shaped metal wires and support rods of the slit screen? Answer: There are many types of specifications. Figure 3 introduces the specifications of various special-shaped metal wires and support rods from a foreign company (the inch series and numbers of other companies will not be detailed). There are also wire specifications of 3.5, 4.0, 4.5 and 4.8 mm. Figure 3 Specifications of special-shaped metal wires and support rods: What materials are used to make slit screens? Answer: Different materials are selected according to process conditions. The most commonly used ones are austenitic stainless steel 304, 304H, 321, 321H and 316L. In addition, Cu-Ni alloy, alloy 400, alloy 600, alloy 800, titanium and carbon steel can be used. 　　ask: Who are the manufacturers of slit screens? Answer: There are several foreign manufacturers in the United States, France, Japan and Australia. Domestic manufacturers currently certified by Sinopec Group include Tangshan Fengnan Screen Factory and Liaoyang Petrochemical Fiber Company Fuda Machinery Factory. The former has manufactured slit screens for more than 20 sets of catalytic reforming units in China. ； The latter's products have been used in the catalytic reforming unit of Liaoyang Petrochemical Fiber Company, the gas stripping unit of Fushun Ethylene Chemical Company, and the styrene unit of Dalian Petrochemical Company. The product quality has been well received.