Structure of the MRF-Z synthesis tower

Reply to 1# wfy2195: The MRF-Z type reactor of TEC: Figure 3 shows TEC’s MRF-Z reactor. The MRF reactor is a multi-stage indirectly cooled radial flow reactor; forced circulation of water from a shell-and-tube boiler is used to cool the by-product steam. The reaction gas flows radially through catalyst layers located outside the multiple cooling tubes arranged radially, resulting in a multi-stage Z-shaped temperature distribution. This improved temperature distribution helps to extend the lifespan of the catalyst； Radial flow reduces the resistance to gas flow through the bed ； The porous plate ensures uniform gas distribution ； The catalyst is packed outside the tube, which appropriately increases the catalyst packing factor of the reactor and facilitates larger-scale production; however, its structure is complex and manufacturing it is difficult. It is understood that TEC can achieve a production capacity of 5,000 tons per day using a single MRF-Z type reactor; the methanol tower has a diameter of 5 meters, the reactor tubes are 22.4 meters long, and the catalyst loading amount is 350 M3. For a reactor with a capacity of 140,000 tons per year, the diameter is 2.5 meters, the bed height is 12 meters, the catalyst loading is 43 M3, the synthesis pressure is 5.82 MPa, and the catalyst production rate is approximately 0.4 tons/M3·h.

This post was last edited by TH373637 on 2011-6-10 09:55. To overcome the drawbacks of traditional methanol synthesis processes, such as low single-pass conversion rates, high recycle ratios, and high energy consumption, the Japanese companies Toyoe Engineering Corporation and Mitsui Toyo Chemical Corporation jointly developed a new type of energy-saving and consumption-reducing methanol synthesis reactor of the multi-stage indirect-cooling type Radial Flow (abbreviated as MRF). This tower features mature technology, a compact structure, easy operation, and reliable mechanical performance. It has a diameter of 4,700 mm, a height of 14,100 mm, a weight of 420 t, a pressure drop of 0.05 MPa, and a production capacity of 2,500 t/day. 2.5 GJ of heat can be recovered for every 1 t of methanol produced. This synthesis tower was introduced into the 600 kt/a methanol plant of Hainan Ocean Petroleum Fudao Chemical Co., Ltd. in our country, with commissioning planned for 2006; it was also used in the renovation of methanol plants in Trinidad and Tobago. The MRF methanol synthesis tower is a vertical cylindrical pressure vessel, consisting of a pressurized shell, a catalyst basket with a central tube, and vertical boiler tubes connected to the boiler feedwater vaporization header and the steam collection header. The tubes are arranged in several layers of concentric circles and installed vertically above the catalyst bed, perpendicular to the horizontally radial-flowing syngas stream. The boiler feed water enters the cooling tubes from the bottom of the furnace, and the steam generated collects in the steam collection main before being discharged from the top of the tower. The arrangement of the cooling tubes is a patented technology of the MRF synthesis tower. The outer diameter of the cooling tubes is 50 mm, the spacing between the tubes is 150 mm, and they are arranged in an equilateral triangle pattern. The temperature difference across the tube wall is 140°C, the temperature of the bed layer is 260°C, and the temperature of the recovered steam is 120°C. The gas flow in the MRF synthesis tower is as follows: The preheated methanol synthesis gas enters the tower from the bottom along the central pipe and then reaches the outer frame of the catalyst bed. After passing through the adiabatic reaction zone and the heat-exchange reaction zone, which correspond to multiple stages of catalyst beds, the gas flows radially into the annular space between the catalyst frame and the outer shell of the tower. The synthesis gas undergoes reactions as it moves radially, and the heat generated by these reactions is removed in the heat-exchange zone by the production of steam. The gas after the reaction exits the tower through the central tube of the preheater located at the outlet of the synthesis tower. Inside the tower, the heat of reaction is transferred to the boiler tubes via a packing bed with high heat transfer efficiency. The reaction gas also passes vertically through the surface of the tubes; at the same gas flow rate, the heat transfer coefficient in this configuration is 2 to 3 times higher than that of a parallel flow system. According to available information, the advantages of this new type of methanol synthesis tower are as follows: (1) Low gas pressure drop. Since there is only one catalyst bed with radial flow, the path of the syngas through the catalyst bed is short, the flow velocity is low, and the pressure drop is only 1/10 that of a conventional axial tower; (2) more heat can be recovered. The syngas flows vertically across the surface of the boiler tubes, resulting in a high heat transfer coefficient even at low gas flow rates; (3) the temperature is well controlled. The arrangement of the boiler tubes results in a reaction temperature that is nearly in line with the ideal temperature distribution curve, leading to a high methanol yield, with the concentration of crude methanol at the outlet of the synthesis tower exceeding 8.5%; (4) the catalyst has a long service life. The reaction heat is removed promptly and effectively, the bed temperature remains stable, less catalyst is required, and the operation takes place under mild conditions; (5) High production capacity. By combining the tubeless design with a high specific methanol yield, synthesis towers for large or super-large methanol production plants can be manufactured, with a maximum production capacity per unit of 5,000 t/d; (6) it offers significant energy-saving benefits. By reducing the pressure drop inside the tower and the gas circulation speed, the power consumption was reduced by 50%, thereby saving a large amount of energy; the energy consumption per ton of methanol in the synthesis cycle system dropped from 111.6 MJ in the quench tower to 57.6 MJ.