The transformation system high-variation system transformation still uses high-variable string low-variation process. As the water-to-carbon ratio of the conversion system drops to 3.2, the gas volume increases by 3%, the CO content increases, the load of the conversion system increases, the system resistance increases accordingly, and the gas volume of the syngas compressor is affected. In order to meet the production conditions required for the transformation and reduce the energy consumption, the following measures were taken: one additional axial low-pressure furnace was added. In the case of an increase of 15%, the CO content of the low-pressure furnace outlet is reduced from 0.3% to 0.2% to save natural gas consumption. The small low-altering furnace is placed between the original high-altering furnace and the low-altering furnace. Two small low-variable quenching separators are added to control the temperature of the furnace, increase the water-gas ratio, improve the reaction equilibrium conditions, and improve the conversion rate. They are respectively set in the small low-pressure furnace before and after entering the small low-pressure furnace. The shift gas is saturated and quenched by the quenched water to perform gas-liquid separation to prevent the droplets from being carried into the shift furnace.
The high-altering furnace is changed from the axial type to the Casali axis radial mixing flow type to reduce the resistance of the conversion system by about 0.05 MPa, which can solve the problem of increasing the resistance of the conversion system caused by the increased gas volume and the small low-temperature furnace, and can be extended. Change the service life of the catalyst. The transformation of the decarbonization system and the modification of the ammonia decarburization system are mainly to carry out the four-stage flashing of the semi-lean liquid and then send the semi-lean liquid pump.
The flash pressure is controlled by the steam ejector 1107-L. The steam used for the injection is 78% of the low gas produced in the low pressure boiler 1104-C, and the 1104-C boiler feed water is from the regeneration tower top return tank, which is recycled. The heat reduces the entrainment of the lye and reduces the load on the CO2 water cooler. Urea system transformation. The urea plant performs the modification of the hydrogen peroxide anti-corrosion passivation to improve the quality of the urea product and reduce the consumption. In order to cope with the completion of the transformation, it is necessary to reduce the hydrogen content in the CO2 gas to reduce the risk of high-pressure exhaust gas explosion, to ensure the safe operation of the urea, and to recover the H2 flashed in the CO2 gas.
The decarbonization system adds a CO2 upgrading system after the hydraulic turbine. The rich liquid flashes in the flash tank 602-F and enters the regeneration tower. The flash vapor is washed by the lean liquid and the washing water, and then enters the separator 603-F. After that, return to the process system or send it to the flue burner for combustion. After the upgrading system is put into use, the CO2 component of the urea plant sent out from the regeneration tower is raised from 98.5% to 99.5%. Reduce the inlet temperature of the syngas compressor. The inlet temperature of the original syngas compressor is 38 °C. After the transformation, an ammonia cooler 1115-C is added to reduce the inlet temperature of the syngas compressor to 4.5 °C, thus reducing the synthesis gas compression. The water content of the inlet gas of the machine reduces the volume flow of the inlet gas and saves the compression work. The H2 recovery unit is equipped with a device for recovering H2 from the purge gas. The recovered H2 is returned to the syngas compressor, which increases the process air volume of the second stage furnace, thereby reducing the outlet temperature of the first stage furnace and reducing the fuel consumption. .
The original synthesis tower of the synthetic tower is modified into an axial type, which is changed to the radial type of the Casali axis. After the transformation, the resistance is reduced. Therefore, the small particle catalyst is used to greatly increase the activity, the net ammonia value rises, the system pressure drops, and the synthesis tower The increase in export temperature increases heat recovery, reduces compressor energy consumption, and achieves energy savings. Syngas compressor turbine In order to reduce the high pressure steam consumption and the superheated steam coil load of a section of furnace, the high pressure steam turbine 103-JAT is changed into a high efficiency three-stage rotor. The transformation content is: change the original secondary rotor to three Stage rotor; increase radial seal to reduce leakage; adopt full arc and radial blade; modify valve to reduce resistance loss.
The condensate reformed condensate steam reforming condensate was originally designed to use low-pressure steam stripping, which wasted low-pressure steam, and the stripped air body caused secondary pollution to the environment. In order to achieve environmental protection and energy saving, a medium-pressure steam stripping device is added, and the NH3-N in the condensate is extracted by the superheated medium-pressure steam, and part of the condensate is vaporized, and the stripping steam is fed into the conversion section as process steam. It not only ensures the purity of the condensate, but also reduces the environmental pollution. At the same time, the stripped steam is used for conversion, which achieves the purpose of energy saving.
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