Persian Diary II

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Persian Diary 2: Since the east and west converged, nineteen days have passed. It’s possible to roughly follow the clues and go to the site to find out for oneself; although it’s not thorough enough yet, the outline of the device is gradually becoming clear. It is a massive facility capable of producing 5,000 tons per day of AA-grade methanol; this amounts to 1.5 million tons per year over a period of ten months, or 1.8 million tons per year over a twelve-month period. As one instructor said, driving this time is both a challenge and a rare opportunity to learn. Compared to the devices I remember from before, this setup seems much more sophisticated; it has extremely low energy consumption, which has been very inspiring to me. Due to the addition of saturation and pre-conversion units to the conversion and entire steam system, almost all waste gases, vent gases, even the non-condensable gases from distillation, the exhaust gases from the tank areas, various condensates, wastewater, and waste liquids are all recovered. Gases with a high calorific value are used as fuel gas, while those with a low calorific value are added to the combustion air. In addition to burning for process requirements, the combustion chamber of a furnace functions as an additional incinerator designed for environmental protection and energy savings; it consists of 576 torches capable of recovering heat. Process condensate, steam condensate, and boiler wastewater all flow into the saturation tower. Using the moderately pressurized saturated steam from the syngas vessel as a heat source, these condensates are vaporized in the saturation tower and then brought into full contact with natural gas, thereby converting the \"dry basis\" natural gas into a \"wet basis\" process gas saturated with water. In addition, a small amount of superheated steam is introduced into the process system to help maintain a stable water-to-carbon ratio. The slightly excess condensate from the saturated tower is discharged to the excess condensate storage tank via saturated drainage, and can eventually be sent back to the desalinated water system for reuse. Once all the condensate and wastewater has been recovered, the amount of wastewater discharged becomes extremely small. As for the environmental protection facilities, apart from a flare, it’s hard to believe that this plant doesn’t have any wastewater discharge outlets. Water flows between the tubes of the synthesis tower; copper-based catalysts are installed inside these tubes. The temperature of the catalyst bed is extremely uniform, so there is no need to monitor its temperature. There are no temperature monitoring points in the catalyst bed either; it is sufficient to adjust the pressure in the gas holder based on the temperatures at the inlet and outlet of the synthesis tower. The methanol content in the synthetic crude methanol is as high as 87%; a distillation column at atmospheric pressure is used first, followed by a pressurized column. The fusel oils are collected on the pressurized side, and these fusel oils are directly added to the process steam. The bottom stream containing 59 ppm of alcohol is heated to process steam, saturated with natural gas, and then used in the conversion reaction. This solves the problem of alcohol-containing water. The high-pressure boiler feed pump and the medium-pressure boiler feed pump are combined into one unit; a stream is drawn from between the stages of the high-pressure pump to serve as make-up water for the medium-pressure drum. Most of the make-up water comes from the condensate of medium-pressure steam generated in the saturation unit. In fact, steam between the tubes of the saturation tower heats the process condensate flowing upward to the tower, and then this condensate condenses in the lower tower. It passes through the syngas drum and exchanges heat with the synthesis reaction taking place within the tubes of the synthesis tower, thereby turning back into saturated steam, and this cycle repeats continuously. The portion lost due to wastewater discharge is replenished by adding a small amount of fresh boiler feed water to maintain saturated water balance. The low-temperature waste heat from the converted gas is handled by the reboiler of the distillation tower, replacing the low-pressure waste boiler; there is no longer a need to transfer energy using water as a medium. This results in more direct utilization of thermal energy, lower losses, and also eliminates the need for an additional set of low-pressure boilers. The conversion two-stage furnace and the gas transfer main pipe lack water jackets, and the pure oxygen burner in the two-stage furnace also has no cooling water protection system; the pure oxygen burner burns dry. Two sets of baffles are installed inside the converted waste boiler, which allow for the regulation of the high-temperature gas exiting the second-stage furnace in the flow division; this enables the adjustment of the proportion of waste heat utilized upstream and downstream of the cooling chain, depending on the process requirements. In some domestic conversion processes, pre-conversion is used; there is no secondary furnace, and low energy consumption is achieved by sacrificing part of the lifespan of the primary furnace, with the outlet temperature of this furnace even having to be raised above 850°C. Some have one or two-stage reactors, but no pre-conversion is carried out. Although the conversion tubes are durable and the residual carbon content is low, since the off-gases and condensates are not fully recovered and the distillation process does not make direct use of the waste heat from conversion, the methanol consumption per ton remains high. This system seems to incorporate most of the advantageous features of similar systems available in the world today, namely: desulfurization + saturation + pre-conversion + primary furnace + secondary furnace; all off-gases are recovered and used for hydrogen rebalancing and as fuel. After all, I really want to see what its actual energy consumption will be in the end Electricity, water, gas, steam, and various solvents – plus with this furnace running, the conversion tube won’t turn red anymore! According to available information, 850 cubic meters of natural gas are required to produce one ton of AA-grade refined methanol. It is also equipped with an LTM temperature and load automatic control system, which automatically adjusts the load increase or decrease once operation is successful. It’s just too large – the pressure at the outlet of the synthetic compressor is 80–90 kilograms, and the flow rate is over two million cubic meters. The 32-inch stainless steel high-pressure check valve must have an outer diameter of almost two meters. The methanol vapor pipeline at the top of the low-pressure distillation tower is actually 72 inches in diameter. I imagine that when that compressor with over 50,000 horsepower starts operating, with more than 2 million cubic meters of circulating gas flowing at a pressure of 80 kilograms, what kind of roar would that create… Hehehe, gurgling noises, whooshing sounds, chirping noises～.