Post title Release time Views Replies Brief description of the process flow of each section of coking gas purification - crude benzene distillation section

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This post was last edited by Haichuan Laoyu on 2026-7-3 09:05 The 25th National "Safety Production Month" in 2026 Everyone pays attention to safety and everyone will investigate and rectify potential risks on an emergency basis -------------------------------------------------- Why does the crude benzene distillation section need to recycle crude benzene? Crude benzene is a complex mixture of various hydrocarbons. Crude benzene itself has little use. However, benzene, toluene, xylene, trimethylbenzene and other components refined from crude benzene are important raw materials for the production of yellow explosives, plastics, etc. In addition, it also contains unsaturated compounds, sulfides, saturated hydrocarbons, phenols and pyridine bases. The yield of crude benzene is generally 0.75%~1.1% of the dry coal blend, so the gas escaping from the carbonization chamber contains 28~35g/m3 of crude benzene. The main components of crude benzene are distilled before 180°C, and the distillate after 180°C becomes solvent oil. When measuring the content of each component in crude benzene and calculating the yield, the amount of distillation before 180°C is usually calculated as 100%, so the amount of distillation before 180°C is used as one of the indicators to identify the quality of crude benzene. The amount of crude benzene distilled before 180°C depends on the process flow and operating system of the crude benzene section. The more distillation volume before 180℃, the better the quality of crude benzene. Generally, the distillation volume of crude benzene is required to be 93% to 95% before 180°C. 1. Process flow: The rich oil sent from the final cooling benzene washing device is sent through the oil-steam heat exchanger, the poor-rich oil heat exchanger, and then heated to 190°C by the tubular furnace before entering the benzene removal tower, where the direct steam from the regenerator is used for stripping and distillation. The crude benzene vapor escaping from the top of the tower passes through the oil-vapor heat exchanger and the crude benzene condensation cooler and then enters the oil-water separator. The separated crude benzene is sent to the crude benzene reflux tank, part of which is sent to the top of the tower by the crude benzene reflux pump as reflux, and the rest enters the crude benzene intermediate tank, and is then pumped to the oil depot by the crude benzene product pump. The lean oil discharged from the lean oil tank at the bottom of the benzene removal tower is cooled to 27-29°C by a hot lean oil pump through the lean-rich oil heat exchanger and the first and second stage lean oil coolers, and then goes to the final cooling benzene washing device. At the top of the benzene removal tower, there is a broken tray and an oil-water separator outside the tower to lead out the water accumulated at the top of the tower and stabilize the operation. The naphthalene oil fraction is drawn from the side line of the benzene removal tower to reduce the naphthalene content in the lean oil. The extracted naphthalene oil fraction enters the residue tank. In order to ensure the quality of the washed oil, 1 to 1.5% rich oil is drawn from the lean oil from the hot lean oil pump and sent to the regeneration tower for steam blowing and regeneration with superheated steam from the tubular furnace. The regeneration residue is discharged into the residue tank and pumped to the oil depot. The separated water discharged from each oil-water separator is discharged into the separation water tank through the control separator, and is sent to the remaining ammonia water tank of the condensation blower device by a pump. The non-condensable gas from each storage tank is centrally directed to the gas suction pipe. 2. Process characteristics 1) The upper section of the benzene removal tower is equipped with a broken tray to prevent water accumulation on the tray and facilitate the operation of the benzene removal tower. 2) The tube of the tube furnace is made of stainless steel. 3) The rich-poor oil heat exchanger and the oil-vapor heat exchanger are made of stainless steel. 4) The gas released from each storage tank is sucked back into the gas pipeline through the pressure balance system, and the waste gas is not discharged outside. 3. Main technical operating indicators: Rich oil temperature after the tubular heating furnace 190°C Top temperature of the debenzene tower 92°C Lean oil temperature at the bottom of the debenzene tower 185°C Superheated steam temperature entering the regenerator 400°C Lean oil temperature after the two-stage lean oil cooler 27~29°C Bottom pressure of the debenzene tower 0.04MPa Top pressure of the regeneration tower 0.05MPa 4. Main environmental protection measures 1) The gas released from each storage tank is sucked back into the gas pipeline through the pressure balance system, and the waste gas is not discharged outside. 2) The vented water, vented oil and leakage liquid in the system are collected and collected into the underground venting tank, and then returned to the system without being discharged. 5. Working principle of main equipment Tube furnace The tube furnace consists of three parts: a cylindrical radiation chamber, a rectangular convection chamber and a chimney. Along the length of the furnace tube, the distribution of heat intensity is uneven. Generally, small cylindrical furnaces have a radiation cone made of high-chromium-nickel alloy steel above the radiation chamber. Its radiation effect can increase the thermal intensity of the upper part of the furnace tube, so that the furnace tube is heated more evenly along the length direction. The convection chamber is placed above the radiation chamber, and the convection tube is placed horizontally. Among them, the two rows of horizontal pipes close to the radiant section are superheated steam pipes, which are used to superheat the direct steam for debenzene removal to above 400°C. The remaining rows of pipes are used for preliminary heating of rich oil. The rich oil with a temperature of about 130℃ first enters the convection section in two passes, and is heated to 180~200℃ before going to the benzene removal tower. Regenerator The middle part of the oil washing regenerator is equipped with a feed pipe with a distribution device, and the lower part is equipped with a residue discharge pipe. In order to reduce the evaporation temperature of the wash oil, a direct steam pipe is provided at the bottom of the regenerator, which introduces most or all of the steam required for debenzene distillation. Two arc-shaped partitions are placed below the rich oil inlet pipe to increase the steam level of the oil wash in the regenerator. Three block-shaped partitions are installed above the rich oil inlet pipe to capture oil droplets. The oil gas and superheated steam from oil-rich regeneration enters the bottom of the benzene removal tower from the top of the regenerator as oil-rich benzene removal steam. The partial pressure of the crude benzene vapor in this steam is close to the crude benzene vapor pressure on the hot lean oil liquid surface of the debenzene removal tower. It is difficult to further reduce the benzene content of the debenzene-depleted lean oil. The benzene mass content of the lean oil is generally around 0.4%. The bubble cap benzene removal tower heated by a tubular furnace is divided into two sections, the upper section is the rectification section and the lower section is the stripping section. The distillation section is equipped with 8 trays, each tray has several circular bubble caps, and the distance between the plates is 600mm. The second tray and the bottom tray of the rectification section are broken trays so that the liquid mixed with condensed water on the trays can be directed to the oil-water separator. After the water is separated, it is returned to the lower tray in the tower to prevent the normal operation of the distillation tower from being damaged by the accumulation of condensed water in the tower. The stripping section is equipped with 3 trays with a spacing of 1000mm. There are several round high bubble caps and coil heaters on each tray to maintain a high liquid level on the tray so that it can submerge the heater. Heavy benzene is discharged from the bottom of the stripping section. 6. The main factors that affect the recovery of crude benzene. The factors that affect the recovery rate include the content of crude benzene in the gas and wash oil, gas flow rate and pressure, wash oil circulation volume and molecular weight, absorption operating temperature, and benzene absorption tower structure.