3D Process Flow -- Aromatic Hydrocarbons Complex Plant Process Flow
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The aromatics complex is a core unit in modern petrochemical industry, and its main task is to convert naphtha and cracked gasoline into basic petrochemical intermediates: benzene, toluene, and xylene (collectively referred to as BTX). A typical aromatic complex is composed of several core process units that are closely coupled through complex material circulation and heat integration. The following three high-precision 3D engineering cross-sections detail the entire manufacturing process, from raw material preprocessing to the refinement of the final product. 1. Raw material pretreatment and aromatic formation (NHT & CCR) This section describes the upstream processes of the plant. The feed naphtha is first processed in a hydrogenation unit (NHT) to remove impurities, providing qualified feedstock for downstream processes. Subsequently, the refined naphtha enters the continuous catalytic reforming unit (CCR), which serves as the \"aromatic compound generator\" of the entire plant, converting aliphatic hydrocarbons into aromatic compounds. NHT unit (upper section): The feed naphtha is pumped and heat-exchanged, then heated to the reaction temperature in a heating furnace before entering the fixed-bed hydrogenation reactor (R-101). After cooling and separation of the reaction effluent, light components are removed in a stripping tower (C-101), yielding refined naphtha at the bottom of the tower. CCR unit (lower section): Refined naphtha is mixed with recycled hydrogen; after being heated in a large Packinox shell-and-tube heat exchanger and a primary heater, it enters a unique “overlapped” reactor bank (R-201A-D). The reactant materials undergo endothermic reactions in four series-connected radial flow reactors, with multiple heating steps in between. The raw catalyst flows out from the bottom and is sent to the catalyst regeneration tower at the top via a lift pipe for continuous regeneration.
2. Aromatic extraction and benzene-toluene fractionation: The C6-C7 fraction from the reforming unit is rich in benzene and toluene, but still contains non-aromatic compounds. This section describes the process of separating aromatic and non-aromatic compounds using sulfolane as a solvent, and obtaining high-purity benzene and toluene products through distillation. Aromatic extraction (upper section): The C6-C7 feed enters the middle part of the main extraction column (C-301), where it comes into countercurrent contact with the lean solvent flowing from top to bottom. The oil extracted from the top of the tower is sent out after washing with water ； The rich solvent at the bottom of the tower enters the stripping tower (C-303) and the vacuum-operated solvent recovery tower (SRC, C-304) in sequence, where the mixed aromatics (extract) and lean solvent are separated. BT fractionation (lower section): After the mixed aromatics have had trace amounts of olefins removed in the clay tower (D-401), they enter the benzene tower (C-401), from whose top high-purity benzene is produced. The material at the bottom of the tower is fed into the toluene tower (C-402), from where toluene is produced; the heavy aromatics at the bottom of the tower are sent to the xylene circuit.
3. The discrimination and xylene loop (Tatoray & Xylene Loop) is the most complex and highly integrated part of the plant, designed to maximize the production of high-value p-xylene (PX). It includes a disproportionation unit that converts toluene and C9 into benzene and xylene, as well as a closed-loop cycle consisting of xylene distillation, adsorption separation (Parex), and isomerization (Isomar). Disproportionation unit (upper section): Toluene and C9 aromatics are mixed with hydrogen; after being heated in a heater, they enter a fixed-bed reactor where they undergo conversion. The products are separated in a stripping tower, and the material at the bottom of the tower is recycled back to the benzene tower or xylene tower. Xylene circuit (main body): C8+ aromatics from multiple streams are fed into the giant xylene tower (C-601). The mixed xylene at the top of the tower enters the Parex unit, where high-purity PX product is separated through complex rotary valves and multi-bed adsorption chambers (A/B). The raffinate with low PX content enters the Isomar unit, where it is re-isomerized into xylene of equilibrium composition in a radial flow reactor. After separation in a heptane removal column, it is recycled back to the xylene column, creating a closed loop to increase the overall PX yield.
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