Elution benzene process flow

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The benzene washing process starts with the raw gas from the thiamine production section; after being cooled in the final cooling tower, this gas enters the benzene washing tower at its bottom. It moves upward through the packing layer of the tower, where it comes into countercurrent contact with the circulating washing oil sprayed from the top of the tower. The benzene contained in the gas is absorbed by this circulating washing oil, and after mist droplets are removed in the mist capture section of the tower, the gas is sent on to the desulfurization section. The rich oil at the bottom of the benzene washing tower is pressurized by a rich oil pump and sent to the crude benzene condenser, where it exchanges heat with the crude benzene vapor coming from the top of the debenzing tower, thereby preheating the rich oil to around 60°C. It then goes to an oil-to-oil heat exchanger to exchange heat with the hot lean oil coming from the bottom of the debenzing tower, rising in temperature from 60°C to around 130°C; ideally, it should be sent to a crude benzene tubular furnace to be heated to around 180°C before entering the debenzing tower. The crude benzene-liquid mixture vaporized from the top of the debenzing tower enters the crude benzene condenser, where it is cooled to around 30°C by the oil-rich stream coming from the bottom of the crude benzene tower and by refrigerated water at 16°C. Subsequently, it enters the crude benzene oil-liquid separator; the separated crude benzene is sent to the crude benzene reflux tank. Part of this crude benzene is fed back to the top of the debenzing tower as reflux, while the remaining portion goes into the crude benzene storage tank. Periodically, it is pumped by crude benzene transfer pumps to the storage tanks in the finished product area for storage and subsequent sale. List of Main Equipment for Benzene Elution Unit
Serial Number | Equipment Name | Specification Model | Unit | Quantity | Remarks
1 | Rich and lean oil pump | Q=100m3/h, H=76m | Set | 3 | —
2 | Motor | N=45kW, Voltage 380V | Set | 3 | —
3 | Crude benzene transfer pump | Q=30m3/h, H=50m | Set | 2 | —
4 | Motor | N=11kW, Voltage 380V | Set | 2 | —
5 | Crude benzene return pump | Q=2–9m3/h, H=40–60m | Set | 2 | —
6 | Motor | N=5.5kW, Voltage 380V | Set | 2 | —
7 | Condensate transfer pump | Q=7.5–15m3/h, H=50m | Set | 2 | —
8 | Motor | N=15kW, Voltage 380V | Set | 2 | —
9 | Submersible pump for underground vent tank | Q=28.8m3/h, H=24.5m | Set | 1 | —
10 | Motor | N=5.5kW, Voltage 380V | Set | 1 | —
11 | Fuel heat exchanger | F=250m2 | Set | 3 | —
12 | First-stage rich oil cooler | F=200m2 | Set | 2 | —
13 | Second-stage rich oil cooler | F=200m2 | Set | 2 | —

The desulfurization and sulfur recovery process: The crude gas from the benzene elution unit first enters the lower part of the desulfurization tower, where it comes into countercurrent contact with the desulfurization liquid sprayed from the top of the tower. As a result, the H2S content in the gas is reduced to ≤0.02g/Nm3. After the mist droplets are removed in the mist removal section, the gas exits the desulfurization tower. Part of this gas is sent to the coke oven as recycled gas, another part is used as fuel in the crude benzene tubular furnace, and the remaining portion is sent to the 200,000-ton/year methanol project at Shaanxi Shanjiao. The desulfurization solution, which has absorbed H2S and HCN from the desulfurization tower, is sent to the solution circulation tank. From there, it is pumped to the lower part of the regeneration tower where it undergoes regeneration in parallel with the compressed air supplied by the air compressor station. The regenerated desulfurization solution is then returned to the top of the desulfurization tower for cyclic spraying to carry out desulfurization. Sulfur foam is discharged from the expanded section at the top of the regeneration tower into the sulfur foam tank, and then pressurized by a sulfur foam pump before being sent to a centrifuge to produce sulfur paste, which is sold externally. List of Main Equipment for Desulfurization and Sulfur Recovery Units
Serial Number | Equipment Name | Specification Model | Unit | Quantity | Remarks
1 | Solution circulation pump | Q=576–972 m3/h, H=50–60 m | Unit | 3 | —
2 | Motor | N=220 kW, Voltage: 10 kV | Unit | 3 | —
3 | Sulfur foam pump | Q=18.5 m3/h, H=40 m | Unit | 2 | Motor: N=11 kW, Voltage: 380 V
4 | Alkali solution transfer pump | Q=3.8 m3/h, H=40 m | Unit | 2 | Motor: N=2.2 kW, Voltage: 380 V
5 | Centrifuge | Dimensions: 1950×1380×1100 mm | Unit | 1 | Motor: N=5.5 kW, Voltage: 380 V
6 | Solution heat exchanger | F=100 m2 | Unit | 3 | —