SO3 gas goes through SO3 filter with precise concentration (%), then reacts with organic raw material in the reactor. The reaction heat is removed by recycle cooling water in the reactor shell side. The exhaust gas goes to the exhaust gas treatment unit by passing the gas-liquid separator and cyclone separator; the organic acid goes to aging and stabilization unit or neutralization and dioxane stripping unit.    The flow rate of organic raw material is controlled by a mass flow meter and control valve (or VFD of gear pump); the liquid level in the gas-liquid separator is controlled by a level transmitter and VFD of discharge pump; the flow rate and density of organic acid are detected by a mass flow meter and its density is cascade controlled to adjust the raw material flow rate. The recycle cooling water inlet temperature remains constant by supplement water; cooling water flow is adjusted by the control valve, whose rate depends on the water temperature difference of the reactor in each path.     Features: WEIXIAN has more than three important improvements to increase the reliability of the reactor. Meanwhile, the size of each reactor tube, distributor, and nozzle is in high uniformity. The reactor tube is treated by high precision rolling and oxygen-free annealing process, which makes the finish degree of all tubes and each part of the tube of high uniformity. Compared to the competitors' technology, our plant has longer continuous running time and lower dioxane when producing SLES.