Technical Calibration and Economic Benefit Analysis of Reinjecting Overhead Cut Water into the Electric Desalting Process at a Heavy Road Asphalt Unit

Abstract: This paper discusses a technical retrofit scheme that reinjects the overhead cut water from the primary distillation tower, atmospheric tower, and vacuum tower back into the electric desalting system. Through process retrofit and calibration analysis of a 3.5 million t/a heavy road asphalt unit, the feasibility of this technology is verified. The results show that the weakly acidic characteristics of the overhead cut water (pH 6.5–7.0) are compatible with the acidic environment required for electric desalting water injection, which facilitates the performance of the calcium removal agent. After the retrofit, the main indicators of the electric desalting cut water (COD, sulfide, petroleum content, etc.) all meet discharge requirements. Although the ammonia nitrogen content fluctuates occasionally, it remains within the acceptable range of the downstream wastewater unit, reducing the specific consumption of stripping water from 0.09 to 0.01, with an estimated annual cost saving of about 525,600 yuan.

Keywords: heavy road asphalt unit; overhead cut water; electric desalting; technical retrofit; economic benefit