Abstract:

The by-product waste acid from sulfuric acid alkylation unit has a complex composition and strong corrosiveness, making its efficient regeneration crucial for reducing environmental treatment burdens and enabling sulfur resource recycling. Waste acid cracking and regeneration technologies have developed into two main routes, i.e., dry process and wet process, and are gradually evolving toward multi-unit coupling and integrated treatment of various sulfur-containing materials. The dry process can stably produce concentrated sulfuric acid with a mass fraction above 98%, but suffers from long process flow, high investment and energy consumption, and wastewater generation. In contrast, the wet process features compact process flow, efficient waste heat recovery, and zero wastewater discharge; however, it faces challenges such as insufficient removal of fine particulates, system clogging, and fluctuating product acid concentration. Therefore, balancing the stable production of high-concentration sulfuric acid with the low energy consumption and low emissions of the unit has become the core challenge in upgrading waste acid regeneration technology. To address these issues, this paper focuses on reviewing two new technologies, i.e., dry-wet coupling process and hydrogen sulfide - waste acid cracking and regeneration combined process. The former integrates dynamic wave scrubbing, coalescing demisting, steam reheating, and dry air condensation to achieve synergistic process gas purification, moisture control, and energy utilization. The latter enables coordinated treatment of waste acid and sulfur-containing materials such as hydrogen sulfide through acid gas heating, merging of two furnace gas streams, and sharing conversion-absorption system. Engineering operation results show that the dry-wet coupling process achieves an overall dust removal efficiency of up to 99.9%, produces sulfuric acid with a mass fraction exceeding 98%, and improves waste heat recovery efficiency by over 20%. The hydrogen sulfide - waste acid cracking and regeneration combined unit can be operated stably within a wide load range, and the waste acid treatment capacity and operation flexibility can be improved by adopting acid gas heating and sharing conversion-absorption system. This paper further compares the applicable scenarios, technical bottlenecks, and engineering performance of different technical routes, providing theoretical basis and engineering reference for selecting waste acid regeneration schemes, retrofitting existing units, and promoting the integrated utilization of multiple sulfur-containing materials.

Key words: alkylation waste acid')">

alkylation waste acid, sulfuric acid regeneration, dry and wet processes, coupling process, integrated treatment