1t/h Sodium hydrosulfide single-effect evaporation and concentration equipment

The company's main business is the synthesis of sulfide dyes and organic intermediates. Its hydrogenation reduction and sulfidation reaction processes generate approximately 24 tons of low-concentration sodium hydrosulfide solution daily, with a concentration of only 8% to 12%. Direct transportation for disposal is costly and carries significant transportation risks. To achieve the resource recovery and reuse of sodium hydrosulfide and eliminate the potential for hydrogen sulfide emissions, the company commissioned the construction of a single-effect vacuum evaporation and concentration unit in 2025, with a processing capacity of one ton per hour.

This single-effect evaporation system is specifically designed to address the highly corrosive, easily decomposed, and malodorous characteristics of sodium hydrosulfide. The main body of the equipment is constructed using Hastelloy C276 for the heating and evaporation chambers, which is resistant to corrosion from sodium hydrosulfide and trace amounts of hydrogen sulfide. Equipped with a water ring vacuum pump unit, it maintains a system negative pressure above 0.08 MPa and controls the evaporation temperature between 60 and 65 degrees Celsius, effectively suppressing the risk of hydrogen sulfide gas generation from the decomposition of sodium hydrosulfide at high temperatures. The evaporator employs a forced circulation structure, with a circulation pump driving the solution through the heating tubes at a flow rate of two meters per second. This prevents scaling and clogging of the heat transfer surfaces due to increased viscosity or impurity accumulation during the later stages of concentration. An alkaline spray absorption device is installed in the top gas phase space to instantly neutralize and absorb trace amounts of escaping hydrogen sulfide. The exhaust gas concentration of hydrogen sulfide is measured to be below ten milligrams per cubic meter, meeting the most stringent odor pollutant emission standards.

The system operation is simple and efficient. A low-concentration sodium hydrosulfide solution, after preheating, enters the evaporator and evaporates under vacuum conditions. Water continuously vaporizes and is condensed by the vacuum system. The concentrated liquid is automatically discharged when its density reaches 1.35 grams per cubic centimeter or higher, maintaining a stable concentration between 38% and 40%, and is directly pumped into the synthesis workshop for reuse in the sulfidation reaction. The evaporation condensate, after cooling, enters the greywater reuse system for equipment cleaning and replenishing circulating cooling water, achieving near-zero wastewater discharge.

Since commissioning, this one-ton-per-hour single-effect evaporation and concentration unit has operated stably and reliably. The system boasts a simple structure and convenient operation and maintenance, requiring only one operator for routine inspections per shift. The comprehensive recovery rate of sodium hydrosulfide exceeds 94%, with an annual effective concentration recovery of approximately 700 tons, resulting in savings of over 3 million yuan in raw material procurement and hazardous waste disposal costs. The equipment operates for over 7,000 hours annually with minimal unplanned downtime, validating the technical applicability of single-effect evaporation technology for treating small-batch, highly corrosive, and strongly odorous chemical waste.

The successful implementation of this project provides an economically feasible technical approach for treating sodium hydrosulfide waste from industries such as dyes, leather auxiliaries, and pesticide intermediates. The processing capacity of one ton per hour precisely matches the production rhythm of small and medium-sized enterprises. Single-effect evaporation, with its low equipment investment and simple system configuration, achieves closed-loop recycling of high-value chemical raw materials, combining excellent economic and environmental benefits.