Process principle, flow diagram, and characteristics of the waste gas condensation recovery unit

　　 Waste Gas Condensation and Recovery Unit It is suitable for the recovery of a wide range of volatile VOCs and can meet the requirements of different condensation temperature ranges. Now, let’s take a look at the process principle, flow diagram, and key features of the waste gas condensation recovery unit.

　　I. Condensation Process of the Waste Gas Condensation and Recovery Unit

　　1. Collect the dichloromethane gas discharged from each vent (such as the swan‑neck outlets) into a centralized main intake duct.

　　2. The main pipeline pressure sensor feeds the pressure signal back to the control system;

　　3. The collected dichloromethane vapor is routed to the dichloromethane condensation and recovery unit. In the condensation section, the vapor undergoes staged cooling to condense most of the dichloromethane into liquid form, which is then directly recovered into downstream storage tanks. Any uncondensed gas is reheated and sent to downstream equipment for further processing.

　　II. Waste Gas Condensation and Recovery Unit Process Principle

　　1. Pure condensation technology for waste gas condensation and recovery units;

　　The waste gas condensation and recovery unit employs a multi-stage condensation process to progressively cool the dichloromethane vapor to approximately −70°C (with the temperature profile adjustable according to actual requirements), directly liquefying and recovering the majority of the dichloromethane from the mixed gas, while the remaining trace amounts are routed to downstream processes.

　　2. Dichloromethane Gas Condensation and Liquefaction Separation System

　　Methylene chloride vapor enters the condensation unit for multi‑stage condensation (with adjustable cooling levels at each stage) and then passes through a heat exchanger, where it is cooled to −40°C. Most of the condensed methylene chloride liquid is routed via the heat exchanger’s hot‑water outlet into a recovery tank. The low‑temperature, low‑concentration uncondensed methylene chloride gas separated during condensation is further cooled in a cryogenic heat exchanger, where any remaining methylene chloride in the gaseous phase is liquefied. The resulting liquid is discharged into the tank through the heat exchanger’s hot‑water outlet. The residual low‑concentration non‑condensable exhaust gas is returned to the upstream heat exchanger for heat exchange; upon exiting, its temperature has been restored to near ambient conditions. At this point, the thermal recovery and utilization cycle for the methylene chloride stream is complete.

　　3. Low-temperature condensation principle:

　　The waste‑gas condensation and recovery unit receives high‑temperature, high‑pressure refrigerant vapor discharged from the compressor, which then enters the condenser and is condensed into a high‑pressure subcooled liquid. This liquid is throttled by the expansion valve, reducing its pressure and temperature to a low‑temperature, low‑pressure liquid phase that flows into the dichloromethane air‑cooled tank collector (comprising multi‑stage heat exchangers). There, it exchanges heat with dichloromethane vapor, causing the vapor to condense. The condensed dichloromethane—of varying concentrations—transfers its heat to the low‑temperature refrigerant, thereby cooling down. Leveraging the differences in saturation vapor pressure at different temperatures, the system lowers the temperature to induce supersaturation and condensation of the dichloromethane vapor, enabling direct liquid recovery. A small portion of the remaining gas is routed back to the condensation unit for further processing.

　　III. Waste Gas Condensation and Recovery Unit System Installation

　　1. Automatic Control System for the Waste Gas Condensation and Recovery Unit

　　The system is configured with an industrial‑grade programmable controller, a user‑friendly LCD display, and a Chinese‑language menu interface, enabling real-time monitoring of the unit’s operating status. It features robust control logic, strong anti‑interference capabilities, and excellent resistance to cold and heat, along with rapid response. Operational management functions: The unit automatically shuts off power during designated operating dates and time periods, and dynamically adjusts its operating mode based on the consumption of dichloromethane, ensuring that the system remains in energy‑saving mode at all times.

　　Fault self-diagnosis function: The system is equipped with multiple protection features, including motor overheating, current overload, fan interlock, phase loss, over‑range high/low voltage, start‑up delay, and high liquid level in the recovered dichloromethane tank. When a fault occurs, the equipment triggers an audible alarm and shuts down.

　　2. Process Flow and Equipment Design

　　The waste gas condensation and recovery unit is equipped with a gas–liquid separation device to prevent recovered dichloromethane from being carried into the exhaust‑gas discharge equipment or the downstream adsorption system in the event of blockage in the dichloromethane flow path. The unit’s cabinet is constructed of stainless steel, and all internal dichloromethane and gas pipelines and valves are also made of stainless steel. The dichloromethane vapor‑capture heat exchanger employs a copper‑tube, stainless‑steel‑fin design.

　　3. Electrical Design

　　The exhaust gas condensation and recovery unit is equipped with multiple protective features, including motor overheating protection, overcurrent protection, overpressure protection, undervoltage protection, and start-up delay, ensuring reliable operation of the unit.