The solvent in the exhaust gas of the workshop is often not the same variety: ethyl acetate, acetone, toluene, etc. are commonly mixed in the process of paint matching, cleaning and extraction, and the exhaust gas is naturally a mixed component. The idea of graded condensation is to separate the components with different boiling ranges: the temperature is graded from high to low, the high boiling point components are condensed first, the low boiling point components are condensed later, and each belongs to you. In this way, the recovered liquid is not mixed and the burden on the latter part is small.
When the mixed gas is cooled, the component with the highest boiling point first reaches saturation and starts to condense. The condenser is arranged into several stages according to the temperature. The first stage has the highest temperature level, and high boiling point components are condensed in large quantities here. The gas continues to move forward, the second stage has a lower temperature level, and the medium boiling point component condenses. The last stage has the lowest temperature level, and the remaining light components are cleaned up as much as possible. Each stage is equipped with independent liquid collection and metering, and the recovered liquid is stored separately according to the stage.
The premise of classification is to know the composition of tail gas. Which solvents are used in each process and how the approximate ratio is, this information determines the number of grades and the temperature level of each level, which is the input condition of process configuration.
The principle of temperature level arrangement is to deepen step by step and the gradient is reasonable. The first stage usually uses circulating water or normal temperature refrigerant to reduce the intake air temperature, and the high boiling point components are collected first. This stage has low energy consumption and large recovery volume, which is the most cost-effective section in the whole process. The following stages use the lower temperature level to collect the low boiling point components.
Series is not the more the better. Each level of equipment, piping and control are complex, and the benefits depend on the boiling point difference between the components to cash in. When the boiling range of the components in the tail gas is concentrated, two stages are often enough. Only when the boiling range is open and all of them are worth recovering can three or more be meaningful.
A typical staged condensation system consists of a precooler, a condenser at all levels, a refrigeration unit, a liquid collection and metering device, a pipeline and a control system. The precooler reduces the high-temperature intake air to protect the low-temperature section; the condenser at all levels configures the heat exchange area according to the temperature level; the refrigeration unit provides cold capacity for the low-temperature section; the liquid collection device collects and measures the condensate at all levels separately.
| Device | Location | Function |
|---|---|---|
| Precooler | System Entry | High-temperature intake cooling to protect the low-temperature section |
| Primary condenser | Normal temperature or water cooling temperature level | High boiling point components, the largest amount of recovery |
| Secondary and below condenser | Step-by-step lower temperature level | Low boiling point components |
| Refrigeration unit | Low temperature section matching | Provide cold energy for low temperature condensation |
| Liquid collecting metering device | Outlet of condenser at all levels | Graded collection and separate metering of condensate |
| Control system | System-wide | Temperature monitoring, differential pressure alarm and linkage |
Single component general single-stage condensation can be, classification is for mixed components. However, if the intake air temperature is high, the arrangement of pre-cooling and re-condensation is still necessary, which is different from classification.
Look at the boiling point distribution and recovery requirements of tail gas components. Two stages of components with boiling range concentration are usually sufficient. Only when the boiling range is pulled open and each component is worth recovering can more stages be considered. The more stages, the more complex the system.
Each component is collected separately, and the recovered liquid can be reused without further separation, with guaranteed quality. If mixed collection is carried out, purification and separation links should be added before reuse, and energy consumption and input will come up.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
Mr. Li 13526990215
Hotline
