Is sodium hypochlorite or concentrated sulfuric acid better for purifying acetylene gas?
Thread Content
Acetylene gas contains impure gases such as sulfur and phosphorus, which need to be purified. But is sodium hypochlorite a good choice for a cleaning agent? Is concentrated sulfuric acid still the better choice? Compared to concentrated sulfuric acid, which one has stronger oxidizing power: sodium hypochlorite or concentrated sulfuric acid? It’s best to have theoretical support. Thank you all!
It is sufficient to properly purify acetylene gas; the method of purification to be used is determined by the way in which calcium carbide slag is utilized.
Reply to 2# xhzmq: Without considering wastewater reuse, this is merely a comparison of the oxidizing strength of hypochlorite and concentrated sulfuric acid.
Concentrated sulfuric acid still has a stronger oxidizing power.
Currently, some enterprises use sulfuric acid for cleaning processes, but dealing with the waste acid resulting from this cleaning is rather troublesome. Sodium hypochlorite-based cleaning generates a large amount of wastewater, and for enterprises that also produce cement, there is the need to consider the utilization of power plant slag. Nevertheless, today’s enterprises tend to opt for sulfuric acid cleaning processes.
It depends on what your supporting processing system is Using concentrated sulfuric acid for cleaning yields good results, but it is highly oxidizing; therefore, a method must be found to handle the waste acid generated. If there is a subsequent use for this acid in fertilizer factories or if there are methods for its treatment, then concentrated sulfuric acid can be used for cleaning. If it is for integrated cement production, it is still better to use sodium hypochlorite as a cleaning agent. It should be noted that if PVA is produced using dry acetylene, it is necessary to use concentrated sulfuric acid for cleaning, as the vinyl acetylene present in dry acetylene can affect the quality of the PVA product. By using concentrated sulfuric acid, a strong oxidizing agent, to oxidize the vinyl acetylene, its impact on the quality of the PVA product is eliminated.
In calcium carbide-based acetylene production plants, the hyposodium cleaning process is used in the vast majority of cases, while concentrated sulfuric acid cleaning is only being gradually adopted. 1. The main problem with sodium hypochlorite cleaning is the system level balance issue, whereas the wastewater generation in the concentrated sulfuric acid cleaning process is lower than that in the sodium hypochlorite process. If the water balance issue cannot be resolved, environmental pressures will drive companies to adopt concentrated sulfuric acid cleaning processes. 2. The concentrated sulfuric acid cleaning process requires consideration of waste disposal issues; if there are no fertilizer factories in the vicinity, the cost of disposing of the resulting waste will be very high. If the calcium carbide contains high levels of sulfur and phosphorus impurities, the waste generated by the concentrated sulfuric acid process (mainly sulfides) is very smelly, resulting in a poor working environment. 3. The acetylene gas produced by the dry acetylene process contains a large number of impurities (according to our analysis of samples sent for testing, there are more than 40 types of organic compounds, such as benzene and its derivatives, vinyl acetylene, etc.). The purification process must be selected by taking into account the requirements of downstream users.
I. Problems associated with using sodium hypochlorite for drying: 1. A large amount of wastewater is generated. Although currently, waste sodium hypochlorite is combined with concentrated sodium hypochlorite to **reduce the volume of wastewater discharged, a certain amount of wastewater still has to be released due to concentration issues. 2. It is very important to control the concentration of sodium hypochlorite; explosions can occur easily if the effective chlorine content of sodium hypochlorite exceeds 0.15% or when the temperature is high, posing significant safety risks ； 3. Acetylene gas after secondary treatment contains a high level of moisture, which also poses difficulties for subsequent processing. II. Advantages: 1. Mature manufacturing process. 2. There is no issue with purchasing concentrated sulfuric acid or selling it; the sodium hypochlorite produced internally is sufficient to meet the production needs. III. Basic principle of purification using concentrated sulfuric acid: 1. Purification with concentrated sulfuric acid takes advantage of its pre-oxidizing property, which allows it to effectively absorb trace impurities such as hydrogen sulfide and phosphine present in acetylene gas, converting them into acidic gases that can be removed. 2. Utilize the strong water-absorbing capacity of concentrated sulfuric acid to remove trace amounts of moisture from acetylene gas. Disadvantages of drying with concentrated sulfuric acid: 1. High temperature – concentrated sulfuric acid has a strong oxidizing effect on acetylene gas; above 50 degrees Celsius, acetylene undergoes severe decomposition and carbonization reactions under the action of concentrated sulfuric acid, preventing the production equipment from functioning properly. Concentrated sulfuric acid turns black, the top and bottom of the tower get clogged, and the pressure difference increases. So, under normal circumstances, acetylene gas is cooled to around 7 degrees. 2. Concentrated sulfuric acid releases a large amount of heat when it absorbs moisture, and excessive moisture can raise the temperature of the material. 3. The equipment must have excellent resistance to corrosion by both concentrated and dilute acids.