The application of molecular sieves in acetylene dehydration process is mainly reflected in the drying and purification of acetylene gas. The following is a detailed introduction to the application of molecular sieves in acetylene dehydration process:

1. Basic characteristics of molecular sieves

Molecular sieve is a type of silicoaluminate microporous crystal, composed of silicon and aluminum connected by oxygen bridges to form a basic skeleton structure. The structure has many uniformly sized pores and neatly arranged holes with a large internal surface area. These characteristics enable molecular sieves to selectively adsorb substances, i.e. only those molecules smaller than the pore size of the molecular sieve, especially those with high affinity for polar and unsaturated molecules. At the same time, molecular sieves have strong water absorption capacity, even at high temperatures, high air velocities, and low water content.

2. Basic principles of acetylene dehydration process

Acetylene dehydration refers to the removal of moisture from the raw gas to improve the purity of acetylene gas. The moisture in acetylene gas has adverse effects on the subsequent production process, therefore dehydration treatment is required. The traditional methods for acetylene dehydration mainly include condensation, adsorption, and fractionation, among which adsorption is a commonly used method. Molecular sieves, as adsorbents, have significant advantages in acetylene dehydration processes.

3. Application of Molecular Sieve in Acetylene Dehydration Process

1) Acetylene molecular sieve segmented dehydration process:

a) In this process, acetylene and hydrogen chloride are dehydrated separately. The acetylene drying tower adopts a multi-layer structure for adsorption, usually including a protective layer, an adsorption layer, etc., to ensure that the moisture in the acetylene gas is effectively removed.

b) After saturation of molecular sieve adsorption, regeneration treatment is required. The regeneration process usually includes steps such as nitrogen cold blowing, nitrogen hot blowing, high-temperature cycling, and cooling cycling to ensure the recovery of the adsorption capacity of the molecular sieve.

2) Operation of acetylene molecular sieve drying device:

a) Acetylene gas first enters the water washing tower to remove impurities such as dirt and rust carried by the gas flow.

b) Then it enters the cooler for cooling to further remove moisture from acetylene.

c) The cooled acetylene gas enters the demister to remove water mist and then enters the molecular sieve drying tower for dehydration treatment.

d) The dried acetylene gas enters the subsequent production process.

3) Dehydration effect of molecular sieve:

The molecular sieve drying process can significantly improve the purity of acetylene gas and reduce the moisture content in acetylene. According to monitoring data, the water content volume fraction of acetylene gas processed by the acetylene molecular sieve drying device is within 0.003%, which is much lower than the water content volume fraction of the mixed gas processed by the mixed dehydration process (averaging around 0.052%).

4. Precautions for using molecular sieves

1) The pore size of the molecular sieve must be selected and made according to the actual diameter of the dried raw gas molecules to ensure the adsorption effect of the molecular sieve.

2) The mechanical strength and number of regenerations of molecular sieves are important indicators that affect their lifespan. It is recommended to extend the adsorption time of molecular sieves as much as possible, reduce the number of regenerations, and minimize temperature differences and mechanical wear during the regeneration process.

3) The drying capacity of molecular sieves is limited, and the service life and processing capacity of molecular sieve dryers should be calculated based on the loading amount of molecular sieves at the design pressure.

4) Impurities carried by the feed gas can easily cause blockage of the molecular sieve pores, affecting the drying effect. Therefore, thorough washing and impurity removal should be carried out before the raw gas enters the drying tower.

In summary, molecular sieves have significant application advantages and effects in acetylene dehydration process. Through reasonable process design and operational control, the purity and quality of acetylene gas can be ensured to meet production requirements.