The previous generations of packing elements are made of rigid structure that has high structural strength but low mass transfer area. As the knowledge of mass transfer became more advanced, it was quickly discovered that the absorption process is actually a mass transfer process. The current generations of packing elements are made of flexible structure that provides a large mass transfer area but has low structural strength.
The packing element has rigid structures that provide strength and flexible structure that provides mass transfer area. The performance of the new packing element was measured based on pressure drop performance and mass transfer performance. Two methods were used to analyze the pressure drop and mass transfer performance; analytical and experimental method.
Besides that, experiments performed on mirv-1 show that the pressure drops and mass transfer performance of mirv-1 are within the acceptable range used in industry. In addition, I would like to express my gratitude to TESCO for providing the necessary material to construct the new packaging element.
INTRODUCTION
- Background of study
- Packing elements
- Problem Statement
- Objectives
- Scope of study
The function of the packed bed is usually to improve the contact between the two liquid phases in the process. The drawback of the new generation packing element is that, although the packing can provide a high mass transfer area, the flexible structure will be crushed or deformed at the bottom of a packed tower if the packing height is high. This is due to the weight of the top pack exerting force on the bottom pack.
The next generation sealing element can be a combination of the rigid structure of the previous generation packaging elements and the flexible structure of the new generation of packaging elements. To study the characteristics/performance of the newly developed charging element and compare it with other existing charging elements present in the market. In this phase of the project, the properties/performance of the new packaging element will be analyzed through experimentation and/or use of the developed ones.
In this phase of the project, the performance of the new packaging element will be compared with existing packaging elements in the industry using existing data. The final conclusion will be made based on the results of the study on the characteristics/performance of the new charging element and the comparison of the performance of the new charging element with the existing charging elements in.
LITERATURE REVIEW
Mass transfer efficiency
The formula for volumetric mass transfer coefficient was developed based on the combination of equations developed for liquid phase mass transfer coefficient, βL, and effective interfacial area for mass transfer per volume unit, ae. According to Mackowiak (2011), the effective interfacial area for mass transfer per unit volume, ae, identical to the droplet surface, while the total liquid content, hL, corresponds to the droplet's liquid accumulation. According to equation (3), the effective interfacial area for mass transfer per unit volume, ae, is directly proportional to the specific liquid accumulation, hL, and is inversely proportional to the average droplet diameter, dT.
Based on equations (5) and (6), the effective interfacial area for mass transfer per volume unit, ae, directly proportional to the geometric surface area of packing per volume unit, a, which is determined by the design of the package. Therefore, packing design with a high surface area per volume packing contribute to a high effective interfacial area for mass transfer per volume unit, e.g. Effective interfacial area for mass transfer per unit volume, ae, is inversely proportional to the average droplet diameter, dT.
Based on equation (14) and (15), the volumetric mass transfer coefficient, βL.ae, is proportional to the geometric area of the package per unit volume, a. This shows that the volumetric mass transfer coefficient, βL.ae, is affected by the design of packaging.
Pressure drop and Ergun’s equation
Based on equation (21), the pressure drop across a packed bearing is inversely proportional to the void fraction of the bearing, e, and equivalent spherical diameter of the packing element. For a packing with a high void ratio and large equivalent spherical diameter of the packing element, the pressure drop across the packed bearing can be almost zero. Another important thing to note is that the pressure drop across a packed bed is directly proportional to the superficial velocity of the fluid, the fluid density, and the length of the packed bed in the column.
Therefore, a column with a long packed bed will have a higher pressure drop compared to a column with a shorter packed bed. In addition, operation at high liquid and gas loads will cause a large pressure drop across the packing bed. The constant k2 describes the ratio of the turbulent flow to the pressure drop across the packed layer, while k1 describes the ratio of the laminar flow to the pressure drop across the packed layer.
This equation is a linear equation and value k1 and k2 can be compared between different packing elements.
Packing design for packed towers
2013), a combination of the rigid structure of the previous generation and the flexible structure of the new generation can be used to develop the next generation of packing elements.
Wetted wick
According to equation and (14), the higher the geometric surface area of the packaging, a, the higher the effective interfacial area for mass transfer per unit volume of packaging, ae. According to Lee and Hwang (1989), the wet-core absorption column offers many features that improve the disadvantages observed in conventional packed tower.
Designing the new type of packing elements …
Conducting experiment
The hydrodynamic performance of the new packing element is evaluated based on the pressure drop of the packing element in a packed column. The mass transfer efficiency of the new packing element is evaluated based on aspects such as mass transfer rate, HETP, volumetric mass transfer coefficient and wetting efficiency. The Ergun equation and correlations from Mackowiak (2011), Schultes (2011) and Higbie (1935) are used to evaluate the performance of the new packaging against other packaging elements in the industry.
Based on Figure 7, air is supplied from the lower side of the column and exits at the upper side. Water is supplied from the upper side of the column and collected on the lower side. A new packing element is placed in the middle of the column as shown in Figure 8.
When air comes into contact with water, some water will evaporate into the air, causing an increase in air humidity. To perform the experiment, one of the parameters to be measured is the flow rate of the inlet air through the absorption column. From the continuity equation, the velocities can be replaced by the flow cross-sectional areas and the volumetric flow rate Q;.
The actual flow profile at location 2 downstream of the orifice is complex, making the effective value of A2 uncertain. For the experiment, I designed an orifice flowmeter to measure the velocity of air flow entering the packed column. The design basis for the designed nozzle flow meter is summarized in the following table;.
To calculate the volumetric flow using equation (21), the air density can be found in the psychrometric chart based on the dry and wet bulb temperatures of the inlet air. Based on the orifice design, an Excel spreadsheet was created that includes all this data and equations to calculate the air flow rate through the absorption column based on the pressure drop across the orifice. Attach wet paper towels to one of the two digital thermometer probes at the inlet and outlet of the gas flow.
Result and analysis
Tools required
Gantt chart
Based on Figure 34, an experimental value was selected for the volumetric mass transfer coefficient, βL.ae, for Pall Ring Metal 25 mm. After that, the calculated value for volumetric mass transfer coefficient, βL.ae, for Pall Ring Metal 25 mm was taken from Figure 35 based on the experimental value selected in Figure 34. According to Equation (3), (5) and (7 ), the effective interfacial area for mass transfer per unit volume is directly proportional to the geometric area of the packaging.
Based on Figure 36, the effective interfacial area for mass transfer per cubic meter of packing for mirv-1 at different specific liquid loading is higher than VSP Ring Metal 50mm, Pall Ring Plastic 35mm and Pall Ring Metal 25mm. However, Bialecki Ring Metal 12mm still provides a better effective interfacial area for mass transfer compared to mirv-1 because it has larger geometric surface area compared to mirv-1. Based on Figure 37, the liquid phase mass transfer coefficient for mirv-1 is higher compared to VSP Ring Metal 50mm, Pall Ring Plastic 35mm, and Bialecki Ring Metal 12mm.
According to equation (14), the volumetric mass transfer coefficient is proportional to the geometric surface area of packaging. Based on Figure 38, the volumetric mass transfer coefficient for mirv-1 is higher compared to VSP Ringmetal 50mm, Pall Ring Plastic 35mm, and Bialecki Ringmetal 12mm. According to equation (14), the effective interfacial surface area for mass transfer per unit volume is directly proportional to the geometric surface area of packaging.
However, the Bialecki Ring Metal 12mm still provides a better volumetric mass transfer coefficient compared to the mirv-1 because it has a larger geometric surface compared to the mirv-1. The expected result is that the mass transfer rate will increase as the specific loading of the fluid increases. This is because a higher specific liquid load will increase the wetting efficiency of mirv-1, making more surface area available for mass transfer.
Based on Figure 40, the volumetric mass transfer coefficient, βL.ae, increases with increasing airflow. The expected result is that the volumetric mass transfer coefficient, βL.ae, will increase as the specific fluid loading increases. This is because a higher specific liquid load will increase the wetting efficiency of mirv-1, resulting in an increase in the volumetric mass transfer coefficient, βL.ae.
As the volumetric mass transfer coefficient, βL.ae, increases, the mass transfer rate will also increase. The steps and calculation to find the volumetric mass transfer coefficient, βL.ae, are as follows;.
