# Designing a Horizontal Gravity Decanter for Efficient Separation

## How to calculate the size of a horizontal gravity decanter vessel?

What are the factors considered in determining the vessel dimensions?

## Calculating the Size of a Horizontal Gravity Decanter Vessel

The size of a horizontal gravity decanter vessel can be calculated based on various factors such as flow rates, vessel configuration, and required separation efficiency.

When designing a horizontal gravity decanter for the separation of impurities in crude mono-chlorobenzene (MCB), the vessel size plays a crucial role in achieving optimal performance. The vessel dimensions are calculated based on the flow rates of MCB and wash water, as well as the desired separation efficiency.

To calculate the vessel size, the first step is to convert the flow rates of MCB and wash water to volume flow rates. In this case, the volume flow rate of MCB is 67.65 ft3/hr, and the volume flow rate of wash water is 140% of the MCB rate, which is 94.71 ft3/hr.

Using a vessel L/D ratio of 4 and neglecting the volume of fluid in the vessel heads, the required vessel volume is then determined by averaging the volume flow rates and multiplying by the vessel L/D ratio. In this scenario, the vessel volume is calculated to be 608.52 ft3.

Next, to determine the vessel dimensions, 3\" is added to the calculated diameter and rounded off to the nearest 3\". The resulting vessel diameter is 6 ft - 0 in, and the vessel length is 4 times the diameter. The final vessel size is rounded to the nearest 3\", resulting in a size of 15 ft - 6 in (length) x 6 ft - 0 in (diameter).

Additionally, the height of the external MCB leg is calculated by adding the height of the MCB layer (40% of the vessel height) and the distance that some MCB droplets may need to travel (60% of the vessel diameter). Taking into account these factors, the required height of the external MCB leg is determined to be 2 ft - 3 in.

Overall, the size of a horizontal gravity decanter vessel is crucial for efficient separation processes, and careful consideration of flow rates and separation requirements is essential in the design process.