What is the purpose of trays in a distillation column?
Column trays The trays have openings to allow vapor to flow upward through the column, as well as conduits (downcomers) to allow condensed liquid to flow downward (Figure). The tray is designed to promote intimate contact between the upward-moving vapor and downward-moving liquid.
What causes weeping in a tray?
Weeping/Dumping This phenomenon is caused by low vapour flow. The pressure exerted by the vapour is insufficient to hold up the liquid on the tray. Therefore, liquid starts to leak through perforations.
What causes pressure drop in distillation column?
The differential pressure between two locations in a distillation column has two components. They are static head due to the mass of the vapor between them and dynamic pressure drop due to the resistance of internal to the flow.
How do you fix a flooded distillation column?
Some of the more common methods used to eliminate flooding involve temporarily decreasing the feed rate, the reflux rate, or both, to reduce the amount of liquid in the column, and decreasing the vapour in the column by reducing the reboiler steam.
What is the function of tray?
A tray is a flat dish or container that’s used to carry or serve food.
What is flooding and weeping in distillation column?
What is Flooding of Distillation Column? Flooding of a distillation column is a phenomenon when liquid flows across a tray and goes toward the outlet weir. The liquid starts overflowing the outlet weir and drains through the downcomer to the tray below.
How do you maintain pressure in a distillation column?
Pressure Control in Atmospheric Column For atmospheric distillation, column pressure is controlled by having the column open to the atmosphere. By varying the airflow in and vent gas out of the column through the column vent. If the air ingression into the system is undesirable, an inert purge is done at the vent.
What is dry tray pressure drop?
Dry tray pressure drop (ΔPd) is a design parameter that supplies preliminary information about total pressure drop. This work aimed to assess correlations for ΔPd prediction for different types of trays without downcomer and to evaluate the effect of free area ratio (φ) and hole diameter (d) on ΔPd.
What causes flooding in absorption column?
In absorption-desorption packed columns, if any or certain combinations of liquid or gas flow in combination with the reboiler heat pressure and stripper feed power is too high, the column becomes flooded with the liquid.
How many trays are there in the distillation column?
There are five major types of tray column; bubble cap tray, sieve deck tray, dual flow tray, valve tray and baffle tray.
What are trays in distillation?
Trays are separation devices used in process plants, most often in distillation towers. The tray column is one the most widely used types of distillation columns. It is also at times referred to as a plate column.
What happens when a distillation column floods?
Flooding is a common abnormal process condition wherein the distillation column stops generating a separation, thus causing the quality of the top and/or bottom products to go off specification.
How do you prevent weeping in a distillation column?
- Reduce reboiler duty on temporary basis so liquid hold up comes down and then again do it normal.
- Reduce feed to the distillation column becuase column already flooded with the liquid.
- If it is continue for long time it means perforation of tray choked so operate column on minimum capacity for better purity.
What happens when you increase pressure in a distillation column?
When pressure increases, relative volatility between the components will decrease. This will increase reflux ratio and molar flow rates in the column, As a result, the area required for vapour flow will increase.
Is pressure constant in distillation column?
Pressure Profile In steady state distillations the pressure in the column is held constant, and the temperature is varied to control the composition of the product streams.
How do you find the height of a tray distillation column?
The height of the column containing packing is usually calculated by Z = (NTP) (HETP), where (HETP) = Height of Packing Equivalent to One Theoretical Plate.
What is Valve tray?
A valve tray is a flat perforated plate, with each perforation fitted with a movable disk (the “valve”). See the Figure below. The perforations and disks may be circular or rectangular. The disks (valves) are the movable component of the tray – see the Figure below.