Foaming System And Its Defoaming Components

There are some frothing systems in practical industrial production, such as potassium carbonate system assimilating carbon dioxide, light hydrocarbon system shedding methane etc. The frothing nature results in a series of problems, such as reduction of the ability of production, serious droplet foam, early flooding and damages done to the normal production in the column. With increasing expansion of production scale, the problem attracts more and more attentions. Some measures have been taken in industrial production and engineering design, such as adding bubble-removing agent. However, all of these methods are passive, some even result in negative effects.This thesis adopts a new way and obtains a new mechanical bubble-removing method by experiments. The results show that the method can reduce the excessive foam of the frothing system with reduced or none bubble-removing agent.To observe the motion of bubbles in the liquid layer of the sieve tray and debug instrument, pre-experiments are done on the behaviors of the sieve tray with only one hole with air-water system in a transparent Plexiglas rectangular column of 300mmx200mm. The purpose of the pre-experiment is to measure the bubble group diameter in liquid, the bubble diameter in the bubble group and gas holdup in different gas volume with the same liquid volume of 4001/h. Based on the pre-experiments, the formal experiments are made in a Plexiglas rectangular column of 200mmx70mm, during which the liquid on the sieve tray has no horizontal flow. The experimental frothing system and the reference system are respectively air-5% potassium carbonate solution and air-water system. The purpose of the experiment is to measure the foam height of the frothing system and the reference system, the bubble diameter and gas holdup. After the experiments are finished, the effects of the different bubble-removing components to reduce the foam height of the frothing system are measured.The experiment results show that:1. Under the conditions of hole diameter from 7mm to 13 mm and hole kinetic energy factor from 1.15m-s"'-kg1/2-m"3/2 to 25 nvs"'-kgl/2-m'3/2, the gas entering liquid through hole is not single bubble but bubble group. The bubble group diameter is correlated with the hole kinetic energy factor and the hole diameter:D,=7.87507x (F0)-?-0.00576xd25+3.06707x (F0)02xd092. The structure property of the foam layer of frothing system demonstrates 70mm height above the experimental sieve tray as a turning point. Above 70mm, the foam fluctuation is turbulent and the bubble is large, sparse and uneven. Under 70mm, the bubble is small, compact.3. An effective method of putting mechanical components to implement bubble-removing in the sieve tray is found by experiments. This method is more economical and easier to implement than the current existing methods like adding bubble-removing agent in the practical industrial production.4. The effectiveness of bubble-breaking by putting corrugated plate packing, screen packing and shutter fender on the sieve tray are compared for the same experimental conditions including the same gas volume, liquid volume and bubble-break components put on the same position. The effects of reducing foam height among the three bubble-break components are compared. The results show that corrugated plate works almost equally well as silk packing and both are superior to shutter fender. In view of the fact that the price of corrugated plate packing is much lower than silk packing, we suggest it to be adopted as bubble-removing component in engineering.