Scientific developments

APPLICATION OF AN ENERGY-SAVING MASS EXCHANGED TECHNOLOGY WITH A SEPARATED PHASE MOTION
- The capital and current costs of the industrial separation processes are inversely proportional to the efficiency of the mass transfer between steam (gas) and liquid exchange. In its turn, the latter depends on the character of the phase equilibriums, the phase contact surface area and the mass-transfer coefficient. Thus, when increasing each of the components of the basic mass-transfer equation, we can substantially decrease the prime cost of the end product.
- In case of the tray-type column units the reserves for increasing of the process driving force, and therefore for increasing in efficiency, are hidden in the arrangement of the phase movement in the column.

Theoretical part.
It is well known that the efficiency of the rectification (sorption) depends on the flow structures on the trays. Most effective separation of components can be achieved by the maximum liquid and steam displacement and an unidirectional movement of liquid on adjacent contact stages. Lewis shoved that under the aforesaid conditions the efficiency of component separation can be two or three times as much as the separation efficiency of the theoretical tray. At the same time, the local efficiency (equilibrium condition between steam and liquid) does not exceed 100%.
But, under real conditions it seems impossible to achieve an ideal displacement.
In addition to the generally recognized mode there is also a so-called cycling mass-exchange one that was suggested by Cannon in the sixties. In this mode the mediums being in contact move within the column in antiphase (separated phase motion, SPM).
Relying upon the available findings, we have developed a formalized mathematical process model. Our theoretical studies shows that SPM mode is similar to the steady mode in case of an unit-directional motion of liquid on the adjacent contact stages and an ideal liquid and steam displacement. The explicit functions we derived reflect the changes in concentration of a volatile component in contacting mediums. After positioning them in Y – X coordinates, we suggested the existence of a theoretical tray with an ideal displacement. Besides, a process tie line theory (steam and liquid concentration distribution lines on column trays) has being developed. Even in case of an equimolar mass exchange the tie lines shove a convexity that is opposite to that of the equilibrium line. The present L/G tie line is a special case of hydrodynamic conditions of the SPM mode. In addition, we got the relationship between the tray efficiency and local efficiency, diffusion potential factor and hydrodynamic conditions of inter-tray liquid flowing.
The SPM mode – components' time separation (on the contact stage), the steady (stationary) mode – space separation (along the liquid flow path and on the contact stage). But, under real conditions only the SPM mode can provide an ideal liquid and steam displacement.
On the basis of the theoretical studies we suggested and patented several contact devices that meet the major process requirements namely:
the contact mediums move within column in antiphase,
when supplying steam, there is no inter-tray liquid flowing,
when liquid overflowing, there is no liquid intermixing on adjacent trays.

 

 

The theoretical results about a high efficiency of the SPM mode have been confirmed under conditions of the alcohol production. The first industrial HF distillation column demonstrated a 3-4 times increase in separation efficiency (number of trays decreased) while the energy consumption decreased 2-3 times.

This, the introduction of this mode on the industrial basis can provide a considerable economic effect in the following respects:
- capital expenditure saving,
- current energy saving,
- increase in product's quality,
- increase in product's yield,
- environment enhancement.

If the subject stated above of interest to you, we can invite you to Ukraine in order to get familiar with the operation of the equipment and discuss the terms of our cooperation.