Technological advantages of using cyclic distillation process in the production of ethanol food grade

The one of the main factor that provides high quality of ethanol food grade is distillation columns. Nowadays before the producers are strict market conditions on qualitative of ethanol, and reduced specific energy costs per unit of output. Nowadays manufacturers have strict conditions on the quantitative and organoleptic indicators of alcohol quality. At once market conditions dictate reduced specific energy costs per unit of output. This problem can be solved only by constantly improving technology of removing impurities by increasing the efficiency of mass transfer. Application of cyclic modes is one of the methods to increase the efficiency of interaction phases in distillation column, which essentially boils down to a circular motion phases in the contact zone. Mass transfer occurs on a tray in the absence of fluid flow. This allows you to achieve hydrodynamic regime that close to the ideal displacement as in a liquid, and a pair in real conditions. There is observed especially significant difference between standard and cyclic processes at high reflux. This scheme of contact phase makes it possible to get  number of structural and technological advantages : reduce the number of trays in the column 2 ... 2.5 times; reduce square of trays in 1.5 ... 2 times; reduce steam consumption is 1.5 .... 2, 5 times; increase the load on the liquid 1.5 ... 2 times; improve quality and increase the additional output of ethanol.

Let demonstrate the benefits of the transfer distillation column in cyclic mode on the example of the column final purification and column of concentration of impurities.

The Column of the final purification of ethanol, operating in the hydroselection mode: reduces the content of methanol in 1.3 ... 2 times, reduces the aldehydes content of 0.2 mg / liter; increases oxidation ethanol per 1 ... 2 min; improves organoleptic properties of ethanol. This specific steam consumption in the cyclic mode is 0.3 ... 0.4 kg / liter (for bubble column in standard mode is 0.6 ... 0.8 kg / liter).

The Column of impurities concentration performs the function of additional hydroselection column for the purification of contaminated flows. Release of additional ethanol for 3 ... 4 % is possible due to the higher concentration of impurities main character (esters and aldehydes) namely of 0.6 ... 0.7 % of plant capacity and specific consumption of steam 0.07 ... 0.08 kg / liter (for bubble column in standard mode is 0.3 ... 0.4 kg / liter).

Distillation column in a cyclic mode allow to reduce capital costs for the construction of new and reconstruction of existing ethanol plant, while reducing the cost and improving the quality of the final product.

ENERGY-SAVING TECHNOLOGY OF MASS TRANSFER IN TRAY COLUMNS WITH SEPARATE PHASE MOVEMENT

The costs for industrial processes of separation in tray columns, both capital and current, are inverse to efficiency of the mass transfer between steam (gas) and liquid. For such type of equipment the separation efficiency improvement potential in related to organization of phase movement in the column.

The most efficient component separation is achieved upon perfect displacement by liquid and steam. By means of the customary technological regimes and contact devices it seems impossible to reach the desired result. But this problem can be solved by the mass exchange technology with separate phase movement (cyclic process), implemented as follows: lack of outflow of liquids to the trays vapor admission; lack of mixing of liquids in adjacent trays upon outflow of liquid. The perfect displacement effect is achieved by means of using of the coordinate system for changing of concentration of the volatile component on contact stage during the steam supply. It allows actually eliminating the mixture of liquid in the tray with various concentrations of high-volatile component. The mathematic modeling allowed offering theoretical stage model with perfect displacement with a trayed column for description of the mass transfer process with separate phase movement. Meanwhile analytically it was proved that the existing theoretical tray and perfect displacement theoretical tray are two extreme cases of hydrodynamic mass transfer regimes in the trays – perfect mixing and perfect displacement. Theoretical developments were implemented in special contact devices patented in numerous countries. Industrial implementation was held in Ukraine in food alcohol production. The first industrial column has been in operation for 6 years already. The tests showed the component separation efficiency improvement by 3 to 4 times, while the process power consumption reduced 1.5 to 2 times.