| 摘要 |
FIELD: chemistry.SUBSTANCE: invention relates to a process for starting up a separating process for purificative removal of acrylic acid crystals from a suspension S of crystals thereof in mother liquor with a hydraulic wash column, which has a crystal melt circuit including crystal melt space and also a process space and a distributor space which are separated by a floor with passages connecting the two spaces, where the crystal bed is formed for the first time by first filling the crystal melt circuit and, at least partly, the process space with an acrylic acid-comprising startup liquid, whose acrylic acid crystal formation temperature is less than or equal to the temperature of the suspension S increased by 15°C, and then continuing the filling of the wash column with the suspension S and optionally with control liquor until the difference between the pressure in the crystal melt space and the pressure in the distributor space falls suddenly, the arithmetic mean of the total waste liquor flow flowing through the filters of the filter tubes of the wash column up to this point in time, based on the area of all the filters, being not more than 80 m/(m·h). In the course of startup of the separating process for first development of the crystal bed in the process space the crystal melt circuit comprising the crystal melt space, and the process space of the previously unfilled wash column, are at first filled with an acrylic acid-comprising startup liquid AT such that the fill height of the startup liquid AT in the process space overtops at least the removal device, then the filling of the wash column is continued by using the pump P2 to conduct a stream ST* of the suspension S from the source QS through the delivery connections E1, E2 via the distributor space and through the passages U into the process space of the wash column and optionally using the pump P3 to conduct a substream of the waste liquor stream SM* conducted out of the wash column through the filter tubes as source QT*, as control liquor stream SL* through the delivery connections C1, C2 via the distributor space and the passages U and/or directly into the process space of the wash column, at least until the time t, is attained at which the pressure difference P=P-P, where P- is the pressure existing at any desired point in the crystal melt space at a particular time in the supply of the stream ST*, and P- is the pressure which exists at the same time at any desired point in the distributor space, no longer rises or remains constant as a function of the duration of the supply of the stream ST* but decreases suddenly, with the proviso that, until the time tthe mean superficial velocity on the filters F, calculated as the arithmetic mean of the total waste liquor flow ST* which flows at the particular time through the filters F of the filter tubes during the supply of the stream SM*, divided by the total area of all filters F, is not more than 80 m/(m·h), the acrylic acid-comprising startup liquid AT is one from which, in the course of cooling until crystallization sets in, the crystals which form in the course of crystallization are acrylic acid crystals, and between the crystal formation temperature Treported in degrees Celsius, of these acrylic acid crystals in the startup liquid AT, and the temperature Treported in degrees Celsius, of the suspension S of the stream ST*, the following relationship is satisfied T?T+15°C.EFFECT: method provides a steady-state separation process.28 cl, 3 dwg, 1 ex |
