Method and apparatus for purifying nitration products

A production plant for nitrating nitratable aromatic compounds with subsequent purification of the crude nitrated products formed in the nitration, wherein the production plant comprises the following units:

• (a) a nitration unit for nitrating aromatic compounds, wherein the nitration unit comprises one or more appropriate reaction vessels for carrying out the nitration reaction(s);
• (b) optionally, arranged in the production line downstream of the nitration unit, at least one separation device for separating off the residual nitrating acid from the crude nitrated products;
• (c) arranged in the production line downstream of the nitration unit and the optional separation device if present, at least one washing device for carrying out washing of the crude nitrated products, where the washing device comprises:
• at least one dispersing device for contacting and emulsifying the crude nitrated products to be purified and the washing medium, and
• arranged downstream of the dispersing device, a tube reactor for introduction of the emulsion comprising the crude nitrated products to be purified and the washing medium and produced in the dispersing device, wherein the tube reactor is configured such that the impurities initially present in the crude nitrated products are removed during passage of the emulsion through the tube reactor and/or such that the impurities initially present in the crude nitrated products are transferred into the washing medium and neutralized thereby during passage of the emulsion through the tube reactor, wherein the tube reactor is equipped with one or more mixing elements for introduction of additional mixing energy, wherein the mixing elements are configured as plates, as impingement plates, as deflection plates, as orifice plates, as static mixers or as flow dividers and wherein the mixing elements are configured such to provide a mixing energy of from 10 to 1,000 joule/liter;
• (d) optionally, arranged in the production line downstream of the washing device, a stirred vessel for increasing the contact and residence time between nitrated products and washing medium;
• (e) arranged in the production line downstream of the washing device and the optional stirred vessel if present, a separation device for separating off the nitrated products which have been freed of the impurities from the washing medium.

A production plant for nitrating nitratable aromatic compounds with subsequent purification of the crude nitrated products formed in the nitration,

• wherein the production plant comprises the following units:
• (a) a nitration unit for nitrating aromatic compounds, wherein the nitration unit comprises one or more appropriate reaction vessels for carrying out the nitration reaction(s);
• (b) optionally, arranged in the production line downstream of the nitration unit, at least one separation device for separating off the residual nitrating acid from the crude nitrated products;
• (c) arranged in the production line downstream of the nitration unit and the optional separation device if present, at least one washing device for carrying out washing of the crude nitrated products, where the washing device comprises:
• at least one dispersing device for contacting and emulsifying the crude nitrated products to be purified and the washing medium, and,
• arranged downstream of the dispersing device, a tube reactor for introduction of the emulsion comprising the crude nitrated products to be purified and the washing medium and produced in the dispersing device, wherein the tube reactor is configured such that the impurities initially present in the crude nitrated products are removed during passage of the emulsion through the tube reactor and/or such that the impurities initially present in the crude nitrated products are transferred into the washing medium and neutralized thereby during passage of the emulsion through the tube reactor, wherein the tube reactor is equipped with one or more mixing elements for introduction of additional mixing energy, wherein the mixing elements are configured as plates, as impingement plates, as deflection plates, as orifice plates, as static mixers or as flow dividers and wherein the mixing elements are configured such to provide a pressure drop per mixing element in the range from 0.1 bar to 3.0 bar;
• (d) optionally, arranged in the production line downstream of the washing device, a stirred vessel for increasing the contact and residence time between nitrated products and washing medium;
• (e) arranged in the production line downstream of the washing device and the optional stirred vessel if present, a separation device for separating off the nitrated products which have been freed of the impurities from the washing medium.