System and method for continuously preparing furfural using lignocellulosic raw material

A system for continuously preparing furfural using lignocellulosic raw material, wherein the system comprises:

• an acid solution output unit, the acid solution output configured to output a first acid solution and a second acid solution, respectively;
• a raw material mixing unit connected to the acid solution output unit, the raw material mixing unit configured to mix the lignocellulosic raw material with the first acid solution so as to form a first mixture, the raw material mixing unit further configured to continuously output the first mixture;
• a feeding unit connected to the raw material mixing unit, the feeding unit configured to receive the first mixture, compress the first mixture and output the first mixture;
• a main reaction unit connected to the feeding unit and the acid solution output unit, the a main reaction unit configured to receive the first mixture and the second acid solution respectively, and sufficiently stir and mix the first mixture with the second acid solution under a pressure higher than a normal pressure in such a way that the first mixture reacts with the second acid solution so as to produces a second mixture;
• a discharging unit connected to the main reaction unit, the discharging unit configured to perform solid-liquid separation of the second mixture and output an acid-containing pentose solution;
• a stripping reaction column comprising, a vapor outlet formed at a top portion of the stripping reaction column, a first raw material inlet formed at the top portion of the stripping reaction column, a stripping vapor inlet formed at a bottom portion of the stripping reaction column, and an acid solution outlet formed at the bottom of the stripping reaction column;
• wherein the first raw material inlet is configured to receive an acid-containing pentose solution of a first temperature from the discharging unit as a raw material so as to perform a dehydration/cyclization reaction, wherein the stripping vapor inlet is configured to receive a stripping vapor of a second temperature, wherein the vapor outlet is configured to supply a furfural-containing vapor obtained from the dehydration/cyclization reaction, and wherein the acid solution outlet is configured to extract an acid solution from the bottom of the column;
• a separation unit connected to the vapor outlet, the separation unit configured to neutralize an acid in the furfural-containing vapor and separate the resulting salt from the furfural-containing vapor so as to provide a furfural-containing vapor with a reduced acid content;
• and
• a purification unit connected to the separation unit, the purification unit configured to purify the furfural-containing vapor.