Systems and methods for co-producing xylitol and caramel pigment by utilizing xylose mother liquid

A method for co-producing a xylitol and a caramel pigment by utilizing a xylose mother liquid, comprising following steps:

• step one, transporting a raw material of the xylose mother liquid in a raw material tank to a filter via a pipeline for filtering impurities to obtain a filtered raw material of the xylose mother liquid, and transporting the filtered raw material of the xylose mother liquid to a nanofiltration membrane device for a decolorizing process to obtained a decolorized xylose mother liquid;
• step two, transporting the decolorized xylose mother liquid to a first ion exchange device for a desalting process to obtain an ion exchange liquid;
• step three, transporting the ion exchange liquid to a chromatographic separation device for a chromatographic separation process and obtaining an extracted liquid and a raffinate liquid after the chromatographic separation process, wherein a xylose component content of the extracted liquid is higher than a xylose component content of the raffinate liquid, performing a refined hydrogenation process on the extracted liquid by a refined hydrogenation assembly to obtain a crystal xylitol with a purity over 99%, and performing a browning reaction process on the raffinate liquid by a browning reaction assembly to obtain the caramel pigment;
• wherein
• in the step one, a mass percentage concentration of a dry matter of the xylose mother liquid is 50˜60 wt %, wherein, in the dry matter, a content of glucose is 12˜18 wt %, a content of xylose is 40˜50 wt %, a content of arabinose is 17˜23 wt %, a content of mannose is 10˜22 wt %, and a content of galactose is 0˜6 wt %;
• in the step one, during the decolorizing process, an operating temperature of the nanofiltration membrane device is 40° C. to 48° C., an operating pressure of the nanofiltration membrane device is 25 bar to 35 bar, and a yield rate of the nanofiltration membrane device reaches 90% to 98%;
• in the step two, during the desalting process, an electrical conductivity rate is controlled to be smaller than 50 us/cm, and a yield rate reaches 90% to 98%;
• the refined hydrogenation process in the step three includes:
• transporting the extracted liquid after evaporation and concentration to a crystallization tank for crystallization to obtain a crystal xylose, dissolving the crystal xylose with water to obtain a xylose liquid, transporting the xylose liquid to a hydrogenation reactor for a hydrogenation reaction to obtain a xylitol solution, settling the xylitol solution to remove a catalyst after the hydrogenation reaction, adopting a second ion exchange device for performing the desalting process on a supernatant after settling the xylitol solution to obtain a desalted solution, performing vacuum evaporation and concentration on a desalted solution by using a vacuum crystallization assembly, and performing vacuum boiling of sugar and crystallization to precipitate a crystal, and obtaining the crystal xylitol by performing a centrifugation operation and a drying operation on the crystal;
• in the step three, while dissolving the crystal xylose with water, a refraction of the xylose liquid is 50% to 60% and a pH value of the xylose liquid is 5.00 to 7.00, a nickel catalyst with a mass percentage of 0.01% to 0.02% is added into the xylose liquid, a reaction temperature is controlled to be between 130° C. to 140° C. and a steam pressure is controlled to be above 0.4 MPa, and the hydrogenation reaction is performed for 60 minutes to 120 minutes;
• the raffinate liquid is concentrated to the refraction being between 75% to 85% and a pH value is adjusted to be between 7.00 to 9.00, a compounded amino compound with a mass percentage of 6% to 12% is added as a catalyst, and a reaction temperature of the browning reaction is controlled to be between 120° C. to 140° C. and a time of the browning reaction is 60 minutes to 240 minutes;
• and
• the browning reaction process in the step three includes:
• obtaining a caramel pigment liquid by performing a concentration process, the browning reaction process, and a filtering process on the raffinate liquid, wherein a red index of the caramel pigment liquid is over 7, and an absorbance of the caramel pigment at 610 nm is over 0.07.