NL2024457B1 - Method for simultaneously recovering furfural product and sulfuric acid catalyst from furfural residue - Google Patents

Abstract

The present invention discloses a method for simultaneously recovering a furfural product and a sulfuric acid catalyst from furfural residue. The method for simultaneously recovering the furfural product and the sulfuric acid catalyst from furfural residue includes 5 the following three steps: step 1, furfural residue is washed with circulating wastewater for dissolving residual furfural and sulfuric acid in the circulating wastewater; step 2, the mixture of the furfural residue and the circulating wastewater is subjected to solid—liquid separation; and step 3, the circulating wastewater in which the residual furfural and the sulfuric acid are dissolved is subjected to evaporation concentration in a wastewater 10 evaporator, and the product furfural and the catalyst sulfuric acid are simultaneously recovered. The method for simultaneously recovering the furfural product and the sulfuric acid catalyst from the furfural residue avoids additional energy consumption and water consumption, prevents the furfural and sulfuric acid in the furfural residue from polluting air, realizes yield increase of the furfural and recycling of the sulfuric acid catalyst, and 15 significantly improves the economic efficiency of furfural production.

Description

METHOD FOR SIMULTANEOUSLY RECOVERING FURFURAL PRODUCT AND SULFURIC ACID CATALYST FROM FURFURAL RESIDUE

BACKGROUND Technical Field The present invention relates to a method for environmentally treating furfural residue, and in particular relates to a method for simultaneously recovering a furfural product and a sulfuric acid catalyst from furfural residue by using a wastewater evaporator in a furfural process. Related Art Furfural residue is the residual solid reaction product of furfural plants after furfural is extracted from corn cobs, mainly containing cellulose and lignin, and also containing a small part of residual unstripped furfural and a large part of sulfuric acid catalyst. At present, furfural plants use the furfural residue as boiler fuel. Before the furfural residue enters a boiler for combustion, the furfural residue containing water is baked by the residual heat of flue gas, so that the water content of the furfural residue is reduced to 35% or below, and then the furfural residue is fed into the boiler for combustion. However, in the process of baking the furfural residue, the atmospheric boiling point of an azeotrope formed by part of furfural and water remaining in the furfural residue is 79.7°C. The azeotrope of the furfural and water entering the atmosphere will cause air pollution. In addition, in the baking process, the sulfuric acid catalyst remaining in the furfural residue is also partially volatilized into the atmosphere, causing air pollution. After baking, part of the sulfuric acid still remaining in the furfural residue is combusted and decomposed into sulfur trioxide subsequently in a boiler furnace. If directly discharged into the atmosphere, the sulfur wuioxide will cause air pollution. If the sulfur trioxide is recovered by a desulfurization tower, higher equipment costs and operating costs are required. Therefore, there is an urgent need for a new technology suitable for environment-friendly treatment of furfural residue.

SUMMARY In order to overcome the defect of air pollution caused by residual furfural and sulfuric acid in the existing furfural treatment, the present invention provides a method for simultaneously recovering a furfural product and a sulfuric acid catalyst from furfural residue.

The technical solution adopted by the present invention to solve the technical problem thereof 1s as follows: step 1, furfural residue is washed with circulating wastewater for dissolving residual furfural and sulfuric acid in the circulating wastewater; step 2, the mixture of the furfural residue and the circulating wastewater is subjected to solid-liquid separation; and step 3, the circulating wastewater in which the residual furfural and the sulfuric acid are dissolved is subjected to evaporation concentration in a wastewater evaporator; mixed vapor of evaporated water, furfural and a small amount of sulfuric acid in the wastewater evaporator is introduced into the bottom of a reactor; the concentrated sulfuric acid solution at the bottom of the wastewater evaporator is mixed with a supplemental sulfuric acid solution as a circulating acid solution to enter a batching tank, and the mixed sulfuric acid solution is mixed with a biomass raw material in the batching tank; and the ingredients are fed into the reactor for reaction to produce furfural.

The specific operational flow of the technical solution of the present invention is as shown in the accompanying drawing, and the process is described as follows: furfural residue S1 and circulating wastewater S2 are mixed at a mass ratio of (1:2)-(1:4) and fully stirred in a washing tank 1; the furfural and the sulfuric acid remaining in the furfural residue are fully dissolved in the circulating wastewater S2; then a solid-liquid mixture S3 in the washing tank 1 is conveyed into a filter press 2 and subjected to solid-liquid separation; filter residue S4 is discharged into a filter residue tank 3 and used as boiler fuel when dried; filtrate S5 is input into an evaporator 4; the temperature of the evaporator 4 is controlled at 170-190°C; mixed vapor S7 of evaporated water vapor, furfural and a small amount of sulfuric acid 1s introduced into the bottom of a reactor 6; the water vapor is used as a stripping medium; the furfural and the newly produced furfural are stripped together out of the reactor and recovered; the sulfuric acid is trapped in a biomass raw material and liquid water to catalyze hydrolysis reaction of the biomass raw material; after the liquid at the bottom of the evaporator 4 is concentrated until the sulfuric acid mass content is 4%-6%, the liquid is input into an acid tank 7 as a concentrated sulfuric acid circulating liquid feed S8; after the concentrated sulfuric acid circulating liquid feed S8 is mixed with a supplemental sulfuric acid solution S11 having a sulfuric acid mass content of 5%, the mixed liquid is input into a batching tank 8 as a concentrated sulfuric acid circulating liquid discharge S9 and mixed with a solid biomass raw material at a liquid-to-solid ratio of (35:100)-(55:100); a mixture is input into the reactor 6 as a reactor feed S10; the reactor temperature is controlled at 170-190°C for reaction to produce furfural; a small amount of sludge S6 deposited at the bottom of the evaporator 4 is input into a sludge tank 5; and the sludge is dried to be used as a raw material for preparing carbon materials.

Compared with the prior art, the beneficial effects of the present invention are embodied as follows.

The method of the present invention uses the wastewater evaporator of furfural plants, achieves the effect of simultaneously recovering furfural and sulfuric acid from furfural residue, avoids additional energy consumption and water consumption, prevents the furfural and the sulfuric acid in the furfural residue from polluting air, realizes yield increase of the furfural and recycling of the sulfuric acid catalyst, and significantly improves the economic efficiency of furfural production.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of the process flow of the present invention.

Numbers in the drawing: 1 washing tank, 2 filter press, 3 filter residue tank, 4 evaporator, 5 sludge tank, 6 reactor, 7 acid tank, 8 batching tank, S1 furfural residue, S2 circulating wastewater, S3 solid-liquid mixture, S4 filter residue, S$ filtrate, S6 sludge, S7 mixed vapor, S8 concentrated sulfuric acid circulating liquid feed, S9 concentrated sulfuric acid circulating liquid discharge, S10 reactor feed, S11 supplemental sulfuric acid solution

DETAILED DESCRIPTION The present invention is further described below in conjunction with embodiments. Embodiment 1 Furfural residue S1 and circulating wastewater S2 were mixed at a mass ratio of 1:2.5 and fully stirred in a washing tank 1. The furfural and the sulfuric acid remaining in the furfural residue were fully dissolved in the circulating wastewater S2. Then a solid-liquid mixture S3 in the washing tank 1 was conveyed into a filter press 2 and subjected to solid-liquid separation. Filter residue S4 was discharged into a filter residue tank 3. Filtrate S5 was input into an evaporator 4. The temperature of the evaporator 4 was controlled at 180°C. Mixed vapor S7 of evaporated water, furfural and a small amount of sulfuric acid was introduced into the bottom of a reactor 6. After the liquid at the bottom of the evaporator 4 was concentrated until the sulfuric acid mass content was 5.4%, the liquid was input into an acid tank 7 as a concentrated sulfuric acid circulating liquid feed S8. After the concentrated sulfuric acid circulating liquid feed S8 was mixed with a supplemental sulfuric acid solution S11 having a sulfuric acid mass content of 5%, the mixed liquid was input into a batching tank 8 as a concentrated sulfuric acid circulating liquid discharge S9 and mixed with a solid biomass raw material at a liquid-to-solid ratio of 45:100. The mixture was input into the reactor 6 as a reactor feed S10. The reactor temperature was controlled at 180°C for reaction to produce furfural. A small amount of sludge S6 deposited at the bottom of the evaporator 4 was input into a sludge tank 5. The sludge was dried to be used as a raw material for preparing carbon materials. According to the above operation, the yield of furfural may be improved by 2%, and 95% of sulfuric acid may be recovered. Embodiment 2 Furfural residue S1 and circulating wastewater S2 were mixed at a mass ratio of 1:4 and fully stirred in a washing tank 1. The furfural and the sulfuric acid remaining in the furfural residue were fully dissolved in the circulating wastewater S2. Then a solid-liquid mixture S3 in the washing tank 1 was conveyed into a filter press 2 and subjected to solid-liquid separation.

Filter residue S4 was discharged into a filter residue tank 3. Filtrate S5 was input into an evaporator 4. The temperature of the evaporator 4 was controlled at 190°C.

Mixed vapor S7 of evaporated water, furfural and a small amount of sulfuric acid was introduced into the bottom of a reactor 6. After the liquid at the bottom of the 5 evaporator 4 was concentrated until the sulfuric acid mass content was 4.5%, the liquid was input into an acid tank 7 as a concentrated sulfuric acid circulating liquid feed S8. After the concentrated sulfuric acid circulating liquid feed S8 was mixed with a supplemental sulfuric acid solution S11 having a sulfuric acid mass content of 5%, the mixed liquid was input into a batching tank 8 as a concentrated sulfuric acid circulating liquid discharge S9 IO and mixed with a solid biomass raw material at a liquid-to-solid ratio of 55:100. The mixture was input into the reactor 6 as a reactor feed S10. The reactor temperature was controlled at 180°C for reaction to produce furfural.

A small amount of sludge S6 deposited at the bottom of the evaporator 4 was input into a sludge tank 5. The sludge was dried to be used as a raw material for preparing carbon materials.

According to the above operation, the yield of furfural may be improved by 1.5%, and 96% of sulfuric acid may be recovered.

It should be understood that the examples and embodiments described herein are merely illustrative and that various modifications and changes, made by those skilled in the art without departing from the spirit and scope of the present invention, fall within the scope of the present invention.

Claims (2)

{onclusies{conclusions 1. Een werkwijze voor het gelijktijdig terugwinnen van een furfural product en een zwavelzuurkatalysator uit een furfural residue, omvattende: het mengen en volledig roeren van het furfural residu en circulerend afvalwater, vervolgens onderwerpen van een vastestof-vloeistofmengsel aan vastestof-vloeistofscheiding in een filterpers, het filterresidu drogen als ketelbrandstof, invoeren van het filtraat in een afvalwaterverdamper voor verdamping en concentratie, gemengde damp van verdampt water, furfural en een kleine hoeveelheid zwavelzuur wordt ingevoerd in de bodem van de reactor, nadat de vloeistof op de bodem van de verdamper is geconcentreerd wordt de vloeistof gemengd met aanvullend zwavelzuur als een geconcentreerde zwavelzuur circulerende vloeistof, en vervolgens ingevoerd in een batchtank, en gemengd met een vaste biomassa materiaal, en vervolgens wordt het mensel ingevoerd in de reactor voor katalytische reactie om furfural te bereiden.A method for the simultaneous recovery of a furfural product and a sulfuric acid catalyst from a furfural residue, comprising: mixing and completely stirring the furfural residue and circulating wastewater, then subjecting a solid-liquid mixture to solid-liquid separation in a filter press, drying the filter residue as boiler fuel, feeding the filtrate into a waste water evaporator for evaporation and concentration, mixed vapor of evaporated water, furfural and a small amount of sulfuric acid are fed into the bottom of the reactor, after the liquid is concentrated at the bottom of the evaporator the liquid is mixed with additional sulfuric acid as a concentrated sulfuric acid circulating liquid, and then fed into a batch tank, and mixed with a solid biomass material, and then the mixture is fed into the reactor for catalytic reaction to prepare furfural. 2 De werkwijze voor het gelijktijdig terugwinnen van een furfural product en een zwavelzuurkatalysator uit een furfural residue volgens conclusie 1, waarbij de massamengverhouding van het furfural residu en gerecycled afvalwater 1:2 tot 1:4 is, de verdamper temperatuur 170 - 190°C is, de vloeistof op de bodem van de verdamper wordt geconcentreerd tot een zwavelzuur massagehalte van 4% tot 6%, de massaverhouding van vloeistof-vastestof van reactiematerialen ingevoerd in de reactor 35:100 tot 55:100 1s, de reactortemperatuur 170 - 190°C is. -0-0-0-0-0-The method for simultaneously recovering a furfural product and a sulfuric acid catalyst from a furfural residue according to claim 1, wherein the mass mixing ratio of the furfural residue and recycled wastewater is 1:2 to 1:4, the evaporator temperature is 170-190°C , the liquid at the bottom of the evaporator is concentrated to a sulfuric acid mass content of 4% to 6%, the mass ratio of liquid-solid of reaction materials introduced into the reactor 35:100 to 55:100 1s, the reactor temperature 170 - 190°C is. -0-0-0-0-0-