A method for dissolving furfural high-temperature polymerized coke

Abstract

This invention discloses a method for dissolving furfural high-temperature polymerized coking deposits, comprising the following steps: ① Adding an alkaline solution to a wastewater evaporator, and maintaining the temperature inside the evaporator at 40-60°C for 6-8 hours by circulating hot water or steam at the bottom, allowing the alkaline solution to fully dissolve the polymerized coking deposits; ② Stopping heat exchange at the bottom of the evaporator, allowing molten oily substances to slowly flow to the bottom of the evaporator. After the molten oily substances have flowed to the bottom of the evaporator, an organic mixture is added from the top of the evaporator. The organic mixture dissolves the coking deposits again and extracts and separates the alkaline solution, with a reaction time of 3-4 hours; ③ Allowing the dissolved mixture to stand and separate into layers, with the upper oil layer and the lower water layer being separately processed by a distillation unit. This invention uses a combination of high-concentration alkaline solution and organic mixture, which can achieve the dissolution and cleaning of furfural polymerized coking deposits at low temperatures, and can also effectively achieve the component separation and recycling of the organic mixture.

Description

Technical Field

[0001] This invention belongs to the field of furfural production technology, specifically relating to a method for dissolving furfural high-temperature polymerized coke. Background Technology

[0002] The polymerized coke from the furfural production system is mainly formed by the self-oxidative polymerization of furfural in aldehyde vapor at temperatures ≥170℃ under the influence of acid and non-condensable gases; it is also formed by the ring-opening polymerization of furfural with acetic acid and acetone in wastewater under high temperature and acidic conditions. The polymer is mainly a black, blocky carbide, containing 5.0-6.5% moisture, 3.0-4.0% ash, 35.5-42.7% fixed carbon, and 0.08%-0.52% sulfur. It is readily soluble in alkaline solutions and toluene, but insoluble in water.

[0003] Currently, furfural high-temperature polymers in furfural production systems are mainly concentrated in steam-slag separators and wastewater evaporators. At present, the main treatment methods for furfural high-temperature polymers are: the polymerized coking material in the steam-slag separator is mainly removed by external force impact; the coking material in the wastewater evaporator is mainly removed by high-pressure water jet washing. However, high-pressure washing has high washing costs and will cause water pollution and waste. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for dissolving high-temperature polymerized coking products of furfural, based on the physicochemical properties of the furfural system's high-temperature polymerized coking products, combined with the characteristics of chemicals on the market and existing conditions such as the company's waste heat.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is a method for dissolving furfural high-temperature polymerized coke, comprising the following steps:

[0006] ① Add 4-10wt% sodium hydroxide solution to the wastewater evaporator as an alkaline solution. Maintain the temperature inside the wastewater evaporator at 40-60℃ for 6-8 hours by passing hot water or steam through the bottom. This allows the alkaline solution to fully dissolve the polymerized coking material, which then decomposes into a molten oily substance with slight fluidity.

[0007] ② Heat exchange is stopped at the bottom of the wastewater evaporator, allowing the molten oily substance to slowly flow to the bottom. After the molten oily substance has flowed to the bottom of the wastewater evaporator, an organic mixture is added from the top of the wastewater evaporator, filling the bottom end cap and heat exchange tubes of the wastewater evaporator. The organic mixture dissolves the coking material again and extracts and separates the alkaline solution. The equipment temperature is maintained at no less than 40°C, and the reaction time is 3-4 hours. The organic mixture is prepared according to the mass ratio of furfural, toluene, and ethanol of 10-15:15-25:60-75.

[0008] ③ After dissolving, allow the mixture to stand and separate into layers. The upper oil layer and the lower water layer are then separately fed into a distillation unit for further processing.

[0009] Preferably, in step ③, the liquid drawn from the top of the oil tower is collected and reused in the order of toluene and furfural fractionation, and the residue in the bottom of the tower is sent to the boiler for combustion; the ethanol and water distilled from the top of the water tower are reused, and the concentrated waste brine in the bottom of the tower is sent to the sewage treatment plant for treatment.

[0010] Preferably, the mass ratio of the alkaline solution in step ① to the organic mixture in step ② is 1:0.3-0.5.

[0011] In this invention, the solvent for dissolving furfural high-temperature polymerized coke consists of a high-concentration alkaline solution and an organic mixture. The high-concentration alkaline solution is used first, and the organic mixture is added after the alkaline solution has reacted for a period of time.

[0012] The coking products of furfural high-temperature polymerization are mainly ester organic compounds formed by the self-polymerization of furfural or ester organic compounds formed by furfural with acetic acid, acetone, etc. These ester organic compounds can decompose into alcohols and organic salts in alkaline solutions. Therefore, the purpose of using high-concentration alkaline solutions is to decompose the furfural high-temperature polymerization coking products into alcohols and organic salts; the higher the concentration and the higher the temperature, the faster the decomposition rate. Considering cost, a concentration of 4-10% sodium hydroxide is selected. Considering the volatility of the organic mixture added later, the alkaline dissolution temperature is controlled at 40-60℃. The alkaline decomposition products are mainly alcohols and organic salts. The alcohols are mainly five-membered chain alcohols formed by ring opening of furfural, ethanol formed by the cleavage of acetone, or polyols. The organic salts are mainly furan salts or short-chain salts.

[0013] Based on the principle of "like dissolves like" and the miscibility of furfural and toluene, and considering the different boiling points and azeotropic phenomenon of toluene, furfural, and ethanol, this invention uses furfural, toluene, and ethanol to form an organic mixture. Furfural and toluene primarily dissolve furan salts or furan compounds, while ethanol primarily dissolves five-membered alcohols, polyols, water, and alkaline solutions. Based on the characteristic of furfural and toluene azeotropically removing inorganic substances, ethanol, water, alkaline solutions, and polyols can be separated from furfural, toluene, and furan salts. By separating ethanol, water, alkaline solutions, and polyols according to their different boiling points, and further separating furfural, toluene, and furan salts, the organic mixture can be recycled and reused.

[0014] In this invention, the waste heat of the furfural system can be used to heat exchange the 4-10% sodium hydroxide solution to 40-60°C. Then, the heat-exchanged alkaline solution enters from the top of the wastewater evaporator and can completely cover the polymer or coking material. After a period of deesterification reaction, the polymer or coking material is basically decomposed into alcohol and sodium furan salt. Finally, a properly prepared organic mixture is added for dissolution and extraction, which can achieve complete dissolution of the polymer or coking material.

[0015] The beneficial effects of this invention are: the combination of high-concentration alkaline solution and organic mixture can achieve the dissolution and cleaning of the coking material of furfural system at low temperature, and can also effectively achieve the separation and recycling of the components of the organic mixture. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0017] Example 1

[0018] Add 12m of 10% sodium hydroxide solution to the wastewater evaporator 3 Maintain the alkaline dissolution reaction temperature in the evaporator at 60℃ for 6.0 hours. The high-temperature polymerized coking material decomposes into a molten oily substance with slight fluidity. Then add 5t of an organic mixture of furfural:toluene:ethanol (mass ratio) = 15:25:60, maintain the equipment temperature at no less than 50℃ for 3.0 hours, and the coking material is basically dissolved in the solvent. The solvent can be recovered and reused by extraction and distillation.

[0019] Example 2

[0020] Add 12m of 10% sodium hydroxide solution to the wastewater evaporator 3 Maintain the alkaline dissolution reaction temperature in the evaporator at 40℃ for 7.5 hours. The high-temperature polymerized coking material decomposes into a molten oily substance with slight fluidity. Then add 5t of an organic mixture of furfural:toluene:ethanol = 15:25:60 (mass ratio), maintain the equipment temperature at no less than 40℃ for 3.6 hours, and the coking material is basically dissolved in the solvent. The solvent can be recovered and reused by extraction and distillation.

[0021] Example 3

[0022] Add 12 ml of 4% sodium hydroxide solution to the wastewater evaporator. 3 Maintain the alkaline dissolution reaction temperature in the evaporator at 60℃ for 7.0 hours. The high-temperature polymerized coking material decomposes into a molten oily substance with slight fluidity. Then add 5t of an organic mixture of furfural:toluene:ethanol = 10:15:75 (mass ratio), maintain the equipment temperature at no less than 55℃ for 3.4 hours, and the coking material will be basically dissolved in the solvent. The solvent can be recovered and reused by extraction and distillation.

[0023] Example 4

[0024] Add 12 ml of 4% sodium hydroxide solution to the wastewater evaporator. 3Maintain the alkaline dissolution reaction temperature in the evaporator at 60℃ for 8 hours. The high-temperature polymerized coking material decomposes into a molten oily substance with slight fluidity. Then add 5t of an organic mixture of furfural:toluene:ethanol = 10:15:75 (mass ratio), maintain the equipment temperature at no less than 50℃ for 3.8 hours, and the coking material will be basically dissolved in the solvent. The solvent can be recovered and reused by extraction and distillation.

[0025] Example 5

[0026] Add 12m of 10% sodium hydroxide solution to the wastewater evaporator 3 Maintain the alkaline dissolution reaction temperature in the evaporator at 60℃ for 6.5 hours. The high-temperature polymerized coking material decomposes into a molten oily substance with slight fluidity. Then add 5t of an organic mixture of furfural:toluene:ethanol = 10:15:75 (mass ratio), maintain the equipment temperature at no less than 50℃ for 3.6 hours, and the coking material is basically dissolved in the solvent. The solvent can be recovered and reused by extraction and distillation.

[0027] The economic benefits of adopting the technical solution in Example 5 are as follows: The entire process from shutdown of the wastewater evaporator to completion of coking removal and commissioning can be completed in just 48 hours, without the need for equipment cooling, thus reducing heat loss. Higher-pressure water flushing can save 5 days of downtime, making coking removal more efficient and simpler to operate, saving approximately 12,000 yuan in flushing costs each time. Environmental benefits: The effective components of the alkaline solution and organic mixture can be recovered and reused through distillation. The bottom liquid of the distillation column contains coking material and has high calorific value, which can be directly sent to the boiler for combustion. Using solvent dissolution instead of high-pressure water jet flushing reduces environmental pollution caused by flushing wastewater and lowers the waste of primary water resources.

Claims

1. A method of dissolving high temperature polymeric cokes of furfural, characterized by, The method comprises the following steps: ①adding 4-10wt% sodium hydroxide solution as lye into the wastewater evaporator, and maintaining the temperature of the wastewater evaporator at 40-60℃ by supplying hot water or steam at the bottom for 6-8h, so that the lye can sufficiently alkali-dissolve the polymerization coking substance, and the polymerization coking substance is decomposed into molten oily material; ②stopping heat exchange at the bottom of the wastewater evaporator, so that the molten oily material slowly flows to the bottom of the wastewater evaporator, and after the molten oily material flows into the bottom of the wastewater evaporator, organic mixed liquid is added from the top of the wastewater evaporator, the organic mixed liquid can dissolve the coking substance again and extract and separate the lye, the temperature is maintained at no less than 40℃, and the reaction time is 3-4h; the organic mixed liquid is prepared according to the mass ratio of furfural, toluene and ethanol of 10-15:15-25:60-75; ③the dissolved mixed liquid is left to separate into upper oil liquid and lower water liquid, and the oil liquid and the water liquid are respectively introduced into a rectification device for treatment; in step ③, the liquid collected from the top of the oil liquid column is collected and reused according to toluene and furfural in turn, and the residual liquid in the column is sent to a boiler for combustion; ethanol and water are distilled from the top of the water liquid column and reused, and concentrated waste brine in the column is sent to a sewage treatment plant for treatment; the mass ratio of the lye in step ① to the organic mixed liquid in step ② is 1:0.3-0.5.