CN-121974793-A - Process for efficiently recovering butyric acid from concentrated wastewater of polyol device

CN121974793ACN 121974793 ACN121974793 ACN 121974793ACN-121974793-A

Abstract

The invention provides a process for efficiently recovering butyric acid from concentrated wastewater of a polyol device, which relates to the technical field of recycling of industrial wastewater, and comprises the following steps of S1, pretreatment of wastewater, S2, acidification and neutralization, wherein the concentrated wastewater of the polyol device containing sodium butyrate and sodium hydroxide is filtered to obtain pretreated wastewater, sulfuric acid is added into the pretreated wastewater for acidification reaction, the pH value of a reaction end point is controlled to be 1.5-2.5, sodium hydroxide is neutralized, sodium butyrate is converted into butyric acid, and the invention ensures the efficient and complete conversion of sodium butyrate into butyric acid through precisely controlling the acidification pH value and the reaction conditions, and the mass transfer efficiency of butyric acid from complex water phase to organic phase is obviously improved by adopting a two-stage countercurrent extraction process, the total extraction rate can reach more than 92%, the final butyric acid recovery rate is more than or equal to 85%, and the product purity is more than or equal to 99.0%, thereby meeting the industrial use requirements.

Inventors

JIN HONGLEI
ZHANG ZHAOFEI
LIU ZHONGKAI
ZHANG SHENGNAN
FENG MENGLIN
QIN JITAO
Song Qingye
Tao Xianhao

Assignees

聊城鲁西多元醇新材料科技有限公司

Dates

Publication Date: 20260505
Application Date: 20251225

Claims (10)

1. A process for efficiently recovering butyric acid from concentrated wastewater of a polyol plant, comprising the steps of: S1, wastewater pretreatment, namely concentrating wastewater by a polyol device containing sodium butyrate and sodium hydroxide, and filtering to obtain pretreated wastewater; S2, acidizing and neutralizing, namely adding sulfuric acid into the pretreated wastewater to perform acidizing reaction, controlling the pH value of the reaction end point to be 1.5-2.5, neutralizing sodium hydroxide, and converting sodium butyrate into butyric acid; s3, extracting and separating, namely, carrying out contact extraction on the acidified mixed solution and an ethyl acetate extractant, and separating to obtain an extraction phase rich in butyric acid and a raffinate phase containing inorganic salt; S4, solvent recovery and product purification, namely sequentially carrying out first-stage vacuum flash evaporation and second-stage vacuum flash evaporation on the extraction phase, wherein the first-stage flash evaporation is used for evaporating and recovering ethyl acetate, and the second-stage flash evaporation is used for evaporating and collecting butyric acid products.
2. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 1, wherein in S1, the concentrated wastewater contains 15 to 25 percent of sodium butyrate and 8 to 12 percent of sodium hydroxide by mass, the COD (chemical oxygen demand) is 600000 to 700000mg/L, in S1, a 316L stainless steel precision filter is adopted for filtration, the filtration precision is 5 to 10 μm, the filtration operating pressure is 0.1 to 0.3MPa, the filtration temperature is 20 to 30 ℃, and the content of suspended matters in the pretreated wastewater after filtration is less than or equal to 10mg/L.
3. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 1, wherein in S2, the mass concentration of sulfuric acid is 40%, the sulfuric acid is added in a constant pressure dropwise manner, the dropwise addition rate is 5-10mL/min, the adding amount of sulfuric acid is 1.0-1.2 times of the theoretical calculation amount, the theoretical calculation amount is accurately calculated by the following formula, the pH value is monitored every 5min in the reaction process, in S2, the acidification reaction temperature is 30-40 ℃, the stirring rate is 300-350r/min, the reaction time is 30-60min, and the theoretical calculation formula of sulfuric acid is: V(H 2 SO 4 )=[(m(NaBu)×2)/M(NaBu)+(m(NaOH)×2)/M(NaOH)]×M(H 2 SO 4 ))/(ρ(H 2 SO 4 ))×w(H 2 SO 4 ))), Wherein V (H 2 SO 4 )) is the volume (unit: L) of sulfuric acid with the required 40% mass concentration, M (NaBu) is the mass (unit: kg) of sodium butyrate in the pretreated wastewater, which is determined by high performance liquid chromatography detection after wastewater sampling, M (NaOH) is the mass (unit: kg) of sodium hydroxide in the pretreated wastewater, which is determined by acid-base titration detection after wastewater sampling, M (NaBu) is the molar mass (unit: g/mol) of sodium butyrate, the fixed value is 110.09g/mol, M (NaOH) is the molar mass (unit: g/mol) of sodium hydroxide, the fixed value is 40.00g/mol, M (H 2 SO 4 )) is the molar mass (unit: g/mol) of sulfuric acid, the fixed value is 98.08g/mol, ρ (H 2 SO 4 )) is the density (unit: kg/L) of sulfuric acid with the 40% mass concentration, the fixed value is 1.303kg/L at 25 ℃, and the fixed value is 40%.
4. A process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 3, wherein in S2, the mass conversion coefficient of sodium butyrate to butyric acid by acidification reaction is more than 0.8, the conversion coefficient is defined as the ratio of the mass of actually produced butyric acid to the mass of theoretically produced butyric acid, wherein the mass of theoretically produced butyric acid=m (NaBu) ×M (HBu)/M (NaBu), M (HBu) is the molar mass of butyric acid, the fixed value is 88.11g/mol, and the mass of actually produced butyric acid is determined by high performance liquid chromatography detection.
5. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 1, wherein in S3, extraction and separation are two-stage countercurrent extraction, a mixer-settler or a pulse extraction tower is adopted as extraction equipment, the operation pressure is 0.1MPa, the extraction operation temperature is 25-35 ℃, and the volume ratio of ethyl acetate to acidified mixed solution is 1:3-1:5.
6. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 5, wherein the total butyric acid extraction rate of the two-stage countercurrent extraction is not lower than 92%, the extraction rate is calculated by gas chromatography detection, the detection condition is that the carrier gas is nitrogen with purity of not less than 99.99%, the column temperature is 80-120 ℃, the detector is a hydrogen flame ionization detector FID, and the detection accuracy is +/-0.5%.
7. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 1, wherein in S3, the obtained raffinate phase is neutralized to pH6-9 and enters a subsequent wastewater biochemical treatment system, the neutralizing agent adopts food grade sodium carbonate or lime milk, the neutralization temperature is 25-35 ℃, the neutralization stirring rate is 200-250r/min, and solid impurities are removed by plate and frame filter pressing after neutralization.
8. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 1, wherein in the step S4, a falling film type flash evaporator is adopted for the first-stage vacuum flash evaporation and the second-stage vacuum flash evaporation, the operation condition of the first-stage vacuum flash evaporation is that the temperature is 50-55 ℃, the absolute pressure is 0.03-0.04MPa, the feeding rate is 5-10L/h, the operation condition of the second-stage vacuum flash evaporation is that the temperature is 90-100 ℃, the absolute pressure is 0.01-0.02MPa, the feeding rate is 3-8L/h, and the tail gas of the two-stage flash evaporation is discharged after condensation recovery.
9. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 8, wherein the ethyl acetate recovered from the first-stage vacuum flash distillation is recycled after being purified by rectification under normal pressure, the purity of the ethyl acetate recovered by recycling is not lower than 99.5% and the recycling rate is not lower than 80%, wherein the rectification tower adopts a stainless steel packed tower, and the packing height is 3-5m.
10. The process for efficiently recovering butyric acid from concentrated wastewater of a polyol device according to claim 9, wherein in S4, the purity of the butyric acid product obtained after the second-stage vacuum flash evaporation is not lower than 99.0%, the flash evaporation residual phase is high boiling point organic impurities and sodium salt, and the obtained product is collected and sent to an incinerator for incineration treatment at 1000-1200 ℃ for more than or equal to 2S.

Description

Process for efficiently recovering butyric acid from concentrated wastewater of polyol device Technical Field The invention relates to the technical field of industrial wastewater recycling, in particular to a process for efficiently recycling butyric acid from concentrated wastewater of a polyol device. Background Polyol (e.g., 1, 4-butanediol, 1, 3-propanediol, etc.) production units produce large amounts of highly concentrated wastewater during operation. The wastewater has complex composition, usually contains 15-25% of sodium butyrate and 8-12% of sodium hydroxide by mass percent, has extremely high Chemical Oxygen Demand (COD), and if discharged directly, serious water eutrophication and soil pollution are caused, and the sodium butyrate is wasted as a valuable chemical raw material; At present, the method for recovering organic acid from wastewater mainly comprises an extraction method, an adsorption method, a membrane separation method and the like, and patent CN202110498464 discloses a method for separating n-butyric acid and water by combining liquid-liquid extraction with heterogeneous azeotropic distillation, wherein the method uses a specific mixed solvent and double-tower distillation, although the high-purity separation of the n-butyric acid-water binary system can be realized, the process is complex, the equipment investment is high, and the method is mainly aimed at a simulation system with simple components, and is difficult to adapt to the complex environment of a large amount of complex organic impurities and high-concentration inorganic salts existing in the polyol wastewater. In addition, the traditional recovery process often has incomplete sodium butyrate conversion, low single-stage extraction efficiency and high subsequent separation energy consumption, and redundant steps such as back extraction and the like are often required to be introduced, so that the overall process is long, the operation cost is high, and secondary pollution is possibly generated. Disclosure of Invention Aiming at the problems, the invention provides a process for efficiently recovering butyric acid from concentrated wastewater of a polyol device, which ensures the efficient and complete conversion of sodium butyrate to butyric acid by precisely controlling the acidification pH and the reaction conditions, and remarkably improves the mass transfer efficiency of butyric acid from a complex water phase to an organic phase by adopting a two-stage countercurrent extraction process, wherein the total extraction rate can reach more than 92%, the final butyric acid recovery rate is more than or equal to 85%, the product purity is more than or equal to 99.0%, and the industrial use requirement is met. The invention aims at realizing the technical scheme that the process for efficiently recycling butyric acid from the concentrated wastewater of a polyol device comprises the following steps of: S1, wastewater pretreatment, namely concentrating wastewater by a polyol device containing sodium butyrate and sodium hydroxide, and filtering to obtain pretreated wastewater; S2, acidizing and neutralizing, namely adding sulfuric acid into the pretreated wastewater to perform acidizing reaction, controlling the pH value of the reaction end point to be 1.5-2.5, neutralizing sodium hydroxide, and converting sodium butyrate into butyric acid; s3, extracting and separating, namely, carrying out contact extraction on the acidified mixed solution and an ethyl acetate extractant, and separating to obtain an extraction phase rich in butyric acid and a raffinate phase containing inorganic salt; S4, solvent recovery and product purification, namely sequentially carrying out first-stage vacuum flash evaporation and second-stage vacuum flash evaporation on the extraction phase, wherein the first-stage flash evaporation is used for evaporating and recovering ethyl acetate, and the second-stage flash evaporation is used for evaporating and collecting butyric acid products. The further improvement is that in the S1, the concentrated wastewater contains 15-25% of sodium butyrate and 8-12% of sodium hydroxide by mass percent, the chemical oxygen demand COD is 600000-700000mg/L, in the S1, a 316L stainless steel precision filter is adopted for filtering, the filtering precision is 5-10 mu m, the filtering operation pressure is 0.1-0.3MPa, the filtering temperature is 20-30 ℃, and the suspended matter content of the pretreated wastewater after filtering is less than or equal to 10mg/L. The method is further improved in that in the step S2, the mass concentration of the sulfuric acid is 40%, the sulfuric acid is added in a constant pressure dropwise adding mode, the dropwise adding rate is 5-10mL/min, the adding amount of the sulfuric acid is 1.0-1.2 times of the theoretical calculation amount, the theoretical calculation amount is accurately calculated through the following formula, the pH value is monitored every 5min in the reaction process,