Method for purifying organic waste gas containing epoxypropane or ethylene oxide

[0052] Example 1

[0053] The exhaust gas in this embodiment comes from the process of polymerization reaction of propylene oxide, propylene glycol, sorbitol, sugar, etc., with propylene oxide to produce polyether polyol under the action of a strong alkaline catalyst. The exhaust gas treatment process is as follows: figure 1 As shown, the exhaust gas treatment steps are as follows:

[0054] (A) The exhaust gas is buffered in the buffer tank through the fan, so that the maximum flow rate and the highest concentration of the exhaust gas are homogenized, and the average gas volume is maintained at 3000Nm 3 /Day, the PO concentration is about 30v%; other components in the waste gas include: organic amine 58ppm, ethanol 320ppm, low molecular polyether 810ppm, metal ions K, Fe, Na, and the rest are nitrogen. The specific content is shown in Table 2.

[0055] (B) The homogenized exhaust gas enters the solvent absorption tower filled with modified activated carbon filler. The residence time of the exhaust gas in the tower is 2s, and the solvent circulation volume in the tower is 10Nm 3 /hr (The solvent is water when the device is started up. As the exhaust gas enters the solvent absorption tower and the solid acid catalytic unit, the solvent is converted into an aqueous solution of propylene glycol or ethylene glycol). The amount of modified activated carbon filler used is 6m 3. Other impurity components in the exhaust gas and 10% by weight of propylene oxide in the total amount of propylene oxide are absorbed and removed by the solvent; the modified activated carbon filler is made by passing active carbon particles made from coconut shell through 6wt% in a sulfuric acid catalytic reactor. After immersing in the sulfuric acid aqueous solution for 2 hours, wash with water to a neutral pH of about 7, take it out and dry. After performing the above operations three times in succession, the dried sample was calcined under nitrogen protection at 400° C. for 1 hour, then immersed in a 20 wt% propylene glycol aqueous solution for 0.5 hours, taken out and dried.

[0056] (C) The exhaust gas treated by the solvent absorption tower then enters the solid acid catalytic unit for treatment. The solid acid catalyst is a sulfonic acid type cation exchange resin (Rohm and Haas-35), and the residence time of the exhaust gas is 8s. The solid acid catalytic unit The amount of solvent used is 2Nm 3 /hr, the solvent is a mixture of propylene glycol and water, the concentration is 10wt%, and the usage amount of solid acid catalyst is 4m 3. Propylene oxide, which accounts for 60% by volume of the total propylene oxide in the exhaust gas, is converted into propylene glycol.

[0057] (D) The waste gas after being treated by the solid acid catalytic reaction unit enters the sulfuric acid aqueous solution catalytic unit with a concentration of 6wt%, the residence time of the waste gas is 2s, and the amount of inorganic acid solution used is 5Nm 3 /hr. Converting 30v% of propylene oxide in the exhaust gas, which accounts for the total amount of propylene oxide, into propylene glycol, and in the organic exhaust gas catalyzed by inorganic acid, the concentration of propylene oxide is less than 1800 ppm.

[0058] (E) The waste gas treated by the inorganic acid catalytic reaction unit enters the activated carbon fiber adsorption tower, and the amount of activated carbon fiber used is calculated according to the adsorption treatment amount of 0.01g propylene oxide/g activated carbon fiber. The residence time of the exhaust gas in the adsorption tower is 5s, the residual propylene oxide in the exhaust gas is adsorbed by the activated carbon fiber, and the propylene oxide content in the exhaust gas is 1 ppm.

[0059] After the solvent absorption tower, the removal effect of other impurities in the exhaust gas is as follows:

[0060] Table 2 Treatment effect of solvent absorption tower on other impurity components

[0061]

[0062] The effects of each process on propylene oxide treatment are as follows:

[0063] Table 3 Treatment effect of high-concentration propylene oxide waste gas

[0064]

[0065] The exhaust gas is adsorbed on the activated carbon fiber tower for an average of 8 hours and then the activated carbon fiber is saturated with adsorption. 2 kg of pressure steam is used for analysis for 0.2 hours. After the analysis, the steam is condensed in two stages. In the second stage, the non-condensable gas is further condensed, and the propylene oxide is recovered for reuse. After condensation, the non-condensable gas will be sent to the fan inlet for repurification.

[0066] When the concentration of propylene glycol in the solvent of the solid acid catalytic unit exceeds 25%, the concentration of wastewater from the activated carbon fiber tower analysis is 0.1wt% propylene glycol aqueous solution according to 2m 3 /hr flow is introduced into the solid acid catalyst unit for solvent replacement. At the same time, the solid acid catalytic unit is 2m 3 /hr flow rate of the absorption liquid in the system to the solvent absorption tower, the solvent absorption tower is 2m 3 /hr flow efflux the waste liquid from the system to the inorganic acid catalytic unit. Finally, the solvent concentration of the solid acid catalyst unit was 20% by weight after solvent replacement for 0.15 hours.

[0067] In the solvent absorption tower, the absorption liquid absorbs the propylene oxide in the exhaust gas and reacts in the modified activated carbon filler to catalyze the conversion of organic matter in the exhaust gas into propylene glycol. As the absorbed waste liquid is discharged to the inorganic acid catalytic unit for further treatment, under the catalysis of the inorganic acid catalyst, all the propylene oxide in the waste liquid is further converted into propylene glycol. At the same time, as the propylene oxide in the exhaust gas is catalyzed by the inorganic acid, the concentration of propylene glycol in the waste liquid of the inorganic acid catalytic unit reaches 70% by weight, which is returned to the polyether reaction system after alkali neutralization treatment as raw material for reuse.

[0068] Example 2

[0069] The exhaust gas in this embodiment comes from the process of polymerization reaction of ethylene oxide with ethylene oxide to produce polyether polyol from the initiator ethylene glycol, sorbitol, sugar, etc. under the action of a strong alkaline catalyst. The exhaust gas treatment steps are as follows:

[0070] (A) The organic waste gas is buffered by a buffer tank to homogenize the maximum flow rate and the highest concentration part of the waste gas, and maintain an average gas volume of 3000Nm 3 /Day, EO concentration is about 35v%; other impurity components in the exhaust gas include: organic amine 83ppm, ethanol 240ppm, low-molecular-weight polyether 634ppm, metal ions K, Fe, Na, the rest is nitrogen, the specific content is shown in Table 4;

[0071] (B) After homogenization, it enters into the solvent absorption tower filled with modified activated carbon filler, the residence time of waste gas in the tower is 10s, and the solvent circulation volume in the tower is 20Nm 3 /hr, modified activated carbon filler usage is 4m 3. Other impurities in the exhaust gas and ethylene oxide accounting for 5v% of the total ethylene oxide are absorbed and removed by the solvent to become waste liquid intermittently and discharged to the inorganic acid catalytic unit for further treatment;

[0072] The modified activated carbon filler is made by immersing coconut shell activated carbon particles in a sulfuric acid catalytic reactor with a 4 wt% sulfuric acid aqueous solution for 2 hours, washing them with water to a neutral pH value of about 7, then taking out and drying. After performing the above operations three times in succession, the dried sample was roasted under nitrogen protection at 400℃ for 1 hour, then soaked in 20% ethylene glycol aqueous solution for 2 hours, removed and dried to obtain a modified coconut shell activated carbon filler .

[0073] (C) The exhaust gas treated by the solvent absorption tower then enters the solid acid catalytic unit for treatment. The solid acid catalyst is a sulfonic acid type cation exchange resin (Langxess K2620). The residence time of the exhaust gas in it is 2s. The solvent usage of the solid acid catalytic unit At 10Nm 3 /hr, the solvent is a mixture of ethylene glycol and water, the concentration is 15wt%, and the solid acid catalyst usage is 2m 3. 70v% of ethylene oxide in the exhaust gas is converted into ethylene glycol;

[0074] (D) The exhaust gas treated by the solid acid catalytic unit enters the catalytic unit with a concentration of 4wt% sulfuric acid aqueous solution, the residence time of the exhaust gas is 8s, and the amount of inorganic acid solution used is 10Nm 3 /hr. Convert 25v% of ethylene oxide in the exhaust gas, which accounts for the total amount of ethylene oxide, into ethylene glycol. In the organic exhaust gas catalyzed by inorganic acid, the concentration of ethylene oxide is less than 1600ppm;

[0075] (E) The exhaust gas treated by the inorganic acid catalytic unit enters the activated carbon fiber adsorption tower, and the amount of activated carbon fiber used is calculated according to the adsorption treatment capacity of 0.1gEO/g activated carbon fiber. The residence time of the exhaust gas in the adsorption tower is 1s, the residual ethylene oxide in the exhaust gas is adsorbed by the activated carbon fiber, and the ethylene oxide content in the exhaust gas is 2ppm.

[0076] After the solvent absorption tower, the removal effect of other impurities in the exhaust gas is as follows:

[0077] Table 4 Treatment effect of solvent absorption tower on other impurity components

[0078]

[0079] The effects of each process on propylene oxide treatment are as follows:

[0080] Table 5 Treatment effect of high-concentration ethylene oxide waste gas

[0081]

[0082] The exhaust gas is adsorbed on the activated carbon fiber tower for an average of 6 hours and then the activated carbon fiber is saturated with adsorption. 4kg of pressure steam is used for analysis for 0.1 hour. After the analysis, the steam is condensed in two stages. The first stage condenses the analysis water vapor to obtain a concentration of 0.1wt% ethylene For the alcohol aqueous solution, the second stage will further condense the non-condensable gas, and recover the ethylene oxide for reuse. After the condensation, the non-condensable gas will be sent to the fan inlet for re-purification.

[0083] When the concentration of ethylene glycol in the solvent of the solid acid catalytic unit exceeds 20wt%, the activated carbon fiber tower analysis wastewater is 1m 3 /hr flow is introduced into the solid acid catalyst unit for solvent replacement. At the same time, the solid acid catalytic unit is 1m 3 /hr flow rate of the absorption liquid in the system to the solvent absorption tower, the solvent absorption tower is 1m 3 /hr flow efflux the waste liquid from the system to the inorganic acid catalytic unit. Finally, the solvent concentration of the solid acid catalytic unit was 20wt% after solvent replacement for 0.2h.

[0084] In the solvent absorption tower, the absorption liquid absorbs ethylene oxide in the exhaust gas and reacts in the modified activated carbon filler to catalyze the conversion of organic matter into ethylene glycol. As the absorption waste liquid is discharged to the inorganic acid catalytic unit for further treatment, under the catalysis of the inorganic acid catalyst, all the ethylene oxide in the absorption liquid is further converted into ethylene glycol. At the same time, as the ethylene oxide in the exhaust gas is catalyzed by the inorganic acid, the concentration of the ethylene glycol in the reaction solution in the system reaches 60wt%, and it is sent back to the polyether reaction system as a raw material after alkali neutralization treatment.