Energy-saving and emission-reducing method for preparing epoxypropane by saponification method
The waste heat recovery method through chlorohydrin solution-solid solid treatment and heat pump technology solves the problems of high waste slag treatment and energy consumption in propylene oxide production, achieving efficient waste slag treatment and significant energy consumption reduction.
Patent Information
- Application Number
- CN202510257065.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-05
- Publication Date
- 2025-05-02
AI Technical Summary
In the existing propylene oxide production process, waste slag produced by chloropropanol saponification method is difficult to deal with, resulting in environmental pollution, and at the same time, the process energy consumption is high, and there is a need for energy conservation and emission reduction.
The chlorine hydrolyzate solution is used to dissolve and solid treatment of the saponification reaction waste residue, and then the waste heat of the saponification solution is recovered by heat pump technology to reduce water vapor consumption, and reduce the consumption of lime milk through acidity reduction and reaction design.
The treatment volume of saponification waste residue of more than 95% of the propylene oxide is achieved, which reduces the acidity of the chlorine hydrolyzate, reduces the consumption of lime milk, and reduces the consumption of water vapor in the distillation tower of the saponification reaction, achieving savings of more than 85%.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of environmental protection and energy saving in a compound preparation process, and in particular to a waste residue treatment technology and a saponification heat pump energy-saving process in a process of preparing propylene oxide by saponifying high-concentration chloropropanol. Background Art
[0002] Propylene oxide is an important raw material for petrochemical production. Propylene oxide is used to manufacture other chemicals, mainly polyether polyols, propylene glycol and various non-ionic surfactants. Among them, polyether polyols are important raw materials for the production of polyurethane foams, thermal insulation materials, elastomers, adhesives and coatings. Various non-ionic surfactants are widely used in the petroleum, chemical, pesticide, textile, daily chemical and other industries. The main end use of propylene glycol is the production of polyester polymers. It is also used as a plasticizer and antifreeze. Secondly, it is used to produce downstream products such as isopropylene glycol ether, dipropylene glycol, and propylene carbonate.
[0003] At present, there are four main methods for producing propylene oxide, namely, the chloropropanol method, the co-oxidation method (PO / SM method), the direct oxidation method of hydrogen peroxide (HPPO method) and the cumene hydroperoxide method (CHP method). The chloropropanol saponification method is a classic method for producing propylene oxide.
[0004] Main reaction:
[0005] Side effects:
[0006] The process flow of the co-oxidation method is complex, the reaction conditions are harsh, the initial investment is large, and there are many raw material varieties; the direct oxidation method has high temperature and pressure reaction conditions, high equipment cost, long construction period, complex process flow and high purity requirements for raw material propylene; the CHP process flow is relatively complex, involving multi-step reactions and catalyst participation, difficult operation, high investment cost, and limited market application. The process flow of the chloropropanol method is simple and mature, with low investment, large operating load flexibility, and no special requirements for equipment. The product quality can meet the production requirements of downstream products. However, the chlorohydrin method is subject to national industrial policies, and the amount of fresh water used and waste residue generated per ton of product is strictly limited. At the same time, the price of raw materials such as lime will rise in the future due to tight supply. Therefore, it is imperative to reduce the cost and emission of lime in the chlorohydrin method propylene oxide unit. Summary of the invention
[0007] In view of the shortcomings of the prior art, the object of the present invention is to provide a waste residue treatment technology and a saponification heat pump energy-saving process in the process of preparing propylene oxide by saponification of chloropropanol, so that the production of propylene oxide (PO) has the characteristics of simple equipment, high yield, low energy consumption and low pollution.
[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:
[0009] The present invention provides an energy-saving and emission-reducing method for preparing propylene oxide by a saponification process, comprising the following steps:
[0010] The saponification residue after filtration is mixed with the chloropropanol solution in a pulping machine to obtain a residue slurry, which is then fed into a dissolving tower and mixed with the chloropropanol solution filled in the tower for dissolving. The insoluble matter in the tower that cannot be acid-lyzed settles to the bottom of the tower, the suspended liquid at the bottom is sent to the residue washing unit, and the chloropropanol clear liquid at the top is sent to the saponification unit.
[0011] The process of preparing propylene oxide by the chlorohydrin method: using propylene and chlorine as raw materials, adopting chlorohydrinization, saponification, distillation and other processes. First, add excess propylene to the mixture of water and chlorine, and generate chloropropanol through chlorohydrinization reaction. The remaining propylene and the hydrogen chloride and part of the organic chloride (dichloropropane, etc.) generated during the reaction are discharged from the top of the reactor, and then condensed to remove the hydrogen chloride and organic chloride, and the propylene is recycled. The bottom of the reactor produces a chloropropanol solution containing HCl. Then add a saponifying agent (lime milk) to saponify the chloropropanol to generate crude propylene oxide, and the crude propylene oxide is sent to the distillation tower for separation and purification to obtain the propylene oxide product.
[0012] The "saponification residue" mentioned above refers to the waste residue produced by the saponification unit, that is, the waste residue produced by the "saponification reaction distillation tower (saponification unit)" described herein.
[0013] The "chloropropanol solution" mentioned above refers to the acidic chlorohydrin solution (e.g., 3.8% chloropropanol content, 1.5% HCl content) produced in the propylene chlorohydrin chemical stage.
[0014] In some embodiments, the mixing mass ratio of the saponification residue to the chloropropanol solution is 1:2; the filter press residue is completely mixed with the chloropropanol solution in a pulping machine to form an emulsion slurry.
[0015] In some embodiments, while the residue slurry enters the dissolution tower, the dissolution tower is additionally supplemented with chloropropanol solution (the chlorohydrin liquid supplement pipe of the dissolution tower extends to the bottom of the dissolution tower), and the supplementary amount of the chloropropanol solution is 1 to 1.5 times the molar amount of the acid-lyzable substance in the saponification residue (the molar ratio of HCl in the chlorohydrin liquid to the acid-lyzable substance in the saponification residue is 1 to 1.5:1).
[0016] In some embodiments, the residence time of the residue slurry in the dissolution tower is 5 to 15 minutes.
[0017] In some embodiments, the top chloropropanol clear liquid is premixed with lime milk in a mixer, and the mixed liquid is sent to a saponification reaction distillation tower for reaction distillation.
[0018] In some embodiments, the energy saving and emission reduction method further comprises the following steps:
[0019] The gas phase at the top of the saponification reaction distillation tower goes to the condensation system, and the condensed reflux liquid is refluxed to the saponification reaction distillation tower; the residual liquid at the bottom of the saponification reaction distillation tower is discharged to the saponification residual liquid buffer tank, and a heat pump compressor is added to the top of the tank to recover the heat of the saponified liquid at the bottom of the tower, and the recovered steam at the compressor outlet is discharged into the kettle of the saponification reaction distillation tower.
[0020] The dissolved chloropropanol clear liquid enters the saponification reaction distillation tower to undergo saponification reaction with lime milk, and at the same time, water vapor is introduced into the bottom of the tower for direct heating. A heat pump compressor is arranged at the bottom of the saponification reaction distillation tower to recover the heat of the saponification liquid and reduce the consumption of stripping steam introduced into the bottom of the saponification reaction distillation tower.
[0021] In some embodiments, the compression ratio of the heat pump compressor is 2-5.
[0022] The saponification process of propylene oxide (calcium saponification) can produce a large amount of waste residues, causing serious environmental pollution. The present invention utilizes the acidic chlorohydrinization liquid produced in the propylene chlorohydrinization chemical section to process the waste residues, and a large amount of calcium oxide, calcium hydroxide, magnesium oxide and other substances in the waste residue react with the hydrogen chloride in the chlorohydrinization liquid, and are converted into soluble salts such as calcium chloride and magnesium chloride, which enter the sewage treatment system together with the saponification waste water, so that the waste residue discharge of about 95% can be reduced. At the same time, the chlorohydrinization liquid first digests a part of the hydrogen chloride, and the acidity of the chlorohydrinization liquid is reduced. Then, entering the saponification section can significantly reduce the consumption of lime milk. In addition, the high-temperature saponification waste water produced at the bottom of the saponification reaction distillation tower adopts heat pump technology to recycle heat, and the recycled heat is used to supplement the stripping steam at the bottom of the saponification reaction distillation tower, and the low-pressure steam consumption can be reduced by more than 85%.
[0023] Technical effects:
[0024] The present invention adopts chlorohydrinization liquid to carry out solution-solid treatment on saponification reaction waste residue, and then the chlorohydrinization clear liquid is subjected to saponification reaction and then enters the saponification reaction distillation tower; a heat pump compressor is added to the bottom of the saponification reaction distillation tower to recycle the waste heat of the saponification liquid and reduce the consumption of water vapor in the saponification reaction distillation tower. The present invention can achieve a treatment capacity of about 95% of propylene oxide saponification waste residue, and at the same time, the solution-solidification process reduces the acidity of the chlorohydrinization liquid, which can further reduce the consumption of lime milk raw materials for the saponification reaction; the consumption of water vapor in the saponification reaction distillation tower is greatly reduced, and the consumption can be reduced by more than 85%.
[0025] The present invention has been described in detail above, but the above embodiments are only illustrative in nature and are not intended to limit the present invention. In addition, this article is not limited by any theory described in the above prior art or invention content or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1This is the process flow chart for the treatment and energy saving of propylene oxide waste residue by saponification process.
[0027] Diagram: 1-chloropropanol solution; 2-filter press residue; 3-residue washing unit; 4-pulping machine; 5-residue pump; 6-solidification tower; 7-mixer; 8-lime milk; 9-low-pressure steam; 10-saponification reaction distillation tower; 11-condensation system; 12-condensation reflux liquid; 13-crude propylene oxide; 14-saponification residue buffer tank; 15-heat pump compressor; 16-saponification residue. DETAILED DESCRIPTION
[0028] The present invention is further described below in conjunction with examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed for the present invention.
[0029] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.
[0030] Chloropropanol content: The chloropropanol content in the chlorohydrin solution was determined by gas chromatography to be 3.8%.
[0031] The amount of propylene oxide saponification waste residue treated (waste residue degradation rate): the percentage of the filter press residue amount dissolved by the dissolution tower to the total amount of filter press residue.
[0032] The percentage reduction of water vapor consumption of the saponification reaction distillation tower (water vapor consumption reduction rate of the saponification reaction distillation tower): (low-pressure steam consumption before waste residue treatment - low-pressure steam consumption after adding the heat pump compressor) / low-pressure steam consumption before waste residue treatment * 100%.
[0033] Example 1
[0034] The saponification process of propylene oxide waste residue treatment and energy saving process flow chart is as follows Figure 1 shown.
[0035] (1) Solution-solidification section: 1.7m 3 / h 3.8% chloropropanol solution 1 (hydrogen chloride content of 1.5%) is mixed with 1t / h filter press residue 2 and made into filter press residue slurry in pulping machine 4. Dissolving tower 6 is filled with chloropropanol solution, and the slurry enters the dissolving tower. At the same time, 49.1m 3 / h of 3.8% chloropropanol solution by mass concentration, the residence time of the slurry in the dissolving tower is 5min, 87.5% of the filter press residue is rapidly acidified by the chlorohydrinating liquid, and the remaining insoluble matter of the residue that cannot be acidified settles to the bottom of the tower, and the suspension is sent to the residue washing unit 3 through the residue pump 5, the chlorohydrinating clear liquid obtained at the top of the dissolving tower is pre-mixed with lime milk 8 in the mixer 7, and the mixed liquid is sent to the saponification reaction distillation tower 10 for reaction distillation.
[0036] (2) Heat pump energy-saving section: low-pressure steam 9 is introduced into the saponification reaction distillation tower 10 at the bottom, the gas phase at the top of the tower is sent to the condensation system 11, the condensate reflux liquid 12 is refluxed to the saponification reaction distillation tower, and the crude propylene oxide 13 is directly discharged to the next unit; the residual liquid at the bottom of the saponification reaction distillation tower is discharged into the saponification residual liquid buffer tank 14, and the saponification residual liquid 16 is discharged from the bottom of the tank. A heat pump compressor 15 is added to the top of the tank. The heat of the saponified liquid at the bottom of the saponification reaction distillation tower is recovered with a compression ratio of 2. The recovered steam at the compressor outlet is discharged into the kettle of the saponification reaction distillation tower, and the steam consumption of the saponification reaction distillation tower is reduced by 77.4%.
[0037] Example 2
[0038] (1) Solution-solidification section: 1.7m 3 / h 3.8% chloropropanol solution 1 (hydrogen chloride content of 1.5%) is mixed with 1t / h filter press residue 2 and made into filter press residue slurry in pulping machine 4. Dissolving tower 6 is filled with chloropropanol solution, and the slurry enters the dissolving tower. At the same time, 58.9m 3 / h of 3.8% chloropropanol solution by mass concentration, the residence time of the slurry in the dissolving tower is 10min, 91.8% of the filter press residue is rapidly acidified by the chlorohydrinating liquid, and the remaining insoluble matter of the residue that cannot be acidified settles to the bottom of the tower, and the suspension is sent to the residue washing unit 3 through the residue pump 5. The chlorohydrinating clear liquid obtained at the top of the dissolving tower is pre-mixed with lime milk 8 in the mixer 7, and the mixed liquid is sent to the saponification reaction distillation tower 10 for reaction distillation.
[0039] (2) Heat pump energy-saving section: low-pressure steam 9 is introduced into the saponification reaction distillation tower 10 at the bottom, the gas phase at the top of the tower is sent to the condensation system 11, the condensate reflux liquid 12 is refluxed to the saponification reaction distillation tower, and the crude propylene oxide 13 is directly discharged to the next unit; the residual liquid at the bottom of the saponification reaction distillation tower is discharged into the saponification residual liquid buffer tank 14, and the saponification residual liquid 16 is discharged from the bottom of the tank. A heat pump compressor 15 is added to the top of the tank. The heat of the saponified liquid at the bottom of the saponification reaction distillation tower is recovered with a compression ratio of 2. The recovered steam at the compressor outlet is discharged into the kettle of the saponification reaction distillation tower, and the steam consumption of the saponification reaction distillation tower is reduced by 80.8%.
[0040] Example 3
[0041] (1) Solution-solidification section: 1.7m 3 / h 3.8% chloropropanol solution 1 (hydrogen chloride content of 1.5%) is mixed with 1t / h filter press residue 2 and made into filter press residue slurry in pulping machine 4. Dissolving tower 6 is filled with chloropropanol solution, and the slurry enters the dissolving tower. At the same time, 68.7m 3 / h of 3.8% chloropropanol solution by mass concentration, the residence time of the slurry in the dissolving tower is 15min, 95.6% of the filter press residue is rapidly acidified by the chlorohydrinating liquid, and the remaining insoluble matter of the residue that cannot be acidified settles to the bottom of the tower, and the suspension is sent to the residue washing unit 3 through the residue pump 5. The chlorohydrinating clear liquid obtained at the top of the dissolving tower is pre-mixed with lime milk 8 in the mixer 7, and the mixed liquid is sent to the saponification reaction distillation tower 10 for reaction distillation.
[0042] (2) Heat pump energy-saving section: low-pressure steam 9 is introduced into the saponification reaction distillation tower 10 at the bottom, the gas phase at the top of the tower is sent to the condensation system 11, the condensate reflux liquid 12 is refluxed to the saponification reaction distillation tower, and the crude propylene oxide 13 is directly discharged to the next unit; the residual liquid at the bottom of the saponification reaction distillation tower is discharged into the saponification residual liquid buffer tank 14, and the saponification residual liquid 16 is discharged from the bottom of the tank. A heat pump compressor 15 is added to the top of the tank. The heat of the saponified liquid at the bottom of the saponification reaction distillation tower is recovered with a compression ratio of 2. The recovered steam at the compressor outlet is discharged into the kettle of the saponification reaction distillation tower, and the steam consumption of the saponification reaction distillation tower is reduced by 85.3%.
[0043] The technical indicators of the results obtained by applying the process and equipment for treating propylene oxide waste residue by saponification and treating heat pump energy saving provided by the present invention are as follows:
[0044]
[0045]
[0046] (1) The saponification residue treatment capacity of the present invention can be as high as 95% or more, which is far lower than the saponification waste residue per ton of product stipulated by national policies.
[0047] (2) The present invention adopts a heat pump treatment energy-saving process to recover the waste heat of the saponified liquid at the bottom of the tower, which can reduce the water vapor consumption by 85% and save energy.
[0048] Comparative Example 1
[0049] The acid is directly used to dissolve the waste residue of propylene oxide produced by the saponification process, converting it into calcium chloride, which is then discharged into the sewage treatment plant. This process increases the difficulty of sewage treatment and adds a large amount of acid to the entire system, which is very corrosive to the equipment.
[0050] Comparative Example 2
[0051] Purchase high-purity calcium hydroxide, or change the traditional lime rotary kiln wet ash treatment to dry digestion powder selection technology, and appropriately add carbide slag (the main component of carbide slag is calcium hydroxide, with a content of 54-72%) to reduce costs and increase efficiency. Increasing the concentration of effective calcium in calcium hydroxide to more than 95% can effectively reduce the amount of saponified slag. However, carbide slag contains sulfur, phosphorus, silicon and other components, which will have a certain impact on production.
[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and essence of the claims of the present invention; and these modifications or replacements are still within the scope defined by the claims of the present invention.
Claims
1. A method for energy saving and emission reduction of propylene oxide by saponification, characterized in that: The following steps are involved: The saponification residue after filtration is mixed with the chloropropanol solution in a pulping machine to obtain a residue slurry, which is then fed into a dissolving tower and mixed with the chloropropanol solution filled in the tower for dissolving. The insoluble matter in the tower that cannot be acid-lyzed settles to the bottom of the tower, the suspended liquid at the bottom is sent to the residue washing unit, and the chloropropanol clear liquid at the top is sent to the saponification unit.
2. The method according to claim 1, characterized in that The mixing mass ratio of the saponification residue to the chloropropanol solution is 1:
2.
3. The method according to claim 1, characterized in that: When the residue slurry enters the dissolution tower, the dissolution tower is additionally supplemented with chloropropanol solution, and the supplementary amount of the chloropropanol solution is 1 to 1.5 times the molar amount of the acid-decomposable substance in the saponification residue based on the molar amount of HCl in the chloropropanol solution.
4. The method according to claim 1, characterized in that The residence time of the residue slurry in the dissolution tower is 5 to 15 minutes.
5. The method according to claim 1, characterized in that The top chloropropanol clear liquid is premixed with lime milk in a mixer, and the mixed liquid is sent to a saponification reaction distillation tower for reaction distillation.
6. The method according to claim 5, characterized in that The energy saving and emission reduction method also includes the following steps: The gas phase at the top of the saponification reaction distillation tower goes to the condensation system, and the condensed reflux liquid is refluxed to the saponification reaction distillation tower; the residual liquid at the bottom of the saponification reaction distillation tower is discharged to the saponification residual liquid buffer tank, and a heat pump compressor is added to the top of the tank to recover the heat of the saponified liquid at the bottom of the tower, and the recovered steam at the compressor outlet is discharged into the kettle of the saponification reaction distillation tower.
7. The method according to claim 6, characterized in that The compression ratio of the heat pump compressor is 2-5.