阅读说明：本技术 一种提高溴化丁基橡胶中溴利用率的工艺 (Process for improving bromine utilization rate in brominated butyl rubber ) 是由 张阳 任纪文 丁旭东 邢朝辉 周文祥 沈晓伟 彭照亮 崔再伟 于 2019-12-02 设计创作，主要内容包括：本发明提供了一种提高溴化丁基橡胶中溴利用率的工艺,通过废水净化、蒸馏、粗溴回用和尾气回收完成对溴的回收和再利用。具体通过蒸馏和尾气处理将溴的回收率提高至94%以上,蒸馏得到纯度98%的粗溴,满足实际生产需求,直接与溴化丁基生产无缝连接,不必进一步精馏,有效降低能耗,节约成本,外排水溴离子含量小于400ppm,满足环保要求；尾气处理将蒸馏产生的不凝气中的溴蒸汽碱洗后返回至溴回收装置继续回收溴,避免溴的排放。通过上述过程使得整个丁基橡胶生产中的溴利用率由原先的45-50%提高到95%以上,能够有效降低溴离子的外排,大幅度降低溴化胶的生产成本,减少污水处理成本。(The invention provides a process for improving the utilization rate of bromine in brominated butyl rubber, which finishes the recovery and reutilization of bromine through wastewater purification, distillation, crude bromine recycling and tail gas recovery. The recovery rate of bromine is improved to more than 94% by distillation and tail gas treatment, crude bromine with the purity of 98% is obtained by distillation, the actual production requirement is met, the crude bromine is directly connected with butyl bromide production in a seamless mode, further rectification is not needed, the energy consumption is effectively reduced, the cost is saved, the content of bromine ions in external drainage water is less than 400ppm, and the environmental protection requirement is met; and the tail gas treatment is to return bromine steam in the non-condensable gas generated by distillation to the bromine recovery device after alkali washing to continuously recover bromine, so that the emission of bromine is avoided. Through the process, the bromine utilization rate in the whole production of the butyl rubber is improved to more than 95 percent from the original 45 to 50 percent, the discharge of bromide ions can be effectively reduced, the production cost of brominated rubber is greatly reduced, and the sewage treatment cost is reduced.)

1. A process for improving the utilization rate of bromine in brominated butyl rubber comprises the following steps:

a. production of brominated butyl rubber: mixing a bromohexane solution and a butyl glue solution for bromination reaction, feeding the glue solution after the bromination reaction into a neutralization kettle, neutralizing the glue solution by using alkali liquor, then feeding the neutralized glue solution into a condensation kettle, removing a solvent by using steam, adding bromine-containing water from a halogenated water tank to form colloidal particle water, and dehydrating the colloidal particle water to form dry glue;

b. purifying waste water: the bromine which is not utilized exists in the water phase in the form of bromide ions, the bromine enters a bromine recovery device after dehydration, the bromine in the water is recovered, the bromine-containing water is introduced into a dissolved air floatation tank, the adhesive foam and the auxiliary agent powder are removed, the water is separated, and relatively clean water liquid at the bottom of the floatation tank is delivered to a water purification area;

c. and (3) distillation: the purified water enters a buffer tank, the water is heated by a preheater and then enters a distillation tower, low-pressure steam and chlorine are introduced into the tower bottom to react in the tower, the generated bromine steam and a small amount of water steam are extracted from the upper part of the distillation tower, sewage is discharged from the tower bottom, and is neutralized by dilute alkali solution and discharged to a sewage treatment system;

d. and (3) recycling crude bromine: cooling bromine steam and water steam extracted from the upper part of the distillation tower, then feeding the cooled bromine steam and water steam into a bromine-water separation bottle for separating bromine and bromine water, overflowing water containing bromine from the upper part of the bromine-water separation bottle back to the distillation tower, adding hexane into crude bromine at the bottom to prepare a bromohexane solution, and reusing the bromohexane solution for producing brominated butyl rubber;

e. tail gas recovery: the noncondensable gas which is not condensed at the outlet of the distillation tower and contains part of chlorine and bromine steam enters a tail gas recovery tower, bromine-containing water which is from a buffer tank and is cooled is introduced into the tower to react with the chlorine in the noncondensable gas, liquid bromine-containing water returns to the distillation tower, gas phase contains a small amount of chlorine and bromine steam and enters a tail gas alkaline washing tower to be absorbed, and high-concentration bromine water discharged from the tail gas alkaline washing tower returns to a dissolved gas floatation tank to extract bromine again.

2. The process according to claim 1 for increasing bromine utilization in brominated butyl rubber, wherein: the pH of the wastewater subjected to bromine recovery is 9-12, and the bromine content in the water is 5-10 g/L.

3. The process according to claim 2 for increasing bromine utilization in brominated butyl rubber, wherein: and after the bromine content in the alkali liquor in the tail gas alkali washing tower reaches 10g/L, replacing the alkali liquor.

4. The process according to claim 1 for increasing bromine utilization in brominated butyl rubber, wherein: the prepared bromohexane solution has the concentration of 10-16 percent and the temperature of 20-35 ℃.

5. The process according to claim 1 for increasing bromine utilization in brominated butyl rubber, wherein: the preheating temperature is 70-85 ℃.

6. The process according to claim 1 for increasing bromine utilization in brominated butyl rubber, wherein: the distillation tower is a packed tower, and the tower temperature is 80-95 ℃.

7. The process according to claim 1 for increasing bromine utilization in brominated butyl rubber, wherein: and d, cooling the bromine and the water vapor at the temperature of 30-45 ℃.

8. The process according to claim 7, wherein said process comprises the steps of: and e, cooling the bromine-containing water to 35-45 ℃ by a condenser, and feeding the bromine-containing water into a tail gas recovery tower.

9. The process according to claim 1 for increasing bromine utilization in brominated butyl rubber, wherein: two stages of filter screens are arranged at the outlet of the dissolved air floatation tank, and the aperture of each filter screen is 4-6 mu m.

10. The device for realizing the process for improving the bromine utilization rate in the brominated butyl rubber according to claim 1 is characterized in that: the device comprises a production device and a bromine recovery device, wherein the bromine recovery device comprises a crude bromine recycling system and a tail gas recovery system; the production device comprises a bromine storage tank (13), a liquid bromine metering tank (12), a reaction tank (1), a neutralization kettle (2), a condensation kettle (3) and a halogenated water tank (4) which are sequentially connected through pipelines, wherein a liquid return pipeline (41) for conveying bromine-containing water in the halogenated water tank (4) to the condensation kettle (3) for recycling is also arranged between the condensation kettle (3) and the halogenated water tank (4); the crude bromine recycling system comprises a dissolved air flotation tank (5), a buffer tank (6), a preheater (7), a distillation tower (8), a condenser (10), a tail gas condenser (14) and a bromine water separation bottle (11) which are sequentially connected through pipelines, wherein an outlet (8) at the bottom of the distillation tower is connected with a water inlet (9) of a neutralization kettle, an overflow pipeline is also arranged between the bromine water separation bottle (11) and the distillation tower (8), and an outlet of the bromine water separation bottle (11) is connected with a water inlet of a liquid bromine metering tank (12); the water inlet of the dissolved air floatation tank (5) is connected with the outlet of the halogenated water tank (4) through a pipeline, and the pipeline is connected with the liquid return pipeline (20) in parallel; the tail gas recovery system comprises a tail gas recovery tower (15), a first cooler (16), a tail gas alkaline washing tower (17), an alkaline washing tank (18) and a second cooler (19); the bottom inlet of the tail gas recovery tower (15) is connected with the top outlet of the distillation tower (8) through a pipeline on one hand, and is also connected with the gas phase outlet of the tail gas condenser (14) through a pipeline on the other hand; the top outlet of the tail gas recovery tower (15) is connected with the bottom inlet of the tail gas alkaline washing tower (17) through a pipeline, and the top inlet is connected with the outlet of the first cooler (16) through a pipeline; the inlet of the first cooler (16) is connected with the outlet of the buffer tank (6) through a pipeline, and the pipeline is connected in parallel with the pipeline connecting the buffer tank (6) and the preheater (7); the tail gas alkaline washing tower (17), the alkaline washing tank (18) and the second cooler (19) are sequentially connected through a pipeline, and a return pipeline (191) is further arranged between the second cooler (19) and the tail gas alkaline washing tower (17); the alkaline washing tank (18) is also connected with the dissolved air floatation tank (5) through a recycling pipeline (181), and a liquid pump is arranged on the recycling pipeline (181).

Technical Field

The invention belongs to the technical field of brominated butyl rubber, and particularly relates to a process for improving the utilization rate of bromine in brominated butyl rubber.

Background

The basic principle of brominated butyl rubber is that liquid bromine reacts with butyl rubber to produce brominated butyl rubber. The reaction process of bromination of butyl rubber is a substitution reaction, i.e. Br₂The theoretical maximum effective utilization rate of bromine atoms in the reaction is not more than 50 percent, the utilization rate of the bromine atoms in the production process of the common brominated rubber is only 45 to 50 percent, and more than half of the bromine atoms do not enter the product rubber and exist in water in the form of bromide ions. If the wastewater is directly discharged, the environment is seriously polluted and resources are wasted, so that the treatment of the wastewater not only needs to meet the environmental requirement, but also needs to recover bromine in the wastewater so as to obtain better economic benefit.

A known method for increasing the bromine utilization in the bromination of butyl rubber is to use at least 0.5mol of an oxidizing agent, such as hydrogen peroxide, alkali metal hypochlorite, alkaline earth metal hypochlorite, per mole of brominating agent, which oxidizes hydrogen bromide back to elemental bromine under the action of an emulsifier, and the regenerated bromine can be further used for the bromination of butyl rubber, thereby increasing the bromine utilization. The method needs to disperse the oxidant in the glue solution in the form of emulsion to avoid the oxidation of rubber caused by the direct contact of the oxidant and the rubber, the conversion rate of bromine atoms depends on the dispersion performance of the oxidant in the glue solution, but the bromination reaction of the butyl rubber and the hydrogen bromide oxidation reaction occur in the same system, the dispersion space of the oxidant is limited, and the good dispersion degree is difficult to control all the time, so the utilization rate of the bromine atoms is limited, the generation speed of the regenerated bromine directly influences the bromination reaction rate, and the continuous and stable bromination reaction is difficult to ensure.

According to the physical and chemical characteristics of bromine, bromine can be recovered by adopting a distillation method, the bromination reaction of the butyl rubber and the bromine recovery are separated and independently carried out, the mutual influence of the bromination reaction and the bromine recovery is avoided, and the recovery rate of bromine in the steam distillation process reaches over 90 percent through experimental research. The Chinese invention patent application with the application number of 201410477976.8 discloses a bromine preparation method and a device by steam distillation of waste water of brominated butyl rubber, wherein 90 percent of bromine in the waste water is recovered by preheating, chlorine oxidation and steam distillation, so that the emission of the bromine meets the environmental protection requirement; and the crude bromine obtained by distillation is subjected to condensation separation and three-stage rectification, so that bromine is refined, and a finished bromine product is used as a raw material for producing brominated butyl rubber in an enterprise, thereby greatly reducing the enterprise cost. The invention effectively improves the utilization rate of bromine, but needs a large amount of condensation and rectification equipment, the three-stage rectification and purification of the crude bromine can generate larger energy consumption, the operation is complex, and meanwhile, the rectification of the bromine can bring the risks of bromine leakage and the like, and the safety investment needs to be increased; in addition, the treatment of non-condensable gas of a plurality of devices is not thorough, liquid is recycled and distilled only after brine is recycled, gas is emptied from the top of the recovery tower, bromine steam possibly carried is discharged along with the gas, the environment is affected, and waste is caused.

Disclosure of Invention

In order to solve the problems, the invention provides a process for improving the utilization rate of bromine in brominated butyl rubber, which realizes the reuse of crude bromine by adopting a distillation method for production wastewater, also recovers the bromine from tail gas generated in the distillation process, does not need a complicated rectification process, simplifies equipment, reduces energy consumption, recycles the recovered bromine for the production of the brominated butyl rubber, effectively improves the utilization rate of the bromine, only generates external drainage in the distillation process in the whole recovery process, and meets the requirement of environmental protection.

In order to achieve the purpose, the invention adopts the following specific technical scheme:

a process for improving the utilization rate of bromine in brominated butyl rubber comprises the following steps:

a. production of brominated butyl rubber: mixing a bromohexane solution and a butyl glue solution for bromination reaction, feeding the glue solution after the bromination reaction into a neutralization kettle, neutralizing the glue solution by using alkali liquor, then feeding the neutralized glue solution into a condensation kettle, removing a solvent by using steam, adding bromine-containing water from a halogenated water tank to form colloidal particle water, and dehydrating the colloidal particle water to form dry glue;

b. purifying waste water: the bromine which is not utilized exists in the water phase in the form of bromide ions, the bromine enters a bromine recovery device after dehydration, the bromine in the water is recovered, the bromine-containing water is introduced into a dissolved air floatation tank, the adhesive foam and the auxiliary agent powder are removed, the water is separated, and relatively clean water liquid at the bottom of the floatation tank is delivered to a water purification area;

c. and (3) distillation: the pretreated water enters a buffer tank, the water is heated by a preheater and then enters a distillation tower, low-pressure steam and chlorine are introduced into the tower bottom to react in the tower, the generated bromine steam and a small amount of water steam are extracted from the upper part of the distillation tower, sewage is discharged from the tower bottom, and is neutralized by dilute alkali solution and discharged to a sewage treatment system;

d. and (3) recycling crude bromine: cooling bromine steam and water steam extracted from the upper part of the distillation tower, then feeding the cooled bromine steam and water steam into a bromine-water separation bottle for separating bromine and bromine water, overflowing water containing bromine from the upper part of the bromine-water separation bottle back to the distillation tower, adding hexane into crude bromine at the bottom to prepare a bromohexane solution, and reusing the bromohexane solution for producing brominated butyl rubber;

e. tail gas recovery: the noncondensable gas which is not condensed at the outlet of the distillation tower and contains part of chlorine and bromine steam enters a tail gas recovery tower, bromine-containing water which is from a buffer tank and is cooled is introduced into the tower to react with the chlorine in the noncondensable gas, liquid bromine-containing water returns to the distillation tower, gas phase contains a small amount of chlorine and bromine steam and enters a tail gas alkaline washing tower to be absorbed, and high-concentration bromine water discharged from the tail gas alkaline washing tower returns to a dissolved gas floatation tank to extract bromine again.

Preferably, the wastewater subjected to bromine recovery has a pH of 9-12 and a bromine content of 5-10g/L in water. The method is the water quality condition of the bromine-containing wastewater generated in the production process of the invention, and the setting of the process parameters of bromine recovery is established on the basis.

Further, after the bromine content in the alkali liquor in the tail gas alkali washing tower reaches 10g/L, the alkali liquor is replaced. Because the bromine content of the waste water subjected to bromine recovery is 5-10g/L, and the alkali liquor in the tail gas alkaline washing tower returns to join with the waste water after absorbing bromine, the bromine content in the alkali liquor reaches 10g/L and then is recovered as high-concentration bromine water, so that the bromine content of the waste water can be controlled within a reasonable range, and the bromine recovery always keeps high efficiency.

Preferably, the prepared bromohexane solution has the concentration of 10-16% and the temperature of 20-35 ℃.

Preferably, the preheating temperature of the preheater is 70-85 ℃. The purpose of preheating is mainly to maintain the temperature of water entering the tower constant, thereby stabilizing the operation condition of the tower kettle.

Preferably, the distillation tower is a packed tower, and the tower temperature is 80-95 ℃.

Preferably, the bromine and water vapor cooling temperature in step d is 30-45 ℃.

And further, cooling the bromine-containing water in the step e to 35-45 ℃ by a cooler, and feeding the cooled bromine-containing water into a tail gas recovery tower. The bromine ions in the bromine-containing water in the tail gas recovery tower and the chlorine in the non-condensable gas are subjected to chlorination reaction so as to absorb the chlorine, and the temperature is 35-45 ℃ matched with the condensation temperature of the non-condensable gas and is a proper reaction temperature.

Preferably, the outlet of the dissolved air floatation tank is provided with two stages of filter screens, and the aperture of each filter screen is 4-6 μm. After the wastewater is subjected to solid-liquid separation preliminarily in a dissolved air flotation tank, the wastewater is further filtered to remove impurities, so that the water quality is improved, the primary filtration mainly filters the rubber powder and relatively large solid impurities, and the secondary filtration mainly filters auxiliary agent particles such as calcium stearate.

It is another object of the present invention to provide an apparatus for use in the above process.

The device for improving the bromine utilization rate process in the brominated butyl rubber comprises a production device and a bromine recovery device, wherein the bromine recovery device comprises a crude bromine recycling system and a tail gas recovery system; the production device comprises a bromine storage tank, a liquid bromine metering tank, a reaction tank, a neutralization kettle, a condensation kettle and a halogenated water tank which are sequentially connected through pipelines, wherein a liquid return pipeline for conveying bromine-containing water in the halogenated water tank to the condensation kettle for recycling is also arranged between the condensation kettle and the halogenated water tank; the crude bromine recycling system comprises a dissolved air flotation tank, a buffer tank, a preheater, a distillation tower, a condenser, a tail gas condenser and a bromine-water separation bottle which are sequentially connected through pipelines, wherein an outlet at the bottom of the distillation tower is connected with a water inlet of a neutralization kettle, an overflow pipeline is arranged between the bromine-water separation bottle and the distillation tower, and an outlet of the bromine-water separation bottle is connected with an inlet of a liquid bromine metering tank; the water inlet of the dissolved air floatation tank is connected with the outlet of the halogenated water tank through a pipeline, and the pipeline is connected with the liquid return pipeline in parallel; the tail gas recovery system comprises a tail gas recovery tower, a first cooler, a tail gas alkaline washing tower, an alkaline washing tank and a second condenser; the bottom inlet of the tail gas recovery tower is connected with the top outlet of the distillation tower through a pipeline on one hand, and is also connected with the gas phase outlet of the tail gas condenser through a pipeline on the other hand; the top outlet of the tail gas recovery tower is connected with the bottom inlet of the tail gas alkaline washing tower through a pipeline, and the top inlet is connected with the outlet of the first cooler through a pipeline; the inlet of the first cooler is connected with the outlet of the buffer tank through a pipeline, and the pipeline is connected in parallel with a pipeline connecting the buffer tank and the preheater; the tail gas alkaline washing tower, the alkaline washing tank and the second cooler are sequentially connected through pipelines, and a return pipeline is further arranged between the second cooler and the tail gas alkaline washing tower; the alkaline washing tank is also connected with the dissolved air floatation tank through a recycling pipeline, and a liquid pump is arranged on the recycling pipeline.

The invention improves the recovery rate of bromine by two aspects of distillation purification and tail gas further absorption, recycles the recovered bromine completely and effectively improves the utilization rate of bromine. The specific process is as follows: the micelle water dehydration in the brominated butyl rubber production process, the bromine element who is not utilized exists in aqueous phase with the bromine ion form, and the bromine-containing water that is got rid of gets into the water pitcher of halogenating, and the water pitcher of halogenating distributes this bromine-containing water, and the part is used for circulating to get back to the coagulum kettle and forms the micelle water, and the part gets into bromine recovery unit and carries out the recovery of bromine, not only the water economy resource, the recovery processing volume of the waste water that has more significantly reduced. Because the rubber foam and the auxiliary agent powder of the bromine-containing wastewater can influence the subsequent recovery and need to purify water, the solid-liquid separation is primarily completed through the dissolved air flotation tank, and the water quality is improved through liquid separation and two-stage filtration. The purified water is used for distilling and recovering bromine and is also used for providing bromine ions for chlorine absorption in the tail gas. The prior art typically acidifies the water to improve the efficiency of distillation column bromine recovery,the invention does not acidify the water system, adopts a packed tower, and then improves the bromine recovery rate of the distillation tower by adjusting the chlorine mixing ratio, the steam quantity of the distillation tower and the temperature of the tower, the bromine recovery rate of the distillation tower can reach more than 93 percent, the content of bromide ions in the discharged water is less than 400ppm, the bromine utilization rate is effectively improved, and the emission pollution is reduced. The bromine water is separated from the gas extracted from the upper part of the distillation tower after cooling, the purity of the crude bromine at the bottom of the liquid separation bottle can reach 98 percent, and the production requirement is met, so the bromine water is seamlessly connected with the production of brominated butyl rubber, the prepared bromohexane solution directly enters the bromination production process, and the water containing bromine at the upper part of the liquid separation bottle overflows back to the distillation tower for recycling. The invention introduces bromine-containing water (namely purified wastewater) into a tail gas recovery tower to absorb chlorine, the bromine-containing water returns to the distillation tower, and the residual bromine steam recovers Br by alkaline washing₂Conversion to Br^-Returning to the dissolved air floatation tank for continuously recovering bromine; further absorb bromine through tail gas caustic wash tower, can further improve bromine atom's recovery rate, reduce the emission of bromine. The bromine recovery rate of the bromine recovery device reaches more than 94 percent, and the bromine utilization rate in the whole butyl rubber production reaches more than 95 percent through process optimization and bromine atom reutilization.

More specifically, to achieve maximum utilization of bromine, strict control of the process steps is required for various parameters. The device for improving the bromine utilization rate comprises a production device and a bromine recovery device, wherein the pH of wastewater generated by the production device is 9-12, the bromine content in water is 5-10g/L, the preheating temperature of a preheater is controlled to be 70-85 ℃, the temperature of a distillation tower is controlled to be 80-95 ℃ according to the water quality condition by combining the treatment capacity of the distillation tower, and the chlorine distribution ratio and the steam quantity of the distillation tower are adjusted according to the quantity of wastewater to be treated, so that bromine is recovered by the distillation tower to the maximum extent in the load range of the distillation tower. Further treating tail gas generated in the distillation process, wherein the tail gas contains chlorine and part of bromine steam chlorine, the chlorine is absorbed by bromine-containing water, and the bromine steam returns to a bromine recovery device after alkaline washing to continuously recover bromine; the bromine-containing water inlet and the distillation tower water inlet in the chlorine recovery process are both from a buffer tank, water distribution is carried out by the buffer tank according to the treatment capacity and the treatment capacity of the distillation tower, and then the bromine-containing water is cooled to 35-45 ℃ and the non-condensable gas is cooled to 30-45 ℃ to provide proper temperature for chlorination reaction, so that the reaction is full and excessive byproducts are avoided; the bromine steam alkali washing process controls the bromine ion content of the alkali liquor to reach 10g/L, and then recovers and extracts bromine, so that the bromine content of the wastewater is controlled in the range of 5-10g/L, and the recovery can be continuously and efficiently carried out.

The invention has the following beneficial effects:

bromine-containing waste water is purified to improve water quality and then is recycled, a flocculating agent is not added in waste water purification, a pure physical mode is adopted, other impurities cannot be introduced, the operation is convenient, and an ideal state can be achieved.

The recovery rate of bromine is improved to more than 94% through distillation and tail gas treatment, wherein crude bromine with the purity of 98% is obtained through distillation, the actual production requirement is met, the crude bromine is directly connected with butyl bromide production in a seamless mode, further rectification is not needed, the energy consumption is effectively reduced, the cost is saved, the content of bromine ions in discharged water in the distillation process is less than 400ppm, and the environment-friendly requirement is met; the tail gas treatment process converts bromine steam in the non-condensable gas generated by distillation into bromine ions and then returns to the bromine recovery device to continuously recover bromine, so that the emission of bromine is avoided. Through the process, the bromine utilization rate in the whole butyl rubber production is improved to more than 95% from the original 45-50%, the discharge of bromide ions can be effectively reduced, the production cost of brominated rubber is greatly reduced, the sewage treatment cost is reduced, and the environment friendliness is facilitated.

Drawings

FIG. 1: the process of the invention is schematically represented in the flow.

The device in the figure: 1-a reaction tank, 2-a neutralization kettle, 3-a condensation kettle, 4-a halogenated water tank, 5-a dissolved air flotation tank, 6-a buffer tank, 7-a preheater, 8-a distillation tower, 9-a neutralization kettle, 10-a condenser, 11-a bromine water separation bottle, 12-a liquid bromine metering tank, 13-a bromine storage tank, 14-a tail gas condenser, 15-a tail gas recovery tower, 16-a first cooler, 17-a tail gas alkaline washing tower, 18-an alkaline washing tank, 19-a second cooler, 41-a liquid return pipeline, 181-a reuse pipeline and 191-a reflux pipeline.

Materials in the figure are as follows: a-hexane, B-bromohexane solution, C-butyl glue solution, D-steam, E-halogenated circulating hot water, F-brominated butyl rubber, G-low-pressure steam, H-chlorine gas, I-dilute alkali solution, J-crude bromine and K-high-concentration bromine water.

Detailed Description

The present invention will be further described with reference to the following specific examples.