CN107899402A - Propylene oxide by chlorohydrination device exhaust processing method - Google Patents

Abstract

In the chlorohydrin method propylene oxide device tail gas treatment method of the present invention, the chloroalcoholization of organic waste gas in the propylene oxide device removes acid gas through an alkali washing tower; After the supplementary air is mixed, it enters the fan together; the gas in the outlet pipeline of the fan is detected by the VOC online gas detector to detect the combustible gas content, and then it is measured by the remote flowmeter and then transported to the safety water-sealed tank of the caustic soda device; then enters the molten salt furnace as a combustion-supporting air Incineration is performed and includes interlock control methods to ensure safety on the job. This process is to dilute the tail gas in a large amount to reach below 25% of the explosion limit concentration of each component of the tail gas, and then incinerate as the combustion-supporting air of the incinerator, which is not only safe in operation, but also can completely and effectively treat the waste gas. It can even recover heat or save fuel usage.

Description

Tail gas treatment method of chlorohydrin method propylene oxide plant

technical field

The invention provides a method for treating tail gas of a propylene oxide plant by a chlorohydrin method, which is applied to a chemical plant producing organic waste gases such as alkanes, olefins, and alkynes.

Background technique

Existing tail gas treatment technologies are as follows:

1. Adsorption method: mainly use adsorbents, such as activated carbon, to adsorb organic tail gas, and replace the adsorbents regularly. However, in this method, the adsorbent needs to be supplemented and regenerated; the exhaust gas with high temperature needs to be cooled first; the complex exhaust gas needs to be pretreated.

The main disadvantage of this method is that it needs to be operated under certain pressure conditions. For the tail gas of the chlorohydrin method propylene oxide plant, the concentration of oxygen in the tail gas is about 45%. If the tail gas is compressed, there will be an explosion. danger. Secondly, if the desorption process is not properly selected, there will be problems such as secondary pollution, so the adsorption method is not suitable for the treatment of the tail gas of the propylene oxide plant by the chlorohydrin method.

2. Low-temperature plasma method: The exhaust gas after water washing passes through the demister to remove moisture and then enters the low-temperature plasma equipment treatment system. The gas entering the low-temperature plasma equipment is free of moisture, dust, and particles. Under the action of electrons, the odor molecules are excited, and the chemical bonds between charged particles or molecules are interrupted. At the same time, water and oxygen in the air will also produce strong oxidizing substances such as OH free radicals and active oxygen under the bombardment of high-energy electrons. These highly oxidizing substances react with organic gas molecules causing them to break down. This method has potential safety hazards; it occupies a large area and may produce secondary pollution, and the mechanism remains to be studied.

The main disadvantages of this method are: spark discharge is easy to occur, and the reactor is prone to spark discharge under high peak voltage. For the tail gas of the propylene oxide plant, the oxygen content in the organic tail gas is very high, which is prone to explosion. Moreover, low-temperature plasma equipment has high requirements on the configuration design, manufacturing precision, and tightness of equipment components. For example, for parameters such as electric field frequency, voltage, and high-frequency pulses, if one of the parameters in the complete set of equipment fails to meet the requirements, such as low voltage, too high or too low frequency, etc., it will cause a large amount of plasma generation. At present, the low-temperature plasma technology used in domestic waste gas treatment is immature and in the stage of exploration, so this technology is not suitable for the tail gas treatment of the chlorohydrin method propylene oxide plant.

3. Photocatalytic oxidation method: The exhaust gas enters the main pipeline first and then is sent to the exhaust gas purification unit for chemical pretreatment in the concentration homogenizer. The washing liquid used is acid washing liquid. This kind of absorption liquid has obvious effect on the absorption and release of exhaust gas. Through the absorption of the main components of the exhaust gas by the absorption liquid, the stability of the exhaust gas concentration is ensured. The exhaust gas pretreated by the scrubber enters the photocatalytic oxidation reaction tower. Photochemical oxidation technology is to oxidize and degrade organic pollutants under the action of visible light or ultraviolet light, and the gas is finally discharged at high altitude through fans and exhaust pipes.

Disadvantages of catalytic oxidation technology: This method uses photocatalyst, which has the problem of catalyst deactivation; for high bond energy chemical bonds, it cannot be opened, and the oxidation efficiency is limited. Intermediate, so this technology is not suitable for the treatment of tail gas from propylene oxide plant by chlorohydrin method.

At present, none of the existing tail gas treatment processes in the petrochemical industry can effectively and thoroughly treat the tail gas of the chlorohydrin method propylene oxide plant. After analyzing the components of the chlorohydrin method tail gas and the properties of each component, we invented the chlorohydrin method. The technology that the tail gas of the oxypropane plant is diluted to a safe concentration and used as combustion-supporting air for incineration. This technology is different from the traditional tail gas incineration technology. In oil refining and other chemical equipment, the tail gas is used as fuel for incineration. If the tail gas of the chlorohydrin method propylene oxide device is directly incinerated, the concentration of organic combustibles is low and it is not easy to burn. Furthermore, chlorohydrin The oxygen concentration in the tail gas of the French propylene oxide plant is relatively high, and there is a risk of flashback and explosion during the incineration process. This process is not only safe in operation, but also can completely and effectively treat exhaust gas, and can even recover heat or save fuel consumption on specific combustion equipment.

Contents of the invention

1. Technical problems to be solved

In order to solve the defects in the prior art, such as potential safety hazards, need for secondary treatment, and incomplete purification, the present invention provides a method for treating the tail gas of a propylene oxide plant by chlorohydrin method, which solves the problems of organic waste gases such as alkanes, alkenes, and alkynes in chemical plants. pollution problems caused by emissions.

2. Technical solution

The purpose of the present invention is mainly achieved through the following technical solutions.

Chlorohydrin method propylene oxide plant tail gas treatment method of the present invention, comprises the following steps:

1) The chloroalcoholization organic waste gas of the propylene oxide plant removes the acid gas through the alkali washing tower;

2) Introduce the organic waste gas from the removal of acid gas into the safety water-sealed tank, and the water-sealed tank is equipped with a supplementary air inlet, and the chloroalcoholized organic waste gas and supplementary air are mixed and enter the fan together;

3) The gas in the fan outlet pipeline is detected by the VOC online gas detector to detect the combustible gas content, and then transported to the safety water-sealed tank of the caustic soda device after being measured by the remote flow meter;

4) The gas in the safety water-sealed tank of the caustic soda device is sent to the molten salt furnace by the caustic soda fan as a combustion-supporting air for incineration.

Also includes an interlocking control method, the interlocking control method realizes the following interlocking through the detected parameters through the total concentration of propylene and propane in the tail gas, the ratio K value of chlorine and propylene in the tail gas, the flow rate of the fan and the working state of the fan control:

(1) When the total concentration of propylene and propane > 0.5%, the vent regulating valve and vent quick-opening valve are opened at the same time, the fan chain trips and stops, and the caustic soda cut-off valve is closed;

(2) When the ratio K value > 0.6200, the vent regulating valve and the vent quick-opening valve are opened at the same time, the fan chain trips and stops, and the caustic soda cut-off valve is closed;

(3) When the flow rate of the fan is less than 5000m ³ /h, the vent regulating valve and the vent quick-opening valve are opened at the same time, the fan chain trips and stops, and the caustic soda delivery cut-off valve is closed;

(4) When the fan stops running suddenly, the vent regulating valve and the vent quick-opening valve are opened at the same time, and the caustic soda delivery shut-off valve is closed.

Furthermore, as the gas of the combustion-supporting air, the concentration of each combustible component reaches below 25% of its explosion limit concentration.

Further, in step 4), the caustic soda blower is provided with drainage facilities with "N" bends for drainage and maintaining the internal pressure of the pipeline.

Further, according to the requirements of the safety control of the gas transportation process, an emergency emptying valve is installed at the vent port of the propylene oxide alkali washing tower, an emergency shut-off valve is installed at the outlet pipeline of the fan, and an emergency valve is installed at the air inlet of the safety water-sealed tank of the caustic soda device. Vent valve.

3. Beneficial effects:

Compared with the prior art, the beneficial effect of the chlorohydrin method propylene oxide plant tail gas treatment method of the present invention is:

The traditional tail gas incineration process is generally used in oil refineries and chemical plants with high tail gas concentration. Such devices are generally equipped with combustion furnaces or torches, and the tail gas is used as fuel for direct combustion. For tail gas with very low oxygen content and high content, traditional incineration technology cannot be used. First of all, the tail gas concentration of the chlorohydrin method propylene oxide plant is very low, and the combustion is very unstable or cannot be ignited; secondly, even if the combustion is carried out by increasing the fuel, due to the high concentration of oxygen in the tail gas, there is a danger of flashback and explosion. Two characteristics determine that the organic waste gas from the chlorohydrin method cannot be burned by the traditional incineration process.

Therefore, the scheme of the present invention carries out a large amount of air dilution to the exhaust gas of the chlorohydrin method propylene oxide plant, and dilutes the concentration of the main organic combustibles to below 25% of the lower explosive limit of the organic matter in the air, which meets the National Environmental Protection Standard of the People's Republic of China " According to the safety requirements of Article 6.4.5 of HJ2000-2010 Technical Guidelines for Air Pollution Control Engineering, it is then incinerated as the combustion-supporting air of the incinerator. The tail gas with similar composition in other petrochemical plants can also be thoroughly treated. Through incineration, the organic waste gas is thoroughly treated, and there is no problem of secondary pollution. The process technology is safe and reliable, and it can save fuel or recycle on specific combustion equipment. thermal energy.

2) The present invention is characterized in that although it is a tail gas incineration treatment process, it is different from the traditional incineration process, and the operation of this process is more economical and safer.

Description of drawings

Fig. 1 is the apparatus flow chart of the production method of the present invention.

In the figure: 1-alkali washing tower, 2-safety water-sealed tank, 3-fan, 4-caustic soda device safety water-sealed tank, 5-caustic soda fan, 6-molten salt furnace, 7-VOC detector, 8- Remote flowmeter, 9-cut-off valve for caustic soda delivery, 10-quick opening valve for venting, 11-regulating valve for venting, 12-secondary alkali tank, 13-"N" type bend, 14-clean water.

Detailed ways

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings, and those skilled in the art can clearly understand the present invention and implement the present invention according to the detailed description. Without departing from the principles of the present invention, the features in different embodiments can be combined to obtain new implementations, or some features in certain embodiments can be replaced to obtain other preferred implementations.

Fig. 1 has shown the tail gas treatment method of the propylene oxide plant of chlorohydrin method that constitutes according to the preferred embodiment of the present invention. As shown in Figure 1, after the chloroalcoholization tail gas of the propylene oxide plant removes the acid gas through the alkali washing tower 1, it is introduced into the safety water-sealed tank 2, and the water-sealed tank 2 is equipped with an air inlet, and the chloroalcoholized organic waste gas and supplementary air are mixed and enter together Fan 3, the gas in the outlet pipeline of the fan is detected by the VOC online gas detector 7 to detect the combustible gas content, and then measured by the remote flow meter 8, then transported to the safety water-sealed tank 4 of the caustic soda device, and then enters the molten salt through the caustic soda fan 5 Furnace 6 is incinerated as combustion-supporting air. Since the gas has passed through a safe water seal, the moisture content in the gas is relatively high. During the gas transportation process, the low point of the caustic soda fan pipeline is designed with "N" type bend 13 drainage facilities, which can not only drain water, but also maintain the pressure in the pipeline. According to the safety control requirements of the gas transportation process, an emergency emptying valve is installed at the vent of the propylene oxide alkali washing tower, an emergency shut-off valve is installed at the outlet pipeline of the fan, and an emergency emptying valve is installed at the air inlet of the water-sealed tank of the caustic soda device.

Among them, the tail gas composition of the chlorohydrin method propylene oxide plant:

In order to realize the safe treatment of chloroalcoholization tail gas, the tail gas treatment device is provided with the following interlocks: between the fan 3 and the safety water seal tank 4 of the caustic soda device, a VOC online gas detector 7, a remote flow meter 8, a delivery The caustic soda shut-off valve 9 is connected with the vent quick-opening valve 10 and the vent regulating valve 11 above the caustic washing tower 1 . The VOC online gas detector 7 detects the total concentration of propylene and propane in the tail gas; the interlock control system also detects the ratio K value of chlorine and propylene in the tail gas, the flow rate of the fan and the working state of the fan; the interlock control system The interlocking control is realized through the detected parameters, and the specific control is as follows:

(1) The VOC detector detects that the total gas concentration of propylene (C3H6) and propane (C3H8) is >0.5%. The result of interlocking is that the vent regulating valve 11 and the vent quick-opening valve 10 are opened at the same time, and the fan 3 is chain-stopped to send caustic soda Shut-off valve 9 is closed.

(2) Proportioning K value > 0.6200, the result of interlocking is that the vent regulating valve 11 and the vent quick-opening valve 10 are opened simultaneously, the fan 3 is interlocked and stopped, and the caustic soda cut-off valve 9 is closed; the K value is the chlorine gas in the organic tail gas And the ratio of propylene.

(3) The flow rate of the fan is less than 4000m ³ /h, the result of the interlocking is that the vent regulating valve 11 and the vent quick opening valve 10 are opened at the same time, the fan 3 is interlocked and stopped, and the caustic soda delivery cut-off valve 9 is closed.

(4) The fan stops running suddenly, and the result of the interlock is that the vent regulating valve 11 and the vent quick-opening valve 10 are opened simultaneously, and the caustic soda cut-off valve 9 is closed.

Although the present invention has been described above with reference to specific embodiments, those skilled in the art will understand that many modifications can be made to the configurations and details disclosed in the present invention within the principles and scope of the present invention. The protection scope of the present invention is determined by the appended claims, and the claims are intended to cover all modifications included in the equivalent literal meaning or scope of the technical features in the claims.

Claims (4)

1. propylene oxide by chlorohydrination device exhaust processing method, comprises the following steps：

1) propylene oxide unit chlorohydrination organic exhaust gas removes sour gas through caustic wash tower；

2) organic exhaust gas for removing sour gas is introduced into safe water sealed cans, water sealed tank is equipped with air intlet, chlorohydrination organic waste Enter wind turbine together after gas and supplement air mixing；

3) gas detects fuel gas content through the online gas detecting instruments of VOC in fan outlet pipeline, then through remote control liquid flowmeter meter Piece alkali equipment safety water sealed tank is delivered to after amount；

4) gas is burned by piece alkali wind turbine feeding molten salt furnace as combustion air in piece alkali equipment safety water sealed tank；

It is characterized in that：Further include interlocking control method, the interlocking control method is total dense by propylene in tail gas and propane Proportioning K values, compressor flow and the blower fan work state of chlorine and propylene in degree, tail gas, pass through detected parameter and realize such as Lower interlocked control：

(1) as the total concentration ＞ 0.5% of propylene and propane, emptying regulating valve and emptying quck-opening valve are opened at the same time, and wind turbine is chain Stop jumping, send piece alkali stop valve to close；

(2) when matching K value ＞ 0.6200, emptying regulating valve and emptying quck-opening valve are opened at the same time, and the chain stop jumping of wind turbine, send piece alkali Stop valve is closed；

(3) as compressor flow ＜ 5000m³During/h, emptying regulating valve and emptying quck-opening valve are opened at the same time, and the chain stop jumping of wind turbine, send piece Alkali stop valve is closed；

(4) when wind turbine is out of service suddenly, emptying regulating valve and emptying quck-opening valve are opened at the same time, send piece alkali stop valve to close.

2. propylene oxide by chlorohydrination device exhaust processing method as claimed in claim 1, it is characterised in that as combustion air Gas, wherein the concentration of each combustible component reaches less than the 25% of its explosible limit concentration.

3. propylene oxide by chlorohydrination device exhaust processing method as claimed in claim 2, it is characterised in that in step 4), Piece alkali wind turbine is provided with the curved pumping equipment of band " N " type, for draining and keeps manifold pressure.

4. propylene oxide by chlorohydrination device exhaust processing method as claimed in claim 3, it is characterised in that conveyed according to gas The requirement of process safety control, emergent evacuation valve is set in Caustic Wash Tower of Epoxy Propane drain, is set in wind turbine conveying outlet line Quick action emergency valve is put, emergent evacuation valve is set in piece alkali equipment safety water sealed tank air inlet.