A chlorinated paraffin tail gas purification device, process and application thereof

Abstract

The present invention relates to a chlorinated paraffin tail gas purification device, comprising an oil removal unit, a water removal unit and a chlorination unit connected in sequence; the oil removal unit is used to cool and recover wax oil and chlorinated products thereof in the chlorinated paraffin tail gas; the water removal unit is used to absorb water in the chlorinated paraffin tail gas; the chlorination unit comprises a chlorination reactor (8), which selectively absorbs chlorine in the tail gas through a ferrous chloride solid absorbent. The present invention also relates to a chlorinated paraffin tail gas purification process using the chlorinated paraffin tail gas purification device and an application of the chlorinated paraffin tail gas purification device. Compared with the prior art, the present invention has the advantages that the chlorinated paraffin tail gas purification device can simultaneously reduce the oil content, water content and chlorine content in the chlorinated paraffin tail gas, and has high efficiency and low energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of chlorinated paraffin production, and in particular to a chlorinated paraffin tail gas purification device, process and application thereof. Background Art

[0002] Chlorinated paraffin is a light yellow to orange-yellow viscous liquid, which is a mixture of chlorinated derivatives formed by free radical reaction of C10-C30 straight-chain alkanes with different carbon numbers with chlorine. Chlorinated paraffin has the characteristics of being odorless, non-toxic, flame retardant, low volatility and good compatibility with PVC resin. It is often used as a plasticizer for polyvinyl chloride, an additive for rubber, coatings, inks, an additive for mechanical processing lubricants, an anticoagulant, and a flame retardant for plastics and rubber.

[0003] The production method of chlorinated paraffin is a typical chlorination reaction of organic matter. In actual production, there are often situations such as excessive chlorine, incomplete reaction contact, and inadequate control of reaction parameters, which lead to a certain amount of chlorine in the tail gas of hydrogen chloride. The tail gas of chlorinated paraffin production mainly contains three types of substances: paraffin and its chlorinated products, chlorine, and hydrogen chloride. Excessive chlorine content in the tail gas will bring the following adverse effects: first, the unit consumption of chlorine in production increases; second, the amount of oil entrained in the tail gas from the absorption kettle increases, the unit consumption of wax oil in production increases, and the oil content of the subsequent absorption device increases; third, the operation of the subsequent water absorption hydrogen chloride production hydrochloric acid system is affected; fourth, the subsequent tail gas production epichlorohydrin system is affected due to the low purity of the raw materials. Therefore, it is necessary to absorb the tail gas to reduce energy consumption and ensure the safe and stable operation of the device. The purification and utilization of the tail gas from chlorinated paraffin production needs to be divided into three stages: first, the separation and recovery of paraffin and its chlorinated products; second, the absorption and utilization of chlorine; third, the utilization of hydrogen chloride.

[0004] Paraffin and its chlorides are organic substances, and their properties are quite different from those of chlorine and hydrogen chloride. They are usually separated by deep condensation, solvent absorption, adsorption, etc. Chlorine and hydrogen chloride have similar properties and are difficult to separate. The water absorption-desorption method is commonly used in industry. The mixed gas of chlorine and hydrogen chloride is absorbed by water to produce hydrochloric acid and hypochlorous acid. Hypochlorous acid is easily decomposed by heat, and then the hypochlorous acid is decomposed into hydrogen chloride by heating to achieve the purpose of removing chlorine. However, this method has low efficiency, high energy consumption, and low economic efficiency. In the water absorption-desorption method, the hydrogen chloride in the tail gas is used to prepare hydrochloric acid, but in recent years, the glycerin method for preparing epichlorohydrin has gradually gained favor, and the research on the use of hydrogen chloride to prepare epichlorohydrin after tail gas treatment has also gradually received attention.

[0005] The invention patent with patent application number CN200510025910.6 (publication number CN1865127A) "A method for separating and purifying mixed waste gas containing chlorine and hydrogen chloride" proposes to use solvents such as benzene, sulfur monochloride, and carbon tetrachloride to physically absorb chlorine in hydrogen chloride, and then separate chlorine through desorption operation to regenerate the absorbent. The disadvantage of this method is that the physical absorbent has low solubility in chlorine and the desorption operation must be frequently performed in actual operation, resulting in high energy consumption and low equipment efficiency in the whole process.

[0006] The invention patent "A method for dechlorinating and purifying hydrogen chloride from tail gas of chlorination reaction" with patent application number CN201610852214.0 (publication number CN106477525A) proposes to use allyl alcohol, tripropylene phosphite, tripropylene phosphate, dipropylene carbonate, tetrapropylene silicate and other chemical absorption of chlorine in hydrogen chloride, and the product generated after the reaction is directly or indirectly converted into dichloropropanol, and dichloropropanol and residual hydrogen chloride in tail gas are used as raw materials for producing epichlorohydrin. The advantage of this method is that it makes full use of chlorine and absorbent, but the disadvantage is that the reaction rate is limited and the amount of chlorine that can be processed is limited; in addition, the reaction generates more dichloropropanol impurities, which will have a greater impact on the quality of epichlorohydrin produced subsequently, and the subsequent separation and treatment are more complicated, and the degree of reaction is difficult to control. Summary of the invention

[0007] The first technical problem to be solved by the present invention is to provide a chlorinated paraffin tail gas purification device which can simultaneously reduce the oil content, water content and chlorine content in the chlorinated paraffin tail gas in view of the current status of the prior art.

[0008] The second technical problem to be solved by the present invention is to provide a chlorinated paraffin tail gas purification process using the above-mentioned chlorinated paraffin tail gas purification device.

[0009] The third technical problem to be solved by the present invention is to provide an application of the above-mentioned chlorinated paraffin tail gas purification device.

[0010] The technical solution adopted by the present invention to solve the first technical problem is: a chlorinated paraffin tail gas purification device, characterized in that: the chlorinated paraffin tail gas purification device comprises an oil removal unit, a water removal unit and a chlorine removal unit connected in sequence;

[0011] The oil removal unit comprises a cyclone separator, a circulating water cooler, a chilled water cooler and an oil mist collector which are connected in sequence, and is used to cool and recover the wax oil and its chlorinated products in the tail gas of chlorinated paraffin;

[0012] The dehydration unit comprises a bubble tower, an acid mist capture tower and an alumina filler adsorption tower which are connected in sequence, and is used to absorb moisture in the chlorinated paraffin tail gas;

[0013] The dechlorination unit comprises a dechlorination reactor, which selectively absorbs chlorine in tail gas through a ferrous chloride solid absorbent.

[0014] Preferably, the cyclone separator has a first air inlet, a first air outlet and a first liquid outlet, so as to ensure that the liquid wax oil and its chlorinated products in the tail gas can be discharged in time after cyclone separation;

[0015] The circulating water cooler has a second air inlet at the top and a second air outlet at the bottom, and the circulating water of the circulating water cooler flows from bottom to top in the circulating water cooler, and the second air inlet of the circulating water cooler is connected to the first air outlet of the cyclone separator through a pipeline;

[0016] The chilled water cooler has a third air inlet at the top and a third air outlet at the bottom, and the cooling water of the chilled water cooler flows from bottom to top in the chilled water cooler, and the third air inlet of the chilled water cooler is connected to the second air outlet of the circulating water cooler through a pipeline;

[0017] The oil mist trap has a fourth air inlet, a fourth air outlet and a second liquid outlet, and the fourth air inlet of the oil mist trap is connected to the third air outlet of the chilled water cooler through a pipeline.

[0018] Further, the bubble tower has a fifth air inlet, a fifth air outlet, a concentrated sulfuric acid feed port and a dilute sulfuric acid discharge port, and the fifth air inlet of the bubble tower is connected to the fourth air outlet of the oil mist trap through a pipeline;

[0019] The acid mist capture tower has a sixth air inlet, a sixth air outlet and a third liquid outlet, and the sixth air inlet of the acid mist capture tower is connected to the fifth air outlet of the bubble tower through a pipeline;

[0020] The alumina filler adsorption tower has a seventh air inlet and a seventh air outlet, and the seventh air inlet of the alumina filler adsorption tower is connected to the sixth air outlet of the acid mist capture tower through a pipeline.

[0021] Furthermore, the bubble tower is provided with a sulfuric acid circulation outlet and a sulfuric acid circulation inlet, and a sulfuric acid circulation pump, a sulfuric acid cooler and a sulfuric acid circulation tank are sequentially connected between the sulfuric acid circulation outlet and the sulfuric acid circulation inlet for cooling the sulfuric acid.

[0022] Furthermore, the dechlorination reactor has an eighth air inlet and an eighth air outlet, and the eighth air inlet of the dechlorination reactor is connected to the seventh air outlet of the alumina filler adsorption tower through a pipeline.

[0023] Furthermore, a tail gas transport compressor is installed near the eighth air inlet of the dechlorination reactor.

[0024] Preferably, the ferrous chloride solid absorbent is ferrous chloride powder with a diameter less than 1 mm, ensuring good contact between the ferrous chloride absorbent and the gas.

[0025] Preferably, the number of the oil mist collectors is at least two, and the oil mist collectors are connected in parallel with one in operation and the other in standby.

[0026] Preferably, the number of the dechlorination reactors is at least two, and the dechlorination reactors are connected in series to ensure that chlorine and ferrous chloride react fully and reduce the chlorine content as much as possible.

[0027] The technical solution adopted by the present invention to solve the second technical problem is: a chlorinated paraffin tail gas purification process using the above-mentioned chlorinated paraffin tail gas purification device, comprising the following steps:

[0028] The first step is to remove oil from tail gas: the tail gas of chlorinated paraffin is passed into the oil removal unit, the droplets in the tail gas of chlorinated paraffin are removed by a cyclone separator, the gaseous oil content in the tail gas is reduced by cooling with a circulating water cooler and a chilled water cooler, and the gaseous oil is converted into liquid oil and then removed through an oil mist collector to remove the wax oil and its chlorinated products in the tail gas of chlorinated paraffin and enter the water removal unit;

[0029] The second step is to remove water from the tail gas: the concentrated sulfuric acid in the bubble tower absorbs the water in the tail gas, and then the acid mist is captured by the acid mist capture tower. Finally, the alumina in the alumina packing adsorption tower further absorbs the water in the tail gas and then enters the dechlorination unit;

[0030] The third step is to remove chlorine from the tail gas: the chlorine in the tail gas is selectively absorbed by the ferrous chloride solid absorbent in the dechlorination reactor.

[0031] Preferably, the temperature of the chlorinated paraffin tail gas after the refrigerated water cooler is 5-15°C, the oil content of the chlorinated paraffin tail gas after the oil mist collector is less than 10ppm, the temperature of the concentrated sulfuric acid at the inlet of the bubble tower is 20-30°C, the water content of the chlorinated paraffin tail gas after the acid mist collector is less than 100ppm, the water content of the chlorinated paraffin tail gas after the alumina filler adsorption tower is less than 20ppm, and the chlorine content of the chlorinated paraffin tail gas after the dechlorination reactor is less than 10ppm. Appropriately lowering the tail gas temperature can ensure that paraffin and its chlorinated products are completely liquefied and separated and that the subsequent process is carried out normally. Appropriately lowering the concentrated sulfuric acid temperature can ensure that the bubble tower fully absorbs the moisture in the tail gas, reduces the water content of the tail gas at the outlet of the acid mist collector, and ensures that the alumina filler adsorption tower can achieve the expected dehydration effect. Multi-stage absorption reduces the water content of the tail gas, which can prevent the ferrous chloride absorbent from deliquescing and deteriorating, affecting the fluidization effect of the fluidized bed reactor and the full reaction of the ferrous chloride absorbent and chlorine.

[0032] Preferably, the dechlorination reactor is a fluidized bed reactor, the reaction pressure is 0-10 kPa gauge pressure, the reaction temperature is 40-60° C., the gas flow rate is 0.2-0.6 m / s, and the bed height after fluidization is 1.5-2.5 m. The dechlorination reactor is a fluidized bed reactor with low cost but good gas-solid contact, which can ensure that the ferrous chloride absorbent has good contact with the gas and solve the problem of insufficient reaction that may exist in the gas-solid reaction.

[0033] The technical solution adopted by the present invention to solve the third technical problem is: an application of the above-mentioned chlorinated paraffin tail gas purification device, using the chlorinated paraffin tail gas treated by the chlorinated paraffin tail gas purification device as a reactant in a glycerol catalytic process for preparing epichlorohydrin.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] (1) The present invention adopts a cooling and capturing method to recover the wax oil and its chlorides in the tail gas in a simple and efficient manner. The significance of the tail gas deoiling process is that the gaseous oil content in the tail gas is reduced by cooling, and the gaseous oil is converted into liquid oil, and then more than 99% of the wax oil and its chlorides in the tail gas are removed by an oil mist collector, thereby preventing organic matter from affecting the subsequent tail gas dehydration and tail gas dechlorination processes;

[0036] (2) The present invention adopts a bubble tower and a packed adsorption tower to perform multi-stage absorption of water in the tail gas. The significance of the tail gas dehydration process is that ferrous chloride has a strong water absorption capacity. If the tail gas is not dried before the dechlorination reactor, it is easy to cause the absorbent to deliquesce and deteriorate, affecting the actual operation effect of the dechlorination reactor;

[0037] (3) The present invention uses a chemical absorbent to selectively absorb chlorine in the hydrogen chloride tail gas. The reaction conditions are mild, the raw materials are safe and environmentally friendly, and it has a higher absorption efficiency than the physical absorbent. The chlorine in the hydrogen chloride tail gas can be removed to 3×10 - 5 g / L (10ppm, volume ratio) or less;

[0038] (4) The dechlorination reactor selectively absorbs chlorine in the tail gas through ferrous chloride particles to generate ferric chloride solid. The ferric chloride solid can be used as a flocculant after proper treatment, which is in line with the concept of green, environmental protection and efficient utilization of new chemical production. This chemical process can be expressed by the following formula:

[0039] 2FeCl2+Cl2→2FeCl3

[0040] FeCl3+3H2O→Fe(OH)3↓+3HCl;

[0041] (5) The present invention adopts ferrous chloride solid absorbent to absorb chlorine in hydrogen chloride tail gas, which has the following advantages compared with the traditional ferrous chloride solution absorption: first, the absorption amount is large and the service life of the absorbent is long; second, no huge tower equipment is required, and the equipment cost is low; third, no moisture is introduced into the treated tail gas, which avoids the corrosion of subsequent compressors, equipment and pipelines by the water-containing hydrogen chloride tail gas or affects the efficiency of the catalyst in the glycerol catalytic process for preparing epichlorohydrin; fourth, the solid ferric chloride generated by the reaction is simpler to handle than the ferric chloride solution when used as a flocculant, and is easier to store and use.

[0042] (6) The method of the present invention is simple and reliable, efficient and environmentally friendly, with low investment, low energy consumption and cost, and has great advantages over traditional methods;

[0043] In summary, the chlorinated paraffin tail gas purification device of the present invention can simultaneously reduce the oil content, water content and chlorine content in the chlorinated paraffin tail gas, with high efficiency and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic structural diagram of an embodiment of a chlorinated paraffin tail gas purification device of the present invention;

[0045] Figure 2 for Figure 1 Schematic diagram of the structure of the oil removal unit;

[0046] Figure 3 for Figure 1 Schematic diagram of the structure of the water removal unit;

[0047] Figure 4 for Figure 1 Schematic diagram of the structure of the chlorine removal unit. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below with reference to the accompanying drawings.

[0049] like Figure 1 As shown, it is a preferred embodiment of the chlorinated paraffin tail gas purification device of the utility model. The chlorinated paraffin tail gas purification device includes an oil removal unit A, a water removal unit B and a chlorination unit C connected in sequence, the oil removal unit A includes a cyclone separator 1, a circulating water cooler 2, a chilled water cooler 3 and an oil mist collector 4 connected in sequence, which are used to cool and recover the wax oil and its chlorinated products in the chlorinated paraffin tail gas; the water removal unit B includes a bubble tower 5, an acid mist collection tower 6 and an alumina filler adsorption tower 7 connected in sequence, which are used to absorb the moisture in the chlorinated paraffin tail gas; the chlorination unit C includes a chlorination reactor 8, which selectively absorbs chlorine in the tail gas through a ferrous chloride solid absorbent.

[0050] The cyclone separator 1 has a first air inlet 11, a first air outlet 12 arranged at the top, and a first liquid outlet 13 arranged at the bottom. The cyclone separator 1 can preliminarily remove liquid droplets in the chlorinated paraffin tail gas.

[0051] The circulating water cooler 2 has a second air inlet 21 at the top and a second air outlet 22 at the bottom, and the circulating water of the circulating water cooler 2 flows from bottom to top in the circulating water cooler 2. The second air inlet 21 of the circulating water cooler 2 is connected to the first air outlet 12 of the cyclone separator 1 through a pipeline.

[0052] The chilled water cooler 3 has a third air inlet 31 at the top and a third air outlet 32 ​​at the bottom, and the cooling water of the chilled water cooler 3 flows from bottom to top in the chilled water cooler 3. The third air inlet 31 of the chilled water cooler 3 is connected to the second air outlet 22 of the circulating water cooler 2 through a pipeline. The circulating water cooler 2 and the chilled water cooler 3 will perform multi-stage cooling on the chlorinated paraffin tail gas, cooling most of the wax oil and its chlorides from the gas phase to the liquid phase.

[0053] The oil mist collector 4 has a fourth air inlet 41, a fourth air outlet 42 at the top, and a second liquid outlet 43 at the bottom. The fourth air inlet 41 of the oil mist collector 4 is connected to the third air outlet 32 ​​of the chilled water cooler 3 through a pipeline. In this embodiment, there are two oil mist collectors 4, and each oil mist collector 4 is connected in parallel. The oil mist collector 4 can remove more than 99% of wax oil and its chlorides, preventing organic matter from affecting the subsequent tail gas dehydration and tail gas dechlorination processes.

[0054] The bubble tower 5 has a fifth air inlet 51 at the bottom, a fifth air outlet 52 at the top, a concentrated sulfuric acid feed port 53 at the top, a dilute sulfuric acid discharge port 54 at the bottom, a sulfuric acid circulation outlet 55 at the bottom, and a sulfuric acid circulation inlet 56 at the top. Since the concentrated sulfuric acid absorbs water and releases heat, a sulfuric acid circulation pump 57, a sulfuric acid cooler 58, and a sulfuric acid circulation tank 59 are sequentially connected between the sulfuric acid circulation outlet 55 and the sulfuric acid circulation inlet 56 for circulating and cooling the sulfuric acid. The fifth air inlet 51 of the bubble tower 5 is connected to the fourth air outlet 42 of the oil mist trap 4 through a pipeline. The concentrated sulfuric acid with a concentration of 98% in the bubble tower 5 can absorb moisture in the tail gas.

[0055] The acid mist capture tower 6 has a sixth air inlet 61, a sixth air outlet 62 at the top and a third liquid outlet 63 at the bottom, and the sixth air inlet 61 of the acid mist capture tower 6 is connected to the fifth air outlet 52 of the bubble tower 5 through a pipeline. The acid mist capture tower 6 can remove sulfuric acid droplets brought out by the gas.

[0056] The alumina packing adsorption tower 7 has a seventh air inlet 71 at the bottom and a seventh air outlet 72 at the top, and the seventh air inlet 71 of the alumina packing adsorption tower 7 is connected to the sixth air outlet 62 of the acid mist capture tower 6 through a pipeline. The alumina in the alumina packing adsorption tower 7 can further adsorb moisture in the tail gas.

[0057] The dechlorination reactor 8 has an eighth air inlet 81 at the bottom and an eighth air outlet 82 at the top. The eighth air inlet 81 of the dechlorination reactor 8 is connected to the seventh air outlet 72 of the alumina filler adsorption tower 7 through a pipeline, and a tail gas delivery compressor 83 is installed near the eighth air inlet 81 of the dechlorination reactor 8. In this embodiment, the number of dechlorination reactors 8 is two, and each dechlorination reactor 8 is connected in series, and the dechlorination reactor 8 is a fluidized bed reactor, and the ferrous chloride solid absorbent is ferrous chloride powder with a diameter of less than 1 mm. The dechlorination reactor 8 selectively absorbs chlorine in the tail gas through the ferrous chloride solid absorbent to generate ferric chloride solid, which can be used as a flocculant in the refining of raw salt in the chlor-alkali plant after proper treatment.

[0058] The present invention also provides a chlorinated paraffin tail gas purification process using the chlorinated paraffin tail gas purification device.

[0059] Embodiment 1:

[0060] The first step is to remove oil from tail gas: the tail gas (i.e., chlorinated paraffin tail gas, which refers to the tail gas from the paraffin chlorination reaction, which is absorbed by the wax oil absorption kettle and has a chlorine content of less than 0.5 vol%) escaping from the absorption kettle is passed into the degreasing unit A, and is separated by the cyclone separator 1 to obtain a liquid phase (chlorinated paraffin and wax oil) and a gaseous tail gas. The liquid phase is recovered through the wax oil collection pipe after being discharged from the first liquid outlet 13, and the gaseous phase is cooled by the circulating water cooler 2 and the chilled water cooler 3 in turn to reduce the gaseous oil content in the tail gas, and the chilled water inlet temperature of the cooler 3 is maintained at 3°C. By controlling the flow rates of the circulating water and the cooling water, the tail gas temperature at the third gas outlet 32 ​​of the chilled water cooler 3 is controlled at 5°C. After the gaseous oil is converted into liquid oil, the wax oil and its chlorinated products in the chlorinated paraffin tail gas are removed by the oil mist collector 4 and enter the dehydration unit B;

[0061] The second step is to remove water from the tail gas: the tail gas from the oil mist collector 4 absorbs the water in the tail gas through the concentrated sulfuric acid with a concentration of 98% in the bubble tower 5, and the sulfuric acid temperature at the concentrated sulfuric acid feed port 53 of the bubble tower 5 is controlled to be 20° C. The acid mist is then captured by the acid mist capture tower 6, and finally the aluminum oxide in the aluminum oxide filler adsorption tower 7 further absorbs the water in the tail gas and enters the dechlorination unit C;

[0062] The third step is to remove chlorine from tail gas: the tail gas from the alumina packing adsorption tower 7 enters the fluidized bed reactor with a bed diameter of 1.2m, an initial bed height of 1m, and a bed height of 1.5m after fluidization at a flow rate of 0.4m / s, and reacts with ferrous chloride. The reaction temperature of the fluidized bed reactor is controlled to be 60°C and the reaction pressure is 10kPa;

[0063] The chlorine content and oil content of the final tail gas are tested.

[0064] Embodiment 2:

[0065] The difference from Example 1 is that in step (1), the exhaust gas temperature at the third gas outlet 32 ​​is controlled at 10°C.

[0066] Embodiment 3:

[0067] The difference from Example 1 is that in step (1), the exhaust gas temperature at the third gas outlet 32 ​​is controlled at 15°C.

[0068] Embodiment 4:

[0069] The difference from Example 1 is that in step (2), the sulfuric acid temperature at the concentrated sulfuric acid feed inlet 53 of the bubble tower 5 is 30°C.

[0070] Embodiment 5:

[0071] The difference from Example 1 is that the flow rate entering the bed in step (3) is 0.2 m / s.

[0072] Embodiment 6:

[0073] The difference from Example 1 is that the flow rate entering the bed in step (3) is 0.6 m / s.

[0074] Embodiment 7:

[0075] The difference from Example 1 is that the reaction temperature of chlorine and ferrous chloride in step (3) is 40°C.

[0076] Embodiment 8:

[0077] The difference from Example 1 is that the reaction temperature of chlorine and ferrous chloride in step (3) is 50°C.

[0078] Embodiment 9:

[0079] The difference from Example 1 is that in step (3), the reaction pressure of chlorine and ferrous chloride is 0 kPa (gauge pressure).

[0080] Embodiment 10:

[0081] The difference from Example 1 is that in step (3), the reaction pressure of chlorine and ferrous chloride is 5 kPa (gauge pressure).

[0082] Comparative Example 1:

[0083] On the basis of Example 1, the tail gas deoiling process was removed, and other processes remained unchanged, and the process conditions were kept the same.

[0084] Comparative Example 2:

[0085] On the basis of Example 1, the tail gas dehydration process is removed, and other processes remain unchanged, and the process conditions are kept the same.

[0086] Comparative Example 3:

[0087] On the basis of Example 1, the tail gas dechlorination process was removed, and other processes remained unchanged, and the process conditions were kept the same.

[0088] Comparative Example 4:

[0089] The tail gas is collected directly without going through a purification process.

[0090] The present invention also provides an application of the chlorinated paraffin tail gas purification device: the chlorinated paraffin tail gas treated by the chlorinated paraffin tail gas purification device is used as a reactant in a glycerol catalytic process for preparing epichlorohydrin.

[0091] The performance test steps are as follows:

[0092] (1) Oil content test method: Take 20 mL of n-hexane and place it in a conical flask. Pass the tail gas into the conical flask at a flow rate of 1 L / min for 5 min. Then take the sample and add it to a 1 cm quartz cuvette. Use a 7520 UV spectrophotometer with a wavelength of 260 nm and n-hexane as a blank sample to measure the absorbance of the sample. According to the absorbance, look up the standard curve to obtain the weight of the oil.

[0093] Oil content (ppm, mg / L) = oil weight (mg) / (flow rate (L / min) × duration (min));

[0094] (2) Water content test method: Take 10g of anhydrous sodium sulfate and place it in a drying tube. Pass the exhaust gas into the drying tube at a flow rate of 1L / min for 5 minutes, then weigh and record the weight of the drying tube;

[0095] Water content (ppm, mg / L) = weight difference before and after ventilation (mg) / (flow rate (L / min) × duration (min));

[0096] (3) Chlorine content test method: Take 20mL of NaOH aqueous solution and place it in a conical flask, pass 200mL of tail gas into the NaOH solution, plug the glass stopper, and let it stand for 2h; then take 5mL of the sample, add 10mL of 100g / L potassium iodide solution and 10mL of sulfuric acid solution, and titrate with Na2S2O3 standard solution, using 2mL of starch solution as an indicator, and the end point is when the solution in the conical flask turns blue. Record the amount of Na2S2O3 standard solution used;

[0097] Chlorine content (ppm, mg / L) = amount of Na2S2O3 standard solution used (mL) × concentration of Na2S2O3 standard solution (g / mL) / (2 × molar mass of Na2S2O3 (g / mL)) × molar mass of Cl2 (g / mL) × 250000 / exhaust gas introduction amount (mL).

[0098] The performance test results of all the above embodiments and comparative examples are shown in Table 1.

[0099] It can be seen from Table 1 that:

[0100] (1) From the data of experimental groups F to I, it can be seen that the oil removal process, water removal process and chlorine removal process in this process can respectively significantly remove chlorinated paraffin and paraffin, water and free chlorine in the tail gas, thereby improving the purity of hydrogen chloride in the tail gas, so that the purified tail gas can be used as an important raw material for many chlorine-containing processes.

[0101] (2) From the data of experimental group A, it can be seen that increasing the exhaust temperature at the third outlet 32 ​​in step (1) will significantly increase the oil content and chlorine content of the purified exhaust gas. The reason is that the lower the exhaust temperature, the lower the saturated vapor pressure of the wax oil, and the better the effect of the exhaust gas deoiling process. At the same time, the high oil content of the exhaust gas is easy to cause the ferrous chloride particles to stick to each other, affecting the fluidization effect of the fluidized bed and the full reaction of ferrous chloride and chlorine.

[0102] (3) From the data of experimental group B, it can be seen that increasing the sulfuric acid temperature at the dilute sulfuric acid outlet 54 of the bubble tower 5 in step (2) will significantly increase the water content and chlorine content of the purified tail gas. The reason is that the lower the sulfuric acid temperature, the better the effect of absorbing water. At the same time, high water content in the tail gas can easily lead to deliquescence of ferrous chloride particles, affecting the fluidization effect of the fluidized bed and the full reaction of ferrous chloride and chlorine.

[0103] (4) From the data of experimental group C, it can be seen that the flow rate entering the bed in step (3) should be selected to an appropriate value. Too large or too small will obviously lead to an increase in the chlorine content of the purified tail gas. The reasons are: if the flow rate is too small, the fluidization effect of the bed is poor, the porosity is small, and the gas-solid contact is insufficient; if the flow rate is too large, the gas residence time is too short, the reaction time is too short, and the gas-solid reaction is insufficient.

[0104] (5) From the data of experimental group D, it can be seen that appropriately increasing the temperature of the fluidized bed reactor can reduce the chlorine content of the purified tail gas. The reason is that appropriately increasing the reaction temperature can increase the reaction rate and make the reaction of ferrous chloride and chlorine more complete, but the energy consumption and dechlorination effect must be considered comprehensively.

[0105] (6) From the data of experimental group E, it can be seen that appropriately increasing the reaction pressure of the fluidized bed reactor can reduce the chlorine content of the purified tail gas. The reason is that appropriately increasing the reaction pressure is conducive to the forward absorption reaction, making the reaction of ferrous chloride and chlorine more complete, but it is necessary to comprehensively consider energy consumption, reaction vessel design pressure and dechlorination effect.

[0106] Under the process conditions of Example 1, the degree of reaction between ferrous chloride and chlorine is determined by detecting the mass change of the fluidized bed reactor, and then it is determined whether the ferrous chloride solid in the reactor needs to be replaced.

[0107] Table 1 Performance test results of all embodiments and comparative examples

[0108]

Claims

1. A chlorinated paraffin tail gas purification process, characterized in that: The chlorinated paraffin tail gas purification process is applied with a chlorinated paraffin tail gas purification device, which includes an oil removal unit, a water removal unit and a chlorine removal unit connected in sequence; The oil removal unit comprises a cyclone separator (1), a circulating water cooler (2), a chilled water cooler (3) and an oil mist collector (4) which are connected in sequence and are used to cool and recover the wax oil and its chlorinated products in the tail gas of chlorinated paraffin; The dehydration unit comprises a bubble tower (5), an acid mist collection tower (6) and an alumina filler adsorption tower (7) which are connected in sequence and are used to absorb moisture in the chlorinated paraffin tail gas; The dechlorination unit comprises a dechlorination reactor (8), which selectively absorbs chlorine in the tail gas through a ferrous chloride solid absorbent; The chlorinated paraffin tail gas purification process comprises the following steps: The first step is to remove oil from the tail gas: the chlorinated paraffin tail gas is passed into the oil removal unit, and the droplets in the chlorinated paraffin tail gas are removed by a cyclone separator (1). The gaseous oil content in the tail gas is reduced by cooling through a circulating water cooler (2) and a chilled water cooler (3). After the gaseous oil is converted into liquid oil, the wax oil and its chlorinated products in the chlorinated paraffin tail gas are removed by an oil mist collector (4) and enter the water removal unit; The second step is to remove water from the tail gas: the concentrated sulfuric acid in the bubble tower (5) absorbs the water in the tail gas, and then the acid mist is captured by the acid mist capture tower (6). Finally, the aluminum oxide in the aluminum oxide filler adsorption tower (7) further absorbs the water in the tail gas and then enters the dechlorination unit; The third step is to remove chlorine from the tail gas: the chlorine in the tail gas is selectively absorbed by the ferrous chloride solid absorbent in the dechlorination reactor (8).

2. The chlorinated paraffin tail gas purification process according to claim 1, characterized in that: The cyclone separator (1) has a first air inlet (11), a first air outlet (12) and a first liquid outlet (13); The circulating water cooler (2) has a second air inlet (21) arranged at the top and a second air outlet (22) arranged at the bottom, and circulating water of the circulating water cooler (2) flows from bottom to top in the circulating water cooler (2), and the second air inlet (21) of the circulating water cooler (2) is connected to the first air outlet (12) of the cyclone separator (1) through a pipeline; The chilled water cooler (3) has a third air inlet (31) arranged at the top and a third air outlet (32) arranged at the bottom, and cooling water of the chilled water cooler (3) flows from bottom to top in the chilled water cooler (3), and the third air inlet (31) of the chilled water cooler (3) is connected to the second air outlet (22) of the circulating water cooler (2) through a pipeline; The oil mist collector (4) has a fourth air inlet (41), a fourth air outlet (42) and a second liquid outlet (43); the fourth air inlet (41) of the oil mist collector (4) is connected to the third air outlet (32) of the chilled water cooler (3) through a pipeline.

3. The chlorinated paraffin tail gas purification process according to claim 2, characterized in that: The bubble tower (5) has a fifth air inlet (51), a fifth air outlet (52), a concentrated sulfuric acid feed port (53) and a dilute sulfuric acid discharge port (54); the fifth air inlet (51) of the bubble tower (5) is connected to the fourth air outlet (42) of the oil mist collector (4) through a pipeline; The acid mist capture tower (6) has a sixth air inlet (61), a sixth air outlet (62) and a third liquid outlet (63), and the sixth air inlet (61) of the acid mist capture tower (6) is connected to the fifth air outlet (52) of the bubble tower (5) through a pipeline; The alumina filler adsorption tower (7) has a seventh air inlet (71) and a seventh air outlet (72); the seventh air inlet (71) of the alumina filler adsorption tower (7) is connected to the sixth air outlet (62) of the acid mist capture tower (6) through a pipeline.

4. The chlorinated paraffin tail gas purification process according to claim 3, characterized in that: The bubble tower (5) is provided with a sulfuric acid circulation outlet (55) and a sulfuric acid circulation inlet (56), and a sulfuric acid circulation pump (57), a sulfuric acid cooler (58) and a sulfuric acid circulation tank (59) are sequentially connected between the sulfuric acid circulation outlet (55) and the sulfuric acid circulation inlet (56) for cooling the sulfuric acid.

5. The chlorinated paraffin tail gas purification process according to claim 3, characterized in that: The dechlorination reactor (8) has an eighth air inlet (81) and an eighth air outlet (82); the eighth air inlet (81) of the dechlorination reactor (8) is connected to the seventh air outlet (72) of the alumina filler adsorption tower (7) via a pipeline; and an exhaust gas delivery compressor (83) is installed near the eighth air inlet (81) of the dechlorination reactor (8).

6. The chlorinated paraffin tail gas purification process according to any one of claims 1 to 5, characterized in that: The ferrous chloride solid absorbent is ferrous chloride powder with a diameter less than 1 mm.

7. The chlorinated paraffin tail gas purification process according to any one of claims 1 to 5, characterized in that: The number of the oil mist collectors (4) is at least two, and the oil mist collectors (4) are connected in parallel with each other; the number of the dechlorination reactors (8) is at least two, and the dechlorination reactors (8) are connected in series with each other.

8. The chlorinated paraffin tail gas purification process according to any one of claims 1 to 5, characterized in that: The temperature of the chlorinated paraffin tail gas treated by the refrigerated water cooler (3) is 5-15°C, the oil content of the chlorinated paraffin tail gas treated by the oil mist collector (4) is less than 10 ppm, the bubble tower (5) controls the temperature of the inlet concentrated sulfuric acid to be 20-30°C, the water content of the chlorinated paraffin tail gas treated by the acid mist collector (6) is less than 100 ppm, the water content of the chlorinated paraffin tail gas treated by the alumina filler adsorption tower (7) is less than 20 ppm, the chlorine content of the chlorinated paraffin tail gas treated by the dechlorination reactor (8) is less than 10 ppm, and the dechlorination reactor (8) is a fluidized bed reactor with a reaction pressure of 0-10 kPa gauge pressure, a reaction temperature of 40-60°C, a gas flow rate of 0.2-0.6 m / s, and a bed height of 1.5-2.5 m after fluidization.

9. An application of the chlorinated paraffin tail gas purification process according to any one of claims 1 to 8, wherein the chlorinated paraffin tail gas treated by the chlorinated paraffin tail gas purification process is used as a reactant in a glycerol catalytic process for producing epichlorohydrin.

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