CN105732342A - Formaldehyde production method based on exhaust gas circulating process - Google Patents
Formaldehyde production method based on exhaust gas circulating process Download PDFInfo
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- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
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- C07C45/38—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups being a primary hydroxyl group
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Abstract
The invention relates to the technical field of formaldehyde production, and particularly discloses a formaldehyde production method based on an exhaust gas circulating process. The formaldehyde production method comprises the following steps: allowing quaternary mixed gas to pass through an electrolytic silver contact agent layer from top to bottom in an oxidizer, and performing the reaction to generate formaldehyde gas, wherein the reaction temperature is 630 to 660 DEG C, an oxygen-to-alcohol ratio of the quaternary mixed gas is 0.4 to 0.5, a water-to-alcohol ratio is 1.5 to 1.7, an exhaust-gas-to-alcohol ratio is 1.1 to 1.3, the retention time of the quaternary mixed gas in the oxidizer is 0.009 to 0.011s, the gas generated in the oxidizer is quenched by virtue of a quenching section of the oxidizer, the temperature of the generated gas is lowered to 130 to 160 DEG C in 0.1 to 0.3 s, and the quenched gas discharged from the oxidizer is sent into an absorption unit. According to the formaldehyde production method, by reasonably selecting various process parameters in the production process, side reactions in the formaldehyde preparation process are obviously reduced, the methanol conversion rate is remarkably improved, and the concentration of the obtained formaldehyde product can reach 50 to 55 percent.
Description
Technical field
The present invention relates to Formaldehyde Production technical field, be specifically related to a kind of prepn. of formaldehyde based on exhaust gas circulation process.
Background technology
Industrial formol produces and all uses methanol both at home and abroad at present is raw material, and production technology has silver-colored catalytic oxidation, ferrum molybdenum catalytic oxidation and methylal oxidation method etc., and wherein the overwhelming majority adopts silver catalytic oxidation.
Domestic silver-colored catalytic oxidation divides traditional handicraft and exhaust gas circulation process.In traditional handicraft, tail gas all burns to exhaust gas treating device, reclaims heat energy, and the steam of generation delivers to drum for production and application.Exhaust gas circulation process flow process is similar to traditional handicraft, and its Main Differences is in that a part of tail gas burns to exhaust gas treating device, reclaims heat energy, and a part of circulation of tail gas is to the blender stabilizer as reaction heat.Exhaust gas circulation process has the advantages such as the formaldehyde that methanol conversion is high, unit consumption is low and produces variable concentrations than traditional handicraft.Therefore, exhaust gas circulation process becomes the process that formaldehyde industry is conventional.But, with regard to present production technology level, Formaldehyde Production also has a lot of place needing research and transformation.
In actual production, silver catalytic oxidation produces the chemical reaction of formaldehyde reaction process, except the primary responses such as methanol oxidation and dehydrogenation, also having the side reactions such as methanol burning and oxidation of formaldehyde, these reactions are main as shown in following reaction equation (various middle exothermic heat of reaction is heat when 25 DEG C).
Primary response:
CH3OH=CH2O+H2-85.270kJ/mol
Side reaction:
CH3OH+O2=CO+2H2O+393.009kJ/mol
HCOOH=CO+H2O-10.278kJ/mol。
Additionally, due to the change of reaction condition, it is also possible to there is one or several side reaction in following reaction:
CH2O=CO+H2-5.375kJ/mol
CH2O+O2=CO2+H2O+519.441kJ/mol
CH3OH=C+H2O+H2+40.657kJ/mol
CH3OH+H2=CH4+H2O+115.505kJ/mol
2CH2O+H2O=CH3OH+HCOOH+90.173kJ/mol。
The existence of side reaction not only can reduce reaction yield, also can reduce concentration and the purity of formaldehyde products.Therefore also need to explore and find better reaction condition further on producing, to be reduced as far as the generation of side reaction, improve reaction yield.
Summary of the invention
It is an object of the invention to provide a kind of prepn. of formaldehyde, this prepn. of formaldehyde adopts exhaust gas circulation process.By the reasonable selection to technological parameter each in production process, in formaldehyde preparation process, side reaction significantly reduces, and methanol conversion significantly improves, and the formaldehyde products concentration obtained is up to 50～55%.
In order to realize object above, the technical solution adopted in the present invention is: a kind of prepn. of formaldehyde based on exhaust gas circulation process, including step:
Refined methanol in refined methanol groove is delivered to methanol evaporator by methanol pump and is heated, and the methanol gas in methanol evaporator from methanol evaporator top out, then removes through demister and enters quaternary blender after droplet；
Air by air filter, is sent into air heater preheating by roots blower, is entered described quaternary blender afterwards after alkali cleaning, washing remove impurity；
For the steam of dispensing from steam distributor through vapor filter, then entered described quaternary blender by after regulating valve regulating flow；
Opening exhaust fan, partial tail gas is preheated by heater exhaust gas, enters described quaternary blender afterwards；
nullQuaternary gas in described quaternary blender: methanol gas、Air、Steam、Tail gas，Mix homogeneously in quaternary blender，Obtain quaternary mixing gas，Quaternary mixing gas is through fire-retardant filter filtering and heating，Send into oxidator reaction afterwards and prepare formaldehyde，Oxidator is built with catalyst electrolytic silver，Described quaternary mixing gas enters from oxidator top，Quaternary mixing gas passes through electrolytic silver catalyst layer in oxidator，There is oxidation and the dehydrogenation reaction of methanol，Generate formaldehyde gas，Reaction temperature is 630～660 DEG C，The oxygen-methanol ratio of quaternary mixing gas is 0.4～0.5，Water alcohol ratio is 1.5～1.7，Tail alcohol ratio is 1.1～1.3，The quaternary mixing gas time of staying in oxidator is 0.009～0.011s，The gas generated in oxidator is quenched by the quench zone of described oxidator，130～160 DEG C are reduced the temperature in 0.1～0.3s，From oxidator out through be quenched gas send into absorptive unit；
First grade absorption tower and two-level absorption tower that described absorptive unit is set by string form, initially enter in first grade absorption tower, carry out absorption operation from the oxidator gas through being quenched out, formaldehyde finished product is by described first grade absorption tower extraction, absorb and added by two-level absorption tower tower top with supplementary fresh water (FW), after rare aldehyde liquid pump at the bottom of two-level absorption tower tower is got, part is absorbed by two-level absorption tower self-loopa, and part sends into the first order absorption column overhead supplementary absorption liquid as first grade absorption tower；The unabsorbed tail gas part of two-level absorption tower tower top sends into burning in tail gas burning furnace after vapour liquid separator, liberated heat is for indirectly producing steam, another part tail gas enters described exhaust fan, preheated by described heater exhaust gas, enter back into described quaternary blender and carry out circulation of tail gas.
Preferably, the refined methanol liquid level in described refined methanol groove is maintained at more than 50%.
The liquid level of described first grade absorption tower remains 30～50%；First order absorption tower top temperature≤55 DEG C.
The liquid level of described two-level absorption tower remains 30～50%；Temperature≤45 DEG C, two-level absorption tower top.
Described catalyst electrolytic silver is the silver catalyst through electrolytic purification, its silver content more than 99.99%, and iron content is less than 3ppm, and content of calcium and magnesium summation is less than 10ppm.
Described catalyst electrolytic silver granularity is 8 orders, 12 orders, 24 orders, 30 orders or 35 orders.
The following detailed description of beneficial effects of the present invention.
One, find by studying the industrial processes of formaldehyde, the performance of catalyst is reacted with state oxidation of formaldehyde and is had impact.The performance of catalyst is the key factor of impact reaction, and the quality of its performance will be directly connected to the degree that primary response carries out.The catalyst that the present invention adopts is the silver catalyst through electrolytic purification, and purity is high, and adopts particulate electrolytic silver, and granularity is 8 orders, 12 orders, 24 orders, 30 orders or 35 orders.This catalyst has active, the stronger mechanical strength of high catalysis and certain poison resistance, and this catalyst defines active and uniform surface, and catalytic performance is good.Owing to adopting particulate electrolytic silver, the electrolytic silver catalyst layer paved can make gas flow through beds uniformly, and hot-spot will not be occurred to react, and causes bed sintering or breaks.Sintering can increase SR and drop, and breaks, and can produce bypass.Both can affect the performance of catalyst and shorten the service life of catalyst.
Two, the reaction of reaction temperature oxidation of formaldehyde also has impact, methanol generate two primary responses of formaldehyde, and namely methanol oxidation and methanol dehydrogenation reaction are all very close with the relation of temperature, and temperature is very big on their impact.Oxidation reaction for heat release, according to Le Chatelier's principle, heats up making reaction the Direction of Reaction towards heat absorption move, namely heats up oxidation reaction is unfavorable, and its equilibrium constant reduces with the rising of temperature.Even so, but PARA FORMALDEHYDE PRILLS(91,95) reduction reaction, even if under the high temperature of 700 DEG C, its equilibrium constant is still little.Even if it means that at high temperature, methanol oxidation almost still can proceed to the end.Therefore, although heat up exothermic reaction is unfavorable, but consider that equilibrium constant is relatively big, therefore still elect to higher reaction temperature.Methanol dehydrogenation reaction for heat absorption, intensification is advantageous for, the equilibrium constant of methanol dehydrogenation reaction raises with temperature and increases, cooling is then unfavorable to methanol dehydrogenation reaction, methanol dehydrogenation reaction is little to carry out at low temperatures, its spontaneous minimum temperature carried out is 481.6 DEG C, and the reaction temperature of actual production should be higher than that this temperature.Suitable reaction temperature is selected to need from equilibrium conversion and response speed etc. because usually considering.From response speed angle, the speed of general chemical reaction dramatically speeds up with the rising of temperature.This is because along with the rising of temperature, the motion of molecule is accelerated, intermolecular collision opportunity increases, and makes the increased number of anakmetomeres, thus adding the chance of intermolecular effective combination.Therefore, to oxidation or dehydrogenation reaction is all favourable to improve temperature.But, in actual production, reaction temperature is unsuitable too high.This is because other factor must also be considered.First, with the rising of temperature, the primary response not only generating formaldehyde is accelerated, and consumes methanol and generate CO and CO2Side reaction also will be accelerated, therefore reaction temperature must suitably.Secondly, at high temperature formaldehyde easily decomposes, and the response speed of the Formaldehyde decomposition absorbed heat is again than the dehydrogenation reaction speed of heat absorption more faster, and therefore reaction temperature is also unsuitable too high.It addition, the too high meeting of temperature makes catalyst melt, cause voidage to reduce the change with physical arrangement, finally can cause catalyst activity reduction, the lost of life, affect course of reaction.In a word, reaction temperature is a key factor of impact reaction, and it not only affects equilibrium conversion and the response speed of reaction, but also affects the performance of catalyst efficiency.Therefore, when selective response temperature, methanol should be considered and be converted into the factors such as the equilibrium conversion of formaldehyde, main side effect speed, the activity of catalyst, bed resistance, reactor diameter size and structure of reactor.Considering, the reaction temperature of the present invention is defined as 630～660 DEG C.
Three, investigate the impact of oxygen-methanol ratio oxidation of formaldehyde reaction.Oxygen-methanol ratio, the i.e. mol ratio of oxygen and methanol.Oxygen-methanol ratio increases, and namely oxygen increases in the ratio of unstripped gas, and amount of oxygen increases.Otherwise, then reduce.According to Le Chatelier's principle, increase amount of oxygen by making oxidation reaction move towards the direction consuming oxygen, therefore that the oxidation reaction of methanol is favourable.And the dehydrogenation reaction for methanol, although reaction itself does not consume oxygen, but hydrogen and oxygen combine and generates water, increases oxygen amount and can fall more hydrogenating conjunction, promotes dehydrogenation reaction to move to the direction generating formaldehyde.Therefore, oxygen amount is increased by two primary responses are all favourable.But, increase oxygen amount the side reaction generating hydrocarbon is also favourable.So oxygen amount increase should appropriateness.It addition, the height of oxygen amount also directly influences reaction temperature.If oxygen amount is too high, then reaction temperature is too high；And oxygen amount is very little, reaction temperature is too low again, all will affect the extent of reaction.Therefore, oxygen-methanol ratio is a very important parameter, because it is related to the significant problems such as the conversion ratio of Formaldehyde Production course of reaction, selectivity and production safety.During commercial production formaldehyde, controlling methanol concentration and operate more than the upper limit of explosive range, namely methanol is excessive and oxygen amount is not enough.Quaternary of the present invention mixing gas oxygen-methanol ratio is 0.4～0.5.
Four, the impact that water alcohol reacts than oxidation of formaldehyde, water alcohol ratio, the i.e. mol ratio of water and methanol.Increase water alcohol ratio, namely increase the content of water in quaternary mixing gas.And the Main Function of water is to make a part of reaction heat be only absorbed by the water, to take away the waste heat in course of reaction, maintain reaction temperature in the scope required.Therefore, water can play the effect of heat stabilizer.Increase water alcohol ratio, not only improve control reaction temperature, reaction can be made again to carry out at a lower temperature, it is also possible to improve the concentration of oxygen in charging and do not occur overheated, it is thus possible to improve conversion ratio and improve yield.But, improve water alcohol ratio and to be subject to product design and the restriction of tower absorption efficiency.If water alcohol ratio is excessive, maintain the amount of water of two towers again, will result in product design and decline；And to ensure product design, certainly will reduce again by two tower amount of water, make the absorption efficiency of two towers decline.Therefore, water alcohol ratio must control suitably.Quaternary of the present invention mixing gas water alcohol ratio is 1.5～1.7.
Five, the impact of air speed oxidation of formaldehyde reaction.The time of staying is also named time of contact, refers to that mixed raw material gas passes through the time needed for catalytic bed, and its unit represented with the second.The time of staying and space velocity (abbreviation air speed) are in reciprocal relation.That is:
In formula: the T-time of staying, s；
VEmpty-air speed, h-1；
Space velocity refers in normal conditions, the volume flow number of the mixed raw material gas that per volume of catalyst is passed through.Course of reaction and the time of staying of mixed raw material gas, air speed are relevant.As air speed is too big, namely the time of staying is too short, then unstripped gas has little time reaction in beds and just passes through, and causes conversion ratio to reduce.Otherwise, as air speed is too little, then according to absorption principle, gas is not easily overcome external diffusion resistance, makes the probability of arrival catalyst surface reduce, and conversion ratio also reduces.Again owing to the air speed little then time of staying is long, the product generated after reaction can not leave beds in time, and will result in side reaction increases, and also makes productivity decline.The quaternary of the present invention mixing gas time of staying in oxidator is 0.009～0.011s.
It addition, also there is certain requirement reaction product time of staying in the reactor.This is because formaldehyde is at high temperature very unstable, easily resolving into carbon monoxide and hydrogen, more than 500 DEG C, this decomposition is very rapid.For making the pyrolysis of formaldehyde be preferably minimized, the gas generated in oxidator in production is quenched by the quench zone of oxidator, reduces the temperature to 130～160 DEG C in 0.1～0.3s.
Six, tail alcohol ratio is mainly by adding tail gas amount, and the method improving oxygen-methanol ratio further, thus reducing alcohol content, improving the purpose of content of formaldehyde.The tail alcohol ratio of quaternary of the present invention mixing gas is 1.1～1.3, can reach the content of formaldehyde of 50～55%, obtain high-concentration formaldehyde product.
First grade absorption tower, two-level absorption tower liquid level remain 30～50%.Liquid level is too high, if exceeding the entrance of gas phase pipeline, making reacted gas cannot enter tower, causing SR to increase severely, even the accident such as Roots's machine tripping operation.Liquid level is too low or fans the air, then will result in circulating pump and export without circulation fluid, and tower liquid capacity of returns is progressively reduced until and does not spray, and causes that tower temperature rise, absorption operation interrupt, and makes formaldehyde gas effusion contaminated environment.During production operation, for ensureing the quality of formaldehyde products, first grade absorption tower, the stablizing of two-level absorption tower liquid level should be remained.Control tower temperature main purpose is to reduce the temperature absorbing liquid under the premise preventing oxymethylene polymerization as much as possible, reaches to improve the effect of formaldehyde absorption rate.In first order absorption tower top temperature≤55 DEG C, under the condition of temperature≤45 DEG C, two-level absorption tower top, effect is best.
Prepn. of formaldehyde provided by the invention, by the reasonable selection to technological parameter each in production process, in formaldehyde preparation process, side reaction significantly reduces, and methanol conversion significantly improves, and the formaldehyde products concentration obtained is up to 50～55%.
Detailed description of the invention
Below by specific embodiment, technical scheme is described in detail.
Embodiment 1
A kind of prepn. of formaldehyde based on exhaust gas circulation process, including step:
Refined methanol in refined methanol groove is delivered to methanol evaporator by methanol pump and is heated, and the methanol gas in methanol evaporator from methanol evaporator top out, then removes through demister and enters quaternary blender after droplet；
Air after alkali cleaning, washing remove impurity, is sent into air heater preheating by roots blower by air filter, enters quaternary blender afterwards；
For the steam of dispensing from steam distributor through vapor filter, then entered quaternary blender by after regulating valve regulating flow；
Opening exhaust fan, partial tail gas is preheated by heater exhaust gas, enters quaternary blender afterwards；
nullQuaternary gas in quaternary blender: methanol gas、Air、Steam、Tail gas，Mix homogeneously in quaternary blender，Obtain quaternary mixing gas，Quaternary mixing gas is through fire-retardant filter filtering and heating，Send into oxidator reaction afterwards and prepare formaldehyde，Oxidator is built with catalyst electrolytic silver，Quaternary mixing gas enters from oxidator top，Quaternary mixing gas passes through electrolytic silver catalyst layer in oxidator，There is oxidation and the dehydrogenation reaction of methanol，Generate formaldehyde gas，Reaction temperature is 630 DEG C，The oxygen-methanol ratio of quaternary mixing gas is 0.5，Water alcohol ratio is 1.5，Tail alcohol ratio is 1.3，The quaternary mixing gas time of staying in oxidator is 0.01s，The gas generated in oxidator is quenched by the quench zone of oxidator，160 DEG C are reduced the temperature in 0.1s，From oxidator out through be quenched gas send into absorptive unit；
First grade absorption tower and two-level absorption tower that absorptive unit is set by string form, initially enter in first grade absorption tower, carry out absorption operation from the oxidator gas through being quenched out, formaldehyde finished product is by first grade absorption tower extraction, absorb and added by two-level absorption tower tower top with supplementary fresh water (FW), after rare aldehyde liquid pump at the bottom of two-level absorption tower tower is got, part is absorbed by two-level absorption tower self-loopa, and part sends into the first order absorption column overhead supplementary absorption liquid as first grade absorption tower；The unabsorbed tail gas part of two-level absorption tower tower top sends into burning in tail gas burning furnace after vapour liquid separator, liberated heat is used for producing steam, another part tail gas enters exhaust fan, is preheated by heater exhaust gas, enters back into quaternary blender and carry out circulation of tail gas.
Wherein, the refined methanol liquid level in refined methanol groove is maintained at more than 50%.
The liquid level of first grade absorption tower remains 30～50%；First order absorption tower top temperature≤55 DEG C.
The liquid level of two-level absorption tower remains 30～50%；Temperature≤45 DEG C, two-level absorption tower top.
Catalyst electrolytic silver is the silver catalyst through electrolytic purification, its silver content more than 99.99%, and iron content is less than 3ppm, and content of calcium and magnesium summation is less than 10ppm.Catalyst electrolytic silver granularity is 8 orders.
Embodiment 2
A kind of prepn. of formaldehyde based on exhaust gas circulation process, including step:
Refined methanol in refined methanol groove is delivered to methanol evaporator by methanol pump and is heated, and the methanol gas in methanol evaporator from methanol evaporator top out, then removes through demister and enters quaternary blender after droplet；
Air after alkali cleaning, washing remove impurity, is sent into air heater preheating by roots blower by air filter, enters quaternary blender afterwards；
For the steam of dispensing from steam distributor through vapor filter, then entered quaternary blender by after regulating valve regulating flow；
Opening exhaust fan, partial tail gas is preheated by heater exhaust gas, enters quaternary blender afterwards；
nullQuaternary gas in quaternary blender: methanol gas、Air、Steam、Tail gas，Mix homogeneously in quaternary blender，Obtain quaternary mixing gas，Quaternary mixing gas is through fire-retardant filter filtering and heating，Send into oxidator reaction afterwards and prepare formaldehyde，Oxidator is built with catalyst electrolytic silver，Quaternary mixing gas enters from oxidator top，Quaternary mixing gas passes through electrolytic silver catalyst layer in oxidator，There is oxidation and the dehydrogenation reaction of methanol，Generate formaldehyde gas，Reaction temperature is 660 DEG C，The oxygen-methanol ratio of quaternary mixing gas is 0.4，Water alcohol ratio is 1.7，Tail alcohol ratio is 1.1，The quaternary mixing gas time of staying in oxidator is 0.009s，The gas generated in oxidator is quenched by the quench zone of oxidator，130 DEG C are reduced the temperature in 0.3s，From oxidator out through be quenched gas send into absorptive unit；
First grade absorption tower and two-level absorption tower that absorptive unit is set by string form, initially enter in first grade absorption tower, carry out absorption operation from the oxidator gas through being quenched out, formaldehyde finished product is by first grade absorption tower extraction, absorb and added by two-level absorption tower tower top with supplementary fresh water (FW), after rare aldehyde liquid pump at the bottom of two-level absorption tower tower is got, part is absorbed by two-level absorption tower self-loopa, and part sends into the first order absorption column overhead supplementary absorption liquid as first grade absorption tower；The unabsorbed tail gas part of two-level absorption tower tower top sends into burning in tail gas burning furnace after vapour liquid separator, liberated heat is used for producing steam, another part tail gas enters exhaust fan, is preheated by heater exhaust gas, enters back into quaternary blender and carry out circulation of tail gas.
Wherein, the refined methanol liquid level in refined methanol groove is maintained at more than 50%.
The liquid level of first grade absorption tower remains 30～50%；First order absorption tower top temperature≤55 DEG C.
The liquid level of two-level absorption tower remains 30～50%；Temperature≤45 DEG C, two-level absorption tower top.
Catalyst electrolytic silver is the silver catalyst through electrolytic purification, its silver content more than 99.99%, and iron content is less than 3ppm, and content of calcium and magnesium summation is less than 10ppm.Catalyst electrolytic silver granularity is 35 orders.
Embodiment 3
A kind of prepn. of formaldehyde based on exhaust gas circulation process, including step:
Refined methanol in refined methanol groove is delivered to methanol evaporator by methanol pump and is heated, and the methanol gas in methanol evaporator from methanol evaporator top out, then removes through demister and enters quaternary blender after droplet；
Air after alkali cleaning, washing remove impurity, is sent into air heater preheating by roots blower by air filter, enters quaternary blender afterwards；
For the steam of dispensing from steam distributor through vapor filter, then entered quaternary blender by after regulating valve regulating flow；
Opening exhaust fan, partial tail gas is preheated by heater exhaust gas, enters quaternary blender afterwards；
nullQuaternary gas in quaternary blender: methanol gas、Air、Steam、Tail gas，Mix homogeneously in quaternary blender，Obtain quaternary mixing gas，Quaternary mixing gas is through fire-retardant filter filtering and heating，Send into oxidator reaction afterwards and prepare formaldehyde，Oxidator is built with catalyst electrolytic silver，Quaternary mixing gas enters from oxidator top，Quaternary mixing gas passes through electrolytic silver catalyst layer in oxidator，There is oxidation and the dehydrogenation reaction of methanol，Generate formaldehyde gas，Reaction temperature is 650 DEG C，The oxygen-methanol ratio of quaternary mixing gas is 0.5，Water alcohol ratio is 1.5，Tail alcohol ratio is 1.3，The quaternary mixing gas time of staying in oxidator is 0.011s，The gas generated in oxidator is quenched by the quench zone of oxidator，150 DEG C are reduced the temperature in 0.1s，From oxidator out through be quenched gas send into absorptive unit；
First grade absorption tower and two-level absorption tower that absorptive unit is set by string form, initially enter in first grade absorption tower, carry out absorption operation from the oxidator gas through being quenched out, formaldehyde finished product is by first grade absorption tower extraction, absorb and added by two-level absorption tower tower top with supplementary fresh water (FW), after rare aldehyde liquid pump at the bottom of two-level absorption tower tower is got, part is absorbed by two-level absorption tower self-loopa, and part sends into the first order absorption column overhead supplementary absorption liquid as first grade absorption tower；The unabsorbed tail gas part of two-level absorption tower tower top sends into burning in tail gas burning furnace after vapour liquid separator, liberated heat is used for producing steam, another part tail gas enters exhaust fan, is preheated by heater exhaust gas, enters back into quaternary blender and carry out circulation of tail gas.
Wherein, the refined methanol liquid level in refined methanol groove is maintained at more than 50%.
The liquid level of first grade absorption tower remains 30～50%；First order absorption tower top temperature≤55 DEG C.
The liquid level of two-level absorption tower remains 30～50%；Temperature≤45 DEG C, two-level absorption tower top.
Catalyst electrolytic silver is the silver catalyst through electrolytic purification, its silver content more than 99.99%, and iron content is less than 3ppm, and content of calcium and magnesium summation is less than 10ppm.Catalyst electrolytic silver granularity is 24 orders.
Claims (6)
1. the prepn. of formaldehyde based on exhaust gas circulation process, it is characterised in that include step:
Refined methanol in refined methanol groove is delivered to methanol evaporator by methanol pump and is heated, and the methanol gas in methanol evaporator from methanol evaporator top out, then removes through demister and enters quaternary blender after droplet；
Air by air filter, is sent into air heater preheating by roots blower, is entered described quaternary blender afterwards after alkali cleaning, washing remove impurity；
For the steam of dispensing from steam distributor through vapor filter, then entered described quaternary blender by after regulating valve regulating flow；
Opening exhaust fan, partial tail gas is preheated by heater exhaust gas, enters described quaternary blender afterwards；
nullQuaternary gas in described quaternary blender: methanol gas、Air、Steam、Tail gas，Mix homogeneously in quaternary blender，Obtain quaternary mixing gas，Quaternary mixing gas is through fire-retardant filter filtering and heating，Send into oxidator reaction afterwards and prepare formaldehyde，Oxidator is built with catalyst electrolytic silver，Described quaternary mixing gas enters from oxidator top，Quaternary mixing gas passes through electrolytic silver catalyst layer in oxidator，There is oxidation and the dehydrogenation reaction of methanol，Generate formaldehyde gas，Reaction temperature is 630～660 DEG C，The oxygen-methanol ratio of quaternary mixing gas is 0.4～0.5，Water alcohol ratio is 1.5～1.7，Tail alcohol ratio is 1.1～1.3，The quaternary mixing gas time of staying in oxidator is 0.009～0.011s，The gas generated in oxidator is quenched by the quench zone of described oxidator，130～160 DEG C are reduced the temperature in 0.1～0.3s，From oxidator out through be quenched gas send into absorptive unit；
First grade absorption tower and two-level absorption tower that described absorptive unit is set by string form, initially enter in first grade absorption tower, carry out absorption operation from the oxidator gas through being quenched out, formaldehyde finished product is by described first grade absorption tower extraction, absorb and added by two-level absorption tower tower top with supplementary fresh water (FW), after rare aldehyde liquid pump at the bottom of two-level absorption tower tower is got, part is absorbed by two-level absorption tower self-loopa, and part sends into the first order absorption column overhead supplementary absorption liquid as first grade absorption tower；The unabsorbed tail gas part of two-level absorption tower tower top sends into burning in tail gas burning furnace after vapour liquid separator, liberated heat is used for producing steam, another part tail gas enters described exhaust fan, is preheated by described heater exhaust gas, enters back into described quaternary blender and carry out circulation of tail gas.
2. prepn. of formaldehyde according to claim 1, it is characterised in that the refined methanol liquid level in described refined methanol groove is maintained at more than 50%.
3. prepn. of formaldehyde according to claim 1 and 2, it is characterised in that the liquid level of described first grade absorption tower remains 30～50%；First order absorption tower top temperature≤55 DEG C.
4. prepn. of formaldehyde according to claim 3, it is characterised in that the liquid level of described two-level absorption tower remains 30～50%；Temperature≤45 DEG C, two-level absorption tower top.
5. prepn. of formaldehyde according to claim 4, it is characterised in that described catalyst electrolytic silver is the silver catalyst through electrolytic purification, its silver content more than 99.99%, iron content is less than 3ppm, and content of calcium and magnesium summation is less than 10ppm.
6. prepn. of formaldehyde according to claim 5, it is characterised in that described catalyst electrolytic silver granularity is 8 orders, 12 orders, 24 orders, 30 orders or 35 orders.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201610177243.1A CN105732342A (en) | 2016-03-25 | 2016-03-25 | Formaldehyde production method based on exhaust gas circulating process |
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| CN201610177243.1A CN105732342A (en) | 2016-03-25 | 2016-03-25 | Formaldehyde production method based on exhaust gas circulating process |
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