CN114100167A - Energy-saving maleic anhydride absorption deep analysis refining process - Google Patents
Energy-saving maleic anhydride absorption deep analysis refining process Download PDFInfo
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- CN114100167A CN114100167A CN202111416950.9A CN202111416950A CN114100167A CN 114100167 A CN114100167 A CN 114100167A CN 202111416950 A CN202111416950 A CN 202111416950A CN 114100167 A CN114100167 A CN 114100167A
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Abstract
The invention discloses an energy-saving maleic anhydride absorption depth analysis process, wherein a dehydrated rich solvent at the bottom of an absorption tower enters an analysis tower, a poor solvent at the bottom of the analysis tower enters a reheating flash tower, the poor solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the poor solvent at the top of the analysis tower enters the absorption tower to remove light components such as acrylic acid and the like, and maleic anhydride is recovered; extracting the side line of the resolution tower to a product tower, exchanging heat between the extracted gas phase at the side line of the product tower and the feeding material of the product tower to recover energy, and then condensing to obtain a superior liquid maleic anhydride; and recovering energy from the gas phase at the top of the product tower to the lower side of the lower-layer packing of the feeding material of the desorption tower. The invention has the advantages of low investment, low power consumption and low steam consumption, and the yield of the maleic anhydride is improved by adopting the reheating type post flash tower.
Description
Technical Field
The invention belongs to the maleic anhydride industry, and particularly relates to an energy-saving maleic anhydride absorption deep analysis refining process.
Background
The absorption and desorption process in the existing maleic anhydride industry has the following defects:
maleic anhydride reacts with water in the air and water generated by the reaction in the absorption tower to generate maleic acid and trace fumaric acid, and the continuous operation of the device is influenced and the yield of the maleic anhydride is reduced by exceeding a certain amount, so that a rich solvent dehydration unit is required to be arranged.
At present, two methods for dehydrating the rich solvent exist in the production process, and both the methods need to be provided with a dehydration unit, so that the energy consumption is increased, and the investment is high. One is to use a stripping tower, the top of the tower enters a heated rich solvent, flows downwards, and transfers heat and mass with hot air entering from the bottom of the tower, free water and part of maleic acid dehydrated water in the rich solvent are carried out by the air and returned to an absorption tower, and the maleic acid in the rich solvent is reduced to a required value of the process, and the process needs a rich solvent pump and power of stripping air and the rich solvent is heated to consume steam. The other method is vacuum dehydration, the rich solvent at the bottom of the absorption tower enters a vacuum dehydration tank, free water in the rich solvent is vaporized after flash evaporation and is pumped away by a vacuum pump, maleic acid in the rich solvent cannot be increased continuously, and the process has no good dehydration process of a stripping tower and needs power of the vacuum pump and power consumption of a rich solvent pump.
The components at the bottom of the desorption tower are difficult to vaporize under the operation condition at the bottom of the tower, the establishment of thermosiphon is difficult, forced circulation is forced to pass through a reboiler for heating, and then the components are flashed at the bottom of the desorption tower to provide medium steam upwards along the tower for the desorption tower to transfer heat with liquid flowing downwards in a packing of the desorption tower, so that desorption rectification is realized. The reboiler at the bottom of the desorption tower of the process needs forced circulation, and electric energy is wasted.
The reboiler at the bottom of the analysis tower and the feeding heater of the back flash tower both need to use high-grade saturated steam of more than 3.5MPa, so that the heat transfer temperature difference of the heat exchanger is ensured, if the steam pressure is reduced, the heat exchange area needs to be greatly increased, and if the steam pressure is too low, the heat exchange area is large again and cannot work.
Since the saturation temperature of the heater using 3.5MPa steam is high, the temperature at the bottom of the desorption tower is up to 198 ℃, the solvent decomposition rate is increased, and the solvent decomposition amount is larger.
No high-grade maleic anhydride can be extracted from the side line of the desorption tower, and crude anhydride, namely unqualified maleic anhydride, is extracted, wherein the side line contains solvolysis products, such as dimethyl maleate, monomethyl maleate, phthalic acid, phthalic anhydride and monoester phthalate.
The yield of the absorption and analysis system is low. The post flash tower adopts one flash evaporation, and the maleic anhydride content in the poor solvent at the bottom of the tower is 0.25 percent by weight. Resulting in high COD of the wastewater generated in the subsequent solvent regeneration section. If the content of the maleic anhydride in the lean solvent is reduced, the distilled solvent is too large, and the yield of an absorption tower or a vent washing tower is influenced.
The energy consumption of the crude anhydride refining system is high.
Disclosure of Invention
The invention aims to provide an energy-saving maleic anhydride absorption depth analysis process, wherein a rich solvent at the bottom of an absorption tower does not need dehydration treatment, so that the contact time of maleic anhydride and water is reduced, and the generation amount of maleic acid and trans-acid is reduced; the equipment investment and the operating cost of the dehydration unit are saved.
In order to achieve the purpose, the invention provides the following technical scheme:
an energy-saving maleic anhydride absorption depth analysis process comprises the steps that dehydrated rich solvent at the bottom of an absorption tower enters an analysis tower, lean solvent at the bottom of the analysis tower enters a falling film evaporation reboiler at the bottom of the analysis tower (the gas phase of a reboiler enters the bottom of the analysis tower), the solvent at the bottom of a falling film reboiler at the bottom of the analysis tower enters a reheating flash tower, the lean solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the lean solvent at the top of the analysis tower is extracted and enters the absorption tower to remove light components such as acrylic acid, and maleic anhydride is recovered; and (3) carrying out gas phase heat exchange between the side line of the desorption tower and the side line of the product tower (the feeding part of the product tower is fed to the top of the product tower, and the part of the feeding part of the product tower is fed to the first layer of packing on the product tower) to recover energy, and then carrying out recondensation on the side line of the product tower to obtain the high-grade liquid maleic anhydride. And recovering energy from the gas phase at the top of the product tower to the lower side of the lower-layer packing of the feeding material of the desorption tower.
The specific process flow is as follows:
and (3) enabling the gas mixture containing maleic anhydride at the temperature of 125-185 ℃ in the upstream process to enter an absorption tower, and upwards passing through a 2-layer high-temperature stripping section to remove maleic acid in a rich solvent flowing down from the absorption tower. The rich solvent without maleic acid flows to the low-temperature gas stripping section by means of gravity to remove free water in the rich solvent, then the rich solvent without maleic acid and free water passes through an absorption tower bottom pump, a lean rich solvent heat exchanger and the upper part of a lower packing of an analytical tower, after negative pressure flash evaporation, light components flow upwards through two sections of packing to a condenser at the top of the analytical tower, condensate of the condenser is sent to the top of the analytical tower by a reflux pump, flows downwards to transfer heat with gas rising in the packing, liquid maleic anhydride is extracted from the upper first layer of packing, part of the liquid maleic anhydride is sent to the top of a product tower, part of the liquid maleic anhydride passes through a lateral line for heat exchange and then is sent to the upper first section of packing of the product tower, then gas phase is extracted from the lower side of the upper second layer of the product tower, most of the gas phase is condensed after heat exchange with feed to obtain high-grade liquid maleic anhydride, and the uncondensed gas phase light components enter the upper first layer of the product tower.
The gas rising from the absorption tower passes through the first cooling circulation section, transfers heat with the semi-rich solvent left at the upper part, and absorbs the maleic anhydride in the gas phase at a controlled temperature to flow downwards into the semi-rich solvent; the gas phase which flows upwards through the first cooling circulation passes through the second cooling circulation section, and is subjected to mass and heat transfer with the semi-lean solvent left at the upper part, and the maleic anhydride in the temperature-controlled absorption gas phase flows downwards into the semi-lean solvent; the gas phase which flows through the second cooling circulation section in an ascending way passes through the lean solution absorption section, and the gas phase and the lean solvent left at the upper part are subjected to mass and heat transfer, so that the maleic anhydride in the gas phase is absorbed and flows down into the lean solvent; the gas phase which ascends and flows through the barren solution absorption section is completely deprived of maleic anhydride, and the tail gas is removed from the top of the absorption tower to be burned.
Heavy components of a feed rich solvent of the desorption tower, which are flashed in the desorption tower, flow downwards to a lower section of packing and transfer heat with vapor generated by reboiling at the bottom of the tower, gas phase enters an upper section of packing layer, liquid phase is pumped to a falling film reboiler, light components are vaporized, and the heavy components flow to a reheating flash tower by virtue of gravity; analyzing a tower top extracted and drawn on a tower tray at the layer 8 of the absorption tower, removing acrylic acid, and recovering maleic anhydride; the lean solvent at the bottom of the reboiler of the desorption tower flows to the reheat flash tower by virtue of gravity, the lean solvent and liquid condensed by the condenser at the top of the reheat flash tower perform mass transfer and heat transfer with a vapor phase rising between a packing layer and a falling film evaporator, the vapor passing through the packing layer enters the condenser at the top of the tower, the heavy component flow passing through the packing layer enters the falling film evaporator for re-evaporation to provide rising vapor, the lean solvent at the bottom of the reheat flash tower has the anhydride content of 0.05-0.10 percent, and the lean solvent is pumped to the top of the absorption tower, exhausted to the top of the washing tower and a solvent regeneration system, and the solvent is regenerated and then sent to the top of the absorption tower.
The feeding of the product tower is extracted and provided by a side line of the desorption tower, wherein part of the feeding is sent to the top of the product tower, part of the feeding exchanges heat with the side line of the product tower and then is sent to the first layer of packing on the product tower, and the flashed gas phase flows upwards and then is sent to the third section of packing on the desorption tower through the top of the product tower; the liquid phase and the liquid phase left at the top of the tower transfer heat downwards with the gas phase provided by a reboiler at the bottom of the tower, and the heavy components at the bottom of the product tower are sent to a feeding section of the desorption tower to recover materials; the ascending vapor phase is extracted under the second layer of the packing on the product tower, exchanges heat with the feeding material of the product tower and is condensed into liquid superior cis-butenedioic anhydride.
The absorption tower utilizes a maleic anhydride-containing gas mixture at 125-185 ℃ in an upstream process to enter the tower, the rich solvent is stripped, the maleic acid content in the rich solvent is reduced by less than 0.60 wt%, and a float tray or a filler is arranged in a high-temperature stripping section.
And stripping the rich solvent at the bottom of the absorption tower by using air or water-removed air, wherein the stripped rich solvent flows to a stripping section by virtue of gravity, so that the content of maleic acid in the rich solvent is less than 0.60 wt%, and the operation temperature of the rich solvent discharged from the bottom of the absorption tower is 106-135 ℃.
The method realizes that the low-temperature stripping gas is not supplied to the absorption tower by optimizing the operating parameters of the absorption tower.
The height difference of the desorption tower bottom and the falling film evaporation reboiler at the desorption tower bottom is larger than that of the desorption tower bottom, the minimum resistance of the vapor evaporated by the falling film evaporator is required to enter the desorption tower bottom, and the gravity flow feeding is adopted for feeding the deep desorption reheating type post-flash tower.
The process comprises the steps of adopting a falling film evaporator at the bottom of a reheating type after-flash tower where the solvent at the bottom of the desorption tower enters, arranging a condenser at the top of the tower, and adopting falling film evaporation for a solvent heater containing the feed of the after-flash tower.
And a reboiler at the bottom of the desorption tower and a reboiler at the bottom of the reheat type post-flash tower feeding or reheat type post-flash tower reboiler for deep desorption of the solvent at the bottom of the desorption tower use 2.0-2.8 Mpa saturated steam.
The gas phase at the top of the product tower enters a third layer of packing on the upper part of the desorption tower, and energy is recovered; and the gas phase extraction at the side line of the product tower exchanges heat with the feeding material of the product tower to recover energy.
Compared with the prior art, the invention has the beneficial effects that:
the absorption tower is provided with a first-stage circulation and a second-stage circulation which are used for controlling the temperature at the top of the absorption tower and the temperature at the bottom of the absorption tower. The temperature at the top of the tower is higher than 72 ℃, and the solvent loss is increased; the temperature of the bottom of the column is lower than 105 ℃ and the maleic acid in the rich solvent is increased.
The lower part of the gas phase feeding of the absorption tower is provided with a maleic acid removing section, and the lower part of the maleic acid removing section is provided with a gas stripping section. The high-temperature gas from the cooler of the upstream process two and the rich solvent flowing down from the upper part of the absorption tower are used for dehydrating the maleic acid in the rich solvent to generate maleic anhydride and part of free water. The rich solvent continuously flows downwards into the stripping section and is in mass transfer and heat transfer with hot air (or dehydrated air) supplemented at the bottom of the tower, free water in the rich solvent is carried away by the air flowing upwards, and the rich solvent with the maleic acid content of less than 0.6% flows out from the bottom of the tower. The process does not need a rich solvent delivery pump and does not need external supplementary heat, thereby achieving the purpose of energy conservation.
The falling film reboiler at the bottom of the desorption tower is arranged at the lower part of the desorption tower, a liquid film on the tube wall flows downwards under the working state of a heat exchange tube of the falling film evaporator, the middle space of the tube is connected with a gas phase at the bottom of the desorption tower, and gas evaporated by the falling film evaporator can smoothly flow to the bottom of the desorption tower, so that the operation pressure is reduced, and the operation temperature is further reduced. Greatly reduces the decomposition amount of the solvent.
The invention adopts a reheating type post flash tower. The solvent at the bottom of the reboiler of the desorption tower enters a reheating type post-flash tower, the liquid after flash evaporation flows into a packing layer to transfer heat with the evaporated gas of the falling-film evaporator at the bottom of the tower, the gas flows to a condenser at the top of the tower to be partially condensed, the condensed liquid flows back to the packing layer, the non-condensable gas enters a gas-discharging washing tower at a subsequent working section, and the lean solvent at the bottom of the falling-film evaporator has extremely low maleic anhydride content and is used for an absorption tower and the gas-discharging washing tower.
Because the desorption tower and the reheating flash tower both use the falling film evaporator, the vapor pressure for desorption can be reduced to 2.2-2.5 MPaG. The back pressure can be used to recover pressure energy from the turbine.
A first-stage circulating hot water cooler and a lean solvent hot water cooler are added, and the generated high-temperature water is supplied to a butane evaporator and a carbon four-separation system for use, so that the aim of saving energy is fulfilled.
The outlet temperature of a secondary cooler in the upstream procedure is required to be 125-135 ℃ and enters an absorption tower, the circulation volume of the first section and the second section is reduced, and electric energy is saved.
Due to deep resolution, the content of maleic anhydride in the poor solvent at the bottom of the reheating flash evaporation tower is reduced to 0.05-0.10% by weight, but the yield of the maleic anhydride is improved by 0.3% by weight, and the total amount of COD (chemical oxygen demand) generated in the subsequent solvent regeneration section of a maleic anhydride device is reduced by 30%.
The gas phase at the top of the product tower enters the upper third layer of packing of the desorption tower, and the gas stripping desorption tower feeds the heavy components after flash evaporation, so that the energy is recovered; and the gas phase extraction at the side line of the product tower exchanges heat with the feeding material of the product tower to recover energy.
Low investment, low power consumption and low steam consumption. Compared with the traditional process, the vacuum pump of a dehydration unit and a crude anhydride refining unit is not provided, and the investment is reduced when the grade of a steam pipe network is reduced. And a rich solvent pump for a dehydration process and a forced circulating pump of a reboiler at the bottom of the desorption tower are not provided, so that the power consumption of a maleic anhydride device is reduced. The heat of the product tower is recovered, and the steam consumption is greatly reduced.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention.
In the figure, G312-two-stage circulating pump, E312-two-stage water cooler, T310-absorption tower, G310-absorption tower bottom pump, G311-one-stage circulating pump, E311A-one-stage circulating first cooler, E311B-one-stage circulating second cooler, E310A-lean rich agent heat exchanger, E310B-lean agent warm water cooler, E310C-lean agent hot water cooler, G324-after flash tower bottom pump, E323-flash reboiler, E324-after flash tower top condenser, T320-desorption tower, E320-bottom falling film reboiler, G320-desorption tower bottom pump, G321-desorption tower top reflux pump, G330-product tower bottom recombination partial pump, T330-product tower, E330-product tower bottom reboiler, E331-product tower feed heat exchanger, E332-product tower side line condenser, G332-side line product outlet pump, e321-analysis tower top condenser, G321-analysis tower top reflux pump.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention include, but are not limited to, the scope shown in the following examples.
Referring to fig. 1, an energy-saving maleic anhydride absorption depth analysis process, a dehydrated rich solvent at the bottom of an absorption tower T310 enters an analysis tower, a lean solvent at the bottom of the analysis tower enters an analysis tower bottom falling film reboiler (the gas phase of the falling film reboiler returns to the bottom of the analysis tower), a falling film reboiler at the bottom of the analysis tower enters a reheating flash tower, the lean solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the lean solvent at the top of the analysis tower enters the absorption tower T310 to remove light components such as acrylic acid, and maleic anhydride is recovered; and (3) performing heat exchange between the side liquid phase extraction of the desorption tower T320 and the side gas phase extraction of the product tower (the side line of the desorption tower T320 is the part of the feeding material of the product tower to the top of the product tower, and the part of the feeding material of the product tower is arranged below the first layer of packing on the product tower T330) to recover energy, and then performing recondensation on the side line of the product tower T330 to obtain the high-grade liquid maleic anhydride. The gas phase at the top of the product tower returns energy to the lower side of the lower packing of the feed of the desorption tower T320.
The energy-saving maleic anhydride absorption, analysis and refining process flow comprises an upstream process mixed gas flow, an absorption tower bottom rich solvent flow and a lean solvent flow, and each flow is specifically explained as follows:
an upstream process mixed gas flow: the mixed gas containing maleic anhydride at high temperature in the reaction section enters an absorption tower T310, and after going through 2 layers of deacidification tower trays upwards along the tower, the mixed gas is subjected to mass transfer and heat transfer with a solvent flowing downwards through 28 layers of tower trays, maleic anhydride in the gas is absorbed by the solvent to generate a rich solvent which flows downwards, and tail gas without maleic anhydride is discharged to an incinerator from the top of the tower. The rich solvent flowing downwards flows into the deacidification section of the absorption tower to transfer heat with the high-temperature anhydride-containing gas coming from the upstream process of the tower, and the maleic acid in the rich solvent is taken away by the rising air and is discharged to a tail gas incinerator from the top of the absorption tower. The deacidified rich solvent passes through a low-temperature stripping section at the bottom of the tower to remove free water in the rich solvent, and the deacidified and dehydrated rich solvent enters a rich solvent pump at the bottom of an absorption tower. The tower top temperature controls the absorption tower top to 70 ℃ through the second-stage circulation amount and the second-stage cooled temperature; the temperature of the bottom of the absorption tower is controlled by the first-stage circulation amount and the first-stage cooled temperature.
Absorption tower bottom rich solvent flow: the rich solvent of the absorption tower bottom pump passes through the absorption tower bottom pump → the lean rich solvent heat exchanger → the upper part of the packing at the lower part of the desorption tower T320, after negative pressure flash evaporation, the light component flows upwards through the 2 sections of packing to the condenser E321 at the top of the desorption tower, the condensate is sent to the top of the desorption tower through the reflux pump G321 at the top of the desorption tower, flows downwards to transfer heat with the gas rising in the packing, and the liquid maleic anhydride is pumped out from the first layer of packing from the top to feed the product tower T330. The heavy component after the rich solvent flash evaporation flows downwards to the lower section of packing and transfers heat with the steam generated by the reboiling at the bottom of the tower, the gas phase enters the upper 2 sections of packing layers, the liquid phase is pumped to the falling film reboiler through the pump, the light component is vaporized, and the heavy component is pumped to the reheating flash tower through the bottom of the falling film reboiler. The bottom discharging temperature of a falling film reboiler E320 at the bottom of the desorption tower is controlled to be 183-195 ℃ by controlling the steam quantity of the reboiler and the pressure at the top of the tower; the temperature of the top of the desorption tower is controlled to be 78-85 ℃ by controlling the reflux quantity. And extracting from the top of the desorption tower, pumping the tower tray 8 of the absorption tower T310, removing acrylic acid, and recovering maleic anhydride.
By optimizing the operating parameters of the absorber T310, the supply of the low-temperature stripping gas can be stopped, which is more energy-saving.
Lean solvent flow scheme: and (3) pumping the lean solvent containing 0.25-1.20% of maleic anhydride at the bottom of a falling film reboiler E320 at the bottom of the desorption tower to a packing layer of a reheating flash tower by a pump, enabling the liquid after flash evaporation to flow downwards, enabling the liquid condensed by a condenser E324 at the top of the flash tower and the packing layer to perform mass transfer and heat transfer with the vapor phase rising from the reboiler E323, enabling the vapor passing through the packing layer to enter the condenser E324 at the top of the flash tower, and controlling the outlet temperature at the top of the flash tower to be 90 ℃ by controlling warm water of the condenser E324 at the top of the flash tower to enter the process exhaust washing tower. Heavy components passing through the packing layer flow into a flash distillation reboiler E323 to be evaporated again to provide rising gas, the content of lean solvent anhydride at the bottom of the reheating flash distillation tower is 0.05-0.10 percent, the lean solvent anhydride is pumped to the top of the absorption tower, the top of the exhaust washing tower and a solvent regeneration system, and the solvent is sent to the top of the absorption tower after being regenerated.
And controlling the content of the poor solvent anhydride at the bottom of the reheat flash tower by controlling the steam quantity at the bottom of the reheat flash tower.
Finally realizing the stable circulation of the absorption tower bottom rich solvent → the desorption tower, the desorption tower bottom lean solvent → the reheating flash tower, the reheating tower bottom lean solvent → the absorption tower top and the three towers, and balancing the solvent decomposition amount in the rich solvent by using the regenerated solvent. When the solvent in the system is insufficient, the solvent can be supplemented.
The specific process parameters of the process of the invention are shown in the following table.
The invention is not limited to the examples, and any equivalent changes to the technical solution of the invention by a person skilled in the art after reading the description of the invention are covered by the claims of the invention.
Claims (9)
1. An energy-saving maleic anhydride absorption depth analysis process is characterized in that:
the dehydrated rich solvent at the bottom of the absorption tower enters an absorption tower, the lean solvent at the bottom of the absorption tower enters a reheating flash tower, the lean solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the lean solvent at the top of the absorption tower enters the absorption tower to remove light components such as acrylic acid and the like, and maleic anhydride is recovered; extracting the side line of the resolution tower to a product tower, exchanging heat between the extracted gas phase at the side line of the product tower and the feeding material of the product tower to recover energy, and then condensing to obtain a superior liquid maleic anhydride; and recovering energy from the gas phase at the top of the product tower to the lower side of the lower-layer packing of the feeding material of the desorption tower.
2. The energy-saving maleic anhydride absorption depth analysis process according to claim 1, characterized in that:
the specific process flow is as follows:
enabling a maleic anhydride-containing gas mixture at 125-185 ℃ in an upstream process to enter an absorption tower, and upwards passing through a 2-layer high-temperature stripping section to remove maleic acid in a rich solvent flowing down from the absorption tower; the rich solvent without maleic acid flows to the low-temperature gas stripping section by means of gravity to remove free water in the rich solvent, then the rich solvent without maleic acid and free water passes through an absorption tower bottom pump, a lean rich solvent heat exchanger and the upper part of a lower packing of an analytical tower, after negative pressure flash evaporation, light components flow upwards through two sections of packing to a condenser at the top of the analytical tower, condensate of the condenser is sent to the top of the analytical tower by a reflux pump, flows downwards to transfer heat with gas rising in the packing, liquid crude maleic anhydride is extracted from the upper first layer of packing, part of the liquid crude maleic anhydride is sent to the top of a product tower, part of the liquid crude maleic anhydride is sent to the upper first section of packing of the product tower after lateral line heat exchange, then gas phase is extracted from the lower side of the upper second layer of the product tower and is subjected to heat exchange with feed and then mostly condensed to obtain high-grade liquid maleic anhydride, and the uncondensed gas phase light components are sent to the upper first layer of the product tower.
3. The energy-saving maleic anhydride absorption depth analysis process according to claim 2, characterized in that:
gas rising from the absorption tower passes through the first cooling circulation section, and is subjected to mass and heat transfer with the semi-rich solvent flowing downwards from the upper part, and maleic anhydride in a gas phase is absorbed by controlling the temperature to flow into the semi-rich solvent and the lower part of the semi-rich solvent; the gas phase which flows upwards through the first cooling circulation passes through the second cooling circulation section, and is subjected to mass and heat transfer with the semi-lean solvent left at the upper part, and the maleic anhydride in the gas phase is absorbed by controlling the temperature to flow into the semi-lean solvent and flow down the semi-rich solvent; the gas phase which flows through the second cooling circulation section in an ascending way passes through the lean solution absorption section, and the gas phase and the lean solvent left at the upper part are subjected to mass transfer and heat transfer to absorb the maleic anhydride in the gas phase to flow down the semi-rich solvent in the lean solvent; the gas phase which ascends and flows through the barren solution absorption section is completely deprived of maleic anhydride, and the tail gas is removed from the top of the absorption tower to be burned.
4. The energy-saving maleic anhydride absorption depth analysis process according to claim 3, characterized in that:
heavy components of a feed rich solvent of the desorption tower, which are flashed in the desorption tower, flow downwards to a lower section of packing and transfer heat with vapor generated by reboiling at the bottom of the tower, gas phase enters an upper section of packing layer, liquid phase is pumped to a bottom falling film reboiler of the desorption tower, light components are vaporized, and the heavy components flow to a reheating flash tower by virtue of gravity; the tower top is analyzed and extracted to the tower tray of the layer 8 of the absorption tower, acrylic acid is removed, and maleic anhydride is recovered; the lean solvent at the bottom of the reboiler of the desorption tower flows to the reheat flash tower by virtue of gravity, the lean solvent and the liquid condensed by the condenser at the top of the reheat flash tower perform mass transfer and heat transfer with the ascending vapor phase of the packing layer and the falling film evaporator, the vapor passing through the packing layer enters the condenser at the top of the tower, the heavy component flow passing through the packing layer enters the falling film evaporator for re-evaporation to provide ascending vapor, the lean solvent at the bottom of the reheat flash tower has the anhydride content of 0.05-0.10 percent, and the lean solvent is pumped to the top of the absorption tower, exhausted to the top of the washing tower and a solvent regeneration system, and the solvent is regenerated and then sent to the top of the absorption tower.
5. The energy-saving maleic anhydride absorption depth analysis process according to claim 4, characterized in that:
the feeding of the product tower is provided by side line extraction of the desorption tower, wherein part of the feeding is sent to the top of the product tower, part of the feeding exchanges heat with the side line of the product tower and then is sent to the first layer of packing on the product tower, and the flashed gas phase flows upwards and then is sent to the third section of packing on the desorption tower through the top of the product tower; the liquid phase and the liquid phase flowing down from the top of the tower transfer heat with the gas phase provided by the reboiler at the bottom of the tower, and the heavy component at the bottom of the tower is sent to the feeding section of the desorption tower to recover the material; the ascending vapor phase is extracted under the second layer of the packing on the product tower, exchanges heat with the feeding material of the product tower and is condensed into liquid superior cis-butenedioic anhydride.
6. The energy-saving maleic anhydride absorption depth analysis process according to claim 5, characterized in that:
the absorption tower utilizes a maleic anhydride-containing gas mixture at 125-185 ℃ in an upstream process to enter the tower, stripping the rich solvent, reducing the maleic acid content in the rich solvent to be less than 0.60 wt%, and arranging a float tray or a filler in a high-temperature stripping section;
stripping the rich solvent at the bottom of the absorption tower by using air or dehydrated air, wherein the stripped rich solvent flows to a stripping section by virtue of gravity, so that the content of maleic acid in the rich solvent is less than 0.60 wt%, and the operation temperature of the rich solvent discharged from the bottom of the absorption tower is 106-135 ℃;
the method realizes that the low-temperature stripping gas is not supplied to the absorption tower by optimizing the operating parameters of the absorption tower.
7. The energy-saving maleic anhydride absorption depth analysis process according to claim 6, characterized in that:
the height difference of the bottom of the analysis tower to the falling film evaporation reboiler at the bottom of the analysis tower must meet the requirement that the minimum resistance of vapor evaporated by the falling film evaporator enters the bottom of the analysis tower, and the feeding of a deep analysis post-flash tower adopts gravity flow feeding;
adopting a falling film evaporator at the bottom of a post flash tower into which the solvent at the bottom of the desorption tower enters, and arranging a condenser at the top of the tower; a solvent heater for feeding the flash tower adopts falling film evaporation;
and a reboiler at the bottom of the desorption tower and a reboiler at the bottom of the post-flash tower for deep desorption of the solvent at the bottom of the desorption tower are used, and saturated steam of 2.0-2.8 MPa is used.
8. The energy-saving maleic anhydride absorption depth analysis process according to claim 7, characterized in that:
the gas phase at the top of the product tower enters the upper third layer of packing of the desorption tower, and the gas stripping desorption tower feeds the heavy components after flash evaporation, so that the energy is recovered; and the gas phase extraction at the side line of the product tower exchanges heat with the feeding material of the product tower to recover energy.
9. The energy-saving maleic anhydride absorption depth analysis process according to claim 8, characterized in that:
the bottom of the resolution tower reboiler is additionally provided with a pump for generating a lean solvent with an anhydride content of less than 0.2% at the bottom of the resolution tower reboiler.
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| CN115385303A (en) * | 2022-08-31 | 2022-11-25 | 鲁西化工集团股份有限公司硅化工分公司 | Dilute hydrochloric acid analysis system and process method thereof |
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