RU2372130C2 - Thermal separation method for separating at least one mass flow, concentrated with acrylic acid - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a thermal separation method using fractional condensation of a product-gas mixture, obtained through heterogeneous catalysed partial oxidation of propene and/or propane in gaseous phase to acrylic acid, for separating at least one mass flow, concentrated with acrylic acid, from a product-gas mixture containing acrylic acid, which involves continuous static operation of at least one device for thermal separation, containing at least one effective separation chamber with a fractionation column which has mass-transfer trays as built-in separating elements, in which the product-gas mixture is loaded, containing acrylic acid as at least one mass flow, and from which at least one mass flow containing acrylic acid is unloaded under the condition that, the overall mass flow loaded into the effective separation chamber and obtained from combining separate mass flows loaded into the separating chamber, contains X wt % components distinct from acrylic acid, the mass flow which is unloaded from the effective separation chamber with the largest content of acrylic acid, contains Y wt % components distinct from acrylic acid, ratio X:Y is ≥5, effective separation chamber, except the loading and unloading place, is bordered by a solid phase and contains, besides the mass-exchange trays as built-in separating elements in the fractionation column, at least one circulating heat exchanger, and total volume of the chamber, filled with liquid phase, is ≥1 m³, wherein temperature of the liquid phase is at least partially ≥80°C, when the effective separation chamber is divided into n separate volume elements, wherein the highest and lowest temperature of liquid phase in a separate volume element differ by not more than 2°C, and the volume element in the effective separation chamber is solid, total dwell time t_total.

≤20 h, where A = (T_i-T_o)/10°C, T_o= 100°C, T_i = arithmetic mean value of the highest and lowest temperature of the i^th volume element in the liquid phase in °C, m_si = total mass of acrylic acid in the volume of the liquid phase of the i^th volume element, m_i = total liquid phase mass unloaded from the i^th volume element, and

is the sum of all volume elements i, under the condition that, volume elements i with liquid phase mass m_i and

as volume elements with a dead zone are also not included in the sum of all volume elements i, as well as volume elements i, which do not contain liquid phase, and total amount of liquid phase contained in volume elements with a dead zone is not more than 5 wt % of the total amount of liquid phase contained in the effective separation chamber.

EFFECT: separation of mass flow concentrated with acrylic acid.

10 cl, 12 dwg, 2 ex, 2 tbl

Description

The present invention relates to a technology for the separation of substances, more particularly a thermal method for fractional condensation separation of a product gas mixture obtained by heterogeneous catalyzed partial oxidation of propene and / or propane to acrylic acid in the gas phase to separate at least one mass stream enriched in acrylic acid.

A known method of separating (meth) acrylic acid or (meth) acrolein from a product gas mixture, which is obtained by catalytic oxidation in the gas phase of propane and / or propene, which consists in the fact that first (meth) acrylic acid and / or (meth ) acrolein is separated by absorption into a solvent (for example, water or an organic solvent) or fractional condensation of the product gas mixture, and then the precipitated condensate or absorbate is finally separated by rectification (usually in several stages) to obtain more or less pure (m e) acrylic acid or (meth) acrolein (see, for example, EP-A 717019, EP-A 1125912, EP-A 982289, EP-A 982287, DE-A 19606877, DE-A 1011527, DE-A 10224341, DE-A 10218419, DE-A 10247240 and DE-A 10243625).

The fractional condensation mentioned above differs from conventional distillation, mainly in that the mixture to be separated is fed into the effective separation chamber in gaseous form (i.e., completely converted to vapor form).

The gaseous and / or liquid mixtures containing (meth) acrylic monomers mentioned above may contain (meth) acrylic monomers in more or less pure or diluted form (for example, with a solvent or diluent gases). In this case, the solvent can be either liquid or organic, and the type of organic solvent, as a rule, is insignificant. The diluent gas may be, for example, nitrogen, carbon monoxide (CO, CO ₂ ), oxygen, hydrocarbon, or a mixture of these gases.

This means that to obtain (isolate) (meth) acrylic monomers, various thermal methods of separation (described above) from gaseous and / or liquid mixtures of substances are used, the content of (meth) acrylic monomers in which can be 2 wt.%, Or ≥10 wt.%, or ≥20 wt.% or ≥40 wt.%, or ≥60 wt.%, or ≥80 wt.%, or ≥90 wt.%, or ≥95 wt.%, or ≥99 wt. % (of course, the content of (meth) acrylic monomers is always ≤100 wt.%). Often the content of (meth) acrylic monomers of such mixtures is from 10 to 40 wt.% Or from 90 to 99.5 wt.%.

Typically, such mixtures of substances in the implementation of the method according to the invention as a mass stream containing (meth) acrylic monomers, is fed into at least one effective separation chamber.

Often, an effective separation chamber in the thermal separation methods described above comprises a distillation column. Moreover, enrichment of (meth) acrylic monomers can occur both in the head and in the cube of the distillation column. Of course, fractions enriched in (meth) acrylic monomers can be selected in the upper, lower or middle portion of the distillation column.

Integrated into an effective separation chamber, for example a separation column, separation elements additionally used in an effective separation chamber, when implementing thermal separation methods, are designed to increase the surface necessary for heat and mass transfer.

Such integrated dividing elements may be, for example, gaskets, nozzles and / or mass transfer plates.

Especially often, as distillation columns with built-in separation elements in the implementation of thermal separation methods, those are used which, as at least one part of the built-in separation elements, contain a series of mass transfer plates.

Mass transfer plates are used to provide places in the distillation column in the form of liquid layers with closed liquid phases. In this case, the surface of the vapor or gas stream ascending in the liquid layer and crushed in the closed liquid phase is the exchange surface. The plates are preferably snug against the surrounding wall. The classic plate is a strainer plate. In this context, it should be understood as plates that, as the place of passage of the upward flow of the gas or vapor phase (the concepts of “gas” and “steam” are used in this context as synonyms) contain simple holes and / or slots.

In this case, the sieve plates, as a rule, are divided into two groups, namely: with forced supply of fluid and without forced supply of fluid.

In general terms, a forced supply of fluid in the sieve trays is obtained by equipping the mass transfer trays with at least one drain shaft (outflow) through which the liquid, regardless of the direction of steam flow, flows from the higher to the lower trays (inflow). The horizontal fluid flow in the direction from the inflow to the outflow is selected in accordance with the task laid down in the basis of the method. Gas or steam passes through open cross sections of the plate of the plate.

If liquid is supplied through the plate in the reverse flow (the inflow and outflow of the plate are placed on one side of the plate), then we are talking about plates of reverse flows. In the case of plates of radial flows, the fluid flows radially from the middle (inflow) to the outflow at the edge of the plate.

Under the plates with a transverse current, it is understood that the fluid, considered over the entire area of fluidity, flows across the plate from the inflow to the outflow. Typically, transverse current plates are single-threaded. This means that the inflow and outflow are located on opposite sides of the plate. Although they can also be dual-threaded (or multi-threaded). In this case, the inflow can, for example, be located in the center, and each outflow can be on opposite sides of the plate.

Thus, in the case of sieve trays, a forced fluid supply is obtained by equipping the sieve trays, along with the places of passage of the upward flow of the gas or vapor phase, with at least one drain shaft (outflow) through which the liquid, irrespective of the direction of flow of steam, flows from upstream to located below the plate (inflow). The liquid flows, for example, by transverse current through the plate from at least one inflow to at least one outflow, the inlet and outlet pipes guarantee a liquid shutter and the required level of liquid in the plate. Often (especially with insignificant column diameters) the strainer plates with forced liquid supply are single-threaded, that is, the inflow and outflow are placed on opposite sides of the plate. Although they can also be dual-threaded (or multi-threaded). In this case, the inflow can, for example, be placed in the center, and each outflow can be on opposite sides of the plate. Thus, such sieve plates are hereinafter referred to as forced sieve plates. When using them, the “sprinkling” of the liquid, which weakens the separation effect, cannot be prevented with the help of gas exhaust pipes (as in the case of a hydraulically sealed plate with a transverse current), into which the through holes lead, which requires a minimum vapor phase load. The steam passes through the through holes through the upward flow and flows dropwise through the liquid layer of the exhaust pipe.

Double-flow or sprinkler sieve trays differ from forced trays in that they do not contain an outlet segment. Due to the lack of outlet segments (drainage shafts), the upward gas flow of the irrigation sieve trays and the downward flow of liquid from the distillation column pass through the same places in the passage of the plate. In the case of sprinkler sieve trays, as in the case of forced sieve trays, they require a minimum vapor phase load to achieve the desired separation effect. If this load is significantly reduced, the upward gas flow and the downward return flow without exchange pass each other, as a result of which there is a danger of drying of the plate.

This means that in the case of sprinkling sieve plates, there must be a low top speed so that a certain layer of liquid is maintained in the plate, which would enable the plate to function. In a normal working area, the liquid of the sprinkler sieve plate drips through the through holes from the plate to the plate, and a closed gas phase of the separated liquid phase is passed between the plates.

Hydraulically sealed (sealed) trays with transverse current differ from sieve trays in that they cannot idle when the column is turned off, with the exception of a tiny idle hole (its cross section, as a rule, is more than 200 times smaller than the total transverse cross-section of passage places), which, out of the principles of expediency, contain each plate with a transverse current.

Thus, even at low column loads, hydraulically sealed transverse current trays contain accumulated liquid (reflux and / or supplied liquid) and are not at risk of drying out. This is due to the fact that in the case of passage points of hydraulically sealed trays with transverse current, in contrast to sieve trays, we are not talking about openings for venting gases. Rather, on the contrary, each passageway ends with a gas exhaust pipe that prevents drying. Swivel covers (caps) are applied over the pipe, immersed in the accumulated liquid of the plate. Often the edges of the caps have slots or teeth. The caps change the direction of the current of the upward flow of gas, which then flows parallel to the plate, i.e. across the column, into the accumulated liquid.

Steam bubbles that exit from adjacent caps, which are usually located above the plate and equidistant from each other, form a gushing layer in the accumulated liquid.

The exhaust pipes or segments, which, as a rule, alternately left or right from the plate, regulate, using valves, the liquid level of the mass transfer plates and supply liquid to the lower plates. For hydraulic sealing, it is important that the exhaust pipes or segments of the upper plate are immersed in the accumulated liquid of the plate below it. Preferably, no valves are used. The height-adjustable caps allow you to adjust the flow regimes and equalize the height of the shutters in case of uneven receipt, so that all the caps of the plate aerate the same way.

Depending on the shape and location of the caps, single-flow hydraulically sealed transverse current plates are divided into round caps (the passage, the gas pipe and the cap are round), tunnel plates (the passage, the gas pipe and the cap are rectangular, the caps arranged one after the other, with the longest rib parallel to the direction of the transverse fluid flow) and the Tormann plates (the passageway, the gas exhaust pipe and the cap are rectangular and, the caps are arranged one after another, the longest rib being perpendicular to the direction of the transverse fluid flow).

Valve plates in this context mean transverse current plates that contain openings equipped with poppet, ballast or lift (floating) valves with stroke limiters, which adjust the size of the passage opening to the corresponding column load. An upward gas stream is diverted, it flows parallel to the plate into the accumulated reflux and forms a gushing layer. Equipped with valves, exhaust pipes direct phlegm from plate to plate. Often they are dual-threaded, although they can be three-and multi-threaded (for example, up to eight-threaded).

Mass transfer plates, in which there is a balance between a downward flow of liquid and an upward flow of steam, are called theoretical plates.

This concept can be transferred to all other built-in separation elements (for example, packing and packing) suitable for countercurrent distillation (rectification), as well as to other thermal separation processes, for example, sorption and extraction. In the case of the latter, the built-in separation elements mentioned above contribute to an increase in the interface between the two liquid phases.

In this case, it is advisable to talk about the theoretical stages of separation. The theoretical separation stage is understood to mean a unit of volume, which contributes to enrichment in accordance with thermodynamic equilibrium.

The purpose of the thermal separation method for separating at least one mass stream enriched in (meth) acrylic monomers from a mixture containing (meth) acrylic monomers, on the one hand, is to achieve the highest degree of enrichment for the separated, enriched (meth) acrylic monomers mass flow with a monomer of (meth) acrylic acid, on the other hand, is the achievement of the highest yields in terms of volume and time of the separated mass flow.

The disadvantage of the thermal separation method described above is the fact that those measures that increase the degree of enrichment under constant boundary conditions at the same time reduce the yield in volume and time (for example, by increasing the number of theoretical stages of separation, as a rule, it is possible to improve the degree of enrichment; time as under constant boundary conditions, an increase in the number of theoretical stages of separation, as a rule, reduces the output in volume and time).

An object of the present invention is to provide a thermal method for fractional condensation separation of a product gas mixture obtained by heterogeneous catalyzed partial oxidation of propene and / or propane to acrylic acid in the gas phase to separate at least one mass stream enriched in acrylic acid from the product mixture -gas containing acrylic acid, which allows to achieve a high degree of enrichment, while ensuring a high yield in volume and time.

The problem is achieved by the proposed thermal method for fractional condensation separation of a product gas mixture obtained by heterogeneous catalyzed partial oxidation in the gas phase of propene and / or propane to acrylic acid, to separate at least one mass stream enriched in acrylic acid from a product gas mixture containing acrylic acid, which includes continuous stationary operation of at least one device for thermal separation containing at least one effective separation chamber with a distillation column having mass transfer plates as integrated separation elements, into which a mixture of product gas containing acrylic acid is loaded as at least one mass stream containing acrylic acid, and from which at least at least one mass stream containing acrylic acid, provided that

- the mass stream, which is generally loaded into an effective separation chamber and obtained by adding the individual mass flows loaded into the effective separation chamber, contains X wt.% other than (acrylic acid components,

- the mass stream, which is discharged from the effective separation chamber with the largest weight fraction of acrylic acid, contains Y wt.% components other than acrylic acid,

- the ratio of X: Y is ≥5,

- an effective separation chamber, with the exception of the loading point and the discharge discharge point, is limited by the solid phase and contains, in addition to the mass transfer plates, as built-in separation elements in the distillation column, at least one circulation heat exchanger,

- the total volume of the chamber filled with the liquid phase is 1 m ³ , and the temperature of the liquid phase is at least partially ≥80 ° C.

When dividing the effective separation chamber into n individual volumetric elements, the higher and lower temperatures of the liquid phase located in a separate volumetric element differ by no more than 2 ° C, and the volumetric element in the effective separation chamber is continuous,

total time t _total

is ≤20 h

moreover

A = (T _i -T _o ) / 10 ° C,

T _about = 100 ° C,

T _i = arithmetic mean of the highest and lowest temperatures of the volume element i in the liquid phase in ° C,

m _si = total mass of (meth) acrylic monomers contained in the volume of the liquid phase of volume element i,

= общее количество выгружаемого из объемного элемента i потока жидкофазной массы,

= total amount of liquid phase mass discharged from volume element i,

в качестве объемных элементов с мертвой зоной также мало включены в сумму всех объемных элементов i, как объемные элементы i, которые не содержат жидкую фазу, и общее количество жидкой фазы, содержащейся в объемных элементах с мертвой зоной, составляет не более 5 вес.% от общего количества жидкой фазы, содержащейся в эффективной разделительной камере.provided that the volume elements i with the contained liquid phase mass m _i and

as volumetric elements with a dead zone, they are also little included in the sum of all volumetric elements i, as volumetric elements i that do not contain a liquid phase, and the total amount of liquid phase contained in volumetric elements with a dead zone is not more than 5 wt.% of the total amount of liquid phase contained in an effective separation chamber.

The concept of stationary operation in this context means that the content of substances and the magnitude of the flows in mass flows during stationary operation can vary by a maximum of 5% (in terms of the average value taken as a basis for comparison). According to the invention, said variations are preferably ≤4%, particularly preferably ≤3% and most preferably ≤2% or ≤1%.

(Meth) acrylic monomers, in particular acrylic acid, are important starting compounds for the production of polymerization products, which, for example, are used as adhesives.

Acrylic acid on an industrial scale is preferably obtained by catalytic gas phase oxidation of propene and / or propane.

In this case, as a rule, a product gas mixture is obtained, from which it is necessary to separate acrylic acid.

To carry out such separation, one or more of the methods of thermal separation described above are used. They, as a rule, are carried out continuously, moreover, under constant conditions, they are continuously loaded into an effective separation chamber and mass flows are unloaded from this chamber. Characteristic of the above thermal separation is the fact that the separation effect obtained with their use requires the supply (for example, for evaporation) and / or the removal (for example, for condensation) of thermal energy, and also liquid phases (present in the effective separation camera).

Typically, this thermal energy is removed and / or fed through a circulation heat exchanger. The circulation heat exchanger is a part of an effective separation chamber necessary for the implementation of the method described above, into which a liquid and / or gas phase taken from another part of the chamber is supplied. In a circulation heat exchanger, this liquid and / or gas phase from a source that is not included in the effective separation chamber is directly (for example, by introducing the source into the chamber) and / or indirectly supply and / or remove thermal energy. Then, the cooled or heated liquid (which during heat transfer can be partially and / or completely converted into a vapor phase) and / or the gas phase (which during heat transfer can be partially and / or completely condensed) is returned to another part of the chamber, and the place of collection and return can be spatially located separately from each other. In many cases, at least one of the circulation heat exchangers is a circulation evaporator.

The achievement of the effect of thermal separation (that is, the implementation of the thermal separation method) is possible in efficient separation chambers that do not contain built-in separation elements, as, for example, in the case of simple distillation. In this case, the liquid mixture is partially evaporated, and the resulting vapor phase, the composition of which differs from the composition of the liquid mixture, is isolated in vaporous and / or condensed form.

Often, the thermal effect of separation is also achieved with the help of built-in separation elements, and several times supply gas (often upward flow) and liquid (usually downward) flows in parallel or opposite directions. As a result of the imbalance between the flows, heat and mass transfer occurs, which ultimately leads to the desired separation. As a rule, built-in separation elements are located in a distillation column.

A characteristic feature of the thermal separation method in this text is the fact that individual chemical compounds that pass through an effective separation chamber chemically change by less than 20 mol.% (In terms of the total number of individual chemical compounds passed through the chamber) compounds, with the exception of Michael addition of acrylic acid; it should not be regarded as such a chemical change).

Often, the percentages of the thermal separation according to the invention are ≤10 mol%, or ≤7 mol%, or ≤3 mol%, or ≤1 mol%.

The basis of the method according to the invention is the fact that acrylic acid during the implementation of single or multiple Michael additions form oligomers or polymers (Michael addition products), which are characterized by the general formula I

,

,

in which y, in particular, is from 1 to 6, partially also> 6.

Among other things, the Michael addition formation scheme is also known from EP-A 733617, EP-A 765861, DE-A 19536191, DE-A 19851984, DE-A 19927722, EP-A 780360, EP-A 780359, WO 98/08798 WO 97/48669 and DE-A 19924533.

The disadvantage of the formation of Michael addition products from (meth) acrylic monomers, in particular acrylic acid, is the fact that the formation is also carried out as part of thermal separation methods to separate at least one mass stream enriched with (meth) acrylic monomers, from a mixture containing (meth) acrylic monomers, while both the degree of enrichment and the yield in volume and time are reduced. The only possible solution to the problem proposed in the prior art is to isolate and subsequently separate the Michael addition products (see, for example, EP-A 780359, EP-A 780360, WO 98/08798 and DE-A 19924533).

In solving this problem, it should be taken into account that the formation of Michael addition products from (meth) acrylic monomers occurs mainly only in the liquid phase.

In addition, it must be taken into account that the formation of Michael addition products in the liquid phase is significantly accelerated both with increasing temperature and with an increase in the mass fraction of (meth) acrylic monomers in the liquid phase, and a temperature increase of 10 ° С doubles the reaction rate. At temperatures well below 100 ° C, Michael addition of acrylic monomers can be neglected.

This means that in the continuous implementation of the thermal separation method to separate at least one acrylic acid enriched mass stream from a mixture containing acrylic acid in a stationary device, it is necessary to ensure that the residence time of acrylic acid in the liquid phase is especially short in the zone of high temperature and increased mass fraction of acrylic acid in the liquid phase, which can significantly reduce the volume of unfavorable formation of acrylic acid according to Michael in terms of thermal their separation methods.

Thus, the corresponding average value is the total average residence time of acrylic acid, calculated accordingly from individual indicators of the residence time, during the implementation of the thermal method of separation in the liquid phase.

To this end, an effective separation chamber is divided into n individual volumetric elements. The sizes and the number n of these volumetric elements are, as a rule, insignificant, that is, individual volumetric elements can be the same or different sizes. The only essential condition is that the highest and lowest temperature of the liquid phase of the volumetric element does not differ by more than 2 ° C, and the volumetric element in the effective separation chamber is continuous (this temperature condition, as indicated below, affects the temperature dependence joining according to Michael).

Thus, the individual residence time t _{i of} acrylic acid in the volumetric element i is calculated according to the formula

означает общее количество выгружаемого из объемного элемента i потока жидкофазной массы (в стационарном состоянии он подобен загружаемому в объемный элемент i потоку жидкофазной массы).Moreover, m _i means the total amount of the liquid-phase mass contained in the volume element i, a

means the total amount of the liquid-phase mass flow discharged from the volume element i (in a stationary state, it is similar to the liquid-phase mass flow loaded into the volume element i).

In order to take into account the mass fraction of acrylic acid in the volume element i, this separate residence time is multiplied by the coefficient m _si / m _i .

Factor 2 ^A , in which A = (T _i -T _o ) / 10 ° C, further increases the value of the individual residence time and takes into account the temperature in the liquid phase of the volume element i. Then, all volume elements i containing the liquid phase are summed.

или ≥300 ч, или ≥400 ч, или ≥500 ч, или ≥750 ч, или ≥1000 ч.Volume elements with a dead zone i are not included in the amount, since they practically do not participate in the separation process. This is especially true when

or ≥300 h, or ≥400 h, or ≥500 h, or ≥750 h, or ≥1000 h.

When implementing the separation method according to the invention, volumetric elements with a dead zone practically do not participate in the exchange processes preceding the separation. Moreover, by such volumetric elements is meant basically isolated volumetric elements, which are once filled with a liquid phase and over time contain basically the same liquid phase.

As a rule, when carrying out the method according to the invention, such volumetric elements with a dead zone should be avoided, primarily because they are associated with an increased likelihood of a radical polymerization of the acrylic acid contained in them.

This means that the method according to the invention is advantageous when the total amount of the liquid phase contained in the volumetric elements with a dead zone does not exceed 4 wt.%, Preferably 3 wt.%, Particularly preferably 2 wt.% And most preferably 1 wt. % or even trace amounts.

In addition, it is important for the method according to the invention that X: Y≥5. This means that the method according to the invention does not adversely affect the number of theoretical stages of separation, moreover, when implementing the method according to the invention, the separate residence time t _{i is} not taken into account primarily if m _si / m _i and A are high and failure from t _i will not significantly affect the number of theoretical stages of separation.

Thus, the method according to the invention is also applicable when X: Y 8 8, or 10 10, or или 15, or 20 20, or 30 30, or 40 40, or 50 50.

Typically, X: Y when implementing the method according to the invention does not exceed 200. In most cases, X: Y when implementing the method according to the invention is ≤175, ≤150 or ≤100.

The method according to the invention is preferred when the total volume V of the effective separation chamber filled with the liquid phase is large, for example, it is ≥2 m ³ , or ≥4 m ³ , ≥5 m ³ , or ≥7 m ³ , or ≥9 m ³ , ≥10 m ³ , or ≥15 m ³ . As a rule, V does not exceed 500 m ³ . This means that when implementing the method according to the invention, V 4 450 m ³ , often 400 400 m ³ , more often ³ 350 m ³ , in most cases 300 300 m ³ .

Due to the high boiling point of acrylic acid, the temperature of the liquid phase in the effective separation chamber during the implementation of the method according to the invention is often at least partially ≥90 ° C, or ≥100 ° C, or ≥110 ° C, or ≥120 ° C , or ≥130 ° С, or ≥140 ° С, or ≥150 ° С, or ≥160 ° С, or ≥170 ° С, or ≥180 ° С. However, the highest temperature of the liquid phase in the volume element i in the method according to the invention, as a rule, does not exceed 250 ° C. Typically, this highest temperature is ≤230 ° C, often ≤210 ° C and more often ≤200 ° C. When carrying out the above-mentioned separation reactions, as a rule, it is not possible to reach such temperatures, since these reactions provide that the separation products continuously lose their equilibrium.

Preferably, the total residence time t _total when implementing the method according to the invention is ≤15 hours or ≤10 hours. Particularly preferably, t _total according to the invention is ≤8 hours, or ≤6 hours, or ≤4 hours, or ≤2 hours. Typically, t _total at the implementation of the method according to the invention ≥0.5 hours or ≥1 hours

The method according to the invention can be used to carry out the distillation method described in EP-A 648732 and EP-A 270999 for the purification of the crude (meth) acrylic acid described in DE-A 19924533, DE-A 10247240 and DE-A 10243625 for fractional condensation separation crude acrylic acid from a product gas mixture obtained by partial oxidation of propene and / or propane to acrylic acid as described in EP-A 717029 of a rectification method for the separation of crude (meth) acrylic acid from a mixture containing (meth) acrylic acid and as The main component is an inert hydrophobic organic liquid with a higher boiling point than the (meth) acrylic acid described in DE-A 4308087 for the absorption of acrylic acid from the reaction gases of the catalytic partial oxidation of propene and / or acrolein, as well as for the others described in this application, as well as in EP-A 990636, EP-A 861820, EP-A 778255, EP-A 551111, EP-A 695736, EP-A 1026145, DE-A 10251328 and / or cited in other literature sources of distillation, sorption and / or extractive thermal methods section Nia for separating at least one mass stream enriched in the (meth) acrylic monomers from a mixture comprising (meth) acrylic monomers.

Often when implementing the methods described above, as well as the method according to the invention, an effective separation column includes at least one circulation heat exchanger and at least one column with or without integrated separation elements.

Since the absorption separation, as a rule, proceeds with the release of heat, at least one of the heat exchangers performs the function of heat removal. This is carried out in an indirect way using a refrigerant coolant (refrigerant), which never enters an effective separation chamber, which means that only one of the two walls of the heat exchanger chamber is an integral part of an effective separation chamber. The other is outside and brings in refrigerant. The mass flow to the wall of the heat exchanger, which belongs to an effective separation chamber, is carried out, as a rule, using at least one pump.

When carrying out a large number of thermal separations other than absorption, heat is supplied to the effective separation chamber through a circulation heat exchanger. In most cases, this also happens in an indirect way with the help of refrigerant, which never enters the efficient separation chamber. In other words, only one of the two walls of the heat exchanger chamber is an integral part of an effective separation chamber. The other is located outside and brings the coolant. Often so much heat is supplied that a boiling effect occurs in the wall of the heat exchanger belonging to the effective separation chamber.

In this case, the circulation heat exchanger is called a circulation evaporator. The mass flow to the wall of the heat exchanger, which belongs to the effective separation chamber, can be carried out using a pump (forced circulation) and / or by natural circulation (the latter, due to the difference in mass density, occurs between the heated and unheated mass flow).

A circulation evaporator is used as a circulation heat exchanger, especially if rectification is meant by the thermal separation method according to the invention.

Basically, in the method according to the invention, all known types of indirect heat exchangers can be used as indirect circulation heat exchangers. Preferably, they are selected so that the volume of the liquid phase in them is minimal.

In the case of a circulating evaporator, for example, Robert evaporators integrated into the distillation column (evaporators with natural circulation) are used, as shown in Fig. 1 (1 — distillation column, 2 — cogeneration steam, 3 — condensate steam cogeneration, 4 - cube unloading, 5 - liquid level, 6 - evaporation pipe, 7 - central drain pipe, 8 - circulation direction).

In addition, as a circulating evaporator, a forced-circulation evaporator withdrawn from the distillation column can be used, which is shown in Fig. 2 (1 — distillation column, 2 — circulation pump, 3 — tube evaporator, 4 — heat recovery steam, 5 - condensate of heating steam, 6 - unloading of bottoms product, 7 - direction of rotation (circulation), 8 - separation device, 9 - outflow, 10 - inflow, 11 - liquid level).

Of course, a forced-circulation reduction evaporator can also be used as a circulation evaporator, which is schematically shown in Fig. 3 (1 - distillation column, 2 - circulation pump, 3 - throttling device, 4 - tube evaporator, 5 - heating steam, 6 - condensate of heating steam, 7 - unloading of bottoms product, 8 - direction of circulation, 9 - separation device, 10 - outflow, 11 - inflow, 12 - liquid level). The forced-circulation reduction apparatus, in contrast to the forced-circulation evaporator, is separated from the distillation column by a throttling device. A portion of the liquid contents of the distillation column under pressure P _{x is} continuously taken and pumped into the tributaries of the tube evaporator (shell-and-tube heat exchanger) using a circulation pump. A coolant, such as heating steam (usually pressurized water vapor), flows at internal tubes of a tubular evaporator, the temperature of which is higher than the temperature of the liquid medium of the distillation column. Passing through the inlet and outlet pipes of the tubular evaporator, the liquid discharged from the distillation column is heated by indirect heat exchange to a temperature Т _у , which is higher than the temperature of the liquid medium of the distillation column.

The throttling device divides the tube evaporator and the distillation column and allows, by varying the capacity of the circulation pump, to establish _the initial pressure of the throttling device P _y exceeding P _x , which is higher than the boiling pressure P _{y ′} corresponding to the temperature T _{y ′ of the} liquid unloaded from the distillation column. The above methods manage to suppress the boiling of the liquid fraction pumped from the distillation column into the pipes of the tubular evaporator. The liquid pumped from the distillation column into the tubes of the tube evaporator is significantly overheated compared to the pressure of P _x existing in the liquid medium of the distillation column, thus the boiling process moves towards the passage of the throttling device (in other words, the contents of the tubes of the tube evaporator are single-phase, the tube evaporator functions only as a superheater). The release of superheated liquid through the throttling device into the distillation column can be carried out directly into the liquid contents of the distillation column (distillation column cube). Under such conditions, the temperature of the liquid contents of the distillation column bottom usually corresponds to the boiling point T _x at a pressure P _x above the bottom liquid.

As a rule, the release of superheated liquid through a throttling device into the distillation column occurs above the liquid level of the distillation column cube. Under such conditions, the temperature of the liquid contents of the distillation column bottom is usually lower than the boiling point T _x at a pressure P _x above the bottom liquid. It is important that the boiling-off effect of the tubular evaporator located outside the distillation column first occurs in the distillation column, that is, outside the circulation evaporator. In this case, throttling can, for example, be carried out mechanically (jumpers, valves) and / or hydrostatically (using the corresponding high column above the passage of the superheated liquid).

As a circulation evaporator, a direct circulation evaporator can also be used, for example, as shown in Fig. 4, into which a coolant obtained outside the limits of an effective separation chamber is fed and subjected to direct contact with the liquid to be evaporated.

Liquid is unloaded from the cube 9 of the distillation column 8 and / or a high-boiling fraction is discharged using the collecting plate located at the bottom of the distillation column 1. Then, one or both of the discharged liquids is sprayed into a direct circulation evaporator 6, in which, for example, they are mixed in a parallel stream with a higher temperature product gas mixture 2 obtained by partial oxidation of propene and / or propane as a direct heat carrier and subjected to direct heat exchange, while at least partially evaporating. After that, the entire mixture 10 is returned to the liquid of the distillation column cube (the return can also be carried out without immersion), and the resulting gas mixture stream is subjected to fractional condensation. The liquid discharged from the distillation column is supplied with the help of pumps 4, 5. Under the reference designation 3 is meant the discharge of bottoms product, and under 7 - the level of bottoms liquid. The evaporator with direct circulation, as a rule, does not contain built-in separation elements and has a cylindrical shape. The gas and liquid phase can also be separately discharged from the evaporator with direct circulation into the distillation column. Such a direct circulation evaporator is shown schematically in FIG. Positional designations have the same meanings as in figure 4.

10a means the gas phase returned to the distillation column, and 10b means the liquid phase returned to the distillation column. 11 means the liquid level in the evaporator with direct circulation.

The distillation column may not contain or contain built-in separation elements, and for the implementation of the method according to the invention are suitable all mentioned in this application built-in separation elements separately or, if necessary, in combination with other built-in separation elements.

At the same time, for example, Rashig glass rings, saddle-shaped nozzles, wire mesh nozzles, V2A spirals, Pall rings and Shtadman capsules, as well as nozzles of the second, third and fourth generation are used as bulk nozzles.

As nozzles, the diameter of which practically corresponds to the inner diameter of the column, packings of different types are used. In this case, as a rule, we are talking about permeable three-dimensional metal, plastic and / or ceramic grids with a large surface area.

If the implementation of the thermal separation method according to the invention involves fractionating condensation of a gas mixture obtained by one- or two-stage heterogeneous catalyzed oxidation of propene and / or propane to acrylic acid, the distillation column, as built-in separation elements, preferably first contains double-flow plates, and then hydraulically sealed transverse current trays (e.g., Thormann® trays, or modified Thormann trays) as described but in DE-A 19924532, DE-A 10243625 and DE-A 10247240.

The number of theoretical stages of separation is from 15 to 30, preferably 20. The evaporator is the above-described evaporator with direct circulation. If another carbon dioxide cooler is integrated in the condensation column, valve plates described in DE-A 19924532, DE-A 10243625 and DE-A 10247240 are preferably used as integrated separation elements in this zone of the condensation column.

значения

являются по возможности малыми. Иными словами, поставленную согласно изобретению цель удается достичь, среди прочего, путем уменьшения общего количества находящейся в разделительной камере в стационаоном состоянии жидкой фазы при сравнительно одинаковых показателях массовых потоков и теоретических стадиях разделения, что осуществляют предпочтительно в тех объемных элементах, в которых жидкая фаза имеет более высокую температуру и уменьшение количества жидкой фазы в которых не повлечет за собой уменьшения количества теоретических стадий. Прежде всего с этой целью используют следующие возможности. Первая возможность состоит в уменьшении поперечного сечения трубопровода эффективной разделительной камеры, через который пропускают жидкую фазу, содержащую акриловую кислоту, за счет неминуемой потери давления (при одинаковых объемных потоках), а также уменьшения длины трубы.According to the general formula for t _total, when implementing the method according to the invention, the values of t _total are insignificant if, for large values

values

are as small as possible. In other words, the goal set according to the invention can be achieved, inter alia, by reducing the total amount of the liquid phase in the separation chamber in the stationary state at relatively identical mass flow rates and theoretical separation stages, which is preferably carried out in those volumetric elements in which the liquid phase has higher temperature and a decrease in the amount of the liquid phase in which will not entail a decrease in the number of theoretical stages. First of all, the following possibilities are used for this purpose. The first possibility is to reduce the cross-section of the pipeline of the effective separation chamber, through which the liquid phase containing acrylic acid is passed, due to the inevitable loss of pressure (at the same volume flows), as well as to reduce the length of the pipe.

In the case of fractional condensation described above, in the framework of the present invention, preference is given to a method in which no other circulation heat exchanger, except for the evaporator with direct circulation, belongs to an effective separation chamber.

Thus, in contrast to FIG. 1 and FIG. 2, DE-A 19924533 or FIG. DE-A 19924532, and also unlike DE-A 10247240 according to the invention, it is advantageous to completely abandon the circulation heat exchanger 8 of the above figures and use exclusively the heat of vaporization of the product gas mixture obtained by partial oxidation of propene and / or propane to acrylic acid. In this case, the direct circulation evaporator according to the invention preferably has the structure shown in Fig. 4 rather than in Fig. 5, in which the mixture of gas and liquid as a two-phase system is fed directly to the distillation column, as a result of which, in contrast to the method according to figure 5, it is possible to avoid the occurrence of an additional liquid level (with an increase in the individual residence time). At the same time, the cross section of the evaporator with direct circulation is reduced with constant circulating quantities (at the same time, the direct circulation evaporator also serves as a direct cooler for the product-gas mixture obtained by partial oxidation; to maintain the heat balance, the circulating quantities should be minimal) in order to reduce the amount of liquid phase in an effective separation chamber.

If the effective separation chamber comprises mass transfer plates as integrated separation elements, as such, according to the invention, preferably sieve trays are used, particularly preferably sprinkler sieve trays (double-flow trays). Since the latter do not contain any overflow valves, they are used at a particularly low liquid level, and, according to the invention, they are more preferred in comparison with hydraulically sealed trays with transverse current. The latter are used only if the separation effect obtained with the help of sprinkling sieve plates is insufficient.

If the effective separation chamber contains prefabricated trays (for example, as a component of a distillation column) through which, for example, the separated liquid mass stream is discharged from the effective separation chamber (for example, to a settling tank or circulation heat exchanger), they are used according to the invention at the lowest liquid level. This is possible, for example, by applying displacers to prefabricated plates. They allow an increase in liquid level with a reduced volume. An alternative solution to the problem is DE-A 10159825 in the form of prefabricated differential plates.

In carrying out the method according to the invention, suitable displacers were also preferred for cube segments (cube chambers) of the distillation column. They are, as a rule, those camera components that are geometrically located under the lower integrated dividing elements. In the case of distillation as a thermal separation method according to the invention, bottoms are regularly unloaded from the bottom sections and fed to a forced-circulation heat exchanger. At the same time, still liquid is usually in a state of boiling.

In order to avoid the fact that the pump necessary for the forced supply of substances to the forced circulation heat exchanger, for example, in the event of a malfunction, pumps too much gas (which, as a rule, reduces the power of the pump and can in the worst case cause its destruction, since the pump usually used to pump liquid), a safe liquid level is set in the cube segment.

Such a safe level according to the invention with a reduced cube volume is achieved by the preferred method of applying displacers onto the cube chamber or by insulating the cube chamber as shown in FIG. 6. Of course, in the method according to the invention, it is possible to reduce the volume of the cube.

According to the invention, a reduction in the volume of the cube is preferable in each case compared to the solutions proposed in Fig. 7, where a buffer vessel for bottoms liquid is provided between the pump and the cube of the column for safety reasons. The pumps used in the method according to the invention are selected so that they retain as little liquid phase as possible.

The temperatures T _i during the implementation of the method according to the invention can be determined by a simple experimental method (for example, using suitably located thermocouples).

As a rule, the choice of volumetric elements i in the method according to the invention is arbitrary, it practically does not affect the result for t _total . However, for many cases, there are the most favorable options for volumetric elements i.

In the case of force-fed mass transfer plates, a volumetric element i is used that takes into account the liquid level on the mass transfer plate and the flow of liquid to the mass transfer plate below, as shown schematically in Fig. 8 with a shaded section. 1 means the place of the inflow to the volumetric element, 2 - the place of the outflow from the volumetric element, 3 - the overflow valve, 4 - the column wall and 5 means the mass transfer plate having passage points (6 - the liquid level in the drain or receiving shaft).

определяют, например, таким образом: в сливную шихту встраивают улавливающую тарелку, из которой выгружают тот же поток жидкости ректификационной колонны, анализируют, после чего возвращают ниже места оттока в сливную шихту (см. фиг.9; 1 - стенка колонны; 2 - сливной патрубок; 3 - улавливающая тарелка; 4 - нагнетательный насос; 5 - измерение потока). Кроме того,

можно определить, принимая во внимание

путем загрузки через место притока индикатора и его выгрузки через место оттока по прошествии определенного времени. Последнее, например, можно осуществлять путем непрерывного отбора малой пробы в месте 7 на фиг.8. Местом выгрузки индикатора, как правило, является место 8 на фиг.8.m _{si is} determined, for example, in this way: the active places of the inflow and outflow are simultaneously closed, and then the mass of the liquid phase m _i contained in the volume element i is determined. Using a chemical analysis of the content from m _i, m _{si is obtained} .

determined, for example, in this way: a trap plate is built into the drain charge, from which the same liquid stream of the distillation column is unloaded, analyzed, and then returned below the outflow into the drain charge (see Fig. 9; 1 - column wall; 2 - drain pipe; 3 - catching plate; 4 - pressure pump; 5 - flow measurement). Besides,

can be determined taking into account

by loading through the place of inflow of the indicator and unloading it through the place of outflow after a certain time. The latter, for example, can be accomplished by continuous sampling of a small sample at location 7 in FIG. The indicator unloading place, as a rule, is place 8 in Fig. 8.

In the case of sprinkler strainers, it is possible to act accordingly. Moreover, as a volumetric element i, a volumetric element is selected that registers the liquid level on the mass transfer plate and the space under the mass transfer plate to the beginning surface of the liquid level of the next mass transfer plate.

над ситчатой тарелкой устанавливают улавливающую тарелку. Из нее выгружают имеющуюся жидкость, анализируют соответствующий поток, после чего ее возвращают непосредственно над ситчатой тарелкой (см. фиг.10; 1 - ситчатая тарелка; 2 - улавливающая тарелка; 3 - нагнетательный насос; 4 - измерение потока).In this case, to determine

a trap plate is mounted above the sieve plate. The existing liquid is discharged from it, the corresponding flow is analyzed, and then it is returned directly above the sieve plate (see Fig. 10; 1 - sieve plate; 2 - trap plate; 3 - pressure pump; 4 - flow measurement).

The amount of liquid located on the sprinkler plate can also be analyzed by differential pressure measurement according to FIG. 11 (U-shaped vacuum gauge method). Moreover, Δp = ς · g · h _L (h _L - 1 in Fig. 11), where ς means the mass density of the liquid phase, g means the gravitational constant, ah _L means the level of the liquid phase on the sprinkler sieve plate, allows you to directly take readings h _L and calculate the amount of liquid on the sprinkler strainer.

The amount of fluid between the two sprinkler sieve trays can be determined by simultaneously closing both trays and determining the amount of fluid collected on the bottom plate. As a result of chemical analysis of m _i get m _si .

в кубе с зафиксированным уровнем жидкости определяют непосредственно с помощью измерений. То же самое касается циркуляционного насоса, циркуляционный теплообменник может быть обработан подобным образом. Участки колонны, содержащие сыпучие насадки или наполнители, могут быть обработаны аналогичным способом, как и объемные элементы массообменных тарелок.In accordance with this m _si in the cube of the column is calculated from the level of bottoms liquid, determined using the outflow, as well as by analyzing the composition of the bottoms liquid,

in a cube with a fixed liquid level is determined directly using measurements. The same goes for the circulation pump, the circulation heat exchanger can be processed in a similar way. Portions of the column containing loose packing or fillers can be treated in the same way as the bulk elements of the mass transfer plates.

Inside the distillation column, the values of m _si and m _i can also be determined by similar semi-empirical methods (see, for example, Johann Stichlmair; Grundlagen der Dimensionierung des Gas / Flüssigkeit-Kontaktapparates, Bodenkolonne, Verlag Chemie (1978) and Technische Fortschrittsberichte, Grundlagen der Dimensionierung von Kolonnenböden, von Dr.-lng. Klaus Hoppe und Dr.-lng. Manfred Mittelstrass, Magdeburg, Verlag Theodor Steinkopff, Dresden (1967)).

For this purpose, first, for example, the corresponding temperatures of the various mass transfer plates are determined. Then determine the composition of the inflows and outflows from the distillation column. After that, using the Raoult law (vapor and liquid equilibrium) and the balance of mass and energy, the concentration distribution in the column is calculated and the necessary indicators of the amount of liquid and gas flow are obtained. The indicator m _{si is} determined in this way: first, during separate tests (gas is supplied from below, and liquid is washed from above), the hydrodynamic properties of the built-in separation elements, for example, mass transfer plates, are determined from which m _i are then obtained, on the basis of which indicators are obtained for the concentration distribution m _si .

Unexpected when implementing the method according to the invention was the fact that by reducing the values of t _total under constant boundary conditions, it is possible to improve the output in time and volume, as well as the degree of enrichment.

As shown in the exemplary embodiment below, the method according to the invention with a value of t _total ≤10 h allows the separation of crude acrylic acid, the content of the fraction of acrylic acid in which is ≥95 wt.%, From a product gas mixture obtained by one- or two-stage heterogeneous catalyzed partial oxidation propene and / or propane to acrylic acid, the content of the fraction of acrylic acid in which is from 5 to 15 wt.%.

The thermal separation method used here includes continuous stationary operation of the thermal separation device comprising an effective separation chamber with integrated separation elements, which is shown schematically in FIG.

The chamber consists of a distillation column 28 (which, as built-in separation elements, contains only mass transfer plates; they mean double-flow plates placed from bottom to top and then hydraulically sealed plates with transverse current separated by valve plates; additionally, the distillation column contains prefabricated plates), which does not contain integrated dividing elements of the evaporator with direct circulation 1, carried out using pump 7 and pump 29, as well as pipelines 6, 6 ′, 3, 3 ′ and 2. Such a separation column is described in more detail in DE-A 19924532, DE-A 10247240 and DE-A 10243625. The number of theoretical separation stages, as a rule, is from 15 to 30, preferably 20 All elements of this effective separation chamber can be used as components of the used device for thermal separation, however, they are not part of the effective separation chamber used according to the invention. Its expansion increases the value of t _total and does not contribute to thermal separation. The method according to the invention is used primarily when the thermal separation method used includes the method according to the invention. The product-gas mixture obtained by the one- or two-stage heterogeneous catalyzed partial oxidation of propene and / or propane to acrylic acid is at the same time a direct heat source for the direct circulation evaporator.

The following example and comparative example illustrate the invention without limiting its general applicability. Polymerization inhibitors are added to the liquid phases obtained by carrying out the method according to the invention, which contain acrylic acid, by known methods.

Example and comparative example (digital indicators relate to FIG. 12; the gray shaded portion in FIG. 12 indicates the effective separation chamber in question)

Comparative example (stationary state described; suitable materials are, for example, stainless steel grades 1.4539 or 1.4571)

By heterogeneous catalyzed partial oxidation in the gas phase of propylene with a purity of "polymer grade", a product-gas mixture of the following composition is obtained having a temperature of 270 ° C:

11.80 wt.% Acrylic acid,

0.264 wt.% Acetic acid,

5.0984 wt.% Water,

0.0275 wt.% Formic acid,

0.0989 wt.% Formaldehyde,

0.1473 wt.% Acrolein,

0.0028% by weight of propionic acid

0.0033 wt.% Furfurals,

0.0014 wt.% Allyl acrylate,

0.0005 wt.% Allyl formate,

0.0038 wt.% Benzaldehyde,

0.1350 wt.% Maleic anhydride,

0.0112 wt.% Benzoic acid,

0.0147 wt.% Phthalic anhydride,

4.0324 wt.% Oxygen,

1.8067 wt.% Carbon dioxide

0.5904 wt.% Carbon monoxide,

0.5520 wt.% Propane,

0.2696 wt.% Propylene and

75.1399 wt.% Nitrogen.

No other components were detected. The product gas mixture (170008 kg / h) in a heat exchanger with direct circulation 1 and direct current is cooled to a temperature of 120.2 ° C. Direct circulation 1 heat exchanger with direct current does not contain built-in elements. It has a cylindrical shape. Its diameter is 2.2 m and its height is 15.5 m. The liquid phase to be heated in a direct-circulation heat exchanger 1 is a mixture of cubic liquid discharged from chamber 5 and a hardly boiling fraction that was unloaded from the first collecting plate 10, adjacent to the camera 5 cube distillation column 28.

The amount supplied to the heat exchanger with direct circulation of 1 cubic fluid is 247305 kg / h, it has the following composition (mass density = 989.22 kg / m ³ ):

27.2977 wt.% Acrylic acid,

0.1446 wt.% Acetic acid,

0.6007 wt.% Water,

0.0069% by weight of formic acid

0.0007 wt.% Formaldehyde,

0.0087 wt.% Acrolein,

0.0149% by weight of propionic acid

0.2041 wt.% Furfurals,

0,0008 wt.% Allyl acrylate,

0.0001 wt.% Allyl formate,

0.2490 wt.% Benzaldehyde,

4.4377 wt.% Maleic anhydride,

0.7354 wt.% Benzoic acid,

0.9605 wt.% Phthalic anhydride,

19.5513 wt.% Diacrylic acid,

40.1375 wt.% Polyacrylic acid (Michael addition product),

0.4855 wt.% Phenothiazine,

0.5560 wt.% Hydroquinone monomethyl ether (MEHQ),

4.6079% by weight of other high boiling components and

0,0002 wt.% Oxygen.

The temperature of the bottom liquid is 118.3 ° C, the vapor pressure is 1.48 bar. The amount of the hardly boiling fraction supplied to the direct-circulation heat exchanger 1 is 63009 kg / h; it has the following composition (mass density = 969.94 kg / m ³ ):

90.4867 wt.% Acrylic acid,

0.3672 wt.% Acetic acid,

1.4207 wt.% Water,

0.0142 wt.% Formic acid,

0.0016 wt.% Formaldehyde,

0.0109 wt.% Acrolein,

0.0535 wt.% Propionic acid,

0.6232 wt.% Furfurals,

0.0025 wt.% Allyl acrylate,

0.0002 wt.% Allyl formate,

0.5317 wt.% Benzaldehyde,

4.9046 wt.% Maleic anhydride,

0.0401 wt.% Benzoic acid,

0.0344 wt.% Phthalic anhydride,

1.4102 wt.% Diacrylic acid,

0.0201 wt.% Phenothiazine,

0.0779 wt.% MENQ and

0.0004 wt.% Oxygen.

The temperature of the high boiling fraction is 100.4 ° C, the vapor pressure is 1.48 bar.

The high-boiling fraction is fed into the heat exchanger (evaporator) with direct circulation 1 through a pipe 3 with a diameter of 150 mm and a length of 10 m towards a centrifugal pump 29 (liquid capacity: 50 l) and from there through a pipe 3 'with a diameter of 150 mm and a length of 15 m - to the evaporator with direct circulation 1 (alternatively, the high-boiling fraction can be fed through the overflow valve into the cube chamber and loaded into the evaporator with direct circulation as an integral part of the still liquid).

VAT liquid discharged from the chamber 5 cubes, in the amount of 249905 kg / h through the pipeline 6 with a diameter of 300 mm and a length of 10 towards the centrifugal pump 7 (liquid capacity: 100 l) and from there in the amount of 247305 kg / h through the 6 'length 10 m and a diameter of 300 mm (in this context, the diameter of pipelines is understood as the internal diameter) - in a direct circulation evaporator 1. 2300 kg / h of discharged bottoms are fed for separation, and 300 kg / h of discharged bottoms are fed to carry out the following cooling cycle I in order to rubbing undesired polymerization (in both cases, the feed is carried out through the piping 8). A mixture of bottoms liquid and high boiling fraction with a nozzle (spray tip with a reflector according to WO 02/50011) is sprayed in a direct circulation evaporator 1.

The two-phase mixture unloaded from the evaporator with direct circulation 1, having a temperature of 120.2 ° C, is returned to the chamber 5 cubes through the pipe 2 (diameter: 1500 mm; length: 10 m).

The pressure in the chamber of 5 cubic meters and in the evaporator with direct circulation 1 is 1.48 bar. The height of the distillation column 28 (columns for fractional condensation, which contains only mass transfer plates as built-in effective separation elements; they mean double-flow plates placed from bottom to top, and then hydraulically sealed plates with transverse current (Tormann plates), separated by valve plates) is 54 ,3m.

The inner diameter of the distillation column 28 in the area of the Tormann plates is 6.5 m, and the rest is 6.0 m.

A separation device (which, for example, does not belong to an effective separation chamber), to which 2300 kg / h of bottoms liquid unloaded from the chamber 5 is fed, consists of a pressure reducing evaporator with forced circulation and two-way rectification column plates placed on it in a seamless way. The number of plates is 50.

The forced-circulation reduction apparatus consists of a separation boiler, a heat exchanger, a pump and related pipelines. Substances discharged from the boiler through a pipeline are fed to a centrifugal pump, which loads them into a shell-and-tube heat exchanger. Then part of the heated liquid is returned through the pipeline to the boiler, and the other part of the heated liquid, having determined its viscosity, density or temperature, is fed into the tank described below, into which methanol is added.

Like distillation column 28, this distillation column is isolated from the external environment. The internal diameter of the distillation column, including all double-flow trays, is 2.4 m, its height is 27 m. Double-flow trays in the distillation column are equidistant from each other (400 mm). Their relative aperture is 12%. Looking from the bottom up, the diameter of the holes of the first eight double-flow plates is 25 mm (the location of the holes clearly corresponds to the triangular sectors), and the diameter of all other double-flow plates is 14 mm (the location of the holes clearly corresponds to the triangular sectors). The still liquid to be separated is fed into eight double-flow plates (bottom).

20,000 kg / h of subsequently superheated and compressed circulating gas discharged from the head of the condensation column (as auxiliary gas) is supplied to the separation tank for the pressure reducing apparatus with forced circulation (pressure = 2.9 bar; temperature = 160 ° C).

The composition of the circulating gas:

0.2288 wt.% Acrylic acid,

0.0885 wt.% Acetic acid,

2.6689 wt.% Water,

0.0052 wt.% Formic acid,

0.1724 wt.% Acrolein,

0.0002 wt.% Propionic acid,

0,0003 wt.% Furfurals.

0.0012 wt.% Allyl formate,

4.7392 wt.% Oxygen,

2.1235 wt.% Carbon dioxide,

0.6939 wt.% Carbon monoxide,

0.6487 wt.% Propane,

0.3169 wt.% Propylene and

88.3123 wt.% Nitrogen.

522,963 kg / h of the liquid phase having a temperature of 161 ° C and a pressure of 1.71 bar are continuously discharged from the separation tank of the pressure reducing reduction evaporator with forced circulation, of which 522,246 kg / h are returned to the separation tank after passing through the heat exchanger at a temperature of 166 ° C and a pressure of 3 bar. The remaining 717 kg / h are degassed, diluted with methanol, and the precipitate is burnt.

The cracked gases generated in the separation tank are supplied to the distillation column by means of auxiliary circulating gas, where they rise in an upward flow of recirculation liquid.

A mixture (consisting of circulating gas and cracking gas) having a temperature of 99.8 ° C and a pressure of 1.60 bar is unloaded from the head of a distillation column in an amount of 33129 kg / h, and cooled by direct cooling in a direct current spray cooler (cooling cycle) I) to a temperature of 63.3 ° C and subject to partial condensation.

The gas mixture remaining after cooling in an amount of 21883 kg / h, having the composition below, is returned to the chamber 5 of the cube 5 of the condensation column 28 (without immersion) through the pipe 9:

8.7215 wt.% Acrylic acid,

0.0976 wt.% Acetic acid,

2.5067 wt.% Water,

0.0056 wt.% Formic acid,

0.0001 wt.% Formaldehyde,

0.1584 wt.% Acrolein,

0.0019 wt.% Propionic acid,

0.0017 wt.% Furfurals,

0.0001 wt.% Allyl acrylate,

0.0011 wt.% Allyl formate,

0.0004 wt.% Benzaldehyde,

0.0039 wt.% Maleic anhydride,

4.3313 wt.% Oxygen,

1.9407 wt.% Carbon dioxide,

0.6342 wt.% Carbon monoxide,

0.5929 wt.% Propane,

0.2896 wt.% Propylene and

80.7122 wt.% Nitrogen.

As a cooling liquid I, a mixture of 300 kg / h of cubic liquid discharged from a chamber of 5 cubes and condensate formed during direct cooling in a cooling cycle I is used. 104207 kg / h of this mixture is cooled by indirect cooling to 32 ° C and sprayed into spray cooler I cycle I. 11546 kg / h of the same mixture at a temperature of 63.3 ° C as a recirculation liquid is returned to the upper double-flow plates placed in the tank for separation of the distillation column.

Coolant I has the following composition:

93.7485 wt.% Acrylic acid,

0.4937 wt.% Acetic acid,

3.7513 wt.% Water,

0.0143 wt.% Formic acid,

0.0328 wt.% Acrolein,

0.0207 wt.% Propionic acid,

0.0240 wt.% Furfurals,

0.0005 wt.% Allyl acrylate,

0.0017 wt.% Allyl formate,

0.0099 wt.% Benzaldehyde,

0.1591 wt.% Maleic anhydride,

0.0192 wt.% Benzoic acid,

0.0250 wt.% Phthalic anhydride,

0.5083 wt.% Diacrylic acid,

1.0429 wt.% Polyacrylic acid,

0.0126 wt.% Phenothiazine,

0.0146 Bec.% MEHQ,

0.1198 wt.% Other high boiling components and

0.0011 wt.% Oxygen.

A centrifugal droplet separator is integrated into the chamber 5 of the cube of the condensation column 28, which prevents droplets of still liquid from rising from the cube chamber. At the lower end of the cube chamber 5, a so-called “Chinese cap” is installed for better gas / liquid separation. The holding capacity of the liquid phase in the chamber system of the cube 5, from pipeline 6 to the circulation pump 7, circulation pump 7, pipeline 6 'of the circulation pump 7 to the evaporator with direct circulation 1, the evaporator with direct circulation 1 and pipe 2 of the evaporator with direct circulation 1 in a chamber of 5 cubic meters is 80 m ³ .

The cube chamber of the distillation column 28, as mentioned above, at a column height of 7.80 m (like any other height measured from the bottom of the cube) is closed using the first trap plate 10 (collection plate, plate having 16 equally distant gas exhaust pipes ; pipe diameter: 600 mm; pipe height: 1 m).

The collecting plate 10 has double walls 2 with recesses inward, a central drain bowl and drain pipes (DN ~ 200). The live gas cross section is approximately 30%.

From this first collecting plate, as described above, 63009 kg / h of liquid is discharged (T = 100.4 ° C, p = 1.48 bar) and, using a centrifugal pump 29, is loaded into an evaporator with direct circulation 1. The volume of liquid on the collecting plate 10 is 2 m ³ (the holding capacity of the liquid in the liquid volume system on the collecting plate 10, from the pipeline 3 to the circulation pump 29, the circulation pump 29 and from the pipeline 3 'of the circulation pump 29 to the evaporator with direct circulation 1 is 3 m ³ )

After 2.0 m above the first catching plate 10, there is the first (11) of the next 15 two-stream plates equally spaced from each other (hole diameter 14 mm, number of holes 33678, relative aperture 18%), while the distance between the plates is 380 mm. The openings are rounded openings with a diameter of 14 mm, and their edges in the distillation column points down. The location of the centers of the through holes clearly corresponds to the triangular sectors.

The fifteenth dual-flow plate (12) is designed as a distribution plate. For this purpose, two replaceable pipes (DN ~ 150) are applied over it, each of which contains 40 outlets (diameter: 15 mm).

The first series of double-flow trays is closed in accordance with WO 03 047714 using a second trap 14 (prefabricated trays, trays with 16 equally spaced exhaust pipes; pipe height approx. 1.70 m, central drain pan and drain pipes (DN ~ 250), live the gas cross section is approximately 30%), which is deposited 1.50 m above the last double-flow plate.

From this second catching plate 14 through the pipe 15 at a pressure of 1.47 bar continuously uncleaned acrylic acid having a temperature of 101.2 ° C (mass density = 956.99 kg / m ³ ) and the following composition:

96.8011 wt.% Acrylic acid,

0.4598 wt.% Acetic acid,

1.4762 wt.% Water,

0.0137 wt.% Formic acid,

0.0015 wt.% Formaldehyde,

0.0087 wt.% Acrolein,

0.0647 wt.% Propionic acid,

0.2856 wt.% Furfurals,

0.0027 wt.% Allyl acrylate,

0.0002 wt.% Allyl formate,

0.0744 wt.% Benzaldehyde,

0.2381 wt.% Maleic anhydride,

0.5430 wt.% Diacrylic acid,

0.0120 wt.% Phenothiazine,

0.0180 wt.% MENQ and

0.0004 wt.% Oxygen.

The volume of liquid on the second collecting plate 14 is 10 m ³ . 455855 kg / h of crude acrylic acid discharged from the second catching plate 14 is heated to 111.2 ° C by indirect heat exchange and through the pipe 30 it is returned to the condensation column 28 directly under the dual-flow plate 16 going upstream of the second catching plate 16 (p = 1.50 bar).

89978 kg / h of crude acrylic acid discharged from the second trap plate forms a mass stream containing (meth) acrylic monomers separated in an effective separation chamber, this acid in several stages by indirect heat exchange (preferably using the mother liquor to be returned to the distillation column 28 ) cooled to a temperature of 29 ° C. Then, 1144 kg / h of water (25 ° C.) is added to the cooled crude acrylic acid. The resulting mixture is again cooled by indirect heat exchange to a temperature of 20 ° C and then fed to 2-3 crystallizers with cooling.

This is a working chamber in which there are 20-24 rounded cooling plates hanging one after another (inside of which there is a cooling medium (a mixture of water and glycol; glycol content = 10 to 50 wt.%, Preferably 25 to 35 weight .%)) equidistant from each other at a distance of from 20 to 40 cm (the diameter of the plate is from 2 to 4 m, preferably from 2.5 to 3 m). In this case, the cooling medium is countercurrent with respect to the mixture to be cooled and passed through the mold from plate to plate. In addition, it can be divided into 2 or 3 parallel flows and fed over the cooling plates. The temperature of the cooling medium at the inlet (brine) is from -2 to + 5 ° C, the outlet temperature is 2-7 ° C higher. By cleaning the cooling plates, the formation of a crystalline layer is avoided. Diluted with water, the crude acrylic acid from back to front is continuously passed through a mold (pumped or overfilled with valves). In this case, a single-phase crude acrylic acid diluted with water is concentrated (residence time from 0.5 to 4 hours, preferably from 1.5 to 2.5 hours), and a two-phase suspension is formed, which contains acrylic acid crystals as a solid phase, having a temperature of 6 to 11 ° C and a solids content at the outlet of 20 to 35 wt.%. The speed of the cleaners is from 2 to 15 rotations per minute, preferably from 4 to 10 revolutions per minute. The shaft that drives the cleaners, which runs in the center of the cooling mold, is covered with stuffing boxes washed with water (packing threads are made of Teflon or graphite).

In places inaccessible to cleaners, a concave profile is applied (for example, welded) (for example, according to the simplest form of pipe implementation), heated (to a temperature above the crystallization temperature; more often, to a temperature of 8 to 20 ° C, preferably 10 to 14 ° C) using a second coolant (for example, a mixture of water / glycol).

In addition, the radial cleaners are preferably divided into segments (typically ≥2, ≥6 segments). The specific pressure force of the cleaners in the integrated state perpendicular to the cooling surface is from 1 to 10, preferably from 3 to 5 N per cm, of the active length of the cleaner. In addition to the cleaners, the shaft also drives the blades (between two plates, and two more are symmetrically located in front of the first and last plates), which contribute to better mixing.

The surface properties of the cooling plates and the location of the cleaners determine the fact that the distance between the cleaner and the surface of the cooling plate does not exceed 6 mm anywhere (preferably, the distance should not exceed 4, 2 or 1 mm or adjacent at each point; particularly preferably adjacent along the outer radius) .

In the rear part of the mold (preferably behind the last cooling plate), the suspension in a closed pipe (preferably with immersion; alternatively, the suspension can flow through an overflow valve into a collector from which it is loaded into the wash column) is fed into the hydraulic wash column described in DE-A 10156016 and DE-A 10223058, in order to isolate the mother liquor from the suspension crystallizate. The wash column is loaded with a suspension crystallizate using a centrifugal or rotary piston pump. The control current pump, like a centrifugal or rotary piston pump, is equipped with a control valve. The pressure at the bottom of the wash column is typically ≥100 mbar and ≤5 bar lower than the pressure at the head of the column. The pressure in the head of the column, as a rule, is up to 6 bar, usually from 0.5 to 4 bar. Meter speed> 0 and ≤100 / min or ≥60 / min. The temperature of the melting cycle, as a rule, is from 13 to 16 ° C. The determination of the filtration front is carried out according to DE-A 10036880 using 2-4 optical sensors. The wash front is controlled by measuring the temperature in the crystalline layer.

The total height of the crystalline layer, as a rule, is from 300 to 1500 mm, more often from 400 to 1000 mm. The flushing front is usually located at a height of 10 to 400 mm, more often 20 to 250 mm above the meter. As a pump, a centrifugal pump is used, which flushes the shaft packing (contact sealing ring) or a pump with a magnet that washes the sliding bearing. The amount of substance undergoing the melting cycle is from 2 to 30, more often from 5 to 20 m ³ / h per ton of purified crystallizate analyzed by the meter. The stabilization of the melting cycle is carried out using 100-300 wt.-m.h. MEHQ. Additionally, air is fed into this cycle, the excess of which (= the fraction not dissolved in the melt) is discharged before the melt is loaded into the wash column using a gas separator.

[(a) To obtain an esterification capable acrylic acid, it is sufficient to separate the suspension crystallizate in a fusible washing column using a centrifuge (for example, a 2- or 3-stage centrifuge with an ejector). The corresponding mesh size is from 150 to 300 mm; the centrifugal acceleration used is from 500 to 900 g, more often from 600 to 800 g; a suitable number of strokes is 40 to 80 shifts / min.

The crystals, preferably separated into 2 or 3 stages of the centrifuge, are washed with 0.15-0.3 kg of washing liquid per kg of crystallizate. The temperature of the liquid is from 15 to 30 ° C., preferably from 20 to 30 ° C. In order to avoid deposits, the drain shaft for solids is washed with washing liquid heated to 15-30 ° C. The washing and washing liquid is preferably obtained from a molten centrifuge separated and washed crystallize. In order to avoid deposits and the formation of a crystalline crust, the centrifuge body, the suspension inlet pipe and the pipe supplying the washing liquid are heated to a temperature of ≥15 ° C and ≤40 ° C. The central chamber of the centrifuge is inert with nitrogen or a mixture of air and nitrogen. The shaft seal is washed with gas (for example, nitrogen or a mixture of air and nitrogen) or water;

(b) as an alternative to suspension crystallization, layer crystallization can be carried out (e.g., film crystallization according to EP-A 616998 or a fully streamlined pipe) comprising 3 or more (e.g. 3 to 4) purification steps. Instead of returning the mother liquor to a subsequent purification step to the previous purification step, it can be returned to the condensation column.]

From melting cycles stabilized by using 3 kg / h of MEHQ, 18538 kg / h of crude acrylic acid of the following composition are obtained:

99.8335 wt.% Acrylic acid,

0.0970 wt.% Acetic acid,

0.0334 wt.% Water,

0.0206 wt.% Propionic acid,

0.0001 wt.% Furfurals,

0.0001 wt.% Maleic anhydride,

0.0003 wt.% Diacrylic acid and

0.0150 wt.% MEHQ.

They can be particularly advantageously used for the production of poly-Na-acrylate absorbent materials.

13 kg / h of PTZ are dissolved in 829 kg / h of crude acrylic acid to obtain inhibitor solution I. In 30 kg / h of inhibitor solution I, 19 kg / h of MEHQ is dissolved to form inhibitor solution II.

The mother liquor separated in the wash column is first fed to a heated collector and then to a reservoir. There it is heated to 90 ° C and in the amount of 71759 kg / h through the pipe 13 is returned to the fifteenth double-threaded plate 12 of the condensation column 28 (bottom). The returned mother liquor has the following composition:

94.4349 wt.% Acrylic acid,

0.5504 wt.% Acetic acid,

3.4362 wt.% Water,

0.0172 wt.% Formic acid,

0.0018 wt.% Formaldehyde,

0.0109 wt.% Acrolein,

0.0756 wt.% Propionic acid,

0.3580 wt.% Furfurals,

0.0034 wt.% Allyl acrylate,

0.0003 wt.% Allyl formate,

0.0933 wt.% Benzaldehyde,

0.2986 wt.% Maleic anhydride,

0.6808 wt.% Diacrylic acid,

0.0150 wt.% Phenothiazine,

0.0233 wt.% MENQ and

0.0005 wt.% Oxygen.

Additionally, 15,224 kg / h of crude acrylic acid (32) unloaded from the collecting tray 14 is returned to the two-threaded plate 12.

After 2.9 m above the second trap plate 14, in the condensation column 28 there is the first (16) of the next 21 double-flow trays equally spaced from each other (hole diameter 14 mm, number of holes 32020, relative aperture 17.4%), while the distance between plates is 380 mm. The return from the area of the Tormann plate to the area of the double-flow plate is carried out using a distribution system integrated into the column. Alternatively, the return can be carried out by unloading the circulation liquid from the lower Tormann plate of the condensation column using a pump and returning it through two (or more) pipes located above the higher double-flow plate.

800 mm above the last trap plate, the condensation column expands conically. 500 mm above the last trap plate, this expansion of the condensation column ends, and its diameter is 6.50 m.

At this height, that is, 1.50 m above the last catching plate (17), 28 ordinary single-threaded Tormann plates are equally spaced from each other (distance between plates = 500 mm). The Tormann plates are arranged in such a way that by placing the slots in the plate caps in the transverse current grooves, it is possible to achieve the opposite direction of the fluid flow.

The ratio of the holes of the Tormann plates is 14%. The ratio of the surface of the pipe for the removal of gases to the surface of the outlet of the slot is 0.8. The height of the pipe and the height of the drain threshold is 40 mm. The clearance of the plate (the distance between the lower edge of the slot and the plate) is 10 mm. The height of the slot is 15 mm. The angle between the slot and the edge of the cap is 30 degrees. The rib length of the cap is a maximum of 800 mm. At the end of the column, the length of the cap is reduced to 200 mm in order to fit it to the round shape of the column. The distance between the two caps in the transverse current direction is 66 mm. The drain area of the drain pipe is 1.5% of the transverse current plate area. The distance between the two lower edges of the cap is 64 mm.

At the height of the highest plate of Thormann 20, the distillation column begins to taper again conically. At a distance of 700 mm above the highest Tormann plate, such a narrowing is completed, and the inner diameter of the column again becomes 6.00 m.

At a distance of 1.70 m above the highest Tormann plate there is a third catching plate 22 (a collecting plate, a plate having 16 equally spaced pipes for venting gases; the pipe height is about 1.50 m). The volume of liquid on the third trap plate is 8 m ³ (mass density = 964.38 kg / m ³ ).

533617 kg / h of acidic water are discharged from the third trap plate through line 23 at a temperature of 68.6 ° C and a pressure of 1.24 bar.

Acidic water has the following composition:

11.3387 wt.% Acrylic acid,

4.1574 wt.% Acetic acid,

81.6277 wt.% Water,

0.5256 wt.% Formic acid,

2.3082 wt.% Formaldehyde,

0.0154 wt.% Acrolein,

0.0089 wt.% Propionic acid,

0.0024 wt.% Furfurals,

0.0135 wt.% Allyl formate,

0.0001 wt.% MENQ and

0.0021 wt.% Oxygen.

29015 kg / h of discharged acidic water (68.6 ° C) (21) together with inhibitor solution II (31) is returned to the highest Tormann plate (20).

812 kg / h of inhibitory solution I (bottom) is loaded onto the 19th Tormann plate (18) (at a temperature of 25 ° C and a pressure of 3 bar through line 19).

7282 kg / h of discharged acidic water are burned.

298392 kg / h of discharged acidic water through line 25 at a temperature of 29 ° C is fed to a sixth (24) valve disc (bottom) (pressure 3 bar). In the case of foaming, it is advisable to add an antifoam agent (for example, alkoxylated alcohols, such as Dekresa® SD 23, or mixtures of fatty acids, polyglycol, emulsifiers and paraffin mixtures of mineral oils, such as Naico® 71-D-5) to a third trap plate (for example, in an amount of 30 ml / h).

198928 kg / h of discharged acidic water through line 27 at a temperature of 22.5 ° C (p = 3 bar) is returned to the highest (26) valve disc.

At a distance of 2300 mm above the third catching plate 22 in the condensation column 28 at the same distance from each other (distance between the plates = 500 mm) are 11 double-flow valve plates. The height of the drain threshold is 35 mm. The ratio of the holes is 18%, and the sum of the drainage areas of the drain pipes of two sequentially located valve plates is 10% of the area of the transverse plate current. As valves, W12 valves of the company Stahl, DE, Viemheim are used.

The pressure at the head of column 28 is 1.2 bar. From the head of the distillation column 28 with the help of a mist eliminator, 164650 kg / h of exhaust gas (33) is unloaded, having a temperature of 33.5 ° C and the following composition:

0.2288 wt.% Acrylic acid,

0.0885 wt.% Acetic acid,

2.6689 wt.% Water,

0.0052 wt.% Formic acid,

0.1724 wt.% Acrolein,

0.0002 wt.% Propionic acid,

0,0003 wt.% Furfurals,

0.0012 wt.% Allyl formate,

2.1235 wt.% CO ₂ ,

0.6939 wt.% CO,

0.6487 wt.% Propane,

0.3169 wt.% Propylene,

4.7392 wt.% O ₂ and

88.3123 wt.% N ₂ .

In an indirect heat exchanger, the exhaust gas is heated to 38 ° C, after which 91196 kg / h of this gas is subjected to oxidation in the gas phase and subsequent separation as a diluent gas using a circulation gas compressor (for example, a centrifugal compressor), and 73455 kg / h of exhaust gas gas is burned.

In general, separate streams that have such acrylic acid contents are loaded into an effective separation chamber:

170008 kg / h of a product gas mixture obtained by oxidation in the gas phase of propylene, in which the acrylic acid content is 11.8 wt.%;

21883 kg / h through line 9 with an acrylic acid content of 8.7215 wt.%;

15,224 kg / h through line 32 with an acrylic acid content of 96.8011 wt.%;

71759 kg / h through line 13 with an acrylic acid content of 94.4349 wt.%;

455855 kg / h through line 30 with an acrylic acid content of 96.7887 wt.%;

81.2 kg / h through line 19 with an acrylic acid content of 98.3360 wt.%;

29015 kg / h through line 21 with an acrylic acid content of 11.3387 wt.%;

and 49 kg / h through line 31 with an acrylic acid content of 60.2057 wt.%.

Thus, a total of 764,605 kg / h of mass flow, the acrylic acid content of which is 71.907 wt.%, Is loaded into the effective separation chamber as a whole. Thus, X = 28.09 wt.%.

The mass stream that is discharged from the efficient separation chamber at the highest acrylic acid content is crude acrylic acid discharged from the second collecting plate, the content of the acrylic acid fraction in which is 96.8011 wt.%. Thus, Y = 3.20 wt.%, And X: Y = 8.78.

The total volume of the effective separation chamber filled with liquid is 167.5 m ³ . The temperature of this liquid, at least in part, is 120.2 ° C (for example, in a direct-circulation heat exchanger).

Volumetric elements i are indicated in Table 1 below (where “plate i" here means volume element i, which includes the liquid phase located on the mass transfer plate i and the liquid phase located in the area under the mass transfer plate i (with the exception of the liquid phase located between them plate)). The numbering of the mass transfer plates of the distillation column begins from the bottom up.

.In addition, table 1 shows the temperature values T _i , the calculated values of m _si and the values of mass flows

.

Table 1 also contains individual values.

Thus, t _total = 34.06 hours

When this value of t _commonly as discharged from the separation chamber effective mass stream containing (meth) acrylic monomers, acrylic acid content which is 89,978 kg / hr, using crude acrylic acid, acrylic acid content fraction which amounts to 96.8011 wt.% .

Example (stationary state described)

All is carried out, as described in the comparative example, the volume of the cube chamber 5 is reduced so that the holding capacity of the liquid in the cube chamber 5 is 59974.2 kg lower than in the comparative example (thus, the holding capacity of the liquid in the volumetric element i including the pipe 6 , 6 'and 2, as well as pump 7, a cube chamber 5 and a direct circulation evaporator 1, from the comparative example is 79,995.6 kg, and the example is 19991.4 kg).

In addition, the number of high-boiling fractions discharged from the first collecting plate 10 and loaded into the evaporator with direct circulation 1, is 74083 kg / h instead of 63009 kg / h.

These changes are necessary in order to achieve a decrease in the boiling point in the evaporator with direct circulation 1 by changing the composition of the bottoms liquid in the chamber 5 of the cube.

Table 2 is similar to table 1 of the example.

Thus, t _total is only 8.79 hours

At the same time, at this value of t _total , as a mass stream separated in an effective separation chamber containing (meth) acrylic monomers, the acrylic acid content of which is 90987 kg / h, crude acrylic acid with an acrylic acid content of 96.9333 weight is used. %

The analysis showed that this improvement is primarily due to the fact that the liquid phase in cube 5 in the example, as a result of reducing the residence time, contains only 19.27 wt.% Polyacrylic acid (Michael addition product).

Claims (10)

1. A thermal method for fractional condensation separation of a product gas mixture obtained by heterogeneous catalyzed partial oxidation in the gas phase of propene and / or propane to acrylic acid to separate at least one mass stream enriched in acrylic acid from a product gas mixture, containing acrylic acid, which includes continuous stationary operation of at least one device for thermal separation containing at least one effective separation chamber with rect a friction column having mass transfer plates as integrated spacer elements into which a product gas mixture containing acrylic acid is charged as at least one mass stream containing acrylic acid and from which at least one mass stream is discharged containing acrylic acid, provided that
the mass stream, which is generally loaded into an effective separation chamber and obtained by adding the individual mass flows loaded into the effective separation chamber, contains X% by weight components other than acrylic acid,
the mass stream that is discharged from the effective separation chamber with the highest proportion of acrylic acid contains Y wt.% of components other than acrylic acid,
X: Y ratio is ≥5,
an effective separation chamber, with the exception of the loading point and the discharge discharge point, is limited by the solid phase and contains, in addition to the mass transfer plates, as built-in separation elements in the distillation column, at least one circulation heat exchanger, and
the total volume of the chamber filled with the liquid phase is ≥1 m ³ , and the temperature of the liquid phase is at least partially ≥80 ° C,
when the effective separation chamber is divided into n individual volumetric elements, the highest and lowest temperatures of the liquid phase being in a separate volumetric element differ by no more than 2 ° C, and the volumetric element in the effective separation chamber is continuous, the total residence time t _total.

≤20 h
moreover
A = (T _i -T _o ) / 10 ° C
T _about = 100 ° C
T _i = arithmetic mean of the highest and lowest temperatures of the volume element i in the liquid phase, ° C;
m _si = total mass of acrylic acid contained in the volume of the liquid phase of volume element i;

= total amount of liquid phase mass discharged from volume element i,
and

,
provided that the volume elements i with the contained liquid phase mass m _i and

as volumetric elements with a dead zone are also not included in the sum of all volumetric elements i, as well as volumetric elements i that do not contain a liquid phase, and the total amount of liquid phase contained in volumetric elements with a dead zone is not more than 5 wt.% of the total amount of liquid phase contained in an effective separation chamber. 2. The method according to claim 1, characterized in that X: Y≥8. 3. The method according to claim 1 or 2, characterized in that the total volume of an effective separation chamber filled with a liquid phase is ≥5 m ³ . 4. The method according to claim 1 or 2, characterized in that the temperature of the liquid phase in the effective separation chamber, at least partially, is ≥100 ° C. 5. The method according to claim 1 or 2, characterized in that t _total. ≤15 hours 6. The method according to claim 1 or 2, characterized in that t _total. ≤10. 7. The method according to claim 1 or 2, characterized in that the circulation heat exchanger is a circulation evaporator. 8. The method according to claim 1 or 2, characterized in that the circulating heat exchanger is an evaporator with direct circulation. 9. The method according to claim 1 or 2, characterized in that t _total. ≤10 h, the content of the fraction of acrylic acid in the product gas of partial oxidation in the gas phase is from 5 to 15 wt.%, And the mass stream discharged from the effective separation chamber containing the largest weight fraction of acrylic acid is crude acrylic acid, the content fraction of acrylic acid which is ≥95 wt.%. 10. The method according to claim 1, characterized in that under the mass transfer plates from the bottom up, first we are talking about double-flow plates, then hydraulically sealed plates with transverse current, and then valve plates.

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