WO2020214053A1

WO2020214053A1 - Method for producing paraffin heat-retaining materials and device for the implementation thereof

Info

Publication number: WO2020214053A1
Application number: PCT/RU2019/000261
Authority: WO
Inventors: Анатолий Викторович ВИШНЕВСКИЙ; Сергей Сергеевич КРУГЛОВ; Григорий Львович ПАТАШНИКОВ
Original assignee: Общество с ограниченной ответственностью "Парафин Энерджи"
Priority date: 2019-04-15
Filing date: 2019-04-19
Publication date: 2020-10-22
Also published as: RU2708577C1

Abstract

The invention relates to a method and device for producing paraffin heat-retaining materials from petroleum and synthetic paraffins that are capable of absorbing thermal energy by transitioning from one phase state to another and releasing energy upon transitioning back. A device for producing paraffin heat-retaining materials comprises a vacuum rectification unit, an adsorption purification unit, a crystallization fractionation unit and a filter press. A crystallizer in the form of a cylindrical housing comprises fittings for feeding in raw material, inert gas and coolant; fittings for discharging suspension and coolant; and two coaxial rotary mixers for axial and radial mixing, each of which has its own drive mechanism. In the rectification unit, non-target fractions and the target broad n-alkane fraction C₁₆ are removed from paraffin C₁₄-C₁₇. The broad n-alkane fraction is separated into two narrower fractions and processed in the adsorption purification unit and in the crystallization fractionation unit. The target product is obtained from the suspension that has formed in the filter press and after drying and liquefaction. The invention makes it possible to obtain paraffin heat-retaining materials with a narrower fractional (n-alkane) composition, increased heat retention capacity, improved performance characteristics and increased operational reliability.

Description

METHOD FOR PRODUCING PARAFFIN HEAT-ACCUMULATING

MATERIALS AND DEVICE FOR ITS IMPLEMENTATION

FIELD OF TECHNOLOGY

The invention relates to a method and device for producing paraffinic heat storage materials (PTAM) from petroleum and synthetic paraffins, capable of absorbing thermal energy due to the transition from one phase state to another and release it during the reverse transition.

LEVEL OF TECHNOLOGY

The use of paraffinic heat-storage materials (PTAM), capable of absorbing thermal energy due to the transition from one phase state to another (melting) and release it during the reverse transition (solidification), allows you to effectively use solar energy, the difference between night and day air temperatures, and other natural sources heat / cold, as well as "waste" industrial heat. The use of PTAM contributes to solving the urgent problem of modern scientific and technical progress - ensuring energy efficiency and energy saving, which covers almost all industrial sectors and the domestic sphere: construction industry, transport, agriculture (greenhouses), electronics, space, health care, light industry (textiles), etc. ...

From the prior art, a method is known for obtaining individual n-alkanes by separating them from liquid paraffins by the method of urea dewaxing (US4070410A, 01.24.1978). This method consists in contacting liquid paraffin with crystalline carbamide in the presence of an activator, forming a complex, washing it, heating it 2-5DC above the decomposition temperature and gradually separating individual n-alkanes.

The disadvantages of this method are the high cost of the process, the complexity of the hardware design and the limited range of melting temperatures (5-30DC) of the obtained PTAM.

There is also known a method for preparing a composition of various PTAMs consisting of mixtures of pure n-alkanes (US20160090521A1, 03/31/2016). This method consists in mixing pure n-octadecane and n-hexadecane and / or n-heptadecane in predetermined concentrations to achieve a high latent heat of fusion of PTAM.

The disadvantage of this method is the high price of the obtained PTAM, which is several times higher than the cost of commercial analogues. There is also known a method of obtaining PTAM (WO2013064539A1, 05/10/2013). This method consists in synthesizing paraffin from natural gas in the Fischer-Tropsch process, hydrogenating the resulting paraffin to remove olefins with oxygenates from it and then isolating narrow fractions from it by rectification, suitable for the production of PTAM.

The disadvantages of this method are large capital investments, low paraffin yield for raw materials and high cost of the resulting products.

The closest method is described in the information source CN103131393B, 04/08/2015. This method is carried out as follows. The fractions of petroleum paraffin, preliminarily narrowed in terms of boiling points, containing up to 16.5% of oil, are sent for rectification, first, to the first and then to the second rectification column. Both columns operate under vacuum at temperatures of 160-195DC. As a result, three fractions, which are narrower in terms of boiling points and n-alkane composition, are obtained. Then the obtained fractions are subjected to alternately deoiling by means of a sweating process, as a result of which the concentration of n-alkane hydrocarbons in them increases. At the final stage, these fractions are purified with an adsorbent to remove resinification products accumulated during high-temperature vacuum rectification. As a result, PTAM is obtained with a heat storage capacity of 130 to 180 J / g, which, after encapsulation, are used as a filler for house walls.

The disadvantages of this method are: high capital, operational, energy costs, increased consumption of adsorbent and low heat storage capacity of the resulting PTAM.

Known disc crystallizer (US2008312486A1, 18.12.2008). This crystallizer consists of a cylindrical horizontal body filled with slurry, inside of which there are cooling discs through which the refrigerant flows. The shaft is equipped with scrapers designed to remove crystallized wax deposits from the cooling surfaces of the discs.

The disadvantage of this crystallizer is that it is able to separate wide paraffinic fractions into narrower ones only when the raw material is diluted with a solvent, which requires the use of additional expensive and energy-intensive units: regeneration and drying of the solvent, vacuum filtration of the suspension, circulation of an inert gas, a refrigeration unit, etc.

A crystallizer is also known from the prior art (US6145340A, 07.16.1998). This crystallizer is intended for fractionation of paraffins, oils, fats and waxes, which, when crystallized, have poor adhesion to vertical crystallization surfaces. The device is a sealed body, inside of which there are vertical cooled and heated from the inside plates, on the surface of the plates the process of paraffin crystallization and melting proceeds. For fractionation, the paraffinic melt is first cooled at the surfaces of the plates, forming crystals that contain the desired substance. The remaining liquid phase or mother liquor drains off. Then the resulting crystals are slowly heated so that they sweat and then flow down in the form of a fraction having a lower melting point. Crystals with a higher melting point and high purity remain on the plates. Then they are melted, thus obtaining a paraffin with a higher melting point. The advantage of this device lies in its operational reliability, in the absence of moving mechanisms and in the possibility of carrying out the process without the use of a solvent.

The disadvantages of the apparatus are its size and metal consumption, a long working cycle in time, and most importantly, the impossibility of obtaining paraffin fractions with melting temperatures below 30 and above 55PS, while the consumer market requires PTAM with melting temperatures from minus 10 to 100DC. Therefore, this apparatus is used only for the production of commercial paraffins.

The closest device in design is the information source US4403868A, 09/13/1983. This device is designed for efficient mixing of liquids, including a solid phase, a kind of which is a paraffin suspension. Although it is not identified as a mold in the description of the device, it can nevertheless fulfill this function. For example, when filling this device with a liquid paraffin fraction and its subsequent cooling, a suspension will be formed, which can be separated by filtration or centrifugation into two narrower fractions, differing in melting points and n-alkane composition. The main advantage of this device is the presence of two stirrers to improve the mixing of heterogeneous solutions in the volume of the apparatus.

The disadvantages of the device, if used as a crystallizer, include: the complexity and unreliability of the design of the combined drive for two mixers, the absence of special plate elements necessary to remove paraffin deposits from the cooling surface during the crystallization of paraffin mixtures, and a device for unloading the suspension

The claimed invention eliminates the indicated disadvantages and makes it possible to achieve the claimed technical result. DISCLOSURE OF THE INVENTION

The technical problem that the proposed technical solution solves is the production of paraffinic heat-storage materials of narrow fractional (n-alkane) composition with an improvement in the economic performance of their production, using the crystallization fractionation method and the device for its implementation.

The technical result consists in obtaining paraffinic heat storage materials with a narrower fractional (n-alkane) composition, improving operational characteristics, increasing the heat storage capacity of paraffinic heat storage materials, increasing the filtration rate and clarity of separating the suspension into solid and liquid phases, preventing thickening of the suspension during its unloading, elimination of wear, deformation and breakage of plate elements, reduction of operating and capital costs, reduction of energy consumption in production, increase in operational reliability and maintainability.

The technical result is achieved due to the fact that the method for producing paraffinic heat storage materials consists of the following stages:

- on the unit of vacuum rectification, the raw material is heated in a heat exchanger and then heated in a furnace;

- feed is sent to the first rectification column equipped with stripping, a vacuum system and a refrigerator, while steam is introduced into the lower part of the first rectification column and stripping;

- a non-target n-alkane fraction is withdrawn from the top of the first rectification column and a non-target n-alkane fraction from the bottom of the first rectification column, in the form of a residue;

- the target wide n-alkane fraction is isolated in stripping and fed first to the furnace for heating, and then, as a raw material, to the second rectification column, into the lower part of which steam is introduced, equipped with a vacuum system and a refrigerator;

- the broad n-alkane fraction is divided into two fractions of the rectified and the residue in the second rectification column, which are narrower in terms of the n-alkane composition;

- obtained at the unit of vacuum rectification of the fraction of rectified and the residue are sequentially processed at the unit of adsorption treatment;

- after successive processing at the adsorption purification unit, the obtained purified and stable n-alkane fractions of the rectified product and the residue are fed for processing to the crystallization fractionation unit; - on the crystallization fractionation unit, the rectified fraction or the residual fraction is heated at 4-6 ° C above the cloud point and loaded into the crystallizer;

- upon completion of the crystallization process, the resulting suspension, at constant temperature and slow stirring, is pumped onto a membrane filter press;

- as a result of filtration of the suspension, a paraffin cake is obtained, dried with a downward flow of an inert gas and compressed with a filter press membrane;

- after drying with an inert gas and compression of the paraffin cake with a filter press membrane, the compressed cake is dropped into a heated container, where it is melted;

- then the melt of the liquid cake and the filtrate obtained earlier on the filter press are pumped out into the corresponding tanks of the commercial product park.

In the process of drying the paraffin cake with an inert gas flow, the temperature of the inert gas supplied for drying the cake is within ± 1 ° C compared to the temperature of the cake.

In the process of crystallization, the initial stage of crystallization is carried out at low values of the rate of cooling of raw materials 0.3-2.0 ° C / hour, followed by its gradual increase to 10 ° C / hour at the final stage of crystallization.

The adsorption treatment unit is located in front of the crystallization fractionation unit.

The device for the production of paraffinic heat storage materials contains a cylindrical body with an upper convex bottom-cover and a lower conical bottom-cover, a raw material input connection and an inert gas supply connection made on the upper convex cover-bottom, as well as a suspension outlet connection made in the lower part of the lower conical bottom-cover, while inside the body there are two coaxial rotating mixers, one of which is made with plate elements for radial mixing, and the second with blades for axial mixing, each of which has its own drive, while the cylindrical body of the device has an external cooling jacket equipped with a lower connection for the inlet of the circulating coolant into the inner space of the jacket and the upper connection for the outlet of the coolant, and between the plate elements of the agitator for radial mixing and the inner surface of the cylindrical body, a fixed gap is made, and the mixer for axial mixing Ania has an additional blade.

The agitator drive for radial mixing is installed on the upper bottom-cover, and the agitator drive for axial mixing is installed on the lower bottom-cover.

The agitators are made with the possibility of rotation, both in the opposite direction and in the same direction relative to each other. An additional agitator blade for axial mixing is located in the area of the slurry outlet.

A multipoint temperature sensor is located inside the cylindrical body. The radial agitator is equipped with a stiffening ring.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 - Scheme of production of PTAM according to the proposed technology;

Fig. 2 - Diagram of the crystallization fractionation unit;

Fig.Z - Scheme of production of PTAM according to known technology;

Fig. 4 - Sketch of the mold, top view;

Fig. 5 - Sketch of the mold, front view.

The figures indicate the following elements:

1 - raw material (liquid paraffin C14-C17);

2 - heat exchanger;

3 - oven;

4 - the first rectification column;

5 - stripping;

6 - a system for creating a vacuum;

7 - refrigerator;

8 - water vapor;

9 - non-target n-alkane fraction C14-C15;

10 - non-target n-alkane fraction C 17;

11 - target broad n-alkane fraction C16;

12 - oven;

13 - the second rectification column;

14 - system for creating a vacuum;

15 - refrigerator;

16 - fraction of rectified material;

17 - residue fraction;

18 - purified and stable fraction of rectified material;

19 - purified and stable residue fraction;

20 - purified and stable rectified fraction or residual fraction;

21 - crystallizer;

22 - coolant inlet fitting; 23 - coolant outlet fitting;

24 - suspension;

25 - membrane filter press;

26 - inert gas;

27 - paraffin cake;

28 - heated tank;

29 - melt of liquid paraffin cake;

30 - filtrate;

31 - cylindrical body;

32 - convex bottom-cover;

33 - conical bottom-cover;

34 - raw material input fitting;

35 - inert gas supply fitting;

36 - suspension outlet fitting;

37 - cooling jacket;

38 - stirrer for radial mixing;

39 - mixer for axial mixing;

40 - multipoint temperature sensor;

41 - rigidity ring;

42, 43, 44, 45, 46 - blades for mixing the suspension;

47 - additional blade to prevent thickening of the suspension;

ВР - vacuum rectification unit;

VR-1 - the first unit of vacuum rectification of the well-known scheme;

VR-2 - the second unit of vacuum rectification of the well-known scheme;

AO - block of adsorption cleaning;

KF - crystallization fractionation unit;

PTAM - paraffinic heat storage material.

CARRYING OUT THE INVENTION

The claimed method is described by the example of the technology for the production of four types of PTAM from a wide n-alkane fraction Cie, which is part of the commercial liquid paraffin C-Ci ₇ , obtained on a unit for selective adsorption of n-alkanes on molecular sieves.

The technological scheme includes three sequential blocks (Fig. 1): VR - vacuum rectification unit, AO - adsorption purification unit, KF - crystallization fractionation unit. Raw materials (1), for example, liquid or solid paraffin C ₁₄ -C _{17, are} first heated in a heat exchanger (2), then in a furnace (3), and sent to the first distillation column (4) equipped with stripping (5), a system for creating vacuum (6) and refrigerator (7). In the lower part of the first distillation column (4) and stripping (5), steam (8) is introduced to ensure their operation. From the top of the first distillation column (4), the non-target n-alkane fraction C ₁₄ -C ₁₅ (9) is distilled off in the form of a rectification, and from the bottom, in the form of a residue, the non-target n-alkane fraction C ₁₇ is distilled off (10). Both off-target fractions are by-products, since in this example technologies for obtaining PTAM are not used. The target wide n-alkane fraction Ci ₆ (1 1) is isolated in stripping (5) and is fed first to the furnace (12) for heating, and then, as a raw material, to the second distillation column (13), in the lower part of which is also introduced water vapor (8) equipped with a vacuum system (14) and a refrigerator (15). In the second rectification column (13), the wide n-alkane fraction Ci ₆ (11) is divided into two fractions narrower in terms of the n-alkane composition: rectified (16) and residue (17).

The fractions of the rectified (16) and residue (17) obtained at the unit of vacuum rectification (VR) are then successively processed at the unit of adsorption purification (AO) in order to increase the stability and improve the color of the fractions by removing from them the resinification products formed during the vacuum rectification.

The adsorption treatment unit is located in front of the crystallization fractionation unit. Bleaching clay is used as an adsorbent. The flow diagram of the adsorption purification unit is not shown in Fig. 1, since the technology of this process is simple, well known and often used in practice for the purification of paraffins.

The obtained purified and stable n-alkane fractions: rectified (18) and residue (19), are fed for processing to the crystallization fractionation unit (CF) (Fig. 2).

The operating mode of the crystallization fractionation unit is periodic.

At the KF unit, purified and stable fraction of rectified material or residual fraction

(20) is heated 4-6 ° C above the cloud point and loaded into the crystallizer

(21), which has an external cooling jacket, through the space of which a coolant (chemically purified water) circulates. To enter the coolant into the inner space of the cooling jacket, a lower fitting (22) is provided, and for its output - an upper fitting (23). As a result of a slow decrease in the temperature of the coolant, the turbidity of the raw material occurs, which indicates the beginning of the crystal formation process. This initial stage of the crystallization process is carried out at low values of the cooling rate of the raw material - 0.3-2.0 ° C / hour, followed by its gradual increase to 10 ° C / hour at the final stage of crystallization. This mode of regulation of the cooling rate of raw materials is necessary for obtaining large crystals of n-alkanes of regular shape, capable of easily separating from the liquid phase during further filtration of the suspension.

Upon completion of the crystallization process, a suspension (24) is formed, which, at constant temperature and slow stirring, is pumped (not shown in Fig. 2) to a membrane filter press (25). As a result of filtration of the suspension, a paraffin cake is formed, which is a compacted particles of paraffin crystals containing a certain amount of filtrate, which is dried by a downward flow of an inert gas (26) before being compressed by a filter press membrane. The temperature of the inert gas supplied to dry the cake should be within ± 1 ° C compared to the temperature of the cake. An increase in the temperature of the inert gas by more than 1 ° C above the target is undesirable, since in this case the crystals may melt and partially stick together, which will complicate the flow of the filtrate through the intercrystalline channels in the cake and will not reduce its moisture content. Reducing the temperature of the inert gas by more than 1 ° C below the target value is also not recommended, due to the possibility of the formation of new crystals in the filtrate, which will reduce the filtration rate and the clarity of the separation of the suspension into solid and liquid phases.

The low initial cooling rate of the raw material in the crystallizer and its subsequent gradual increase at the final stage of the suspension cooling, as well as the use of a downward flow of an inert gas with a clearly regulated temperature to dry the cake before it is compressed by the filter press membrane, together make it possible to obtain a PTAM with a narrower fractional ( n-alkane) composition than when using a known technology based only on the rectification process (Fig. 3).

After purging with an inert gas (26) and compressing the paraffin cake with a filter press membrane (25), the compressed cake (27) is discharged into a heated container (28), in which it is melted due to the supply of water vapor to the coil (8). Then the melt of the liquid cake (29) and the filtrate (30) obtained earlier on the filter press are pumped out into the corresponding tanks of the market of commercial products.

Both n-alkane fractions, the rectified fraction and the residual fraction, are processed in the KF unit in the same way as described above.

As a result, four types of commercial PTAM are obtained (Fig. 1) with a narrow fractional (n-alkane) composition, differing from each other in melting points and thermophysical characteristics.

In Fig.Z, for example, shows a diagram of the production of PTAM according to a well-known technology.

For the production of four types of PTAM from similar raw materials according to known technology, a scheme with three sequential blocks (FIG. 3) is also required, which differs from the proposed scheme (FIG. 1) in the composition of the blocks. The first vacuum rectification unit (VR-1) of the known scheme (Fig. 3) does not differ in technology and equipment from the vacuum rectification unit (VR) in the proposed scheme (Fig. 1), followed by the second vacuum rectification unit - VR-2 and the third block is an adsorption treatment unit (AO).

Replacement of the second block BP-2 of the known scheme (Fig. 3), the hardware composition of which includes columns, furnaces, refrigerators, vacuum creating systems, hot pumps and pipelines, and also uses fuel gas and water vapor, with the KF block of the proposed scheme (Fig. .1), allows, in addition to narrowing the fractional (n-alkane) composition of PTAM, to reduce capital, operating and energy costs for their production.

The location of the KF block at the end of the PTAM production process chain (Fig. 1), after the AO block, creates optimal conditions for obtaining high-quality PTAM with a narrow fractional (n-alkane) composition, since even the minimal presence of foreign microparticles and impurities in the raw material processed on block KF, leads to disruption of the crystallization process and is the cause of clogging of the filter surface of the filter press.

The main differences of the proposed method from analogs are that instead of the second unit of vacuum rectification, designed to separate the raw material - a wide paraffinic fraction into narrower fractions, the technology of which is based on the difference in their boiling points, a crystallization fractionation unit is used, the technology of which is based on the separation of components raw materials by their melting points. The use of the crystallization fractionation (CF) process for the production of PTAM makes it possible to obtain PTAM with a narrow fractional (n-alkane) composition while reducing the capital, operating and energy costs of production.

In this case, the block of crystallization fractionation is located at the end of the technological chain of PTAM production. The location of the KF unit at the end of the PTAM production process chain after the adsorption treatment (AO) unit (Fig. 1) creates optimal conditions for obtaining PTAM with a narrow fractional (n-alkane) composition, since the raw material processed at the KF unit should not contain foreign microparticles and impurities (even in minimal amounts), which disrupt the crystal formation process and cause clogging of the filter baffles on the filter press. Thus, the proposed location of the KF unit contributes to obtaining high-quality PTAM with a narrow fractional (n-alkane) composition and reducing operating costs for repair and maintenance of filter presses.

Moreover, the crystallization fractionation unit operates at a specially selected temperature regime at the crystallization stage and at the subsequent filtration stage - when the paraffin cake is dried with an inert gas before it is compressed by a membrane on a filter press. The specified values of the cooling rate of raw materials at the initial and the final stages of crystallization (description to figure 2), as well as the temperature of the inert gas supplied to the drying of the paraffin cake at the filtration stage, are the most important technological parameters of the KF process, allowing to obtain PTAM of a narrow fractional (n-alkane) composition.

The claimed method was implemented in laboratory conditions when obtaining PTAM from n-hexadecane fraction.

Example 1: The fraction of rectified product, isolated by vacuum distillation from liquid paraffin C14-C17, consisting mainly of n-hexadecane (C16H34) and an admixture of n-pentodecane (C15H32), is heated 4 ° C above the cloud point of the raw material and fed into the crystallizer. In the crystallizer, this fraction is cooled without speed control, but slowly so as not to miss the cloud point of the raw material, which indicates the beginning of the crystallization process. Further initial cooling of the suspension is carried out at a rate of 2 ° C / hour, and at the final stage of crystallization it increases, but not more than up to 10 ° C / hour.

Example 2: The fraction of the residue, isolated by vacuum distillation from liquid paraffin C14-C17, consisting mainly of n-hexadecane (C16H34) and an impurity of n-heptadecane (C17H36), is heated 6 ° C above the cloud point of the raw material and is fed into the crystallizer. In the crystallizer, this fraction is cooled without speed control, but slowly so as not to miss the cloud point of the raw material, which indicates the beginning of the crystallization process. Further initial cooling of the suspension is carried out at a cooling rate of 0.3 ° C / hour, and at the final stage of crystallization increases, but not more than up to 10 ° C / hour.

This temperature regime is necessary to obtain large crystals of n-alkanes of regular shape, which can easily be separated from the liquid phase.

In both described examples, the resulting suspensions in laboratory experiments were separated in a centrifuge, as a result of which two target products (PTAM) were obtained with the concentration of the target product (n-hexadecane) not less than 98 wt%.

It should be noted that the raw material heating temperatures and suspension cooling rates indicated in the above modes are selected not from the type of the processed fraction (rectified or residue), but from their melting temperatures, fractional and n-alkane composition.

Fig. 4 and Fig. 5 show a crystallizer, which is designed to separate paraffinic fractions into narrower fractions by fractional (n-alkane) composition and is a vertical apparatus with a cylindrical body (31), an upper convex bottom-cover (32), lower conical bottom-cover (33), with a feed-in connection (34) and an inert gas supply connection (35) made on the upper convex bottom-cover (32), as well as with a suspension outlet (36) made in the lower part of the lower conical bottom-cover (33), to facilitate transportation of the suspension through the drainage pipeline.

The cylindrical body of the apparatus has an external cooling jacket (37) with a lower connection for inlet of the circulating coolant into the inner space of the jacket (22) and an upper connection for the coolant outlet (23). Inside the mold body there are two rotating coaxial stirrers - for radial mixing (38), which is a group of L-shaped frame elements fixed on the upper vertical shaft and located symmetrically relative to the axis of rotation of the shaft in the cross-sectional plane of the apparatus body and along the inner cylindrical surface of the apparatus body , and for axial mixing (39), which is a group of blade elements fixed on the lower vertical shaft and located symmetrically relative to the axis of rotation of the shaft in the cross-sectional plane of the apparatus body. The individual mixers are located coaxially relative to each other with a certain pitch along the direction of the shaft axis.

The mixer for axial mixing and the mixer for radial mixing are located coaxially relative to each other and relative to the axis of the cylindrical body of the apparatus.

The agitators are set in rotation by means of two separate drives (not shown in Fig. 4), which can rotate both in opposite directions, as provided in the known device, and in the same direction relative to each other, which provides a more uniform macro and micro -stirring the suspension throughout the entire volume of the apparatus. Rotation of the stirrers in the same direction is often preferable, especially when crystallizing low-viscosity paraffinic fractions.

The agitator drive for radial mixing (not shown in Fig. 4) is installed on the upper bottom (32) of the crystallizer, and the agitator drive for axial mixing (not shown in Fig. 4) is installed on the lower bottom (33) of the crystallizer. This design of the apparatus increases its operational reliability and maintainability.

The crystallizer is equipped with a multi-point temperature sensor (40) located inside the body (at the middle radius of the body, i.e. at an equal distance from the inner cylindrical surface of the body and the axis of the apparatus), for better control and regulation of the temperature regime of crystallization in the entire volume of the suspension, which contributes to obtaining PTAM with a narrow fractional (n-alkane) composition.

The agitator for radial mixing (38) is equipped with a stiffening ring (41) and plate elements (not shown in Fig. 4) of various designs - clamped by means of springs or fixed loosely and designed to remove paraffin deposits from the inner cylindrical cooling surface of the housing (31) when no direct physical contact with the specified surface. Ring rigidity is connected to the vertical sections of the L-shaped frame elements of the mixer for radial mixing and is located at a height from a quarter to half of the length of the vertical mixer element from the lower edge of the element (the final height is determined by the strength calculation of the mixer design). The non-contact removal of the paraffin layer from the cooling surface excludes wear, deformation and breakage of plate elements, which leads to the formation of overcooled agglomerations of microcrystals. These agglomerations are poorly destroyed by stirring the suspension, which further leads to an undesirable decrease in the filtration rate of the suspension and an increase in the content of the liquid phase in the cake. Therefore, the proposed design of the mold provides for a fixed gap between the plate elements and the cooling surface. The range of values of this gap in the proposed device is 0.5 - 2 mm, which ensures reliable and uniform removal of the upper loose layer of microcrystals not associated with agglomerates. The agitator for axial mixing (39), in addition to the blades designed for stirring the suspension (42, 43, 44, 45 and 46), is equipped with a special additional blade (47) located in the area of the suspension outlet (36), which is necessary to prevent thickening of the suspension when unloading it from the crystallizer. The size, type and design of this blade may differ from the rest of the blades intended for mixing the suspension due to their different functional purposes. The agitator for axial mixing (39) can be additionally equipped with various mountings, for example, side supports (props), which serve to provide additional mechanical strength to the agitator structure.

The proposed design of the device (crystallizer), in combination with the above-described operating mode of the KF unit, makes it possible to obtain a wide range of PTAMs characterized by a narrow fractional (n-alkane) composition and high thermophysical characteristics. The design of the claimed crystallizer, in comparison with the known solution, is simple and reliable.

The mode of operation of the crystallizer (figure 4) is periodic. First, the apparatus is purged with an inert gas to exclude the formation of an explosive and fire-hazardous mixture of the n-alkane fraction with air oxygen, then it is filled with heated raw materials to the required level. After that, both mixers are brought into rotation, the number of revolutions and the direction of rotation of which are selected optimal for a particular type of raw material. Then, the circulation of the coolant is started through the cooling jacket, the temperature of the coolant is controlled using a refrigeration unit (not shown in Fig. 4) and it is lowered at a rate that provides the required temperature regime for the crystallization process, after which the resulting suspension is discharged from the crystallizer into the drain line to receive the pump (not shown in Fig. 4), which feeds it to the membrane the filter press shown in FIG. 2. During the filtration process, the operating mode of the mixers, the temperature of the circulating coolant and the temperature of the suspension in the crystallizer are kept constant.

The main differences of the proposed device (crystallizer) from analogs are that the stirrers are rotated both in opposite and in the same directions relative to each other, which provides a more uniform macro- and micro-mixing of the suspension with mixers, which is necessary to obtain PTAM with a narrow fractional (n-alkane) composition.

In this case, instead of one common drive of the mixers, two separate ones are used: the upper one for radial mixing and the lower one for axial mixing, which increases the operational reliability and maintainability of the crystallizer (Fig. 4), reduces the cost of repair and maintenance.

Moreover, the agitator for radial mixing is equipped with plate elements that are not in contact with the cooling surface, which eliminates wear, deformation and breaks of the plate elements of the radial mixer, prevents a decrease in the suspension filtration rate and deterioration of the PTAM quality. Also, the capital and operating costs for the purchase and use of additional filter presses are reduced, and the mixer for axial mixing is equipped with a special blade to prevent the suspension from thickening when it is unloaded from the crystallizer, which ensures a stable technological mode of operation of the KF unit, minimizes its downtime and reduces operating costs.

The use of the KF process, which includes a new crystallizer with greater selectivity compared to the vacuum rectification process, provides PTAM with improved performance characteristics, since a narrower fractional (n-alkane) composition improves the performance of products, in particular, by 15 -30% increase the heat storage capacity of PTAM. Due to the smaller amount of expensive and metal-intensive technological equipment (columns, furnaces, refrigerators, vacuum-creating systems, etc.), capital costs of production are reduced by 15-20%. Also, lower costs for maintenance and repair of technological equipment are provided, operating costs of production are reduced by 30-40%. In addition, the minimum amount of energy-consuming equipment (columns, furnaces, refrigerators, vacuum-generating systems, hot pumps and pipelines, etc.) provides a lower steam consumption and a smaller volume of pumping of technological streams; energy consumption during production is reduced by 40-50%.

Claims

CLAIM

1. A method for producing paraffinic heat storage materials, characterized by the fact that it consists of the following stages:

- the target wide n-alkane fraction is isolated in stripping and fed first to the furnace for heating, and then, as a raw material, to the second rectification column, into the lower part of which water vapor is introduced, equipped with a vacuum system and a refrigerator;

- after successive processing at the adsorption purification unit, the obtained purified and stable n-alkane fractions of the rectified product and the residue are fed for processing to the crystallization fractionation unit;

- on the crystallization fractionation unit, the rectified fraction or the residual fraction is heated at 4-6 ° C above the cloud point and loaded into the crystallizer;

2. The method according to claim 1, characterized in that in the process of drying the paraffin cake with an inert gas stream, the temperature of the inert gas supplied for drying the cake is within ± 1 ° C compared to the temperature of the cake.

3. The method according to claim 1, characterized in that in the process of crystallization the initial stage of crystallization is carried out at low values of the cooling rate of the raw material 0.3-2.0 ° C / hour, followed by its gradual increase to 10 ° C / hour at the final stage crystallization.

4. A method according to claim 1, characterized in that the adsorption purification unit is located upstream of the crystallization fractionation unit.

5. A device for obtaining paraffinic heat storage materials for implementing the method according to claim 1, characterized in that it contains a cylindrical body with an upper convex bottom-cover and a lower conical bottom-cover, a raw material input fitting and an inert gas supply fitting made on the upper convex bottom - the cover, as well as the suspension outlet, made in the lower part of the lower conical bottom of the cover, while inside the body there are two coaxial rotating mixers, one of which is made with plate elements for radial mixing, and the second with blades for axial mixing, each of which has its own drive, while the cylindrical body of the device has an external cooling jacket, equipped with a lower fitting for the circulating coolant in the inner space of the jacket and an upper fitting for the coolant outlet, and between the plate elements of the agitator for radial mixing and the inner surface of the cylindrical housing The mustache has a fixed gap, and the mixer for axial mixing has an additional blade.

6. The device according to claim 5, characterized in that the agitator drive for radial mixing is installed on the upper bottom-cover, and the agitator drive for axial mixing is installed on the lower bottom-cover.

7. A device according to claim 5, characterized in that the stirrers are rotatable, both in the opposite direction and in the same direction relative to each other.

8. The device according to claim 5, characterized in that the additional agitator blade for axial mixing is located in the area of the slurry outlet.

9. The device according to claim 5, characterized in that a multipoint temperature sensor is located inside the cylindrical body.

10. A device according to claim 5, characterized in that the radial stirrer is equipped with a stiffening ring.