CZ2020146A3 - Recuperative screw heat exchanger, especially for bulk materials - Google Patents

Abstract

The screw heat exchanger, especially for bulk materials, is formed by a tubular shell (1), in which a driven hollow, heat-exchanging surface forming a shaft (4) on both faces provided with holes (5) is rotatably mounted, which is welded on the outer surface into helically wound outer belt (6) for transporting heated material through the cavity (7) between the housing (1) and the shaft (4) and welded to the inner surface a helically wound inner belt (8) for transporting material transmitting sensible heat, the belts (6, 8) are wound in the opposite direction of the pitch.

Description

APPLICATION OF THE INVENTION

Published pursuant to Section 31 of Act No. 527/1990 Coll.

(22) Registered: 17.03.2020 (40) Publication Date of Published Application: 05.05.2021 (Bulletin No. 18/2021) (21) Document Number:

2020-146 (13) Document's type: A3 (51) Int. Cl .:

F28D11 / 04 (2006.01)

B65G 33/14 (2006.01)

B65G 33/30 (2006.01) (19)

CZECH REPUBLIC

INDUSTRIAL PROPERTY OFFICE (71) Applicant:

University of Mining - Technical University

Ostrava, Ostrava, Porubá, CZ (72)

doc. Dr. Ing. Bohumír Čech, Ostrava, Koblov, CZ

Ing. Zbyszek Szeliga, Ph.D., Bohumin, Skrecon, CZ

Ing. Pavel Dvorak, Ostrava, Petrkovice, CZ

Ing. Radim Fojtů, Kunčice pod Ondřejníkem, CZ (74) Representative:

Ing. Libor Markes, patent attorney, Grohova 145/54, 602 00 Brno, Veveří

CZ 2020 -146 A3 (54) Title of the invention application:

Recuperative screw heat exchanger, especially for bulk materials (57)

The screw heat exchanger, especially for bulk materials, consists of a tubular shell (1), in which a driven tube is rotatably mounted with clearance, a heat exchange surface forming a shaft (4) provided with holes (5) on both faces, which is welded on the outer surface to helically wound outer belt (6) for transporting heated material through the cavity (7) between the housing (1) and the shaft (4) and welded to the inner surface a helically wound inner belt (8) for transporting material transmitting sensible heat, the belts (6, 8) they are wound in the opposite direction to the rise.

CZ 2020 - 146 A3

Recuperative screw heat exchanger, especially for bulk materials

Field of technology

The invention relates to the construction of a screw recuperative heat exchanger, in particular for use in the production of building materials and in power engineering in the mode of heat transfer bulk material - bulk material.

Prior art

The SNCR (selective non-catalytic reduction) method is a method of reducing the content of nitrogen oxides in the emissions of power plants burning coal, biomass or waste. Ammonia water or urea is injected into the boiler furnace, while the flue gases react with nitrogen oxides at a temperature of 760 to 1000 ° C. The resulting products are molecular nitrogen, carbon dioxide and water. In addition to the denitrification reaction, the injection produces undesirable ammonia compounds which condense on the surface of the fly ash at lower temperatures to form ammonia salts. These salts limit the use of fly ash in construction, because the addition of water and any alkali, such as calcium, releases ammonia salts, which results in an unpleasant odor of the building material.

A possible solution to this problem is the chemical way of displacing ammonia salts from fly ash. However, this degrades the desired properties of the fly ash, especially its cementing properties. Another solution is the thermal displacement of ammonia salts by sublimation at temperatures from 200 to 400 ° C. Although this method does not degrade the cementing properties of fly ash important for the construction industry, the disadvantage of this is its energy intensity. The fly ash must be additionally heated to temperatures of 200 to 400 ° C and re-cooled to a level safe for storage and subsequent handling.

A similar problem occurs in the production of any bulk building material, such as cement, lime or gypsum, which emerges from the high temperature production process. This must be reduced to a safe level. The sensible heat removed by the product, eg by cooling water, is then dissipated to the surrounding environment without further use.

RU 2616630 describes a device for pyrolytic treatment of household waste, in which the material is guided by a screw conveyor through a cylindrical pyrolysis chamber, through the hollow shell of which passes a heating medium - exhaust gases of a cogeneration unit additionally heated to 1100 ° C. It is a screw heat exchanger, the construction of which, however, does not allow heat transfer between bulk materials.

From DE 3012829 a fermentation device is known, in the axis of which a vertically arranged cylindrical vessel a stirrer in the form of a screw conveyor is guided and on the wall of which a helically wound strip is wound. This arrangement only serves to perfectly mix the liquid filling of the container.

It is an object of the invention to provide a heat exchanger structure contained in a bulk material for preheating the bulk material, which can be used at temperatures up to 400 ° C.

The essence of the invention

This task is solved by a screw heat exchanger, especially for bulk materials, the essence of which consists in the fact that it consists of a tubular shell in which a driven hollow, heat exchange surface is rotatably mounted with a clearance, forming a shaft on both faces provided with holes and welded on the outer surface. a helically wound outer belt for transporting heated material through the cavity between the housing and the shaft and a helically wound inner belt welded on the inner surface for transporting the material transmitting sensible heat, the belts being wound in the opposite direction of the pitch.

CZ 2020 - 146 A3

In one embodiment, the exchanger may be provided at one end with a material inlet into the cavity between the shell and the shaft and the material outlet from the inner shaft space, and at the other end the cavity between the shell and the shaft is then connected to the inner shaft space. to heat the material.

In another embodiment, the exchanger is provided at one end with an inlet of heated material to the cavity between the shell and the shaft, as well as an outlet of sensible heat transfer material from the inner space of the shaft, and at the other end with an outlet of heated material, the inner space of the shaft being connected at the other end. for the supply of material transmitting sensible heat.

The strip wound into the helix at the other end preferably protrudes from the inner space of the shaft so as to engage in the connection of the cavity and the inner space of the shaft, respectively. into the material supply.

The cavity between the casing and the shaft may be provided with vents for the removal of gaseous products.

The shaft bearings are preferably provided with sealing air inlets.

The edges of the cavity between the housing and the shaft can be provided with intermediate rings for the supply of separating air.

The helically wound strip on the outer or inner surface of the shaft may be interrupted, in which case the sections of the strip at the rear end may be bent against the direction of rotation of the shaft, or may be provided with holes in the line of contact with the shaft.

The subject of the invention is the construction of a continuous screw heat exchanger between two bulk materials of different temperatures, which, in contrast to known types of bulk material exchangers, allows heat transfer directly between bulk materials of different temperature levels without intermediate heat transfer medium.

The basic structural element of the exchanger is a pair of strips wound in the opposite direction of the pitch welded on the outer, respectively. the inner surface of the rotating hollow shaft, which during heat exchange transport the material along the wall of the hollow shaft in opposite directions. During transport, heat is exchanged via the wall of the hollow shaft or the material is preheated from a foreign heat source.

The high heat exchanger efficiency is due to the fact that the heat exchange between the warmer and colder material takes place in countercurrent.

Explanation of drawings

The invention is further elucidated by means of the drawings, in which Fig. 1 shows in schematic longitudinal section the end sections of a screw heat exchanger, in which the bulk material is first heated from an external source to reach the temperature required to discharge unwanted impurities, and then heat is felt in the heated material. used to preheat the incoming material. Giant. 2 is a schematic longitudinal section of another embodiment of a screw heat exchanger intended for cooling a hot output bulk feedstock, e.g. in the cement industry, or in the production of lime and gypsum, and for transferring its sensible heat to the incoming material. Giant. 3 to 5 show an embodiment of a hollow shaft with an intermittent outer belt, resp. sections of the outer belt, in the exemplary embodiment according to FIG. 4 the belt sections at the rear end are bent against the direction of rotation of the shaft, and in the example according to FIG. 5 holes are provided in the line of contact with the shaft.

CZ 2020 - 146 A3

Examples of embodiments of the invention

The screw heat exchanger according to Figs. 1 and 2 is formed by a tubular shell 1, in which it is by means of two half-axles 2 - see Fig. 1, resp. by means of one half-axle 2 and a bearing 3 - see Fig. 2 a driven hollow, heat-exchanging surface forming a shaft 4 provided with holes 5 on both faces is rotatably mounted with play 5. The hollow shaft 4 has an outer strip 6 wound on a helix wound on the outer surface. of the shaft 4 for transporting the heated material to the left through the cavity 7 between the housing 1 and the shaft 4. The hollow shaft 4 has a helically wound inner belt 8 wound into a helix wound on the inner wall to transport material sensing heat to the right through the interior of the shaft 4. Belts 6, 8 they are basically screw conveyors, they are wound in the opposite direction.

In the embodiment according to Fig. 1, intended for temporary heating of the material and its subsequent cooling, the exchanger at the right end has a material inlet 9 into the cavity 7 between the casing 1 and the shaft 4 and a material outlet 10 from the inner space of the shaft 4. between the shell 1 and the shaft 4, which connects the cavity 7 with the inner space of the shaft 4. At the other end, the exchanger is further provided with an external heat source 12 for heating the material. It can be, for example, a gas burner or a heat exchanger using the waste heat of the flue gases.

In the embodiment according to Fig. 2, intended to use the sensible heat of the fired raw material, the exchanger at the right end has an inlet 9 of heated material into the cavity 7 between the shell 1 and the shaft 4 and an outlet 10 of material which has transmitted its sensible heat and falls through the opening 5 from the interior. At the left end, the exchanger has an outlet 13 of heated material from the cavity 7. The inner space of the shaft 4 is connected at this end to a supply 14 of hot material transmitting sensible heat, e.g. fired clinker from a cement kiln.

In both embodiments, the inner band 8 at the left end protrudes from the inner space of the shaft 4 so as to engage in the gap 11 and 11, respectively. material supply 14 and facilitated the entry of material into the inner space of the shaft 4.

In the case of the embodiment according to FIG. 1, the cavity 7 between the housing 1 and the shaft 4 is provided with vents 15 for the removal of gaseous products.

In both embodiments, the shaft bearings 4 are provided with sealing air inlets 16 and the edges of the cavity 7 between the housing 1 and the shaft 4 are provided with intermediate rings 17 for the supply of separating air.

In other embodiments of the invention, for example, the outer strip 6 is mounted on the outer surface of the shaft 4, resp. divided into sections - see Figs. 3 to 5. The sections of the belt 6 can then be bent at the rear end against the direction of rotation of the shaft - see Fig. 4, or holes are provided in the line of contact with the shaft 4, see Fig. 5.

In the embodiment of the exchanger according to Fig. 1, the material to be heated is fed through an inlet 9 into the cavity 7 between the shaft 4, in which the outer helical strip 6 welded on the rotating shaft 4 rotates and is moved to the left by the unheated section of the exchanger. In the end section provided with a foreign heat source 12, it is heated to the desired temperature. At the left end of the exchanger, the heated material fills the gap 11 at the end of the heated space and enters the inner space of the hollow shaft 4, where it is moved to the right 10 by the inner belt 8 with the opposite winding direction. with the cavity 7. At the same time, air containing a sublimed component, e.g. ammonia and its compounds, is discharged in this section through the vents 15 for trapping or neutralization. At the right end of the hollow shaft 4, the material falls through the hole 5 into the outlet 10 of the exchanger. To reduce dust, a small amount of sealing air is supplied to the air inlets 16 in the area of the bearings at both ends of the screw exchanger and also a small amount of separating air is supplied at the edges of the cavity 7 to the intermediate rings 17 which pressure-separate the cavity 7 from the outlet space. The screw exchanger is provided with thermal insulation 18.

CZ 2020 - 146 A3

The embodiment according to FIG. 2 represents a countercurrent heat exchanger, in which material with a higher temperature level enters the exchanger through a supply 11 of hot material and is drawn into this space by an inner belt 8 protruding from the inner space of the hollow shaft 4. As the shaft 4 rotates, the material moves from left to right via the inner belt 8, transfers its sensible heat through the wall of the hollow shaft 4, cools and falls from the exchanger through the opening 5 in the front of the hollow shaft 4 through the outlet 10.

Cold bulk material, usually a charge, is fed through an inlet 9 into the cavity 7 and is entrained in it from right to left. The preheated material exits the exchanger via an outlet 13. To reduce dust, a small amount of sealing air is supplied to the air inlets 16 in the bearing area at both ends of the screw exchanger and also a small amount of separating air is supplied at the edges of the cavity 7 through an inlet 17 into intermediate rings which pressurize the cavity. 7 from the hot material supply 14, resp. output space. The screw exchanger is also provided with thermal insulation 18.

In order to improve the heat transfer, in other embodiments of the heat exchanger, the spirally wound strips 6, 8 can be interrupted - see Figs. 3 to 5 and their sections shaped and welded to the outer, respectively. the inner surface of the shaft 4 at a suitable inclination.

They can be curved at the end, see type no. 2 or they can have 4 holes for material overflow at the point of welding to the shaft. By pouring the material over the wall of the shaft 4, the heat transfer through the wall of the shaft 4 is intensified and thus the efficiency of the exchanger is increased.

The exchanger according to the invention must be operated at temperatures above the dew point of water vapor.

The exchanger is designed in two variants:

In the embodiment according to FIG. 1, the exchanger serves to heat the bulk material to a certain desired temperature by an external heat source and to subsequently reuse the sensible heat of the cooling heated material to heat the incoming material.

In the embodiment according to Fig. 2, the exchanger is intended to use the sensible heat of the hot bulk material leaving the heat treatment device, to preheat the raw material entering this device. A typical example is the cement industry, where a high raw material feedstock needs to be cooled to a safe level.

The exchanger according to the invention is particularly suitable where it is necessary to work continuously with a larger amount of material. Such a case is in particular exchangers for the application of denitrification methods, in which the ashes leaving the combustion process must be thermally freed of ammonia salts.

Claims (10)

Screw heat exchanger, in particular for bulk materials, characterized in that it consists of a tubular shell (1) in which a driven hollow, heat-exchanging surface forming a shaft (4) provided with openings (5) on both faces is rotatably mounted, which has a helically wound outer belt (6) on the outer surface for transporting the heated material through the cavity (7) between the housing (1) and the shaft (4) and a helically wound inner belt (8) on the inner surface for transporting the material transmitting the tangible material heat, the strips (6, 8) being wound in the opposite direction. Exchanger according to claim 1, characterized in that it is provided at one end with a material inlet (9) into the cavity (7) between the housing (1) and the shaft (4) and a material outlet (10) from the inner space of the shaft (4) and at the other end the cavity (7) between the housing (1) and the shaft (4) is then connected to the inner space of the shaft (4), while at the other end the exchanger is provided with means (12) for heating the material. Exchanger according to claim 1, characterized in that at one end an inlet (9) of heated material is provided in the cavity (7) between the housing (1) and the shaft (4) as well as an outlet (10) of sensible heat transfer material from the inner space of the shaft (4), and at the other end is provided with an outlet (13) of heated material, the inner space of the shaft (4) being connected at the other end to a supply (14) of material transmitting sensible heat. Exchanger according to one of Claims 1 to 3, characterized in that the inner strip (8) projects at the other end from the inner space of the shaft (4). Exchanger according to Claim 2, characterized in that the cavity (7) between the housing (1) and the shaft (4) is provided with vents (15) for the removal of flue gases. Exchanger according to one of Claims 1 to 5, characterized in that the shaft bearings (4) are provided with sealing air inlets (16). Exchanger according to one of Claims 1 to 6, characterized in that the edges of the cavity (7) between the housing (1) and the shaft (4) are provided with intermediate rings (17) for the supply of separating air. Exchanger according to one of Claims 1 to 7, characterized in that the strip (6, 8) wound into the helix is interrupted. Exchanger according to Claim 8, characterized in that the belt sections (6, 8) are bent at the rear end against the direction of rotation of the shaft (4). Exchanger according to claim 8, characterized in that the belt sections (6, 8) are provided with holes in the line of contact with the shaft (4).