CZ2019252A3 - Heat recovery plate heat exchanger - Google Patents

Abstract

The recuperative plate heat exchanger consists of at least two parallel, identically oriented and spaced-apart heat exchange walls (1), each of which is formed by two trapezoidal plates (2), with alternating grooves (3) and fins (4), bevelled by their face surfaces so that the lamellae (4) of the two plates (2) touch and the grooves (3) form channels (5) for the passage of the second medium, while the space (6) between the heat exchange walls (1), which is blinded around the entire circumference , serves for the passage of the first medium, wherein an opening (7) for the passage of the first medium is formed in the lamellae (3) of the heat exchange walls at each end of the lamella (4) and wherein the plates (2) of each pair are at the side edges (8) (9) the openings (7) are gas-tightly connected and the blind contact (10) with the heat exchange walls (1) is sealed.

Description

Recuperative plate heat exchanger

Field of technology

The invention relates to the construction of a plate heat exchanger for gaseous working media, in particular for use in flue gas-flue gas or air-flue gas energy. It is a recuperative heat exchanger usable especially in reducing NO _X emissions in flue gases by the SCR method in the "Tail End" variant, ie in purified and desulphurised flue gases. The exchanger can also be used to preheat combustion air during combustion processes. The invention falls into the field of thermal energy, flue gas cleaning and catalytic reduction of NO _X emissions.

Prior art

Currently, when using selective catalytic reduction (SCR) of NO _X emissions, two basic types of heat recovery exchangers are used, i.e. to increase and subsequently decrease the flue gas temperature for an efficient reaction on the catalytic bed. They are regenerative and recuperative exchangers.

Regenerative heat exchangers are of the rotary type, known as Ljungstróm. They are filled with a mass of corrugated sheets placed vertically in baskets on a rotating shaft, where hot medium is fed to one circular section into the exchanger and on the other hand cold medium is fed to the other circular section, usually as countercurrent, for heating. The means of heat exchange between the media is the mass of the charge, which is heated on one side and transfers heat to the other medium on the other. With these types of heat exchangers, leaks occur due to moving parts, which impair the resulting efficiency.

Recuperation exchangers are used of tubular, plate or pocket constructions. The tubes can be smooth, ribbed or otherwise shaped to improve heat transfer and increase the heat transfer area. The efficiency of the exchangers is determined by the size of the heat exchange surface and the method of design solution of the supply of individual media - hot and cold - to the exchanger. With regard to the weight of the exchanger and material costs, the size of the exchanger and thus the efficiency cannot be increased indefinitely, and exchangers of this type are always a compromise between the price and the achieved parameters.

Plate heat exchangers are known, the structural element of which are trapezoidal sheets; these are mainly radiators for heating rooms. GB 1238491 discloses a plate heat exchanger formed by a bundle of adjacent plates, the middle zone of which in the direction of flow of the media is trapezoidal corrugated, the end zones being smooth. The waves in the trapezoidal zone of two adjacent plates are offset from each other and, after the plates abut one another, form alternately channels for the passage of one and the other medium. One medium is fed to and discharged from the exchanger in the direction of the channels and the other is fed sideways into one end zone and is discharged from the other end zone. The heat exchanger made of plastic is designed for small amounts of air with a relatively low temperature.

It is an object of the present invention to provide a heat exchanger construction of affordable elements for use in the power industry for heat exchange between gaseous media in large volumes and temperatures up to 300 ° C.

The essence of the invention

This task is solved by a recuperative plate heat exchanger, the essence of which consists in that it consists of at least two parallel, identically oriented and spaced apart heat exchange walls, each of which consists of two trapezoidal plates, with alternating grooves and lamellae, bevelled by their faces. surfaces so that the lamellae of both plates touch and

- 1 CZ 2019 - 252 A3 grooves form channels for the passage of the second medium, while the space between the heat exchange walls, which is blinded around the entire circumference, serves for the passage of the first medium, an opening for the passage of the first medium being formed in the lamellae of the heat exchange walls media and wherein the plates of each pair are gas-tightly connected at the side edges and around the perimeter of the openings and the blind contact with the heat exchange walls is sealed.

To prevent deformation of the heat exchange walls and to encourage turbulence in the flow of the first medium, spacers can be inserted between the heat exchange walls.

The channels in the heat exchange wall open at the ends to the supply or the discharge pipe of the second medium and the opening in the lamellas of the extreme heat exchange walls open into the supply, resp. discharge heads of the first medium.

In a preferred embodiment of the heat exchanger, the baffle nozzles protrude from the supply head by a freely passing series of holes in the lamellae for directing the first medium into the spaces between the heat exchange walls.

For cleaning purposes, the spaces between the heat exchange surfaces on the side can be provided with closable cleaning openings at the lowest point.

Explanation of drawings

The invention will be further elucidated by means of the drawings, in which Fig. 1 shows in axonometric projection a section of two adjacent heat exchange walls according to the invention, Fig. 2 is the whole heat exchange wall, also in axonometric projection, Fig. 3 is a blinding of the space between the heat exchange walls. Fig. 4 is a top view of the filler of the heat exchanger according to the invention, Fig. 5 is the supply head of the first medium with baffle nozzles and Fig. 6 is a complete exchanger provided with a jacket, the arrows indicating the inlet and outlet of the media.

Examples of embodiments of the invention

The heat exchanger according to the invention, the overall shape of which is shown in Fig. 6, is formed by a bundle of parallel, identically oriented and spaced apart heat exchange walls 1. Each of these walls 1 - see Fig. 1 - is formed by two trapezoidal plates 2, namely trapezoidal sheets, with alternating grooves 3 and lamellae 4. The plates 2 are chamfered by their faces so that the lamellae 4 of the two plates 2 touch and the grooves 3 form channels 5 for the passage of the second medium. In this case, the space 6 between the heat exchange walls 1 serves for the passage of the first medium. An opening 7 for the passage of the first medium is formed in the lamellae 4 of the heat exchange walls 1 at each end of the lamella. The plates 2 of each pair are gas-tightly connected at the side edges 8 and around the circumference 9 of the openings 7 and the contact of the blind 10 with the heat exchange walls 1 is sealed.

The channels 5 in the heat exchange wall 1 open at both ends into the supply or the discharge line of the second medium. These pipes are not shown in the drawing. The openings 7 in the lamellae 4 of the extreme heat exchange walls 1 open into the feeder, resp. discharge heads 11, 12 of the first medium - see Fig. 6. From the supply head 11 protrude rectifying nozzles 13 freely passing through a series of holes 7 in the lamellae 4 to direct the first medium into the spaces 6 between the heat exchange walls L

To prevent deformation of the heat exchange walls and to encourage turbulence in the flow of the first medium, spacers can be inserted between the heat exchange walls.

For cleaning, the spaces 6 between the heat exchange walls 1 on the side at the lowest point can be provided with closable cleaning openings.

-2EN 2019 - 252 A3

The newly proposed design differs from other types of heat exchangers in that it consists of conventional rolled thin-walled profiles of the trapezoidal type folded flat in pairs and joined in a suitable manner to achieve the required tightness.

Rolled sheet metal profiles are commonly produced in lengths of 6 to 12 meters and the final price of these profiles is favorable compared to pipes and other profiles. In addition, the described construction is characterized by adequate rigidity, which allows easy assembly and handling. Any major leaks can be removed by blinding the appropriate vent.

The basic part of the exchanger is a pair of trapezoidal sheets folded so that the emerging waves protrude against each other. The pairs of sheets are joined longitudinally on the longer sides to each other by welding, soldering, gluing or other suitable tight sealing. In this way, all pairs of trapezoidal sheets, which are the structural basis of the exchanger, are connected. In these pairs, rectangular holes 7 are cut at both ends, the edges of which are gas-tight welded, soldered or glued. This pair of sheets then forms the basic building block of the exchanger - the heat exchange wall 1.

At both ends of each pair thus formed, i.e. on both its shorter sides, the space between them is blinded by a suitably shaped sheet metal - by blind 10 see Fig. 3, which can be welded, soldered or tightened by screw connection and glued. Similarly, the spaces 6 between the pairs are blinded on the sides. Subsequently, these elements are assembled side by side and form the structural basis of the exchanger.

The supply of the second - hot medium (flue gas) intended for cooling in the exchanger opens into the inlets of the channels of 5 trapezoidal sheets. Cooled flue gases are discharged from the other opposite side of the trapezoidal sheets. The first medium - air or flue gases to be heated - is fed from the side into the rectangular openings 7 formed at the end of the trapezoidal sheets. For the supply of the heated medium, a supply head 11 provided with nozzles 13 for dividing the medium into spaces 6 between the pairs of trapezoidal sheets is intended as a special inlet part. These nozzles 13, the profile of which coincides with the shape of the rectangular openings 7 and their number with the number of rows of openings 7, form the inlets of the first cold medium. They are inserted into the holes 7 in the trapezoidal pairs of sheets and sealed on the side wall of the exchanger by welding, soldering or gluing.

The same adjustment is made at the opposite end of the exchanger. Inside the exchanger, these nozzles 13 do not have to be sealed in the openings 7, and thus can be made with sufficient clearance for mounting. The distribution of the heat exchange walls 1 along the cross-section of the proposed heat exchanger can be seen in Fig. 4. With larger heat exchanger dimensions, spacers made of flat steel strips can be inserted between the pairs of connected trapezoidal sheets, which secure the sheets against undesired deformation and at the same time

This construction differs significantly from the previous design of recuperative heat exchangers. The individual plates of the trapezoidal sheet metal have the same shape and significantly simplify serial production and assembly. The more complex inlet and outlet parts of the heat exchanger can currently be manufactured with sufficient accuracy and reliable function.

The advantage of the proposed solution is the almost ideal countercurrent solution of the exchanger, which ensures high efficiency of use and heat recovery. Trapezoidal sheets are commonly rolled, different types and different thicknesses of material can be used. Production costs are significantly lower than for tube heat exchangers. Repeated production of identical parts of trapezoidal sheets reduces production costs.

Cleaning and inspection of the exchanger can be performed through inspection holes in the inlet and outlet part of the exchanger. The exchanger is completely assembled in the production plant and can be transported to the construction site as a whole.

This type of heat exchanger is especially suitable where it is necessary to work with large volumes of flue gases or air for preheating or temperature reduction. Such a case is especially exchangers

-3 CZ 2019 - 252 A3 for flue gas denitrification methods by the system of selective catalytic reduction of SCR on catalysts operating at temperatures of 200 to 300 ° C, where the flue gases must first be heated to the required temperature and then cooled to the flue gas outlet to the chimney or cooling tower. Minor heat losses are compensated by steam heating or additional burners for gaseous or liquid fuel.

Another possible use of the heat exchanger according to the invention is for preheating the combustion air supplied to the combustion processes or for other technological processes working with predominantly clean media, e.g. The condition is operation above the dew point of air and gases.

Claims (5)

PATENT CLAIMS Recuperative plate heat exchanger, characterized in that it consists of at least two parallel, identically oriented and spaced-apart heat exchange walls (1), each of which is formed by two trapezoidal plates (2) with alternating grooves (3) and lamellae (4), bevelled with their faces so that the lamellae (4) of the two plates (2) touch and the grooves (3) form channels (5) for the passage of the second medium, while the space (6) between the heat exchange walls (1) ), which is blinded around the entire circumference, serves for the passage of the first medium, an opening (7) for the passage of the first medium being formed in the lamellae (3) of the heat exchange walls at each end of the lamella (4) and the plates (2) of each pair being the side edges (8) and the circumference (9) of the openings (7) are gas-tightly connected and the blind contact (10) with the heat exchange walls (1) is sealed. Heat exchanger according to claim 1, characterized in that spacers are inserted between the heat exchange walls (1). Heat exchanger according to Claim 1 or 2, characterized in that the channels (5) in the heat exchange wall (1) open at the ends into the supply and / or heat exchangers. of the second medium discharge pipe and the openings (7) in the lamellae (4) of the extreme heat exchange walls (1) open into the supply resp. discharge heads (11, 12) of the first medium. Heat exchanger according to claim 3, characterized in that rectifying nozzles (13) protrude from the supply head (11) freely passing through a series of openings (7) in the fins (4) to direct the first medium into the spaces (6) between the heat exchange walls ( 1). Heat exchanger according to one of Claims 1 to 4, characterized in that the spaces (6) between the heat exchange surfaces (1) are provided on the side at the lowest point with closable cleaning openings.