HUT70101A - A method of cooling and cleaning waste gases from an industrial process and apparatus therefor - Google Patents

Abstract

The invention relates to a method of cooling and cleaning waste gas from an industrial process wherein the waste gas under pressure is caused to pass transversely through a series of pebble bed heat exchangers, the passage of the waste gas through a pebble bed being effective to cause both heat exchange between the gases and the pebbles of the pebble bed, and also removal of a contaminant carried in the waste gas, and wherein the heated pebbles are subsequently used to transfer heat to a cooler gas. The invention also relates to apparatus for operating this method, including apparatus for cooling and cleaning waste gas from a glass melting furnace. The invention helps reduce levels of metal volatiles, oxides of nitrogen, oxides of sulphur, dioxins and particulates in the waste gas. It also makes use of the heat from the waste gas.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the cooling and purification of gases produced in industrial processes and to an apparatus for carrying out the process.

There are many industrial processes that generate hot gas or, where appropriate, a gas mixture that can be released into the open air. Often, however, it is a requirement that the heat contained in the waste gas be used to increase the temperature of the cold air that is fed and thus increase the efficiency of the whole process by supplying hot air instead of cold air. Many different heat exchangers are known and are used for such purposes.

Waste gases from industrial processes often contain a large number of impurities, possibly in the form of particles, volatile substances, metal substances, sulfur oxides, nitrogen oxides and dioxin. All of which must be removed from the waste gas before being released to the outside atmosphere. Official procedures are becoming stricter and the limits that these substances can release to the outside atmosphere are being tightened.

It is an object of the present invention to provide a process and apparatus wherein the heat exchange is effected simultaneously with the effective removal of the pollutant in the case of waste gases. According to the invention, the amount of pollutant in the waste gas is reduced to a level that is environmentally acceptable and

we release the chilled and purified gas to the outside atmosphere.

The process of the present invention is based on the use of a pebble bed heat exchanger, described in C.L. Norton Jnr, Vol. 29 of the Journal of The American Ceramic Society, 1946, issue 7, pages 187-193. pages. GB 2 225 002 is incorporated herein by reference. U.S. Pat. No. 4,123,125 discloses a solution I have previously implemented wherein a pebble bed heat exchanger is used to remove sulfur and other particles from the waste gas by flowing the waste gas upward through a chamber through which pebble or spherical balls move downward. The waste gas is then passed in an upward direction through a similar chamber where various pebbles or other spherical particles also move downward.

In its broadest sense, a pebble bed heat exchanger is considered to be a chamber comprising heat-absorbing particles that can flow through the chamber.

Experience has shown that the efficiency of the heat exchanger is not very good when using a pebble bed heat exchanger, since the gas will flow along the periphery of the pebble bed as a low resistance part in a pebble bed arrangement and thus the chamber wall and The gravel bed near the perimeter will be relatively hot, but the heat exchange in the middle of the gravel bed will be relatively small.

The present invention relates to a process for cooling and purifying waste gas from industrial processes and forcing the waste gas under pressure to flow transversely through a series of horizontally located coexistent gravel bed heat exchangers. The route of the waste gas through the gravel bed will thus be extremely efficient, providing both heat exchange between the gas and the gravel bed particles, while also removing impurities in the waste gas and using the preheated particles to with their help we transfer the heat to the cooler gas.

The process according to the invention essentially combines the purification of the waste gas with the regenerative heat exchange, thereby increasing the efficiency of the industrial process. The process according to the invention realizes the advantages it provides in a reliable manner.

The particles in the gravel bed may be static or they may be moved in a batch or continuous manner. Advantageously, the particles in the pebble bed are continuously moved by gravity.

A preferred embodiment of the invention is that at least one of the pebble bed heat exchangers produces a temperature drop in the waste gas such that certain components of the waste gas are discharged through the waste gas through this pebble bed heat exchanger. By sequentially placing a plurality of pebble bed heat exchangers, each of which removes a specific component of the waste gas, the process of the present invention essentially

breaks down the process in such a way that the individual components of the mixture of components in the waste gas can be removed separately. The waste gas particle components are removed by a pebble bed heat exchanger by settling the particles on the pebble bed heat exchanger. This deposition, for example, occurs when the temperature range at which the gas is cooled in a given bed-type heat exchanger is the condensation temperature of the volatile metal particles in that gas. The precipitated or precipitated volatile metal particles can then be removed from the pebble bed heat exchanger by depositing it on the pellets and then removing the already clean pellets from the pellet bed to the top of the pebble bed heat exchanger.

In the process of the present invention, the temperature change that is designed to pass through the waste gas through a special pebble bed heat exchanger may be such that more dirt is deposited in the pebble bed heat exchanger at the same time.

Pollutants in the waste gas can also be removed by a pebble bed heat exchanger such that a chemical reaction takes place in the pebble bed heat exchanger between the pollutant and other substances therein before the gas itself enters the pebble bed, or by reacting the pollutant in the pebble bed takes place.

For example, if the waste gas contains nitrogen oxides, they are reacted with ammonia introduced into the gravel bed heat exchanger • ·· ·

- 6 steps so that ammonia water is introduced into the heat exchanger before the waste gas is introduced into the pebble bed heat exchanger. There are temperatures where a catalyst is required to react between the nitrogen oxides (NO _X ) and ammonia. However, it is preferable to introduce the ammonia water into the pebble bed heat exchanger so that the temperature change is between 1090 ° C and 870 ° C, since the reaction between the ammonia and the nitric oxide takes place in this temperature range without the need for a catalyst. If the ammonia water is introduced into the pebble bed heat exchanger so that the temperature is outside this range, a catalyst must be introduced into the pebble bed heat exchanger to facilitate the reaction between the nitrogen oxides and the ammonia.

Lime in the form of calcium hydroxide can be introduced into an additional pebble bed heat exchanger in order to react with the acid gases in the waste gas. Lime is particularly suitable for the removal of sulfur oxides in the waste gas. Optional caustic soda or magnesium oxide may be used. The transfer of heat from the gravel bed to the cold gas can be accomplished in a manner known per se by passing the cooler gas transversely through the heated particles.

The temperature jump between the pebble beds is ensured by placing the pebble beds at a distance and filling this range with gas. This arrangement prevents heat transfer between adjacent gravel beds, while

It provides the batch operation according to the invention and also ensures that the temperature control is within the required range.

The process according to the invention advantageously cools and purifies the waste gas produced during glass production. In the process, adjacent pebble bed heat exchangers are used, in the pebble bed heat exchanger, the arrangement of granules or spherical elements comprises pebble beds such that the pellets or spherical particles in the pebble beds are able to move continuously in a vertical direction under gravity and waste gas. to flow through each successive row of gravel beds. The heat exchange between the gas and the particles in the pebble bed is carried out in each of the pebble bed heat exchangers, and the pollutants contained in the gas will be deposited in an appropriate portion of the row of pebble bed heat exchangers. Essentially, therefore, the waste gas flows through a series of gravel-bed heat exchangers and one or more impurities are deposited in each of the gravel bed heat exchangers.

The invention also relates to an apparatus for cooling and purifying waste gases from industrial processes. The apparatus comprises that the apparatus comprises a first housing and a second housing, each housing having a first and a second closure wall, and the first housing being successively and horizontally arranged with pebble bed heat exchangers, each pebble bed exchanger comprising a the second sealing member 9, which is closer to the closure wall of the first housing, is separated from the portion closest to the sealing wall, and the portion between each pair of porous filtering elements is filled with particles, and the apparatus comprises a structure, by which the waste gas is introduced between one of the side walls of the first housing and the first wall of the first of the series-connected heat exchangers, and further comprising an element between the series of sequentially-connected heat exchangers gas e and includes an element for introducing cooler gas into the preheated particulate system and heating the cooler gas in reverse order to the gravel bed heat exchangers.

In an exemplary embodiment of the apparatus according to the invention, the first housing and the second housing, and the cold gas heating means, comprise a reversing switching means for alternately directing the waste gas to the first end of the first housing and once to the first housing. cold air to the second end of the second housing, ···· ·· * ·

10 or else the cold air is led to the second end of the first housing and the waste gas to the first end of the second housing.

The invention is further exemplified. In an embodiment, the first housing is one of a three-housing arrangement, each consisting of a series of similar pebble bed heat exchangers connected in series, the three housings being arranged substantially vertically above each other, a structure for heating the cold gas. an element that transmits the particles contained in the gravel bed to the upper, middle, and lower housings on the respective successive pebble bed heat exchangers before cleaning the particles and returning them to the appropriate gravel bed of the uppermost house; an element for conveying the hot waste gas to the first end of the uppermost housing, and a means for introducing the cold gas to the first end of the lowest housing and the partially preheated gas from the second end of the lowest housing to the second end of the middle housing.

Also preferred is an embodiment of the invention wherein the first pebble bed heat exchanger particles are of refractory material, or wherein at least one pebble bed heat exchanger comprises particles having a diameter smaller than the other pebble bed heat exchanger particles.

The invention will now be described in more detail by way of exemplary embodiments in the accompanying drawings.

Figure 1 shows the gas 1 of the present invention for cleaning and heat exchanger waste gases, which is provided with a housing 2 made of refractory alumina. The housing 2 has a rectangular cross-sectional side closure walls 3 and 4, a cover plate 5 and a base plate 6. The housing 2 is provided with a tube 7 and a tube 8, which is connected to the sealing wall 3 and the tube 8 is connected to the sealing wall 4 after the last heat exchanger.

The interior of the housing 2 is divided into pores 9 and 10 in pairs, portions being arranged one after the other, as shown in FIG. Optionally, in the housing 2 itself, unlike the exemplary embodiment, where there are four porous filter element pairs 9 and 10, a plurality of filter element pairs 9 and 10 may be formed. Each of the porous filter elements 9 or 10 completely fills the cross-section of the inner surface of the housing 2, so that the gas from one end wall 3 of the inside of the housing 2 to the other end wall 4 to pass further through these porous filter elements 9 and 10.

The porous filter elements 9 and 10 are preferably made of refractory alumina in order to provide adequate resistance to the temperature that occurs. The porous filter elements 9 and 10 are provided with openings 11.

• · · · • · ·

12 On the cover 5 of the gas purifier and heat exchanger 1, above each pair of porous filter elements 9 and 10 is a funnel element 12 which guides the particles 13 in the pebble beds 19-22 and into the space delimited by the porous filter elements 9 and 10, a detached interior of the house 2 directs it downwards by gravity. In the base plate 6 of the housing 2 is located substantially opposite the funnel elements 12 and below the space defined by the porous filter elements 9 and 10 there is a drainage element 14 through which the particles 13 from the housing part between the porous filter elements 9 and 10, for example. pebble elements can be removed. The drained particles 13 are then cleaned by passing them through a slightly inclined rotating drum 15.

Each drain member 14 is connected by a pipeline 54 to the respective rotary drum 15, only one such rotary drum 15 being shown in Figure 1. thus, the resulting fractions of waste can be collected.

The movement of the spherical particles 13 or particles through the rotating drum 15 captures the collected waste. The spherical particles 13 and the deposited debris are passed through gravity through the drum 15 and then led to a filter screen 16, to which is attached a vibrator 17 which moves the filter screen 16. The sieve size of the filter screen 16 is chosen to be slightly smaller than the diameter of the spherical particles 13, so that only the contaminants will catch the filter 16.

Passing through a sieve 13 and passing through a filter sieve 16 to a vented conveyor 18 can be recycled back to the funnel member 12 and hence to the corresponding gravel bed 19-22 into the spaces between each of the porous filter elements 9 and 10.

The porous filter elements 9 and 10 may need cleaning and may need to be removed from time to time to remove dirt. This can be accomplished by removing a suitable sliding mechanism 50, which has been shown for a single porous filter element 9a.

The sliding mechanism 50 incorporates porous filter elements 9a and 10a until the porous filter elements 9 and 10 are properly cleaned. As an example! In the embodiment, four gravel beds 19, 20,21 and 22 are arranged in the housing 2.

In operation, the treatment of the waste gas from an industrial process, such as that emitted by a glass melting furnace, is effected by introducing the waste gas through a pipe 7 in the direction of the arrow 2 shown in FIG. house. In this case, the waste gas temperature can be 1400 ° C or higher. This waste gas is thus introduced into the pipe 7 and is first passed through a gravel bed 19 between the closure wall 3 and the porous filter element 9. The pressure of the waste gas in this part of the space is such that the waste gas must pass through the winding path,

located between the spherical beads 13 in the pebble bed 19 between the next porous filter element 9 and the subsequent porous filter element 10 and must also pass through the interior portion of the pebble bed 19 which is the porous filter element 10 and the next 9 porous filter element. As the waste gas passes through the gravel bed 19, heat exchange between the waste gas and the gravel bed 13 particles takes place and certain materials are deposited on the surface of the spherical particles 13 in the gravel bed 19.

The already partially cooled and partially purified waste gas passes similarly through the space inside the housing 2 and formed between the gravel beds 19 and 20, and then passes through a curved path formed by spherical particles 13 of the gravel bed 20 to the next 21 and 22 gravel beds. . Finally, the cooled and purified waste gas leaves the housing 2 via a fan 52 via a conduit 8, the direction of flow being indicated by an arrow 24.

Typically, 1-8 m ^{3 of} waste gas (at 20 ° C atmospheric pressure) can be cleaned in such a pebble bed gas purifier and heat exchanger. Of course, larger volumes can also be cleaned if larger 19-22 gravel beds or more and smaller 13 particles are placed. The only limiting factor for sufficient reaction between the surface of the particles 13 and the waste gas is that, if necessary, the outer surface of the particles 13 must be enlarged.

Thus, the total thickness of the four 19,20,21 and 22 pebble beds is preferably 50-60 cm, which means that each of the 19,20,21 or 22 pebble beds has a thickness of 12-15 cm. .

The particles 13 used in the gravel beds 19-22 are preferably made of a refractory material such as alumina, and preferably each of the particles 13 is spherical in shape with a diameter of about. 19mm. These pebble beds 19-22, which contain spherical particles 13, have been found to provide extremely good heat exchange and, at the same time, are capable of removing any particles larger than 2x10 ^-6 m in diameter.

Generally speaking, for every 10 ⁸ joules of energy that passes through, for example, a gravel bed 19, it takes about 10 minutes to clean. A particle 13 of mass 2 kg is required and must be in the gas flow path.

One or more pebble beds of other designs are also required to effectively remove particles smaller than 2 microns from the waste gas. The gravel bed 22 may be formed, for example, by about. Metal spheres with a diameter of 5 mm form the particles 13, preferably made of stainless steel. By using these metal spheres, it is possible to minimize that the particles 13 block the gravel beds 19-22.

If the particle size 13 is 19 mm, the apertures 12 on porous filter elements 9 and 10 should be selected to be slightly smaller than 17 mm in diameter, thus maximizing the flow of waste gas while at the same time preventing 13 grains go from one part to another or simply leave. The openings 11 also help to ensure that the waste gas flow on the gravel beds 19,20,21 and 22 is relatively uniform, i.e. no local gas concentrations are formed. After the waste gas passes through the gravel beds 19,20,21 and 22, the temperature of the waste gas will be less than 250 ° C, possibly even lower than 200 ° C.

By appropriately selecting the thickness of the pebble beds 19,20,21 and 22 and by selecting the composition of the granules 13 in each pebble bed 19,20,21 and 22, the temperature jump occurring in each of the pebble beds 19,20,21 and 22 can be appropriately controlled. and, at the same time, the removal of various impurities in the waste gas becomes simpler and easier. If the pebble beds 19,20,21 and 22 are properly formed, it is possible for the gas in a given pebble bed 19,20,21 or 22 to cool to a temperature which is the condensation temperature of the specially selected metal vapors in the waste gas. In this way, it is possible to ensure that a particular metal vapor is deposited in a particular pebble bed 19,20,21 or 22, and the precipitated metal or metal composition can then be recovered by cleaning the particles 13 of that pebble bed 19,20,21 or 22. thus, the various metals present in the waste gas can be separated independently from each other in the various pebble beds.

For example, as described above, zinc, iron or lead is removed

- 17 can be operated from waste gas. Each metal is deposited on different pellets 13 of different gravel beds 19,20,21 or 22, so that the apparatus of Fig. 1 also functions as a mechanical fractionator.

It is often the case that the exhaust gases contain significant amounts of evaporated metal or metal-containing material or alloys, and even nine or ten different metals may be present in the gas emission.

If the apparatus of the present invention is constructed using a limited number of 19-22 gravel beds in such cases, the first group of metals, e.g. chromium, copper or zinc is deposited in one of the 19-22 pebble beds and another group of metals such as lead and cadmium can be deposited in another pebble bed.

The waste gas from industrial processes optionally contains nitrogen oxides (NO _x ) and sulfur oxides (S0 _x ) and these gases cannot be released into the atmosphere until these N0 _x and S0 _x gases have been removed. Both NO _x and S0 _x gases can be effectively removed by passing the waste gas through a combination of gas purifier and heat exchanger shown in Figure 1. N0 _x Removal of the gas is, for example, to shift a reaction with ammonia, which ammonia is introduced into the housing 2 in a region where the temperature containing 1090 to 870 ° C, and to which ammonia water, for instance nátronszódás water is introduced, this temperature range as the reaction proceeds without a catalyst. Such a temperature range in the exemplary embodiment of Fig. 1 is in the range of the housing 2 between the 19 and 20 gravel beds. This means that ammonium-containing water is introduced into the area between housing 19 and 20 of the gravel bed, for example by means of a nozzle 25.

In a further embodiment, the waste gas flow must be effected by, for example, introducing ammonia-containing water into the gravel bed 20, since this is the range where 1090-870 ° C is provided. In this case, the water containing caustic soda is led to the pellets 13 of the pebble bed 20 before being introduced into the porous filter elements 9 and 10 of the pebble bed. Thus, in practice, the particles 13 are contacted with caustic water before being introduced into the gravel bed 20.

Similarly, the S0 _x content of the waste gas can be removed by contacting the particles 13, for example, in the form of calcium hydroxide with lime, before being introduced into the appropriate pebble bed 19-22, where the temperature is already preferably in the range of 600-400 ° C. You can also use caustic soda or magnesium oxide to reduce the S0 _x content.

The gravel bed arrangement of the present invention may also be used for other treatment of waste gas. If, for example, the particles 13 are made of stainless steel and coated with a slight acidic solution such as hydrochloric acid to remove excess ammonia in the gas. In a similar way • ♦ ♦♦

Alkaline solutions 19 may be used on the particles 13 to completely remove the S0 _x content. Optionally, water may be injected into the waste gas into the space between the two successive gravel beds, thereby removing the last of the alkaline batteries. Any remaining water or aerosol residues can be removed by the use of an evaporator.

In addition, a number of purification stages may be provided which result in the final purification of the gas and allow the combined apparatus of the present invention to function as intended. The pellets 13, which can be spherical balls, for example, pass relatively slowly through a pebble bed 19-22 at a rate of 4-9 kg / h.

The combined gas purifier and heat exchanger 1 according to the invention and shown in Fig. 1 should be periodically reversed, preferably at intervals of 1-1.5 minutes, and opposed by means of a switch. In this case, the waste gas from the industrial process is provided by a valve 53, also provided with a reversing switch, to transfer the waste gas to a second similar heat exchanger and gas cleaning arrangement, while utilizing the apparatus shown in FIG. Usually, 8 tubes are used to introduce and heat cold air at ambient temperature of 20 ° C. The already heated air is then removed from the housing 2 via the pipe 7 after passing through the beds 22, 21, 20 and gravel. Experience has shown that, by using the gravel bed arrangement of the present invention in this way, cold, ca. The air at 20 ° C can be heated to a temperature substantially equal to 90% of the temperature of the waste gas introduced into the housing 2.

A further exemplary embodiment of the invention is shown in Figure 2. In the embodiment shown in Figure 2, there are three housings 26,27 and 28 which are vertically superimposed. Each housing 26,27 and 28 is configured so that air flows through them in the longitudinal direction, that is, as shown in the embodiment of FIG. Similarly, each housing 26,27 and 28 is subdivided into pebble beds 2940, but each pebble bed 29-40 is formed of elements that flow vertically from one housing 26 to another housing 27 such as freeboard. Each housing 26,27 and 28 is provided with four pebble bed portions similar to the pebble beds 19,20,21 and 22 shown in Figure 1. The pebble beds 22,30,31 and 32 are housed in the housing 2 6, the pebble beds 33,34,35 and 36 are housed in the housing 27 and the pebble beds 37, 38,39 and 40 in the housing 28. The other elements are substantially the same as the layout shown in Figure 1, and are not shown here.

In the exemplary embodiment, the particles 13, which are fed to the housing 26, are subsequently fed to the housing 27 and 28 as well.

- 21 are led through before we get out of the 28 houses • 9 · 4 · 9 · 9 · · · · · · · · · · · · · · · · · · · · · · · · · · ·

22 and cleaned back to the second section above housing 26 as shown in FIG. Thus, the particles 13 used in the pebble bed 29 for cooling and purifying the waste gas in the apparatus 26 are thus used. The particles 13 are then guided further through a coupling member 41 to the housing 27 where they form a gravel bed 23 and from there through a coupling member 42 to the housing 28 where they form a gravel bed 37. Similarly, portions of housing 27 and 28 are connected to elements of housing 26, namely, gravel beds 30,31 and 32 with gravel beds 34,35 and 36 in housing 27, which are formed to form gravel beds 38, 39, and 40 in housing 28. The housing 26 forms a combined gas purifier and heat exchanger 43 which operates in a manner similar to the embodiment shown in Figure 1 and which cools the waste gas. The housings 27 and 28 together form a heating part of the apparatus in which the cold air is heated and the particles 13 cooled. Cold air having a temperature of 20 ° C or less is introduced into the housing 28 via a tube 44 such that the cold air is in direct contact with particles 13 of the pebble bed 37, which is one of the pebble beds 37,38,39 and 40 the highest temperature and thus these particles can cool down to a great extent. The heated air is then passed through the gravel beds 38, 39, and 40, each of which has a lower temperature, and thus the air discharged from the housing 28 to the pipe 45 is otherwise introduced * · • · · · 9 ·

- It is only partially heated to 23 gas temperatures. This partially heated air is then introduced through the tube 46 into the housing 27, first into the gravel bed 36 and then into the gravel bed 35.34 and 33, where the air temperature is 80 to 90% of the waste gas introduced into the housing 26. already reaches, and this air is then routed through the conduit 47.

With the combined gas purifier and heat exchanger shown in Figures 1 or 2, the waste gas purification can be carried out in a very fast manner in a series-connected gravel bed arrangement. This is important in order to ensure that the dioxin is also decomposed. It is known that dioxin decomposes on combustion, but the elements of dioxin are still present in the gas when cooled by known cooling systems. If cooling is not fast enough, these elements have the potential to recombine and re-create dioxin. In contrast, with the combined gas purifier and heat exchanger 1 and 43 of the present invention, the cooling of the waste gas is effected efficiently and rapidly enough, without leaving time for the dioxin to recombine.

The invention is described by way of example only. In its embodiment, the high temperature (1400-250 ° C), the gravel bed arrangement used in these arrangements serves both to recover heat and to transfer the waste gas and acts as a primary purification and decontamination system. In the embodiment shown in Figure 1 ···

24, the flow direction of the gravel bed heat exchanger is reversible by utilizing valve 53 as a reversing switch and utilizes an extremely high efficiency unit to heat the supply air from the cooling and purification mode and operates at significantly better efficiency than the return systems are in a known regeneration furnace. In the embodiment shown in Fig. 2, there is even an advantage over the one shown in Fig. 1, that no reversing valve is required, and thus any difficulties associated with the operation of such valves can be completely eliminated.

The present invention has been described to purify the gas emitted by glass furnaces where 90% of the particles larger than 2 microns in diameter can be removed in this way, and the NO _x gases can be reduced by 80% in a non-catalytic manner at a temperature of 870-1090 ° C. so that the excess ammonia was removed from the system. Various impurities, including the heaviest impurities, such as lead, in the form of oxides and / or sulfates, were also able to be captured by the system and sodium sulfate was also captured. A significant portion (50% or more) of the sulfur present as sulfate by gas emission was also filtered out, and the remaining sulfur dioxide was removed by the known lime, caustic soda or magnesium oxide treatment, which was introduced into the pebble bed heat exchanger.

In the process of the present invention, the process comprises:

For 25 implementations, the pressure change through the gravel beds 19-22 and 29-40 is approx. 3 kPa, it was found that 98% of the particles larger than 20 microns in diameter, 15% of the particles larger than 10 microns in diameter, 90% of the particles of 8-10 microns in diameter and 2 to 8 microns in diameter. we can completely filter out 60% of the particles. The particle diameter of the non-melted material and contained in the waste gas is greater than 2 microns. Particles with a diameter of less than 2 microns are evaporated metal particles and metal alloys, less than 50% of which are separable by physical settling and then separated after condensation.

The process of the invention and the apparatus implementing the process can operate over a very wide range of pressures, thus eliminating the need for various venturi systems or other pressure relief devices. The point is that the gas passing through the gravel bed must be adequately pressurized.

Claims (15)

Claims CLAIMS 1. A method for cooling and purifying waste gas from industrial processes, wherein the waste gas is passed through pressurized gravel bed heat exchangers at successive distances such that heat is exchanged between the gas and the pebble bed during flow of the waste gas through these heat exchangers. however, impurities in the waste gas are also removed and the heated particles are used to heat the cold gas. Method according to claim 1, characterized in that the particles in the gravel beds are continuously moved downwards by gravity. 3. The method of claim 1 or 2, wherein at least one of the heat exchangers generates a temperature surge in the waste gas that removes particulates from the waste gas as it passes through said heat exchanger. 4. The process of claim 3, wherein the particles that are removed from the waste gas during passage through the gravel bed are volatile metal particles having a precipitation temperature equal to a change in temperature within this range and the volatile metal particles being at least one of are settled in a pebble bed heat exchanger. 5. The method of claim 3, further comprising introducing into said at least one heat exchanger material to remove at least one selected component of the waste gas. 6. A process according to claim 5, wherein the particles in the heat exchanger are fed with ammonia water to the gravel bed heat exchanger. The process of claim 6, wherein the temperature change in at least one of the pebble bed heat exchangers is in the range of 1090-870 ° C. The process of claim 5, wherein at least one of the pebble bed heat exchangers is fed with caustic soda or magnesium for reaction with acidic gases. 9. A method for purifying waste gas from glass making comprising placing a plurality of gravel bed heat exchangers side by side, moving the particles in each of the gravel bed heat exchangers substantially vertically with the gravitational space, flowing the waste gas horizontally under pressure through each of the series of gravel bed heat exchangers and generating a heat exchange between the pellets in the pebble bed heat exchanger and removing at least one of the predetermined impurities in the waste gas in at least one of the pebble bed heat exchangers and transferring the heated pellets to a cooler gas after use. • · Apparatus for cooling and purifying waste gases from industrial processes, characterized in that the apparatus comprises a first housing (2) and a second housing 26), each housing having a first and a second closure wall (3,4), and a first housed (2) successively and horizontally arranged in a pebble bed heat exchanger, each pebble bed heat exchanger comprising a porous filter element (9,10) which is a portion of the first housing (2) closer to the first sealing wall (3), which is closer to the second barrier wall (4), is separated and the portion between each pair of porous filter elements (9,10) is filled with particles (13), and the apparatus comprises a device by means of which the waste gas is side wall and the first one of the sequentially connected heat exchangers between the first wall and an element which ely discharges gas from the last of the sequentially connected heat exchangers from the last to the other end wall (4) of the housing and includes an element for introducing cooler gas into the preheated particle system and heating the cooler gas flow through the gravel bed heat exchangers in sequence. Apparatus according to claim 10, characterized in that the first housing and the second housing and the cold gas heating means comprise a reversing switching means for alternately guiding the waste gas to the first end of the first housing (2) alternately. and the cold air - 29 ·· * · ·· ····························································· · it is cold air 9 ··· • · · ··· «« · • · ♦ * ·· «· 4 4 · • · · · · · · · · · · · · · · · · · · · · - guides 30 to the second end of the first housing (2) and discharges the waste gas to the first end of the second housing. Apparatus according to claim 10, characterized in that the first housing (2) is one of an arrangement of three housings (26,27,28) each consisting of a series of similar pebble bed heat exchangers connected in series, 27,28) arranged substantially vertically above each other, the structure for heating the cold gas comprises an element which transmits the particles contained in the pebble bed (29-40) to the corresponding successive pebble bed heat exchangers, in the center and bottom housing (26,27,28), before purifying the particles and returning it to the appropriate gravel bed (29-31) of the uppermost housing, the apparatus is provided with an element which provides hot waste gas to the uppermost housing (26). ) to a first end thereof, and a device for supplying the cold gas to the first end of the lowest housing (28) and the partially preheated gas to the lowest end leading from the second end of the housing (28) to the second end of the central housing. 13. A 10-12. Apparatus according to any one of claims 1 to 4, characterized in that the particles (13) forming the first pebble bed heat exchanger are made of refractory material. 14. A 10-13. Apparatus according to any one of claims 1 to 4, characterized in that at least one pebble bed heat exchanger comprises particles having a diameter smaller than the diameter of the other pebble bed heat exchanger. 15. A 10-14. Device according to any one of claims 1 to 6, characterized in that the particles in at least one of the gravel bed heat exchangers are made of a material which, in response to one of the contaminants in the waste gas, removes the dirt therefrom in this gravel bed heat exchanger.