MXPA00010726A - Web dryer with fully integrated regenerative heat source - Google Patents

Abstract

Integrated web dryer (10) and regenerative heat exchanger (20), as well as a method of drying a web of material using the same. The apparatus and method of the present invention provides for the heating (22) of air and the converting of VOC's to harmless gases in a fully integrated manner via the inclusion of a regenerative combustion device as an integral element of the drying apparatus.

Description

FLOOR DRYER WITH COMPLETELY INTEGRATED REGENERATIVE HEAT SOURCE FIELD AND BACKGROUND OF THE INVENTION The control and / or elimination of undesirable impurities and byproducts from several production operations have gained considerable importance in view of the potential contamination that impurities and by-products can generate. A conventional approach to eliminate or at least reduce these contaminants is by thermal oxidation. Thermal oxidation occurs when heated contaminated air that contains enough oxygen at too high a temperature and for a sufficient length of time to convert the undesirable compounds into harmful gases such as carbon dioxide and water vapor. Control of the screen drying apparatus, including float dryers capable of withstanding less contact and drying a movable web of material, such as paper, film or other sheet material, via hot air exiting from a series of nozzles for Ref: 124452 typically opposite air, requires a heat source for hot air. Additionally, as a result of the drying process, volatile, undesirable organic compounds (VOCs) can be emitted from the web of moving material, especially where the drying is from an ink coating or the like on the plot. Such VOCs are required by law to become harmful gases prior to release to the environment. The flotation drying apparatus of the prior art has been combined with various incinerator or afterburner devices in a separating manner in which the hot oxidized gases are recovered from the outlet of the thermal oxidant and returned to the drying device. These systems are not considered fully integrated due to the separation of oxidizing components and dryers and the requirements of the additional heating device in the drying room. Other systems of the prior art combine a thermal-type oxidant integrally within the drying enclosure, also using volatile malodorous gases from the weft material as a fuel. However, this so-called straight thermal combustion system does not use any kind of means or heat recovery device and requires relatively high amounts of supplemental fuel, especially in cases of low concentrations of volatile malodorous gases. Still other prior art apparatuses combine a flotation dryer with the so-called thermal recuperative type oxidant in a truly integrated mode. A disadvantage of these systems is the limitation of heat recovery effectiveness due to the type of heat exchanger employed, thus preventing the extremely low supplemental fuel consumption capabilities and which frequently avoid any autothermal operation. This limitation in effectiveness results from the fact that a high efficiency heat exchanger will preheat the incoming air at too high temperatures to cause accelerated oxidation of the heat exchanger tubes which result in tube failure, leakage, reduced efficiency and destruction of volatile products. In general, the thermal recovery type device has a reduced reliability of system components such as the heat exchanger and burner due to exposure of metal to high temperature service performance. Yet another completely integrated system uses a catalytic co-bustor to convert malodorous gases and has the power to provide all the heat required for the drying process. This type of system can use a highly effective heat exchanger because the presence of a catalyst allows oxidation to occur at low temperatures. Thus, even a high efficiency heat exchanger can not preheat the inlet air to harmful temperatures. Nevertheless, a catalytic oxidant is susceptible to poison the catalyst by certain components of malodorous gases, so it becomes ineffective in the conversion of these malodorous gases to harmful components. Additionally, catalytic systems typically employ a metal-type heat exchanger for primary heat recovery purposes, which has a limited service life due to performance during high temperature service. For example, the North American Patent No. 5,207,008 discloses an air flotation dryer with a movable afterburner. The solvent charged air that results from the drying operation is directed past a burner where the volatile organic compounds are oxidized. At least a portion of the resulting heated burned air is then recirculated to the air nozzles to dry the floating web. U.S. Patent No. 5,210,961 discloses a screen dryer that includes a burner and a recuperative heat exchanger. EP-A-0326228 discloses a compact heating device for a dryer. The heating device includes a burner and a combustion chamber, the combustion chamber defining a U-shaped path. The combustion chamber is in communication with a recuperative heat exchanger.

In view of the high cost of the fuel necessary to generate the heat required for oxidation, it is advantageous to recover as much heat as possible. For this purpose, US Pat. No. 3,870,474 describes a thermal regenerative oxidant comprising three regenerators, two of which are in operation at any given time while the third receives a minor purge of purified air to force any untreated or contaminated air. from this and discharge into a combustion chamber where the contaminants are oxidized. At the completion of a first cycle, the flow of contaminated air is reversed through the regenerator from which the purified air is previously discharged, to preheat the contaminated air during the passage through the regenerator prior to its introduction into the chamber. combustion. In this way, heat recovery is achieved. U.S. Patent No. 3,895,918 discloses a thermal rotating regeneration system in which a plurality of spaced, non-parallel heat exchange beds are arranged towards the periphery of a central, high temperature combustion chamber. Each heat exchange bed is filled with ceramic heat exchange elements. The exhaust gases from industrial processes are supplied to an inlet duct, which distributes the gases to the selected heat exchange sections depending on whether an inlet valve for a given section is open or closed. It may be desirable to take advantage of the efficiencies achieved with regenerative heat exchange in air flotation dryers.

BRIEF DESCRIPTION OF THE INVENTION The problems of the prior art have been overcome by the present invention, which provides an integrated screen dryer and regenerative heat exchanger, as well as a method of drying a web of material using it. The apparatus and method of the present invention provide for air heating and the conversion of VOCs to malodorous gases in a fully integrated form via the inclusion of a regenerative combustion device as an integral element of the drying apparatus. In one embodiment, the dryer is an air flotation dryer equipped with air rods that with less contact support the path of travel with hot air from the oxidant.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic representation of one embodiment of the apparatus and process of the present invention; Figure 2 is a perspective view of a monolithic bed according to the present invention; Figure 3 is a schematic representation of a second embodiment of the present invention; Figure 4 is a schematic representation of a third embodiment of the present invention; Figure 5 is a schematic representation of a fourth embodiment of the present invention; Figure 6 is a schematic representation of a fifth embodiment of the present invention; Figure 7 is a schematic representation of a single or single bed regenerative oxidant integrated with a dryer; and Figure 8 is a schematic representation of the single bed regenerative oxidant of Figure 7.

DESCRIPTION OF THE INVENTION Fundamental to the realization of a fully integrated dryer and regenerative thermal oxidation device is the requirement that all the energy needed for the drying process is derived from the combustion and conversion of the VOCs released with little or no added fuel. In accordance with the present invention, it is possible to achieve an autothermal or self-heating process mode. Many of the VOCs are exothermic in the chemical reaction and as such can be considered as fuel in an integrated system that displaces supplemental fuel, such as natural gas. The resulting apparatus provides sufficient effectiveness to recover high heat to provide an autothermal condition, or at least a too minimal supplemental fuel input, in a controlled and sustained manner with high component reliability and almost complete conversion of volatile, undesirable malodorous gases, to harmful components. Turning now to Figure 1, a single-zone flotation dryer 10 with an integrated regenerative thermal oxidant is shown schematically. The flotation dryer 10 includes an input slot of the frame 11 and an exit slot of the frame 12 spaced from the input slot of the frame 11, through which a path of travel 13 is driven. In the dryer 10, the path of travel is supported in a floating manner by a plurality of air bars 14. Although preferably the air bars 14 are placed in opposite staggered relationship as shown, those skilled in the art will recognize that others are possible. arrangements To achieve good flotation and high heat transfer, the 1 commercially available HI-FLOAT® air bars from MEGTEC Systems are preferred, which cause the weft 13 to float in a sinusoidal path through the dryer 10. Improved drying can be achieved by incorporating infrared heating elements in the drying zone. The upper and lower air rod assemblies are in communication with respective headers 16, 16 ', each of which receives a source of hot air via the supply fan 17, and directs it to the respective air rods 14. A Fill air regulator 25 is provided in communication with fan 17 to supply fill air to the system where necessary. Those skilled in the art will appreciate that although a flotation dryer is illustrated, dryers in which non-contact weft support is not necessary, are also included within the scope of the present invention. The regenerative oxidant 20 that is integrated with the dryer 10 is preferably a two-column oxidant, although a column (Figures 7 and 8) with the burner in the inner plenum or three or more columns or a rotating stylet could be used. With regenerative thermal technology, the heat transfer zones in each column should be regenerated periodically to allow the heat transfer medium (usually a ceramic stoneware or chair or bedpan) in the suppressed energy zone to be supplied . This is done by periodically alternating the heat transfer zone through which the cold and hot fluids pass. Specifically, when the hot fluid passes through the heat transfer matrix, the heat is transferred from the fluid to the matrix, whereby the fluid is cooled and the matrix is heated. Conversely, when the cold fluid passes through the hot matrix, the heat is transferred from the matrix to the fluid, resulting in the cooling of the matrix and the heating of the fluid. Consequently, the matrix acts as a thermal store, which alternately accepts heat from the hot fluid, storing this heat, and then releasing it to the cold fluid.

The alternative of heat transfer zones to provide regeneration of the matrix is done via the appropriate three-way valves. In an embodiment of the present invention, it is a three way valve by the heat transfer zone, and preferably the three way valves are pneumatic bar type valves whose frequency of change or cycle is a function of volumetric flow rate so that a reduced flow allows the extended periods between changes. Although three-way valves provide the means for regeneration of the matrix, the act of regeneration therein results in an emission of untreated fluid of short duration directed to the atmosphere, which causes a decrease in the efficiency of destruction of the compound volatile organic (VOC), and in cases involving high boiling point VOCs, potential opacity outlets, unless some method of trapping this combined or switched air is employed. Then, a holding chamber 90 is preferably used to increase the efficiency of the apparatus.

Figure 1 generally shows at 10 a two-column regenerative thermal oxidant. The gas to be processed is directed from the dryer enclosure 10 to the oxidant 20 via a suction fan 30 and suitable pipes, through the appropriate three-way valve or valves 21 ', and in (or out of) one of the columns 15, 15 'of medium regenerative heat exchange filled with heat exchange. A combustion zone 18 having associated heating means such as one or more gas ignition burners 22 with associated combustion fan 23 and the valvule gas pipe is in communication with each regenerative heat exchange column 15, 15 '. or, and it is also in communication with the dryer supply or feeder fan 17. Ideally, the operation of the heating means of the combustion zone is necessary only during the start, to bring the combustion zone 18 and the heat exchange columns 15, 15 'to the operating temperature. Once the operating temperature is reached, the heating means is preferably disconnected (or placed in the "pilot mode") and an autothermal condition is maintained. The operating temperatures of the suitable combustion zone 18 are generally within a range of 760 ° C-982.2 ° C (1400-1800 ° F). Those skilled in the art will appreciate that although the term "combustion zone" has typically been used in the industry for the identification element 18, most or all of the combustion can be carried out in the heat exchange beds, and little or nothing of combustion can, indeed, take place in the combustion zone 18. Therefore, the use of this term throughout the specification and rei indications should not be constructed as to imply that combustion must take place in this zone. Preferably, the heat exchange columns 15, 15 'are oriented horizontally (i.e., the gas flow through them proceeds in a horizontal path) in the apparatus to save space. In order to minimize the undesirable accumulation of the process gas and also to induce the distribution of the process gas throughout the heat exchange medium, a combination of the random packing means is preferably used which includes gaps allowing the passage of gas through the the particles of the medium, and the structured medium. In a preferred embodiment, the gaps in the random packing medium are larger than the gaps that exist in the interstices formed between the middle particles. If the holes are too small, the gas will have to flow into the interstices faster than through the holes in the particles. These exchange particles are made of a single material and are characterized by projections or vanes that extend from the center of the particle. The spaces between the projections provide a fraction of the ideal gap for the passage of gases, so that the pressure drop characteristics of the aggregate thermal exchange bed are improved. This random packing medium may also have a catalyst applied to the surface. Those skilled in the art will recognize that other shapes suitable for the random packing means of the present invention may be used, including pins or pads, preferably 1/2"(1.27 cm) or cotter pins, etc. A second portion of the heat exchange medium is a monolithic structure used in combination with the aforementioned random packing medium.The monolithic structure preferably has about 50 cells / 6.45 cm (inch) shape, and allows laminar flow and pressure drop The same has a series of small channels or passages formed in it that allow the gas to pass through the structure in predetermined trajectories.The suitable monolithic structures are alveolar of mulite ceramic having 40 cells per element (other diameter 150 mm x 150 mm) commercially available from By zellanf abr ik Frauenthal GmbH In the preferred embodiment of the present invention, monolithic structures having dimensions of approximately 15.01 x 15.01 x 30.48 cm (5.91"x 5.91" x 12.00") are preferred. These blocks contain a plurality of parallel square channels (40-50 channels per 6.45 cm2 (square inch)). , with a single channel cross section of approximately 3mm x 3mm surrounded by a wall of approximately 0.7mm thickness, Thus, a free cross section of about 60-70% and a specific surface area of about 850 to 1000 m2 / m3 Monolithic blocks with dimensions of 15.01 cm x 15.01 cm x 15.24 cm (5.91"x 5.91" x 6") are also preferred. In some applications, a catalyst is applied to the monolithic surface. The resistant randomly packed portion of relatively high flow of the medium is preferably placed where the process gas to be treated enters the heat exchange column, whereby the gas passing through the cross section is effectively assisted. of the column. The resistant monolithic portion of relatively slow flow of the medium is preferably placed over the outlet of the random packing medium, where the gas distribution has already occurred. Within a regenerative bed where oxidation is occurring, the bed exit section has higher fluid temperatures than the inlet section. The higher temperature means both the increased viscosity and the actual increased velocity of the fluid, which then generates a high pressure drop. Thus, the use of the structured medium, which has an inherently lower pressure drop, in this portion of the column is advantageous. Those skilled in the art will appreciate that a multi-layer bed of the heat exchange medium may consist of more than two distinct layers of the medium. For example, the randomly packed medium at the entrance of a column may be a combination of different sized skins or cotters, such as a first layer of pins or 1/2 split pins followed by a second layer of 2.52 split skins or cotter pins. cm (1") The monolithic layer could then follow towards the outlet of the column In a similar manner or in addition, the monolithic layer can be, for example, a first layer of monoliths having cross sections of the 3 mm x 3 channel mm, followed by a second layer of monoliths having a channel cross section of 5 mm x 5 mm In a system where only a single heat exchange column is used, the bed of the multi-layer medium may be a first layer of the randomly packed medium, a second layer of the monolithic medium, and a third layer of the randomly packaged medium. Those skilled in the art will appreciate that the particular design of the multilayer bed depends on the fall of the Desired pressure, thermal efficiency and tolerable cost. A 100% monolithic structure is more preferred, as shown in Figure 2. In the horizontal arrangement shown, the blocks are stacked to construct the desired cross-sectional flow area and the desired flow length. To build an integrated dryer with a regenerative oxidant, which includes a trap chamber, which will be fixed in the existing process lines such as a pressure line that prints the graphic technique, a compact thermal exchange bed is required, which It is best obtained with the monolithic bed. An alternative monolithic bed design would have a catalyst applied to the monolithic surface. For a monolithic structure of 100%, the uniformity of the air flow in the monolith is critical for the operation of the internal heat exchanger. In Figure 1, flow distribution or expansion devices 95, such as perforated plates, are used at the outlet and inlet of each column to equally distribute the air flow through the bed of the heat exchanger exchanger. Such flow distributors become optional where the random packing medium is used, since the randomly packaged media helps to distribute the air flow. Valve or suitable valving 40 is provided to direct gases into the atmosphere or purge within the enclosure of the apparatus (or trap chamber 90) for optimal destruction efficiencies. Proper pressure and / or temperature attenuators 92 can be provided as shown to decrease the effects of switching or changing the valve during the cyclization of the regenerative heat exchanger. This switching or changing of the valve can create pressure pulses and / or prevent temperature that can adversely affect the operation of the dryer. The pressure pulses can enter the dryer through the hot air supply pipe or line and disturb the slightly negative pressure (relative to the atmosphere) of the dryer enclosure. This could allow the air charged in the solvent to come out or spill from the slots in the weft or dryer rolls. The temperature fluctuations which must occur during the switching or changing process may make it more difficult to control the temperature of the dryer's air at the desired location. The attenuator 92 could reduce the pressure pulses by introducing a flow resistance in the line feeding the dryer enclosure. Temperature fluctuations are reduced by introducing a device from the raised surface area and the high thermal capacity in the flow line to the dryer enclosure. The oxidant is integrated with the dryer in the process direction, ie the apparatus is a compact arrangement whereby the dryer is dependent on the oxidant for heating and for cleaning of VOC. This can be done by enclosing the oxidant and the dryer in a single enclosure, or by coupling the oxidant to the dryer, or by placing it in close proximity to the dryer. The oxidant can also be heat isolated from the dryer. Preferably there is a common wall between the dryer and the thermal exchange bed (s) of the oxidant. In one embodiment of the present invention, the cooled air can be designed past the oxidant and added to the interior of the dryer as recovered air. This procedure cools the oxidant and preheats the recovered air, adding the efficiency of the system. Figure 3 shows a flotation dryer with an integrated regenerative thermal oxidant as in Figure 1, except that the dryer is a dual-zone dryer with a return of hot air. Each zone includes recirculation means 17, 17 'such as a fan for supplying the air rods 14 with air that blows hot drying via the appropriate pipe in communication with the headers 16, 16'. The majority of the supply of hot air to the first zone is from the regenerative thermal oxidizer, when it is regulated by the hot air supply valve 41. The second zone receives its supply of hot air from the recirculation. Figure 4 shows a flotation dryer with an integrated regenerative thermal oxidant as in Figure 1, except that the dryer is a multi-zone dryer (three zones shown) with a return of hot air. Each zone includes recirculation means 17, 17 'such as a fan for supplying the air rods 14 with hot air which hits drying via the appropriate pipe in communication with headers 16, 16'. All but the end zone receives more hot air supply from the regenerative thermal oxidizer, as regulated by the hot air supply valve 41. The final zone receives its supply of hot air from the recirculation. Figure 5 shows a flotation dryer with an integrated regenerative thermal oxidant as in Figure 1, except that the dryer is a multi-zone dryer (three zones shown) with a return of hot air, with the final zone being an area of conditioning. Each zone includes means of recirculation 17, 17 ', such as a fan for supplying the air rods 14 with hot shock air for drying via the appropriate pipe in communication with heads 16, 16'. The integrated conditioning zone is as described in U.S. Patent No. 5,579,590, the description of which is incorporated by reference. The conditioning zone contains air conditioning which is substantially free of contaminants and is at too low a temperature to absorb heat from the screen, effectively decreasing the evaporation rate of the solvent and mitigating condensation. The pressure control means 45 is provided so that the vapors of the solvent will not escape from the dryer enclosure and so that air recovered from the environment can be regulated when required via the control means 46.

Figure 6 shows a similar modality to Figure 5, except that the oxidant purges the dryer's shock chamber (and the corresponding valve) is eliminated. An optional catalytic cell cleaner 50 is shown for the further destruction of VOCs that come out into the atmosphere, to increase the overall efficiency of the apparatus. Returning to Figure 7, a single-bed oxidant integrated with a two-zone air flotation dryer is shown. The suction fan 30 directs the solvent charged air from inside the dryer enclosure and directs it to the regenerative oxidant for treatment. The three-way or shift valve (s) 21 directs (n) the air to the inlet side of the bed of the heat exchange medium 15. (The inner side of the bed of the medium 15 alternates from one side of the bed the other according to a predetermined change period.) The bed of the heat exchange medium 15 is a solitary accumulation of material without occlusion for a combustion chamber. A combustion zone exists inside the bed where sufficiently high volumetric temperatures occur to convert VOCs to final products of carbon dioxide and water vapor. The location and size of the combustion zone can be moved within the bed of the medium 15 according to the particular combination of the fuel / solvent velocity, the velocity of the mass air flow and the changeover time. The heat exchange medium may be comprised entirely of any various types of random packaging material or a combination of randomly packaged and structured material. The preferred embodiment is a combination of media types in which the structured media is located on the so-called cold faces of the bed and the randomly packed material is placed in the center section of the bed. Thus, the heat exchange accumulation of the single bed is preferably comprised of, in the flat form, normal to the direction of the air flow, first a depth of the structured medium followed by a section of the medium randomly packed and in turn immediately followed by a second section of the structured medium of the same depth as the first. The orientation of the bed may be such that the flow is vertical or horizontal, but the flow must be normal to the planes of several sections of the medium.

A suitable heat source such as the fuel gas line or preferably an electric heating element is located in the center, the section of the medium randomly packed for the purpose of initially heating the exchange bed. It is understood that the electric element will become the solvent over time and / or the fuel will be present in the bed. Preferably, a fuel, such as natural gas, is introduced into the gas to be treated prior to its entry into the heat exchange bed for purposes of maintaining bed temperatures when insufficient quantities of the process solvent are available to withstand combustion temperatures. required. A portion of the combustion gases are directed or traced from the center of the heat exchange bed for purposes of mixing with and heating the supply air which is directed to the web of the material 13. The hot gas is traced or directed from the section central of the randomly packed material via a full 75 hot air collection which runs longitudinally along the middle section randomly packed, from the center. The purpose of the plenum is to direct or trace an equal amount of gas through the bed of the exchange medium to prevent temperature variations within the bed caused by an uneven flow regime. The final supply air temperature which causes an effect on the web of material 13 is determined by the amount of hot gases mixed with recirculating air prior to the fan of supply 17. The quantity of hot gases is regulated by the hot air supply valve 4 'which is in communication with the hot air collection plenum 75 attached to the heat exchange bed. The described regenerative heat source is capable of supplying sufficient heat to a dryer consisting of one or more (two shown) different control zones as demarcated by the individual supply fans. The heat of the oxidizing section can be directed to one or more of the individual zones when necessary and under process control. The design of the dryer can incorporate one or more cooling zones that operate in conjunction with and integrate with the control of the heating zone. The atmosphere inside the dryer is actively controlled via a regulator 25 of the absorption air. Figure 8 shows the preferred embodiment of a thermal exchange bed comprised of a solitary accumulation of heat exchange material without elongated occlusion for a combustion chamber. A described combustion zone mn exists within the bed around and approximately in the center of the bed in the direction of flow. The size and location of the combustion zone is determined by a significant and sufficient increase in the temperature gradient inside the bed "so that the combustion and conversion of volatile gases can occur. A / D outlet provides profiles of equal velocity to the cold faces or surfaces of the heat exchange bed 15. A perforated distribution plate 77 may be provided upstream of the cold surfaces in the direction of air flow to provide additional pairing of the air. speed profile prior to the entrance of the heat exchange bed The heat exchange bed preferably consists of structured medium 15a, which has excellent pressure loss efficiency, and the random packing means 15B, which allows to easily embed heating coils or coils in and allow to remove the hot gas to heat the supply air of the drying section. . The heating means 60, preferably an electrical resistance heating element, are controlled by the energy control 61 and heat the bed during start-up or start-up. The fuel gas injection valves 9 regulate the amount of fuel injected into the effluent to maintain a minimum fuel atmosphere within the combustion zone to support the conversion of the solvent and fuel to carbon dioxide and water vapor. In any of the modes shown, to improve the efficiency of destruction of the VOC and eliminate the opacity output resulting from the regeneration of the matrix, the untreated fluid can be diverted away from the oxidant cell and into a "receptacle housing" or VOC retention chamber 90. The function of the retention chamber 90 is to contain the piece of untreated fluid which is present during the too long regeneration process of the matrix so that the majority can be recirculated slowly (ie. say, at a very slow flow rate) again at the oxidant inlet for treatment, or it can be supplied to the combustion blower 23 as combustion air, or slowly mixed into the atmosphere through the exhaust pipe. The untreated fluid in the retention chamber 90 must be completely evacuated within the period of time subscribed between the regeneration cycles of the matrix since the process must be repeated by itself for all subsequent matrix regenerations. In addition to its volume capacity, the interior design of the retention chamber 90 is critical for its ability to contain and return the untreated fluid back to the oxidant inlet for treatment within the subscribed period between regeneration cycles. of the matrix of the exchanger thermointer. Any untreated volume that does not properly return within this cycle will escape into the atmosphere via the exhaust pipe, whereby the effectiveness of the trapping device is reduced, and the total efficiency of the oxidant unit is reduced. For some operating conditions, the amount of volatile solvents in the dryer output stream will be less than that required for the autothermal operation. To avoid the use of a combustion burner to provide supplemental energy, supplemental fuel can be introduced into the system, such as in the output stream, to provide the necessary energy. A preferable fuel is natural gas or other conventional combustible gases or liquids. The elimination of the operation of the burner is advantageous because the combustion air required for the operation of the burner reduces the efficiency of the oxidant and can cause the formation of NOx. The introduction of combustible gas can be done by sensitizing the temperature in some location, such as in the heat exchange columns. For example, temperature sensors can be located in each of the heat exchange beds, approximately 18 inches below the top of the heat exchange medium in each bed. Once the normal operation of the apparatus has started, the fuel gas of the fuel is applied to the process gas, by means of a connection T prior to the entry of the process gas to the heat exchange column, based on the average of the temperatures detected by the sensors in each heat exchange bed. If the average of the temperatures appreciated falls below a predetermined point, the additional fuel gas is added to the contaminated effluent that enters the oxidant. Similarly, if the average of the perceived temperatures rises above a predetermined point, the addition of the fuel gas stops. Alternatively, the temperature of the combustion zone can be controlled indirectly by measuring and controlling the energy content of the exhaust air entering the oxidant. A suitable Lower Explosive Limit (LEL) sensor, as available from Control Instruments Corporation, can be used to measure the total solvent plus the fuel content of the exhaust air at a suitable point followed by the pint of supplemental fuel injection. This measurement is then used to modulate by appropriate control means the fuel injection rate to maintain a predetermined, constant level of the total fuel content, typically in the range of 5 to 35% LEL, preferably in the range of 10. to 20% of LEL. If the LEL measured by the sensor is less than the desired point, the amount of the supplemental fuel injected is increased as operated by the control valve 9. If the measured LEL is above the point, the injection rate of the supplemental fuel is reduced as by closing the flow valve 9. In the event that the solvent content of the drying process is greater than the desired point of LEL equal without fuel injection, the exit velocity of the drying process can be increased to reduce the LEL such as by adjusting the flow through the suction fan 30. This adjustment of the outflow is well known to those skilled in the art, and is preferably performed with a variable speed action or pulse in the fan 30, or by a flow control gate. If the concentration of the fuel components in the gas to be treated becomes too high, excessive temperatures will occur in the apparatus which can be detrimental. To avoid such excessive temperatures in the incineration or combustion zone at elevated temperature, the temperature can be detected or sensed by a thermocouple properly positioned in the combustion zone and / or in one or more of the heat exchange columns, and when a predetermined elevated temperature is reached, the gases that could normally be passed through the cooling heat exchange column can instead be diverted around the column. When placed in the heat exchange columns, the particular location of the temperature sensors is not absolutely critical; it can be located 15.24 cm (six inches), 30.48 cm (twelve inches), 45.72 cm (eighteen inches), 60.96 cm (twenty-four inches) below the top of the middle, for example. Preferably the sensors are positioned from about 30.48 to 45.72 cm (12 to 18 inches) below the top of the medium. Each sensor is electrically coupled to a control means. A heat bypass conduit receives a signal from the control means that modulates the gate to maintain a temperature when measured by the sensor at a predetermined desired value. Those skilled in the art will appreciate that the actual or actual point used depends in part on the actual depth of the temperature sensor in the stoneware container, as well as on the desired value of the combustion chamber. A suitable reference point is in the range of approximately 871.11 ° C (1600 ° F) to approximately 898.88 ° C (1650 ° F). The bypass gases can be released into the atmosphere, combined with other gases that have already been cooled as a result of their normal passage through the cooling heat exchange column or used for some other purpose.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property.

Claims (18)

1. A dryer for a web of material and having an integrated regenerative heat source, characterized in that it comprises: an input of the web and an exit of the web spaced from the entrance of the web; a plurality of nozzles for drying the weft; a regenerative heat source comprising at least one heat exchange column, at least one column having a gas inlet and a gas outlet, at least one column which is in communication with a combustion zone, and which contains thermal exchange; valve means for alternatively directing the gas from the dryer at the inlet of at least one heat exchange column; and means in communication with the combustion zone to direct a portion of the gas therein to one or more of the plurality of nozzles.

2. The dryer according to claim 1, characterized in that there are at least two columns of heat exchange.

3. The dryer according to claim 1 or 2, characterized in that at least some of the plurality of nozzles are flotation nozzles for floatingly supporting the web in the housing.

4. The dryer according to claim 1, 2 or 3, characterized in that the heat exchange material is a combination of the randomly packaged medium and the structured medium.

5. The dryer according to claim 1, 2 or 3, characterized in that the heat exchange material is a monolith.

6. The dryer according to claim 2 or 3, characterized in that it also comprises a retention chamber having an inlet in communication with the valve means.

7. The dryer according to claim 1, 2 or 3, characterized in that it also comprises means for introducing a fuel into at least one heat exchange column.

8. The dryer according to claim 1, 2 or 3, characterized in that the heat exchange material comprises a catalyst.

9. The dryer according to claim 1, 2 or 3, characterized in that it also comprises the means of attenuation in communication with the combustion zone.

10. The dryer according to claim 9, characterized in that the attenuation means attenuates the pressure.

11. The dryer according to claim 9, characterized in that the attenuation means attenuates the temperature.

12. The dryer according to claim 1, characterized in that it also comprises means sensitive to the temperature in the regenerative heat source, and means for bypassing in response to it to extract a portion of gases from the regenerative heat source when the means Sensitive to temperature perceive or detect a predetermined temperature.

13. The dryer according to claim 1, characterized in that it also comprises a sensor to sense the volatile organic solvent concentration of the gas directed towards the inlet.

14. The dryer according to claim 7, further comprising a sensor for sensing the volatile organic solvent concentration of the gas directed towards the inlet, and wherein the amount of the combustion fuel introduced is in response to the perceived concentration.

15. A method for drying a web of travel material, characterized in that it comprises: transporting the web to a dryer having a drying atmosphere; colliding the hot gas on the web with a plurality of nozzles; designing a portion of the drying atmosphere in an integrated regenerative heat source comprising at least one heat exchange column in communication with a combustion zone and containing heat exchange material for heating the portion of the drying atmosphere; burn in the regenerative heat source volatile contaminants contained in the drying atmosphere; and directing a portion of the burned gas from the regenerative heat source. to one or more of the plurality of nozzles.

16. The method according to claim 15, characterized in that it also comprises perceiving the concentration of volatile contaminants in the drying atmosphere.

17. The method according to claim 15 or 16, characterized in that it further comprises introducing a fuel into at least one heat exchange column.

18. The method according to claim 17, characterized in that the amount of fuel gas introduced is in response to the perceived concentration of volatile contaminants.