WO2007060708A1

WO2007060708A1 - Continuous flow thermal regenerator

Info

Publication number: WO2007060708A1
Application number: PCT/IT2006/000822
Authority: WO
Inventors: Mario Amelio; Pietropaolo Morrone
Original assignee: Universita della Calabria
Current assignee: Universita della Calabria
Priority date: 2005-11-28
Filing date: 2006-11-27
Publication date: 2007-05-31
Anticipated expiration: 2008-05-28
Also published as: ITCZ20050018A1

Abstract

The invention consists of two thermal regenerators: the first (3) works as a pre- heater, the second (4) works as accumulator of thermal energy, in which the temperatures of the materials are stationary. In order to avoid that the pre-heater cools progressively in time, it, by means of an opportune system (11) of loose material moving (for example, a screw conveyor) , is provided with hot particles which arrive from the accumulator entrance zone, which temperature, by its position, is always near to that of combustion (the accumulator receives the air just went out of the combustion chamber (6)) . In the same manner, it is necessary to get a correspondent quantity of cold particles from the entrance zone of polluted air in the pre-heater, which has always the temperature near to that of environment, and to integrate them in the exit zone of the clean air from the accumulator which otherwise would tend to heat excessively because of constant passage of hot gas going out of the combustion chamber. In such a way, by means of continuous flow of particles, it is not necessary to have a valve distribution system, and it is possible to obtain a continuous air flow to treat. As a consequence, only two regenerators are needed.

Description

Continuous flow thermal regenerator Technical field of invention

The invention concerns Regenerative (RTO) or Catalytic (CTO) Thermal Oxydizers, devices projected for reducing, by means of thermal oxydation, of volatile organic composits (VOC) released in the air, for example, by varnishing devices and chemical or petrolchemical industries. State of the art

The RTO technology uses the regenerators constituted by inert material (majorly, ceramic one) preheated to deliver heat to the polluted air to treat, which, with reference to the fig. 1 enters into the device by means of a duct (1).

This latter passes through a "hot" bed (3), self-oxydizing for the reason of high temperature of the same, completes the oxydation in the combustion chamber (6), and finally, passes in a subsequent "cold" bed (4), passing to it the combustion heat and, hence, preheating it for the following cycle. The exhausted smokes are released in the environment by means of the duct (7). The bed (4) heated in such a way is ready to operate the pre-heating of the entering effluent in a new treatment cycle obtained by inverting the flow.

In such a way the system achieves the self-substaining, so it is not necessary to inject in a continuous way auxilary combustible (it is necessary only to set the system during the initial phase and to permit the ignition if the concentration of the polluters is not sufficient). When the valve of air immission (8') of the regenerator (3) is closed in order to invert the flow (Figure 2), and the valve of descharge (9") of the regenerator (4) is closed and the valve of immission (8") of the regenerator (4) is opened, the gases to treat contained in the regenerator (3) have not been completely oxydized yet. To avoid that the gases to be treated contained in the regenerator (3) go into the descharge duct (7) without being oxidized completely. In the instant when the immission valve (8') of the regenerator (3) is closed the washing valve (10') of the same regenerator is opened and cleaned air or discharged gas (washed air) is blown in. The washed air pushes the uncombusted gas from the regenerator (3) into the combustion chamber (6) in which the complete oxidation of the gas arriving from the regenerator (4) occurs. The oxidated gases pass from the regenerator (5), which in this phase acts as an accumulator, giving the combustion heat, and are activated in the descharge duct (7) through the descharge valve (9'"), which in this phase is open.

During the subsequent treatment cycle, the polluted air (1) will enter into the hot regenerator (5) through the immission valve (8'") and will heat that which have realized the washing phase (3) while the regenerator (4) will go through the washing phase and so on for the following cycles.

Instead, a continuous flow would do so that the preheater would cool more because cold gas to treat would continuously enter into it, while the accumulator would achieve higher temperatures reducing up to zero the efficiency of thermal recovery of the entire device.

The limitations of this traditional technology are the following: - the necessity to use complex systems of valves to realize the flows inversion in the regenerators and to guarantee its sealing; the necessity of a washing phase which is a direct consequence of the cyclic inversion of the flows and which leads, on its turn, to the usage of material in excess in comparison to that really needed for the recovery function for the needs of the third regenerator.

Brief description of the figures

Fig. 1: Device scheme of an RTO in which the represented flows illustrate the operations of pre-heating of the polluted air in the bed (3) and the heat recovery in the bed (4). The bed (5) is in stand-by.

Fig. 2: Device scheme of an RTO in which the represented flows illustrate the operations of pre-heating of the polluted air in the bed (4) and the heat recovery in the bed (5). The bed (3) is in stand-by.

Fig. 3: Scheme of innovative device characterized by two regenerators (3 and 4), by one combustion chamber (6) which is obteined inside the duct which links them. The inert loose material is shifted with continuity by means of screw conveyors (16) from one regenerator to another.

Fig. 4: Scheme of the innovative device characterized by two regenerators (3 and 4), by one combustion chamber (6) described according to another innovative solution in which the two regenerators are placed one above the other.

Fig. 5: The regenerator structure. The bottom is a grill (19) which substains the inert material and permits an easy air passage. Description of some embodiments of the invention

The present invention consists of two thermal regenerators constituted by two bins containing inert loose material casually packed. One works as a preheater of polluted air to treat and another works as an accumulator of energy released after the oxidation process, as a combustion chamber and as two transport systems of inert loose material. The principle of functioning can be described making reference to figures 3 and 4, which show two possible embodiments of the invention. The examples described here concern the RTO devices, but the application may also concern the Catalytic Regenerative Oxydizers (CRO).

The setting will take place after a transitory phase which is realized as follows. The polluted air just went out of the combustion chamber (6) enters into the accumulator (4) which initially has the environment temperature. After a period of time sufficient to enhance the accumulator (4) temperature, the systems of loose material (11) transport are activated in order to transport the granular material from the zone of the accumulator in which the just combusted air enters (the part of the accumulator with higher temperature) to the zone of the preheater (3) from which the polluted air goes out in order to go subsequently in the combustion chamber. In the same way, the correspondent quantity of cold particles is taken out by means of the other transport system (11), from the zone of entrance of polluted air in the preheater (3). It always has a temperature near to that of environment and is transported to the zone of exit of the cleaned air from the accumulator (4), which, otherwise would tend, with time, to heat excessively, because the hot air went out of the combustion chamber always passes there. During regular functioning the profiles of temperature of the preheater and accumulator are stabilized, remaining constant in the time and the air to treat (with environment temperature), introduced into the duct (1) by means of a flow distributor (15), will enter into the preheater (3) and will be heated to the temperature near to that of oxidation before being sent into the combustion chamber (6). After that it will transmit the thermal energy created during the oxidative process inside the accumulator (4), before being released to the descharge duct (7).

The preheater (3) will be able to guarantee the permanent air heating, so, without the necessity to invert the flow, thanks to the continuous integration of hot particles which come from the most hot zone of the accumulator (4). The same accumulator (4) on the other side will maintain its function of accumulation of thermal energy thanks to the continuous integration of cold particles which come from the coldest zone of the preheater (3).

Definitely, by means of continuous process of picking up and transport of particles from one regenerator to another, it is possible to maintain the profiles of temperature of the regenerators, in the different sections, constant in time, allowing the treatment of the polluted air without flow inversion.

A driver (12) manages the engines (16) which feed the transport systems (11) which move the material. The driver (12) acts in a way to maintain constant, at a predefined value, the temperature of exit of the cleaned air from the accumulator. It, by means of a temperature sensor (13), will maintain the temperature of exit of the cleaned air from the accumulator inside a pre-chosen band of error, regulating the velocity, and consequently the flow rate, of the inert material exchanged between the two regenerators. It determines a less usage of material and, in fact, reduces the space requirement of the traditional systems. The Figure 4 shows another constructive solution, in which the regenerators are positioned one above the other. Nevertheless the space requirements in vertical are major, the combustion chamber can be realized in a more easy way. Figure 5 shows one possible form of the bins which contain the loose material. The peculiar elements are the inclination assigned to the bottom of the regenerator, such to guarantee a uniform flow of particles through the exit duct (18) and the grill (19) with which the same bottom is constituted, suitable to guarantee a uniform flow of air inside the regenerator.

The proposed device does not use "flowed beds". Moreover, the velocity of gases passing must be such to avoid the fluidisation. In fact, it would lead to a uniformity of the temperatures of the inert material and to a drastic reduction of the recovery efficiency.

Finally, we observe that the particles transport from one silos to another obliges to connect environments with different pressures (preheater entrance with accumulator exit and accumulator entrance with preheater exit). It leads to undesired narrow passage flows of gas which can be eliminated by means of an opportune injection of cleaned air or of gases already cleaned picked up from the ducts of device exit, inside the systems of loose inert material (11) transport, through a duct (14) placed in an intermediate point of material passage.

In definite, the peculiar characteristics of the invention are the following: • the circulation of the inert material between the regenerators, realized in a way to make stationary the profiles of temperature in the same material inside the regenerator as well as, consequently, those of the gases;

• the use of bins having a form such to guarantee a uniform emptying of loose material from the regenerator with the inclination (Fig. 4) assigned according to the angle of friction of the particles;

• the elimination of the valves for the distribution of the flow which permits the better use of the inert material eliminating the entire regenerator and makes the device more compact;

• the absence of the valves permits the definite reduction of the sealing problems because the problem remains concentrated on the devices for the moving of the loose material, in which ducts, in an opportune intermediate point, it is possible to blow in the cleaned air or already cleaned gas picked up from the smokes exit duct, in the quantities sufficient to avoid the undesired narrow passage flows;

• the simplification of the device management obtained with the substitution of the apparatus of actuation of the valves distributors of the flows with a system of regulation of the engines of the transport devices, for which the measuring of the temperature of the air in the exit from the accumulator as a feedback signal is sufficient.

The invention, certainly, is not limited, to the representation of the figures, but can receive perfections and modifications from men skilled in the art, without going out of the patent frames. Present invention permits numerous advantages and, particularly, allows to overcome the difficulties that could not be superated using the systems that are actually in commerce.

Claims

1) Regenerative (RTO) or Catalytic (CTO) Thermal Oxydizer for the treatment of air polluted by volatile organic composits (VOC), by means of oxydation process, constituted by two thermal regenerators realized as bins containing inert loose material casually packed, by a combustion chamber, characterized by the fact that one of the regenerators permanently assumes the function of preheater of the polluted air which enters into the device, and the other permanently assumes the function of accumulator of thermal energy released after the thermal oxydation process, that two transport systems of inert loose material are used, that one of two systems of inert loose material transport is used to transport the material itself from the zone of entrance of polluted air in the preheater to the zone of exit of cleaned air of the accumulator, that the other of two systems of transport of inert loose material is used to transport the material itself from the zone of entrance of the cleaned air into the accumulator to the zone of exit of the polluted air from the preheater.

2) Regenerative (RTO) or Catalytic (CTO) Thermal Oxydizer according to the claim 1, characterized by the fact that the bins which contain the inert loose material and which constitute the regenerator present an opportune inclination of the bottom suitable to guarantee a continuous flow of inert loose material.

3) Regenerative (RTO) or Catalytic (CTO) Thermal Oxydizer according to the claim 1 or 2, characterized by the fact that the sealing necessary to eliminate the narrow passage flows between the regenerators is guaranteed by means of injection of cleaned air or purified gas inside the system of transport of inert loose material through a duct.

4) Regenerative (RTO) or Catalytic (CTO) Thermal Oxydizer according to the claim 2 or 3, characterized by the fact that the management of the device functoning is realized by means of a driver or a system controlling the engines commanded by a temperature sensor placed at the exit of the accumulator.