EP0610120A1 - Process and installation for the thermolysis of solid waste without the condensation of hydrocarbons - Google Patents

Abstract

A method for the treatment of solid products which cannot be discharged without harming the environment, according to which solid products to be treated are dehydrated in a dehydration zone (1), they are thermolysed in a thermolysis zone (2), solid residues are extracted from this thermolysis zone, thermolysis gases formed in this thermolysis zone are sucked out using pumping means (10, 20) so as to keep this thermolysis zone under reduced pressure, characterised in that these thermolysis gases are maintained, from this thermolysis zone as far as at least the inlet of the pumping means (10, 20), at a temperature of greater than approximately 100@C, and these gases are used as fuel in a boiler (12) and heat energy is recovered at the outlet of this boiler. <IMAGE>

Description

The present invention relates to a method and an installation for the treatment by thermolysis of solid products, the rejection of which is harmful to the environment, and more particularly aims at the treatment of the thermolysis gases which are formed therein.

Traditionally, these products are either stored or treated by incineration. In the first case, the potential danger remains and can be aggravated by possible pollution of the groundwater. In the second case, the temperatures of the incineration treatment are high and cause rapid wear of the equipment and a high operating cost; moreover, the gaseous products of the incineration treatment are discharged into the atmosphere before any control, which does not make it possible to give all the guarantees required as regards non-pollution of the environment.

We already know from document FR-2.106.844, a garbage processing device comprising a succession of zones of increasing temperatures (up to 800-1300 ° C) which are passed through the garbage after packaging. in a porous coating material; this garbage is gradually rid of its water vapor and then pyrolyzed. However, this solution requires still high temperatures, which again leads to rapid wear and a high operating cost.

The Applicant sought, in the document W0-92 / 16599, to overcome the aforementioned drawbacks by allowing treatment by thermolysis at medium temperature, around 600 ° C. for example, while allowing continuous control of the decomposition products.

Document W0-92 / 16599 thus describes a system for the treatment of solid products, the rejection of which is harmful to the environment, comprising a reactor successively integrating a dehydration zone and a thermolysis zone, characterized in that this reactor comprises, downstream of the thermolysis zone, a cooling zone and in that the dehydration zone is provided with a sealed entry door, the cooling zone is provided with a sealed exit door, and airlocks isolate the thermolysis zone, on the one hand with respect to the dehydration zone, on the other hand with respect to the cooling zone so as to limit the entry of air into the thermolysis zone during the introduction of the products and during the extraction of the residues, this thermolysis zone being provided with a gas extraction line thanks to which it is under vacuum. The above areas are therefore separated into isolated rooms.

Preferably the thermolysis zone was maintained without free oxygen, and the thermolysis zone was at a temperature between 400 ° C and 750 ° C and at a pressure less than or equal to 800 millibars.

The products to be treated were preferably introduced into the reactor in carriages which passed successively from the dehydration chamber to the thermolysis chamber and from the thermolysis chamber to the cooling chamber using a mechanical system of the pinion type. and rack for example, or even of the electromagnetic drive type. The carriages were designed so that solid residues - glass, metals, rubble for example - remain in the carriages while being easily removed after cooling at the exit of the cooling chamber.

The dehydration chamber and the thermolysis chamber were advantageously heated by thermoreactors also called catalytic radiant panels supplied on the one hand with pure oxygen or air and, on the other hand with pyrolysis gas originating from thermolytic decomposition as well as by electric resistors placed inside the rooms or glued to the walls outside the rooms.

The carbon dioxide and water vapor generated in the oxidation of the pyrolysis gases in the catalytic radiant panels could participate in the heating by convection and radiation of the products.

The pyrolysis gases formed in the thermolytic decomposition as well as, where appropriate, the gases of catalytic oxidation formed in the catalytic radiant panels were preferably cooled and purified at the outlet of the reactor in a gas washer where the water condensation, separation of noncondensable gases and heavy condensed hydrocarbons.

The halogenated and sulfur compounds could be removed in the washer by dissolving in the wash water.

The gas flow at the outlet of the reactor advantageously entrained the coal formed in the thermolytic decomposition towards the scrubber where it is cooled.

The heavy hydrocarbons and the coal were preferably recovered by decantation of the washing water at the outlet of the washer in a decanter.

The gas flow at the outlet of the washer was preferably sucked by a vacuum pump.

The gases leaving the vacuum pump were, for example, sent to a washer containing, for example, an aqueous solution of potassium carbonate to remove the carbon dioxide.

The pyrolysis gases purified from halogenated, sulfur-containing compounds and carbon dioxide were for example used in the heating of the reactor and the surplus was for example put in reserve for later use.

The control of the kinetics of the thermolytic transformation in the thermolysis chamber was for example obtained by the regulation of electric heating and of catalytic heating by the implementation of conventional systems for measuring temperatures and regulating gas and current flow rates. electric.

The solution described in this document W0-92 / 16599 gives all satisfaction. However, as has been explained above, it results in cooling and purifying the gases from the thermolysis in a washer, then pumping them to maintain the desired vacuum in the thermolysis zone. In general, pumping is ensured by mechanical pumps and in particular liquid ring pumps which have the advantage of ensuring additional leaching of the gases in the liquid rings. In fact, in this washer, supplied with cold water, hydrocarbons in practice condense which are sent to a storage tank and any subsequent use of which will require prior treatment consuming energy. In fact, the cooling of the gases at the outlet of the thermolysis zone is done without energy recovery; this cooling nevertheless has the advantage of preserving the mechanical pumping means which would wear excessively if the gases which they pumped had a temperature above about 80 ° C. It should be noted that these mechanical pumping means consume energy in electrical form. On the other hand, it can be noted that the gases after treatment must be reheated for recycling in the installation.

In addition, certain regulations tend to require for a good treatment of gases from a waste treatment, a passage of a few seconds at high temperature (for example of the order of 850 ° C. for household waste, or even about 1200 ° C for hospital waste).

The object of the invention is to improve from an energy point of view (both quantitative and qualitative, lower energy losses, better recovery of by-products, and lower requirements as to the nature of the energy to be supplied) the treatment of the gases sampled in a thermolysis chamber working in practice in vacuum, without inducing degradation of the performance of this treatment. The invention applies in particular, but not exclusively, to the system described and taught by document WO092 / 16599. In the alternative, the invention aims to further improve the performance of this treatment.

The invention teaches for this purpose a method for the treatment of solid products whose rejection is detrimental for the environment, according to which one dehydrates in a dehydration zone the solid products to be treated, one thermolyses them in a thermolysis zone, one extracts solid residues from this thermolysis zone, suction is carried out with the aid of pumping means of the thermolysis gases formed in this thermolysis zone so as to maintain this thermolysis zone under vacuum, characterized in that these gases are maintained thermolysis from this thermolysis zone to at least the inlet of the pumping means at a temperature above about 100 ° C., and these gases are used as fuel in a boiler and thermal energy is recovered at the outlet of this boiler.

The invention thus teaches to maintain the gases pumped into the thermolysis zone at a temperature higher than the condensation temperature of the tars (about 80 ° C.) capable of forming in the gaseous state during thermolysis: this allows, Unlike what was proposed in document W0-92 / 16599, to keep these tars in the gaseous state and therefore to apply them as fuel in a boiler, which allows a direct recovery to generate thermal energy. . This thermal energy can either be recycled in the installation, or be applied to a turbine which performs a conversion into electrical form, or be used for any other function, possibly foreign to the installation.

The invention thus goes against the reflex of a person skilled in the art of cooling and condensing in order to purify well.

Preferably, not only are the thermolysis gases not cooled, but they are heated above 850 ° C. (or even 1250 ° C. and above) to improve the degradation of these thermolysis gases, in the sense of the regulations indicated above. above.

Preferably, the boiler also uses fuel (coal) contained in the solid residues.

• on chauffe ces gaz avec des fumées de la chaudière,
• on aspire les gaz de thermolyse en les faisant passer dans un éjecteur à vapeur d'eau utilisant de la vapeur d'eau formée dans la chaudière, puis dans un séparateur d'où sort, en outre de ces gaz de thermolyse, de l'eau alimentant la chaudière,
• on neutralise l'eau sortant du séparateur avant de la faire rentrer dans la chaudière pour être transformée en vapeur d'eau,
• on utilise les fumées de la chaudière pour chauffer la zone de déshydratation.

According to other preferred characteristics of this process, possibly combined:

• these gases are heated with fumes from the boiler,
• thermolysis gases are sucked by passing them through a steam ejector using water vapor formed in the boiler, then in a separator from which, in addition to these thermolysis gases, water supplying the boiler,
• the water leaving the separator is neutralized before entering it into the boiler to be transformed into water vapor,
• the fumes from the boiler are used to heat the dehydration zone.

For the implementation of this method, the invention provides an installation for the treatment of solid products, the rejection of which is detrimental to the environment, comprising a dehydration zone into which the solid products penetrate, a thermolysis zone downstream of the dehydration zone, an outlet zone for solid residues and pumping means communicating by an extraction line with the thermolysis zone to maintain it in depression and to suck thermolysis gases therein, characterized in that the pumping means have a range of operating temperatures at least in part greater than about 100 ° C., in this that the extraction line is insulated over its entire length to the pumping means, and in that these pumping means communicate by a fuel gas inlet line with a boiler capable of burning these thermolysis gases.

• elle comporte un réacteur disposé en aval de la zone de thermolyse dans lequel pénètrent les résidus solides, et communiquant avec la chaudière par une ligne d'arrivée de combustible solide,
• la ligne d'extraction traverse un réchauffeur,
• ce réchauffeur est un échangeur de chaleur alimenté par les fumées de la chaudière,
• les moyens de pompage comportent une pompe à vide à fonctionnement à sec,
• les moyens de pompage comportent un éjecteur à vapeur d'eau muni d'une arrivée de vapeur d'eau communiquant avec une sortie de la chaudière, et en ce que cette installation comporte en outre, en aval de cet éjecteur, un séparateur muni d'une sortie de gaz reliée à la ligne d'arrivée de gaz combustible, et d'une sortie d'eau reliée par une ligne d'arrivée à une entrée d'eau de la chaudière,
• un réservoir de neutralisation est disposé sur la ligne d'arrivée d'eau, et est muni d'une ligne d'arrivée de réactifs de neutralisation,
• les zones de déshydratation et de thermolyse sont munies d'enceintes communiquant par une ligne avec la sortie de fumées de la chaudière,
• une turbine est montée à la sortie de la chaudière.

According to preferred characteristics of this installation, possibly combined:

• it includes a reactor placed downstream of the thermolysis zone into which the solid residues penetrate, and communicating with the boiler by a solid fuel inlet line,
• the extraction line passes through a heater,
• this heater is a heat exchanger supplied by the fumes from the boiler,
• the pumping means include a dry-running vacuum pump,
• the pumping means comprise a water vapor ejector provided with a water vapor inlet communicating with an outlet of the boiler, and in that this installation further comprises, downstream of this ejector, a separator provided with '' a gas outlet connected to the fuel gas inlet line, and a water outlet connected by an inlet line to a water inlet of the boiler,
• a neutralization tank is placed on the water inlet line, and is provided with an inlet line for neutralizing reagents,
• the dehydration and thermolysis zones are provided with chambers communicating by a line with the smoke outlet of the boiler,
• a turbine is mounted at the outlet of the boiler.

• la figure 1 est un schéma de principe d'une installation conforme à l'invention, et
• la figure 2 est un schéma d'une forme préférée de réalisation de cette installation.

Objects, characteristics and advantages of the invention appear from the following description, given by way of nonlimiting example, with reference to the appended drawings in which:

• FIG. 1 is a block diagram of an installation in accordance with the invention, and
• Figure 2 is a diagram of a preferred embodiment of this installation.

The installation of FIG. 1 comprises a dehydration zone 1 into which the solid products penetrate in order to be at least partially dehydrated therein, then a thermolysis zone 2 in which the solid products, partially or totally dehydrated, are brought to their thermal decomposition temperature (commuted and fixed in advance) for example around 600 ° C (typically between 400 ° C and 750 ° C). Preferably, this thermolysis chamber is followed by a cooling zone 3 where the solid residues from the heat treatment are brought to room temperature.

The thermolytic transformation is advantageously carried out in the total absence of free oxygen at an average temperature of 600 ° C.

Preferably, as taught by document WO-92/16599, the zones 1, 2 and 3 are chambers insulated from one another in a substantially sealed manner, for example by guillotine doors (not shown) actuated by cylinders; the door between chambers 1 and 2 and the door between chambers 2 and 3 are movable transversely in watertight housings, the crossing of the lifting cylinders being by cable gland. In addition, watertight doors are provided at the entrance to chamber 1 and at the exit from chamber 3 whereby the dehydration 1 and cooling zones are, at will, isolated from the outside and / or thermolysis zone 2; they can be movable vertically or horizontally or around a joint according to the dimensions of the reactor, the space available and the free choice of the designer.

It will be appreciated that the seal provided by the entry and exit doors is between the outside and zones 1 and 3 of moderate temperatures, much lower than those of chamber 2.

The introduction of the products and the extraction of the residues are thus carried out, to avoid the entry of air into the chamber 2, by airlocks which alternately isolate, as required, the dehydration chamber from the thermolysis chamber when introduces the products into the dehydration chamber, and the thermolysis chamber of the cooling chamber when the residues from this third chamber are extracted.

Chambers 1 and 2 of the reactor are insulated to limit heat loss.

Chambers 1 and 2 are provided with heating means of all suitable known types. The temperature of chamber 2 is for example maintained around 600 ° C. while that of chamber 1, lower, is maintained above 100 ° C., for example around 120 ° C.

The heating means, some of which are shown diagrammatically at 100, can be, as in the aforementioned document, catalytic radiant panels. They can also be flame burners using thermolysis gases and / or commercial (inexpensive) combustible gases arriving via a line 101.

The chambers 1A and 2A of these chambers 1 and 2 are heated by radiation from the interior wall of the chambers heated by the flames of the burners according to technological arrangements similar to those used in the aforementioned document. Heating is also ensured by convection of the gases in the mass of products to be treated, convection provided by expansion of the combustion gases in the chambers.

Chamber 2 is kept under vacuum, typically at a pressure less than or equal to 800 mbar, or even 500 mbar. Preferably, the same set pressure is chosen in rooms 1, 2 and 3.

This vacuum is maintained by pumping means 10 communicating with the thermolysis zone by an extraction line 11.

According to the invention, these pumping means 10 have a range of operating temperature at least in part greater than approximately 100 ° C., which allows these pumping means to be traversed by gases of temperatures greater than 80 ° C. (temperature of condensation of the tars). In addition, the extraction line 11 is provided over its entire length with means capable of maintaining the gases which circulate therein at a temperature at least equal to approximately 100 ° C. (it may suffice for good insulation, shown diagrammatically in 11A, of which the sizing is within the reach of the skilled person). Finally, the installation comprises a boiler 12 provided with a burner 12A communicating with the outlet of the pumping means 10 by a line 13 of arrival of combustible gas and adjusted so as to be able to use the thermolysis gases as fuel.

This installation makes it possible to maintain these thermolysis gases (including the tars they may contain) in gaseous form, from the thermolysis zone to the boiler, through pumping means, which allows very good degradation. while providing thermal energy.

The boiler preferably communicates by a line 14 of solid fuel arrival, with a reactor 15 of any type known per se where inert materials are removed, evacuated by a line 16, and coal in pulverulent practice. This reactor is for example of the rotary drum type.

This boiler 12 comprises a line 17 for evacuating smoke which advantageously communicates with the chambers of rooms 1 and 2 to participate in their heating.

Finally, this boiler has a supply inlet 18A, and an outlet 18B which can be connected to a turbine 19 intended for example to convert hot gas (in practice steam) supplied by this boiler into electricity. The input 18A is for example connected to a gas or water tank (not shown in this figure 1).

Of course, this boiler can have a third inlet 12B for additional fuel, solid or gaseous depending on availability.

Preferably, not only is minimized by thermal insulation cooling of the thermolysis gases until at least their entry into the pumping means 10, but in addition the extraction line is not direct but passes through a heater 50 whereby the temperature of the thermolysis gases is high up to a temperature preferably greater than 850 ° C. (case of solid products of household origin) or even greater than 1250 ° C. (case of solid products of hospital origin). The total length of the line 11 and the heating temperature in the heater 50 are preferably chosen so that the gases remain at least two seconds above these bearings, so as to ensure good thermal purification.

This heater 50 is for example a heat exchanger traversed, in one direction, by these thermolysis gases and, in the other direction, by part of the fumes from the boiler.

In the example of FIG. 1, the pumping means are formed by a dry-running vacuum pump, such as, for example, those developed by DEGUSSA. It can easily, as we know, operate at temperatures up to 150 ° C, that is to say above 100 ° C.

FIG. 2 represents a preferred embodiment, where elements similar to those of FIG. 1 are designated by the same reference signs.

The main differences of this installation compared to that of FIG. 1, result from the choice, as pumping means, of a water vapor ejector noted 20, of any suitable known type; as is known, the operating temperature of such a pumping means can without problem very significantly exceed 100 ° C. This choice uses the fact that there is a thermal energy source, namely the boiler 12.

More precisely, there is a downstream of this ejector 20 a gas / liquid separator 22 where water from steam is separated and a condensed fraction of the thermolysis gases (which may contain water), and thermolysis gases still containing tars. The liquid fraction from this separator in practice comprises acids (in particular hydrochloric, hydrofluoric, sulfuric) so that it is advantageously passed through a neutralization reactor 23 into which are injected by a line 24 reagents intended to bring the pH to 7 (this injection can vary depending on the instantaneous pH value). The water thus neutralized enters the boiler to be vaporized there and brought by a line 20A to the ejector 20. A loop is thus obtained.

It will be appreciated that this solution makes it possible to directly recover the fuels contained in the thermolysis gases (or even in the solid residues) and allow efficient pumping at high temperature (allowing this direct recovery) without requiring electrical energy. In addition, this solution ensures good purification of soluble compounds at high temperature thanks to the intimate mixture of thermolysis gases and water vapor.

For example, the steam applied to the ejector 20 (there may of course be several) is at a pressure of 10 bars for a flow rate depending on the quantity treated and at a temperature of 200 ° C. , and the thermolysis gases are taken from the thermolysis chamber at a temperature of 600 ° C. at a flow rate of 20% of the water vapor flow rate and reach the ejector with a temperature at least equal to 850 ° C. after heater 50, neutralization in reactor 23 is obtained by injection of reagents consisting of CO₃Ca.

It goes without saying that the above description has been offered only by way of nonlimiting example and that numerous variants can be proposed by those skilled in the art without departing from the scope of the invention. So in particular, the vacuum pump of FIG. 1 is advantageously supplied with electric energy supplied by the turbine 19. On the other hand, the steam from the ejector of FIG. 2 can be obtained by cogeneration or drawing off in this steam turbine 19. Finally, the heater 50 may include burners using part of the thermolysis gases.

It will be appreciated that, according to the invention, thermolysis by-products are recovered by obtaining a mixture which can be sent directly to a recovery boiler, under good thermodynamic conditions and without going through the stage of recovery of heavy hydrocarbon products.

Claims (17)

Process for the treatment of solid products, the rejection of which is harmful to the environment, according to which solid products to be treated are dehydrated in a dehydration zone (1), they are thermolysed in a thermolysis zone (2), solid residues from this thermolysis zone, thermolysis gases formed in this thermolysis zone are sucked up using pumping means (10, 20) so as to maintain this thermolysis zone in depression, characterized in that maintains these thermolysis gases from this thermolysis zone up to at least the inlet of the pumping means (10, 20) at a temperature above about 100 ° C., and these gases are used as fuel in a boiler (12) and we recover thermal energy at the outlet of this boiler. A method according to claim 1, characterized in that fuel recovered from solid residues is further applied (14) to the boiler. Method according to claim 1 or claim 2, characterized in that the thermolysis gases drawn into the thermolysis zone are heated (50) to a temperature above about 850 ° C before being applied to the inlet of the pumping means (10, 20). Method according to claim 3, characterized in that these thermolysis gases are heated to a temperature at least equal to approximately 1250 ° C. Method according to claim 3 or claim 4, characterized in that these gases are heated (17) with fumes from the boiler (12). Process according to any one of Claims 1 to 5, characterized in that the thermolysis gases are sucked by passing them through a steam ejector (20) using steam formed in the boiler ( 12), then in a separator (22) from which, in addition to these thermolysis gases, comes water supplying the boiler. Method according to claim 6, characterized in that the water leaving the separator is neutralized (23) before entering it into the boiler to be transformed into water vapor. Process according to any one of Claims 1 to 7, characterized in that the fumes from the boiler are used (17) to heat the dehydration zone. Installation for the treatment of solid products, the rejection of which is harmful to the environment, comprising a dehydration zone (1) into which the solid products penetrate, a thermolysis zone (12) downstream from the dehydration zone, an outlet zone solid residues and pumping means (10, 20) communicating by an extraction line (11) with the thermolysis zone to maintain it in depression and to suck thermolysis gases therein, characterized in that the pumping means ( 10, 20) have a range of operating temperatures at least in part greater than about 100 ° C., in that the extraction line (11) is insulated (11A) over its entire length up to the pumping means (10 , 20), and in that these pumping means communicate by a fuel gas inlet line (13) with a boiler (12) capable of burning these thermolysis gases. Installation according to claim 9, characterized in that it comprises a reactor (15) arranged downstream of the thermolysis zone into which the solid residues penetrate, and communicating with the boiler (12) by a solid fuel inlet line (14). Installation according to claim 9 or claim 10, characterized in that the extraction line (11) passes through a heater (50). Installation according to claim 11, characterized in that this heater (50) is a heat exchanger supplied by the fumes from the boiler (12). Installation according to any one of claims 9 to 12, characterized in that the means for pumping (10) includes a dry running vacuum pump. Installation according to any one of claims 9 to 12, characterized in that the pumping means (20) comprise a steam ejector (20A) provided with a steam inlet communicating with an outlet of the boiler, and in that this installation further comprises, downstream of this ejector, a separator (22) provided with a gas outlet connected to the fuel gas inlet line, and a connected water outlet by a finish line at a boiler water inlet. Installation according to claim 14, characterized in that a neutralization tank is arranged on the water inlet line, and is provided with an inlet line (24) for neutralizing reagents. Installation according to any one of claims 9 to 15, characterized in that the dehydration and thermolysis zones are provided with chambers (1A, 2A) communicating by a line with the smoke outlet of the boiler. Installation according to any one of claims 9 to 16, characterized in that a turbine (19) is mounted at the outlet of the boiler.

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