EP0610120B1 - Process and installation for the thermolysis of solid waste without the condensation of hydrocarbons - Google Patents

Description

The present invention relates to a method and a installation for thermolysis treatment of products solids the discharge of which is harmful to the environment, and more particularly aims at the treatment of thermolysis that are formed there.

Traditionally, these products are either stored, or treated by incineration. In the first case, the potential danger remains and may worsen from a possible pollution of groundwater. In the second case, the temperatures of the incineration treatment are high and result in rapid wear of the equipment and high operating cost; also gaseous products from incineration treatment are discharged into the atmosphere before any control which does not allow to give all the guarantees required for non-pollution of the environment.

We already know from document FR-2.106.844, a garbage processing device comprising a succession zones of increasing temperatures (up to 800-1300 ° C) that we pass through in the garbage after conditioning in a porous coating material; this garbage are gradually rid of their water vapor and then pyrolyzed. However, this solution requires temperatures still high, which further 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 control continuous decomposition products.

Document W0-92 / 16599 thus describes a system for the treatment of solid products whose rejection is harmful to the environment, including a reactor successively integrating a dehydration zone and a thermolysis zone, characterized in that this reactor comprises, downstream of the thermolysis zone, a zone of cooling and in that the dehydration zone is fitted with a watertight entry door, the cooling zone has a watertight 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 so as to limit the entry of air into the thermolysis zone during product introduction and during residue extraction, this thermolysis zone being provided with a gas extraction line whereby it is in depression. 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 passing carriages successively from the dehydration chamber to the chamber thermolysis and from the thermolysis chamber to the cooling using a mechanical system of the kind pinions and rack for example, or even electromagnetic drive. The carts were designed so that solid residues - glasses, metals, rubble by example - stay in carts while being removed easily after cooling at the outlet of the cooling.

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

Carbon dioxide and water vapor generated in oxidation of pyrolysis gases in radiant panels catalytic could participate in warming up by convection and radiation of products.

Pyrolysis gases formed in decomposition thermolytic as well as, where appropriate, the oxidation gases catalytic formed in the catalytic radiant panels were preferably cooled and purified on leaving the reactor in a gas scrubber where condensation took place water, the separation of noncondensable gases and heavy condensed hydrocarbons.

Halogenated and sulfur compounds could be removed in the washer by dissolving in washing.

The gas flow at the outlet of the reactor entailed advantageously the coal formed in the decomposition thermolytic to the washer where it is cooled.

Heavy hydrocarbons and coal were preferably recovered by decanting the wash water in the outlet of the washer in a decanter.

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

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

Pyrolysis gases purified from halogenated compounds, sulfur and carbon dioxide were for example used in reactor heating and the excess was for example stored for future use.

Control of the kinetics of the transformation thermolytic in the thermolysis chamber was for example obtained by regulating electric heating and catalytic heating by the use of systems conventional temperature measurement and regulation gas and electric flow rates.

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

In addition, certain regulations tend to be required for proper treatment of gases from treatment of waste, a passage of a few seconds at temperature high (e.g. around 850 ° C for waste household, even around 1200 ° C for hospital waste).

The object of the invention is to improve from the point of energetic view (both quantitative and qualitative: lower energy losses, better recovery by-products, and lower requirements as to the nature of the energy to be supplied) the treatment of gases taken from a thermolysis chamber working in practice in depression, without degrading the performance of this treatment. The invention applies in particular, but not exclusively, to the system described and taught by document W0-92 / 16599. In the alternative, the subject of the invention is 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 harmful for the environment, according to which we dehydrate in a dehydration zone for the solid products to be treated, thermolysis in a thermolysis zone, we extract solid residue from this thermolysis zone, we aspire to by means of pumping thermolysis gases formed in this thermolysis zone so maintain this zone of vacuum thermolysis, characterized in that it maintains these thermolysis gases from this thermolysis zone to at least the entry of the pumping means at a temperature higher than about 100 ° C, and these gases are used as fuel in a boiler and we recover energy thermal at the outlet of this boiler.

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

The invention thus goes against the reflex of the skilled person to cool and condense to purify well.

Preferably, not only is it not cooled not the thermolysis gases but we heat them beyond 850 ° C (or even 1250 ° C and above) to improve the degradation of these thermolysis gases, in the sense of the regulations indicated above.

Preferably, the boiler also uses fuel (coal) contained in 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 through a separator from which, in addition to these thermolysis gases, leaves the 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 offers a facility for processing products solids the discharge of which is harmful to the environment, with a dehydration zone where the solid products, a thermolysis zone downstream of the zone dewatering, a solid residue outlet area and pumping means communicating by an extraction line with the thermolysis zone to maintain it in depression and suck thermolysis gases into it, characterized in that the pumping means have a range of operating temperatures at least partly above about 100 ° C, in this that the extraction line is insulated over its entire length to the pumping means, and in that these means pumps communicate via a gas supply line fuel with a boiler capable of burning these gases thermolysis.

• 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 comprises a reactor placed downstream from 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 in Figure 1 has a zone dehydration 1 where solid products penetrate to be at least partially dehydrated first, then an area of thermolysis 2 in which the solid products, partially or totally dehydrated, are brought to their temperature thermal decomposition (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 solid residues of the heat treatment are brought to the temperature ambient.

The thermolytic transformation is advantageously performed in the total absence of free oxygen at a average temperature of 600 ° C.

Preferably, as taught by document W0-92 / 16599, zones 1, 2 and 3 are chambers insulated from each other substantially watertight, for example by guillotine doors (not shown) actuated by cylinders; the door between the rooms 1 and 2 and the door between rooms 2 and 3 are movable transversely in watertight housings, the crossing lifting cylinders by cable gland. In addition watertight doors are provided at the entrance to bedroom 1 and at the exit of room 3 thanks to which the zones of dehydration 1 and cooling are, at will, isolated from the outside and / or from the thermolysis zone 2; they can be moved vertically or horizontally or around a joint according to the reactor dimensions, available space and 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, far below those of bedroom 2.

The introduction of products and the extraction of residues are thus produced, to prevent the entry of air into chamber 2, by airlocks which isolate alternately, according to the needs, the dehydration chamber of the thermolysis when the products are introduced into the dehydration, and the thermolysis chamber of the cooling when we extract the residue from this third bedroom.

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

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

Heating means, some of which are schematically in 100 can be, as in the document supra, catalytic radiant panels. They can also be flame burners using the gases of thermolysis and / or commercial combustible gases (good market) arriving by line 101.

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

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

This depression is maintained by means of pumping 10 communicating with the thermolysis zone by a extraction line 11.

According to the invention, these pumping means 10 have an operating temperature range at least in part higher than about 100 ° C, which allows these means to pumping to be crossed by gases of higher temperatures at 80 ° C (temperature of condensation of the tars). In in addition to the extraction line 11 is provided on all of its length of means capable of maintaining the gases circulating therein at a temperature at least equal to around 100 ° C (there may be sufficient for good insulation, shown schematically in 11A, of which the sizing is within the reach of the skilled person). Finally, the installation comprises a boiler 12 provided with a 12A burner communicating with the output of the pumping means 10 by a fuel gas inlet line 13 and regulated in sort of being able to use thermolysis gases as combustible.

This installation keeps these gases from thermolysis (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 energy thermal.

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

This boiler 12 has a discharge line 17 smoke which communicates advantageously with chambers of bedrooms 1 and 2 to participate in their heater.

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

Of course, this boiler can include a third input 12B for make-up fuel, solid or gaseous depending on availability.

Preferably, not only do we minimize thermally insulating gas cooling until at least their entry into the pumping means 10, but in addition the extraction line is not direct but goes through a heater 50 whereby the temperature thermolysis gas is raised to a temperature of preferably above 850 ° C (case of solid products of household origin) or even above 1250 ° C (case of solid products of hospital origin). The total length of line 11 and the reheating temperature in the heater 50 are preferably chosen so that the gases remain at least two seconds above these levels, so as to ensure good thermal purification.

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

In the example of Figure 1, the means of pumping are formed by a vacuum pump operating at dry, such as, for example, those developed by DEGUSSA. It can easily, as we know, operate at temperatures up to 150 ° C, i.e. higher at 100 ° C.

Figure 2 shows a preferred form of realization, where elements similar to those of the figure 1 are designated by the same reference signs.

The main differences of this installation compared to that of figure 1, follow from the choice, as pumping means, of a water vapor ejector denoted 20, of any suitable known type; as we know, the temperature of operation of such a pumping means can without problem very significantly exceed 100 ° C. This choice uses the fact that we have a thermal energy source, know the boiler 12.

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

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

By way of example, the water vapor 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 CO ₃ Ca.

It goes without saying that the above description does not has been proposed as a non-limiting example and that many variations can be proposed by the man of art without departing from the scope of the invention. So in particular, the vacuum pump of figure 1 is advantageously supplied by electrical energy supplied by the turbine 19. On the other hand, the vapor from the ejector of FIG. 2 can be obtained by cogeneration or withdrawal in this turbine Finally, the heater 50 may include burners using part of the thermolysis gases.

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

Claims (17)

1. Process for the treatment of solid products, the dumping of which is harmful to the environment, according to which solid products to be treated are dehydrated in a dehydration area (1), they are thermally dissociated in a thermolysis area (2), solid residues are extracted from this thermolysis area, and thermolysis gases formed in this thermolysis area are sucked out by pumping means (10, 20) so as to keep this thermolysis area under negative pressure, characterised in that from this thermolysis area at least until the inlet of the pumping means (10,20) the thermolysis gases are kept at a temperature above approximately 100°C , and these gases are used as a fuel in a boiler (12) and heat energy is recovered at the outlet of this boiler.
2. Process according to Claim 1, characterised in that fuel recovered from the solid residues is also (14) applied to the boiler.
3. Process according to Claim 1 or Claim 2, characterised in that the thermolysis gases sucked from the thermolysis area are heated (50) to a temperature above approximately 850°C, before they are applied to the inlet of the pumping means (10, 20).
4. Process according to Claim 3, characterised in that these thermolysis gases are heated to a temperature of at least 1250°C approximately.
5. Process according to Claim 3 or Claim 4, characterised in that these gases are heated (17) with fumes from the boiler (12).
6. Process according to any one of Claims 1 to 5, characterised in that the thermolysis gases are sucked out by passing them through a steam ejector (20) using steam formed in the boiler (12), and then into a separator (22) from which emerges, in addition to these thermolysis gases, water supplying the boiler.
7. Process according to Claim 6, characterised in that the water emerging from the separator is neutralised (23) before it is returned to the boiler to be converted into steam.
8. Process according to any one of Claims 1 to 7, characterised in that the boiler fumes are used (17) to heat the dehydration area.
9. Installation for the treatment of solid products, the dumping of which is harmful to the environment, including a dehydration area (1) into which the solid products enter, a thermolysis area (12) downstream of the dehydration area, an outlet area for solid residues and pumping means (10, 20) communicating via an extraction line (11) with the thermolysis area in order to keep it at negative pressure and suck thermolysis gases from it, characterised in that the pumping means (10, 20) have a range of operating temperatures higher, at least in part, than approximately 100°C, in that the extraction line (11) is insulated (11A) over its entire length as far as the pumping means (10, 20), and in that these pumping means communicate via a fuel gas feed line (13) with a boiler (12) suitable for burning these thermolysis gases.
10. Installation according to Claim 9, characterised in that it includes a reactor (15) disposed downstream of the thermolysis area into which the solid residues enter and communicating with the boiler (12) via a solid fuel feed line (14).
11. Installation according to Claim 9 or Claim 10, characterised in that the extraction line (11) passes through a heater (50).
12. Installation according to Claim 11, characterised in that this heater (50) is a heat exchanger supplied by fumes from the boiler (12).
13. Installation according to any one of Claims 9 to 12, characterised in that the pumping means (10) include a dry-operation vacuum pump.
14. Installation according to any one of Claims 9 to 12, characterised in that the pumping means (20) include a steam ejector (20A) provided with a steam inlet communicating with an outlet of the boiler, and in that this installation also includes, downstream of this ejector, a separator (22) provided with a gas outlet connected to the fuel gas feed line, and with a water outlet connected via a feed line to a water inlet of the boiler.
15. Installation according to Claim 14, characterised in that a neutralization tank is disposed on the water feed line, and is provided with a neutralization reagent feed line (24).
16. Installation according to any one of Claims 9 to 15, characterised in that the dehydration and thermolysis areas are provided with enclosures (1A, 2A) communicating via a line with the boiler fume outlet.
17. Installation according to any one of Claims 9 to 16, characterised in that a turbine (19) is mounted at the boiler outlet.

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