FR2701035A1 - Method and installation for the thermolysis treatment of solid waste, without condensation of hydrocarbons. - Google Patents

Abstract

A process for the treatment of solid products the discharge of which is detrimental 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), they are extracted solid residues of this thermolysis zone, are sucked using pumping means (10, 20) of the thermolysis gases formed in this thermolysis zone so as to maintain this thermolysis zone in depression, characterized in that ' these thermolysis gases are maintained from this thermolysis zone up to at least the inlet of the pumping means (10, 20) at a temperature greater than approximately 100 ° C, and these gases are used as fuel in a boiler (12) and thermal energy is recovered at the outlet of this boiler.

Description

The present invention relates to a method and an installation for the

  thermolysis treatment of products

  solids, the rejection of which is harmful to the environment, and more particularly aims at treating 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 worsen possible pollution of the groundwater In the second10, the temperatures of the treatment by incineration are high and cause a rapid wear of equipment and 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 to the non-pollution of the environment.

  We already know from document FR-2 106 844,

  a waste treatment device comprising a success

  Zion of zones of increasing temperatures (up to 800-

  1300 'C) which is taken to the garbage after a condi-

  operation in a porous coating material; this garbage is gradually rid of its water vapor and then

  However, this solution requires temperatures

  res still high, which further leads to rapid wear

and a high operating cost.

  The Applicant sought, in the document

  WO-92/16599, to overcome the aforementioned drawbacks by allowing

  both a treatment by thermolysis at medium temperature, around 600 ° C. for example, while allowing continuous control of the decomposition products.5 Document WO-92/16599 thus describes a system for the treatment of solid products whose rejection is harmful to the environment, comprising a reactor successively integrating a dehydration zone and a thermolysis zone, characterized in that this reactor 10 comprises, downstream of the thermolysis zone, a cooling zone and in that the dehydration zone East

  fitted with a watertight entry door, the cooling zone

  This is equipped with 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 zone so as to limit the air inlets in 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-mentioned zones 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 the solid residues of glass, metals, rubble for example remain in the carriages while being easily removed after cooling at the outlet of the cooling chamber.

  The dehydration chamber and the thermolysis chamber were advantageously heated by thermo

  reactors also called catalytic radiant panels supplied on the one hand with pure oxygen or air and, on the other hand with pyrolysis gas coming from thermolytic decomposition as well as by electrical resistors placed inside the chambers or glued to the walls to

the exterior of 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 up

  by convection and radiation of products.

  Pyrolysis gases formed in decomposition

  thermolytic as well as, where appropriate, the gases from the oxidation

  catalytic tion formed in the catalytic radiant panels

  that were preferably cooled and purified after leaving the

  reactor in a gas washer where the condensate was

  tion of water, the 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 decomposition

  thermolytic to the washer where it is cooled.

  The heavy hydrocarbons and the coal were preferably recovered by decantation of the wash water

  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 an aqueous solution of potassium carbonate to remove the

carbon dioxide.

  The pyrolysis gases purified from halogenated compounds

  born, sulfur and carbon dioxide were used for example 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 WO-92/16599 gives all satisfaction However, it leads, as explained above, to cooling and purifying in a washer the gases resulting from the thermolysis, then to 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 providing additional washing

  gage of gases in the liquid rings In fact, in this washer, supplied with cold water, in practice condensate the hydrocarbons which are sent to a storage tank

  and any subsequent use of which will require treatment

  pre-consuming energy In fact, the cooling

  Dissement of the gases at the exit 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 800 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 waste

  household, even around 1200 ° C for hospita-

  liers). 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 gases taken from a thermolysis chamber working in practice in vacuum,

  without degrading the performance of this milking

  The invention applies in particular, but not exclusively-

  ment, to the system described and taught by document WO-

  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 prejudicial

  safe 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 zone of thermolysis, one aspirates using means of pumping of the thermolysis gases formed in this thermolysis zone so as to maintain this thermolysis zone in depression, characterized in that these thermolysis gases are maintained from this thermolysis zone up to at least the inlet of the pumping means at a temperature above about 1000 C, and these gases are used as fuel in a boiler and energy is recovered

  thermal at the outlet of this boiler.

  The invention thus teaches to maintain gases

  pumped into the thermolysis zone at a higher temperature

  lower than the condensation temperature of the tars (about 800 C) liable to form in the gaseous state during thermolysis: this allows, unlike what was proposed in document WO92 / 16599, to keep these tars at gaseous state and therefore apply them as

  fuel in a boiler, which allows a valori-

  direct station to generate thermal energy This

  thermal energy can either be recycled in the installation

  tion, either be applied to a turbine which converts it 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 more) 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.

  According to other preferred characteristics of this process, possibly combined: these gases are heated with fumes from the boiler, the thermolysis gases are sucked by passing them through a steam ejector using steam formed in the boiler, then in a separator from which water supplied to the boiler leaves, in addition to these thermolysis gases, the water leaving the separator is neutralized before entering it into the boiler to be transformed into steam of water, we use the fumes from the boiler to heat the area

dehydration.

  For the implementation of this process, the invention provides an installation for the treatment of solid products whose rejection is detrimental to the environment, comprising a dehydration zone where 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 partly above about 1000 C, in 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.

  According to preferred characteristics of this installation, possibly combined: it comprises a reactor arranged 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 boiler fumes, the pumping means comprise a dry-running vacuum pump, the pumping means comprise a steam ejector provided with an inlet steam 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 arranged on the water inlet line, and is provided with '' an inlet line for neutralization reagents, the dehydration and thermolysis zones are provided with chambers communicating by a line with the boiler's smoke outlet,

  a turbine is mounted at the outlet of the boiler.

  Objects, characteristics and advantages of

  the invention will become apparent from the description which follows, given to

  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 o penetrate the solid products to be at least partially dehydrated there first, then a zone of

  thermolysis 2 in which the solid products, partial-

  or completely dehydrated, are brought to their tempera-

  ture of thermal decomposition (commuted and fixed in advance) for example around 6000 ° C. (typically between 400 ° C. and 7500 ° C.) Preferably, this thermolysis chamber is followed by a cooling zone 3 o the residues heat treatment solids are brought to room temperature.

  Thermolytic transformation is advantageous-

  ment carried out in the total absence of free oxygen at an average temperature of 6000 C. Preferably, as taught by the document W 0-92 / 16599, zones 1, 2 and 3 are chambers isolated from each other significantly

  watertight, for example by guillotine doors (not shown

  tees) 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 done by stuffing box In addition watertight doors are provided at the entrance to the chamber 1 and at the exit of chamber 3 whereby the dehydration 1 and cooling zones are, as desired,

  isolated from the outside and / or the thermo-zone

  lysis 2; they can be vertically or horizontally movable

  talement or around a joint according to the dimensions of the reactor, the available space 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 bedroom 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 combustible gases (good

  market) arriving by line 101.

  The heating of the chambers 1 A and 2 A of these chambers 1 and 2 is ensured by the radiation of the interior wall of the chambers heated by the flames of the burners according to technological arrangements similar to those adopted in the aforementioned document Heating is also ensured by convection of 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, 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 a

extraction line 11.

  1 O According to the invention, these pumping means 10 have an operating temperature range at least in part greater than about 1000 C, which allows these pumping means to be traversed by gases of higher temperatures. at 800 C (temperature of condensation of the tars) In addition the extraction line 11 is provided on all its

  length of means capable of maintaining the gases circulating therein at a temperature at least equal to approximately 1000 ° C. (it may be sufficient for good insulation, shown diagrammatically in 11 A, 10 of which the dimensioning is within the reach of man of job).

  Finally, the installation comprises a boiler 12 provided with a burner 12 A communicating with the outlet of the pumping means by a line 13 of arrival of combustible gas and adjusted so as to be able to use the thermolysis gases as

combustible.

  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.

  reactor is for example of the rotary drum type.

  This boiler 12 has an evacuation line 17

  smoke cuation which advantageously communicates with the chambers of rooms 1 and 2 to participate in their

heater.

  Finally, this boiler has a supply inlet 18 A, and an outlet 18 B which can be connected to

  a turbine 19 intended for example to convert into electric

  cited hot gas (in practice steam) supplied by this boiler The 18 A input is for example connected to a tank

  gas or water (not shown in this figure 1).

  1 1 Of course, this boiler can have a third inlet 12 B for additional fuel, solid or gaseous depending on availability. Preferably, not only is minimized by thermal insulation the cooling of the thermolysis gases until at least their entry into the pumping means, but in addition the extraction line is not direct but passes through a heater 50 thanks to what the temperature of the thermolysis gases is high up to a temperature preferably greater than 850 ° C. (in the case of solid products of household origin) or even greater than 1250 ° C. (in the 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 15 remain at least two seconds above these stages,

  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 vacuum pump operating at

  dry, such as, for example, those developed by DEGUSSA.

  It can easily, as we know, operate at temperatures up to 1500 C, that is to say higher

at 1000 C.

  Figure 2 shows a preferred embodiment, o elements similar to those of Figure

  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 we know, the temperature

  ture of operation of such a pumping means can without problem very significantly exceed 100 ° C. This choice uses the fact that there is a source of thermal energy,

know 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 the thermolysis gases still containing the tars The liquid fraction resulting from this separator in practice comprises acids (in particular hydrochloric, hydrofluoric, sulfuric) so that it is advantageously passed through a neutralization reactor 23 o are injected by a line 24 of the reagents intended to reduce p H to 7 (this injection may vary depending on the instantaneous value of p H) The water thus neutralized enters the boiler to be vaporized and brought by a 20 A line to the 20 On ejector

thus obtains a loop.

  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) and this 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 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 thermo gases

  lysis 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 8500 ° C. after the heater 50, neutralization in

  reactor 23 is obtained by injection of reagents consisting

both in CO 3 Ca.

  It goes without saying that the above description does not

  has been proposed as a non-limiting example and that many variants can be proposed by those skilled in the art without departing from the scope of the invention Thus in particular, the vacuum pump of Figure 1 is advantageously supplied by electrical 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 can include burners using a part of the thermolysis gases. It will be appreciated that, according to the invention, byproducts of thermolysis are valorized by obtaining

  of a mixture which can be sent directly to a recovery boiler, under good thermo-conditions

  dynamic and without going through the recovery stage of

heavy hydrocarbon products.

Claims (12)

  1 Process for the treatment of solid products the rejection of which is harmful to the environment, according to which one dehydrates in a dehydration zone (1) of the 5 solid products to be treated, one thermolyses them in a thermolysis zone (2), one extracts solid residues from this thermolysis zone, thermolysis gases formed in this thermolysis zone are sucked up by means of pumping (10, 20) so as to maintain this thermolysis zone in depression, characterized in that these thermolysis gases are maintained from this thermolysis zone up to at least the inlet of the pumping means (10, 20) at a temperature above about 1000 C, and these gases are used as fuel in a boiler (12) and we recover from   thermal energy at the outlet of this boiler.   2 Method according to claim 1, characterized   in addition that (14) is applied to the boiler of the fuel   target recovered from solid residues.   3 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 applying   at the entrance of the pumping means (10, 20).   4 Method according to claim 3, characterized in that these thermolysis gases are heated to a temperature at least approximately 1250 ° C.   Method according to claim 3 or claim 4, characterized in that these gases are heated (17)   with boiler fumes (12).   6 Method according to any one of the claims   tions 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) o leaves, in addition to these thermolysis gases, the water supplying the boiler. 7 Method according to claim 6, characterized in that neutralizes (23) the water leaving the separator before making it enter the boiler to be transformed in water vapor.   8 Method according to any one of claims 1 to 7, characterized in that the fumes (17) are used   of the boiler to heat the dehydration zone.   9 Installation for the treatment of solid products, the discharge of which is detrimental to the environment, comprising a dehydration zone (1) where the solid products penetrate, a thermolysis zone (12) downstream from the dehydration zone, a outlet of solid residues and pumping means (10, 20) communicating by a line   extraction (11) with the thermolysis zone for maintenance   to go into depression and 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 1000 ° C., in that the extraction line ( 11) is insulated (11 A) over its entire length up to the pumping means (10, 20), and in that these means   pumping communicate via a fuel gas inlet line   ble (13) with a boiler (12) capable of burning these thermolysis gases. Installation according to claim 9, characterized in that it comprises a reactor (15) disposed downstream of the thermolysis zone into which the solid residues penetrate, and communicating with the boiler (12) by   a solid fuel inlet line (14).   11 Installation according to claim 9 or the   claim 10, characterized in that the extraction line   tion (11) passes through a heater (50).   12 Installation according to claim 11, characterized in that this heater (50) is an exchanger   heat supplied by the fumes from the boiler (12).   13 Installation according to any of   claims 9 to 12, characterized in that the means for   pumping (10) include a vacuum pump operating at   dry. 14 Installation according to any one of claims 9 to 12, characterized in that the means of   pumping (20) comprise a water vapor ejector (20 A) 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 (22) provided with a gas outlet connected to the fuel gas inlet line, and a water outlet connected by an inlet line to a boiler water inlet.   Installation according to claim 14, characterized in that a neutralization tank is arranged on the water supply line, and is provided with a line   (24) arrival of neutralization reagents.   16 Installation according to any of   Claims 9 to 15, characterized in that the areas of   dehydration and thermolysis are provided with chambers (1 A, 2 A) communicating by a line with the smoke outlet of the boiler.   17 Installation according to any of the   Claims 9 to 16, characterized in that a turbine (19)   is mounted at the outlet of the boiler.