EP0795594A1 - Plant for the environmentally friendly thermal treatment of industrial, hospital, domestic and the like waste - Google Patents

Abstract

Installation for heat treating industrial, medical, domestic and similar waste at low temperature and under partial vacuum, whether they are in solid, liquid or gaseous form to meet set environmental protection limits contains the following critical elements: a heat treatment furnace (3); two distillation chambers (2); a condenser for the distillation gas (7); means of placing the distillation chambers under partial vacuum (9); a washing column (10); a system for water treatment (15); and a system for sorting the solid parts of the waste (24-26). The furnace is characterised by its mobility and is mounted on a driven rolling arch which moves along rails. The arch is closed at its two ends by lifting, guillotine doors. The top position of the doors allows the furnace to move from one distillation chamber to the other. To obtain the most efficient convection heating in these temperature ranges, the furnace has a turbine forcing ambient air to circulate through electrical resistance heaters.

Description

The present invention relates to an installation implementing a process for the thermal treatment of industrial, hospital, household and similar waste, at low temperature and under partial vacuum, whether in solid, liquid or gaseous form.

The techniques currently used require either a preliminary sorting of the products which implies risks for the personnel, either a specific conditioning, or a transfer, therefore a maneuver, during treatment. In addition, in a closed process, even at low temperature, the cycle time is extended very substantially by the cooling phase of the solid secondary material, which penalizes the profitability of the installation. On the other hand, the gases resulting from the treatment must be sucked in by a pumping group and for this to be cooled beforehand. The materials installed upstream of the vacuum pump can become clogged or, if the technique of bubbling gases into water is used, this is brought to an excessive temperature which makes it unsuitable for rejection without a new treatment . In the case where the products are treated by incineration, that is to say at high temperature, the gaseous products are discharged into the atmosphere which does not give any guarantee as to the protection of the environment.

The system which is the subject of the present invention claims to remedy these drawbacks.

The products are distilled by heat treatment at 500 ° C and under partial vacuum (100 mb). This process accelerates the decomposition of organic matter by facilitating molecular bursting and avoids self-combustion by lack of oxygen. The added or substituted atoms, in ionized (gaseous) form, are treated by neutralization. At the end of the decomposition of organic products, due to heat treatment, the products are transformed into gas, hydrocarbons, coal.

• l'équipement de traitement thermique comportant un four mobile à chauffage électrique et deux enceintes étanches,
• le système de traitement des gaz issus de la distillation des produits,
• le système de traitement des eaux de neutralisation et des condensats,
• le matériel de tri des éléments solides des rejets,
• l'ensemble du matériel de contrôle et de mesure, d'analyse et de commande destiné à la gestion et au suivi de l'exploitation de l'installation.

The installation according to the present invention is composed of the following assemblies and equipment:

• heat treatment equipment comprising a mobile oven with electric heating and two sealed enclosures,
• the system for treating gases from the distillation of products,
• the neutralization water and condensate treatment system,
• material for sorting solid elements from rejects,
• all the control and measurement, analysis and control equipment intended for the management and monitoring of the operation of the installation.

The products to be treated are deposited, without prior sorting or conditioning, in a collecting bucket (1/1) which is introduced into a distillation chamber (2/1). This is hermetically closed, then purged of its atmosphere by a pumping group (9/1), the heating (plate 2/3) is then put into service for a free rise up to 150 ° C. This temperature will be maintained for 30 minutes, which constitutes the level of dehydration and vaporization of certain products. At the end of this plateau, the temperature rise is resumed up to 500 ° C., at this level it is maintained for one hour. At the end of this period the oven (3/1) is moved to put the enclosure in the open air and thereby accelerate its cooling which can be improved by precipitation of water. During the thermal cycle (plate 2/3) the gases are sucked in by a pumping group (9/1) through a condenser (7/1) and discharged into a washing column (10/1) in order to eliminate halogens. They are taken up and compressed for storage for later use.

The aqueous phase of the washing column and the condensates are adjusted to "pH" and precipitated in a settling tank (15/1) to recover the hydrocarbons in suspension, then filtered. After analysis, the water is either reused by the installation itself, or discharged to the sewer (22/1) for the rest.

After disengagement of the mobile oven (3/1), as soon as the temperature of the distillation chamber (2/1) has dropped to a value below 80 ° C, a signal warns the operator of the installation of the end of the processing and the possibility of unloading.

The collecting bucket (1/1) is then extracted from the enclosure (2/1) and placed on a rocker which will pour its solid stream onto a conveyor (23/1). The solids will be sorted for recovery or landfill without harming the environment.

The installation according to the invention implements the equipment described below.

Heat treatment equipment which includes collection bins (1/1), two sealed distillation chambers (2/1) and the oven itself (3/1).

• accélération du refroidissement des produits traités par mise à l'air libre de l'enceinte de distillation et précipitation d'eau,
• possibilité de mettre en chauffe une enceinte pendant le refroidissement de l'autre et ainsi augmenter le rendement du matériel.

The oven is of the "rolling vault" type (see plate 3/3) whose mobility represents the following advantages:

• acceleration of the cooling of the treated products by venting the distillation chamber and precipitation of water,
• possibility of heating one enclosure during the cooling of the other and thus increasing the efficiency of the equipment.

The collection bins (1/1) are bins made of stainless steel sheet that can be mounted on engineered pads allowing their gripping by a lifting machine, or on cast iron wheels for manual handling when the mass of products to treat is weak. The sides of the tanks are equipped with a rotation axis for tilting during unloading. The tanks receive directly, without sorting or human manipulation, therefore without risk for the operator, the products to be treated.

The distillation chambers (2/2) are parallelepiped boxes made of stainless steel closed at one end by a watertight door fitted with a gasket with a metallic structure. The door pivots on an axis to come to be presented parallel to the frontage of the enclosure on which it is pressed by a system with catches and skewed wedges. The speakers are installed face to face, separated from each other by a loading table. They rest on cradles placed on the floor of the oven. Inside, andirons in the form of raceways, rails or trays, receive the collection bucket. A stainless steel tube opening at a low point in the enclosure will connect it to the distillation gas extraction system. During precipitation cooling, water will be collected in a receptacle located under the enclosure.

The oven (3/1) consists of a casing, welded construction, sheet metal and commercial profiles. It travels on rails, from one enclosure to another, by means of two motorized rollers and free rollers. It is closed at its two ends by doors called "guillotine" operated by winches. The high position of the doors allows the oven to be moved. In the low position, the doors are pressed onto the facades by a system of jacks. Plating the doors authorizes heating. The casing and the doors are thermally insulated by a lining of ceramic fibers. The electric heating of the furnace is ensured by resistant elements, formed in waves, in Nickel / Chromium alloy. A recirculation turbine will ensure forced convection of the ambient air. The electrical supply of the heating elements, the turbine and the operating devices is done by a bundle of cables mounted in a festoon to follow the movements of the oven. The heating regulator is a thyristor power unit. The two hearths of the furnace are refractory concrete bases placed directly on the floor of the room.

According to the invention, the distillation gas treatment system comprises the main elements described below.

The condenser (7/1) has two functions: trapping the condensable gases and cooling the incondensable gases before their aspiration.

The device consists of a sealed stainless steel container in which baffle plates are arranged. These plates, having a large heat exchange surface, are kept at low temperature by circulation of water, previously refrigerated (14/1), in coils welded to it.

The pumping unit (9/1) consists of a rotary piston pump without lubrication and a menbran pump. Upstream of the group is installed a particle filter (8/1).

The washing column (10/1) is in the form of a sealed stainless steel silo in which a constant water level is maintained. According to the invention, the gases discharged by the pumping group are conveyed in a sheath, comprising a washing ramp forming a film of water, which plunges below the level of the water table. The gases are therefore washed by precipitation and bubbling.

At the outlet of the washing column, the gases are taken up and compressed (11/1) for storage (12/1) for later use.

The various elements described above are interconnected by stainless steel sheaths, largely dimensioned to avoid possible clogging and facilitate maintenance. Solenoid valves make it possible to automate the operation of the installation on the basis of the information given by the measuring, control and analysis devices.

The water requirements of the installations are as follows: the cooling water of the condenser plates, the maintenance of the level in the washing column, the water precipitated on the distillation chamber to be cooled, the water for washing the premises and equipment. On the other hand, a certain amount of water is recovered after condensation of the vapors coming from the distillation chamber. The liquids to be treated come from the condenser, the gas washing column, the collection of clean water from premises and equipment. The condenser cooling water is clean and has the advantage of being cooled. The cooling water of the enclosure is also clean but can be charged with dust, it will be filtered (17/1) before being switched back on. The essential elements constituting the water treatment system are: the reservoir intended to preserve the adequate quantity of water (13/1), the apparatus for refrigerating the plates of the condenser (14/1), the washing column (10 / 1), the suitable tank for decanting hydrocarbons (15/1), the oil storage tank (16/1), the system controlled by the results of analyzes of the addition of washing liquid to the water to be neutralized. This system is classic to water chemistry and is not the subject of a particular description.

The residual solid elements are on the one hand, poured onto a conveyor (23/1), on the other hand, for the coals, sucked up (24/1) and put in silo (25/1). Heavy materials made clean are sent to a sorting (26-27-28-29 / 1) conventional to the recovery industries.

Monitoring and management of operations are ensured on a continuous basis by a set of devices, the choice and redundancy of which guarantee the reliable operation of the installation.

According to the invention, there are four types of measurements to be made: the operating measurements which initiate the different phases of the process, the security measures which must ensure the protection of the equipment and consequently of the personnel, the quality measures which must guarantee and prove respect for the environment, profitability measures for the installation.

The measurements are carried out by probes or sensors which are associated with monitoring or control devices. In addition, certain measures deemed essential are archived in graphic form or in the form of alphanumeric messages. This archiving assists in the maintenance of the equipment and the conservation of the processing history. The management of the entire installation is entrusted to a programmable controller, monitoring of measurements in real or delayed time is ensured by a computerized display system.

The operating measurements relate to: the internal temperature of the distillation chamber which is taken into account by a regulator / programmer which itself controls the thyristor power unit, the value of the vacuum in the chamber which triggers the start-up of the heating, the flow rate of aspirated gases, the temperature upstream of the pumping unit, the level of the liquids collected at the base of the condenser, the level in the washing column, the filling rate of the tanks.

The safety measures concern: the temperature of the heating elements of the oven to avoid overheating which is detrimental to the behavior of the equipment over time, the internal pressures of the condenser and of the washing column, the gas flow rates at the inlet and outlet of the condenser , the refrigeration temperature of the condenser plates.

The quality measures relate to: the analysis of incondensable gases, the analysis of recycled water, the analysis of the atmosphere of the room, the temperature and the flow rate of the water to be discharged into the sewer.

The profitability measures concern: the weight of the products to be treated, the consumption of electrical energy and the consumption of city water. These measures will make it possible to establish an operating balance sheet.

Claims (6)

Installation using a thermal treatment process for industrial, hospital, household and similar waste, at low temperature and under partial vacuum, whether in solid, liquid or gaseous form with environmental protection beyond the standards set . The installation is characterized by the following essential elements: - a mobile heat treatment oven (3/1), - two sealed distillation chambers (2/1), - a distillation gas condenser (7/1), - a group for evacuating the two chambers (9/1), - a washing column (10/1) - a water treatment system (15/1), - a system for sorting solid elements from rejects (24-26 / 1). The heat treatment furnace, according to claim 1, is characterized by its mobility (plate 3/3). It consists of a motorized rolling vault moving on rails. The vault is closed at its two ends by lifting doors called "guillotine". The high position of the doors allows the movement of the oven from one distillation chamber to another. To obtain more efficient convection heating in these temperature ranges, the oven is equipped with a turbine forcing the circulation of ambient air on the electrical heating resistors. According to claims 1 and 2 the installation is characterized by two sealed distillation chambers (2/1) resting on refractory concrete floors. These enclosures, made of stainless steel, receive the products to be treated and are, depending on the position of the oven, subjected to the heating phase, by the electrical resistances, or to the cooling phase by venting the enclosure and water spray. According to claims 1 and 3 the sealed enclosures are evacuated by a pumping group. The system is characterized by the installation, upstream of the pumping unit, of a distillation gas condenser. It is composed of a watertight box inside which are placed stainless steel plates cooled by circulation of cold water. These plates have a large heat exchange surface, they are mounted in baffles which can be automatically oriented to more or less brake the circulation of the fluid as a function of its temperature. According to claims 1, 3 and 4 the system is characterized by the passage of gases in a washing column in which a constant water level is maintained. The non-condensable gases are conveyed, at the discharge of the pumping unit, in a sheath whose end is immersed in the water table. In its upper part, the sheath is equipped with a spraying ramp which forms a film of water through which the gases pass. Washing is therefore done by precipitation of water and bubbling in a single device. According to claim 1, the heat treatment process is characterized by automatic programming of the heating cycle (plate 2/3). This cycle takes place in 6 successive segments. Segment 1: purging of the sealed distillation chamber; segment 2: temperature rise of 150 ° C; segment 3: maintaining the temperature at 150 ° C. for dehydration of the products; segment 4: temperature rise of 500 ° C; segment 5: maintaining the temperature at 500 ° C for processing products; segment 6: cooling phase of the enclosure before unloading.

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