ITBS980013A1 - PROCESS AND DEVICE FOR DISPOSAL BY COMBUSTION OF LIQUID WASTE - Google Patents

Description

DESCRIPTION

of the PATENT FOR INDUSTRIAL INVENTION

having as title:

"PROCESS AND DEVICE FOR DISPOSAL BY

COMBUSTION OF LIQUID WASTE "

The present invention relates to a process for the disposal by combustion of both toxic-noxious and non-toxic liquid waste, and a device for setting up such a disposal process.

The limitations and problems deriving from the disposal of liquid waste are known, especially, but not only, if toxic-harmful, due to the variety of substances and particles that may be present in said waste and the risk of causing environmental pollution if the disposal treatment is certainly not complete and reliable.

The object of the present invention is to remedy these problems and to achieve an efficient disposal of liquid waste regardless of their compositions and without negative collateral influences.

Such an object is achieved, according to the invention, with a liquid waste combustion disposal process according to claim 1 and with a treatment device according to claim 7.

The disposal process proposed here essentially consists of a molecular dissociation of the liquid to be treated. It includes in particular a preventive nebulization of the starting liquid, a pressurized combustion of the atomized liquid in a reactor in the presence of a comburent formed by a mixture of combustible gas and an oxidizing reagent, an expansion of the combustion products downstream of the reactor followed by a further partial cooling for the condensation and collection of the solidifying materials and by a subsequent passage of the residual gases in a scrubbing bubbler and in a water vapor condenser before discharging the residual gases.

The oxidizing mixture can be expressed in the following brute molecular formula:

where (Xm Ok) represents the reactant (where X stands for nitrogen or hydrogen ,, m is a numerical value from 0 to 10 and k is a numerical value from 1 to 16); a varies from about 30,000 to about 35,000 mol / ton of liquid; and b varies from 600 to 10,000 mol / ton liquid, depending on the average calorific value of the liquid to be treated.

The reagent can be selected for example and advantageously from:

- Nitrogen peroxide (X = N; m = 1; K = 2) - Oxygen (m = 0; k = 2)

- Hydrogen peroxide (X = H; m = 2; k = 2)

The process pressure P can vary from 5 to Pmax absolute bar, depending on the smaller or larger quantity of metals or metalloids present in the liquid to be treated. The maximum value is not specific but depends exclusively on the mechanical resistance of the process device: for the liquids examined, Pmax = 30 bar.

The first characteristic of the process is its reaction speed, which is higher than that of normal combustion at atmospheric pressure. Indicating with d = fixed number (44.643 mol / mc)

f = fraction of oxidizable elements in the treated liquid

q = bk = moles (average value) of oxygen needed to oxidize 1 mol of oxidizable compound in the liquid, excluding methane,

the molar volumetric concentrations C and C, respectively, of oxygen and oxidisables are (mol / mc):

in which a is negligible, therefore the reaction rate V, proportional to the product of the two concentrations, is valid, omitting the proportionality coefficient:

In the case of normal combustion, the values result

and its reaction rate

for which the ratio R between the reaction rates in the two cases is:

EXAMPLE 1

In a treatment (particularly unfavorable) for the disposal of spent lubricating oil, mixed with 50% of washing water, we have:

In the cases of the various types of reagent proposed, we have:

Since, in the example cited, oxidizable elements that are normally incombustible are absent, the reaction pressure can be reduced, so that the value P = Pmin = 5 bar is adopted.

Nevertheless, the values of R in the three cases mentioned are respectively 93,124,73.

In case of presence of metals, metalloids, etc., which are normally incombustible, for example P = 25 bar is adopted, so the values of R are respectively 2325, 3088, 1813.

EXAMPLE 2

In example 1 above, the combustion of methane and the oxidation of a fraction f of the elements C and H generate useful heats (taking into account the heats of vaporization), respectively:

The remaining number of non-oxidized molecules holds

The heat absorbed by the vaporization of the water and the non-oxidized liquid is:

Specific heats vary with temperature. As a first approximation, it is possible to assume an average value

The temperature difference ΔΤ obtained is worth:

By introducing into the process 10 Nmc / ton of methane, corresponding to a = 450 moles / ton, we obtain:

that is, the oxidation of only 32% of the oxidizable elements is sufficient to reach the expected temperature, with a consequent reduction of mk and therefore of the quantity of necessary reagent.

Furthermore, the additional thermal energy available in addition to that deriving from the combustion of methane is valid (taking into account the condensation heat of the water:

for which ΔTmax = 1820 ° C would represent the maximum temperature increase in the (absurd) hypothesis of a = ∞. Furthermore, in this case, the value a = 450 mol / ton does not correspond to any physically achievable result, while, for example, for a = 6300 mol / ton (1400 Nmc / ton, or 1 ton of methane / ton of liquid, industrially impossible hypothesis), the temperature increase would not exceed 1450 ° C, with the absence of additional thermal energy.

The increase in the reaction speed and temperature makes the process effective and self-propagating both for the combustible elements contained in the liquid to be treated, and for those normally not combustible, with a considerable increase in the thermal energy available (if energy recovery is considered convenient ).

The cold start of the process can be achieved by:

-Electric distributor

-Hydrogen Peroxide + Magnesium Permanganate: (Hypergolic mixture);

- Hydrogen Peroxide + Hydrazine Hydrate: (Hypergolic Blend).

The temperatures reached allow the complete dissociation of the molecules of the treated liquid, eliminating any toxicity.

The main process volume is followed, through an adjustable nozzle, by an expansion volume, in which the process vapors expand, reducing the temperature to about 800-900 ° C, thus preventing any possible recombination.

The vapors are then sent to a heat exchanger, to an acidifier and neutralizer for the halogens, to a water condenser, and finally to the chimney at about 80 ° C.

During the phases following the primary process, the condensed elements are collected according to their respective melting-solidification temperatures.

During the process, special thermobarometric probes send the data to a process computer, which separately regulates the flow rates of liquid, methane and reagent, as well as regulating the diameter of the expansion nozzle.

A description of the device for the implementation of the above process now follows, with reference to the attached drawing, which represents a diagram of the device itself.

The device is composed of a reactor bottom (1), a drain (13), a cooling duct (15), a scrubbing bubbler (18) and a water vapor condenser (19).

The metallic cylindrical furnace-reactor (1), with a length / diameter ratio approximately equal to 4, for example length 6 m and diameter 1.5 m.

The peripheral internal surface of the furnace (1) is separated from the process volume by groups of refractory material (2) in a honeycomb shape placed side by side, which can be easily removed or replaced from / in the furnace (1) in case of maintenance.

The head wall of the furnace (1) consists of a metal front plate (3) flanged to the furnace (1) itself, in which a certain number are inserted on a circumference concentric to the axis of the furnace (1), such as example 4, of injectors-nebulizers (4) for the introduction of the liquid to be treated, fed by a pumping group of suitable capacity, for example 10 Ton / h, not shown.

A double concentric comburent nozzle (5) is inserted in the center of the front plate (3) for introducing the comburent-reagent mixture into the oven (1) by means of a pumping unit not shown.

At the center of the combustion nozzle (5) there is a double ignition electrode (6), served by a low voltage distributor, not indicated, whose operation, controlled by a process computer, can also take place during operation. fully operational, if the rate of combustion were to be reduced to non-self-sustaining levels.

The front plate (3) is insulated on the internal face of the oven (1) by a suitable refractory layer.

The bottom wall of the furnace (1) consists of a rear metal plate (7) flanged to the furnace (1) itself, in the center of which an expansion nozzle (8) with variable diameter is inserted, controlled by the process computer.

The rear plate (7) is insulated on the internal face of the oven (1) by a suitable refractory layer.

On the internal surface of the furnace (1) some nozzles (9) are inserted to allow the peripheral introduction of additional comburent controlled by the process computer, if the temperature data provided by thermometric probes (11) indicate the need for post-combustion in the second part of the oven volume (1).

The additional comburent flows into the process volume through a gap existing between the internal surface of the furnace (1) and the external surface of the refractory groups (2), and through radial openings made in the refractory groups themselves (2).

On the external surface of the oven (1) there are housings for the installation of thermometric probes (11) and barometric probes (12); the probes (11) and (12) send the temperature and pressure data to the process computer for process regulation and control.

The discharger (13) consists of a parallelepiped metal volume lined internally with refractory, into which the expanded vapors enter through the expansion nozzle (8), at a temperature between 750 and 1000 ° C, and in which condensation begins in solid form of the elements such as (Fe, Cu, Si, Mg, etc.) possibly present, whose melting-solidification temperature is higher than the indicated values, which are collected in a special condenser (14).

In one wall of the trap (13), the cooling duct (15) is installed, for example vertically. This consists of a circular metal conduit internally lined with refractory, in which a tube bundle (16) is inserted, consisting of an appropriate number of stainless steel tubes, externally insulated with refractory, in which pumped air flows with adequate flow from a specific pumping unit (17).

The cooling duct (15) can be combined with a heat exchanger for the production of saturated or superheated steam for a possible production of electricity, if required.

The vapors coming from the drain (13) flow into the interspace between the cooling duct (15) and the tube bundle (16). The tube bundle (16) is sized in such a way that the temperature of the vapors coming from the discharger (13) decreases during the path in the tube bundle (16) itself, up to values, for example, not lower than about 250 “C. products whose melting-solidification temperature is between 1000 "C and 250" C (Al, Pb, etc.) condense along the tube bundle (16), and are collected in special condensers similar to the condenser (14). of a vertical cooling pipe (15), the condensates in the trap (13) and in the cooling pipe (15) are collected together by gravity in the condenser (14). traditional fume purifiers, is located after the cooling duct (15) and connected to the tube bundle (16), and carries out the following processes:

- Washing of the vapors from any residual dust - Acidification and neutralization, for example with milk of lime or products and systems usually used, of the chlorine and fluorine that may be present in the vapors.

-Decrease in the temperature of the vapors up to values not lower than 150 ° C

With methods and devices normally associated with traditional bubblers, the washing water of the bubbler (18) is filtered from the powders and the halogen neutralization products, and cooled by a usual closed circuit exchanger. The bubbler (18) can be replaced by a dry purifier, which is also normally available.

The steam condenser (19) consists of a normal tube bundle heat exchanger with air or water cooling by means of a pumping unit not shown. The vapors coming out of the bubbler (18) circulate outside the tube bundle of the condenser (19) so that their temperature decreases to 80-90 ° C. In the condenser (19) the water vapor due to the combustion of methane condenses in liquid form, that introduced by the bubbler (18) as well as that possibly present in the treated liquid.

From the condenser (19) the residual gas, consisting almost essentially of carbon dioxide and traces of nitrogen oxides, sulfur dioxide, etc., in quantities and concentrations much lower than the maximum levels provided for by the current legislation, are sent to the chimney (20) and discharged into the atmosphere.

Claims (11)

R I V E N D I C A Z I O N I 1. Process for the disposal of toxic-noxious and non-toxic liquid waste, comprising a preventive nebulization of the starting liquid and its injection into a reactor, a pressurized combustion of the atomized liquid in the reactor in the presence of a comburent formed by a mixture of combustible gas (methane) and a reagent (oxidant) to oxidize any substance in the atomic form or compound present in the liquid, an adiabatic expansion of the combustion products downstream of the reactor to prevent any molecular recomposition, followed by a first partial cooling of the combustion products for the condensation and collection of the solidifying materials and from the subsequent passage of the residual gases in a scrubbing bubbler and in a steam condenser for further cooling of the fumes before their discharge to the atmosphere. 2. Process according to claim 1, wherein combustion is carried out at a pressure of about 5 to 30 bar or more. 3. Process according to claim 1, wherein the oxidizing mixture is generically represented by the molecular formula: where where (Xm Ok) represents the reactant (where X stands for nitrogen or hydrogen, m is a numerical value from 0 to 10 and k is a numerical value from 1 to 16); a varies from about 30,000 to about 35,000 mol / ton of liquid; and b varies from 600 to 10000 mol / ton of liquid depending on the average calorific value of the liquid to be treated. 4. Process according to claim 3, wherein the reactant (Xm Ok) is at least one compound selected from nitrogen peroxide, oxygen and hydrogen peroxide. 5. Process according to the preceding claims, in which the process speed is at least about 100 times the normal combustion speed at atmospheric pressure, and the process temperatures higher than 2000 ° C reached also with the caloric contribution of incombustible elements or compounds oxidized. 6. Process according to the preceding claims, in which the combustion is self-propagating and can be sustained with an additional supply of comburent in various parts of the reactor for a post-combustion action. 7. Device for the disposal of toxic-noxious and non-toxic liquid waste with the process of claim 1, characterized by a reactor (1) maintained at a given pressure, by injectors-nebulizers for the delivery of a nebulized liquid to be disposed of at the inlet in said reactor, by at least one comburent nozzle for the introduction of a comburent-reactant mixture in said reactor, by an electric or chemical igniter for starting the combustion process in the reactor, by a trap at the outlet of said reactor for a cooling of the combustion products through an adiabatic expansion for a first condensation of solids, followed by a heat exchanger for a further reduction of the temperature of the gases and the condensation of other solids from a gas scrubber and a condenser of the water vapor before the gases are discharged from a final stack. 3. Device according to claim 7, in which the furnace-reactor has a ratio between its length and its width of not less than 4. 9. Device according to claims 7 and 8, in which the furnace-reactor has lateral outlets for the introduction of an additional comburent. 10. Device according to claims 7-9, wherein the trap comprises an adjustable expansion nozzle. 11. Process and device for the disposal by combustion of solid waste, as substantially described above, illustrated and claimed for the specified purposes.