FR2792061A1 - METHOD AND APPARATUS FOR PROCESSING JUICES OF WASTE STORAGE PITS INTENDED TO BE INCINERATED IN AN INCINERATION PLANT - Google Patents

Abstract

The invention relates to a method for treating the juice of waste storage pit (s) intended to be incinerated in a plant. A method and an installation for treating the juice of waste storage pits for incineration in an incineration plant. incineration characterized in that it comprises the steps of: - subjecting said pit juice (s) an evaporation step leading to a gaseous fraction enriched in volatile constituents and a pellet containing most of the pollutants of said juices ; condensing said gaseous fraction so as to obtain a condensate consisting essentially of water; conveying said pellet to an incineration furnace of said incineration plant, or to said pit. The invention also relates to an installation for carrying out such a method.

Description

Process and installation for treating the juice of storage pits

  waste to be incinerated in an incineration plant.

  The invention relates to the field of waste treatment by incineration. The invention is particularly applicable in the field of incineration of household waste. Garbage, particularly those collected in some parts of the world such as Asia, is characterized by a large fraction of kitchen, food and plastic waste. This waste is stored in pits before being destroyed by incineration in factories provided for this purpose. The high proportion of water initially present in this garbage, as well as the mechanisms of degradation of the fermentable compounds they contain,

  generate highly charged juices of organic matter.

  So far, these pit juices are collected and either diverted to wastewater treatment plants (where economic and regulatory conditions permit), or pulverized in incineration furnaces for burning. The latter solution, however, has the major disadvantage of causing a decrease in the efficiency of the incinerator related to low PCI (close to 0 kcal) of

these juices.

  The main objective of the present invention is to propose a new process for the treatment without liquid discharge of these pit juices not involving

  the disadvantage mentioned in the previous paragraph.

  Another objective of the present invention is to propose such a method which makes it possible to limit the impact it generates on the operation

incineration furnaces.

  Another object of the invention is to describe such a process which can be implemented by means of compact processing means and

  integrating easily into an incineration unit.

  These various objectives are achieved by means of the invention which relates to a process for treating waste pit juice (s) intended to be incinerated in an incineration plant, characterized in that it comprises the steps of:

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  subjecting said pit juices to an evaporation stage leading to a gaseous fraction enriched with volatile constituents and a pellet containing most of the pollutants of said juices; condensing said gaseous fraction so as to obtain a condensate consisting essentially of water; conveying said pellet to an incineration furnace of said plant

  incineration, or to said pit.

  The invention thus proposes in an original way to subject the pit juice evaporation allowing to concentrate in the base most of the pollution of these pit juices. Such an evaporation step presents

many advantages.

  First, it should be noted that the calories needed for this step are widely present in waste incineration plants such as factories

  heat treatment of household waste.

  In the second place, it will also be noted that the pellets obtained during such a step have a reduced volume which does not cause any disturbance

  significant impact on the energy balance of the incinerator.

  Finally, it should also be noted that the condensate obtained from the gaseous fraction originating from the evaporation stage is very low in pollutants and can generally be directly discharged into the natural environment. We'll see

  however below that this condensate can be valued in different ways.

  According to a preferred embodiment of the invention, the evaporation step is conducted at a pressure below atmospheric pressure. The pressure used may vary depending on the nature and quantity of treated pit juice. In practice, a pressure of between 0.5 and 0.9 bar will be preferred. In a way

  most preferred, a pressure of 0.75 bar will be used.

  The temperature at which the evaporation step will be carried out may also be determined according to the nature and the quantity of pit juices to be treated by the process according to the invention. Preferably, a temperature of between 75.degree. C. and 100.degree. C. will be used.

will use a temperature of 90 C.

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  As already mentioned above, the condensate obtained at the end of the step of condensing the gaseous fraction from the evaporation stage consists essentially of water. However, some pollutants may remain in this condensate. According to a variant of the invention, the method may therefore also include a condensate purification step. This purification step may be carried out using any conventional purification process including a biological purification process or a process

purification by filtration.

  According to a preferred variant of the invention, the process also comprises a step of adding at least one anti-foaming agent to the pit juices before or during said evaporation step. Indeed, it can occur during this step a development of large amounts of foams consist of soap type compounds, surfactants. Such foams can disturb the evaporation step. It will be noted in particular that such foams

  can interfere with temperature regulation during the evaporation step.

  These foams can also pollute the equipment used and be found

  in the condensates or deposit in the ducts.

  In the context of the process according to the present invention, it is possible to use various types of anti-foam agents known from the state of the art. However,

  preferably, a silicone antifoam agent will be used.

  This antifoaming agent could be added in a variable amount, depending on the nature of the treated pit juice. However, according to a preferred variant, it will be

  added at a rate of 50 to 150 mg / l. Most preferably, the anti-inflammatory agent

  Moss will be added to pit juice at a rate of 100 mg / l.

  According to a particularly advantageous variant of the invention, the condensate obtained at the end of the above-mentioned condensation step, consisting essentially of water, may, after a treatment of possible purification, be conveyed at least in part towards the cooling system classically put

  in the incineration plant, or in the slag extractor.

  The invention also relates to an installation for carrying out such a method characterized in that it comprises at least one waste storage pit to be incinerated in an incineration plant, at least one evaporation unit. said juice, at least one condensing member of the gas fraction from said evaporation unit, at least one pipe for conveying the pellets from said evaporation unit to said incineration plant. Preferably, said installation includes means for dispensing at least one anti-foam agent into said juices before they enter said

evaporation unit.

  Preferably, said installation comprises at least one pipe for conveying condensates from said body of

  condensation towards said incineration plant.

  The invention, as well as the various advantages that it presents, will be

  more easily understood thanks to the following description of a mode not

  limiting embodiment thereof given with reference to the single figure which shows schematically an installation implementing the method

in question.

  With reference to FIG. 1, the installation represented for the implementation of the method comprises a refuse storage pit I and a

  storage tank the juice from this pit.

  The installation also comprises an evaporation unit 2 to which the juice from the storage unit is conveyed through a pipe 3 and 4 pumping means adequate. The installation further comprises a condensing unit 5 towards which the gaseous fraction

  from the evaporator 2 is conveyed through a pipe 7.

  The installation also comprises a pipe 8 conveying the pellets from the evaporation unit 2 to the incineration plant 9 used to

  destroy garbage from the pit 1.

  The evaporation unit 2 is heated by means of a steam circuit 10 coming from a turbine 9a integrated into the incineration plant (represented by

  distinct way on the diagram for the sake of clarity of the description).

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  The condensing member 5 operates by means of water obtained by cooling steam from said turbine 9a and flowing in a

  circuit 11 incorporating a heat exchanger 12 and pumping means 13.

  Note that this water serves not only the condenser member 5 but also serves to cool the excess steam from the circuit 10 into another condensing member 14 provided thereon. Water from circuits 10 and

  I 1 is then fed into a reservoir 15.

  According to the present invention, the condensates from the condensing member 5 are conveyed by a pipe 16 to the circuit

  17 of the incineration plant.

  It will be noted that to facilitate the evaporation of pit juice, the installation also comprises means for introducing an anti-foam agent 18 into

  these provided on line 3.

  Tests were carried out on a pilot installation using the principle of the installation shown in the single figure. A raw sample of pit juice was taken. This sample is mostly composed of water and is heavily loaded with organic matter. Table 1 below summarizes the

  main characteristics of this sample.

  sample pH 8 Water content in% 89 COD (mg / l) 2000 PCI (kcal) <0.01

Table 1

  ml of this sample was placed in an evaporation unit with a 500 ml evaporation flask. The temperature has been raised to

   C. The boiling was regulated by the addition of some grains of pumice stones.

  This evaporation was carried out at a reduced pressure of 0.75 bar in the presence

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  an anti-foam agent introduced into the raw effluent at the rate of 17 mg for mi. At the end of this evaporation step, a pellet having the characteristics mentioned in Table 2 below was obtained: Brut Pellet Volume (ml) 200 25

PCI <0.01 <0.01

  Water (mass%) 90 86 COD (mg / l) 2,000> 104 Cd (mg / l) - <1 Cr (mg / l) - <1 Pb (mg / l) - <1 Sn (mg / l) - 5 Fe (mg / l) - 30 Cu (mg / l) - <1 Zn (mg / l) <1 Al (mg / l) - 45 Ni (mg / l) - <1 Mg (mg / l) - 310 Mn (mg / l) - <1

Table 2

  The pellet is mainly composed of water and has a very high COD greater than 10 '.

very important pollution.

  The gaseous fraction obtained after the evaporation step has been condensed and has the characteristics mentioned in Table 3 which include

  also the standards of rejection standards currently in force in France.

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  Aqueous phase Requirements for the discharge standard pH 8.8 5.5 to 8.5

  Condensed volume (ml) 160 Water (% by mass) 100 -

  COD (mg / l) 150 From 125 to 130 depending on the flow of BOD5 (mg / l) <5 30 Cd (mg / l) <0.01 0.2 Cr (mg / l) 0.03 0.5 Cu (mg / l) <0.01 0.5 Fe (mg / l) 0.03 5 Mn (mg /) <0.01 1 Hg (mg / l) <0.01 0.05 Ni (mg / l) ) 0.02 0.5 Pb (mg / l) 0.04 0.5 Zn (mg / l) 0.5 2 AI (mg / l) 0.03 5 Fluorides (mg / l) <0.4 15 Nitrates (mg / l) 0.86 30 Phosphates (mg / l) 1.56 10

MES E 100

  Hydrocarbons Not likely 10 Organic compounds <0.001 1 halogenated -----

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Table 3

  These analyzes show that the aqueous phase obtained after condensation

  complies with French rejection standards.

  The embodiment of the invention described here is not intended to reduce the scope thereof. As a result, there may be

  numerous modifications without going outside the scope.

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Claims (15)

  1. A method of treating waste pit juice (s) waste to be incinerated in an incineration plant characterized in that it comprises the steps of: - subjecting said pit juice (s) a step evaporation leading to a gaseous fraction enriched in volatile constituents and a pellet containing most of the pollutants of said juices; condensing said gaseous fraction so as to obtain a condensate consisting essentially of water; conveying said pellet to an incineration furnace of said incineration plant. 2. Method according to claim 1 characterized in that said step   evaporation is conducted at a pressure below atmospheric pressure.   3. Method according to claim 2 characterized in that said step   evaporation is conducted at a pressure between 0.5 and 0.9 bar.   4. Method according to claim 2 characterized in that said step   evaporation is conducted at a pressure of 0.75 bar.   5. Method according to any one of claims 1 to 4 characterized in that   that said evaporation step is carried out at a temperature between  C and 100 C.   6. Method according to claim 5 characterized in that said step   evaporation is carried out at a temperature of 90 C.   7. Method according to any one of claims 1 to 6 characterized in that   it comprises a purification step of said condensate.   8. Process according to any one of Claims 1 to 7, characterized in that   it consists in adding at least one antifoaming agent to the said juice of pits before   or during said evaporation step.   9. Method according to claim 8 characterized in that said anti-aging agent Foam is silicone based.   10. The method of claim 8 characterized in that said anti-aging agent   foam is added to said pit juice at a rate of 50 to 150 mg / l. 2792061   11. The method of claim 10 characterized in that said anti-aging agent   foam is added to said pit juice at a rate of 100 mg / l.   12. Process according to any one of claims I to 11, characterized in   it comprises a step of conveying at least a portion of said condensate into the cooling circuit of said incineration plant or in the slag extractor.   13. Installation for carrying out the process according to any one   claims I to 12 characterized in that it comprises at least one   pit (1) for storing waste for incineration in an incineration plant (9), at least one evaporation unit (2) for said juice, at least one condensing unit (5) for the gas fraction from said evaporation unit, at least one pipe (8) for conveying the caps   from said evaporating unit to said incineration plant.   14. Installation according to claim 13, characterized in that it includes means (18) for dispensing at least one defoaming agent in said juices.   before entering said evaporation unit (2).   15. Installation according to claim 14 characterized in that it comprises at least one pipe (16) for conveying condensates from said condensing member (5) to the cooling circuit (17) of said incineration plant.