RU2483814C1 - Method of disposal of solid toxic ashy wastes from incinerator plant filters - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to disposal of solid toxic wastes by thermal treatment. Solid toxic ashy wastes are fed into worm reactor mounted inside incinerator above fore-grates behind combustion zone. Said wastes are carried by worm reactor conveyor simultaneously with feeding of inert gas in said reactor at pressure exceeding that of saturation of ash chlorine-bearing components to prevent desorption of said components from the surface of ashy toxic wastes. Toxic ashy wastes are heated on conveyor to temperature of detoxication and formation of nontoxic stable natural minerals. Obtained minerals are directed to further recovery.

EFFECT: higher ecological safety.

3 cl, 1 tbl

Description

The invention relates to the field of disposal of solid toxic waste and can be used for waste disposal of gas treatment systems of incinerators (MSZ) by heat treatment.

A known method of disposal of solid toxic ash waste from filters MSZ (JP 2000176414 A, published. 06/27/2000). The method provides detoxification of heavy metals in solid ash waste and fly ash at low cost. The method includes vacuum heating of ash, removal of gas generated in the stage of vacuum heating of ash, supply of an inert gas to cool the vacuum heater. It is preferable to heat the ash in vacuum at a temperature of 1600-1800 ° C and a pressure of 4.8 × 10 ⁸ Pa.

A disadvantage of the known invention is the detoxification of ash from heavy metals only, since under the stated conditions, organochlorine compounds from the ash are desorbed and dissociated in a vacuum in a gas phase, and upon subsequent cooling in a gas phase, recombinant dioxins arise. These dioxins enter the gas treatment system again and are again sorbed by ash and activated carbon. Thus, the destruction of dioxins and final detoxification according to the claimed method does not occur.

The prototype of the proposed invention is a method for the disposal of solid toxic ash waste from MSZ filters (JP 2002081631, published. 03.22.2002), which is aimed at reducing the concentration of dioxins in the ash of the incinerator.

According to the invention, the ash generated after the waste burning zone in the incinerator is conveyed through a sluice through a sluice to a second rotary kiln together with high-temperature exhaust gases. The furnace organizes the process of heating slag and ash at high pressure, which prevents the desorption of toxic substances, thereby neutralizing the ash.

The disadvantage of this method is a rather complicated technology that requires quite sophisticated equipment in the form of an additional rotary kiln, in which not only toxic ash, which is less than 1% of the mass of waste burned, but also non-toxic slag, up to 30%, is heated. In this case, contamination of non-toxic slag by diffusion by toxic compounds and elements is possible.

The invention achieves the technical result, which consists in increasing the environmental safety of the MSZ through the detoxification of solid toxic residues of gas treatment of incinerators with the production of non-toxic stable classified natural minerals.

The specified technical result is achieved as follows.

In the method for the disposal of solid toxic ash waste from the filters of the incinerator, the supply of solid toxic ash waste is carried out in a screw reactor installed inside the furnace of the incinerator above the grate after the combustion zone.

Solid toxic ash waste is transported by the conveyor of the screw reactor with the simultaneous supply of inert gas to the screw reactor under a pressure higher than the saturation pressure of toxic chlorine-containing ash components and preventing the desorption of these components from the surface of toxic ash waste particles. When moving along the conveyor, toxic ash wastes are heated to a temperature at which the detoxification process occurs with the formation of solid non-toxic stable natural minerals. The supply of the obtained minerals is carried out for further disposal.

In the method, an inert gas is supplied at a pressure of 1.12 × 10 ⁵ Pa to 1.16 × 10 ⁵ Pa.

In addition, the heating temperature of toxic ash waste when moving along the conveyor is from 750 ° C to 900 ° C.

As a result of heat treatment of solid toxic ash wastes in an inert environment, the destruction of dioxins and the formation of stable non-toxic chlorine-containing natural minerals occur:

Ca ₁₂ (Al _10.6 Si _3.4 O ₃₂ ) Cl _5.6 - Wadalite,

Ca _9.4 (SO ₄ ) ₃ (SiO ₄ ) ₃ Cl _0.8 - Chlorellstadite 2 (Clorellstadite 2);

Ca ₁₀ · (SO ₄ ) ₃ (SiO ₄ ) ₃ Cl ₂ — Chlorellstadite 1 (Clorellstadite 1);

CaOHCl - sodium hypochloride;

NaCl - sodium chloride;

KCl - potassium chloride.

When carrying out the process according to the proposed method, dioxins are not desorbed from the surface of the particles of the ash of the incineration plant into the gas phase, but toxic compounds in the solid phase are destroyed and free chlorine forms in the identified natural non-toxic minerals, which is confirmed by the absence of chlorine in the gas phase when the process according to the proposed way.

The invention is illustrated in the drawing, which shows the technological scheme of thermal detoxification of ash waste from MSZ filters.

The drawing shows a waste incinerator 1, an airtight screw reactor 2, an electric motor 3, a sluice 4, a tubular heat exchanger 5, an inert gas supply line 6, filter ash ash supply line 7, slag 8, ash 9 after heat treatment.

The invention is as follows.

Solid toxic ash waste is fed through line 7 to a sealed screw reactor 2, installed in the hearth of the furnace 1 for the incineration of waste 1 of the MSZ under the repulsive gratings.

The ash, moving along the conveyor belt of reactor 2, is heated to a temperature at which the detoxification process occurs with the formation of solid non-toxic stable natural minerals, which include:

Ca ₁₂ (Al _10.6 Si _3.4 O ₃₂ ) Cl _5.6 - Wadalite;

Ca _9.4 (SO ₄ ) ₃ (SiO ₄ ) ₃ Cl _0.8 - Chlorellstadite 2 (Clorellstadite 2);

Ca ₁₀ · (SO ₄ ) ₃ (SiO ₄ ) ₃ Cl ₂ — Chlorellstadite 1 (Clorellstadite 1);

CaOHCl - sodium hypochloride;

NaCl - sodium chloride;

KCl - potassium chloride.

The temperature of heating toxic ash wastes when moving along conveyor 2 is from 750 ° C to 900 ° C. In accordance with the results of preliminary experiments and calculations, this temperature range corresponds to the maximum reaction rates of dissociation of toxic chlorine-containing ash components and the maximum reaction rates of formation of solid non-toxic stable natural minerals. When the temperature drops below 750 ° C, the time of the detoxification process increases significantly. This reduces the economic efficiency of the proposed process. If the temperature exceeds 900 ° C, the detoxification reaction zone must be additionally heated with an external heat source, while at temperatures below 900 ° C, the heat source in the reaction zone is the exhaust gases in the incinerator.

At the same time, inert gas is supplied to screw reactor 2 through line 6 at a pressure higher than the saturation pressure of toxic chlorine-containing ash components and preventing the desorption of these components from the surface of toxic ash waste particles. The indicated inert gas pressure is from 1.12 × 10 ⁵ Pa to 1.16 × 10 ⁵ Pa. In this pressure range, the transition to the gas phase of the products of dissociation of toxic chlorine-containing compounds is impossible and they enter into synthesis reactions with solid components of the gas treatment products, such as calcium hydroxide, activated carbon, silicon dioxide and alumina. As a result of synthesis reactions, solid non-toxic stable natural minerals are formed.

The obtained non-toxic stable natural minerals are fed for further disposal along with non-toxic slag.

Warm heated inert gas, such as argon, enters the water tube heat exchanger 5, where it is cooled and returned to the screw reactor 2 to create a protective inert atmosphere.

An example implementation of the invention is illustrated in table 1, which shows the concentration of solid non-toxic stable natural minerals at various stages of heating toxic chlorine-containing components of ash MSZ No. 2 in Moscow.

As follows from the results presented in the table, the completeness of the detoxification process corresponds to 100%.

Table 1 T ° C 20 ° C 300 ° C 600 ° C 900 ° C Concentration, vol.% Total% Cl,% Total% Cl,% Total% Cl,% Total% Cl,% NaCl 7.14 4.3328 6.63 4.0212 7.48 4.53630 6.65 4.0317 Kcl 3.07 1.4605 1.88 0.8947 3.08 1.4651 5.41 2.5735 Clorestadite 1 7.15 0.4525 6.61 0.418834 4.88 0.3093 0 0 Clorestadite 2 5.62 0.1514 0.17 0.004715 11/13 0.35285 25.97 0.69914 Wadalite 0 0 0 0 0 0 10.07 0.121214 CaClOH 3.18 1.21870 4.21 1.61338 1.270 0.48678 1.816 0.69572 Toxic organochlorine compounds 1-4 0.44044-1.76176 0 0 0 0 0 0 Total: one hundred%

$$\Delta \left|\frac{18.7}{5.3}\right|$$

$$\Delta \left|\frac{23.75}{11.25}\right|$$

$$\Delta \left|\frac{13.41}{0.8}\right|$$

Claims (3)

1. The method of disposal of solid toxic ash waste from the filters of the incinerator, in which the supply of solid toxic ash waste is carried out in a vise reactor installed inside the furnace of the incinerator above the grate after the combustion zone, the movement of solid toxic ash waste is carried out by a conveyor of a screw reactor with simultaneous feeding into inert gas screw reactor under a pressure exceeding the saturation pressure of toxic chlorine-containing ash components and preventing de orbtsii these components from the surface of the ash particles of toxic waste, heating is carried out of toxic waste ash when moving along the conveyor to a temperature at which the detoxification process to form stable nontoxic solid natural minerals, and minerals derived performed supply for further recycling. 2. The method according to claim 1, in which the inert gas is supplied under pressure from 1.12 · 10 ⁵ Pa to 1.16 · 10 ⁵ Pa. 3. The method according to claim 1, in which the temperature of the heating of toxic ash waste when moving along the conveyor is from 750 ° C to 900 ° C.

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