RU2249766C2 - Method of incineration of solid household and other organic wastes and a device for its realization - Google Patents

Abstract

FIELD: methods and devices for incineration of the household and other organic wastes.

SUBSTANCE: the invention is dealt with non-polluting methods and devices for incineration of solid household and other organic waste materials and may be used, in particular, in the communal-general services at incineration of waste products with the guaranteed reduction of hazardous substances including dioxins and with utilization of a heat of incineration of the wastes products and production of commercial lime. The technical result is creation of an ecologically profitable process of incineration of solid household and other organic waste materials with a guaranteed reduction of hazardous substances, including dioxins, present in the gas blowouts, an increase of profitability of incineration plants at the expense of realization of the commercial products produced in the process of the utilization. The method of incineration of the solid household and other organic waste materials includes incineration of the waste products at feeding of preheated air, afterburning of gaseous products of incineration, after-treatment for binding HCl, Cl₂, HF, passing through a heat exchanger-boiler, a gas-cleaning. Before feeding into a furnace for incineration the waste products are separated, an organic part of the waste products is comminuted up to the sizes of not exceeding 100 mm. Then the wastes are mixed with the air heated up to temperature of 300-400° С and fed tangentially into a cyclone furnace with a linear speed of no less than 28 m/s. Incineration is realized at the temperatures of 1320-1350° С, afterburning is realized in the chamber of catalytic afterburning at the temperatures of 1300-1500° С, the binding treatment of HCl, Cl₂, HF is conducted in the chamber of a decarbonization of a limestone flour with production of unslaked lime. Before feeding into the boiler the treated products of incineration are passing through the air heater, and after the boiler - through a system of wet gas purification. At that a thermal energy of the boiler is fed to consumers. There is a description of an installation for realization of the method is described.

EFFECT: the invention ensures creation of an ecologically profitable process of incineration of solid household and other organic waste materials, reduction of hazardous substances present in the gas blowouts, increased cost effectiveness of incineration plants.

5 cl, 2 dwg, 2 ex

Description

The invention relates to environmentally friendly methods and devices for burning solid household and other organic waste and can be used, in particular, in the household sector when burning waste with guaranteed suppression of harmful substances, including dioxins, with the utilization of the heat of combustion of waste and production commodity lime.

There is a known method of garbage processing at the Moscow special plant No. 3 ("Sanitary cleaning and cleaning of populated areas". Handbook, 1990), the main technological equipment for which was supplied by the Volund company (Denmark). A distinctive feature of this design is a rotary afterburning drum installed behind a cascade of inclinedly pushing grate grates, which allows high-humidity waste to be burned in the boiler unit.

The disadvantage of this method is the thermal processes in incineration plants due to the presence of a dry ash and slag removal system and, therefore, to avoid slagging of technological equipment occur at temperatures of 900 ... 1000 ° C and therefore do not allow to solve the problem of suppressing hazards, in particular, dixins.

Irreversible destruction of thermally stable organochlorine compounds (dioxins) occurs at temperatures close to 1400 ° C.

A known method of processing solid waste in a slag bath under design conditions of smelting, where by loading a certain amount of the necessary fluxes, for example, containing silica (sand, quartz fluxes, etc.), is selected according to viscosity and melting point (usually 1300-1500 ° C) slag composition (RU 2030684 C1, F 23 G 7/00, 03/10/1995). The process is carried out at a controlled oxygen potential (oxidizing conditions), which is specified by the specific oxygen consumption per tonne of charge.

The disadvantage of this method is not taken into account the ability of dioxins to a new synthesis at low temperatures. This is especially promoted by the characteristic conditions of a large removal of dust and toxic metal compounds characteristic of the known method.

A known method of heat treatment and destruction of garbage and household waste in a device, which is a vertically located housing lined with refractory material (RU 2023211 C1, F 23 G 5/00, 11/15/1994). Waste is loaded from above and goes through all stages of processing - drying, pyrolysis, gasification, combustion - in compartments separated by remote-controlled shutters. The gasification process is completed by the formation of combustible (pyrolysis) gas, which can be sent as fuel to thermal power plants.

The technical problem solved in the known invention is to increase the efficiency of garbage processing associated with the continuous flow of processes of storage, gas removal, drying, pyrolysis, combustion and ash removal in a single lock monoblock.

The disadvantage of this method is that it is necessary to strictly monitor the temperature of the process to prevent sintering of coked debris and waste on the wings. For this, the air entering the combustion is humidified, maintaining the temperature in the combustion zone not higher than the melting temperature of the ash, and the waste is fed from the zone to the zone in controlled doses, periodically shaking.

Thus, the involvement of additional thermal operations (pyrolysis, gasification) complicates the process of burning garbage, increases operating costs, makes the waste disposal process unprofitable and does not solve the problems with the synthesis of dioxins.

The closest analogue is the method of incineration of municipal solid waste in accordance with RU 2114357 C1, F 23 G 5/00, 06/27/1998 / 1 /.

The known method / 1 / includes incineration of waste at temperatures above 1340 ° C with the supply of primary air with a temperature of up to 400 ° C, afterburning of gaseous products of combustion at temperatures above 850 ° C, subsequent processing to bind HCl, Cl ₂ , HF, etc. passing through an electrostatic precipitator to a heat exchanger, which is used as a boiler, the thermal energy of which is transferred to the consumer.

The disadvantages of this method are as follows.

Firstly, the inclined-repulsive grate (usually made of heat-resistant cast iron) is not designed to burn fuel with a temperature higher than 1000 ° С; therefore, the operation of inclined-repulsive grate with a temperature higher than 1340 ° С will lead to their rapid wear and firebox failure.

Secondly, it is well known that the afterburning temperature of 850 ° C does not contribute to the decomposition of dioxins and furans in the combustion products, which is indirectly confirmed by the authors of the known method by installing an adsorber after the afterburning chamber, where the combustion products are purified using specially prepared milk of lime, in particular , from hydrogen chloride (a necessary and sufficient component of dioxins and furans).

Thirdly, the use of lime milk in an adsorber (where the products of combustion with a temperature of 850 ° C go) is completely unacceptable for two reasons: first, there will be almost instantaneous evaporation of the liquid phase of the lime milk, accompanied by a sharp drop in the temperature of the combustion products (heat loss to 600 kcal per 1 kg H ₂ O); secondly, milk of lime is an aqueous suspension of calcium hydroxide at a maximum water: lime weight ratio of 1: 0.15, so after converting the aqueous component to steam, the amount of solid lime will be so negligible that the absorption effect will be close to zero.

Fourth, in the known method for stabilizing the process, additional energy is used (gas, fuel oil), which will lead to a significant increase in the cost of operating costs.

The objective of the invention is to increase the efficiency of the process of burning waste at temperatures exceeding 1300 ° C, improving the process of afterburning of products of combustion of waste under the conditions of catalytic oxidation at temperatures of 1350-1400 ° C, deepening the neutralization of combustion products due to the chemisorption of halogens, nitrates, sulfites and other harmful substances on the active surfaces of calcium oxide synthesized by decarbonization from limestone flour; full use of the internal energy of the waste without involving additional energy resources for the functioning of the process.

The objective of the invention is solved due to the fact that in the method of burning solid household and other organic waste, including burning waste with the supply of preheated air, afterburning of gaseous products of combustion, subsequent processing to bind HCl, Cl ₂ , HF, passing through a heat exchanger - boiler, gas purification - before serving in the furnace for burning, the waste is separated with the separation of the inorganic part, the organic part of the waste is crushed to a size of not more than 100 mm, the waste is mixed with air heated to a temperature of 300-400 ° C , feeding to the cyclone furnace is carried out tangentially with a linear velocity of at least 28 m / s, combustion is carried out at temperatures of 1320-1350 ° C, afterburning is carried out in a catalytic afterburning chamber at temperatures of 1300-1500 ° C, processing for binding of HCl, Cl ₂ , HF lead in the decarbonization chamber of limestone flour to produce quicklime, before being fed into the boiler, the processed combustion products are passed through an air heater, and after the boiler, through a wet gas purification system, and the thermal energy of the boiler is supplied to the consumer.

A device for implementing the method comprises waste separation and grinding equipment, a waste hopper feeder, a cyclone furnace with a tangential inlet of a mixture of ground waste and heated air, a catalytic afterburner operating on the principle of a flameless burner, a decarbonization chamber equipped with a hopper and feeder for limestone flour, air heater, heat exchanger, wet gas cleaning system.

The essence of the method lies in the fact that before feeding into the furnace, the waste is separated with the separation of the inorganic part (metal, glass, ceramics), the organic part of the waste is crushed to a particle size of not more than 100 mm, the crushed waste is fed into a cyclone furnace with a tangential inlet with a stream heated to 300- 400 ° С of air, the linear velocity of which is not lower than 28 m / s; the resulting combustion products pass through a catalytic afterburner operating on the principle of a flameless burner, and a decarbonization chamber, where limestone flour (CaCO ₃ ) is sprayed towards the gas flow to trap HCl, SO ₂ , NO _x , which, as a result of thermal exposure, turns into quicklime (CaO ), on the surface of which as a result of interaction, in particular, with chlorine, CaCl ₂ crystals are formed, which do not impair the marketable properties of quicklime.

Thus, in the decarbonization chamber, the secondary formation of dioxins is minimized, up to the complete exception, since it is known that the reactions of their formation occur on the surface of flying ash particles in the presence of chlorine compounds during catalysis by iron and copper compounds.

Further, the combustion products pass through the air heater, heating the blast air to 300-400 ° C, and enter the heat exchanger, from where they are sent to the wet cleaning system, where residual SO ₂ , NO _x and dust are suppressed. The purified gases are emitted into the atmosphere, and the thermal energy taken from the heat exchanger circuit and commercial lime are supplied to consumers.

Justification of the limits of the claimed object.

The size of the grinding of organic waste substances not more than 100 mm was selected for reasons of technological expediency, since larger fragments make it difficult to feed the waste into the furnace with a tangential entry.

The temperature of the heated air in the range of 300-400 ° C is limited by the technical capabilities of the existing air heaters.

The quality of combustion of waste in a cyclone furnace is limited by the linear velocity of the injected mixture of air with waste: the higher the speed, the higher the quality of combustion.

It was experimentally established that at speeds below 28 m / s the percentage of chemical and physical underburning increases sharply, which ultimately leads to the synthesis of dioxins.

Limestone powder (CaCO ₃ ) at temperatures of 1300-1500 ° C is decarbonized almost instantly within a fraction of a second by reaction:

CaCO ₃ → CaO + CO ₂

The essence of the device for implementing the method is shown in figure 1 and figure 2.

Figure 1 schematically shows a device, a vertical section bB; figure 2 is a section aa.

A device for burning solid household and other organic waste contains a waste feed hopper 1, a channel 2 for the joint supply of ground waste and heated air, a cyclone furnace 3 with a tangential inlet of a mixture of waste and air, a catalytic afterburner 4 operating on the principle of a flameless burner, a chamber decarbonization 5, equipped with a hopper 6 and a disk feeder 7 for limestone flour.

In the chamber of the air heater 8, a metal air heater 12 is mounted. The blower fan 10 supplies heated air through the duct 11 to the hopper with ground waste.

Example 1 of the practical implementation of the method and device for burning solid household and other organic waste with guaranteed suppression of harmful substances, including dioxins.

For example, the performance of an incinerator operating on the proposed method is 6 tons / hour.

The operation of the plant is as follows.

Inorganic waste (metals, glass, ceramics, etc.) is separated at the separation stage, which is usually about 6%. For these operations, typical magnetic and air separation equipment is used.

The organic part, after separation, consisting of waste paper, food waste, wood, textiles, leather, rubber, plastic is fed to grinding to a piece size of not more than 100 mm. Grinding is carried out in standard equipment, for example in gear crushers. Then, with a stream of air heated to 300-400 ° C at a speed of not less than 28 m / s, a mixture of air and crushed waste is blown into the furnace, where it burns at a temperature of about 1320-1350 ° C.

The resulting combustion products pass through a catalytic afterburner, which is a vertical slotted shaft made of aluminosilicate refractories, operating on the principle of a flameless burner, where heavy hydrocarbons and soot fragments are guaranteed to burn, resulting in a temperature of combustion products increasing by 50-70 ° С.

Further, the combustion products enter the decarbonization chamber, which is a hollow vertical shaft, from bottom to top, where limestone flour (CaCO ₃ ) is sprayed towards them in an amount of 270 kg / hour (estimated amount per 6 tons / hour of waste).

The resulting quicklime (CaO) in an amount of approximately 155 kg / h traps chlorine in the combustion products, thereby eliminating the possibility of secondary synthesis of dioxins.

Neutralized combustion products pass through the chamber of the air heater, heating the blast air, and enter the heat exchanger, which can be used as a steam or hot water boiler.

After the heat exchanger, the exhaust gases are finally wet cleaned to neutralize residual SO ₂ , NO _x and dust.

As a wet gas scrubber, a disintegrator or wet scrubber can be used.

Spent, decontaminated and refined combustion products are released into the atmosphere.

Obtained as a result of the implementation of the method of burning solid household and other organic waste with guaranteed suppression of harmful substances, including dioxins, commercial products - thermal energy in an amount of not less than 12.0 Gcal / hour and quicklime in an amount of up to 150 kg / hour - is released consumers that pays for the money spent.

Example 2 practical implementation of the proposed method.

Suppose that the capacity of a waste incineration plant (MSZ) for municipal solid waste (MSW) is 10 t / h. MSW arriving at the MRZ have the following morphological composition (% by mass):

- paper - 35.1;

- food waste - 18.5;

- wood - 2.2;

- textiles - 7.6;

- skin - 2.8;

- rubber - 3.3;

- plastics - 8.7;

- glass, concrete, ceramics - 10.3;

- metals - 11.5.

The average design humidity of solid waste is 32%.

Inorganic waste (glass, concrete, ceramics, metals) is separated at the separation stage, in total 21.8%. For these purposes, magnetic, mechanical, air and partially manual separation equipment is used.

The organic part after the selection of inorganics is in the wet state:

The same is in absolutely dry condition:

The average elemental composition of absolutely dry solid waste for the case under consideration: C - 44.0%, N - 5.2%; O - 28.5%; S - 0.1%; Cl - 0.3%; N - 4.4%; ash - 17.5%.

Therefore, 5.32 t of absolutely dry solid waste contains: C - 2.34 t; H - 0.28 t; O - 1.52 t; S - 0.0053 t; Cl - 0.016 t; N - 0.23 t; ash - 0.93 tons

The organic part of solid waste with a moisture content of 32% is subjected to grinding to fragments with dimensions not exceeding 100 mm. Grinding is carried out, for example, in gear crushers. Next, the crushed organic waste is blown into the cyclone furnace with a stream of heated air up to 300-400 ° C, while the speed of the stream is not lower than 28 m / s. In a cyclone furnace, solid waste is burned.

We calculate the heat engineering and physico-chemical parameters of this process.

To burn 5.32 tons of absolutely dry solid waste, an amount of air is required, determined by the stoichiometric ratio of oxidative reactions:

C + O ₂ = CO ₂

H ₂ + 0.5O ₂ = H ₂ O

S ₂ + 2O ₂ = 2SO ₂

or equivalent mass quantities:

2.34 t C + 6.25 t O ₂ = 8.79 t CO ₂

0.28 t H ₂ +2.24 t O ₂ = 2.52 t H ₂ O

0.0053 t S + 0.0053 t O ₂ = 0.01 t SO ₂

Total oxygen is 8.4953 tons. With an oxidizer excess coefficient of α = 1.4, the oxygen demand is 11.89 tons. Subtract the oxygen available in the MSW:

11.89-1.52 = 10.37 t.

The amount of air required for blasting, we find from the calculation of the content of 0.233 kg of oxygen in 1 kg of air:

B = 10.37 / 0.233 = 44.5 t / h

The heat content of 44.5 tons of air at a temperature of 300-400 ° C is 3.34-4.54 Gcal.

Thus, to burn 5.32 t / h of absolutely dry organic solid waste substance, 44.5 t / h of air is required, while 49.82 t / h of combustion products of the composition are formed:

CO ₂ - 8.79 t

H ₂ O - 2.52 t

SO ₂ - 0.01 t

O ₂ - 1.88 t

Cl - 0.016 t

N - 35.674 t

ash - 0.93 t

If the MSW humidity is 32%, then the waste contains, in addition to the absolutely dry part, another 2.5 tons of physical water, so the total amount of combustion products will be 52.32 t / h with the following compounds:

CO ₂ - 8.79 t 24.6%

H ₂ O - 5.02 t 14.1%

SO ₂ - 0.01 t 0.028%

O ₂ - 1.88 t 5.27%

Cl - 0.016 t 0.045%

N - 35.674 t 53.36%

ash - 0.93 t 2.6%

As a result of combustion of 2.34 tons of carbon (with its calorific value of 8100 kcal / kg), thermal energy will be released in the amount of:

Q _c = 2340.8100 = 18954000 kcal

The same with the combustion of hydrogen (with its calorific value of 32,400 kcal / kg):

Q _h = 280032400 = 9072000 kcal

The same with the combustion of sulfur at a calorific value of 2070 kcal / kg:

Q _s = 5.32070 = 10970 kcal

In total, the heat generation during the theoretically complete combustion of solid waste will be:

Q _total = 18954000 + 9072000 + 10970 = 28036970 kcal

Together with the heat content of the heated air, the theoretical amount of heat released reaches 32.6 Gcal / h.

The actual amount of released thermal energy depends on the mechanical and chemical burns and heat loss to the environment. Typically, these losses total up to 20%. Therefore, the actual release of thermal energy during combustion in a cyclone furnace of the wet organic part of solid waste will be:

Q _p = 32.6 Gcal 0.8 = 26.0 Gcal / h

The temperature of the combustion products at the outlet of the cyclone furnace:

26000000 kcal - thermal productivity of the furnace,

52320 kg - the amount of combustion products,

0.375 kcal / (kg · deg) - specific heat of combustion products at 1325 ° C.

From the cyclone furnace, the combustion products pass through the channels of the catalytic afterburner, resulting in the almost complete oxidation of products related to chemical underburning, as a result - the heat content of the combustion products increases by 5-6% (1.3-1.6 Gcal / h) , and the temperature increases by 60-70 ° C and reaches 1385-1400 ° C.

Further, the combustion products (52320 kg / h) enter the decarbonization chamber, the vertical shaft, from bottom to top. Limestone flour (CaCO ₃ ) is sprayed towards the flow in an amount of 2200 kg / h with an average particle diameter of 0.15 mm.

From the practice of calcining limestone (Yu.M. Butt et al. Chemical Technology of Cementing Materials, Moscow: Vysshaya Shkola, 1980), it is known that the time for complete dissociation of limestone particles with a particle size of 0.1-0.15 mm at a temperature of 1100-1200 ° С is approximately 0.002 min (0.12 s), i.e. almost instantly, accompanied by a strong loosening of the structure of the formed calcium oxide. During this period, calcium oxide is extremely active in the absorption of halogens, nitrates, and sulfur.

The work of NIIStromcomposite in Krasnoyarsk established a functional relationship between the amount of absorbed substances and the fractional composition of limestone flour, which dissociates at temperatures of 1100-1200 ° C. In particular, for indicative calculations, these indicators are as follows:

HCl absorption - 12.9 g / kg CaCO ₃ ,

the absorption of SO ₂ - 11.4 g / kg CaCO _3.

If in the combustion products the Cl content is 16 kg, and the SO ₂ content is 10 kg (see above), then the required amount of CaCO ₃ for the absorption of these compounds will be:

HCl - 16000 g: 12.9 g / kg = 1240 kg CaCO ₃ ,

SO ₂ - 10,000 g: 11.4 g / kg = 877 kg of CaCO _3.

Total: 2117 kg of CaCO ₃ , taken 2200 kg of CaCO _3.

As a result of dissociation, 2200 kg of CaCO ₃ produces an average of 1270 kg of CaO and 930 kg of CO ₂ . Chlorine and sulfur dioxide chemisorbed on the surface of CaO synthesize CaCl ₂ and CaSO ₄ , respectively, the first in an amount of 25 kg, the second in an amount of 17 kg. In total, these impurities in the CaO mass amount to no more than 3.3%. These impurities (calcium chloride and gypsum) have a beneficial effect on lime hardening, therefore their presence does not worsen, but improves the quality of burnt lime.

For the dissociation of CaCO _3, it is necessary to spend 425 kcal per 1 kg of carbonate, therefore, during the dissociation of 2200 kg of CaCO _3, 0.935 Gcal of thermal energy is absorbed, and the volume of combustion products increases by 930 kg of CO ₂ (53250 kg).

The neutralization of combustion products in the amount of 53,250 kg with a heat content of 25.8 Gcal (the costs of dissociation, heat removal with decomposition products, heat loss to the environment are taken into account) are sent to the air heater chamber. The temperature of the combustion products at the inlet to the air heater is equal to:

As a result of heating the air to a temperature of 400 ° C, 1.6 Gcal of thermal energy is expended. Consequently, 53250 kg of combustion products with an approximate heat content of 24.2 Gcal and a temperature of 1200 ° C will enter the steam or hot water boiler from the air heater.

The combustion products will leave the boiler with a temperature of 150 ° C, so their heat content will be:

53250 · 0.25 · 150 = 1996875 kcal, accepted 2 Gcal.

The amount of thermal energy processed in the boiler is:

24.2-2 = 22.2 Gcal / h.

If the boiler efficiency is assumed to be 0.92, then the commodity thermal energy of the boiler will be:

22.2 · 0.92 = 20.4 Gcal / h.

Thus, if the capacity of the waste recycling plant according to the claimed method is 10 t / h of solid waste, then after sorting when burning the organic part of these wastes with disinfection of the combustion products, initially in the catalytic afterburner due to an increase in temperature to 1400 ° C and then in the decarbonization chamber at a flow rate limestone flour 2200 kg / h due to the chemisorption interaction of halogens, nitrates, sulfites, etc. with the active surface of the synthesized calcium oxide completely neutralized products Rania, the yield of marketable holds lime in an amount of 1270 kg / h, and neutralized by passing the combustion gases through the heat exchanger occurs marketable yield heat to 20.4 Gcal / hr.

Claims (5)

1. A method of burning solid household and other organic waste, including burning waste when applying preheated air, burning off gaseous products of combustion, subsequent processing to bind HCl, Cl ₂ , HF, passing through a heat exchanger - boiler, gas purification, characterized in that before feeding the waste is separated into the incinerator, the organic part of the waste is crushed to a size of not more than 100 mm, the waste is mixed with air heated to a temperature of 300-400 ⁰ , the flow to the cyclone furnace is carried out tangentially with a line at a speed not lower than 28 m / s, combustion is carried out at temperatures of 1320-1350 ⁰ С, afterburning is carried out in a catalytic afterburning chamber at temperatures of 1300-1500 ⁰ С, treatment for binding of HCl, Cl ₂ , HF is carried out in a limestone decarbonization chamber to obtain quicklime, before being fed into the boiler, processed combustion products are passed through an air heater, and after the boiler, through a wet gas purification system, and the thermal energy of the boiler is supplied to consumers. 2. The method according to claim 1, characterized in that during separation the inorganic part of the waste is separated. 3. The device for implementing the method according to claim 1, characterized in that it contains equipment for the separation and grinding of waste, a waste hopper, a cyclone furnace with a tangential inlet of a mixture of ground waste and heated air, a catalytic afterburner operating on the principle of a flameless burner , a decarbonization chamber equipped with a hopper and feeder for limestone flour, an air heater, a heat exchanger, a wet gas purification system. 4. The device according to claim 3, characterized in that the catalytic afterburner is made of a slit of aluminosilicate refractories. 5. The device according to claim 3 or 4, characterized in that the decarbonization chamber of limestone flour is made in the form of a vertical shaft, in which hot gases rise from bottom to top, and the limestone powder sprayed in the upper part of the shaft moves from top to bottom.

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