KR20010036853A - A method of combustion of stock breeding in fluidized bed - Google Patents

Abstract

PURPOSE: An incineration method of livestock waste by fluidized-bed is provided, which can incinerate livestock waste regardless of water content at a fluidized-bed temperature of more than 650deg.C and can reduce the weight to less than 5%. The residue containing much inorganic material can be used as a neutralizer of acidic soil and as a source of nutrition for crops. CONSTITUTION: The incineration method comprises the followings: (i) feeding fluid particles being 'B' particles or 'D' particles of furan molding sand to a fluidized-bed furnace; (ii) feeding air beneath the bed at a rate of 1-1.5m/s; (iii) preheating the furnace; (iv) feeding livestock waste crushed into less than 30mm to the furnace; and (v) burning the waste at 750-800 deg.C.

Description

Incineration of livestock waste by fluidized bed {A METHOD OF COMBUSTION OF STOCK BREEDING IN FLUIDIZED BED}

The present invention relates to a method for incineration of livestock waste by a fluidized bed.

In Korea, meat consumption increased gradually due to the rapid economic growth and improvement of national income. For example, pork consumption increased from 6.3kg in '80s to 15.3kg in '98. In addition, the number of livestock raising gradually increased to 7,544 thousand heads as of December '98, and the production of livestock manure increased, making it impossible for pig farming manure to be used as a manure directly. As a result, composting and purifying treatment of pig manure is required, and its treatment capacity reaches a limit, causing serious environmental pollution, which has been a challenge to resolve.

The treatment of livestock manure is an urgent problem to be solved for the stable development of the livestock industry, and the livestock manure is extremely low in digestibility compared to human food, resulting in a lot of livestock manure. Livestock manure has been used as a fertilizer for a long time, but its use decreases every year due to the spread of chemical fertilizers, and its improper treatment is not only soil and groundwater contamination, but also manure treatment due to collective mass breeding, which is the cause of eutrophication of the lake. Its management and disposal should be hygienic.

Livestock waste treatment methods include bioavailability using biomass directly in farmland, composting using organic microorganisms as a nutrient source for crops, and landfilling, drying and incineration.

Incineration is a treatment method that stabilizes organic matter in waste and safely harms secondary pollutants generated during combustion by physical, chemical or biological methods. Since waste is stabilized and reduced through the combustion process and the heat of combustion can be utilized, it is recognized as the most effective method of intermediary treatment of waste, and developed countries already rely on incineration for a large part of the treatment.

Incineration methods include grate, rotary kiln and fluidized bed incineration. In the incineration method described above, the combustion in the fluidized bed is a method in which a fuel is injected into a solid fluidized bed made of a high temperature inert material, and the combustion reaction is very fast and the carbon concentration in the bed is kept very low at about 1%.

Examples of using the fluidized bed incineration method include waste treatment, but there have not been reported examples of treatment of livestock waste, and conventionally, livestock waste has been treated mainly depending on septic tank treatment.

The present invention is applied to the flexibility of the fuel used in the fluidized bed, such as coal, oil and gas, high combustion efficiency, effective desulfurization, low NO _x emission concentration, easy to insert the combustion products, excellent heat transfer rate, etc. It is an object of the present invention to provide a method for effectively combusting livestock waste by using excellent heat transfer characteristics.

1 is a schematic diagram illustrating a general theory of a fluidized bed.

2 is a schematic diagram of a fluidized bed combustion apparatus used in the present invention.

3 is a detailed view of the fluidized bed combustion furnace in the fluidized bed combustion apparatus of FIG. 2.

4A is a detailed view of the dispersion plate in the fluidized bed combustion furnace of FIG. 3.

FIG. 4B is an enlarged view of portion 'A' of FIG. 4A.

Figure 5 is a graph showing the emission of NO in the combustion exhaust gas in the embodiment of the present invention.

Figure 6 is a graph showing the emission of NO ₂ in the combustion exhaust gas in the embodiment of the present invention.

7 is a graph showing the amount of SO ₂ emissions from the combustion exhaust gas in the embodiment of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

1: fluidized bed combustion furnace 3: fluidized bed

10: Air injected 11: Blower

16: air room 24: fluid floor

33: fluidized bed 36: dispersion plate

37: Air room

In order to achieve the above object, the present invention injects fluid particles into a fluidized bed combustor, injects air to form a fluidized bed by applying pressure to the lower part of the fluidized particles, and then preheats the fluidized bed combustor, and then, Provided is a method for incineration of livestock waste by fluidized bed combustion, wherein the livestock waste is injected into the combustion furnace and combusted in the fluidized bed.

In the above method, the combustion temperature in the fluidized bed is 650 ° C. or higher, and particularly the environmentally friendly combustion temperature range is 750-800 ° C.

In the present invention, a fluidized bed refers to a mixed bed in which a liquid, a solid, or a liquid / solid mixture is mixed with a gas by a flow of a gas having a constant flow rate. The general theory of the fluidized bed is explained with reference to FIG. 1 as follows.

As shown in (a) of FIG. 1, the solid particle layer 2 is disposed on a dispersion plate (indicated by a dotted line) in which gas is dispersed and injected into the combustion furnace 1, and the dispersion plate is as shown in FIG. When air is injected into the solid particle layer 2 from the bottom and the pressure change ΔP is measured, ΔP increases until the weight of the particle layer is equal to the weight of the air layer 10 injected. When the pressure change is equal to the weight of the solid particle layer 2, that is, when the drag force applied to the solid by the gas is equal to gravity, the solids shake and start to move. This is called the minimum fluidized state, and the solid particle layer 2 is changed into a state in which the injected air 10 flows, that is, the fluidized bed 3. The velocity of the gas injected at this time is called the minimum fluidization rate.

In general, the theoretical minimum fluidization used in the fluidized bed assumes that the pressure loss through the packed bed (before the solid particle bed flows) equals the weight of the particles per unit area. The pressure loss through the packed bed is determined by the physical properties, flow rate, size and porosity of the flowing particles. As shown in FIG. 1C, when the flow velocity of the injected air 10 continuously increases, the pressure drop in the fluidized bed 4 remains constant, but the fluidized bed 4 gradually expands and the solid particles separate from each other and behave. The layer begins to exhibit liquid-like properties as a whole. As the injected air 10 is further increased, bubbles are formed in the fluidized bed as shown in Fig. 1 (d), and these bubbles rise with the solids as they rise and bubbles are broken up and separated from the solids at the fluidized bed upper surface. . This phenomenon forms the rise of particles by bubbles and the downward movement of particles filling this space in the layer, and the larger the bubble flow, the more intense and solid mixture becomes. Flow in the fluidized bed by bubbles causes abrasion and fugitive leakage of solid particles and accelerates rapidly as the flow rate of injected air increases. This shape is called the bubble fluidized bed 5.

The continuous increase in the flow rate increases the frequency of the bubbles to improve the uniformity of the layer, which is called the turbulent layer 6. As shown in FIG. 1E, in the turbulent bed 6, the concentration of the solid decreases but the fluidized bed is maintained. In the turbulent bed 6, the gas residence time in the bed is shorter than in the bubble bed, but the gas-solid contact effect is better, which is advantageous for the fluidization of the tacky solid, which is difficult to fluidize in the bubble fluidized bed. In addition, because of the high flow rate, the fluid throughput is large and the backmixing is considerably smaller than that of the bubble fluidized bed 5.

As the flow velocity further increases from the turbulent layer, as shown in FIG. 1 (f), the scattering of particles rapidly increases, and finally the particle transport speed is reached. If the flow rate exceeds the particle transport rate, all particles in the bed will be scattered and the particle concentration in the bed cannot be maintained without recycling by cyclone. This is called a fast bed 7 and the particle concentration in the furnace depends on the flow rate of the solid. In this region, the change in pressure in the bed tends to decrease due to the decrease of particle concentration with increasing flow velocity, and the trend becomes more gentle as the flow rate of solid increases.

In the method for incineration of livestock waste according to the present invention, the livestock waste, which is a fuel material, is combusted in the flowing layer of FIG. 1 (d) or (e).

The flow rate of the injected gas in the formation of the fluidized bed is an important parameter. The flow rate is defined by simulating an empty column with a cross section at temperature and pressure, and is called the ball column fluidization rate or fluidization rate. The range of flow rates at which the fluidized bed is formed depends on the particle size distribution in the solid particle bed, which can be viewed from the minimum fluidization rate of the solid particle bed to the allowable particle scattering flow rate. Examples of the application of a gas-solid fluidized bed include a pressure fluidized bed coil combustor (PFBC) reduction process of steel stone, a fluidized bed incinerator for the transport and mixing of particles, and the treatment of industrial waste coal gasification, adsorption, Metal heat treatment and waste heat recovery. Gas and solid fluidized beds have been actively studied for such various applications, and recently, they have been applied to waste combustion and regeneration of Furan foundry in nuclear power.

On the other hand, combustion in the fluidized bed is a method of injecting fuel into the air fluidized bed made of a high temperature inert material and combusts, and has a very fast combustion reaction. Solid material having an appropriate density and particle size distribution may be used as a layer material, and ash in coal may serve as a layer material when coal is used as a fuel. The first ignition of a fluidized bed combustor uses solids such as sand as bed material.

Fuel injected into the steady-state fluidized bed combustor is quickly dispersed throughout the bed with good in-bed solid mixing effects, and the burning particles transfer the heat of combustion to the bed material and gas stream, which is then transferred to the heat transfer surface The phenomenon in which the material is locally heated to melt is prevented. As such, the layered material plays a mediating role in transferring the furnace to the heat transfer surface, so unlike other conventional furnaces, the burning particles are kept at a much lower temperature. In general, the burning particles are maintained at about 200 ° C. above the bed temperature and the bed temperature is maintained at about 200 ° C. below the ash softening temperature. The fuel may be solid, liquid, gas, sludge, or the like, and in order to obtain high combustion efficiency, it is important that the fuel is mixed quickly and uniformly throughout the layer. The solid mixing characteristics at a certain solid particle size of the bed materials are greatly influenced by the fluidization rate and the gas distribution, and in order to obtain a uniform solid mixing effect, it is important to select an appropriate fluidization rate and to make the fuel fast and uniform throughout the bed. It is important to mix. In some cases, special air distributors may be used. In particular, when burning liquid fuel such as waste oil, special attention must be paid to the distribution of fuel in order to prevent agglomeration of layer particles and carbonization of the fuel.

The weight of bed material in a fluidized bed combustor is determined by considering the complete combustion of fuel and the installation of the bed heat transfer area. At normal bed temperatures, on the other hand, the combustion speed is fast enough and the weight of the bed material is determined to satisfy the heat transfer area in the bed. In the fluidized bed, there is a fireboard on the bed. In the combustion space, the velocity of the gas is small, so that the coarse particles scattered from the bed surface by the bubbles can afford to return to the fluidized bed, and some combustion reaction takes place. In addition, a heat transfer surface may be installed in the combustion space for heat extraction.

The use of combustible waste as fuel in a fluidized bed combustor results in a fluidized bed incinerator. Fluidized bed incinerators can incinerate a wide variety of waste types, from crushed solid waste, sludge or liquid waste. The characteristics of the fluidized bed incinerator are almost complete mixing of the bed materials, so the injected waste is also well mixed and shows an even mixing distribution, making it ideally in contact with the air for combustion. This is possible. In addition, since the injected waste is dried at a high temperature almost sequentially and the combustion efficiency of the heating components in the bed is high, the reduction effect of the waste is large and the combustion can be maintained at a high temperature by staged combustion in the combustion space, thereby reducing the unreacted gas by secondary combustion. Can be maximized. On the other hand, because the heat capacity in the layer is large, the size of the furnace can be reduced, and damage to the refractory is less because no local heating occurs in the furnace. In particular, since there are no mechanical driving parts inside the furnace, there are almost no failures in the furnace. In addition, since the high temperature layer material sinks during operation stop, intermittent operation is possible or very easy because the temperature drop rate is small until the new operation starts. In addition, the pumpable waste oil, waste liquid and general plant waste can be treated. When combined with multi-stage or multi-furnace, the process of drying, drying and combustion is carried out in stages, so that the incineration of low calorific value and high yield can be consumed with less auxiliary fuel consumption than other incinerators.

A schematic diagram of the fluidized bed combustion apparatus used in the present invention is shown in FIG.

The air supplied to the combustion device is stabilized while passing through the constant pressure tank 12 in the blower 11 and is sent to the flowmeters 13 and 21. The air passing through the flowmeter 13 is preheated to 200 ° C in the electric heater 14. After passing through the air chamber 16 is homogenized in the air dispersion plate (not shown) to fluidize the fluid particles in the combustion furnace, the air passed through another flow meter 21 is a gas flow meter ( 22 is mixed with propane gas 20 passing through to heat the fluid particles in the fluidized bed 24, the gas passed through the fluidized bed 24 is externally through an exhaust fan 25 in the upper part of the fluidized bed combustion furnace Is discharged. At this time, the discharged combustion gas may be analyzed by the gas analyzer 18 connected to the upper part of the furnace to store data in the computer 26. In addition, the controller 15 is connected to the electric heater 14, and a digital thermometer 17 for measuring the temperature of the fluidized bed 24 is mounted outside the combustion furnace.

FIG. 3 is a detailed view of the fluidized bed combustion section in which the fluidized bed 33 in which fluidization takes place is made of stainless steel of ø210 × 430H × 3t, and the upper part is a scattering prevention layer 31 of ø290 × 365H × 2t. This prevents the scattering of particles and adds combustion materials. Under the fluidized bed 33, an air chamber 37 (ø306 × 200H × 6.4t) is installed to prevent particles from scattering, and there is enough space for the air and propane gas to be mixed. A ø80 X 400L steel pipe is installed by welding as an induction pipe for the supplied air. The furnace has a structure that can withstand thermal stress by using a flange of 12 M14 bolt holes with a pitch circle diameter of 260 mm and a distributor between the air chamber 37 and the fluidized bed 33. 36). A burner nozzle 38 was installed at the 100 mm point above the distribution plate 36 in the fluidized bed 33 to increase the fluidized bed temperature, and a gas inlet 34 and an air inlet 35 were connected to the burner nozzle 38. have. On the other hand, the outside of the furnace was formed of a thermal insulation layer 32 which was first thermally insulated with 50 t of ceramic insulation and then secondly thermally treated with rock wool to minimize heat loss.

The detail of the dispersion plate is shown in FIG. 4A. Since the dispersion plate has a great influence on the fluidization velocity of the fluidized bed, it must be able to supply a uniform flow gas. For this purpose, a hole of 912EA-ø1 is drilled with a square pitch of 6 mm with a nozzle in the working area of ø210, and the porosity is 2.07%. The material of the dispersion plate is stainless steel, the size is ø290 × 3t, the hole of the flange bolt (12EA × M14) is ø16, and the stainless steel is installed on the dispersion plate so that the fluid particles in the fluidized bed fall into the air chamber through the hole. Prevent it. There is a 4t ceramic gasket between the distribution plate and the upper and lower flanges to maintain the airtightness between the flange and the distribution plate. FIG. 4B is an enlarged view of portion 'A' of FIG. 4A.

The fluid particles used in the present invention are furan cast sand, and their particle size distribution is shown in Table 1.

Table 1. Particle size distribution of furan casting sand used in the present invention

Particle size (μm) Weight (g) content (%) To 250 8.67 1.43 250 to 355 55.29 9.10 355-420 216.15 35.60 420 to 500 152.28 25.08 500-600 140.72 23.18 600 to 710 32.05 5.28 710 to 850 2.00 0.33 system 607.16 100

Furan Foundry Sand is a foundry sand with the property of hardening at room temperature and adding a curing agent to the binder to accelerate the curing reaction at a room temperature. It is recyclable and recovers more than 90% of the foundry sand since the 1970s. Its use is increasing rapidly. The classification of particles is taken according to KS standards and corresponds to 'B' and 'D' in the particle classification group.

The most important factors for combustion in a fluidized bed are the combustion temperature and the minimum fluidization rate. The minimum fluidization temperature is 0.25 ~ 0.3m / s in the range of 650 ~ 800 ℃ of fluidized bed combustion in the case of B particles in industrial casting sand, and the fluidization speed in the fluidized bed combustor operates at 4 ~ 6 times the minimum fluidization speed. It is suitable to increase the combustion efficiency of waste by injecting and incinerating livestock waste with diameter of 30mm or less.

By incineration of at least about 95% of the combustibles of the livestock waste by the effective incineration treatment of the present invention it is possible to obtain the effect of reducing the landfill and the generation of leachate due to the stable treatment of waste and the reduction of landfill amount.

Hereinafter, the present invention will be described in detail with reference to pig meal in livestock waste.

Example

After the injection of Furan casting sand 4000cc as a fluid particle into a fluidized bed combustor, the temperature in the fluidized bed was first heated to 200 ° C. using an electric heater at a fluidization rate of 1 to 1.5 m / s. After heating with propane gas burner, 500cc of pigs were burned in four stages (650, 700, 750 and 800 ℃) at 50 ℃ intervals to 800 ℃ while maintaining the temperature in the fluidized bed at 650 ℃. The contents were burned in 15%, 25%, 50% and 75% fractions. Combustion residues (pig) were taken at 30 second intervals (30, 60, 90, 120 and 150 seconds) and the flue gas analyzer was checked for changes.

NO, NO ₂ in the combustion exhaust gases according to the combustion temperature (650, 700, 750 and 800 ° C) and moisture content (15%, 25%, 50% and 75%), which are the main factors of the experiment, in the combustion process of swine powder. 5 and 7 show the results of analyzing the emissions of, and SO ₂ with a gas analyzer. In Figures 5 and 6 it can be seen that the NO and NO ₂ is discharged about 7 ~ 95ppm, 0 ~ 3.5ppm, respectively, significantly less than the environmental regulation value of 200ppm, Figure ₂ is 2 ~ 83ppm for SO ₂ About discharged. This can be seen that the amount is very small compared to the 300ppm environmental regulations. In the case of NO theoretically, the higher the combustion temperature is discharged, but the results shown in FIG. 5 shows that in the present invention, the combustion temperature in the fluidized bed is low and is emitted at a low concentration without being greatly influenced by the combustion temperature. In Fig. 6, the amount of NO ₂ discharged from 0.0189 to 3.3830 ppm was almost negligible, showing the characteristics of combustion in a fluidized bed which can be burned at a low temperature, and from 0 to 6.9808 ppm during the combustion of 750 ° C to 800 ° C in FIG. Given that SO ₂ is released, this range is the optimum temperature for fluidized bed combustion. SO ₂ is discharged below 7ppm at the combustion temperature above 750 ℃, which shows the characteristics of combustion in the fluidized bed. Sulfur in pigs is converted to SO ₂ during combustion, and SO ₂ reacts with CaO to produce CaSO ₄ as shown in the following equation.

SO ₂ + CaO + 1/2 O ₂ → CaSO ₄

As shown in the above scheme, 1 mol of Ca is required to remove 1 mol of S, and the Ca / S mol ratio is defined as the molar amount of pig S, and the ratio of Ca for SO _x removal, and assumes 100% reaction. The theoretical minimum Ca / S mol ratio is 1: 1. In case of artificial CaCO ₃ injection for desulfurization during combustion, most of the reaction takes place on the surface of the particle during combustion, and the center of the particle does not react, but the pig meal contains 0.83% S and 2.48% CaO. Since desulfurization during combustion occurs naturally, it can be seen that fluidized bed combustion is one of the environmentally friendly pig flour treatment.

On the other hand, the content of organic matter (Organic matter) was measured by the incineration method of the organic quantification method. After drying pigs for 24 hours at 110 ℃ and heating 100g in a 700 ℃ porcelain crucible for 2 hours, the remaining weight after cooling in a desiccator was 19.6g, and it contained 80.4% of organic matter. I think it is.

C = organic matter / 1.8

Applying the above equation, C is analyzed to be 44.7%.

In addition, after burning the pig flour having the components shown in Table 2, the results of analyzing the components of the pig using an inductively coupled plasma mass spectrometer (ICP spectrometer) showed that inorganic matters such as P ₂ O ₅ , K ₂ O, MgO, etc. In the presence of a large amount, the moisture content of raw pig meal was reduced to less than 5% by weight, considering that it is about 76%.

As a result, the residue has stabilized, making it easier to reclaim and use it as a nutrient source for crops.

Table 2. Ingredients of pig meal before combustion

C T-N P K Ca Mg S 44.7 3.09 2.51 1.33 3.57 1.17 0.83

According to the present invention, it is possible to effectively incinerate livestock waste by combustion in a fluidized bed, and it is possible to combust livestock waste at a fluidized bed temperature of 650 ° C. or higher, regardless of water content. 800 ° C. is appropriate. By the combustion of the livestock waste according to the present invention it can be reduced to less than 5% and the presence of a large amount of minerals in the combustion residues can be used as a storage source of livestock waste, neutralization of acidic soil and nutrient sources of crops. In addition, the composition of NO, NO ₂ and SO _{2 in} the combustion gas in the fluidized bed is much less than the environmental regulations, it is possible to environmentally friendly treatment of livestock waste.

Claims (5)

Injecting fluid particles into the fluidized bed combustion furnace, and by injecting air to apply pressure to the lower part of the fluidized particles to form a fluidized bed, and then preheating the fluidized bed combustion furnace, livestock waste as fuel material into the combustion furnace A method for incineration of livestock waste by a fluidized bed comprising burning at a temperature of 650 ° C or higher in the fluidized bed. The method of incinerating livestock waste by a fluidized bed according to claim 1, wherein the combustion is performed at a temperature range of 750 to 800 ° C. The method of incinerating livestock waste by a fluidized bed according to claim 1, wherein the velocity of the injected air is in the range of 1 to 1.5 m / s. The method according to claim 1, wherein the fluid particles are livestock waste incineration method by a fluidized bed using 'B' particles or 'D' particles of furan foundry. The method for incineration of livestock waste by a fluidized bed according to claim 1, wherein the livestock waste is crushed to a diameter of 30 mm or less and introduced into a fluidized bed combustion furnace.