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INVENTION
Patent of the Russian Federation RU2266468
WASTE INJURY METHOD IN A PSEUDOGENIZED LAYER
AND DEVICE FOR ITS IMPLEMENTATION
The name of the inventor: Golubkovich A.V. (RU); Chizhikov AG (RU); Kurbanov K.K.
The name of the patent holder: State Scientific Institution All-Russian Research Institute of Agricultural Mechanization (State University of VIM)
Address for correspondence: 109428, Moscow, 1 st Institutskiy pr-d, 5, State University of Ukraine, Patent Department
Date of commencement of the patent: 2004.06.15
The invention relates to the incineration of plant wastes in a fluidized bed. The method for incineration of waste in a fluidized bed consists in the organization of recirculation of the solid heat carrier, mixing of waste with recirculation, drying and incineration of the latter in a fluidized bed. The coefficient of recirculation K is determined from the amount of necessary drying by formula 
, And the temperature of the fluidized bed is further controlled by feeding the drying vapors to the superlayer cavity, furthermore, the drying of the waste is carried out, at least until the free moisture is removed. The fluidized bed incinerator comprises a fluidized bed combustion chamber, a superstructure cavity, a drying chamber, a condenser, a steam line, a solid coolant recirculation system, a drying chamber connected by a steam line to the superlayer cavity, with the possibility of steplessly supplying vapors from the drying of the waste. The invention makes it possible to increase the efficiency of incineration of wet waste.
DESCRIPTION OF THE INVENTION
The invention relates to the incineration of plant wastes in a fluidized bed, primarily for the production of a heat carrier gas, and can be used in agriculture for drying grain, but also for energy.
A method for burning fuel in boilers with cooling of circulating particles in a heat exchanger installed outside the furnace (the Lurgi scheme) is known. According to this method, a stationary fluidized bed of fuel and an inert gas with a temperature of 820 ... 870 ° С is maintained in the device on the gas distribution grid, which provides favorable environmental conditions (suppression of the formation of sulfur and nitrogen oxides) and reliability (absence of grating and heat exchange Surfaces of the device) [1].
However, it is effective for boilers and is ineffective for furnaces producing heat carrier gas, since it does not allow for the placement of heat exchange surfaces in the stationary fluidized bed with a heat transfer gas, and the temperature of the flue gases at the inlet of the heat exchanger is controlled by secondary and tertiary blowing, dilution to an acceptable temperature, Which reduces the efficiency of the process.
A device for carrying out the known method [1] is also known, comprising a furnace, a cyclone, a convective gas flue, superheaters, an air heater and other working bodies. This device can be used for incineration of waste, but in the unit with boilers, in addition, it is inefficient for equipping agricultural facilities, in particular grain dryers.
A method for burning waste (low-grade fuels) in a fluidized bed with the use of thermal contact drying is known. It consists in the organization of recirculation of a solid heat carrier, mixing of waste with recirculation, drying and incineration of the latter in a fluidized bed. The moisture vapor condenses using latent heat. This method is the closest to the claimed for the totality of technical features and adopted for the prototype [2].
However, it does not allow to regulate the degree of drying of the waste and does not provide the desired temperature of the flue gases at the inlet to the air heater without changing the wide range of excess air to dilute them, this is uneconomic.
An apparatus for carrying out the known method is also known, comprising a fluidized bed combustion chamber, a superstructure cavity, a drying chamber, a condenser, a steam line, and a solid-liquid-system recirculation system. This device is the most closely related to the claimed characteristics and taken as a prototype [2].
However, the use of the heat of moisture vapor in the condenser is quite difficult and can not be directly used to control the combustion temperature of the waste.
The object of the invention is to improve the efficiency of the method for burning wet waste.
The objective is achieved by the fact that in a fluidized bed incineration process consisting in the organization of a recirculation loop of a solid heat carrier, mixing of waste with recirculation, drying and incineration of the latter in a fluidized bed, the recycling ratio K is determined according to the invention based on the amount of drying required by formula
Where K is the recirculation coefficient, equal to G p / G m ;
G t - waste incineration for incineration, kg / h;
G p - recirculation feed for mixing with waste, kg / h;
R is the heat of evaporation of moisture from the free surface, kJ / kg;
W 1 and W 2 - initial and final moisture of the waste,%;
T 1 and T 2 are the initial recirculation temperature and the final temperature of the mixture of recirculation and waste, ° C;
C is the heat capacity of the recirculation, kJ / kg ° C,
And the temperature of the fluidized bed is further controlled by feeding the drying vapors to the superlayer cavity, furthermore, drying the waste is carried out at least until free moisture is removed.
The above object is achieved by the fact that in the waste incinerator, comprising a combustion chamber with a fluidized bed, an overlay cavity, a drying chamber, a condenser, a steam pipe, a solid-coolant recirculation system, according to the invention, the drying chamber is connected by a steam line to the superlayer cavity, Vapors from drying of waste.
Comparison of the claimed method with the prototype shows that the new in the process is that the degree of drying is determined by the recirculated feed rate from the formula
And the temperature of the fluidized bed is further controlled by feeding the drying vapors to the superlayer cavity, furthermore, the drying of the waste is carried out at least until the free moisture is removed.
Comparison of the claimed device with a prototype shows that the new in the device is that the drying chamber is connected by a steam pipe to the superlayer cavity with the possibility of adjustable feeding of vapors from drying of the waste therein.
Thus, the invention corresponds to the criterion of "novelty".
The proposed method and device are connected by a single inventive concept, tk. This method can be implemented by this technical solution.
The invention corresponds to the criterion "inventive level, since a result can be achieved that satisfies a significant need, namely, increasing the efficiency of waste reduction.
The invention is also "industrially applicable", as it can be used in agriculture.
The invention is explained in the drawing.
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The figure shows a device for incineration of waste in a fluidized bed. The circuit of the device includes a combustion chamber with a fluidized bed 1, a superlayer 2, a heat exchanger 3, a cyclone 4, a drying chamber 5, a grate 6, an air channel 7, a primary blast 8, a secondary blast 9, a heat carrier gas 10, a screw 11, a condenser 12, Valves 13, thermocouple 14, fuel 15, ash discharge 16, steam line 17, recirculation 18, outside air 19, cleaned flue gases 20. |
THE METHOD IS PROVIDED AS FOLLOWS:
The original wet fuel is mixed with recirculation, dried, burned in a fluidized bed, the degree of drying being determined by the recirculated feed rate from formula
The temperature of the layer is further controlled by feeding the drying vapors to the superlayer cavity, and further drying of the waste is carried out at least until the free moisture is removed.
The device is operated as follows.
The vegetable waste 15 is fed to the dryer 5 and the screw 11 moves them to the combustion chamber 1. In this dryer, recycle 18 is fed from the cyclone 4. Upon contact with the recirculation, the fuel particles are heated, dried, fed into the fluidized bed 1, ignited, burned, Combustion is carried out to the superlayer cavity 2 and then enters the tubular heat exchanger 3 in which the heat carrier gas 10 is prepared. The solid phase is separated in the cyclone 4 and in the form of the recirculation 18 enters the dryer 5. Saturated steam along the steam line 17 enters the superlayer cavity 2 of the device or Is discharged to the condenser 12 with the release of latent heat. If necessary, a secondary blast 9 is fed into the cavity 2, and the cleaned flue gases 20 from the cyclone are discharged into the atmosphere or disposed of.
The device for burning plant waste according to the claimed method is characterized by a relatively low coefficient of recirculation (no more than 3), an increased content of combustibles in the layer (up to 5 ... 7%), low height of the stationary fluidized bed (up to 0.6 m), that Causes relatively low head loss (up to 2 ... 3 kPa), reduced heat-accumulating capacity and good maneuverability of the layer. These factors reduce its cost and increase competitiveness in comparison with installations in which flaring is carried out in a torch or in a dense layer, on the other hand, they increase the sensitivity to the humidity of the fuel (straw sticks, sunflower husks, rice, flax, cereals, cobs, crushed Stalks of sunflower, corn, etc.).
When combustion waste with a moisture content of more than 22 ... 25% is degraded, the combustion conditions deteriorate, the adiabatic combustion temperature drops below 700 ° C, and at the inlet to the heat exchanger below 600 ° C, the content of combustibles in the ash increases, the losses with mechanical and chemical underburning .
In order to improve the efficiency of work, waste drying is organized by recirculating heat separated in a cyclone. When preparing the heat carrier gas, the flue gases and solid phase removed from the cyclone have an elevated temperature, in particular up to 220 and 300 ° C, respectively.
It is not economical to reduce the temperature of the exhaust flue gases to a temperature of the order of 120 ... 130 ° C and correspond to the recirculation as is organized in boilers with a recirculating fluidized bed, since it is necessary to significantly increase the dimensions of the heat exchanger due to the low heat transfer coefficient, which in the optimum case is 35 ... 40 W / m 2 ° C, which is one or two orders of magnitude lower than the heat transfer coefficient in boilers, but it is advisable to use recirculation heat, in particular, for drying wet waste.
The recirculation factor K is selected so that the attracted heat provides drying of the waste to a humidity of 22 ... 25%, which corresponds to the removal of free moisture, which is easily realized by thermal contact drying. Free moisture has a weak bond with the fuel material and evaporates easily and is removed in the form of steam. The return of steam to the superfloor cavity of the fluidized bed allows further adjustment of the combustion temperature and, eventually, the temperature of the fluidized bed in the 800 ... 850 ° C range, which is optimal from the point of view of the efficiency of combustion and the accident-free operation of the heat exchanger.
Indeed, by implementing the distribution of the amount of steam entering the condenser and the superlayer cavity using a thermocouple immersed in the fluidized bed, a predetermined temperature range can be maintained using the automatic control system (not shown in the drawing) at a constant recycling factor K. The fuel supply for combustion can be measured And maintain the dispenser, and recirculated into the drying chamber, set, for example, according to the calibration schedule, depending on the flow rate of the blast, built when the device is adjusted.
Consider the thermal and material balances of drying the waste to a moisture content of 22 ... 25%. The amount of evaporated moisture from the waste can be determined from
Where W 1 , W 2 - initial and final moisture of the waste,%;
G t - waste supply, kg / h.
On evaporation 
The amount of moisture needed to spend the following amount of heat
Where r is the heat of evaporation of moisture from the free surface, r ~ 2625 kJ / kg.
The amount of heat supplied with the recirculation dryer
Where G P - recirculated flow rate, kg / h,
T 1 , T 2 - initial recirculation temperature and final mixture temperature ° C.
C is the heat capacity of the recirculation, kJ / kg ° C.
Equating the quantities Q m and Q m' , we obtain
Paying attention to K = G P / G m , we finally obtain
The claimed method is supposed to be used primarily in devices for obtaining heated air for drying grain in shaft and other types of grain dryers with a capacity of 10 ... 50 t / h, the required heat capacity of furnace furnaces of dryers from 1 to 5 MW at a coolant flow rate heated to 130 ° С, from 50 to 250 thousand m 3 / h.
During harvesting and post-harvest processing, from every ton of grain fed to drying, up to 1.2 tons of straw and grain waste are generated, which are taken to the dumps. These wastes, in the first place, can serve as raw materials for obtaining a coolant.
Example 1. In a combustion device TPO-1 with a power of ~ 1.0 MW, a straw stump was burnt in a suspended layer with a moisture content of 20 ... 22%, an adiabatic combustion temperature of 870 ... 900 ° C was achieved and a stable combustion process with a temperature Flue gases at the inlet to the air heater ~ 800 ° C. At the exit from the air heater, the temperature of the flue gases was 220 ... 240 ° C, and the temperature of entrainment in the sedimentation chamber was ~ 270 ° C. Wastewater waste with a moisture content of 27% burned unstably, the adiabatic combustion temperature did not exceed 600 ° C, the necessary parameters of the coolant for grain drying were not achieved.
Example 2. Let's determine the value of K when drying according to the declared method of incineration of plant waste with W 1 = 30% and W 2 = 22% at T 1 = 240 ° C and T 2 = 100 ° C (the temperature of the mixture is assumed equal to the vapor temperature at atmospheric pressure ). The heat capacity of the ash of the solid heat carrier is C = 1.257 kJ / kg. The value of r is given above. Substituting these values of the parameters into the formula 5, we obtain K = 1.52.
Additional regulation of the adiabatic combustion temperature can be achieved by feeding steam to the superlayer cavity of the fluidized bed. When more steam is supplied, the temperature decreases, as the oxygen content in the gas medium decreases, the supply increases, and this regulation can be carried out automatically using a thermocouple, a control system with a drive to the steam line valve (not indicated in the diagram), excess vapor In the condenser.
The use of the invention will improve the efficiency of the combustion device on wet fuel, and the use of heat from flue gases leaving the cyclone or sedimentation chamber, for example in a drum dryer, will increase the efficiency of the combustion device to 80% or more.
USED BOOKS
1. Baskakov A.P., Matskov V.V., Raspopov I.V. Boilers and furnaces with fluidized bed. M., Energoatomizdat, 1995, p.224, 225.
2. Puzyrev E.M. Investigation of furnace processes and development of boilers for low-temperature combustion of combustible waste and local fuels. Author's abstract. On the Soscan. Doctor of Science, Barnaul, 2003, p.8, 9 (prototype).
CLAIM
1. A method for incineration of waste in a fluidized bed, comprising: recirculating a solid heat carrier, mixing the waste with a recycle, drying and burning the waste in a fluidized bed, characterized in that the recirculation ratio K is determined from the amount of necessary drying by formula
Where K is the recirculation coefficient, K = G p / G m ;
G t - waste incineration for incineration, kg / h;
G p - recirculation feed for mixing with waste, kg / h;
R is the heat of evaporation of moisture from the free surface, kJ / kg;
W 1 and W 2 - initial and final moisture of the waste,%;
T 1 and T 2 are the initial recirculation temperature and the final temperature of the recirculation and waste mixture, ° C;
C is the heat capacity of the recirculation, kJ / (kg ° C),
And the temperature of the fluidized bed is further controlled by feeding the drying vapors to the superlayer cavity.
2. A method for incineration of waste according to claim 1, characterized in that the drying of the waste is carried out, at least until free moisture is removed.
3. A device for incineration of waste in a fluidized bed containing a fluidized bed combustion chamber, a superlayer cavity, a drying chamber, a condenser, a steam pipe, a solid-liquid-system recirculation system, characterized in that the drying chamber is connected by a steam pipe to the superlayer cavity, From drying of waste.
print version
Publication date 20.02.2007gg
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