(1) Purpose of thermal calculation The purpose of thermal calculation is as follows:
(1) Find the relevant parameters of the dry material to select the specifications and number of dryers.
(2) Calculate the fuel and fuel parameters to determine the fuel consumption and the geometry of the furnace (furnace volume, grate area, furnace height) and type.
(3) Find the air consumption to select the specifications and number of blowers.
(4) Find the flue gas consumption and resistance to select the specifications and number of the induced draft fan and dust collecting equipment.
(2) Calculating the original data needed
The raw materials required for thermal calculation are as follows:
(1) Information on dry materials:
1) Absolutely dry material amount G.kg / h;
2) the weight of the wet material G 1 , kg / h;
3) moisture W 1 ,% of the material before drying;
4) moisture W 2 ,% of the material after drying;
5) The temperature T 1 of the material before the drying and the fuel coal is generally close to the ambient temperature, ° C;
6) The temperature T 2 of the material after drying is selected according to the nature of the material and the final moisture. The lower the final moisture, the higher the surface temperature of the material. If the final moisture requirement is about 6%, generally it can take 100-75 °C, if it is between 4 and 1%, it should be 150 °C. If it is low, it should be about 200 °C;
7) The particle size of the dried material is d, mm.
(2) Air data entering the combustion chamber:
1) air temperature t 0 , °C;
2) Air humidity Ñ„ 0 , according to local climatic conditions, generally 60~65% when there is no data;
3) The relevant indicators of dry air can be obtained by using the Id diagram (below);
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4) The heat content of air I 0 , kJ / kg dry air;
5) The moisture content of air d 0 , g / kg.
(3) The temperature t 1 of the dry flue gas or gas entering the dryer is selected as follows:
1) Downflow cylinder dryer t 1 = 600 ~ 800 ° C;
2) Counterflow cylinder dryer t 1 =1100～1300°C;
3) airflow dryer t 1 =400 ° C;
4) boiling dryer t 1 =1100 ° C;
5) The temperature of the gas t = 850 ~ 900 ° C.
(4) The temperature of the exhaust gas discharged from the dryer t 2 is selected according to the actual production data of the factory, and the cylinder dryer is directly heated.
(5) Information on fuel composition:
1) Ash (A ) , moisture W Y and elemental analysis C Y , H Y , O Y , N Y , S Y of fuel (after coal selection) are expressed in %;
2) Components of gas H 2 S, CO 2 , O 2 , H 2 , N 2 , CH 4 , C 2 H 2 , C 2 H 6 , C 3 H 6 , C H8 , C 4 H 8 , C 4 H 10 , C 5 H 12 , C X H Y .
3) specific heat capacity of coal gas C n , kJ / (kg · K) and density Ï 0 , kg / m 3 .
(6) Information on the vaporization (evaporation) intensity of the dryer:
(3) Thermal calculation method A: After the selection of medium coal as fuel (1) The amount of vaporized water in the drying process:
Where W—the amount of vaporized water in the drying process, kg/h;
G 1 ———weight of wet material before drying. kg/h;
W 1 ———the moisture content of the wet material before drying, %;
W 2 ———The moisture of the material after drying, %.
(2) The calorific value of burning one kilogram of coal:
Q YDW =[81C Y +246H Y -26(O Y -S Y )-6W Y ]×4.1868 (2)
Q YGW =[81C Y +300H Y -26(O Y -S Y )]×4.1868 (3)
Where Q YDW ———the low calorific value of coal, kJ/kg;
C Y , H Y , Q Y , S Y , W Y — carbon, hydrogen, oxygen, sulfur and moisture in coal, all expressed in %;
Q YGW ———High calorific value of coal, kJ/kg.[next]
(3) Theoretical value of the amount of air required to burn one kilogram of coal:
Where L 0 ———the weight of the theoretical air amount, kg/kg;
V O — the volume of theoretical air usage, m 3 /kg;
Ï———the density of air in the standard state [1.01×10 5 Pa(760 mmHg), 0°C], Ï=1.293kg/m 3 ;
C Y , H Y , O Y , S Y — The content of carbon, hydrogen, oxygen and sulfur in coal is expressed in %.
(4) Total air excess coefficient of combustion chamber and mixing chamber:
Where a—the total air excess coefficient of the combustion chamber and the mixing chamber;
Q YGW ———High calorific value of coal, kJ/kg;
Η—the thermal efficiency of the combustion chamber and the mixing chamber, generally taking 0.85 to 0.9;
C M T M1 ———heat brought by coal, kJ/kg; c M T M1 =1.08T 1 This value is small and negligible;
c M ———the specific heat capacity of coal, kJ/(kg · K);
T M1 ———the temperature of the coal before drying, °C;
C 2 ———The specific heat capacity of dry flue gas, kJ/(kg · K). It can be calculated as follows:
t 1 ———the temperature of the dry flue gas, °C;
I—the heat content of steam in dry air (or dry flue gas), kJ/kg.
i=(595+0.47t 1 )×4.1868 (6b)
I O ———The outdoor air temperature is t 0 , the humidity is ф 0 , the heat content of air, kJ/kg;
d 0 ———When the outdoor air temperature is t 0 and the humidity is ф 0 , the moisture content of the air is the wet content of the outdoor air entering the combustion chamber, g/kg;
H Y , A Y , W Y --- hydrogen, ash and moisture content in coal, expressed in %;
L 0 ———Theoretical air consumption, kg/kg.
(5) The amount of water vapor produced by burning one kilogram of coal:
Where g1—the amount of water vapor, kg/kg;
H Y · W Y — The hydrogen content and moisture in coal are expressed in %.
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