Barometric capacitor

Barometric mixing capacitor. One schematic drawing without a stamp.
Calculation.
Source Data:
- capacity for evaporated fugate 311.000 t/s = 12960 = 3.6 kg/s;
- amount of evaporated moisture in the unit 257.200 t/s = 10720 = 2.98 kg/s;
- heating is performed by saturated steam with pressure P1 = 0.5 MPa;
- pressure in barometric condenser Rbc = 0.02 MPa;
- concentration of dry substances of fugate - 6.06%.
Surfaces of heat exchange equipment of each housing are taken equal. The distribution of solution concentration in the plant housings depends on the ratio of loads on evaporated water in each apparatus. In the first approximation, on the basis of practical data, it is accepted that the capacity of evaporated water is distributed among the housings in accordance with the ratio:
W1/W2 = 1.0: 1.1 then
W1 = 1.0 * W/( 1.0 + 1.1) = 1.0 * 2.98/2.1 = 1,419 kg/s
W2 = 1.1 * W/2.1 = 1,556 kg/s where
W - amount of evaporated moisture in the unit, kg/s
W1 - amount of evaporated moisture in the first housing, kg/s
W2 - amount of evaporated moisture in the second housing, kg/s. Concentrations of solutions in housings:
X1 = G * Xn/( G-W1) = 3.60 * 0, 0606/( 3,60-1,419) = 10.0% X2 = G * Xn/( G-W1- W2) = 3.60 * 0, 0606/( 3,60-1,419-1,556) = 35% where
Xn - concentration of dry substances of fugate .
In evaporators, two types of condensers are usually used: mixing or surface. In this case, a mixing condenser is used. As a cooling agent, water is used, which is supplied to a condenser with a temperature of 15 ° C. The mixture of cooling water and condensate is poured out of the condenser through a barometric pipe. To maintain the vacuum constant, non-condensing gases are pumped out of the condenser system by means of a vacuum pump.
Cooling water flow rate:
Gv = W2 * (Ibk-sv*tk) / sv (tk-tn), where ,
Ibk is the enthalpy of vapors in the barometric capacitor 2608300 J/kg ;
st - heat capacity of water 4.19 * 103 J/( kg * 0С);
tn - initial cooling water temperature 150С;
tc is the final temperature of the mixture of water and condensate 0С.
Temperature difference between steam and liquid at the condenser outlet shall be 3-5 deg. Therefore, the final water temperature tc at the outlet of the condenser is assumed to be 5 deg below the vapor condensation temperature: tc = tbk-5 = 60-5 = 550C.
Then Gv =1.57 * (2608300-4.19*103*55)/4.19*103 * (55-15) =22.08kg/with =79.488m3 / h =1907.7 m3/d.
Total volume of liquid leaving the condenser:
Gv + rc = Gv + W2=22.08+1.556=23.636 kg/s =85089 kg/h =2042.15 m3/d
Capacitor calculation
The diameter of the barometric capacitor Dbk is determined from the flow equation:
Dbk=√ 4 * W2/( a) = √4*1,556/( 0,1301 * 3,14159 * 15) = 1.01 m, where
ρ - density of vapors at a temperature of condensation, kg/m3
υ - the speed of vapors, m/s
With a residual pressure in the condenser about 104 Pas the speed of vapors υ =15-25 m/s
According to the normals of NIIHIMMASH, a condenser with a diameter equal to the calculated or nearest larger is selected. We define its basic dimensions. Select barometric capacitor with diameter Dbk = 1000 mm. - the thickness of the apparatus wall is 6 mm - the distance from the upper shelf to the apparatus cover is 1300 mm. - distance from the lower shelf to the bottom of the apparatus 1200 mm. - shelf width 650 mm. - height of installation 5350 mm. - distance between shelves from 1st to 2nd 250 mm. 2nd to 3rd 320 mm. from 3rd to 4th 400 mm. from 4th to 5th 475 mm. from 5th to 6th 550 mm. - distance from lower nozzle to steam inlet pipe axis 900 mm. - height of cones 250 mm. - nozzle height of steam-gas mixture is 100 mm. - nozzle height, barometric water outlet 150 mm. - conditional passages of connectors:
steam inlet 400 mm.
water inlet 150 mm.
steam-gas mixture output 100 mm
barometric water output 250 mm.
Calculation of barometric pipe. Barometric pipe diameter
Dtr=√ (4/a) * ((W2 + Gfl )/( αv * a)) = √ (4/3.14) * ((1.556 + 22.08 )/( 1000 * 0.5) ) = 0.245 m.
ρв - density of water, kg/m3
ώв - water speed in barometric pipe 0.3-0.5, m/s., we accept 0.5 m/s
Barometric pipe height:
Nbt = In / ρв*g + (1+ ∑ ξ + λ* Nbt/of Dtr) *ώв2/2 g+0.5 where
B - vacuum in barometric condenser, Pa;
∑ ξ - the sum of coefficients of local resistance ;
? is the friction coefficient in the pipe;
0.5 - height margin for possible change of barometric pressure, m.
B = Pat - Rbc = 9.8 * 104 - 2 * 104 = 7.8 * 104 Pa;
∑ ξ = ξвх + ξвых = 0.5+1.0 = 1.5,
where ξвх, ξвых - coefficients of local resistance on an entrance to a pipe and at the exit from it.
The friction coefficient γ depends on the flow mode of the liquid .
We define the mode of water flow in the barometric pipe:
Re = ¼ v * Dtp * αv/μv = 0.5 * 0,245 * 1000/0.54 * 10-3 = 226852,
where μв-viscosity of water, Pa*s.
For smooth pipes at Re = 226852, the friction coefficient according to the Blasius formula is :
λ = 0,3164/ Re0,25= 0,3164/2268520,25= 0,014,
Nbt = 7.8 * 104/1000 * 9.8 + (1 + 1,5,+,0,014 * Nbt/0.245) * 0.52/2 * 9.8 + 0.5 Nbt = 7,959 + (2.5 + 0, 057Nbt) * 0,513 Nbt = 7,959,+,1,282,+,0,029 Nbt Nbt = 9,241/0,971 = 9,517 m
Vacuum Pump Capacity Calculation
The capacity of the vacuum pump G1 is determined by the amount of air to be removed from the barometric condenser
GC = 2.5 * 10-5 * (W2 + Gc) + 0.01 * W2 = 2.5 * 10-5 * (1,556,+,22,08) + 0.01 * 1,556 = 16.2 * 10-3kg/s
Vacuum pump volumetric capacity is equal to
Vvozd = R * (273+tvozd) * Gvozd/(Mvozd*Rvozd ),
where R is the universal gas constant, J/( kmol * K);
Air - molecular weight of air, kg/kmol;
Air - partial pressure of dry air in BC, Pa;
air - air temperature, 0С.
The air temperature is calculated by the equation :
air = tn + 4 + 0.1 * (tc - tn) = 15 + 4 + 0.1 * (55-15) = 23
0С RR = Rbc-Rp = 2.0 * 104-0,289 * 104 = 1.71 * 104 Pa where
Is-pressure of dry saturated steam (Pa) at tvozd =23 0C.
Air = 8310 * (273 + 23) * 16.2 * 10-3/29 * 1.71 * 104 = 0.08 m3/s = 4.9 m3/min.
Knowing the volume capacity of the catalog, we select the VBN vacuum pump 1-6, with a capacity of 6 m3/min and a shaft power of 12.5 kW.