# Rotary dryer design calculation for wood chips ## Rotary Dryer Detailed Description:

Rotary Dryer from Qingdao Palet Machinery can reduce the biomass material moisture content from 40-55% to below 10% -15%, according to the customers’ request. How to choose the rotary dryer design for wood chips? We have finished a successful project for wood chips dryer in Malaysia.

## How to calculate the dimension of the rotary dryer for wood chips?

The information as follows:

The material: wet wood chips, sawdust

The output: 3ton per hour

A：Drying intensity (35kg/m3h)

G1：Dry Material Production (3t/h)

V：Dry Space needed(m3)

W1：Initial Moisture Content(55%)

W2：Final Moisture Content(12%)

## Material Calculation：

For every 1000kg wet material evaporation and moisture content：

W=1000×（0.55-0.12）/(1-0.12)=488.6kg(H20)

For every 1000kg wet material quantity after evaporate：M=1000-488.6=511.4kg

To produce 1000kg of end product need to feed in：

G=1000/511.4×1000=1955.4kg(wet raw material)

Rotary Dryer Calculation：

Volume calculation:

G1=AV÷｛1000×〖W1—W2〗÷〖100—W1〗｝

3=AV÷｛1000×(55-12)/(100-55)｝=AV/956

V=81.9m3

Provided Drum dimension:φ2.2×24m

V=πr²L=3.14x（1.1）²x24=91m>82m3（fulfill requirement)

## Rotary Dryer Energy Balance

Air Flow Velocity:  v=1.5m/s,

Dry Air Density:  ρ=1.2kg/m3,

Air Humidity:  H=0.007kg/kgdry air

Ambient Air Temperature: t0=30°

Inlet Hot Air Temperature: t1=250°

Outlet Hot Air Temperature: t2=70°

Dry air consumption：

L=πr2vρ3600=3.14×12x1.5×1.2×3600=20347.2kg/h

Wet air consumption：

L1=L(1+H)=20347.2X(1+0.007)=20490kg/h

Heating value for ambient air：

Q1=L(1.01+1.88H)(t2-t0)=20347.2÷3600x（1.01+1.88×0.007）x（70-30）=231.3kw

Heating value for evaporating moisture：

Q2=W(2490+1.88t2-4.187×30°）

=955.4÷3600x（2490+1.88×70-125.61)=622.4kw

Heating value for wet material：

Q3=Gc（ wood ）（t2-t0）=1955.4×2.5×103x40÷3600÷1000=54.3kw

Heating value loses：

Q4=（Q1+Q2+Q3）0.22=908×0.22=199.76kw

Total Heating Value：

Q=Q1+Q2+Q3+Q4=1107.76kw

## Rotary Dryer Gas Quantity Needed

For standard condition

Dry Air Density:ρ=1.29kg/m3
Air Specific Heat Capacity:c=1.0×103J/(kg.℃)

Q=V（T-t2）ρc=V（400-70）ρc

V=2303.4*3.6×106/370*1.29*103=17373m3

## Single Rotary Dryer System Air Flow Rate

Evaporation=955.4kg，t1=250°，t2=70°

System Air Flow Rate=Evaporation*3000/(t1-t2）=16000m3/h

Air Flow Rate =1.3*System Air Flow Rate=20800m3/hm3/h

Provided model：4-72-8C-22kw

## Rotary Dryer Draft Fan Air Flow Rate

Draft Fan Air Flow Rate=2*System Air Flow Rate=32000m3/h

Provided model：4-72-10C-45kw