1. DESIGN AND MANUFACTURING OF BIOMASS
CARBONIZING FURNACE

2. Introduction
• The most critical aspect to the design of the carbonizing furnace is the
insulation. If the rate of heat loss from the carbonizing chamber is high,
adequate temperature required for carbonization to occur inside the
chamber will not be achieved. The concept used is that the furnace is
capable of providing insulation for a greater rate of heat generation than
actually taking place in the production process.

3. Assumptions:
• Rice husk biomass yield per unit mass = 36.97%
• Specific heat capacity of rice husk biomass, Cb = 1.5KJ/kg°C
• Ambient temperature = 22°C
• Thermal resistance for mild steel = 3.066 x 10-5 K/W
• Calorific value of fuel (biomass carbonized charcoal) = 23MJ/kg
• Carbon content of rice husk carbonized charcoal per unit mass = 75%
• Calorific value of carbon, CVc = 32MJ/kg
• Heating rate of rice husk biomass, HRb = 5°C/min

4. Energy
o Energy required to heat the biomass feedstock the required temperature for carbonization, Q1
𝑄1 = 𝑚𝑏 × 𝑐𝑏 𝑇𝑐 − 𝑇𝑎 = 27 𝑥 1.5 450 − 22
𝑄1 = 17334𝐾𝐽
 Heat required to maintain carbonization process, Q2
𝑄2 = 𝑚𝑏 × 𝑐𝑏 𝑇𝑐2 − 𝑇𝑐1 = 27𝑥 1.5 700 − 450
𝑄2 = 10125 𝐾𝐽
 Heat transfer due to the conduction, Qcond
𝑄𝐶𝑜𝑛𝑑 =
𝑡𝑐 − 𝑡𝑎
𝑅𝑡
=
450 − 20
3.066 𝑥 10−5
= 14025𝑘𝐽
 Net energy required for the carbonization furnace, Qnet
Q1 + Q2 +Qcond = 41484KJ

5. Mass of fuel
Mass of the fuel required to produce 41484KJ
From:
Qnet = mf x Cv
But 𝑚𝑓 =
𝑄𝑛𝑒𝑡
𝐶𝑣
𝑚𝑓 =
41565𝑘𝐽
23000𝑘𝐽
= 1.8𝑘𝑔 ≈ 2𝑘𝑔
• Therefore, the mass of fuel to produce the energy required for carbonization will be 2kg.

6. Duration of carbonization process
• Heating time
𝑡1 =
𝑡𝑐 − 𝑡𝑎
𝐻𝑅𝑏
=
(450 − 22)°𝑐
5°𝐶/𝑚𝑖𝑛
= 86𝑚𝑖𝑛 = 1.4ℎ𝑟
Time = 1hr: 26min
Carbonization time
𝑡2 =
𝑡𝑐𝑓−𝑡𝑐𝑖
𝐻𝑅𝑏
=
(700−450)°𝑐
5°𝐶/𝑚𝑖𝑛
=50min
• Total time
T = 𝑡1 + 𝑡2
=136min
=2.3hrs
T=2hrs: 16mins (total time to carry out the carbonization process)

7. Thermal efficiency of the furnace
1. Thermal efficiency
𝑛𝑡ℎ =
𝑄𝑜𝑢𝑡
𝑄𝑖𝑛
× 100%
=
𝑚𝑏 𝑥 𝐶𝑏 𝑥 ∆𝑇
𝑚𝑓×𝐶𝑣
× 100% =
27 𝑥 1.5(700−22)
2 𝑥 2300𝑘
X 100%
• Thermal efficiency is 0.597 or 59.7% approximately 60%.

8. Simulation study

10. Simulation study
The temperature distribution measured in the traditional process
of rice husks biomass carbonization shows non- uniform heating
of the rice husk biomass charge inside the carbonization
chamber.