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The proximate, elemental analysis of carbon, hydrogen, nitrogen and oxygen, and the energy properties of chars and recovered liquor properties at each carbonization temperature from both HTC processes is presented in Table 5.

Table 5

Properties of chars and liquor recovered from both HTC process

 M-HTC
C-HTC
160 °C180 °C200 °C160 °C180 °C200 °C
Solid char 
 Proximate analysis (%) 
  TS 10.8 ± 0.1 11.4 ± 0.3 12.9 ± 0.2 10.3 ± 0.2 10.9 ± 0.1 12.7 ± 0.2 
  VS 65.5 ± 2.1 62.6 ± 1.1 58.6 ± 0.7 67.1 ± 0.3 62.9 ± 0.9 59.2 ± 0.0 
  FS 34.5 ± 1.9 37.4 ± 1.3 41.4 ± 0.6 32.9 ± 0.2 37.1 ± 0.7 40.8 ± 0.8 
 Elemental analysis (%) 
  C 38.1 ± 0.4 38.0 ± 0.1 38.2 ± 0.2 39.2 ± 0.1 38.8 ± 0.3 37.9 ± 0.7 
  H 5.2 ± 0.04 5.1 ± 0.02 5.0 ± 0.02 5.5 ± 0.09 5.1 ± 0.04 4.8 ± 0.05 
  N 3.6 ± 0.03 3.2 ± 0.1 2.6 ± 0.03 3.4 ± 0.08 3.0 ± 0.02 2.8 ± 0.01 
  Oa 53.1 ± 0.5 53.7 ± 0.2 54.2 ± 0.2 51.9 ± 0.3 53.1 ± 0.4 54.5 ± 0.8 
 Carbon properties 
  CDFb 1.04 1.03 1.04 1.07 1.06 1.04 
  CRWc 61.4 54.4 50.7 62.0 53.5 45.9 
  CSFd 0.23 0.21 0.19 0.25 0.22 0.19 
 Energy properties 
  HHV (MJ/kg) 16.8 ± 0.6 16.4 ± 0.2 16.8 ± 0.3 16.7 ± 0.1 16.2 ± 0.4 16.3 ± 0.3 
  EEFe 1.06 1.04 1.06 1.06 1.03 1.03 
  EY (%)f 64.9 56.6 53.5 63.8 53.9 47.4 
Liquor 
 pH 4.39 4.81 4.86 4.85 4.91 5.07 
 TOC (g/l) 9.3 ± 0.2 9.7 ± 0.1 10.3 ± 0.4 9.6 ± 0.3 10.3 ± 0.5 9.9 ± 0.4 
 COD (g/l) 30.8 ± 0.8 31.5 ± 0.5 32.3 ± 0.6 34.1 ± 0.4 35.6 ± 0.1 36.8 ± 0.6 
 VFA (g/l) 7.1 ± 0.01 6.2 ± 0.02 5.7 ± 0.3 7.0 ± 0.1 5.3 ± 0.2 4.9 ± 0.2 
 M-HTC
C-HTC
160 °C180 °C200 °C160 °C180 °C200 °C
Solid char 
 Proximate analysis (%) 
  TS 10.8 ± 0.1 11.4 ± 0.3 12.9 ± 0.2 10.3 ± 0.2 10.9 ± 0.1 12.7 ± 0.2 
  VS 65.5 ± 2.1 62.6 ± 1.1 58.6 ± 0.7 67.1 ± 0.3 62.9 ± 0.9 59.2 ± 0.0 
  FS 34.5 ± 1.9 37.4 ± 1.3 41.4 ± 0.6 32.9 ± 0.2 37.1 ± 0.7 40.8 ± 0.8 
 Elemental analysis (%) 
  C 38.1 ± 0.4 38.0 ± 0.1 38.2 ± 0.2 39.2 ± 0.1 38.8 ± 0.3 37.9 ± 0.7 
  H 5.2 ± 0.04 5.1 ± 0.02 5.0 ± 0.02 5.5 ± 0.09 5.1 ± 0.04 4.8 ± 0.05 
  N 3.6 ± 0.03 3.2 ± 0.1 2.6 ± 0.03 3.4 ± 0.08 3.0 ± 0.02 2.8 ± 0.01 
  Oa 53.1 ± 0.5 53.7 ± 0.2 54.2 ± 0.2 51.9 ± 0.3 53.1 ± 0.4 54.5 ± 0.8 
 Carbon properties 
  CDFb 1.04 1.03 1.04 1.07 1.06 1.04 
  CRWc 61.4 54.4 50.7 62.0 53.5 45.9 
  CSFd 0.23 0.21 0.19 0.25 0.22 0.19 
 Energy properties 
  HHV (MJ/kg) 16.8 ± 0.6 16.4 ± 0.2 16.8 ± 0.3 16.7 ± 0.1 16.2 ± 0.4 16.3 ± 0.3 
  EEFe 1.06 1.04 1.06 1.06 1.03 1.03 
  EY (%)f 64.9 56.6 53.5 63.8 53.9 47.4 
Liquor 
 pH 4.39 4.81 4.86 4.85 4.91 5.07 
 TOC (g/l) 9.3 ± 0.2 9.7 ± 0.1 10.3 ± 0.4 9.6 ± 0.3 10.3 ± 0.5 9.9 ± 0.4 
 COD (g/l) 30.8 ± 0.8 31.5 ± 0.5 32.3 ± 0.6 34.1 ± 0.4 35.6 ± 0.1 36.8 ± 0.6 
 VFA (g/l) 7.1 ± 0.01 6.2 ± 0.02 5.7 ± 0.3 7.0 ± 0.1 5.3 ± 0.2 4.9 ± 0.2 

aDetermined by difference, i.e. [100–{C + H + N}]%.

bCarbon densification factor, .

c%Weighted carbon retained in chars from raw, .

d.

e.

fEnergy yield, .

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