Process, system and apparatus for passivating carbonaceous materials

Abstract

A process, system and apparatus is provided for passivating carbonaceous material against spontaneous combustion. The process involves drying the carbonaceous material in a low oxygen environment and pre-conditioning the carbonaceous material by contacting it with volatile matter contained in a countercurrent gas stream. The volatile matter coats the particles of dried carbonaceous material and plugs the micropores of the dried carbonaceous material, thereby passivating it against adsorption of water and oxygen, and thus spontaneous combustion. The pre-conditioned dried material then undergoes devolatilisation at temperatures at which volatile matter is evolved. The evolved volatile matter mixes with the countercurrent gas stream and is used to pre-condition dried carbonaceous material located upstream.

1 . A process for preparing a passivated carbonaceous material comprising the steps of:
 a) drying a carbonaceous material feed stream;   b) treating the dried carbonaceous material with volatile matter, and   c) devolatilising the treated dried carbonaceous material feed stream and forming the passivated carbonaceous material and volatile matter.   
   
   
       2 . The process according to  claim 1 , wherein the step of pre-conditioning the dried carbonaceous material feed stream comprises contacting the dried carbonaceous material feed stream with a gas stream containing volatile matter. 
   
   
       3 . The process according to  claim 2 , wherein the gas stream containing volatile matter is directed in a counter current flow relative to the dried carbonaceous material. 
   
   
       4 . The process according to  claim 2 , wherein the volatile matter contained in the gas stream comprises volatile matter evolved during step c). 
   
   
       5 . The process according to  claim 4 , wherein the volatile matter evolved during devolatilisation of the dried carbonaceous material is augmented by doping the carbonaceous material feed stream with materials containing large amounts of hydrophobic aromatic moieties. 
   
   
       6 . The process according to  claim 2 , wherein the volatile matter contained in the gas stream comprises volatile matter evolved from devolatilisation of a volatile matter feedstock distinct and separate from the carbonaceous material feed stream of the present process. 
   
   
       7 . The process according to  claim 6 , wherein the volatile matter feedstock comprises materials containing large amounts of hydrophobic aromatic moieties. 
   
   
       8 . The process according to  claim 2 , wherein the volatile matter contained in the gas stream comprises volatile matter evolved during step a). 
   
   
       9 . The process according to  claim 1 , wherein the step of drying the carbonaceous material feed stream comprises heating the carbonaceous material fees stream from about 100° C. to 400° C. 
   
   
       10 . The process according to  claim 1 , wherein the drying step is conducted under a low oxygen (0-5% O 2  v/v) and high moisture (up to 50% v/v) atmosphere. 
   
   
       11 . The process according to  claim 9 , wherein the carbonaceous material feed stream is directly heated. 
   
   
       12 . The process according to  claim 11 , wherein the carbonaceous material feed stream is directly heated by contacting the carbonaceous material feed stream with a hot gas stream having a low oxygen content. 
   
   
       13 . The process according to  claim 12 , wherein the oxygen content of the hot gas stream is less than 5% v/v. 
   
   
       14 . The process according to  claim 13 , wherein the oxygen content of the hot gas stream is less than 1% v/v. 
   
   
       15 . The process according to  claim 12 , wherein the hot gas stream is contacted with the carbonaceous material feed stream in a countercurrent direction relative to the carbonaceous material feed stream. 
   
   
       16 . The process according to  claim 12 , wherein volatile matter evolves at the temperatures at which the carbonaceous material feed stream is dried. 
   
   
       17 . The process according to  claim 16 , wherein the volatile matter evolved during step a) mixes with the hot gas stream and is directed in a countercurrent flow relative to the carbonaceous material feed stream, and subsequently contact the dried carbonaceous material thereby treating the dried carbonaceous material. 
   
   
       18 . The process according to  claim 12 , wherein the step of contacting the dried carbonaceous material with a gas stream containing volatile matter is facilitated by directing a countercurrent flow of the hot gas stream relative to the dried carbonaceous material, whereby the hot gas stream is used to heat the carbonaceous material feed stream to temperatures at which step a) is performed. 
   
   
       19 . The process according to  claim 1 , wherein step a) and step b) are performed at substantially the same time. 
   
   
       20 . The process according to  claim 1 , wherein the step of devolatilising the dried carbonaceous material comprises heating the dried carbonaceous material from about 400° C. to 900° C. 
   
   
       21 . The process according to  claim 20 , wherein the step of devolatilising the dried carbonaceous material comprises heating the dried carbonaceous material from about 600° C. to 800° C. 
   
   
       22 . The process according to  claim 1 , wherein the devolatilising step is conducted under a low oxygen (0-5% O 2  v/v) atmosphere. 
   
   
       23 . The process according to  claim 20 , wherein the dried carbonaceous material is directly heated. 
   
   
       24 . The process according to  claim 23 , wherein the dried carbonaceous material is directly heated by contacting the dried carbonaceous material with a hot gas stream having a low oxygen content. 
   
   
       25 . The process according to  claim 24 , wherein the oxygen content of the hot gas stream is less than 5% v/v. 
   
   
       26 . The process according to  claim 25 , wherein the oxygen content of the hot gas stream is less than 1% v/v. 
   
   
       27 . The process according to  claim 24 , wherein the same hot gas stream is contacted with the dried carbonaceous material in a countercurrent direction relative to the dried carbonaceous material. 
   
   
       28 . The process according to  claim 24 , wherein the same hot gas stream is used in step c) and then subsequently in step a). 
   
   
       29 . The process according to  claim 28 , wherein the volatile matter mixes with the hot gas stream and is directed in a countercurrent flow relative to the dried carbonaceous material, and subsequently contacts the dried carbonaceous material located upstream, thereby treating the dried carbonaceous material before it is devolatilised. 
   
   
       30 . The process according to  claim 1 , wherein the passivated carbonaceous material feed stream produced by the process of the present invention has its moisture content reduced to between 0-20% moisture and its volatile matter content reduced to 0-25% in comparison with the moisture and volatile matter content of the carbonaceous material feed stream. 
   
   
       31 . The process according to  claim 1 , further comprising the step of quenching the passivated carbonaceous material. 
   
   
       32 . The process according to  claim 31 , wherein the passivated carbonaceous material is quenched with water and/or cool insert gas. 
   
   
       33 . The process according to  claim 31 , wherein the passivated carbonaceous material is quenched with untreated carbonaceous material, including but not limited to wet screened coal. 
   
   
       34 . A system for preparing passivated carbonaceous materials comprising:
 a dryer for drying a carbonaceous material feed stream;   a pyrolyser for devolatilising dried carbonaceous material and forming passivated carbonaceous material and volatile matter; and   a carrier vehicle for facilitating contact of volatile matter with the dried carbonaceous material.   
   
   
       35 . The system according to  claim 34 , wherein the dryer comprises a rotary kiln, a multiple hearth furnace (MHF), flash dryer, or a circulating fluid bed (CFB). 
   
   
       36 . The system according to  claim 35 , wherein the rotary kiln is configured at an angle of up to 10° above the horizontal to facilitate passage of the carbonaceous material feed stream through the rotary kiln under gravity. 
   
   
       37 . The system according to  claim 35 , wherein the rotary kiln is provided with a means to rotate the rotary kiln about its central longitudinal axis, and the rotational speed thereof is typically selected to correspond with the length of the rotary kiln such that a residence time of the carbonaceous material feed stream in the rotary kiln is bout 15-40 minutes. 
   
   
       38 . The system according to  claim 34 , wherein the dryer is arranged to heat the carbonaceous material feed stream to 100° C. to 400° C. 
   
   
       39 . The system according to  claim 38 , wherein the dryer is heated by a hot gas stream (400° C. to 800° C.) having a low oxygen content. 
   
   
       40 . The system according to  claim 39 , wherein the oxygen content of the hot stream of gas is less than 5% v/v and preferably less than 1% v/v. 
   
   
       41 . The system according to  claim 34 , wherein the pyrolyser for devolatilising the dried carbonaceous material feed stream and forming the passivated carbonaceous material and volatile matter comprises any one or more in combination of a rotary kiln, multiple hearth furnace (MHF), or a circulating fluid bed (CFB). 
   
   
       42 . The system according to  claim 41 , wherein the dried carbonaceous material feed stream in the pyrolyser is directly heated with a hot gas stream having a low oxygen content to temperatures of about 600° C.-800° C. 
   
   
       43 . The system according to  claim 42 , wherein the oxygen content of the hot gas stream is less than 5% v/v and preferably less than 1% v/v. 
   
   
       44 . The system according to  claim 38 , wherein the system is further provided with an external burner to generate the hot gas stream used for directly heating the pyrolyser and heating the dryer of the system, respectively. 
   
   
       45 . The system according to  claim 44 , wherein the hot gas stream is directed in counter current flow against the dried carbonaceous material in the pyrolyser and the carbonaceous material feed stream in the dryer. 
   
   
       46 . The stream according to  claim 45 , wherein the hot gas stream combines with the volatile matter evolved in the gas pyrolyser and thus acts as the carrier vehicle for the volatile matter. 
   
   
       47 . The system according to  claim 34 , wherein the system further comprises a means for feeding the dried carbonaceous material to the pyrolyser. 
   
   
       48 . The system according to  claim 47 , wherein the means for feeding the dried carbonaceous material to the pyrolyser comprises a closed pneumatic system. 
   
   
       49 . A process for reducing inherent moisture in and/or increasing a specific energy of a carbonaceous material comprising the steps of:
 a) drying a carbonaceous material feed stream; and   b) carbonising the dried carbonaceous material by contacting the dried carbonaceous material with a counter current gas stream having a low oxygen content.   
   
   
       50 . The process according to  claim 49 , wherein the gas stream is contacted with the dried carbonaceous material at a temperature of between 400° C. and 800° C. 
   
   
       51 . The process according to  claim 49 , wherein the oxygen content of the gas stream is less than 5%. 
   
   
       52 . The process according to  claim 51 , wherein the oxygen content of the gas stream is less than 1%. 
   
   
       53 . The process according to  claim 49 , wherein steps a) and b) are both carried out by contacting the carbonaceous material with the gas stream having a low oxygen content whereby said gas stream initially dries the carbonaceous material and then proceeds to carbonise the carbonaceous material. 
   
   
       54 . The process according to  claim 49 , wherein the gas stream contains volatile matter. 
   
   
       55 . The process according to  claim 54 , wherein the volatile matter evolves during step b) and mixes with the gas stream. 
   
   
       56 . The process according to  claim 54 , wherein the volatile matter evolves during step a) and mixes with the gas stream. 
   
   
       57 . A process for improving the coking characteristics of non-coking carbonaceous material comprising the steps of:
 a) drying a non-coking carbonaceous material feed stream;   b) treating the dried non-coking carbonaceous material with volatile matter, and   c) devolatilising the treated dried non-coking carbonaceous material and forming a carbonaceous material with improving coking characteristics and volatile matter.   
   
   
       58 . A process for quenching hot passivated char comprising contacting the hot passivated char with a particulate material. 
   
   
       59 . The process according to  claim 58 , contacting the hot passivated char with the particulate material comprises blending the hot passivated char with the particulate material and facilitating a solid-solid head exchange between particles of the hot passivated char and the particulate material. 
   
   
       60 . The process according to  claim 58  wherein the particulate material is at ambient temperature. 
   
   
       61 . The process according to  claim 58 , further comprising mixing the hot passivated char and the particulate material blend with a cool insert gas stream to facilitate further quenching thereof. 
   
   
       62 . The process according to  claim 58 , wherein the particulate material is a carbonaceous material. 
   
   
       63 . The process according to  claim 62 , wherein the particulate material is wet screened coal. 
   
   
       64 . The process according to  claim 59 , wherein the step of blending the carbonaceous material and passivated char is conducted in a substantially oxygen-free atmosphere. 
   
   
       65 . An apparatus, for use in a continuous process, for passivating carbonaceous material, the apparatus comprising:
 a) an inlet for receiving a feed stream of carbonaceous material;   b) an inlet for receiving a gas stream containing volatile matter;   c) a reaction portion configured to allow the carbonaceous material to come into contact with the gas stream containing volatile matter,   d) an outlet for receiving the passivated carbonaceous material after it has passed through the reaction portion; and   e) an outlet for receiving the gas after it has passed through the reaction portion.   
   
   
       66 . An apparatus for heating oxygen sensitive carbonaceous material in a controlled oxygen environment, the apparatus comprising:
 f) an inlet for receiving a flow of carbonaceous material;   g) an inlet for receiving a flow of gas with a controlled oxygen content containing volatile matter;   h) a reaction portion, configured to allow the carbonaceous material to come into contact with the gas with a controlled oxygen content containing volatile matter,   i) an outlet for receiving the carbonaceous material after it has passed through the reaction portion; and,   j) an outlet for receiving the gas after it has passed through the reaction portion.