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Energy from Biomass - Final Assignment

Pre-treatment of biomass to produce high grade solid fuel:

Bio Coal Hydrothermal Carbonization

Submitted By Group 3:

Easwaran Krishnamurthy - 4323831

Gowrishankar Ramanan - 4322312

Rashi Mor - 4311175

Vidyut Mohan - 4323386

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Table of Contents

1. Introduction ......................................................................................................................... 3

2. Hydrothermal Carbonisation ................................................................................................. 4

2.1 Reaction Mechanisms ................................................................................................................... 4

Hydrolysis ........................................................................................................................................ 4

Dehydration .................................................................................................................................... 4

Decarboxylation .............................................................................................................................. 4

Polymerisation ................................................................................................................................ 4

Aromatisation ................................................................................................................................. 5

2.2 Relevant Process Parameters ....................................................................................................... 5

Temperature ................................................................................................................................... 5

Pressure .......................................................................................................................................... 6

Residence time ................................................................................................................................ 6

Acetic Acid ....................................................................................................................................... 6

2.3 Process merits and demerits ......................................................................................................... 6

3. Reactor Design and Sizing ..................................................................................................... 8

3.1 Process requirements and Design ................................................................................................ 8

3.2 Choice of feedstock ....................................................................................................................... 9

3.3 Reactor Design ............................................................................................................................ 11

3.4 Mass Balance .............................................................................................................................. 13

3.5 Energy Balance ............................................................................................................................ 13

3.6 Balance of the plant .................................................................................................................... 15

4. Conclusion .......................................................................................................................... 17

References ................................................................................................................................. 18

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1. Introduction

Lignocellulosic materials such as wood, forest and agricultural residue are becoming increasingly

popular as a renewable feedstock for the production of fuels, heat and electric power. However,

various factors like non uniform physical shapes, densities, handling and storage and other chemical

properties of the feedstock make it difficult to optimise the energy generated from the process. Pre-

treatment of feedstock is undertaken to homogenize the feedstock and make the cellulose in the

feedstock material more accessible. Pre-treatment breaks down the protective lignin structure,

disrupts the crystalline structure and hydrolyses it thereby increasing the carbon content and hence

the heating value of the feedstock (Kumar et al).

The conversion of biomass into products with higher carbon contents takes place by different

thermochemical processes. Pyrolysis is a process which occurs under high temperature and in the

absence of oxygen leads to the formation of charcoal. When pyrolysis is carried out in the presence

of sub-critical liquid water, at high temperatures (180C - 280C) and pressures, the process is known

as hydrothermal carbonization (Zeno Robbiani, 2013). It is also known as wet torrefaction,

hydrothermal pre-treatment, coalification and hot compressed water treatment. The biomass is

treated in hot compressed water and forms three product groups (Yan, W. et al., 2010):

Solid fuel (Bio coal) ranges from 55-90% of the feedstock mass and 80-95% fuel value

depending on the process temperature and residence time

Aqueous compounds consist of mainly monosaccharide, organic acids and furfural

derivatives approximately 10-15% by mass of feedstock

Gases which consist of mainly CO2 (90%)

HTC Hydrothermal carbonisation can refine organic waste into bio-coal for use in existing power

plants to produce bio-energy. HTC biocoal is a high quality biofuel, which can be used for co-firing

power plants or for the production of syngas and second generation biomass to liquid biofuels.

A HTC biomass-to-biocoal plant can produce biocoal from a wide variety of sources. The typical types

of organic wastes that can be used are (Hoekman, S.K. et al., 2012):

Grass cuttings

Fallen leaves

Landscape management waste

Bagasse

Straw

Wood chips

Waste from palm oil mills

Rice husks

In this report, the process of hydrothermal carbonisation has been investigated and a hydrothermal

carbonisation plant has been designed according to various process requirements. In Section 2, a

short overview of the process, the various reaction mechanisms, and the relevant operating

parameters have been elucidated. The various merits and demerits of this process with regards to

other coalification process have also been listed. Section 3 comprises of the design of the HTC plant

from the feedstock to optimizing process parameters and sizing the reactor.

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2. Hydrothermal Carbonisation

Hydrothermal carbonisation is characterised by the following operating parameters:

Within subcritical conditions

Process temperature should be greater than 180oC.

In order to maintain a liquid water phase, the minimum pressure needs to be saturated

pressure

The feed must be completely submerged during the process

Acidic conditions are favoured as basic conditions result in different products that are not as

useful as the products achieved with acidic conditions. The pH value drops during the

process automatically due to the formation of acids.

Residence times vary from 30 min to 72 hours in literature. Reaction rates and reaction

mechanisms are still ambiguous leading to the wide range.

Various reactions occur in hydrothermal carbonisation due to the complex nature of the organic

compounds present in the feedstock. Due to the uncertain reaction rates associated with the

reactants and the intermediate products that form due to multiple side reactions, it is hard to

establish definite parameters and equations which can predict the quality of the products.

2.1 Reaction Mechanisms

The main reaction mechanisms involved in HTC include hydrolysis, dehydration, aromatization,

decarboxylation, polymerization and hydrogenation. A brief description of the different mechanisms

has been derived from Funke & Ziegler (2011).

Hydrolysis

Hydrolysis leads to the cleavage of esters and ethers by the addition of water. The products include

saccharides of cellulose and phenolic fragments of lignin.

Dehydration

Dehydration entails the removal of water from the biomass matrix without changing its chemical

constitution, significantly lowering the hydrogen-carbon (H/C) and oxygen-carbon (O/C) ratios. An

example of a dehydration reaction has been provided below (Funke, A. & Ziegler, F., 2011).

4(C6H10O5)n 2(C12H10O5)n+10H2O

Decarboxylation

Decarboxylation is the degradation of carboxyl and carbonyl groups yielding CO and CO2. During the

degradation of cellulose, a large amount of formic acid is formed, which decomposes into CO2 and

H2O. Other possible sources are the formation of CO2 during the cleavage of bonds and

condensation reactions.

Polymerisation

The knowledge about detailed polymerisation sequences during the course of HTC is essentially

missing. Polymerisation forms a solid precipitate and is regarded as an unwanted side reaction.

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Aromatisation

Crosslinking of aromatic rings makes up for natural constituents of natural coal. Aromatic structures

are highly stable and considered as basic building blocks of the resulting HTC coal. Cellulose and

hemicellulose form aromatic structures in both non-hydrous and hydrothermal conditions.

The reactions involved and associated products formation in complete sequence can be illustrated

from figure 1 below (Kruse et al., 2013).

Figure 1: Chemical processes involved in HTC

2.2 Relevant Process Parameters

The presence of water has a distinguishing effect on the outcome of the process. Apart from the

presence of water, the following are relevant operating parameters which greatly influence the

results of the hydrothermal carbonisation process.

Temperature

As with any chemical process/reaction, temperature has a great impact on the rate of reaction. HTC

is generally conducted under a temperature range of 180oC to 280oC. Literature survey shows that

the mass yield decreases as the temperature increases and becomes nearly constant at higher

temperatures. A likely explanation could be that the further degradation of sugar at higher

temperatures resulting in less deposition. As a consequence of the carbon content remaining the

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same and the mass yield decreasing with increasing temperature, the energy content follows an

increasing trend with increasing temperature.

Pressure

The pressure under which the process takes place is normally the saturated pressure as the process

takes place in basically a pressurised vessel with a fixed volume. The pressure in the vessel tends to

be slightly higher than the saturation pressure due to the presence of gaseous volatile components

(Xiao, L.-P. et al., 2012).

Residence time

In order to quantify the intensity of the reaction, researchers have come up with term reaction

severity. Reaction severity can be increased by either increasing the temperature and/or increasing

residence time of the feed. Experimental results show an increase in the carbon content of the

product and a corresponding decrease in the mass yield, translating to a greater higher heating value

(HHV) of the coal.

Acetic Acid

Research conducted by Lynam et al (2011) shows that the addition of 0.4g of acetic acid per gram of

feedstock increases thee HHV by 30% and reduces the mass yield of the solid product. Acetic acid

performs a catalytic role in HTC. Due to such a significant increase in the HHV, the usage of acetic

acid has been considered in the mass and energy balances of the hypothetical plant.

2.3 Process merits and demerits

HTC is a relatively new process in the biofuel industry and brings with it many advantages, while

having certain limitations. The merits and demerits of the process have been described in this

section with regards to other coalification processes such as torrefaction. Torrefaction is a mild

form of pyrolysis done between 200 and 320 C.

The char produced by the HTC process are called as bio char, bio coal, HTC-char. Biocoal

finds itself used in catalysis, water purification, carbon sequestration, soil amendment, etc.

apart from being used as a Solid Biofuel.

Advantages

HTC can utilize wet feedstock (green waste), manure, municipal waste stream, peat, algae. Inorganic nutrients are retained in the aqueous by-products, raising the possibility of using HTC to produce biocoal from algae, while recycling the nutrients to promote additional algae growth.

Due to the high heat transfer in an aqueous environment, HTC process proceeds more rapidly than torrefaction at a given temperature.

The hydrochar produced by HTC has a greater energy densification by reducing the mass of the solid product and increasing its higher heating value (HHV) than obtained from torrefaction.

Also, it is more amenable to pelletisation than the char from torrefaction, thus producing pellets. (Lynam J. G., 2011)

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The energy densification ratio i.e ratio of the heating value of the pretreated solid fuel product to the original biomass can be increased from 3% to 47% by using hydrothermal carbonization. (Lynam J. G., 2011)

HTC is an efficient process for carbon sequestration to mitigate climate change. When biomass is composted, anaerobically digested or fermented, some of the carbon in the substrate is converted into CO2 and lost to the atmosphere. With HTC, most of the carbon present in the substrate stays bound to the final coal product.

HTC requires lower process temperature (180 250 C) when compared to pyrolysis (400 C) (Zeno Robbiani, 2013)

HTC can be carried out more quickly than torrefaction and easily accommodates a broader range of feedstock, as the initial moisture level is not a concern. (Hoekman S. K. et. al, 2011).

Reduction in equilibrium moisture content in pre-treated biomass indicates a more hydrophobic nature, leading to better storage properties.

Limitations

HTC produces non-combustible gases and aqueous wastes unlike torrefaction which produces volatile materials which are used as a combustible fuel as its by product.

Information suggests that HTC method is quite expensive when compared to torrefaction, although not much comprehensive techno-economic comparison has been made (Uslu et al, 2008).

The disadvantage of HTC is that it does not work well with biomass which has a high content of lignin in it. (Ava-CO2, 2010)

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3. Reactor Design and Sizing

The ways by which biomass is fed into the system can be categorised into three different categories:

continuous, semi-continuous and batch type systems. The biomass is fed at a constant rate in the

continuous system. In the batch type system, the biomass is refilled with new biomass only after the

process is complete. In the semi-continuous system, the process works at a constant rate, but the

biomass is separated into batch type vessels. The vessels remain in the system until carbonisation is

complete and is replaced by a new vessel of fresh biomass. This process is repeated for the

generation till the required produce is obtained. (Tony Kiuru et. al, 2013)

Batch reactor

Batch reactors are generally cylindrical stirred tanks. The carbonization process begins only when the

reactor is filled. The reactor must be emptied before being loaded with the new material. To

optimize the process, industries operate many reactors in parallel (quasi-continuous multi-batch

system). One of the advantages of this type is that the waste heat from a reaction can be reused to

preheat the input material for the next reaction.

Continuous reactor

Continuous reactors are smaller than batch reactors. They require a complex system to handle the

feedstock as a flowing stream while maintaining a high pressure in the reactor. This system allows

the reactor to stay continuously at the same temperature, without the need to be cooled down and

reheated in between two reaction cycles. (Zeno Robbiani, 2013)

3.1 Process requirements and Design

The general schematic of the Hydrothermal Carbonisation process is illustrated below in figure 2.

Figure 2: The Hydrothermal Carbonisation Process

The selection of an appropriate design depended upon the following criteria:

1. Cost- As the plant is of a significantly large scale, the bio coal produced would most likely be

used by other large scale industries like the power industry or the sugar industry. Therefore,

the components of the plant need to be of high quality to minimise the downtime.

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2. Availability of feedstock- The feedstock chosen should be available in plenty to meet the

plant input demands.

3. Level of Technology- The level of technology should be chosen such that it is easily

reproducible in other parts of the country where sugar cane is cultivated.

4. Durability- The equipment should be of high quality to minimise frequent maintenance and

troubleshooting.

5. Ease of Handling- As the technology has not yet reached the state of maturity; there is lack

of technical knowhow in India in this regard. Thus the operation and maintenance of the

equipment shouldnt need complex infrastructure, and /or expert knowledge.

The entire pre-treatment process of Hydrothermal Carbonisation is described in figure 3 below.

The critical parameters of the plant to be specified and designed are as follows:

1. The feedstock

2. Milling/Grinding equipment

3. Reactor design

4. Balance of the plant

3.2 Choice of feedstock

Various types of feedstock were compared including Tahoe mix (Jeffery pine and white fir), loblolly

pine, Juniper/pinyon, sugarcane bagasse, municipal solid waste, sewage and corn stover. The choice

of a certain feedstock for a certain plant is highly dependent on the location, seasonal availability,

energy content and the available technology to process the feedstock. In order to make a justifiable

choice of feedstock based on the above choices, the location of the plant has been chosen as India.

Reactor

(Wet Torrefaction)

Bagasse (milled to 6mm)

Water

Water

Acetic Acid

Precipitates+ Other Acids

Pre-treated Bagasse

Gas (primarily CO2)

Endothermic heat input

Acetic Acid

Figure 3: General schematic of HTC process reactor

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The plant is going to be set up in India, which produces nearly 340 Million Metric tonnes per year of

sugarcane (Singh, B.R., 2011). For every 100 tons of Sugarcane crushed, a Sugar Factory produces

nearly 30 tons of wet Bagasse (Salmar Zafar, 2013). The moisture content produced in bagasse is

about 40-50%. The selling point for the use of HTC increases over other coalification processes when

the feedstock has a moisture content greater than 40%.Since bagasse fulfils this criteria and also has

a high Higher Heating Value (HHV, 17,317-19,407 kJ/kg) , it was chosen over rice husk (moisture

content 8.66-10.44%) (Jenkins, January 1993 ).

Figure 4: Yield parameters for different types of feedstock (Hoekman, S.K. et al., 2012)

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3.3 Reactor Design

A parallel stirred tank multi batch reactor system was selected due to the high level of maturity of

technology and low levels of complexity leading to ease of handling .Table 1 below compares the

batch and continuous mode for HTC systems.

Table 1: Comparison of batch and continuous mode for HTC systems (Robbiani, April 2013)

The main goal in designing the HTC plant was to get a pre-treated product similar to Lignite. The

extent of oxygen conversion was chosen as the main parameter in deciding the extent of conversion

and hence the residence time. The extent of conversion is governed by the following equation:

Where,

f= Degree of conversion of feedstock to solid biocoal

t= time for conversion or residence time, Seconds, s

T= Operating Temperature of the reactor, Kelvin, K = 513 K (240 Degrees C)

Ofeed= Oxygen content of the Sugarcane Bagasse feed, %= 46.05% (Hoekman et al., December 2012)

Ot= Oxygen content at time t (chosen according to Oxygen content of Lignite, 30%), % (Dunne et al.,

May 2007)

On substitution of the oxygen values the degree of conversion comes out to be 40% (f=0.40).

A study was conducted to decide the residence time, t, by varying the reaction temperature and

degree of conversion using the above equation. The results can be seen in the figure 5 below. The

graph was plotted for temperature varying from 210-270C between the reaction time and oxygen

conversion.

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Figure 5: Residence time Vs Oxygen conversion

For 40% conversion to meet the requirements for Lignite type coal, a temperature of 240 degrees C

was found optimum. Literature suggests that energy content in the product fuel produced levels out

after 240C (refer figure 6 below). Additionally, the increase in pressure at temperatures greater

than 240 degrees mandates the use of thicker reactor vessels, thus increasing the cost of the system.

The marginal increase in energy content of the fuel does not justify substantial increase in

equipment cost. Also, similar scale HTC projects had a residence time of 6 hours for batch reactors

which was satisfied by this temperature condition (AVA-CO2, June 2013).

Figure 6: Energy content Vs Reaction Temperature (Hoekman et al., December 2012)

0

1000

2000

3000

4000

5000

6000

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Tim

e (

ho

urs

)

Oxygen conversion

210 degrees C

230 degrees C

240 degrees C

270 degrees C

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3.4 Mass Balance

Inputs

Biocoal product output= 5000 kg/hr

Biocoal percentage in the output =59.09% (of total input feedstock) (Hoekman et al., December

2012)

Thus Sugarcane Bagasse feed rate (A) = 5000/0.5909 kg/hr= 8461.67 kg/hr= 9.61 m3/hr (Density of

milled bagasse= 880 kg/m3)

Water to feedstock ratio = 5:1 (by weight)( Yan et al., January 2010)

Therefore, water feed rate (B) = 8461.67 x 5 kg/hr= 42308.35 kg/hr= 42.308 m3/hr

As an input acetic acid is fed at the rate of 0.4kg/kg biomass (Lynam J.G. et al., February 2011)

Thus, acetic acid feed rate(C) = 3384.67 kg/hr= 3.22 m3/hr (Density of acetic acid= 1050 kg/m3)

Therefore Total input feed rate (D) = A+B+C= 54154.69 kg/hr= 55.138 m3/hr

Now residence time, t, is given by:

Taking a residence time of 6 hours, the total volume of the reactors was found out to be,

V= 330.828m3= 330,828 L

From a similar project by TFC engineering (Robbiani, April 2013), the size of the reactor was found

out to be 10,000L.

Thus, estimated number of reactors= 33

Outputs

Non- Volatile residues (NVR) = Acid solution and precipitates (10% of input feedstock)+ Acetic acid

catalyst= 846.1 kg/hr+ 3384.67 kg/hr= 4230.78 kg/hr

Water outflow rate=water inflow rate= 42,308.35 kg/hr

Evolved gases and volatile substances (31% of feedstock) = 2615.57 kg/hr

Product coal= 5000 kg/hr

Thus total output feed rate (D) = 54154.69 kg/hr= Total input feed rate

3.5 Energy Balance

Based on the specific heats of the reactants and products involved, the required input energy and

energy released is calculated. The calculations conclude whether the HTC process is endothermic or

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exothermic. The table 2 below shows the specific heat capacities, mass flow rates and

correspondingly the energy required for a temperature change of 25C (room temperature) to 240C

(process temperature). The specific heat capacities of bagasse, water, acetic acid are used from the

specific heat capacity tables. The output gas is assumed to be consisting mainly CO2 since the HTC

output gas has been reported to consist of 90% CO2 (Yan, W. et al., 2010). Hence the specific heat

capacity of gas is used as that of carbon dioxide. The precipitates in the output stream are mainly

sugars and hence specific heat capacity of glucose has been used. The specific heat capacity of

produced hydro char is assumed to be that of lignite coal and is calculated using the equation below.

(Pakowski Z., et al, 2012)

Input of batch reactor Output of batch reactor

Reactant Mass

flow (in

kg/hr)

Specific

heat

capacity

(in

kJ/kg.K)

Enthalpy (in

kJ/hr)

Product Mass

flow (in

kg/hr)

Specific

heat

capacity

(in

kJ/kg.K)

Enthalpy (in

kJ/hr)

Bagasse 8461.67 1.6 2910814.48 Hydro char 5000 1.51 1612500

Water 42308.35 4.4 40023699.1 Water 42308.35 4.4 40023699.1

Acetic

Acid

3384.67 2.05 1491793.303 Acetic Acid 2030.8 2.05 895075.1

Precipitates

(mainly

glucose)

2199.97 1.21 572322.1955

Gas (mainly

CO2)

2615.57 1.01 567971.0255

Total Enthalpy of Reactants 44426306.883 Total Enthalpy of Products 43671567.42

Table 2: Energy balance of the reactor process

It can be seen from the table above that net heat of reaction (Enthalpy of products Enthalpy of

reactants) is -754739.4615, thereby concluding the HTC process reaction to be exothermic. This

released energy can be used for drying the obtained hydro char and also reused as energy input for

the next batch reactor.

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3.6 Balance of the plant

The balance of the plant would consist of the following systems:

Filtering system - It would consist of a mesh with a size of 4mm to filter out the biocoal

particles (6mm particle size as mentioned earlier) from the liquid.

Drying system - To bring down the moisture content in the biocoal to around 20% a drying

system needs to be employed. For this purpose conventional Fluidised Bed Thermal Dryers

(FBD)can be employed which are designed to dry low rank coals (Dunne et al., May

2007).The various kinds of fluidised bed reactors are: Multi-stage FBD, Multi- Level FBD,

Pulsed FBD, FBD with immersed heater. Out of all of these options the pulsed FBD system is

the most suitable for low rank coals as the other dryers lead to higher attrition of friable

materials such as Lignite( which is close to HTC coal).The pulsed FBD dryer is illustrated in

figure 7.

Figure 7: Schematic diagram of a Pulsed Fluidised Bed Dryer(Osman H.et al., August 2011)

The specific energy consumption of a PFBD is 0.19 MJ/kg H2O compared to 0.33 MJ/kg H2O

for other fluidised bed drying processes.

Now the output of coal is 5000kg/hr or 1.39 kg/s. Assuming it has 50% moisture content:

Moisture flow rate= 0.69 kg/s

Bringing down the moisture content to 30% would involve a 20% conversion.

Flow rate of moisture to be converted= 0.278 kg/s

Thus power of dryer= 0.19 x 0.278 =0.052 MW =52.82KW.

Apart from the above two components, process water recirculation pumps and feed water pumps

would also be needed to meet the flow rate demands. A conveyor/hopper system would also be

needed to feed the raw biomass to numerous storage tanks.

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Milling - Before feeding the bagasse feedstock to the HTC reactor, the feed particle size

needs to be reduced to

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4. Conclusion

A literature review of the process of hydrothermal carbonisation was conducted and the main

findings have been presented. Based on the know-how gained from the literature review, a plant

location and a specific feedstock type were selected. Based on an output of 5 tonnes/ hour, a

hypothetical plant has been conceptualised. The mass and energy balances have been conducted to

investigate the feasibility of the process. The mass balance returns identical values for input mass

and output mass. The energy balance shows that the process is exothermic. However, it is

acknowledged that heat losses and inefficiencies would require a certain heat input to the plant.

Additionally, a preliminary sizing of the milling equipment, drying equipment has been specified. The

filtration system, feed pumps and conveyor belt and hopper system for the balance of the plant have

been briefly described.

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References

Andrea Kruse, Axel Funke and Maria-Magdalena Titirici, 2013, Hydrothermal conversion of biomass

to fuels and energetic materials

AVA-CO2, October 2010, AVA-CO2 and Hydrothermal Carbonization (HTC)

Dunne, D.J. & Agnew, J.B., 1992. Thermal Upgrading of Low-Grade, Low-Rank South Australia

Coal.Energy Sources, 14(2), pp.169181. Available at:

http://www.tandfonline.com/doi/abs/10.1080/00908319208908718 [Accessed April 13, 2014]

Funke Funke, A. & Ziegler, F., 2011. Heat of reaction measurements for hydrothermal carbonization of biomass. Bioresource technology, 102(16), pp.75958. Available at: http://www.ncbi.nlm.nih.gov/pubmed/21646017 [Accessed March 27, 2014]

Gil, M., Gonzalez, A. & Gil, A., 2010. Evaluation of Milling Energy Requirements of Biomass Residues in a Semi-industrial Pilot Plant for Co-firing

Hoekman, S.K. et al., 2012. Hydrothermal carbonization (HTC) of selected woody and herbaceous biomass feedstocks. Biomass Conversion and Biorefinery, 3(2), pp.113126. Available at: http://link.springer.com/10.1007/s13399-012-0066-y [Accessed April 13, 2014]

Kruse, A., Funke, A. & Titirici, M.-M., 2013. Hydrothermal conversion of biomass to fuels and energetic materials. Current opinion in chemical biology, 17(3), pp.51521. Available at: http://www.ncbi.nlm.nih.gov/pubmed/23707262 [Accessed March 31, 2014]

Lynam, J.G. et al., 2011. Acetic acid and lithium chloride effects on hydrothermal carbonization of lignocellulosic biomass. Bioresource technology, 102(10), pp.61929. Available at: http://www.ncbi.nlm.nih.gov/pubmed/21411315 [Accessed April 13, 2014]

Osman, P.H. et al., 2011. Drying of low-rank coal ( LRC ) A review of recent patents and innovations. , (August)

Pakowski, Z., Adamski, R. & Kwapisz, S., 2012. Effective diffusivity of moisture in low rank coal during superheated steam drying at atmospheric pressure. Chemical and Process Engineering, 33(1), pp.4351. Available at: http://www.degruyter.com/view/j/cpe.2012.33.issue-1/v10176-012-0004-3/v10176-012-0004-3.xml [Accessed April 13, 2014]

Parveen Kumar, Diane M. Barrett, Micheal J. Delwiche and Pieter Stroeve, 2009, Methods for

pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production

Robbiani, Z., 2013. Hydrothermal carbonization of biowaste / fecal sludge Conception and

construction of a HTC prototype.

Salman Zafar, November 2013, Energy Potential of Bagasse. Available at:

www.bioenergyconsult.com/energy-potential-bagasse

Singh, B.R., 2011. Study on Future Prospects of Power Generation by Bagasse , Rice Husk and

Municipal Waste in Uttar Pradesh. , 2(2)

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Tony Kiuru, Jukka Hyytiainen, 2013, Review of current Biocoal Production Technology

Uslu A, Faaij APC, Bergman PCA, 2008, Pretreatment technologies and their effect on international

bioenergy supply chain logistics and their effect on international bioenergy supply chain logistics,

techno-economic evaluation of torrefaction, fast pyrolysis and pelletisation

Xiao, L.-P. et al., 2012. Hydrothermal carbonization of lignocellulosic biomass. Bioresource

technology, 118, pp.61923. Available at: http://www.ncbi.nlm.nih.gov/pubmed/22698445.

Yan, W. et al., 2010. Mass and Energy Balances of Wet Torrefaction of Lignocellulosic Biomass .

Energy & Fuels, 24(9), pp.47384742. Available at: http://pubs.acs.org/doi/abs/10.1021/ef901273n

[Accessed March 25, 2014]