Bulletin of the JSME Vol.3, No.5, 2016 Mechanical

J STAGE Advance Publication date: 8 August, 2016Paper No.16-00334

© 2016 The Japan Society of Mechanical Engineers[DOI: 10.1299/mej.16-00334]

Vol.3, No.5, 2016Bulletin of the JSME

Mechanical Engineering Journal

0123456789

-

Material and heat flow analysis in thermal energy storage and

transport system utilizing unused heat from bagasse boiler

Shoma FUJII*, Yuichiro KANEMATSU**, Yasunori KIKUCHI** and Takao NAKAGAKI* *Department of Modern Mechanical Engineering, Waseda University

3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan

E-mail: [email protected]

**Presidential Endowed Chair for “Platinum Society”, The University of Tokyo

7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

1. Introduction

Isolated areas such as islands rely on imported fossil fuels to a greater extent than in other areas; the sustainability

of industry in these areas decreases day by day. “Industrial Symbiosis”, which is a concept for utilizing the unused

materials and energy from one industry in neighboring industries, has become important in alleviating these issues

(Kikuchi et al., 2016). Tanegashima is an isolated island located south of Kyushu in Japan; the cultivation and milling of

sugarcane is the main industry. A sugar mill produces raw sugar which is shipped to a domestic sugar refinery in Osaka,

and a large amount of bagasse. Bagasse is fibrous residue obtained from milled sugarcane after the sugar juice has been

extracted, and the bagasse boiler of the sugar mill combusts the bagasse as a biomass energy. Bagasse is a useful biomass

energy source with an established collection system. However, it is difficult to store raw bagasse because its moisture

content causes it to be perishable. Accordingly, more bagasse is burned in the bagasse boiler than is required for mill

turbine and power generation. Hence, the temperature of the flue gas is high, and a large amount of unused heat at

approximately 200 °C is exhausted during mill operation, typically from December to April.

There are many other factories in Tanegashima, such as a liquor factory, which generally use oil-fired package boilers

to generate process steam at temperatures up to 120 °C and a total amount of heat demand at the liquor factory is 1556

GJ/year. Furthermore, the affiliate sugar-refinery in Osaka uses city gas boilers to constantly generate a large quantity of

steam at 150 °C for the crystallization and refining processes and a total amount of heat demand at the sugar refinery is

315315 GJ/year.

Abstract

Sugar production is the main industry in Tanegashima, Japan. Whilst the sugar mill recycles sugarcane bagasse

as a fuel, it concurrently generates large amounts of unused 200 °C heat during operation. Raw sugar is

shipped to a refinery in Osaka for the final stages of production, which uses a city gas boiler to continuously

generate a large quantity of 150 °C heat. However, factories in Tanegashima need a continuous supply of

process steam at temperatures of up to 120 °C. To resolve this spatial and seasonal mismatch of heat, we

propose a thermal energy storage and transport system using a zeolite adsorption/regeneration cycle. A process

flow diagram of the sugar mill has been developed, and the amount of available heat, the potential storage

capacity, and the transportable amount of heat have been calculated. Two scenarios were analyzed, in which

the stored heat is shipped to Osaka, or used on the island. This was achieved by calculating the rate-based

storage capacity of zeolite, based upon an adsorption and regeneration test. The transportable quantity of

zeolite determines the feasibility of using waste heat. In the first case, transport of heat to the sugar refinery in

Osaka has little possibility of being implemented. In the second case, transport of heat to a liquor factory in

Tanegashima can potentially reduce its usage of heavy oil by 83 %, equivalent to 33 kL/year.

Key words: Heat storage, Biomass energy, Zeolite adsorption and regeneration cycle, Sugarcane bagasse,

Sugar milling process, Unused heat utilization

Received 30 May 2016

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2© 2016 The Japan Society of Mechanical Engineers

Fujii, Kanematsu, Kikuchi and Nakagaki, Mechanical Engineering Journal, Vol.3, No.5 (2016)

[DOI: 10.1299/mej.16-00334]

The sugar mill is operated from winter to spring according to the sugarcane harvest, however other factories including

the liquor factory and the sugar refinery are operated all year around with the constant heat demand. If unused heat from

the bagasse boiler in the sugar mill can compensate for the heat demand supplied by boilers, both the fossil fuel and the

accompanying CO2 emissions can be reduced. In order to resolve the spatial and seasonal mismatch, we propose a thermal

energy storage (TES) and transport system using zeolite steam adsorption and regeneration cycle as shown in Fig. 1.

Many TES systems have already been reported. L. F. Cabeza et al. summarized CO2 reduction for a variety of TES

case studies, including a solar power plant, and mobile heat storage (Cabeza et al., 2015). “Heat on wheels”, transporting

unused heat by truck using PCM (Phase Change Material) in Sweden was assessed from a technical and economic

perspective (IEA ECES annex 25, 2015). This system has the potential to overcome pipe-based systems for wide area

heat distribution. However, PCM is not suitable for Tanegashima because PCM cannot resolve a seasonal mismatch.

TES technology using materials with a reversible process is the only solution to allow for a seasonal mismatch, and

can be classified in terms of reversible chemical reactions, or physical adsorption and desorption cycling. Oguraa et al.

proposed an energy recycling system using calcium sulfate, which is a typical thermochemical energy storage material

using reversible hydration and dehydration reactions. It was shown that a system that used a chemical heat pump container

was more efficient than similar transportation systems, which used latent heat storage and sensible heat storage systems

(Oguraa, 2012). Heat storage materials that use chemical reactions still have a few problems, while they also have some

attractive features such as large heat storage capacity and high-temperature capability. One of the problems is degradation

because of cumulative chemical compounds produced by irreversible reactions with minor contaminants. Another

problem is the difficulty in controlling reaction rates because of positive feedback between the exothermic heat release

reactions and the Arrhenius law. Physical adsorption materials such as zeolite have advantages from this perspective, so

we selected zeolite as a storage media for the Tanegashima case. Krönauer et al. demonstrated a TES and transport system

using zeolite (Krönauer et al., 2015). Zeolite was regenerated by extraction of steam from a waste incineration plant, and

supplied adsorption heat for a gas-fired drying process located 7 km from the storage station. They reported that the

energy storage capacity achieved 2.3 MWh, and 616 kg per cycle CO2 emissions could be reduced in comparison with

the conventional plant operation. Also, the results showed that it was possible to overcome cost barriers against oil and

gas by using 50 tons of zeolite. IEA ECES annex 18 summarized the price per MWh heat comparing the adsorption

system with PCM and hot water storage. It was clearly shown that the adsorption system is capable of overcoming the

cost barrier against the oil and natural gas (IEA ECES annex 18, 2010).

This study analyzes material and heat flow in two TES and transport systems using a zeolite adsorption and

regeneration cycle applied to the unused heat from the sugar mill. The first case supplies heat between the sugar mill in

Tanegashima and the sugar refinery in Osaka; the second case supplies heat to a local liquor factory in Tanegashima.

Fig. 1 Concept of TES & Transport system

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[DOI: 10.1299/mej.16-00334]

2. Process flow diagram of the sugar mill

Figure 2 is a schematic of the sugar mill in Tanegashima around the bagasse boiler. Bagasse is fired in the bagasse

boiler as fuel, and the combustion heat generates steam to drive a mill turbine and a steam turbine which supplies

electricity for the sugar mill. The latent heat of the exhaust steam flows from the mill and steam turbines are used in the

evaporators and crystallizers for raw sugar making. Flue gas is exhausted from the stack after electrostatic precipitation.

To calculate the potential storage capacity of zeolite, the flow of unused heat has to be quantified by the analysis of mass

and heat balance for the sugar mill.

The heating value of dried bagasse Hh-dry and wet bagasse Hh-wet were estimated using Eq. (1) (Klass, 2004) and (2):

70.271.45 cH dryh (1)

)1( wHH dryhweth (2)

where c is the mass fraction of carbon in dried

bagasse and w is the moisture content of wet bagasse.

The mass fraction of carbon and moisture content of

bagasse were determined by an elemental analysis

and a drying test, respectively. Wet bagasse samples

were dried in an electric furnace, and the change in

sample weight was measured. Then, the dried bagasse

samples were pulverized into powder and analyzed by

elemental analysis. The moisture content of bagasse

and the lower heating value of wet bagasse Hl were

determined by Eq. (3) and (4):

wet

drywet

m

mmw

(3)

)9(44.2 whHH wethl (4)

where mwet and mdry are the mass of wet and dried bagasse, and h is the mass fraction of hydrogen in the dried bagasse,

obtained by elemental analysis. Table 1 shows the results of the elemental analysis, the bagasse drying test and the heating

values of bagasse.

Figure 3 is the process flow diagram (PFD) of the sugar mill, which was developed using the process simulator

Aspen HYSYSⓇ, based on the actual operating data of the sugar mill and the heating value of bagasse which had been

already quantified. The boiler was modeled by using a combination of a heater block and a heat exchanger block

connected by a combustion gas stream. The air pre-heater and the electrostatics precipitator were placed after the boiler,

and heat loss of the air pre-heater and the precipitator were calculated by the temperature difference between inlet and

outlet streams obtained from operating data. The main steam was generated at the boiler and split into the mill turbine

and the steam turbine. Blow steam in the PFD represents excess steam. Table 2 summarizes a snapshot of the actual

operating data of the sugar mill at 12:00 on February 1st, 2013. As solid modeling is not available in the software, the

composition of Bagasse stream in the PFD was treated as the composition of the exhaust gas after stoichiometric

combustion of dried bagasse. The oxygen used for stoichiometric combustion of bagasse was removed from ambient air

in the simulation and the resultant composition was regarded as the composition of the air stream in the PFD. Table 3

shows the input data of the composition of bagasse and air streams in the PFD. The mass flow rate of air was adjusted

until the oxygen concentration in the boiler outlet stream reached the operating level (10.25%). The mass flow of bagasse

was also adjusted until the boiler outlet temperature reached a target value (296.1 °C).

Fig. 2 Schematic of the sugar mill in Tanegashima

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[DOI: 10.1299/mej.16-00334]

Table 2 Actual operating data of the sugar mill (At 12:00 on February 1, 2013)

Temperature

[°C]

Pressure

[kPa]

Mass flow

[ton/h]

Steam

Main steam 344.6 1853 27.26

Turbine inlet 343.7 1803 15.62

Turbine outlet 161.5 75

Mill turbine

342.8 -

8.38

Others 1.87

Blow steam 1.39

Exhaust

gas

Boiler outlet 296.1 101.7

Adjusted Air pre-heater 199.3 104.6

Precipitator 178.1 102.1

(ambient pressure)

Table 3 Composition of bagasse and air stream

Composition N2 O2 Ar H2O CO2 NO2

Bagasse - - - 0.2307 0.7668 0.0025

Air 0.8428 0.1330 0.0144 0.0092 0.0005 -

Fig. 3 Process flow diagram of the sugar mill

Table 1 Estimation of heating values of bagasse

Elemental analysis of dried bagasse [wt%] Moisture

[wt%]

Hhd

[MJ/kg]

Hhw

[MJ/kg]

Hl

[MJ/kg] C H N O

46.12 5.69 0.17 48.02 44.38 18.38 10.22 8.445

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[DOI: 10.1299/mej.16-00334]

3. Potential storage capacity

3.1 Current process (wet bagasse process)

From the analysis of the mass and heat balance for the sugar mill, the flow of unused heat was calculated. Figure 4

shows a schematic of the regeneration-air heater to desorb the water molecules of zeolite using hot air. The regeneration-

air heater was placed after the electrostatic precipitator and heated by the flue gas. Ambient air was compressed to 110

kPa and heated to 138 °C by the flue gas via an air heater. The mass flow rate of the steam for the turbine was increased

according to the additional electricity used for the compressor. The minimum temperature approach between

regeneration-air and flue gas was assumed to be 40 °C. The flow of unused heat was calculated using the temperature

difference between the flue gas and ambient air. The heat duty of the regeneration-air heater, which can be translated into

“Potential storage capacity” was also calculated using the process simulator. As a result, the flow of unused heat and

potential storage capacity were 9.7 GJ/h and 1.8 GJ/h, respectively as shown in Fig. 4.

3.2 Dried bagasse process

In general, bagasse has a high moisture content as shown in Table 1, so it is important to improve the calorific value

of bagasse as a fuel by applying a drying process. Therefore, the PFD of the wet bagasse process was modified, and the

increase in the unused heat of flue gas was quantified. The mass flow rate of moisture-free bagasse drybm

can be

expressed by the following equation:

)1( wmm wetbdryb (5)

where wetbm is the mass flow rate of bagasse in the wet bagasse process. Then, the overall heat transfer coefficient of

the boiler was recalculated using the mass flow and inlet temperature of the combusted gas. The air ratio was kept as

1.741, which was similar to the wet bagasse process.

By applying the dried bagasse process, the flue gas temperature of the boiler outlet was increased to 465 °C. To cool

the flue gas down to a temperature lower than the maximum allowable temperature of the precipitator (350 °C), the

regeneration-air heater was moved upstream of the electrostatic precipitator, as shown in Fig. 5. The heat loss at the

precipitator was assumed to be equal to that of the wet bagasse process. To avoid the acid dew point, the temperature of

the flue gas exhausts from the stack was set to the same value as the wet bagasse process (150 °C). As a result, the flow

of unused heat and potential storage capacity were 22.2 GJ/h and 10.1 GJ/h, respectively as shown in Fig. 5.

Fig. 4 Schematic of the regeneration-air heater and Sankey diagram for the wet bagasse process

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[DOI: 10.1299/mej.16-00334]

Fig. 5 Schematic of the regeneration-air heater and Sankey diagram for the dried bagasse process

4. Rate-based storage capacity based on adsorption / regeneration tests

In the previous section, the flow of unused heat and the potential storage capacity were calculated. However, the total

amount of the potential storage capacity cannot be stored in zeolite because the rate-based storage capacity is limited by

the regeneration rate of zeolite. This was quantified experimentally by regeneration tests using a fixed bed packed with

zeolite 13X particles (F-9 zeolite, TOSOH CORPORATION). Also, the adsorption test was conducted to saturate the

zeolite with water before the regeneration tests and the data concerning adsorption amount and adsorption isotherms were

obtained simultaneously.

4.1 Experimental apparatus

The experimental apparatus was based on the design of Simo et al. (Simo, 2009). Figure 6 shows the apparatus used

for the adsorption and regeneration tests. Air was supplied from a compressed air cylinder, the flow rate of which was

controlled by a mass flow controller (Model: FLOW COMPO MODEL 3660, 10SCCM-20SLM, KOFLOC, Japan). The

air was humidified by a humidity conditioning unit which consisted of a mantle heater/ stirred flask (Model: MS-ES-3

300mL, AS ONE, Japan) and a 300 mL flask, as shown in Fig. 6. The humidity of the air was controlled by changing the

water temperature in the flask. The humidified air was heated using ribbon heaters and the temperature of the humidified

air at the inlet of the reactor was measured by thermocouple 1 (TC1) and controlled using a temperature controller. A 1/2

inch stainless steel tube packed with 15 grams of zeolite was placed into the electric furnace. The air temperature at the

outlet of the reactor was also measured by thermocouple 2 (TC2).

Adsorption isotherm data were obtained from the adsorption tests at 130 °C. These were operated at a range of

water temperatures in the flask from 20 °C (partial pressure ~ 2.3 kPa) to 50 °C (~12 kPa). After the humidity of the air

Fig. 6 Experimental apparatus Fig. 7 Adsorption isotherms

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[DOI: 10.1299/mej.16-00334]

reached a steady state, humidified air was poured into the reactor and the change of outlet humidity was measured and

logged by a humidity transmitter (Model: HF 53, ROTORONIC, Switzerland) every 5 seconds until the vapor pressure

returned to the initial condition.

Regeneration tests were conducted after the adsorption tests at 70 °C. Dry air supplied from the compressed air

cylinder was poured into the reactor and the outlet humidity change was measured.

4.2 Adsorption test

Table 4 summarizes all of the experimental conditions and results. The maximum adsorption amounts were estimated

using the Langmuir adsorption isotherms equation:

Tp

pK

Tp

pKq

q

s

s

1

max

(6)

where qmax and p are the maximum adsorption of the zeolites, and the vapor pressure, respectively, and ps is the saturated

vapor pressure. The adsorption isotherms equation was determined from the results of adsorption tests wherein the vapor

pressure was changed. The adsorption isotherms at 130 °C obtained from the Langmuir adsorption isotherms equation is

shown in Fig. 7. The constants K and qmax were evaluated to be 20.80 and 0.2510 kg/kg by fitting the results of the

adsorption tests at 130 °C, respectively. This isotherm roughly agrees with Tosoh catalogue data at 25 °C, and maximum

adsorption amount is almost the same as the test data (test data from TOSOH CORPORATION; qmax = 0.26 kg/kg).

Therefore, the validity of this experimental method was shown.

Also, the adsorption isotherms at 70 °C and 180 °C were determined using the same K and qmax obtained from the

results at 130 °C. Figure 8 shows the experimental results of run 4. After the beginning of the humidified air supply, the

vapor pressure of the outlet gas sharply dropped and approached zero because almost all of the supplied steam was

adsorbed by the packed bed of the zeolites. After a lapse of 1100 seconds, the vapor pressure and temperature at the outlet

of the reactor increased, and a time lag between the temperature drop and the vapor pressure rise of the outlet gas was

observed. The inlet gas was heated by the adsorption heat of the zeolites packed in to the upper section of the reactor at

the early stage. However, the zeolites packed in to the lower section of the reactor did not generate heat because most of

the inlet steam was adsorbed by the upper section, and less steam remained at the lower section. Consequently, the heated

gas was cooled by the sensible heat of the zeolites packed in to the lower section of the reactor.

Table 4 Summary of adsorption test results

Run Temperature

[°C]

Weight of zeolites

[g]

Vapor pressure

[kPa]

Equilibrium adsorption

amount

[kg/kg]

1 130 13.43 2.939 0.0455

2 130 14.14 5.747 0.0785

3 130 14.63 7.905 0.0955

4 130 14.98 10.578 0.1116

5 180 14.48 6.498 0.0445

6 180 13.22 9.992 0.0426

7* 70 13.19 6.294 0.1706

8 70 12.60 13.52 0.1857

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[DOI: 10.1299/mej.16-00334]

4.3 Regeneration test

Figure 9 shows the results of the regeneration test after the adsorption test at 70 °C (run 7). In the regeneration tests,

the air temperature at the outlet of the reactor was not recorded because the temperature change was minimal. A residue

adsorption amount of 0.1 kg/kg was assumed in this system, then, the vapor pressure corresponding to an adsorption

amount of 0.1 kg/kg was calculated (0.987 kPa) using the Langmuir equation that had been already obtained from

adsorption tests, and the time until the vapor pressure fell below 0.987 kPa was regarded as the regeneration time t (=

2915 sec). The air flow rates required for regenerating 1 gram of adsorbed vapor from zeolite at 70 °C was calculated

using Eq. (7):

)1.0*(*

qm

tFV

z

MFCreg (7)

where FMFC is the air flow rate controlled by the mass flow controller. And mz* and q* are the amount of zeolite and

adsorbed vapor at run 7 of adsorption test, respectively. The regeneration rate r was calculated using Eq. (8) and the

amount of zeolites which could be regenerated at the sugar mill mz in Tanegashima was calculated using Eq. (9):

310reg

PFD

V

Fr (8)

)1.0( max

q

rmz (9)

where FPFD is the equilibrium air flow rate of regeneration-air in PFD. The rate-based storage capacity QR of both wet

and dried bagasse processes were calculated using Eq. (10):

HΔrQR (10)

where ΔH is adsorption heat of zeolite 13X which is measured in other literature (Nakaso et al., 2011). The results of

regeneration rates and rate-based storage capacity are shown in Table 5.

Fig. 8 Change in vapor pressure and temperature of the

outlet gas with time in the adsorption test

Fig. 9 Change in vapor pressure with time in the

regeneration test at 70 °C

100

110

120

130

140

150

160

170

0

2

4

6

8

10

12

0 1000 2000 3000 4000 5000

Tem

per

atu

re °

C

Vap

or

pre

ssu

re k

Pa

Time s

Vapor pressure

Temperature

0

1

2

3

4

5

6

7

0 2000 4000 6000 8000

Vap

or

pre

ssu

re k

Pa

Time sRegeneration time

2915

0.987

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[DOI: 10.1299/mej.16-00334]

5. Results

5.1 CASE 1 (Transport to the sugar refinery in Osaka)

The sugar refinery in Osaka uses city gas boilers to generate steam at 150 °C for the crystallization and refining

process all year around. Operating time of the sugar mill and the sugar refinery are 3000 hours and 6840 hours (285 days

× 24 hours), respectively. The transportable quantity of the zeolite was calculated using the operating data of the weekly

cargo shipments between Tanegashima and Osaka. The maximum load capacity of the cargo ship is 1,200 tons; 700 tons

of which are raw sugars transported to Osaka. Assuming use of the surplus load capacity of the cargo ship, 500 tons/week

of heat transport container packed with zeolites can be transported. The weight ratio between container and zeolites was

assumed to 1:1. Transportable amount of heat, QT, was determined using Eq. (11):

ZTT QmQ (11)

where mT is the transportable mass of the zeolite which can be calculated as 250 tons from the previous assumption, and

Qz is the storage density of the zeolite, which can be expressed as the following equation:

664)1.0( max qHΔQZ [kJ/kg] (12)

where the residual adsorption of zeolite is assumed to be 0.1 kg/kg.

The results of the material and heat flow of the system in CASE 1 are shown in Tables 6, 7 and Fig. 10. Both the

potential and the rate-based storage capacity are too low against the heat demand at the sugar refinery, and the

transportable amount of heat is the minimum value and restricts the maximum available amount of heat. Fuel reduction

rate at the sugar refinery by applying the TES and transport system was calculated by Eq. (13):

100 εQ

Qf

D

T (13)

where QD is heat demand at the sugar refinery. The coefficient ε considering the sensible heat of zeolite was determined

using Eq. (14):

87.0)(

1AD

Z

pz

Q

TTcε (14)

where cpz is specific heat capacity of zeolite obtained from other literature (Nakaso et al., 2011), and TD is the required

temperature at the heat demand side. TA is the ambient temperature (25 °C). In this case, the sugar refinery is assumed as

a heat demand, and TD is 150 °C. The fuel reduction rate by applying the TES and transport system of CASE 1 results in

only 0.8% reduction in fuel usage, which is equivalent to 66,000 m3 city gas and has little impact on the fuel consumption

at Osaka.

Table 5 Summary of regeneration test results

Process Time

[sec]

FMFC

[m3/h]

Vreg

[m3/g]

FPFD

[m3/h]

r

[kg/h]

mz

[kg/h]

QR

[GJ/h]

Wet bagasse 2915

0.061

(1018 [ccm]) 0.0531

17963 338.3 2241 1.488

Dried bagasse 55380 1043 6907 4.588

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[DOI: 10.1299/mej.16-00334]

5.2 CASE 2 (Transport to the liquor factory in Tanegashima)

A liquor factory in Tanegashima, which operates a conventional package boiler, was used as an example model of

heat demand to estimate fuel savings by applying the TES and transport system. The rated flow rate and pressure of

saturated steam of the boiler are 1.0 ton/h and 0.6 MPa, respectively. Under normal operation, the liquor factory requires

0.8 ton/h process steam at temperatures around 120 °C. The amount of oil used by the liquor factory was assumed to be

40,000 L per year. The operating time of the boiler of the liquor factory was assumed to be 180 days per year. A

conventional 12-ton truck was selected for transportation and it was assumed that transportation truck was operated once

per operating day of the liquor factory. Tables 6, 7 and Fig. 10 summarize the results of the material and heat flow of the

system in CASE 2. The transportable amount of zeolite is the minimum value and restricts the maximum available amount

of heat through the system. The fuel reduction rate of the liquor factory achieved by applying TES and the transport

system results in about an 83% reduction in fuel usage, which is equivalent to 33 kL/year heavy oil. The coefficient ε

considering the sensible heat of zeolite increased to 0.90 by applying the required temperature at the liquor factory (TD =

120 °C) to Eq. (14).

Fig. 10 Result of heat flow

Table 6 Summary of material and heat flow

Process

Unused

heat

[GJ/year]

Potential storage capacity Rate-based storage

capacity Heat demand

(Sugar refinery)

[GJ/year]

Heat demand

(Liquor factory)

[GJ/year]

Energy

amount

[GJ/year]

Required

zeolite

[ton/year]

Energy

amount

[GJ/year]

Required

zeolite

[ton/year]

Wet

bagasse 29076 5450 8205 4465 6722

315315 1556 Dried

bagasse 66709 30440 45825 13766 20723

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[DOI: 10.1299/mej.16-00334]

6. Conclusions

We proposed the introduction of a thermal energy storage and transport system for two different cases using a steam

adsorption and regeneration cycle of zeolite, and analyzed the material and heat flow by using commercial process

simulator “Aspen HYSYS®” and adsorption and regeneration tests. The main results of the analysis are summarized as

follows.

The flow of unused heat and potential storage capacity of the current process (wet bagasse process) of the sugar mill

were quantified. By applying the dried bagasse process, the temperature of flue gas was increased and the flow of unused

heat and potential storage capacity were increased. From zeolite adsorption and regeneration tests, adsorption isotherms,

maximum adsorption amount and approximate regeneration rate were quantified, then the rate-based storage capacity

was calculated.

In the first case the system was implemented between the sugar mill in Tanegashima and the sugar refinery in Osaka.

Heat storage capacity at the sugar mill is too low for the sugar refinery, and the transportable amount of zeolite by the

weekly cargo shipment restricts the maximum available amount of heat through the system in this case. It is difficult to

implement this system because of limited impact on the fuel consumption at the sugar refinery in Osaka.

In the second case we analyzed whether the system could provide heat for the local liquor factory, by using unused

heat from the sugar mill. The transportable amount of zeolite by truck also restricts the maximum available amount of

heat through the system in this case. However, the fuel consumption of the liquor factory reduced by 83%, which is

equivalent to 33 kL/year heavy oil, and this system has potential to give a considerable impact on the self-sufficiency of

local energy use.

Acknowledgments

The authors acknowledge the support of Shinko Sugar Mill Co., Ltd. and would like to express our gratitude.

References

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(2010)

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Table 7 Transportable amount of zeolite and energy

CASE 1 CASE 2

Load

capacity

[ton/week]

Raw sugar

[ton/week]

Surplus

[ton/week]

Transportable energy Load

capacity

[ton/cycle]

Transportable energy

[GJ/week] [GJ/year] [GJ/cycle] [GJ/year]

1200 700 500 166 2965 12 8.0 1434

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[DOI: 10.1299/mej.16-00334]

Nakaso, K., Okutariani, E., Noda, A., Itaya, Y., Nakagawa, T. and Fukai, J., Development of adsorption heat pump system

for regenerating high temperature steam – basic concept and estimation of effective utilization of energy-, Journal

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Nomenclature

Symbol

subscript

c Mass fraction of carbon in dry bagasse [%] A Ambient

cp Specific heat capacity [kJ/kgK] b Bagasse

F Air flow rate [m3/h] D Demand

f Fuel Reduction rates [%] max Maximum

h Mass fraction of hydrogen in dry bagasse [%] dry Dried bagasse

Hh Higher Heating value of bagasse [MJ/kg] MFC Mass flow controller

Hl Lower heating value of wet bagasse [MJ/kg] PFD Process flow diagram

m Amount [kg/h] reg Regeneration

m Mass flow rate [kg/h] s Saturated

p pressure [kPa] T Transportable

Q Amount of heat [GJ/h] R Rate-based

q Adsorption amount [kg/kg] wet Wet bagasse

T Temperature [°C] z Zeolite

t Regeneration time [h]

V The volumetric air flow [m3/g]

w Moisture content of wet bagasse [%]

∆H Heat of adsorption (=4400 ) [kJ/kg]

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Bulletin of the JSME Vol.3, No.5, 2016 Mechanical