Kyushu University Global COE Program
Journal of Novel Carbon Resource Sciences, Vol. 6, pp. 29-35, Sep. 2012

Comparative Studies on the Combustion Kinetics of Chars
Prepared from Brown and Bituminous Coals under Air (O2/N2) andOxy-fuel (O2/CO2) Conditions
Hyun-Seok Kim*1, Nozomi Wada*2, Sohey Nozawa*2, Yohsuke Matsushita*2,
Tsuyoshi Yamamoto*3, Motohira Oomori*4, Tatsuro Harada*5,
Jin Miyawaki*1, Seong-Ho Yoon*1,2, Isao Mochida*2*1

Institute for Materials Chemistry and Engineering, Kyushu University
Research and Education Center of Carbon Resources, Kyushu University*3Department of Chemical Engineering, Kyushu University*4
Kyuden Sangyo.Co., Inc.
*5
Research Laboratory, Kyushu Electric Power Co., Inc.

*2

(Received July 4, 2012; accepted July 20, 2012)
This paper deals with the application of a solid-gas reaction model which can describe the combustion and gasification mechanism for air (O2/N2) and oxy-fuel (O2/CO2) conditions. Loy Yang brown coal was used as a sample
after pyrolysis, together with Newlands coal as bituminous coal for comparison of coal ranks. By carrying out thethermogravimetric analysis (TGA) run under non-isothermal conditions, chemical reaction rates of partial oxidation
reaction and gasification reaction were estimated. Heat and mass transfer between the single pulverized char particle
and gas were numerically simulated, thus, overall reaction rate including mass transfer rate, chemical reaction rate
could be evaluated. In the low temperature region, the reaction rate is mainly controlled by the chemical reaction, on
the other hand, it becomes dominated by mass transfer, (diffusion as well as convection effects), in high temperature
region. Using this solid-gas reaction model, burn-off time of each char was also estimated under the various conditions, i.e., air (5% O2/N2) and oxy-fuel (5% O2/CO2) conditions with consideration of absence and presence of CO2
gasification reaction effect.

1. Introduction

Although a future energy mix of fossil fuels and renewable energies is considered as one of the pragmatic
scenarios, there are still restrictions in that there are limited fossil fuel deposits and undeveloped technologies for
extraction and power generation. Coal, especially lowrank coals, which are particularly abundant, is considered to be included in the future energy mix. However,coal has many disadvantages, for example, firing of coalresults in emissions that contain many contaminants andespecially greenhouse gases, CO2.
CO2 generated from coal combustion in air comprises
approximately 15% of the flue gas, and it would not be
economically advantageous to separate this CO2 fromflue gas because of its relatively low concentration. Pureoxygen can be used as an oxidant, however, it causes ahigh adiabatic flame temperature. To address these problems, a new method has been developed, so called oxyfuel combustion. Unlike conventional boilers, duringoxy-fuel combustion, a combination of highly pure oxygen, nearly 95%, and recycled flue gas is used to control
the flame temperature and to make up the missing N2.
In addition, the main components in oxy-fuel-generated
flue gas are CO2 and steam, and the concentration of CO2
can be as high as 98% 1).
Therefore, there is a need to evaluate char-O2 as well as
char-CO2 reaction rates in the oxy-fuel system by comparison with that of combustion in usual boilers operatedusing O2/N2. Usually, the activation of char with oxidant,
O2 or CO2, is heterogeneous gas-char reaction and pore
structure and surface area of the char particles are changing with the reaction. These structural variations and other phenomena such as mass transfer, pore diffusion, andchemical reaction have to be considered simultaneously
in the kinetic modeling of the reaction 2). In the case ofchar-O2 reaction, for particles below 50 μm, the reaction
rate is determined by the slowest rate of the reaction step,
whereas for particles larger than 100 μm the diffusion
limits the combustion rates. For the char-CO2 reaction,
for char particle sizes (< 300 μm) and lower temperature(< 1,000 oC), gasification rate is normally controlled by
the chemical reaction rate and occurs nearly uniformly
throughout the interior surfaces of the char particles1, 3-5).
However, for smaller pulverized char particles (< 100μm) at higher temperatures (> 1,000 oC) pore diffusion
becomes important6-7).
The motivation for this study is to focus on comparing
the partial oxidation reaction rate, gasification reaction
rate and mass transfer rate of oxygen in N2 and CO2 according to the presence or absence of CO2 gasification.

2. Experimental

Loy Yang brown coal and Newlands bituminous coal,for comparison of coal ranks, were used as samples andthe proximate and ultimate analyses of these samples areshown in Table 1.

Journal of Novel Carbon Resource Sciences, Vol.6, Sep. 2012

Table 1 Proximate and ultimate analyses of samples
Proximate analysis (wt. %)SampleM(db)Ash(db) VM(db) FC(db)
Loy Yang
1.16
52.25
46.59
Newlands
15.14
28.20
56.67

SampleLoy Yang
Newlands

Ultimate analysis(wt. % daf)
C
H
O
N
S
70.85
4.56
23.69
0.63
0.26
84.63
4.69
8.69
1.70
0.29

M: Moisture, VM: Volatile material, FC: Fixed carbon,
db: dry basis, daf: dry ash free.

Although, various types of apparatus have beenused for the kinetic study of gasification reaction,
TGA(Thermogravimetry analysis) has been most widelyused because of its advantages such as rapid analysis,cost effectiveness, and applicability of various parameters to the observed data. Hence this study was also carried out by TG-DTA (TG-DTA 2000SA, Bruker AXS)
for the estimation of heterogeneous chemical reaction
rate of char-O2 and char-CO2 by using Eq. (1).

EdX
= k 0 ⋅ exp(− a ) ⋅ (1 − X ) n 		
dt
RT

(1)

where, X is the conversion rate of char particle, i.e., 1- m/
mi, k0 is the pre-exponential factor, Ea is the activationenergy, R is the gas constant, T is the temperature, n is
the reaction order.
Table 2 Experimental conditions
Parameter
Condition
Char particle size
125~150 µm
Gas concentration 21% O2 in N2 (Air)100% CO2
Sample mass
0.5 mgHeating rate
50 K/minMaximum
1) 1,473 K for air atmospheretemperature2) 1,873 K for CO2 atmosphere

3. Numerical simulation

3.1 Reaction models for char partial oxidation andgasification
The most widely used heterogeneous partial oxidation
reaction and gasification reaction are based on a simple
global reactions.
C + 0.5O2 → CO		C + CO2 → 2CO		

(R-1)
(R-2)

These equations can be written in Arrhenius form as
follows:

rC = k 0 ⋅ exp(−Ea) ⋅ mp ⋅ poxi 		
RT(2)

where, rC is the chemical reaction rate, mp is the particle
mass, Poxi is the partial pressure of oxidant8).
The mass transfer rate, rCM, of oxidant to the surface ofchar particle is estimated from Mulcahy’s models basedon some assumptions9).
r CM ≅ (DOxi,00.5d p− ln(1 − γ f v ,Oxi )ñ TM)( 0 )( ) 0.75 [] ⋅ S p ⋅ C (3)
γ
ν
T
M
0
Oxi

where, DOxi,0 is the diffusion coefficient of oxidant at thestandard conditions, dp is the particle diameter, ρ 0 is gas
density around the particle, M is the averaged gas molecular weight, T, T0 are gas temperature and its standard
temperature, fv,Oxi is mole fraction of oxidant, Sp is surface
area of particle, Mc is molecular weight of char, and vOxi
is stoichiometric coefficient of the oxidant. These models
have been previously validated by Matsushita et. al.10).
In addition, γ is non-dimensional parameter which can
describe the convection as well as diffusion behavior ofCO, which is the product of reaction (R-2). In the case of
combustion this parameter is equal to -1, whereas, in thecase of CO2-gasification it varies with volume fraction ofoxidant11).
Using the chemical reaction rate, rC, together with themass transfer rate, rcM , it is possible to determine theoverall reaction rate, rO, as follows:1
1
1=+ c 		
rO rC r M

(4)

3.2 Governing equation
To estimate the burn-off time, heat and mass transfer
around a single char particle were considered as a balance
equation. Variation of char particle temperature during
the partial oxidation reaction has been simulated under
the assumption that the total heat transfer is completely
controlled by three terms, convective heat transfer, Qconv,
radiation heat transfer, Qrad, and reaction heat transfer,
Qreac:
QTotal = Qconv + Qrad + Qreac ;mp C pdTp
dt= h (Tg − Tp ) ⋅ Ap + ε σ (Tw 4 − Tp 4 ) ⋅ Ap + ∑ ξ ΔH ⋅ rO

(5)
where, mp is the mass of char particle, Cp is the specific heat, t is reaction time, h is convective heat transfer
coefficient, Tp and Tg are temperature of char particle andgas temperature, respectively, Ap is the surface area ofchar particle, ε is the emissivity of char particle, σ is the
Stefan-Boltzmann’s constant, ξ is the contribution ratioof reaction heat, (0.5), ∆H is the formation heat of prod-

Comparative Studies on the Combustion Kinetics of Chars Prepared from Brown and Bituminous Coals under Air (O2/N2) and Oxy-fuel (O2/CO2) Conditions

dmp
dt= − rO O 2 − rO CO 2 		

(6)

where, rOO2 and rOCO2 are the overall reaction rate of partial oxidation reaction of char with oxygen and carbon
dioxide as an oxidant, respectively.
As mentioned in previous section, to estimate theburn-off time, the numerical simulation was limited tothe chemical and mass transfer rate under the following
additional assumptions.
1.
2.
3.
4.
5.
6.

The shape of char particle is spherical.
There is no temperature distribution inside thechar particle.
There is no reaction in pores of the particle, or theparticle is assumed as non-porous spherical particle.
The temperatures of gases and the wall of the gasifier are constant.
The char is fully devolatized, thus, there is no volatile matters in the particle.
The contribution percentage of reaction heat, ξ,
generated on the particle surface is set as 50%, inother words, the heat generated by the reaction isequally distributed to solid and gas phases.

It can be seen that there will be some errors in calculation due to the above assumptions, in particular, the over
simplification of the particle shape. Despite these shortcomings, the application of this solid-gas reaction model
remains applicable due to the dominance of surface reactions over reactions in the pores of the char particles.
To evaluate the influence of oxidant types (O2 and CO2)
on the partial oxidation characteristics, and to estimate
the behaviors of O2 in different bath gases such as N2
and CO2, the calculations were carried out under theconditions shown in Table 3.
Table 3 The calculation conditions
Parameter
Condition
Char particle diameter
150 µmO2 concentration in N2
5% / 95%
O2 concentration in CO2
5% / 95%(Gasification reaction effect was ignored)

O2 concentration in CO2
Initial particle temperature
Gas temperature
Wall temperature

5% / 95%
300 Ka) 1,500 Ka) 1,200 K

4. Results and discussion

4.1 TG results and evaluation for estimating thechemical reaction rate
Using Eq. (1) from the results of TG-DTA, pre-exponential factor, k0, and the activation energy, Ea were ob-tained. Note that the chemical reaction was assumed tobe the first-order reaction.
In the case of partial oxidation reaction in N2, for Loy
Yang char, since it appeared that the conversion rate, X
was affected by the mass transfer of oxidant at X > 0.4,of the data obtained at X = 0.15-0.4 (T = 760-775 K) was
designated as the chemical reaction range for fitting.
For Newlands char, the conversion rate appeared to beunaffected by the mass transfer over the entire range of
conversion, so the whole data at X = 0.0-1.0 (T = 8141,105 K) were used for the numerical fitting. In the caseof gasification reaction in CO2, these ranges were set as
0.02-0.98 (T = 912-1,186 K) and 0.2-0.6 (T = 1,102-1,180
K) for Loy Yang char and Newlands char, respectively.
Fig. 1 shows the Arrhenius plots fitted according to themethod mentioned above and Table 4. shows k0 and Ea
for each coal.

1ln[(dX/dt)/(1-X)1]

uct, ro is the overall reaction rate.
In addition, the char consumption rate, or the reduction
rate of char particle mass, can be expressed as:0

O2/N2 conditions-1

Newlands
Loy Yang

-2
-3
-4
-5
-6

O2/CO2 conditions-7

Newlands
Loy Yang

-8
-9

0.7

0.8

0.9

1.0

1.1

1,000/T [K-1]

1.2

1.3

Fig. 1 Arrhenius plots for each of the coals under air
and oxy-fuel conditions.
Table 4 Estimated Arrhenius parameters for reaction rate

Condition
Char-O2
Char-CO2

SampleLoy Yang
Newlands
Loy Yang
Newlands

k0 [sec-1]
1.07 × 1018
2.17 × 105
1.06 × 107
2.15 × 106

E [J/mol]
2.86 × 105
1.30 × 105
2.33 × 105
2.29 × 105

Results of partial oxidation reaction carried out by
TG for two coals were examined as shown in Fig 2 (a)with dotted lines. Reaction initiation temperature of Loy
Yang char is 150 oC lower than that of Newlands char,and the higher slope of reaction rate for Loy Yang char isobserved in comparison to that for Newlands char. Abovetendencies show that the reactivity of Loy Yang coal asbrown coal is larger than that of Newlands bituminouscoal. It can be seen that there is differnce between two
partial oxidation processes, Loy Yang char has twostages: chemically rate determining step and masstransfer rate determining step, which can be verified byJournal of Novel Carbon Resource Sciences, Vol.6, Sep. 2012

the chage of slope aroud at X = 0.4. On the other hand,for Newlands char, the rate of change in weight loss, i.e.,change of the slope, is almost the same from initiaion
to completion of the reaction, which means that there is
only one stage, chemecally rate determining step.
The graphs drawn with solid line are analyzed data using factors described in Table 4 and show good agreementwith TG results. Note that the chemical reaction isassumed to be a first-order reaction and analyzed.
On the other hand, in the case of CO2 gasification
reaction, there is no rapid slope change region in the
progress of reaction regardless of coal ranks as shownin Fig 2 (b).

Loy Yang char
Newlands charCalculation

0.2
0.4
0.6
0.8
1.0
600

800

1000

1200

Temperature, T [K]

1400

(a)

rM O in N

r

2

10-9

rOO in N
22

Loy Yang

2

rOO in CO22

rOO in CO
2

2

rM O in CO2

2

Newlands
rC O in N
2rC

2

O2 in CO2

0.6

0.8

1.0

1.2

1.4

1,000/T [1/K]

0.4
0.6

1.0

T [K]1000

Fig. 3 Comparison of partial oxidation rates in 5% O2/
N2 with those in 5% O2/CO2 for Loy Yang charand Newlands char: It was assumed that there
was no CO2 gasification reaction effect in 5%
O2/CO2 conditions.

0.2

0.8

1500

O2 in N2
O

10-10
0.4

0.0

Convertion rate, X [-]2500 2000
10-8

Reaciton rate, r [kg/s]

Convertion rate, X [-]0.0

no differences in the oxidation and gasification reaction
rate of each coal. The difference of overall reaction rateof oxygen, rOO2 , in N2 (air) and CO2 (oxy-fuel) conditionsis attributed only to the difference of the mass transferrate, more exactly due to the difference in γ and D values,
or model parameter and diffusion coefficient in Eq.(3).
Note that being evaluated the reaction rate of oxygen,rO2 , in CO2, the gasification reaction was ignored to focus
on the comparison of oxygen behavior in different atmosphere gases.
The transition from chemical to mass transfer control region for Loy Yang char begins at around 800 K,
whereas for Newlands char it begins at 1,200 K, indicating that the reactivity of Loy Yang char is greater thanthat of Newlands char. These results are consistent withthe weight loss results.

Loy Yang char
Newlands charCalculation

1200

1400

Temperature, T [K]

1600

(b)
Fig. 2 Comparison of TG results and analyzed data
between (a) partial oxidation and (b) gasification
reaction.

4.2 Calculation results and discussion
Chemical reaction rate denoted by Eq. (2), mass transfer rate of oxidant to char particle surface by Eq. (3) andtheir overall reaction rate by Eq. (4) for Loy Yang coaland Newlands coal in the air and oxy-fuel conditions areshown in Fig. 3. Since the same chemical reaction model
is employed for the air and oxy-fuel conditions, there are

Fig. 4 shows the particle weight loss as well as charparticle temperature with elapsed time for two coals
calculated under conditions shown in Table. 3. Time required to achieve maximum temperature is about 0.05
s. As mentioned above, the transition temperature fromchemical to mass transfer control region of rO2 are 800 K
and 1,200 K for Loy Yang and Newlands char, respectively, and for partial oxidation reaction by oxygen bothin N2, CO2 conditions, the char particle temperature, TP,reaches above these transition temperature ranges, thus
the initiation of weight decrease could be observed.
The difference in weight decrease rate in (a) and (b) in
Fig. 4 is mainly attributed to the lower diffusivity of O2
in CO2 in comparison to the diffusivity in N2 which canaffect the transport of O2 to the surface of the char particle leading to the reduced partial oxidation reaction rate.
As evaluated in previous section, in Fig. 4, because thechar particle temperature, Tp is an important factor that

Comparative Studies on the Combustion Kinetics of Chars Prepared from Brown and Bituminous Coals under Air (O2/N2) and Oxy-fuel (O2/CO2) Conditions

0.02

Energy, Q [W]determines the reaction rate, there was a need to estimate
the energy balance of a single char particle as shown in
Fig 5.
Total energy balance was achieved around 0.05 s after
heating up according to the setting values, especiallygas temperature, Tg, and wall temperature, Tw. In theinitiation step, the heating sources were convection andradiation, however, as reaction proceeds reaction heatbecame more important.

0.01

0.8

Loy Yang

1,500

-0.01

0.02

0.4

600

Loy Yang

0.2

0.4

0.0
0.5

5% O2 in N2 (Air)
0.0

0.1

0.2

0.3

Elapsed time, t [s]Energy, Q [W]

Newlands

900

300

1,800

0.8

Loy Yang

0.4

0.5

Convection: Char-CO2

Total

0.00

Reaction: Char-O2

Reaction: Char-CO2

-0.01

0.0

0.02

0.4

900

Loy Yang

600

0.2

5% O2 in CO2 (Oxy-fuel)
0.0

0.1

0.2

0.3

Elapsed time, t [s]

0.4

0.0
0.5

Energy, Q [W]

Newlands

(b)

0.1

0.2

Radiation: Char-CO2

0.3

Elapsed time, t [s]
(b)

0.4

0.5

5 % O2 in N2: Newlands

1,800

Newlands

0.4

900
Loy Yang

600

5% O2 in CO2 (Oxy-fuel)(Gasification reaction is ignored)

0.0

0.1

0.2

0.3

Elapsed time, t [s]

0.4

0.2
0.0
0.5

(c)
Fig. 4 Weight losses and particle temperatures withelapsed time for Loy Yang char and Newlands
char: (a) 5% O2 in N2 (air condition), (b) 5% O2
in CO2 (oxy-fuel conditions regardless of gasification reaction), (c) 5% O2 in CO2 (oxy-fuelcondition).

Energy, Q [W]

0.6

1,200

0.00

Total

-0.01

Radiation: Char-O2

0.0

0.02

0.8

Loy Yang

Convection: Char-O2 Reaction: Char-O
2

0.1

1.0

Weight ratio, mp/m0 [-]Newlands

1,500

0.01

-0.02

2,100

Temperature, Tp [K]

0.3

0.6

1,200

300

Convection: Char-O2

1.0

Weight ratio, mp/m0 [-]Temperature, Tp [K]Newlands

1,500

0.2

Elapsed time, t [s](a)5 % O2 in CO2: Loy Yang

0.01

-0.02

2,100

0.1

Radiation: Char-O2

(a)

300

0.0

0.6

1,200

Total

Radiation: Char-O2

1.0

Weight ratio, mp/m0 [-]Temperature, Tp [K]Newlands

1,800

Reaction: Char-O2

Convection: Char-O2

0.00

-0.02
2,100

5 % O2 in N2: Loy Yang

0.2

0.3

Elapsed time, t [s]
(c)

0.4

0.5

5 % O2 in CO2: Newlands

0.01

Convection: Char-O2

Convection: Char-CO2

Reaction: Char-O2

0.00

Total

Reaction: Char-CO2-0.01
Radiation: Char-O2

-0.02

0.0

0.1

0.2

Radiation: Char-CO2

0.3

Elapsed time, t [s]
(d)

0.4

0.5

Fig. 5 Contributions of energies and their balances
under Char-O2/N2, and Char-O2/CO2, Char-CO2
conditions for each coal: (a), (b) Loy Yang char,(c), (d) Newlands char.

Journal of Novel Carbon Resource Sciences, Vol.6, Sep. 2012

Loy Yang

Newlands

6.570

6.740

7

Burn-off time [s]Especially outstanding differences in reaction heat
were revealed between partial oxidation reaction,
char-O2/CO2 and gasification reaction, char-CO2, asshown in Fig. 5 (b), (d). This difference was mainly due
to the endothermic gasification reaction leading to the
reduction of char particle temperature.
For Loy Yang char, when compared the reaction heat ofchar-O2/N2 with that of char-O2/CO2 in Fig. 5 (a), (b), thevariation of reaction heat is also noticeable. This is attributed to the difference of diffusivity, as it were, the larger
diffusivity of O2 in N2 in comparison to CO2 causes comparatively higher mass transfer rate of oxidant to the surface of char particle, and therefore increases the reaction
rate. On the other hand, this tendency was not as significant for Newlands char ((c), (d) in Fig. 5) when comparedto that of Loy Yang char. In addition, the difference inreaction heat of char-O2/N2 between Loy Yang char andNewlands char is significant and the reaction rate of Loy
Yang char is higher than that of Newlands char in bothcases, partial oxidation and gasification, indicating thatapart from the differences in burning conditions, the coalrank may be an important factor in reactivity and this isconsistent with the results of burn-off time.
Another aim of this study is to derive the burn-off timealong with the variation of burning conditions, whichleads to find out the difference in air and oxy-fuel conditions. The burn-off times of two coals were thus estimated and depicted in Fig. 6.
The burn-off times of Loy Yang char are about 8-10
times shorter than those of Newlands char. Due to thedifference in diffusivities of O2 in N2 and in CO2, theburn-off times were also slightly affected as shown in thecases of Char-O2/N2 and Char-O2/CO2 without consideration of effect of gasification reaction.
Although it may appear that the burn-off time in charO2/CO2 should be shorter in comparison to that of charO2/N2 due to the synergy effect between char-O2 andchar-CO2 separately, the effect of combining the two reactions increases the burn-off time due to the endothermic gasification reaction as shown in Fig. 6.

6.736

6
5
4
3
2
1
0

0.603

0.781

Char-O2 / N2

Char-O2 / CO2 Char-O2 / CO2

0.741: Without effectof gasification

Fig. 6 Comparison of burn-off time between Loy
Yang char and Newlands char: (Char-O2/N2)vs (Char-O2/CO2 regardless of gasification
reaction) vs (Char-O2/CO2).

5. Conclusions

Within the limits of the current experimental
conditions, the following conclusions were made:1. The transition from chemical to mass transfer control region for Loy Yang char begins atapproximately 800 K, whereas for Newlands charit begins at 1,200 K, indicating that the reactivityof Loy Yang char is greater than that of Newlandschar.
2. The overall reaction rate of carbon dioxide, rOCO2 ,under N2 is much slower than that of oxygen, rOO2 ,under the same conditions due to the differencein the mass transfer rate, more exactly, because of
the difference in D, γ values, i.e., diffusion coefficient and model parameter.
3. The most dominant factor affecting the particle
temperature which determines the reaction rate
ultimately is reaction heat. Although it may appear
that the overall reaction rate in char-O2/CO2 should
be faster than in char-O2/N2 by virtue of char-CO2
gasification reaction, the effect of combining thetwo reactions decrease the burn-off time due to theendothermic gasification reaction.

Comparative Studies on the Combustion Kinetics of Chars Prepared from Brown and Bituminous Coals under Air (O2/N2) and Oxy-fuel (O2/CO2) Conditions

Nomenclature

Ap
Cp
d
D
E0
f
H
k0
M
m
n
P
R
r
S
t
T
X

Q

ν
ρ
γ
ε
σ
ξ
∆

con
g
m
M
o
p
rad
reac
Total
v
0

References2

surface area
specific heat
diameterdiffusion coefficient
activation energy
fractionformation heatpre-exponential factor
average molecular weight[m ][J/(kg K)][m][m2/s]
J/mol K[-]

mass
reaction orderpartial pressure
universal gas constantreaction ratesurface areareaction time
temperature
conversion rate of charparticle, (1- m/mi)
heat

[kg]
[-]
[atm]
[J/mol K][kg/s]
[m2]
[s]
[K]
[-]

Greek symbols
stoichiometric coefficientgas density
non-dimensionalparameter
emissivity
Stefan-Boltzmann's
constant
the contribution ratio ofreaction heat
the difference between
reactant and product
Subscripts
convective
gas
mass
mass transferoxidant
char particle
radiation
reactionsum of items
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1)2)