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Chinese Science Bulletin, Volume 64 , Issue 5-6 : 621-623(2019) https://doi.org/10.1360/N972018-01090

Numerical simulation of cleanliness of glass window in solar CO2 coal gasification reactor

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  • ReceivedNov 6, 2018
  • AcceptedNov 20, 2018
  • PublishedJan 25, 2019

Abstract

Solar CO2 coal gasification technology uses highly concentrated solar radiation to generate high temperature above 1000°C, so that the pulverized coal particles can react with CO2 to generate CO in the solar reactor. Compared with common industrial coal gasification technology, solar CO2 coal gasification has the advantages of reducing CO2 emissions and producing high quality and high purity gaseous fuels in a clean and energy efficient manner. Solar coal gasification stores intermittent and unstable solar energy in clean fuels, which has promising application and has attracted the interest of many researchers around the world.

As the core component of solar thermochemical, solar reactors are mainly divided into direct and indirect types. The direct reactor is easy to realize and has many advantages,which is convenient for transport and liquid slagging. However, a major problem of the direct solar reactor is that coal particles may contaminate the reactor glass window which will affect the efficiency and safety of the reactor. So keeping the reactor quartz glass clean is the key to increase reactor efficiency and safety. The reactor windows are typically purged with argon to avoid contamination by coal ash and tar, but this also results in reducing thermal efficiency and difficulties of separating from the gas. In this paper, CO2 gas is used as the reactant and also used to clean the quartz glass window in a solar gasification reactor.

This paper establishes a three dimensional mathematical model of a directly-irradiated cyclone-flow solar thermochemical reactor. UDF is used to realize the flux ellipsoid distribution and concentrating in fluent software.A gas-solid two-phase flow model is established and the participating media radiation and chemical reaction kinetic models of coal particles and gases are coupled by Euler-Lagrange method. The numerical results are validated by comparing with the experimental results of ETH cyclone reactor. Then the effect of CO2 intake mass flow ratio and coal particle mass flow on the deposition of coal particles on the quartz glass window surface was studied.

The calculation results show that maintaining the glass window cleaning mainly depends on the intake mass flow ratio of the sweeping glass and the cavity. When the sweeping glass window intake CO2 mass flow is too small, coal particles are easy to contaminate the glass. When the sweeping glass window intake CO2 mass flow is too large, the molar ratio of CO2 to coal particles will increase which reduce CO2 conversion. The coal particle inlet CO2 mass flow accounts for a small amount of total intake gas mass flow, mainly as a gas for transporting coal particles. When the molar ratio of CO2 to coal particles is in the range of 1.3−1.8 and the mass flow rate of the cavity, sweeping glass and conveying coal particles takes the percentage of the total CO2 intake mass flow rate in the range of 71.9%−78.2%, 15.7%−20.7% and 5%− 10%, respectively, the glass window cleanliness is optimal. The increase of mass flow rate of coal particles (1.5×10-4−4×10-4 kg/s) can significantly reduce the molar ratio of CO2 to coal particles, but the turbulence of coal particle trajectory will increase, which causes a small amount of coal particles to move toward the glass window through the opening aperture.


Funded by

国家自然科学基金(51476163)


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References

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  • Figure 1

    (Color online) 10 kW reactor structure. (a) Geometry with inlet points; (b) dimensions of the solar reactor. 1, Window; 2, window screening flow inlets (usf); 3, CPC, compound parabolic collector; 4, the first cyclone inlets (ucf1); 5, the second cyclone inlets (ucf2); 6, outlet; 7, the opening aperture; 8, particle seeding inlet (ucf0); 9, cavity

  • Figure 2

    (Color online) Changing the cavity (ucf1, ucf2) intake gas mass flow, coal particle residence time trace

  • Figure 3

    (Color online) Changing the sweeping glass (usf) intake gas mass flow, coal particle residence time trace

  • Figure 4

    (Color online) Changing the conveying coal particle intake gas mass flow, coal particle residence time trace

  • Figure 5

    (Color online) Changing the coal particles mass flow, coal particle residence time trace

  • Table 1   Grid independent test results

    编号

    网格

    腔体质量加权平均温度(K)

    误差(%)

    0#

    28260

    921

    7.0

    1#

    161420

    1003

    1.3

    2#

    263146

    991

    0.1

    3#

    410738

    990

    -

  • Table 2   Compare the experimental conditions and results with ETH cyclone reactor and numerical calculations

    #

    mcoal(g/min)

    mH2O(g/min)

    nAr(mol/min)

    Qsolar(kW)

    Tcavity(K)

    Tcavit y (K)

    误差(%)

    16

    3.5

    9.0

    0.27

    6.6

    1671

    1526

    8.7

    21

    3.5

    9.0

    0.27

    5.0

    1439

    1284

    10.8

    22

    3.5

    9.0

    0.27

    4.3

    1355

    1212

    10.6

  • Table 3   The mass flow rate and molar ratio of CO and coal particle

    #

    ucf0

    usf

    ucf1

    ucf2

    (%)

    玻璃窗口沉积煤颗粒密度(kg/m3)

    玻璃窗

    口清洁a)

    (×10-4 kg/s)

    (a)

    1.4

    2.5

    7

    7

    17.9

    2.5

    78.2

    1.953

    1.02×10-9

    Y

    (b)

    1.4

    2.5

    6

    6

    15.9

    2.5

    75.5

    1.735

    1.73×10-12

    Y

    (c)

    1.4

    2.5

    5

    5

    13.9

    2.5

    71.9

    1.516

    2.15×10-8

    Y

    (d)

    1.4

    2.5

    4

    4

    11.9

    2.5

    67.2

    1.298

    2.31×10-11

    Y

    (e)

    1.4

    2.5

    5

    3

    11.9

    2.5

    67.2

    1.298

    6.22×10-6

    N

    (f)

    1.4

    2.5

    6

    2

    11.9

    2.5

    67.2

    1.298

    1.91×10-6

    N

    a) Y为是, N为否

  • Table 4   The mass flow rate and molar ratio of CO and coal particle

    #

    ucf0

    usf

    ucf1

    ucf2

    mCO 2

    mcoal

    u sf /m CO2

    (%)

    nCO 2: nco al

    玻璃窗口沉积煤颗粒密度(kg/m3)

    玻璃窗口清洁

    (×10-4 kg/s)

    (a)

    1.4

    0.5

    6

    6

    13.9

    2.5

    3.6

    1.516

    4.76×10-5

    N

    (b)

    1.4

    1.5

    6

    6

    14.9

    2.5

    10.1

    1.625

    2.13×10-7

    Y

    (c)

    1.4

    2.5

    6

    6

    15.9

    2.5

    15.7

    1.735

    1.73×10-12

    Y

    (d)

    1.4

    3.5

    6

    6

    16.9

    2.5

    20.7

    1.844

    0

    Y

    (e)

    1.4

    4.5

    6

    6

    17.9

    2.5

    25.1

    1.953

    0

    Y

    (f)

    1.4

    5.5

    6

    6

    18.9

    2.5

    29.1

    2.062

    6.49×10-7

    Y

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