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© М.А. Таймаров, В.К. Ильин, Е.Г. Чикляев, Р.Г. Сунгатуллин
UDC 662.611 DOI: 10.30724/1998-9903-2019-21-3-109-116
FEATURES OF APPLICATION OF THE METHANE-HYDROGEN FRACTION AS FUEL FOR THERMAL POWER PLANT BOILERS
M.A. Taymarov, V.K. Ilyin, E.G. Chiklyaev, R.G. Sungatullin
Kazan State Power Engineering University
Abstract: The methane-hydrogen fraction is a gaseous hydrocarbon by-product during oil processing for obtaining petroleum products. Until recently, the methane-hydrogen fraction was used as furnace oil in internal technological processes at a refinery. Some of the low-calorie methane-hydrogen fraction was burned in flares. Driven by the prospect of the methane-hydrogen fraction use as a fuel alternative to natural gas for burning in thermal power plants boilers, it became necessary to study the methane-hydrogen fraction combustion processes in large volumes. The conversion of ON-1000/1 and ON-1000/2 furnaces from the combustion of the methane-hydrogen fraction with combustion heat of25.45 MJ/m3 to the combustion of the composition with combustion heat of 18.8 MJ/m3 leads to a decrease in temperature in the flame core for 100 °C as an average. The intensity of flame radiation on the radiant tubes decreases. Therefore, the operation of furnaces during combustion of methane-hydrogen fraction with a low heat of combustion at the gas oil hydro-treating unit is carried out only with a fresh catalyst, which allows lower flame temperatures in the burner.
The experiments to determine the concentration of nitrogen oxides NOx and the burning rate w of the methane-hydrogen fraction in the ON-1000/1 furnace and natural gas in the TGM-84A boiler, depending upon the heat of combustion Qnr were carried out. The obtained results showed that the increase in the hydrogen content Н2 from 10.05 % to 18.36% (by mass) results in an increase in the burning rate w by 45%. The burning rate of natural gas with methane CH4 content of98.89% in the TGM-84A boiler is 0.84 m/s, i.e. it is 2.5 times lower than the burning rate of the methane-hydrogen fraction with H2 content of 10.05%. The distributions of heat flux from the flame qf over the burner height h in the TGM-84A boiler were obtained in case of natural gas burning and calculation of burning of the methane-hydrogen fraction with a hydrogen content of 10.05% and methane of 28.27%. The comparison of the obtained data shows that burning of methane-hydrogen fraction causes an increase in the incident heat flux qf at the outlet of the burner.
Keywords: thermal power plants; methane-hydrogen fraction; burning; combustion; heating oil; vacuum gas oil; power boilers; burning rate; temperature; natural gas; heat; flame; burners; boiler.
For citation: Taymarov MA, Ilyin VK, Chiklyaev EG, Sungatullin RG. Features of application of the methane-hydrogen fraction as fuel for thermal power plant boiler. Power engineering: research, equipment, technology. 2019; 21(3):109-116. (In Russ). doi:10.30724/1998-9903-2019-21-3-109-116.
ОСОБЕННОСТИ ПРИМЕНЕНИЯ МЕТАНО-ВОДОРОДНОЙ ФРАКЦИИ В КАЧЕСТВЕ ТОПЛИВА ДЛЯ КОТЛОВТЭС
М.А. Таймаров, В.К. Ильин, Е.Г. Чикляев, Р.Г. Сунгатуллин
Казанский Государственный Энергетический Университет, г. Казань, Россия.
Проблемы энергетики, 2019, том 21, № 3
Резюме: Метано-водородная фракция является побочным газообразным углеводородным продуктом при переработке нефти с получением конечных нефтепродуктов. До последнего времени метано-водородной фракция использовалась как печное топливо на НПЗ во внутренних технологических процессах. Некоторая часть низкокалорийной метано-водородной фракции сжигалась в факелах. В связи с перспективной использования метано-водородной фракции как топлива альтернативного природному газу для сжигания в энергетических котлах тепловых электростанций возникла необходимость изучения процессов горения метано-водородной фракции в больших объемах. Перевод печей ОН-1000/1 и ОН-1000/2 с сжигания метано-водородной фракции с теплотой сгорания 25,45 МДж/м3 на сжигание состава с теплотой сгорания 18,8 МДж/м3 приводит к снижению температуры в ядре факела в среднем на 100 С. Интенсивность излучения факела на радиантные трубы уменьшается. Поэтому эксплуатация печей при сжигании метано-водородной фракции с низкой теплотой сгорания на установке гидроочистки газойля проводится только при свежем катализаторе, допускающем более низкие температуры факела в топке.
Полученные авторами результаты экспериментов по определению концентрации оксидов азота NOx и скорости горения w метано-водородной фракции в печи ОН-1000/1 и природного газа в котле ТГМ-84А в зависимости от теплоты сгорания Qнр показали, что увеличение содержания водорода Н2 с 10,05 % (по массе) до 18,36 % приводит к росту скорости горения w на 45 %. Скорость горения природного газа с содержанием метана СН4 98,89 % в котле ТГМ-84А составляет 0,84 м/с, то есть в 2,5 раза ниже скорости горения метано-водородной фракции с содержанием Н2 10,05 %. Распределение тепловых потоков от факела qrp по высоте топки h в котле ТГМ-84А при сжигании природного газа в сравнении с расчетными данными при сжигании метано-водородной фракции при содержании водорода 10,05 % и метана 28,27 % показывает, что сжигание метано-водородной фракции вызывает рост падающих тепловых потоков qф на выходе из топки.
Ключевые слова: тепловые электрические станции; метано-водородная фракция; сжигание; горение; печное топливо; вакуумный газойль; энергетические котлы; скорость горения; температура; природный газ; теплота; факел; горелки; котел
Introduction
The methane-hydrogen fraction is formed at the refinery during the process of deep oil processing. It is a by-product that, at its large production volumes is used as fuel for technological furnaces, depending on the composition and its calorific value, and at small production volumes it is burned in flames [1-5]. Nowadays, it is planned to use the methane-hydrogen fraction as a gaseous alternative fuel for power boilers of thermal power plants (TPP). However, there are some features of the chemical composition and combustion process of the methane-hydrogen fraction associated with the hydrogen content. This circumstance does not allow utilizing the methane-hydrogen fraction as a substitute for natural gas without a detailed study of its heat and energy characteristics during combustion. Therefore, the study on this topic is relevant.
Object description
The properties of the methane-hydrogen fraction were experimentally studied using the operating furnace equipment 0N-1000/1 and 0N-1000/2 of the vacuum gas oil hydrotreatment unit of workshop No. 2 at JSC Ryazan Oil Refining Company. TGM-84A boilers were considered as research objects where it is planned to use the methane-hydrogen fraction as fuel instead of natural gas. During the experiments, the TERA-50 total radiation radiometers were used to measure the heat fluxes, and dual chromel-alumel thermocouples [6] and the ThermaCAMP-50F thermographic camera were used to determine the flame temperature. The composition of the samples of the methane-hydrogen fraction was analyzed in the central factory laboratory. The experimental procedure for measuring the operation parameters of furnaces and the boiler is described in [7]. The operation parameters of the TGM-84B boilers during combustion of the
© M.A. TauMapoB, B.K. MnbUH, ET. ^UKJMeB, P.r. Cy^amymuH
methane-hydrogen fraction were calculated using [8-12]. The scheme of the ON-1000/1 and ON-1000/2 furnaces, which were used to study the regime parameters of the combustion process of the methane-hydrogen fraction, is shown in Fig. 1.
The dimensions of the burners of the ON-1000/1 and ON-1000/2 furnaces are: length is 8.6 m, width is 3.3 m, height is 5.5 m. LE-CFSG-2W bottom gas burners 1 in the amount of 40 pcs. are made as single pipes with an outlet diameter of gas supply openings of 6.3 mm and provide a flow rate of methane-hydrogen fraction per furnace in the amount from 1000 to 1500 m3/h.
Fig. 1. Cross section of the 0N-1000/1 and 0N-1000/2 furnaces: 1 - burners; 2 - hatches; 3 - radiate coil; 4 - convective coil
Research methodolo
The heat fluxes and temperatures incident from the flame were measured through the side hatches 2. The heat of combustion of the methane-hydrogen fraction is received in the burner by radiating coils 3 (see Fig. 1), which provide heating of vacuum gas oil in the amount of 177 t/h in a mixture with hydrogen-containing gas in the amount of 97.4 thousand m3/h and convective coils 4 in the chimney.
The product is heated from 322 °C to 347 °C. The temperature of the outer surface of the radiant coils as measured by ThermaCAMP-50F thermographic camera is 530 °C. The scheme of the TGM-84A boiler, for which the possibility of using the methane-hydrogen fraction as a fuel instead of natural gas is considered, is shown in Fig. 2.
Fig. 2. The scheme of the TGM-84A boiler 111
Проблемы энергетики, 2019, том 21, № 3
The TGM-84A boiler is a gas-oil drum boiler, which is characterized by steam capacity of 420 t/h, steam parameters of 560 °C and pressure of 14 MPa. The furnace is divided in height into two halves by a partition wall. The burner has the following dimensions: width is 15 m, depth is 7.5 m, height is 27 m. Burners of 2 pcs. are located at heights of 7.2 and 11.8 m. The natural gas consumption for the TGM-84A boiler at a nominal capacity of 420 t/h is 32.5 thousand m3/h for the lower calorific value Qnr=34.24 MJ/m3 and the following gas composition: methane CH4=98.89% (by mass), ethane C2H6=0.47%, propane C3H8=0.18%, nitrogen N2=0.76%. The HF-TsBK-VTI-TKZ vortex burners are installed at the TGM-84A boiler, with a unit power of 76.7 MW when operating on gas, with peripheral tubular gas distribution: 12 pcs. of the 023, and 12 pcs. of the 033. The air swirl is dual-flow in hot air and consists of two sections of the axial (central) swirl and one section of the tangential (peripheral) swirl.
Research results
The compositions of the methane-hydrogen fraction used as fuel for the 0N-1000/1, ON-1000/2 furnaces for heating vacuum gas oil at JSC Ryazan Oil Refining Company are given in Table. 1.
Table 1
Compositions of samples of methane-hydrogen fraction used as fuel for furnaces ON-1000/1 and ON-1000/2 for heating of vacuum gas oil at a hydrotreating unit
Sample No. Density p at 760 mm Hg and 0 °c, 0nr Hydroge n, % by mass Methane, % by mass Ethene, % by mass Ethane, % by mass Propene, % by mass Propane, % by mass I-Butane, % by mass N- Butane, % by mass Sum of butylenes, % by mass
1 0.440 14.75 18.53 2.06 12.45 3.34 13.26 5.40 9.95 0.71
2 0.380 18.36 18.28 0.86 10.74 1.00 13.34 4.55 12.94 0.20
3 0.444 14.33 24.41 0.54 10.50 0.73 14.45 4.87 13.39 0.35
4 0.431 13.76 36.71 0.55 9.86 0.66 12.48 2.88 7.03 0.36
5 0.481 11.04 44.18 0.50 8.08 0.36 10.56 3.15 8.44 0.00
6 0.400 15.42 31.51 1.07 8.43 0.57 8.04 2.17 4.67 0.06
7 0.445 15.99 3.64 0.03 7.26 0.04 16.54 6.13 18.46 0.00
8 0.434 14.59 24.82 0.73 10.85 1.72 14.71 5.05 8.85 0.24
Sample No. I-Pentane, % by mass N-Pentane , % by mass Hexane and higher, % by mass Oxygen, % by mass Nitrogen, % by mass Carbon oxide, % by mass Carbon dioxide, % by mass Hydroge n sulfide, % by mass Calorific value Qnr, MJ/m3
1 4.21 2.39 0.00 2.95 9.27 0.11 0.58 0.03 20.91
2 4.96 4.78 0.23 1.91 7.25 0.03 0.36 0.20 22.83
3 3.94 4.10 0.19 1.35 5.98 0.03 0.36 0.48 21.27
4 2.39 2.76 0.60 1.79 7.65 0.06 0.18 0.28 23.98
5 3.50 3.06 0.27 1.57 4.93 0.03 0.25 0.10 22.96
6 1.20 1.14 0.00 6.18 19.19 0.03 0.20 0.12 25.45
7 7.32 5.03 0.39 5.06 13.93 0.00 0.18 0.00 18.80
8 3.40 2.58 0.20 3.03 8.29 0.06 0.23 0.67 21.88
© M.A. TaüMapoB, B.K. MnbUH, ET. ^umneB, PT. Сунгатуmин
h, m 4
2
700 1000 f, °C
30 60 q0, kW/m2
Fig. 3. Distribution of flame temperature tf and heat flux from internal lining q0 along the height h of 0N-1000/1 and 0N-1000/2 furnaces when burning methane-hydrogen fraction with the sample compositions No. 6 and 7 at an excess air coefficient of 1.3
The obtained experimental data of the nitrogen oxides NOx concentration and the burning rate w of methane-hydrogen fraction in the ON-1000/1 furnace and natural gas in the TGM-84A boiler, depending on the calorific value Qn\ are given in Table. 2.
Table 2
The obtained experimental data of the burning rate w of methane-hydrogen fraction in the 0N-1000/1 furnace and natural gas in the TGM-84A boiler, depending on the calorific value Qnr
Calorific value Qn, MJ/m3 Density p, kg/m3 H2 content, % by mass CH4 content, % by mass Excess air coefficient a Fuel consumpti on, m3/h Temperatu re at the outlet from burner Tb, °C NOx concentratio n, mg/m3 (in terms of a=1.4) Burning rate w, m/s
25.43 0.540 10.1 28.3 1.3 1115 802 84.8 2.02
26.68 0.536 10.05 28.27 1.1 1375 881 63.6 2.11
22.83 0.38 18.36 18.28 1.1 1458 884 56.1 3.07
33.94 0.69 - 98.89 1.1 32500 1150 136 0.84
The distribution of heat fluxes from flame qf over the burner height h in the TGM-84A boiler during the combustion of natural gas is shown in Fig. 4. The calculated data for the combustion of the methane-hydrogen fraction with a hydrogen content of 10.05% and methane 28.27% is also presented in Fig.4.
npo6neMbi энергетики, 2019, moM 21, № 3
Fig. 4. Heat fluxes from flame qf over the burner height h in the TGM-84A boiler during the combustion of natural gas (CH4 =98.89 %) in comparison with the calculated data for the combustion of the methane-hydrogen fraction (H2=10.05 %, CH4 =28.27 %) for steam load of 255 t/h and with data [13] for the boiler PK-41
Discussion
As it is seen from table 1, the calorific value of the methane-hydrogen fraction is 55.5-75.1% of the calorific value of natural gas used as fuel for TPP boilers. The experimentally obtained distribution of the flame temperature and heat fluxes qa incident from the inner lining over the height h of the burners in the ON-1000/1 and ON-1000/2 furnaces when burning the methane-hydrogen fraction with the samples composition No. 6 and 7 at an excess air ratio of 1.3 is shown in fig. 3.
As it can be seen from fig. 3, the conversion of 0N-1000/1 and 0N-1000/2 furnaces from the combustion of the methane-hydrogen fraction with combustion heat of 25.45 MJ/m3 (sample No.6) to the combustion of the composition with combustion heat of 18.8 MJ/m3 (sample No.7) leads to a temperature decrease in the flame core for 100 °C as an average. Heat fluxes qa also significantly decrease; therefore, the operation of furnaces during the combustion of the methane-hydrogen fraction with low heat of combustion at the gas oil hydrotreatment unit is carried out only with a fresh catalyst that allows lower flame temperatures in a burner.
As it can be seen from table 2, an increase in the hydrogen H2 content from 10.05% to 18.36% (by mass) leads to an increase in the burning rate w by 45%. The burning rate of natural gas with methane content of 98.89% in the TGM-84A boiler is 0.84 m/s, i.e. 2.5 times lower than the burning rate of the methane-hydrogen fraction with H2 content of 10.05%. Due to the low heat of combustion of the methane-hydrogen fraction, the concentration of nitrogen oxides NOx is on average 2 times lower compared to that during combustion of natural gas.
As it can be seen from fig. 4, the burning of the methane-hydrogen fraction (H2=10.05 %, CH4=28.27 %) causes an increase in the incident heat fluxes qf at the outlet of the furnace, which is accompanied by an increase in heat loads of the TGM-84A boiler superheater and leads to a decrease in efficiency, compared to that during operation of this boiler on natural gas. However, the distribution of heat fluxes of flame over height h during combustion of the methane-hydrogen fraction is most suitable for a direct-flow boiler PK-41 [13] of supercritical pressure having a burner chamber pinch.
Conclusions
1. The burning of the methane-hydrogen fraction with a high, over 10% (by mass), hydrogen content instead of natural gas in the TPP power boilers is accompanied by increased values of the incident heat fluxes at the outlet of the burner.
© М.А. Таймаров, В.К. Ильин, Е.Г. Чикляев, Р.Г. Сунгатуллин
2. To reduce the amount of incident heat fluxes at the outlet from the boiler burner, it is necessary to increase the methane share in the methane-hydrogen fraction, which will reduce the rate of fuel combustion and ensure fuel combustion within the burner volume.
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Authors of the publication Mikhail A. Taymarov - Kazan State Power Engineering University. Vladimir K. Ilyin - Kazan State Power Engineering University. Evgeniy G. Chiklyaev- Kazan State Power Engineering University. Rais G. Sungatullin- Kazan State Power Engineering University.
Received December 11, 2018
