• Journal of the Korean Institute of Gas
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• v.19 no.3
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• pp.9-17
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• 2015

Almost all of the natural gas consumed in South Korea is compressed into very high pressure for the transportation through the underground pipelines, then reduced in pressure regulation stations before delivery to the consumer. For pressure reduction, expansion valves have been used due to the simple and effective installation, but recover none of the energy in the gas during compression. Hence, turbo-expanders are proposed instead of the valves to accomplish the same pressure letdown function and recover some of the compression energy in the form of shaft work converting into electric powers. Here we have theoretically calculated the electric powers at the pressure reduction from 68.7 bar to 23 bar (which are the average values taken at the inlet and outlet points of the expansion valve in medium-pressure regulation stations) according to the inlet conditions of temperature and flow rate. The natural gas is considered as two cases of a pure methane and the mixture of hydrocarbons with a very small amount of nitrogen, and the Peng-Robinson equation of state is employed for the calculation of required thermodynamic properties. The electric energy is recovered as much as 1596 MW(methane) and 1567 MW(mixture) based on the total supply of natural gas in 2013.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.12
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• pp.840-846
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• 2012

Global climate changes caused by $CO_2$ emissions are currently debated around the world; green sources of energy are being sought as alternatives to replace fossil fuels. The sustainable use of biogas for energy production does not contribute to $CO_2$ emission and has therefore a high potential to reduce them. Catalytic steam reforming of a model biogas ($CH_4:CO_2$ = 60%:40%) is investigated to produce $H_2$-rich synthesis gas. The biogas utilized 3D-IR matrix burner in which the surface combustion is applied. The ruthenium catalyst was used inside a reformer. Parametric screening studies were achieved as Steam/Carbon ratio, biogas component ratio, Space velocity and Reformer temperature. When the condition of Steam/Carbon ratio, $CH_4/CO_2$ ratio, Space velocity and Refomer temperature were 3.25, 60% : 40%, $14.7L/g{\cdot}hr$ and $550^{\circ}C$ respectively, the hydrogen concentration and methane conversion rate were showed maximum values. Under the condition mentioned above, $H_2$ yield, $H_2$/CO ratio, CO selectivity and energy efficiency were 0.65, 2.14, 0.59, 51.29%.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.1002-1007
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• 2008

The purpose of this paper studied the optimal hydrogen production condition of plasma reforming system to operate the PEMFC. Plasma reforming reactor used with Ni catalyst reactor at the same time, So $H_2$ concentration increased. Also the WGS and PrOx reactor were designed to remove CO concentration under 10 ppm, because CO has effect on catalyst poisoning of PEMFC. The maximum $H_2$ production condition in plasma reforming system was S/C ratio 3.2, $CH_4$ flow rate 2.0 L/min, catalytic reactor temperature $700{\pm}5^{\circ}C$ and input power 900 W. At this time, the concentration of produced syngas was $H_2$ 70.2%, CO 7.5%, $CO_2$ 16.2%,$CH_4$ 1.8%. The hydrogen yield, hydrogen selectivity and $CH_4$ conversion rate were 56.8%, 38.1% and 92.2% respectively. The energy efficiency and specific energy requirement were 37.0%, 183.6 kJ/mol. In additional, The experiment of $CO_2/CH_4$ ratio proceeded. Also WGS reactor experiment was proceeding on optimum condition of plasma reactor and the exit concentration were $H_2$ 68%, CO 337 ppm, $CO_2$ 24.0%, $CH_4$ 2.2%, $C_2H_4$ 0.4%, $C_2H_6$ 4.1%. At this time, experiment result of PrOx reactor were $H_2$ 51.9%, CO 0%, $CO_2$ 17.3%.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.420-424
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• 2019

In SNG (synthetic natural gas) process by proposed RIST(Research Institute of Industrial Science & Technology)-IAE(Institute for Advanced Engineering) (including three adiabatic reactors and one isothermal reactor), the methanation reaction and water gas shift (WGS) reaction take place simultaneously, and the supply of steam with syngas might control the temperature in catalyst bed and deactivate the catalyst. In this study for development of SNG process, the characteristics of the methanation reaction with a Ni-based catalyst by prepared RIST and using a low $H_2/CO$ mole ratio (including $CO_2$ 22%) are evaluated. The operating conditions ($H_2O/CO$ ratio of the $1^{st}$ adiabatic reactor, operating temperature range of $4^{th}$ isothermal reactor, etc.) were reflected the results from previous studies and in the same condition a pilot scale SNG process is carried out. As a results, the pilot scale SNG process is stable and the CO conversion and $CH_4$ selectivity are 100% and 96.9%, respectively, while the maximum $CH_4$ productivity is $660ml/g_{cat}{\cdot}h$.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.50-59
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• 2010

A pilot-scale test for production of biogas was conducted in an specially designed anaerobic digester (KH-ABC) in which the highly concentrated organic waste (food-waste and piggery-manure) was treated. The effect of inhibitive material to the reaction on anaerobic digestion and the feasibility of digested fluid for the liquefied fertilizer were investigated. The production rate of biogas, the concentration of methane($CH_4$) in biogas, and the digesting rate of volatile solid(VS) were analyzed in the variance of the operating conditions ; the influent rate, the mixture ratio of food waste and piggery manure, and the hydraulic retention time(HRT), etc. The production rate of biogas increased from 1.2 to $2.0kg-VS/m^3{\cdot}d$ with the organic loading rate(OLR). The most suitable operating conditions were recorded at $6m^3/day$ of an influent rate, 2:3 of the raw material mixture ratio(food waste : piggery manure) and 25 days of HRT, respectively. Under those conditions, the production rate of biogas, the concentration of methane($CH_4$) in biogas and the digesting rate of volatile solid(VS) were $220m^3/day$, 64%, and 70%, respectively. The concentration of inhibitive materials was below toxic standard and the anaerobic digested fluid(raw material mixture ratio of 3:7) could meet the condition of the liquefied fertilizer.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.648-652
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• 2010

Catalytic activities of the partial oxidation of methane (POM) to hydrogen were investigated over Pd(5)/Ti-SPK and Pd(5)/Zr-SPK in a fixed bed flow reactor (FBFR) under atmosphere, and the catalysts were characterized by BET, XPS, XRD. The BET surface areas, pore volume and pore width of Horvath-Kawaze, micro pore area and volume of t-plot of Pd(5)/Ti-SPK and Pd(5)/Zr-SPK were $284m^2/g$, $0.233cm^3/g$, 3.9 nm, $30m^2/g$, $0.015cm^3/g$ and $396m^2/g$, $0.324cm^3/g$, 3.7nm, $119m^2/g$, $0.055cm^3/g$, repectively. The nitrogen adsorption isotherms were type IV with hysteresis. XPS showed that Si 2p and O 1s core electronlevels of Ti-SPK and Zr-SPK substituted Ti and Zr shifted to slightly lower binding energies than SPK. The oxidation states of Pd on the surface of catalysts were $Pd^0$ and $Pd^{+2}$. XRD patterns showed that crystal structures of fresh catalyst changed amorphous into crystal phase after reaction. The conversion and selectivity of POM to hydrogen over Pd(5)/Ti-SPK and Pd(5)/Zr-SPK were 77, 84% and 78, 72%, respectively, at 973 K, $CH_4/O_2$ = 2, GHSV = $8.4{\times}10^4mL/g_{cat}{\cdot}h$ and were kept constant even after 3 days in stream. These results confirm superior activity, thermal stability, and physicochemical properties of catalyst in POM to hydrogen.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.127-127
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• 2017

우리나라 음식물 폐기물은 수분함량 및 유기물 함량이 높기 때문에 부패와 악취, 침출수의 원인이 된다. 하지만 이를 혐기 소화 처리한다면 구성성분에 따라 60-80%가 생분해되어(한국유기성폐자원학회, 2001) 친환경적으로 처리가능하고, 혐기소화 결과물로 발생한 메탄가스를 대체에너지로 사용할 수 있어 유기물을 효과적으로 처리할 수 있다. 그러나 유기성 폐기물은 계절 및 지역에 따라 구성성분의 비가 다르며, 성분 중 지방 함량이 많을 때 바이오가스 생산이 지연되어 생산효율 감소의 주된 원인이 된다(Kafle and Kim, 2013). 전국음식물 폐기물 중 지방함량이 높은 어육류의 발생량은 3차 조사(환경부, 2008)에 비해 2배 이상 증가하였고, 향후 음식 섭취의 서구화로 인한 육류 소비가 증가할 것으로 예상된다(환경부, 2013). 따라서 본 연구는 지방함량이 높은 유기물의 효율적 처리를 위해 지방산 종류에 따라 포화 불포화 지방산을 포함하는 부산물의 혐기소화 능력 및 바이오가스 생산 성능을 구명하는데 목적이 있다. 본 연구 결과, 불포화 지방산 함량이 높은 수준인 부산물의 바이오가스는 629.96-749.14 mL/g VS 이며, 포화 지방산 함량이 높은 수준의 부산물은 560.18-715.43 mL/g VS 였다. 불포화 지방산 함량이 25.31%-46.26%로 많아질수록 초기 순응기간은 13일에서 25일로 증가하였고, 총 바이오가스 생산량의 90%가 생산되는 기간인 T90은 57일에서 72일로 증가하여 바이오가스 생산 속도가 감소한 것으로 판단된다. 포화 지방산은 함량이 24.10-48.74%로 증가할수록 초기 순응기간의 변화는 없었고, T90은 69일에서 62일로 감소하였다. 또한 불포화 지방산이 많은 유기물은 모두 바이오가스 생산 과정에서 2단계의 지연현상을 보였지만, 포화지방산은 함량이 증가하여도 1단계의 지연현상을 보였다. 이러한 차이는 두 지방산에 관여하는 미생물의 차이(Diana, 2007)와 불포화 지방산의 굴곡된 형태가 지방산과 미생물이 상호 작용 방식에 악영향 미치기 때문으로 판단된다(Diana, 2013). 결론적으로, 두 지방산의 소화 방식은 차이가 있으며, 불포화 지방산 함량이 많은 유기물은 탄수화물 함량이 많은 유기물을 10% 이상 혼합하여 지연상을 감소시킬수 있다(Kim, 2017). 포화 지방산 함량이 많은 유기물은 초기 지연 현상 해결을 위한 연구가 추가적으로 요구된다.

• KSBB Journal
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• v.20 no.6
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• pp.438-442
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• 2005

Batch experiments were performed to investigate the effects of volumetric mixing ratio(v/v) of two substrates, food wastes(FW) and waste activated sludge(WAS). In batch experiments, optimum mixing ratio for hydrogen production was found at $10{\sim}20$ v/v % addition of WAS. CSTR(Continuous Stirred tank reactor) was operated to investigate the hydrogen productivity and the microbial community under various HRTs and volumetric mixing ratio(v/v) of two substrates. The maximum yield of specific hydrogen production, 140 mL/g VSS, was found at HRT of 2 day and the volumetric mixing ratio of 20:80(WAS:FW). The spatial distribution of hydrogen producing bacteria was observed in anaerobic fermentative reactor using fluorescent in situ hybridization(FISH) method.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.143-143
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• 2010

GTL(Gas-to-Liquids)공정 중 합성가스 제조공정(Reforming Process)인 ATR(Auto-Thermal Reforming), SCR(Steam Carbon Reforming), POx(Partial Oxidation)의 시뮬레이션 연구를 수행하였다. Reforming 공정에서 생산된 합성가스는 GTL 합성유 제조공정인 FT(Fischer-Thropsch) 반응기로 주입되며, 합성유 생산에 최적의 효율을 보이는 H2/CO 비(합성가스에 포함된 반응물비)는 2.0으로 알려져 있다. FT공정은 합성가스를 원료로 고온 및 고압 반응을 거쳐 GTL 공정의 최종 생산품인 FT합성유를 제조하는 공정이다. 본 연구에서는 FT공정 효율 극대화를 위해 reforming 공정에서 생성되는 합성가스 내 H2/CO의 비를 2로 수렴토록 모사조건을 설정하였으며, 상기 조건을 만족하는 reforming 공정들의 운전 온도 및 feed 조성을 분석하고 비교하고자 한다. 현재 GTL 플랜트관련 산업계에 적용 혹은 주 연구대상인 reforming 공정으로는 ATR, SCR, POx 공정이 있다. ATR 공정은 $850{\sim}1100^{\circ}C$에서 메탄, 스팀 및 산소를 원료로 활용하여 H2 및 CO를 생산하는 공정으로 발열/흡열 반응이 상존하여 에너지 비용이 낮지만 공정구조 상 열회수설비 및 ASU(Air Separation Unit)이 필요하기에 CAPEX(초기설비 설치비용)가 높은 편이다. SCR공정은 CH4, Steam 및 CO2를 연료로 하기에 이산화탄소가 일정부분 포함된 가스전에도 적용이 가능하나 공정 운전 중 지속적으로 외부에서 열을 공급해야 하기에 에너지 투입비용이 높은편이며, 탄소침적의 문제가 있어 대용량 플랜트에는 적합하지 않다. POx공정은 약 $1,500^{\circ}C$의 고온에서 CH4가 O2에 의해 부분 산화되는 방식으로 촉매가 필요없어 설비비가 타 공정에 비해 저렴하나 생산가스의 H2/CO비가 다소 낮아 전체적인 GTL 공정효율이 저하되는 단점이 있다. 상기 세 공정은 GTL 산업계에서 실증 및 효율증대를 위해 주로 연구되는 공정이기에 본 연구의 분석대상으로 설정하였다. 본 연구에서는 상용공정모사기인 Aspen Plus를 활용하여 reforming 공정별로 FT합성공정의 최적 조건(H2/CO=2)을 만족하는 합성가스 생산조건 분석 및 비교를 수행할 예정이다. 운전조건인 공정 운전온도 및 feed 가스조성 등을 모사하기 위해 합성가스 reforming 공정을 모델링하고 공급유량 및 압력 등의 운전변수는 GTL국책과제 1단계 연구수행 결과를 토대로 선정하고자 한다. GTL공정의 경우, 설비의 운전조건이나 연료가스의 구성 및 유량에 따라 적합한 reforming 공정이 다르기에 본 시뮬레이션 결과를 향후 GTL 플랜트 공정모델 설계시 reforming 공정선정에 참고자료로 활용하고자 한다.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.54-61
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• 2007

The influences of pH were investigated for anaerobic hydrogen gas production under the constant pH condition ranged from pH 3 to 10. Carbon dioxide and hydrogen gas were main components of the gas but methane was not detected in the produced gas when sucrose was added in enrichment medium. When the modified Gompartz equation was applied for the statistical analysis of experimental data, a hydrogen production potential and maximum gas production rate at pH 5 were 1,182 mL and 112.46 mL/g dry wt biomass/hr. The hydrogen conversion ratio was 22.56%. The butyrate/acetate ratios at pH 5 and pH 6 are 1.63 and 0.38. Higher butyrate/acetate ratio produced more hydrogen gas generation. The Haldane equation model was used to find the optimum pH and fitted well with the experimental data$(r^2=0.98)$. The optimum pH and specific hydrogen production were 5.5 and 119.61 mL/g VSS/h.