MODULE 14. “Life Cycle Assessment (LCA)”

1. MODULE 14. “Life Cycle Assessment (LCA)” 4 steps of LCA, approaches, software, databases, subjectivity, sensitivity analysis, application to a classic example.

2. Tier IIIOpen-ended problem Module 14 – Life Cycle Assessment

3. Prerequisites for tier III What are the prerequisites for this tier? It is further assumed that students already have an introductory-level background in Life Cycle Assessment (LCA) (from Tier I and Tier II) and the basic knowledge in petrochemical processes, such as would normally be part of any undergraduate engineering curriculum. Module 14 – Life Cycle Assessment

4. Statement of intent What is the purpose of this module? Open-Ended Design Problem. Is comprised of an open-ended problem to solve real-life application of LCA to the oil and gas sector. The global aim of that problem is to quantify the total environmental benefits and drawback of a process. Module 14 – Life Cycle Assessment

5. References • Spath and Mann. (2001) ”Life Cycle Assessment of Hydrogen Production via Natural Gas Steam Reforming“. National Renewable Energy Laboratory. • Spath and Mann. (1999) “Life Cycle Assessment of Coal-fired Power Production”. National Renewable Energy Laboratory. • Mann and Spath. (1997) “Life Cycle Assessment of Biomass Gasification Combined-Cycle System”. National Renewable Energy Laboratory. • Rojey A., Minkkinen A., Arlie J.P. and Lebas E. “Combined Production of Hydrogen, Clean Power and Quality Fuels”. Institut Français du Pétrole (IFP). Module 14 – Life Cycle Assessment

6. References • D. Gray, G. Tomlinson, “Opportunities For Petroleum Coke Gasification Under Tighter Sulfur Limits For Transportation Fuels,” Presented at the Gasification Technologies Conference, San Francisco, California, October 8–11, 2000 • H. Baumann, A.M. Tillman(2004). ‘’The hitch Hicker’s Guide to LCA. An orientation in life cycle assessment methodology and application’’. Studentlitteratur AB. Lund, Sweden • The Environmental Foundation Bellona :http://www.bellona.no/en/energy • University of Newbrunswick (Canada) (Petroleum and Natural Gas Processing):http://www.unb.ca/che/che5134/smr.htm Module 14 – Life Cycle Assessment

7. Tier III: Content Tier III is broken in six parts: • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • Report Structure • Recommendations • Index Unlike the previous two sections, this section does not have a quiz. The student must interpret the results of the above work and elaborate a succinct project report (15 - 20 pages). Module 14 – Life Cycle Assessment

8. Tier III: Units of measure Metric units of measure are used. Therefore, material consumption is reported in units based on the gram (e.g., kilogram or metric tonne), energy consumption based on the joule (e.g., kilojoule or megajoule), and distance based on the meter (e.g., meter). When it can contribute to the understanding of the analysis, the English system equivalent is stated in parenthesis. The metric units used for each parameter are given below, with the corresponding conversion to English units. Mass: kilogram (kg) = 2.205 pounds Metric tonne (T) = 1.102 ton (t) Distance: Meter (m) = 6200 mile = 3281 feet Area: hectare (ha) = 10,000 m2 = 2.47 acres Volume: cubic meter (m3) = 264.17 gallons normal cubic meters (Nm3) = 0.02628 standard cubic feet (scf) at a standard temperature & pressure of 15.6°C (60°F) and 101.4 kPa (14.7 psi), respectively Module 14 – Life Cycle Assessment

9. Tier III: Units of measure Pressure: kilopascals (kPa) = 0.145 pounds per square inch Energy: kilojoule (kJ) = 1,000 Joules (J) = 0.9488 Btu Gigajoule (GJ) = 0.9488 MMBtu (million Btu) Terajoule (Tj) = 1.0 x 109 Joules (J) kilowatt-hour (kWh) = 3,414.7 Btu Gigawatt-hour (GWh) = 3.4 x 109 Btu Power: megawatt (MW) = 1 x 106 J/s Temperature: °C = (°F - 32)/1.8 Hydrogen Equivalents: 1 kg H2 = 423.3 scf gas = 11.126 Nm3 gas Module 14 – Life Cycle Assessment

10. Tier III: Abbreviations and Terms Btu - British thermal units CO2-equivalence- Expression of the GWP in terms of CO2 for the following three components CO2, CH4, N2O, based on IPCC weighting factors EIA - Energy Information Administration GWP - global warming potential HHV - higher heating value HTS - high temperature shift IPCC- Intergovernmental Panel on Climate Change kWh - kilowatt-hour (denotes energy) LCA - life cycle assessment LHV - lower heating value LTS - low temperature shift MMSFCD - million standard cubic feet per day MW - megawatt (denotes power) N2O - nitrous oxide Nm3 - normal cubic meters NMHCs - non-methane hydrocarbons NOx - nitrogen oxides, excluding nitrous oxide (N2O) NREL - National Renewable Energy Laboratory PSA - pressure swing adsorption SMR - steam methane reforming SOx - sulfur oxides, including the most common form of airborne sulfur, SO2 Stressor - A term that collectively defines emissions, resource consumption, and energy use; a substance or activity that results in a change to the natural environment Stressor category - A group of stressors that defines possible impacts wt% - percentage by weight Module 14 – Life Cycle Assessment

11. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions • Data • Report Structure • Recommandations • Index Module 14 – Life Cycle Assessment

12. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming Module 14 – Life Cycle Assessment

13. Description of the context: Hydrogen production via natural gas steam reforming1.1. Hydrogen (H2) Hydrogen is used in a number of industrial applications, with today’s largest consumers being ammonia production facilities (40.3 %), oil refineries (37.3%), and methanol production plants (10.0%). Because such large quantities of hydrogen are required in these instances, the hydrogen is generally produced by the consumer, and the most common method is steam reforming of natural gas. The figure below shows a simplified flowsheet of the process utilised in this context for hydrogen production. Module 14 – Life Cycle Assessment

14. Description of the context: Hydrogen production via natural gas steam reforming1.2. The process Hydrogen can be produced from natural gas, oil or coal. Synthesis gas production is a key step, as it gives access to a wide range of options. Synthesis gas which is formed mainly by a mixture of CO and H2 is obtained either by steam-reforming, in the case of natural gas or by partial oxidation. Steam methane reforming is the most common and least expensive method of producing hydrogen. About half of the world's hydrogen is produced from SMR (Gaudernack, 1998). The process can be used also with other light hydrocarbon feedstocks, such as ethane and naphtha. The process is endothermic and synthesis gas is typically produced in a tubular reformer furnace. Module 14 – Life Cycle Assessment

15. Description of the context: Hydrogen production via natural gas steam reforming Inlet temperatures are within the range 450-650°C and the product gas leaves the reformer at 700-950°C, depending on the applications (Rostrup-Nielsen, 1993). The desulphurized feedstock is mixed with process steam and reacted over a nickel based catalyst contained in high alloy steel tubes. Although the plant requires some stream for the reforming and shift reactions, the highly exothermic reactions results in an excess amount of steam produced by the plant. Due to the high operating temperature in the reformer, the reformer effluent contains about 10-15 vol % CO (dry basis). A high-temperature shift (HTS) operating at an inlet temperature of 343 to 371°C makes possible to convert about 80 to 90% of the CO. This step uses a catalyst which is typically composed of copper oxide-zinc oxide on alumina. A Pressure Swing Adsorption unit (PSA) is used for removing CO and other contaminants present with hydrogen. Module 14 – Life Cycle Assessment

16. Description of the context: Hydrogen production via natural gas steam reforming If the CO2 which is present typically at the level of 15-20% has to be recovered, it may be more appropriate to use a specific step for separating CO2 from hydrogen by solvent scrubbing. An amine solvent is typically used for such a separation step. The hydrogen thus obtained, can be exported. Refining is presently the main consumer of hydrogen. It can be used also in a combined cycle for generating electricity. Such a scheme provides therefore an attractive option for producing electricity, without emitting CO2. Synthesis gas produced during the initial step, can also be used for producing liquid hydrocarbon fuels, through Fischer-Tropsch synthesis. Thus, it is possible to transform any fossil fuel or biomass into hydrogen, electricity and liquid fuels. Module 14 – Life Cycle Assessment

17. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement Module 14 – Life Cycle Assessment

18. 2. Problem Statement An oil & gas plant seeks to modernize by looking at 3 process options: improving the environmental aspects, improving the performance of some units of production to maximize the hydrogen production and finaly to install a better system of electronic control of the process. Your are the process engineer in this firm. Your boss, the plant manager, wants you to do a study on the the total environmental aspects (quantification and analysis) of producing 48 MMscfd of hydrogen via natural gas steam reforming for the intern study. In recognition of the fact that upstream processes required for the operation of the Steam Methane Reforming (SMR) plant also produce pollutant and consume energy and natural resources. The data colletion and validation have already been done by another engineer. Module 14 – Life Cycle Assessment

19. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent Module 14 – Life Cycle Assessment

20. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries Module 14 – Life Cycle Assessment

21. Statement of the intent3.1. System boundaries This LCA should be performed in a cradle-to-grave manner, for this reason, natural gas production and distribution, as well as electricity generation, were included in the system boundaries. The steps associated with obtaining the natural gas feedstock are drilling/extraction, processing, and pipeline transport. The next figure shows the System Boundaries for Hydrogen Production via Natural Gas Steam Reforming. Module 14 – Life Cycle Assessment

22. Statement of the intent3.1. System boundaries For this study, the plant life was set at 20 years with 2 years of construction. In year one, the hydrogen plant begins to operate; plant construction takes place in the two years prior to this (years negative two and negative one). In year one the hydrogen plant is assumed to operate only 45% (50% of 90%) of the time due to start-up activities. In years one through 19, normal plant operation occurs, with a 90% capacity factor. During the last year the hydrogen plant is decommissioned. Therefore, the hydrogen plant will be in operation 67.5% (75% of 90%) of the last year. Module 14 – Life Cycle Assessment

23. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions Module 14 – Life Cycle Assessment

24. Statement of the intent3.2. Major assumptions A pretreatment on the natural gas is necessary to avoid emposoinment of the catalysts with the sulphur. The H2S is removed in a hydrogenation reactor and then in a ZnO bed. After pretreatment, the natural gas and 2.6 MPa steam are fed to the steam reformer. The resulting synthesis gas is then fed to high temperature shift (HTS) and LTS reactors where the water gas shift reaction converts 92% of the CO into H2. Hydrogen Plant Block Flow Diagram Module 14 – Life Cycle Assessment

25. Statement of the intent The hydrogen is purified (to 99.9% mol.) using a pressure swing adsorption (PSA) unit. The reformer is fueled primarily by the PSA off-gas, but a small amount of natural gas is used to supply the balance of the reformer duty. The PSA off-gas is comprised of CO2 (47.06 mol%), H2 (24.26 mol%), CH4 (19.59 mol%), CO (7.8 mol%), N2 (0.55 mol%), and some water vapor. The steam reforming process produces 4.8 MPa steam. Electricity is purchased from the grid to operate the pumps and compressors. The hydrogen plant energy efficiency is defined as the total energy produced by hydrogen plant divided by the total energy into the plant, determines by the following formula: The base case of this analysis assumed that 1.4% of the natural gas that is produced is lost to the atmosphere due to fugitive emissions. Module 14 – Life Cycle Assessment

26. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions • Data • Construction material Requirement Module 14 – Life Cycle Assessment

27. Statement of the intent3.4.1. Construction material requirement: Construction Plant Materials Requirements and pipeline The next table list materials requirements used for the plant in this study. A sensitivity analysis was performed how changing these numbers would affect the results. Hydrogen Plant Material Requirement (Base Case) Module 14 – Life Cycle Assessment

28. Statement of the intent To move the natural gas from the oil or gas wells to the hydrogen plant, we use pipelines. Because the main pipeline is shared by many users, only a portion of the material requirement was allocated for the natural gas combined-cycle plant. For this analysis, the total length of pipeline transport for the natural gas combined-cycle plant is assumed to be 425 km, it was sized so that the total pressure drop in the pipe is of 0.05 psi/100 feet (0.001 MPa/100 meters). The pipe has a diameter of 31 inches assuming a wall thickness of 1 inch. The steel used for the pipe construction has a density of 7700 kg/m3. Module 14 – Life Cycle Assessment

29. Statement of the intent3.4.1. Air Emissions due to materials’ construction Air emissions due to the plant construction The construction of materials requirements also produce a lot of air emissions. Because of lack of data, we will suppose that those constructions emit 2.8652 ton of particulate/hectare of the mill/month of activity. You can suppose that NMHCs = 50% mass. benzene + 50% mass. Toluene. Module 14 – Life Cycle Assessment

30. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions • Data • Construction material Requirement • Natural gas composition and lost Module 14 – Life Cycle Assessment

31. Statement of the intent3.4.2. Natural gas composition and loss While natural gas is generally though of as methane, about 5-25% of the volume is comprised of ethane, propane, butane, hydrogen sulfide, and inerts (nitrogen, CO2 and helium). The relative amounts of these components can vary greatly depending on the location of the wellhead. The next table gives the composition of the natural gas feedstock use in this analysis, as well as typical pipeline and wellhead compositions. The composition used in this study (first column) assumes that the natural gas has undergo a pretreatment before entering the desulphurization reactor. The natural gas feedstock contains up to 7 ppmv total sulfur, max. 5 ppmv in the form of hydrogen sulphide (H2S) and max. 2 ppmv organic sulfur as mercaptane. Module 14 – Life Cycle Assessment

32. Statement of the intent Natural Gas Composition Module 14 – Life Cycle Assessment

33. Statement of the intent In extracting, process, transmitting, storing and distributing natural gas, some is lost to the atmosphere. Over the past two decades, the natural gas industry and others have tried to better quantify the losses. There is a general consensus that fugitive emissions are the largest source, accounting for about 38% of the total, and that nearly 90% of the fugitive emissions are a result of leaking compressor components. The second largest source of methane emissions comes from pneumatic control devices, accounting for approximately 20% of the total losses. The majority of the pneumatic losses happen during the extraction step. Engine exhaust is the third largest source of methane emissions due to incomplete combustion in reciprocating engines and turbines used in moving the natural gas through the pipeline. These three sources make up nearly 75 % of the overall estimated methane emissions. The remaining 25% come from sources such as dehydrators, purging of transmissions/storage equipment, and meter and pressure regulating stations in distribution lines. Module 14 – Life Cycle Assessment

34. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions • Data • Construction material Requirement • Natural gas composition and lost • Production and distribution of electricity Module 14 – Life Cycle Assessment

35. Statement of the intent3.4.3. production and distribution of electricity Electricity is purchased from the grid to operate the pumps and compressors. The production was assumed to be the generation mix of coal, lignite (hard coal), oil and fuel/natural gas. The process consume approx. 129,104 Mj/day. Each fuel provide respectively 3%, 2%, 72% and 23% of the total energy needed by the process. The stressors associated with this mix should also determined in a cradle-to-grave manner. The table below presents the quantity (in kg) of air emissions for each fossil fuel used for electricity production. Those data relate to a functional unit of 1 Tj net electricity delivered from the power plant. Module 14 – Life Cycle Assessment

36. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions • Data • Construction material Requirement • Natural gas composition and lost • Production and distribution of electricity • H2 Production plant Module 14 – Life Cycle Assessment

37. Statement of the intent3.4.4. H2 Production plant Hydrogenation and Desulphurization As the reformer catalyst is sensitive to poisoning from sulfur, sulfur in the natural gasis processed in a Hydrogenation Reactor. Sulfur is totaly converted to hydrogen sulfide in this Hydrogenation reactor and will be absorbed on the zinc oxide by conversion of ZnO to ZnS in the desulphurization reactor. Natural gas leaving the reactor will have a residual sulfur content of less than 0.2 ppmv. The total adsorption capacity of the desulphurization catalyst, based on total 7 ppmv sulfur in the feedstock will be for minimum 2 years of uninterrupted operation. A small amount of hydrogen, which is recycled from the product stream, is used in the Hydrogenation step to adjust the pressure in the reactor. The table below gives the caractheristics of the inflow of the hydrogenation reactor. Inflows to the hydrogenation reactor Module 14 – Life Cycle Assessment

38. Statement of the intent3.4.4. H2 Production plant Steam reforming In the steam reforming, the mixture of desulphurized natural gas and process steam (3358 kmol/h at 2.6 MPa (380 psi)) is reformed under application or external heat. The principle chemical reactions taking place in the steam reformer are as follows: Steam reforming Water-gas Shift reaction (which is highly exothermic) The effluent contains besides the products CO2 and residual CH4 and H2O. The reformed gas leaves the SR at 810ºC and approx. 25 kg/cm2 abs.. All reactions take place simultaneously at about 560ºC. However, the reaction as a whole is endothermic. Those reactions take place over a nickel-based catalyst. The waste heat contained in the furnace flue gas is utilized for superheating of the reformer feedstock, generating of medium pressure steam, superheating of the medium pressure steam and preheating of the combustion air. Those gases leave the reformer at approx. 1000ºC. Module 14 – Life Cycle Assessment

39. Statement of the intent The reformed gas composition Module 14 – Life Cycle Assessment

40. Statement of the intent The combustion air given is based on 5% excess air and enters the burner at 380ºC and approx. 1.2 kg/cm2, at a rate of 123488 kg/h. It is composed of 20.4% mol. O2, 76.77% mol. N2 and 2.83% of H2O. Waste heat is recovered from the flue gas as well as from the reformed gas to preheat and superheat process streams and for steam production. The natural gas utilized as fuel for the burner contains 5 ppmv of H2S and 2 ppmv of mercaptane and has the following composition and characteristics: Module 14 – Life Cycle Assessment

41. Statement of the intent Molar composition of of the natural gas used in the burner The table below presents the composition of the flue gas at the outlet of the burners. Module 14 – Life Cycle Assessment

42. Statement of the intent3.4.4. H2 Production plant High Temperature Shift (HTS) The carbon monoxide, which is produced in the steam reformer, is converted by means of water vapor on a catalyst in a HTS reactor to hydrogen and carbon dioxide, according to the following reaction: This reaction is highly exothermic, which leads to temperature rise of about 50ºC. The CO-content at the outlet of the Shift reactor is less than 2 mol-%. Subsequently the shifted gas is cooled down in different exchangers to approx. 36ºC. Process condensate is separated in multiple liquid-gas separators. The gas is then routed to the PSA Unit. Module 14 – Life Cycle Assessment

43. Statement of the intent3.4.4. H2 Production plant Separators The outflow gas from the HTS passes by different exchangers and liquid-gas separators. At the outlet of the last separator, we obtain two flows. On flow of 481 kg/h of liquid water at 35ºC and a gaseous flow principally composed of hydrogen (H2) and carbon dioxide (CO2) at a rate of 43186 kg/h (3945 kmol/h). The table bellow gives the molar composition of this gaseous flow: Molar composition of the gaseous outflow of the last separator before the PSA unit Module 14 – Life Cycle Assessment

44. Statement of the intent3.4.4. H2 Production plant Pressure Swing absorption (PSA) For final purification a Pressure Swing Adsorption process is used. The reminder of undesired components are removed from the bulk of hydrogen by means of adsorption on molecular sieves using a PSA. The purification of hydrogen is based on selective adsorption of gas components such as CH4, CO, CO2, N2 and H2O. Hydrogen does not absorb and leaves the PSA unit as a product gas with high purity. Subsequently the pure hydrogen product is compressed and a small amount is recycled to upstream of the Hydrogenation Reactor. The adsorbed gases in the PSA are released and routed as off-gases to the off gas which ensures a stable and constant supply of fuel gas to the burners of the reformer. The Hydrogen (H2) obtained from the PSA has a 99% molar purity. It leaves the PSA Unit at 40ºC at 5149 kg/h (2525 kmol/h). Module 14 – Life Cycle Assessment

45. Statement of the intent3.4.4. H2 Production plant Steam Generation System Waste heat from the process is utilized for steam generation. As the main source of energy, the sensible heat of the reformed gas downstream Steam Reformer is used for steam production in Reformed Gas Waste Heat Boiler. An other source of heat for steam generation is the waste heat of the flue gas leaving the steam reformer. Here additional steam is produced in Flue Gas Waste Heat Boiler. Module 14 – Life Cycle Assessment

46. Statement of the intent3.4.4. H2 Production plant Shut down The process is shuted down for 24 hours every 2 years to change the catalysts. Duringstart-up of the process or PSA Unit failure, we use a burners’ fuel (for the SR) composed in majority of natural gas (12.88 the mole rate of the natural gas used in normal operation case) completed with Raffinery fuel. The mole ratio of thoses two fuels is 8.5. Module 14 – Life Cycle Assessment

47. Tier III: Outline • Description of the context: Hydrogen production via natural gas steam reforming • Problem statement • Statement of the intent • System boundaries • Major assumptions • Data • Report structure Module 14 – Life Cycle Assessment

48. 4. Report structure4.1. Questions for discussion 1- Quantify the environmental loads - resource use and pollutant air emissions - of the system. 2- Make the results more environmentally relevant by translating the emissions using environmental themes method. Identify and evaluate the environmental impacts of the process by making an impact assessment by calculating the total impact. The index list is in the Index towards the end of the problem. Module 14 – Life Cycle Assessment

49. 4. Report structure4.1. Questions for discussion 3- Make a sensitivity study and identify the most important parameters toward their influence on the results of this study. 4- Examine the net emission of greenhouse gases, as well as the major environmental consequences. 5- Substitutions scenarios: What possible improvements on the system could we do ? 7- Make a cost-benefit Analysis, typically involves an economic ROI study. 8- Since Risk is another matter not dealt with in LCA, we won’t ask you about it but you should write a short paragraph about the Ecological Risk Assessment (ERA) related to this process. Module 14 – Life Cycle Assessment

50. 4. Report structure4.2. Suggestion for Report Table of Contents • Executive summury • Introduction • Objectives • Summury of results • Sensitivity Analysis • Impact Assessment • Impovement Opportunities • Conclusions Module 14 – Life Cycle Assessment