Spring 2010 ENCH446 Project 1

Transcription

1 Spring 2010 ENCH446 Project 1 Raymond A. Adomaitis March 8, 2010 To be covered: Class syllabus ( adomaiti/ench446), grading Team selection (4 members per team) Initial project description Approximate schedule for year

2 What you should know from ENCH444 Flowsheet synthesis, simple material and energy balances, rapid evaluation of design alternatives Shortcut distillation, absorber column, and flash drum calculations Reactor vessel, distillation/absorber column, heat exchanger, pump, and compressor sizing and costing Return on investment, discounted cash flow calculations, project value ChemCAD simulation, detailed designs, elements of process optimization Process utility calculations, heat exchanger networks, pinch design Separation sequences using simplified distillation columns

3 Gas treating plants Figure 1. Generalized Natural Gas Processing Schematic Lease Operations Gas-Oil Separator * Gas Reservoir Condensate Separator Lease or Plant Plant Operations Gas Stream Dehydrate Oil Reservoir A B * Remove Contaminants Nitrogen Extraction Dry Gas (to Pipeline) Oil Condensate Free Water C Water D * E DeMethanizer Fractionator Dry (Residue) Gas (to Pipeline) H 2 S Co 2 etc Nitrogen * Optional Step, depending upon the source and type of gas stream. Source: Energy Information Administration, Office of Oil and Gas, Natural Gas Division. F * G * Natural Gas Liquids (NGLs) Ethane Propane Butane Pentanes Natural Gasoline

4 Methane from landfills Third largest emitter of (human produced) methane to the atmosphere Produced by the reaction of cellulose by bacteria (C 6 H 10 O 5 ) n + n H 2 O 3n CH 4 + 3n CO 2 Landfill gas: 50/50 mixture of CO 2 /CH 4 ; saturated with water Large landfills can produce 2 million scf/day; largest to 5 MMscf 1 /day 95% of NASA Goddard SFC heat is supplied by landfill gas 1 MM = million; standard conditions: 60 deg. F, 1atm

5 Project statement Each team represents the engineering design group of a company evaluating landfill gas treating plants Will determine the economic break-even point with respect to landfill gas production rate ranging [0, 5] MMscf/day Breakeven point = 10% return on investment assuming 20 year plant life Base case plant capacity = 1MMscf/day

6 Product specifications Pipeline quality CNG, compressed and stored at 225bar, suitable for transportation use (e.g., Metro buses). From Interstate natural gas - Quality, specifications, and interchangeability published by the Center for Energy Economics, University of Texas, Dec. 2004: 1. < 2 % CO 2 by volume 2. < 7 lbs water/mmscf Question for report 1: are these specifications consistent?

7 Process alternatives Three processing alternatives are to be evaluated at the preliminary design stage: 1. Gas dehydration, followed by CO 2 removal; 2. CO 2 removal followed by gas dehydration; 3. Simultaneous CO 2, water removal. Main sorbents: Monoethanolamine for CO 2 removal (MEA); diethylene glycol (DEG) as desiccant; Both are available in ChemCAD

8 MEA plant - CO 2 removal From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

9 MEA absorber/regenerator data - CO 2 partial pressure From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

10 MEA absorber/regenerator data - MEA/water VLE From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

11 MEA absorber/regenerator design notes 1. MEA normal boiling point: 171 o C 2. 1 to 2 moles solvent/mole acid gas to 30 wt.% MEA in water 4. heat of reaction = 825 BTU/lb CO 2 5. high pressure absorber, low pressure regenerator 6. packed or tray columns

12 Glycol plant - water removal From: Gas Purification, 2nd ed., F. C.Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

13 Glycol plant - absorber design 1 theoretical tray 0.25% tray efficiency glycol concentration set by product gas specifications From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

14 Glycol plant - regenerator design Max (decomposition) DEG temperature = 329 o F From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

15 Combined MEA-Glycol plant From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl, Gulf Publishing, (1974).

16 Additional design specifications 1. All steam must be generated on-site; 2. No waste to sewers; 3. Storage for make-up MEA and DEG; 4. Provisions for flaring the raw landfill gas must be provided; 5. The gas treating facility must be safe with respect to power outages and must be able to restart after an arbitrarily long power outage; 6. Evaluate CO 2 disposal options; 7. Cooling water must be recycled on-site.

17 Design report 1 1. Literature review of gas treating processes relevant to our MEA/DEG system; 2. Reaction chemistry of MEA and CO 2 ; VLE of DEG/water system; 3. Convert all quantities to SI units; 4. Table of inlet and outlet stream properties; Weekly report format 1. Title page listing team member contributions (time/effort) and the team member(s) responsible for the report; 2. Summary of design calculations and design conclusions 3. Design calculation details in appendix (electronic form only)

18 Design report 2 Initial material and energy balances for the first process option (dehydrate then scrub CO 2 ; 1. Isothermal, single stage absorber at 25C; assume P = 0, compute pressure, DEG lean flow and composition, inlet and outlet gas compositions; 2. DEG regenerator single stage calculation; determine operating temperature and waste gas stream flowrate; consider adding additional stages if desired separation is not achieved; 3. Isothermal, single-stage MEA absorber; compute pressure, MEA lean flow and composition, inlet and outlet gas compositions; consider adding additional stages if desired separation is not achieved; 4. Isothermal, single-stage MEA regenerator; set pressure, and determine stage temperature and waste stream composition; consider adding stages to recover MEA lost in waste stream; Report all flows in mol/min, temperature in K, pressure in bar.

19 Design report 3 Primary goal: integrated process design with absorber/regenerator energy integration. 1. Continue refinement of column designs, calculating number of true stages; 2. Create a list of additional equipment to be designed, e.g., final gas compressor, gas storage facilities, MEA and DEG make-up storage, etc. 3. Create a list of potential safety and environmental issues to be examined.

20 Design report 4 Primary goal: initial ChemCAD simulation and economic analysis 1. Set up initial ChemCAD simulation; for the report include a process flow diagram and the process stream compositions, all given in mole/min, for your final hand-calculated design and the preliminary ChemCAD simulation; 2. Prepare at most a single-page discussion of the differences found; give reasons for any major differences; 3. Prepare a single-page summary of the economic basis to be used for estimating equipment and operating costs, project return on investment; 4. Create a to-do list of all secondary equipment designs still needed and outstanding environmental and safety issues to be considered (one page max).

21 Design report 5 Primary goal: assess process profitability potential 1. Full process ChemCAD simulation, including 1.1 energy integration 1.2 all process compressors and pumps 1.3 on-site steam generation and cooling water processing 2. Process economic analysis, breaking down the 1 MMscf landfill gas plant process 2.1 capital costs (assume land is available for free) 2.2 operating costs (esp. electricity, human operator(s), if needed) 2.3 Safety equipment costs 2.4 ROI 3. Group plans for CO 2 use/disposal

22 Subproject 1 final design report Title page with team members, table of contents 1/2 page executive summary, 1/2 page plot of ROI vs. MMscf landfill gas One page of conclusions, including engineering design findings, economics of the process, safety and environmental issues One page of engineering design assumptions, basis for design, in outline form One page describing the economic basis used for the ROI calculations A clear, single-page process flowsheet with equipment and streams labeled Stream summaries, including only temp (K), pressure (bar), and component flows (mol/min)

23 Subproject 1 final design report, continued Brief equipment summaries (tabular form, only), indicating temperature, pressure, important design parameters (e.g., trays, compressor stages), equipment capital cost and operating cost One page summarizing differences between hand and ChemCAD calculations Summary of engineering analysis Summary of economic analysis

24 Subproject 1 presentation A 4 minute presentation, in powerpoint or pdf, brought on a usb drive: That contains no background information Presents the group s best estimate for the project ROI as a function of MMscf landfill gas flow Shows the final design process flowsheet Summarizes feed, product, and waste streams Summarizes only major equipment designs/costs Describes any unique design features