Spring 2010 ENCH446 Project 1 - UMD ISRadomaiti/ench446/2010ProjectPart1.pdf · Spring 2010 ENCH446...

Spring 2010 ENCH446 Project 1

Raymond A. Adomaitis

March 8, 2010

To be covered:

I Class syllabus (http://www.isr.umd.edu/˜ adomaiti/ench446),grading

I Team selection (4 members per team)

I Initial project description

I Approximate schedule for year

Raymond A. Adomaitis Spring 2010 ENCH446 Project 1

What you should know from ENCH444

I Flowsheet synthesis, simple material and energy balances,rapid evaluation of design alternatives

I Shortcut distillation, absorber column, and flash drumcalculations

I Reactor vessel, distillation/absorber column, heat exchanger,pump, and compressor sizing and costing

I Return on investment, discounted cash flow calculations,project value

I ChemCAD simulation, detailed designs, elements of processoptimization

I Process utility calculations, heat exchanger networks, pinchdesign

I Separation sequences using simplified distillation columns


Gas treating plants

Lease Operations

Energy Information Administration, Office of Oil and Gas, January 2006

2

In 2004, approximately 24.2 trillion cubic feet (Tcf) of raw

natural gas was produced at the wellhead.6 A small portion of

that, 0.1 Tcf, was vented or flared, while a larger portion, 3.7

Tcf, was re-injected into reservoirs (mostly in Alaska) to

maintain pressure. The remaining 20.4 Tcf of “wet”7 natural

gas was converted into the 18.9 Tcf of dry natural gas that

was put into the pipeline system. This conversion of wet

natural gas into dry pipeline-quality natural gas, and the

portion of the natural gas industry that performs that

conversion, is the subject of this report.

Background

Natural gas processing begins at the wellhead (Figure 1). The

composition of the raw natural gas extracted from producing

wells depends on the type, depth, and location of the

underground deposit and the geology of the area. Oil and

6

Energy Information Administration, Natural Gas Annual 2004

(December 2005), Table 1. http://www.eia.doe.gov/oil_gas/natural_gas/data

_publications/natural_gas_annual/nga.html. 7

Wet gas is defined as the volume of natural gas remaining after removal

of condensate and uneconomic nonhydrocarbon gases at lease/field

separation facilities and less any gas used for repressurization.

natural gas are often found together in the same reservoir.

The natural gas produced from oil wells is generally

classified as “associated-dissolved,” meaning that the natural

gas is associated with or dissolved in crude oil. Natural gas

production absent any association with crude oil is classified

as “non-associated.” In 2004, 75 percent of U.S. wellhead

production of natural gas was non-associated.

Most natural gas production contains, to varying degrees,

small (two to eight carbons) hydrocarbon molecules in

addition to methane. Although they exist in a gaseous state at

underground pressures, these molecules will become liquid

(condense) at normal atmospheric pressure. Collectively, they

are called condensates or natural gas liquids (NGLs). The

natural gas extracted from coal reservoirs and mines (coalbed

methane) is the primary exception, being essentially a mix of

mostly methane and carbon dioxide (about 10 percent).8

8

The Energy Information Administration estimates that about 9 percent of

2004 U.S. dry natural gas production, or about 1.7 Tcf, came from coalbed

methane sources, which do not contain any natural gas liquids. U.S. Crude

Oil and Natural Gas, and Natural Gas Liquids Reserves: 2004 Annual

Report. http://www.eia.doe.gov/oil_gas/natural_gas/data_publications/

Fractionator

Nitrogen

Extraction

DeMethanizer

Remove

Contaminants

Condensate

Separator

Dehydrate

Natural Gas

Liquids (NGLs)

Free

Water

Con-

densate

H2S

Co2

etc

Oil

Gas

Stream

Nitrogen

Dry (Residue)

Gas

(to Pipeline)

Plant OperationsLease or Plant

Oil

Reservoir

Gas

Reservoir

Ethane

Propane

Butane

Pentanes

Natural Gasoline

A

B *

D

C

E

G *

Figure 1. Generalized Natural Gas Processing Schematic

* Optional Step, depending upon the source and type of gas stream.

•Source: Energy Information Administration, Office of Oil and Gas, Natural Gas Division.

*

F *

Gas-Oil Separator *

Lease Operations

Dry Gas

(to Pipeline)

Water

Fractionator

Nitrogen

Extraction

DeMethanizer

Remove

Contaminants

Condensate

Separator

Dehydrate

Natural Gas

Liquids (NGLs)

Free

Water

Con-

densate

H2S

Co2

etc

Oil

Gas

Stream

Nitrogen

Dry (Residue)

Gas

(to Pipeline)

Plant Operations

Oil

Reservoir

Gas

ReservoirLease or Plant

Ethane

Propane

Butane

Pentanes

Natural Gasoline

A

B *

D

C

E

G *

Figure 1. Generalized Natural Gas Processing Schematic

* Optional Step, depending upon the source and type of gas stream.

•Source: Energy Information Administration, Office of Oil and Gas, Natural Gas Division.

*

F *

Gas-Oil Separator *

Dry Gas

(to Pipeline)

Water


Methane from landfills

I Third largest emitter of (human produced) methane to theatmosphere

I Produced by the reaction of cellulose by bacteria

(C6H10O5)n + n H2O → 3n CH4 + 3n CO2

I Landfill gas: 50/50 mixture of CO2/CH4; saturated with water

I Large landfills can produce 2 million scf/day; largest to 5MMscf1/day

I 95% of NASA Goddard SFC heat is supplied by landfill gas

1MM = million; standard conditions: 60 deg. F, 1atmRaymond A. Adomaitis Spring 2010 ENCH446 Project 1

Project statement

Each team represents the engineering design group of a companyevaluating landfill gas treating plants

I Will determine the economic break-even point with respect tolandfill gas production rate ranging ∈ [0, 5] MMscf/day

I Breakeven point = 10% return on investment assuming 20year plant life

I Base case plant capacity = 1MMscf/day


Product specifications

Pipeline quality CNG, compressed and stored at 225bar, suitablefor transportation use (e.g., Metro buses).

From Interstate natural gas - Quality, specifications, andinterchangeability published by the Center for Energy Economics,University of Texas, Dec. 2004:

1. < 2 % CO2 by volume

2. < 7 lbs water/MMscf

Question for report 1: are these specifications consistent?


Process alternatives

Three processing alternatives are to be evaluated at the preliminarydesign stage:

1. Gas dehydration, followed by CO2 removal;

2. CO2 removal followed by gas dehydration;

3. Simultaneous CO2, water removal.

Main sorbents: Monoethanolamine for CO2 removal (MEA);diethylene glycol (DEG) as desiccant;

Both are available in ChemCAD


MEA plant - CO2 removal

From: Gas Purification, 2nd ed., F. C. Riesenfeld and A. L. Kohl,Gulf Publishing, (1974).


MEA absorber/regenerator data - CO2 partial pressure



MEA absorber/regenerator data - MEA/water VLE



MEA absorber/regenerator design notes

1. MEA normal boiling point: 171oC

2. 1 to 2 moles solvent/mole acid gas

3. 10 to 30 wt.% MEA in water

4. heat of reaction = 825 BTU/lb CO2

5. high pressure absorber, low pressure regenerator

6. packed or tray columns


Glycol plant - water removal

From: Gas Purification, 2nd ed., F. C.Riesenfeld and A. L. Kohl,Gulf Publishing, (1974).


Glycol plant - absorber design

From: Gas Purification, 2nd ed., F.C. Riesenfeld and A. L. Kohl, GulfPublishing, (1974).

I 1 theoretical tray

I 0.25% tray efficiency

I glycol concentration set byproduct gas specifications


Glycol plant - regenerator design

From: Gas Purification, 2nd ed., F.C. Riesenfeld and A. L. Kohl, GulfPublishing, (1974).

I Max (decomposition) DEGtemperature = 329oF


Combined MEA-Glycol plant



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 poweroutages and must be able to restart after an arbitrarily longpower outage;

6. Evaluate CO2 disposal options;

7. Cooling water must be recycled on-site.


Design report 1

1. Literature review of gas treating processes relevant to ourMEA/DEG system;

2. Reaction chemistry of MEA and CO2; VLE of DEG/watersystem;

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)


Design report 2

Initial material and energy balances for the first process option(dehydrate then scrub CO2;

1. Isothermal, single stage absorber at 25C; assume ∆P = 0,compute pressure, DEG lean flow and composition, inlet andoutlet gas compositions;

2. DEG regenerator single stage calculation; determine operatingtemperature and waste gas stream flowrate; consider addingadditional stages if desired separation is not achieved;

3. Isothermal, single-stage MEA absorber; compute pressure,MEA lean flow and composition, inlet and outlet gascompositions; consider adding additional stages if desiredseparation is not achieved;

4. Isothermal, single-stage MEA regenerator; set pressure, anddetermine 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.Raymond A. Adomaitis Spring 2010 ENCH446 Project 1

Design report 3

Primary goal: integrated process design with absorber/regeneratorenergy integration.

1. Continue refinement of column designs, calculating number oftrue stages;

2. Create a list of additional equipment to be designed, e.g., finalgas compressor, gas storage facilities, MEA and DEG make-upstorage, etc.

3. Create a list of potential safety and environmental issues to beexamined.


Design report 4

Primary goal: initial ChemCAD simulation and economic analysis

1. Set up initial ChemCAD simulation; for the report include aprocess flow diagram and the process stream compositions, allgiven in mole/min, for your “final” hand-calculated designand the preliminary ChemCAD simulation;

2. Prepare at most a single-page discussion of the differencesfound; give reasons for any major differences;

3. Prepare a single-page summary of the economic basis to beused for estimating equipment and operating costs, projectreturn on investment;

4. Create a to-do list of all secondary equipment designs stillneeded and outstanding environmental and safety issues to beconsidered (one page max).


Design report 5

Primary goal: assess process profitability potential

1. Full process ChemCAD simulation, including

1.1 energy integration1.2 all process compressors and pumps1.3 on-site steam generation and cooling water processing

2. Process economic analysis, breaking down the 1 MMscflandfill 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 costs2.4 ROI

3. Group plans for CO2 use/disposal


Subproject 1 final design report

I Title page with team members, table of contents

I 1/2 page executive summary, 1/2 page plot of ROI vs. MMscflandfill gas

I One page of conclusions, including engineering design findings,economics of the process, safety and environmental issues

I One page of engineering design assumptions, basis for design,in outline form

I One page describing the economic basis used for the ROIcalculations

I A clear, single-page process flowsheet with equipment andstreams labeled

I Stream summaries, including only temp (K), pressure (bar),and component flows (mol/min)


Subproject 1 final design report, continued

I Brief equipment summaries (tabular form, only), indicatingtemperature, pressure, important design parameters (e.g.,trays, compressor stages), equipment capital cost andoperating cost

I One page summarizing differences between hand andChemCAD calculations

I Summary of engineering analysis

I Summary of economic analysis


Subproject 1 presentation

A 4 minute presentation, in powerpoint or pdf, brought on a usbdrive:

I That contains no background information

I Presents the group’s best estimate for the project ROI as afunction of MMscf landfill gas flow

I Shows the final design process flowsheet

I Summarizes feed, product, and waste streams

I Summarizes only major equipment designs/costs

I Describes any unique design features


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