Own Use Gas
description
Transcript of Own Use Gas
Copyright © 2005 Advantica Inc. (USA Only) and Advantica Ltd. (Outside USA). All rights reserved by the respective owner.
Own Use Gas
Review of 2000 Model
Overview
• Summary of 2000 OUG project• Information and data• Model overview• Original assumptions and recommendations• Pre-heater energy losses overview• Uncertainties
• Shipper concerns• Possible solutions• Initial recommendations
• Seeking a collaborative approach to estimation of OUG
Shrinkage
• Based on overall throughput• Leakage from low pressure network• Own Use Gas for pre-heaters• Theft of Gas
• Advantica carried out study into the estimation of OUG in 2002 using data from 2000
The methodology and model
• Typical PRS layout
Information and data
• All NTS and LTS sites using pre-heating • Flow, inlet, outlet pressure, exit temperature • Data unavailable for some LDZs
• Basic pre-heater meter readings from ~80 sites• Generally poor quality
• Total system throughput• Pre-heater survey data
• Site name, location etc• Operational measurements/limits
• Ground temperatures – from work on statistical analysis of national and regional temperatures (2000)
Information and data cont…
• The percentage of sites from which suitable data was acquired was:
• NTS: 64% - missing data for West Midlands LDZ North Wales LDZ
• LTS: 34% - missing data for East Anglia, North West, and Scotland LDZs
• Giving an overall site coverage of 42% for hourly data over the year 2000.
• Over 3Gb of data was received, filtered and processed
The methodology and model
• The method is based around the equation
• Where:• is the mass flow rate (kg/h),
• is the rise in temperature in the heater (deg C),
• is the specific heat capacity of the gas (kJ/kg/K),
• is the efficiency of the heater and
• is the energy used in the heater (in kJ/h)
1
)/( CpmhkJP T
mT
Cp
P
Assumptions
• Initial gas inlet temperatures set to Ground Temperature data for each LDZ throughout the year• Outlet temperature set to 0 deg C if no set-point available
• Heaters are operational throughout the year
• Preheat requirements are assigned to each station rather than by heater
• LDZ pre-heater efficiencies are the same as NTS pre-heater efficiencies.
Assumptions cont…
• OUG usage estimated for missing LDZs using monthly scaling factor based on other LDZ data
• A range of Hot Water Bath pre-heat efficiencies used in analysis• Used a figure of 50% based on previous OUG model assumptions
and research reports
Hot Water Bath Efficiencies
• E7 Transco technical Specification for Gas Fired Water Bath Heaters Part 1 Basic Heater requirements 1993.• “Heat loss in flue gases shall not exceed 25% of gross heat input.”• “Heat losses from outer shell and associated gas pipe work shall
not exceed 1% of the declared heater output.”
• Thermal efficiency of Water Bath Heaters at Alrewas AGI MRS 403• Efficiencies under various operating conditions between 53 and
66%
• Efficiency tests on Water Bath Heaters at Coleshill AGI MRS I 2912 • Quotes range 58 to 66.5%
Typical Water Bath Heater
OHT 9.1
Surface losses 0.5-1%
Flue Losses
25-40%
Hot Water Bath Energy Losses
• A number of studies carried out in the early 80’s
• Main energy losses via flue gas in the heating process
• Surface losses account for 0.5-1% total energy lost
• Highlighted that most pre-heaters operated below design efficiency (design efficiency typically around 70%)• Typically 30-42% in flue losses
• Experiments showed this could be improved with correct burn/air flow rates
Model Validation 2000
0.00E+00
1.00E+06
2.00E+06
3.00E+06
4.00E+06
5.00E+06
6.00E+06
7.00E+06
8.00E+06
9.00E+06
1/4
/00
2/4
/00
3/4
/00
4/4
/00
5/4
/00
6/4
/00
7/4
/00
8/4
/00
9/4
/00
10/4
/00
11/4
/00
12/4
/00
Months
kW
Hrs
Towton A+B+C
0.00E+00
5.00E+05
1.00E+06
1.50E+06
2.00E+06
2.50E+06
3.00E+06
3.50E+06
4.00E+06
4.50E+06
Jan-00
Feb-00
Mar-00
Apr-00
May-00
Jun-00
Jul-00
Aug-00
Sep-00
Oct-00
Nov-00
Dec-00
Months
kWH
rsTowton
OUG Usage
Efficiency Total Flow (kWh)
Total OUG (kWh)
% OUG
100% 7.13E+11 4.03E+07 0.0057
70% 7.13E+11 5.76E+07 0.0081
60% 7.13E+11 6.72E+07 0.0094
50% 7.13E+11 8.07E+07 0.0113
40% 7.13E+11 1.01E+08 0.0141
30% 7.13E+11 1.34E+08 0.0188
Uncertainties
• Pre-heater efficiencies
• Control regime of pre-heaters
• Ground temperature assumptions
• Scaling factor to estimate pre-heater consumptions for LDZs with missing data
Uncertainties cont…
• 95% confidence intervals attributed to missing data
• 0.0102% (assuming a heater efficiency of 50%).
and
• 0.0137% (assuming a heater efficiency of 50%).
• Including variation in efficiency of the pre-heaters, the actual OUG percentage figure may lie between:
• 0.0073% (with 70% efficiency) and
• 0.0229% (with 30% efficiency)
Recommendations 2002
• Better estimation of pre-heater efficiencies
• Include control strategies for pre-heaters
• Improve mapping of sites with pre-heat and incomplete telemetry to similar sites
• Extend metering of pre-heaters to improve model validation
Summary of Shipper Concerns
• Original study is 4 years old, data is 6 years old and likely to be out of date
• Limited data impacts the accuracy of the model
• Real pre-heater efficiencies are much lower than quoted in report
• Insufficient meter readings to properly validate the model
Solutions – Age of the model
Investigate
model sensitivity
Large variation
in % OUG
Model suitable
for other years
partial analysis
using 2005
data for 3-4 LDZs
Small %OUG
variation
Review findings,
potentially do
remaining LDZs
Solutions – impact of missing data
Investigate
model sensitivity
No - need
improvement plan
partial analysis
using 2005
data for 3-4 LDZs
Has data
quantity/quality
improved for
key variables?
Review findings,
potentially do
remaining LDZs
Solutions – pre-heater efficiencies
• Summarise findings of previous pre-heater efficiency trials• Covers various pre-heater efficiency tests • Provides evidence of typical pre-heater efficiencies from the
output of the experiments conductedProvides information needed to carry out on-site efficiency tests
• Carry out pre-heater efficiency tests• Requires on-site monitoring equipment • Timeline significant as tests require variety of operating conditions• Use efficiencies to validate the model• Test pre-heaters makes/models that are most commonly installed
• Use OUG model to calculate efficiencies
Alternative solution – use model
Site flows,
pressures,
temperatures
Pre-heater
metering
Compare OUG
vs consumption
Determine Hot
Water Bath
efficiency
Use model to
calculate OUG
Solutions - validating the model
Site flows,
pressures,
temperatures
Pre-heater
metering
Determine Hot
Water Bath
efficiency
Compare OUG
vs consumption
Use model to
calculate OUG
Initial Recommendations
• Model sensitivity analysis
• Summary of pre-heater efficiency work• And/or• Validate model by carrying out pre-heater efficiency tests
on sites with good telemetry and metering
• Determine pre-heater efficiencies using wider sample of meter readings assuming model correct
• Report findings and present back to forum