In 1970-1971 the utilities in Texas were planning on installing gas fired units almost exclusively in the 1975-1990 period, except for a few lignite units early in the period and a few nuclear units late in the period. Today the utilities are not planning on installing any future gas fired units but are planning on the bulk of their future generating facilities to be coal/ lignite fired or nuclear. This change in planning is estimated to result in an increase in investment of approximately $15.6 billion based on todays costs with no consideration given to escalation.

The conversion of the existing and committed gas fired units to oil is estimated to cost $2.0 billion over and above the investment required for new generating units based on 1975 planning. This conversion investment would increase the bus bar power costs by approximately 2.0 mills/kWh for capital charges only based on 1975 expected generation.

The replacement of the existing and committed gas fired boilers with coal fired boilers is estimated to cost $14.8 billion over and above the investment required for new generating units based on 1975 planning, and increase the bus bar power costs by 14.5 mills/kWh based on expected 1975 generation.

D - MANUFACTURING CAPABILITY

The magnitude of the effort to convert gas fired boilers to oil firing or

(1) Does not include conversion costs of units already converted or in the process of being converted to oil firing.

to add coal firing capability to plants in Texas would have a substantial impact on the industry. The manufacturers of steam generating equipment could only engineer and fabricate a small percentage of the required conversions from gas to oil and a still smaller percentage of the required coal fired boilers in any one year. This work load would be imposed on top of their normally expected level of business.

The US Boiler Manufacturers have a capability of producing boilers equivalent to about 25,000 MW per year. All of this production capacity could not be dedicated to making boiler conversions for the utilities in Texas. If 15 percent of this capacity was directed to converting units for Texas, approximately 3,750 MW per year could be converted. This rate would require about 10 years to convert the Texas units from gas to coal firing. The conversion to oil firing could be made in a shorter period of time except for the need to restrict the percent of capacity removed from service in any one year to assure meeting load requirements.

The manpower required to engineer and construct the conversions on top of the engineering and construction requirements for new generating units in Texas would be substantial and would have a significant effect on the schedules which could be maintained.

E

CONVERSION OF GAS FIRED UNITS TO BURN NO. 5 OIL CONTINUOUSLY

A steam generating unit designed for gas firing cannot successfully burn fuel oil continuously without significant modifications to the unit. Additions must also be made to the plant to permit the receipt, transport, storage and heating of oil. This section reviews the problems encountered in attempting to burn oil continuously in units designed for gas firing, the modifications required to the boiler and plant to accomplish the conversion and the time schedule required to complete the conversion.

1- Burning of Oil in a Boiler Designed for Gas Firing

The criteria used to design a boiler for gas firing generally precludes the firing of oil continuously in that boiler. The main problems experienced with oil firing are discussed as follows:

7

a - The increased furnace absorption due to the radiant
characteristics of an oil flame may result in an
excessive heat flux in the furnace wall tubes. It
may be necessary to reduce load about 20 percent to
burn oil continuously in a boiler designed for gas
firing.

b- The increased furnace absorption results in a lower
gas temperature entering the superheater and reheater
surfaces with oil firing as compared to gas firing.
The superheater and reheater steam temperature would
be lower with oil firing resulting in a loss in unit
efficiency and capacity.

c - Oil firing leaves a deposit on the tubes in the convection

d

e

Soot

pass which would ultimately result in pluggage.
blowers are required to keep this surface clean.
Regenerative type air heaters are generally used on modern
day boilers. Boilers designed for gas firing have close
spaced surfaces not conducive to firing fuel containing
ash. In time these surfaces would plug. Boilers equipped

with tubular air heaters would require air heater replacement.
Economizers on gas designed boilers are equipped with

closely spaced fins to obtain a maximum heat transfer in

a minimum space and at least cost. This spacing is too

close for continuous oil firing and would result in

pluggage. It would be necessary to modify or replace

the economizer for oil firing.

2 - Revisions Required to Gas Fired Boilers to Burn Residual Oil Continuously

A number of revisions generally must be made to gas fired boilers to make them acceptable for burning oil on a continuous basis.

are tabulated below:

a The installation of oil burners.

The required revisions

b

The addition of gas recirculation fans and associated
ductwork are generally required to reduce the heat

absorption in the furnace, increase superheater and
reheat temperatures and lower nitrous oxide emissions.

c The addition of sootblowers in convection pass and air
heaters to keep the surfaces clean.

Provisions to waterwash the air heaters to remove deposits which cannot be removed by sootblowers.

Modifications to control system to insure safety and permit automatic operation with oil firing.

Additional superheat and reheat surfaces may be required

to maintain the design temperatures.

Replacement of the air heater baskets with wider spaced
surfaces to reduce the possibility of pluggage. This
surface change would result in a slightly poorer efficiency.

Replacement or modification of economizer to increase

spacing.

This revision would probably result in slightly poorer efficiency.

The sulfur content in oil may require the use of steam coil

air heaters to minimize air heater corrosion.

The addition of an ash hopper to collect bottom ash.

The replacement of the forced draft fans and the addition

of induced draft fans may be required.

Further revisions would be required to the boiler to burn

a high sulfur residual oil:

1)

Provisions to add metallic oxides of magnesium and
alumina to the oil to modify the ash composition,
thereby mitigating the corrosive attack of deposits
on boiler heating surfaces.

2) The addition of an electrostatic precipitator or
scrubber to reduce particulate emissions from the
boiler to meet EPA emission regulations.

3) An absorber must be installed to remove SO2 from
the stack gases to meet EPA emission regulations.

Revisions Required to a Gas Fired Plant to Burn Residual Oil

Burning of oil requires revisions to many of the plant facilities as well as the boiler. These additions are as follows:

a

b

Provisions for receiving, storing and pulverizing

limestone for use in the absorbers.

Provisions to store sludge effluent from the absorbers.

C - The installation of a ground supported chimney to
release stack gases at a reasonably high level so as

to meet EPA ambient criteria.

d - Arrangements must be made at the plant for receipt of
oil by truck, rail, ship, barge or pipeline.

1) Provisions for receipt of oil by truck or rail.

a) A 600 MW plant burns 25,000 barrels of

oil per day at full load.

b) To support the plant approximately 200 truck
loads would be required per day if the oil is
delivered by truck.

c) Rail delivery would require the use of approximately

40 cars per day.

2) Delivery of oil by water

a) Docking facilities at the plant would be required

to handle the vessel with a draft of approximately
40 ft or provisions made for receiving barged oil
from an unloading facility.

by A storage facility at the point of unloading of
approximately 350,000 barrels would be required.