Incinerator Package

 

 

 

PURPOSE

The purpose of this document is to define the process design and condition for Incinerator of the Bitumen Production Plant.

 

The proposed bitumen blowing unit is designed to convert straight run vacuum column bottom from crude unit of refinery into marketable paving asphalt.

This project has been defined for basic / detail design of bitumen plant at refinery for production of bitumen 60/70 grade in base and 40/50 and 85/100 grades of bitumen with different rates.

The duty of this plant is heating and blowing of refinery produced vacuum bottom and vacuum slops as feed. The plant capacity is 15000 bblpd.

 

Unit introduction

The thermal incineration system consists of a vertical natural draught refractory-lined combustion

Chamber and an integral refractory-lined stack discharging at 76m above grade. The incinerator and stack are supported by an external derrick, designed and supplied by Contractor. The incinerator combustion chamber is mounted on concrete piers to allow access to the burner which is mounted in the floor of the combustion chamber and arranged axially for firing upwards. The proposed incineration temperature is 875 °C to achieve the required destruction efficiency for CO which is higher than the 750 °C mentioned in the specification. The waste streams from units     KD-1001 A/B and V-1001 A/B are introduced through nozzles in the incinerator combustion chamber. The burner uses natural gas at start-up to heat the incinerator to the normal operating temperature and to maintain the temperature in case of variations in the waste stream flow rate and/or composition.

Part of the combustion air is introduced through the burner while the remainder is introduced directly to the combustion chamber under natural draught.

A fuel skid is provided with all necessary valves and all required instrument devices for control of fuel gas flow and pressure and automatic control of burner and pilot. A hazardous area control panel with lamps and pushbuttons for local operation is provided on the fuel skid.

Hot surfaces on the incinerator and stack in accessible areas will have personnel protection in the form of mesh. An aluminium windshield is provided on the stack and incinerator combustion chamber to maintain a hot shell to avoid dew point corrosion.

Products of combustion are discharged to atmosphere at high temperature.

 

 

 

basis of design

Because of varying gas composition and characteristics and supply temperature, there are two cases considered as incinerator sizing base. For Low Temp the combustible content of the waste gas is assumed to be at minimum with only methane (CH4) to represent CxHy and minimum concentration of CO with no hydrogen or hydrogen sulphide.  The gas is supplied at the minimum temperature of 120 °C. For high temp the combustible content of the waste gas is assumed to be at maximum with alkanes from C1 to C6 to represent CxHy and maximum concentration of CO, hydrogen and hydrogen sulphide.  The gas is supplied at the maximum temperature of 200 °C. For both cases the oxygen concentration is assumed at minimum which is worst case for incinerator design, determination of combustion air flow and burner sizing.

The incinerator is designed to burn the specified waste stream as follow:

 

Waste Gas Specification

Case

Low Temp Design (%Vol)

High Temp Design (%Vol)

Low Temp Normal (%Vol)

High Temp Normal (%Vol)

O2

5.00

5.00

5.00

5.00

CO

0.50

1.00

0.50

1.00

CO2

8.50

9.30

8.50

9.30

C1

2.00

0.33

2.00

0.33

C2

0.00

0.29

0.00

0.29

C3

0.00

0.51

0.00

0.51

C4

0.00

0.29

0.00

0.29

C5

0.00

0.15

0.00

0.15

C6

0.00

0.43

0.00

0.43

N2

75.00

73.55

75.00

73.55

H2O

9.00

9.00

9.00

9.00

NO

0.00

0.00

0.00

0.00

SO2

0.00

0.00

0.00

0.00

H2

0.00

0.10

0.00

0.10

H2S

0.00

0.05

0.00

0.05

SUM

100

100

100

100

Low Heat Value (kJ/kg)

610

1720

610

1720

MW (kg/kmol)

28.4

29.2

28.4

29.2

Temperature (°C)

120

200

120

200

Flowrate (kg/hr)

16183

16183

14712

14712

Waste gas Pressure, barg

0 ~ 0.5

 

 

 

incinerator operating conditions

 

  

Operating Temperature

875 ºC

Pressure

ATM

Retention Time

Min.1s

Design Temperature

Incinerator Shell design temperature

min 200 ºC – max 343 ºC ( note 1)

Incinerator refractory lining

1700 ºC

Design Pressure

3.5 barg

    

 

Note 1: The design temperature for the incinerator vessel shell in normal operation has to be maintained above the gas dew point temperature and below the point of at which carbon steel loses structural strength.

 

 

 

Utilities Specification

Fuel Gas

Fuel gas is used to heat the system to its design operating temperature.

Refinery Fuel Gas is available as below:

 

Composition

 

Value

Methane

Vol%

69.36

Ethylene

Vol%

0.15

Ethane

Vol%

7.43

Propylene

Vol%

1.02

Propane

Vol%

3.45

n-Butane

Vol%

0.56

i-Butane

Vol%

0.52

Butylene

Vol%

0.19

n-Pentane

Vol%

0.05

i-Pentane

Vol%

0.14

Hydrogen

Vol%

15.15

Pentene

Vol%

Trace

H2S

Vol%

0.6 (Note 1)

CO2

Vol%

1.37

 

Note 1: H2S reaches 3 vol% at the emergency conditions. 

 

 

 

 

Steam distribution

Steam specification at unit battery limit is as followes:

 

DESCRIPTION

LOW PRESS.STEAM

Press .     min . bar (g)

4.0

        norm. bar (g)

4.5

      max. bar (g)

5.0

Temp.      min   °C

150

 norm. °C

155

max  °C

159

 

 

Air system

DESCRIPTION

 

INSTRUMENT AIR

Quality

 

Oil Free

Supply Temp, °C

(Norm/Des.)

45/85

Supply Press., barg

min

4.5

 

norm

6.5

 

Max

7

Dew Point

max

-20

 

 

 

Utilities

Waste Gas

Temp.                                                       120-200 °C

Press.                                                       0 ~ 0.5 barg

 

Combustion Air

Temp.                                                          -1, +47 °C

 

Fuel Gas

Fuel Gas                                         As Table Section 3.2.1              

Temp.                                                            Amb.

Header Pressure                          3-3.5 barg (At incinerator BL)

Net Heat Value                                         48.11 MJ/kg  

Hydrogen Sulphide                 0.6 %Vol (Emergency case: 3%Vol)

 

 

 

 

 

 

 

 

UTILITIES CONSUMPTION

 

Fuel Gas

 

Flowrate,

Pilot fuel consumption, Kg/hr

4

Main Burner Flow @ stand-by, cold Amb. air, Kg/hr

260

Main Burner Flow @ stand-by, hot Amb. air, Kg/hr

218

Main Burner Norm flow, Kg/hr

45-348

Main Burner Max flow, Kg/hr

358

Steam

Max (During Purging), Kg/hr

5000

Instrument Air

Flame Scanner, STD m³/hr

6.78

Dilution air damper, lit

2 lit per stroke

Control valve, STD m³/hr

1 X 0.24

Actuated valve, lit

6 x 0.7 lit per stroke per valve

 

ELECTRICITY

230 Volt/ 50 Hz/ 1 phase

 

 

Fuel Gas

 

Flowrate,

Pilot fuel consumption, Kg/hr

4

Main Burner Flow @ stand-by, cold Amb. air, Kg/hr

260

Main Burner Flow @ stand-by, hot Amb. air, Kg/hr

218

Main Burner Norm flow, Kg/hr

45-348

Main Burner Max flow, Kg/hr

358

Steam

Max (During Purging), Kg/hr

5000

Instrument Air

Flame Scanner, STD m³/hr

6.78

Dilution air damper, lit

2 lit per stroke

Control valve, STD m³/hr

1 X 0.24

Actuated valve, lit

6 x 0.7 lit per stroke per valve

 

 

 

Emissions

 

The following emission limits are guaranteed:

 

NOx (as NO2)             350 ppm (v)

CO                               120 ppm (v)

 

The above emissions are corrected for dry gas with 3% oxygen.

The estimated SO2 concentration in incinerator compounds depends on the concentration of sulphur compounds at the inlet and fuel gas is not affected by incinerator design or operation. With 3% H2S in fuel gas at emergency condition, the estimated SO2 concentration will be 2000 to 4000 mg/Nm3 of SO2 in stack gases but based on the gas composition in the table in the design calculations (normal operation), estimated concentration of SO2 is 0.03% by volume (300 ppmv), say 900 to 1000 mg/Nm3, based on fuel gas with 0.6% H2S, 40 ppm SO2 and 500 ppm H2S in waste gas. Just In the case of normal operation (0.6% H2S in fuel gas and 500 ppm H2S in waste gas), the amount of SO2 emission will be in the range of allowable limits of DOE pollutants consideration. Since SOx emissions are entirely dependent on the S content of fuel and waste gas streams, any variation of specified amounts of sulphur in the waste gas and fuel gas are not guaranteed. Compliance with other emissions limits is neither implied nor guaranteed.