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.
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:
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.
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 |
|
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)
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 |
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.
