China Factory Offered 10,000 Kg/hr - 90,000 Kg/hr Multi-Fuel Boiler
1 Project Overview
SB7 is a multi-fuel boiler firing on a varying mix of natural gas and waste gases: hydrogen and carbon monoxide. The unit currently is required to produce up to 120 te/h of 44 barg steam (Super-high Pressure Steam - SPS) for the operation of the A4 Syngas/A4 Acetic Acid plants and for let-down to 17 barg steam (High Pressure Steam - HPS) for distribution to the Saltend Chemicals Park.
The emissions from SB7 are covered by The Industrial Emissions Directive (IED), the Large Combustion Plant (LCP) BREF and The Large Volume Organic Chemical BREF. The IED has an absolute compliance date of July 2021. The current NOX emissions from SB7 exceed the limit set in the IED for this type of equipment.
natural gas and waste gases fired boiler
2 Datasheet Context
The current site boiler “SB7” is used to provide steam for a variety of applications on the A4 plant and demand varies depending upon a combination of A4 plant output and imports from other Saltend Chemical Plant users.
Maximum demand is during the restart of the A4 plant either after a trip or routine maintenance. Maximum demand at this time is in the region of 90,000-100,000 kg/hr
Normal running demand is in the region of 45,000 kg/hr
Minimum demand is 10,000 kg/hr
The project looks to replace the current SB7 “like for like” as close as possible with a target design flowrate of 100,000 kg/hr.
The current SB7 uses treated condensate from the plants deaerator as its feedwater. The attached datasheet gives the properties of the feedwater after the existing feedwater treatment plant.
The project intends to use condensate as the feedstock for the replacement boiler.
The project intends to re-use the existing feedwater treatment plant however will review options for the provision of new if this offers any significant time savings during the commissioning process.
2.3 Outlet Conditions
The outlet steam temperatures and pressures are set at 382oC and 45barg based upon the requirements of the A4 plant.
The current SB7 provides the pressure control for the remainder of the plants SPS steam main, the replacement boiler will also need to provide this control. The current design pressure of this main is 53.8 barg.
The deviation of steam main pressure is set at 0.1 barg/min to protect other equipment downstream of the boiler that is unable to tolerate large fluctuations in steam pressure without causing significant damage.
One of the uses of the steam generated from SB7 is as provision of motive force on turbines therefore the maximum silica carryover is important to prevent rotor imbalance.
2.4 Fuel Options
The current SB7 burns Natural Gas and has the ability to burn both Hydrogen and CO which are both generated onsite.
The replacement boiler should have the primary fuel as Natural Gas however due to process variations the following situations can occur:
-Excess Hydrogen production – preference is to burn this on the boiler therefore the ability to burn mixtures of Natural Gas & Hydrogen in combinations from 0-100% hydrogen are requested
-Excess Carbon Monoxide production – currently the only output for excess CO is through the boiler therefore design should accommodate this.
2.5 Emission Limits
The sites Environmental permit specifies the following:
- CO 30 mg/m3
- SOx 35 mg/m3
- Particulates 5 mg/m3
- NOx 100 mg/m3
The NOx limits are dependent upon the fuel being burnt however for Natural Gas the limit would be 100 mg/m3