Bagasse-fired boiler systems

TIBS can offer specialist suspension firing systems to support the finer by-products produced by modern sugar cane milling processes. We have converted many pile burning boilers into suspension firing boilers, so that the finer raw material stays within the boiler combustion chamber, to ensure no combustible material passes through the exhaust duct system. We also have experience in retrofitting dump grate systems with steam pinhole grate systems.

CONVERSION FROM PILE BURNING TO SUSPENSION FIRING

TIBS have developed systems to convert existing boilers from pile burning to suspension firing. Conversion to suspension firing improves combustion, increases steam output, reduces refractory maintenance and increases boiler efficiency. Modern sugar cane preparation produces a finer bagasse which burns well in suspension.

We have carried out in excess of 30 conversions from pile burning to suspension firing world-wide and always conduct a boiler plant feasibility study prior to any modifications. This study involves a design appraisal of the original equipment and a thermal study calculation to identify possible improvements in performance. The site survey confirms if the boiler is suitable for conversion and identifies other refurbishment needs onsite. Provided we are satisfied that a conversion will benefit the customer, we can then design, supply and install a tailor-made system. The TIBS suspension firing system is usually combined with either a TIBS dump grate or a TIBS steam-cleaned static grate system, the decision on which type of grate to be installed is usually dependent upon the site operational requirements. Details of the two grate options are given below:

 

THE DUMP GRATE SYSTEM

TIBS have supplied over 50 dump grate systems worldwide for new boilers as well as retrofitted boilers, when using pile firing combustion. The dump grate is a flat bed constructed of cast iron blocks through which preheated combustion air passes. The cast iron blocks are set on shafts which rotate to discharge the ash into a hopper beneath. The grate is divided into sections, which are operated in a sequence to allow de-ashing to occur. The ash is then removed mechanically with a discharge system or manually with an operator. The decision on which system to use, is based on capital expenditure versus operational requirements.

Advantages of a dump grate suspension firing system over pile burning:

1) Burns the finer bagasse now produced by improved milling techniques,
2) Operates with lower un-burned losses,
3) The boiler responds more quickly to load changes,
4) Minimal steam generation losses during de-ashing,
5) Reduction in radiation losses,
6) Lower excess air requirement which improves boiler efficiency,
7) Reduces capital & maintenance costs of refractory,
8) Cleaner operation improves the boilerhouse working environment,
9) Reduces de-ashing time and manning levels.

 

TIBS STEAM CLEANED STATIC GRATE SYSTEM

TIBS supply well proven steam cleaned static grates for bagasse suspension firing. The grate is constructed from cast iron blocks through which pre-heated combustion air passes. These blocks rest on either water tubes or air tubes for cooling. The ash is removed from the grate by steam nozzles set into the cast iron blocks above the grate level. The nozzles are operated in zones to allow the grate to be completely de-ashed with minimal disruption to the boiler firing rate. The ash is then blown to a single transverse hopper for removal.

Advantages of a static steam grate suspension firing system over pile burning:

1) Advantages of the dump grate suspension firing system over pile burning, plus
2) Higher under grate air temperatures can be used due to the cooling effect of the support tubes. This allows bagasse of a higher moisture content to be burned in the boiler
3) Ash is discharged to a single collection point for faster removal
4) There are no moving parts, therefore low maintenance