The effective production of sugar from either sugar cane or beet is heavily dependent on the availability of a reliable steam supply. Many sugar processing plants are located in semi remote areas. Steam is not only required for the evaporation of sugar crystals in these semi-remote locations, it is also necessary for power production to supply electricity to the site and sometimes for the local community that supports the mill.
Sugar processing produces vast amounts of organic biomass waste in the form of bagasse. Traditionally boilers played an important role in disposing of this waste stream by incinerating the bagasse. In fact, boilers were once deliberately designed to achieve relatively low efficiencies to ensure high bagasse incineration rates. Some boilers even incorporated a flue gas bypass facility to enable variable control of incineration rates. However, the increasing value of green power has shifted the emphasis from bagasse incineration to maximizing steam production for electricity generation purposes.
Bagasse typically has a relatively high moisture content and burning it requires a specialized application of grate firing technology to enable suspension firing.
Design Boiler have had a long association with the sugar industry and have carried out numerous diagnostic and design investigations involving depleted performance and combustion issues on sugar refinery boilers. We have also resolved multiple circulation issues on bagasse fired boilers.
Areas of speciality which we have provided exclusively to the sugar refining sector include:
Downcomer Instability/ Circulation Defects: A boiler that had operated at a sugar refinery for a number of years was prone to frequent superheater priming. The problem appears at specific threshold loads. Design Boiler were engaged to investigate the problem. A computer model of the boiler circulation was setup to assess the possibility that the problem was associated with poor circulation. The results of the circulation modelling indicated that the Downcomer flow velocity was below optimum limits prompting a need to investigate the possibility that the priming problem was caused by Downcomer Instability . It was also noted that there was a distinct disparity in water level between either side of the steam drum. Drum level disparities are a common indicator of Downcomer instability. An in-depth analysis of the Downcomer flow identified a problem with the allocation Downcomer tubes. Essentially it was caused by the positioning of the drum baffle plate which allocated too many downcomer tubes in the main convection bank. The baffle plate was re positioned and the priming and drum level disparity problem were immediately resolved. A more detailed case study on a similar problem can be found here.
Sagging Furnace Roof Tubes/Circulation Defects: Throughout its entire operating life, the roof tubes on a boiler installed in a medium sized sugar refinery was prone to sagging. The plant operators had tried several strategies to address the problem including installing a support beam above the roof and fitting supporting rods between the roof and the beam. However, the condition of the tubes continued to deteriorate to an extent that they required replacement. Design Boiler were engaged to investigate the possible cause of the problem and see if there was any practical way of fixing the problem. The boiler was subjected to a circulation analysis using Design Boiler’s in house boiler modelling software. The circulation analysis identified a major defect in the circulation configuration that was causing the problem. Effectively the heated length of the front wall that was producing the driving head for the roof circulation was insufficient. A strategy involving a mud drum baffle was derived to boost the driving head across the front wall / roof circuit and was tested using the circulation model. The baffle was fitted into the mud drum and proved to provide an effective resolution to the sagging roof tube problem. More details on this problem are contained in a case study which can be found here.
Combustion Problems: Design Boiler have been engaged to address major combustion problems on biomass / wood waste grate fired boilers. Poor combustion within grate fired boilers burning wood waste can cause a raft of operational problems including:
(a) back end metal fires in air heaters and dust collectors,
(b) high particulate emission issues,
(c) furnace pressure control problems;
(d) an inability to achieve the rated boiler mcr output; and
(e) difficulties achieving superheater steam temperatures.
We have addressed combustion problems on a number of biomass/wood fired boilers by modifying combustion controls and redesigning the secondary air system. A more detailed case study on the impact of poor waste wood combustion on raising particulate emission levels can be found here.
High Temperature Drier /Swirl Burner Technology: Our contribution has been fundamental in the development of cost-effective technologies to increase boiler output and boost the thermal efficiencies of existing bagasse fired boilers. We have provided considerable boiler design support to the Sugar Research Institute in its development of the high temperature bagasse drier/ swirl burner technology. .
Boiler Efficiency and Acceptance Testing: Our engineers have been involved in plant efficiency and boiler acceptance testing for the purposes of demonstrating boiler plant performance for contract verification purposes. We are also very familiar with either ASME, ISO or British Standards acceptance testing methods for both fired and HRSG boilers.
Design Boiler’s broad range of specialised boiler design and computer modelling resources are available to support boiler problems in the sugar refining sector.
