Caustic Recovery Using Membrane Filtration

Food and beverage processors that use dilute caustic solutions for cleaning process equipment have shown increased interest in recovering the used caustic. The primary reason is that the price of caustic has increased significantly in the past year or so. Membrane filtration technology can be used to remove suspended solids (clarify with microfiltration) and/or dissolved solids (purify with nanofiltration) from these used caustic solutions. These treated caustic solutions are suitable for reuse within the processing plant as cleaning solutions. While an end-user’s specific process, performance, capital and operating cost parameters require pilot testing and process design evaluations to determine the economic viability of caustic recovery, the existing body of information from commercial and process development work allows for an evaluation of a “typical” caustic recovery application. Paper published with permission.

Update on Huanglongbing Progression and Current Research in Florida

Citrus Huanglongbing (HLB) or citrus greening disease has been in Florida since at least 2005 and has spread to all of the citrus producing regions. The Asian citrus psyllid (Diaphorina citri) is the insect that transmits the suspected causal bacterium which is tentatively named Candidatus Liberibacter asiaticus. Symptoms of the disease are first the yellow shoot (huanglongbing) and the development of the blotchy mottle symptom in the leaves. Mineral deficiency symptoms are often found on infected trees and may mimic normal deficiency symptoms. Fruit on infected trees may be small and lopsided and may abscise prematurely and therefore productivity is reduced. Tree decline eventually occurs. The suspected causal bacterium has not been obtained in pure culture and a polymerase chain reaction (PCR) test along with symptoms, is the only way to verify infected trees. All citrus cultivars appear susceptible. Current management strategies are chemical and biological control to reduced psyllid populations, inspections for infected trees and removal of infected trees to reduce the available pathogen inoculum. Current research on psyllid control, psyllid transmission, symptomology, detection, culturing the causal agent, development of new detection methods, alternative hosts of the psyllid and the causal agent, physiology of the disease, resistant or tolerant cultivar development and more is discussed. HLB is a major problem for citrus production and often limits commercial production. Paper published with permission.

Florida Citrus Processing Facility Takes Leadership Role in Conducting a Facility Wide Insulation Energy Assessment

After attending a National Insulation Association (NIA) presentation on Insulation, The Forgotten Technology at ASME’s 2007 Citrus Engineering Conference, a major citrus processing facility in central Florida decided to examine the condition of their insulation systems and determine the potential energy savings that could be achieved by replacing or repairing their existing insulation. Facility management had previously examined abbreviated energy assessments for above and below ambient systems but had not commissioned an extensive below ambient assessment. Due to the age, complexity, and recent weather history of the facility (i.e. hurricanes), management wanted to examine the condition of the thermal insulation systems and any effect its condition may have on the refrigerant piping and overall system operating costs. The assessment process was more complex than originally anticipated and yielded a wealth of meaningful information. The facility covers about 50 acres and consists of a variety of production, warehousing, and shipping/receiving facilities. It is estimated that the facility processes roughly one billion pounds of oranges and grapefruits each year into juice and juice products. Refrigeration for the site is provided by a large and complex ammonia refrigeration system. A total of eight “engine rooms” house electric driven compressors and associated vessels and equipment. Installed capacity is roughly 3,000 tons of refrigeration with an estimated energy cost on the order of $2 million per year. The ammonia refrigerant is distributed throughout the site via a complex and interconnected refrigerant piping system. The total refrigerant charge in the system is roughly 300,000 lbs of ammonia. Paper published with permission.

Sulfur Emissions Reduction Project at Southern Gardens Citrus

Southern Gardens Citrus and the Florida Department of Environmental Protection (FDEP), in a cooperative effort at the Clewiston citrus processing facility, reduced SO2 emissions by 80% and particulate matter emissions by 73%. This project also reduced costly diesel fuel use by 25%, increased citrus pulp feed mill operation efficiency, and saved the company more than $4 million a year. Paper published with permission.

Future Trends in Ammonia Refrigeration Design

While many citrus processing plants already enjoy the excellent benefits of ammonia refrigerant, its continued use must be effective and safe. This paper explores the design and application trends that will shape the use and application of ammonia in central refrigeration systems in the future. Paper published with permission.

Current Challenges of Mechanical Harvesting Technology for Citrus

In recent years, the use of citrus mechanical harvesting machines has significantly increased in Florida. In 2007, the total acreage of citrus orchards harvested by mechanical means was 14,420 ha (35,633 acres) which is about 7% of the total citrus production area in Florida up from only 1% in 2004. In addition, the Florida Department of Citrus initiated a program to register abscission compounds for citrus. Abscission compounds reduce the amount of force required to detach the fruit from the stem, making it easier to harvest. According to the plan, the abscission compounds will become available by 2011. It is expected that the trend in adoption of mechanical harvesting machines will accelerate if abscission compounds become commercially available. In addition to fruit, mechanical harvesting machines cause removal of leaves and branches, some percentage of which end up to the harvested load. Currently, the amount of trash, i.e. leaves and branches, in the mechanically harvested citrus load is considerably higher than when harvested by hand and is a major concern for juice processors. While these machines reduce the cost of harvesting and allow citrus growers to be more competitive in the global market, the large amount of fruit they can harvest in a short time can cause issues with load allocations. The implications resulting from these technologies are discussed in this paper, as well as initial results from a computer vision technique to quantify the trash in the load. Paper published with permission.

Converting Citrus Waste to Ethanol and Other Co-Products

Conversion of citrus processing waste (CPW) generated during juice production into value added co-products is an important aspect of the juice industry as it offers a solution to waste disposal issues. Currently the practice of drying citrus waste to produce citrus pulp pellets (CPP) for use as cattle feed is profitable. However, until the recent rise in value, CPP value was marginal and often did not meet production costs. Another concern has been volatile organic emissions during CPP production. Only one third of the residual peel oil present in citrus waste is recovered during CPP production with most being vented to the atmosphere during drying and is a growing environmental concern. Improvements in limonene recovery and development of alternative value added co-products obtained from CPW could add substantial value to the citrus crop. For current CPP production, the energy required to dry CPW is the major cost involved and approximately 25 lb of limonene are obtained per ton of CPP produced. Since limonene is recovered during evaporation/concentration of pressed peel juice using a waste heat evaporator, little additional cost is associated with limonene recovery. The concentrated citrus molasses produced may be added back to the press cake or fermented to make ethanol, but only contains a third of the sugars in CPW that are fermentable by conventional yeast. While utilizing the entire CPW stream for ethanol using hydrolysis and fermentation is more involved, three times the amount of ethanol can be obtained compared to using press liquor alone. Most of the limonene must be removed as it inhibits fermentation. In the process developed 85–95% of the limonene contained in CPW can be removed and recovered by steam stripping. This greatly reduces concerns associated with the release of volatile organic compounds (VOCs) during processing of CPW and the limonene recovered has a value equal or greater than stripping costs. Using a mixture of enzymes and yeast, the CPW is then hydrolyzed and fermented simultaneously to produce ethanol followed by distillation to remove and recover the ethanol. Enzyme costs to hydrolyze and liquefy CPW have been reduced to less than a dollar per gallon of ethanol produced, and the economics for distillation are still being optimized. The distillation residues contain half the solids of raw citrus waste that can still be utilized as a CPP product. Other uses for the residues such as incorporation of the pectic materials into building product and paper additives, and ion exchange materials for wastewater remediation are also in development. Paper published with permission.