Optimal dairy servings to meet calcium needs: learn why two to three servings of dairy products are not enough to meet the recommended intake of calcium
There is little disagreement about the public health benefits of adequate consumption of calcium. In addition to its importance to bone health early in life, the importance of calcium to maintain skeletal integrity across the life span is also well accepted. Low dairy food intake and thus, inadequate calcium intake in youth sets the stage for skeletal fragility later in life. This can result in osteoporosis and an increased risk of bone fracture. Osteoporosis is now recognized as a “pediatric disease with geriatric consequences” since more than 90% of peak bone mass is achieved by about age 20.
Dairy products have long been recognized its nutrient-dense foods due to their high-calcium content and bioavailability, high levels of other essential nutrients and relatively low cost. Getting adequate amounts of calcium and other nutrients from dairy has also been demonstrated to help reduce the risk of high blood pressure and colon cancer. Other potential benefits of calcium that have been reported include lowering the risk for kidney stones and premenstrual syndrome. And most recently, evidence is mounting that diets high in calcium and. in particular, from calcium-rich dairy foods, are effective in enhancing body weight and body fat loss in calorie-restricted diets.
The recognition by nutrition experts of calcium’s critical role in bone health contributed substantially to the Institute of Medicine of the National Academy of Sciences” decision in 1997 to increase calcium intake recommendations for adolescents, adults and adults more than 51 years of age. Unfortunately, national nutrition surveys show that few Americans are meeting the dietary recommendations for calcium intake.
While it is difficult to accurately estimate inadequate intake of calcium, currently, only about 32% of boys and 12% of girls aged 12 to 19 years consume the recommended amounts of calcium. In adult men and women 20 years and over, only 27% and 10.2%, respectively, meet recommended amounts of calcium. In the elderly 70 years and over. only 13% of men and 4% of women meet recommended calcium intakes. Clearly. Americans’ low calcium intake is recognized as a major public health problem and is identified its one of the priority nutrition problems in the United States.
Health professional organizations agree that conventional foods are the preferred source of calcium and that low-fat dairy products are the best sources of calcium. This is because not only are they rich in calcium, they also contain essential nutrients including protein, phosphorus, potassium, riboflavin, magnesium, zinc, and vitamins A, [B.sub.12] and D. which are all necessary lot optimal bone health and human growth and development. To help children, adolescents and adults meet their calcium needs, government education programs and health professional organizations including the American Heart Association, the American Academy of Pediatrics, the National Medical Association and Health Canada encourage up to four servings of milk throughout the day.
Milk matters more
The Dietary Guidelines for Americans–2000 recommends that Americans two years and older consume two to three dairy servings per day depending on age, with each serving supplying 3001rig calcium. These recommendations are based on idealized diets that were developed for the Food Guide Pyramid (FGP) using recommended dietary patterns that include significant amounts of non-dairy calcium (250-475mg pet day) derived from recommended intakes of vegetables, whole and enriched grams, fruits and meat. However, most Americans consume substantially less than the recommended servings of whole and enriched grains, dark-green leafy vegetables, legumes and fruit. For example, the FGP recommendations of four servings of dark-green leafy and deep yellow vegetables and legumes per day, for u 2,200 calorie diet is three to four times higher than current consumption by Americans two through 70 years of age and six to 8 1/2 times higher than current consumption by children two to 19 years old.
The suggested amounts of whole grains recommended for u 2,200 and 2,800 calorie diet are, on average five times higher than what Americans currently consume. Thus, while intake of vegetables, whole grains and fruits should be encouraged, it is highly unlikely, bused on current trends in vegetable and grain consumption, that Americans will get the amount of calcium from these sources as suggested by the FGP. The result: Recommended diets may end up exacerbating low calcium retake by promoting the intake of foods that are generally poor sources of calcium and that have a low probability of consumption, while limiting the intake of excellent sources like low-fat dairy products, which have a substantially greater probability of consumption.
Researching needed servings
Given the low consumption of whole grains, vegetables and fruit by Americans, it is unclear whether the actual calcium intake in persons who consume the FGP recommended two to three servings of dairy are meeting the recommended Adequate Intake (AI) of calcium established by the Institute of Medicine. Researchers have recently evaluated the “actual” consumption of calcium from non-dairy and dairy food sources using the Continuing Survey of Food Intake by Individuals (CSFII) and the National Health and Examination Survey (NHANES), two very large nationally representative dietary surveys that monitor the food and nutrient intakes of U.S. children, adolescents and adult men and women. Their findings were highly consistent between both surveys. The chart to the right shows the ideal number of dairy servings required to meet the AI for calcium for each age group.
These results indicate that the number of dairy servings recommended by the FGP should be increased by one serving for all age groups nine years old and greater in order to reduce the likelihood of inadequate intakes of calcium. These results also raise some important considerations for dietary recommendations. It is clear that the FGP recommends idealized diets and thus, if certain foods in the diet are not consumed us suggested, then the intake of certain nutrients may be low. For example, the Dietary Guidelines for Americans 2000 suggests that certain non-dairy sources (e.g., canned fish with bones, fortified orange juice, fortified soy beverage, tofu and some dark-green leafy vegetables) could be consumed to increase calcium in the diet. In CSFII, however, less than 0.2% of the foods consumed by Americans were derived from these items as compared to 10% for milk, cheese and yogurt. These data looked at actual food consumption and suggests that adding one additional serving of dairy products might be more effective for meeting calcium needs than trying to increase non-dairy foods sources. The critical need of dairy products to meet calcium needs is underscored in Healthy People 2010: Objectives for Improving Health. It states: With current food selection practices, use of dairy products may constitute the difference between getting enough calcium in one’s diet or not.
A growing body of literature also exists indicating that consumption of three to four servings of dairy foods per day may help to lower the risk of chronic disease conditions, many of which are costly as well as responsible for considerable morbidity and mortality.
For example, a considerable body of scientific evidence exists showing the beneficial effects of dairy food consumption on reducing blood pressure. The results of clinical studies suggest that the consumption of recommended levels of dairy products can contribute to lower blood pressure in individuals with normal and elevated blood pressure. The blood pressure-lowering effect of dairy products is best exemplified by the Dietary Approaches to Stop Hypertension (DASH) clinical trials. These studies demonstrated that at low-fat dietary pattern high in fruits and vegetables and dairy products produced greater reductions in systolic blood pressure and diastolic blood pressure than either at diet high in only fruits and vegetables or at control diet low in both dairy and fruits and vegetables.
Also, rapidly emerging research provides consistent support for a beneficial effect of increased dairy foods on body weight and fat loss. Recent clinical studies have demonstrated enhanced body weight/body fat loss can be achieved when adequate calcium is provided front calcium supplements but is further enhanced by dairy foods, indicating that additional nutrients from dairy foods are playing an important role. In all of these clinical studies the dietary (dairy) calcium intake was equivalent to three to four servings of dairy products (milk, cheese and yogurt) per day as part of a reduced-calorie diet.
No relationship found between calcium intake and body size in Pima Indians
Recent research has suggested that calcium intake may have a protective effect against obesity, with calcium from dairy products providing a greater ‘anti-obesigenic’ effect than supplemental sources of calcium. Early studies in animal models and cell culture noted a physiological influence of intracellular calcium on glucose transport, lipogenesis, and lipolysis, suggesting a role for calcium in obesity and diabetes.
Since the time of the animal studies, an inverse relationship between body weight and calcium intake has been observed in multiple studies. Due to these findings, advertising campaigns and Web sites promoting milk consumption as part of a weight-loss regimen have appeared. In contrast, an extensive review of the literature by Barr concluded, “there is little support for an effect of dairy products or calcium supplementation in reducing body weight or fat mass.”
The mechanism by which calcium may modulate body weight is yet unclear, however researchers hypothesize that increased intakes of dietary calcium result in decreased levels of intracellular calcium, triggering increased lipolysis. Conversely, low intake of dietary calcium may stimulate the release of circulating parathyroid hormone and 1,25-dihydroxyvitamin D, therefore increasing adipocyte intracellular calcium, and favoring lipogenesis.
As the prevalence of obesity in the United States has increased, the calcium intake from dairy products has decreased. The Pima Indian population of Arizona is highly prone to the development of obesity and diabetes, and since 1982 has participated in many National Institute of Health (NIH)conducted studies. A large-scale dietary survey of the Pima Indians found that most adults consumed at least two-thirds of the recommended dietary allowance for calcium, suggesting that this obesity-prone population was not markedly calcium deficient.
A recent study aimed to determine if calcium intake in Pima Indians was related to body weight and adiposity. Both children and adults were studied. Sixty-five adult Pima Indians and 78, healthy, Indian children participated.
All adult subjects were healthy. Height and body weight was measured and body composition was determined using dual-energy X-ray absorptiometry. Body mass index (BMI) was calculated. Daily nutrient intake by the adults during the previous year was assessed using the Block 1998 Food Questionnaire. The analysis of this questionnaire provided an assessment of total calcium intake but did not distinguish between dairy and nondairy sources of calcium. Children’s food intake was assessed by 24-hour recall.
There were significant (P = .0001), all) positive correlations between calcium intake and energy intake in the whole group (r = 0.69), and in men (r = 0.71) and women (r = 0.65) separately. Calcium intake was not significantly correlated with percentage of energy consumed as fat in the entire group or in men (r = -. 10, P = .43; r = -0.11, P = .53; respectively); however, in women there was a significant inverse association between calcium intake and percentage of energy as fat (r = -0.35, P = .05). The correlations between calcium intake and measures of weight and adiposity in the adults were not significant (body weight, r = 0.05, P = .71; body fat, r = -0.16, P =. 19; BMI, r = 0.01, P = .97). In children, there were not significant relationships between either calcium intake or estimated dairy intake and body weight (r = 0.04, P = .73; r = 0.03, P = .75, respectively), body fat (r = 0.07, P = .53; r = 0.09, P = .43, respectively), or BMI (r = 0.03, P = .78; r = 0.04, P = .71, respectively). In multiple linear regression models accounting for sex, age, and energy intake, calcium intake was not a significant determinant of BMI or adiposity in either adults or children.
Calcium intake-kidney stones
Recent studies offer conflicting advice about dietary calcium intake and its contribution to kidney stone formation. About 80% of all kidney stones are composed of calcium phosphate or calcium oxalate. The headline for a widely-publicized, 2005 press release from the University of Texas Southwestern Medical Center of Aging recommends restricting calcium intake. A 2004 study, however, that used data from the Nurses’ Health Study II found that women with a higher dietary calcium intake had less risk of developing kidney stones.
“UT Southwestern Researchers Find Calcium Intake Contributing Factor In Formation Of Kidney Stones” reads the headline for the university press release and corresponding article at www.sciencedaily.com. The article refers to two studies. The first looks at formation of calcium oxalate stones and appears in Kidney International (November 2004). The other focuses on calcium phosphate stones and appears in the Journal of Urology (December 2005). Both conclude that “urinary calcium–the amount of calcium in a person’s urine–is an important contributing factor in the formation of both types of kidney stones.” Both studies use data from UT South western’s kidney stone registry: 667 patients with predominantly calcium oxalate stones for the first and 133 patients with predominantly calcium phosphate stones for the second. Using “a newer, lower stability constant [mathematical formula],” the researchers found that urinary calcium is as important as oxalate or phosphate in kidney stone formation. However, neither study looked specifically at how much calcium the patients actually consumed. Several conditions lead to increased blood levels of calcium (affecting urinary calcium levels), including primary parathyroid dysfunction, sarcoidosis, hyperthyroidism, and renal tubular acidosis. Yet, two of the authors quoted in the press release take the leap that people with stones “may need to carefully monitor their calcium dietary intake.”
In the 2004 study, Gary C. Curhan, MD, ScD, and colleagues examined dietary factors and risk of kidney stone among 96,245 female nurses (age 27 to 44 years) in the Nurses’ Health Study II (Arch Intern Med. 2004; 165:885-891). None of these women had a history of kidney stones. The researchers documented the development of 1,223 kidney stones over an eight-year period. “Women who consumed the most calcium (top 20% of calcium intake) had a 27% lower risk of developing kidney stones compared to women who reported consuming the least amount of calcium (lowest 20% of calcium intake).”
In the Background section of the Nurses’ Health Study II article, Curham and colleagues said that previous studies involving older women and men showed that “greater intakes of dietary calcium, potassium, and total fluid reduce the risk of kidney stone formation, while supplemental calcium, sodium, animal protein, and sucrose may increase the risk.” This study, involving younger women, showed no association between calcium supplementation and kidney stone risk. The researchers also found that “[w]omen who consumed the most phytate (top 20% of phytate intake) in the study group had a 37% lower risk of developing kidney stones compared to women who consumed the least amount of phytate (lowest 20% of phytate intake).” Phytate inhibits mineral absorption and is found in whole grains, pulses (peas, beans, lentils), and soy beans.
Spalling from de-icers - Problem Clinic
Q. I would like to know the effect of de-icers on fresh concrete poured in the fall. A de-icer was used on concrete that was poured 30 days earlier. When spring came, we had severe spalling. The concrete was air-entrained and met all the state highway specifications at the time it was placed, and all the test cylinders met the specified 4000-psi compressive strength. Why did the de-icer create such a problem?
A. ACI recommends that concrete exposed to de-icers have a compressive strength of 4500 psi. If the concrete was placed late in the fall in cool weather, it is doubtful that it had reached its full strength. The properly cured test cylinders may have, but not the slab. The rate of cement hydration doubles for each 18 degrees–that is, concrete takes almost twice as long to reach 4000 psi at 50 degrees as it would at 70. Slabs placed in cool weather should be kept warm and protected with insulating blankets for 3 to 7 days to allow strength development. Then allow a 2-week minimum drying out period before applying any type of sealer. The slab should not be allowed to freeze in a saturated condition.
Any time you place a driveway late in the fall in cold weather, there is a risk. That is why de-icing chemicals are not recommended on concrete less than 1 year old. But de-icing chemicals can cause problems even in aged concrete when the de-icer melts ice on the concrete surface during the daytime. This melt is new moisture to the slab, which will refreeze during the night. In other words, the de-icers are causing the freeze/thaw cycle to intensify during the season. The distress is caused by the cycling–not the de-icer. If one is not going to remove the ice, it is best to keep the slab frozen.
While the damage is likely caused by these physical processes, chemical deterioration is not impossible. Normal de-icing chemicals are based on sodium chloride, calcium chloride, or urea, which do not have any adverse chemical effect on concrete. But there have been cases where de-icing chemicals have contained either ammonium sulfate or calcium sulfate. These compounds will result in a chemical attack and subsequent deterioration of the concrete surface. In extreme cases, the attack can extend deep into the concrete. This type of deterioration can sometimes be identified by closely examining the concrete surface. If it appears whitish and when probed with a dental pick or nail seems a little mushy, then chemical attack would be a prime suspect. A more detailed petro-graphic analysis of the concrete is then warranted to confirm that chemical attack has occurred.
Invensys and ChevronTexaco Sign Marketing Agreement for PETRO Refinery Planning System
Invensys Production Management, a world leader in resource productivity, recently signed an agreement with a unit of ChevronTexaco Corporation (San Francisco, CA), that provides Invensys with global marketing rights for the PETRO Linear Programming (LP) refinery planning system. This marketing arrangement combines ChevronTexaco’s refinery economic optimization expertise with Invensys global marketing and engineering support capabilities.
The PETRO software was originally developed by ChevronTexaco in the 1970s. The company continued to pioneer LP system development with the introduction of Distributive Recursion, an LP approach that enables construction of realistic refinery-wide models. More recently, ChevronTexaco introduced a full-featured Microsoft Windows(R) version of the software. The PETRO software is currently in use at ChevronTexaco and other refineries around the world. Attesting to the capability of the PETRO solution, Solomon Associates, a leading refining industry benchmarking organization, ranked ChevronTexaco’s U.S.-based refineries in the top one percent of all refineries in the use of economic tools support.
Under this agreement, ChevronTexaco will continue the company’s ongoing development activities relative to PETRO, while Invensys will assume global marketing, implementation, and support responsibilities for new third-party customers.
“PETRO clearly represents the best in class for refinery LP planning systems, said Lanny Carr, vice president of the Invensys Process Solutions business unit. “PETRO complements our current portfolio of advanced refinery economic optimization applications from Simulation Sciences and other Invensys companies. PETRO’s state-of-the-art features will result in higher productivity for refinery planners, while helping to increase refinery profitability through more accurate LP models. For example, PETRO enables detailed economic planning around shutdowns. When exploited correctly, this can save many millions of dollars by maintaining overall refinery profitability, even when individual units are shut down for planned maintenance. In addition, PETRO’s structure allows users to exploit the synergies with process simulation models - such as provided by SimSci PRO/II software - to create high-fidelity LP models which result in high-accuracy, LP-based refinery economic decision-support tools.”
Invensys is helping to improve performance, safety, and profitability in the world’s largest refineries and petrochemical plants. Invensys’ best-in-class product and software application portfolio for the HPI includes: Foxboro field instrumentation and I/A Series(R) control systems, Triconex ESD; Invensys Process Magnetic Resonance Analyzers (MRA); plus Simulation Sciences Connoisseur(R) MPC advanced control, ROMeo(R) real-time optimization, PRO/II(R) plant simulation and design, ARPM on-line performance monitoring, and Upstream Optimization Suite. Invensys has also recently introduced Advanced Planning and Scheduling packages for both refineries and ethylene plants. World-class application engineering, implementation, and support services for these and many third-party products and software applications are available globally via Invensys centers of excellence in North America, Europe, and Asia/Pacific.
Invensys plc, the international production technology and energy management group, specializes in helping companies to improve efficiency, performance and profitability. Invensys is headquartered in London, England.
Our Production Management businesses work closely with customers in order to drive up performance of their production assets and maximize the return on investments in product technologies. The division includes Foxboro, Wonderware, Triconex, APV, Eurotherm, Simulation Sciences, Esscor, Avantis, and Baan and it addresses the oil, gas, and chemicals; food beverage and personal healthcare; and discrete and hybrid manufacturing sectors.
Our Energy Management businesses actively work with clients involved in both the supply and consumption of energy, developing systems using innovative technologies that improve the reliability and security of power supplies. The division includes Energy Solutions, Metering Systems, Home, Appliance and Climate Controls and Power Systems and focuses on markets connected with power and energy infrastructure and commercial and residential buildings.
Electricity - consumption and production statistics
Overview. Electricity is produced by electric utilities, which are the traditional, regulated part of the industry, and nonutility power producers, which are expanding rapidly as the industry moves away from regulated entities.
In 2002, U.S. electricity net generation totaled 3.9 trillion kilowatthours. Electric utilities generated 2.6 trillion kilowatthours (66 percent of the total) and nonutility power producers generated 1.3 trillion kilowatthours (34 percent). The Nation imported 36 billion kilowatthours of electricity and exported 15 billion kilowatthours.
Net Generation. The December 2002 forecast for total net generation of electricity was 344 billion kilowatthours, 13 percent higher than in December 2001. At utilities, net generation was forecast at 229 billion kilowatthours, 9 percent higher than in December 2001, while at nonutility power plants, net generation was forecast at 115 billion kilowatthours, 24 percent more than the net generation 1 year earlier.
At utilities in December 2002, fossil fuels (primarily coal) were forecast to account for 73 percent of net generation, nuclear 18 percent, and renewable resources 10 percent. At nonutility power plants, fossil fuels were forecast to account for 73 percent of net generation, nuclear accounted for 19 percent, and renewable resources 8 percent of the total.
Electric Utility Retail Sales. The December 2002 forecast for total utility sales of electricity to end users was 285 billion kilowatthours, up 6 percent, compared with December 2001. December 2002 electricity sales to residential consumers were forecast at 109 billion kilowatthours , commercial users 88 billion kilowatthours , industrial consumers 78 billion kilowatthours of electricity , and other users 9 billion kilowatthours .
Consumption of Fossil Fuels. The December 2002 forecast for the consumption of coal to generate electricity was 94 million short tons, 15 percent more than a year earlier. Of the total, 74 million short tons, 10 percent higher than a year earlier, was forecast to be consumed by electric utilities and 20 million short tons, 39 percent more than a year earlier, was forecast to be consumed by nonutility power producers.
The December 2002 forecast for the consumption of natural gas to generate electricity was 570 billion cubic feet, 17 percent higher than a year earlier. Of the total, 161 billion cubic feet, 5 percent more than a year earlier, was forecast to be consumed by electric utilities and 409 billion cubic feet, 22 percent more than a year earlier, was forecast to be consumed by nonutility power producers.
Stocks of Coal and Petroleum. The end-of-December 2002 forecast for coal held in storage for electricity generation was 163 million short tons, 9 percent more than a year earlier. Of the total, 112 million short tons, 5 percent less than a year earlier, was forecast to be held by electric utilities and 52 million short tons, 60 percent more than the level a year earlier, was forecast to be held by nonutility power producers.
Cellulose dreams: the search for new means and materials for making ethanol
Alternative energy is hitting the headlines. Last year, former Vice President Al Gore scored a surprise hit with his climate-change documentary An Inconvenient Truth. Currently, drivers are steeling themselves against gasoline prices that could shoot well past $3 per gallon. The war in Iraq continues to draw attention to the United States’ dependence on imported oil and has prompted calls for a shift toward domestic sources of fuel.
More and more, policy makers are touting a homegrown solution–literally–to the nation’s energy and global warming problems: ethanol made from plants. Mixing ethanol into gasoline reduces overall greenhouse-gas emissions from vehicles because plants recycle carbon: The fuel that they yield produces carbon dioxide, just as fossil fuels do, but the plants consume carbon as they grow. And because ethanol molecules contain oxygen, their presence makes gasoline burn more completely, reducing carbon monoxide and other harmful tailpipe emissions.
Ethanol figures significantly in the Bush Administration’s promotion of biofuel. Currently, the United States produces about 6 billion gallons of ethanol annually, mostly from corn. The President’s Twenty in Ten initiative sets a goal to reduce gasoline usage by 20 percent in 10 years–in part by increasing the production of renewable fuels to 35 billion gallons per year by 2017.
But to reach that goal, corn alone won’t do. Researchers are looking to trees, grasses, and waste organic matter as possible raw materials for ethanol production. The basic idea is to extract the cellulose locked up in plants’ cell walls, break it down into its component sugars, and ferment those sugars into ethanol.
In February, the Department of Energy (DOE) announced that it would spend up to $385 million over the next 4 years to work with commercial partners on six ethanol pilot plants. Then in June, DOE granted $375 million to fund three new Bioenergy Research Centers to develop technology for cellulosic ethanol and other biofuels.
“I equate what we’re doing to society saying, ‘We’re going to the moon, or ‘We’re going to sequence the human genome,’” says Tim Donohue, a bacteriologist at the University of Wisconsin-Madison. “To me, this is a critically grand scientific mission that we’re just setting off on today.”
BILLION-TON VISION People figured out long ago how to make alcohol from grains, and now a similar process is used to turn corn into ethanol for fuel. First, corn kernels are ground into a coarse flour and combined with water and the enzymes alphaamylase and glucoamylase, which convert starch into sugar.
After this mash is cooked and sterilized–to destroy the two amylase enzymes–yeast is added to ferment the sugars into ethanol. The final step, distillation, separates the ethanol from water, solids, and other chemical products of fermentation.
Corn sugar is almost entirely glucose, which yeast readily ferments into ethanol, Donohue says. But because corn is a foodstuff for people and animals, diverting large amounts of it into ethanol production could push up prices and even cause shortages. That’s why plants that aren’t currently used in other ways are attractive alternatives to corn.
In 2005, the Oak Ridge National Laboratory in Tennessee issued a report for the Departments of Energy and Agriculture estimating that the United States could produce 1.3 billion tons of plant matter that, if turned into ethanol, could fill more than 30 percent of the nation’s petroleum needs. Agricultural waste forms a large part of that estimate.
But in order to reach that ambitious billion-ton goal without impinging on food supplies, high-cellulose crops, such as poplar, switchgrass, and wheatgrass, must also be grown specifically for ethanol production. All three plants are relatively undomesticated, so there’s plenty of opportunity for breeding them to improve their value as cellulose sources, says Brian Davison of the Oak Ridge lab.
The nagging problem with these plants and others is that the cellulose in their cell walls is hard to get out, a problem that researchers call “recalcitrance of biomass.”
“Nature developed plants so they’re not easily degraded,” says Martin Keller, also at Oak Ridge. The rigid cell wall has a complex structure built from three polymers: cellulose, hemicellulose, and lignin. Cellulose consists of long chains of glucose molecules (simple sugars with six carbon atoms) organized into tiny fibers. These fibers form a scaffold that supports hemicellulose, a polymer composed mostly of xylose (simple sugars with five carbon atoms). Lignin is a compound of various polymers that gives the plant strength and rigidity, but how it links with cellulose and hemicellulose is not well understood.
Current ethanol-making strategies require a number of difficult steps to dismantle a cell wall. Treatment with heat, pressure, or acids first removes hemicellulose and lignin from the long cellulose fibers. The cellulose and hemicellulose are then separately processed into ethanol, though doing so is challenging. The cellulose fibers don’t dissolve well in water, making it difficult for the amylase enzymes to access the cellulose and break it down into glucose. Microbes are used to break hemicellulose into its component sugars and ferment them, but they produce a lot of by-products and not much ethanol.
Indium gets boost from raw materials shortage - Nonferrous
Indium prices were firming up in a higher range as supplies tighten and Japanese demand for indium-tin oxide for use in flat-panel displays remains healthy.
Sources quoted prices in a range of $160 to $185 per kilogram, up from a previous $150- to $180-per-kg range. Sources said prices have been steady in recent weeks and continue to be supported by tightening supply.
“It’s taking a bit of a breather,” one source said, adding that even though prices are steady, demand is still strong and he expects it to be even stronger next year. “The majority of indium is going to the flat-panel display industry,” he said. “We are getting a lot of requests all the time from Japan….”
While some industry observers said demand continues to boom in Japan, one source said it is not moving much at the moment.
“Prices are really stuck right now and it will depend on what the Japanese need, but they are not on a buying spree,” the source said. He added that if China can’t sell material to Japan, it goes to other places.
China has been scaling back production of indium because of a lack of concentrates. “China is at the other end of the equation and they are tight indium-bearing concentrates,” another source said.
The tightness stems from the Nandan mine disaster in 2001, sources said, along with the recent shutdown of Liuzhou Zinc Product Co.’s 20 tonnes per year of indium production in the Guangxi autonomous region due to the raw materials shortage.
“One of the largest suppliers can’t get feed … the shortage is real,” the source added.
Sources said prices are likely to rise and could hit $250 a kg by the end of the year. Indium prices were as low as $70 a kg at the start of 2003 before shooting up more than $100 per kg.
pH control nerves of steel
Software overcomes common process industry temperature and acid problem areas
A steel caster is the most critical operating unit in a modern steel plant.
The caster transforms the liquid steel into solid slabs, ready for the rolling mill to produce the final product, steel sheets.
The liquid steel cools to form a molded shell, with the shape, thickness, and width established by the mold. The mold consists of water-cooled copper plates attached to steel water boxes, forming a rectangle.
Several thousand gallons of caster cooling water pump in per minute at high pressure through the mold to cool the steel. Since the water temperature affects the condition of the steel slabs, it is one of the most critical quality related process variables, and it needs to be tightly controlled.
Let’s look at what it takes to control effectively the caster cooling water temperature and pickle-line rinse water pH value. This feature will also discuss model-free adaptive (MFA) control technology, which is helping Nucor Steel to improve product quality and plant efficiency.
The mold water process
Nucor Steel’s Decatur, Ala., plant has a caster cooling water system that supplies non-contact cooling water to two 90mm medium thickness continuous slab casters.
During normal operations, two of the three pumps run and supply water flow at 3000-4000 gallons per minute, depending on casting machine status. Since the mold water leaving the casters so hot, it passes through three heat exchangers for cooling.
Controlling of the mold water temperature takes place by manipulating the cooling water flow to the heat-changers. Previously, three PID controllers regulated each of the three cooling water valves.
The goal is to control the temperature of the supply mold water to the casters at 95 or 96°F with no deviation of more than +/- 2°F during any system transients.
During the steady state, the PID based control system could maintain the mold water temperature well. However, during a caster start-up or tail-out, there could be up to eight degrees Fahrenheit deviation, which could cause product quality problems.
In addition, the system is sensitive to the ambient temperature change from winter to summer. PID controllers need retuning seasonally to make up for the fluctuations in the cooling tower operating conditions.
Challenge and analysis
1. During system-transients when a caster is starting up or shutting down, the temperature disturbance to the mold water leaving the casters can be quite large. The PID controllers controlling the temperature for the mold water leaving the heat exchangers cannot react fast enough to compensate for the disturbance.
2. The temperature that needs to be controlled is not necessarily the temperature of the water leaving the heat exchanger, but the temperature of the supply mold water leaving the expansion tank. Therefore, it is better to add a controller to directly control the supply-mold water temperature.
3. The challenge is the supply-mold water temperature loop will have a large time delay of about five minutes. It is difficult to use a PID to control this loop.
4. The ambient temperature variations due to seasonal changes cause the cooling water temperature and other operating conditions to change. The elimination of the manual tuning of PID controllers would be best and is desirable.
We learned about MFA control at ISA EXPO. MFA control is attractive to us because:
* MFA does not require the user to build a mathematical model for the process.
* It can adapt to fit new operating conditions.
* MFA can control complex systems.
* It is easy to use and maintain.
Unlike PID, which is just one controller, there are actually many different types of MFA controllers available, and each one solves a specific control problem.
Some MFA controllers can solve the type of control problems commonly seen in a large process plant.
This means, we can simply select the appropriate controller, do some straightforward parameter configurations having to do with entering the sample interval, process-acting type, and estimated process time constant, and then we are ready to launch the MFA controller.
Single signal control water
In February, we launched a MFA control system with two controllers. We selected a single in single out (SISO) controller to control the caster mold water temperature by manipulating all three cooling water valves at the same time.
We also selected an anti-delay controller to handle the actual supply-mold water temperature, which has a large time delay. A feedforward controller as part of the SISO controller can produce quick control actions to compensate for the large disturbances occurring during process transient conditions.
The system works as a cascade control system with Cl and C2 as primary and secondary controllers, respectively. C3 is the Feedforward controller. Processes 2 to 4 represent the sub-processes of the cascade system. The inner loop consists of C2 and P2, and the outer loop consists of C1 and P1, where Pl consists of C2, C3, P2, P3, and P4. Notice Pl as shown by the dotted line represents the process for Cl to control, where the process variable is the supply-mold water temperature. Since controller C2 is an MFA controller, the closed-loop dynamics of the inner loop will not change much, even though the process dynamics of P2 may change a lot. This means the interconnection of the outer loop and the inner loop becomes much weaker. A more stable inner loop contributes to a more stable outer loop, and vice versa.
Kanban Can Cut Inventory
Luvata, a manufacturer of stainless steel and copper products headquartered in London, faced two bottlenecks in its manufacturing process: knowing what to build and ensuring materials were on hand. The company established an electronic inventory control system, or e-kanban, to form a loop between its customer in Mexico and the actual production cell that makes the copper product. Within seconds of customers consuming product, the production cell manager now knows exactly what he needs to build and when to buy.
Kanban is a visual cue to manufacturers to replenish, said Tom Cutler, president and chief executive of TR Cutler, Inc., a manufacturing marketing firm in Fort Lauderdale, Fla. When a relationship begins between a manufacturer and a supplier, they define a service level agreement. This includes “items such as negotiated lead times, packaged quantities, order receipt confirmations, and advanced shipment notices,” which they need to spell out specifically. “An e-kanban system monitors to make sure each of these service level agreements is being met by the supplier in real time,” he said. “If they’re not, a series of alerts and notifications goes out to all parties. This gives everyone a chance to adjust their behavior to bring performance back in line in real time.”
E-kanban also makes all this real-time information available for historical analysis, Cutler said. It’s available over the internet 24 hours a day, so all parties can see trends in performance. Everyone is aware of late shipments, short shipments, and other supply chain performances, and “these visuals give everyone in the supply chain information about how to focus their energies.”
The old system at Luvata required personnel to send monthly Excel forecasts to the customer service representative, who entered it into the ERP system and re-entered data into the shop floor control system. Daily telephone calls changing order requirements meant the process had to start all over again, sabotaging efficiency in the manufacturing process.
The e-kanban system helps Scott Stringer, operations manager at Luvata’s Franklin, Ky., plant, link the customer’s demand with production efforts. The key is “trying to produce what they really need and streamlining the whole communication effort,” he said. Since it is Web-based, any computer that has access to the Internet can look at the e-kanban levels. So Stringer’s daily routine is, “get my cereal and bring up the Web site to see where the card levels are on the kanban. We’ll link up with customers via a third-party Web site kanban system. A large manufacturing firm will call the third-party company and say it wants the supply base delivered from kanban. Then the large manufacturer brings on one of its suppliers one by one,” he said.
The Luvata product (copper tube for condenser and evaporator coils) deals with microfins pressed inside a tube to increase turbulence and surface area for better heat transfer. “There’s a lot of effort and expense of capacity put in place to manufacture this tube,” Stringer said. That’s where the e-kanban helps. Copper prices three years ago were at 80 cents a pound; now they’re at $3 a pound, he said. With prices like that, “we need to bring inventory down and utilize capacity better.”
Firewall challenges
Firewalls can be a challenge in the e-kanban process, Stringer said, because manufacturers need a trusted port number with which to communicate. “Another challenge for us is we were going to our customers with this, and we had to combine benefits so they win too,” he said. “This brings down their inventory levels. It seemed with the old system “we would always be building the wrong part. The expediting going on was horrendous,” he said. If the customer was out of inventory, they’d call and request break down of the setup or overnight shipments.
The old process was to use SAP, an ERP system, which would try to generate a list of parts that were needed for the manufacturing plan. Customers would send a list, but they’d have to exactly execute the plan. So demand was constantly changing and elicited a round of e-mails. With the e-kanban system on the computer, “it linked our customer shop floor with our shop floor. We bypassed all the other management involved,” he said. “As they use a box of our parts on our shop floor, they go and scan the barcode, and that tells us through the Web site they used a box of these parts, so we build one box for them. That keeps happening 24/7.”
Anybody can use e-kanban, Stringer said, because you can plug in part numbers, give lead time and daily usage part information, and the system does the rest. “So basically it doesn’t care what it is, as long as it knows how much the supply pull or how much the tack time is,” Stringer said. It then calculates the number of cards in the system. “As long as each party is telling what’s being consumed, and the other party is telling what’s being built and shipped, we’ve linked that into our shop floor system, so that’s automated.”