Urea capacity

In the future, developing nations are expected to continue to account for most of the increases in ammonia and urea capacity. Ammonia capacity is expected to increase by about 20 million tonnes and urea capacity by about 12 million tonnes of nitrogen between 1996 and 2002. The availability of relatively low-cost feedstock (usually natural gas) will be a major determinant as to where this new capacity is installed. Ammonium nitrate and ammonium phosphate capacity are also expected to rise35. The following tables summarize anticipated world capacity for nitrogen products by year (Table 3.1) and by major regions or countries (Table 3.2)148. 

DSM Melamine plans to start up a new 30,000 tonne per year melamine plant towards the end of 2002. The investment estimate is EUR 90 million. However part of the investment will be used to expand urea capacity at the site115. 

In the future developing nations are expected to continue to account for most of the increases in ammonia and urea capacity. Ammonia capacity is expected to increase by about 13.5 million tonnes and urea capacity... 

The consumption in the USA in 1996 was 3.83 10 t N, of which 83% was used in fertilizers. Half of the consumption in fertilizers was utilized in liquid fertilizers e.g. in urea-ammonium nitrate. solutions, the rest being used in solid fertilizers. 7% of urea was utilized for animal nutrition and 6% for urea-formaldehyde resins, glues and melamine. In the period between 1984 and 1996 there was a reduction in urea capacity in Western Europe of 39% to 2.5 10 t/a N (Table 2.2-7). 

Because an excess of ammonia is fed to the reactor, and because the reactions ate reversible, ammonia and carbon dioxide exit the reactor along with the carbamate and urea. Several process variations have been developed to deal with the efficiency of the conversion and with serious corrosion problems. The three main types of ammonia handling ate once through, partial recycle, and total recycle. Urea plants having capacity up to 1800 t/d ate available. Most advances have dealt with reduction of energy requirements in the total recycle process. The economics of urea production ate most strongly influenced by the cost of the taw material ammonia. When the ammonia cost is representative of production cost in a new plant it can amount to more than 50% of urea cost. 

The estimated world production capacity for hydrazine solutions is 44,100 t on a N2H4 basis (Table 6). About 60% is made by the hypochlorite—ketazine process, 25% by the peroxide—ketazine route, and the remainder by the Raschig and urea processes. In addition there is anhydrous hydrazine capacity for propellant appHcations. In the United States, one plant dedicated to fuels production (Olin Corp., Raschig process), has a nominal capacity of 3200 t. This facihty also produces the two other hydrazine fuels, monomethyUiydrazine and unsymmetrical dimethyUiydrazine. Other hydrazine fuels capacity includes AH in the PRC, Japan, and Russia MMH in France and Japan and UDMH in France, Russia, and the PRC. 

Incremental steam capacity is also convenient for exporting motive steam to other iategrated processes, such as urea. 

Uses. Since 1947, 70 to 85% of the annual USA production of nitric acid has gone into the production of NH4 nitrate fertilizer, initially in the form of solid prills currently, increasing amounts have been supplied mixed with excess ammonia and/or urea as aqueous nitrogen solution for direct application to the soil. Some 15% is used in explsj (nitrates nitro compds), and about 10% is consumed by the chemical industry. As the red fuming acid or as nitrogen tetroxide, nitric acid is used extensively as the oxidizer in proplnts for rocketry. It is estimated that current USA capacity for nitric acid is in excess of 10 million tons (Refs 30, 34, 36 37)... 

Nitrogen compounds commonly determined are creatinine, urea, and uric acid. Creatinine is an end product of the energy process occurring within the muscles, and is thus related to muscle mass. Creatinine in urine is commonly used as an indicator and correction factor of dilution in urine. Creatinine in serum is an indicator of the filtration capacity of the kidney. Urea is the end product of the nitrogen luea cycle, starting with carbon dioxide and ammonia, and is the bulk compoimd of urine. The production of uric acid is associated with the disease gout. In some cases, it appears that the excess of uric acid is a consequence of impaired renal excretion of this substance. 

Estimate the specific heat capacity of urea, CH4N2O. 

Table 9-4 gives the capital costs for six ammonia plants that were built between 1959 and 1969. When plant no. 5 is compared with the three other plants that have a capacity of 1,000 tons/day, it appears that its reported cost is in error. This could be a misprint, or the plant might be producing urea, nitric acid, and/or ammonium nitrate as well as ammonia. The reader must always be careful, since errors occur frequently in printed material. This is why care should be used when the cost of a plant is estimated from only one piece of information. 

Cows and calves fed low-zinc diets of 25 mg Zn/kg ration showed a decrease in plasma zinc from 1.02 mg/L at start to 0.66 mg/L at day 90 cows fed 65 mg Zn/kg diet had a significantly elevated (1.5 mg Zn/L) plasma zinc level and increased blood urea and plasma proteins (Ram-achandra and Prasad 1989). Biomarkers used to identify zinc deficiency in bovines include zinc concentrations in plasma, unsaturated zinc-binding capacity, ratio of copper to zinc in plasma, and zinc concentrations in other blood factors indirect biomarkers include enzyme activities, red cell uptake, and metallothionein content in plasma and liver (Binnerts 1989). 

In comparison, the vampire bat has a capacity for urea synthesis approximately 1000-fold greater than that of a human. A bat consumes one half of its weight in blood in 10-15 minutes so that the massive amount of protein that is metabolised produces a massive amount of ammonia which must be removed as quickly as possible. Indeed, it also ingests sufficient fluid so that it is too heavy to fly. Hence, it urinates very quickly. 

In July of 1997, a cooling tower at an ammonia and urea plant, originally constructed in 1968, caught fire and was destroyed. The plant produced 1,450 tons/day (1,315 tonnes/day) of ammonia and 240 tons/day (218 tonnes/day) of urea. The coolingtowerwasa 5-cell, induced draft, cross flow unit. It was constructed of redwood with steel supports and fiberglass fill. The capacity of the cooling tower was 50,000 gallons (190,000 liters). 

Brydon and Roberts- added hemolyzed blood to unhemolyzed plasma, analyzed the specimens for a variety of constituents and then compared the values with those in the unhemolyzed plasma (B28). The following procedures were considered unaffected by hemolysis (up to 1 g/100 ml hemoglobin) urea (diacetyl monoxime) carbon dioxide content (phe-nolphthalein complex) iron binding capacity cholesterol (ferric chloride) creatinine (alkaline picrate) uric acid (phosphotungstate reduction) alkaline phosphatase (4-nitrophenyl phosphate) 5 -nucleotidase (adenosine monophosphate-nickel) and tartrate-labile acid phosphatase (phenyl phosphate). In Table 2 are shown those assays where increases were observed. The hemolysis used in these studies was equivalent to that produced by the breakdown of about 15 X 10 erythrocytes. In the bromocresol green albumin method it has been reported that for every 100 mg of hemoglobin/100 ml serum, the apparent albumin concentration is increased by 100 mg/100 ml (D12). Hemolysis releases some amino acids, such as histidine, into the plasma (Alb). 

Solvolysis of urea analogues (200) in aqueous KOH leads to hydrolysis of the amide rather than substitution at nitrogen, in keeping with the poor leaving capacity of alkox-ide (equation 28). This reaction is an excellent source of Af,Af-dialkoxyamines (203), a relatively little known class of compounds . 

---