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Peterborough, Canada -- Potash is an impure form of potassium carbonate mixed with other potassium salts. Potash deposits occur in sediments beds at only a few locations worldwide. Potash is found over 1000 meters underground.
Potash has been used since antiquity in the manufacture of glass and soap, and as fertilizer. The word originated from ‘pot’ and ‘ash’, which refers to its discovery by early North American settlers in water-soluble wood ash. Potassium derived from potash helps plants fight stress, diseases and injury.
Potash is critical to the growth of many of the world’s most important crops. In the US, about two-thirds of all potash is used on corn, wheat and soybeans – all crops that benefit greatly from the nutrient’s qualityenhancing properties. In the EU, the majority of potash is used for fruits, vegetables and grain.
Since the beginning of 2000, global potash demand has grown by 40 percent, or almost 16 million tons. About 90 percent of that growth has come from Asia and Latin America. Over the same period, new capacity has increased by only 7 million tons. While prices have risen sharply, so have project and infrastructure costs. It is increasingly important that potash producers maximize their production with specialized equipment.
Challenge
An integrated potash producer of fertilizer, industrial and animal feed products is the world’s largest fertilizer enterprise by capacity. This company produces three primary plant nutrients – potash, nitrogen and phosphate. Its primary facility is an underground mining operation with an annual capacity of 1.36 million tons KCl (potassium chlorate). The mine produces white soluble and granular product, and K-Prills. A prill is a small aggregate, most often a dry pellet, formed from a liquid. A K-Prill is a potassium prill, where the ‘K’ represents potassium.
Potassium ore is mined by boring machines, and then transported through a maze of tunneled roads to the surface where it is milled, and then measured. This producer required a replacement for the nuclear densitometer (nuclear belt scale) used to measure potash prill product flow on an inclined conveyor belt. Nuclear densitometers use a radiation source placed on one side of a conveyor and a detector on the opposite side. The density of the material passing through the densitometer determines the absorption of radiation and the amount of radiation that reaches the detector. The nuclear densitometer is calibrated to compute the strength of the detection signal combined with the rate of belt movement, to give a gross measurement of the material passing through the densitometer.
The company wanted to remove the radioactive densitometer from the site in order to reduce the work and costs associated with managing the nuclear device in accordance with government regulations. Also, because the prill product is round and rolls backwards, the nuclear belt scale weighed the material multiple times causing reporting errors.
A suitable continuous weighing solution had to be capable of measuring flow rates up to 15,000 kilograms per hour, and to counter the rollback of the potash prill. Such a device would also have to be compatible with the dusty and slightly corrosive material.
Solution
After evaluation by an applications engineer, Siemens supplied the Milltronics E-40 solids impact flowmeter with a stainless steel sensing plate and a stainless 6" flow guide. The solids flowmeter uses a Milltronics SF500 to integrate the signal from the ILE-37 sensing head into a material flow rate in order to calculate daily totals.
The flowmeter installation incorporated a long feed chute to connect the process to the Milltronics E-40 flowmeter, allowing the material to be weighed as it flows downward, and eliminating the possibility of material rollback. A dead box used to reduce the velocity of the potash prills, was installed above the flow guide.
The Milltronics E-series flowmeter monitors dry bulk materials from powders to granules up to 25 mm (1") in diameter, handling flow rates from 200 kg/h to 300 t/h (440 lbs/hr to 330 STPH).
Milltronics SF500 is a full feature integrator for use with solids flowmeters. The SF500 operates with any solids flowmeter with up to two strain gauge load cells or LVDT sensor. The integrator processes sensor signals for accurate flow rate indication and totalized weight of bulk solids. It can take on lower level control functions traditionally handled by other devices, and it supports popular industrial communication buses. Its patented load cell balance function eliminates matching of load cells.
Milltronics SF500 may be used for ratio blending and controlling additives with optional dual PID control. Batching, load out, and alarm functions are also provided by the SF500.
Benefits
The E-40 solids flowmeter solution provided by Siemens meets the company’s strict mining requirements. Because the material flows downward with the new system, the flowmeter does not suffer from inaccuracies created by material rollback. Furthermore, substantial long-term cost savings, by eliminating the nuclear source from the plant, have been sustained.
Siemens Milltronics flowmeters accurately measure and control product flow rate to maintain quality and plant effi ciency. They have an enclosed design to eliminate product waste or contamination, and reduce plant maintenance. Because flowmeters are dust tight, they provide a healthier work environment, especially when hazardous substances are monitored.
Source: http:// www.siemens.com/
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