Patent Application
20190292113
Farmers typically apply granulated sulfur to their fields in one of three forms; gypsum, ammonium sulfate or elemental sulfur. Gypsum, calcium sulfate dihydrate, contains 17% sulfur. Ammonium sulfate contains 24% sulfur, while elemental sulfur typically contains 90-100% sulfur. Gypsum and ammonium sulfate have an advantage in the fact that they contain sulfur in the sulfate form. This is the only kind of sulfur growing crops can readily absorb, and these fertilizers can have an almost immediate impact on the crop.
The high concentration of sulfur in elemental sulfur makes it economical, but it takes time for the elemental sulfur to convert into the sulfate form in the soil. This time required for this conversion varies according to soil temperature, soil health and composition. In the upper Midwest of the United States of America, it's generally assumed that elemental sulfur requires weeks or months to break down into the sulfate form. These are weeks and months that the crop receives no benefit from the fertilizer that has just been applied.
Moreover, the delay in crop availability has caused a shift from elemental sulfur use toward gypsum and ammonium sulfate in recent years. Ammonium sulfate (AMS), which contains 24% sulfate sulfur has become a very common recommendation for fields across the upper Midwest. AMS also contains 21% nitrogen. One key downside to the use of AMS is the fact that it is one of the most acidifying fertilizers on the market. In areas where pH is lower than desirable for a certain crop, additional liming would be required if ammonium sulfate is used. Gypsum doesn't have this problem with acidification, but with an analysis of 17% and 21% calcium, it has roughly ⅓ less sulfur than ammonium sulfate.
This disadvantage is partially countered by the desire for farmers to apply fertilizers in the fall, after harvest. It is difficult for farmers to both fertilize and plant all of their fields in a short period of time each spring. They want to fertilize as much of their operation as possible in the fall, but due to better understanding of the environmental impacts of phosphorus and nitrogen runoff, post-harvest application of ammonium sulfate has come under scrutiny in many areas. Farmers are now looking for a sulfur fertilizer that can be applied in either spring or fall with little or no runoff risk. Moreover, these farmers want a fertilizer that provides sulfur in the sulfate form for the early stages of a crop's development, while providing economical elemental sulfur that will convert to the sulfate form over the course of the crop's lifecycle. In short, they want maximum application flexibility combined with season-long crop nutrition.
Embodiments of this invention overcome deficiencies of the prior art by using an innovative formulation and manufacturing process to produce an improved sulfur fertilizer with higher sulfur levels, no risk of nitrogen runoff and season long availability of sulfur. Aspects of the invention provide new product produced in the same facility without retooling comprising about 60-80% gypsum and about 20-40% elemental sulfur, along with the process used to produce it.
In one embodiment, elemental sulfur may be added to synthetic gypsum at a level ranging from 20% to 40% by total weight prior to being formed by extrusion, agglomeration or briquetting.
In another embodiment, a process of adding the elemental sulfur to the synthetic gypsum is also provided. The most economical type of elemental sulfur is molten sulfur, or brimstone. It must be handled with great care, because it must be kept at a temperature above 239-degrees Fahrenheit. At temperatures above 320-degrees Fahrenheit, it can begin to produce toxic gases such as hydrogen sulfide. It also reacts explosively with oxidizing agents such as chlorates and nitrates, along with metals such as zinc, sodium and potassium—all three of which are micronutrients needed by crops.
Due to these risks, combining molten sulfur with other fertilizers in the factory requires tremendous expenditures in materials handling and processing equipment. Dry sulfur is easier to handle, however, but powdered (dusting) sulfur is prohibitively expensive. Lump sulfur as an intermediate is primarily available only in Asia. However, the applicant has discovered that, with low-quality (from a fertilizer standpoint) sulfur prills manufactured in the United States, and used in oil and gas operations around the world, using these prills and combining them with synthetic gypsum in a muller mixer similar to those used in foundry applications, an appropriate mixture suitable for forming via an extruder, agglomerator or briquetter may be produced efficiently.
Furthermore, embodiments of this invention overcome deficiencies of the prior art by using an innovative manufacturing and production process to produce an improved FGD gypsum with superior durability and desirable solubility properties. In one embodiment, FGD gypsum products are engineered to maintain its integrity well past its initial contact with water, dissolving at a significantly slower rate that is more comparable to potash than to all other gypsum granules. This property is desirable and advantageous over the prior uses because this keeps the nutrients where they can be absorbed by the crop without creating unwanted run-off into watersheds.
Moreover, by removing a complete drying cycle and redundancies of running the gypsum through dryers at least twice in the manufacturing process (see dryer 102 and dryer 104 in
Aspects of the invention provide a safer, economically viable process for combining elemental sulfur with gypsum to create a fertilizer containing both sulfate and elemental sulfur. Molten sulfur requires millions of dollars in capital expenditures to handle and process safely. Elemental sulfur in the powdered (dusting), and pelleted form are cost prohibitive. Lump sulfur in the intermediate form isn't available in the US. Only industrial sulfur prills, used primarily in oil and gas operations provide a relatively safe, cost-effective intermediate for a fertilizer combining sulfate and elemental forms of the element. These prills can be pulverized and mixed with moist synthetic gypsum and a binder in a muller mixer before feeding the mixture to an extruder, agglomerator or briquetter.
Another aspect of the invention is its chemical composition. Because the targeted product chemical composition is 60-80% gypsum and 20-40% elemental sulfur, the final product may contain 30-50% sulfur by weight. Moreover, this embodiment may contain both sulfur in the sulfate form for immediate uptake by the crop, as well as elemental sulfur which will provide nutrition for the crop in the later stages of its life cycle. At an 80/20 gypsum to elemental sulfur ratio, the product would contain roughly 14% sulfate sulfur ready for prompt uptake and 20% elemental sulfur by weight. At a 60/40 gypsum to elemental sulfur ratio, the product would contain roughly 10% sulfate sulfur ready for prompt uptake and 40% elemental sulfur by weight.
The invention confers a number of economic and environmental benefits. In terms of economic benefits, the cost per unit of sulfur is much lower than that of ammonium sulfate, yet the invention provides season-long sulfur nutrition to the growing crop. This is particularly important for grasses like corn, which utilize sulfur at a nearly even rate throughout their life cycles. Moreover, the invention allows farmers to apply sulfur in both fall and spring without increased concern about nitrogen runoff.
The inventor intends to increase and customize these environmental benefits for specific markets through the use of various rates of a variety of binders such as lignosulfonate, corn starch, guar, and CMC and paper mill residue. These modifications can allow for varying dissolution speed in the presence of water from moments (lignosulfonate binder), to something approaching true timed-release (CMS or paper mill residue as binder) to be discussed below.
Gypsum has long been used as a source of sulfur and calcium for growing crops. Granulated gypsum from mined sources has been widely available for decades. In recent years, large amounts of gypsum produced by utilities have become available for agriculture as a result of the flue gas desulfurization process, producing so-called synthetic gypsum or flue-gas desulfurization (FGD) gypsum (collectively referred to as synthetic gypsum below), which became popular for coal-fired power plants after passage of the 1990 Clean Air Act. In 2004, the Ohio State University estimated that at least 12 million tons of this highly pure gypsum are produced in the US annually. The FGD gypsum is a powder with typical particle sizes of 200-300 microns. The powder has a typical moisture content of 8-12% water upon leaving the power plant.
In terms of solubility, all currently available synthetic gypsum fertilizers behave like mined gypsum, in other words, they dissolve almost instantaneously upon contact with water. Firms are successfully marketing a granulated gypsum pellet from synthetic gypsum with these properties. While solubility is necessary for soil absorption, and ultimately for crop nutrient uptake, the ready solubility of many commercial fertilizers plays a significant role in nutrient runoff, and therefore, water pollution.
However, when attempting to pelletize synthetic gypsum, firms discovered that the synthetic gypsum forms quite differently than the typical mined gypsum.
At the same time, these firms have only focused on producing a pellet durable enough to be blended and spread with other common fertilizers. No effort has been made to significantly alter the in-field performance of the fertilizer itself. Like most other modern fertilizers, gypsum is soluble in water.
Consequently, these firms use conventional manufacturing techniques to pelletize gypsum using either a calcium lignosulfonate or an ammonium lignosulfonate binder to achieve a product that is hard enough to blend with other commercial fertilizers. The single design variable appears to have been crush strength or another metric of fertilizer durability.
Aspects of the invention further provide a more efficient process for manufacturing fertilizer granules from FGD gypsum. Other manufacturers have simply followed a process that mimics the manufacture of fertilizer granules from mined gypsum, such as those depicted in
Referring now to
In another embodiment, while it is desirable to receive the raw synthetic gypsum with a moisture content between 8-12%, if the synthetic gypsum's moisture content is at the low end of the moisture range, an alternative water inlet may be used to add slightly more water, at 308, such as 0-3%, to the process at this stage. On the other hand, if the synthetic gypsum's moisture content is toward the upper end of this range, the process in this embodiment recognizes the inherent moisture level and does not need any additional water to be added.
Once the pellets exit the extruder, the extruded mixture is fed to a tumbling drum, tumbler, or spheronizer 204 at 310 for 5-10 minutes. The tumbled mixture forms dense pellets for the drying step. In one embodiment, the tumbler 204 is connected to an inlet feeding dry, relatively cool air across the formed pellets to avoid calcination. In another embodiment, the formed pellets are fed to a dryer 206 to dry the formed pellets at 312. In one embodiment, the drying temperature may be at a temperature between about 150-190 degrees Fahrenheit for about 3 to 10 minutes. It is well understood at this stage that aspects of the invention provide a streamlined process that eliminates:
(a) the need to dry the material from 8-12% moisture to <1% moisture initially;
(b) the need to rehydrate the material to a higher moisture level;
(c) the need to utilize a separate mixer; and
(d) the need to dry the formed pellets from an excessive moisture level back to <1% in the final drying step.
After the drying process, the dried pellets are ready for storage and shipment 208. In one embodiment, the resulting or finished pellets include moisture content of less than 1% by weight.
In another embodiment,
Aspects of the invention may be further fine-tuned or custom-configured without removing individual parts. In a second embodiment, in order to achieve or target solubility of the end product, the manufacturing process or flow may be conveniently and efficiently configured to effect a change or modification in the solubility profile of the gypsum granules. For example, powdered synthetic gypsum, as raw materials, may be mixed in a combination mixer/forming device with a polysaccharide binder such as guar gum, CMC or a corn starch, instead of using ammonium or calcium lignosulfonate to give their products form and durability. The primary measure of this durability is known as crush strength.
Manufacturers of pellets using mined gypsum tend to achieve a crush strength of 1.5-3.5 pounds per square inch. This is tested by placing pellets of a comparable size and using a force pressure gauge to measure that amount of force it takes to crush the pellet into dust. Higher crush strengths are preferred, as crush strengths below 3.0 psi are considered too soft for achieving sound fertilizer blends and application using modern impeller-based fertilizer spreaders. By using a higher rate of lignosulfonate, prior technology manufacturers of pelletized gypsum using synthetic gypsum are able to achieve crush strengths of 3.0-8.0 psi.
These firms compete on crush strength and price. But there is another axis of potential competition that has gone unexamined—relative solubility. Lignosulfonate does nothing to retard the dissolution of pelletized gypsum in the presence of water. If dropped into water, these pellets dissolve almost immediately. In simulated rainfall testing, it takes less than one-half of an inch of heavy rain to make these pellets disappear. Given that these pellets are spread in the spring and fall of the year, rainfall events greater than 0.5 inches are the rule, not the exception. How much of the sulfur in these pellets leaves the field as surface water runoff? How much of this sulfur bought by the farmer is wasted? Prior art fails to address these questions.
Aspects of the invention take a different approach. As illustrated above, the manufacturing process exemplified by embodiments of the invention begins with a forming device, such as an extruder, that tends to produce a denser, harder pellet than the standard agglomeration disk from the outset. The backpressure at the extruder's face plate, in one embodiment, may compress the gypsum and binder mixture sufficiently to reduce the voids in the formed pellets to allow for slower water absorption. In these embodiments, the formed pellets from the forming device are next tumbled aggressively to round them and to provide a source of secondary compaction. This two-staged compaction, without having a re-wetting process between two drying processes as in prior art, produces moisture absorbing characteristics desirable for optimal use of synthetic gypsum pellets as agricultural fertilizers.
As a result of the different approach to the manufacturing process, the focus of the binder search has been on an entirely new axis of competition—optimal solubility. By using a 0.5%-2.0% rate of a pre-gelled corn starch, inventors of the invention recognize it would increase the amount of simulated rainfall necessary to completely dissolve our agricultural grade pellets to 0.5-2.0 inches. This is comparable to potash and several other common commercial fertilizers, and it reduces nutrient loss due to runoff.
While the traditional axis of competition in the pelletized gypsum market has been durability, as measured by crush strength, embodiments of the invention have created an entirely new value proposition while simultaneously improving environmental and economic benefits. Instead of just searching for a way to keep the gypsum particles bound together long enough to get them to the field, aspects of the invention seek to change the fundamental properties of the gypsum itself by changing the way it behaves in the field. Embodiments of the invention create synthetic gypsum granules utilizing different polysaccharide binders that result in the dissolution profiles during simulated rainfall testing example shown below:
about 1.0% pre-gelled cornstarch shows it may require about 1.0 inches of heavy simulated rain;
about 1.0% dry guar gum powder may require about 0.5 inches of heavy simulated rain;
about 1.0% CMC powder may require about 2.0 inches of heavy simulated rain;
In another embodiment, as another example, using an industrial-sized equipment in an industry production, the dissolution profiles may be changed showing the following characteristics:
about 1.5% pre-gelled cornstarch shows it may require about 2.0 inches of heavy simulated rain, while smaller rates can dissolve in as little as about ½ inch of simulated rain;
about 1.0% dry guar gum powder may require about 0.75 inches of heavy simulated rain;
about 1.0% CMC powder may require about 3.0 inches of heavy simulated rain.
In other words, aspects of the invention may adjust or modify solubility and the dissolution profile may depend on calibration of backpressure, binder type, binder rate, and granule size. For example, after the inventor of embodiments of the invention recognizes the relationship and characteristics of the following, the percentage of the above may be modified or altered:
1. Lignin binders may dissolve immediately;
2. Guar binders may dissolve more slowly;
3. Starch binders may dissolve slower than guar binders; and
4. CMC binders may dissolve slower than starch binders.
According to another embodiment, the manufacturing process discussed herein may be calibrated to produce products tailored to fit low-moisture environments such as Kansas, Texas and Oklahoma. In laboratory trials, inventors of the invention discovered that a 1-5% solution of bentonite clay added to the binders above could accelerate the breakdown and increase the dispersion of the pellet once the moisture threshold was met and the pellet began to dissolve.
In a further embodiment of our invention, inventors further take the basic manufacturing process and reduce the amount of polysaccharide binder to 0.5% or less. With this adjustment, paper mill residue may be added to the mixture from 2-5% by weight. The result is no longer just delayed dissolution, but actual timed release. With this formulation, aspects of the invention may produce pellets for application in the spring will dissolve steadily with each rain, along with other mechanical and biological forces acting upon it. Sulfur and calcium will be released at a relatively steady rate across the growing season. We have successfully created a variety of formulations with nutrients that include zinc, boron and humic acid. We are also experimenting with the addition of urea into the extruder, which should have significant environmental advantages.
Sulfur and calcium are used by plants at a steady rate across the growing season, but nitrogen are used by crops like corn at varying rates depending on the plants' stage in life. But because it is difficult to apply nitrogen on more mature plants, over-application occurs early in the plant's life to increase the odds of having some left over when the plant needs it. Products produced above utilizing the properties of paper mill residue, embodiments of the invention could combine urea with gypsum to create a much more effective controlled-release fertilizer that reduces surface runoff and increases nitrogen availability when it's needed by the plant. Aspects of the invention may create a true timed-release product that may reduce over application early in the target crop's life cycle. This approach provides both economic benefits to the farmer and water quality benefits to the environment.
The process for manufacturing fertilizer granules from FGD gypsum according to aspects of the invention may be significantly more efficient than that used by other manufacturers. Other manufacturers dry the raw material from 7-12% moisture to <1% moisture, then rehydrating it back to as much as 20% moisture. To the contrary, embodiments of the invention use the moisture inherent in the raw material, which completely eliminates both the initial drying and rehydrating steps.
As described above and illustrated in the figures, manufacturing process of embodiments of the invention involves both extrusion and tumbling and produces a denser granule with inherently greater crush strength than comparable granules made on an agglomeration disk.
Moreover, formulations developed in the embodiments of the invention utilize polysaccharide binders such as pre-gelled starches and biogums that slow down the dissolution of our fertilizer granules in the presence of water. The rest of the industry is focused solely on crush strength.
Additionally, manufactured granules according to aspects of the invention contain micronutrients useful to crop nutrition such as zinc, boron or humates. In addition, another aspect of the invention includes a process to utilize paper mill residue to create a true timed-release product that should reduce over application early in the target crop's life cycle. As such, embodiments of the invention provide advantages over prior approaches by using 5-7 times less water than the current manufacturing process. At the same time, embodiments of the invention evaporate away (e.g., dry) as little as 9-12 percentage points of moisture, versus a total of 15-29 percentage points of moisture in the current manufacturing process. Further, embodiments of the invention have in-dwelling dryer times of 3-10 minutes at temperatures of 150 to 190-degrees Fahrenheit. The prior manufacturing process would require either longer in-dwelling time or higher temperatures.
Furthermore, granules produced according to embodiments of the invention with significantly lower binder use rates. The prior manufacturing process produces a less dense granule, necessitating lignin binding use rates of 4-8% by weight to keep the gypsum grains together. Our process uses binder use rates of 0.5-2.0% by weight.
After realizing such advantage, formulations on achieving optimum dissolution rates in the presence of water may be attainable based on embodiments of the invention. Internal tests on currently marketed gypsum fertilizer granules showed that they dissolved completely with 0.5-1.0″ of simulated rainfall. In the same tests, aspects of the invention dissolve in about 2.0-3.0 inches of simulated rainfall. Moreover, embodiments of the invention include a 1.0%-5.0% mixture of bentonite clay to increase the physical dispersion of the gypsum grains that make up the finished granules per a given amount of simulated rainfall.
A fertilizer containing 30-50% sulfur by weight. This fertilizer contains approximately 10-14% sulfate sulfur and 20-40% elemental sulfur for late-season plant uptake
Environmental benefits accruing from not containing nitrogen, making this invention a more suitable choice than ammonium sulfate for fall applications
A process for sourcing economical industrial sulfur prills and safely combining them with gypsum and binder prior to feeding the mixture to a forming device such as an extruder, agglomerator or briquetter
The composition of the above mixture, where additional micronutrients such as boron, zinc, etc., are added into the mixture prior to being formed on an extruder, agglomerator or briquetter
Moreover, in one embodiment, wherein the binder used may be varied to provide economic and environmental benefits through the control of dissolution speed. In one embodiment, a lignosulfonate binder could be used if immediate dissolution is desired. In one example, golf course greens would be an example of where this property is important. In another embodiment, paper mill residue could be used as the binder if the product were to be applied in the fall into a field where no beneficial nutrient uptake would occur until spring. This would be a desirable property for many Iowa cornfields.
The order of execution or performance of the operations in embodiments of the invention illustrated and described herein is not essential, unless otherwise specified. That is, the operations may be performed in any order, unless otherwise specified, and embodiments of the invention may include additional or fewer operations than those disclosed herein. For example, it is contemplated that executing or performing a particular operation before, contemporaneously with, or after another operation is within the scope of aspects of the invention.
Embodiments of the invention may be implemented with computer-executable instructions within the central control unit. The computer-executable instructions may be organized into one or more computer-executable components or modules. Aspects of the invention may be implemented with any number and organization of such components or modules. For example, aspects of the invention are not limited to the specific computer-executable instructions or the specific components or modules illustrated in the figures and described herein. Other embodiments of the invention may include different computer-executable instructions or components having more or less functionality than illustrated and described herein.
When introducing elements of aspects of the invention or the embodiments thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
Having described aspects of the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of aspects of the invention as defined in the appended claims. As various changes could be made in the above constructions, products, and methods without departing from the scope of aspects of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This is a nonprovisional application of U.S. provisional application, Ser. No. 62/646,366, filed on Mar. 21, 2018, whose disclosure is incorporated by reference in its entirety. This application is also a continuation-in-part application of the non-provisional application Ser. No. 15/408,384 filed on Jan. 17, 2017, which claims priority to a provisional patent application Ser. No. 62/379,576, filed on Jan. 15, 2016, whose disclosures are incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62646366 | Mar 2018 | US |
