MANUFACTURING OF MATERIAL BASED HYDROGEN FUEL FOR LIGHTWEIGHT VEHICLES
Item Type text; Electronic Thesis
Authors KHAGHANI, ALI
Publisher The University of Arizona.
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Download date 23/09/2021 12:36:34
Link to Item http://hdl.handle.net/10150/613155
MANUFACTURING OF MATERIAL BASED HYDROGEN FUEL FOR LIGHTWEIGHT VEHICLES
By
ALI KHAGHANI
______
A Thesis Submitted to The Honors College In Partial Fulfillment of the Bachelors degree With Honors in
Chemical Engineering
THE UNIVERSITY OF ARIZONA
M A Y 2016
Approved by:
______Dr. Kimberly Ogden Chemical and Environmental Engineering
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Abstract Vehicles powered by hydrogen fuel cells store hydrogen as a cooled liquid at 20 degrees kelvin or a compressed gas at 10,000 pounds per square inch. An alternative that eliminates the need for these extremes of temperature and pressure is to heat a compound containing covalently bonded hydrogen, causing it to release the hydrogen to the fuel cell. Ammonia borane, which is stable at ambient conditions, requires minimal energy for dehydrogenation, and is rich in hydrogen, is a possible storage medium for hydrogen. If a viable storage system could be engineered, demand for ammonia borane as a source of hydrogen would increase. The goal of this project is to develop a processing plant and to optimize design specifications for scaling up processing of ammonia borane through the metathesis reaction pathway. Optimization of individual unit operations was determined using quality-by-design concepts, which allowed the team to confirm scalability, design limitations, and competitive market pricing. The final design involves the application of two mixers, two reactors, and four separators. The plant design should yield 99 percent pure ammonia borane. Executive Summary
Material based hydrogen storage systems are beginning to change the way we provide hydrogen gas to fuel cells in lightweight vehicles. Traditional storage systems fall into one of two categories; cryogenic (cooled and stored as a liquid) or compressed (stored at very high pressures). Utilizing materials that “soak up” hydrogen and release the compound on demand provides a safer and more practical method for storing hydrogen. Although this third category is relatively new, much attention and effort put forth to select and manipulate a material to achieve the following target goals set by the department of energy (DOE):
I. The material must have a relatively high hydrogen content (<10 wt.%) in order to maximize energy per volume of fuel II. Kinetic reversibility provides the ability to reuse the material based fuel with minimum effort. III. Overall production of this material must be competitive in the current market
Ammonia borane was chosen to be D.A.B Chemicals primary molecule for storing hydrogen by bonds formed within the compound itself. The molecule is made up of 19 wt.% hydrogen, but only 14% is accessible due to the final mechanistic stage in the reaction. Scale up processing has been optimized and determined to yield a microcrystalline product (Ammonia borane) that is 99% pure. Although the synthetic process was carried out to
-2- produce large quantities of ammonia borane; an intermediate chemical ammonium borohydride would be a better candidate if the stability was enhanced.
The main reaction of the ammonia borane synthesis takes place in a single CSTR and known as the metathesis reaction. Multiple mixers prepare the solution before entering the first reaction; along with an additional stream of liquid ammonia to stabilize the highly hindered intermediate ammonium borohydride. Once the reaction has reached its desired residence time, the slurry is pumped to three settling vessels to allow the intermediate to decompose to ammonia borane. Recycling the expensive solvents (tetrahydrofuran and ammonia) and extraction of our product is carried out using a series of rotary vacuum filtration drums and a flash distillation.
Due to the limited amount of published information on ammonia borane and its intermediate ammonium borohydride, certain assumptions were made. Physical properties including density, enthalpy, molecule size and resistance were all assumed or averaged based on previous process designs and clues found in the literature. For example, the particle size of ammonia borane was ascertained to be smaller than sodium chloride but larger than THF based on scientific reports and patents found online. Assumptions were made to be viable and as accurate as possible given the information.
For the D.A.B company to profitable, ammonia borane must be sold at $8.97 a kilogram. While this is significantly lower than the current market price of $400 a kilogram, it will need to be reduced further to be able to compete with gasoline prices. 38 kg of ammonia borane product is necessary for 314 miles of driving. A 314-mile fill-up currently costs on average $29 for gasoline, while the ammonia borane will require $314. Gasoline prices would need to increase by 1100% in the United States and 345% in Europe for D.A.B to be competitive. Complete analysis of economic impacts can be found in section 5 of the report. Thus, it was decided that the process and production of ammonia borane for hydrogen fuel cell vehicles is not profitable or feasible at this time.
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II. Table of Contents
Abstract/Executive Summary…………………………………………………….…….………....i
Section 1: Introduction/Background………………………………………………………...…5
Section 2: Overall Process Description, Rationale and Optimization………….…..7
Section 3: Equipment Description, Rationale, and Optimization……………..……..23
Section 4: Safety/Environmental Factors……………………………………………………..29
Section 5: Economic Analysis……………………………………………..……………………….38
Section 6: Conclusion and Recommendations………………………………………………45
Section 7: Nomenclature……………………………………………….…………...………………..48
Section 8: References……………………………….……………...………………………………….49
Section 9: Appendices…….………………………………………...…………………………………56
Appendix A: Process Calculations………………………………….……………………………..58
Appendix B: Equipment Sizing and Costs ……………………………………………………..63
Appendix C: Economic Calculations…………………………………….……………………….. 93
Appendix D: Other Process, Calculations, and Numbers …………..…..…………..…..104
Appendix E: Mass Balance………………………………………….…………………………….....108
Appendix F: Meeting Logs………………………………………..………………………………....109
.
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Section 1: Introduction
1.1: Overall Goal Fuel cell technology is currently being touted as the next leap forward in clean and sustainable transportation because of its broad range of benefits including high reliability, low maintenance, reduction in oil resources, and efficient energy conversion. Currently hydrogen fuel cell vehicles (HFCV) transport hydrogen in a compressed form under 10,000 psi. However there are current doubts about the safety of transporting compressed hydrogen gas in vehicles due to the potential hazard of it igniting or rupturing, which could create an explosion. Also, due to significant weight involved with carrying these containers (around 200 kg empty) long range capabilities are not practical. In light of this, our senior design’s goal was to identify and design a plant to mass produce a material based hydrogen source for fuel cells. The material fuel should be produced and sold at a competitive price to gasoline to attract investors.
Figure 1.1.1 was used to determine what compound we chose (Materials-Based Hydrogen Storage, Web). Ammonia borane was identified as an excellent source for the hydrogen required to fuel the vehicles. Ammonia borane has 146 g H2/L compared to the 40 g H2/L that compressed hydrogen has at 10,000 psi (Hosmon, Print). The hydrogen is also released at a temperature of 100C, making it readily feasible for modern cars. Scale up using literature values would give us an ammonia borane purity of 99%. This purity could be further refined using certain solvents to achieve a 99.9% purity, but is not covered in this report. The byproducts of the reaction are hydrogen gas and sodium chloride, which will be sold to further maximize profits.
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An initial theoretical production of 10,000 tons of ammonia borane has been determined. This allows for future growth while also taking into account that not every hydrogen fuel cell car may employ this technology. Figure 1.1 shows the estimated sales of FCEV vehicles and was used to determine our production number. From this production D.A.B can refuel 237,017 tanks a year.
1.2: Current Market Section Current demand for the product is theoretical as it is a completely new and is not currently being used in modern hydrogen fuel cell vehicles. To make the product competitive with the gasoline market we agreed that the material must be sold so that a full tank, capable of going at least 314 miles, must be priced to within five dollars. We have determined our preferred market to be the United States rather than international. The current market for gasoline is at the lowest it has been since 2009, with an average US gas price of $2.069 per gallon (EIA, Web), and an average of 21.6 miles per gallon in light duty vehicles. To be competitive currently, ammonia borane must be sold at $.87 per kilogram (see Appendix D- 3). Due to the current gas price, the production of this product is not feasible at this time, and we will not be going forward with our process as ammonia borane must be priced at $8.97 a kilogram.
1.3 Project Premises and Assumptions The process design was based on the 2020 goals set by the department of energy. We assumed that if the process was feasible, there would be a market for the new technology and that car manufacturers would be able to create a system to release the hydrogen from the ammonia borane. We assumed many qualities of the ammonium borohydride intermediate due to the complete lack of information in both web and book resources regarding even the most basic properties. We also had to do this to a lesser extent with the ammonia borane. We also assumed that a 99% product purity would be sufficient to fuel the vehicles.
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Section 2: Overall Process Description, Rationale, and Optimization
2.1: Overall Process Description
Based on the Block Flow Diagram (see Figure 2.3.1), the process outlined in the following subsections is divided into 3 major categories in order to group similar operations of the plant. Section 2.1.1 describes the initial processes for creating the solutions to be fed into the first reactor. The next section will provide a detailed description of the metathesis and decomposition reactions that occur in the reactor and vessels respectively. Finally, that last section will focus on the separating units that involve not only extraction of our products, but the recycle streams for the catalysts and stabilizer. The PFD and BFD can be viewed in section 2.3 and 2.4.
2.1.1: Initial Preparation
Our plant operations begin with a feed of four chemicals; ammonia (NH3), sodium borohydride (NaBH4), ammonium chloride (NH4Cl) and tetrahydrofuran ((CH2)4O) (Figure 2.4). Stream 1, containing tetrahydrofuran, is fed into the system at 20⁰C and 1.01 bar. Stream 1 is combined with stream 34, which is the recycle stream of tetrahydrofuran, before entering P-101A/B, creating stream 2 at 20.12 ⁰C and 2.37 bar. A valve on stream 2 splits feed into streams 3 and 4, which exhibit conditions similar to that of stream 2 depending on varying flow rates required for plant operation. Stream 3 supplies tetrahydrofuran into MX 101-103 and similarly stream 4 supplies tetrahydrofuran into MX 104-106. Sodium borohydride in stream 5 is fed into MX 101-103 at 20⁰C and 1.01 bar. A delivery system for solid feed was not designed but a conveyor system would be a proper solution. Ammonium chloride is supplied to MX 104-106 by stream 6 at 20⁰C and 1.01 bar. Streams 7 & 8 will be well mixed, only varying the salts, sodium borohydride with tetrahydrofuran in stream 7 and ammonium chloride with tetrahydrofuran in stream 8 (Table 2.5.1). To overcome equipment pressure drops, P-103 A/B and P-104 A/B are
-7- installed in streams 9 & 10. Streams 9 & 10, operating at 20.24⁰C and 2.37 bar, must be cooled close to -78⁰C prior to entering R-101. Heat exchangers are then required to achieve ideal operating temperatures. HX-101 and HX-102 are used to reduce the temperature of streams 9 & 10 from 20.24⁰C to ideal reactor inlet conditions. Stream 11, containing tetrahydrofuran and sodium borohydride will enter R-101 at -76.23⁰C and 2.25 bar. Stream 12, containing tetrahydrofuran and ammonium chloride, will enter R-101 at - 76.23⁰C and 2.25 bar. The final inlet into R-101 will be ammonia. Initial conditions of ammonia in stream 13 are 20⁰C and 1.01 bar. This stream is then condensed to a liquid using HX-103. Liquid ammonia in stream 14 is at -73.33 ⁰C and 0.77 bar, and is then pumped using P-102 A/B and combined with the recycle stream 25 (Figure 2.4). Finally, stream 26 containing ammonia is fed into R-101 at -73.27⁰C and 2.37 bar (Tables 2.5.2 & 2.5.3).
2.1.2: Reactor and Vessel Conditions
Entering reactor R-101 are streams 11 and 12, which contain the major solutes that undergo the metathesis reaction shown in reaction 2.2.3. Stream 26, is essential for enhancing the stability of the highly hindered intermediate, ammonium borohydride. Maximum contact between ammonia and ammonium borohydride occurs when ammonia is in the liquid phase, therefore, the reactor operates at atmospheric pressure and slightly above the melting point of ammonia(-78⁰C). Cooling coils will be used to maintain reactor temperature. The effluent exits the reactor in stream 16, which contains sodium chloride, ammonia, tetrahydrofuran and ammonium borohydride at -78⁰C and 1.01 bar. Trace amounts of sodium borohydride and ammonium chloride will also exist in this stream. A centrifugal pump, P-105 A/B, will transport the fluid to HX-104 at -77.9⁰C and 2.37 bar. The next step in the process is the decomposition of ammonium borohydride to ammonia borane. HX-104 raises the temperature of stream 17, to -34⁰C with a calculated pressure drop of 0.12 bar, creating stream 18.
To decompose ammonium borohydride, we are using V-101, V-102 and V-103 A/B (Figure 2.4). The second mechanistic step shown in reaction 2.2.3 is carried out at 1.01 bar and
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20⁰C. Although the residence time for decomposition is 1.5 hours, the three vessels are alternated to accommodate for the filling and draining times required. Two streams will be exiting the vessels. Stream 19 will be a vapor stream containing hydrogen and ammonia at 19.85⁰C and 1.01 bar and stream 27 will contain tetrahydrofuran, ammonia borane, sodium chloride and small amounts of ammonium borohydride at standard conditions (Table 2.5.3).
2.1.3: Separation and Recycle
To isolate our final product a set of rotary drum vacuum filtration units are used. Stream 28 exiting P-106 A/B is fed into VF-101 at 20.11⁰C and 2.37 bar. Sodium chloride will form a solid cake on the filter cloth of VF-101 and is collected for sale in stream 29. To collect our final product of ammonia borane, stream 30 is pumped through P-107 A/B and cooled to begin crystallization of ammonia borane. Stream 31 enters HX-106 at 20.18⁰C and 2.37 bar and exits at -62.41⁰C and 2.25 bar. In VF-102 ammonia borane forms a filter cake, removing it from tetrahydrofuran solution and then collected for sale (Table 2.5.4), The liquid stream exiting VF-102, stream 34, is liquid tetrahydrofuran and is recycled back into the start of the process.
The vapor stream leaving the decomposition reactors, stream 19, contains ammonia and hydrogen. It is desired to isolate hydrogen for sale and ammonia to recycle back into the process. To begin separation we must cool the vapor stream. HX-105 is used and cools stream 20 to -73.15⁰C. This stream is then pumped into the flash drum to isolate hydrogen, entering S-101 at -73.15⁰C and 1.01 bar. Liquid ammonia is flash distilled from hydrogen, creating stream 22. Stream 22 ,containing liquid ammonia, is pumped using P-109 A/B back into the system for recycle. Hydrogen exits the flash separator in stream 23 and is compressed using CP-101. Stream 24 is the final product stream of hydrogen and is collected for sale (Table 2.5.3).
2.2: Rationale for Process Choice
Ammonia Borane can be prepared almost effortlessly in lab with quantities produced ranging from 1 to 30 grams. In order to accommodate the demands of a hydrogen economy,
-9- quantities ranging on the order of 10,000 metric tons per year will have to be produced at a competitive price. As scale up proceeds, many factors play an important role in determining a feasible synthesis route for the hydrogen rich product. The following reaction pathways below were explored before selecting a final processing choice for our plant.
2����! + ��! !��! !"# !.!"! ) 2��!��! + ��!��! + 2�! (2.2.1) ℃,!"!
����! + ���!��! !"!!"#$%& !"#$%&' !! ) ��!��! + �����! + �! (2.2.2) ℃,!"!
!"#$"% !" ����! + ��!�� ! ��!��! !"# ��!��! + �! (2.2.3) ! ℃,!"! ℃,!"!
On small scale studies, reaction 2.2.1 displayed impressive results for obtaining 23.9 grams of ammonia borane with a 98% chemical purity (Ramachandran et al., 2007). In addition to these results, the processing conditions (40℃, 1 ���) and short processing time (2 hours) were favorable, even if conditions deviated when considering scale up design. However, literature later suggested difficulties that arose due to the use of a diluted reaction medium which developed concerns for large scale processing (Ramachandran et al., 2014). This ultimately led to a second reaction mechanism, reaction 2.2.2, which involved a more concentrated solution of ammonium formate in dioxane. Reaction 2.2.2 was carefully considered due to the fact that processing conditions were still very desirable.
The lab scale apparatus in the literature for this process was placed in a fume hood to remove the hydrogen gas formed as a byproduct of this reaction. The authors mentioned during the experiment that the accumulation of hydrogen gas is a potential fire hazard , however, an additional compound involved in the process also required the use of a fume hood (Ramachandran et al., 2007). Dioxane, which is the solvent for this reaction, is suggested to be a probable human carcinogen and poses as a huge health hazard if not properly handled. From this information alone, handling large quantities of dioxane is not suitable for large scale synthesis of ammonia borane. The final reaction looked at was
-10- reaction 2.2.3, which became our best choice for the processing route for the following reasons.
When considering scale up design, it is important to research whether or not the amount of raw materials needed are practical and available in large quantities. Sodium borohydride, ammonium chloride, tetrahydrofuran (THF), and ammonia are all available in the required amounts needed for a yearly 10,000 metric ton production of ammonia borane. THF is introduced as a catalyst in the second step of the reaction to allow a kinetically favorable decomposition time of ammonium borohydride. The first step in the mechanism is carried out by what is known as a metathesis reaction. The ionic constituents of sodium borohydride and ammonium chloride exchange bonds with one another to yield sodium chloride and the highly unstable intermediate ammonium borohydride. Decomposition of this intermediate at ambient conditions will yield ammonia borane when in the presence of ammonia.
Liquid ammonia is used as a stabilizer for ammonium borohydride and is essential for the proper decomposition to occur. A hydrogen isomer of ammonia borane produced in the absence of ammonia during decomposition is known as diammoniate of diborane (DADB). Therefore, the reaction requires ammonia to be cooled (-78℃) to ensure direct contact with the intermediate and mitigate the formation of the undesirable isomer. Early on, it was determined from further research that this entire process is interchangeable in regards to alternative pathways when introducing the solvents and stabilizers (Heldebrant et al., 2008). This reaction mechanism was then chosen due to the overall flexibility of the process without obstructing the purity or quantity of the product produced.
Although THF is used as a catalyst in the second step of the reaction, we have decided to modify the traditional form of reaction 2.2.3 and introduce this solvent in the beginning of the process. This innovative idea eliminates the need to add additional heat exchangers to the condense the ammonia recycle and inlet streams because ammonia is no longer the initial solvent. All of the mixers responsible for creating a suspended solution are now free to operate at nominal conditions and are not required to be adiabatic. Moreover, THF is in
-11- the liquid phase at ambient conditions; making it much cheaper and easier to handle as the primary solvent.
2.3: Block Flow Diagram
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2.4: Process Flow Diagram
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2.5: Stream Tables
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2.6: Equipment Tables
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2.7: Utility Tables
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Section 3: Equipment Description, Rationale, and Optimization
Equipment selection for the synthesis of ammonia borane was derived for a finite yearly production based on expected future demands. The following sections describe the final pieces of equipment chosen for this process.
3.1: Mixers
For ideal feed into R-101, mixers are required to combine sodium borohydride with tetrahydrofuran and ammonia chloride with tetrahydrofuran. Sodium Borohydride and Tetrahydrofuran will be mixed with M-101, 102 and 103 (Figure 2.4). Similarly, ammonia chloride and tetrahydrofuran will be mixed in M-104, 105 and 106 (Figure 2.4). It was decided that having one large mixer for each mixing process was too dangerous due to the size of the agitator necessary, so it was split into three separate mixers. Due to this there is a total of six mixers. Each mixer will be 680 m3 and constructed of 316 stainless steel because of its corrosion resistance. The agitator motors will be powered by 62 HP electric motors. Design of three mixers for each stream will prevent plant shut down from failure of mixers or pumps, making this a non-critical maintenance, unless two mixers fail simultaneously.
3.2: Heat exchangers
To minimize corrosive effects of the fluid, 316 stainless steel was the chosen material for both shell and tube side components. The majority of the processing conditions require stream cooling to maintain desired operating conditions; with the exception of HX-104. Multiple cooling mediums chosen to pass through the tubes of an exchanger were explored and a final decision of ethylene proved to provide a wide range without experiencing unwanted phase transitions. HX-104 is the only heat exchanger that requires a separate
-23- medium to increase the temperature of the processing fluid. Ethylene glycol was the medium chosen based off similar properties of melting and boiling points.
Common tube lengths and diameters found in processing are 16ft and 0.75in, respectively (Seider et al., 3rd Edition). This parameter was then used to calculate the outside shell size based on a ratio of shell to tube provided in literature (Seider et al., 3rd Edition). Once the dimensions of each heat exchanger were calculated, the mass flow rate of medium was found using the known heat duty required for processing (see Appendix B-9 –B-14). The following section offers more insight on pressure drops experienced in shell and tube exchangers and allowed pumps to be determined based on this information.
3.3: Pumps
The overall process from raw materials to product requires nine pumps composed of hastelloy steel, due to its resistance to corrosive fluids. Sizing a pump for a certain step in the process requires knowledge of pressure drops across pipes, valves and equipment. A basis output pressure of 10atm was initially assumed to be feasible to drive the fluid to succeeding processes. Although frictional loss from pipes was not required for this report, calculations were made to estimate the pressure drop across shell and tube heat exchangers (see Appendix B-9 – B-14). Pipe length can be adjusted to account for the desired output pressure each piece of equipment operates at.
Literature provided us with an expected pressure drop range of 2-10psi over the shell side of heat exchangers (Seider et al., 3rd Edition). Aspens simulation results confirm this range of values with a more accurate approach, using our calculated area of exchange. From the equipment tables it can be shown that due to frictional loss, a heat exchanger experiences a pressure drop of ~3.7psi (see Table 2.6.1). Our initial basis for pumps was shown to be much higher than was needed to flow fluids throughout the plant. The final outlet pressure for the pumps was set at 2.37bar to accommodate for frictional losses in the shell of exchangers.
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3.4: Reactor
The first mechanistic step in the reaction (see Reaction 2.2.3) responsible for producing the highly unstable intermediate, ammonium borohydride, is carried in in reactor R-101. The liquid phase mediums that are interacting with the reactor during operation are tetrahydrofuran and ammonia. Both solvents demonstrate corrosive behavior, which led to a limited range of options for the material choice of the reactor. Hastelloy steel, a nickel based alloy, was used in previous small scale studies due to its high resistance to corrosion (Ramachandran et al., 2014). Although desirable, the material itself from an economic standpoint would not be suitable for a reactor volume of 219m3. Instead, low carbon steel lined with a corrosive resistant material seemed to be a feasible method for creating a suitable reaction environment.
A corrosive resistant brick lining is more economically feasible than a reactor constructed of 316 Stainless Steel. The choice for a corrosive lining brick from KochKnight LLC and is the Knight-Ware Acid Proof Brick Type II (Pressed) and Type III-WR (KochKnight LLC, web). For safety precautions a two layer, 0.305 meter thick lining system will be created to prevent the process fluid ever reaching the carbon steel structure of R-101. The base layer will be constructed of Type II Pressed brick, sealed with KochKnight ACIDSIL mortar (KochKnight LLC, web). The exposed, active layer will be constructed from Type III-WR brick since it has preferred characteristics of abrasion resistance in acidic process slurries. Also, Type III-WR has the lowest brick porosity and acid solubility. Utilizing brick lining will become an advantage if operating conditions change, requiring only a change in lining systems and not an entirely new reactor. It is important to review liner options before final construction plans are submitted, a lining system will account for a volume loss within the reactor.
The reaction takes place at ideal operating conditions of -78℃ and 1atm, which is slightly above the melting point of liquid ammonia. This temperature ensures that liquid ammonia will be in direct contact with solid ammonium borohydride as the reaction proceeds. Insufficient contact between the two will lead to immediate decomposition of ammonium
-25- borohydride to produce the diammoniate of diborane and hydrogen gas. Literature proposed a residence time of 1 hour for the first mechanistic step (Ramachandran et al., 2014). The reactor volume described above was calculated based on the residence time and amount of material needed for a yearly 10,000 metric ton production of product (see Appendix B-2).
3.5: Semi-Batch Vessels
The second mechanistic step in the reaction (see Reaction 2.2.3) involves the decomposition of ammonium borohydride to produce ammonia borane and hydrogen gas. This is carried out in three 325m3 vessels (V-101, V102, V-103A/B) connected in parallel to each other and in series with reactor R-101 (see Figure 2.4.1). Vessel volumes were approximated using the highest experimental residence time for 99% yield of ammonia borane. From here, the decomposition half-life was used to find a new residence time, corresponding to a 99.99% conversion (see Appendix B-1). The vessels are controlled by valves to regulate the cycles each undergoes during operation. One cycle is defined here by the filling, decomposing and draining phases that occur in each vessel.
Although a residence time of 1.51 hours was calculated, it was decided to start the timer when the tank is completely filled. This was decided due to the uncertainty in physical parameters for the ammonium borohydride and ammonia borane. Therefore, the total residence time for each cycle of the semi batch vessels is 4.51 hours. Reactor size was chosen so that there would always be one reactor empty, to allow maintenance when required, and to minimize the time the other reactors are empty. Using 325 m3, each reactor will be empty for only 24 seconds after full discharge before it starts refilling (see Appendix B-1). The vessels operate at ambient conditions (20℃ ,1atm), leading to vapor formation of ammonia and hydrogen gas. Each tank was modified with an extraction fume hood, to remove the evolving ammonia and hydrogen gas from the slurry. The material of choice for the vessels were similar to that of reactor R-101. Stainless steel 316 was chosen, along with an inner glass liner to prevent corrosion from forming. For maintenance purposes, we have decided to add an additional tank to keep the process fully operational.
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3.6: Vacuum Filtration
Before evaporating THF, sodium chloride must be separated from ammonia borane. Many small scaled experiments documented in a patent, reveal the separation of solid sodium chloride from dissolved ammonia borane via vacuum filtration (Autrey, 2009) Scaling up this apparatus, a common continuous unit operation suitable for solid-solute separation is known as a rotary drum vacuum filtration system (RDVF). It was decided that with proper maintenance, a stainless steel 316 drum filter would be sufficient for this process. Typical RDVF systems operate between 0.1 to 2 rpm with 30% of the drum submerged in the slurry (McCabe, pg. 1010). The area of the drum calculated was 55.2 m2 by assuming a cake thickness of 10.16cm and an average rotational speed of two revolutions per minute (see Appendix B-6).
Ammonia borane and THF leave the first vacuum filtration system and enter a second rotary drum filter (VF-102). The pore size of the second filter is decreased from the first, in order to build up ammonia borane on the outer drum surface. This is the final separation process, where the solid product is separated from the recycle stream. Assuming an average rotational speed of two revolutions per minute and a cake thickness of 10.16cm, the area of the drum is determined to be 55.5 m2 (see Appendix B-6). Stainless steel 316 is again the superlative choice due to its resistance to corrosion. Optimization of product can be obtained by driving the liquid solution towards the eutectic point; which causes the dissolved ammonia borane to crystallize. However, there is no recorded information on the heat of fusion for ammonia borane or vapor pressure at temperatures. This makes an SLE graph almost impossible, as shown by the attempt in Appendix D-1. A eutectic point will have to be found experimentally and then compared to viscosity at that temperature to ensure acceptable flow ability.
Although the literature fails to mention the specific filters used in lab, assumptions were made for the overall process due to solid-liquid separation. Sodium chloride has an average particle diameter of 250um and is filtered first (askavantor.force, 2006). A particle
-27- diameter has not been determined yet, but a particle distribution of 20um for THF is known. Therefore, ammonia borane must fall between the two ranges and a mesh should be chosen slightly above and below the critical values. The particle size for ammonia borane was set to 115um for simulation purposes in computer aided design (see Figure 2.4.4). Filter cloths for both RDVFs have not been determined due to limited information on particle sizes. Vacuum filtration is calculated using the formulas shown on Appendix B-6. However, this requires the resistance of the filter medium and the specific cake resistance. No values could be found for either of these variables so the area determined is a general approximation and must be corrected by experimentation once the plant is operational. In some small scale operations, a rotary evaporator is used to purify the ammonia borane product instead of vacuum filtration. Thus an evaporator was first considered for separating the THF and ammonia borane. The equipment price of the evaporator was feasible however, due the large amount of THF present, the required steam for the necessary vaporization would be in the billions of dollars (see Appendix B-3). It was not logical to continue discussing an evaporator after this conclusion was made.
3.7: Flash Drums One flash drum was used to separate the ammonia and hydrogen gases leaving the extraction fume hoods placed on the top of the vessels (Figure 2.4.1). The ammonia is recycled back into R-101 while hydrogen proceeds to the compressor. Both separators will be made of 316 stainless steel. The feed for S-101 enters at 200K and will be a mixture of vapor and liquid. 1,832,321 mol/hr of liquid ammonia and 35 moles of hydrogen liquid will come out the bottoms of the separator and be recycled back into our process. 35,233 moles/hr of hydrogen and 1834 moles/hr of ammonia vapor leave from the top stream. The vapor stream will continue to the compressor. Separator S-101 will have a diameter of 14 ft and a length of 42 ft, which correlates to a total volume 183.1 m3.
3.8: Compressor
Since the hydrogen gas byproduct is coming out at only 14.7 psi a compressor must be used to pressurize for the subsequent sale. This is carried out in a two stage reciprocating
-28- compressor. The compressor will be made of stainless steel, with ductile iron being used for the o-rings and pistons. A 95% hydrogen vapor mixture enters the compressor at 28.85 psia and is compressed to 1014.7 psia. The compressor was sized to 577.62 m3/hr of hydrogen product, with a piston displacement requirement of 1708.5 m3/hr. The hydrogen will enter at 200K and would leave at 563K. An intercooler will be required to cool the hydrogen back down to a reasonable temperature, which will be done using water. The compressor will work at 6700 rpm, and require 62.32 kW/h. Compressed hydrogen will then travel to the necessary storage containers and will be sold as a byproduct.
Section 4: Safety and Environmental Factors
4.1: Safety
In the hypothetical construction of the plant for D.A.B Chemicals, safety was a main priority. Detailed hazard and operability study were developed for the four major equipment pieces in the plant and can be viewed online.
The decomposition reactors are inherently dangerous due to the large amount of vapor that is being siphoned off the ammonia borane product. This means that the fume hoods are critical to ensure safe operations of the equipment. If the fume hood malfunctions, the pressure that the gasses place on the reactors could create a catastrophic rupture. If any ignitable sources are present, there is the possibility that hydrogen will ignite and explode. Due to the possible repercussions of a fume hood malfunctions, it will be placed as a critical system to plant operation and safety. Along with this an emergency release valve will be installed, allowing us to vent the tank in case of extreme gas buildup. This will initially vent to any empty space in the hydrogen storing tanks, and then to the atmosphere if the emergency persists.
-29-
NH3BH3 gfschemicals, NaBH4 MSDS, CH4Cl MSDS, NaCl MSDS, Hydrogen MSDS, Ammonia MSDS, Tetrahydrofuran MSDS
The most dangerous scenario identified for the plant is failure of the cooling systems to R- 101. R-101 operates at a temperature of -78 C, as liquid ammonia is necessary for the stabilization of the ammonium borohydride intermediate. If the heat exchangers upstream malfunction, it has not only major repercussions in the reactor itself but of many pieces downstream. If there is complete failure of the coolant, ammonia would vaporize out either in the pipe leading to the reactor or within the reactor itself. If it vaporized in the pipes leading to the reactor it could cause a major rupture in the pipe, possible leading to concentrated and toxic ammonia being released into the atmosphere. If the ammonia vaporizes in the reactor vessel it would create significant pressure in the reactor, which is only rated for 1 atm, leading to explosion. If this happens ammonia, ammonium borohydride, THF, sodium chloride, ammonium chloride and sodium borohydride would all be released into the immediate area. The big concern is the release of ammonium borohydride and sodium borohydride. As stated in the previous paragraphs sodium borohydride will react violently with water or moisture. This reaction produces flammable
-30-
NaBH4 datasheets, CH4Cl Osha, NaCl MSDS, Hydrogen Osha, Ammonia Osha, Tetrahydrofuran Osha gasses that are nontoxic. Ammonium borohydride has unknown hazards as it is a very new compound, however it does naturally degrade to hydrogen with a half-life of only 9 minutes
(Appendix B-1). This degradation produces hydrogen gas, which is extremely flammable. This, mixed with the flammable gasses that can be produced by sodium borohydride reactions, could create a ‘doomsday’ scenario. Any ignition sources could potentially light the gasses. The last potential hazard of this is that explosions caused by the rupture could damage storage containers for pressurized hydrogen or other materials leading to possible reactions between the chemicals.
-31-
NaBH4 Datasheets, CH4Cl Osha, NaCl MSDS, Hydrogen Osha, Ammonia, Osha, Tetrahydrofuran Osha Several actions are required to mitigate this potential hazard. The reactor will be made from 316 stainless steel, giving it extra strength in case of slight pressure build up (and for the corrosion resistance). An emergency vent valve will placed into the reactor itself. If a pressure buildup is sensed the vent will open, releasing any forming ammonia gas. This vent will lead to a storage area normally reserved for the hydrogen gas byproduct. This storage area can hold up to 4100 m3 of gas. This should allow the necessary time to cut flow into the reactor. A backup generator will also be installed and connected to the cooler, allowing the continued operation of this equipment in case of power failure.
The chemicals that require special attention are sodium borohydride and hydrogen. Sodium borohydride is the most dangerous solid chemical that is used in our process and special precautions should be taken when handling the material. It is a flammable material and is corrosive in liquid form. If it ignites use a dry powder for small fires and fog for larger fires. It should be stored in a place without ignition sources, and all equipment should be grounded. Up to a month's worth of sodium borohydride, 1072 tons, will be kept at the plant at all times (Appendix A-1). Container should be placed in a cool area and separate from other materials. Containers should not be placed in any place near water, as corrosion to containers can cause interaction between sodium borohydride and outside contaminants (Sodium Borohydride MSDS, web).
-32-
A vapor and dust respirator should be worn at all times when handling the solid compounds, along with other basic PPE gear. Anyone using or transporting sodium borohydride on plant grounds should be trained and have experience dealing with dangerous materials (Sodium Borohydride MSDS,web).
Hydrogen is the most dangerous gas currently used on site. Large amounts, up to a week's worth, can be stored on plant property at any one time. Hydrogen is an odorless compound, and is not easily identifiable when it leaks. Containers should be stored in a separate area, and away from any ignition sources. Pressurized vessels will be filled from the storage and sent off to customers. Hydrogen is an extremely flammable compound and will ignite rapidly with a lower explosion limit of just 4%. All containers must be inspected on a regular basis for corrosion or damage as some steel containers can corrode while storing the material under high pressure. Hydrogen is the lightest gas known, and thus can sometimes be trapped at the top of structures or buildings if there is not proper ventilation. Any areas that handle hydrogen must have proper ventilation installed and proper PPE equipment must be worn at all times (Hydrogen MSDS, web).
4.2: Environmental Impact The D.A.B chemical plant has associated risks in regard to the environment, but ultimately the project furthers the cause of green energy.
Ammonia borane was developed for use in hydrogen fuel cell vehicles, a leader in green transportation. Currently cars and trucks account for ⅕ of all emissions in the US. Roughly 24 pounds of greenhouse gasses are emitted for each gallon of gas, with 5 pounds being made before delivery and a further 19 pounds being emitted out the tailpipe of every vehicle. Hydrogen fuel cell vehicles only release water and heat, using the electrons on the hydrogen to create electricity for the motor. This means that ammonia borane has the theoretical capacity to completely replace gas in motorized vehicles. The only greenhouse gasses that are released are creating the actual product, transporting it to customers and disposing of the waste material (Ucsusa, Web).
-33-
NaBH4 datasheet, CH4Cl Detail Chemical, NaCl Eurochlor, Hydrogen NovaChem, Ammonia Colostate, boron nitride Lenntech, Tetrahydrofuran Pubs
Environmental risk is dependent on the individual materials used in the process. The GWP (global warming potential) is commonly used to measure the environmental effect of waste gasses. The GWP works by measuring how much energy one ton of gas will absorb over a set time interval relative to a single ton of carbon dioxide. The GWP is usually measured in terms of 100 years.
Table 4.2.1 shows the GWP for the process chemicals as well as that for boron nitride. Boron nitride is not a process chemical but it is the expected end product of the ammonia borane combustion. To be thorough in our research of the environmental impact of our chemical and production, D.A.B Chemicals agreed that boron nitride should be included in the analysis. Once again, as this is a relatively new reaction and process, there is very little information on the ammonium borohydride intermediate and the ammonia
-34- borane products. Further research will have to be done at the plant so as to be aware of potential environmental effects.
The boron nitride end product for the ammonia borane is considered nontoxic and is not an environmental contaminant. In the process, boron nitride will be considered waste and will be dumped. However, there is a possibility of recycling the product and rehydrating it back to ammonia borane, but this is past the scope of the project.
Table 4.2.2 details specific information on how to deal with accidental release, disposal method and other important factors for each process chemical. Once again, there was no information on the ammonium borohydride intermediate but D.A.B was able to obtain information on ammonia borane. It was hard to find specifics on certain chemicals, for example, information was found showing that ammonia borane was soluble in water but not its specific solubility.
In general accidental release measures were to avoid creating dusty situations with the solid chemicals, while gaseous chemicals required proper ventilation and nullification of ignition sources. Disposal of chemicals were unique however, and all personnel should have proper education and training in dealing with each situation. During disposal or accidental release, all safety equipment should be worn in accordance to plant standards.
In 1976 congress passed a law called RCRA (Resource Conservation and Recovery Act) governing the disposal of solid hazardous waste. RCRA is maintained by the EPA, and is under EPA policy and guidance. EPA defines solid waste as any “discarded material that is not excluded under § 261.4(a) or that is not excluded by a variance granted under §§ 260.30 and 260.31 or that is not excluded by a non-waste determination under §§ 260.30 and 260.34.(2)(i) A discarded material is any material which is:(A) Abandoned or (B) Recycled or(C) Considered inherently waste-like” (Government Publishing Office, Web).
-35-
A waste is hazardous if it contains one of the following four characteristics: toxicity, ignitability, corrosivity, or reactivity. Ammonia, sodium chloride, hydrogen, sodium borohydride, and tetrahydrofuran are all listed as hazardous in title 40 of the code of federal regulations. RCRA states that any transaction regarding these chemicals must be tracked. If the chemical is traded to another company or person, a copy of that transaction is sent back down to everyone who has been involved previously (Legal Information Institute, web).
D.A.B Chemicals will be considered a large quantity generator as it will generate over 1000 kg of waste product a month. Due to this, an EPA identification number must be obtained from the state environmental office. All wastes must be packaged, labeled, marked, and placarded properly in compliance with EPA and state regulations. As D.A.B Chemicals will store hazardous chemicals, it must also obtain a RCRA permit. Non compliance with EPA rules could incur penalties of up to $27,500 per day (Bergeson & Campbell, Web).
-36-
-37-
Section 5: Economic Analysis
There are currently no reliable or reported manufacturers of ammonia borane on the market that produce the same amount the D.A.B plant would hypothetically make. The largest reported on the web can produce approximately 1200 tons of ammonia borane a year, only 12% of the amount the D.A.B Chemicals plant plans to make. This is not surprising, as while ammonia borane has been identified as a suitable substitute for hydrogen storage, there isn’t currently a high demand for large amounts of the product. No market data currently exists on the amount of ammonia borane sold globally.
Due to the limited amount of suppliers of the product, introduction of D.A.B chemical ammonia borane to the global market could significantly affect both the global price for the material as well as the global supply of the material. As D.A.B intends to to sell this at the lowest price possible, it could suddenly upturn the market. Current prices are stable at $700/kg for the product (Alibaba, Web), but to be as competitive as possible D.A.B will sell ammonia borane as low as $9.00/kg. This will effectively not only price out our competitors but significantly shift the global price.
A stable market price was assumed for the sodium borohydride and ammonium chloride reagents. Global market sales for sodium borohydride could not be determined, but multiple vendors were found that had the capacity to sell at up to 3000 tons a month. It was concluded that the amount sold to D.A.B. would not affect global prices or demand. The same was concluded for ammonium chloride. No global sales or production could be found, but suppliers were found that had the capacity to create 600,000 tons a year.
Ammonia and tetrahydrofuran are used as stabilizers and catalysts in our production. We assumed a stable price and supply for both of these chemicals. Worldwide production of ammonia in 2006 was 122,000,000 metric tons while THF production was 800,000 tons.
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Our production requirements are miniscule compared to these numbers, and should not create any impact globally. THF is 100% recycled in our process while we lose 16,065,840 moles a year of ammonia. Both these chemicals are replaced yearly.
Suppliers able to give D.A.B the required reagents were found on Alibaba. However, the prices quoted were often for either a gram, a kilogram, a single ton, or an order of 20-50 tons. It was concluded that the prices would not give us a completely accurate statement of material costs for the large purchases required. Due to this, bulk price graphs were generated by using multiple suppliers. Minimum order quantity (tons) was graphed versus price ($), and a line of fit was generated. Using the formula of the line, monthly requirements were inputted and bulk price was found. The numbers were discussed by the team to understand if they were plausible. Final prices can be found in Appendix A-3. An example can be seen at figure 5.1. All prices were used except the bulk price of ammonia, as that was deemed to be too low.
Ethylene glycol and ethylene were used as coolants in the heat exchangers. Ethylene glycol is priced at $1,085 a ton and ethylene is priced at $978 a ton (Alibaba, Web). Total amounts of cooling was found by using the ASPEN numbers generated for required flow. A total price of $1,581,012.11 a year was calculated with ethylene being the largest cost (88% of total cost). Calculations can be found in table 2.7.3.
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Hydrogen and sodium chloride are byproducts of the ammonia borane production and will be sold to maximize profit. While a greater profit could be recorded if we sold each at a per pound basis, it was decided that a bulk price sale would be more realistic. Due to the bulk sale, D.A.B profits were reduced to as low as 14% of the per pound sale. Salt is sold at $57 a metric ton and hydrogen at $2900 a metric ton. Total sales can be seen in figure 5.2.
Transportation of product will generally be customer's responsibility. The Texas area has numerous rail networks to easily transport large amounts of material, so this will be D.A.B.’s preferred method. Transportation cost will generally priced at $0.035/lb which will include freight and lease/ownership costs (“RE Question”).
The D.A.B plant will require significant energy needs to fuel its operation. The total equipment kilowatt requirement is 363 million kW a year, which is roughly $29 million a
-40- year at the Houston average price of $0.08 a kW (Powertoswtich, Web).The six heat exchangers (HX-101-106) account for about 67% of total cost as shown in figure 5.4. The vacuum filters are the next major user of electricity, with $7 million. The decomposition reactor was assumed to take negligible electricity, as only the sensors and fume hood would require any energy. The CSTR calculations were found using agitator power requirements. The flash drum was also assumed to have negligible power needs as the heat exchanger downstream cools the stream. Total costs can be found in figure 5.4.
The cost D.A.B would have to sell ammonia borane for was calculated using an ROI (return of investment) of 25%. With this ROI, the D.A.B. plant will have a payback period of 3.26 years and the product will have to be sold at $8.97 a kilogram (Appendix C).
The plant will employ 21 operators, with an average of two operators per process section. They will be employed in five shifts, which was indicated by the (Seider et al). Five shifts are commonly used because it takes into account illness, vacation, holidays, training,
-41- special assignments, and overtime. The total labor-related cost will be $8,472,920 annually with the largest portion coming from annual direct wages and benefits.
Due to our operations having a solid-fluid flow a 4.5% maintenance rate was required, instead of the 3.5% commonly seen for a liquid only flow. Total annual maintenance cost will be roughly $3.8 million and shown in figure 5.7.
Property taxes are rated at 0.02% of total direct costs. An 8% direct plant depreciation and a 6% allocated plant rate was used for total depreciation. A straight line depreciation model was advised, which is not entirely accurate in the long term. This led to a total cost of production of 65,222,000, with a gross earnings of $19 million and net profit $12 million (Figure 5.7).
Cash flow profiles were generated for the NPV’s at different interest rates and are shown in figure 5.6. Typically an interest rate of 15% is chosen, however it would take over 30 years for the D.A.B. company to produce a positive cash flow profile at this number. If a 9% interest is used, it will take 13 years to become positive. A 14% interest would generate a positive cash flow at 30 years. The quickest we can get a net positive cash flow is at a zero interest rate, which would be at 9 years. However this is not realistic. After 30 years, the D.A.B process is at $435 million at 0% interest, $47 million at 10%, -$4 Million at 15%, and -$30 million at 20%.
The ammonia borane production process is very dependent on the price of electricity. If electricity were to increase, even marginally, it would cause significant changes to our
-42-
-43- profits. Currently electricity accounts for 95% of all utility costs. This is due to the sheer amount of THF and ammonia we have flowing through our system at any time, and the energy requirements to continuously cool and heat the mixture (Figure 5.5).
Our economics is unstable in the fact that many of our calculations were based off theoretical numbers. We could see a significant decrease, or increase, in actual numbers once the plant becomes operational and certain parameters can be experimentally determined. The overall goal is to try to get plant costs down to a level where we could sell ammonia borane competitively against gasoline in the global market.
To cut costs D.A.B recommends focusing on building a power plant on site to deal with the energy requirements for the process. If this is not feasible, finding and dealing with certain electricity suppliers could significantly reduce power costs. The 0.08kW/hr cost was found by averaging out every power supplier in the Houston area, but certain prices as low as 0.06 kW was found. At that price, our power requirements would fall from $29 million to $21 million dollars, a net saving of $8 million a year.
There is an inherent economic hazard in the process, and that is the price of ammonia borane to gasoline. The ammonia borane produced is intended for hydrogen fuel cell vehicles, and thus has to be competitive to global gasoline prices. Currently, that is not
-44- possible because gasoline would have to rise to the incredible amount of $23.62 a gallon. Even if it reaches this number, ammonia borane sales would not be ensured because gasoline prices can fluctuate rapidly.
Section 6: Conclusion and Recommendations
Material based hydrogen storage is still a new area of research, with many other compounds being studied. Although ammonia borane is made up of 19% hydrogen (wt/wt%), the final reaction to form boronitride and hydrogen gas is not practical due to a high initiation temperature of 500℃. In addition to this extreme temperature, the accompanied product boronitride reduces the life of a fuel cell (Himmelberger, 2010). Ammonia borane, as it stands, is not economically feasible for current market conditions. Future work to mitigate the large gap between solid storage solutions and current high pressure systems will need to continue.
For our compound to be competitive in the current global market, we would need to sell it for $0.87 a kilogram (Appendix D-2). Using this price, with an average US mile per gallon of 21.4 (Rita, Web) and a $2 price per gallon, there would be a $4.23 difference in refuels prices (EIA, Web). However, this is economically disastrous for the D.A.B company as the net profit would be $ -29.6 million.
Gas prices would have to rise by 1100%, to $23.62 a gallon, to have a reasonable payback in the United States (see Appendix A-1). However, selling on the european market would be more feasible as prices can go up to $1.81 a liter (which is $6.85 a gallon). A rise of 345% in gas prices would make the D.A.B company profitable in the Europe. If this is chosen, marine cargo transport prices must be taken into account.
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Since ammonia borane is a green process, and will be used in hydrogen fuel cell vehicles, certain tax breaks are applicable to our process and the purchasing of HFCV. Section 30B and 30D in the federal tax laws give significant credits to those who purchase green cars. Current incentives can pay out as much as $40,000 for large vehicles. Section 30C in the tax laws also state that up to 50% credit can be received for installing qualified clean refueling property. This amount can go up to $50,000 normally, and up to $200,000 for hydrogen sources (Grant Thorton, Web). This may allow us to lower our price of ammonia borane, but by how much is still to be understood.
A compound with a higher wt% of hydrogen and a simplified process is ideal to become a competitive company in the current and future market. This solution can become a reality if the ability to stabilize the reactive intermediate ammonium borohydride is improved. Ammonia poses as a human health hazard and should not be used as a suspension medium in lightweight transportation vehicles. By truncating after the first part of the mechanism in reaction 2.2.1 many pieces of equipment, shown in figure 2.3.1, can be eliminated after reactor R-101. The cost reduction for producing this new product, as well as the higher hydrogen content of 24.5% (wt/wt%) would be achieved. D.A.B Chemicals recommends implementing stability research to formulate a stronger and more feasible compound for future material based storage systems.
Another way to reduce costs in the process would be to develop a fuel cell that is compatible and capable of removing all the hydrogen from ammonia borane and produces boron nitride. This would mean that only 25 kg of ammonia borane is required for 314 miles of driving rather than 38kg. Corresponding gas prices would then only have the be $15.74 for the process to be profitable. That is only a 230% rise in european gas prices and a 787% rise in US prices. This would be difficult however, due to the sheer temperature required.
If selling ammonia borane for vehicle fuel purposes is not feasibile, there may be a market for alternative uses. Currently ammonia borane sells for $400-700 a kg, while we can
-46- produce and sell it for $8.97. This would mean D.A.B could create a monopoly in the ammonia borane market. However, current demand does not seem to require the 10,000 tons we produce annually. There will need to be further research into this alternative route before it can be commented on in any significant way.
While this process unfortunately cannot be done currently, there is hope that someday it could become a reality. As gas and oil continues to dwindle there will need to a focus on alternative sources of energy that can fuel our world needs. Material based hydrogen storage is still seen as an exciting and feasible way to contribute to our demands, and should continue into the foreseeable future.
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Section 7: Nomenclature
Symbol Units Description A ft2 Heat Transfer Area ACFM ft2/min Actual Cubic Feet per Minute Cb $ Base Cost Cp Btu/lb-oF Specific Heat Added Cost for Ladders and Cpl $ Platforms D ft/m/in Diameter E Weld Efficiency FBM Base Module Factor FM Material Factor H ft Pressure Head Hf kJ/s Enthalpy entering system Hl kJ/s Enthalpy of Liquid Hp Hp Horse Power Hv kJ/s Enthalpy of Vapor kW kJ/s Kilowatt L m, ft, in Length m kg/min Mass Flow Rate N Number of Tubes Ps bar Pressure Suction Pd bar Pressure Discharge PD M3/hr Piston Displacement Q Btu/hr Heat Transfer Rate gallons/min, m3/min, Qf ft3/min Flow Rate R Compression Ratio S psi Maximum Allowable Stress SCFM ft2/min Standard Cubic Feet per Minute Tin oF Temperature Inlet Tp in Wall Thickness Tout oF Temperature Outlet U Btu/lhr-ft2-oF Overall Heat Transfer Coeff U perm ft/s Permeability V m3, ft3 Volume
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Section 8: References
alibaba.com. Web. price-THF_60336365332.html?spm=a2700.7724857.29.230.JoAzMi>. " First-Order Reactions ." UC Davis Chemwiki. Web. Order_Reactions>. "99.8% Liquid Ammonia." alibaba.com. Web. 99-8-Liquid-Ammonia_60383542010.html?spm=a2700.7724857.29.12.dLsZ0I>. Air Products. "Material Safety Data Sheet Ammonia." December 1999. Web. ---. "Material Safety Data Sheet Hydrogen." June 1994 Web. "Ammonium Chloride." Alibaba.com. Web. Ammonium-Chloride-with- reasonable_60349428188.html?spm=a2700.7724857.29.30.2snf8T&s=p>. "Ammonia Production." ChemEngineering. Web. 19 Apr. 2016. Autrey, S. T., D. J. Heldebrant, J. C. Linehan, et al. Process for Synthesis of Ammonia Borane for Bulk Hydrogen Storage . Patent US20090291039 A1. Nov 26, 2009. -49- Autrey, S. T., David J. Heldebrant, J. C. Linehan, et al. Process for Synthesis of Ammonia Borane for Bulk Hydrogen Storage. Patent US 7,897,129 B2. March 1, 2011. "Average Fuel Efficiency of U.S. Light Duty Vehicles." www.rita.dot.gov. Web. n_statistics/html/table_04_23.html>. "Cars and global warming." http://www.ucsusa.org. Web. vehicles/car-emissions-and-global-warming#.Vx5urvkrKM9>. "Code of Federal Regulations." Government Publishing Office. 7 Jan. 2012. Web. 19 Apr. 2016. part261.xml#seqnum261.30).>. "Compressors." Web. Selection%20and%20Sizing.pdf>. Davis, H. Ted, and Raul A. Caretta. "Analysis of a Continuous Rotary-Drum Filtration System." AIChE Journal 56.7 (2010): 1737-8. Print. "Disposal of Solid chemicals in the Normal Trash." Web. Engineering toolbox. "Specific Heat ratio." Web. heat-ratio-d_608.html>. -50- "Ethylene Glycol (EG) Prices and Pricing Information." http://www.icis.com/. Web. and-pricing-information/>. Fisher Scientific. "Material Safety Data Sheet Ammonium Chloride." August 2, 2000 June, 1999. Web. ---. "Material Safety Data Sheet Sodium Chloride." 8/14/2001 7/12/1999. Web. "Gas Encyclopedia." encyclopedia.airliquide.com. Web. 18>. "Gas Encyclopedia." http://encyclopedia.airliquide.com. Web. "Gas Price History Graph." zfacts.com. Web. "Gasoline and Diesel Fuel Update." www.eia.gov. April 18, 2016 2016. Web. GFS Chemicals. "Ammonia Borane Material Safety Data Sheet." 2008. Web. S%20US.pdf>. "Green Tax Incentives and Credits for Businesses and Individuals." Grant Thorton. 2010. Web. 20 Apr. 2016. files/GreenTaxCreditsWhitepaper2010.pdf >. -51- "HAZARDOUS WASTE MANAGEMENT UNDER RCRA FREQUENTLY ASKED QUESTIONS." Bergeson & Campbell PC. Web. Heldebrant, David J., et al. "Synthesis of Ammonia Borane for Hydrogen Storage Applications." Energy & Environmental Science 1.1 (2008): 156-60. Print. Himmelberger, Daniel W. "Hydrogen Release from Ammonia Borane." Doctor of Philosophy University of Pennsylvania, 2010. Print. Hosmane, Narayan S. Boron Science: New Technologies and Applications. Ed. Narayan S. Hosmane. 1st ed. CRC Press, 2011. Print. "Houston Electric Rates." power2switch.com. Web. "Knight-Ware Acid Proof Brick." KochKnight LLC. Web. lining.html>. LearnChemE. "Single-Effect Evaporator: Heat Transfer Area." 2012. Web. "Materials-Based Hydrogen Storage." The Office of Energy Efficiency and Renewable Energy. The Fuel Cell Technologies Office's, n.d. Web. 27 Apr. 2016. "Material Safety Data Hydrogen." http://avogadro.chem.iastate.edu. Web. McCabe, Warren L., and Julian C. Smith. Unit Operations of Chemical Engineering. New York: McGraw-Hill, 1976. Print. "Mesh (Scale)." en.wikipedia.org. Web. -52- Overall Heat Transfer Coefficients for some Fluids and Heat Exchanger Services. http://www.engineeringtoolbox.com/overall-heat-transfer-coefficients-d_284.html: The Engineering ToolboxPrint. "Question." Message to the author. 19 Feb. 2016. E-mail. Ramachandran, P. Veeraraghavan, and Pravin D. Gagare. "Preparation of Ammonia Borane in High Yield and Purity, Methanolysis, and Regeneration." Inorganic chemistry 46.19 (2007): 7810-7. Print. Ramachandran, P. Veeraraghavan, et al. "Ammonia-Mediated, Large-Scale Synthesis of Ammonia Borane." Dalton Transactions 43.44 (2014): 16580-3. Print. Resource Conservation and Recovery Act. 42 U.S.C. §6901 et seqPrint. "Resource Conservation and Recovery Act (RCRA)." Legal Information Institute. Web. 17 Apr. 2016. Santa Cruz Biotechnology. "Material Safety Data Sheet Sodium Borohydride." July 17, 2009. Web. ScienceLab.com. "Material Safety Data Sheet Tetrahydrofuran." 5/21/2013 10/10/2005. Web. Seider, Warren D., et al. Product and Process Design Principles. 3rd ed. Wiley, 2008. Print. Shen, Jerry. "Sodium Borohydride 98%." Web. quality-Sodium-borohydride-98- 16940_501364237.html?spm=a2700.7724857.29.144.N0BuoQ>. -53- "Sodium Chloride- Particle Size." askavantor.force.com. Web. Susannah, Scott. "Standard Operating Procedure Sodium borohydride." 2013 2012. Web. pdf>. "Tetrahydrofuran 99.9%." alibaba.com. Web. quality-Tetrahydrofuran-THF-99-9_316011086.html?spm=a2700.7724857.29.260.3ONVMA>. "Tetrahydrofuran 99.9%." alibaba.com. 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Print. -55- Section 9: Appendices Appendix A: Process Calculations A-1 Theoretical Material Balance A-2 ChemCad Material Flow A-3 Material Bulk Price Appendix B: Equipment Pricing and Sizing B-1 Decomposition Reactor B-2 CSTR Reactor B-3 Evaporator B-4 Storage B-5 Compressor B-6 Vacuum Filtration B-7 Mixers B-8 Pumps B-9 HX-101 B-10 HX-102 B-11 HX-103 B-12 HX-104 B-13 HX-105 B-14 HX-106 B-15 Heat Exchanger Cost B-16 Flash drum Appendix C: Economic Calculations C-1 Total labor-related operations annual cost C-2 Maintenance -56- C-3 Operation Overhead C-4 Property Taxes and Depreciation C-5 Cost of Manufacture and General Expenses C-6 Total Cost of Production and Working Capital C-7 Total Capital Investment C-8 TCI, ROI, PBP, VP, Ca C-9 Product Selling Price C-10 Present Value Appendix D: Other Process, Calculations, and Numbers D-1 Attempted Eutectic D-2 Competitive Material Calculation D-3 Hazard Statements Appendix E: Overall Mass Balance Appendix F: Meeting Logs -57- Appendix A: Process Calculations A-1 Theoretical Material Balance -58- -59- A-2 ChemCad Material Flow -60- A-3 Material Bulk Price -61- -62- Appendix B: Equipment Sizing and Costs B-1 Decomposition Reactor -63- -64- B-2 CSTR Reactor -65- -66- B-3 Evaporator -67- -68- B-4 Storage -69- -70- B-5 Compressor -71- B-6 Vacuum Filtration -72- -73- -74- -75- B-7 Mixers -76- B-8 Pumps -77- B-9 HX-101 -78- -79- B-10 HX-102 -80- -81- B-11 HX-103 -82- -83- B-12 HX-104 -84- -85- B-13 HX-105 -86- -87- B-14 HX-106 -88- -89- B-15 Heat Exchanger Cost -90- B-16 Flash drum -91- -92- Appendix C: Economic Calculations C-1 Total labor-related operations annual cost -93- C-2 Maintenance -94- C-3 Operation Overhead -95- C-4 Property Taxes and Depreciation -96- C-5 Cost of Manufacture and General Expenses -97- C-6 Total Cost of Production and Working Capital -98- C-7 Total Capital Investment -99- C-8 TCI, ROI, PBP, VP, Ca -100- C-9 Product Selling Price -101- C-10 Present Value -102- -103- Appendix D : Other Process, Calculations, and Numbers D-1 Attempted Eut -104- 450 400 350 300 250 THF Ammonia Borane Temp (C) 200 Series3 150 Series4 100 50 0 0 0.2 0.4 0.6 0.8 1 1.2 X -105- D-2 Competitive Material Calculation -106- D-3 Statements -107- Appendix E: Mass Balance -108- Appendix F: Meeting Logs January 18, 2016 • Review current materials being used • Find references for top candidates for hydrogen storage • Start files to keep track of work done and references in google docs January 25, 2016 • Create a timeline for entire semester of work o Review of current technology o In depth material review o Final material selection o Determine amount of chemical needed o Review on plant setup o Chemcad Simulation o Design of plant o Review waste products o Design of waste streams o Design of recycle streams o Review of current documents on selected material o Finalize all project material o Write report January 28, 2016 • Picked ammonia borane as storage material • Started in depth review of ammonia borane February 2, 2016 • Looked into amounts of ammonia borane required to fuel majority of hydrogen fuel cell cars in the future • Look into different processing routes for ammonia borane, using different feed stocks • Determine distance traveled per kilogram of ammonia borane • Compare gas to hydrogen fuel cell distance traveled February 5, 2016 • Meet with Dr. Blowers to discuss using refworks to keep track of sources • How to price bulk material and production needs February 8, 2016 • The team determined we would need to produce 10000 kg of ammonia borane per year to supply the increasing need of hydrogen fuel in the coming years • Using feed stocks of ammonium chloride, sodium borohydride, tetrahydrofuran and ammonia • Determined average distance traveled per tank to be 317 miles February 11, 2016 -109- • Start design of chemical processing plant, starting with amount of initial feed stocks required • Look into patents for ammonia borane production • Begin searching for heat of vaporization, melting points, density and all other important information for feedstocks, intermediates and final products February 16, 2016 • Determine reactor conditions at -78 C and 1.01 bar • Block flow diagram creation • Completed a material balance for both ammonium borohydride reaction and ammonia borane decomposition reaction February 19, 2016 • Determined mole feed required of feedstock • Started looking into pricing of required feed stocks on Alibaba.com February 23, 2016 • Finished compiling information on our feedstocks intermediates and final products • Took a deeper look into reaction mechanism for producing ammonium borohydride intermediate • Continued searching for additional data for ammonia borane February 26, 2016 • Look into catalyst lifetime (ammonia and THF) • March 1, 2016 • 38.28 kg of ammonia borane can fuel a car for 314 miles • Decomposition reaction will take 1.5 hours • Ammonium borohydride reaction will have 96% yield March 3, 2016 • Meeting with Dr. Blowers to discuss problem items • Physical properties of ammonium borohydride and ammonia borane • Go over block diagram and plant design March 4, 2016 • Using alibaba and multiple suppliers we are able to create a bulk price curve for all our feed stocks at the required amounts we will be purchasing • Look into what price ammonia borane will need to sold at to make a profit March 10,2016 • Start working on the safety analysis of our plant • Start writing introduction to our paper • Work on our process flow diagram and determine final equipment selections -110- March 12-20, 2016 • Spring break March 22,2016 • Write reaction pathway report • Recycle stream analysis • Full plant equipment selections including what is needed for recycle March 25, 2016 • Meeting with Dr. Blowers to discuss: • Help with chemcad simulation • Pump pricing and conditions within chemcad • Discuss how separation will work March 28, 2016 • Look into losses that we might encounter for THF and ammonia • Account for cost of loses • Determine plant location of houston area April 1, 2016 • Completed final simulation of Chemcad! April 4, 2016 • Meeting with Dr. Blowers to discuss: • Reactor design • Recycle streams April 6, 2016 • Start writing report and making size and cost calculations as we go • Reactor sizing and cost • Pump sizing and cost • Deeper look into safety precautions April 11,2016 • Finished separator calculations • Heat exchanger design using aspen April 14, 2016 • Meeting with Dr. Blowers for help with: • Further help on separation calculations • Workforce cost • Final progress report with the report April 16, 2016 • Work on completing written report April 21, 2016 -111- • Work on completing written report April 27, 2016 • Final report editing -112- Contributions Executive Summary (Jared, Ian) Section 1: Introduction/Background(Ian, Jared) Section 2: Overall Process Description, Rationale and Optimization (Solomon, Jared) Section 3: Equipment Description, Rationale, and Optimization (Ali ,Jared, Solomon, Ian) Section 4: Safety/Environmental Factors (Ali ,Ian) Section 5: Economic Analysis (Ali ,Ian,) Section 6: Conclusion and Recommendations (Ian, Jared) Section 7: Nomenclature (Ian, Solomon) Section 8: References (Solomon) Section 9: Appendices (Ian) (Below regarding excel documents/sheets) Appendix A: Process Calculations (Ian, Jared) Appendix B: Equipment Sizing and Costs (Ali ,Ian, Jared, Solomon) Appendix C: Economic Calculations (Ali, Ian) Appendix D: Other Process, Calculations, and Numbers (Ian, Jared) Appendix E: Mass Balance (Ali ,Ian) Appendix F: Meeting Logs (Solomon) Specific Unit Ops completed: Decomp Reactor, compressor (Ian), Reactor 1 (jared), Solomon (Heat exchangers), Vacuum filtration, mixer (Ali) -113-