Oklahoma State University

Comparison of Bio-mass to Bio-oils Reactor Systems: Direct Conversion vs. Companion Coal Gasification

2013 AIChE Contest Problem

Daniel

3/14/2013

Table of ContentsTitle Page

Executive Summary.......................................................................................................................................3

Introduction....................................................................................................................................................3

Conclusions....................................................................................................................................................4

Recommendations..........................................................................................................................................4

Project Premises.............................................................................................................................................5

Process Flow Diagrams..................................................................................................................................5

Stream Attributes Table.................................................................................................................................6

Process Description........................................................................................................................................7

Married Process.........................................................................................................................................7

Equipment..............................................................................................................................................7

Direct Process............................................................................................................................................8

Equipment..............................................................................................................................................8

Process Control Strategy............................................................................................................................9

Safety...........................................................................................................................................................10

Environmental..............................................................................................................................................11

Utility Summary...........................................................................................................................................12

Operating Cost Summary.............................................................................................................................13

Equipment Information Summary...............................................................................................................14

Capital Estimate...........................................................................................................................................15

Economic Analysis......................................................................................................................................16

Innovation & Optimization..........................................................................................................................17

References....................................................................................................................................................18

Engineering Calculations.............................................................................................................................19

Computer Programs.....................................................................................................................................20

Computer Process Simulations....................................................................................................................21

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Executive Summary

The energy consumption of the U.S in 2001 required that 45% of all petroleum products utilized were imported. The U.S has massive reserves of biomass and coal, which can be used to displace the need of foreign oil. Biomass and coal can be transformed into usable liquid fuels through a process called pyrolysis.

A cost analysis was performed for a direct pyrolysis process only involving biomass and a ‘married’ process involving the gasification of coal along with biomass pyrolysis. This was achieved through the use of material and energy balances around commercialized gasification technology along with an integrated pyrolysis reactor. This preliminary balance was then modeled in Aspen Plus in order to size equipment and gain clearer and more substantial values.

Emissions were monitored and found to be above minimum levels of EPA regulation so additional permits were requested and project initiation was delayed a year to accommodate the process. Safety within both processes was held to the highest standards to protect workers, the nearby population, and the surrounding environment. Due to high temperatures and pressure inherent in almost every piece of equipment protective gear is assigned a mandatory for all workers within plant area.

Subsequent economics for both process can be found in””. It is recommended that the direct process be utilized due to the high capital costs associated with the coal gasification process. The usage of the direct process allows for more locations to be utilized instead of relying on areas with access to coal in high quantities.

Introduction

The energy consumption of the U.S in 2011 required that 45% of all petroleum products utilized were imported. The U.S has massive reserves of biomass and coal, which can be used to displace the need of foreign oil. Biomass and coal can be transformed into usable liquid fuels through a process called pyrolysis.

The first goal of this project was to do a preliminary engineering design on the direct pyrolysis method and on the married process involving coal gasification and biomass pyrolysis. The direct process has a number of pieces of equipment to be purchased before implementation, such as a conveyor, agitator, pyrolysis chamber, cyclone, pumps, heat exchangers, accumulator, upgrade vessel, recovery vessel, compressor, fired heater, and initial biomass processing. The married process differs in capital investments from the direct process due to its need for a gasifier and the lack of a compressor and fired heater.

The design was completed and an economic analysis was carried out to calculate the price per lb. of bio oil produced for each process. The analysis takes into account the initial capital investment, labor costs,

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working capital, utilizes, and maintenance. Depending on the results coal and biomass will be utilized in different methods to create the greatest energy gain for the U.S.

ConclusionsThe total capital investment for the married process over a period of 5 years was 575 million dollars. This process produced 405 million pounds of bio-oil in the same time span, resulting in a cost per pound of bio-oil of $1.43. The total capital investment for the direct process over a period of 5 years was 30 million dollars. This process produced 405 million pounds of bio-oil in the same time span, resulting in a cost per pound of bio-oil of $0.02.

Both processes are commercially available in 2013 and both processes allow for the processing of nearby biomass into bio-oil. The vastly different capital costs, the married being almost 60 times that of the direct process, along with the increased production of bio-oil makes the direct conversion process the cheaper of the two options.

Recommendations An advanced look at the bio-oil reconstruction process should be commenced due to the

perceived lower yields in the married process despite there being more material Further evaluation of the steam producing capabilities of the heat exchangers and a reevaluation

of their design due to the vaporization. Developing the cost of the biomass feed due to the environmental considerations and plant

location Information on the kinetic rates of reformation and hydrotreating in order to better integrate them

into the process

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Project PremisesDue to the information provided at the end of the project, a project life of 5 years was selected in order to simplify calculations. The start date of the project was assumed to be 2013, however all capital cost calculations were made in reference to 2012 due to the availability of CEPCI data. Construction begins the beginning of 2013 and carries through to the beginning of 2014 where the process is started once proper emission permits are obtained and a qualified workforce is hired.

From various resources, an ideal form of biomass was developed along with pyrolysis yields in order to preserve a material balance. Bio-oil treating was modeled as an ideal process with an emphasis on the minimization of Gibbs free energy along with the removal of the possibility of certain products. The equation of state utilized was SRK due to the number of light hydrocarbons present in the bio-oil and the liquid fuels.

Costs of utilities were obtained from Turton with coal being viewed as a utility for the married process. Any steam produced was viewed as accredit towards utilities. Cost of labor in the plant was done on a scaling basis from bio-oil production, ex. more bio-oil produced means more labor costs. Char and slag present in the process are removed from consideration due to their usage as combustion resources and continuing heat for the processes.

Syngas produced was not evaluated in this project due to the lack of standards presented and the knowledge base to clean and ready for commercialization. A selling price for the bio oil was not evaluated because of the varying octane levels of the product in both cases. It is assumed to bring the produced bio-oil to a stand it is blended and treated with ethanol for selling. Taxes were not considered in this evaluation because revenue was not considered, it is understood that all costs for this project will be written off or expensed in other areas of project development.

Process Flow Diagrams

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Stream Attributes Table

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Process Description

Married ProcessThe process begins with the gasification of a coal/water slurry. Then the raw gas exits and begins to heat up a biomass/water slurry and initiates the process of pyrolysis. The exiting vapor runs through two cyclones to remove the by-product char, which causes secondary reactions and is soluble in bio oil. From the exit of the cyclones the vapor is then quenched to prepare for hydro treating. The quenched vapor passes into a flash drum in order to remove the lighter gases from the process. The liquid remaining is then enters in a combined F-T and hydrotreating vessel to upgrade the remaining bio-oil. Finally the product enters a flash drum held close to standard conditions in order to collect and store the liquid fuel produced.

EquipmentConveyor: Transports ground coal to be combined with water. A 10ft long, 1.3 ft. wide belt moving at 4.264 ft/s moves 117.52 lb. of coal per second to be mixed.

Agitator/Mixer: Blends coal and water mixture for gasification. A 2ft wide agitator rotating at 100 rev/min distributes coal through out the slurry.

Coal Slurry Pump: Increases pressure of slurry to direct flow towards gasifier. A 733 gpm, 300 hp pump with a pressure differential of 625 psi pushes slurry to gasification

Gasifier: Transforms coal slurry into highly pressurized and hot gas by utilizing high heat fluxes.

Rotary Cutter: Reduces size of incoming biomass to facilitate pyrolysis. Reduces 56.76 lb/s of biomass to pieces with high surface area to volume ratios.

Biomass Slurry Pump: Pumps biomass slurry into pyrolysis chamber. A 413 gpm, 175 hp pump with a pressure differential of 625 psi directs slurry for pyrolysis.

Pyrolysis Chamber: Transforms biomass slurry to bio-oil through high pressure, temperature, and heat flux conditions. A 572 ft3 reactor with inner refractory operating at a temperature of 932F and 640 psia.

Cyclones: Used for solid particle removal from pyrolysis vapor stream. Large enough to accommodate 366 ft3/s of vapor with an efficiency of 90%

Hi-Steam Pump: Increases pressure of water entering Quench Heat exchanger. A 289 gpm, 30 hp pump with a pressure differential of 147 psi directs water for vaporization.

Quench Heat Exchanger: Lowers temperature rapidly to minimize side reaction from occurring. A 990 ft2 heat exchanger vaporizes 289 gpm of 161 psia water, to produce saturated steam, while cooling 102,000 gpm of pyrolysis vapor from 932F to 500F.

Lo-Steam Pump: Increases pressure of water entering Split Heat exchanger. A 350 gpm, 20 hp pump with a pressure differential of 73 psi directs water for vaporization.

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Split Heat Exchanger: Lowers temperature to utilize waste heat before vapor flash drum. A 3900 ft2 heat exchanger vaporizes 351 gpm of 87 psia water, to produce saturated steam, while cooling 66,000 gpm of pyrolysis vapor from 500F to 350F.

Split Flash Drum: Used to promote vapor-liquid separation. A 713 ft3 tank, which maintains a liquid level of 50%, a temperature of350F, and a pressure of 640 psi, allows time for liquid particles to dropout of vapor stream.

Upgrade Vessel: High pressure and high temperature vessel which promotes intermolecular interaction to break down large hydrocarbon molecules. A 2400 ft3 tank, kept at a temperature of 450F and a pressure of 640 psi, in which compounds collide and reform into usable fuel.

Recovery Flash Drum: Used for liquid fuel extraction. A 600 ft3 tank, is maintained at atmospheric pressure and 100F, siphons off liquid fuels.

Direct ProcessBiomass is reduced in size and then added to water to produce homogenous biomass/water slurry. This slurry is then pyrolized through the usage of syngas later in the process and heat generated from the combustion of solid byproducts. This vapor subsequently passes through a cyclone to remove char particles travelling along. It is then rapidly cooled to slow secondary reactions and prepare for upgrading. It then passes into a flash drum to remove light gases, which are then compressed, heated, and recycled back into the pyrolysis chamber, before being upgraded in a combined F-T and hydro treating vessel. In the last step the product is directed to a flash drum, where liquid product is extracted and stored.

EquipmentRotary Cutter: Reduces size of incoming biomass to facilitate pyrolysis. Reduces 56.76 lb/s of biomass to pieces with high surface area to volume ratios.

Pyrolysis Chamber: Transforms fluidized biomass to bio-oil through high pressure, temperature, and heat flux conditions. A 72 ft3 reactor with inner refractory operating at a temperature of 932F and 640 psia.

Cyclones: Used for solid particle removal from pyrolysis vapor stream. Large enough to accommodate 29 ft3/s of vapor with an efficiency of 90%

Hi-Steam Pump: Increases pressure of water entering Quench Heat exchanger. A 101 gpm, 10 hp pump with a pressure differential of 147 psi directs water for vaporization.

Quench Heat Exchanger: Lowers temperature rapidly to minimize side reaction from occurring. A 275 ft2 heat exchanger vaporizes 101 gpm of 161 psia water, to produce saturated steam, while cooling 13,000 gpm of pyrolysis vapor from 932F to 500F.

Split Flash Drum: Used to promote vapor-liquid separation. A 500 ft3 tank, which maintains a liquid level of 50%, a temperature of 350F,and a pressure of 640 psi, allows time for liquid particles to dropout of vapor stream.

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Upgrade Vessel: High pressure and high temperature vessel which promotes intermolecular interaction to break down large hydrocarbon molecules. A 2000 ft3 tank, kept at a temperature of 450F and a pressure of 640 psi, in which compounds collide and reform into usable fuel.

Recovery Flash Drum: Used for liquid fuel extraction. A 260 ft3 tank, is maintained at atmospheric pressure and 100F, siphons off liquid fuels.

Process Control StrategyPreventing loss of containment is the principle that drives the entire process control strategy. For each of the process vessels, heat exchangers, and flash drums pressure and temperature are maintained using control loops with control valve place in line. For the pyrolysis chamber a control valve is placed at its exit to control the production of the entire process, a flow meter measures the production of bio-oil while a controller modifies the valve position to maintain product quantity.

For process vessels and flash drums a liquid level loop is included to regulate what enters and exit the vessel. A control loop is placed on the vapor exit line to control pressure within. Temperature is measured at the exit of the vessel and the entering flow rate is adjusted to meet specifications. For the fired heater a temperature loop that measure the temperature exiting the pyrolysis chamber regulates the amount of heat provided to the vapor recycle stream.

For the heat exchangers a control loop regulates the entrance of the condensate, by varying the previous pump, in order to take advantage of all of the heat exchanger area present. Another control loop is placed in the exit of the shell line in order to maintain a pressure balance and promote vaporization of steam. A temperature transmitter, which measures the exit of the tube side, is placed in line with a control valve to control flow rates entering and insure the necessary temperature drops.

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Safety

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Environmental

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Utility Summary

Operating Cost Summary

Equipment Information Summary

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Capital Estimate

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Economic Analysis

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Innovation & Optimization

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References

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Engineering Calculations

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Computer Programs

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Computer Process Simulations

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