To: CHME 4497 Design Teams

Subject: Cost Estimate of Cyclohexylamine Production Process

summary

A process for manufacturing cyclohexylamine has been developed and must be further evaluated. Specifically, a bare module cost estimate must be developed for the manufacture of 8 million kilograms per year of cyclohexylamine. Major equipment items must be sized and their costs estimated. Total capital cost must be estimated assuming the process will be constructed and operated within an existing part of the facility. Working capital and manufacturing cost must also be estimated for future economic evaluation. Areas where optimization is possible should be explored and discussed. Homework2 will be due in three weeks (Oct. 18^th, 2016)

Requirements

• Based on the process flow diagram (PDF) for the manufacture of cyclohexylamine, a capital cost estimate must be developed. This estimate is to be based on a bare module construction. Storage tanks for the raw material aniline, crude product (from reactor) and finished product are required. The capital cost will also include such auxiliaries as transfer pumps and heat exchangers.
• The cost to manufacture cyclohexylamine must be estimated based on capital cost (both bare module and working capital), raw materials, utilities, labor and waste treatment cost.

Discussion/Background

A new cyclohexylamine (CHA) facility is outlined in the attached process flow diagram (PFD). This facility must be capable of producing 8,000 metric tones per year of finished product. The new facility must include a storage tank for the raw material aniline, and storage tanks for the crude and finished product; one high-pressure reactor; a filter; a distillation column, including two heat exchangers (a condenser and a reboiler) and a reflux drum; and transfer pumps. Since the new facility will be constructed in an existing part of the plant, the total capital cost will not include infrastructure items. Design teams must size each piece of equipment and estimate both the working capital and total capital costs. Other costs such as raw materials, utilities, labor and waster treatment must be estimated to get an overall cost of manufacturing (COM) for CHA.

The CHA production process begins by charging aniline and catalyst to a high-pressure reactor. Hydrogen is then fed at a controlled rate until the pressure reaches 65 bar. The reaction between aniline and hydrogen is very fast and energetic. Heat generated from the reaction (2,200 kJ/kg aniline) is removed by circulating cooling water through the reactor jacket. The process temperature in the reactor is controlled at 80 °C or lower

The catalyst has a finite lifespan and after 40 batches it must be removed and sent back to the supplier for regeneration. Typically, about 70% of the catalyst is recovered during regeneration; the supplier makes up the difference with fresh catalyst. Catalyst removal (for the purpose of regeneration) is accomplished by washing the spent catalyst with at least 100 times its volume with water to thoroughly remove all residual aniline and then back flushing the filter with additional water to form a catalyst/water slurry. Wash water is treated in the wastewater treatment facility. The catalyst/water slurry is transferred to containers for shipment to the regeneration plant.

The second step in the manufacturing process involves distillation. The crude product is fed to a distillation column, where the finished product is recovered overhead and the bottoms material is sent offsite to a waste disposal facility. The distillation column operates at atmospheric pressure and requires a reflux ratio of 1.5:1 to achieve the desired product purity specification. Distillation will be accomplished in a packed column that is 0.8 meters in diameter and contains 22 theoretical plates, with a height of 0.5 meters per plate. The reflux drum should be sized to provide for a residence time of five minutes.

All heat exchangers have a maximum allowable temperature increase of 15 °C. Overall heat transfer coefficients are assumed to be 850 W/m²/°C for condensers and 1140 W/m²/°C for reboilers.

Materials of construction for any equipment in contact with aniline, the crude product or the finished product must be stainless steel. Material of construction for any equipment in contact with hydrogen can be carbon steel. All storage tanks can operate at atmospheric pressure (0 barg).

Pump shaft power can be estimated from the following equation:

where P = power, kilowatts

= volumetric flowrate, m³/min

DP = pressure change, bar (discharge pressure – suction pressure)

e = efficiency (assume 45% efficiency)

Filtration equipment sizing and cost are dependent on flowrate. For this design, a total filtration time of 1.5 hours has been assumed. Filters should be sized for no more than 0.041 m³/min/m² (1.0 gal/min/ft²). A stainless steel horizontal plate filter having a total filtration area of 10.3 m³ was purchased for $24,000 in 1996. It is expected that filters of this type will have a cost exponent of 0.65, and a Lang factor of 4.74 will convert equipment cost to bare module cost.

Use the following assumptions. Clearly list other assumptions, including explanation and/or justification:

• Assume an onstream factor of 92% for this facility. Assume the total reaction cycle time is eight hours; this includes all raw material charging and filtering.
• The storage tanks must be capable of storing at least two days worth of production demand. At a minimum, the storage tanks must be capable of receiving full tankwagons of material (40,000 lbs or 18,100 kg). Assume storage tanks are vertical, have a height to diameter ratio of 3:1, operate at atmospheric pressure and do not require demister pads.
• All equipment must be constructed of stainless steel. The reactor vessel must be rated for operation up to 75 barg to prevent over pressurization from the hydrogen supply.
• All transfer pumps are centrifugal; assume an efficiency of 45%.
• Assume the reactor is vertical, has a height to diameter ratio of 2:1, and does not require a demister pad. The reactor must be equipped with an agitator; assume agitators are 30% of the vessel equipment cost. Also, assume an additional premium of 20% of the vessel cost for instrumentation and miscellaneous auxiliaries.
• The current CEPCI is 397.

All elements of the manufacturing cost for CHA should be calculated based on the following information:

Aniline	$0.86 per kg
Hydrogen	$0.23 per m3
Catalyst	$5000 per kg
Process Water	$0.067 per 1000 kg
High Pressure Steam	$16.64 per 1000 kg
Cooling Water	$14.80 per 1000 m3
Waste Treatment	$120 per 1000 kg
Wastewater Treatment	$56 per 1000 m3

Labor costs must be estimated based on the amount of equipment in the proposed process and the current cost of labor. Assume an operating labor expense of $58,000 per year per operator.

 

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