Preliminary design work has been done on a process to recover a valuable product from an effluent gas stream. The gas will be scrubbed with a solvent in a packed column; the recovered product and solvent separated by distillation; and the solvent cooled and recycled. The major items of equipment

Question

Preliminary design work has been done on a process to recover a valuable product from an effluent gas stream. The gas will be scrubbed with a solvent in a packed column; the recovered product and solvent separated by distillation; and the solvent cooled and recycled. The major items of equipment that will be required are detailed below.

1. Absorption column: diameter 1 m, vessel overall height 15 m, packed height 12 m, packing 25 mm ceramic intalox saddles, vessel carbon steel, operating pressure 5 bar.

2. Recovery column: diameter 1 m, vessel overall height 20 m, 35 sieve plates, vessel and plates stainless steel, operating pressure 1 bar.

3. Reboiler: forced convection type, fixed tube sheets, area 18.6 [latex]m ^{2}[/latex], carbon steel shell, stainless-steel tubes, operating pressure 1 bar.

4. Condenser: fixed tube sheets, area 25.3 [latex]m ^{2}[/latex], carbon steel shell and tubes, operating pressure 1 bar.

5. Recycle solvent cooler: U-tubes, area 10.1 [latex]m ^{2}[/latex], carbon steel shell and tubes, operating pressure 5 bar.

6. Solvent and product storage tanks: cone roof, capacity 35 [latex]m ^{3}[/latex], carbon steel.

Estimated service requirements:

Steam 200 kg/h

Cooling water 5000 kg/h

Electrical power 100 kWh/d (360 MJ/d)

Estimated solvent loss 10 kg/d; price £400/t. Plant attainment 95 per cent.

Estimate the capital investment required for this project, and the annual operating cost; date mid-2004.

Accepted Answer

Purchased cost of major equipment items.

Absorption column

Bare vessel cost (Figure 6.5a) £21,000; material factor 1.0, pressure factor 1.1

[latex] ext { Vessel cost }=21,000 imes 1.0 imes 1.1=£ 23,000[/latex]

Packing cost (Table 6.3) £840/ [latex]m^{3}[/latex]

Table 6.3. Cost of column packing. Cost basis mid 2004
	Cost	[latex]£ / m^{3}\left(\$ / m^{3} ight)[/latex]
Size, mm	25	38	50
Saddles, stoneware	840 (1400)	620 (1020)	580 (960)
Pall rings, polypropylene	650 (1080)	400 (650)	250 (400)
Pall rings, stainless steel	1500 (2500)	1500 (2500)	830 (1360)

[latex] ext { Volume of packing }=(\pi / 4) imes 12=9.4 m ^{3}[/latex]

[latex] ext { Cost of column packing }=9.4 imes 840=£ 7896[/latex]

Total cost of column 21,000 + 7896 = 28,896, say £29,000

Recovery column

Bare vessel cost (Figure 6.5a) £26,000; material factor 2.0, pressure factor 1.0

[latex] ext { Vessel cost } 26,000 imes 2.0 imes 1.0=£ 52,000[/latex]

Cost of a plate (Figure 6.7a), material factor 1.7 = 200 [latex] imes 1.7[/latex] = £340

Total cost of plates = 35 [latex] imes 340[/latex] = £11,900

Total cost of column = 52,000 + 11,900 = 63,900, say £64,000

Reboiler

Bare cost (Figure 6.3a) £11,000; type factor 0.8, pressure factor 1.0

[latex] ext { Purchased cost }=11,000 imes 0.8 imes 1.0=£ 8800[/latex]

Condenser

Bare cost (Figure 6.3a) £8500; type factor 0.8, pressure factor 1.0

[latex] ext { Purchased cost }=8500 imes 0.8 imes 1.0=£ 6800[/latex]

Cooler

Bare cost (Figure 6.3a) £4300; type factor 0.85, pressure factor 1.0

[latex] ext { Purchased cost }=4300 imes 0.85 imes 1.0=£ 3700[/latex]

Solvent tank

[latex] ext { Purchase cost }( ext { Table } 6.2)=1400 imes(35)^{0.55}=£ 9894 ext {, say } £ 10,000[/latex]

Table 6.2. Purchase cost of miscellaneous equipment, cost factors for use in equation 6.7. Cost basis mid 2004
Equipment	Size unit, S	Size range	Constant		Index n	Comment
Equipment	Size unit, S	Size range	C,£	C,$	Index n	Comment
Agitators
Propeller	driver	[latex]5-75[/latex]	1200	1900	0.5
Turbine	power, kW		1800	3000	0.5
Boilers
Packaged						oil or gas fired
up to 10 bar	kg/h steam	[latex](5-50) imes 10^{3}[/latex]	70	120	0.8
10 to 60 bar			60	100	0.8
Centrifuges
Horizontal basket	dia., m	[latex]0.5-1.0[/latex]	35,000	58,000	1.3	carbon steel
Vertical basket			35,000	58,000	1	[latex] imes 1.7 ext { for ss }[/latex]
Compressors
Centrifugal	driver	[latex]20-500[/latex]	1160	1920	0.8	electric,
	power, kW					max. press.
Reciprocating			1600	2700	0.8	50 bar
Conveyors	length, m
Belt		[latex]2-40[/latex]	1200	1900	0.75
0.5 m wide			1800	2900	0.75
1.0 m wide
Crushers	t/h
Cone	kg/h	[latex]20-200[/latex]	2300	3800	0.85
Pulverisers			2000	3400	0.35
Dryers	[latex] ext { area, } m ^{2}[/latex]
Rotary		[latex]5-30[/latex]	21,000	35,000	0.45	direct
Pan		[latex]2-10[/latex]	4700	7700	0.35	gas fired
Evaporators	[latex] ext { area, } m ^{2}[/latex]
Vertical tube		[latex]10-100[/latex]	12,000	20,000	0.53	carbon steel
Falling film			6500	10,000	0.52
Filters	[latex] ext { area, } m ^{2}[/latex]
Plate and frame		[latex]5-50[/latex]	5400	8800	0.6	cast iron
Vacuum drum		[latex]1-10[/latex]	21,000	34,000	0.6	carbon steel
Furnaces
Process	heat abs, kW
Cylindrical		[latex]10^{3}-10^{4}[/latex]	330	540	0.77	carbon steel
Box		[latex]10^{3}-10^{5}[/latex]	340	560	0.77	[latex] imes 2.0 ss[/latex]
Reactors	[latex] ext { capacity, } m ^{3}[/latex]
Jacketed,		[latex]3-30[/latex]	9300	15,000	0.4	carbon steel
agitated			18,500	31,000	0.45	glass lined
Tanks	[latex] ext { capacity, } m ^{3}[/latex]
Process				2400	0.6	atmos. press.
vertical		[latex]1-50[/latex]	1450	2900	0.6	carbon steel
horizontal		[latex]10-100[/latex]	1750
Storage
floating roof		[latex]50-8000[/latex]	2500	4350	0.55	[latex] imes 2 ext { for }[/latex]
cone roof		[latex]50-8000[/latex]	1400	2300	0.55	stainless

Product tank

Purchase cost same as solvent tank = £10,000

Total purchase cost of major equipment items (PCE)

Absorption column 29,000

Recovery column 64,000

Reboiler 8000

Condenser 6000

Cooler 3000

Solvent tank 10,000

Product tank 10,000

Total £130,000

Estimation of fixed capital cost, reference Table 6.1, fluids processing plant:

Table 6.1. Typical factors for estimation of project fixed capital cost
Item	Process type
Item	Fluids	Fluids- solids	Solids
1. Major equipment, total purchase
cost	PCE	PCE	PCE
[latex]f_{1}[/latex] Equipment erection 0.4 0.45 0.50	0.40	0.45	0.50
[latex]f_{2}[/latex] Piping	0.70	0.45	0.20
[latex]f_{3}[/latex] Instrumentation	0.20	0.15	0.10
[latex]f_{4}[/latex] Electrical	0.10	0.10	0.10
[latex]f_{5}[/latex] Buildings, process 0.15 0.10 0.05	0.15	0.10	0.05
[latex]* f_{6}[/latex] Utilities	0.50	0.45	0.25
[latex]* f_{7}[/latex] Storages	0.15	0.20	0.25
[latex]* f_{8}[/latex] Site development	0.05	0.05	0.05
[latex]* f_{9}[/latex] Ancillary buildings	0.15	0.20	0.30
2. Total physical plant cost (PPC)
[latex]\begin{array}{r} PPC = PCE \left(1+f_{1}+\cdots+f_{9} ight) \= PCE imes\end{array}[/latex]	3.40	3.15	2.80
[latex]f_{10}[/latex] Design and Engineering	0.30	0.25	0.20
[latex]f_{11}[/latex] Contractor’s fee	0.05	0.05	0.05
[latex]f_{12}[/latex] Contingency	0.10	0.10	0.10
Fixed capital =[latex]317,520(1+0.3+0.1)=44,528 ext { round up to } £ 4445,000[/latex]	1.45	1.40	1.35

[latex] ext { *Omitted }[/latex] for minor extensions or additions to existing sites.

PCE £130,000	_
[latex]f_{1}[/latex] Equipment erection	0.40
[latex]f_{2}[/latex] Piping	0.70
[latex]f_{3}[/latex] Instrumentation	0.20
[latex]f_{4}[/latex] Electrical	0.10
[latex]f_{5}[/latex] Buildings	none required
[latex]f_{6}[/latex] Utilities	not applicable
[latex]f_{7}[/latex] Storages	provided in PCE
[latex]f_{8}[/latex] Site development	not applicable
[latex]f_{9}[/latex] Ancillary buildings	none required

[latex] ext { Total physical plant cost }( PPC )=132,300(1+0.4+0.7+0.2+0.1)=£ 317,520[/latex]

[latex]f_{10}[/latex] Design and Engineering	0.30
[latex]f_{11}[/latex] Contractor’s Fee	none (unlikely to be used for a small, plant project)
[latex]f_{12}[/latex] Contingencies	0.10

[latex] ext { Fixed capital }=317,520(1+0.3+0.1)=44,528 ext { round up to } £ 445,000[/latex]

Working capital, allow 5% of fixed capital to cover the cost of the initial solvent charge = [latex]445,000 imes 0.05=£ 22,250[/latex].

[latex] ext { Total investment required for project }=445,000+22,250=467,250 ext {, say } £ 468,000[/latex]

Annual operating costs, reference Table 6.6:

Table 6.6. Summary of production costs
Variable costs		Typical values
1. Raw materials		from flow-sheets
2. Miscellaneous materials		10 per cent of item (5)
3. Utilities		from flow-sheet
4. Shipping and packaging		usually negligible
	Sub-total A	. . . . . . . . . . . . . . . . . . . . . .
Fixed costs
5. Maintenance		5 -10 per cent of fixed capital
6. Operating labour from manning estimates		from manning estimates
7. Laboratory costs		20 -23 per cent of 6
8. Supervision		20 per cent of item (6)
9. Plant overheads		50 per cent of item (6)
10. Capital charges		10 per cent of the fixed capital
11. Insurance		1 per cent of the fixed capital
12. Local taxes		2 per cent of the fixed capital
13. Royalties		1 per cent of the fixed capital
	Sub-total B	. . . . . . . . . . . . . . . . . . . . . .
Direct production costs A + B		. . . . . . . . . . . . . . . . . . . . . .
13. Sales expense		20- 30 per cent of the direct
14. General overheads		production cost
15. Research and development
	Sub-total C	. . . . . . . . . . . . . . . . . . . . . .
Annual production cost = A + B + C=D		. . . . . . . . . . . . . . . . . . . . . .
[latex] ext { Production cost } € / k g=\frac{ ext { Annual production cost }}{ ext { Annual production rate }}[/latex]

Operating time, allowing for plant attainment [latex]=365 imes 0.95=347 d / y , \quad 347 imes 24=[/latex] 8328 h/y.

Variable costs:

1. Raw materials, solvent make-up [latex]=10 imes 347 imes 400 / 1000=[/latex] £ 1388

2. Miscellaneous materials, 10% of maintenance cost (item 5) = £ 2200

3. Utilities, cost from Table 6.5:

Table 6.5. Cost of utilities, typical figures mid-2004
Utility	UK	USA
Mains water (process water)	60 p/t	50 c/t
Natural gas	0.4 p/MJ	0.7 c/MJ
Electricity	1.0 p/MJ	1.5 c/MJ
Fuel oil	65 £/t	100 $/t
Cooling water (cooling towers)	1.5 p/t	1 c/t
Chilled water	5 p/t	8 c/t
Demineralised water	90 p/t	90 c/t
Steam (from direct fired boilers)	7 £/t	12 $/t
Compressed air (9 bar)	[latex]0.4 p / m ^{3}( Stp )[/latex]	[latex]0.6 c / m ^{3}[/latex]
Instrument air (9 bar) (dry)	[latex]0.6 p / m ^{3}( Stp )[/latex]	[latex]1 c / m ^{3}[/latex]
Refrigeration	1.0 p/MJ	1.5 c/MJ
Nitrogen	[latex]6 p / m ^{3}( Stp )[/latex]	[latex]8 c / m ^{3}[/latex]

Steam, at 7£/t [latex]=7 imes 8328 imes 200 / 1000=[/latex] £11,659

Cooling water, at 1.5 p/t [latex]=(1.5 / 100) imes 8328 imes 5000 / 1000=[/latex] £ 625

Power, at 1.2 p/MJ [latex]=(1.2 / 100) imes 360 imes 347=[/latex] £ 1499

4. Shipping and packaging not applicable

Variable costs = £17,371

Fixed costs:

5. Maintenance, take as 5% of fixed capital = 445,000 ð 0.05 = £22,250

6. Operating labour, allow one extra man on days. It is unlikely

that one extra man per shift would be needed to operate

this small plant, and one extra per shift would give

a disproportionately high labour cost.

Say, £30,000 per year, allowing for overheads = £30,000

7. Supervision, no additional supervision would be needed

8. Plant overheads, take as 50% of operating labour = £15,000

9. Laboratory, take as 30% of operating labour = £ 9000

10. Capital charges, 6% of fixed capital (bank rate 4%) £26,700

11. Insurance, 1% of fixed capital £ 4450

12. Local taxes neglect

13. Royalties not applicable

Fixed cost = £107,400

Direct production costs = 17,396 + 107,400 = £124,796

14. Sales expense not applicable

15. General overheads not applicable

16. Research and development not applicable

Annual operating cost, rounded = £125,000

Question 6.4: Preliminary design work has been done on a process to recove...

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