perating vessels)

calculation of hydrocarbon losses from process equipment in a 500 MM Ib./yr. ethylene plant. loss factor ('1

0.15 Ib./day/valve 3.2 Ib./day/seal 150 pumps x 3.2 = 3.2 Ib./day/seal 10 comp. x 2 x 3.2 = 5.4 Ib./day/seal 1 comp. x 5.4 =

6.0 Ib./MM Gal./circulated = 430

150 lb./1.000 Bbl. capacity

100 lb./1,000 Bbl. capacity

50,000 gpm x 60 x 24 x 6

20,000 Bbl. X 150

20,000 Bbl. X 100

2.9 Ib./day/valve 400 valves x 2.9 0.6 Ib./day/valve 14 tanks X 2 valves X 0.6 = 17

4.8 lb./day/1,000 Bbl. capacity

1.7 lb./day/1.000 Bbl. capacity

10 lb./day/1,000 Bbl. capacity 20,000 Bbl. X 10

Total calculated hydrocarbon emission

Weight %loss on plant feed@)

. 1 . These baa fad078 are applicable lo plants weight o plant through ut The lower a&, cabulatedf here is appzicde io an area such as

a. %he range of enkisdons frm hydrmarba pro- Lo8 Angeles cant# where stringent m t r o l is cesmng plants may range from 0.1 to 0.670 by practiced.

racticing extensioe hydrocarbon control.

dif- involved in th is grouping. The tabu- greater (5). It is because of th ia 4). lat ion also i l lustrates examples of almost universal exposure that SO, 'ng pollutants that can be exhausted t o haa become the arch fiend in the ion the atmorrphere. demonology of air ContaminaMon.

EXCHANGER AND DRAINS FROM NON.

SPILL AREAS),

ng wtmhemical planks. Because of various losses from

f&rs to individual pieces of plant equipment. One source of these fac- tors is Public Heakh Service publi- cation No. 763 ( 8 ) . An example of a calculation using values from this booMet for a 600 MM Ib./yr. olefin plant is shown in Table 2. Most calculations of this sort show that total emission of hydrocarbons is between 0.1 to 0.6% of the total plant throughput; however, it is obvious that this number has t o be a close function of plant mainte- nance. The emission total calcu- lated in the example of Table 2 is based on “JAM Angelas County” factors, and these factors, because sbringent mntrol is practiced in Los Angeles Gounhy, are lower than in mmt other parts of the world. It should also be emphasized that =ti-

housekeeping .which can be used t o maintain a low level of hydrocarbon emissions include: 1. In&all&on of floating roof

tanks to control evaporation of light hydrocarbons.

2. Installation of vapor recovery lines to vents of vessels that are continually filled and emp-

3. Manifolding of purge lines used for startups and shub downs to vapor recovery sys- tems or to the flare system.

4. Venting of vacuum jet exhaust

in plank designs, plant maintenance, types of feed&cks processed and products produced, the use of such

6. covering of wmke w&er sepa- rators normally open to the

Some techniques other than good lines discharge to atmosphere. amount of’ ox‘

DISCHARGE

involved, such as when a sour crude oil is used as the feedatoek to a re- finery-petmchemical complex, then

.e.- on this subject later.

ration. from the caustic solutions used for

etripping regenerates the caustic for re-use and liberates the mercap- tans for burning. Flue gae strip- - ping converts the mercaptans chem- ically, and the solution can then be nxhemiesl

of H,8 are tion for the Advancemen* of Sci-

ence in its book on air conserva- tion (15) gives as an example of profitable waste management a survey of several hydmarbon p m - essing plants. It draws the conclu- sion that when these planta applied all of the best availtable air pollu- tion control techniques bo their op- erations a t a capital expenditure of between three and five percent of total plant investment, “one-half of the expenditures provided prudent profit by their culvtomary standards (S-year payout for productive equipment, 7-year payout for utility equipme&), one quarter of the ex- penditures returned a profit a t a slower rate of 2 to 5% annually which was not considered prudent, and the other quarter a 1088. On the whole, they seem to have found that the total expenditures balanced out at a slight profit.” “In addition,” as the Association points out, “the.re- sulting conservation of hydrocar- bons and sulfur was a definite gain t o the nation.”

It is difficult to associate eco- nomic conclusions to waste man- agement of air (even without the complications of tax writeoffs for contml equipment, or ad valorem property tax relief). However, it is probably safe to s a y - a t least as a minimum-that clean air will cost money, but dirty air will ultimately cost us even more.

Water pollution The bulk of water used in hydro-

carbon processing industrim is used for cooling purposes and does .not ordinarily become contaminated. However, during process opera- tions, waste streams are released from equipment to the sewers at many points because of leaks, water purging, line breakage, and the like.

In addition, polluted water streams are often diegorged in the following processing operations :

1. Crude oil desalting 2. Steam distillation 9. Steam stripping 4. Water washing of prbducts

following chemical treatment 5. Barometric condensing of

steam driven prime movers 6. Catalyst regeneration 7. Partial pressure reduction

with dilution steam 8. Boiler and cooling tower blow-

downs 9. Drainage of contaminated

areaa-rain water runoff. 10, Treatment of water-Le., nl-

tlvtte addition for caustic em+ brittlement control

11. Trmmferring and storing oils

Figure 2. Proposed sulfur recovery system for refinery-base

12. Vessel cleaning operations The terminal waste dirvposal prw- These oper&ions foul the waters wses found sin bhese sewer systems

with salts, acids, alkalies, sulfides, are briefly described later. Refer- solids, and hydrocarbons of all sorts ences to soume material on the sub- such as phenolics and high molecu- jecrts are alm shown for further lar weight oils. information.

Sometimes, the concentration of Water management economics : ~~ ~ ~ ~~ ~~ ~~~~ pollubnba in a waste stream is low, and so a simple discharge without In the hydrocarbon processing in- treatment is possiblhfor instance, dustry, the economic payout of a

, . 8 boiler feed water blowdown SYS- water " w m n t program is no b m will concentrate salts in its less difficult to evaluate than that blowdown stream; these salts were for air. Recent waste control pro- presene in the water at the original grams-those having its manage- intake source, and thus if this ment high enough in the corporate stream is diluted wihh a much organization to influence policy and larger stream-say, plank cooling make independent decisions con- water blowdown-then the' concen- cerning expenditures-are attempt- D. Ec tration of the salts is returned to ing to clarify the economies aeso-

' ' where i t was originally. However, ciated with these programs; how- solutions such as this are becoming ever, they are often confounded less and less available. with political and m i d issues that

From an overall plant design make ra4,ional economic considera- viewpoint hydrccmrbon pmessing tions come out second best. plamts are usually 80 large that it is to cohplstely plan and often desirable to have separate define any waste managaent pro- sewers and treatment facilities for gram, and judge the anomice, the various waste water Sti-". or perhaps more accurately its net

must be studied: and treatmenh of such waste waters. Essentially, the streams and treab ment facilities may be elassified as:

1. Oily water or prwesa water

2. Sanitary sewers 3. Demineralizer sewers 4. Storm or oil-free sewers

A. Problem analysis 1. The contaminants+egree

sewers

degree and kind

we feel that the best

four alternate

odifiwtion for conversion

As seen from the

market sa tight,

the ecanomies of such a recovery sy&em can be quite attractive (18, 19).

An example of the recycling and re-use of a chemical reagent is found in the sulfuric acid alkylation proc- em. Sulfuric acid is used as a cata- lyst during the formation of com- plex sakurated molecules by direct union of saturated and unsaturated hydrocarbon molecules. A problem which often presents itself CO manu- facturers is the choice of the route to be used for the disposal of spent sulfuric acid. The acid concentra- tion is approximately 90% H,SO,, 6% H,O, and 4% hydmarbons. Its market valuNepending on wheth- er it is wasted, sold for spent acid, or whether it is used for the treat- ment of phosphate rock for ferti- lizer manufacture-varies (accord- ing to the price of elemental sulfur) from 0 to $10/60n. If the acid could be reconstituted at the plant and recycled back CO the alkylation unit, its re-use value would be between $22-$26/ton. A recent Texaco proc- ess (20 ) and a new M. W. Kellogg process both show promise in this area.

other examples of process re- thinking are the salvage of waste HCL produced in large quantities in chlorination reactions, the sub- stitution of CS, for CH, in the pro- duction of CCI,, and the speciacular reorientation of the synthetic de- tergent industry within a two-year period from a refractory alkylben- zenmulfonate type of detergent to a linear alkyl biodegradable deter- gent.

A summary of recent prwess im- provements which have aided in pollution abatement has been pre- sented in the literature (21, 9 9 ) . These impmvements include :

a) The elimination of the need for speeial product chemical treatment

b) The minimization of the pro- duotion of spent chemicals re- quiring disposal

e) The removal of noxious sub- stances bv conversion and de- toxific;uti&

dl The aroduction of salable co-produots from previously wasted toxic chemicals

The olefin plant The production of olefins by the

thermal c m k h g of hydrocarbons is probably the most important petro- chemical p m s W a y (both in kind and degree). This process il- lustratea the sophisticated develop- ment of by-product usage in the

ulsrr weight poly- produd formed hydrogenation of

untreated water is shown in pollution problem economically ab

ssed for two reasons:

from ateam generation).

c reduction of plant makeup This someames is disposed of, in

howing waste streams.

is faster than either method alone. able geological formation is a n

cations call for extremely tight con- trol over toxic substances. Ponds wtmchemieal industry. A re and lagoons rely on natural p m - e m and large hold up times to

used to any great

these PrO’XSmS is found in

RESS (Vd. 0. No. IO)