COMMERCIAL SCALE GLASS EQUIPMENT W. A. KATES Corning Glass Works, Corning, N. Y .
T
HE rapidly broadening use of glass in chemical plant eauiDment is increasing. woof of its value as an engineering material. It is ‘als‘o acknowledgment of the rapidly increased technic of manufacture which makes feasible shapes and weights of single glass pieces previously considered impossible. Fractionating columns, pump casings, bearings for heavy shafts of pickling vat rollers-these are only illustrative of the diverse shapes made feasible and economical by modern fabrication methods. Glass piping, from installations of one piece to one of more than 20 miles, serving the chemical, food, and many other industries, is illustrative of another of the most adaptable glass shapes.
Piping
Of broadest application to chemical plants is glass in the last mentioned form of pipe. While sometimes viewed askance, the design of glass pipe lines requires attention only to those factors considered in well-engineered designs for other materials. Long straightaway runs must provide for expansion to a greater degree for glass than for metals because supporting structures are commonly of metals or building materials of higher thermal expansion. Such expansion is readily accommodated by a simple type of joint. Proper alignment and support are of importance as in any wellengineered design, Alignment corrections in installation, as well as in subsequent operation, are readily accomplished with glass because of the inherent visibility feature. “Pocketing” may be detected by even a casual inspection, and align-
CooLnN7-
-Llsvlp
-+
c
( A ) . BUBBLE-CAP FRACTIONATINQ OR ABSORPTION COLUMN
FIQIJRE1. HORIZONTAL TUBULAR HEATEXCHANGER 398
For certain processes, batch cooling is required and circulation of liquids is not feasible. -The c o o l i n g of liquids \1 h e r e i s frequently a c c o m p l i s h e d by means of an immersed coil. In corrosion-resistant materials such coils are relatively heavy and costly, and in addition are difficult to support properly. Such support difficulties may be obviated by the use of transverse tubing passed through the walls of the tank, through which the coolant is circulated. While eliminating one difficulty of mechanical support i t introduces another of packing. A type of cooler shown in Figure 2 obviates both difficulties and is quite simple. It consists of a plurality of pipes projecting like fingers into liquid to be cooled, the coolant being introduced a t the lower end of the glass tube and flowing upwards for its entire length. Tubes may be readily supported above the liquid bath and out of direct contact with it. This type of cooler possesses the advantages of simplicity and flexibility, cooling speed, and therefore increase in system output being effected by the addition of inexpensive units. Effective evaporators are formed by the use of parallel banks of exchanger tubes arranged vertically as shown in Figure 3. Liquid for evaporation is admitted by bottom manifold, heat is supplied from the conventional exchanger jacket, and vapor removed from the upper manifold. The use of standard pipe fittings, together with the possibilities of unit construction and ready expansion of capacity, are points in favor of this type of construction. Feasible, also, for glass construction is the conventional type of heat exchanger involving tube sheets and connecting
ment or slope of line can be adjusted to give complete drainage. As concerns pressures, the range up to 50 pounds per square inch is feasible in all installations, and 100 pounds is prac. tical in a great majority of them. Protection against accidental impact should be given adequate consideration. The degree required depends to a large extent on the location of the line. Lines in remote locations or seldomused areas may req u i r e less consideration t h a n those adjacent to much frequented p a s s a g e s . Pipe in the latter case s h o u l d b e well protected against impact. The possibility of ins t a n t a n d complete inspection of pipe and contents, however, and the minimum need for replacement substantially counterbalance necessary shielding requirements. Piping specialties-i. e., injector pipes, aspirators, etc.-of wide variety can be deFIGURE2. PIPECOOLER FOR BATCH COOLING signed in glass almost as their metal counterparts. The fused type of joint, shaping in the blast lamp, and grinding are substituted for the threaded, welded, or bolted metal joint and conventional cutting and fitting methods. The fused joint, inspectable visually, is unexcelled by any other type.
Heat Exchangers Of great practical importance in chemical plants is the interchange of heat between corrosive fluids and other liquids, and for this purpose glass pipe is admirably adapted. A general treatise of the theory and calculation of heat exchange is beyond the scope of this discussion. It is here worthy of note, however, that the relative size of glass heat exchange equipment is not as great as is indicated by the coefficient of heat transmission of glass per se as given in tables and handbooks. The substantial parts of the total temperature drop through an exchanger wall occur in surface films, even above critical velocities, and these films are common to walls of all materials. Glass surface smoothness and hardness minimize change of rating with time. Over-all sizes of glass exchangers therefore compare excellently with those of other corroRion-resistant materials. For heat absorption or extraction from a circulating fluid, or for condensation, the conventional jacketed horizontal tubular type exchanger (Figure 1) is quite satisfactory. This employs glass pipe and standard metal pipe jackets. Series or parallel connections, both of pipe and jackets, may be effected. The usual traps and provisions for condensate drain are required. Surface type or cascade evaporation coolers are obviously a special adaptation of these with jackets ornitted.
(B). 399
CONSTRUCTION DETAILS OF FRACTIONATINQ COLUMN
INDUSTRIAL AUD EXGINEERING CHEMISTRY
VOL. 29, NO.4
tubes. Problems of packing and tube sheet construction are somewhat more difficult than in the types mentioned before and generally mitigate against their application where any tubular type is feasible.
Fractionating and Absorption Equipment In fractionating or absorption processes, glass columns enable tspeciaUy accurate translation of pilot plant resultg to production scale utilizing bubble or porforated plates, or packed sections. Complete visibility and its advantages are ohvious, since the section walls are inexpensive glass cylinders. The construction of Figures A , B, and Cfacilitates adjustment of plate spacing if this is required. In this design the dead weight of the column and liquid is counterbalanced by weights connected to column sections a t appropriate intenrals. These weights are attached by cables as shown in the detailed view. The removal and replacement of any intermediate column section, for change of plate spacing, may he readily acoomplished by loosening the section clamping stays, raising the upper assembled portion, and inserting a wall section cylinder of appropriate length. The upper part of tfle column can then be lowered and reas~emhlyeffected in a short time.
(0.SOME OF THE IaAROEBT ONE-PIECE GLASS TUBES PHODUCED TO
DATE
Diameter. 4 % incles: length. 12 feat.
The limitations of shape for mechanical adaptation r e a s o n s are d e p e n d e n t on the fabrication method best suited f r o m over-all considerations. As with m e t a 1 s , heat treatment after forming gives definite characteristics to the finished part. With transparent glass, however, the results of such heat treatment can be determined by proper interpretation of polariscope examination. Visible, also, is the internal structure of any glass part in a manner not true of any other construction material, which makes every mechanic an inspector.
Thus trial runs may be made a n d observed in detail, plate separations can be corrected for d if f e r e n ces from pilot plant prediction, and the ma imum eficienc8 for a given size of apparatus can be quickly and economically obtained.
k
Special Apparatus Although the foregoing comments refer to the most extensive uses of glass for plant equipment, others are additionally illust r a t i v e of its versatility as a highly c o r r o sion-re s i s t a n t construction material. Some of its p o s s i bilities and also its, limitations for engineering use m a y be visualized b y considering it as a high-temperature plastic. I n c o m mon with other plastics, it may be e x t r u d e d , drawn as tubing, f u s e d o r w e
