ELECTRIC LIQUEFIED PETROLEUM GAS VAPORIZER

Abstract: A compact economical electrically heated vaporizer (10) having a fast response time and capable of vaporizing liquified petroleum gas at a rate of 37.85 to 151.41 liters or more per hour with safety and without excessive superheating and/or cracking of the liquified petroleum gas utilizes a metal casting (12) having a closed internal cavity separated into two chambers (18 and 20) by an integral barrier (21). The casting (12) serves as a pressure vessel and heat sink as well as providing a heated interface between electric resistance heaters (40) received in passageways (36) in the barrier (21) and the liquified petroleum gas. The heat generated by the heaters (40) is disseminated uniformly throughout the casting (12) surrounding the chambers (18 and 20). A liquified petroleum gas inlet (26) at one end of the casing connects with the end of one chamber (18). Multiple small passageways (30 and 32) in the barrier (21) at the other end of the casting connect the other end of the one chamber (18) to the adjacent end of the other chamber (20). The passageways (30 and 32) are configured to create a turbulent flow which improves heat transfer. An outlet (28) connects with the other end of the other chamber (20) for discharge of the vaporized gas. The electrical and temperature controls for controlling the operation of the heaters (40) and the flow of liquified petroleum gas through the chambers (18 and 20) are housed within an enclosed chamber formed by an end cover (16) on the other end of the casting. The temperature sensors for the temperature controls are received in passageways (38) in the barrier (21).

Description: TITLE ELECTRIC LIQUEFIED PETROLEUM GAS VAPORIZER Technical Field This invention relates to an apparatus for uni¬ formly and economically vaporizing liquefied petroleum gas. Background Art Electric vaporizers for vaporizing liquefied petroleum gas are known. Such units employ electric re¬ sistance heaters which are directly immersed in storage tanks for the liquefied petroleum gas or which are im¬ mersed in a liquid bath to heat the liquid bath which in turn, heats the liquefied petroleum gas to vaporize the same. U.S. Patent Nos. 2,166,922; 2,193,006; and 2,775,- 683; all disclose the use of electric resistance heaters for vaporizing liquefied petroleum gas, the resistance heaters enclosed directly in the storage tank holding the liquefied petroleum gas. U.S. Patent No. 2,348,546 dis- closes an electric vaporizer in an installation adjacent the liquefied petroleum gas tank through which the lique¬ fied petroleum gas is fed. Direct heating of liquefied petroleum gas described by the above references creates a safety hazard. Additionally, the high temperature of a heating element directly in contact with the liquefied gas causes excessive cracking of the liquefied petroleum gas. Indirect heating of liquefied petroleum gas by water baths, oil baths or other such means performs well when high vaporization capacity is needed; however, for low or medium vaporization capacities such units are both uneconomical and inefficient. DISCLOSURE OF INVENTION The primary object of this invention is to pro- vide an electric liquefied petroleum gas vaporizer unit which is compact, economical and safe. -BUKEAi OMPI , W1PO Another object of this invention is to provide an electric liquefied petroleum gas vaporizer utilizing a highly heat-conductive metal casting heated by electric resistance heaters, the casting functioning as a pressure vessel and heat interface between the heat source and the liquefied petroleum gas, as well as a heat sink to uni¬ formly vaporize liquefied petroleum gas. A further object of this invention is to pro¬ vide an electric liquefied petroleum gas .vaporizer cap- able of uniformly vaporizing the liquefied petroleum gas without excessive superheating and/or cracking of the liquefied petroleum gas and which gives superior response time. A further object of this invention is to pro- vide an electric liquefied petroleum gas vaporizer which is capable of vaporizing liquefied petroleum gas to the full capacity of the unit within minutes after it is started. These and other objects are accomplished by a compact, economical vaporizer employing a heat-conduc¬ tive casting having a closed internal cavity bridged by an integral divider dividing the cavity into two separate chambers. The chambers are interconnected at the end op¬ posite the point of entry of the liquefied petroleum gas by multiple passageways of considerably reduced dimension relative to the dimensions of each of the chambers. The passageways increase the efficiency of the unit by creat¬ ing turbulence which promotes heat exchange for more ef¬ ficient vaporization. An inlet opening in the casting for liquefied petroleum gas communicates with one of the chambers and an outlet opening in the casting adjacent the inlet opening communicates with the other chamber. Passageways in the integral divider are provided for installing electric resistance heater units which allow close control of the system. The heat generated by these units is uniformly disseminated by conduction over the 3 surface area of the casting surrounding each of the cham--- bers. Temperature sensing means are included in the casting for maximum control of the power delivered to the electric resistance heaters to ' maintain the temperature of the casting uniform. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the vaporizer unit in relation to a storage tank for liquefied petro¬ leum gas; Fig. 2 is a vertical cross section through the vaporizer of Fig. 1 along section line 2-2 of Fig. 1; Fig. 3 is a cross section of the vaporizer unit along section line 3-3 of Fig. 2.; and Fig. 4 is a wiring diagram of the vaporizer unit employing three resistance heaters. BEST MODE FOR CARRYING OUT THE INVENTION Referring to Fig. 1, the vap ' orizer unit 10 is shown in relation to a storage tank for liquefied petro¬ leum gas 1. An inlet liquid gas line 2 of sufficient size to supply the vaporizer unit at full flow capacity and accommodate rapid flow changes in or out of the unit with minimum pressure drop extends from the storage tank to the vaporizer unit. Generally the liquefied petroleum gas may be pumped from the storage tank to the. unit by a pump (not shown). The vaporizer unit 10 may be an integral metal casting 12 which is of a highly heat conductive material such as aluminum. The casting may be jacketed with one or more layers of a heat insulating material if desired. The casting is supported on legs 14 which are secured to a concrete pad or other suitable support. Liquefied gas enters the vaporizer unit through line 2 and is heated during its passage through the casting and exits the unit as a gas vapor through outlet line 3 which is directly above the inlet line 2. If desired, the inlet and outlet to the casting can be reversed. The casting may be iϊuκε-ur OMPI A 'A,r__ WW11PPOO .*£ 4 mounted horizontally or vertically. A pressure relief valve 4 is threaded through the casting 12 to communicate with the interior of the vaporizer unit for safety pur¬ poses. An outlet solenoid valve 5 connects to gas vapor outlet line 6 as illustrated. This outlet valve acts as a safety device and prevents vapor flow from the outlet line beyond the valve until the unit is properly operating. The valve closes if the unit functions im- properly. The electrical wiring for the solenoid is op¬ eratively connected to the controls for the unit through a conduit (not shown). Other types of control valves may be used if desired. All of the electrical components for control of the unit as well as the wiring therefor are housed within end cover 16 located at the opposite end of the casting from the liquid gas inlet and gas vapor outlets 2 and 3. In this way all of the wiring is enclosed and is totally out of contact with any liquid gas or gas vapor. The start and stop push buttons 7 and , 8 for the unit are lo¬ cated within the support leg 14 adjacent the end of the casting where the electrical controls are located. By locating all of the wiring and electrical controls inter¬ nally in the unit the end cover 16 can be readily removed for servicing of the unit without having to cut or remove any wiring. Fig. 2 illustrates a vertical cross section of casting 12. The casting is cylindrical and may be symme¬ trical about its vertical and horizontal axes. The shape of the casting is not critical, however, and may be of any desired configuration. The casting has an internal cavity separated into two chambers 18 and 20 by an inte¬ gral divider 21. As illustrated the chambers 18 and 20 are of equal size although this is not critical. The openings 22 and 24 at the end of the casting adjacent the end cover 16 are plugged with a suitable material so that no gas flow can escape the casting. Liquid gas inlet pipe 2 is threaded into the lower opening 26 and gas va¬ por outlet pipe 3 is threaded into the upper vapor outlet 28 of the casting as illustrated in Fig. 2. The two com- partments 18 and 20 within the casting are interconnected by passages 30 and 32 which are of considerably reduced size relative to the size of the compartments 18 and 20. The passages 30 and 32 are configured to create a turbu¬ lent flow of the gas or gas-liquid mixture in the casting to aid in heat transfer from the walls of the casting to the liquefied gas. As illustrated in Fig. 2 each of the passageways is wedge-shaped. • The integral divider 21 " separating the internal cavity of the casting into the two compartments 18 and 20 includes integral multiple fins 34 extending from the divider respectively.into the chambers 18 and 20. The fins 34 expose a greater amount of the surface area of the casting to the liquefied gas being introduced into the internal cavity of the casting to aid in heat trans- fer. The integral divider 21 also includes multiple bore openings 36 extending the length of the casting between the passageways 30 and 32 interconnecting the chambers 18 and 20. These passageways are designed to receive elec¬ tric resistance heaters as will be described. One or more additional bore openings 38 are provided in the in¬ tegral divider of the casting between the passageways 36. These passageways 38 are designed to receive temperature sensing means, the temperature sensing means connected to control means for controlling power to the electric re- sistance heaters. A liquid gas carryover sensor 39 ex¬ tends into the upper chamber 20 through the plug in open¬ ing 22 to sense, by measurement of temperature, liquefied gas carryover from the unit. One or more electric resistance heater units 40 enclosed in a sheath of the same diameter as the diameter of passageways 36 is inserted in the passageways as il- lustrated in Fig. 2. A close fit of the electric resis¬ tance heater in the casting is desired to insure maximum heat transfer between the resistance heater and the cast¬ ing. The close fit also plugs each of the passageways 36 to maintain the explosion-proof condition of the electri¬ cal system of the unit. A ledge 33 at the end of each passageway 36 keeps the resistance heater from being pro¬ jected from the casting, should an explosion occur. The vaporizing unit is capable of readily meet- ing the demand for vaporization capacities ranging from- 37.85 to 151.41 or more liters per hour. The same cast¬ ing can be used for vaporization of 37.85 liters per hour as for ' 151.41 liters per hour. The only difference in the units is in the number and size of electrical resis- tance heaters utilized. For example, a unit capable of vaporizing 37.85 liters per hour utilizes one 2.5 kw ele¬ ment. A unit vaporizing 75.71 liters per hour utilizes two 2.5 kw elements and a unit vaporizing 113.56 liters per hour utilizes three 2.5 kw elements. A 151.41 liters per hour unit would employ three 3.25 kw elements, etc. Each of the electrical resistance heaters 40 is connected to a source of electrical power through control and safety relays which are interconnected with the tem¬ perature sensing means to insure proper operation of the unit. Fig. 4 illustrates a wiring diagram for the vapor¬ izer unit.. Resistance heaters 40 are connected through contacts 41, 42 and 43 of control relay 44 and contacts 45, 46, 47 and 48 of safety relay 49 to a source of suit¬ able voltage such as a source of single phase 240V, 50/60 Hz power or three phase power. The unit is started by allowing liquefied gas to flow into the lower chamber 18 of the unit and depressing switch 7 until the unit has warmed to operating temperature (about 43.33°C). When the switch 7 is released solenoid outlet valve 5 is ac- tuated to allow vapor flow through line 6. Temperature sensing means connected to operating temperature switch -BUKh OMPI 51 retains the switch in closed position until the maxi¬ mum operating temperature (about 98.89°C.) is reached. When the switch 51 closes it deactivates control relay 44 to open contacts 41, 42 and 43 to disrupt current flow to 5 the resistance heaters 40. A high temperature sensing means is positioned in the casting and set at a predeter¬ mined temperature (such as about 148.89°C). If the tem¬ perature of the casting exceeds the predetermined temper¬ ature safety switch 52 opens, interrupting current to 10. safety relay 49, resulting in opening of contacts 45, 46, 47 and 48 to interrupt power to the heaters 40. When any of the safety limits are reached, solenoid valve 5 closes. Manual restart of the unit is required. A liquefied gas carryover switch 53 connected to sensor 39 15 in the casting remains open until it senses the absence of liquid. The safety switch 53 is manually bypassed during startup. The vaporizer is started by allowing liquefied petroleum gas to flow into the lower chamber 18 of the 20 vaporizer unit through the inlet line 2. The vaporizer unit is warmed up to minimum operating temperature by pressing the "start" switch 7 as previously mentioned and holding it for two to three minutes. When the start but¬ ton is released the outlet solenoid valve 5 opens to al- 25 low gas vapor to exit the vaporizer unit through gas va¬ por line 6. The flow of gas vapor at full capacity of the unit is generally available five minutes after the start switch is initially depressed. Should, for some reason, the temperature of the unit exceed the preset temperature 30 of the high temperature switch which is generally about 148.89°C. the power will be disconnected to the electric resistance heaters. The liquid carryover switch 53, pre¬ viously described, provides an extra safety measure. Should liquefied gas be sensed, solenoid valve 5 closes, 35 power to the electric resistance heaters is disrupted and manual restart is required. The liquefied petroleum gas enters the lower chamber as a liquid and is heated to its vaporization point. The passageways 30 and 32 between the upper and lower chambers are small enough to create turbulence and disperse the liquefied gas into small droplets which rapidly flash to gas vapor as the liquefied gas flows through the passageways. The upper chamber further heats the vaporized gas to a .proper superheated condition. The unit is stopped by pressing switch 8 to deactivate relays 49 and 44, outlet valve 5 and heaters 40. The unit as described is a compact versatile unit for vaporizing liquefied petroleum gas employing a heat sink in the form of a highly heat conductive metal casting also serving as a pressure vessel and heat inter- face between a source of heat and the liquefied petroleum gas.. Flow surges can be readily accommodated.. Excessive superheating of the liquefied petroleum gas is prevented by the relatively low temperature of the heat sink in contrast to direct contact of the liquefied petroleum gas with a heat source which causes cracking of the gas, re¬ sulting in polymerization, tarry residues and undesired components to form. The unit can go from no load to full load almost instantaneously — a matter of seconds and can thus quickly respond to load changes. OMPI

Claims: CLAIMS: 1. A compact economical electric vaporizer unit for vaporizing liquefied petroleum. gas comprising: a heat-conductive casting having an internal cavity bridged by an integral divider dividing the ca¬ vity into separate chambers, multiple passageways through one end of the divider interconnecting the separate chambers, the pass¬ ageways of considerably reduced dimension relative to the dimension of each of the chambers, a liquefied petroleum gas inlet opening in the casting spaced from the multiple passageways and communi¬ cating with one of the chambers, a gas outlet opening in the casting adjacent the inlet opening and spaced from the multiple passage¬ ways communicating with the other chamber, one or more passageways in the integral divider holding electric resistance heater units, c-ne or more temperature sensing ports in the casting including temperature sensing means, electric power means connected to the electric resistance heaters, and control means operatively connected to the sensing means and electric power means for maintaining the temperature of the casting uniform. 2. The vaporizer of claim 1 wherein the inter¬ ior surface of each of the chambers includes fins to in¬ crease the overall surface area to which the liquefied petroleum gas entering the chambers is exposed. 3. The vaporizer of claim 1 wherein the cast¬ ing is symmetrical about its vertical and horizontal axes. 4. The vaporizer of claim 1 including an end cover sealing the exposed ends of the electric resistance heater units and control means therefor. 5. The vaporizer of claim 1 wherein the cast- OMPI ing is an aluminum casting. 6. The vaporizer of claim 1 wherein contact of the electric resistance heaters with the casting is such as to insure maximum heat transfer between the electric resistance heater units and the casting. 7. The vaporizer of claim 1 wherein .the tem¬ perature sensing port and sensing means are located be¬ tween the electric resistance heater units. 8. The vaporizer of claim 1 wherein the cham- bers are of equal volume and wherein the multiple pass¬ ageways are configured to minimize liquid petroleum gas carry-over and create turbulent flow of the liquefied petroleum gas as it passes from one chamber to " the oth¬ er. 9. The vaporizer of claim 1 wherein the cen¬ tral cavity provides a labrinyth passageway leading to the outlet opening for vaporizing liquefied petroleum gas introduced into the inlet opening. 10. A compact economical vaporizer having a vaporization capacity of ten to forty gallons of lique¬ fied petroleum gas per hour or more, comprising: a heat-conductive aluminum casting having an enclosed central cavity bridged by an integral divider dividing the central cavity into at least two separate vaporization chambers, multiple passageways interconnecting the two chambers, the passageways of considerably reduced dimen¬ sion relative to the dimension of each of the vaporiza¬ tion chambers, a liquefied petroleum gas inlet opening in the casting at the opposite end of the casting from the mul¬ tiple passageways communicating with one of the cham¬ bers, a gas outlet opening in the casting adjacent the inlet opening communicating with another of the cham¬ bers, BU O W1 11 passageways in the integral divider, each hold¬ ing an electric resistance heater unit, . temperature sensing passageways in *he casting adjacent the electric resistance heaters including tem¬ perature sensing means, electric power means connected to the electric resistance heater units at the end of the casting oppo¬ site the inlet and outlet openings, control means at the end of the casting oppo¬ site the inlet and outlet openings operatively connected to the sensing means and electric power means for main¬ taining the temperature of the casting uniform, and an end cover sealing the exposed ends of the electric resistance heaters and control means.

Inventors: DENSMORE B, DRAGOY J
Applicants: DICK IND INC SAM, SAM DICK IND INC
Application year: 1979
Main classification: F17C7
IPC codes: F17C7, F17C9