EP0044198A2

EP0044198A2 - Oil delivery system

Info

Publication number: EP0044198A2
Application number: EP81303145A
Authority: EP
Inventors: William Sherritt Jennings
Original assignee: Clayton Manufacturing Co
Current assignee: Clayton Manufacturing Co
Priority date: 1980-07-11
Filing date: 1981-07-09
Publication date: 1982-01-20
Also published as: ES8301346A1; EP0044198A3; NO812376L; JPS5741520A; GR74292B; DK303881A; ES503845A0; FI812188L

Abstract

An oil delivery system for supplying heavy oil from a source that is contaminated with water to burners (34,336).

Control apparatus (8, 14) heats the heavy oil solution until it is preheated above the saturation temperature of water at the pressure in a de-watering tank (18) which is connected to the control apparatus and receives the preheated heavy oil solution. The tank (18) is maintained at a pressure sufficient to permit any liquid water contained in the heavy oil solution to vaporize and thus be removed from the heavy oil. A low pressure pump (26,28) delivers the de-watered heavy oil from the tank (18) to a combustion apparatus such as a marine power generator or oil burner (34,36).

Description

The present invention relates to an oil delivery system and especially to a low pressure heavy oil burner system and method for removing contaminating fluid constituents from heavy oil prior to delivery to a burner.
From the early days of burning oil for boiler combustion, it has been recognized that it is desirable to remove any water that has become mixed with the fuel oil or that condensates into the fuel oil prior to delivery to the boiler assembly. Two early patents granted at the turn of the century, U.S. Patent Nos. 744,373 and 758,224, disclosed an early desire to preheat heavy oil and to separate liquid such as water from the oil.
It has frequently been found that a No. 6 fuel oil will normally have a water content of 1-2% and in some cases, as much as 6% water has been found. As can be readily appreciated, a burner fuel control system, for example, of the type that would fire a boiler, is frequently operated cyclicly. When the burner is cycling to an off position, the fuel oil line system will drop to atmospheric pressure and any water at an elevated temperature above 100⁰ celsius will flash to steam when it approaches atmospheric pressure. The volumetric steam expansion of the water will displace the oil in the fuel lines and will have a tendency to force the oil out of the nozzle tip of the burner nozzle assembly. This dripping of the fuel oil will foul the burner assembly and will also create pollution problems because a suitable spray pattern is necessary for combustion purposes. Additionally, during an automatic start, the partially voided fuel line requires a period of time to restore the desired oil flow and to build up to the normal pressure. The resultant slowly- forming spray pattern will not ignite cleanly and will cause smoke to form, creating pollution problems and soot.
These problems have been recognized in the industry and attempts have been made to provide various forms of burner nozzle assemblies to solve this problem for both a single and double stage burner. In one such nozzle assembly, manufactured by the Weishaupt Company of Germany, a ball valve mounted on a nozzle piston in the fuel oil line functions as a check valve which only permits oil to pass after the oil pressure has been built up tc a predetermined point. In another oil burner nozzle assembly, manufactured by the same company, a needle valve that is spring controlled is positioned in the fuel line and again performs a check valve function to ensure that the fuel oil is not released until approximately a pressure of 180 psi (1241 kPa gauge pressure) has been achieved. Thus, the prior art has attempted to compensate for the high percentage of water in heavy fuel oil by assuring that elevated pressures keep the water from flashing to steam in a fuel line.
U.S. Patent No. 2,753,928 discloses a heavy oil burner system designed to preheat heavier grades of oil for reducing their viscosity prior to delivery to the combustion chamber.
_U.S. Patent No. 3,177,919 discloses a method and apparatus for removing gas vapors and foams in fuel oils by preheating. U.S. Patent No. 1,623,074 and U.S. Patent No. 3,009,537 are of general interest on preheating oil.
With the rising cost of energy, the industry is still seeking economic means to maximize the use of relatively less expensive and poorer quality oil sources, such as heavy fuel oil.
The present invention provides an improved low pressure oil burner system for burning a heavy fuel oil that can be contaminated with water. The heavy fuel oil can be contaminated by either subsequent condensation or can even be initially delivered with a relatively high content of water. A pumping system is attached to a storage tank that holds the heavy fuel oil and delivers it to a heater assembly. A control apparatus is attached to the heater assembly and controls the delivery of the heavy fuel oil to a de-watering tank. The control apparatus monitors the heavy fuel oil until it is pre-heated above a temperature of 100⁰ celsius at or above atmospheric pressure. The heavy fuel oil, when heated to this high temperature, is then delivered to the de-watering tank which is vented to permit any liquid water contained in the heavy fuel oil to vaporize and to be removed. The de-watered heavy fuel oil at a temperature above 100 celsius is then capable of being delivered to one or more burners for combustion by a low pressure pumping system.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in conjunction with the accompanying drawings, in which the sole figure, Fig. 1, is a schematic illustration of a typical application of the heavy oil burner system for water removal embodying the invention.
A description of the preferred embodiment is provided to enable any person skilled in the boiler or burner industry to make and use the invention. The best mode contemplated by the inventor in carrying out his invention is disclosed. However, various modifications will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide an improved low pressure heavy oil burner system particularly adapted to the burning of heavy oil that may be contaminated with water.
Referring to the drawing, a schematic of a heavy fuel oil system with water removal.is disclosed in the environment of a multiple steam generator installation. The heavy fuel oil solution refers to a mixture of heavy heating oil, such as bunker C fuel oil, water and/or light hydrocarbons. Quite frequently, the heavier heating oils will have water in them because of incomplete separation processes in handling and as a result of a storage such as from condensation. A primary purpose of the present invention is to provide a simplified de-watering of this heavy fuel oil to provide a stable burner operation while permitting delivery of the fuel oil at low pressure and at a temperature above the boiling point of water. By providing a higher oil temperature, it is also possible to maintain high quality burner performance and to continue to meet the tightening pollution and efficiency standards required today.
While the main application of the present invention is in steam generator and boiler facilities, it shoud be recognized that the present'.invention has other uses, for example, in maritime power generators. In the maritime field, it has been found that fuel quality has been deteriorating with an increase in the density of the fuel oils. Presently, centrifugal separation is utilized in cleaning the maritime fuel oil to remove sediments and water. The present '.invention is thus capable of solving the water problem in marine applications.
An additional factor of high labor and fuel energy costs has accentuated a demand for automatic steam boiler operations and more efficient uses of the available sources' energy. One of the more available and cheap sources of fuel oil is the residual oil No. 6 or bunker oil C. This oil has generally been utilized in larger boiler systems and requires a pre-heating to a viscosity of approximately 68 _Saybolt seconds universal (12.3 x 10 m².s^-1) which is fairly close to the viscosity of diesel oil. To achieve this viscosity, No. 6 fuel oil must be heated to approximately 150° celsius. A No.5 fuel oil must be heated to approximately 100 celsius. In general, the heavier oils must be heated to a temperature range between 65° and 150° celsius.
The prior art approach of using a high pressure fuel line system to maintain any contaminating water in a liquid state is eliminated or substantially improved by the present invention by flashing the water to steam in a de-watering tank.prior to delivery to the burner nozzles of the steam generators.
Although the prior art has utilized elevated temperature heavy fuel oil, its use has been dependent.upon maintaining'high pressure environment to solve any of the problems created by contaminating water in the fuel oil. The present invention is directed to a burner fuel control system wherein the oil is heated to a temperature of approximately 150 celsius, but can be delivered to the burner nozzle at a pressure less than 50 psig (345 kPa gauge pressure) by removing the water in the heavy oil solution. The present invention eliminates eratic delivery of fuel oil through the burner nozzle that would result in the burner chugging or pulsing rapidly. As is well known in the art, such pulsing of the burner can result in poor burner performance and.higher maintenance cost. The present invention separates the water from the fuel oil before being admitted to the burner pump and burner delivery and control systems. The result is a smoother and cleaner burning of the fuel with improved thermal efficiency in burners because the burners may then be operated with less excess air and still comply with regulations governing smoke and other products of combustion.
The present invention has a particular advantage in burners having combustion chambers which require a high rate of burning per unit of volume (low fuel residency time) and fuel oil temperatures which must exceed 100 celsius. The resultant delivery of the fuel oil to the burner is controllable and allows a fine tuning of the air fuel ratio for maximum thermal efficiency consistent with pollution control considerations for the general area of use of the burner system. The present invention further reduces operating expense by eliminating the need for dispersants and emulsifying additives for the fuel oil.
The present invention is particularly advantageous in burner oil systems that use air or steam atomization and lower fuel pressure, e.g. in the range of 25-50 psig (172-345 kPa gauge pressure) Since water at approximately 150⁰ celsius will flash to steam below 50 psig (345 kPa gauge pressure), the de-watering of the fuel oil will not only prevent pump pulsing but also will prevent instability in the remainder of the fuel system when it is used at lower pressures and higher temperatures than are generally used in earlier boiler systems.
Referring to the drawing, an oil storage tank 2 is connected to a fuel pump 4 that supplies fuel oil via a delivery line 5 controlled by a check valve 6. The delivery line is connected to a steam oil heat exchanger 8, such as a typical shell and tube heat exchanger. A return line 10 is connected to the oil storage tank 2 and is controlled by a pressure-limiting regulator valve 12. In normal operation, the heavy fuel oil will be heated, for example, by a steam heat exchanger (not shown) in the oil storage tank 2 to approximately 30-65⁰ celsius and will be continually recycled.
The steam heat exchanger 8 is controlled by a steam temperature control valve 14 coupled to a temperature monitor mounted at the outlet conduit from the exchanger 8 to measure the temperature of the fuel oil leaving the exchanger 8. The heat exchanger 8 also is connected to a steam trap 16 which functions in a normal manner. The steam temperature control valve 14 is set to ensure that the o heavy fuel oil is heated under pressure to approximately 150 celsius and, more specifically, within the range of 100° to 163 celsius. At this temperature range, the heated heavy oil is delivered to an oil de-watering unit or tank 18.
The oil de-watering unit 18 is maintained at a low pressure sufficient to permit any liquid water contained in the heavy oil to vaporize and be removed from the heated heavy oil. The vapor vent line 20 can be opened to the atmosphere or, alternatively, as shown in the drawing, connected to a condenser 22 to condense the oil vapor and water vapor to liquid form. The condenser unit 22, while optional, may be required in certain installations to comply with local pollution control regulations.
The oil de-watering unit or tank 18 is controlled by a float valve assembly 24 which ensures that a sufficient quantity of oil is maintained within the tank 18. Both the vent line 20 and the tank 18 can further be insulated, if desired. Alternatively, the heat exchanger 8 could be enlarged and vented to atmospheric pressure to. remove the necessity of the separate de-watering tank 18.
The steam generator system disclosed in the figure is of a typical multiple steam generator installation. It should be appreciated, however, that the present invention is equally applicable to a single steam generator of boiler unit. A low pressure pump, such as a positive displacement gear pump, is capable of operating to provide a supply of heated fuel oil that is water-free at a pressure range of approximately 25-50 psig. Such pumps 26 and 28 are shown attached, respectively, to boiler combustion chambers 34 and 36. Each of the respective pumps are capable of pumping approximately 200% of the normal requirement of a burner and generally 50% of the capacity of the pump is bypassed through the respective independent pressure regulator valves 42 and 44 to a low pressure return line 50. Check valves 46 and 48 can prevent return flow as a safety measure. An electric heater 52, which may be augmented by a supplemental steam heater (not shown) , can be utilized for cold starts and for temperature trimming to offset any radiation losses on a light load. This electric heater'is regulated by a temperature control valve 54 that monitors the high pressure line 56.
An air compressor 32 is connected to the fuel nozzle (not shown). As a result of the low pressure pump system, the present invention can save power consumption by requiring less power for the air crompressor since lower air pressure is required.
As can be readily appreciated, the individual elements of the present invention can be chosen from the prior art and accordingly it is not necessary to disclose a detailed construction to enable a _' person skilled in this field to practice the present invention.
A person skilled in the steam generation field is capable of perforring the method of the present invention to accomplish a clean and efficient burning of heavy fuel oil that has been contaminated with water vapor by reference to the above specification. The primary goal in accomplishing the method of the present invention is the heating of the heavy fuel oil, that can be contaminated on the average with as much as 2% water, to a temperature in the range of 100° celsius to approximately 163 celsius. This heated heavy fuel oil solution of water and oil is then subjected to a pressure low enough to permit any water in the heavy fuel oil to vaporize. The.. large difference in density between the liquid oil and the water and light oil vapors (gases) permits an efficient and complete separation in the de-watering tank 18. Prior art separators tried to separate the oil and water in a liquid form, although at a high temperature. That approach required long settling time periods and larger tanks. Additionally, that approach is not readily adaptable to a low pressure pumping system.
This vaporized water is then removed from the heavy fuel oil. Since the heavy fuel oil is now at an elevated temperature, its viscosity is low enough to be pumped by a low pressure pumping system so that the heavy fuel oul can be delivered to the burner at a pressure in the approximate range of 25-50 psig (172-345 kPA gauge pressure). As a result of this method, a smoother and cleaner burning of fuel oil is accomplished without any pulsing of the burner that can result in poor burner performance and higher maintenance cost. Additionally, pollution problems are minimized with an improved thermal efficiency since the boilers may be operated at a lower air fuel ratio and still comply with regulations governing. smoke and other products of combustion. The present invention has the particular advantage of operating with combustion chambers that require a high rate of heat per unit volume and with fuel oil temperatures that must exceed 100 celsius.
As can be readily appreciated, it is possible to deviate from the above embodiments of the present invention, and it will be readily understood by those skilled in the art that the invention is capable of many modifications and improvements within the scope and spirit thereof, for example, the function of the de-watering tank could be combined with the heat exchanger. Accordingly, it will be understood that the invention is not to be limited by the specific disclosed embodiment, but only by the scope and spirit of the appended claims.

Claims

1. An oil delivery system for a heavy oil solution that may be contaminated with water having a storage tank (2) for holding the heavy oil solution, a pumping system (4,6). to remove the heavy oil solution from the storage tank (2), a heater assembly (8) for heating the heavy oil solution from the storage tank and means (26,28) for delivering the heavy oil for combustion, characterised by a control apparatus (8,14) for heating the heavy oil solution in the heater assembly until it is preheated above a saturation temperature of water, and a de-watering tank (18) connected to the control apparatus and configured to receive the preheated heavy oil solution, the tank (18) being maintained at a pressure sufficient to permit any liquid water contained in the heavy oil solution to vaporize and be removed from the heavy oil, the heavy oil at a temperature above 100 celsius then being capable of being delivered for combustion.

2. An oil delivery system according to claim 1, characterised in that the means (26,28) for delivering the heavy oil for combustion is a low pressure pump apparatus operating to provide a supply pressure range of approximately 50 psig (345 kPa gauge pressure) or less.

3. An oil delivery system according to claim 2, characterised in that the control apparatus (8,14) for heating the heavy oil heats the oil to approximately 163⁰ celsius.

4. An oil delivery system according to claim 3, characterised in that condenser means (22) are connected to the de-watering tank (18) for condensing any water and oil vapor.

5. A low pressure burner oil delivery system particularly adapted to the burning of heavy oil that may be contaminated with water comprising:

a storage source (2) of heavy oil; and

means (8) for heating the heavy oil from the storage source (2) , and characterised by means (18, 20, 22) for removing any water mixed with the stored heavy oil,

means (14) for controlling the delivery of any heated oil and any water to the means (18, 20, 22) for removing so that the heated oil and any water is preheated to a temperature above 100° celsius at atmospheric pressure whereby any water will be vaporized and separated from the oil, and

low pressure pump means (26,28) for delivering the separated oil at a temperature above 100 celsius to a burner (34, 36).

6. A low pressure burner oil delivery system according to claim 5, characterised in that the means (14) for controlling the delivery of heated oil heats the oil to a temperature in the approximate range of 100° celsius to 163° celsius.

7. A low pressure burner oil delivery system according to claim 5, characterised in that the low pressure pump means (26, 28) operation in the approximate range of 25 to 50 psig. (172 to 345 kPa gauge pressure).

8. A method of delivering heavy fuel oils contaminated with water to be combusted in a boiler system having a storage tank for holding the heavy fuel oil, a pumping system to remove the heavy oil from the storage tank, a heater assembly for heating the heavy oil from the storage tank and means for delivering the heavy oil to a combustion chamber, characterised by the steps of:

heating the heavy fuel oil in the range of 100° celsius to ₁₆₃ ⁰ celsius;

subjecting the heavy fuel oil to a pressure low enough to permit any water in the heavy fuel oil to vaporize;

removing the vaporized water from the heavy fuel oil; and delivering the water-free heavy fuel oil to the burner at a pressure in the approximate range of 25 to 50 psig (172 to 345 kPa gauge pressure).