Burner for the production of synthesis gas and related cooling circuit

Abstract

A burner system (100) for the combustion of a hydrocarbon feedstock with an oxidant, comprising at least one burner (1) and a cooling circuit (2), where in: the burner system (100) comprises a fuel side (3, 15) and an oxidant side (4, 14); the burner (1) comprises a cooling chamber (5) connected to said cooling circuit(2); said cooling circuit (2) comprises a reservoir tank(8) for said cooling fluid and a circulation pump(16); said system (100) comprises pressure equalizing line (15b) arranged to establish a fluid communication between the inside of said reservoir tank (8) and at least one of said fuel side and oxidant side.

Claims

1. A burner system for the combustion of a hydrocarbon feedstock with an oxidant, comprising at least one burner body and a cooling circuit, wherein: the burner system comprises a fuel side and an oxidant side; the at least one burner body comprises a cooling chamber connected to said cooling circuit for the passage of a cooling fluid; wherein: said cooling circuit comprises a reservoir tank for said cooling fluid and a circulation pump; said burner system comprises pressure equalizing means adapted to equalize the pressure inside said cooling circuit to the pressure of at least one of said fuel side and oxidant side, said means including at least one pressure equalizing line arranged to establish a fluid communication between the inside of said reservoir tank and said fuel side, wherein said cooling circuit is configured to provide said cooling fluid to said at least one burner body while said at least one burner body combusts said hydrocarbon feedstock with said oxidant.

2. The burner system according to claim 1, wherein said at least one pressure equalizing line is arranged to provide a fluid communication of said fuel side with a region of the reservoir tank which is above a liquid level of the cooling fluid, so that the pressure of said at least one pressure equalizing line is transferred to a free surface of the cooling fluid contained in the reservoir tank.

3. The burner system according to claim 2, wherein the cooling fluid contained in the reservoir tank acts as a seal against a mass transfer from said at least one pressure equalizing line into any part of the cooling circuit other than the reservoir tank.

4. The burner system according to claim 1, wherein said at least one burner body comprises a fuel duct, and said at least one pressure equalizing line provides a fluid communication directly between said fuel duct, and said reservoir tank.

5. The burner system according to claim 1, said at least one pressure equalizing line being arranged to connect the reservoir tank with a fuel inlet.

6. The burner system according to claim 1, wherein the cooling circuit also comprises at least one item suitable to introduce a concentrated pressure drop of the cooling fluid between a cooling fluid outlet from the cooling chamber and said reservoir tank, and the magnitude of said concentrated pressure drop is such that, in operation, the pressure of the cooling fluid in the cooling circuit is greater than the gas pressure of said fuel side.

7. The burner system according to claim 6, wherein said item is either a valve or an orifice.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a sectional view of a process burner and a scheme of a related cooling system, according to an embodiment of the invention.

DETAILED DESCRIPTION

(2) FIG. 1 shows a burner system 100 suitable for use in an ATR or in a POX reactor. Said burner system 100 is generally located at the upper end of said ATR or POX reactor, and is positioned above a combustion chamber (not shown in the FIGURE).

(3) The burner system 100 comprises a burner body 1 and a cooling circuit 2.

(4) The burner body 1 comprises coaxial outer duct 3 and inner duct 4 connected to a hydrocarbon fuel inlet 6 and to an oxidant inlet 7, respectively. The burner body 1 also comprises a cooling chamber 5 connected to the cooling circuit 2 for circulating a cooling fluid, such as water, around the walls of said fuel duct 3 and oxidant duct 4.

(5) The fuel duct 3 and the oxidant duct 4 emerge into said combustion chamber. In operation, the end surfaces of the body 1, such as the surface 21, face directly the combustion chamber.

(6) The cooling chamber 5 surrounds the outer surface of the fuel duct 3, and is provided with a cooling fluid inlet opening 9 and a cooling fluid outlet opening 10 which are connected to the cooling circuit 2.

(7) The burner body 1 has a gas side subjected to a gas pressure (namely the inside of ducts 3, 4); combustion chamber-facing parts and surfaces, such as the surface 21, and a water side subjected to the pressure of water (or any other cooling fluid) in the circuit 2.

(8) FIG. 1 shows a preferred embodiment where the cooling chamber 5 comprises an outer jacket 11 and an inner jacket 12. The inner jacket 12 is in contact with the fuel duct 3. The outer jacket 11 is in fluid communication with the cooling fluid inlet 9 and the inner jacket 12, instead, is in fluid communication with the cooling fluid outlet opening 10. The two jackets 11 and 12 are in communication via a conduit 20 and a connecting chamber 13 at the tip region of the burner body 1.

(9) The cooling circuit 2 comprises essentially a reservoir tank 8 for the storage of said cooling fluid, a circulation pump 16 and a valve 19. The valve 19 is designed to introduce a selected pressure drop on the circuit 2, and said valve is preferably located in the portion of said circuit 2 between the cooling fluid outlet 10 and the reservoir tank 8. The pump 16 is preferably located in the portion between said tank 8 and the inlet 9.

(10) The pressure drop of the valve 19 ensures that the pressure of the cooling fluid is always greater than the pressure of the process gas of the burner, namely of fuel and oxidizer, as will be explained below in a greater detail. In equivalent embodiments, the valve 19 may be replaced by a suitable orifice or by one or more items suitable to introduce the same pressure drop.

(11) The operation is as follows.

(12) A gaseous fuel 15 such as natural gas is introduced into the fuel duct 3 via the inlet opening 6 and a suitable oxidant 14 is introduced into the oxidant duct 4 via the inlet opening 7. Said oxidant 14 is preferably air, enriched air or oxygen. The fuel inlet 6 is in communication with the reservoir tank 8 via a duct 15b, in such a way that the fuel inlet pressure P.sub.1 is transmitted to the cooling fluid contained in said tank 8. Hence, the duct 15b acts as a pressure equalizing line of the reservoir tank 8. The gas fuel 15 enters the fuel duct 3 at 15a, as illustrated.

(13) It can be noted that the pressure equalizing duct 15b enters the reservoir tank 8 above the free surface 22 of the cooling fluid, under operation. The pressure P1 is then transmitted to said free surface 22 while the cooling fluid itself isolates the duct 15b, which is part of the fuel side, from the cooling fluid line 17. The duct 15b acts only as a pressure equalizing line, by pressurizing the inside of the tank 8; no fuel contaminates the cooling circuit 2 thanks to said sealing effect.

(14) The cooling fluid, such as water, is circulated by the pump 16, enters the cooling chamber 5 via the inlet 9, traverses the jackets 11 and 12 and leaves the body 1 via the outlet 10. The circulation pump 16 compensates for the pressure losses through the circuit 2 and the cooling chamber 5.

(15) The connection between the fuel gas inlet 15 and the reservoir tank 8, via duct 15b, determines a pressure P.sub.2 of the cooling fluid at the outlet of the tank 8 (namely the suction pressure of the pump 16) substantially equal to the fuel inlet pressure P.sub.1.

(16) The pressure P3 of the cooling fluid at the outlet 10 of the chamber 5 can be expressed as:
P.sub.3=P.sub.1+ΔP.sub.0+ΔP.sub.1
wherein ΔP.sub.0 is the pressure drop across the valve 19 and ΔP.sub.1 includes the distributed pressure loss of the circuit. Generally ΔP.sub.0 is significantly greater than ΔP.sub.1 which means that the outlet pressure P.sub.3 is determined by the pressure loss of the valve 19.

(17) Accordingly, the delivery pressure P.sub.4 of the pump 16 is determined as P.sub.3 plus the pressure loss through the cooling chamber 5.

(18) By means of an appropriate choice of the pressure loss ΔP.sub.0 introduced with the valve 19, said pressure loss ΔP.sub.0 being above a threshold value, it is ensured that the pressure in the circuit 2 is always above the pressure P.sub.1, in particular the pressure in the water circuit is greater than P.sub.1 by a certain amount which is dictated by the choice of ΔP.sub.0.

(19) Hence the invention provides that the pressure in the cooling circuit 2 is always above the pressure in the gas side of the burner, avoiding the risk of gas (e.g. fuel or oxidizer or mixture thereof) entering the circuit 2 in case of a seal leakage. In particular, ΔP.sub.0 shall be greater than the pressure loss in the cooling chamber 5. At the same time, the pressure of the cooling circuit 2 is governed by the pressurization of the reservoir tank 8 by means of the line 15b, which means that the pressure of the cooling fluid follows the gas pressure during transients. Accordingly, the walls of the burner body 1 are not stressed by excessive water pressure when the gas pressure inside drops. The present invention thus achieves the aims set out above.

(20) A related advantage is that an embodiment with a reduced wall thickness is possible, which reduces the thermal inertia. Reducing the thermal inertia is beneficial in particular for surfaces such as the surface 21 facing the combustion chamber and exposed to a high thermal stress.

(21) FIG. 1 illustrates a single-body embodiment of the burner. The invention is also applicable to multi-body burner systems including several burner bodies (e.g. for POX).

(22) In a multi-body embodiment, the burner bodies are preferably connected to a common cooling circuit 2. In this case, the cooling fluid is circulated by the pump 16 and is split into a number of streams, each one being independently fed to a respective burner body 1 via a corresponding inlet 9 and leaving the body itself via a corresponding outlet 10.