Process for heating an ATR

Abstract

The present invention relates to a process for heating an ATR or POX comprising the steps of heating a process stream by at least one heating means, admitting the heated process stream to an ATR or POX reactor through a main burner, and heating the ATR or POX reactor to or above autoignition temperature of the process stream via the heated process stream.

Claims

1. A process for heating and igniting an ATR (autothermal reformer) or POX (partial oxidation reformer), said process comprising the steps of: heating a hydrocarbon containing process stream comprising less than 5% H.sub.2 by at least one heating means to obtain a heated process stream comprising less than 5% H.sub.2, admitting the heated process stream to an ATR or POX reactor through a main burner, heating the ATR or POX reactor to or above autoignition temperature of the process stream via the heated process stream, admitting an O.sub.2 containing stream via the main burner at a first oxygen:hydrocarbon ratio to obtain autoignition and ignite the heated process stream in the reactor, and operating the ATR or POX reactor after autoignition at a temperature of between 1000 C.-1300 C. while admitting an O.sub.2 containing stream via the main burner at a second oxygen:hydrocarbon ratio greater than the first oxygen:hydrocarbon ratio.

2. The process according to claim 1, wherein the hydrocarbon containing process stream is heated to a temperature of 450 C.-600 C.

3. The process according to claim 1, wherein the heated process stream is ignited at temperatures between 450 C.-600 C.

4. The process according to claim 1, wherein the ATR or POX reactor is heated to a temperature of 450 C.-600 C.

5. The process according to claim 1, wherein pressure in the ATR or POX reactor is 10-25 bar during ignition.

6. The process according to claim 1, wherein the first oxygen:hydrocarbon ratio in the ATR or POX reactor is 0.05-0.30 at ignition and the second oxygen:hydrocarbon ratio is 0.50-0.70 during operation.

7. The process according to claim 1, wherein the ATR or POX reactor is preheated by an inert gas.

8. The process according to claim 1, wherein the hydrocarbon containing process stream comprises a natural gas comprising C1-C5 hydrocarbons.

9. The process according to claim 1, wherein the hydrocarbon containing process stream comprises steam, 2%-3% H.sub.2 and natural gas comprising C.sub.1-C.sub.5 hydrocarbons.

10. The process according to claim 1, wherein the hydrocarbon containing process stream is desulfurized before steam addition.

11. A plant arranged to carry out the process according to claim 1.

Description

EXAMPLE

Start Up (SU) Without Dedicated SU Burner

(1) In the present example an ATR unit consists of a system for providing feeds to the ATR reactor, a fired heater, a prereformer, the ATR reactor itself, and equipment for post-treatment of the product gas.

(2) The streams consist of natural gas, steam oxygen and hydrogen. All gasses are compressed to the operating pressure and heated to the operating temperature. The natural gas is desulphurized before entering the ATR reactor.

(3) In the tests the feeds were combined into two streams and were send to the burner of the ATR. The burner used in the example is described in U.S. Pat. No. 5,496,170, which by reference is included herein.

(4) A first feed stream (process stream) contained natural gas, hydrogen and steam. This was heated to a variable temperature in the range 300 to 650 C.: A second feed stream contained oxygen and steam. The second stream was heated to approx. 200 C.

(5) In the ATR reactor, the substoichiometric combustion and subsequent catalytic steam reforming and shift reactions are carried out. The inlet and exit gas compositions are measured by gas chromatograph.

(6) The tests were successfully carried out to demonstrate that flame ignition can be obtained at low temperature with fuel rich conditions with the configuration described above.

(7) In each test the feed stream composition or the operating conditions have been changed and it has been detected if ignition is obtained or not. The first stream I.e. the hydrocarbon containing stream is passing the ATR reactor continuously.

(8) Before entering the ATR the hydrocarbon containing stream is mixed with steam and heated in a fired heater and then led to an adiabatic prereformer. Prereformer is optional and can be bypassed. The effluent stream from the prereformer is sent to a separate fired heater section and heated to a temperature in the range of 300-650 C.

(9) The preheated mixture is sent to the ATR reformer and its burner. At the burner the hydrocarbon feed mixture may be mixed with a small steam flow which is used to cool the burner.

(10) Before ignition no oxygen is flowing and the first stream i.e. the feed mixture (process stream) is flowing isothermally through the combustion chamber as no reaction is taking place as no oxygen is admitted.

(11) The feed mixture is passing a catalyst bed in which adiabatic steam reforming is taking place and the temperature is decreasing as the steam reforming reactions are endothermic.

(12) In the test an oxidant stream (mixture of pure 99% oxygen and saturated steam) is introduced to the burner periodically for short periods. Flame ignition is detected by temperature increase monitored by thermocouples. The feed mixture is in the present tests allowed to equilibrate for min 120 seconds. Flame ignition should be detected within this time period.

(13) The test data is for a case with adiabatic prereformer and the test result show that at 15 bar g the autoignition is obtained for temperatures >475 C.

(14) The applicant has furthermore shown that the ignition temperature decrease with increasing pressure and that the ignition temperature decrease with increased Oxygen/NG ratio.

(15) TABLE-US-00002 TABLE 2 S/C ratio Ox/NG ratio Mole Pressure Temperature Ignition Nm.sup.3/Nm.sup.3 H.sub.2O/mole C bar g C. yes or no 0.20 1.80 15.0 490 Yes 0.20 1.80 15.0 490 Yes 0.20 1.79 15.0 490 Yes 0.20 1.81 15.0 485 Yes 0.20 1.79 15.0 485 Yes 0.20 1.80 15.0 480 Yes 0.20 1.80 15.0 480 Yes 0.20 1.80 15.0 475 Yes 0.20 1.80 15.0 470 No 0.20 1.80 15.0 470 No 0.20 1.79 15.0 465 No 0.20 1.80 15.0 465 No