Low NOx Gasification Startup System
Disclosed is a low NO x gasification startup system and a method for starting up a low NO x startup system. During startup of a gasification unit, a gasifier must be pre-heated via combustion of a fuel source, which thereby generates pollutants. Once pre-heated, the gasifier initially generates off-spec syngas that requires disposal via combustion, thereby generating additional pollutants. The low NO x gasification startup system substantially lowers emission rates of NO x , CO, and/or VOCs during the startup process. During normal operation of the gasification unit, O 2 and CO 2 may be produced, stored, and later used during startup processes. The stored O 2 and CO 2 may be sent to one or more combustion devices and utilized as an oxidant for combusting undesired gases during the startup process. This CO 2 /O 2 mixture provides a higher oxygen content than air and contains substantially less nitrogen than air, thereby substantially reducing NO x formation within the combustion device's emissions.
1 . A low NO x startup system, comprising:
a combustion device;
an O 2 stream entering the combustion device; and
a CO 2 stream entering the combustion device;
wherein the O 2 stream and the CO 2 stream are combined to form a CO 2 /O 2 mixture comprising a CO 2 composition and an O 2 composition.
2 . The low NO x startup system of claim 1 , wherein the CO 2 composition within the CO 2 /O 2 mixture ranges from about 75% to about 80% and the O 2 composition within the CO 2 /O 2 mixture ranges from about 20% to about 25%.
3 . The low NO x startup system of claim 1 , wherein the CO 2 composition within the CO 2 /O 2 mixture ranges from about 65% to about 85% and the O 2 composition within the CO 2 /O 2 mixture ranges from about 15% to about 35%.
4 . The low NO x startup system of claim 1 , wherein the combustion device is a startup pre-heat burner, the startup pre-heat burner being coupled to a gasifier.
5 . The low NO x startup system of claim 1 , wherein the combustion device is a startup thermal oxidizer, the startup thermal oxidizer receiving an off-spec syngas.
6 . The low NO x startup system of claim 1 , wherein the O 2 stream is a vapor O 2 stream provided from an air separation system.
7 . The low NO x startup system of claim 1 , wherein the O 2 stream is stored as a liquid O 2 in an O 2 storage tank, the O 2 storage tank being fluidly coupled to the combustion device.
8 . The low NO x startup system of claim 7 , wherein the liquid O 2 is generated within an air separation system, the air separation system being fluidly coupled to the O 2 storage tank.
9 . The low NO x startup system of claim 1 , wherein the CO 2 stream is a vapor CO 2 stream provided by from an acid gas removal system.
10 . The low NO x startup system of claim 1 , wherein the CO 2 stream is stored as a liquid CO 2 in a CO 2 storage tank, the CO 2 storage tank being fluidly coupled to the combustion device.
11 . The low NO x startup system of claim 10 , wherein the liquid CO 2 is generated within an acid gas removal system, the acid gas removal system being fluidly coupled to the CO 2 storage tank.
12 . The low NO x startup system of claim 1 , wherein the O 2 stream and the CO 2 stream are mixed together prior to entering the combustion device.
13 . The low NO x startup system of claim 1 , wherein the O 2 stream and the CO 2 stream are mixed together after entering the combustion device.
14 . A low NO x startup system, comprising:
an air separation system, the air separation system producing a liquid O 2 ;
an O 2 storage tank fluidly coupled to the air separation system, the O 2 storage tank receiving and storing the liquid O 2 ;
an acid gas removal system, the acid gas removal system producing a liquid CO 2 ;
a CO 2 storage tank fluidly coupled to the acid gas removal system, the CO 2 storage tank receiving and storing the liquid CO 2 ; and
a combustion device fluidly coupled to the O 2 storage tank and the CO 2 storage tank, the combustion device receiving an O 2 stream from the O 2 storage tank and a CO 2 stream from the CO 2 storage tank;
wherein the O 2 stream and the CO 2 stream are combined to form a CO 2 /O 2 mixture comprising a CO 2 composition and an O 2 composition.
15 . The low NO x startup system of claim 14 , wherein the CO 2 composition within the CO 2 /O 2 mixture ranges from about 75% to about 80% and the O 2 composition within the CO 2 /O 2 mixture ranges from about 20% to about 25%.
16 . The low NO x startup system of claim 14 , wherein the CO 2 composition within the CO 2 /O 2 mixture ranges from about 65% to about 85% and the O 2 composition within the CO 2 /O 2 mixture ranges from about 15% to about 35%.
17 . The low NO x startup system of claim 14 , wherein the O 2 stream and the CO 2 stream are mixed together prior to entering the combustion device.
18 . The low NO x startup system of claim 14 , wherein the O 2 stream and the CO 2 stream are mixed together after entering the combustion device.
19 . A method for starting up a low NO x startup system, comprising:
providing a combustion device;
providing an O 2 stream to the combustion device; and
providing a CO 2 stream to the combustion device;
wherein the O 2 stream and the CO 2 stream are combined to form a CO 2 /O 2 mixture comprising a CO 2 composition and an O 2 composition.
20 . The method of claim 19 , wherein the CO 2 composition within the CO 2 /O 2 mixture ranges from about 75% to about 80% and the O 2 composition within the CO 2 /O 2 mixture ranges from about 20% to about 25%.
21 . The method of claim 19 , wherein the CO 2 composition within the CO 2 /O 2 mixture ranges from about 65% to about 85% and the O 2 composition within the CO 2 /O 2 mixture ranges from about 15% to about 35%.
22 . The method of claim 19 , wherein the O 2 stream is a vapor O 2 stream provided from an air separation system.
23 . The method of claim 19 , wherein the O 2 stream is stored as a liquid O 2 in an O 2 storage tank, the O 2 storage tank being fluidly coupled to the combustion device.
24 . The method of claim 23 , wherein the liquid O 2 is generated within an air separation system, the air separation system being fluidly coupled to the O 2 storage tank.
25 . The method of claim 19 , wherein the CO 2 stream is a vapor CO 2 stream provided by from an acid gas removal system.
26 . The method of claim 19 , wherein the CO 2 stream is stored as a liquid CO 2 in a CO 2 storage tank, the CO 2 storage tank being fluidly coupled to the combustion device.
27 . The method of claim 26 , wherein the liquid CO 2 is generated within an acid gas removal system, the acid gas removal system being fluidly coupled to the CO 2 storage tank.
28 . A method for starting up a low NO x startup system, comprising:
providing a first O 2 stream, a first CO 2 stream, and a natural gas stream to a pre-heat burner located within a gasification system;
providing a second O 2 stream and a second CO 2 stream to a thermal oxidizer;
reacting the first O 2 stream, the first CO 2 stream, and the natural gas stream within the pre-heat burner to produce an effluent stream;
upon pre-heating the pre-heat burner to a desired temperature, providing the first O 2 stream and a coal/coke stream into the gasification system to produce a scrubbed reacted gas stream;
providing the scrubbed reacted gas stream to a shift reactor system, the shift reactor system removing a substantial portion of water from the scrubbed reacted gas stream and producing a sour syngas stream;
providing the sour syngas stream to the thermal oxidizer;
reacting the second O 2 stream, the second CO 2 stream, and the sour syngas stream within the thermal oxidizer to produce a first thermal oxidizer discharge stream;
upon the shift reactor system reaching a first desired pressure, providing the sour syngas stream to an acid gas removal system to produce an off-spec syngas stream;
providing the off-spec syngas stream to the thermal oxidizer;
reacting the second O 2 stream, the second CO 2 stream, and the off-spec syngas stream within the thermal oxidizer to produce a second thermal oxidizer discharge stream; and
upon the acid gas removal system reaching a second desired pressure, producing a spec syngas stream.
29 . The method of claim 28 , wherein the desired temperature is an initiation temperature.
30 . The method of claim 29 , wherein the initiation temperature is about 2500° F.
31 . The method of claim 28 , wherein the first O 2 stream and the second O 2 stream are generated from an air separation system.
32 . The method of claim 28 , wherein the first CO 2 stream and the second CO 2 stream are generated from the acid gas removal system.