Method of Operation of Process to Produce Syngas from Carbonaceous Material
A process is provided for producing syngas that is effective for use in downstream processes. The process for producing syngas includes operating a gasification apparatus in a start-up mode until the gasification apparatus and equipment downstream of the gasification apparatus are adequately warmed up to a first target temperature. Upon reaching a first target temperature, the process is then operated in a production mode to produce a second syngas with a higher CO/CO 2 molar ratio. Operation in a start-up mode until reaching a first target temperature, provides a process that is effective for reducing fouling in downstream equipment and for providing a second syngas can be more effectively cooled and cleaned.
1 . A process for producing syngas, the process comprising:
gasifying carbonaceous material to provide a first syngas having a CO to CO 2 molar ratio of less than about 0.5 until the first syngas reaches a first target temperature; and
upon reaching the first target temperature, gasifying carbonaceous material to provide a second syngas having a CO to CO 2 ratio of greater than the first syngas.
2 . The process of claim 1 wherein the gasifying of carbonaceous material occurs in a gasification apparatus.
3 . The process of claim 1 wherein molecular oxygen is introduced at a rate of about 0 to about 100 lb-mole per ton of carbonaceous material on a dry basis to provide the first syngas.
4 . The process of claim 2 wherein the temperature of the first syngas is measured at one or more points inside and/or downstream of the gasification apparatus.
5 . The process of claim 4 wherein when the temperature of the first syngas at one or more points inside and/or outside the gasification apparatus reaches the first target temperature, molecular oxygen is introduced at a rate of about 0 to about 100 lb-mole per ton of carbonaceous material on a dry basis to provide the second syngas.
6 . The process of claim 1 wherein the first target temperature is about 700° C. to about 1000° C.
7 . The process of claim 1 wherein at least a portion of the first syngas is passed through a syngas cooler to produce a cooled first syngas and wherein at least a portion of the second syngas is passed through a syngas cooler to produce a cooled second syngas.
8 . The process of claim 7 wherein syngas is passed through the syngas cooler at a linear velocity of greater than about 24 meters per second.
9 . The process of claim 1 wherein at least a portion of the first syngas is provided to a thermal oxidation unit until the first syngas reaches the first target temperature.
10 . A process to produce syngas, said method comprising:
(a) adding carbonaceous material and molecular oxygen to a gasification apparatus to produce a first syngas with CO/CO 2 molar ratio less than 0.5;
(b) measuring temperature of said first syngas downstream of said gasification apparatus; and
(c) upon said temperature of said first syngas prior to entry in said syngas cooler attaining a first target temperature, reducing the addition of molecular oxygen per unit mass of carbonaceous material in said gasification apparatus to produce a second syngas with CO/CO 2 molar ratio greater than that of said first syngas.
11 . The process of claim 10 wherein the temperature of said first syngas is measured prior to entry into a syngas cooler.
12 . The process of claim 10 wherein the temperature of said first syngas is measured downstream of a syngas cooler.
13 . The process of claim 10 wherein at least a portion of said first syngas is passed through said syngas cooler to produce a cooled first syngas and at least a portion of said second syngas is passed through said syngas cooler to produce a cooled second syngas.
14 . The process of claim 10 wherein a source of molecular oxygen in step (a) is selected from the group consisting of air, oxygen enriched air, pure oxygen, and combinations thereof.
15 . The process of claim 10 wherein a source of molecular oxygen in step (c) is selected from the group consisting of air, oxygen enriched air, pure oxygen, and combinations thereof.
16 . The process of claim 10 wherein the source of molecular oxygen in step (a) comprises air.
17 . The process of claim 10 wherein the source of molecular oxygen in step (c) comprises pure oxygen.
18 . The process of claim 10 wherein said first target temperature is about 700° C. to about 1000° C.
19 . The process of claim 10 wherein said first target temperature is about 750° C. to about 850° C.
20 . The process of claim 10 wherein reduction of addition of molecular oxygen per unit mass of carbonaceous material is accomplished by increasing rate of addition of carbonaceous material.
21 . The process of claim 10 wherein reduction of addition of molecular oxygen per unit mass of carbonaceous material is accomplished by decreasing rate of addition of molecular oxygen.
22 . The process of claim 13 further comprising mixing at least a portion of said cooled first syngas with said portion of first syngas prior to passing through said syngas cooler to produce said cooled first syngas.
23 . The process of claim 13 further comprising mixing at least a portion of said cooled second syngas with at least a portion of said second syngas prior to passing through said syngas cooler.
24 . The process of claim 22 wherein linear velocity of mixture of said cooled first syngas and said first syngas flowing through said syngas cooler is greater than about 24 meter/second.
25 . The process of claim 23 wherein linear velocity of mixture of said cooled second syngas and said second syngas flowing through said syngas cooler is greater than about 24 meter/second.
26 . The process of claim 10 wherein the CO/CO 2 molar ratio of said second syngas is greater than about 1.0.
27 . The process of claim 10 wherein the CO/CO 2 molar ratio of said second syngas is greater than about 1.5.
28 . The process of claim 10 wherein said gasification apparatus is selected from the group consisting of moving bed, fixed bed, fluidized bed, entrained flow, counter-current (“up draft”), co-current (“down draft”), counter-current fixed bed, co-current fixed bed, counter-current moving bed, co-current moving bed cross draft, hybrid, cross flow, cross flow moving bed, part thereof, and combinations thereof.
29 . The process of claim 10 wherein said gasification apparatus comprises one or more reaction zones.
30 . The process of claim 10 wherein said gasification apparatus comprises a gasification zone for gasification of carbonaceous material to produce a raw syngas and a heat treatment zone for thermal treatment of said raw syngas to produce first syngas or second syngas.
31 . The process of claim 30 further comprising: attaining at least about 900° C. temperature in said heat treatment zone prior to step (c).
32 . The process of claim 30 further comprising: attaining at least about 1000° C. temperature in said heat treatment zone prior to step (c).
33 . The process of claim 10 further comprising treating at least a portion of one or more of said first syngas, second syngas, cooled first syngas, and cooled second syngas in a thermal oxidation unit.
34 . The process of claim 10 further comprising treating at least a portion of said first syngas in a thermal oxidation unit until said temperature of first syngas downstream of said gasification apparatus attains a first target temperature.
35 . The process of claim 30 further comprising treating at least a portion of said first syngas in a thermal oxidation unit until attaining at least about 900° C. temperature in said heat treatment zone.
36 . The process of claim 10 wherein said syngas cooler is selected from the group consisting of shell-and-tube heat exchanger, plate heat exchanger, plate-and-frame heat exchanger, tubular heat exchanger, double-pipe heat exchanger, hair-pin heat exchanger, single-pass heat exchanger, multi-pass heat exchanger, plate-fin heat exchanger, spiral heat exchanger, and combinations thereof.
37 . The process of claim 10 further comprising adding one or more of steam and CO 2 in step (c).
38 . The process of claim 10 wherein less than about 50 lb-mole steam per ton of carbonaceous material on a dry basis or less than about 50 lb-mole CO 2 per ton of carbonaceous material on a dry basis is added in step (a).
39 . A process comprising gasifying carbonaceous material in a gasification apparatus to produce a syngas, said method comprising:
(a) adding carbonaceous material and adding molecular oxygen in said gasification apparatus to produce a first syngas with CO/CO 2 molar ratio less than 0.5;
(b) passing at least a portion of said first syngas through said syngas cooler to produce a cooled first syngas;
(c) passing at least a portion of said cooled first syngas through a dust collection system to produce a cleaned syngas;
(d) measuring a temperature of said cleaned syngas at an exit of the dust collection system; and
(e) upon said temperature of cleaned syngas attaining a second target temperature, reducing addition of molecular oxygen per unit mass of carbonaceous material in said gasification apparatus to produce a second syngas with CO/CO 2 molar ratio greater than that of said first syngas.
40 . The process of claim 39 wherein said second target temperature is about 100° C. to about 200° C.
41 . The process of claim 39 wherein said second target temperature is about 100° C. to about 150° C.
42 . The process of claim 39 wherein the syngas contains less than 10 ppm tars.
43 . A process for cooling syngas comprising:
passing a syngas through a syngas cooler to produce a cooled syngas; and
recycling at least a portion of the cooled syngas to an inlet of the syngas cooler to maintain a temperature at the inlet of the syngas cooler of 760° C. or less and a linear velocity through an inlet of the syngas cooler of at least 24 meters per second.
44 . The process of claim 43 wherein the syngas CO to CO 2 molar ratio is maintained less than about 0.5 when the first syngas is below a target temperature prior to mixing with the recycled cooled syngas
45 . The process of claim 44 wherein the target temperature is about 700° C. to about 1000° C.
46 . The process of claim 43 wherein the syngas CO to CO 2 molar ratio is maintained above about 1 when the first syngas is above a target temperature prior to mixing with the recycled cooled syngas.
47 . The process of claim 46 wherein the target temperature is about 700° C. to about 1000° C.
48 . The process of claim 47 wherein the target temperature is about 750° C. to about 850° C.
49 . The process of claim 43 wherein a tar equivalent content of the syngas is maintained below about 10 ppm.
51 . The process of claim 49 wherein the tar equivalents are equivalent to a hydrocarbon selected from the group consisting of benzene, alcohol, and mixtures thereof.
52 . The process of claim 43 wherein the CO to CO 2 molar ratio is maintained by controlling the addition of molecular oxygen per unit mass of carbonaceous material to the gasification apparatus.