Two stage dry feed gasification system and process
View Patent ↗A dry feed two stage gasification system and process is disclosed for gasifying feedstock such as carbonaceous materials with improved energy efficiency, along with reductions in feedstock consumption and carbon dioxide emissions. The feedstock is first dried and pretreated with the hot syngas in the upper section of the gasifier to generate a dry char that is low in volatile-matter content. This dry char is sent to the first stage of a two stage gasifier where it reacts with oxygen in the presence of steam to produce a hot syngas stream.
1. A gasification process, comprising the steps of:
(a) providing a gasification reactor comprising a reactor upper section and a reactor lower section;
(b) introducing a substantially dry solid carbonaceous feedstock into the reactor upper section and reacting therein with a first mixture product from a reactor lower section, thereby forming a second mixture product,
wherein the first mixture product comprises syngas,
wherein the second mixture product comprises a second solid product and a second gaseous product,
wherein the temperature of the second mixture product leaving the reactor upper section is in a range of between 1500° F. to 2000° F.,
wherein the second gaseous product comprises syngas and residual solid fines and particulates;
(c) separating the second mixture product in a first separating device to produce a separated second solid product and a separated second gaseous product,
(d) passing the separated second solid product into the reactor lower section;
(e) cooling the separated second gaseous product in a heat recovery unit to produce a cooled second gaseous product and steam;
(g) separating the cooled second gaseous product in a particulate filtering device to separate out residual solid fines and particulates and passing them into the reactor lower section;
(h) combining a gas stream comprising oxygen, the separated second solid product of step (d), the residual solid fines and particulates of step (g) and the steam of step (e) in the reactor lower section and reacting them to evolve heat and form said first mixture product of step (b);
(i) mixing at least a portion of a solid carbonaceous feedstock with the separated second gaseous product of step (c) to form a warm solid-gas mixture, wherein said warm solid-gas mixture is maintained at a temperature that minimizes the formation of tar;
(j) separating the warm solid-gas mixture in a second separating device to produce the substantially dry solid carbonaceous feedstock of step (b) and a separated second gaseous product;
(k) passing the separated second gaseous product to a particulate filtering device to separate out at least a portion of the residual solid fines and particulates;
(l) passing the residual solid fines and particulates separated by the particulate filtering device to the reactor upper section.
2. The process of claim 1 , wherein said warm solid-gas mixture is maintained at a temperature in a range of 300° F. to 1000° F.
3. The process of claim 1 , wherein said warm solid-gas mixture is maintained at a temperature in a range of 500° F. to 800° F.