A transport gasifier loop, comprising: a mixing zone having a lower mixing zone and an upper mixing zone, the lower mixing zone being coupled to a lower gas inlet section and being configured to receive at least one gasification agent via the gas inlet section, the upper mixing zone being coupled to the lower mixing zone, the upper mixing zone including an upper gas inlet section configured to receive the at least one gasification agent and a mixture of circulating solids, the upper mixing zone being further coupled to a solids feeder; a riser coupled to the upper mixing zone, the riser being configured to receive the mixture of circulating solids, the gasification agent and gaseous products from the upper mixing zone, the riser further comprising a bend coupling the riser to an inclined crossover, wherein the gaseous products result from a reaction between the mixture of circulating solids and the at least one gasification agent; a first stage cyclone coupled to the inclined crossover, the first stage cyclone being configured to separate solids particles from the gaseous products; a seal-leg comprising a downcomer connecting a lower portion of the first stage cyclone to a horizontal leg portion, and a vertical seal-leg riser section connecting the horizontal leg portion to an inclined section, the seal-leg being configured to receive solids from the first stage cyclone; a standpipe cyclone coupled to an output of the first stage cyclone, the standpipe cyclone being configured to separate finer particles from the gaseous products; and a standpipe coupled to the inclined section of the seal-leg, the standpipe cyclone and the first stage cyclone, the standpipe being configured to receive solids particles from the first stage cyclone through the seal-leg, and the finer particles from the standpipe cyclone, the standpipe being further configured to recycle the mixture of circulating solids to at least one of the lower mixing zone and the upper mixing zone. a mixing zone having a lower mixing zone and an upper mixing zone, the lower mixing zone being coupled to a lower gas inlet section and being configured to receive at least one gasification agent via the gas inlet section, the upper mixing zone being coupled to the lower mixing zone, the upper mixing zone including an upper gas inlet section configured to receive the at least one gasification agent and a mixture of circulating solids, the upper mixing zone being further coupled to a solids feeder; a riser coupled to the upper mixing zone, the riser being configured to receive the mixture of circulating solids, the gasification agent and gaseous products from the upper mixing zone, the riser further comprising a bend coupling the riser to an inclined crossover, wherein the gaseous products result from a reaction between the mixture of circulating solids and the at least one gasification agent; a first stage cyclone coupled to the inclined crossover, the first stage cyclone being configured to separate solids particles from the gaseous products; a seal-leg comprising a downcomer connecting a lower portion of the first stage cyclone to a horizontal leg portion, and a vertical seal-leg riser section connecting the horizontal leg portion to an inclined section, the seal-leg being configured to receive solids from the first stage cyclone; a standpipe cyclone coupled to an output of the first stage cyclone, the standpipe cyclone being configured to separate finer particles from the gaseous products; and a standpipe coupled to the inclined section of the seal-leg, the standpipe cyclone and the first stage cyclone, the standpipe being configured to receive solids particles from the first stage cyclone through the seal-leg, and the finer particles from the standpipe cyclone, the standpipe being further configured to recycle the mixture of circulating solids to at least one of the lower mixing zone and the upper mixing zone.