The present invention relates to a composite treatment and recovery technique of polluted water body and soil. Iron-rich straw biomass, after being crushed, is mixed and granulated with sludge, and is pyrolytic charred by programmed heating, to obtain bulk loaded zero-valent iron biochar and sludge biochar composite particles, which are packed as fillers in a filled bed or as filters in filter cells of a fixed bed, for effective recovery of complex polluted water, polluted by heavy metals, organics, nitrogen, phosphorus, and the like.

The invention provides a system for pyrolysis, comprising: (i) a gas producer comprising a gasification zone and a producer gas outlet, wherein the gas producer is configured to: oxidise at least one carbon-containing feed in the presence of an oxidising gas in the gasification zone to form a producer gas; and discharge the producer gas from the gasification zone via the producer gas outlet, wherein a residual oxygen content of the producer gas is substantially depleted or maintained below a maximum predetermined amount by controlling a ratio of oxygen fed to the gasification zone to the carbon-containing feed, (ii) a pyrolyzer comprising a pyrolysis zone and one or more pyrolyzer gas outlets, wherein the pyrolyzer is configured to: feed the producer gas discharged from the gasification zone to the pyrolysis zone; pyrolyze a pyrolyzable organic feed in the pyrolysis zone in the presence of the producer gas to produce a carbonaceous pyrolysis product and a gas mixture comprising combustible components comprising pyrolysis gas; and discharge the gas mixture from the pyrolysis zone via the one or more pyrolyzer gas outlets, and (iii) a first combustor comprising a combustion zone, wherein the first combustor is configured to: receive the gas mixture discharged from the pyrolysis zone in the combustion zone; feed an oxygen-containing gas to the combustion zone; and combust at least a portion of the combustible components present in the gas mixture in the combustion zone to produce a combustion product gas.

The invention provides a system for pyrolysis, comprising: (i) a gas producer comprising a gasification zone and a producer gas outlet, wherein the gas producer is configured to: oxidise at least one carbon-containing feed in the presence of an oxidising gas in the gasification zone to form a producer gas; and discharge the producer gas from the gasification zone via the producer gas outlet, wherein a residual oxygen content of the producer gas is substantially depleted or maintained below a maximum predetermined amount by controlling a ratio of oxygen fed to the gasification zone to the carbon-containing feed, (ii) a pyrolyzer comprising a pyrolysis zone and one or more pyrolyzer gas outlets, wherein the pyrolyzer is configured to: feed the producer gas discharged from the gasification zone to the pyrolysis zone; pyrolyze a pyrolyzable organic feed in the pyrolysis zone in the presence of the producer gas to produce a carbonaceous pyrolysis product and a gas mixture comprising combustible components comprising pyrolysis gas; and discharge the gas mixture from the pyrolysis zone via the one or more pyrolyzer gas outlets, and (iii) a first combustor comprising a combustion zone, wherein the first combustor is configured to: receive the gas mixture discharged from the pyrolysis zone in the combustion zone; feed an oxygen-containing gas to the combustion zone; and combust at least a portion of the combustible components present in the gas mixture in the combustion zone to produce a combustion product gas.