(1) Coal gasifier
The coal gasifier can be divided into four modes by the movement pattern of the coal in the gasifier: fixed bed (moving bed), fluidized bed, entrained bed and molten bed. While it can be summarized to atmospheric and high pressure styles according to the gasification operating pressure. Based on the feeding method, the coal gasifier contains solid and liquid feeding manners. In the light of the residue-discharge mode, it can be classified into solid and liquid patterns. In industry, the typical coal gasifiers include UGI gas furnace, Lurgi gas furnace, Winkler gas furnace, Texaco gas furnace and Dow Chemical gas furnace. Depending on various technology needs, the coal gasifiers provide air gas, mixed gas, water gas and semi-water gas.
In the coal gasifier device, the volume fractions of CO, CO2, CH4 and H2 are important parameters of process control, and the ability to accurately measure these variables is considered to be one of the most important indicators of the energy efficiency of the entire unit. First, the gas composition analysis can be used to determine the reaction state in the furnace, for example, the content of O2 is a critical control parameter in the production of semi-water gas. Additionally, it is necessary that the concentrations of CO and H2 are confirmed to be under the explosive limit before ignition, preventing any explosion. As we know, it is necessary to carry out N2 exchange until the feeding operation, but stilly, the O2 content in the furnace must be determined because the feeding coal slurry enters firstly, and it may reacts with O2 causing an explosion.
The online/portable fuel gas analyzer, which is produced by â€˜Wuhan Cubic Optoelectronics Co., Ltdâ€™, can fully satisfy various gasifiersâ€™ processes controls and safety testing requirements. It detects six gases compositions (CO, CO2, CH4, H2, O2 and CnHm) at the same time, with simple operation and easy maintenance.
Table 1. Composition of the production gas of variety gasifiers
Type of the gasifier H2 / % CO / % CO2 / % CH4 / %
UGI gas furnace 50 18 - 20 5 3 - 4
Lurgi gas furnace 37 - 39 17 - 18 32 8 - 10
Winkler gas furnace 35 - 46 30 - 40 13 - 25 1 - 2
K-T gas furnace 31 58 10 0.1
Texaco gas furnace 35 - 36 44 - 51 13 - 18 0.1
(2) Biomass gasifier
The main materials of the biomass gasifier are agricultural and wood wastes, which have the feature of wide sources and low price. Fuel gases produced by biomass gasifiers are mainly used for power generation (IGCC) or sent to city residents for cooking and heating through the pipe network.
Similar with the coal gasifier, the accurate measurements of the gas composition (CO, CO2, H2 and CH4) of the biomass gasifier can help to improve the gasification quality and the gas production efficiency. In addition, the total heating value of the mixed fuel gas is also an important parameter in energy calculation for pricing. According to various concentrations of fuel gasesâ€™ components, the total heating value Q is computed by the following equation, and the total energy value can be easily obtained with an additional volume flow meter.
Q = 126[CO] + 108[H2] + 359[CH4] + 665[CnHm] MJ/m3
Table 2. Composition of the production gas of biomass gasifier
Composition of the production gas H2 CO CO2 CH4 O2 CnHm N2
Volume fraction / % 15 10 14 1.6 3 < 1 56
Contact: Roy Chung
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