Chongqing city, which is located in the southwest of China, suffers from acid rain damage caused by SO₂ in coal combustion gas. Particularly, stoker type boilers in medium and small factories have no emission control facility in spite of using coal with high sulfur content (3-5%), so that a suitable countermeasure is required in angles of the cost, technological level and social conditions.
We proposed a coal briquette combustion with the additive of limestone or slaked lime as one of the countermeasure. The possibility of coal briquette combustion methods was examined experimentally and compared with other methods from points of view of the cost and energy saving effect. The desulfurization rate of 70% was obtained in the briquette combustion method with the additive of limestone and 80% for slaked lime. Most of sulfur in the coal (both organic and pyritic) was trapped as gypsum anhydride (CaSO₄). The desulfurization rate slightly depended on initial oxygen concentration in the supplied gas and size of limestone, while it was not influenced by briquetting pressure.
The desulfurization cost of coal briquette was calculated as 20-30% of semi-dry or fluidized bed process. The briquette combustion method was expected to be effective in improving the human health and forest conservation in Chongqing city.

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Measurements of dilatation and contraction of a briquette were carried out in order to develop the new cokemaking process which can use non-or slightly caking coals . The briquette was composed of coals (caking coal and non-or slightly caking coals) and additives (soft pitch) as a binder. After these components were mixed at various ratios and stirred at 373K, they were molded to the rod-shaped briquette (φ9mm × 30mm, apparent density: 1200kg/m³) by a uniaxial compression briquetting machine. The briquette was carbonized in an infrared image furnace at various heating rates and dilatation and contraction of the briquette were measured. The result showed that the true dilatation of the briquette was irrelevant to the heating rate and the binder content and was about 20%. The contraction coefficient of the briquette had two peaks as well as caking coal. The first peak of them was caused by the release of the volatile matter and the second peak was caused by an increase in the carbon orientation with hydrogen release. Because the binder reacted as a volatile matter in the briquette, the first peak of the contraction coefficient depended on the binder content of the briquette. The additive property was verified by the measured contraction coefficient of the briquette with varying the binder content.

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In order to clarify the influence of the geometry of the mixing chamber on the atomization by the internal mixing twin-fluid atomizer, several flow patterns in the mixing chamber, which were caused by the change of the mixing chamber geometry, were photographed and the Sauter mean diameter was measured by the Fraunhofer diffraction technique. The change of the mixing chamber length has an effect on the flow pattern within the mixing chamber and the Sauter mean diameter of a spray issued from the atomizer. When an atomizing air/water mass ratio is under 0.2, the Sauter mean diameter becomes smaller, as the liquid is more mixed with the atomizing air within the mixing chamber.

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