自然发火一直是困扰煤炭安全开采的主要问题，而降温和隔氧是防治煤自燃及其继发灾害的关键。近年来，随着煤化工行业的迅猛发展，液态CO2产量急增，加之突出的降温、惰化及抑爆等特点，逐渐在各类煤层自燃火灾的治理中扮演着重要的角色。然而，由于对伴随相变发生的松散煤体内热质传输过程掌握不清，严重影响了液态CO2防灭火技术的科学施用和效果预测。为此，本文围绕松散煤体内液态CO2相变传热与传质这一过程进行了研究。取得了以下研究成果： (1) 渗流是传质、传热过程的基础，针对液态CO2相变后以过热、饱和混合气体渗流的特点，采用松散煤体渗透系数测试实验装置研究了不同压力和流量下CO2的渗流压降特征，提出了基于空隙率和粒度的渗透率和非达西因子计算方法，从而揭示了CO2混合气体的非线性渗流机理。 (2) 利用设计搭建的松散煤体内压注液态CO2降温测试系统研究了压注全过程煤体温度的变化特征，依据降温幅度和传输机制划分了相变换热、对流换热和传导换热三个降温区域。并开展了不同压力、口径及流量对相变降温半径影响的试验研究，结果表明，相变降温半径随压力、口径与流量的增大呈现不同程度的增长，并基于各单一因素与降温半径之间的关系模型，给出了多因素影响下的相变降温半径计算公式。最后对压注液N2和液态CO2的降温过程及特点进行了对比分析。 (3) 基于液态CO2相变传热与传质的耦合作用机制，提出了相变点热源耦合实际状态方程动态计算物性参数的方法来模拟松散煤体内液态CO2相变及热质传输过程。通过与实验数据的对比，验证了所采用模型和模拟方法的有效性。并得到了CO2相变扩散过程中呈现突破、快速增长和稳定三个阶段性特征，确定了压力和流量为影响扩散过程的关键因素。 (4) 通过数值分析，研究了采空区开放式压注液态CO2时温度、CO2及O2浓度的分布变化规律，基于模拟结果，拟合得到了压注时间与降温范围及CO2扩散区域的关系式。从惰化效果的角度，提出了先“位置”后“流量”的关键参数制定策略，同时针对不同的压注位置和流量，提出了分析不同压注时间时惰化效果的理论方法。 (5) 最后，开发了直注式长距离液态CO2防灭火工艺及配套装备，解决了因相变形成干冰堵塞管路的问题，并在羊场湾煤矿II020210工作面封闭火区的治理和II020207工作面采空区煤自燃预防工作中获得了成功的应用。

For a long period, the self-ignition was a primal problem which has troubled the safety mining of coal. The key technologies for inhibiting the spontaneous combustion of coal and its correlative disasters included two aspects: cooling and inerting. In recent years, with the fast development of coal chemical industry, considering the production of liquid carbon dioxide has increased greatly and its better cooling, inerting, and explosive-resisted capacity, the liquid carbon dioxide gradually played a more important role in the process of prevention and extinguishment of various coal fires caused by spontaneous combustion. However, the scientific application and effect prediction of liquid carbon dioxide cannot be achieved due to the problems involving phase change, multicomponent transport, and heat transfer in loose coal have not been solved. Accordingly, this paper conducted researches on the process of heat and mass transfer in loose coal with phase change for liquid carbon dioxide According to the seepage characteristics of composite superheated and saturated gas after the phase transition of liquid carbon dioxide, the seepage pressure drop characteristics of carbon dioxide was studied under different pressure and flow rate using the experimental apparatus for permeability coefficient of loose coal. As results, the calculated method of permeability and non-Darcy factor based on the porosity and granularity was proposed, thus the nonlinear seepage mechanism of mixed carbon dioxide gas was obtained. The temperature variation characteristics during the process of liquid carbon dioxide injection were experimental studied. The endothermic phase transition region, convective heat transfer region and conductive heat transfer region were classified according to the reduction of coal temperature as well as the transmission regime of liquid carbon dioxide. Thus, effects of initial pressure, out-let diameter, and flow rate on the radius of the temperature-reduction by phase transition were evaluated. Experimental results indicated that the increments of initial pressure, out-let diameter, and flow rate could certainly enlarge the temperature-reduction region with a relative scope. Subsequently, the mathematical model based on the radius of temperature-reduction region versus multi-influence factors was proposed. Finally, the differences in the temperature-reduction regimes and characteristics of liquid nitrogen and liquid carbon dioxide were analysed. Based on the coupling mechanisms of heat and mass transfer with phase transition for liquid carbon dioxide, the method of calculating the physical parameters of the actual state equation of phase transition point heat source coupling was proposed which to simulate the liquid carbon dioxide phase transition and heat and mass transfer process in loose coal. By comparing with the experimental data, the validity of the model and simulation method was verified and the process of carbon dioxide diffusion showed the three stage characteristics of the breakthrough, the rapid growth and the stability, which the pressure and the flow were identified as key factors of the above process. Through numerical analysis, the evolution of temperature, concentration distribution law of the carbon dioxide and oxygen when liquid carbon dioxide was injected to open mined area, was studied. Based on the simulation results, the relationship between the pouring time and the cooling range and the diffusion region of carbon dioxide was obtained. From the perspective of the inerting effect, proposed the the key development strategy for parameter of "position" should be prior to the parameter of "flow", simultaneously for different injection position and flow, proposed the theoretical method of analyzing the inerting effect at different times of pouring. Finally, the liquid carbon dioxide direct injection for extinguishing coal fires through long distance pipeline transportation was developed, which solved the problem of line clogging by dry ice formed by phase change. Subsequently, a successful application had been achieved in the process of extinguishing sealed fire in II020210 long-wall face and prevention of coal self-heating in II020207 gob for Yangchangwan colliery.