Experimental Study on the Circulating Characteristics of the Return Particles in CFB and the Validity of the Particles to Desulphurization
The cold-model experimental system that particles flow from the top of CFB reactor is set up to study the circulating characteristics of the particles in the reactor. In order to get further information about the particles distribution and interaction with air flow, the two-phase gas-particle flow and particle concentration in the tower are studied with the use of phase-Doppler particle dynamic analyzer (PDA) system. The effects of the operating parameters including the mass flow rate and the superficial gas velocity on the process of the particles return to the main flow were investigated. The definition of valid internal circulation is put forward in this paper to describe the contribution of the particle to the SO 2 removal reaction. The results showed that the concentration distribution tends to be right high and left low in the radial direction. In axial, more particles concentrated in the upper of the reactor, especially in the case of high superficial gas velocity. With the decrease of the superficial gas velocity, the maximum fallback length of particle and the average particle concentration increase quickly. While the valid particle concentration increases slowly. The quantity of valid particles increases a little. Sending the particle from the top of the reactor has little contribution to the SO 2 removal reaction.
Industrial-scale demonstration of a new sorbent reactivation technology for fluidized bed combustors.
To minimize the disposal of highly reactive spent sorbent from a fluidized bed combustor, a new method for reactivation has been developed. The method consists of grinding the spent ash in a rotary mill, hydrating the ash with an excess of water, and mixing the wet ground ash with dry solids to absorb the excess water. The mixing process eliminates the formation of a concrete-like product that normally results as wet fluidized bed combustor ash ages. Pilot-scale combustion trials proved to be successful, and the process was scaled up using a 35MWt utility boiler at Purdue University. The test lasted for 3 days and resulted in net reduction of limestone sorbent use of 18%. The results generated in this work have been used to develop an economic evaluation for a 165MWe circulating fluidized bed (CFB) boiler, which projects significant savings due to reduction of limestone supply and ash disposal costs. The evaluation also suggests that the process is cost competitive with other processes, albeit that those processes have not been demonstrated at industrial scale. Furthermore, it also has the potential to make a small net reduction in CO(2) emissions, due to reduced limestone usage.
Electrophysiological Studies of Penticainide (CM 7857), a New Antiarrhythmic Agent, in Mammalian Myocardium
The intracellular electrophysiologic properties of a new antiarrhythmic substance, penticainide, were studied in isolated rabbit, dog, and guinea pig myocardial preparations superfused or perfused with oxygenated Tyrode's solution. “Therapeutic” concentrations of penticainide (1.5 to 3 x 10-5 M) had little effect on sinus node automaticity; sinoatrial conduction was slightly delayed. In atrial, Purkinje and ventricular fibers, amplitude, and maximal rate of rise of phase 0 (dV/dtmax) were decreased by penticainide; Purkinje-ventricle conduction velocity was depressed. Penticainide did not significantly modify action potential duration (APD) of rabbit atria and dog ventricle and reduced APD and effective refractory period (ERP) of dog Purkinje and guinea pig ventricular fibers. Penticainide reduced APD heterogeneity of Purkinje-ventricle junction with a preferential effect at the gate and decreased tension amplitude of perfused papillary muscle in dog heart. The effect of penticainide on dV/dtmax was voltage and rate dependent; the resting block was weak. Thus, penticainide is a class 1 antiarrhythmic agent with properties of class 1B agents such as APD reduction and properties of class 1C agents such as slow recovery kinetic of rate-dependent block.