Study of the Reaction of SO₂with NaHCO₃and Na₂CO₃

Abstract

The results are presented of a study conducted to examine the reactivity of NaHCO 3 and its thermally decomposed product, Na 2 CO 3 , with SO 2 as a function of temperature and particle size in a simulated flue gas. The NaHCO 3 reaction was found to be significantly more efficient than the Na 2 CO 3 reaction for temperatures less than 450°F (230°C) with a maximum efficiency of conversion occurring between 250 and 350°F. In the temperature range of 450-650°F, both compounds were observed to behave similarly. The Na 2 CO 3 reaction with SO 2 was found to be dependent on particle size in the range of 20-200 /tm for temperatures less than 450°F. The focus on sodium bicarbonate (NaHCOs) as a dry additive injection material for flue gas desulfurization (FGD) systems has come about mainly from the abundance and proximity of nahcolite to oil shale reserves, and the desire to identify an all dry FGD system. Nahcolite is a naturally occurring form of sodium bicarbonate (70% NaHC0 3 , remainder inerts), found in large underground deposits in northwestern Colorado, northeast Utah and southeast Wyoming which places it within a reasonable transportation range for coalfired steam plants located in the western part of the U.S. In addition, trona (Na 2 CO 3 NaHCOg • 2H 2 O) is also a candidate for FGD and is located in large deposits in the.U.S. Data have been collected on a variety of pilot and full scale fabric filter collectors to demonstrate the ability of the above compounds to remove SO2. 1 "" 3 These reports have concluded that the temperature, size of additive and type of injection technique (continuous versus batch) have been observed to affect the performance. Also it has been shown that sodium carbonate (N&2CO3), the product of decomposition of NaHC(>3, does not react as readily with SO2 as the parent NaHCO3. A possible explanation for this behavior may stem from the effect of the heated flue gas on thermally decomposing the NaHCOg into the product Na2COs while undergoing simultaneous reaction with SO2. The decomposition reaction for NaHC03 is given by: 2NaHCO 3 (s) Na 2 CO 3 (s) CO 2 (g) + H 2 O(g) (1)

Off-Gas Desulfurization With Sodium Bicarbonate for Iron Ore Sinter Plants: Investigation of the Influence of the Off-Gas Temperature

“…It shows that the reaction is somewhat slower at 130°C than at 160°C, while a reduction of the temperature to 110°C slows the reaction down substantially. Similar results are also available in the literature (Keener and Davis, 1984). In a pilot system with an electrostatic precipitator instead of the fabric filter, an ETA tot of approximately 50% has been reported at a stoichiometric ratio of 1.0 and a gas temperature of 200°C (Pilat and Wilder, 2007).…”

HCI Sorption by Dry NaHCO3 for Incinerator Emissions Control

“…The effects of temperature, particle diameter, and pollutant concentration on SO 2 sorption by dry sorbents have been investigated using bench-scale fixedbed reactors. Keener and Davis (1984) found NaHC0 3 undergoing simultaneous decomposition and reaction with SO2 to be most reactive in the 250 to 350° F range with decreasing rate of reaction at higher temperatures. 8 Using a thermal gravimetric apparatus, Kimura and Smith (1987) reported similar results.…”

“…10 Keener and Davis found that SO2 sorption by simultaneously decomposing NaHCO3 had at most a weak dependence on particle diameter. 8 Pollutant concentration also influences the sorption of SO2 by dry sorbents. Stern found that the rate of reaction (mass SO 2 sorbed per mass sorbent per time) of SO2 with predecomposed nahcolite at 500° F was directly proportional to SO 2 concentration.…”

Flue Gas Desulfurization by Mechanically and Thermally Activated Sodium Bicarbonate

“…For the same temperature used and contact times of the sorbent with gases containing SO 2 , sodium bicarbonate has a few times higher conversion rate 4 . The reaction of sodium bicarbonate with SO 2 can be described by the equation 5 : 2NaHCO 3(s) + SO 2(g) + x ½ O 2(g) → (1-x) Na 2 SO 3(s) + x Na 2 SO 4(s) + 2CO 2(g) + H 2 O (g) (1) In the literature a several models of this process are described.…”

“…2NaHCO 3 → Na 2 CO 3 + H 2 O(g) + CO 2 (g) (3) Na 2 CO 3 + SO 2 → Na 2 SO 3 + CO 2 (4) The overall conversion of Na 2 SO 3 to NaHCO 3 is the sum of the partial conversions obtained for the established reaction path. The product, sodium sulfi te, which, in contact with oxygen from fl ue gas, forms sodium sulfate according to the reaction: Na 2 SO 3 + ½ O 2 → Na 2 SO 4 (5) Unauthenticated Download Date | 5/12/18 12:09 PM mill, fi ne impact mill and electromagnetic mill, differing in grinding technique. The 100 AFG fl uid bed mill from Hosokawa-Alpine was used for opposed jet milling, where the energy required to mill the material is passed through the intersecting streams of compressed air.…”