New environmental protection lime kiln

Exploration and Attempt of New Environmental Protection Lime Kiln

The designed fuel can be pulverized coal, petroleum coke powder or mixed combustion, equipped with liquefied natural gas ignition and auxiliary combustion, or all liquefied natural gas can be used as fuel.

The pilot production line will be constructed in two phases, and will be planned and implemented in stages.

Overview of test line

The process flow of the lime suspension calcination production line is shown in Figure 3. Crush the block limestone with the moisture content less than 4% (the particle size is generally less than 60mm), and grind it to obtain fine limestone powder with the moisture content less than 1%. The fine limestone powder is collected by the cyclone dust collector and sent to the powder homogenization silo by bucket elevator and other conveying equipment. The homogenized limestone powder is delivered to the lime suspension calcination cooling device by the elevator after being measured by the steady flow. The limestone powder fed is gradually heated by the multi-stage suspension preheater into the suspension calciner to generate powdered lime. The powdered lime out of the suspension calciner is collected by the outlet cyclone separator and sent to the multi-stage suspension cooler. After being gradually cooled by the multi-stage suspension cooler, it is sent to the finished lime storage by the conveying equipment. The cooling air is preheated by the multi-stage suspension cooler and then sent to the suspension calciner as the combustion air.

Phase I is to build limestone powder silo, lime suspension calcination cooling system, waste gas treatment system, lime silo, raw coal storage, pulverized coal preparation, gas storage tank and common works. Phase II will complete the construction of the remaining single projects of the whole production line, including limestone crushing, crushed stone storage, limestone grinding, lime powder packaging, and bagged finished product storage. The first phase of the construction project was completed in May 2016, followed by the commissioning and on load verification test of the lime suspension calcination system (purchased limestone powder)

The lime suspension calcination system was improved. In March 2017, all projects of the test line were completed. In April 2017, the whole line of linkage trial production began. This is also the first lime suspension calcination production line put into industrial trial production in China.

Test purpose

The feasibility of calcining powdered lime with suspension calciner, multi-stage suspension preheater and multi-stage suspension cooler system was verified through the test process, and exploration was carried out, so as to accumulate experience for the process configuration of mass production production line and the development of suspension preheating calcination cooling system of core equipment in the future:

(1) Technical approaches to optimizing the suspension preheating, calcination and cooling process and product blending process;

(2) Reasonable matching and connection of multistage suspension preheater, suspension calciner and multistage suspension cooler;

(3) Thermal characteristics of the cooling process of single lime powder suspension preheating calcination, such as the distribution of thermal parameters and the influence of calcination system on product activity and quality;

(4) The design elements of the suspension calcination cooling system of the core unit, such as the volume requirements of the calcination system and the unit product reactor of the cooling system, and the requirements of the pure limestone powder on the structural characteristics of each constituent monomer (cyclone tube, outlet pipe, etc.);

(5) Accumulate experience in operation management and operation.

Test progress

After exploration, test and improvement, the whole calcination system operates stably and the test has achieved the expected effect. The continuous operation data for more than 72 hours shows that when the CaO content of limestone powder is 52% - 53, and 5%, the calcium carbonate decomposition rate is generally 94% - 96%, the lime output is 100~1200t · d-1, and the lime activity is 330~380mL. The test operation results show that it is feasible and feasible to calcine powdered lime with suspension calciner, multi-stage suspension preheater and multi-stage suspension cooler system, which is suitable for calcining fine limestone powder with particle size<0.8mm, R0 and 18 sieve residue<30%. Through experimental exploration, the technical approach to further improve the decomposition rate of calcium carbonate in lime products has also been clarified, that is, the suspension calcination system is designed to be partially recycled or fully re decomposed to increase the active calcium oxide content of finished powdered lime.

The test line has been transferred to industrial production since April 2018. The main problems existing in the current operation are:

① Due to suspension pre

The number of stages of the heater and the parameters of the main exhaust fan are unreasonable, and the heat consumption is high, about 3973kJ · kg-1 lime (equivalent to 950kal · kg-1 lime). Through improvement and optimization, the heat consumption can be reduced to 3638kJ · kg-1 lime (equivalent to 870kcal · kg-1 lime);

② The test line was transferred to production oriented

The post sales market has not been opened and the operating rate is not high;

③ Use pulverized coal as

When coal ash is used as fuel, it will affect the CaO content of lime products, so it is necessary to limit the ash content of pulverized coal.