1 燃氣內(nèi)燃機燃燒發(fā)電
1. Gas internal combustion engine combustion for power generation
燃料和空氣以適當?shù)谋壤谌細馊細鈨?nèi)燃機的氣缸內(nèi)混合、壓縮、點火、燃燒，火焰迅速傳遍整個燃燒室，同時放出大量熱能。燃燒氣體急速膨脹，壓力和溫度都迅速升高，推動活塞往復運動，通過連桿推動曲軸做功，帶動發(fā)電機發(fā)電，動能轉(zhuǎn)換成電能，利用燃氣、燃油等一次能源作為燃料用于發(fā)電的效率通常在30～40%左右，還有近一半的熱量通常直接散失掉，不僅造成能源的大量浪費，而且加重了環(huán)境污染。如果回收利用燃氣內(nèi)燃機的高溫排煙后將其溫度降低至20℃，約可提高40～50%的能源利用效率[3]。
Fuel and air are mixed, compressed, ignited, and burned in an appropriate proportion in the cylinder of a gas internal combustion engine. The flame quickly spreads throughout the entire combustion chamber, while releasing a large amount of heat energy. The combustion gas expands rapidly, the pressure and temperature rise rapidly, pushing the piston to move back and forth, driving the crankshaft to do work through the connecting rod, driving the generator to generate electricity, and the kinetic energy is converted into electric energy. The efficiency of using Primary energy such as gas and fuel oil as fuel for power generation is usually about 30~40%, and nearly half of the heat is usually lost directly, which not only causes a large waste of energy, but also aggravates environmental pollution. If the high-temperature exhaust gas from a gas internal combustion engine is recycled and reduced to 20 ℃, it can increase energy utilization efficiency by approximately 40-50%.
2 高溫煙氣余熱利用
2. High temperature flue gas waste heat utilization
燃氣內(nèi)燃機的排煙溫度一般在450～550℃左右，通過煙道將排煙收集起來輸送至余熱鍋爐（額定蒸汽壓力2.5MPa），通過余熱鍋爐回收利用該部分熱量，根據(jù)用戶蒸汽需求量調(diào)節(jié)煙氣三通閥門控制進入余熱鍋爐的煙氣量，生產(chǎn)出可用于充裝移動供熱車的飽和蒸汽，當余熱鍋爐不運行時，通過調(diào)節(jié)煙氣三通閥門將煙氣由煙囪排出。燃氣內(nèi)燃機與余熱鍋爐的匹配根據(jù)項目的具體情況可以是單臺燃氣內(nèi)燃機對應一臺余熱鍋爐（一對一），也可以多臺燃氣內(nèi)燃機對應一臺余熱鍋爐（多對一）。上述余熱鍋爐設備采用雙鍋筒縱置式，鍋爐本體主要由上下汽包、對流管束等受壓元件組成，其特點是鍋爐本體中的上下汽包長短相同，下汽包與上汽包由對流管束相連，受熱面積大，具有一定的超負荷能力，屬于全水冷結構，自然循環(huán)運行，運行安全平穩(wěn)。
The exhaust gas temperature of gas internal combustion engines is generally around 450~550 ℃. The exhaust gas is collected through the flue and transported to the waste heat boiler (with a rated steam pressure of 2.5MPa). The heat is recovered and utilized through the waste heat boiler. The three-way valve of the exhaust gas is adjusted according to the user's steam demand to control the amount of exhaust gas entering the waste heat boiler, producing saturated steam that can be used to fill mobile heating vehicles. When the waste heat boiler is not running, By adjusting the flue gas three-way valve, the flue gas is discharged from the chimney. The matching of gas internal combustion engines and waste heat boilers can be based on the specific situation of the project, which can be a single gas internal combustion engine corresponding to one waste heat boiler (one-to-one), or multiple gas internal combustion engines corresponding to one waste heat boiler (many-to-one). The above-mentioned waste heat boiler equipment adopts a double drum vertical arrangement, and the boiler body is mainly composed of pressure components such as upper and lower steam drums, convection tube bundles, etc. Its characteristics are that the upper and lower steam drums in the boiler body are of the same length, and the lower and upper steam drums are connected by convection tube bundles, with a large heating area and a certain overload capacity. It belongs to a fully water-cooled structure, operates naturally, and operates safely and steadily
.
3 低溫煙氣余熱回收
3. Low temperature flue gas waste heat recovery
余熱鍋爐利用后的低溫煙氣溫度仍然有100～190℃左右，在余熱鍋爐排煙口安裝節(jié)能器，把經(jīng)過處理后的鍋爐補水通過管道輸送至節(jié)能器，利用該部分低溫煙氣熱量加熱鍋爐補水，進一步回收余熱鍋爐的排煙熱量，降低排煙溫度，后由煙囪排出。與常規(guī)鍋爐相比，回收這部分熱量可以提高5%以上的效率[3]。但排煙溫度也不宜過低，一方面需要加大換熱面積，設備投資增加，另一方面排煙溫度過低會生成硫酸，腐蝕節(jié)能器中的換熱管道，即酸露點腐蝕，影響系統(tǒng)的安全穩(wěn)定運行，一般設計排煙溫度要高于煙氣酸露點溫度10℃以上[1]；如果燃氣內(nèi)燃機燃料中不含硫，以保證節(jié)能器受熱面不產(chǎn)生凝水為準，即經(jīng)過節(jié)能器回收低溫煙氣熱量后的排煙溫度應高于水的露點溫度10℃以上[4]。所以，綜合考慮煙氣余熱回收效果以及設備投資，節(jié)能器可選擇性價比較高的材料，例如ND鋼。
After the utilization of the waste heat boiler, the low-temperature flue gas temperature is still around 100-190 ℃. An energy-saving device is installed at the exhaust port of the waste heat boiler, and the treated boiler make-up water is transported through pipelines to the energy-saving device. This part of the low-temperature flue gas heat is used to heat the boiler make-up water, further recovering the exhaust heat of the waste heat boiler, reducing the exhaust temperature, and finally being discharged from the chimney. Compared with conventional boilers, recovering this heat can increase the efficiency by more than 5%. However, the exhaust gas temperature should not be too low. On the one hand, it is necessary to increase the heat exchange area and increase equipment investment. On the other hand, if the exhaust gas temperature is too low, it will generate sulfuric acid, corrode the heat exchange pipeline in the energy-saving device, that is, the acid dew point corrosion, and affect the safe and stable operation of the system. Generally, the designed exhaust gas temperature should be above 10 ℃ above the acid dew point temperature of the exhaust gas [1]; If there is no sulfur in the fuel of the gas internal combustion engine, it is necessary to ensure that the heating surface of the energy-saving device does not produce condensation, that is, the exhaust temperature after the low-temperature flue gas heat is recovered by the energy-saving device should be more than 10 ℃ higher than the dew point temperature of the water [4]. Therefore, considering the effectiveness of flue gas waste heat recovery and equipment investment, energy-saving devices can choose materials with higher cost-effectiveness, such as ND steel.
需要注意，燃氣內(nèi)燃機的排煙依次經(jīng)過煙氣管道、煙氣三通閥、余熱鍋爐、節(jié)能器、煙囪，其壓力損失需要經(jīng)過詳細核算，使得其終的排氣壓力必須限制在燃氣內(nèi)燃機大允許排氣背壓值以內(nèi)，以保證燃氣內(nèi)燃機的穩(wěn)定運行。
It should be noted that the exhaust gas of the gas internal combustion engine passes through the flue gas pipeline, flue gas three-way valve, waste heat boiler, energy-saving device, and chimney in sequence. The pressure loss needs to be carefully calculated, so that the final exhaust pressure must be limited to the maximum allowable exhaust back pressure value of the gas internal combustion engine to ensure the stable operation of the gas internal combustion engine.
另外，系統(tǒng)設計時應按照標準選擇合適的管道保溫材料以及保溫厚度，并且盡量縮短燃氣內(nèi)燃機和余熱鍋爐間的煙氣管道長度，不僅能夠降低燃氣內(nèi)燃機排煙在傳輸過程中的熱量損失，還可以減小壓力損失。
In addition, when designing the system, appropriate pipeline insulation materials and thickness should be selected according to standards, and the length of the flue gas pipeline between the gas internal combustion engine and the waste heat boiler should be minimized as much as possible. This not only reduces the heat loss during the transmission process of the exhaust gas from the gas internal combustion engine, but also reduces the pressure loss.
4 余熱鍋爐補水
4. Makeup water for waste heat boiler
通過水處理設備處理后的余熱鍋爐補水，需要經(jīng)過除氧器熱力除氧，然后送至節(jié)能器加熱，為余熱鍋爐運行提供不間斷的水源。另外，為了防止鍋爐補水過程中出現(xiàn)氣蝕的現(xiàn)象，在鍋爐補水泵組與除氧器之間安裝一臺加壓泵。水處理裝置可采用常規(guī)的全自動軟水器，以制取鍋爐軟水，或者根據(jù)鍋爐補水水質(zhì)采取其他水處理裝置，例如反滲透設備、離子交換、EDI電除鹽系統(tǒng)裝置等。
The make-up water of the waste heat boiler treated by the water treatment equipment needs to be thermally deoxidized by the deaerator, and then sent to the energy-saving device for heating, providing uninterrupted water source for the operation of the waste heat boiler. In addition, to prevent cavitation during the boiler water replenishment process, a pressurized pump is installed between the boiler water replenishment pump group and the deaerator. The water treatment device can use conventional fully automatic water softeners to produce boiler soft water, or other water treatment devices such as reverse osmosis equipment, ion exchange, EDI electric desalination system devices, etc. can be used based on the quality of boiler makeup water.
余熱鍋爐排污水通入排污膨脹罐進行減壓處理，不僅可以提高系統(tǒng)運行的安全性能，而且在排污膨脹罐中可產(chǎn)生二次蒸汽，然后通入補水箱中預熱鍋爐補水，提高能源的利用效率。
The waste heat boiler sewage is discharged into the sewage expansion tank for pressure reduction treatment, which not only improves the safety performance of system operation, but also generates secondary steam in the sewage expansion tank, which is then preheated into the make-up water tank to improve energy utilization efficiency.
2.5 蒸汽輸送過程
2.5 Steam transportation process
余熱鍋爐生產(chǎn)出的飽和蒸汽通過蒸汽管道送至分氣缸，然后從分氣缸的出口輸送至充裝系統(tǒng)的干管，經(jīng)由充裝系統(tǒng)的支管分別對移動供熱車進行蒸汽充裝，后運輸至用戶處，釋放出用戶所需壓力的蒸汽。蒸汽充裝系統(tǒng)示意圖見圖2。另外，從分氣缸的其他出口引出部分蒸汽用于余熱鍋爐補水的熱力除氧。
The saturated steam produced by the waste heat boiler is sent to the sub cylinder through a steam pipeline, and then from the outlet of the sub cylinder to the main pipe of the filling system. The mobile heating vehicle is filled with steam through the branch pipes of the filling system, and finally transported to the user to release the steam required by the user. The schematic diagram of the steam filling system is shown in Figure 2. In addition, a portion of steam is extracted from other outlets of the sub cylinder for thermal deoxygenation of the waste heat boiler's makeup water.