制粒工藝過程的水分控制

1、影響顆粒穩(wěn)定度的因素,調(diào)制 20,環(huán)模 15,粉碎粒度 20,配方/原料 40,冷卻 5%,蒸汽調(diào)制的基本作用,熱水分交換使飼料原料軟化，淀粉糊化，促進(jìn)粉料顆粒在壓粒過程中緊密結(jié)合，提高顆粒飼料的穩(wěn)定度，減少含粉量。 降低制粒電耗，提高產(chǎn)量，延長環(huán)模壽命，減少因摩擦生熱導(dǎo)致的有效營養(yǎng)成分損失。,淀粉糊化程度取決于：溫度、水分與時(shí)間 制粒前的常規(guī)蒸汽調(diào)制，淀粉糊化度的提高一般不超過五個(gè)百分?jǐn)?shù)單位 壓粒過程摩擦生熱導(dǎo)致的淀粉糊化無助于提高顆粒穩(wěn)定度,蒸汽調(diào)制的基本作用,調(diào)制料溫、制粒升溫與淀粉糊化的關(guān)系,蒸汽調(diào)制的基本作用,高水分、長時(shí)間蒸汽調(diào)制，如濕法擠壓膨化的預(yù)調(diào)制過程，可使淀粉糊化度提高約

2、20個(gè)百分?jǐn)?shù)單位。,蒸汽調(diào)制的關(guān)鍵,蒸汽質(zhì)量：什么是蒸汽質(zhì)量？如何得到高質(zhì)量蒸汽 根據(jù)飼料類型和調(diào)制時(shí)間長短正確設(shè)定調(diào)制氣壓 原料與成品水分控制,蒸汽調(diào)制過程的熱交換,蒸汽熱量的組成：表觀熱與潛熱 潛熱-物料升溫的主要熱量來源: 每凝結(jié)一個(gè)百分?jǐn)?shù)單位的優(yōu)質(zhì)蒸汽，物料溫度大約上升 15 0c 蒸汽表 蒸汽質(zhì)量,蒸汽表 over,蒸汽質(zhì)量,濕蒸汽蒸汽中含液態(tài)水, 熱量低，易堵塞?？?蒸汽質(zhì)量可用氣態(tài)水在蒸汽中的百分?jǐn)?shù)來表示 測定蒸汽質(zhì)量的方法 過熱蒸汽或不飽和蒸汽 判定過熱蒸汽的方法 理想的蒸汽：100飽和蒸汽,蒸汽質(zhì)量的計(jì)算,蒸汽質(zhì)量% =(w2xt2-w1xt1)/(w2-w1)-hf/hfg

3、x100% w1=注入蒸汽前水重 w2=注入蒸汽前水重 t1=注入蒸汽前水溫 t2=注入蒸汽前水溫 hf=測試壓力下的表觀熱(查蒸汽表) hfg=測試壓力下的潛熱(查蒸汽表),蒸汽表 over,蒸汽系統(tǒng)主要設(shè)備的選擇與設(shè)定,鍋爐 輸汽管道內(nèi)徑的確定 汽水分離器 疏水閥 減壓(穩(wěn)壓)器 流量控制閥,鍋爐的選擇與設(shè)置boiler selection and layout,燃料的選擇要全面考慮供氣穩(wěn)定性、人工、燃料價(jià)格及環(huán)境等因素 fuel type 鍋爐的功率或供氣量要留有余地 boiler size: leave sufficient room 盡可能縮短鍋爐與用汽設(shè)施之間的距離 locatio

4、n of the boiler: close to the pellet mill,id (cm) = w x 3.53 v/30 w=蒸汽流量 (steam flow),kg/min v=給定氣壓下的比體積 (specific volume under given steam pressure),m3/kg (查表) 30 = 最大流速 (allowed steam flow velocity),m/s,輸汽管道內(nèi)徑的確定sizing the pipe,氣水分離器steam separator,根據(jù)機(jī)械原理將蒸汽中的水滴與蒸氣分開以得到優(yōu)質(zhì)蒸汽. using a mechanical adv

5、ice to remove water drip-lets from the steam and obtain high quality steam. 好的氣水分離器可移走98%的水滴. good separator can remove more than 98% of the water drip-lets,其功能為將凝積水(在進(jìn)入調(diào)制器前)從蒸汽系統(tǒng)中排出. to remove water condensate out of the steam system (before the steam going into the conditioner). 疏水閥應(yīng)不時(shí)啟閉使一定壓力下的凝積水

6、移到常壓的回收系統(tǒng)且不丟失蒸気. it must periodically open and close to allow the pressurized condensate to be removed in to an atmospheric condensate return system without losing steam.,疏水閥check valve,只有氣壓穩(wěn)定才能使氣流穩(wěn)定,從而保證制粒過程穩(wěn)定. steady pressure is critical for smooth steam flow and hence smooth pelleting operation.

7、減壓有助于提高蒸汽質(zhì)量. pressure reduction helps improving steam quality. 減壓(穩(wěn)壓)器的主要參數(shù):流量、調(diào)壓范圍及控制的穩(wěn)定性(可用變異系數(shù)度量). parameters for consideration: maximum flow (kg/hour), pressure range, pressure stability (expressed as cv%).,減壓(穩(wěn)壓)器steam pressure reducer-regulator,控制進(jìn)入調(diào)制器的蒸汽流量.只有物料流量與蒸汽流量同步控制才能實(shí)現(xiàn)穩(wěn)定的制粒作業(yè). it meter

8、s the steam flow going into the conditioning chamber- an important device for operator 調(diào)制器操作與流量應(yīng)是線性關(guān)系. a linear response is required between control valve and steam flow. 一般的控制閥的操作與實(shí)際流量不是線性關(guān)系. the gate valve is non-linear - at half opening, small changes in setting results large steam flow variation

9、.,流量控制閥steam flow control valve,減壓、分水、氣壓控制三合一 a separator - trap - pressure regulator “three in one”device. 流量控制閥在自動(dòng)和手動(dòng)控制條件下均與流量呈線性關(guān)系. linear steam flow control valves for both manual and automatic control system -,cospect valve,蒸汽調(diào)制系統(tǒng)參數(shù)的設(shè)定parameter settings in steam conditioning,考慮因素：調(diào)制時(shí)間、蒸汽質(zhì)量、飼料配方

10、. factors to be considered: retention time, steam quality and formulation/ingredients. 對于一般飼料配方，應(yīng)在不塞機(jī)的前提下，盡可能提高料溫. in general, mash temperature should be conditioned “as high as possible” before reaching the “chock point”.,減壓前后的壓力比pressure ratio before after pressure reducing valve,減壓可使蒸汽中的水滴揮發(fā). 減壓幅

11、度過大,在蒸汽質(zhì)量好時(shí),可形成過熱 (不飽和)蒸汽. pressure reduction helps water drip lets flash off but may also produce a supper-heated steam if the pressure drop is too much and the steam quality already very high. 一般推薦: 3.5-4:1 general recommendation: 3-4 to 1,進(jìn)入調(diào)制室的蒸汽壓力設(shè)定steam pressure setting before conditioner,調(diào)制時(shí)間

12、短，蒸汽質(zhì)量好，宜采用低蒸汽壓 (1.5 -0.5 kg /cm2 或 更 低)， 以爭取熱交換時(shí)間(并降低能耗). low pressure (0.5-1.5 kg/cm2) is preferred if retention time is short (20 sec or less). 調(diào)制時(shí)間長，可采用較高蒸汽壓力。 higher pressure works well (2-4 kg/cm2) if retention time is long (40 sec or more). 關(guān)鍵在于有足夠時(shí)間完成熱交換-釋放潛熱. the key is to give sufficient t

13、ime for heat transfer - releasing latent heat.,調(diào)制溫度700c 以控制水分避免塞機(jī) keep mash temperature700c to avoid moisture increase caused stickiness 可考慮采用較高蒸汽壓力甚至過熱蒸汽 higher steam pressure - low steam flow, or supper heated steam may help,高乳清粉乳豬料蒸汽參數(shù)的設(shè)定steam setting for high whey diet,延長調(diào)制時(shí)間有助于水分進(jìn)入并軟化粉料以提高顆粒質(zhì)量

14、extended retention time helps moisture penetration and softens particles for better pellets. 調(diào)制時(shí)間測定(measuring mean retention time): mrt (sec.) = (3600 xw)/(1000 xp) where, w = 調(diào)制器內(nèi)水分校正的物料量, kg moisture adjusted mash weight in conditioner, kg p = 產(chǎn)量, mt/h production rate, mt/h,蒸汽調(diào)制時(shí)間retention time,蒸汽

15、調(diào)制時(shí)間retention time,延長常規(guī)調(diào)制器調(diào)制時(shí)間的簡易辦法:通過調(diào)節(jié)漿片角度提高物料在調(diào)制器內(nèi)的充滿度. extending retention time by adjusting pitch angle 夾層(間接)蒸器的作用 the role of indirect steam .,extending retention time by adjusting pitch angle,mash fill before adjustment,thermometer,conditioner paddle pitch adjustment (top view),mash fill aft

16、er adjustment,延長調(diào)制時(shí)間的設(shè)備,多層調(diào)制器 可變仰角調(diào)制器 熟化調(diào)制器 ripenner ddc,制粒過程的自動(dòng)控制,料流控制 蒸汽流控制 料溫反饋控制，電流反饋控制,常規(guī)蒸汽調(diào)制的局限性limits to traditional steam conditioning,高水分、低溫原料限制料溫升高。 can not achieve high mash temperature when ingredient moisture is high and temperature is low. 解決途徑：烘干-預(yù)熱？投入機(jī)械能? 加壓調(diào)制? solution: drying ? pre

17、-heating ? mechanical energy input ? pressurizing?,whats new ?,- for better pellets -,制粒工藝過程的水分控制,控制關(guān)鍵點(diǎn),調(diào)制前粉料水分: 水分低于12%在混合物機(jī)加水(一般不超過一個(gè)百分點(diǎn)) 調(diào)制后水分可通過料溫上升估測 成品水分: 通過冷卻時(shí)間料層高度調(diào)節(jié),以電容為基礎(chǔ)的快速水分測定器： 不需樣品粉碎 不需稱量 測定誤差不超過0.5百分?jǐn)?shù)單位 手工操作系統(tǒng)，六秒中得結(jié)果,電腦自動(dòng)監(jiān)測系統(tǒng)，每秒20個(gè)以上讀數(shù),關(guān)鍵設(shè)備,制粒問題解難案例pelleting trouble shooting- case by

18、case analyses,例 1(廣東,1985)case 1 (guangdong),問題: 產(chǎn)量偏低,愛環(huán)鏌壽命低 problem: low production rate., die wearing to fast 現(xiàn)場觀察: 進(jìn)入調(diào)制器蒸汽壓: 2.7kg/cm2, on-site observation: steam pressure at conditioner 2.7 kg/cm2 問題所在?如何解決? solution?,例 2 (美國,1990) case 2 (us-1990),問題: 兔顆粒質(zhì)量差,含粉多.problem: poor pellet quality in

19、a rabbit diet. 現(xiàn)場觀察: 未發(fā)現(xiàn)明顯異常. 與工人座談得知唯一改變是粉碎玉米由廠外帶加工. no significant problem found in pelleting operation. only changes recently made was corn meal supplied from toll-milling by an outside contractor. 問題所在?如何解決? solution?,例 3 (美國,1994) case 3 (us-1994),問題: 料溫上不去,顆粒質(zhì)量差,含粉多,產(chǎn)量低 problem: low mash temperature, poor pellet quality, low production rate. 現(xiàn)場觀察: 給汽打滑, 減壓前-后蒸汽壓: 6.5-2.7, 手可握住疏水閥后水管. on site observation: surging when adding steam; steam pressure at boiler: 6.5 kg/cm, after conditioner: 2.7 kg; hands can hold on pipe after check valve. 問題所在?如何解